JPH0224941Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention is aimed at adjusting the pressure in the fuel injection pipe that connects the fuel injection pump and fuel injection nozzle of an engine, especially a diesel engine, to an appropriate state according to the engine speed. The present invention relates to a pipe internal pressure control device in a fuel injection device that controls the pressure in the fuel injection device.

[Conventional example]

Generally, the maximum internal pressure in the fuel injection pipe that connects the fuel injection nozzle and the fuel injection pump increases rapidly in proportion to the engine speed, as shown by the solid line in Figure 1, if no leakage means is installed. There is a tendency. When the maximum pipe internal pressure is high and the injection pressure of the injection nozzle increases, it is extremely effective in improving smoke (black smoke contained in exhaust gas) in the low speed range and improving combustion and improving fuel efficiency. It is something.

However, as mentioned above, the maximum pipe pressure rises in proportion to the engine speed, so when the engine rotates at high speeds, the pressure inside the fuel injection pipe increases abnormally, causing damage to the fuel injection pump and inhibiting the generation of NOx. There was a problem that it was not possible to reduce the

Therefore, in order to solve the above-mentioned problems, for example, as disclosed in Japanese Patent Application Laid-open No. 129250/1983, a fuel injection pipe that connects a fuel injection pump and a fuel injection nozzle is installed in the middle of the fuel injection pipe according to the internal pressure of the pipe. A control valve that opens and closes according to the set pressure of a spring is installed, and when the internal pressure of the pipe exceeds the set pressure when the engine is rotating at high speed, the control valve is opened and a part of the fuel is leaked.
A fuel injection device has been proposed in which the maximum pipe internal pressure is reduced as shown by the dotted line in FIG.

However, in conventional devices such as this, in which a control valve is simply interposed in the fuel injection passage, when the internal pressure of the pipe exceeds the set pressure when the engine rotates at high speed, the control valve is fully opened to drain a portion of the fuel. Due to leakage, the pressure inside the pipes dropped too much, resulting in smoke and poor fuel efficiency, and furthermore, there were problems in that NOx generation could not be effectively reduced.

Furthermore, Japanese Utility Model Application Publication No. 58-94874 proposes a fuel injection device in which a variable capacity chamber is provided in the fuel injection pipe, the volume of which changes in response to changes in injection pressure. When the internal pressure of the pipe during rotation exceeds a certain level, the volume of the fuel injection pipe is increased, which has the disadvantage that the internal pressure of the pipe drops too much, similar to the above-mentioned Japanese Patent Application Laid-open No. 129250/1983.

Furthermore, in Japanese Utility Model Application Publication No. 49-120920, a first piston for low pressure and a second piston for high pressure are arranged side by side, and the second piston for high pressure absorbs the increase in pressure and increases the maximum pressure. Although an injection rate adjusting device structured to maintain a constant state has been disclosed,
In this publication, when the maximum pressure exceeds a certain level, the second stone moves upward and the volume increases, so as with the above-mentioned Japanese Patent Application Laid-Open No. 57-129250, the pipe internal pressure drops too much. There were flaws.

In addition, we have a U.S. patent as a pipe pressure control device.
As shown in Japanese Patent No. 4014213, it is known that a piston provided in a container is energized by a double spring, but a play of a predetermined distance is provided between the outer spring and the inner spring. It's not a thing.

Therefore, in view of the conventional situation mentioned above, the present invention is
It was devised to solve this problem, and was implemented with the purpose of providing a pipe pressure control device for a fuel injection system that can prevent the fuel injection pipe internal pressure from dropping too much in the high-speed range of the engine. .

[Means to solve the problem]

To achieve the above object, the present invention includes a first spring that urges a pressure regulating piston sliding within a pressure regulating cylinder to rise within a predetermined distance, in a casing provided in an injection pipe leading to a fuel injection nozzle; A second spring that energizes the rise beyond a certain distance is arranged vertically so that the second spring does not act within a predetermined distance, and a pressure regulating piston that rises beyond a certain distance is connected to the first spring. second to join
The speed is regulated to a low speed by the biasing force of the spring.

〔Example〕

Embodiments of this invention will be described below based on the accompanying drawings.

FIG. 2 shows a schematic configuration diagram in which the pipe internal pressure control device according to this invention is implemented in a fuel injection device, in which fuel F in a fuel tank 1 is supplied to a fuel injection pump 4 via a fuel filter 3 by a feed pump 2. Fuel F is pressurized by a fuel injection pump 4 and injected into a cylinder (not shown) from a fuel injection nozzle 6 through a fuel injection pipe 5. 7 is a leak-off pipe, and 8 and 9 are overflow pipes, which function to return excess fuel to the fuel tank 1.

In this invention, a control device 10 is interposed in the middle of the fuel injection pipe 5 to suppress an increase in the pipe internal pressure when the pipe internal pressure exceeds a set pressure.

Next, a specific embodiment of the control device 10 will be described based on FIGS. 3 to 5.

In the first embodiment shown in FIG. 3, a control device 10 is installed in the middle of the fuel injection pipe 5 via a joint 13, and the fuel is contained inside a substantially T-shaped casing 14. A passage 15 communicating with the fuel injection passage 5a of the injection pipe 5, and a pressure regulating cylinder 1 branched from this passage 15 via a passage 19.
6, and a cylinder 18 of a larger diameter that is continuous with this pressure adjustment cylinder 16 is formed.

The casing 14 having the cylinders 16 and 18 inside is divided into a body part 14a and a cap part 14b, and a spacer 17 having a thread on the outer periphery is screwed onto the inner surface of the casing 14 at the joint part. . This spacer 17 is formed into a cylinder 18 by the body portion 14a and cap portion 14b.
is divided into a first cylinder 18a and a second cylinder 18b, and these are communicated through a communication hole 17a. Reference numeral 12 denotes a leak passage provided in the cap portion 14a, which returns the fuel F that has flowed into the second cylinder 18b to the fuel tank 1.

A pressure regulating piston 20 is inserted into the pressure regulating cylinder 16 so as to be able to rise and fall freely, and this pressure regulating piston 20 is moved into the first cylinder 18a by a first spring 21 mounted between the spacer 17 and the pressure regulating piston 20.
The pressure regulating cylinder 16 is always biased from the side in a direction to be closed.

Furthermore, the pressure adjustment cylinder 16 and the first cylinder 18a communicate with each other through a fuel relief passage 22 provided in the body portion 14a, and an opening 22a of the fuel relief passage 22 on the pressure adjustment cylinder 16 side is The piston 20 resists the first spring 21 due to the internal pressure of the first cylinder 1.
It is provided so that it communicates with the pressure adjustment cylinder 16 only when it moves a predetermined distance to the 8a side.

On the other hand, a through hole 1 is provided in the center of the spacer 17.
7b, and a push rod 24 having both ends protruding from both sides of the first and second cylinders 18a and 18b is slidably provided in the through hole 17b. This push rod 24 is the second
The second spring 2 provided in the cylinder 18b
3 toward the first cylinder 18a side, and the end portion 24a inside the first cylinder is connected to the end portion 20a of the pressure regulating piston 20 on the first cylinder 18a side, and the piston 20 is biased toward the first cylinder 18a side. Since the pressure regulating piston 20 is held in the cylinder 18 with a distance S in the closed state, the push rod 24, that is, the second spring 23 cannot be energized unless the pressure regulating piston 20 rises beyond the distance S. do not have.

Note that the opening 22a of the fuel escape passage 22
The spring 20 prevents the piston from fully opening when the pressure regulating piston 20 rises against the first spring 21 due to an increase in the pipe internal pressure and its end 20a abuts the end 24a of the push rod 24. It is located in a suitable position. After this, if the pipe internal pressure increases further and the piston 20 rises beyond a predetermined distance (interval S), the piston 20
0 receives the urging force of two springs, the first spring 21 and the second spring 23.

Therefore, the biasing force (setting force) exerted by the springs 21 and 23 on the upward stroke of the pressure regulating piston 20 changes stepwise with the distance S as a boundary, as shown in FIG.

Next, the operation of the control device 10 as described above will be explained. First, when the fuel pressure in the fuel injection passage 5a increases and the pressure regulating piston 20 is raised,
The capacity of the pressure adjustment cylinder 16 increases, and the internal pressure in the pipe decreases slightly by this increase in capacity. Then, when the pressure within the pipe further increases and the pressure regulating piston 20 begins to open the opening 22a of the fuel relief passage, part of the fuel passes through the relief passage 22 and passes through the cylinder 18a, the communication hole 17a, and the cylinder 18b. The leakage begins to return to the fuel tank 1 from the leak passage 12, and its increase is suppressed.

From this state, the engine speed increases further, the pressure inside the pipe increases, and the end 20a of the piston 20 becomes closer to the end 24a of the push rod 24.
comes into contact with. After this, as shown in FIG. 7, the biasing force acting on the piston 20 increases, so that the piston 20 increases less with respect to the increase in pipe pressure, and the opening area of the relief passage 22 becomes smaller. The pressure inside the pipe increases again, exceeding the pressure drop due to the increase in .

The maximum pipe internal pressure due to the characteristics of the control device 10 as described above becomes a curve like the chain line in the diagram of FIG. That is, when the pressure inside the fuel injection passage 5a increases and the pressure regulating piston 20 starts to rise,
The degree of increase in the pipe internal pressure begins to decrease (point When it comes into contact with the push rod 24 and its rate of rise slows down, the pressure inside the pipe starts to increase again (point Z).

As described above, when the pipe internal pressure in the fuel injection passage 5a increases, the biasing force applied to the pressure regulating piston 20 provided in the control device 10 is set in stages in response to the increase in the pipe internal pressure. Therefore, as shown by the chain line in Figure 6, the pipe pressure is lowered in the low engine speed range, suppressed in the middle engine speed range, and increased again in the high engine speed range, thereby reducing fuel consumption and It can improve smoke quality and effectively reduce NOx.

Next, FIG. 4 shows a second embodiment of the control device 10, in which the fuel relief passage 22 is connected to the first embodiment.
This fuel relief passage 22 is formed inside the pressure regulating piston 20 in the embodiment shown in FIG.
It is formed in a substantially T-shape so that the center of the bottom on the fuel injection passage 5a side of the fuel injection passage 5a communicates with the side surface on the side of the first cylinder 18a, and normally the opening 22a on the side surface is formed by the inner wall surface of the pressure adjustment cylinder 16. It is closed.

In this embodiment as well, the opening area of the opening 22a with respect to the stroke of the piston 20 is
If it is kept the same as in the first embodiment, the pipe internal pressure will change in the same way as in the first embodiment.

Note that the other configurations and operations are the same as those of the first embodiment described above, so a description thereof will be omitted.

FIG. 5 shows a third embodiment of this invention, in which the pipe internal pressure is adjusted only by changing the volume of the pressure regulating cylinder 16 without leaking fuel. In this embodiment as well, the pressure regulating piston 20 is moved by the first and second springs 21 and 23 during the upward stroke due to the increase in the pipe internal pressure.
6, the maximum internal pressure changes as shown by the chain line in FIG. 6, as in the previous embodiment.

As a result, the temporal change in pipe pressure in the engine high speed, high load range becomes as shown by the broken line in Figure 8, and the drop in pipe pressure in the engine high speed, high load range is suppressed, reducing NOx and improving fuel efficiency. You can improve your performance.

[Effect of idea]

As explained above, this invention is based on a first spring that urges a pressure regulating piston that slides inside a pressure regulating cylinder to rise within a predetermined distance, and a first spring that urges a pressure regulating piston that slides in a pressure regulating cylinder to rise within a predetermined distance. A second spring that energizes the rise beyond the predetermined distance is arranged vertically with a distance that the second spring does not act within a predetermined distance, and a pressure regulating piston that rises beyond the predetermined distance is attached to the first spring. second to join
Since the speed is restricted to a low speed state by the biasing force of the spring, there is a gap between the first spring and the second spring that bias the pressure regulating piston to rise, respectively, within a predetermined distance where the second spring does not act. Therefore, within the range in which the pressure regulating piston rises within a predetermined distance energized by the first spring, the volume inside the pressure regulating cylinder provided in the casing increases, lowering the pressure inside the pipe and slowing down the engine speed. It is possible to improve fuel efficiency by reducing smoke and improving combustion. Moreover, when the pressure regulating piston rises beyond a predetermined distance, the rate of rise is slowed down by the increase in the urging force of the second spring that is applied to the first spring, and as a result, the pressure inside the pipe increases. Therefore, it is possible to prevent the pipe internal pressure from dropping too much in the high-speed range of the engine, thereby effectively reducing the generation of NOx in the high-speed range of the engine.

[Brief explanation of the drawing]

Fig. 1 is a graph explanatory diagram showing the characteristics of the maximum pipe internal pressure with respect to the conventional engine speed, Fig. 2 is a schematic configuration diagram of the pipe internal pressure control device, Fig. 3 is an enlarged sectional view of the control device of the present invention, and Fig. 4 5 and 5 are cross-sectional views showing other embodiments of the control valve, FIG. 6 is a diagram showing the engine speed-maximum pipe internal pressure characteristic according to the present invention, and FIG. 7 is a piston of the pressure regulating piston according to the present invention. FIG. 8 is a diagram showing stroke-spring set force characteristics; FIG. 8 is a diagram showing time-pipe pressure characteristics according to the present invention. 1...Fuel tank, 4...Fuel injection pump, 5
...Fuel injection pipe, 6...Fuel injection nozzle, 10...
... Control device, 12 ... Leak passage, 14 ... Casing, 16 ... Pressure adjustment cylinder, 17 ... Spacer, 18 ... Cylinder, 20 ... Pressure adjustment piston, 21, 23 ... Spring, 22 ... Relief Aisle, 24... Pushrod, F... Fuel.

Claims (1)

[Scope of utility model registration request] Inside the casing provided in the injection pipe leading to the fuel injection nozzle, there is a first spring that biases the pressure regulating piston sliding within the pressure regulating cylinder to rise within a predetermined distance, and a first spring that biases the pressure regulating piston that slides within the pressure regulating cylinder to rise beyond the predetermined distance. The second springs are disposed vertically opposite each other with a distance that the second springs do not act within a predetermined distance, and the pressure regulating piston that rises beyond the predetermined distance is controlled by the urging force of the second springs applied to the first spring. A pipe pressure control device in a fuel injection system that regulates low speed.