JPH05195901A - Fuel injection pump for dual-fuel engine - Google Patents

Abstract

PURPOSE:To provide a dual-fuel engine with a fuel injection pump injecting two kinds of fuels, namely, main and sub-fuels separately with one fuel pump by a minimum pilot fuel injection without ignition mistake. CONSTITUTION:A large plunger 4 is used for main fuel injection, while a small plunger 5 is used for pilot fuel injection. The large and small plungers 4, 5 are longitudinally integrated with each other, and thereby a fuel injection pump 1 is formed. Pilot fuel injection is carried out prior to main fuel injection. A fuel rack is adjusted such that a minimum pilot fuel amount is injected under a loaded operation. Ignition misfire of an engine is thus prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, methanol,
The present invention relates to a fuel injection pump for a dual fuel engine, which uses an alcohol-based fuel such as ethanol as a main fuel and uses heavy oil that easily ignites as a pilot fuel.

[0002]

2. Description of the Related Art Recently, it has been attempted to use an alcohol fuel such as methanol from the viewpoint of prevention of exhaust gas pollution by a diesel engine. Since this type of fuel is inferior in ignitability, as an auxiliary means for ignition, a fuel such as light oil or heavy oil A, which has excellent ignitability, is pre-injected as a pilot fuel, and in the combustion flame of this fuel, A method of injecting and igniting an alcohol-based main fuel is generally adopted.

Conventionally, a dual fuel diesel engine has been proposed in which gasoline, alcohol, LNG, etc., which are difficult to self-ignite, are used as main fuels, and light oil and heavy oil, which are easily self-ignited, are used as auxiliary fuels to ignite the main fuels by pilot injection. Has been done. For this dual-fuel diesel engine, it is desirable that the pilot fuel be as small as possible. Regarding the combustion situation in a dual-fuel diesel engine, the heat generation rate at high speed and high load is usually adjusted and fixed optimally, pilot combustion is performed first, and then the main fuel is ignited by the afterburning of pilot combustion to burn the main fuel. To perform.
However, when using this engine at low speed and low load, the time interval between pilot combustion and main combustion becomes wider,
Misfire occurs when the pilot combustion time is short. Therefore, it is necessary to increase the amount of pilot fuel injection to prolong the afterburn or to delay the pilot fuel injection timing.

By the way, as to the control means for the above-mentioned binary fuel, Japanese Unexamined Patent Publication No. 3-185234 and Japanese Unexamined Patent Publication No. 2-78729 disclose a single main fuel injection pump and a single pilot fuel injection pump by a link mechanism. A fuel control method that does not decrease or increase the pilot fuel injection amount without connecting the combustion of the main fuel and stopping the combustion of the pilot fuel when the main fuel burns (there is a risk of misfire) Is listed.

First, a conceptual diagram showing a binary fuel injection state of an engine which is generally practiced will be described with reference to FIG.
As shown in FIG. 1, the pilot fuel pump 42 and the main fuel pump 43 are arranged for one engine 41, and the pilot fuel pump 4 is installed prior to the fuel injection of the main fuel pump 43.
2, the pilot fuel is discharged into the engine and ignited, and then the main fuel is injected during the combustion of the pilot fuel. Although not shown in the above-mentioned references, the fuel injection timing is fuel injection adjustment. It is described that a delay device is provided in the rack for. Basically, the timing is adjusted by the mounting angles of the cams 44 and 45, and the cam shafts 46 and 47 are connected to each other or connected by a link mechanism.

Further, in the structure of a conventional general fuel injection pump, as shown in FIG. 9, the fuel injection pump 51 supplies the fuel delivered from the fuel tank 52 through the fuel supply pump 53 to the fuel intake port 54. From the pump chamber 55, the fuel is pumped from the pump chamber 57 by the reciprocating motion of the plunger 56, and the discharge valve 58, the discharge valve cap 59,
The fuel is injected into the cylinder 63 of the internal combustion engine 62 from the fuel injection valve 61 via the fuel injection pipe 60 in sequence. A lubricating oil supply pipe 64 is opened on the outer circumference of the plunger 56.
The fuel injection amount is adjusted by rotating the plunger 56 with the rack 65 and changing the lead angle 66 of the pump chamber 57.

[0007]

However, the conventional dual fuel injection pump is of a type in which two single fuel injection pumps are combined as described above and two types of fuel injection are performed by a link mechanism. Therefore, it was not possible to separately inject two types of fuel with one fuel injection pump. Further, it has been proved by experiments that when an alcohol fuel is used as the main fuel, the sliding portion of the plunger loses lubricity and a strong hit occurs.

The present invention has been made in view of the above-mentioned points, and an ignition error does not occur with the minimum pilot fuel, and
A dual fuel engine fuel injection pump that separately injects two types of fuel, main and sub, using two fuel pumps. At the same time, it is designed to alleviate the strong hit of the plunger part during combustion with alcohol fuel. An object is to provide a fuel injection pump for a fuel engine.

[0009]

In order to achieve the above object, a fuel injection pump for a dual fuel engine of the present invention has a large plunger for main fuel injection and a small plunger for pilot fuel injection. -In a fuel injection pump in which small plungers are vertically combined, pilot fuel injection precedes main fuel injection to prevent engine ignition mistakes.

As described in claim 2, the discharge amount of the pilot fuel may be about 5% of the total heat amount at the time of full-power operation.

As described in claim 3, it is possible to increase the injection amount of the small plunger to an injection amount that can be started, and to limit the fuel rack so that the injection amount does not exceed this amount. ..

As described in claim 4, it is desirable to provide an oil passage for communicating the high pressure fuel from the fuel passage of the pilot fuel at the end of the thrust of the small plunger between the large plunger and the barrel.

According to a fifth aspect of the present invention, an oil introducing portion is provided in a sliding portion on the outer circumference of the large plunger, and an opening of an oil passage from a fuel passage for pilot fuel is provided in the oil introducing portion at a rising position of the large plunger. It is preferable that the small plungers communicate with each other so that the small plungers coincide with the opening position of the pilot fuel barrel port.

[0014]

In the fuel injection pump of the dual fuel engine of the present invention having the above-mentioned structure, the large and small plungers are vertically integrated so that the pilot fuel and the main fuel are separately discharged during the same stroke of the plunger. can do. Then, the lead angle of the large plunger is adjusted so that the injection of the pilot fuel by the small plunger precedes the injection of the main fuel, and the injection amount of the pilot fuel is set to a minimum fixed amount. About 5 of total heat
%, That is, by adjusting the discharge amount of the pilot fuel corresponding to about 2.5% of the injection amount of the large plunger, the engine may stop or the ignition error may occur when alcohol fuel is used as the main fuel. Never.

According to the third aspect of the fuel injection pump, only pilot fuel is injected and no main fuel is injected during idling so that there is no risk of ignition failure during engine startup and no-load operation. To do. In that case, when the pilot fuel is A heavy oil, it is necessary to inject the A heavy oil so that the injection amount is about 10% of the A heavy oil usage amount in the full load region.

Further, in the fuel injection pump according to the fourth or fifth aspect of the invention, the phenomenon that a high-pressure reflected wave is generated at the fuel supply port at the moment when the small plunger moves up and the barrel port opens at the end of the thrust, is utilized. The pressure is introduced between the large plunger and its barrel to use the pilot fuel as lubricating oil, and it is possible to mitigate the strong hit due to oil shortage occurring on the outer periphery of the large plunger.

[0017]

Embodiments of the fuel injection pump for a dual fuel engine of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a vertical sectional view of a fuel injection pump according to an embodiment of the present invention. In the figure, 1 is a pump case. A sleeve 2 and a sleeve 3 are vertically housed in the pump case 1, a large plunger 4 is reciprocally housed in the sleeve 2, and a small plunger 5 is reciprocally housed in the sleeve 3. The large plunger 4 and the small plunger 5 are vertically connected to each other. A main fuel pump chamber 6 is formed in the sleeve 2,
A pilot fuel pump chamber 7 is formed in the sleeve 3.

The main fuel pump chamber 6 communicates with an annular fuel reservoir 9 formed on the outer circumference of the sleeve 2 via a fuel passage 8 formed in the sleeve 2. The pilot fuel pump chamber 7 communicates with an annular fuel reservoir 11 formed on the outer circumference of the sleeve 3 through a fuel passage 10 formed in the sleeve 3. Each of the fuel reservoir 9 and the fuel reservoir 11 communicates with a fuel intake port (not shown). That is, alcohol fuel is used as the main fuel in the fuel reservoir 9,
Fuel oil A will be supplied as a pilot fuel.

A small plunger 5 having a diameter much smaller than that of the large plunger 4 is coupled to the tip of the large plunger 4 so as to reciprocate in the sleeve 3. A land portion 5c having a vertical width a is formed at the upper end of the small plunger 5, an escape groove 5b is formed below the land portion 5c, and a vertical lead groove 5a is formed as shown in FIG. A vertical groove 12 communicating with the main fuel pump chamber 6 and an oblique groove 13 communicating with the vertical groove 12 are formed at the upper end of the large plunger 4.

The base end of the large plunger 4 is connected to the inner bottom of a bottomed cylindrical slide metal 14 having an open top. This slide metal 14 is slidably accommodated in the lower part of the pump case 1, is urged downward by a plunger spring 15, and is removed from the pump case 1 by a snap ring 16 at the lower end of the pump case 1. It has been stopped.
Reference numeral 17 in the drawing is a control barrel for adjusting the large plunger 4 to a predetermined rotation position about its axis, 18 is a pinion gear formed on the outer peripheral surface of the control barrel 17, and 19 is this pinion gear 18
The control barrel 17 is engaged with the control barrel 17 by sliding motion.
It is a control rack that drives the.

A discharge valve seat 22 is provided above the sleeve 3 so as to be in contact therewith, and the discharge valve seat 22 is provided with a discharge valve 20 for the main fuel.
And a discharge valve 21 for pilot fuel. The discharge valve 20 communicates with the main fuel pump chamber 6 and the discharge valve 21 communicates with the pilot fuel pump chamber 7. The discharge valves 20 and 21 have balls 23 and form check valves at the time of fuel injection. The discharge valve seat 22 communicates with the discharge passages 25 and 26 of the discharge valve cap 24 at the upper end of the pump case 1. That is, the main fuel pump chamber 6 and the discharge passage 25 communicate with each other through the discharge valve 20, and the pilot fuel pump chamber 7 and the discharge passage 26 communicate with each other through the discharge valve 21. The discharge valve cap 24 is for connecting the base end of the fuel injection pipe leading to the engine.

In the fuel injection pump shown in FIG. 1, the plunger spring 15 is extended and the slide 14 is attached to the pump case 1.
It shows a state of being pressed against the lower end portion of the large plunger 4 and the small plunger 5 are both at the lowermost end of the stroke. In this state, the pilot fuel passage 10
Is opened to the pilot fuel pump chamber 7, and the fuel passage 8 for the main fuel is opened to the main fuel pump chamber 6. An oil groove 27 is provided on the outer periphery of the large plunger 4 as an oil introducing portion. Oil passage 28 opened at a position a above the oil groove 27
However, the oil passage 28 communicates with the fuel passage 10 for the pilot fuel, and this oil passage 28 is opened between the large plunger 4 and the barrel formed by the sleeve 2 via the sleeve 2 and the sleeve 3 as shown by the solid line. Alternatively, it may pass through the inside of the pump case 1 as indicated by a phantom line.

FIG. 2 is a development view of the upper portion of the small plunger 5,
The height a of the land portion 5c matches the distance a between the oil groove 27 provided on the outer circumference of the large plunger 4 and the lower end opening of the oil passage 28. An escape groove 5b is provided below the land portion 5c.
Further, a vertical lead groove 5a is formed between the upper surface of the land portion 5c of the small plunger 5 and the escape groove 5b, and maintains a constant discharge amount regardless of the rack position for adjusting the oil amount of the large plunger 4.

The operating condition of the fuel injection pump of the present embodiment having the above-mentioned structure will be described together with its operation.

Pilot fuel (A heavy oil) not shown
The fuel in the fuel tank of the fuel tank is pumped through the fuel supply pipe by the fuel supply pump to be supplied to the fuel reservoir 11, and the fuel in the fuel tank of the main fuel (alcohol fuel) is pumped into the fuel supply pipe by the fuel supply pump. Is being supplied to the fuel reservoir 9, and in the same state, the slide plunger 14 is pushed up by a cam or the like to move the large plunger 4 and the small plunger 5 forward, and the restoring force of the plunger spring 15 restores the large plunger 4 and the small plunger 5. When moved, the so-called pump action causes the fuel flowing from the fuel reservoir 11 through the fuel passage 10 to the pump chamber 7 through the barrel port to move into the ball 23.
While pushing up the discharge valve 21, the discharge valve 21 is pressure-fed to the discharge passage 26 of the discharge valve cap 24 and injected from the pilot fuel injection valve into the cylinder of the internal combustion engine through the pilot fuel injection pipe.

The barrel port of the fuel passage 10 comes off the land portion 5c of the small plunger 5 when the small plunger 5 is lifted by a, and the barrel port is opened.
The escape groove 5b communicates with the fuel passage 10.

Pilot fuel passage 1 closed at this time
High-pressure reflected wave of fuel is generated at 0, and pilot fuel passage 1
The pilot fuel pressure at 0 increases instantaneously. At this time, the pilot fuel is bypassed, the opening of the oil passage 28 into the sleeve 2 coincides with the position of the oil groove 27 of the large plunger 4, and the high-pressure pilot fuel oil flows into the oil groove 27 of the large plunger 4. , Enters a space between the outer circumference of the large plunger 4 and the inner circumference of the sleeve 2 and serves as a lubricating oil.

The injection of alcohol fuel as the main fuel by the large plunger 4 is carried out thereafter due to the relationship between the vertical groove 12 and the oblique groove 13 at the upper end of the large plunger 4 depending on the planned rack position. That is, when the control barrel 17 is rotated by sliding the control rack 19 and thereby the large plunger 4 is adjusted to a predetermined rotation position about the axis, the sign of the slant groove 13 and the barrel port of the main fuel passage 8 is changed. The position is adjusted, and the amount of fuel discharged from the main fuel pump chamber 6 is adjusted. In this way, the main fuel whose delivery of fuel from the barrel 9 to the main fuel pump chamber 6 via the main fuel passage 8 is delayed is
While pushing up the ball 23 and pushing up the discharge valve 20,
It is pressure-fed to the discharge passage 25 of the discharge valve cap 24 and is injected from the main fuel injection valve into the cylinder of the internal combustion engine through the main fuel injection pipe.

FIGS. 3 and 4 are diagrams showing the above-mentioned operating conditions, and FIG. 3 shows the crank angle and the rack scale,
FIG. 4 shows the fuel injection tendency of this embodiment showing the relationship between the fuel injection rate and the crank angle. In the figure, TDC is the top dead center of the crank, Lp is the angle between the small plunger injection start position of the crank angle and TDC, L _L is the crank angle between the large plunger injection start position and TDC, and Lp- _LL Is about 3 °.

FIG. 5 is a development view of the small plunger 5 and the large plunger 4 in the fuel injection pump of the second embodiment of the present invention. In the first embodiment described above, FIG.
As shown in FIG. 5, the land portion 5c of the small plunger 5 is constant in the circumferential direction and the lead angle b is zero. However, in this embodiment, as shown in the figure, the land portion 5c of the small plunger 5 has the lead angle b. It is provided. The area between the lead angles b is the effective stroke portion, and the other portions are the invalid stroke portions, which are similar to the state shown in FIG. That is, only a minimum amount of pilot fuel is injected in the invalid stroke portion, and a large amount of pilot fuel is injected in accordance with the inclination of the lead angle b in the effective stroke portion. On the other hand, in the large plunger 4, an invalid stroke portion having an injection amount of zero and an effective stroke portion as a fuel injection position are formed in accordance with the lead angle b of the small plunger 5.

With this structure, misignition was likely to occur when methanol injection was performed during cold start or idle operation in the first embodiment, but only pilot fuel was used until start-up and the load was reduced. In operation, the main fuel, methanol, is ignited by pilot fuel such as heavy fuel oil A to operate, and in the case of methanol injection, the injection amount of pilot fuel is made as small as possible.

FIG. 6 shows the relationship between the fuel injection amount of the fuel injection pump of FIG. 5 and the rack scale. That is, rack limitation is performed with the fuel injection amount Qp that can generate the torque required at the time of starting using only pilot fuel as the upper limit.
Then, the small plunger for pilot fuel can inject up to the upper limit Qp, and the fuel injection of the large plunger during this period is zero. In the load operation, the range of the above limit (lead angle b) of the pilot fuel is released, and the load operation is performed in the minimum fuel injection range. Injection amount of large plunger at this time (the dashed line) and Q _L, the fuel injection quantity of the small plunger and certain minimum injection amount Qpc. The value of Q _{L is, Q L = K · (Qp} -Qpc) K = volume per pilot fuel calorific value / volume per main calorific value Note: K when the main fuel is methanol is about 2.

FIG. 7 shows the relationship between the crank angle and the rack scale of this embodiment corresponding to FIG.

[0035]

As is clear from the above description,
The fuel injection pump of the dual fuel engine of the present invention has the following effects.

(1) A small plunger and a large plunger are provided in series vertically to inject two kinds of fuel separately, and pilot fuel with good ignitability is injected by the small plunger, and then by the large plunger. A compact fuel injection pump capable of injecting main fuel such as alcohol can be obtained.

(2) The fuel injection pump of claim 2 is capable of injecting the main fuel such as alcohol after the minimum injection of pilot fuel during load operation.

(3) In the fuel injection pump of the third aspect, since the operation is performed only with the pilot fuel during the idling of the engine and at the time of starting the engine, it is erroneous to inject the alcohol for the load operation. There is no risk of ignition.

(4) In the fuel injection pump of claim 4 or 5, when alcohol fuel is used as the main fuel, the sliding portion of the plunger loses lubricity and a strong hit occurs, which may damage the plunger. It can be solved by the invention.

[Brief description of drawings]

FIG. 1 is a vertical sectional view schematically showing an embodiment of a fuel injection pump of a dual fuel engine according to the present invention.

FIG. 2 is a development view showing an upper portion of a small plunger of the fuel injection pump shown in FIG.

FIG. 3 is a diagram showing a relationship between a crank angle and a rack scale for explaining the operation of the fuel injection pump of FIG.

4 is a diagram showing a relationship between a fuel injection rate of the fuel injection pump of FIG. 1 and a crank angle.

FIG. 5 is a development view of large and small plungers in a second embodiment of the fuel injection pump of the dual fuel engine according to the present invention.

6 is a diagram showing a fuel injection situation of the fuel injection pump of FIG.

FIG. 7 is a diagram showing a relationship between a crank angle and a rack scale in the fuel injection pump of FIG.

FIG. 8 is a sectional view conceptually showing a dual fuel injection state of a conventional dual fuel engine.

FIG. 9 is a vertical cross-sectional view illustrating the structure of a conventional general fuel injection pump.

[Explanation of symbols]

 1 Pump Case 2 Sleeve 3 Sleeve 4 Large Plunger 5 Small Plunger 6 Main Fuel Pump Room 7 Pilot Fuel Pump Room

Claims (5)

[Claims] 1. A fuel injection pump comprising a large plunger for main fuel injection and a small plunger for pilot fuel injection, in which large and small plungers are vertically combined and the pilot fuel is injected into the main fuel. A fuel injection pump for a dual fuel engine, characterized by being configured to prevent engine ignition mistakes. 2. The fuel injection pump for a dual fuel engine according to claim 1, wherein the amount of discharge of the pilot fuel is about 5% of the total amount of heat in full power operation. 3. The injection amount of the small plunger can be increased to a startable injection amount, and the fuel rack is limited so that the injection amount does not exceed this amount.
A fuel injection pump for a dual fuel engine as described. 4. The dual fuel engine according to claim 1, wherein an oil passage is provided between the large plunger and the barrel so that the high pressure fuel from the fuel passage of the pilot fuel at the end of the thrust of the small plunger is provided between the large plunger and the barrel. Fuel injection pump. 5. An oil introducing portion is provided on a sliding portion on the outer periphery of the large plunger, and an opening of an oil passage from a fuel passage for pilot fuel is communicated with the oil introducing portion at a rising position of the large plunger. 5. The fuel injection pump for a dual fuel engine according to claim 4, wherein the small plunger is aligned with the opening position of the pilot fuel barrel port during communication.