JPH0481555A - Auxiliary fuel supply system - Google Patents

Abstract

PURPOSE:To keep off any occurrence of black smoke at time of low speed, low load running by installing an auxilairy piston in addition to a main piston, while operating the main piston alone at time of the low speed, low load running such as idle running, and reducing a supply of spare fuel. CONSTITUTION:When fuel pressure in a main fuel feed passage 4 is low, a main piston 30 alone operates, and in this case, a supply of spare fuel is little, and when it is high, the main piston 30 and an auxiliary piston 31 both operate and the supply of the spare fuel becomes increased. Consequently, the supply of the spare fuel is alterable according to an engine driving state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an internal combustion engine that uses two or more types of fuel and is used to replenish auxiliary fuel to improve the combustion efficiency of the main fuel. This invention relates to an auxiliary fuel supply device.

[Prior Art] Diesel engines sometimes use alcohol fuel such as methanol as fuel. However, alcohol fuel is relatively difficult to ignite, and measures have been taken to compensate for this ignitability by using light oil or the like as a ignition source.

The light oil used as the spark, that is, the auxiliary fuel, is supplied to the injection nozzle prior to the injection of the main fuel.

In order to supply such auxiliary fuel,
An auxiliary fuel supply device is used, as is known from Japanese Patent Laid-Open No. 8-206859 and Japanese Patent Application Laid-Open No. 62-218648.

FIG. 4 shows a schematic configuration of these conventional auxiliary fuel supply devices.

In FIG. 4, 40 is a body of the auxiliary fuel supply device, and a pump chamber 41 is formed inside this body 40. The body 40 is formed with an auxiliary fuel inlet 42 and an outlet 43 that communicate with the pump chamber 41, and further has a main fuel pressure passage 44 that communicates with the pump chamber 41.

A piston 45 is provided in the body 40 so as to be able to reciprocate and have one end facing the pump chamber 41 and the other end facing the main fuel pressure passage 44.
is urged toward the main fuel pressure passage 44 by a spring 46 provided in the pump chamber 41.

The body 40 is provided with a step 47 and a stopper 48 that determine the amount of movement of the piston 45.
The position of 8 is adjustable, and by adjusting this position, the stroke of the piston 45 can be adjusted.

Further, the auxiliary fuel port 42 of the body 40 has an inflow side check valve 4 that allows the auxiliary fuel to flow into the pump chamber 41.
9 is installed, and the auxiliary fuel outlet 43 is also provided with an outflow side check valve 50 that allows the auxiliary fuel to flow out from the pump chamber 41.

The main fuel pressure passage 44 is connected to the main fuel supply passage 4, and the main fuel supply passage 4 is connected to the main fuel injection pump 3.
(shown in FIG. 1), the pressurized main fuel is sent to the fuel injection valve 5.

Further, the inflow side check valve 49 is connected to the auxiliary fuel oil supply pump 11, and the outflow side check valve 50 is connected to the fuel injection valve 5.

In such an auxiliary fuel supply device, when the main fuel is force-fed to the injection valve 5 through the main fuel supply passage 4, the fuel pressure in the main fuel supply passage 4 increases, so this pressure becomes the main fuel of the auxiliary fuel supply device. The fuel pressure is transmitted to the fuel pressure passage 44. Therefore, the piston 45 is pushed toward the pump chamber 41 against the biasing force of the spring 46, moves until it hits the stopper 48, and pressurizes the auxiliary fuel in the pump chamber 41. The pressurized auxiliary fuel pushes open the outflow side check valve 50 and is therefore sent to the injection valve 5.

In other words, light oil having a value obtained by multiplying the amount of movement X of the piston 45 by the cross-sectional area of the piston 45 is sent to the injection valve.

When the fuel supply to the injection valve 5 through the main fuel supply passage 4 ends, the pressure in the main fuel supply passage 4 decreases, and therefore the pressure in the main fuel pressure passage 44 also decreases. Therefore, the piston 45 is pushed by the biasing force of the spring 46 and moves toward the main fuel pressure passage 44 side.

Therefore, the pressure in the pump chamber 41 decreases, the outflow side check valve 50 closes, and the inflow side check valve 49 opens, so that auxiliary fuel is supplied from the auxiliary fuel feed pump 11 to the pump chamber 41.

Therefore, the auxiliary fuel supply device performs a pumping action according to the pulsating pressure in the main fuel supply passage 4, and constantly supplies a fixed amount of auxiliary fuel.

E Problems to be Solved by the Invention] However, in the case of the above-mentioned auxiliary fuel supply device,
The amount of auxiliary fuel supplied is a value obtained by multiplying the amount of movement X of the piston 45 by the cross-sectional area of the piston 45, and this is constant over the entire operating range of the engine.

However, when the amount of auxiliary fuel supplied is small, ignition performance is poor under high-speed, high-load operating conditions, and misfires are likely to occur.

In order to prevent such problems, conventionally the supply amount of auxiliary fuel has been set to be large.

However, when the supply amount is set in this way, during low-speed, low-load operation such as idling operation, the auxiliary fuel becomes excessive, and this excess auxiliary fuel flows back from the injection nozzle to the main fuel supply passage 4. and fill this passage. If the engine is started in this state, a large amount of auxiliary fuel with a large calorific value will be fed into the engine, causing the problem of generating black smoke.

Furthermore, since the amount of auxiliary fuel consumed increases, there is also the disadvantage that the capacity of the auxiliary fuel tank must be increased.

The present invention has been made based on the above circumstances, and its purpose is to automatically set the optimum supply amount of auxiliary fuel according to the operating condition of the engine.
The present invention aims to provide an auxiliary fuel supply device that can prevent misfires and black smoke, reduce the amount of auxiliary fuel consumed, and reduce the size of the auxiliary fuel tank.

[Means for Solving the Problems] The present invention has a pump chamber formed inside, an auxiliary fuel inlet and an auxiliary fuel outlet communicating with the pump chamber, and a main fuel pressure passage communicating with the pump chamber. a main piston that is reciprocably provided within the body and has one end facing the main fuel pressure passage and the other end facing the pump chamber; and a main piston housed within the pump chamber and facing the main piston. An auxiliary piston provided so as to be able to reciprocate, a means for connecting the main piston side and the pump chamber side separated by the auxiliary piston, and a means provided between the main piston and the auxiliary piston for connecting the main piston to the main fuel a main spring with a low load that presses and urges toward the pressure passage side; an auxiliary spring that is provided in the pump chamber and has a higher load than the low-load spring that presses and urges the auxiliary piston toward the main piston; an inflow side check valve provided at the auxiliary fuel inlet to allow the auxiliary fuel to flow into the pump chamber; and an outflow side check valve provided at the auxiliary fuel outlet to allow the auxiliary fuel to flow out from the pump chamber. It is characterized by the following:

[Function] According to the configuration of the present invention, when the fuel pressure in the main fuel supply passage is low, only the main piston operates; in this case, the amount of auxiliary fuel supplied is small, and when the fuel pressure in the main fuel supply passage is high; The main piston and auxiliary piston operate, increasing the amount of auxiliary fuel supplied.

Therefore, the amount of auxiliary fuel supplied can be changed depending on the operating conditions of the engine.

[Embodiment] The present invention will be described below based on an embodiment shown in FIGS. 1 and 2.

The drawing shows a fuel supply system for a four-cylinder diesel engine that uses methanol as the main fuel and diesel oil as an auxiliary fuel for ignition. In the drawing, 1 is the main fuel tank, 2 is the main fuel oil pump, and 3 is the main fuel injection pump.

This main fuel injection pump 3 has the same number of injection ports as the number of cylinders, and each of these injection ports is connected to a main fuel supply passage 4, and each of these main fuel supply passages 4 is connected to a combustion chamber of the engine. The fuel injection valve 5 is connected to the fuel injection valve 5 provided in the fuel injection valve 5 . As is well known, the fuel injection valve 5 includes a needle valve 6,
This needle valve 6 has a needle body 7 which is housed so as to be slidable in the axial direction, and when the needle valve 6 is lifted by the pressure of fuel, the injection hole 8 is opened and fuel is injected. It has become.

The fuel injection valves 5 are numbered I, ■, ■, ■ and correspond to the numbers of the injection ports of the injection pump 3. In this example, I-m
It is assumed that injection is performed in the order of -IV-n.

10 is an auxiliary fuel tank, 11 is an auxiliary fuel oil pump, 1
2 is an auxiliary fuel supply passage.

The auxiliary fuel supply passages 12 are connected to the fuel injection valves 5, and therefore the number of auxiliary fuel supply passages 12 is the same as that of the fuel injection valves 5.

In this case, the main fuel supply passage 4 supplies main fuel to the injection valve 5 in the injection stroke, but the auxiliary fuel supply passage 12 is configured to supply auxiliary fuel to the injection valve 5 in the next injection stroke. There is.

Each of the auxiliary fuel supply passages 12 is provided with an auxiliary fuel supply device 15 according to the present invention. In this example, only one is shown.

The auxiliary fuel supply device 15 has a main body 20, and a pump chamber 21 is formed inside the body 20.

Further, the body 20 is formed with an auxiliary fuel port 22 and an auxiliary fuel outlet 23 that communicate with the pump chamber 21, and a main fuel pressure passage 24 that communicates with the fuel supply passage 4 from the pump chamber 21.

Note that an orifice 25 is formed in the pressure guiding passage 24.

Inside the pump chamber 21, a stepped portion 26 is formed in the middle, and a stopper 27 is screwed onto the back, and the stopper 27 is attached to be movable forward and backward.

A main piston 30 is provided within the body 20 so as to be reciprocally movable, with one end facing the pump chamber 21 and the other end facing the main fuel pressure passage 24.

Further, an auxiliary piston 31 is provided in the pump chamber 21 so as to be reciprocally movable, with one end facing the main piston 30 and the other end facing the stopper 27. The auxiliary piston 31 is movable between the stepped portion 26 and the stopper 27, and substantially divides the pump chamber 21 into the main piston 30 side and the stopper 27 side, and both chambers are divided into, for example, the auxiliary piston side. 3
Electrical conduction is established through a through hole 32 formed in 1.

A relatively low-load main spring 33 is provided between the main piston 30 and the auxiliary piston 310, and this main spring 33 presses and urges the main piston 30 toward the main fuel pressure passage 24 side. ing.

Moreover, between the auxiliary piston 31 and the stopper 27,
An auxiliary spring 34 with a relatively high load is provided,
This auxiliary spring 34 presses and biases the auxiliary piston 31 toward the main piston 30 side.

Therefore, if the pressure in the main fuel pressure passage 24 increases,
When the main piston 30 moves to the right in the figure against the biasing force of the main spring 33 with a relatively high load, and the pressure in the main fuel pressure passage 24 further increases, the auxiliary piston 31 moves against the biasing force of the auxiliary spring 34 with a relatively high load. It is designed to move to the right side of the diagram against the

Further, the auxiliary fuel port 22 of the body 20 is provided with an inflow side check valve 3 that allows the auxiliary fuel to flow into the pump chamber 21.
5 is installed, and the auxiliary fuel outlet 23 is also provided with an outflow side check valve 36 that allows the auxiliary fuel to flow out from the pump chamber 21.

The inlet check valve 35 is connected to the auxiliary fuel supply pump 11 side of the auxiliary fuel supply passage 12, and the outflow side check valve 36 is connected to the fuel injection valve 5 side of the auxiliary fuel supply passage 12.

The operation of the fuel injection system of a diesel engine having such a configuration will be explained.

Methanol as the main fuel is sent from the main fuel tank 1 to the injection pump 3 via the main fuel feed pump 2, pressurized by the injection pump 3, and distributed under high pressure through each injection port. Such high pressure methanol is sent to the fuel injection valve 5 through the main fuel supply passage 4.

In this case, when the pressure of the first fuel injection valve 5 becomes higher than the opening pressure of the two-dollar valve 6, the needle valve 6 is lifted, the injection hole 8 is opened, and fuel is injected.

When methanol supply from the fuel injection pump 3 ends, the pressure in the fuel injection valve 5 decreases, the needle valve 6 closes the injection hole 8, and fuel injection ends.

On the other hand, light oil as auxiliary fuel is sent from the auxiliary tank 10 to the auxiliary fuel supply device 15 of the present invention via the auxiliary fuel feed pump 11, and is sent into the pump chamber 21 by opening the inflow side check valve 35. There is.

In this case, the oil pressure of the auxiliary fuel oil feed pump 011 cannot push open the outflow side check valve 36, and the pump chamber 21 is filled with light oil.

In this state, high pressure methanol pressurized by the main fuel injection pump 3 passes through the main fuel supply passage 4 to the fuel injection valve 5.
Since the fuel pressure in the main fuel supply passage 4 becomes high when the fuel is sent to the main fuel pressure passage 24, this pressure is guided to the auxiliary fuel supply device 15 through the main fuel pressure passage 24. The pressure introduced through the pressure guiding passage 24 acts on the main piston 30 and pushes the main piston 30 to the right in the figure.

If the introduced pressure is relatively low, the main piston 3
0 moves against the pressing force of the main spring 33. For this purpose, the light oil filled between the main piston 30 and the auxiliary piston 31, that is, the auxiliary fuel, is pressurized.

The pressurized auxiliary fuel passes through the through hole 32 formed in the auxiliary piston 31 and increases the pressure in the pump chamber 21, which forces the outlet side check valve 36 open and flows from the auxiliary fuel supply passage 12 to the fuel injection valve 5. sent to.

However, in this case, the auxiliary fuel is supplied to the injection valve (■) that performs the injection next, and when this injection valve (■) injects, the auxiliary fuel with excellent ignitability is injected before the main fuel is injected. It is something that is done.

When the supply of methanol from the fuel injection pump 3 to the first fuel injection valve 5 is finished, the pressure in the pressure guiding passage 24 decreases, and the main piston 30 is pushed by the main spring 33 and returns to the left side in the figure.

For this reason, the pressure in the pump chamber 21 decreases, and the outlet side check valve 3
6 is closed, the inflow side check valve 35 is opened, and light oil is sent into the pump chamber 21 from the auxiliary fuel oil feed pump 11.

As mentioned above, when the pressure in the pressure guiding passage 24 is relatively low, only the main piston 30 operates, and the injection valve 5 is injected with light oil of a value obtained by multiplying the movement amount X1 of the main piston 30 by the cross-sectional area of the main piston 30. will be sent to.

By the way, when the supply pressure of the main fuel sent out from the fuel injection pump 3 is high, this pressure is guided to the auxiliary fuel supply device 15 through the pressure guiding passage 24 in the same manner as described above.

The pressure led through this pressure guiding passage 24 is applied to the main piston 3.
0 and pushes this main piston 30 to the right in the figure. In this case, since the pressure introduced through the pressure channel 24 is high, the main piston 30 pushes the main spring 33 and further pushes the auxiliary piston 34 against the auxiliary spring 34 .

Therefore, the main piston 30 and the auxiliary piston 31 both move to the right in the figure, pressurizing the light oil in the pump chamber 21.

In this case, the amount of movement of the main piston 30 is the amount of movement x when the injection pressure and the auxiliary spring 34 are balanced with x1.
Therefore, the amount of light oil that is equal to the travel amount xi + x2 of the main piston 30 multiplied by the cross-sectional area of the main piston 30 is pressurized.
6 is pushed open, and the fuel is sent from the auxiliary fuel supply passage 12 to the fuel injection valve 5.

When the supply of methanol from the fuel injection pump 3 to the fuel injection valve 5 is finished, the pressure in the pressure passage 24 decreases, the main piston 30 is pushed by the main spring 33, and the auxiliary piston 34 is pushed by the auxiliary spring 34. and return to the left side of the figure.

For this reason, the pressure in the pump chamber 21 decreases, and the outlet side check valve 3
6 is closed, the inflow side check valve 35 is opened, and the pump chamber 21 is replenished with light oil from the auxiliary fuel oil supply pump 11.

As mentioned above, when the pressure in the pressure guiding passage 24 is relatively high, the main piston 30 and the auxiliary piston 31 operate.
The amount of light oil sent to the injection valve 5 increases.

In a diesel engine, the relationship among engine speed, load (injection amount), and methanol pressure in the main fuel supply passage 4 is as shown in FIG.

From this characteristic diagram, it can be seen that the methanol injection pressure decreases when the engine speed is low and the load is small, and increases when the engine speed becomes high and the load becomes large.

Therefore, during low-speed, low-load operation such as idling operation, the amount of light oil supplied can be reduced by operating only the main piston 30, and during high-speed, high-load operation, both the main piston 30 and the auxiliary piston 31 operate. This makes it possible to increase the amount of light oil supplied. In other words, the amount of light oil supplied as auxiliary fuel can be automatically adjusted depending on the operating conditions of the engine.

Therefore, during low-speed, low-load operation such as idling operation, a large amount of auxiliary fuel with a large calorific value is not sent to the engine, and the generation of black smoke is prevented.
It is possible to improve ignitability under high-speed, high-load operating conditions, and prevent misfires from occurring.

Furthermore, the amount of auxiliary fuel consumed can be saved, and the capacity of the auxiliary fuel tank 10 can also be reduced.

Note that the present invention is not limited to the embodiment shown in FIG.

That is, in the case of the embodiment shown in FIG.
Although the auxiliary piston 31a is formed into a plate shape, the auxiliary piston 31a may be formed into a cap-shaped auxiliary piston as in another embodiment shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, an auxiliary piston is provided in addition to the main piston, and only the main piston 30 is operated to supply auxiliary fuel during low-speed, low-load operation such as idling operation. During high-speed, high-load operation, both the main piston 30 and the auxiliary piston 31 can be operated to increase the amount of auxiliary fuel supplied. This prevents large amounts of auxiliary fuel with a large calorific value from being sent into the engine during low-speed, low-load operation such as idling, preventing the generation of black smoke, and preventing ignition during high-speed, high-load operation. It is possible to improve performance and prevent misfires from occurring. Further, there are advantages such as being able to save on the amount of auxiliary fuel consumed and reducing the capacity of the auxiliary fuel tank.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a configuration diagram showing a fuel supply system of a diesel engine, and FIG.
The figure is a characteristic diagram showing the relationship between engine speed and load, Figure 3 is a configuration diagram of an auxiliary fuel supply system showing another embodiment of the present invention, and Figure 4 is a configuration diagram of a conventional auxiliary fuel supply system. . 1... Main fuel tank, 2... Main fuel oil pump, 3
...Main fuel injection pump, 4...Main fuel supply passage, 5
... Fuel injection valve, 10... Auxiliary fuel tank, 11... Auxiliary fuel feed pump, 12... Auxiliary fuel supply passage, 15... Auxiliary fuel supply device, 20... Body, 21 ...Pump chamber, 22...Inlet, 23...Outlet, 24...Pressure passage, 30...Main piston, 31...Auxiliary piston, 32...Through hole,
33...Main spring, 34...Auxiliary spring,
35... Inlet side check valve, 36... Outlet side check valve. The words of the engine - Figure '2 Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (1)

[Scope of Claims] A body having a pump chamber formed therein, an auxiliary fuel inlet and an auxiliary fuel outlet communicating with the pump chamber, and a main fuel pressure passage communicating with the pump chamber; a main piston that is reciprocably provided within the pump chamber and has one end facing the main fuel pressure passage and the other end facing the pump chamber; an auxiliary piston, a means for connecting the main piston side and the pump chamber side separated by the auxiliary piston, and a means provided between the main piston and the auxiliary piston to press the main piston toward the main fuel pressure passage side. A main spring with a low load that biases the auxiliary piston, an auxiliary spring that has a higher load than the low load spring that is provided in the pump chamber and biases the auxiliary piston toward the main piston, and an auxiliary spring that is provided at the auxiliary fuel inlet. It is characterized by comprising an inflow side check valve that allows the auxiliary fuel to flow into the pump chamber, and an outflow side check valve that is provided at the auxiliary fuel outlet and allows the auxiliary fuel to flow out from the pump chamber. Auxiliary fuel supply device.