JPS6341579Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection pressure adjustment device for a fuel injection valve of a diesel engine, and more particularly to a device for adjusting injection pressure by changing the biasing force of a spring against a valve body.

As an example of a conventional injection pressure adjusting device of this type, there is one shown in Fig. 1 (Jikkosho
(See Publication No. 31-18409).

In FIG. 1, a cam 2 having a handle 3 is rotatably mounted on an upper part of a main body 1 of the fuel injection valve, and a spring 5 biasing a needle valve 4
One end of the cam 2 is supported by the cam 2.

Then, by manually operating the cam 2,
The spring 5 is expanded and contracted to change the urging force and adjust the injection pressure.

However, with such conventional injection pressure adjustment devices, it is necessary to manually change and adjust the biasing force of the spring, which makes the operation complicated, and there are cases where the injection pressure is not adjusted. There is a problem.

Therefore, as an injection pressure adjustment device to solve such problems, a pump driven by an internal combustion engine, etc., and related fluid piping are installed.
There is a system in which the biasing force of a spring is automatically adjusted via a piston or the like by automatically controlling these fluid pressures (Utility Model Application No. 57-35457,
(Refer to Japanese Patent Application Laid-open No. 102527/1983).

However, in such a conventional injection pressure adjustment device, in order to automatically adjust the biasing force of the spring, a fluid piping system separate from the fluid pressure system of the injection pipe that supplies fuel is required. There are problems in that the fuel becomes complicated and large in size.

By the way, in this type of injection pressure adjustment device, the pressure of the injection pipe that supplies fuel may rise abnormally. This tendency is particularly noticeable when the biasing force of the spring is increased.

At present, there is no injection pressure device that automatically avoids such an abnormal increase in injection pipe pressure.

An object of the present invention is to provide an injection pressure regulating device that has a simple structure and can automatically control abnormal increases in injection pipe pressure, thereby improving combustion performance. It is in.

In order to achieve this object, the present invention provides a cylinder chamber in a nozzle holder of a fuel injection valve, and a piston that supports one end of the valve spring is slidably fitted into this cylinder chamber,
Injection pipe pressure is introduced into a chamber on one side of the cylinder chamber that operates the piston in a direction that weakens the biasing force of the valve spring, and a spring that operates the piston in the opposite direction to the aforementioned direction is interposed in the chamber on the opposite side of the cylinder chamber. In addition, by communicating an oil leakage path with a chamber on the opposite side of the cylinder chamber, the biasing force of the valve spring can be automatically changed and adjusted in accordance with the injection pipe pressure with a simple structure. be.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 2 is a longitudinal sectional view showing an injection pressure regulating device which is an embodiment of the present invention, and FIGS. 3 and 4 are diagrams for explaining the operation.

In this embodiment, the fuel injection valve includes a nozzle holder 11 as a main body, and a nozzle 12 is held at the lower end of the holder 11 by a cap nut 13 screwed onto the lower end. Nozzle 12
A sac hole 14 is formed at the lower end of the sac hole 14, and a plurality of nozzles 15 are bored in the sac hole 14. A valve chamber 16 is formed on the center line of the nozzle 12, and a needle valve 1 as a valve body is installed in the valve chamber 16.
7 is fitted so as to be slidable in the direction of the center line. A valve seat 1 is located adjacent to the valve chamber 16 and the suction hole 14.
8 is formed, and a needle valve 1 is mounted on this valve seat 18.
The valve port is configured to be opened and closed by moving the valves 7 toward and away from each other. An oil passage 19 communicating with an injection pipe (not shown) is connected to the valve chamber 16, and the needle valve 17 is configured to be pushed up by the injection pipe pressure introduced from the oil passage 19 into the valve chamber 16. has been done.

An injection pipe connection port 20 to which an injection pipe is connected is formed on the upper outer circumference of the holder 11, and a second oil passage 21 whose other end is connected to the oil passage 19 of the nozzle 12 communicates with this connection port 20. has been done. A fitting chamber 22 in which a valve spring 23 is fitted is formed on the center line of the lower end of the holder 11, and spring receivers 24 and 25 are abutted on the upper and lower ends of the spring 23, respectively. The lower spring receiver 25 is connected to the needle valve 17 via a bushing rod portion 26, and the needle valve 17 is pressed against the valve seat 18 by the biasing force of the spring 23.

A cylinder chamber 27 is formed above the fitting chamber 22 of the holder 11, and a rod 29 is inserted into this chamber 27.
The piston 2 is connected to the upper spring receiver 24.
8 is slidably fitted. Cylinder chamber 27
A stopper part 30 that defines the bottom dead center of the piston 28 is formed at the lower inner circumference of the cylinder chamber 27 , and a control spring 32 is provided in a chamber 31 above the piston 28 in the cylinder chamber 27 so as to press the piston 28 against the stopper part 30 . It is fitted. A third oil passage 34 whose other end is connected to the injection pipe connection port 20 is communicated with the control chamber 33 below the piston in the cylinder chamber 27 . This third oil passage 34 is thus communicated with the injection pipe 20 of the nozzle holder 11,
It is formed inside the nozzle holder 11. With this configuration, a means for guiding the ejection pipe pressure to the control chamber 33 of the cylinder chamber 27 is formed, and in this embodiment, a mechanism for achieving such means is added to the outside of the nozzle holder 11. The configuration is such that it does not need to be provided. Therefore, the structure for automatically adjusting the injection pressure is made as simple and compact as possible.

An oil leakage path 35 communicating with the fuel tank and the like is connected to the upper part of the outer circumference of the holder 11.
A first passage 36 communicating with the valve spring fitting chamber 22 and a second passage 37 communicating with the control spring fitting chamber 31 are respectively connected to the valve spring fitting chamber 22 .

Therefore, the piston 28 generated by the pressure of the injection pipe led to the control chamber 33 via the oil passage 34
When the pushing up force against the control spring 32 overcomes the preset biasing force of the control spring 32, the piston 28 is pushed up against the spring 32. Also, the piston 28 is connected to the spring 32.
In the state in which the piston rod 29 is pushed down by the urging force of
A gap h is set so that the seat is separated from the ceiling surface.

As a result, the valve spring 23 is shortened compared to the state without the gap h, and the urging force is increased by that amount, and the needle valve 17 is pressed against the valve seat 18, closing the valve port.

In addition, in FIG. 2, 38 indicates the holder 11 and the nozzle 1.
A gasket 39 sandwiched between the holder 2 and the holder 2 is a lid body that closes the fitting chamber 31 screwed onto the top of the holder.

In the injection pressure adjustment device for a fuel injection valve having the above configuration, fuel flows from the injection pipe connection port 20 to the oil passage 2.
1 and 19 to the valve chamber 16, and this valve chamber 1
When the pressure at 6 exceeds a set value, the upward force caused by this pressure pushes up the needle valve 17 against the valve spring 23, separating it from the valve seat 18 and opening the valve port. With this valve opening, the valve chamber 1
The fuel in the combustion chamber 6 is injected into the combustion chamber under its own pressure through the suction hole 14 and into the combustion chamber from a plurality of nozzles 15.

In this way, the opening and closing operations of the needle valve 17 are automatically performed by the internal pressure of the injection pipe, so the fuel injection pressure depends on the pressure of the injection pipe when the needle valve 17 is opened and closed. Since the opening and closing operations of the needle valve 17 are realized against the biasing force of the valve spring 23, the fuel injection pressure is eventually determined by the set value of the biasing force of the spring 23.

By the way, it has been revealed that if the biasing force of the valve spring is set uniformly over the entire operating range regardless of the operating conditions, the following problems will occur.

Low-speed operating range, high-speed low-load range, and low-temperature starting of diesel engines (hereinafter referred to as low-speed operating range, etc.)
For example, in a low-speed operating range, the plunger speed of the injection pump (not shown) is low, so the pressure in the injection pipe does not become very high. Even at such pressures, if the spring biasing force is set so that the needle valve opens and closes, the fuel injection pressure will be kept low, which will prevent the fuel spray from becoming sufficiently atomized. , combustion performance deteriorates. For example, pungent odors and blue-white smoke are observed in the exhaust gas.

On the other hand, during the opening and closing periods of high-speed, high-load operation, the opening area of the needle valve orifice is small compared to the total area of the nozzle, so the particles in the fuel spray become enlarged and combustion performance deteriorates. do.

Furthermore, in high-speed, high-load operating ranges, if the biasing force of the spring is set high, an abnormal increase in injection pipe pressure may occur.

The injection pressure adjustment device according to the embodiment described above adjusts the fuel injection pressure according to the situation by increasing or decreasing the biasing force of the spring 23 in a low-speed operating range and a high-speed, high-load operating range. , which solves the above-mentioned disadvantages, and furthermore,
The biasing force of the spring 23 is adjusted in a self-controlled manner using the injection pipe pressure itself.

Next, the adjustment effect of the injection pressure in this embodiment will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing the relationship between the injection pipe pressure and the opening/closing operation of the needle valve in a low speed operating range.

In FIG. 3, the broken line curve shows the relationship between the injection pipe pressure and the opening/closing operation of the needle valve when the biasing force of the valve spring is set uniformly over the entire operating condition.

As is clear from this dashed curve, in this case,
The opening and closing operations of the needle valve are performed during a period when the injection pipe pressure is not sufficiently high. This is because the biasing force of the valve spring is kept low. When the opening/closing operation occurs during such a period, the fuel injection pressure is also suppressed to a low level, so that the spray is not sufficiently atomized and the combustion performance deteriorates.

In FIG. 3, the solid line curve shows the relationship between the injection pipe pressure and the opening/closing operation of the needle valve when the urging force of the valve spring is increased by the injection pressure regulating device according to the above configuration of the present invention.

As is clear from this solid curve, in this case,
The opening and closing operations of the needle valve are performed during a period when the injection pipe pressure is sufficiently high. When the opening/closing operation is performed in such a high pressure region, the injection pressure also increases accordingly, so that the spray becomes sufficiently fine particles and the combustion performance is improved.

The reason why the opening/closing operation is performed in the high pressure region is because the valve spring biasing force is increased.

As shown in FIG. 2, by setting the gap h in the upper spring receiver 24 by the piston 8, the valve spring 23 is compressed extra to increase the stored force, and the biasing force against the needle valve 17 is transferred to the gap h. This is enhanced compared to the case where h is not set. Needle valve 1 resists this biasing force.
In order for valve 7 to open and close, the pressure in the valve chamber 16 needs to be high because the pressure receiving area in the valve chamber 16 remains unchanged. Therefore, the opening/closing operation of the needle valve 17 is performed in a region where the pressure in the valve chamber 16, that is, the pressure in the injection pipe fluidly connected to the valve chamber, is increased by the increased biasing force of the valve spring 23. It is.

Here, the injection pipe pressure is also introduced into the control chamber 33 below the piston through the third oil passage 34, but in order to prevent the piston 28 from being pushed up by this pressure value, the piston 28 in the control chamber 33 is
Since the relationship between the pressure receiving area 8 and the urging force of the control spring 23 is set, the piston 28 is not pushed up. Therefore, the gap h between the upper spring receiver 24 is maintained, and the biasing force of the valve spring 23 remains increased.

FIG. 4 is a diagram showing the relationship between the injection pipe pressure and the opening/closing operation of the needle valve in the high-speed, high-load operating range.

In FIG. 4, the broken line curved portion shows the relationship between the injection pipe pressure and the opening period and closing period of the needle valve when the urging force of the valve spring is set uniformly over the entire area.

As is clear from this broken line curve section, in this case, the valve opening period and the valve closing period exist during periods when the pressure value of the injection pipe is insufficient. This is because the biasing force of the valve spring is kept low. In this way, when the valve opening period and valve closing period exist in the low pressure region,
The responsiveness of the operation decreases, and since the valve opening area is made smaller than the total nozzle area, the spray becomes enlarged and the combustion performance deteriorates.

In FIG. 4, the solid line curve shows the relationship between the injection pipe pressure and the opening/closing operation of the needle valve when the urging force of the valve spring is adjusted by the injection pressure adjusting device according to the above-mentioned configuration of the present invention.

As is clear from this solid curve, in this case,
The valve opening period and the valve closing period exist during periods when the injection pipe pressure is sufficiently high. In this way, when the valve opening period and valve closing period exist in the high pressure region, the responsiveness of the operation is good,
Since the valve opening area becomes commensurate with the total nozzle area, the spray becomes fine particles and combustion performance improves.

The valve opening period and valve closing period are set in the high pressure region.
As before, the valve spring 23 is connected to the piston 2.
This is because the biasing force is increased by being compressed by the gap h by 8.

Even in the valve opening period and the valve closing period, since the injection pipe pressure is below the set value, the piston 28 is not pushed up and the biasing force of the valve spring 23 remains increased.

As described above, if the valve opening period and valve closing period remain set in the high pressure region, the injection pipe pressure may rise abnormally. can be avoided as follows.

In FIG. 2, an oil passage 34 is connected to the injection pipe connection port 20.
control chamber 3 below the piston fluidly connected via
3, that is, the injection pipe pressure, rises to a predetermined set value below the abnormal pressure value, this pressure pushes the piston 28 upward against the control spring 32. When the piston 28 is pushed up, the upper spring receiver 2 supported by the piston 28
4 moves so as to eliminate the gap h. Due to this movement, the valve spring 23 expands and weakens the stored force, and the biasing force against the needle valve 17 is reduced to the gap h.
is weaker than if it had been set. Accordingly, the opening and closing operations of the needle valve 17 are performed in a region where the pressure in the valve chamber 16, that is, the pressure in the injection pipe fluidly connected to the valve chamber, is low by the amount that the biasing force of the valve spring 23 is weakened. become. If the opening/closing operation is performed in the low pressure region in this manner, an abnormal increase in the injection pipe pressure is prevented.

In this way, an abnormal increase in the injection pipe pressure is prevented, and when the injection pipe pressure falls below the set value, the urging force of the control spring 32 overcomes the upward force due to the pressure in the control chamber 33 below the piston, and the piston 28 returns to its original position. It is operated. As a result, the gap h is set again, the valve spring 23 is compressed, and the biasing force against the needle valve 17 is increased. Therefore, the opening and closing operations of the needle valve 17 are performed again in the original high pressure region, and predetermined combustion performance is maintained.

As explained above, according to the present invention, the fuel injection pressure can be increased in the low-speed operating range, etc., so that the fuel spray is made into fine particles and the combustion performance can be improved. In addition, the valve opening and closing timings in the high-speed, high-load operating range can be set in the high-pressure range, which prevents the fuel spray from enlarging and improves combustion performance. When the value exceeds the set value, the opening/closing operation of the needle valve is adjusted to be performed in the low pressure region, which prevents an abnormal increase in the injection pipe pressure.Moreover, this adjustment operation is automatically controlled by the injection pipe pressure itself. Since it is carried out in a controlled manner, there is no risk of a situation in which the adjustment operation is not carried out. In other words, the present invention has the first effect of being able to automatically control abnormal increases in injection pipe pressure. In view of this first effect, there is no problem even if the biasing force of the valve spring is increased, so the second effect is that combustion performance can be improved by increasing the biasing force of the valve spring. . In addition to the above effects, the third effect is that the structure is simple.

It goes without saying that the present invention is not limited to the embodiments described above, and that various changes can be made without departing from the spirit thereof.

For example, in the embodiment described above, a hole nozzle has been described, but the present invention can also be applied to a pintle nozzle or a slot nozzle.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a conventional example, FIG. 2 is a vertical cross-sectional view showing an embodiment of the present invention, and FIGS.
The figures are diagrams for explaining the effects. 11... Nozzle holder, 12... Nozzle, 13
...Fukuro Natsuto, 14...Satsukuhole, 15...
Nozzle, 16...valve chamber, 17...needle valve,
18... Valve seat, 19, 21... Oil passage, 20... Injection pipe connection port, 22... Fitting chamber, 23... Valve spring, 24, 25... Spring receiver, 26
...Push rod section, 27...Cylinder chamber, 2
8... Piston, 29... Rod, 30... Stopper portion, 31... Fitting chamber, 32... Control spring, 33... Control chamber, 34... Oil passage, 35... Oil leakage passage, 36, 37...Aisle, 38...Plate,
39...Lid body.

Claims (1)

[Scope of utility model registration request] In an injection pressure adjustment device that adjusts injection pressure by changing and adjusting the biasing force of a valve spring 23 against a needle valve 17 in a fuel injection valve, a cylinder chamber 27 is provided in the nozzle holder 11 of the fuel injection valve, and a cylinder chamber 27 is provided in the nozzle holder 11 of the fuel injection valve. A piston 28 supporting one end of the valve spring 23 is slidably fitted into the cylinder chamber 27,
Injection pipe pressure is introduced into the chamber 33 on one side of the cylinder chamber 27 to operate the piston 28 in the direction of weakening the biasing force of the valve spring 23, and the piston 28 is introduced into the chamber 31 on the opposite side of the cylinder chamber 27 in the opposite direction. A spring 32 is interposed to actuate the
The injection pressure adjusting device is further characterized in that an oil leakage path 35 is communicated with the chamber 31.