JP4131251B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a hydraulic transmission device that transmits displacement via hydraulic pressure and a hydraulic transmission device that transmits displacement in an enlarged manner. These devices can be suitably used, for example, as a drive portion of a control valve that controls fuel injection in a common rail fuel injection device of a diesel engine.

  In a common rail fuel injection device of a diesel engine, a common rail common to each cylinder is provided to accumulate high-pressure fuel, and an injector is driven at a predetermined timing to inject a predetermined amount of fuel into each cylinder. As a common rail injector, there is a piezo injector using a piezo actuator as a drive unit, and high fuel injection control is expected because of its high responsiveness. Here, the drive unit of the piezo injector is usually provided with a hydraulic transmission device that transmits the displacement of the piezo actuator via hydraulic pressure. Since the piezo actuator has a very small displacement, it is enlarged and transmitted. A hydraulic transmission device has been proposed.

For example, Patent Documents 1 to 3 are known as conventional hydraulic transmission devices that transmit displacement in an enlarged manner. A large-diameter piston and a small-diameter piston are accommodated in a stepped cylinder, and hydraulic pressure is obtained between pistons having different cross-sectional areas. By performing the transmission, a mechanism for enlarging the displacement of the piezo actuator is configured.
JP 2002-115617 A US Patent Application Publication No. 2002-0104976 US Patent Application Publication No. 2003-0155540

  FIG. 5 shows an example of a piezo injector provided with a hydraulic transmission device that expands and transmits displacement. In FIG. 5, a large-diameter piezo piston 62 and a small-diameter valve piston 64 are coaxially arranged below the piezo stack 61 so as to slide in the cylinder 5. In the cylinder 5, an oil-tight chamber 63 is provided at a step portion between the piezo piston 62 and the valve piston 64. The valve piston 64 is in contact with the valve needle 1 of a three-way valve that opens and closes between the control chamber 4 that applies back pressure to the nozzle needle 3, the high pressure passage 15, and the low pressure passage 16. The figure shows a state in which the piezo stack 61 is not energized and the valve needle 1 is in the upper end position where the first needle 22 is seated. The control chamber 4 is connected to the high-pressure passage 15 via the passage 25, the valve chamber 21, and the orifice 24. And the high pressure passage 15 via the sub-orifice 41, the pressure is high. At this time, the nozzle needle 3 is at the lower end position and the nozzle hole 34 is closed.

  In the above configuration, when the piezo stack 61 is energized, the piezo piston 62 is displaced downward, and the valve piston 64 is pushed down as the pressure in the oil tight chamber 63 increases. At this time, the displacement is expanded according to the difference in diameter between the piezo piston 62 and the valve piston 64, and the valve needle 1 moves downward until it is seated on the second seat 23 after being separated from the first seat 22. Then, the communication between the control chamber 4 and the high pressure passage 15 is interrupted and the communication with the low pressure passage 16 is established, so that the control chamber 4 becomes low pressure, the nozzle needle 3 starts to lift, and the fuel reservoir chamber 32 and the sack portion 33 communicate with each other. Then, fuel is injected from the injection hole 34.

  However, in the above configuration, both the piezo piston 62 and the valve piston 64 require a certain amount of sliding length, so that the total length of the hydraulic transmission device becomes long. As a result, there arises a problem that the total length of the injector becomes long.

  Accordingly, an object of the present invention is to shorten the overall length of a device that transmits the displacement of an actuator used in a common rail fuel injection device or the like of a diesel engine, thereby making the injector incorporating the actuator a compact structure. is there.

The invention of claim 1 has an actuator that generates displacement when energized, a first piston that is displaced integrally with the actuator, and a second piston that faces the first piston across an oil-tight chamber, and the displacement of the actuator is hydraulic. transmitted to the second piston via a built-in hydraulic transmission as a drive unit of the control valve for controlling the opening and closing of the nozzle needle, provided with a control chamber for applying a pressure in the closing direction to the nozzle needle, the drive unit A fuel injection device that raises and lowers the nozzle needle by increasing and decreasing the pressure in the control chamber by opening and closing the control valve by the second piston, and one of the first and second pistons is closed at one end. The cylindrical portion is extrapolated to a cylindrical cylinder fixed to the housing. On the other hand, the other one of the first and second pistons is inserted into the cylindrical cylinder so that the first and second pistons are slidable with respect to the inner and outer peripheral surfaces of the cylindrical cylinder, and further, the second piston is connected to the spring. The oil is energized in the direction of the control valve by the energizing force, and the space surrounded by the cylindrical portion, the cylindrical cylinder, and the other of the first and second pistons is filled with hydraulic oil to form the oil tight chamber.

  According to the above configuration, the first and second pistons that are movable members are arranged on the inner and outer circumferences of the cylindrical cylinder that is a fixed member so that the sliding ranges overlap. The overall length (axial length) of the device can be shortened while ensuring the length. Therefore, compared to the conventional structure in which the first and second pistons are arranged in a straight line, the total length of the hydraulic transmission device is shortened, so that an injector or the like using the hydraulic transmission device can have a compact structure.

The invention of claim 2 has an actuator that generates displacement when energized, a large-diameter piston that is displaced integrally with the actuator, and a small-diameter piston that faces the large-diameter piston with an oil-tight chamber interposed therebetween. A hydraulic transmission device that expands and transmits to the small-diameter piston as a control valve drive unit that controls the opening and closing of the nozzle needle, and provides a control chamber that applies pressure in the valve closing direction to the nozzle needle. A fuel injection device that raises and lowers the nozzle needle by increasing and decreasing the pressure in the control chamber by opening and closing the control valve by the small diameter piston of the portion, The cylindrical portion is extrapolated to a cylindrical cylinder fixed to the housing. On the other hand, the small-diameter piston is inserted into the cylindrical cylinder so that the large-diameter and small-diameter pistons can slide with respect to the outer peripheral surface and the inner peripheral surface of the cylindrical cylinder, respectively, and the small-diameter piston is attached to a spring. The oil is energized in the direction of the control valve by the urging force, and the space surrounded by the cylindrical portion of the large-diameter piston, the cylindrical cylinder, and the small-diameter piston is filled with hydraulic oil to form the oil-tight chamber.

  According to the above configuration, the large and small diameter pistons that are movable members are arranged on the inner and outer periphery of the cylindrical cylinder that is the fixed member, and the sliding ranges are overlapped, so that the sliding length of each piston is ensured. In this way, the overall length (axial length) of the device can be shortened. Therefore, compared to the conventional structure in which large and small diameter pistons are arranged in a straight line, the overall length of the hydraulic transmission device is shortened, and the displacement of the large diameter piston can be reduced by combining large and small diameter pistons with different diameters. It can be enlarged and transmitted to a small-diameter piston. Therefore, if this hydraulic transmission device is applied to an injector or the like, the displacement of the actuator can be effectively enlarged, the necessary displacement can be ensured, and a compact structure can be achieved.

  According to a third aspect of the present invention, the closed end portion and the cylindrical portion of the first, second piston or large-diameter piston having the one end closed cylindrical shape are configured as separate members.

  By forming the cylindrical piston closed at one end with a plurality of members, processing in the cylindrical portion on the closed end side becomes easy and can be manufactured at low cost.

  According to a fourth aspect of the present invention, there is provided a communication passage that communicates the oil-tight chamber and the low-pressure portion in the configuration of each of the above-mentioned claims, and the hydraulic oil is supplied to the oil-tight chamber when the pressure in the oil-tight chamber falls below a predetermined pressure. A check valve is provided for inflow.

  In the above configuration, when the pressure in the oil tight chamber falls below a predetermined pressure, the check valve is opened and hydraulic oil flows into the oil tight chamber. Thereby, since the hydraulic oil leaking from the oil tight chamber can be easily replenished, displacement can be efficiently transmitted while maintaining the oil pressure of the oil tight chamber.

  According to a fifth aspect of the present invention, the actuator in the configuration of each of the above claims is a piezo actuator.

  As the member that generates the displacement, if an actuator having a large generated force and a small displacement such as an actuator using a piezo element is used, the displacement can be efficiently transmitted with a compact configuration, and thus the present invention is applied. High effect.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an injector 10 of a fuel injection device to which the present invention is applied, and incorporates a piezo drive unit 101 as a hydraulic transmission device that expands displacement. In this embodiment, an example of application to a common rail fuel injection device of a diesel engine will be described, and an injector 10 provided corresponding to each cylinder of the engine is supplied with fuel (here, light oil) from the common rail. ing. In the common rail, fuel pumped by a high-pressure supply pump is stored at a predetermined high pressure corresponding to the injection pressure.

  In FIG. 1, an injector 10 includes a piezo driving unit 101 (upper half) having a piezo stack 61, a nozzle unit 103 (lower end) having a nozzle needle 3, and a control valve unit 102 (intermediate part) having a three-way valve structure. ). The injector 10 has a housing 14 attached to a combustion chamber wall (not shown). The housing 14 accommodates the components of the above-described parts 101 to 103, and is connected to a common rail (not shown). A passage such as a low-pressure passage 16 that communicates with a drain passage leading to a substantially fuel tank is formed.

  The nozzle portion 103 holds the stepped nozzle needle 3 in a vertical hole 31 formed in the lower end portion of the housing 14 so as to be slidable, and an annular oil sump chamber is provided on the outer periphery of the lower half small diameter portion of the nozzle needle 3. 32 is formed. The oil sump chamber 32 is always in communication with the high pressure passage 15 and is supplied with high pressure fuel from the common rail. Below the vertical hole 31, a sack portion 33 is formed continuously therewith, and a fuel injection nozzle hole 34 is formed through the sack portion 33 forming wall.

  When the nozzle needle 3 is in the lower end position, the conical tip is seated on a seat 35 provided at the boundary between the sack portion 33 and the vertical hole 31, the sack portion 33 is closed, and the oil reservoir chamber 32 is connected to the nozzle hole 34. Shut off the fuel supply. When the nozzle needle 3 is lifted and separated from the seat 35 and the sack portion 33 is opened, fuel is injected.

  A space defined by the upper end surface of the nozzle needle 3 and the wall surface of the vertical hole 31 serves as a control chamber 4 that applies back pressure to the nozzle needle 3. Fuel as control oil is introduced into the control chamber 4 through a valve chamber 21 and an orifice 24 of the back pressure control unit 102, which will be described later, and from the high-pressure passage 15 through a sub-orifice 41. 3 back pressure is generated. This back pressure acts downward on the nozzle needle 3 and urges the nozzle needle 3 in the seating direction together with the spring 42 housed in the control chamber 4. On the other hand, the high-pressure fuel in the oil sump chamber 32 acts upward on the step surface of the nozzle needle 3 to urge the nozzle needle 3 in the seating direction. The sub-orifice 41 has a function of adjusting the opening / closing speed of the nozzle needle 3 by reducing the pressure drop in the control chamber 4 at the start of injection and promoting the pressure increase in the control chamber 4 at the stop of injection.

  The control valve portion 102 of the three-way valve structure is such that the large-diameter valve portion 11 of the valve needle 1 is a three-way valve first sheet 22 on the ceiling surface of the valve chamber 21 or a three-way valve second sheet 23 on the bottom surface. To sit selectively. The first seat 22 and the second seat 23 are provided at opposing positions of the ceiling surface and the bottom center portion of the valve chamber 21, the first seat 22 communicates with the low pressure passage 16 via the low pressure portion 26, and the second seat 23 is The high pressure passage 15 communicates with the passage 25. The valve chamber 21 is always in communication with the control chamber 4 of the nozzle portion 103 via the orifice 24.

  The valve needle 1 has a pressure balance structure, the upper end portion is a large-diameter valve portion 11, and the lower end portion is a sliding portion 13 that slides in the cylinder 27 following the second seat 23. The intermediate portion is a small-diameter portion 12 that connects the valve portion 11 in the valve chamber 21 and the sliding portion 13, and the high-pressure passage 15 is formed in an annular space formed between the small-diameter portion 12 and the cylinder 27. A passage 25 leading to is opened.

  When the valve needle 1 is at the upper end position, the flat top surface of the valve portion 11 is seated on the first seat 22 on the ceiling surface of the valve chamber 21 to block communication with the low pressure passage 16. When the valve needle 1 is in the lower end position, the lower taper surface of the valve portion 11 is seated on the second seat 23 on the bottom surface of the valve chamber 21 to block communication with the high pressure passage 15. The valve needle 1 is moved up and down by being pressed by a piezo drive unit 101. As the operating state is switched, the pressure in the control chamber 4 communicating with the valve chamber 21, that is, the nozzle needle 3 is changed. Back pressure increases or decreases.

  A valve spring 17 is accommodated below the sliding portion 13 of the valve needle 1 to urge the valve needle 1 upward. On the side wall of the cylinder 27 below the sliding portion 13, a communication path reaching the low pressure portion 26 is opened so that the downward movement of the valve needle 1 is not suppressed. With this configuration, the valve portion 11 can be quickly separated from the first seat 22 at the start of injection.

  The piezo drive unit 101 is configured using a piezo stack 61 as a piezo actuator. The piezo stack 61 is accommodated in a vertical hole formed above the valve chamber 21, and a piezo piston 62 that is a large-diameter piston (first piston) and a valve piston 64 that is a small-diameter piston (second piston) are disposed below the piezo stack 61. It is arranged coaxially. The piezo stack 61 has a known structure in which piezoelectric ceramic layers such as PZT and electrode layers are alternately stacked, and is charged and discharged by a drive circuit (not shown) with the stacking direction (vertical direction) as an expansion / contraction direction. . The piezo piston 62 and the valve piston 64 are slidably supported by the cylindrical cylinder 5 fixed in the vertical hole, and an oil tight chamber 63 is formed between the piezo piston 62 and the valve piston 64. The configuration of the pistons 62 and 64 and the oil-tight chamber 63 is a characteristic part of the present invention and will be described in detail below.

  The lower end surface of the piezo stack 61 is supported by a piston member 66 slidably provided in the vertical hole, and the piezo piston 62 is closely disposed below the piston member 66. As shown in FIG. 2, the piezo piston 62 has a cylindrical shape with a closed top end, and slides with respect to the outer peripheral surface of the cylindrical portion 51 by extrapolating the cylindrical portion 621 from above to the cylindrical portion 51 of the cylinder 5. It is free. The cylinder 5 is fixed to the housing 14 by a flange portion 52 projecting outward from the lower end of the cylindrical portion 51, and a piezo spring 65 is provided between the flange portion 52 and the upper end large diameter portion 622 of the piezo piston 62. Thus, a certain initial load is applied to the piezo stack 61 via the piezo piston 62 and the piston member 66. As a result, the piezo piston 62 moves up and down as the piezo stack 61 expands and contracts. The piezo spring 65 may be a coil spring or a slit spring.

  The valve piston 64 is columnar, is inserted into the cylindrical portion 51 of the cylinder 5 from below, and is slidable with respect to the inner peripheral surface of the cylindrical portion 51. A pin-like lower end portion 641 of the valve piston 64 extends toward the three-way valve first seat 22 and is in contact with the top surface of the valve needle 1 in the valve chamber 21. A flange 642 is formed on the outer periphery of the intermediate portion of the valve piston 64, and the valve piston 64 is biased downward by a valve piston preset spring 53 supported on the flange 642. A space surrounded by the cylindrical portion 621 of the piezo piston 62, the cylindrical portion 51 of the cylinder 5 and the valve piston 64 is filled with fuel as hydraulic oil to form an oil tight chamber 63.

  Accordingly, when the piezo stack 61 extends and presses the piezo piston 62 downward, the pressing force is transmitted to the valve piston 64 via the fuel in the oil-tight chamber 63 and functions as a hydraulic transmission device. Further, in this embodiment, since the small-diameter valve piston 64 is used with respect to the large-diameter piezo piston 62, the difference between the inner diameter of the cylindrical portion 621 of the piezo piston 62 and the outer diameter of the valve piston 64 (sliding diameter difference). Accordingly, it functions as a hydraulic transmission device that enlarges and transmits the displacement of the piezo stack 61.

  Next, the operation of the injector 10 in each of the above embodiments will be described. First, in the first embodiment, FIGS. 1 and 2 show a state in which the piezo stack 61 is contracted in a discharged state, and the valve needle 1 is moved upward by the fuel pressure in the valve chamber 21 and the spring 17 force. The valve portion 11 is seated on the first seat 22 by being biased. The second sheet 23 facing the first sheet 22 is opened. Therefore, the control chamber 4 communicates with the high-pressure passage 15 through the orifice 24, the valve chamber 21, and the second seat 23, and communicates with the high-pressure passage 15 through the sub-orifice 41. High pressure. The nozzle needle 3 is seated on the seat 35 by the fuel pressure and the spring 42 force, and fuel injection is not performed.

  From this state, when the piezo stack 61 is energized, the piezo stack 61 is filled and extended. Along with this, the piezo piston 62 moves downward and the hydraulic oil (light oil here) in the oil-tight chamber 63 is compressed. When the valve piston 64 moves downward by the pressure of the hydraulic oil and pushes down the valve needle 1, the valve portion 11 is separated from the first seat 22, further displaced downward, and is seated on the second seat 23. As a result, the control chamber 4 communicates with the low pressure passage 16 via the valve chamber 21 and the first seat 22, the pressure in the control chamber 4 drops, and the downward biasing force of the nozzle needle 3 is less than the upward biasing force. Then, the nozzle needle 3 is separated and fuel injection is started.

  Next, when the piezo stack 61 is discharged again, the piezo stack 61 contracts, the piezo piston 62 moves upward, the pressure in the oil-tight chamber 63 drops, and the pressing force of the valve needle 1 is released. Therefore, the high pressure fuel flowing into the control chamber 4 via the orifice 24 and the sub-orifice 41 raises the control chamber 4 pressure again, the needle 3 is seated, and the injection is finished.

  As in this embodiment, when the piezo stack 61 is used as an actuator, the displacement is very small. Therefore, when a hydraulic transmission device that combines a large-diameter piezo piston 62 and a small-diameter valve piston 64 is used, it is efficient. Power can be transmitted. In that case, when the piezo piston 62 slides on the outer peripheral side of the cylindrical cylinder 5 and the valve piston 64 slides on the inner peripheral side as in the above configuration, both the inner and outer periphery of the cylinder 5 are used as sliding portions. The overall length of the piezo drive unit 101 (hydraulic transmission device) can be greatly shortened while ensuring the piston sliding length. Therefore, a sufficient displacement for driving the control valve unit 102 can be secured, and a compact, high-response and high-performance injector 10 can be realized.

  FIG. 3 shows another example of the configuration of the piezo drive unit 101 (hydraulic transmission device) according to the second embodiment of the present invention. The overall configuration and basic operation of the injector 10 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 3, in the present embodiment, the lower end portion of the cylindrical cylinder 5 is fitted and fixed to a recess provided on the upper surface of the housing 14 in which the valve chamber 21 is formed, and the outer peripheral flange portion 52 is formed on the housing 14. It is set as the structure contacted and supported by the upper surface. The inside of the lower half of the cylinder 5 whose diameter has been expanded is a low-pressure chamber 55, which communicates with the low-pressure portion 26 through a communication hole 54 provided in the side wall of the low-pressure chamber 55.

  Therefore, when the valve needle 1 opens the three-way valve first seat 22, the fuel flows out from the valve chamber 21 to the low pressure portion 26 through the first seat 22, the low pressure chamber 55, and the communication hole 54. Further, the lower end portion 643 of the valve piston 64 is formed in a tapered shape with a diameter decreasing downward, and a valve set spring 53 is disposed between the upper end surface of the tapered portion and the stepped portion of the cylinder 5. .

  Also according to this embodiment, the same effect as the first embodiment can be obtained. Thus, as long as the piezo piston 62 and the valve piston 64 slide on the inner and outer circumferences of the cylindrical cylinder 5, the shape and fixing method of each member are not particularly limited.

  FIG. 4 shows a third embodiment of the present invention, which is different from the second embodiment in the configuration of the valve piston 64. The overall configuration and basic operation of the injector 10 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 4, in this embodiment, the communication passage 7 extending in the axial direction is formed inside the valve piston 64. The upper end of the communication path 7 opens into the oil tight chamber 63, and the lower end communicates with the low pressure chamber 55 through a communication hole 71 that penetrates the side wall of the valve piston 64.

  The upper end portion of the communication passage 7 has a slightly large diameter, and a ball valve 73 is accommodated to constitute a check valve that compensates for leakage in the oil tight chamber 63. A plate member having a communication hole 72 is fitted into the upper end opening of the large diameter portion. As a result, when the pressure in the oil tight chamber 63 decreases, the fuel flowing from the low pressure chamber 55 into the communication hole 71 and the communication passage 7 can push up the ball valve 73 to replenish the oil tight chamber 63.

  Also according to this embodiment, the same effects as those of the above embodiments can be obtained. In the present embodiment, the valve piston preset spring 53 is disposed in the oil tight chamber 63. Thus, the arrangement place of various members other than the valve piston preset spring 53 is not particularly limited and may be changed.

  FIG. 5 shows a fourth embodiment of the present invention, which is different from the second embodiment in the configuration of the piezo piston 62. The overall configuration and basic operation of the injector 10 are the same as those in the first embodiment, and a description thereof will be omitted. As shown in FIG. 5, in this embodiment, the piezo piston 62 has a cylindrical shape with openings at both ends, and a piston member 66 is disposed so as to close the upper end opening, and the piezo piston 62, the piston member 66, and the cylinder are arranged. 5 and the valve piston 64 are defined as an oil-tight chamber 63. Thus, the cylindrical piston of the one end closure which forms the oil-tight chamber 63 can also be comprised with a some member. In the present embodiment, the low pressure portion 26 and the low pressure chamber 55 are communicated with each other through a communication hole 56 that penetrates the flange portion 52 provided at the lower end of the cylindrical portion 51 of the cylinder 5.

  Also according to this embodiment, the same effects as those of the above embodiments can be obtained. Furthermore, in this embodiment, the cylindrical piston closed at one end is divided into two members, a piston member 66 serving as a closed end and a piezo piston 62 serving as a cylindrical portion. The shape part (especially the closed end side) can be easily processed and can be manufactured at low cost. A plate member may be interposed between the piston member 66 and the piezo piston 62 so that the plate member forms the upper wall of the oil-tight chamber 63.

  As described above, according to the present invention, in the mechanism that transmits the displacement of the actuator via hydraulic pressure, the influence of the sliding length on the total length of the mechanism is greatly increased by arranging the two pistons inside and outside the cylindrical cylinder. Decrease. Any actuator may be used as long as it is an element that generates displacement when energized. Examples of the actuator include a magnetostrictive element and the like in addition to the piezoelectric element used in each of the above embodiments. By applying the present invention to an actuator that has a large generated force but a small displacement, such as a piezo element and a magnetostrictive element, a hydraulic transmission device for driving the control valve of the injector 10 can be made compact.

  In each of the above embodiments, an example in which the present invention is applied to a hydraulic transmission device that expands displacement has been described. However, the present invention is not limited to this. For example, the present invention can be applied to an actuator having a small generated force but a large displacement, and the arrangement of the large-diameter and small-diameter pistons can be reversed from the above-described embodiments, whereby a driving force expanding device can be obtained.

It is sectional drawing which shows the whole structure of the injector which shows the 1st Embodiment of this invention. It is principal part sectional drawing of 1st Embodiment. It is sectional drawing which shows the principal part structure of the injector which shows the 2nd Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 3rd Embodiment of this invention. It is sectional drawing which shows the principal part structure of the injector which shows the 4th Embodiment of this invention. It is sectional drawing which shows the whole structure of the conventional injector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Injector 101 Nozzle part 102 Control valve part 103 Piezo drive part 1 Valve needle 11 Valve part 12 Sliding part 13 Small diameter part 14 Housing 15 High pressure path 16 Low pressure path 21 Valve chamber 22 3 way valve 1st sheet 23 3 way valve 1st 2 seat 24 orifice 26 low pressure part 3 nozzle needle 32 oil reservoir chamber 34 injection hole 4 control chamber 41 sub-orifice 5 cylinder 51 cylindrical part 52 flange 53 valve piston preset spring 54 communication hole 55 low pressure chamber 61 piezo stack (actuator)
62 Piezo piston (first piston)
621 Tubular part 622 Flange part 63 Oil tight chamber 64 Valve piston (second piston)
641 Lower end part 642 Flange part 65 Piezo spring 66 Piston member 7 Communication path 71 Communication hole 72 Communication hole 73 Ball valve

Claims (5)

An actuator that generates a displacement by energization; a first piston that is displaced integrally with the actuator; and a second piston that faces the first piston with an oil-tight chamber interposed therebetween, and the displacement of the actuator is controlled by hydraulic pressure. A hydraulic transmission device for transmitting to the second piston is built in as a drive portion of a control valve for controlling the opening and closing of the nozzle needle, and a control chamber is provided for applying a pressure in the valve closing direction to the nozzle needle. In the fuel injection device that raises and lowers the nozzle needle by increasing and decreasing the pressure in the control chamber by opening and closing the control valve by two pistons, one of the first and second pistons is formed in a cylindrical shape with one end closed, The cylindrical portion is extrapolated to a cylindrical cylinder fixed to the housing, while the first and second pistons are attached to the cylindrical cylinder. The other a by interpolation, the first and second piston and slidable with respect to the inner peripheral surface of the tubular cylinder, and biasing the second piston to the control valve direction by the biasing force of the spring The fuel injection device is characterized in that the oil-tight chamber is formed by filling the space surrounded by the cylindrical portion, the cylindrical cylinder, and the other of the first and second pistons. An actuator that generates displacement when energized, a large-diameter piston that is displaced integrally with the actuator, and a small-diameter piston that faces the large-diameter piston across an oil-tight chamber, and the displacement of the actuator is controlled by hydraulic pressure to the small-diameter piston. A hydraulic transmission device that expands and transmits to the piston is built in as a drive unit for a control valve that controls the opening and closing of the nozzle needle, and a control chamber is provided for applying a pressure in the valve closing direction to the nozzle needle. In the fuel injection device that raises and lowers the nozzle needle by increasing or decreasing the pressure in the control chamber by opening and closing the control valve with a small diameter piston , the large diameter piston is formed into a cylindrical shape with one end closed, and the cylindrical portion is While extrapolating the cylindrical cylinder fixed to the housing, inserting the small diameter piston into the cylindrical cylinder, the large diameter And a small-diameter piston and slidable respectively outer and inner peripheral surfaces of the tubular cylinder, and to urge the small diameter piston to the control valve direction by the biasing force of the spring, the cylinder of the large-diameter piston A fuel injection apparatus characterized in that a hydraulic oil is filled in a space surrounded by a cylindrical portion, the cylindrical cylinder, and the small-diameter piston. The fuel injection device according to claim 1 or 2, wherein the closed end portion and the tubular portion of the one-end-closed piston are configured as separate members. The communication passage which connects the said oil-tight chamber and a low-pressure part is provided, The check valve which flows hydraulic oil into the said oil-tight chamber when the pressure of the said oil-tight chamber falls below predetermined pressure was provided in this communication passage from the said 1st 4. The fuel injection device according to any one of 3. The fuel injection device according to claim 1, wherein the actuator is a piezo actuator.

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