JPS6371560A - Accumulator fuel injector - Google Patents

Abstract

PURPOSE:To prevent occurrence of fuel injection quantity error completely, by employing a spool valve as an inlet valve for a plunger chamber and providing means for energizing the inlet valve to one end side at the other end of the spool chamber. CONSTITUTION:An injection valve 3 is provided at the end section of a fuel path 2. While an inlet valve 18 for communicating/interrupting the inlet side of a plunger chamber 10 is provided. A path 26 arranged with a check valve 25 for blocking the counter flow from the plunger chamber 10 is provided from one end of a spool chamber 17 to the plunger chamber 10. Means 33 for energizing the inlet valve 18 to one end side is provided at the other end side of the spool chamber 17. The inlet valve 18 is closed when the inner pressure of the pluger chamber increases to a predetermined level so as to enable setting of valve close timing independently from the operating speed fo engine. Consequently, fuel injection error due to variation of the operating speed can be prevented completely.

Description

[Detailed description of the invention] <Industrial use bone 1! f〉 The present invention relates to a pressure accumulation type fuel injection device used in a diesel engine, etc., and particularly relates to a pressure accumulation type fuel injection device used in a diesel engine, etc. This invention relates to a foil pressure type fuel injection nostle that eliminates control errors.

(Prior art) Generally, a fuel pump that pressurizes fuel into a fuel injection nozzle is composed of a plunger pump, which pumps 311 ft of fuel at a predetermined pressure in accordance with the engine speed in a metered amount. configured to dispense.

Therefore, there is a problem in that the stroke of the plunger changes depending on the discharge amount, and a gap is created between the plunger and the cam or rocker arm that drives the plunger, resulting in impact noise.

In order to solve this problem, there are some devices in which a spring is interposed in the drive system that drives the plunger so that the plunger is always in contact with the cam or the rocker arm.

However, in this case, other problems arise such as the strokes of the plunger being distorted due to vibrations of the spring and vibrations of the driving system such as the mouth and the 7-car arm.

Therefore, a pressure accumulator is provided upstream of the plunger chamber via an inlet valve that opens when the pressure is below a predetermined pressure, that is, the discharge pressure of the plunger, and closes thereafter. It has been proposed to install a check valve upstream.

For example, as shown in FIG. 8, an injection valve 3 for opening and closing the fuel passage 2 is provided at the terminal end of the fuel passage 2 formed in the main body 1, and a check valve 4 for preventing backflow is provided in the middle. As an injection pump connected to a pressure accumulation type nozzle in which a pressure accumulation chamber 5 is formed between the injection valve 3 and the check valve 4, a plunger chamber 10 connected to the flow side of the check valve 4 is used. ,
A plunger 9 that enters and exits the plunger chamber 10 and an inlet valve 35 that connects and disconnects the inlet side of the plunger chamber 10 are installed, and a pressure accumulation chamber 3G is connected further upstream of the inlet valve 35. In this case, a check valve connected further upstream of the pressure accumulation chamber 36 is provided outside the main body 1 and is therefore not shown.

Conventionally, the inlet valve 35 is usually composed of a seat valve.

In this case, after discharging fuel from the plunger chamber 10, when the plunger 9 retreats to the top dead center, fuel is pressurized from the pressure accumulation chamber 36 into the plunger chamber 10 to completely return the plunger 9 to the top dead center, and then When the plunger 9 descends from the second dead center, the fuel flows back into the pressure accumulation chamber 36 from the plunger chamber 10 at a pressure lower than the discharge pressure. When the amount of fuel flowing back from the plunger chamber 10 reaches the amount that was sent from the pressure accumulation chamber 36 to the plunger chamber 0, the internal pressure of the plunge chamber 10 reaches the discharge pressure and the large mouth valve is closed. , plunger chamber 1
Discharge starts from 0.

When the large mouth valve 35 is constituted by a seat valve in this way, the large mouth valve 35 is closed when the internal pressure of the plunger chamber 10 rises due to pushing of the plunger 9, and the plunger chamber 10 is closed.
The check valve 4 is opened with an internal pressure of 0, and the fuel pack 1 is press-fitted into the pressure accumulation chamber 5.

<Problems to be Solved by the Invention> By the way, when the large mouth valve 35 is constituted by a seat valve as described above, when the inlet valve 35 is closed, the plunger chamber 10 side and the upstream side of this valve are connected. A pressure gradient occurs between the two, and this pressure gradient causes the inlet valve 35 to rev l-ff1.
The maximum lift amount of the inlet valve 35 must be set in consideration of the above. However, it is known that the pressure gradient described above changes depending on the operating speed of the engine, and becomes larger as the engine speed increases.

In this way, it is extremely difficult to appropriately set the maximum lift I amount of the inlet valve 35 in response to the pressure gradient that varies depending on the engine speed. There is a problem in that the injection amount increases, and in the low-speed operation region, the closing of the large mouth valve 35 is delayed and the injection amount becomes insufficient.

The present invention has been made in consideration of the above-mentioned circumstances, and is a pressure accumulating fuel that allows a large mouth valve to be closed accurately in accordance with the internal pressure of the plunger chamber, regardless of the operating speed of the engine. The purpose of this invention is to provide an injection device.

Means for Solving the Problems> In order to achieve the object of item 1, the pressure accumulation type fuel injection device according to the present invention opens and closes the fuel passage formed in the main body at the terminal end of the fuel passage. In a pressure accumulation type fuel injection device that is provided with an injection valve and is configured to have a plunger chamber on the upstream side thereof and a large mouth valve that connects and connects the inlet side of the plunger chamber, the inlet valve is configured with a spool valve, The inlet valve has a hollow hole extending from one end to the middle part, and valve holes opening to the peripheral surface from the inner end and the middle part of the hollow hole, and the inlet valve is located in the middle of the spool chamber in which the inlet valve is accommodated. forming a valve hole connected to the upstream side of the part, and
On one end side thereof, there is another valve hole which is shut off from the valve hole from the middle part of the hollow hole when the large mouth valve is located at the dead center of the other end of the spool chamber, and which communicates with the valve hole at other times. The other valve hole is connected to the plunger chamber, and a passage is provided from one end of the spool chamber to the plunger chamber with a check valve interposed therebetween to prevent backflow from the plunger chamber. The present invention is characterized in that a biasing means for biasing the inlet valve toward one end is provided on the end side.

As the above-mentioned (=1 force means), it is possible to use a spring or external fuel supply pressure.

<Operation of the Invention> According to the present invention, when a backflow occurs from the plunger chamber toward the upstream side through the inlet valve, the flow flows from the valve hole on the plunger chamber side of the spool chamber to the hollow hole through the valve hole of the spool. The spool is moved toward the other end of the spool chamber against the urging means by the pressure of the fuel flowing back. This amount of movement is determined by the balance between the internal pressure of the plunger chamber and the biasing means, and is independent of the pressure gradient that occurs between the upstream and downstream sides of the large mouth valve during backflow. When the inlet valve is located at the dead center on the other end side of the spool chamber, the valve hole on the plunger chamber side of the spool chamber is blocked from the valve hole in the intermediate portion of the hollow hole. Therefore, the inlet valve is closed when the internal pressure of the plunger chamber rises to a constant pressure, and the valve closing timing can be set regardless of the operating speed of the engine.

<Effects of the Invention> As described above, according to the present invention, the internal pressure in the plunger chamber can be fixed when it reaches a set value regardless of the operating speed of the engine, and errors in fuel injection presentation due to changes in operating speed can be prevented. can be completely prevented from occurring.

<Example> An embodiment of the present invention will be described based on the drawings.

1 to 4 are longitudinal cross-sectional views of a unit injector according to an embodiment of the present invention, in which FIG. 1 shows the state immediately before fuel is injected into the pressure accumulator, and FIG. 2 shows the state immediately before fuel is injected into the pressure accumulator. FIG. 3 shows the state during press-fitting, FIG. 3 shows the state during fuel injection, and FIG. 4 shows the state immediately after the injection is completed.

This unit injector U has a plunger pump P built into a main body 1 of a pressure accumulating fuel injection nozzle.The lower inlet of a fuel passage 2 is opened at the bottom of the main body 1, and the lower part of the fuel passage 2 is opened at the center of the main body L. An injection hole 8 is opened at the lower end of the injection pipe 6 that protrudes from the lower surface. A plunger chamber 10 into which a plunger 9 of a plunger pump P is fitted so as to be movable in the fuel passage 2 from the lower part to the injection hole 8;
A check valve 4 is interposed therebetween, and an injection valve 3 is provided at the terminal end of the check valve 4.
is provided. This injection valve 3 consists of a needle valve, and its valve shaft 11 penetrates the earthen wall of the injection pipe 6 and enters a closed valve splash chamber 12 provided at the upper center of the main body 1. A portion of the fuel passage 2 extending from the upper end to the lower end of the injection pipe 6 is formed around the valve shaft 11 . This fuel passage 2
A check valve seat 13 is provided in the second part of the valve shaft 11 in the radial direction, and a check valve 4 that comes into contact with and separates from the lower surface of the check valve seat 13 can slide into the fuel passage 2. is incorporated into. This check valve 4 is urged to close by a valve closing spring 14, and when the check valve 4 is closed, it partitions into a valve closing pressure chamber 15 which communicates the fuel passage 2 with the plunger chamber 10 and a first pressure accumulation chamber 16.

The plunger chamber 10 is formed on one side of the main body 1 parallel to the valve shaft 11, and a spool chamber 17 concentric with the plunger 9 is formed inside the plunger 9 inserted through the opening at its upper end. The spool 18, which is slidably housed in the spool chamber 17, has a center hole 19 extending from its lower end surface to an intermediate height. The perpendicularly extending valve holes 20,21 are each opened. On the other hand, at an intermediate height of the peripheral wall of the plunger 9, when the spool 18 is located at the two-way point, the valve holes 20, 2+ are blocked, and at other times, the valve holes 20 and 2+ are closed.
, 21 are provided. This valve hole 22 is connected to the lower inlet of the fuel passage 2, and the valve hole 23 is connected to the pressure chamber 24 defined at the lower end of the plunger chamber 10.
! I'll let you through.

The other pressure chamber 24 is connected to the valve-closing pressure chamber 15 .

The spool 18 is urged downward by a spring 33 inserted into the upper end of the spool chamber 17. The pressure chamber 24 and the spool pressure accumulation chamber 34 at the lower end of the spool chamber 17 are connected to each other by a passage 26 with a minute cross-section and a check valve 25 interposed therebetween to prevent backflow to the pressure chamber 24 and the spool pressure accumulation chamber 34. It is designed to be intermittent.

A valve-closing spring 26 that biases the valve shaft 11 to close is inserted into the valve-closing spring chamber 12, and the injection valve 3 receives the biasing force of the valve-closing spring 26 and the internal pressure of the valve-closing pressure chamber 15. The valve is opened when the internal pressure of the first pressure accumulator 16 overcomes, and closed when the former two overcome the latter.

An annular second pressure accumulation chamber 27 surrounding the valve shaft 11 is formed in the center of the main body 1, and the first pressure accumulation chamber 16 has an inlet passage 28 and an inflow passage parallel to the second pressure accumulation chamber 27. Outflow channel 29
connected via. This inflow path 28 has a check valve 3 that prevents backflow from the second pressure accumulation chamber 27 to the first pressure accumulation chamber 16.
0 is interposed, and the outflow path 29 is connected to the second pressure accumulation chamber 27.
Pressure horn setting valve 3 that maintains the internal pressure at a predetermined set pressure or higher
1 causes 1RI to be closed. These check valves 3
The pressure setting valve 31 is provided on the opposite side of the plunge chamber 1° of the main body.

” - The plunger 9 has a cam 32 rolled into contact with its upper surface.
driven by.

In the above configuration, the plunger 9 is located at the top dead center,
The state in which the spool 18 is located at the bottom dead center (the state shown in Fig. 4)
Then, constant-pressure fuel is supplied from an external fuel supply device to the lower fuel passage 20 in an amount i11 corresponding to the engine speed. This fuel is introduced into the spool pressure accumulation chamber 34 at the lower end of the spool chamber 17 through the valve hole 22 of the plunger 9, the valve hole 20 of the spool 18, and the center hole 19, and as shown in FIG. Raise it to a height halfway between the original point and bottom dead center. Next, when the cam 32 pushes down the plunger 9 from the top dead center toward the bottom dead center, the volume of the pressure chamber 24 decreases, and the fuel corresponding to this decrease is supplied to the valve port 23.
1 and the center hole 19 into the spool pressure accumulation chamber 34, and the spool 18 rises to the top dead center before the plunger 18 reaches the bottom dead center]2. This spool 18 reaches the dual point when the spring 3
It depends only on the urging force of 3 and the internal pressure of the plunger chamber 10,
It is independent of the pressure gradient across the spool 18, which varies in value depending on the operating speed. As a result, the connection between the valve ports 23 and 21 is cut off as shown in FIG. Stop valve 4 is opened. That is, by keeping the pumping pressure from the plunger chamber 10 constant, it is possible to send out the exact amount of fuel jJl across the check valve 4. As a result, the internal pressure of the first pressure accumulating chamber 16 rises, and when this internal pressure exceeds the set pressure of the second accumulating chamber 27, the check valve 30 is opened and the second pressure accumulating chamber 27 is opened.
7 is filled with fuel.

Then, when the internal pressures of the first pressure accumulation chamber 16 and the second pressure accumulation chamber 27 become substantially the same, the check valve 30 is closed. Further, immediately before this point, the check valve 4 is also closed at a time when the differential pressure between the upstream side and the downstream side of the check valve 4 is balanced with the biasing force of the valve closing spring 14, and the first pressure accumulation chamber 16 and the first pressure accumulation chamber 16 are High-pressure fuel is accumulated in the second pressure accumulation chamber 27 . From this state, when the lift amount of the cam 32 begins to decrease, the plunger 9 begins to rise, and the volume of the pressure chamber 24 increases. A smaller amount of fuel than the amount commensurate with this increase in volume first flows from the spool pressure accumulation chamber 34 into the pressure chamber 24 via the minute passage 26, and then enters the pressure chamber 24 through the valve-closing pressure chamber 15 and the pressure chamber 2.
While the internal pressure of the spool 1 is gradually reduced, the spool 1 is positioned at a position where the biasing force of the spring 33 and the internal pressure of the spool pressure accumulation chamber 34 are balanced.
8 descends. When the internal pressure of the valve-closing pressure chamber 15 falls to a predetermined valve-opening pressure, the injection valve 3 begins to open. However, at this stage, the internal pressure of the valve-closing pressure chamber 15 decreases relatively slowly due to the inflow of fuel from the spool pressure accumulation chamber 34 into the pressure chamber 24. As shown in (3), the fuel in the first pressure accumulator 16 is only injected little by little without opening the valve widely. The pressure drop in the first pressure accumulating chamber 1G due to this injection becomes extremely small as shown in FIG. 6 (4). Due to the lowering of the spool 18, the spool pressure accumulation chamber 34 and the pressure chamber 24 are connected to the valve hole 21,
23, and at the same time, the spool pressure accumulation chamber 34 is communicated with the inlet 17 of the fuel passage 2 through the valve hole 20.22, the internal pressure of the closed valve pressure chamber 15 is rapidly reduced.

As a result, a large pressure difference is generated between the valve-closing pressure chamber 15 upstream of the check valve 4 and the first pressure accumulation chamber 16 downstream, and the injection valve 3 is opened further.

As described above, first, by injecting the fuel in the first pressure accumulation chamber 16 having a small volume before ignition and injecting a large amount of fuel from the time of ignition, the amount of fuel injection during the ignition delay period is reduced. Since it can be shifted, it is possible to reduce the explosion sound at the time of ignition and reduce noise.

Here, the cam profile of the cam 32 is formed so that its star 71 to star gradually decreases in a predetermined phase range, and the spool pressure accumulation chamber 34 and the pressure chamber 24 are communicated through the valve holes 21 and 23. By aligning the timing at which the opening area of the injection valve 3 reaches its maximum with ignition, the decrease in injection pressure before ignition is reduced, and the injection valve is opened significantly at the time of ignition.
A large amount of fuel can be injected vigorously, and the injection period can be shortened. In particular, when igniting, the pressure setting valve 3
1 is opened so that the second pressure accumulation chamber 27 and the first pressure accumulation chamber 16 are communicated with each other, the injection pressure becomes a high pressure obtained by adding the high pressure of the second pressure accumulation chamber 27 to the internal pressure of the first pressure accumulation chamber 16. , 6th
As shown in FIG. 4, a large amount of fuel is injected rapidly, and the injection period can be significantly shortened compared to the conventional method.

- In the embodiment shown in FIG. It is also possible to provide the spool 18 outside the plunger 9.

[Brief explanation of the drawing]

Figures 1 to 4 show Unino I according to an embodiment of the present invention.
・These are longitudinal cross-sectional views of the injector. Figure 1 shows the state in which fuel is being directly injected into the pressure accumulator 11↑1, Figure 21'l', l shows the state in which fuel is being injected into the pressure accumulator, and Figure 3 shows the state in which fuel is being injected into the pressure accumulator. 4 shows the state during fuel injection, FIG. 4 shows the state immediately after the end of injection, FIG. 5 is a comparison diagram of the relationship of the rate of change in injection pressure with respect to the change in injection amount between the present invention and the conventional example, and FIG. 6 (1) is a cam profile diagram of the main part of the cam that drives the pusher, and Figure 6 (2)
is a timing diagram showing changes in the lift amount of the injection valve, FIG. 6 (3) is a timing diagram showing changes in the opening area of the injection valve,
FIG. 6 (4) is a timing diagram showing changes in injection pressure and fuel injection rate, FIG. 7 is a longitudinal cross-sectional view of another embodiment of the present invention,
FIG. 8 is a longitudinal sectional view of a conventional example. 1... Main body, 2... Fuel passage, 3... Injection valve, 4
...Check valve, 5...Pressure accumulation chamber, 16...1st pressure accumulation chamber, ]7 River spool chamber, 18...Large mouth valve (spool valve)
, 19... hollow hole, 20.21, 22.23 river valve hole,
33...Biasing means (spring). Patent applicant: Kubota Iron Works Co., Ltd.
Mr. Hisashi Kitatani ---
;',,,',l;Unexamined Japanese Patent Publication No. UG3-715GO (1
2) Procedural amendment (method) 1985 1111281-1

Claims (1)

[Claims] 1. An injection valve 3 for opening and closing the fuel passage 2 is provided at the terminal end of the fuel passage 2 formed in the main body 1, and a plunger chamber 10 is provided on the upstream side of the injection valve 3, and an inlet valve 18 for connecting and connecting the inlet side of the plunger chamber 10. In the pressure accumulation type fuel injection device, the inlet valve 18 is constituted by a spool valve, and this inlet valve 18 has a hollow hole 19 extending from one end to an intermediate portion thereof, and Valve holes 20 and 21 open to the circumferential surface from the end portion and the middle portion, respectively.
A valve hole 22 connected to the upstream side of the spool chamber 17 that accommodates the inlet valve 18 is formed in the middle part of the spool chamber 17, and the inlet valve 18 is connected to the other end of the spool chamber 17 at one end thereof. is blocked from the valve hole 21 from the middle part of the hollow hole 19 when it is located at the dead center of the hollow hole 19, and at other times, the valve hole 21 is
A check valve 25 is interposed to connect the valve hole 23 to the plunger chamber 10 and prevent backflow from the plunger chamber 10 from one end of the spool chamber 17 to the plunger chamber 10. A pressure accumulation type fuel injection device characterized in that a passage 26 is provided, and a biasing means 33 for biasing the inlet valve 18 toward one end is provided at the other end of the spool chamber 17.