JPH06100160B2 - Dual fuel supply system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device for a multi-cylinder internal combustion engine, and more specifically, it uses alcohol or the like, which is difficult to self-ignite by compression, as a main fuel and is excellent in self-ignition by compression. The present invention relates to a dual fuel supply device for a diesel engine that uses light oil or the like as an auxiliary fuel.

[Conventional technology]

It is known that in a multiple fuel supply system that uses alcohol or the like as the main fuel and light oil or the like as the auxiliary fuel, it is preferable to inject them in layers without mixing the alcohol and the light oil. That is, a small amount of light oil is injected first to provide a spark, and then alcohol, which is the main fuel, is injected. JP-A-58-206859 and JP-A-58-2068
Japanese Patent Publication No. 67 discloses such a dual fuel supply device. According to these prior arts, a main fuel is supplied under pressure from a fuel injection pump to a fuel injection nozzle, and a pressure feeder that operates by receiving the pressure of the fuel of the fuel injection pump is provided, and a sub fuel is injected from this pressure feeder. Pressure is supplied to the fuel injection nozzles other than the stroke. Therefore, the sub fuel is stored at the tip of the fuel injection nozzle other than the injection stroke, and is injected together with the main fuel during the injection stroke. Furthermore, the applicant of the present application previously connected a single pressure feeder to the pressure chamber formed at the tip of the plunger of the distribution type fuel injection pump in Japanese Patent Application No. 60-106833, and branched each fuel from this pressure feeder. We have proposed a multiple fuel supply system that supplies auxiliary fuel to the injection nozzle.

[Problems to be solved by the invention]

The auxiliary fuel may be small in amount to ensure compression ignition, and is preferably introduced evenly into each cylinder. Therefore, as suggested in the above-mentioned Japanese Patent Application No. 60-106833, the auxiliary fuel is pumped. It is preferable that the fuel is sent to each cylinder by a branch pipe from a single sending section of. As a result, the auxiliary fuel is introduced into the fuel injection nozzles other than the injection stroke arithmetically, and the uniformity of the introduced auxiliary fuel is improved. However, if this branch pipe is simply formed, a difference occurs in the length of the branch pipe for each cylinder, and even if the auxiliary fuel is introduced arithmetically, the throttling loss of the piping system is not uniform, Since the auxiliary fuel is introduced into the fuel injection nozzle at a pressure lower than that of the main fuel, there arises a problem that the filling amount varies.

[Means for solving problems]

According to the present invention in order to solve the above problems, a fuel injection nozzle provided in each cylinder controls the opening and closing of a nozzle orifice, and a first fuel introduction passage formed around the needle valve, A second fuel introduction passage communicating with the innermost portion on the nozzle orifice side of the first fuel introduction passage, for pressurizing the first fuel and sequentially applying the pressurized first fuel to each fuel injection nozzle. And a fuel injection pump for supplying the second fuel into the second fuel introduction passage of each fuel injection nozzle driven by the pressure of the pressurized first fuel. And a needle for filling the innermost portion of the first fuel introduction passage with the second fuel delivered from the pump when the needle is closed and the needle. When the valve opens, In a dual fuel supply system in which the second fuel with which the portion is filled is first injected from the nozzle orifice, and then the first fuel is injected from the nozzle orifice, a single second fuel from the pump is supplied. Of the fuel delivery section, and the fuel delivery section is connected to the second fuel introduction passage of each fuel injection nozzle via a branched injection pipe, and the fuel delivery section extends from the fuel delivery section to the second fuel introduction passage. The passage resistances in the injection pipe are made equal to each other.

〔Example〕

Referring to FIG. 1, the dual fuel supply system according to the present invention comprises one distribution type fuel injection pump 10, one pump 12 and the same number of fuel injection nozzles 14 as the number of cylinders of a diesel engine. In addition, 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 distributed fuel injection pump 10 has substantially the same basic structure as that of a conventionally known fuel pump, and therefore parts not directly related to the present invention are omitted. It has a feed pump 20 and a cam plate 22 which are driven by a drive shaft (not shown), and the cam plate 22 slides on a roller 24 to reciprocate while rotating with a plunger 26. The plunger 26 is a cylinder 28 provided on the pump body.
It is slidably inserted in the cylinder 28 and the plunger 26.
The pressure chamber 30 is formed by the tip of the. Plunger 26
There is an inhalation group 32 on the outer periphery of the tip of the. The main fuel in the first fuel tank 16 passes from the feed pump 20 through the pump chamber in the pump body and the fuel passage 34, and further into the suction group.
It is sucked into the pressure chamber 30 through 32.

A port 36 extends in the center of the plunger 26, which port 36 opens in the vicinity of an intermediate portion thereof toward a cylinder inner wall surface by a radial distribution port 38. A distribution passage 40 for the number of cylinders is formed at a circumferential position around the plunger 26 in the cylinder 28 and the pump main body, and when the distribution port 38 and the specific distribution passage 40 meet, the main fuel is supplied from the distribution passage 40. Is pumped. It is well known that there is a spill port 42 near the rear end portion of the plunger 26, and the spill ring 44 opens the spill port 42 to end the fuel pumping. It is also well known that the spill ring 44 is controlled by an adjusting lever, a governor mechanism, etc., a fuel cut solenoid valve 46 is arranged in the fuel passage 34, and a delivery passage 40 is provided with a delivery valve. A valve 48 is arranged. The delivery valve 48 keeps the residual pressure constant after the end of injection.

The pump 12 is composed of a main body 50, and a substantially T-shaped internal cavity is formed in the main body 50. The internal cavity portion corresponding to the horizontal side of the T-shape forms a substantially linear passage, and its end is They are the inlet 52 and the outlet 54, respectively. The inlet 52 is connected to the second fuel tank 18 through the feed pump 56 and the second
Fuel is supplied. The inner hollow portion corresponding to the vertical side of the T-shape has a cylinder 60 slidably supporting the pressure piston 58.
Has become. The pressurizing piston 58 reduces the volume of the passage portion and moves the second fuel under pressure when moving to the right in FIG.

The body 50 of the pump 12 is screwed onto the body of the injection pump, and the cylinder 60 of the pump 12 opens into the pressure chamber 30 formed by the tip of the plunger 26 of the injection pump. Therefore,
The pressurizing piston 58 receives the pressure of the pressure chamber 30 from the rear side thereof to reduce the volume of the second fuel passage as described above, and the spring 62 arranged around the fuel passage internal pressurizing piston 58. Is urged toward the pressure chamber 30 side. The pressurizing piston 58 has a collar-shaped bulging portion in the middle thereof so as to come into contact with the stepped shoulder portion of the cylinder 60, and the retracted position of the pressurizing piston 58 is limited.
The tip end of the pressure piston 58 can abut the inner wall of the main body 50, and the advance position of the pressure piston 58 is limited.
Therefore, the stroke of the pressurizing piston 58 becomes constant, and the amount of second fuel pumped for each stroke becomes constant. A check valve near the inlet 52 that allows only fuel to be introduced
64 is disposed, and a check valve 66 that permits only fuel delivery is disposed near the delivery port 54.

Each fuel injection nozzle 14 is composed of a nozzle body 70 having a nozzle orifice 68 at its tip and a needle valve 72 inserted in the nozzle body 70. Although the upper portion of the fuel injection nozzle 14 is omitted in FIG. 1, it will be apparent that a spring for biasing the needle valve 72 is arranged in such an upper portion.

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. Each of the first fuel introduction passages 74 is connected to a specific distribution passage 40 of the distribution type fuel injection pump 10 by a pipe 76. A second fuel introduction passage 78 for introducing the second fuel is further formed in the nozzle body 70, and the second fuel introduction passage 78 is provided near the valve seat of the needle valve 72. aisle
It communicates with 74. 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 is radially formed in the annular portion of the first fuel introduction passage 74 near the tip of the needle valve 72. It is open to. Further, a check valve 80 which allows only the flow toward the nozzle tip portion is arranged in the second fuel introduction passage 78 of each fuel injection nozzle 14.

All fuel injection nozzles have the same structure and are properly attached to the engine. On the other hand, the outlet 54 of the pressure feeder 12 is connected to one injection pipe 84, and this injection pipe 84 is branched into two branch injection pipes 86 having the same length and diameter, and each branch injection pipe 86 is further divided. It is branched into two branch injection pipes 88 having the same length and pipe diameter. In this way, the end portions of the branch injection pipes 88 branched from the common injection pipe 84 are connected to the second fuel introduction passages 78 of the fuel injection nozzles 14, respectively. Accordingly, the branch injection pipes 86, 88 branched from the common delivery portion 90 at the outlet 54 of the pressure feeder 12 or the terminal end of the common injection pipe 84 toward the respective cylinders have the same pipe length. .

Next, the operation will be described with reference to FIG.

Since the operation of a distributed fuel injection pump is well known, it will be briefly explained that during a single reciprocation of the plunger 26, the first fuel is drawn into the pressure chamber 30, pressurized, and meets the distribution port 38. The fuel is injected from the distribution passage 40 to the fuel injection nozzle 14. If this dual fuel supply system is installed in a 4-cylinder diesel engine, the injection sequence is I, III, IV, II, and the injection time of the first cylinder is 0 degree crank angle, as shown in FIG. Injection is completed at pressure P ₄ . This pressure P ₄ is naturally higher than the valve opening pressure of the fuel injection nozzle 14.

At the time of injection in the first cylinder, the pressurizing piston 58 of the pump 12 moves to the right due to the rise in the pressure in the pressure chamber 30 of the injection pump, so that the second fuel is completely injected from the outlet 54 of the pump 12. It is pumped toward the nozzle 14. However, in the fuel injection nozzle 14 of the first cylinder that is currently injecting, the first fuel introduction passage
Due to the high pressure from the injection pump applied to 74, the second fuel cannot proceed and tries to be pushed back.
However, because of the check valve 80, there is no reverse flow from the fuel injection nozzle 14 to the branch injection pipe 88, and the second fuel is the second fuel except for the portion entering the tip portion of the first fuel introduction passage 74. The second fuel in the fuel introduction passage 78 of is maintained therein.

On the other hand, in the remaining three cylinders that are not currently injecting, the second fuel pumped at the pressure P ₁ from the outlet 54 of the pump 12 passes through the common injection pipe 84 and the branch injection pipes 86 and 88 having the same pipe length. The second fuel introduction passage 78 of the fuel injection nozzle 14 of each cylinder
Can be evenly entered. At this time, since the pressure P ₁ is higher than the residual pressure in the first fuel introduction passage 74, the second fuel displaces the first fuel and reaches the tip portion of the first fuel introduction passage 74. Further, since the pressure P ₁ is lower than the valve opening pressure of the fuel injection nozzle 14, the second fuel that has entered the tip portion of the first fuel introduction passage 74 as described above is maintained there without being injected. .

The amount of the second fuel entering the first fuel introduction passage 74 increases with each injection in each injection nozzle. That is, for example, in the second cylinder, the second fuel is filled with the pressure P ₁ at the time of injection in the first cylinder subsequent to the injection in that cylinder.
When the injection in the first cylinder is completed, the pressure in the pressure chamber 30 disappears, so the pressurizing piston 58 moves backward, and the internal space of the pump 12 is newly filled with the second fuel. Then, crank angle 18
When the injection of the third cylinder is performed at 0 degree, fuel pressure is similarly fed to the remaining three cylinders at the pressure P ₁ . In the second cylinder, since the residual pressure in the first fuel introduction passage 74 is low, the amount of the second fuel corresponding to the pressure P ₁ is further filled. Therefore, a total amount equal to the _two pumping pressures P ₂ is filled. Next, crank angle 360
When the injection of the fourth cylinder is performed at a time, a total amount equal to the pumping pressure P ₃ for three times is filled. Then, at the time of injection of the second cylinder at a crank angle of 540 degrees,
Sufficient second fuel has already been filled in the tip portion of the first fuel introduction passage 74, the first fuel is stratified on the upstream side thereof, and the second fuel is first injected at the time of injection start. The first fuel is easily ignited in the compression stroke of the cylinder, and the first fuel which is difficult to self-ignite continuously is easily ignited. Therefore, the tip of each fuel injection nozzle 14 is filled with the second fuel three times evenly before the injection timing of the first fuel in the cylinder. However, the variation is extremely small even though the total amount is extremely small due to the arithmetic average filling.

FIG. 3 shows a second embodiment of the present invention, and the respective structures of the distribution type fuel injection pump 10, the pump 12, and the fuel injection nozzle 14 are the same as those shown in FIG. In FIG.
The piping for supplying the second fuel to each fuel injection nozzle 14 is different from that shown in FIG. That is, in FIG. 2, the injection pipes 92 having the same pipe length and the same pipe diameter are branched and connected directly from the single delivery port 54 of the pressure feeder 12. The operation is similar to that of the example shown in FIG.

FIG. 4 shows a third embodiment of the present invention, which comprises a row type fuel injection pump 10a, a pump 12a having the same number as the number of cylinders, and a fuel injection nozzle 14 having the same number as the number of cylinders. The structure of the nozzle 14 is the same as the example described above. The column-type fuel injection pump 10a may have a conventionally known structure, and although detailed description is omitted here, it is clear that the column-type fuel injection pump 10a has the same number of discharge ports 10b as the number of cylinders. The first fuel introduction passage 7 of each of these discharge ports 10b and each of the fuel injection nozzles 14
4 is connected to the injection pipe 76b. Each of the pumps 12a has a main body 50, a cylinder 60, a pressurizing piston 58, a return spring 62, and a second fuel inlet 52 as in the pump 12 shown in FIG. And outlets 54 and check valves 64, 66 near these ports. Cylinder 60 is connected to each of the injection tubes 76b for the first fuel. Each inlet 5
A second fuel is introduced into 2 by a feed pump 56. Each delivery port 54 is connected to a common injection pipe 84a via an injection pipe 93, and this common injection pipe 84a is provided with branch fuel injection pipes 86a and 88a having the same pipe length as the pipes of FIG. It is connected to the second fuel introduction passage 78 of the injection nozzle 14.

In FIG. 4, the row-type fuel injection pump 10a and a plurality of pumps 12a are used, but each pump 12a has a common injection pipe 84a.
, The second fuel is supplied to each fuel injection nozzle 14 in the same manner as described with reference to FIG. That is, the pump 12 of FIG.
This is because each of the pressure feeders 12a in the figure is pressure-fed once, and the common injection pipe 84a is pressure-fed four times. Therefore, fuel is supplied to the fuel injection nozzle 14 in the same manner as described with reference to FIG.

FIG. 5 shows a fourth embodiment modified from FIG. 4 similarly to the modification of FIG. 3 with respect to FIG. 1, and the delivery port 5 of each pump 12a
Each fuel injection nozzle 1 from the delivery part 90 to which 4 is commonly connected
A branch injection pipe 92a having the same pipe length and pipe diameter extends toward 4.

FIG. 6 shows a fifth embodiment, which is a row type fuel injection pump 10a.
The branch injection pipes 84a, 86a, 88a leading to the second fuel introduction passage of the fuel injection nozzle 14 have the same configuration as that of FIG. In FIG. 6, the structure of each pump 12b is different from the pumps 12 and 12a described above. Although the above-described pumps 12 and 12a are provided with the second fuel inlet 52 and the outlet 54 at positions substantially opposite to each other, in the pump 12b shown in FIG. 6, the first fuel injection pump 10a of the column type fuel injection pump 10a is provided. The common port 55 is only provided at one end of the pressurizing piston 58 that operates by receiving the pressure of the fuel. A check valve 100 is arranged upstream of the pump 12b in the common injection pipe 84a, and a second check valve 100 is operated when the pump 12b operates.
This prevents the fuel from flowing back toward the feed pump 56. It will be apparent that the second fuel is introduced or pressurized delivered through the common port 55 in response to the advancing and retracting of the pressurizing piston 58.

〔The invention's effect〕

As described above, according to the present invention, it is possible to inject the first fuel and the second fuel in layers, and even when the second fuel is supplied in relatively small amounts You can Therefore, good combustion can be performed even when alcohol or the like having relatively poor ignitability is used as the first fuel.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a multiple fuel supply system according to the present invention, and FIG. 2 is a diagram for explaining the operation of the system of FIG.
FIG. 3 is a diagram showing a second embodiment, FIG. 4 is a diagram showing a third embodiment, FIG. 5 is a diagram showing a fourth embodiment, and FIG. 6 is a diagram showing a fifth embodiment. 10 …… Fuel injection pump, 12 …… Pressurizer, 14 …… Fuel injection nozzle, 74 ・ 78 …… Fuel introduction passage, 84 ・ 86 ・ 88 …… Injection pipe.

Claims (1)

[Claims] 1. A needle injection valve provided in each cylinder for controlling the opening and closing of a nozzle orifice, a first fuel introducing passage formed around the needle valve, and a nozzle of the first fuel introducing passage. A second fuel introduction passage communicating with the innermost portion on the orifice side, pressurizing the first fuel and sequentially applying the pressurized first fuel to the first fuel introduction passage of each fuel injection nozzle. A needle for supplying the second fuel into the second fuel introducing passage of each fuel injection nozzle, the needle being provided with a fuel injection pump for supplying the fuel; and a needle driven by the pressure of the pressurized first fuel. When the second fuel discharged from the pump is filled into the innermost portion of the first fuel introduction passage via the second fuel introduction passage while the needle is opened. The innermost portion of the first fuel introduction passage is filled. In a dual fuel supply system in which the second fuel is injected from the nozzle orifice first, and then the first fuel is injected from the nozzle orifice, a single fuel delivery section for the second fuel from the pump is provided. At the same time, the fuel delivery portion is connected to the second fuel introduction passage of each fuel injection nozzle via a branched injection pipe, and the passage resistance in each injection pipe from the fuel delivery portion to the second fuel introduction passage is Multiple fuel supply devices that are equal to each other.