JP3777708B2 - Injector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injector that injects fuel into a combustion chamber using the pressure of a working fluid stored in a pressure accumulating chamber.
[0002]
[Prior art]
Regarding engine fuel injection control, an accumulator fuel injection system is known as a method for increasing injection pressure and optimally controlling injection conditions such as fuel injection timing and injection amount according to the operating state of the engine. ing. The accumulator fuel injection system stores a fuel injection control working fluid pressurized to a predetermined pressure by a pump in a pressure accumulating chamber, and uses the pressure of the working fluid to inject fuel into a corresponding combustion chamber from an injector. This is a fuel injection system. The controller controls the pressure in the pressure accumulating chamber and the control valve provided in each injector so that the pressurized fuel is injected in each injector under the optimal injection condition for the operating state of the engine.
[0003]
One type of accumulator fuel injection system is a system that uses pressurized fuel itself as a working fluid. In this system, the lift of the needle valve is controlled by controlling the fuel pressure in the balance chamber, and high pressure fuel is injected from the injector into the combustion chamber. High-pressure fuel to be supplied to the injector is stored in a common rail as a pressure accumulator from a fuel pump. The controller, which is an electronic control unit, receives signals from various sensors for detecting the operating state of the engine, such as an engine speed sensor, an engine cylinder discrimination sensor, a top dead center detection sensor, and an accelerator pedal depression amount sensor. . Based on these signals, the controller controls the fuel injection conditions by the injector, that is, the fuel injection timing and the injection amount, so that the engine output becomes the optimum output in accordance with the operating state. The common rail is provided with a pressure sensor, and the fuel pressure in the common rail is maintained at a predetermined pressure by the fuel pump and the flow control valve under the control of the controller. The details of the pressure accumulating system are well-known and are not directly related to the present invention.
[0004]
In a common rail type fuel injection system, fuel having a fuel pressure equivalent to the fuel injection pressure is always supplied to the injector, and the needle valve is driven by the operation of the electromagnetic valve, and from the opened nozzle hole. Fuel is injected. For this reason, a sticking phenomenon may occur in which the reciprocating member of the solenoid valve or nozzle is not smoothly guided to the guide member when returning, and does not return to the return position. When such a stick phenomenon occurs, the fuel continues to be injected from the opened nozzle hole, and the engine may be damaged. For this reason, there has conventionally been proposed a flow limiter that restricts the amount of fuel passing through the fuel inlet to the injector and closes the fuel passage when the fuel injection time is long (Japanese Patent Laid-Open No. Hei 4). No. 241767 and JP-A-4-252860).
[0005]
A structure of the same type as the flow limiter disclosed in each of the above publications is shown in FIG. The flow limiter 40 is disposed between a common rail that accumulates high-pressure fuel and a fuel pipe extending to each injector. When the amount of fuel supplied from the common rail to the fuel pipe exceeds a predetermined value, the fuel limiter 40 It stops the flow. The flow limiter 40 includes a piston 43 in a hollow hole 42 in a housing 41, a ball body 44 provided on the injector side of the piston 43 so as to be movable integrally with the piston 43, and a spring that biases the ball body 44 toward the common rail. 45, and a spring seat 46 disposed between the ball body 44 and the spring 45. A regulating member 47 that regulates the movement of the piston 43 toward the common rail is provided. The piston 43 and the regulating member 47 are formed with orifices 48 and 49 that allow the passage of fuel, respectively. Further, a press-fit hole 50 smaller than the outer diameter of the ball body 44 is formed on the injector side of the hollow hole 42.
[0006]
In such a flow limiter, in a normal fuel injection state, high-pressure fuel from the common rail passes through the orifice 49 of the regulating member 47, the orifice 48 of the piston 43, the periphery of the ball body 44, the spring seat 46, and to the injector side. Flowing. At this time, the piston 43 and the ball body 44 move to the injector side, that is, the press-fitting hole 50 side according to the flow rate. When the fuel injection period of the injector is lengthened, the moving amount of the ball body 44 is increased and press-fitted into the press-fitting hole 50, the valve by the ball body 44 is closed, and the supply of fuel to the injector is completely stopped.
[0007]
[Problems to be solved by the invention]
The above-mentioned type of flow limiter requires many components such as the piston 43, the ball body 44, the spring 45, and its seat 46, and has a problem that the structure is complicated. Further, since the differential pressure across the orifice through which the fuel passes is used for the purpose of moving the piston 43 and the ball body 44 against the spring force of the spring, the opening area of the orifice is set to be considerably reduced. ing. The orifice having such a throttle has a problem that it becomes a resistance against the passage of fuel during fuel injection and lowers the fuel injection rate.
[0008]
[Means for Solving the Problems]
The object of the present invention is to solve the above-mentioned problem, and at the tip of the injector, by using the nozzle opening / closing mechanism that the needle valve already has, even if the fuel injection period set by the controller has passed, the fuel still By providing the needle valve with a flow limiter function that restricts the flow of fuel according to the state of continuous injection, the flow limiter function can be achieved easily and at low cost. It is an object of the present invention to provide an injector that does not have a fuel pressure loss caused by using the differential pressure across the orifice as seen in FIG.
[0009]
In order to achieve the above object, an injector according to the present invention includes a fuel supply passage, a hollow hole formed therein, and a nozzle formed with a nozzle hole for injecting fuel supplied through the fuel supply passage at the tip. injector consisting comprises a needle valve main body and said hollow bore being liftable arranged and contact away the valve seat formed in the nozzle body to open and close the injection hole, the needle valve, the valve body and the It is composed of two members of the valve member having a valve face for closing the surface and the injection hole on the side abutting on the disjunctive possible the valve body at a small gap against the tip concave surface of the valve body The valve member is disposed on the surface of the valve member on the side in contact with the valve body in accordance with a state in which the nozzle hole is not closed by the lowering of the valve body after the fuel injection period has elapsed. Size to close It is characterized in that it has to receive the fuel pressure.
[0010]
The injector according to the present invention has the above-described configuration, so that the fuel is injected from the injection hole when the needle valve lifts in the hollow hole of the main body, and the injection hole is closed by the lowering of the needle valve. Is stopped. The valve member of the needle valve, so that disjunctive can abut on the tip concave surface of the valve body, at the time of lift of the needle valve, between each other disjunctive surface to follow the valve body caused negative pressure lifts To do. Fuel injection period, the controller signals from various sensors, in particular, is set according to the engine speed and the accelerator depression amount. If the needle valve is operating normally, the valve member descends with the descending valve body and the nozzle hole is closed. If the needle valve is not lowered even after the fuel injection period has elapsed, the valve member descends based on the fuel pressure received on the surface that comes into contact with the valve body to close the nozzle hole. .
[0011]
Further, in this injector, the fuel pressure received by the surface of the valve member on the side in contact with the valve body is formed in the valve body so as to communicate the fuel supply path and the minute gap, and the fuel supply It is supplied through an oil feed passage having an effective passage area smaller than the effective passage area of the passage. Since the effective passage area of the oil supply passage formed in the valve body is smaller than the effective passage area of the fuel supply passage, the fuel pressure between the valve body and the valve member, which is reduced when the needle valve is lifted, is And then recovers to the fuel pressure in the fuel supply path after the fuel injection period. The recovered fuel pressure acts on the surface of the valve member that contacts the valve body, and lowers the valve member.
[0012]
Further, in this injector, the valve body and the fuel pressure surface on the side is subjected to contact with the valve member, the tip concave surface or on the valve of the valve body so as to communicate with the small gap between the fuel supply passage The member is supplied through an oil feed groove that is formed on the surface of the member that is in contact with the valve main body or on both surfaces and has an effective passage area smaller than the effective passage area of the fuel supply passage. The recovery of the fuel pressure between the valve body and the valve member, which has been reduced when the needle valve is lifted, is the same as in the above case where the oil feed passage is formed in the valve body.
[0013]
Further, in this injector, small gap is formed between the valve body and the side abutting surface of the tip concave surface and a valve member of the valve body. Fuel pressure supplied between the valve body and the side abutting surface of Okuaburaro or oil feed groove tip concave surface of the valve body from such a valve member immediately, of the valve member through the narrow gap The valve member is actuated quickly by acting on the surface of the valve body in contact with the valve body.
[0014]
Furthermore, in this injector, the valve member is a ball or a cone having a tapered surface. The spherical surface of the ball or the tapered tapered surface of the cone has a valve face that can be seated on the valve seat formed on the nozzle body on the tip side, and also receives the fuel pressure of the fuel supply passage to lift the needle valve has a surface, further disjunction capable side in contact with the front end concave surface of the valve body, will comprise a surface for receiving the fuel pressure lowers the valve member.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a fuel injection device according to the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view showing the entire injector according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing the structure of the tip of the injector shown in FIG.
[0016]
One injector used in this type of accumulator fuel injection system is shown in FIG. The number of injectors corresponding to the number of cylinders of the engine is prepared, and high-pressure fuel stored in a common rail (not shown) is supplied to each injector 1 through a branch pipe 18 constituting a part of the fuel flow path. . A branch pipe 18 is connected to the upper side portion of the injector 1 through a fuel inlet joint 20. Fuel passages 21 and 22 are formed inside the main body of the injector 1, and a fuel flow path is constituted by the branch pipe 18 and the fuel passages 21 and 22. The fuel supplied through the fuel flow path is injected into the combustion chamber from the injection hole 5 which is opened when the needle valve 4 is lifted, through the passage around the first fuel reservoir 23 and the needle valve 4. Excess fuel is returned to the common rail through the return pipe 19.
[0017]
The injector 1 is provided with a balance chamber type needle valve lift mechanism for controlling the lift of the needle valve 4. That is, an electromagnetic valve 26 as a control valve is provided at the top of the injector 1, and a control current as a control signal from the controller 38 is sent to the solenoid 28 of the electromagnetic valve 26 through the signal line 27. When the solenoid 28 is energized, the armature 29 rises and opens the opening / closing valve 32 provided at the end of the fuel passage 31, so that the fuel pressure of the fuel supplied from the fuel passage to the balance chamber 30 is increased. Released through 31.
[0018]
A control piston 34 is provided in the central hollow hole 33 formed in the central body of the injector 1 so as to be movable up and down. Rather than the pressing force acting on the control piston 34 by the force based on the reduced pressure in the balance chamber 30 and the spring force of the return spring 35, the tapered surface 36 facing the first fuel reservoir 23 and the tip of the needle valve 4 described later. Since the force to push up the control piston 34 is won based on the fuel pressure acting on the control piston 34, the control piston 34 rises. As a result, the needle valve 4 is lifted and fuel is injected from the nozzle hole 5. The fuel injection amount is determined by the fuel pressure in the fuel flow path and the lift of the needle valve 4 (lift amount, lift period). The lift of the needle valve 4 is sent to the solenoid 28 for controlling the opening / closing of the opening / closing valve 32. It is determined by the injection pulse as the control current sent.
[0019]
FIG. 2 shows an enlarged cross section of the structure of the tip of the injector shown in FIG. The nozzle body 2 of the injector 1 (corresponding to the body of the injector according to the present invention) has a hollow hole 3 formed therein, and the needle valve 4 is accommodated in the hollow hole 3 so as to be liftable. A nozzle hole 5 is formed at the tip of the nozzle body 2. The needle valve 4 has a valve main body 6 that occupies most of the needle valve 4 and a valve member 7 provided at the tip of the valve main body 6. Between the hollow hole 3 and the needle valve 4, there is a first fuel supply path 8 on the upstream side and a downstream side of the first fuel supply path 8, and the effective passage sectional area of the first fuel supply path 8 is slightly larger. A second fuel supply passage 9 having a small effective passage sectional area is formed. The fuel supplied through the first fuel supply passage 8 passes through a second fuel reservoir 10 formed between the tip of the nozzle body 2 and the valve member 7, and then reaches the combustion chamber (not shown) of the engine from the nozzle hole 5. Is injected into the inside.
[0020]
The valve member 7 of the needle valve 4 has a ball shape, and the tip end portion of the spherical surface is a valve face 11. The valve face 11 can be separated from and attached to an annular valve seat 12 formed of a part of a spherical surface formed in the nozzle body 2, and the nozzle hole 5 is in accordance with the separation and contact of the valve face 11 with the valve seat 12. Is opened and closed. The valve member 7 is held by the valve main body 6 about the upper half, but the valve member 7 is in contact with the valve main body 6 so as to be detachable, and the surface 13 on the side in contact with the valve main body is a valve It faces the tip concave surface 14 consisting of a concave spherical surface of the body 6, between the valve body and the surface 13 and the tip concave surface 14 of the side contacting, a small gap 15 is formed. The valve body 6 is formed with an oil feed passage 16 that communicates the first fuel supply passage 8 and the gap 15.
[0021]
The fuel pressure received by the surface 13 of the valve member 7 on the side in contact with the valve body is supplied through an oil feed passage 16 formed in the valve body 6. Since the effective passage area of the oil feed passage 16 is set to be considerably smaller than the effective passage area of the first fuel supply passage 8, even if the pressure in the minute gap 15 decreases, the minute gap The pressure in 15 does not immediately recover to a high fuel pressure corresponding to the injection pressure in the first fuel supply path 8. Therefore, when the valve body 6 of the needle valve 4 is lifted, a negative pressure is generated in the minute gap 15, but the negative pressure does not immediately recover to a high fuel pressure in the first fuel supply path 8. The member 7 lifts following the valve body 6 based on the differential pressure between the low pressure acting on the surface 13 on the side in contact with the valve body and the high fuel pressure in the second fuel supply passage 9. . The pressure in the minute gap 15 gradually recovers to the fuel pressure in the first fuel supply path 8 through the oil feeding path 16, but the period required for the recovery is a normal fuel set by the calculation of the controller 38. It is set longer than the injection period.
[0022]
This injector is configured as described above, and its operation will be described next. When the needle valve 4 is lifted, the valve body 6 is lifted. However, the fuel pressure in the first and second fuel supply passages 8 and 9 cannot be maintained in the minute gap 15 and becomes negative pressure. For this reason, the valve member 7 receives a high fuel pressure corresponding to the injection pressure in the second fuel supply passage 9 on the lower half surface, and is based on a differential pressure between the pressure acting on the surface 13 on the side in contact with the valve body. Then, the valve body 6 is lifted following. Even when the fuel injection period has elapsed, if the fuel injection is continued because the injection hole 5 is not closed by the lowering of the needle valve 4, the fuel pressure in the minute gap 15 is the first The fuel pressure in the fuel supply passage 8 is gradually recovered by being supplied through the oil feed passage 16. During fuel injection, the flow of fuel in the second fuel supply path 9 having a slightly smaller effective passage area than the first fuel supply path 8, that is, around the valve member 7, is fast. The fuel pressure at the bottom is reduced, and the valve member 7 descends away from the valve body 6 based on the differential pressure from the recovered fuel pressure acting on the surface 13, and the valve member 7 closes the injection hole 5. Become.
[0023]
The supply of fuel pressure received by the surface 13 of the valve member 7 in contact with the valve main body is such that one end is opened in the second fuel supply path 9 instead of the oil supply path 16 formed in the valve main body 6. It can also be a oil feed groove formed on the front end a concave surface 14 of the body 6. If one valve member 7 is rotated up and down instead of balls, Okuaburamizo is on the valve body and the surface 13 abutting the side of the valve member 7, or valve tip concave surface and the valve member 7 of the valve body 6 You may form in both on the surface 13 of the side contact | abutted with a main body . In any case, the effective passage area of the oil feeding groove is set to a value smaller than the effective passage area of the second fuel supply passage 9. Although the valve member 7 has been described as a ball, the shape of the valve member 7 is not limited to a ball, and may be formed in a cone having a tapered tapered surface such as a cone.
[0024]
【The invention's effect】
The injector according to the present invention, as described above, composed of two parts of the valve member for opening and closing the disjunction can abut and the injection hole of the needle valve at the tip concave surface of the valve body and the valve body, the fuel injection period In the state where the nozzle hole is not closed due to the lowering of the valve body, the valve member receives a fuel pressure large enough to close the nozzle hole on the surface in contact with the valve body. The valve member of the needle valve is disjunctive capable abutting structure on the tip concave surface of the valve body, lifted following the valve body when the lift of the needle valve, even after the fuel injection period Incidentally needle valve of When the lowering is not performed, the lowering is performed based on the fuel pressure received on the surface on the side in contact with the valve body, and the nozzle hole is closed. Therefore, the flow limiter mechanism for stopping the fuel injection after the fuel injection period has elapsed can be obtained with a simple structure in the injector nozzle, not as a separate device that requires many components from the conventional injector. be able to. In addition, since the pressure drop due to the passage of the fuel through the orifice is not used for the operation of the flow limiter mechanism, there is no resistance to the passage of the fuel at the time of fuel injection, and the fuel injection rate does not decrease as a whole.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of an injector according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a main part of the injector shown in FIG.
FIG. 3 is a cross-sectional view showing an example of a conventional flow limiter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injector 2 Nozzle main body 3 Hollow hole 4 Needle valve 5 Injection hole 6 Valve main body 7 Valve member 8 1st fuel supply path 9 2nd fuel supply path 11 Valve face 12 Valve seat 13 Surface 14 in contact with valve main body 14 Tip concave Surface 15 Small gap 16 Oil supply path

Claims (4)

A nozzle body provided with a fuel supply passage and having a hollow hole formed therein, and a nozzle hole for injecting fuel supplied through the fuel supply passage at the tip thereof, and a liftable arrangement in the hollow hole; and In an injector comprising a needle valve that opens and closes the nozzle hole in contact with a valve seat formed in a nozzle body,
The needle valve has a valve face for opening and closing the valve body and the side surface abutting on the disjunctive possible the valve body at a small gap against the tip concave surface of the valve body injection hole is composed of two members of the valve member with the valve in accordance with the state where the closure is not performed in the injection hole due to the descent of the body after the fuel injection period, the valve member of the valve member and the valve body and those An injector characterized by receiving a fuel pressure of a size that closes the nozzle hole on a surface on a side in contact therewith . The fuel pressure received by the surface of the valve member in contact with the valve body is formed in the valve body so as to communicate the fuel supply path and the minute gap, and an effective passage of the fuel supply path The injector according to claim 1, wherein the injector is supplied through an oil feeding passage having an effective passage area smaller than the area. The fuel pressure surface of the valve body abutting the side of the valve member is subjected, the said tip concave surface or on the valve member of the valve body so as to communicate with the small gap between the fuel supply passage claim characterized in that it is supplied through Okuaburamizo having a smaller effective passage area than the effective passage area of the valve body and abutting on the side surface or formed on both of these surfaces and the fuel supply passage 1 The injector as described in. The injector according to any one of claims 1 to 3, wherein the valve member is a ball or a cone having a tapered surface .

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