JPH0461190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a unit injector for injecting fuel into a combustion chamber of a diesel engine, and particularly to a miniaturized unit injector.

(Prior Art) Conventionally, as a fuel injection device for a diesel engine, there is a so-called unit injector in which a fuel injection pump and a fuel injection valve are integrated. The technique proposed in Japanese Unexamined Patent Publication No. 59-51156 is one example.

Since the unit injector integrates the fuel pump and the fuel injection valve, it is not necessary to install a long pipe that can withstand high pressure to connect the fuel pump and the fuel injection valve. Therefore, the space for installing the unit injector can be reduced, and the injection characteristics at high speed rotation can be improved.

In this unit injector, a valve body (hereinafter referred to as a needle valve) is used to open and close the injection port.
is biased by a spring in the direction of closing the injection port. When the pressure of the fuel supplied to the pressure chamber formed to surround the pressure receiving surface of the intermediate portion of the needle valve rises above the repulsive force of the spring, the pressure acts on the pressure receiving surface and the needle The valve is pushed in the direction of opening the injection port.

When the injection port is opened, fuel is injected into the combustion chamber. When the fuel is injected, the pressure in the pressure chamber decreases, and when the fuel is injected until the pressure becomes equal to or less than the repulsive force of the spring, the injection port is closed again by the needle valve.

(Problems to be Solved by the Invention) The above-described conventional technology had the following problems.

If the repulsive force of the spring is too small and the valve is opened until the fuel injection pressure, that is, the pressure in the pressure chamber, drops extremely, the fuel will not be properly injected, resulting in dripping. Therefore, it is desirable that the injection port be closed before the pressure in the pressure chamber decreases.

If the valve opening pressure is increased by using a spring with a large repulsion force, the injection port can be closed before the pressure in the pressure chamber drops, but it is necessary to secure space to accommodate the large spring, and for this purpose the unit ind. There was a problem that the overall size of Ekta became large.

Furthermore, in order to maintain a good fuel injection condition no matter what rotational state the engine is in, it is desirable that the valve opening pressure can be increased in a high rotational speed and high load range.

However, with the structure of the conventional unit injector, it is not easy to adjust the valve opening pressure. Therefore, there was a problem in that it was difficult to obtain an appropriate valve opening pressure depending on the rotational state of the engine.

The present invention solves the above-mentioned problems and achieves miniaturization.
Moreover, it is an object of the present invention to provide a unit injector that can obtain a large valve opening pressure, and a unit injector that can easily adjust the magnitude of the valve opening pressure.

(Means and effects for solving the problems) The present invention for solving the above-mentioned problems and achieving the objects includes: a plunger that slides inside the barrel; a fuel intake port that sucks fuel into the barrel; and an auxiliary fuel passage for guiding the fuel sucked into the high pressure chamber so that the sucked fuel acts on the needle valve to bias the needle valve in the closing direction. The fuel inlet and the auxiliary fuel passage opened in the barrel are characterized in that the fuel inlet and the auxiliary fuel passage are closed in this order.

In the present invention having the above configuration, in the step of pressurizing the fuel sucked into the barrel and feeding it to the injection port, when the plunger moves inside the barrel, the fuel intake port is first blocked, and this causes a delay in assisting the injection port. The fuel passage is blocked.

In this way, by delaying the timing of closing the auxiliary fuel passage, the auxiliary fuel passage will remain open for a while even if the fuel intake port is blocked, so that the needle can be fed through the auxiliary fuel passage. Fuel pressure acts on the valve, and the fuel pressure is added to the repulsive force of the spring that urges the needle valve in the valve closing direction, acting to increase the valve opening pressure.

The present invention also provides a plunger that slides inside the barrel, a fuel intake port that sucks fuel into the barrel,
an auxiliary fuel passage for guiding the fuel sucked into the high-pressure input chamber, and an end surface having two ends, so that the sucked fuel acts on the needle valve and urges the needle valve in the closing direction. The present invention is characterized in that it includes a plunger that is divided into two parts, each of which has a stepped surface formed at a predetermined angle by the end face of the two parts, and a means for rotating the plunger.

In the present invention having the second configuration, the plunger is rotated to substantially change the level difference of the level difference surface, thereby changing the delay width of the closing timing of the auxiliary fuel passage with respect to the fuel intake port. The pressure of the fuel that biases the needle valve in the closing direction of the fuel injection port can be adjusted.

That is, since the stepped surfaces formed by dividing the end surface into two have a predetermined angle with each other, the step between two points on the circumference of the plunger end surface corresponding to each stepped surface is equal to It varies depending on the position of the two points. Therefore, assuming that the above two points correspond to the positions of the fuel intake port and the auxiliary fuel passage, the positions on the circumference of the plunger corresponding to the above two points can be determined by rotating the plunger. Since the size of the step between the two points can be changed, it is possible to adjust the timing difference in closing the fuel intake port and the auxiliary fuel passage.
As a result, the magnitude of the fuel pressure acting on the needle valve via the auxiliary fuel passage can be controlled, and the valve opening pressure can be adjusted.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

In the figure, a plunger 3 is provided so as to be able to reciprocate within a barrel 2 disposed at the center of an injector body 1. The end surface of the plunger 3 facing the bottom high pressure chamber 2a of the barrel 2 is 2.
It is divided to form stepped surfaces 31 and 32. The details of the shape of the stepped surface will be described later with reference to FIG.

The plunger 3 is provided with a spiral groove 3a. The spiral groove 3a is connected to the high pressure chamber 2a via a vertical groove 3b. By rotating the plunger 3, the spiral groove 3a is
The fuel injection amount, fuel injection timing, etc. can be adjusted by changing the positional relationship between the fuel injection port 10 and the fuel intake port 10.

On the inner peripheral surface of the top of the injector body 1 is a cap 5 that stores a spring 4 for returning the plunger.
is inserted, and the other end of the plunger 3 is engaged with a washer 6 which is in contact with the bottom of the cap 5.

The cap 5 is pushed down in the direction in which the spring 4 is compressed by a cam mechanism (not shown) that is driven as the engine rotates, and is also pushed back in the opposite direction by the repulsive force of the spring 4. In this manner, the plunger 3 reciprocates on the inner surface of the barrel 2 as the cap 5 reciprocates.

The rotation angle adjusting cylindrical member 7 of the plunger 3 is designed to be able to rotate along the outer periphery of the narrow diameter part of the barrel 2, and the plunger 3 is not rotated in the axial direction of the plunger 3 with respect to the cylindrical member 7. Slidable,
In addition, the engagement is restricted in position in the rotational direction.

A worm foil is formed on the flange of the cylindrical member 7, a portion of which engages with the worm 8, and by rotating the worm 8, the cylindrical member 7 rotates around the barrel 2. As a result, the plunger 3 engaged with the cylindrical member 7 also rotates.

A cap 9 is attached to the fuel intake port 1a of the injector body 1, and fuel passes through the cap 9 and the fuel intake port 1a to a fuel intake port 10 having an opening in the side wall of the barrel 2.

Further, an opening 11a of the auxiliary fuel passage 11 is located in the side wall of the barrel 2 at the same level as the fuel inlet 10 in the longitudinal direction of the barrel 2. The auxiliary fuel passage 11 extends up to the cylindrical block 12 and reaches a chamber 14 which houses a spring 13.

The cylindrical block 12 is connected by a pin 15 to a relay pipe 16 and an injection head 17. A needle valve 18 is disposed at the center of the relay pipe 16 and the injection head 17, and has a head 18b formed at one end that also serves as a seat for receiving the repulsive force of the spring 13. The needle valve 1
8 is connected to the injection head 17 by the spring 13.
is biased in the direction of closing the injection port 19 of.

A pressure chamber 20 is formed between the needle valve 18 and the injection head 17, and the pressure chamber 20 and the high pressure chamber 2a of the barrel 2 are connected to the main fuel passage 21.
has been contacted.

The fastening cap 22 is screwed into the threaded part of the injector main body 1, and the injection port 17 and the relay pipe 1 are connected to each other.
6. The cylindrical block 12 and the barrel 2 are firmly fastened and integrated.

Next, the adjustment of the fuel pressure acting on the head 18b of the needle valve 18 will be explained with reference to FIGS. 2 and 3.

FIG. 2a is a perspective view showing the shape of the end of the plunger 3, and FIG. 2b is a side view of the end of the plunger.
In FIG. 2, the end surface of the plunger 3 is divided into two parts, and stepped surfaces 31 and 32 are formed. The stepped surface 31 is a surface perpendicular to the central axis of the plunger 3, and the stepped surface 32 has a predetermined angle with respect to the stepped surface 31.

FIG. 3 is a sectional view showing the positional relationship between the stepped surface 31 and the fuel inlet 10, and the positional relationship between the stepped surface 32 and the opening 11a of the auxiliary fuel passage 11.

FIG. 3a shows the plunger 3 shown in FIG.
A side portion of the plunger forming a stepped surface 31 indicated by the symbol A is located at the fuel intake port 10, and is indicated by the symbol A.
The positional relationship between the barrel 2 and the plunger 3 is shown when the plunger 3 is rotated to adjust its position so that the side portion of the plunger forming the stepped surface 32 indicated by A' is located in the opening 11a. has been done.

In FIG. 3b, the side portion of the plunger 3 forming the stepped surface 31 designated by the symbol B is located at the fuel inlet 10, and the side portion of the plunger forming the stepped surface 32 designated by the symbol B' is shown in FIG. The position of the barrel 2 and the plunger 3 when the plunger 3 is rotated and adjusted so that the part with a larger step difference with respect to the surface 31 than the position A' is located in the opening 11a. relationship is shown.

In addition, in FIGS. 2 and 3, the spiral groove 3a
and the vertical grooves 3b are omitted from the illustration.

In FIG. 3, in the process in which the plunger 3 descends to pressurize fuel and feed it into the pressure chamber 20, first, one stepped surface 31 is connected to the fuel inlet 10.
The fuel intake port 10 is closed when the fuel passes through the . At this point, the other stepped surface 32 has not yet passed through the opening 11a of the auxiliary fuel passage, so the opening 11a is not closed.

Therefore, as the plunger 3 descends thereafter, the fuel in the high pressure chamber 2a is pressurized until the opening 11a is closed, and the fuel in the chamber 14 is also pressurized via the auxiliary fuel passage 11. Ru. The pressure acts to open the needle valve 18 and increases the valve opening pressure, similar to the repulsive force of the spring 13 which urges the needle valve 18 in the opening direction as described above. After the stepped surface 32 passes through the opening 11a and the opening 11a is closed, the pressure of the fuel acting on the chamber 14 does not change.

In the positional relationship shown in Figures 3a and b,
The difference in level between the stepped surfaces 31 and 32 located at the fuel inlet 10 and the opening 11a is larger in the positional relationship shown in FIG. 2B than in the positional relationship shown in FIG.

Therefore, if the plunger 3 is adjusted to the positional relationship shown in FIG. 3b rather than that shown in FIG.
The fuel pressure acting on the valve 4 increases, and the valve opening pressure increases.

Next, the operation of the unit injector having the above structure will be explained with reference to FIG. 1 again.

The plunger 3 is reciprocated by the action of the spring 4 and a cam mechanism (not shown), sucking fuel into the high pressure chamber 2a and feeding fuel into the pressure chamber 20. During the suction stroke in which the plunger 3 moves up due to the repulsive force of the spring 4, fuel is sucked into the high pressure chamber 2a of the barrel 2 from the fuel suction port 10.

After the fuel is sucked, when the plunger 3 is lowered from the stroke end, the fuel sucked into the high pressure chamber 2a is pressurized. Since a stepped surface is formed at the end of the plunger 3, during the fuel pressurization stroke, the fuel intake port 10 is first closed, and then, after a delay corresponding to the step between the two stepped surfaces 31 and 32, the auxiliary fuel is Passage 11 is closed.

By closing the auxiliary fuel passage 11 later than the intake port 10, the fuel trapped in the auxiliary fuel passage 11 and the chamber 14 is pressurized by the descending plunger 3 during the delay time, The pressure of the pressurized fuel acts on the head 18b of the needle valve 18 so as to bias the needle valve 18 in the valve closing direction.

Therefore, the head 18b of the needle valve 18
The pressure acting on the injection port 19 to close the injection port 19 is the sum of the repulsive force of the spring 13 and the fuel pressure acting on the head 18b of the needle valve 18.

After the auxiliary fuel passage 11 is closed, the plunger 3 further descends to increase the pressure in the high pressure chamber 2a. Since the bottom of the high pressure chamber 2a and the pressure chamber 20 are connected through the main fuel passage 21, the pressure in the pressure chamber 20 also increases as the plunger 3 descends.

The pressure in the pressure chamber 20 acts on the pressure receiving surface 18a of the needle valve 18, and the pressure acting on the pressure receiving surface 18a is combined with the repulsive force of the spring 13 acting on the head 18a of the needle valve 18 and the auxiliary fuel passage 1.
1 and the pressure of the fuel confined in the chamber 14, that is, when the pressure reaches the valve opening pressure, the needle valve 18 is pushed up in the direction of compressing the spring 13, and the fuel flows between the needle valve 18 and the injection head 17. The fuel is injected from the injection port 19 into the combustion chamber through a gap with the inner surface of the fuel cell.

As described above, according to this embodiment, fuel pressure can be applied to the head 18b of the needle valve 18, and the magnitude of the fuel pressure can be controlled.

In this embodiment, the end uneven surface 3 of the plunger 3 is
1 is a surface perpendicular to the central axis of the plunger 3, and the stepped surface 32 is formed to have a predetermined angle with respect to the stepped surface 31. However, the stepped surface 32 is made a surface perpendicular to the central axis of the plunger 3, Uneven surface 31
The same effect as that of this embodiment can be obtained even if it is formed to have a predetermined angle with respect to the stepped surface 32.

Also, the auxiliary fuel passage 1 is connected to the fuel intake port 10.
If the opening 11a of the needle valve 1 is provided so as to be shifted toward the bottom of the barrel 2 (in the direction of the injection port), the fuel can be supplied to the head 18 of the needle valve 18 without forming the uneven surface on the end surface of the plunger 3. The advantage is that pressure can be applied and the spring 13 can be made smaller.

In short, whether the stepped surface at the end of the plunger 3 is formed or the openings 11a of the fuel inlet 10 and the auxiliary fuel passage 11 are arranged so that the auxiliary fuel passage 11 is closed later than the fuel inlet 10. It would be good if it was done.

Note that the fuel intake port 10 and the auxiliary fuel passage 11
The openings 11a do not have to face each other across the center of the barrel 2.

The auxiliary fuel passage 11 is not limited to this embodiment in which the fuel is guided from the high pressure chamber 2a to the chamber 14, and for example, the needle valve 18 is provided with a step to form a pressure receiving surface. Alternatively, an auxiliary fuel passage 11 may be provided to guide fuel around the needle valve 18 so that the pressure of the fuel acts in a direction to close the needle valve 18.

(Effects of the Invention) As is clear from the above description, the following effects are achieved according to the present invention.

(1) In addition to the repulsive force of the spring that biases the needle valve in the injection port closing direction, the pressurized fuel pressure can be applied to the injection port closing direction of the needle valve, so the injection port can be closed at the same time. When obtaining valve pressure, the spring can be made smaller. As a result, the space for accommodating the spring can be reduced, and the entire unit injector can be downsized.

(2) Since the pressure of the fuel applied to the spring can be adjusted, a desired valve opening pressure can be easily obtained in accordance with the engine rotational state, load state, etc.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2a is a perspective view showing the shape of the plunger end, and Fig. 2b is a perspective view showing the shape of the plunger end.
3 is a side view of the same, and FIG. 3 is a diagram showing the positional relationship between the end of the plunger and the opening of the fuel inlet and the auxiliary fuel passage. DESCRIPTION OF SYMBOLS 1... Injector main body, 2... Barrel, 2a... High pressure chamber, 3... Plunger, 7... Cylindrical member for rotation angle adjustment, 8... Worm, 10... Fuel inlet, 11...
Auxiliary fuel passage, 11a...Auxiliary fuel passage opening, 1
3... Spring, 14... Chamber, 17... Injection head, 18... Needle valve, 19... Injection port, 2
0...Pressure chamber, 21...Main fuel passage.

Claims (1)

[Scope of Claims] 1. A plunger that slides within the barrel, a needle valve that opens and closes the fuel injection port, a fuel inlet provided on the wall of a high pressure chamber within the barrel, and a fuel inlet into the high pressure chamber. a main fuel passage for guiding fuel to the injection head; and fuel pressure acting on the needle valve;
The needle valve is provided with an auxiliary fuel passage for guiding the fuel sucked into the high pressure chamber so that the needle valve is biased in the valve closing direction, and the plunger is configured to guide the fuel sucked into the high pressure chamber. When the fuel is displaced in the compression direction, the fuel inlet and the opening of the auxiliary fuel passage opened in the wall surface of the barrel are closed by the side surface of the plunger in the order of the fuel inlet and the opening. A unit injector characterized in that the suction port and the opening are arranged offset from each other in the longitudinal direction of the barrel. 2. A plunger that slides inside the barrel, a needle valve that opens and closes the fuel injection port, a fuel intake port provided on the wall surface of the high pressure chamber inside the barrel, and the fuel sucked into the high pressure chamber into the injection head. a main fuel passage for guiding the fuel, and an opening at the same position as the fuel inlet in the longitudinal direction of the barrel, and the pressure of the fuel acts on the needle valve to urge the needle valve in the closing direction. and an auxiliary fuel passage for guiding the fuel sucked into the high pressure chamber, and when the plunger is displaced in the direction of compressing the fuel sucked into the high pressure chamber, the fuel suction The end face of the plunger is divided into two, and the end face of the plunger is divided into two so that the opening of the auxiliary fuel passage opened in the mouth and the wall of the barrel is closed by the side surface of the plunger in the order of the fuel intake port and the opening. A unit injector characterized in that a stepped surface is formed by a stepped end surface. 3. The unit injector according to claim 2, further comprising a means for rotating the plunger, and wherein stepped surfaces of the divided plunger have a predetermined angle to each other. 4. A claim characterized in that the auxiliary fuel passage is provided so as to guide the fuel sucked into the high pressure chamber to at least one of a head of the needle valve and a pressure receiving surface provided on the outer periphery of the needle valve. The unit injector according to item 1, 2 or 3.