JP2010090738A - Fuel injection valve of accumulating fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve of an accumulating fuel injection device capable of performing superior combustion by increasing the averaged effective injection pressure during the fuel injection period and suppressing the pressure pulsation after the needle valve is closed. <P>SOLUTION: The fuel injection device includes the fuel injection valve to which the fuel discharged from a high-pressure pump and accumulated in an accumulator is supplied. The fuel injection valve comprises the needle valve 2 for opening and closing the nozzle hole 4 formed at the tip of a nozzle 1, a command piston reciprocating together with the needle valve 2, a fuel passage 14a for supplying the fuel to a fuel sump 5 communicating with the nozzle hole, and a control chamber which is formed at the rear of the command piston and into which the fuel is introduced. The fuel sump 5 is formed in a ring shape around the needle valve 2. The oil sump 5 extends from the upper side of a needle valve step part 2a formed on the needle valve 2 near a sack part 1a at the tip of the nozzle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention supplies a high-pressure fuel discharged from a high-pressure pump and accumulated in a pressure accumulator to a fuel injection valve, and lifts a needle valve of the fuel injection valve, thereby supplying high-pressure fuel from a nozzle hole to an engine combustion chamber. The present invention relates to a fuel injection valve of a pressure accumulation fuel injection device configured to inject fuel.

Conventionally, mechanical and electronically controlled fuel injection devices used for internal combustion engines (engines) are known. The mechanical fuel injection device has an injection pump with a built-in cam and plunger, lifts the plunger by rotation of the cam, compresses fuel by the vertical movement of the plunger, and when the injection pressure exceeds a predetermined pressure, the nozzle is opened. Through which fuel is injected into the combustion chamber of the engine.
On the other hand, an electronically controlled (accumulation type) fuel injection device has been widely adopted in recent years because it can perform highly accurate fuel injection control, and has the following configuration.

  FIG. 4 is a cross-sectional view showing an example of a conventional pressure accumulation fuel injection device. As shown in the figure, the pressure-accumulation fuel injection device includes a high-pressure pump 21 and a pressure accumulator 22 to which fuel pumped up from a fuel tank 20 is sequentially sent, and fuel to which high-pressure fuel fed from the pressure accumulator 22 is supplied. The injection valve 100 is comprised. The fuel injection valve 100 is provided with a nozzle 1 at the tip, and a sack portion 1a at the tip of the nozzle is provided with an injection hole 4 for injecting fuel. A needle valve 2 is fitted in the inner peripheral hole 1b of the nozzle 1 so as to be slidable back and forth. A fuel reservoir 5 is formed adjacent to the outer periphery of the nozzle 1, and the fuel reservoir 5 communicates with the nozzle hole 4. When fuel is not injected, the tip of the needle valve 2 abuts against the seat portion 5 a of the nozzle 1, the injection hole 4 is closed, and high-pressure fuel is stored in the fuel reservoir 5. The nozzle 1 is fixed to the injection valve body 7 by a nozzle support ring 3.

  A command piston 8 is fitted into the central hole 7b of the injection valve body 7 so as to be reciprocally slidable, and the command piston 8 and the needle valve 2 reciprocate together. A needle valve spring 9 a is interposed under the command piston 8, and a control chamber 32 into which fuel is introduced is formed behind the command piston 8. The high pressure fuel supplied from the pressure accumulator 22 is introduced into the injection valve body 7 through the fuel inlet pipe 12a and the fuel inlet passage 12, and of the two fuel passages branched in the injection valve body 7, Fuel is supplied to the fuel reservoir 5 through the fuel passage 14a, and fuel is supplied to the control chamber 32 through the other fuel passage 14b. The fuel in the control chamber 32 flows through the leak passage 16 to the outside.

The control chamber 32 and the leak passage 16 are opened and closed by a solenoid valve device 15s. The solenoid valve device 15s includes a solenoid coil 15, a control valve 9, and an armature 15a to which the control valve 9 is fixed.
In such a fuel injection valve 100, at the time of fuel injection, when the armature 15a and the control valve 9 are pulled up and opened by the solenoid coil 15, the inside of the control chamber 32 is opened to the leak line 16 to open the fuel passage 14b. .
As a result, the pressure of the high-pressure fuel that has been sent into the fuel reservoir 5 through the fuel passage 14a is open from the lower side of the needle valve 2 because the fuel passage 14b is open as described above. By acting, the needle valve 2 is separated upward from the seat portion 5a and the needle valve 2 is opened. The high-pressure fuel in the fuel reservoir 5 is injected from the nozzle hole 4 of the nozzle 1 into the combustion chamber of the engine through the seat portion 5a.

In such a fuel injection device, in order to achieve good combustion, it is effective to inject fuel into the combustion chamber at a high pressure.
In the mechanical fuel injection device, from the viewpoint of the bulk modulus, it is preferable that the volume of the fuel passage in the system is small in order to increase the pressure quickly up to the valve opening pressure. Accordingly, the volume of the fuel passage in the nozzle of the fuel injection valve is not particularly increased. In particular, a structure that reduces the volume as much as possible from the fuel reservoir to the sack portion has been adopted.

  However, in the case of the accumulator type fuel injection device as described above, if the fuel passage volume in the system is small, the pressure pulsation after the needle valve is closed becomes large, so that the fuel passage volume is preferably large. The same applies to the inside of the nozzle of the fuel injection valve, and it is preferable that the volume of the fuel passage from the fuel reservoir to the sac is larger. However, in the conventional electronically controlled fuel injection device, the volume of the fuel passage from the fuel reservoir to the sac is relatively small. It was formed small. Further, as shown in FIG. 3, the fuel reservoir 5 is often formed only on one side of the needle valve 2. As a general nozzle manufacturing method, after the fuel passage 14a and the needle valve inner peripheral hole 1b in the nozzle are respectively formed, the fuel passage 14a and the needle valve inner peripheral hole 1b are connected by electric discharge machining. However, this is because the fuel reservoir 5 utilizes the space formed at this time and was not manufactured in consideration of the volume of the fuel passage in this portion.

  However, originally, in a pressure accumulating fuel injection device, in order to increase the average effective injection pressure during the injection period, it has been desired to increase the pressure of the sack portion by increasing the volume of the fuel passage. Various structures have been proposed for the structure of the sack portion. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-224746) discloses a configuration in which the shape around the sack portion of the fuel injection valve is optimized. A configuration is disclosed in which the distal end portion of the needle valve is formed in a tapered shape whose diameter is reduced on the distal end side, and the tapered needle valve distal end portion is excised.

JP 2007-224746 A

  Thus, in the conventional accumulator type fuel injection device, the volume of the fuel passage in the system is relatively small, and in particular, the volume of the fuel passage from the fuel reservoir to the sac portion is small. There was a problem of becoming. As described above, in order to achieve good combustion, it is effective to inject fuel into the combustion chamber at a high pressure. However, since the conventional accumulator fuel injection device has a small fuel passage volume, the pressure of the sack portion is reduced. There was a problem that it was difficult to maintain high pressure. In the configuration described in Patent Document 1, space can be expanded by cutting the tip of the needle valve, and the volume of the fuel passage can be increased. However, the volume increase amount is small, and suppression of pressure pulsation, high pressure of fuel is performed. The effect on maintenance was small.

  Therefore, in view of the above-mentioned problems of the prior art, the present invention increases the volume of the fuel passage of the fuel injection valve, increases the average effective injection pressure during the fuel injection period to achieve good combustion, and after the needle valve is closed. An object of the present invention is to provide a fuel injection valve for an accumulator fuel injection device that can suppress the pressure pulsation.

Therefore, in order to solve the problem, the present invention is a fuel injection valve that is supplied with fuel discharged from a high-pressure pump and accumulated in an accumulator,
The fuel injection valve includes a needle valve that opens and closes a nozzle hole formed at a nozzle tip, a command piston that reciprocates integrally with the needle valve, and a fuel that supplies the fuel to a fuel reservoir that communicates with the nozzle hole. A passage, and a control chamber formed behind the command piston and into which fuel branched from the fuel passage is introduced,
The fuel reservoir is formed in a ring shape around the needle valve, and the fuel reservoir extends from above the needle valve stepped portion formed in the needle valve to the vicinity of the sack portion of the nozzle tip. It is characterized by being.

  According to the present invention, the fuel reservoir is formed in a ring shape around the needle valve, and the fuel reservoir extends from the needle valve stepped portion formed in the needle valve to the vicinity of the sack portion of the nozzle tip. Therefore, a large volume of the fuel reservoir can be secured, the pressure of the sack portion can be maintained at a higher pressure, and good combustion can be achieved by increasing the average effective injection pressure during the fuel injection period. In addition, pressure pulsation after the needle valve is closed can be suppressed.

The fuel reservoir is formed so that a ratio of a diameter Db of the fuel reservoir and a diameter Da of the needle valve is Db / Da = 2 or more.
Thus, by forming the fuel sump so that the diameter of the fuel sump is at least twice the diameter of the needle valve, a sufficiently large fuel passage volume in the sac portion can be secured, and the pressure after the needle valve closes. The pulsation can be reliably suppressed, and the average effective injection pressure during the fuel injection period can be increased.

Further, the fuel reservoir is formed in a shape having a cylindrical portion in the nozzle axis direction.
Although there are restrictions on strength conditions in the diameter and axial length of the fuel reservoir, the volume of the fuel reservoir can be maximized by forming the fuel reservoir in a cylindrical shape along the cylindrical shape of the nozzle. Thus, it becomes possible to keep the pressure of the sack portion higher.
Furthermore, it is preferable that the axial length of the fuel reservoir is as long as possible. The clearance between the needle valve and the nozzle needs to have a certain length so that when the needle valve slides, there is no backlash and stable sliding is possible. Therefore, it is preferable to make the axial length of the fuel reservoir as long as possible after securing the length of sliding of the needle valve and the nozzle by a length that ensures stable sliding of the needle valve.

  As described above, according to the present invention, the fuel reservoir is formed in a ring shape around the needle valve, and the fuel reservoir extends from the needle valve stepped portion formed in the needle valve to the vicinity of the sack portion of the nozzle tip. By being extended, the volume of the fuel pool can be secured large, the pressure of the sack portion can be kept higher, and the average effective injection pressure during the fuel injection period can be increased to achieve good combustion. Can do. In addition, pressure pulsation after the needle valve is closed can be suppressed.

In addition, by forming the fuel reservoir so that the diameter of the fuel reservoir is at least twice the diameter of the needle valve, it is possible to secure a sufficiently large fuel passage volume in the sac portion, and to reduce the pressure pulsation after the needle valve is closed. It becomes possible to suppress it reliably and to increase the average effective injection pressure during the fuel injection period.
Further, since the fuel reservoir is formed in a shape having a cylindrical portion in the nozzle axis direction, the volume of the fuel reservoir can be maximized, and the pressure of the sac portion can be maintained at a higher pressure. It becomes.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a cross-sectional view taken along the axial line of a fuel injection device according to an embodiment of the present invention. As shown in FIG. 1, the fuel injection device according to this embodiment includes a high-pressure pump 21 that pumps fuel from a fuel tank 20 that is a fuel supply source and delivers the fuel at a predetermined pressure, and supplies fuel supplied from the high-pressure pump 21 to a predetermined amount. An accumulator (common rail) 22 for accumulating the supply pressure, and a fuel injection valve 100 connected to the accumulator 22 by a fuel inlet pipe 12a are provided.

The fuel injection valve 100 is a valve that injects the high-pressure fuel supplied from the pressure accumulator 22 into the combustion chamber of the engine, and is configured as follows.
The fuel injection valve 100 includes a nozzle 1 in which a nozzle hole 4 for injecting fuel is formed at the tip. The nozzle 1 has a needle valve 2 fitted in an inner circumferential hole 1b so as to be slidable back and forth. A fuel reservoir 5 is formed on the outer periphery of the needle valve 2, and the fuel reservoir 5 communicates with the nozzle hole 4. The fuel reservoir 5 will be described later. When the fuel is not injected, the tip of the needle valve 2 is brought into contact with the seat portion 5 a of the nozzle 1 to close the nozzle hole 4, and the fuel is stored in the fuel reservoir 5.

The nozzle 1 is fixed to the injection valve body 7 by a nozzle support ring 3.
The injection valve body 7 is formed in a cylindrical shape, and a command piston 8 is fitted in a hole 7b in the center thereof so as to be slidable back and forth. The command piston 8 reciprocates integrally with the needle valve 2. A needle valve spring 9 a is interposed between the lower portion of the command piston 8 and the injection valve body 7, and the needle valve spring 9 a serves as a seat portion 5 a of the nozzle 1 at the tip of the needle valve 2 when there is no injection. Is in pressure contact. A control chamber 32 is formed behind the command piston 8.
The control chamber 32 is formed facing the upper end portion of the command piston 8 and communicates with a fuel passage 14b described later through the inlet orifice 13.

An inlet connector 11 is connected to a side portion of the injection valve main body 7, and a fuel inlet passage 12 is formed in the inlet connector 11. The inlet side of the fuel inlet passage 12 is connected to a fuel inlet pipe 12 a extending from the pressure accumulator 22.
The outlet side of the fuel inlet passage 12 is branched into two in the injection valve body 7. One of the branched passages is a fuel passage 14b that communicates with the control chamber 32, and the other passage is a fuel passage 14a that communicates with the fuel reservoir 5 where the needle valve 2 faces.
The fuel passage 14 b communicates with the control chamber 32, and the control chamber 32 communicates with the leak line 16 via the outlet orifice 10. The fuel passage 14 a communicates with the nozzle hole 4 through the fuel reservoir 5.

  A solenoid valve device 15s is installed above the fuel injection valve 100. The solenoid valve device 15s includes a solenoid coil 15, a control valve 9, and an armature 15a to which the control valve 9 is fixed. The control valve 9 opens and closes a fuel passage that leads from the outlet orifice 10 to the leak line 16 by controlling the current supplied to the solenoid coil 15.

In the pressure accumulation fuel injection apparatus having the above-described configuration, the high pressure fuel pumped from the fuel tank 20 and fed at a predetermined pressure from the high pressure pump 21 is accumulated in the pressure accumulator 22. The accumulated high-pressure fuel is supplied to the fuel injection valve 100 through the fuel inlet pipe 12 a and the fuel inlet passage 12.
When the fuel is not injected, the control valve 9 is positioned below and the control chamber 32 and the leak line 16 are closed, and the pressure of the fuel held in the control chamber 32, that is, the command piston 8 and the needle valve 2 are controlled. The pressure to push down becomes larger than the pressure to push them up, the command piston 8 and the needle valve 2 are located below, and the nozzle hole 4 is closed.

  At the time of fuel injection, when the armature 15a and the control valve 9 are pulled up and opened by the solenoid coil 15, the inside of the control chamber 32 is opened to the leak line 16 and the control chamber 32 is opened. As a result, the high-pressure fuel in the control chamber 32 is discharged to the leak line 16 and a pressure drop in the control chamber 32 occurs. Therefore, the pressure of the high-pressure fuel acting from the lower side of the needle valve 2 overcomes the pressure that presses the command piston 8 downward by the control chamber pressure and the pressure that presses the needle valve downward by the needle valve spring 9a. 2 is separated upward from the seat portion 5a, and the needle valve 2 is opened. The high-pressure fuel in the fuel reservoir 5 is injected from the nozzle hole 4 of the nozzle 1 into the combustion chamber of the engine through the seat portion 5a.

In such a fuel injection valve 100, in this embodiment, the average effective injection pressure during the fuel injection period is increased, and the volume of the fuel passage in the vicinity of the nozzle 1 is increased in order to suppress the pressure pulsation after the needle valve is closed. It has a configuration.
As shown in the enlarged view of the nozzle tip shown in FIG. 2, the fuel sump 5 is formed in a ring shape around the needle valve 2, and the fuel sump 5 is provided with a needle valve step formed on the needle valve 2. It is set as the structure extended from the upper direction of the part 2a to the suck part 1a vicinity. The thickness of the sack portion 1a of the nozzle 1 is set based on the material and structural strength conditions. At this time, it is preferable to set the lower end position of the fuel reservoir 5 by reducing the thickness of the sac portion 1a so that the strength of the sac portion 1a can be maintained. The upper end position of the fuel sump 5 is set above the needle valve stepped portion 2a, and preferably the length that the reciprocating sliding of the needle valve 2 is stably guided by the inner peripheral hole 1b of the nozzle 1 is secured. On the upper side, the upper end position of the fuel reservoir 5 may be set as high as possible. The reason why the upper end position of the fuel reservoir 5 is located above the needle valve stepped portion 2a is to push up the needle valve 2 by the pressure in the fuel reservoir 5 when the needle valve is opened.

  On the other hand, the diameter of the fuel reservoir 5 is preferably formed such that the ratio of the diameter Db of the fuel reservoir 5 to the diameter Da of the needle valve 2 is Db / Da = 2 or more. More preferably, the radial thickness of the nozzle 1 is preferably made as thin as possible based on the material and structural strength conditions, and the diameter of the fuel reservoir 5 is increased. At the time of manufacturing the nozzle 1, it is preferable to form the nozzle inner peripheral hole 1b and positively form the fuel reservoir 5 so as to obtain a predetermined volume, and then manufacture the fuel passage 14a and the fuel reservoir 5 in communication with each other. .

Thus, by forming the fuel reservoir 5, a large volume of the fuel reservoir 5 can be secured, the pressure of the sack portion 1a can be maintained at a higher pressure, and the average effective injection pressure during the fuel injection period can be increased. Good combustion can be achieved. This also makes it possible to suppress pressure pulsation after the needle valve is closed.
Furthermore, it is preferable to form the fuel reservoir 5 in a shape having a cylindrical portion 5b in the nozzle axis direction. This is because the diameter and the axial length of the fuel reservoir 5 are limited in terms of strength conditions as described above. Therefore, by forming the fuel reservoir 5 in a cylindrical shape along the cylindrical shape of the nozzle 1, The volume of the reservoir 5 can be maximized, and the pressure of the sack portion 1a can be maintained at a higher pressure.

  The fuel injection valve of the present invention increases the average effective injection pressure during the fuel injection period to achieve good combustion, and can suppress pressure pulsation after the needle valve is closed. Can be suitably used.

It is sectional drawing which follows the axial center line of the fuel-injection apparatus which concerns on embodiment of this invention. It is an enlarged view of the nozzle front-end | tip part of the fuel-injection apparatus which concerns on embodiment of this invention. It is an enlarged view of the nozzle front-end | tip part of the conventional fuel injection apparatus. It is sectional drawing which follows the axial center line of the conventional fuel injection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle 1a Suck part 1b Nozzle inner peripheral hole 2 Needle valve 2a Needle valve stepped part 4 Injection hole 5 Fuel reservoir 5a Seat part 5b Cylindrical part 7 Injection valve body 8 Command piston 9 Control valve 20 Fuel tank 21 High pressure pump 22 Accumulator 100 Fuel injection valve

Claims (3)

A fuel injection valve supplied with fuel discharged from a high-pressure pump and accumulated in an accumulator,
The fuel injection valve includes a needle valve that opens and closes a nozzle hole formed at a nozzle tip, a command piston that reciprocates integrally with the needle valve, and a fuel that supplies the fuel to a fuel reservoir that communicates with the nozzle hole. A passage, and a control chamber formed behind the command piston and into which fuel branched from the fuel passage is introduced,
The fuel reservoir is formed in a ring shape around the needle valve, and the fuel reservoir extends from above the needle valve stepped portion formed in the needle valve to the vicinity of the sack portion of the nozzle tip. A fuel injection valve for an accumulator fuel injection device.   2. The accumulator fuel injection according to claim 1, wherein the fuel reservoir is formed so that a ratio of a diameter Db of the fuel reservoir and a diameter Da of the needle valve is Db / Da = 2 or more. The fuel injection valve of the device.   3. The fuel injection valve of a pressure accumulating fuel injection device according to claim 1, wherein the fuel reservoir is formed in a shape having a cylindrical portion in a nozzle axial direction.

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