JP3903927B2 - Injector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injector used in a common rail fuel injection system of a diesel engine, and more particularly to an injector including a three-way valve driven by an actuator.
[0002]
[Prior art]
2. Description of the Related Art In a diesel engine, a common rail fuel injection system that accumulates high pressure fuel on a common rail common to each cylinder has attracted attention. In the injector for the common rail fuel injection system, for example, a control chamber whose pressure is controlled by a control valve is provided on the back of the nozzle needle that opens and closes the nozzle hole, and the nozzle is moved up and down by driving the control valve by an actuator. Yes. In this configuration, the fuel from the common rail is introduced into the fuel passage of the injector and supplied to the nozzle hole, while it is introduced into the control chamber having the rear end surface of the nozzle needle as the chamber wall, and the nozzle needle is closed in the valve closing direction. Used as control oil to apply pressure.
[0003]
As the control valve, a two-way valve or a three-way valve is usually used. For example, Patent Document 1 describes a control valve having a three-way valve structure. In Patent Document 1, the three-way valve has a large-diameter valve portion and a sliding portion that can be respectively seated on the first seat leading to the low pressure passage or the second seat leading to the common rail, and depending on the seating position, The communication with the low-pressure port or high-pressure port is switched. When the three-way valve is used, the control chamber and the low-pressure port communicate with each other during fuel injection, and the high-pressure port is closed, so that the outflow of fuel can be limited. The sliding portion and the two sheet diameters are made equal to balance the pressure.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-130614
In the above configuration, when the actuator is not operated, the three-way valve is in a position where the control chamber communicates with the high pressure port, and since the control chamber becomes high pressure, the nozzle needle is lowered to close the nozzle hole. When the actuator is operated from this state, the three-way valve opens the low pressure port, and then closes the high pressure port, the pressure in the control chamber decreases, the nozzle needle moves away, and fuel injection is performed.
[0006]
[Problems to be solved by the invention]
However, when the control valve having the three-way valve structure is applied to an injector for a common rail fuel injection system, it has been found that there is a problem that the operation becomes unstable. In addition, although the driving force generation characteristics differ depending on the type of actuator, since this is not taken into consideration, there is a problem that energy loss increases.
[0007]
The present invention has been made in view of the above circumstances, paying attention to the fact that the output characteristics vary greatly depending on the type of actuator, and by proposing a control valve configuration that is compatible with the respective output characteristics, the control valve is stable and reliable. An object is to provide an energy efficient injector that realizes operation and is excellent in reliability.
[0008]
[Means for Solving the Problems]
An injector according to a first aspect of the present invention includes a control chamber for applying a pressure in a valve closing direction to the nozzle needle, and a three-way valve for switching communication / blocking between the control chamber and the high-pressure passage and the low-pressure passage. The nozzle needle is raised and lowered by driving the direction valve to increase or decrease the pressure in the control chamber.
The three-way valve has a lower end portion slidably disposed in the cylinder to be a sliding portion that slides in the vertical direction. The upper end portion is located in the valve chamber and has a larger diameter than the sliding portion. Has become a department. Moreover, it has a narrow diameter portion connecting the valve portion and the sliding portion, and a passage leading to the high pressure passage is connected to a space formed between the narrow diameter portion and the cylinder. The valve portion is selectively seated on either a high-pressure seat provided on the cylinder side of the valve chamber and communicating with the high-pressure passage and a low-pressure seat provided at an opposite position and communicating with the low-pressure passage. A spring for urging the three-way valve upward is provided below the sliding portion.
The drive unit for driving the three-way valve is provided with a solenoid as the actuator and an armature opposed to the upper end surface of the solenoid, and the armature protrudes downward from the lower end surface of the valve unit. Having a rod portion that contacts the top surface of
When the solenoid is energized, the armature is attracted downward, the rod portion is lowered to push down the three-way valve, the valve portion of the three-way valve is separated from the low pressure seat, and the high pressure seat is Sit down and
When the energization to the solenoid is stopped, the armature moves upward, the pressing force to the three-way valve is released, the valve portion of the three-way valve is separated from the high-pressure seat, and the low-pressure seat To sit on
The relationship between the sliding diameter of the sliding portion, the high-pressure sheet, and the low-pressure sheet is such that sliding diameter <low-pressure sheet diameter <high-pressure sheet diameter.
[0009]
In the above configuration, when the solenoid is energized, the three-way valve is pushed down, the valve portion is separated from the low pressure seat, and then seated on the high pressure seat. At this time, since the control chamber communicates with the low-pressure passage, the pressure in the control chamber drops, the nozzle needle lifts, and fuel is injected. Here, in order to balance the hydraulic pressure applied to the three-way valve, conventionally, the valve portion and the sliding portion have the same diameter. In this case, the valve opening of the low-pressure seat is performed. Since the force required for the operation is extremely small, the low-pressure seat may open when the solenoid is not driven. In order to avoid this, the low-pressure sheet diameter may be larger than the diameter of the sliding portion. Moreover, since generally a solenoid which exerts a large driving force as the displacement increases, to increase the driving force at the time of closing of the high-pressure seat than when the valve is opened the pressure seat, i.e. increase the seat diameter of the high-pressure seat can and child. As a result, when the energization of the solenoid is finished, the force to push down the three-way valve is released, and the valve portion is separated from the high pressure seat, and then the valve portion is quickly removed from the high pressure seat. Can be separated. Therefore, it is possible to obtain a high-performance and highly reliable injector with improved operational stability and energy efficiency.
[0010]
An injector according to a second aspect of the present invention is an injector including the control chamber and the three-way valve, and the actuator is an actuator using a piezo stack. The 3-way valve has its lower end is a sliding portion you slide up and down direction is slidably disposed in the cylinder, diameter than the sliding portion upper end is positioned in the valve chamber The valve portion is selectively seated on the high-pressure seat provided on the cylinder side of the valve chamber and communicating with the high-pressure passage and the low-pressure seat provided at the opposite position and communicating with the low-pressure passage. It is what
When the piezo stack as the actuator is charged and the piezo stack is extended, the valve portion of the three-way valve is separated from the low pressure seat, and is seated on the high pressure seat,
When the piezo stack is discharged and the piezo stack contracts, the valve portion of the three-way valve separates from the high pressure seat and sits on the low pressure seat,
Upper SL sliding portion of the slide diameter, seat diameter of the high-pressure seat, the relation between the seat diameter of the low-pressure seat, the slide diameter <has a high-pressure seat diameter <low-pressure seat diameter.
[0011]
In the above configuration, since the piezo stack generally has a characteristic that the generated force decreases as the displacement increases, in order to efficiently use this, the low pressure sheet diameter is preferably larger than the high pressure sheet diameter. Since the force with which the three-way valve is seated on the low-pressure seat is larger when the low-pressure seat diameter is larger, the stability of operation is improved by making the low-pressure seat diameter larger than the high-pressure seat diameter as described above. Improve and increase energy efficiency, resulting in high performance and reliable injectors.
[0012]
According to a third aspect of the present invention, in the second aspect of the invention, the three-way valve is provided with a small diameter portion connecting the valve portion and the sliding portion, and is formed between the small diameter portion and the cylinder. A passage leading to the high-pressure passage is connected to the space.
[0013]
With the above configuration, since the hydraulic pressure from the high pressure passage acts on the high pressure seat side and the sliding portion of the valve portion, the high pressure seat diameter and the sliding portion diameter are appropriately set as described above. As a result, the opening and closing operations of the three-way valve can be performed reliably and efficiently.
[0014]
According to a fourth aspect of the present invention, the high pressure passage is connected to a common rail of a diesel engine, while the low pressure passage is connected to a drain passage leading to a fuel tank.
[0015]
The injector of the present invention is suitably used for a common rail fuel injection system of a diesel engine. Specifically, fuel injection can be controlled with high accuracy by connecting the high-pressure passage to the common rail and the low-pressure passage to the drain passage and switching the communication with the control chamber using the three-way valve.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an injector 10 to which the present invention is applied. The injector 10 is used, for example, in a common rail fuel injection system of a diesel engine, is provided corresponding to each cylinder of the engine, and is supplied with fuel from a common rail. In the common rail, fuel pumped by a high-pressure supply pump is stored at a predetermined high pressure corresponding to the injection pressure.
[0017]
In FIG. 1, an injector 10 includes a nozzle portion 101 (lower end portion) having a nozzle needle 3, a back pressure control portion 102 (intermediate portion) having a three-way valve structure, and a drive portion 103 (upper portion) having a solenoid 51 as an actuator. Half). 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.
[0018]
The nozzle portion 101 holds a stepped nozzle needle 3 in a vertical hole 31 formed in the lower end portion of the housing 14 so as to be slidable. 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.
[0019]
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 leads 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.
[0020]
A space defined by the upper end surface of the nozzle needle 3 and the wall surface of the vertical hole 31 is 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 functions to alleviate the pressure drop in the control chamber 4 at the start of injection, promote the pressure increase in the control chamber 4 at the stop of injection, and gradually open the nozzle needle 3 to quickly close it. Have
[0021]
The back pressure control unit 102 includes a valve needle 1 that is a three-way valve. The valve needle 1 is provided on the first sheet 22 or the bottom surface of the valve unit 11 as a low pressure seat provided on the ceiling surface of the valve chamber 21. the second sheet as a high pressure sheet provided - is adapted to selectively seated on preparative 23. The first sheet 22 and the second sheet 23 are provided at positions opposed to the valve chamber 21 ceiling surface and the center of the bottom surface, the first sheet 22 communicates with the low pressure passage 16 via the low pressure portion 26, and the second sheet 23 passes through the passage The high pressure passage 15 communicates with the high pressure passage 15. The valve chamber 21 is always in communication with the control chamber 4 of the nozzle unit 101 via the orifice 24.
[0022]
The valve needle 1 has a basic structure of a pressure balance type, and a lower end portion thereof is disposed in a cylinder 27 following the second seat 23 and serves as a sliding portion 12 that slides in the vertical direction. The upper end portion is located in the valve chamber 21 as a valve portion 11 having a larger diameter than this, and the high pressure passage 15 is formed in an annular space formed between the narrow portion 13 connecting the valve portion 11 and the sliding portion 12 and the cylinder 27. A passage 25 leading to is opened.
[0023]
When the valve needle 1 is in 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 the drive unit 103, and the pressure of the control chamber 4 communicating with the valve chamber 21 as the operating state is switched, that is, the pressure of the nozzle needle 3 is changed. Back pressure increases or decreases.
[0024]
A spring chamber 17 that houses a valve spring 18 is provided below the sliding portion 12 of the valve needle 1, and the valve needle 1 is biased upward by the valve spring 18. Note that the spring chamber 17 is connected to the low-pressure portion 26 through a communication path. Thereby, the downward movement of the valve needle 1 is not suppressed, and the valve portion 11 is quickly separated from the first seat 22 at the start of injection.
[0025]
The drive unit 103 accommodates the solenoid 51 in a vertical hole formed above the valve chamber 21 and is provided with an armature 52 so as to face the upper end surface thereof. The solenoid 51 has a known structure composed of a cylindrical coil wound around a coil bobbin, and attracts the armature 52 downward by energization. The armature 52 has a rod portion 53 protruding downward from the center of the lower end surface, and the lower end of the rod portion 53 is in contact with the top surface of the valve portion 11 of the valve needle 1. Accordingly, when the solenoid 51 is energized, the armature 52 is attracted downward, and the rod portion 53 is lowered accordingly to push down the valve needle 1.
[0026]
Note that, as shown in FIG. 2 as a second embodiment, the drive unit 103 can also be configured using a piezo stack 61 as an actuator. In this configuration, the drive unit 103 accommodates a piezo stack 61 in a vertical hole formed above the valve chamber 21, and a large-diameter piezo piston 62 and a small-diameter valve piston 64 are coaxially disposed below the piezo stack 61. Become. The piezo piston 62 and the valve piston 64 are slidably held in a cylinder provided in the vertical hole, and the space between the piezo piston 62 and the valve piston 54 is an oil-tight chamber 63.
[0027]
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. . A constant initial load is applied to the piezo stack 61 by a piezo spring 65 provided on the outer periphery of the upper end portion of the piezo piston 62. As a result, the piezo piston 62 moves up and down as the piezo stack 61 expands and contracts.
[0028]
The valve piston 64 has a pin-like lower end extending to the vicinity of the first seat 22 of the three-way valve, and is in contact with the top surface of the valve needle 1 in the valve chamber 21. A flange is formed on the outer periphery of the intermediate portion of the valve piston 64, and the valve piston 64 is urged downward by a spring supported on the flange. An oil-tight chamber 63 is formed between the piezo piston 62 and the valve piston 64 by being filled with fuel. The oil tight chamber 63 has a structure in which a chamber on the piezo piston 62 side and a chamber on the valve piston 64 side are connected by an oil tight chamber restrictor 631, and pressure fluctuation during expansion and contraction of the piezo stack 61 is transmitted by the oil tight chamber restrictor 631. Is preventing.
[0029]
Therefore, when the piezo stack 61 extends and presses the piezo piston 62, the pressing force is transmitted to the valve piston 64 through the fuel in the oil-tight chamber 63. At this time, since the valve piston 64 has a smaller diameter than the piezo piston 62, the displacement of the piezo stack 61 can be enlarged and transmitted to the valve piston 64. The configuration other than the drive unit 103 is the same as that in the first embodiment.
[0030]
Next, the operation of the injector 10 in each of the above embodiments will be described. First, in the first embodiment, FIG. 1 shows a state in which the solenoid 51 is not energized, and since the armature 52 is at the upper end position, the valve needle 1 is operated with the fuel pressure in the valve chamber 21 and the force of the spring 18. Therefore, the valve portion 11 is seated on the first seat 22. 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.
[0031]
When the solenoid 51 is energized from this state, the armature 52 is attracted downward, and the rod 53 pushes down the valve needle 1. As a result, the valve portion 11 is separated from the first seat 22 and further displaced downward to be seated on the second seat 23. Accordingly, when the control chamber 4 communicates with the first seat 22 via the valve chamber 21 and the pressure in the control chamber 4 drops and the downward biasing force of the nozzle needle 3 falls below the upward biasing, the nozzle needle 3 is separated and fuel injection is started. Next, when the energization to the solenoid 51 is stopped, the armature 52 moves upward, and the pressing force of the valve needle 1 is released. As a result, the valve portion 11 is separated from the second seat 23 and then seated on the first seat 22. 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 ends.
[0032]
In the second embodiment shown in FIG. 2, when the piezo stack 61 is charged from the state where the piezo stack 61 is contracted in the discharged state (shown state), the piezo stack 61 is extended and the piezo piston 62 is pushed down. The pressure in the oil tight chamber 63 is increased. When this pressure actuates the valve piston 64 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 first seat 22 via the valve chamber 21, and when the pressure in the control chamber 4 drops and the downward biasing force of the nozzle needle 3 falls below the upward biasing, 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 ends.
[0033]
Here, the configuration of the valve needle 1 which is a three-way valve, particularly the relationship between the seat diameter and the sliding diameter will be examined. In the present invention, the valve needle 1 is substantially pressure balanced in order to make the drive load by hydraulic pressure as small as possible. That is, since the valve needle 1 is constituted by the valve portion 11 and the sliding portion 12 and high pressure fuel is introduced into the outer periphery of the narrow diameter portion 13 connecting them, the first seat 22, the second seat 23, and the sliding diameter are substantially reduced. If the diameters are the same, the hydraulic pressure acting upward on the valve portion 11 of the valve needle 1 and the hydraulic pressure acting downward on the sliding portion 12 are balanced to open the first seat 22 and close the second seat 23. The force required for this can be reduced.
[0034]
However, for example, when the first seat 22 opens with a very small force, when the actuator is not driven, the valve needle 1 may open the valve due to an unintended operation, leading to erroneous injection. In order to avoid this, it is preferable that the diameter of the first seat 22 is made larger than the sliding diameter so that when the first seat 22 is closed, the hydraulic pressure acts in the direction in which the first seat 22 is closed. On the other hand, when the driving of the actuator is stopped, it is preferable that the valve needle 1 is quickly separated from the second seat 23 and returned to the initial position (first seat 22 valve closing position). For this purpose, the diameter of the second seat 23 is preferably made larger than the sliding diameter so that the hydraulic pressure acts in the direction in which the second seat 23 is opened when the second seat 23 is opened.
[0035]
That is, for stable operation of the valve needle 1, it is necessary to make both the first seat 22 diameter and the second seat 23 diameter larger than the sliding diameter so that an upward hydraulic load is applied to the valve needle 1. is there. This relationship does not depend on the type of actuator used in the drive unit 103, and is applied to both the first and second embodiments.
[0036]
Next, the relationship between the diameter of the first sheet 22 and the diameter of the second sheet 23 will be examined. As shown in FIG. 3, since the output characteristics vary greatly depending on the type of actuator, the present invention proposes a seat portion configuration corresponding to each output characteristic. First, a case where the actuator of the first embodiment is a solenoid 51 will be described. As shown in FIGS. 3A and 3C, the solenoid 51 generally generates a greater driving force F as the displacement X increases. When energizing the solenoid 51, the valve needle 1 first opens the first seat 22, and then displaces further downward to close the second seat 23. Therefore, when the first seat 22 is opened. Therefore, a larger driving force can be generated when the second seat 23 is closed.
[0037]
FIG. 4 shows a settable range of the first sheet 22 diameter and the second sheet 23 diameter based on the driving force characteristics of FIG. 3, and the upper limit value that can be set is larger for the second sheet diameter. I understand that The lower limit value shown in FIG. 4 is set larger than the sliding diameter so that a hydraulic load necessary for stable operation is applied. In order to improve the workability, the set value is preferably set to the median value of the settable range so that the sheet diameter tolerance can be as large as possible, and the first sheet 22 diameter and the second value are satisfied so as to satisfy this. When the diameter of the sheet 23 is set, the diameter of the second sheet 23 becomes larger than the diameter of the first sheet 22. From the above, when the actuator is the solenoid 51,
By configuring the back pressure control unit 102 so that the relationship of the sliding portion 12 diameter <the first seat 22 diameter <the second seat 23 diameter is established, operational stability is ensured and energy efficiency is excellent. An injector can be realized.
[0038]
On the other hand, the case where the actuator of the second embodiment is a piezo stack 61 will be described. As shown in FIGS. 3B and 3C, the piezo stack 61 exhibits a driving force characteristic opposite to that of the solenoid 51. Generally, when the displacement X increases, the driving force F decreases. In other words, the driving force generated when the valve needle 1 closes the second seat 23 is smaller than when the valve needle 1 opens the first seat 22. Therefore, as shown in FIG. 4, the upper limit value that can be set for the first sheet 22 diameter is larger than the second sheet 23 diameter. Similarly, if the set value is set to the median of the settable range so that the sheet diameter tolerance can be allowed as large as possible, the diameter of the first sheet 22 is larger than the diameter of the second sheet 23. From the above, when the actuator is the piezo stack 61,
By configuring the back pressure control unit 102 so that the relationship of sliding portion 12 diameter <second seat 23 diameter <first seat 22 diameter is established, operational stability is ensured and energy efficiency is excellent. An injector can be realized.
[0039]
Thus, according to the present invention, it is possible to optimize the injector configuration, particularly the relationship between the seat diameter and the sliding diameter of the three-way valve, focusing on the fact that the output characteristics differ depending on the type of actuator. Therefore, stability of the operation of the injector can be ensured, controllability can be improved, and energy efficiency can be increased by effectively utilizing the generated force of the actuator.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an overall configuration of an injector showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an overall configuration of an injector showing a second embodiment of the present invention.
3A is a cross-sectional view of a solenoid as an actuator, FIG. 3B is a cross-sectional view of a piezo stack as an actuator, and FIG. 3C is a diagram showing driving force characteristics of the solenoid and the piezo stack.
FIG. 4 is a diagram showing a settable range of the sheet diameter when the actuator is a solenoid.
FIG. 5 is a diagram showing a settable range of the sheet diameter when the actuator is a piezo stack.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Injector 101 Nozzle part 102 Back pressure control part 103 Piezo drive part 1 Valve needle (3-way valve)
11 Valve portion 12 Sliding portion 13 Small diameter portion 14 Housing 15 High pressure passage 16 Low pressure passage 22 First seat (low pressure seat)
23 Second sheet (high pressure sheet)
3 Nozzle needle 32 Oil reservoir chamber 34 Injection hole 4 Control chamber 51 Solenoid (actuator)
52 Armature 53 Rod 61 Piezo stack (actuator)
62 Piezo piston 63 Oil tight chamber 64 Valve piston

Claims (4)

A control chamber that applies pressure in the valve closing direction to the nozzle needle, and a three-way valve that switches between communication and blocking between the control chamber and the high-pressure passage and the low-pressure passage. An injector for raising and lowering the nozzle needle by increasing or decreasing the pressure of
The three-way valve has a lower end portion slidably disposed in the cylinder to be a sliding portion that slides in the vertical direction. The upper end portion is located in the valve chamber and has a larger diameter than the sliding portion. A small diameter portion connecting the valve portion and the sliding portion, and connecting a passage leading to the high pressure passage to a space formed between the small diameter portion and the cylinder, The seat is selectively seated on either the high-pressure seat provided on the cylinder side of the valve chamber and communicating with the high-pressure passage and the low-pressure seat provided on the opposite position and communicating with the low-pressure passage. Below the moving part, there is a spring that urges the three-way valve upward,
The drive unit for driving the three-way valve is provided with a solenoid as the actuator and an armature opposed to the upper end surface of the solenoid, and the armature protrudes downward from the lower end surface of the valve unit. Having a rod portion that contacts the top surface of
When the solenoid is energized, the armature is attracted downward, the rod portion is lowered to push down the three-way valve, the valve portion of the three-way valve is separated from the low pressure seat, and the high pressure seat is Sit down and
When the energization to the solenoid is stopped, the armature moves upward, the pressing force to the three-way valve is released, the valve portion of the three-way valve is separated from the high-pressure seat, and the low-pressure seat To sit on
The injector characterized in that the sliding diameter of the sliding part, the sheet diameter of the high-pressure sheet, and the sheet diameter of the low-pressure sheet satisfy the following relationship: sliding diameter <low-pressure sheet diameter <high-pressure sheet diameter. A control chamber that applies a pressure in the valve closing direction to the nozzle needle, and a three-way valve that switches communication / blocking between the control chamber and the high-pressure passage and the low-pressure passage;
An injector that raises and lowers the nozzle needle by driving the three-way valve with an actuator to increase or decrease the pressure in the control chamber;
Diameter upper Symbol 3-way valve becomes a sliding portion that slides vertically its lower end portion is slidably disposed in the cylinder, than the sliding portion upper end is positioned in the valve chamber The valve portion is selectively seated on the high-pressure seat provided on the cylinder side of the valve chamber and communicating with the high-pressure passage and the low-pressure seat provided at the opposite position and communicating with the low-pressure passage. It is what
When the piezo stack is used as the actuator, and the piezo stack is charged and the piezo stack is extended, the valve portion of the three-way valve is separated from the low pressure seat and is seated on the high pressure seat,
When the piezo stack is discharged and the piezo stack contracts, the valve portion of the three-way valve separates from the high pressure seat and sits on the low pressure seat,
Upper SL sliding portion of the slide diameter, seat diameter of the high-pressure seat, the relationship of the seat diameters of the low-pressure seat, the injector, characterized in that the slide diameter <a high pressure seat diameter <low-pressure seat diameter. The 3-way valve has a small diameter portion which connects the valve portion and the sliding portion, claim to connect the passage leading to the high pressure passage in a space formed between said small diameter portion and the cylinder 2 The described injector.   The injector according to any one of claims 1 to 3, wherein the high-pressure passage is connected to a common rail of a diesel engine, and the low-pressure passage is connected to a drain passage.

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