JP2000249016A - Injector - Google Patents

Abstract

(57) [Problem] To provide an injector capable of absorbing axial misalignment and being designed without being restricted by mechanical strength by fluidly connecting a control piston and a needle valve. provide. SOLUTION: A concave portion 53 formed in a lower end portion 14b of a control piston 14 which moves up and down by the action of pressure in a pressure control chamber has an upper end portion 19 of a needle valve 19 which opens and closes an injection hole.
The convex portion 54 formed in a is fitted through a slight gap 57 to form an oil chamber 55. When the control piston 14 is lifted, the oil chamber 55 has a negative pressure, the check valve 58 provided in the communication path 59 communicating from the oil chamber 55 to the fuel chamber 28 closes the communication path 59, and the needle valve 19 follows the lift. I do. When the control piston 14 descends, the check valve 58 opens, excess fuel is discharged into the fuel chamber 28, and the needle valve 19 descends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector for injecting fuel into a combustion chamber from an injection hole formed at a tip by operating a needle valve.

[0002]

2. Description of the Related Art Conventionally, a common rail type fuel injection system is known as a fuel injection system applied to an engine such as a diesel engine. The common rail fuel injection system stores a working fluid for fuel injection control pressurized to a predetermined high pressure determined based on an operating state of the engine by a fuel supply pump in a common rail, and normally stores the fuel stored in the common rail. By injecting a plurality of injectors into the corresponding combustion chambers from injectors operated by solenoid valve control, the injection pressure is increased, and the injection conditions such as fuel injection timing and injection amount are controlled by the engine speed and the engine speed. This is a fuel injection system that enables optimal control in accordance with the operating state of the engine such as the amount of accelerator depression. The controller provided in the system determines the fuel pressure in the common rail and each injector in accordance with the operating state of the engine input as a detection signal from each sensor so that the pressurized fuel is injected under the above-described optimum injection conditions in each injector. And the operation of the solenoid valve provided in the control unit.

An example of an injector used in a fuel injection device of an engine to which a common rail fuel injection system is applied is disclosed in Japanese Patent Application Laid-Open No. 9-32681. This injector is a type of injector that uses high-pressure fuel as a working fluid, and a valve body that is disposed in the injector and that opens and closes an injection hole formed at the tip of the injector by fuel pressure has an end face in a balance chamber. The control piston includes a control piston that exposes the nozzle and a needle that opens and closes the injection hole. The control piston is slidably supported within the holder body, and the needle is slidably supported within the nozzle body. Since both the control piston and the needle are parts having a small diameter and a long length in the axial direction, it is necessary to make the axial center accuracy extremely high if both are manufactured integrally. Accordingly, the control piston is connected to the needle by the connecting member. The connection member holds the control piston and the needle integrally in the axial direction, but has a spring force that allows axial misalignment in a direction orthogonal to the axial direction.

[0004] In the above-mentioned injector, even if a shaft misalignment occurs between the control piston and the needle,
The axial misalignment can be absorbed by the spring deformation of the connecting member, and it is not necessary to align the axial centers of the control piston and the needle with high accuracy. According to this injector, smooth sliding of the control piston and the needle in the axial direction of each other is ensured, and the assembly and connection of the two can be performed with one touch, so that assembling workability can be improved and the manufacturing can be performed. An excellent action and effect that cost can be reduced is obtained.

[0005]

By the way, when the control piston and the needle are connected by mechanical engagement of a connecting member, the connecting member has a connection strength corresponding to the ascending or descending speed (acceleration) of the control piston. Required. In addition, since it is directly connected mechanically, the movement of one of the control piston and the needle immediately reflects the movement of the other without a time lag. In some cases, the presence of the buffering property is preferable as a characteristic of the injector. Therefore, by connecting the control piston and the needle, which are divided and arranged in the axial direction, by fluid means without using mechanical connection means, it is possible to control the design and manufacturing of the injector. There is a problem to be solved in obtaining an injector with few restrictions from a viewpoint.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to control the injector design and manufacturing related to the connection strength by fluidly connecting the control piston and the needle. In addition, the present invention provides an injector that can control the control piston and the needle so that they can be connected to each other with cushioning in the operation in the axial direction, thereby enabling the needle to operate more stably. It is to be.

[0007] In order to achieve the above object, the present invention provides
It is configured as follows. That is, the present invention provides a valve element which reciprocates in a main body having an injection hole for injecting fuel and opens the injection hole by fuel pressure, and the valve element penetrates around the valve element in the main body. A fuel chamber for storing the formed fuel, a pressure control chamber formed in the main body and controlling lift of the valve body by a pressure action of a working fluid on the valve body, wherein the valve body is the pressure control chamber; An end face of one end is exposed and the control piston penetrating the fuel chamber and the end face of the one end and the end face of the other end of the control piston are arranged so as to face each other and face each other. The control piston and the needle are formed of a needle that opens and closes an injection hole. The control piston and the needle have an oil chamber formed between the facing surfaces, and a communication path that communicates the oil chamber with the fuel chamber. A fluid connection portion provided in the communication passage and having a flow rate regulating means for regulating a flow of fuel from the fuel chamber to the oil chamber; and a fuel through the communication passage when the control piston is lifted. The present invention relates to an injector which lifts the needle following the control piston by lowering the fuel pressure in the oil chamber by restricting the inflow into the oil chamber by the flow rate control means.

[0008] Since the injector of the present invention is configured as described above, the control piston lifts in order to inject fuel from the injection hole, and the control piston and the needle tend to move in a direction away from each other. In such a case, the fuel pressure in the oil chamber that has already been formed between the opposing surfaces and that is to be further expanded or that is formed between the opposing surfaces when they are separated from each other decreases or becomes negative. Since the pressure is formed, the balance of the force acting on the needle based on the fuel pressure acts in the lift direction, and the needle follows the control piston and lifts. The needle opens the injection hole and injects fuel into the combustion chamber. When the control piston descends to stop the injection of fuel from the injection hole and the control piston comes close to the needle, the pressure of the fuel in the oil chamber increases and the needle is pushed by the control piston. Descend. At this time, excess fuel is pushed out of the oil chamber into the fuel chamber through the communication passage and the flow rate regulating means. The needle closes the injection hole to stop fuel injection into the combustion chamber. The control piston and the needle are fluidly connected without being restricted by mechanical strength because no mechanical connecting member is used. Also, the fluid connection has a slight delay in following the mechanical connection as compared with the mechanical connection. Therefore, the connection has a damping action or a bounce prevention action on the operation of the control piston and the needle. It has a buffering property that gives

The oil chamber has a wall surface of a concave portion formed on one of the opposing surfaces of the control piston and the needle, and an end surface of a convex portion formed on the other of the opposing surface and loosely fitted in the concave portion. Defined by In this case, the communication passage is formed to penetrate the control piston. A tapered oil sump chamber for lifting the needle is formed around the axial center portion of the needle in the main body, and the tapered oil sump chamber is formed excluding a region where the concave portion or the convex portion is formed. An axial projection area of the facing surface of the needle is set smaller than an axial projection area of the needle facing the oil reservoir. By setting such an area for the needle, when the fuel pressure in the oil chamber drops to a negative pressure, the needle starts lifting based on the fuel pressure in the oil sump chamber.

A sleeve is fitted over the other end of the control piston and the one end of the needle, and the oil chamber is defined by the two opposing surfaces and the inner surface of the sleeve. Is done. A reduced diameter portion may be formed at each of the other end of the control piston and the one end of the needle, and the sleeve may be fitted over the both reduced diameter portions. When the connecting portion is formed using the sleeve, the communication path is formed to penetrate the sleeve. A tapered oil sump chamber for lifting the needle is formed around the axial center portion of the needle in the main body, and the facing surface of the needle excluding the end surface of the reduced diameter portion is formed. Is set smaller than the projected area in the axial direction facing the oil sump chamber. By setting such an area for the needle, when the fuel pressure in the oil chamber drops to a negative pressure, the needle starts lifting based on the fuel pressure in the oil sump chamber.

The flow regulating means is constituted by an orifice formed in the communication passage. The orifice restricts the flow of fuel from the fuel chamber to the oil chamber. The check valve is disposed in the communication passage and allows a flow of fuel in a direction from the oil chamber toward the fuel chamber, but prevents a flow from the fuel chamber to the oil chamber. It is also constituted by When the flow rate regulating means is constituted by a check valve, the check valve includes a ball disposed in an opening of the communication passage that opens on the fuel chamber side, and the control piston in which the communication passage is formed. Alternatively, it is constituted by a leaf spring which is externally fitted to the sleeve and biases the ball in a direction for closing the opening of the communication passage. The check valve further comprises an elastic plate fitted to the control piston or the sleeve in which the communication path is formed, at a position covering an opening of the communication path that opens on the fuel chamber side, The elastic plate may be elastically deformed by the high fuel pressure in the oil chamber to open the opening, and the opening may be closed by its own elasticity when the oil chamber becomes low pressure or negative pressure.

When the control piston lifts with respect to the needle and the oil chamber becomes negative pressure, the ball or elastic plate of the check valve closes the opening of the communication passage, and fuel flows from the fuel chamber to the oil chamber through the communication passage. Prevent inflow. Also,
Excess fuel that has entered the oil chamber due to fuel leakage from the fuel chamber is increased in pressure when the control piston descends, causing the ball to float up from the opening in the communication passage against the spring force of the leaf spring. Since the stop valve is opened or the elastic plate is elastically deformed to open the opening of the communication passage, the fuel in the oil chamber is discharged to the fuel chamber through the communication passage and the check valve.

The pressure control chamber is a balance chamber formed by a control sleeve fixed to the main body and controlling the lift of the valve body by fuel pressure. The injector is provided with an actuator that drives an on-off valve that opens and closes a discharge path from the balance chamber. By driving the on-off valve with the actuator, the fuel pressure in the balance chamber increases the fuel tank through the open discharge path. Returned to

The main body includes a holder main body that supports the control piston so as to be slidable in the axial direction, and a nozzle main body including the injection hole that supports the needle connected to the holder main body so as to be slidable in the axial direction. It is composed of

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an injector according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of an injector according to the present invention, and FIG. 2 is an enlarged sectional view showing a structure of a fluid connection between a control piston and a needle of the injector shown in FIG.

An injector 1 according to the present invention shown in FIG.
Is an injector applied to a common rail injection system or an accumulator injection system (not shown). Common passages and accumulators (hereinafter referred to as fuel injection pumps)
It is called "common rail". ) Is injected from the common rail into each combustion chamber from the injector 1 through a fuel supply pipe (not shown). The injector 1
The main body 2 is attached to a hole (not shown) provided in a base such as a cylinder head or the like in a sealed state via a sealing member, whereby the main body 2 is assembled to an engine.

A fuel inlet plug 3 to which a fuel supply pipe extending from the common rail is connected is attached to a bracket 4 provided on an upper part of the main body 2. The seal between the main body 2 and the fuel inlet plug 3 and the bracket 4 is achieved by sealing members 5 and 6 each comprising an O-ring. An electromagnetic valve 7 as an electromagnetic two-way valve is hermetically fixed to the upper end of the main body 2 by screwing a sleeve nut 8 into a threaded portion formed on the outer periphery of the main body 2. A control current from a control unit 9 is supplied to a solenoid 10 to operate the solenoid valve 7.

The main body 2 has an oil feed hole 12 communicating with the fuel inlet 11 of the fuel inlet plug 3, and a hollow portion 13 communicating with the oil feed hole 12 and extending in the longitudinal direction of the main body 2. A control piston 14 is provided in the hollow portion 13 so as to be able to reciprocate. At a substantially central portion of the hollow portion 13, a reduced-diameter guide portion 15 for guiding the reciprocating motion of the control piston 14 is formed. The main body 2 is a holder main body 2a for guiding the control piston 14 in a reciprocating motion.
And a sleeve nut 1 on the tip side of the holder body 2a.
And a nozzle main body 16 attached by a nozzle 7. A hollow hole 18 communicating with the hollow portion 13 is formed in the nozzle body 16, and a needle 19 is slidably inserted into the hollow hole 18 in a state where a gap 31 serving as a high-pressure fuel passage is left around the needle 19. ing. The needle 19 is connected to the control piston 14 via a connecting portion 20 which is connected by a fluid action.
The valve body 4 and the needle 19 constitute a valve body that reciprocates in the main body 2.

An injection hole 21 for injecting fuel into the combustion chamber is formed at the tip of the nozzle body 16. The tapered surface 22b formed at the other end, which is the tip of the needle 19, can be seated on the seat surface 23 of the nozzle body 16, and the needle 19 closes the injection hole 21 in the seated state. The needle 19 is lifted, and the tapered surface 22b and the seat surface 23
Is opened, the high-pressure fuel is injected from the injection hole 21 into the combustion chamber.

A control sleeve 24 is disposed in the hollow portion 13 of the main body 2 so as to engage with the upper step of the main body 2. The control sleeve 24 is hollowed by a plug 26 screwed into the upper end of the main body 2. It is fixed in the part 13. An annular fuel chamber 25 is formed in the hollow portion 13 around the control sleeve 24. The fuel chamber 25 is provided with an oil feed hole 1 formed in the main body 1.
2 communicates with the fuel inlet 11 of the fuel inlet plug 3. The fuel chamber 25 communicates with a fuel chamber 28 formed around the control piston 14 in the hollow portion 13 through a fuel passage 27 formed in the guide portion 15.
A fuel passage 31 which is a gap between the oil reservoir chamber 30 and the needle 19 and the hollow hole 18 through a fuel passage 29 formed in
Is in communication with The tapered surface 22a of the needle 19 (including the tapered surface 22b formed at the tip of the needle 19 after lifting), which is a part of the wall surface that constitutes the oil reservoir chamber 30, is the first member of the valve body. The fuel pressure acting on one taper surface 22a and 22b gives a force to lift the valve body upward in the drawing.

An upper end portion 14a of the control piston 14 is slidably fitted in a hollow hole 32 opened on the distal end side of the control sleeve 24, and the wall surface and the upper end portion of the control piston 14 are fitted in the hollow hole 32. 14
A balance chamber 33 as a pressure control chamber is formed by the end face formed on the side a. The control sleeve 24 includes a balance chamber 33 and a fuel chamber 25.
A supply path (not shown) with a throttling function is formed, which communicates with. The end face of the control piston 14 constitutes a second pressure receiving surface that receives a fuel pressure in the balance chamber 33 and applies a force in a direction to lower the control piston 14. The control sleeve 24 is formed with a discharge path 34 having one end opened to the balance chamber 33 for discharging the fuel in the balance chamber 33.

A current whose magnitude is controlled is supplied as a control signal from a control unit 9 to a solenoid 10 which is an actuator of the solenoid valve 7. The armature 35 is displaced in the axial direction of the injector 1 in response to the excitation or demagnetization of the solenoid 10 of the solenoid valve 7, and the on-off valve body 36 attached to the armature 35 and sliding in the hollow chamber 37 of the plug 26 discharges. The other opening of the path 34 is opened and closed. By operating the solenoid valve 7 to open and close the discharge path 34, the fuel pressure in the balance chamber 33 is controlled,
The magnitude of the pressing force acting on the control piston 14 is controlled.

The solenoid valve 7 has a negatively operated structure having a return spring 40. That is, the on-off valve body 36
When the solenoid 10 is in a non-energized state, the discharge path 34 is closed by being urged by the spring force of the return spring 40, and when the solenoid 10 is in an energized state, the armature 35 is actuated by the spring force of the return spring 40. , Lift the opening and closing valve body 36 to open the discharge path 34.

A spring support 38 is attached to the control piston 14 at a substantially intermediate position in the axial direction, and a return spring 39 is arranged between the guide portion 15 and the spring support 38 in a compressed state. Have been. The return spring 39 moves the control piston 14 downward in the same direction as the fuel pressure in the balance chamber 33,
That is, a force toward the nozzle tip side is applied. The force based on the fuel pressure in the balance chamber 33, the lift force by the fuel pressure acting on the tapered surface 22a facing the oil reservoir chamber 30 of the needle 19 as the first pressure receiving surface, and the return force of the return spring 39 acting on the valve element. The lift of the needle 19 is controlled by the balance of the force caused by the pressure action of the fuel pressure in the connecting portion 20 described later.

The above structure is the same as the structure of the injector used in the conventional common rail type fuel injection system except for the structure of the connecting portion 20. When the solenoid 10 of the solenoid valve 7 is in the excited state, the structure shown in FIG. As shown in FIG. 1, the armature 35 is lifted upward in the drawing against the spring force of the return spring 40, and the opening / closing valve body 36 opens the discharge passage 34, so that the high fuel pressure in the balance chamber 33 reduces the discharge passage 3
It is released through 4 and falls. The fuel discharged from the discharge passage 34 passes through the solenoid valve 7 and returns to the fuel return pipe 41.
Is returned to the fuel tank. Control piston 1
The needle 4 and the needle 19 are lifted by the return spring 39 and the fuel pressure in the oil reservoir 30, and fuel is injected from the injection hole 21. When the operation of the solenoid valve 7 is turned off, the on-off valve body 36 closes, the fuel pressure in the balance chamber 33 recovers, and the control piston 14 and the needle 1
9, the needle 19 closes the injection hole 21 and stops the injection of fuel.

A fluid connection 20 between the control piston 14 and the needle 19 of the injector 1 shown in FIG.
Is shown in the enlarged sectional view of FIG. An end face 51 of a lower end 14b which is the other end of the control piston 14,
End surface 52 of upper end 19a as one end of needle 19
Are facing each other as a facing surface. A recess 53 is formed in the center of the end face 51 of the control piston 14 between the end faces 51 and 52, and the center of the end face 52 of the needle 19 is less than the depth of the recess 53 corresponding to the recess 53. A projection 54 projecting at a height is formed. The projection 54 of the needle 19 is loosely fitted into the recess 53 of the control piston 14 (loose fit).
An oil chamber 55 is defined by the inner wall 3 and the end wall of the projection 54. The inner diameter of the concave portion 53 is slightly larger (within 10 μm) than the outer shape of the convex portion, and a radial gap 57 is formed between the peripheral wall of the concave portion 53 and the peripheral wall of the convex portion 54. Due to the radial gap 57, axial misalignment between the control piston 14 and the needle 19 is allowed. When the control piston 14 is lifted, the control piston 1
A gap 56 is formed between the lower end 14 b of the needle 4 and the upper end 19 a of the needle 19. Since the radial gap 57 exists, the fuel in the fuel chamber 28 can enter the oil chamber 55.

In the embodiment shown in FIG. 2, a recess 53 is formed in the lower end 14b of the control piston 14, and
9, the projection 54 is formed on the upper end 19a.
Obviously, a convex portion may be formed at b and a concave portion may be formed at the upper end portion 19a. Further, the control piston 14
In the state where the end face 51 of the needle 19 and the end face 52 of the needle 19 are in contact with each other, an oil chamber 55 that is still left between the convex part 54 and the concave part 53 is formed, but the end face 51 of the control piston 14 and the end face 52 of the needle 19 It is also possible that the top surface of the convex portion 54 abuts against the bottom surface of the concave portion 53 before the oil chamber 55 disappears, so that the oil chamber 55 disappears. From the viewpoint of the strength of the opposing surface, it is advantageous to widen the surface that the needle comes into contact with in the valve closed state.

A communication passage 59 communicating from the oil chamber 55 to the fuel chamber 28 is formed inside the control piston 14. The communication passage 59 is provided with a check valve 58 that permits the flow of the fluid from the oil chamber 55 toward the fuel chamber 28 but blocks the flow in the opposite direction. The check valve 58 fits around the ball 61 accommodated in the tapered opening 60 in which the communication path 59 opens to the outer periphery of the control piston 14, and around the lower end 14 b of the control piston 14 including the tapered opening 60. A substantially annular leaf spring 62 that is worn and urges the ball 61 in a direction to close the communication path 59.
It is composed of The leaf spring 62 urges the ball 61 in a direction to close the communication passage 59 by a spring force, and
1 is held so as not to protrude from the tapered opening 60. A stopper 63 that engages with the leaf spring 62 may be provided on the peripheral surface of the control piston 14 so that the leaf spring 62 does not slide down on the peripheral surface of the control piston 14.

This embodiment is configured as described above, and the connecting portion 20 operates as follows. Fuel chamber 2
Supplied to the fuel passage 27 and the fuel chamber 2
8 and the fuel passage 29, the fuel passage 31 around the needle 19 is reached, and the fuel passage and the fuel chamber 28 are filled. The fuel is already supplied from the fuel chamber 28 to the oil chamber 55 through the gaps 56 and 57. Have been. When the solenoid valve 7 is operated to release the fuel pressure in the balance chamber 33, almost no force can be expected to urge the control piston 14 downward based on the fuel pressure in the balance chamber 33. The urging force is substantially only the return force of the return spring 39.

In the connection portion 20, on the control piston 14 side, a force for lifting the control piston 14 based on the fuel pressure constantly acting on the annular surface portion of the end face 51 corresponding to the gap 56 acts. I do. Since this increasing force exceeds the returning force of the return spring 39, the control piston 14 starts lifting, but separates from the needle 19 which cannot immediately follow the lift of the control piston 14.
The oil chamber 55 has a negative pressure, and the check valve 58 is closed to maintain the negative pressure. When the control piston 14 further rises, the pressure in the oil chamber 55 further falls. On the needle 19 side, a force for lowering the needle 19 acts by the fuel pressure constantly acting on the annular surface portion corresponding to the gap 56 of the end face 52, but the fuel pressure acting on the tapered surface 22a is reduced. Therefore, the combined force of the force to lift the needle 19 based on the negative pressure of the oil chamber 55 and the force to lift the needle 19 is superior to the force to lower the needle 19,
The needle 19 lifts and opens the injection hole 21, and fuel is injected from the injection hole 21.

When the fuel pressure in the balance chamber 33 recovers to a high pressure, the control piston 14 is urged downward by the combined force of the force based on the fuel pressure in the balance chamber 33 and the return force of the return spring 39. This resultant force is larger than the force based on the fuel pressure acting on the end face 51, and the end faces 51, 52 approach each other to form a gap 5 between them.
While the control piston 14 descends until 6 is absorbed, excess fuel in the oil chamber 55 passes through the communication passage 59,
The fuel chamber 28 is opened through the check valve 58 in the opened state.
Is discharged.

Control piston 14 and needle 19
Is fluidly connected without using a mechanical connecting member, and the injector can be designed without being restricted by mechanical strength. In addition, since the connection is made via a fluid, there may be a slight delay between the control piston 14 and the needle 19 as compared with the mechanical connection, but on the contrary, due to the delay, the operation of both of them is rather restricted. It is possible to provide a buffering property such as a damping action or a bounce prevention action. It is advantageous that the area of the region forming the oil chamber 55 is large. That is, when the needle is to be pulled up by a lifting force based on the negative pressure of the oil chamber 55, the cross-sectional area of the oil chamber 55 is preferably wide. In order to raise the needle, the smaller the area of the needle facing the gap 56 where the high-pressure fuel pressure always acts, the more the fuel pressure in the oil reservoir chamber 30 acts on the projected area of the needle in the axial direction. The effect of offsetting the lifting force is small. The projected area of the opposing surface 52 of the needle 19 in the axial direction excluding the region where the convex portion 54 is formed is the tapered surface 22 of the tapered oil sump chamber 30.
The area is set smaller than the projected area of the needle 19 facing a. By setting such an area, when the fuel pressure in the oil chamber 55 decreases to a negative pressure, the needle 19 starts lifting based on the fuel pressure in the oil reservoir chamber 30. When the concave portion 53 is formed in the needle valve 19, the setting of the area is performed in the same manner.

Next, another embodiment of the injector according to the present invention will be described. FIG. 3 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention. In the embodiment shown in FIG. 3, the same reference numerals as those used in FIG. 2 denote the same elements and parts as those constituting the connection unit shown in FIG. 3, a lower end 14b of the control piston 14 and an upper end 19a of the needle 19 are provided.
Each has a reduced diameter portion 71, 72 protruding substantially coaxially and opposed to each other at a central portion, and a sleeve 76 is loosely fitted into the 71, 72. Sleeve 7
An oil chamber 75 is defined by the inner peripheral surface 78b of the cylinder 6 and the opposing end surfaces 51, 52 of the reduced diameter portions 71, 72.

Stepped annular surface 7 of control piston 14
1a and the upper end surface 77a of the sleeve 76, and between the stepped annular surface 72a of the needle 19 and the lower end surface 77b of the sleeve 76 according to the lift state of the control piston 14 and the needle 19, respectively. A gap 73 is formed. Control piston 14 and needle 1
9 between the overlapping portions of the peripheral surfaces 71b, 72b of the reduced diameter portions 71, 72 and the inner peripheral surface 78b of the sleeve 76.
A slight radial gap 74 of about μm or less is formed. The needle 19 is provided with a stopper 76a that engages with the sleeve 76 to prevent the sleeve 76 from dropping from a predetermined position. The stopper 76a can be provided on the nozzle body 16 side.

A communication passage 79 is formed in the sleeve 76 for communicating the oil chamber 75 and the fuel chamber 28, and the communication passage 79 is provided with a check valve 58. When the control piston 14 is displaced in the direction away from the needle 19 when lifted, fuel flows into the oil chamber 75 through the gaps 73 and 74. However, since the amount of flow is small, the oil chamber 75 becomes negative pressure and the check valve 58 Closes. When the control piston 14 is displaced in a direction approaching the needle 19 when descending, the excess fuel in the oil chamber 75 is removed from the communication passage 7.
9 and is discharged into the fuel chamber 28 through the opened check valve 58. Injector 1 including actuation of needle 19
The operation of is the same as that of the injector shown in FIG.

Next, still another embodiment of the injector according to the present invention will be described. FIG. 4 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention. In the embodiment shown in FIG. 4, the same reference numerals as those used in FIG. 2 denote the same elements and parts as those constituting the connection unit 20 shown in FIG. . In the connecting portion 80 shown in FIG. 4, the opposite end of the control piston 14 and the needle 19, that is, the lower end 1 of the control piston 14
4b and the upper end 19a of the needle 19 have a straight shape without any processing portion such as a reduced diameter portion. The end surfaces 51 and 52 which are opposing surfaces at both ends are flat end surfaces on which no irregularities are formed. Since such a straight or flat surface can be used as it is, the number of processing steps required for the control piston 14 and the needle 19 is reduced, which is advantageous in manufacturing and cost. A sleeve 86 is fitted over the outer periphery of the lower end portion 14b of the control piston 14 and the upper end portion 19a of the needle 19 by using a relatively extra space of the fuel chamber 28. An oil chamber 85 is formed by the opposed end surfaces 51 and 52 and the inner peripheral surface 88 b of the sleeve 86.

Between the inner peripheral surface 88b of the sleeve 86 and the peripheral surface 81b of the lower end 14b of the control piston 14, and between the inner peripheral surface 88b of the sleeve 86 and the peripheral surface 82a of the upper end 19a of the needle 19. A slight radial gap 84 of about 10 μm or less is formed. The sleeve 86 is provided with a communication passage 89 having an opening at one end facing the oil chamber 85 and an opening at the other end in the fuel chamber 28. In the opening of the communication passage 89 on the side of the fuel chamber 28, a non-return stop having a tapered opening 60, a ball 61 and a leaf spring 62 similar to those used in the embodiment shown in FIGS. A valve 58 is provided. In addition,
Although omitted in the figure, the outer peripheral surface 88a of the sleeve 86
Obviously, a stopper 63 for preventing the leaf spring 62 from dropping may be provided thereon. A stopper 76a can be provided on the needle 19 to prevent the sleeve 86 from dropping. The stopper 76a may be provided on the nozzle body 16 as shown by an imaginary line.

When the control piston 14 is displaced in a direction away from the needle 19 when lifted, the fuel flows into the oil chamber 85 through the radial gap 84, but the amount of inflow is small, so that the oil chamber 85 becomes negative pressure and reverses. The stop valve 58 closes. When the control piston 14 is displaced in the direction approaching the needle 19 when descending, the oil chamber 85
Excess fuel in the valve is connected to the communication passage 89 and the opened check valve 58.
Through the fuel chamber 28. Needle 19
The operation of the injector 1 including the above operation is the same as that of the injector shown in FIG.

The details of the leaf spring 62 are shown in FIGS. 5 to 7, taking the case where it is used in the embodiment shown in FIG. 3 as an example. FIG.
FIG. 6 is a sectional view taken along line AA of FIG. 3, FIG. 6 is a sectional view similar to FIG. 5, showing a modified example of an injector using a leaf spring of another form, and FIG. FIG. 8 is a sectional view similar to FIG. 5 showing a modified example of the injector using the leaf spring shown in FIG. 5, and FIG. 8 is a perspective view of the leaf spring shown in FIG. FIG. 3 is a view B in FIG.
It is a sectional view as seen from -B. The leaf spring 62 has two ends 62a,
This is a substantially annular plate spring having 62a, and fits on the outer peripheral surface 88a of the sleeve 86 by its own elasticity. The leaf spring 62 is easily attached to the sleeve 86 by slightly expanding the both ends 62a, 62a.

In the connection portion 90 of the injector shown in FIG. 6, the communication hole 93 formed in the sleeve 91 can be closed by a check valve 94 provided with a ball 95 fitted from the outside. The leaf spring 96 fitted on the outer peripheral surface 92 of the sleeve 91 by its own elasticity is provided with a bulging portion 9 described later.
7, except for the structure of the leaf spring 62 shown in FIG. Since the ball 95 partially protrudes from the outer peripheral surface of the sleeve 91 even in a state where the communication hole 93 is closed, a bulged portion 97 is formed in the leaf spring 96 by working and the ball spring is accommodated inside the bulged portion 97. A joint recess 98 is formed. Both ends 99 of the leaf spring 96 are bent outward to provide elasticity.

In the connecting portion 100 of the injector shown in FIG. 7, the components and portions having the same functions as those of the connecting portion 90 shown in FIG. I do. Outer peripheral surface 92 of sleeve 91
As shown in FIG. 8 which is a perspective view of the plate spring 106, the ball 95 of the check valve 94
3 has a tapered surface 108 that tapers outward in a radial direction in order to hold the same in a closed state.
It has. Both ends 109, 109 of the leaf spring 106
Is bent outward similarly to the leaf springs 62 and 96 shown in FIGS.

An embodiment of the present invention using an orifice as a flow regulating means is shown in FIGS. FIG.
11 to 11 basically correspond to the embodiments shown in FIGS. 2 to 4, respectively, and are enlarged partial cross-sectional views showing a connection portion of an embodiment of an injector using an orifice as a flow rate regulating means. . Connection part 110 of injector shown in FIG.
In the embodiment, the communication passage 111 formed in the lower end portion 14b of the control piston 14 is entirely or partially configured as an orifice. The communication passage 111 is provided with a needle 19 instead of the lower end 14 b of the control piston 14.
May be formed at the upper end 19a of the communication passage 11 (in phantom lines).
2). Connection 120 of injector shown in FIG.
In the embodiment, instead of the check valve 58 provided in the second communication passage 79 of the sleeve 76, the communication passage 121 itself or a part thereof is formed in an orifice. Further, in the connection portion 130 of the injector shown in FIG. 11, instead of the check valve 58 provided in the communication passage 89 of the sleeve 86, a communication passage 131 is provided.
Is formed in the orifice.

In the embodiment shown in FIG. 9 to FIG.
10 to 130 are communication paths 111 (112), 121, and 13 that communicate the oil chambers 55, 75, and 85 with the fuel chamber 28.
Since 1 is an orifice, after a certain period of time,
From the fuel chamber 28, the communication paths 111 (112), 12
The fuel flows into the oil chambers 55, 75, 85 through 1, 131 to be filled. In the injector, generally, the fuel pressure at the distal end of the needle 19 is reduced in the middle, and a differential pressure is generated between the upper and lower sides due to the negative pressure of the fluid at the time of the outflow, so that the fuel is dripped. There is a possibility of such an abnormal injection state. Connection part 110 using orifice
130 is the oil chamber 55, 75, 85 after the needle 19 is lifted following the lift of the control piston 14.
, The needle 19 is pushed down and has a fail-safe action of stopping fuel injection.

The communication passage for the flow rate regulating means is the fuel chamber 28.
FIG. 12 shows an embodiment in which an elastic plate for blocking the opening facing
14 to FIG. FIGS. 12 to 14 basically correspond to the embodiment shown in FIGS. 2 to 4, respectively, but using an elastic plate for closing the opening where the communication passage faces the fuel chamber as the flow rate regulating means. FIG. 4 is an enlarged partial cross-sectional view showing a connection portion of the embodiment of the injector. In the connection portion 140 shown in FIG. 12, an opening 142 in which the communication path 141 formed in the lower end portion 14b of the control piston 14 faces the fuel chamber 28 is covered with an annular elastic plate 143. The communication path 141 is located at the upper end 19 a of the needle 19.
May be formed. In addition, the elastic plate 143 is
It does not have to be annular as long as 2 can be covered by its own elasticity. When the fuel pressure in the oil chamber 55 increases, the fuel pressure elastically deforms the elastic plate 143 to open the opening 142 to the fuel chamber 28, and releases the fuel pressure.

In the connection portion 150 of the embodiment of the injector shown in FIG. 13, the opening 152 of the communication passage 151 of the sleeve 76 is covered by an annular elastic plate 153. Further, in the connection portion 160 of the embodiment of the injector shown in FIG. 14, the opening 162 of the communication passage 161 of the sleeve 86 is covered by an annular elastic plate 163.
The elastic plates 143, 153 and 163 are preferably engaged with the control piston 14 and the sleeves 76 and 86 in the circumferential direction so as not to rotate blindly. The operation of the embodiment shown in FIGS. 13 and 14 is the same as the operation of the embodiment shown in FIG. 12, and duplicate description will be omitted.

The lift of the needle 19 based on the balance of the forces acting on the needle 19 will be described with reference to FIG. FIG. 15 shows an example of the embodiment shown in FIG.
FIG. 4 is a diagram illustrating a lift of a needle 19; In the closed state of the needle valve, since the gap 73 is absorbed, the pressing force acting on the needle 19 changes the projected area (cross-sectional area A ₂ ) of the control piston 14 in the axial direction of the fuel pressure (rail pressure Pr) in the balance chamber 33. ) and is determined by multiplying the force (Pr × a _2), the sum F ₁ of the spring force of the return spring 39 (Ps) is transmitted through the control piston 14. The lift force acting on the needle 19 is obtained by multiplying the fuel pressure (rail pressure Pr) by the area difference (A ₂ −a ₁ ) of the needle 19 [Pr × (A ₂ −
a ₁ )] and the force obtained by multiplying the pressure (Pc) in the combustion chamber by the axially projected area a ₀ of the tip of the needle 19 (F ₂ ). The area a ₁ is the projected area in the axial direction at the outermost diameter that comes into contact with the nozzle body 16 at the tip of the needle 19, and the projected area in the axial direction of the tapered surface 22 a in the oil reservoir 30 is also the area the difference (A ₂ -a
₁ ) Included in calculations. Normally, force F ₁ is equal to force F ₂
The needle valve remains closed.
When the fuel pressure in the balance chamber 33 is released through the discharge passage 34, the control piston 14 lifts by overcoming the spring force (Ps) of the return spring 39 by the fuel pressure acting on the gap 73, and the pressure in the oil chamber 75 is increased. Becomes negative pressure.

When the needle valve is about to open, the pressing force acting on the needle 19 is reduced by the fuel pressure (rail pressure Pr) acting on the gap 73 at the upper end 1 of the needle 19.
Area difference of 4a (A ₂ -A ₁₎ a force F ₃ obtained by multiplying the
, And the lift force acting on the needle 19, as well as the time of closing of the needle valve, the force _{[Pr × (A 2 -a 1} )] and the distal end area a ₀ of the needle 19 to the pressure (Pc) in the combustion chamber Is multiplied by the force (F ₄ ). The area A ₁ is
It is an axial projection area (cross-sectional area) of the reduced diameter portion 72 of the needle 19. In consideration of the pressure in the oil chamber 75, the areas A ₂ , A ₁ , a ₁ , a ₁ are set so that the force F ₄ is larger than the force F _3.
0 is defined. When a force F ₄ is larger even slightly than the force F _3, the needle 19 is lifted. Some limitations to face when the lift of the control piston 14 to the spring force of the return spring 39, but when a large area A _1, the net lift force increases, is possible to increase the negative pressure in the oil chamber 75 it can. In other embodiments, the lift of the needle 19 is the same, and a detailed description thereof will be omitted.

[0048]

According to the injector of the present invention,
The axial misalignment between the control piston and the needle is caused by a radial gap when the opposing end of the control piston and the needle are fitted into the concave and convex, or by the opposing end of the control piston and the needle and the opposing end thereof The axial gap between the control piston and the needle does not need to be aligned with high precision to each other, because it is absorbed by the radial gap between the sleeve and the sleeve. In addition, the fluid connection by the oil chamber ensures smooth sliding between the control piston and the needle with sufficient responsiveness in the axial direction. Although the fluid connection between the control piston and the needle has a slight delay compared to the mechanical connection, it is expected that a damping action or a bounce prevention action is expected instead, resulting in a favorable result for the operation of the injector. There is. Furthermore, since the assembly connection between the control piston and the needle can be performed with one touch, the assembling workability can be improved and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of an injector according to the present invention.

FIG. 2 is an enlarged sectional view showing a structure of a fluid connection between a control piston and a needle of the injector shown in FIG. 1;

FIG. 3 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention.

FIG. 4 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention.

FIG. 5 is a cross-sectional view of the connection portion of the injector shown in FIG.

FIG. 6 is an enlarged sectional view showing a connection portion of an embodiment having another check valve structure in the injector according to the present invention.

FIG. 7 is an enlarged sectional view showing a connecting portion of an embodiment having still another check valve structure in the injector according to the present invention.

FIG. 8 is a perspective view of a leaf spring used for a check valve at a connection portion of the injector shown in FIG. 7;

FIG. 9 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention using an orifice as a flow regulating means.

FIG. 10 is an enlarged sectional view showing a connecting portion in another embodiment of the injector according to the present invention using an orifice as a flow regulating means.

FIG. 11 is an enlarged sectional view showing a connecting portion in still another embodiment of the injector according to the present invention using an orifice as a flow regulating means.

FIG. 12 is an enlarged cross-sectional view showing a connecting portion in an embodiment of the injector according to the present invention using an elastic plate for closing an opening of a communication passage as a flow regulating means.

FIG. 13 is an enlarged cross-sectional view showing a connecting portion in another embodiment of the injector according to the present invention using an elastic plate for closing an opening of a communication passage as a flow rate regulating means.

FIG. 14 is an enlarged cross-sectional view showing a connecting portion in still another embodiment of an injector according to the present invention using an elastic plate for closing an opening of a communication passage as a flow regulating means.

FIG. 15 is a view for explaining lift of the needle of the injector according to the present invention.

[Description of Signs] 1 Injector 2 Main body 2a Holder main body 7 Solenoid valve 10 Solenoid 13 Hollow part 14 Control piston 14a Upper end (one end) 16 Nozzle main body 19 Needle 20, 70, 80, 90, 100, 110, 120, 1
30, 140, 150, 160 Connection part 21 Injection hole 28 Fuel chamber 33 Balance chamber (pressure control chamber) 34 Discharge path 35 Armature 36 Opening / closing valve body 39 Return spring 51 Control piston end face 52 Needle end face 53 Concave part 54 Convex part 55 , 75, 85 Oil chamber 57 Radial gap 58, 94 Check valve 59, 79, 89, 93, 141, 151, 161 Communication passage 60 Tapered opening 61, 95 Ball 62, 96, 106 Leaf spring 63 Stopper 71 , 72 Reduced diameter portion 76, 86, 91 Sleeve 76a Stopper 97 Swelling portion 98 Engagement concave portion 111 (112), 121, 131 Orifice 142, 152, 162 Opening of communication passage 143, 153, 163 Elastic plate

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02M 61/20 F02M 61/20 N

Claims (14)

[Claims] 1. A valve body reciprocating in a main body having an injection hole for injecting fuel and opening the injection hole by fuel pressure, formed around the valve element in the main body through which the valve body penetrates. A fuel chamber for storing the fuel, a pressure control chamber formed in the main body and controlling a lift of the valve body by a pressure action of a working fluid on the valve body, wherein the valve body is provided in the pressure control chamber. An end face of one end is exposed and the control piston penetrating through the fuel chamber, and an end face of one end and an end face of the other end of the control piston are arranged so as to face each other. A needle for opening and closing a hole, wherein the control piston and the needle are connected to an oil chamber formed between the opposing surfaces, a communication path communicating the oil chamber with the fuel chamber, and the communication A fluid connection portion that is disposed in a passage and has a flow rate regulating means that regulates a flow of fuel from the fuel chamber to the oil chamber. When the control piston is lifted, fuel is supplied through the communication passage. An injector that lifts the needle following the control piston by reducing the fuel pressure in the oil chamber by restricting the inflow into the oil chamber by the flow rate control means. 2. The oil chamber has a wall surface of a concave portion formed on one of the opposing surfaces of the control piston and the needle, and a convex portion formed on the other of the opposing surface and loosely fitted in the concave portion. The injector of claim 1, wherein the injector is defined by an end face. 3. A tapered oil sump chamber for lifting the needle is formed around an intermediate portion in the axial direction of the needle in the main body, and the concave portion or the convex portion is formed. The injector according to claim 2, wherein an axial projected area of the facing surface of the needle excluding a region is set smaller than an axial projected area of the needle facing the oil reservoir. . 4. The injector according to claim 2, wherein the communication passage is formed to penetrate the control piston. 5. A sleeve is fitted over the other end of the control piston and the one end of the needle so as to straddle the oil chamber. 2. The method of claim 1, further comprising:
The injector according to 1. 6. A reduced diameter portion is formed at each of said other end of said control piston and said one end of said needle, and said sleeve is fitted over said both reduced diameter portions, 6. The injector according to claim 5, wherein both opposing surfaces are end faces of the both reduced diameter portions. 7. A tapered oil sump chamber for lifting the needle is formed around an axial center portion of the needle in the main body, and the tapered oil sump is formed by removing the end face of the reduced diameter portion. 7. The injector according to claim 6, wherein an axial projected area of the facing surface of the needle is set smaller than an axial projected area facing the oil reservoir. 8. The apparatus according to claim 5, wherein said communication passage is formed so as to penetrate through said sleeve.
The injector according to the paragraph. 9. The injector according to claim 1, wherein said flow rate regulating means is an orifice formed in said communication passage. 10. The flow rate control means is disposed in the communication passage and allows a flow of fuel in a direction from the oil chamber to the fuel chamber, but blocks a flow of the fuel from the fuel chamber to the oil chamber. The injector according to any one of claims 1 to 8, wherein the injector is a check valve. 11. The check valve according to claim 1, wherein the check valve is externally fitted to a ball disposed in an opening of the communication passage on the fuel chamber side, and to the control piston or the sleeve in which the communication passage is formed. The injector according to claim 10, comprising a leaf spring for urging the ball in a direction to close the opening of the communication path. 12. The check valve is formed from an elastic plate fitted to the control piston or the sleeve in which the communication passage is formed, at a position covering an opening of the communication passage on the fuel chamber side. The elastic plate is elastically deformed by high-pressure fuel pressure in the oil chamber to open the opening, and when the oil chamber becomes low pressure or negative pressure, the opening is closed by its own elasticity. An injector according to claim 10, comprising: 13. The pressure control chamber is a balance chamber formed by a control sleeve fixed to the main body, and controls a lift of the valve body by a fuel pressure. The fuel pressure in the balance chamber is controlled by an actuator by the actuator. The injector according to any one of claims 1 to 12, wherein the injector is released by driving an on-off valve that opens and closes a discharge path from the chamber. 14. The main body includes a holder body that supports the control piston slidably in the axial direction and the injection hole that supports the needle connected to the holder body slidably in the axial direction. 2. A nozzle body according to claim 1.
14. The injector according to any one of claims 13 to 13.