JP3852146B2 - Fuel injection valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection valve for an internal combustion engine that controls fuel injection by an electrostrictive actuator having a piezoelectric element.
[0002]
[Prior art]
In recent internal combustion engines, there are increasing needs for improving response, fuel consumption, and output, and the fuel injection valve plays an important role in meeting such needs.
[0003]
The shorter the time required for opening and closing the fuel injection valve, that is, the better the response of opening and closing, the better the controllability and the performance of the internal combustion engine. An electrostrictive actuator is known as an actuator that can be opened and closed in a short time. However, there is a problem that if the electrostrictive actuator is used to directly open and close the valve, the lift cannot be increased. There has been proposed a fuel injection valve in which a strain type actuator is used as a trigger for opening and closing a valve, and the actual opening and closing of the valve and the maintenance of the opened and closed state are performed by hydraulic pressure.
[0004]
For example, by using a piezoelectric element with excellent high-speed response as electrostriction, to improve the response of the injection valve, to stably supply a small amount of fuel injection when fuel consumption is reduced, or to increase output A technique for expanding the injectable range (dynamic range) has been proposed in Japanese Patent No. 2,522,417, etc., and a hydraulic oil such as fuel is interposed between the piezoelectric element and the needle valve so as to reduce the piezoelectricity. It is disclosed to transmit the displacement of the element to the needle valve.
[0005]
In the fuel injection valve disclosed in Japanese Patent No. 2,522,417, as shown in FIG. 3, a metal needle valve 2 as a movable member is coaxially inserted in a nozzle 1, and this needle A pressure chamber 13 is formed between the valve 2 and the piston 7 joined to the piezoelectric element 6. As the piezoelectric element 6 expands and contracts instantaneously in the order of msec, the pressure in the pressure chamber 13 changes transiently with respect to the pressure in the fuel supply chamber 31 (low during contraction and high during expansion). As a result, the pressure balance between the pressure chamber 13 and the fuel supply chamber 31 is lost, and the needle valve 2 is opened and closed.
[0006]
[Problems to be solved by the invention]
By the way, in this type of fuel injection valve, if the displacement amount of the piezoelectric element 6 is Y and the cross-sectional areas of the base end 2d of the needle valve 2 and the head of the piston 7 are A1 and A2, respectively, the lift amount of the needle valve 2 is E0 × Y × A2 / A1. Here, E0 is displacement expansion efficiency, and 0 ≦ E0 ≦ 1.
[0007]
That is, the lift amount of the needle valve 2 is proportional to the displacement amount Y of the piezoelectric element 6, the cross-sectional area ratio (A2 / A1) between the piston 7 and the base end portion 2d of the needle valve 2, and the displacement expansion efficiency E0. In order to lift the valve 2 as much as necessary, it is necessary to increase the displacement amount Y of the piezoelectric element 6, increase the cross-sectional area ratio A2 / A1, or increase the displacement expansion efficiency E0. However, increasing the size of the piezoelectric element 6 in order to increase the displacement amount Y of the piezoelectric element 6 is not preferable because it leads to an increase in cost and an increase in the size of the fuel injection valve itself. Further, the cross-sectional area ratio A2 / A1 between the piston 7 and the base end portion 2d of the needle valve 2 is determined to some extent by the dimensions of the fuel injection valve, and therefore cannot be varied greatly. Therefore, it is effective to make the displacement expansion efficiency E0 as close to 1 as possible.
[0008]
However, in the conventional fuel injection valve, since the seal between the pressure chamber 13 and the piezoelectric element 6 is performed by the O-ring 8, the piezoelectric element 6 is essentially displaced and the volume in the pressure chamber is V. What is supposed to change by Y × A2 is that the volume change in the actual pressure chamber becomes V−ΔV due to elastic deformation of the O-ring 8 incorporated in the piston 7.
[0009]
That is, as shown in FIG. 4, when the piezoelectric element 6 contracts (displaces in the right direction in the figure), the pressure in the pressure chamber 13 decreases, so the O-ring 8 expands by being pulled toward the pressure chamber 13 side. To do. On the other hand, as shown in FIG. 5, when the piezoelectric element 6 expands (displaces in the left direction in the figure), the pressure in the pressure chamber 13 increases, so the O-ring 8 is pressed against the piezoelectric element 6 and contracts. To do. Such elastic deformation of the O-ring causes a decrease in the above-described displacement expansion efficiency E0, resulting in a problem that the response of the needle valve 2 is lowered.
[0010]
The present invention has been made in view of the above problems of the prior art, and is a fuel injection valve that prevents the elastic deformation of an O-ring and improves the response of pressure generated by displacement of a piezoelectric element. The purpose is to provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a fuel injection valve according to the present invention is provided with a needle valve and a piezoelectric element in a valve body, and a pressure chamber is provided in the valve body between the needle valve and the piezoelectric element. In the fuel injection valve that is formed and changes the pressure of the hydraulic oil in the pressure chamber by the expansion and contraction of the piezoelectric element, and opens and closes the needle valve, the expansion and contraction of the piezoelectric element is between the pressure chamber and the piezoelectric element. A piston that can move in the direction is provided, a seal member that seals the pressure chamber is provided on the outer periphery of the piston, and a labyrinth structure is provided between the seal member and the pressure chamber to supply fuel from the outside. A fuel supply chamber to be formed around the needle valve, a first orifice portion is formed between the fuel supply chamber and the pressure chamber, and between the pressure chamber and the labyrinth structure portion. , Characterized in that the formation of the second orifice section smaller orifice cross-sectional area than the first orifice portion.
[0012]
In the fuel injection valve of the present invention, since the labyrinth structure is provided between the seal member and the pressure chamber, even if the piezoelectric element contracts and the pressure chamber is depressurized, the labyrinth structure is instantaneous. Therefore, the expansion force to the pressure chamber side of the seal member is canceled out, and as a result, the elastic deformation amount of the seal member is reduced.
[0013]
Conversely, even if the piezoelectric element expands and the pressure chamber increases, the volume of the labyrinth structure increases instantaneously and the pressure is reduced, so the compressive force of the seal member toward the counter pressure chamber is canceled out. As a result, the elastic deformation amount of the seal member is reduced.
[0014]
When the elastic deformation amount of the seal member is suppressed in this way, the attenuation amount of the generated pressure due to the displacement of the piezoelectric element is reduced, so that the responsiveness of the needle valve is improved. In addition, since the deformation expansion efficiency E0 approaches 1, the lift amount can be increased even if the piezoelectric elements having the same displacement amount are used. Conversely, if the same lift amount is set, a small piezoelectric element is sufficient. The fuel injection valve itself can be reduced in size.
[0015]
Further, since the elastic deformation amount of the seal member is suppressed, it is difficult to protrude from the piston, the backup ring provided on the outer periphery of the piston can be omitted, the cost can be reduced, and the reliability of the fuel injection valve can be further reduced. Can increase the sex.
Further, the first orifice portion has a fuel feeding action. By making the orifice sectional area of the second orifice portion smaller than the orifice sectional area of the first orifice portion, the pressure chamber and the labyrinth structure portion are separated. The amount of movement of hydraulic oil between them becomes relatively small. Therefore, since the stress on the seal member due to the displacement of the piezoelectric element is reduced, the elastic deformation amount of the seal member is further reduced.
[0016]
In the fuel injection valve of the present invention, the specific structure of the labyrinth structure portion is not particularly limited, and may be any chamber in which the pressure increases or decreases in a direction that cancels the increase or decrease in the pressure of the pressure chamber that varies due to expansion and contraction of the piezoelectric element. That is, when the piezoelectric element contracts and the pressure chamber is depressurized, the volume is reduced and the pressure is increased. Conversely, when the piezoelectric element is expanded and the pressure chamber is increased, the volume is increased. Is a chamber in which the pressure is reduced by increasing. Therefore, what is necessary is just the 2nd pressure chamber which has the cancellation function mentioned above, without being bound by the name of a labyrinth (maze).
[0019]
【The invention's effect】
According to the fuel injection valve of the present invention, since the amount of elastic deformation of the seal member is suppressed by providing the labyrinth structure portion, the response time can be shortened, and the deformation expansion efficiency can be brought close to 1. As a result, the lift amount of the needle valve can be increased without increasing the displacement amount of the piezoelectric element and the area ratio of the pressure acting portion of the piston and the needle valve more than necessary.
[0020]
Further, since the occurrence rate of problems such as protrusion of the seal member is reduced, the backup ring can be omitted, and the reliability can be further improved.
[0021]
In the fuel injection valve of the present invention, the orifice disconnection of the second orifice portion formed between the pressure chamber and the labyrinth structure portion is higher than that of the first orifice portion formed between the fuel supply chamber and the pressure chamber. If the area is reduced, the movement amount of the hydraulic oil between the pressure chamber and the labyrinth structure portion is relatively small, so that the stress acting on the seal member is reduced, and the elastic deformation amount of the seal member is further reduced.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a fuel injection valve of the present invention.
[0023]
In the fuel injection valve of the present embodiment, the valve body is formed by the nozzle 1, the needle holder 3, and the cylindrical casing 5. A piezoelectric element 6 is built in the casing 5. A piston 7 is attached to the distal end portion of the piezoelectric element 6, and an end plate 6 a is attached to the proximal end portion. The piston 7 and the end plate 6 a are formed to have dimensions that allow movement within the casing 5, and the end plate 6 b is joined to the innermost portion of the casing 5 by welding or the like.
[0024]
Reference numeral 5a denotes a lead wire extraction hole of the piezoelectric element 6, and reference numeral 17 denotes a lead wire extraction hole bush of the piezoelectric element 6, which is set as a simple seal of the lead wire extraction portion. The piezoelectric element lead wire 16 passes through the lead wire extraction hole 5 a of the casing 5, passes through the bush 17 and is taken out to the outside, and a high voltage of about 500 V is applied to the piezoelectric element 6 through the lead wire 16. Is done.
[0025]
The needle holder 3 is joined to one end of the casing 5 by welding or the like, and a shim 14 is sandwiched between the joining surfaces. A fitting structure is adopted for the joint 18 between the casing 5 and the needle holder 3 in order to ensure the coaxiality.
[0026]
Reference numeral 4 denotes a disc spring that urges the piston 7 in the right direction in the figure, and its set length is adjusted by a shim 14. In this embodiment, in order to facilitate the assembly of the piston 7, the casing 5 is divided into two in the longitudinal direction, and a casing end (lid) whose setting position can be adjusted is provided at the end of the casing 5. Not. Therefore, the adjustment of the set length of the disc spring 4 cannot be performed by the casing end, but is performed by the shim 14.
[0027]
The nozzle 1 is joined to the needle holder 3 in an oil-tight manner by welding or the like, and is positioned by a knock pin 15. One end of the nozzle 1 forms a poppet valve with the nozzle seat portion 1a and the needle seat portion 2c. Then, fuel is injected or not injected from the nozzle hole 1b for fuel injection according to the opening and closing of the needle valve 2.
[0028]
The needle valve 2 accommodated in the nozzle 1 has annular convex portions 2 a and 2 b and is slidably held on the inner peripheral surface 1 c of the nozzle 1 and the inner peripheral surface 3 a of the needle holder 3. The convex portion 2b of the needle valve 2 and the inner peripheral surface 3a of the needle holder 3 form a first orifice portion 20 that exhibits the posture maintaining function of the needle valve 2 and the fuel orifice function. The first orifice portion 20 guides the fuel from the fuel passage 10 to the pressure chamber 13, and provides a slight clearance that allows only a small amount of fuel to flow when the pressure in the pressure chamber 13 increases or decreases instantaneously. Shaped to keep. In this embodiment, this clearance is set to 6 μm.
[0029]
The convex portion 2a of the needle valve 2 has an action of preventing the needle valve 2 from falling down or buckling. The clearance between the convex portion 2a of the needle valve 2 and the inner peripheral surface 1c of the nozzle 1 may be such that the posture of the needle valve 2 is maintained and a certain amount of fuel can be passed. In the form, it is set to a relatively large value of 30 μm.
[0030]
When the needle valve 2 moves in the right direction in the drawing, the base end portion 2d of the needle valve 2 comes into contact with the stopper member 11, whereby the stroke amount of the needle valve 2 is defined. Reference numerals 32 and 33 and the above-described 13 are first pressure chambers that generate a differential pressure for driving the needle valve 2, and communicate with the fuel supply chamber 31 via the first orifice portion 20. Yes.
[0031]
A coil spring 12 is provided between the needle valve 2 and the needle holder 3 to urge the needle valve 2 leftward in the figure. The nozzle 1 and the needle holder 3 are provided with a fuel passage 10 and communicate with the fuel supply chamber 31.
[0032]
Here, FIG. 2 shows an enlarged cross-sectional view of a portion A in FIG.
An O-ring 8 is incorporated on the outer periphery of the piston 7, and a backup ring 9 is provided on the O-ring 8 on the piezoelectric element 6 side to prevent the O-ring 8 from protruding.
[0033]
The head portion of the piston 7 is formed with an enlarged diameter, and the flange portion 7 a located at the outermost portion forms a second orifice portion 71 with the inner peripheral surface 5 b of the casing 5. The second orifice portion 71 exhibits an orifice function for introducing fuel into the pressure chamber 72 of the labyrinth structure portion.
[0034]
In the present embodiment, the flange portion 7a of the piston 7 is convex toward the piezoelectric element 6 side, and the casing 5 is provided with a concave portion 5c correspondingly. A convex portion 5d is further formed on the inner peripheral side of the concave portion 5c, and the concave portion 7b is provided in the piston 7 correspondingly. The piston 7 moves in the casing 5 in accordance with the expansion / contraction operation of the piezoelectric element 6, but the flange portion 7a and the convex portion 5d are respectively provided with the concave portion 5c and the concave portion 7b even when the piezoelectric element 6 contracts most. It is formed so as not to contact.
[0035]
A space between the flange portion 7a, the concave portion 5c, the convex portion 5d, the concave portion 7b, and the O-ring 8 forms a pressure chamber 72 of the labyrinth structure portion. The pressure chamber 72 of the labyrinth structure has a function of reducing the elastic deformation of the O-ring 8 when the piezoelectric element 6 expands and contracts. By making the pressure chamber 72 into a labyrinth structure, the elasticity of the O-ring 8 is obtained. Almost no deformation can be eliminated.
[0036]
The second orifice portion 71 guides the fuel from the pressure chamber 13 to the pressure chamber 72 of the labyrinth structure portion, and only a small amount of fuel flows when the pressure in the pressure chambers 13 and 72 increases or decreases instantaneously. It is formed so as to maintain a slight clearance, and preferably the orifice sectional area is made smaller than that of the first orifice portion 20. By making the orifice area of the second orifice portion smaller than the orifice area of the first orifice portion, the stress acting on the O-ring 8 accompanying the displacement of the piezoelectric element 6 is reduced, and the elastic deformation of the O-ring 8 is further increased. Can be small.
[0037]
Next, the operation will be described.
When the internal combustion engine is stopped, the tip portion 2c of the needle valve 2 is pressed against the nozzle seat portion 1a by the urging force of the coil spring 12, and the fuel is thereby sealed, so that the stopped state of the fuel is maintained.
[0038]
Before the operation of the internal combustion engine is started, the fuel that is pumped to a high pressure by an electric high-pressure fuel pump (not shown) and kept constant at about 5 MPa by a pressure regulator (not shown) passes through the fuel passage 10 to the fuel supply chamber. 31 is led. At this time, the fuel guided into the fuel supply chamber 31 passes through the first orifice portion 20, is guided to the pressure chambers 32, 33 and 13, and further passes through the second orifice portion 71, so that the labyrinth structure portion To the pressure chamber 72.
[0039]
In this state, since the fuel pressure in each pressure chamber is all equal to the supply pressure, the needle valve 2 is closed by the resultant force of the biasing force from the coil spring 12 and the fuel supply pressure (diameter of the nozzle 1b × fuel supply pressure). The fuel is not injected.
[0040]
In this state, when a voltage of about 500 V is applied from a control drive circuit (not shown) to the piezoelectric element 6 made of, for example, a piezo element, the piezoelectric element 6 instantaneously becomes Z with respect to the axial length of the piezoelectric element itself. Elongate (about 0.1% of length, eg about 50 μm).
[0041]
Assuming that the cross-sectional area of the end plate 6a is A3, the volume of the first pressure chambers 13, 33, 32 decreases by the volume of Z × A3, but the fuel in the pressure chambers 13, 33, 32 is the first. Since the orifice portion 20 does not immediately flow into the fuel supply chamber 31, the fuel in the first pressure chambers 13, 33, and 32 is compressed, and the pressure in the pressure chamber rises above the pressure in the fuel supply chamber 31. To do. At this time, the fuel in the pressure chambers 13, 33, and 32 does not immediately flow into the pressure chamber 72 of the labyrinth structure due to the action of the second orifice portion 71. The needle valve 2 is pressed in the valve closing direction by the upward pressure increase of the fuel and the urging force of the coil spring 12, and the tip end portion 2c of the needle valve 2 is still pressed against the nozzle seat portion 1a. Maintained. The state where the preparation for injection is completed is the initial state.
[0042]
From this initial state, the internal combustion engine is started by the starter, and at the same time, the voltage of 500 V that has been applied to the piezoelectric element 6 is set to 0 V, and the electric charge accumulated in the piezoelectric element 6 is removed. Thereby, the piezoelectric element 6 is instantaneously contracted rightward in the drawing by the self-contracting function and the biasing force of the disc spring 4, and the volume of the pressure chambers 13, 33, 32 is increased by Z × A3.
[0043]
The pressure in the pressure chambers 13, 33, and 32 is maintained at the fuel feed pressure before the piezoelectric element 6 is driven, and the fuel in the fuel supply chamber 31 is instantaneously provided by the presence of the first orifice portion 20. Since it does not move to the pressure chambers 13, 33, 32, the pressure in the pressure chambers 13, 33, 32 decreases from the pressure in the fuel supply chamber 31 due to the contraction of the piezoelectric element 6. As a result, the balance between the fuel supply chamber side and the pressure chamber side of the needle valve 2 is lost, and a force in the valve opening direction acts on the needle valve 2, and when this force exceeds the biasing force of the coil spring 12, the needle The valve 2 is opened and the fuel in the fuel supply chamber 31 is injected from the nozzle 1b.
[0044]
At this time, the volume of the pressure chamber 72 of the labyrinth structure portion is reduced by the driving of the piston 7, but the presence of the second orifice portion 71 and further the flow path resistance is generated by this labyrinth structure, and the fuel in the pressure chamber 72 is Since it does not move to the pressure chamber 31 instantaneously, the pressure in the pressure chamber 72 increases. Due to this momentary increase in pressure, the O-ring 8 is hardly pulled and expanded to the pressure chamber 13 side as in the prior art, and elastic deformation is prevented. Accordingly, the volume change of the pressure chambers 13, 33, 32 is substantially Z × A3, and the displacement expansion efficiency E0 can be brought close to zero. Thereby, the lift characteristic of the needle valve 2 is stabilized.
[0045]
In addition to this, since the orifice sectional area of the second orifice portion 71 is smaller than the orifice sectional area of the first orifice portion 20, the fuel that moves slightly from the fuel supply chamber 31 to the pressure chambers 13, 33, 32. Since the amount of fuel that moves slightly from the pressure chamber 72 of the labyrinth structure portion to the pressure chambers 13, 33, 32 is smaller than the amount, the positive pressure acting on the O-ring 8 can be increased, and the O-ring 8 The amount of elastic deformation can be further reduced.
[0046]
On the other hand, when the valve is closed, a voltage of 500 V is applied to the piezoelectric element 6 to extend it by about 50 μm. At this time, since the fuel flows into the pressure chambers 13, 33, 32 during the above-described valve opening time of the needle valve 2, the amount of fuel is increased compared to the initial valve opening time. In this state, the volume of the pressure chambers 13, 33, 32 is reduced by Z × A3, and the fuel in the fuel supply chamber 3a does not instantaneously flow into the pressure chambers 13, 33, 32 due to the action of the orifice 20. In addition to the original fuel feed pressure, the pressure in the pressure chambers 13, 33, 32 rises to a pressure increased by the amount of fuel that has flowed into the pressure chambers 13, 33, 32 when the valve is opened. The needle valve 2 is closed by this rising pressure and the urging force of the coil spring 12.
[0047]
In this case as well, when the valve 7 is opened, the volume of the pressure chamber 72 of the labyrinth structure portion is increased by driving the piston 7, but the presence of the second orifice portion 71 and further the flow path resistance is generated by this labyrinth structure. Since the fuel in the pressure chamber 31 does not move instantaneously to the pressure chamber 72, the pressure in the pressure chamber 72 decreases. Due to the instantaneous decrease in pressure, the O-ring 8 is hardly pressed against the piezoelectric element 6 and contracts as in the prior art, and elastic deformation is prevented. Accordingly, the volume change of the pressure chambers 13, 33, 32 is substantially Z × A3, and the displacement expansion efficiency E0 can be brought close to zero. Thereby, the lift characteristic of the needle valve 2 is stabilized.
[0048]
In addition, since the orifice area of the second orifice portion 71 is smaller than the orifice area of the first orifice portion 20, the amount of fuel slightly moving from the pressure chambers 13, 33, 32 to the fuel supply chamber 31 is larger. However, since the amount of fuel slightly moving from the pressure chambers 13, 33, 32 to the pressure chamber 72 is reduced, the negative pressure acting on the O-ring 8 can be increased, and the amount of elastic deformation of the O-ring 8 can be further increased. Can be reduced.
[0049]
Here, the relationship between the displacement of the piezoelectric element and the pressure generated by the displacement is shown in the graph of FIG. As shown in the figure, in the conventional fuel injection valve, the response time to the displacement of the piezoelectric element is long due to the elastic deformation of the O-ring, and the attenuation amount of the generated pressure is large. Since the elastic deformation is reduced, the response time to the displacement of the piezoelectric element is short, and the amount of attenuation of the generated pressure is also small.
[0050]
That is, according to the present invention, the responsiveness of the generated pressure can be improved and the needle valve can be obtained without increasing the displacement amount of the piezoelectric element and the area ratio of the pressure acting portion of the piston and the needle valve more than necessary. The lift amount can be increased. As a result, it is possible to reduce the size of the piezoelectric element, increase the degree of freedom in engine layout, and reduce the cost of the piezoelectric element itself.
[0051]
The fuel injection valve of the present invention is not limited to the above-described embodiment and can be variously modified. For example, the shape of the pressure chamber 72 of the labyrinth structure portion is not limited to that of the above embodiment, and the second orifice portion has a normal flow having no orifice function depending on the structure of the pressure chamber. It may be a road.
[0052]
Furthermore, in the above embodiment, the backup ring 9 is provided on the outer periphery of the piston 7 to prevent the O-ring from protruding. However, according to the present invention, the elastic deformation of the O-ring is reduced, and the O-ring is Since the rate of protrusion is extremely small, the backup ring 9 can be omitted. Since the backup ring has a small radial tolerance, the cost can be reduced by omitting this, and the reliability of the fuel injection valve itself can be improved.
[0053]
The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[Brief description of the drawings]
FIG. 1 is an overall cross-sectional view showing an embodiment of a fuel injection valve of the present invention.
FIG. 2 is a cross-sectional view of a main part showing an embodiment of a fuel injection valve of the present invention.
FIG. 3 is a cross-sectional view showing a conventional fuel injection valve.
FIG. 4 is a cross-sectional view of an essential part showing a conventional fuel injection valve (when pressure is reduced).
FIG. 5 is a cross-sectional view of an essential part showing a conventional fuel injection valve (when pressure rises).
FIG. 6 is a graph showing the relationship between the displacement of a piezoelectric element and the pressure generated thereby.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Nozzle 1a ... Nozzle sheet | seat part 1b ... Injection hole 1c ... Inner peripheral surface 2 ... Needle valve 2a, 2b ... Convex part 2c ... Tip part 2d ... Base end part 20 ... 1st orifice part 3 ... Needle holder 3a ... Inner circumference Surface 31 ... Fuel supply chambers 32, 33 ... Pressure chamber 4 ... Belleville spring 5 ... Casing 5a ... Lead wire outlet hole 5b ... Inner peripheral surface 5c ... Concave portion 5d ... Convex portion 6 ... Piezoelectric element 6a ... End plate 7 ... Piston 7a ... Flange part 7b ... Recess 71 ... Second orifice part 72 ... Pressure chamber 8 of labyrinth structure part ... O-ring (seal member)
DESCRIPTION OF SYMBOLS 9 ... Backup ring 10 ... Fuel passage 11 ... Stopper member 12 ... Coil spring 13 ... Pressure chamber 14 ... Shim 15 ... Knock pin 16 ... Lead wire 17 ... Bush 18 ... Joint part

Claims (1)

A needle valve and a piezoelectric element are provided in the valve body, a pressure chamber is formed in the valve body between the needle valve and the piezoelectric element, and hydraulic oil in the pressure chamber is expanded and contracted by the piezoelectric element. In the fuel injection valve for changing the pressure and opening and closing the needle valve,
A piston is provided between the pressure chamber and the piezoelectric element, the piston being movable in the expansion / contraction direction of the piezoelectric element, a seal member for sealing the pressure chamber is provided on the outer periphery of the piston, and the seal member and the pressure are further provided. A labyrinth structure between the room and
A fuel supply chamber to which fuel from the outside is supplied is formed around the needle valve, a first orifice portion is formed between the fuel supply chamber and the pressure chamber, and the pressure chamber and the labyrinth structure A fuel injection valve characterized in that a second orifice portion having a smaller sectional area than the first orifice portion is formed between the first orifice portion and the first orifice portion.

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