JPH01195968A - Fuel injection valve of internal combustion engine - Google Patents

Abstract

PURPOSE:To execute the injection operation at the low injection rate in the early stage of an injection process by mounting a valve body assembly having a nozzle body at the end thereof, placing a needle valve, a nozzle spring, a differential piston, a fuel passage, an operating chamber and an oil pressure chamber inside this assembly and communicating the operating chamber with the oil pressure chamber. CONSTITUTION:In the early stage of an opening process of a needle valve 20, said valve 20 moves from the fully closed position to the fully open position, having the throttle effect on fuel. During said movement, there is a time delay between the point at which the oil pressure reaches the oil pressure chamber 27 of a differential piston 23 and the print at which the oil pressure reaches the operating chamber 26 of the needle valve 20 so that the oil pressure in the oil pressure chamber 27 becomes higher than that in the operating chamber 26. Since the operating chamber 26 is in the proximity of a jet 31 and the open position of the needle valve 20 is increased gradually, the increasing rate of pressure in the operating chamber 26 is lower than that in the oil pressure chamber 27. The opening action of the needle valve 20 is therefore restrained to move at a relatively low speed. As a result, in the early stage of the action the fuel injection rate is low and the slight quantity of fuel is injected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel injection valve used in an internal combustion engine such as a diesel engine, and in particular to a fuel injection valve with improved fuel injection characteristics and needle valve movement characteristics. The target is

[Prior Art] Generally, in this type of fuel injection valve, it is desirable to increase the fuel injection pressure in order to improve the combustion performance of the engine, and for this purpose, it is necessary to set the valve opening pressure high. On the other hand, in order to increase the durability of the needle valve and valve seat, it is necessary to set the valve closing pressure low to reduce the impact when the needle valve seats on the valve seat.

As a technology that satisfies these conditions,
There is a structure described in No. 48. In this structure, a hydraulic damper is configured using a spring receiver of a nozzle spring, and the force applied to the needle valve during the valve closing operation is limited by the hydraulic damper.

[Problems to be Solved by the Invention] However, in this structure, it is necessary to provide a large volume part in the middle of the fuel passage as a hydraulic chamber for the hydraulic damper, and this part exerts a pressure accumulation effect on the fuel. Therefore, there is a time lag between the pressure change of the fuel supplied to the fuel injection valve (change in inlet pressure) and the actual injection operation at the nozzle, making it difficult to accurately control the injection operation. There are cases.

In addition, as a technology that satisfies the above conditions, Japanese Patent Application Laid-Open No. 60-1
There is also a structure described in No. 22269. In this structure, a differential piston (plunger) is provided that is energized by fuel oil pressure, and the differential piston applies a force in the closing direction to the needle valve mainly during the valve opening operation (i.e., increases the valve opening starting pressure). power) is now being effectively exerted.

However, in the structure described in JP-A-60-122269, the injection rate increases rapidly at the same time as the valve starts to open, and the injection operation with a low injection rate is performed in the initial stage. do not have. Therefore, the combustion characteristics of the engine cannot be sufficiently improved.

Furthermore, with this structure, in order to rapidly increase the injection rate at the same time as the valve starts to open as described above, during the valve opening operation, the increase in the volume of the fuel passage due to the rise of the needle valve is replaced by the increase in the volume of the fuel passage due to the protrusion of the differential piston into the fuel passage. It is configured to offset the reduction in the volume of the passage (Line 16 of the lower right column on page 477 of the publication)
20 lines).

However, according to this structure, in order to effectively realize the above-mentioned offset effect, it is essential to increase the volume of the fuel passage, as will be explained in detail below.

That is, even in the above prior art structure, the nozzle spring is provided as the main closing force applying means, and the differential piston is a so-called auxiliary closing force applying means, so its cross-sectional area (pressure-receiving area) is equal to the cross-sectional area of the needle valve. sufficiently smaller than the area
(for example, about 1/2 or less), and if the cross-sectional area of the differential piston is set to a value close to the cross-sectional area of the needle valve,
It becomes impossible to remove the needle valve from the valve seat. In this way, there is a difference in the pressure receiving area between the needle valve and the differential piston, and it is therefore inevitable that there is also a difference in the moving volume between the two.

Despite such a large volume difference, in order to obtain the effect of canceling out the volume change as described above, it is generally necessary to increase the volume of the entire fuel passage and increase the volume change rate of the entire fuel passage (the volume change rate of the entire fuel passage). It is necessary to make the ratio of the volume difference to the volume as small as possible.

Considering this point and considering the structure described in JP-A-60-122269, although it is not clearly stated in the specification, the drawing shows that in the vicinity of the operating piston (central plunger), A structure is described in which a fuel passage section that is much wider than other passage sections is formed over a long range.

From the contents of this drawing and the above explanation, it is clear that this prior art also adopts a structure in which the passage volume is expanded.In other words, in order to obtain the effects described in this publication, It is clear that it is essential to set the passage volume to be significantly larger than the volume required for the original transport function of the passage. Therefore, similarly to the structure described in Utility Model Publication No. 53-648, the structure described in this publication has a large volume fuel passage that exerts a pressure accumulation effect on the fuel, making it difficult to accurately control the injection operation. There are cases where

The present invention aims to provide a structure that solves the problem 1. More specifically, the present invention uses a differential piston to set the valve opening pressure higher than the valve closing pressure, and It is an object of the present invention to provide a fuel injection valve that can perform an injection operation at a low injection rate in the initial stage of the injection operation, and can make the volume of the fuel passage as small as possible.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a generally cylindrical valve body assembly having a nozzle body at its tip, and includes a nozzle nozzle of the nozzle body inside the valve body assembly. A needle valve that opens and closes the
A nozzle spring that biases the needle valve in the closing direction, a differential piston that connects to the needle valve, a fuel passage that extends from the outlet of the external high-pressure oil supply passage to the nozzle, and a hydraulic pressure that applies hydraulic pressure to the needle valve in the opening direction. and a hydraulic chamber for applying hydraulic pressure in the needle valve closing direction to the differential piston, and the working chamber and the hydraulic chamber are communicated with the fuel passage, and in the initial stage of the needle valve opening operation, the needle valve moves from the fully open position to the fully open position while exerting a throttling action on the fuel, and when the above initial stage is completed and the needle valve reaches the fully open tiL position, the increase rate of the fuel injection rate is higher than the rate of increase in the fuel injection rate at the above initial stage. It is characterized by the fact that the fuel injection rate rises to its highest value at an increasing rate.

The hydraulic chamber for the differential piston may be provided at a position separate from the fuel passage, and a throttle may be provided between the two.

[Operation] According to the above structure, in the initial stage of the needle valve opening operation,
The needle valve moves from the fully open position to the fully open position while exerting a throttling effect on the fuel, but in this operation, there is a time delay before the oil pressure that reaches the hydraulic chamber of the differential piston reaches the working chamber of the needle valve. occurs, and the oil pressure in the hydraulic chamber becomes higher than the oil pressure in the working chamber.

In addition, since the working chamber is close to the nozzle from which fuel is spouted, and the opening degree of the needle valve gradually increases (i.e., the flow path area and flow coefficient of the nozzle part change in a direction that promotes the flow of fuel). ), the rate of pressure increase in the working chamber (pressure increase value per unit time) is lower than the rate of pressure increase in the hydraulic chamber.

For these reasons and other reasons, the opening operation of the needle valve is restricted, and the needle valve moves at a relatively low speed. As a result, a small amount of fuel is injected at a low fuel injection rate (injection amount per unit time) in the initial stage, that is, until a certain period of time has passed after the needle valve starts opening.

When the initial stage is completed and the needle valve reaches the fully open position, the fuel injection rate increases to the maximum value at a higher rate of increase (that is, rapidly) than the rate of increase in the injection rate at the initial stage. Such operations occur as a result of the operations at the initial stage described above. That is, after the initial stage is completed, the opening degree of the needle valve does not increase (that is, the flow path area and flow coefficient of the nozzle part do not change in a direction that promotes the flow of fuel), and the fuel is supplied to the fuel passage. The oil pressure and amount of fuel used will continue to increase after the initial stage is over. Furthermore, at the end of the initial stage, the oil pressure upstream of the valve seat has been increased as a result of the throttling operation of the needle valve up to that point. As a result, when the initial stage is completed, high-pressure fuel flows through the working chamber to the injection hole, and the fuel injection pressure at the nozzle and fuel injection rate (injection amount per unit time) rapidly rise to a predetermined maximum value. .

The fuel injection pressure and fuel injection rate thus increased to their maximum values are maintained for a predetermined period of time, and this operating phase becomes the main injection phase.

The main injection phase ends with a reduction in the supply pressure to the fuel injector. The stage in which the injection rate drops from the maximum value to zero is called the late injection stage. In this latter injection stage, the needle valve is quickly moved in the closing direction by the hydraulic pressure in the hydraulic chamber and the elasticity of the nozzle spring, and as a result, the fuel injection operation is abruptly stopped after the main injection is completed. That is, the injection operation can be completed without dripping. However, when the needle valve moves to just before the closed position, the oil pressure in the hydraulic chamber of the differential piston has significantly decreased, so the needle valve is seated on the valve seat almost only by the force of the nozzle spring. Therefore, the force with which the needle valve collides with the valve seat is small, and as a result, wear and tear on the needle valve and the valve seat are effectively prevented.

[In FIG. 1 of the embodiment, the fuel injection valve of the cylinder head 1 is installed by fitting the sleeve 3 into the hole 2 in a fixed state, and fitting the valve body assembly 5 of the fuel injection valve into the sleeve 3 and fixing it. has been done. The valve body assembly 5 is generally cylindrical in its entirety;
The cylinder is arranged in such a manner that its center line O-0 is parallel to the cylinder center line, for example.

In the valve body assembly 5, a nozzle body 8 is seated at the tip of the valve body 6 with an interpiece 7 sandwiched therebetween, and these are integrally fixed by a case nut 9. A screw hole 10 is provided at the base end of the valve body 6. The screw hole 10 has a differential piston body 11 (
The threaded portion of the inlet fitting 12 is screwed together and fixed in a state in which the casing) is fitted. The inlet fitting 12 protrudes outward from the valve body 6, and a high pressure fuel pipe 13 is connected to the protruding end thereof.
outlet is connected. The inlet of the high pressure fuel pipe 13 is connected to a fuel injection pump (not shown).

In addition to the above-mentioned parts, an outlet fitting 15 is attached to the valve body 6 in parallel with the inlet fitting 12 in the vicinity of the inlet fitting 12 . One end of the outlet fitting 15 is screwed into a threaded hole in the valve body 6, and the other end is connected to an inlet of an external oil leak pipe 16.

Each of the above parts constituting the valve body assembly 5 is aligned with the center line O.
It is a cylindrical body extending concentrically or parallel to -0. A needle valve 20 is housed inside the nozzle body 8, and the valve body 6
A spring receiver 21 and its extension part 22 are housed inside,
A differential piston 23 is housed inside the differential piston body 11. The needle valve 20, the spring receiver 21 (and the extension part 22 integrated therewith), and the differential piston 23 are composed of separate parts, and are concentrically connected at adjacent ends by a concave-convex fitting part. There is.

The needle valve 20 has a conical tip surface seated on an annular and tapered valve seat 24 formed on the inner periphery of the nozzle body 8. In order to control the opening and closing operations of the needle valve 20 relative to the valve seat 24, a nozzle spring 25, an operating chamber 26, and a hydraulic chamber 27 are provided.

The spring receiver of the nozzle spring 25 is provided around the extension part 22, and one end is seated on the spring receiver 21, and the other end is seated on an annular step provided on the inner peripheral surface of the valve body 6. Working chamber 2
Reference numeral 6 is formed by four annular portions on the inner peripheral surface of the nozzle body 8, and surrounds the intermediate portion of the needle valve 20 in the longitudinal direction. Needle valve 20
The distal end portion has a smaller diameter than the proximal end portion, and the tapered outer circumferential surface formed between the drawing portions faces the working chamber 26. The hydraulic chamber 27 is formed by a shallow (short length in the direction of the center line O-) circular cross-sectional depression formed in the end surface of the differential piston body 11 on the inlet fitting 12 side.

The elasticity of the nozzle spring 25 and the hydraulic pressure inside the hydraulic chamber 27 relative to the differential piston 23 act in a direction to close the needle valve 20. Also, the hydraulic pressure in the working chamber 26 is controlled by the needle valve 2.
0 in the direction of opening the needle valve 20.

The fuel passage 30 has an inlet connected to an internal passage of the high pressure fuel pipe 13, and an outlet connected to a nozzle 31 formed at the tip of the nozzle body 8. Specifically, the fuel passage 30 is configured as follows.

The center hole of the inlet fitting 12 forms a fuel passage portion extending from the outlet of the high pressure fuel pipe 13 to the hydraulic chamber 27. A hydraulic chamber 27 is provided in a portion near the outer periphery of the differential piston body 11.
A passage hole is formed that extends from the valve body to the joint surface with the valve body 6. A series of passage holes that are connected to the passage in the differential piston body 11 and extend to the working chamber 26 are formed in portions of the valve body 6, the interpiece 7, and the nozzle body 8 near the outer periphery. Further, the passage portion on the downstream side of the hydraulic chamber 27 includes an annular gap between the inner circumference of the nozzle body 8 and the small diameter portion of the needle valve 20, a gap between the valve seat 24 and the needle valve 20, and a gap between the valve seat 24 and the needle valve 20. , is formed by an internal space (sac portion 32) at the tip of the nozzle body 8.

According to the above structure, fuel injection is performed at a relatively low injection rate in the initial stage Tl (time interval), as shown in FIG. 2, which shows the relationship between time and injection rate.

In the subsequent main injection phase T2, the injection rate rapidly increases to reach a predetermined maximum value and remains there. In the latter injection stage T3, the injection rate drops rapidly and injection stops.

In order to perform injection with such characteristics, each part shown in FIG. 1 is configured to operate as follows.

In the initial stage Tl of the needle valve opening operation, the needle valve 20 exerts a throttling action on the fuel while changing from the fully open position (the position where the tip is seated on the valve seat 24) to the fully open position (the large diameter proximal end of the needle valve 20 is move to a position where it abuts the end surface of the interpiece 7). In this operation, the hydraulic chamber 2 near the fuel high pressure pipe 13
The oil pressure of No. 7 rises temporally earlier than the oil pressure of the working chamber 26, and the oil pressure of the hydraulic chamber 27 becomes higher than the oil pressure of the working chamber 26 at the same time. Further, the working chamber 26 has a nozzle 31
close to. Moreover, since the opening degree of the needle valve 20 gradually increases, the rate of pressure increase in the working chamber 26 (pressure increase value per unit time) is lower than the rate of pressure increase in the hydraulic chamber 27.

For these reasons, etc., the opening operation of the needle valve 20 is restricted,
Move at relatively low speed. As a result, injection is performed at a low injection rate in the initial stage. However, since the injection pressure corresponds to the sum of the elasticity of the nozzle spring 250 and the hydraulic load applied to the differential piston 2, it is not possible to operate the needle valve with a conventional device that does not include the differential piston 23, that is, with only the nozzle spring. Compared to a closed structure, the pressure of the fuel supplied to the nozzle 31 is generally higher at the start of injection, and the fuel is injected at a higher pressure.

When the initial stage Tl is completed and the needle valve 20 reaches the fully open position, the opening degree of the needle valve 20 does not increase (that is, the flow path area and flow coefficient of the nozzle section change in a direction that promotes the flow of fuel). (No), and the oil pressure and amount of fuel supplied from the fuel high pressure pipe 13 continue to increase thereafter. Moreover, the initial stage T
At the stage when l has ended, the oil pressure upstream of the needle valve 20 has been increased as a result of the throttling operation of the needle valve 20 up to that point. As a result, when the initial stage TI ends, high-pressure fuel flows to the injection port 31, and the fuel injection pressure and fuel injection rate at the injection port 31 rapidly increase to a predetermined maximum value and are maintained for a predetermined time.

The main injection phase T2 ends with a decrease in the supply pressure to the fuel injector. At this stage, the needle valve 20 is quickly moved in the closing direction by the oil pressure in the hydraulic chamber 27 and the elasticity of the nozzle spring 25, and as a result, the fuel injection operation is abruptly stopped after the main injection is completed. That is, the injection operation can be completed without dripping. However, needle valve 20
When the needle valve 20 moves to just before the closed position, the oil pressure in the hydraulic chamber 27 has decreased significantly, so the needle valve 20 is seated on the valve seat 24 almost only by the force of the nozzle spring 25. Therefore, the force with which the needle valve 20 collides with the valve seat 24 is small, and as a result, wear and damage to the needle valve 20 and the valve seat 24 are effectively prevented.

[Effects of the Invention] As explained above, according to the present invention, the above-described injection rate change characteristics shown in FIG. 2 can be obtained, and the injection pressure can be increased. Moreover, the collision force between the needle valve 20 and the valve seat 24 during the valve closing operation can be set to be small. Therefore, it is possible to improve the operating performance of the engine and to obtain a fuel injection valve with excellent durability.

Furthermore, since fuel injection is performed at a low injection rate at the initial stage of the fuel injection operation, the injection rate is rapidly increased at the same time as the injection operation starts, as in the structure described in Japanese Patent Application No. 60-122269. There is no need for a structure to increase the overall volume of the fuel passage (that is, a device to increase the volume of the entire passage to obtain a volume offset effect). This makes it possible to eliminate the pressure accumulation effect due to the passage by making it as small as possible within the range where it is possible to accurately control the injection operation.

[Another Embodiment] In the above-described structure, the extension portion 22 extending in the needle valve opening/closing direction (direction parallel to the center line OO) and the differential piston 23 are formed as separate parts. Both are connected by a concave-convex fitting portion having a simple structure, and the differential piston 23 is in a state where it can be separated from the extension portion 22 in the needle valve opening/closing direction. The differential piston 24 is located on the opposite side of the needle valve 20 with the spring receiver 21 and its extension 22 interposed therebetween. If such a structure is adopted in an overflow type injection device, the following problems may occur regarding the responsiveness of the injection operation.

That is, in an overflow type injection device, a suction-back stroke necessarily exists. Therefore, if the structure shown in FIG. 1 is used as is, the hydraulic chamber 27 will be in a negative pressure state during the suction and return stroke, and the differential piston 23 will float up to the inlet fitting 12 side by itself, and in this state, the next fuel injection cycle is started.

As a result, even if a pressure wave of fuel reaches the hydraulic chamber 27, immediately after that, the differential piston 23 simply runs idly toward the extension part 22, and after the differential piston 23 is connected to the extension part 22, Otherwise, the differential piston 23 will not initiate any substantial fuel control operation. Therefore, there is a delay in the opening operation of the needle valve 20 in response to an external fuel supply operation, and such a delay becomes a problem particularly in high-speed operating conditions.

In order to solve such problems, the structure shown in FIG. 1a is adopted.

In FIG. 1a, an annular notch 28 is provided in the center of the end face of the inlet fitting 12 facing the differential piston 23, and an auxiliary spring 29 (compression coil spring) is provided between the notch 28 and the hydraulic chamber 27. is the provision. The auxiliary spring 29 is a weak compression coil spring, and both ends are the end face of the differential piston 23 and the annular bottom (step) of the notch 28.
As mentioned above, the differential piston 2
3 from floating away from the extension part 22.

Therefore, with the structure shown in FIG. 1a, it is possible to prevent a delay in the operation of the needle valve 20 with respect to the fuel supply operation from the fuel injection pump.

The embodiment shown in FIG. 3 differs from the embodiment shown in FIG. 1 only in the structure relating to the differential piston 23 and the hydraulic chamber 27. In the structure shown in FIG. 3, the hydraulic chamber 27 has a small diameter and has the same diameter as the other hole in the center of the differential piston body 11. The fuel passage 30 is provided at a position avoiding the hydraulic chamber 27. Furthermore, an annular groove 3 that communicates with the fuel passage 30 is provided on the end surface of the inlet fitting 12 that is joined to the differential piston body 11.
5 is a provision. One end of a passage hole 36 is connected to the groove 35 at a position remote from the fuel passage 30. The other end of the passage hole 36 opens into the inner peripheral surface of the differential piston body 11 at an intermediate portion of the differential piston body 11 . A throttle passage 37 is connected to the opening. Throttle passage 37
is formed by a narrow gap between the inner circumference of the differential piston body 11 and the outer circumference of the differential piston 23. Throttle passage 37
In order to form this, the differential piston 23 is provided with an annular step 38 on the outer periphery of the longitudinally intermediate portion, and the part closer to the hydraulic chamber 27 than the step 38 has a slightly smaller diameter than the part closer to the extension 22. It becomes.

In the embodiment shown in FIG. 3, when the needle valve 20 moves in the opening direction, the differential piston 23 pushes out the fuel in the hydraulic chamber 27 to the passage hole 36 through the throttle passage 37, and this resistance causes the needle valve to move. 20 in the opening direction is further restricted, and the rate of increase in the injection rate at the initial stage is further reduced.

The embodiment of FIG. 4 is basically the same as the embodiment of FIG. 3, but differs in its throttle passage structure. A thin flat plate 40 is interposed between the differential piston body 11 and the inlet fitting 12, and a small diameter hole is formed in the center of the flat plate 40, that is,
A throttle passage 41 is formed. The hydraulic chamber 27 is connected to the fuel passage 30 via a throttle passage 41. In the embodiment shown in FIG. 4, the hydraulic chamber 27 is formed at the end of the center hole of the differential piston body 11, as in the embodiment shown in FIG. is constant.

The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. 1 basically only in the structure of the inlet side portion of the fuel passage 30. In the embodiment shown in FIG. 5, in place of the inlet fitting 12 shown in FIG. 1, a holding fitting 50 without a center hole is fixed to the valve body 6. The inlet fitting 51 (high pressure pipe joint) is attached to a hole provided on the outer periphery of the longitudinally intermediate portion of the valve body 6 at right angles to the center line O-O. The fuel passage 30 branches inside the valve body 6 from near the inlet fitting 51 to the working chamber 26 side and the hydraulic chamber 27 side. The hydraulic chamber 27 is formed by a shallow recess formed in the end face of the presser metal fitting 50. Further, although not clearly shown, the presser fitting 50 also serves as an outlet fitting.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 1a is a partial sectional view of another embodiment, and FIG. 2 is a graph schematically showing the injection characteristics of the fuel injection valve of the embodiment of FIG. Figure 3, Figure 4,
FIG. 5 is a cross-sectional view of yet another embodiment. 5... Valve body assembly, 6... Valve body, 8... Nozzle body, 20... Needle valve, 23... Differential piston,
25... Nozzle spring, 26... Working chamber, 27
...Hydraulic chamber, 30...Fuel passage, 31...Nozzle port,
37... Throttle passage patent applicant Yanmar Diesel Co., Ltd. Procedural amendment (voluntary) December 20, 1988 Commissioner of the Japan Patent Office Tono 1, Indication of matter f [1988 Patent Application No. 210/18 2 , Name of the invention Fuel injection device for internal combustion engine 3, Relationship with the case to be amended Address of applicant 1-32 Chayamachi, Kita-ku, Osaka Name (678) Representative of Yanmar D-Pill Co., Ltd. Representative Director Atsushi Yamaoka 1, Agent Address 7th Floor, East Building, Chiyoda Building, 2-9-4 Higashitenma, Kita-ku, Osaka (530 Yutaka) Telephone: Osaka (06) 353-1635 (□) 1
. Name (0525) Patent attorney Tadashi Tadashi: 5,
Date of amendment order (starting point) Showa year, month, day 6, number of claims increased by amendment 7, subject of amendment Specification () 竪 工 n) d column (1) Amend the scope of claims as shown in the attached sheet do. (2) In the specification, page 81, line 3, "fuel injection valve" is corrected to "fuel injection device." (3) "Fuel injection valve" on page 2, line 19 is corrected to "fuel injection valve in a fuel injection device." (4) Add "in the fuel injection system" after "improved" on page 2, line 20. (5) Add "in fuel injection device" next to "this kind" on page 3, line 3. (6) On page 3, line 10, add "in a fuel injection device" after "such". (7) On page 3, line 20, add "in the fuel injection system" after "for that purpose." (8) Add "in the fuel injection device" after "also," on page 4, line 4. (9) On page 7, line 5, add ``in fuel injection equipment'' next to ``can be made smaller.'' (10) "External...extends" on page 7, lines 13-14.
is corrected as "high pressure that causes high pressure fuel to act on the differential piston". (11) "Connected to the fuel injection pump" on page 11, line 16 of the same page is corrected to "communicated with the plunger for pressure feeding of high-pressure fuel of the fuel injection pump." (12) On page 12, line 8, after "inside" add "communicated with the plunger of the fuel injection pump". (13) "Device" in line 2 of page 16 is corrected to "fuel injection device." (14) "External" in line 10 of page 19 is corrected to "plunger of fuel injection pump." (15) "Fuel injection pump" in lines 5 and 6 on page 20 is corrected to "plunger of fuel injection pump." (16) Add the following statement between lines 17 and 18 on page 22. ``In addition, the high-pressure fuel passage for applying high-pressure fuel to the differential piston in the fuel injection device for an internal combustion engine of the present invention may be appropriately designed in the same manner as those employed in various types of fuel injection devices that are self-evident. Claim 1 provides a generally cylindrical valve body assembly having a nozzle body at its tip, and a needle valve for opening and closing a nozzle of the nozzle body and a needle valve inside the valve body assembly. Closed 11h. a nozzle spring that biases the needle valve in the opening direction; a differential piston that connects to the needle valve; a high-pressure fuel passage that applies high-pressure fuel to the differential piston; an operating chamber that applies hydraulic pressure in the opening direction to the needle valve; A hydraulic chamber for applying hydraulic pressure in the direction of closing the needle valve is provided on the movable piston, and the working chamber and the hydraulic chamber are communicated with the fuel passage, so that in the initial stage of the needle valve opening operation, the needle valve throttles the fuel. The needle valve moves from the fully open position to the fully open position while exerting an action, and when the above initial stage is completed and the needle valve reaches the fully open position, the fuel injection rate increases at a higher rate of increase than the rate of increase in the fuel injection rate at the above initial stage. A fuel injection device for an internal combustion engine, characterized in that the fuel injection device is configured to increase fuel injection to a maximum value. 2. The fuel injection system for an internal combustion engine according to claim 1, wherein the hydraulic chamber for the differential piston is provided at a position apart from the fuel passage, and a throttle is provided between the two. 3. A fuel injection system for an internal combustion engine according to claim 1 or 2, wherein only the hydraulic pressure in the hydraulic chamber is used as means for urging the differential piston in the needle valve closing direction. 4. The spring receiver of the nozzle spring is provided with an extension extending in the opening/closing direction of the needle valve, the differential piston is formed as a separate part from the extension, and the differential piston is formed of the spring receiver and the extension. The differential piston is sandwiched and positioned on the opposite side from the needle valve, and the differential piston and the end of the extension portion adjacent thereto are connected in a direction that allows them to separate from each other along the opening/closing direction, and the piston is connected to the differential piston in the needle valve closing direction. 2. The fuel injection device for an internal combustion engine according to claim 1, further comprising an auxiliary spring for urging.

Claims (4)

[Claims] 1. A generally cylindrical valve body assembly having a nozzle body at its tip is provided, and inside the valve body assembly are a needle valve that opens and closes the nozzle of the nozzle body, a nozzle spring that biases the needle valve in a closing direction, and a needle valve that biases the needle valve in a closing direction. A differential piston to be connected, a fuel passage extending from the outlet of an external high-pressure oil supply passage to the nozzle, an operating chamber for applying hydraulic pressure in the direction of opening the needle valve, and a hydraulic pressure applying the hydraulic pressure in the direction of closing the needle valve to the differential piston. The working chamber and the hydraulic chamber are communicated with the fuel passage, and in the initial stage of the needle valve opening operation, the needle valve moves from the fully closed position to the fully open position while exerting a throttling action on the fuel. When the needle valve reaches the fully open position after the initial stage is completed, the fuel injection rate increases to the highest value at a higher rate of increase than the rate of increase in the fuel injection rate at the initial stage. A fuel injection valve for an internal combustion engine characterized by: 2. 2. The fuel injection valve for an internal combustion engine according to claim 1, wherein the hydraulic chamber for the differential piston is provided at a position apart from the fuel passage, and a throttle is provided between the two. 3. 3. The fuel injection valve for an internal combustion engine according to claim 1, wherein only the hydraulic pressure in the hydraulic chamber is used as a means for urging the differential piston in the needle valve closing direction. 4. The spring receiver of the nozzle spring is provided with an extension extending in the opening/closing direction of the needle valve, the differential piston is formed as a separate part from the extension, and the differential piston is sandwiched between the spring receiver and the extension. located on the opposite side from the needle valve, connecting the differential piston and the end of the extension portion adjacent thereto in a direction that allows them to separate from each other along the opening/closing direction, and urging the differential piston to move the piston in the needle valve closing direction. The fuel injection valve for an internal combustion engine according to claim 1, further comprising an auxiliary spring connected to the fuel injection valve.