JPH0355808Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The present invention relates to a fuel injection device for a multi-cylinder internal combustion engine, and more specifically, the present invention relates to a fuel injection device for a multi-cylinder internal combustion engine, and more specifically, it uses alcohol, etc., which is difficult to cause compression self-ignition as the main fuel, and has excellent compression self-ignition. The present invention relates to a dual fuel supply system for a diesel engine that uses light oil or the like as an auxiliary fuel.

[Conventional technology]

In a dual fuel supply device that uses alcohol or the like as a main fuel and diesel oil or the like as an auxiliary fuel, it is known that it is preferable to inject alcohol and diesel oil in a layered manner without mixing them. That is, a small amount of light oil is first injected to provide a spark,
Next, alcohol, which is the main fuel, is injected. Such dual fuel supply devices are disclosed in Japanese Patent Application Laid-open Nos. 58-206859 and 58-206867.

[Problem that the invention attempts to solve]

The above-mentioned prior art consists of a distribution type fuel injection pump for pumping the main fuel, a pressure feeder and a fuel injection nozzle for pumping the auxiliary fuel, and the pressure feeder is used as the main fuel injection pump during pressure feeding of the distribution type fuel pump. It is operated by fuel pressure.
In order to supply the main and auxiliary fuel in the layered manner described above, the introduction of the auxiliary fuel into the auxiliary fuel introduction passage of a specific injection nozzle is adjusted to the pressure of the main fuel on the way to the main fuel introduction passage of another injection nozzle. This is done by means of a pressure feeder which is operated by the Therefore, the auxiliary fuel is introduced into a particular fuel injection nozzle prior to the injection timing of that nozzle, and the main fuel is injected into that nozzle when its turn comes. Note that the auxiliary fuel is introduced at a pressure that does not reach the valve opening pressure of the nozzle.

Near the tip of the fuel injection nozzle, the main fuel introduction passage and the auxiliary fuel introduction passage communicate with each other, and the auxiliary fuel is introduced by displacing the main fuel. However, although the pressure feeder always delivers the auxiliary fuel at a constant pressure, the residual pressure in the main fuel introduction passage changes as shown in FIG. 3, for example, depending on the engine speed and load. FIG. 3 shows that the residual pressure tends to increase along arrow a depending on the rotational speed and the main fuel (alcohol) injection amount. If the residual pressure reaches a value P ₃ higher than the pressure P' of the pressure feeder, the secondary fuel will enter the fuel injection nozzle even if the pressure feeder operates at time t ₁ as shown in Figure 2A. Therefore, only the main fuel is injected at time _t2 . In order to solve this problem, it is not possible to increase the pumping pressure P' of the pumping device.
This is because the pumping pressure P' must be lower than the valve opening pressure of the fuel injection nozzle. Furthermore, even if the residual pressure is lower than the pumping pressure P', if the differential pressure between them changes, the amount of auxiliary fuel introduced will also change, which is not preferable.

[Means for solving problems]

In order to solve the above problems, a dual fuel supply device according to the present invention includes a fuel injection pump that pumps the first fuel at high pressure, and a plurality of pumps that pumps out the second fuel at relatively low pressure. , a plurality of fuel injection nozzles each having a first fuel introduction passage for introducing the first fuel and a second fuel introduction passage for introducing the second fuel, the pressure feeder comprising: The second fuel is actuated by the pressure of the first fuel being introduced into the first fuel introduction passage of a certain fuel injection nozzle to send the second fuel to the second fuel introduction passage of another fuel injection nozzle. In the dual fuel supply device configured as shown in FIG. It is characterized by the fact that it has been provided.

〔Example〕

In FIG. 1, the dual fuel supply system according to the present invention is composed of one distribution type fuel injection pump 10, pressure feeders 12 of the same number as the number of cylinders of the diesel engine, and fuel injection nozzles 14 of the same number as the number of cylinders of the diesel engine. Ru. Furthermore, there is a first fuel tank 16 for a main fuel such as alcohol and a second fuel tank 18 for a secondary fuel such as light oil.

The distribution type fuel injection pump 10 has almost the same basic structure as a conventionally known pump, and therefore parts not directly related to the present invention have been omitted. It has a feed pump 20 and a cam plate 22 that are driven by a drive shaft (not shown), and the cam plate 22 slides on rollers 24 to rotate together with the plunger 26 and reciprocate. The plunger 26 is slidably inserted into a cylinder 28 provided in the pump body,
A pressure chamber 30 is formed by the cylinder 28 and the tip of the plunger 26. A suction group 32 is provided on the outer periphery of the tip of the plunger 26 . The main fuel of the first fuel tank 16 passes from the feed pump 20 through the pump chamber and fuel passage 34 in the pump body, and further through the suction group 32 to the pressure chamber 30.
can be inhaled.

A port 36 extends through the center of the plunger 26, and the port 36 opens toward the inner wall of the cylinder near its intermediate portion by a radial distribution port 38. Distribution passages 40 corresponding to the number of cylinders are formed in the cylinder 28 and the pump body at positions in the circumferential direction with the plunger 26 as the center, and when the distribution port 38 and a specific distribution passage 40 meet, the main fuel is is pumped. The outlet of the distribution passage 40 is indicated at 41. As is well known, there is a spill port 42 near the rear end of the plunger 26, and when the spill ring 44 opens the spill port 42, the fuel pumping ends. It is also known that the spill ring 44 is controlled by an adjuster steering lever, a governor mechanism, etc., and a fuel cut electromagnetic valve 46 is disposed in the fuel passage 34, and a solenoid valve 46 is disposed in each distribution passage 40. A pumping control means 48 is arranged to maintain the residual pressure substantially constant, which will be explained in detail later.

The pressure feeder 12 includes a main body 50, in which a substantially T-shaped internal cavity is formed, and a portion of the internal cavity corresponding to the horizontal direction of the T forms a linear passage,
The ends thereof serve as an inlet 52 and an outlet 54, respectively. Second fuel is supplied to this inlet 52 from the second fuel tank 18 via a feed pump 56 . An internal hollow portion corresponding to the vertical side of the T-shape serves as a cylinder 60 that slidably supports the pressurizing piston 58. Pressure piston 58
When moving to the right in FIG. 1, the volume of the passage portion is reduced to force-feed the second fuel.

Only one is shown in FIG. Pressure feeder 12
As described above, there are only as many fuel injection nozzles 14 as there are cylinders. This fuel injection nozzle 14
is connected to the outlet 41 of the distribution passage 40 by a pipe 43 so that the main fuel can be introduced. There is another distribution passage outlet 4 near the center of the first
1a is shown, and this outlet 41a is connected to the pipe 4
It is adapted to be connected to a different fuel injection nozzle than that shown in the figure by 3a. The cylinder 60 of the pressure feeder 12 shown in the figure is communicated with the outlet 41a of the another distribution passage, so that the pressurizing piston 58 receives the pressure of the main fuel passing through the distribution passage from the rear side, and the second It is now possible to pump out fuel. The cylinder 60 is a pressurizing piston 58
Abutment stopper surfaces are provided on the front and rear sides of the pressurizing piston 58 to keep the stroke of the pressurizing piston 58 constant, and a spring 62 is disposed on the entire surface of the pressurizing piston 58. A check valve 64 that allows only the introduction of fuel is provided near the introduction port 52.
A check valve 66 that only allows fuel to be delivered is arranged near the delivery port 54, and a pressure chamber 65 is formed between these check valves.

Each fuel injection nozzle 14 includes a nozzle body 70 having a nozzle orifice 68 at its tip, and a needle valve 72 inserted into the nozzle body 70. In Fig. 1, fuel injection nozzle 1
Although the upper part of 4 has been omitted, it will be clear that a spring biasing the needle valve 72 is located in such an upper part.

A first fuel introduction passage 74 for introducing the first fuel is formed in the nozzle body 70 and can communicate with the nozzle orifice 68 when the needle valve 72 is opened. This first fuel introduction channel 74 is connected by a pipe 43 to a particular distribution channel 40 of the fuel injection pump, and the nozzle body 70 also has a second fuel introduction channel for introducing a second fuel.
A fuel introduction passage 78 is formed, and this second fuel introduction passage 78 is formed.
The fuel introduction passage 78 communicates with the first fuel introduction passage 74 near the valve seat of the needle valve 72. In this embodiment, the second fuel introduction passage 78 is formed from the nozzle body 70 through the central portion of the needle valve 72, and extends radially into the annular portion of the first fuel introduction passage 74 near the tip of the needle valve 72. It's open. The second fuel introduction passage 78 is connected to the above-mentioned outlet port 54 of the pressure feeder 12 by a pipe 79.

The pressure control means 48 disposed in each distribution passage 40 of the fuel injection pump 10 consists of a first valve 80 having a structure similar to a conventional delivery valve and a second valve 82 having a structure similar to a check valve. The first valve 80 is urged toward the upstream side of the passage by a spring 84, and opens the passage by the pressure of the fuel when the fuel is being pumped, and closes the passage when the pumping is finished. A groove for sucking back at this time is also provided. A port 86 is formed through the center of the second valve 80, and a check ball 88 carried by the second valve 82 engages with the upstream open end of the port 86. Second valve 82
a spring 90 that urges the
is located. The spring force of this spring 90 is set to be weaker than the spring force of the biasing spring 84 of the first valve 80, so that the first valve 80
When moving to the right in the figure to open the passage, the second valve 82 and check ball 88 also move to follow.
When the first valve 80 moves to the left to close the passage, the second valve 82 and check ball 88 similarly move accordingly. However, if the residual pressure of the first fuel from downstream of the first valve 80 to the fuel injection nozzle 14 is high, the check ball 88 opens and the residual pressure is maintained at a substantially constant level determined by the spring force of the spring 90. Maintain pressure. The second valve 82 is formed in a shape that does not obstruct the flow of fuel within the passage, and supports the check ball 86 so as to properly engage the port 86.

Next, the effect will be explained.

Distribution passage and pipe 43a including outlet 41a
When fuel is injected from the fuel injection nozzle communicating with the fuel injection nozzle, the pressure feeder 12a operates in response to the pressure of the main fuel, and the auxiliary fuel is forced into the second fuel introduction passage 78 of the fuel injection nozzle 14. This pressure is lower than the opening pressure of the needle valve 72 of the fuel injection nozzle 14, so the needle valve 72 does not open, and is lower than the residual pressure in the first fuel introduction passage 74 and the pipe 43 upstream thereof. The auxiliary fuel introduced due to the high fuel pressure displaces the first fuel at the tip of the first fuel introduction passage 74 and fills the tip of the first fuel introduction passage 74. At this time, there is a nozzle orifice 68 in the first fuel introduction passage 74 near its tip.
There is an auxiliary fuel near the auxiliary fuel, and there is a main fuel upstream of the auxiliary fuel. The filling amount of the auxiliary fuel becomes constant due to the constant stroke of the pressurizing piston 58 and the constant pressure relationship. When the injection time of the fuel injection nozzle 14, which is filled with fuel in a stratified manner in this manner, comes to inject, the auxiliary fuel located near the nozzle orifice is injected first and is easily ignited during the compression stroke of the engine, causing it to become a ignition source. The subsequently injected main fuel can be easily ignited. Along with this injection of the injection nozzle 14, another pressure feeder connected to the outlet 41 of the distribution passage 40 fills another injection nozzle with auxiliary fuel.

When injection is terminated by the spill ring 44 opening the spill port 42, the first valve 80 of the pressure control means 48 closes the passage, with residual pressure remaining downstream of the first valve 80. . This residual pressure causes the check ball 88 of the second valve 82 to open, thereby maintaining the residual pressure at a value determined by the spring force of the spring 90. This value is almost constant regardless of the number of revolutions of the diesel engine or the amount of main fuel injection, and
This is a relatively small value compared to the pumping pressure. Therefore, when injection is performed in another related cylinder after this cycle ends, the tip of the injection nozzle 14 is filled with auxiliary fuel by the action of the pressure feeder 12 in preparation for the next injection. FIG. 2B shows this sequence of cycles for a particular cylinder, in which the pressure in the fuel injection nozzle 14 is maintained at a relatively low constant value P ₁ , and at time t ₁ another cylinder When _the injection of
The fuel injection nozzle 14 is filled with the auxiliary fuel at a pressure lower than P ₀ . When the fuel injection timing _t2 for that cylinder comes, the auxiliary fuel is injected, and then the main fuel is injected. When the injection ends, the pressure inside the fuel injection nozzle 14 is again kept at a relatively low constant pressure.
P will be maintained at ₁ .

[Effect of idea]

As explained above, according to the present invention, it is possible to always maintain a constant filling amount of secondary fuel, and even when using alcohol, etc. with low ignitability as the main fuel, the ignitability is improved and stabilized. Combustion can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a dual fuel supply device according to the present invention, FIG. 2 is a diagram showing the pressure of the fuel injection nozzle, and FIG. 3 is a diagram showing the equal residual pressure of the conventional device. 10... fuel injection pump, 12... pressure feeder, 1
4... Fuel injection nozzle, 48... Pressure control means,
80...first valve, 82...second valve.

Claims (1)

[Scope of utility model registration request] a fuel injection pump for pumping a first fuel at high pressure; a plurality of pumps for pumping a second fuel at relatively low pressure; and a first pump for introducing the first fuel.
and a second fuel introduction passage for the introduction of the second fuel.
a plurality of fuel injection nozzles having a fuel introduction passage, and the pressure feeder has a first fuel injection nozzle on the way to be introduced into the first fuel introduction passage of a certain fuel injection nozzle.
In a dual fuel supply device configured to deliver a second fuel to a second fuel introduction passage of another fuel injection nozzle by being actuated by the pressure of the fuel of the fuel injection nozzle from the fuel injection pump, A dual fuel supply device characterized in that a pressure control means for maintaining the pressure substantially constant when the first fuel is not being fed under pressure is provided in the middle of a path connecting the first fuel introduction passages.