JP2547145B2 - Fuel injection pump for dual fuel engine - Google Patents

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 is easily ignited 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 preventing exhaust gas pollution by a diesel engine. Since this kind of fuel is inferior in ignitability, as an auxiliary means for igniting, a fuel such as light oil or heavy fuel oil A having excellent ignitability is pre-injected as 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 to have as little pilot fuel as possible. The combustion situation in a dual-fuel diesel engine is usually adjusted by fixing the heat generation rate at high speed and high load optimally, then pilot combustion is performed first, and then the main fuel is ignited by the afterburning of the pilot combustion. 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 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 type of binary fuel, in JP-A-3-185234 and JP-A-2-78729, a single main fuel injection pump and a single pilot fuel injection pump are linked by a link mechanism. A fuel control method that does not reduce or increase the pilot fuel injection amount without connecting (burning the pilot fuel first and then stopping the combustion of the pilot fuel as the main fuel burns (there is a risk of misfire if stopped) after connecting 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. 3, the pilot fuel pump 42 and the main fuel pump 43 are arranged for one engine 41, and the pilot fuel pump 4 and the main fuel pump 43 are arranged prior to the fuel injection of the main fuel pump 43.
The pilot fuel is discharged into the engine by 2 and ignited, and then the main fuel is injected during combustion of the pilot fuel. Although not shown in the above-mentioned respective documents, the timing of fuel injection is adjusted by fuel injection adjustment. It is described that a delay device is provided in the rack for. Basically, the timing is adjusted by the mounting angle 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 transfers 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 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 periphery 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 and two types of fuel are injected by the link mechanism as described above. 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 a 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 according to the present invention has a large plunger for main fuel injection and a small plunger for pilot fuel injection. · a fuel injection pump comprising attached vertically integrated small plunger, the injection of pilot fuel is preceded injection of the main fuel, as well as configured to prevent ignition miss of the engine, the small plug
From the fuel passage of the pilot fuel at the end of the Nja
Of high pressure fuel between the large plunger and the barrel.
An oil passage is provided. By providing this oil passage
So, pilot fuel between the large plunger and the barrel
Used as a lubricant to prevent oil depletion that tends to occur in this area
It is possible to mitigate strong hits.

As described in claim 2, the large plunge
The oil introduction part is provided on the sliding part on the outer circumference of the
Large plunger rises through opening of oil passage from fuel passage of fuel
At the position, communicate with the oil introduction part, and
Small plunger enlightens pilot fuel barrel port
You may make it correspond with a position. Configure like this
And the small plunger rises and the barrel port at the end of the thrust
A high-voltage reflected wave is generated at the fuel supply port at the moment when
Utilizing an elephant, its pressure is transferred to a large plunger and its barrel.
And use pilot fuel as lubricating oil
And can be done with effective timing
It

As described in claim 3, the pilot
Set the fuel discharge rate to about 5% of the total heat during full-power operation.
Yes. As a result, the injection amount of the large plunger is reduced to about 2.5%.
The amount of pilot fuel to be discharged must be adjusted accordingly.
Therefore, when using alcohol-based fuel as the main fuel
May stop the engine or make a mistake in ignition.
To be prevented.

As described in claim 4, the injection amount of the small plunger can be increased to a startable injection amount, and
Limit the fuel rack so that the injection amount does not exceed this amount
You can do it. With this configuration,
Heart of misfires when starting the engine and at no load operation
Only pilot fuel is injected and idle
Zero injection of main fuel during ring. In that case
When the pilot fuel is heavy fuel oil A
It is necessary to inject A heavy oil to about 10 % of the amount of A heavy oil used in the load range .

[0013]

[0014]

[0015]

[0016]

[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 via 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 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 rotational 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 in contact therewith, and the discharge valve seat 22 is provided with the discharge valve seat 22 for 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 extends and the slide metal 14 serves as the pump case 1.
It shows a state in which it is pressed against the lower end 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
Is communicated 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 is supplied to the fuel reservoir 11 by being pumped through the fuel supply pipe by the fuel supply pump, and the fuel in the fuel tank for the main fuel (alcohol fuel) is pumped to the fuel supply pipe by the fuel supply pump. Is supplied to the fuel sump 9, and in the same state, the slide plate 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 it is 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 into the ball 23.
While pushing up the discharge valve 21, the discharge valve 21 is pushed into 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 and the fuel passage 10 communicate with each other.

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 rises momentarily. 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 between the outer circumference of the large plunger 4 and the inner circumference of the sleeve 2 to serve as 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 position of the rack. 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 rotational position about the axis, the reference numerals of the slant groove 13 and the barrel port of the main fuel passage 8 are indicated. 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 delayed.
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. 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 and TDC of the crank angle, 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, as shown in 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 of 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, mis-ignition 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, the rack limit is performed with the fuel injection amount Qp that can generate the torque required at the time of starting using only the 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 apparent 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 types of fuel separately, and the small plunger injects pilot fuel with good ignitability, and then the large plunger. A compact fuel injection pump capable of injecting earth fuel such as alcohol can be obtained. Moreover, alcohol burns as the main fuel
If the lubricant is used, the sliding parts of the plunger will lose lubricity.
A strong hit may damage the plunger.
However, this invention solves this problem.
It can be erased.

(2) In the fuel injection pump of claim 2 ,
Guide the pilot fuel into the clearance between the large plunger and the barrel.
When entering and using it as a lubricant, a small plunger
The moment when the barrel port rises and the barrel port at the end of the thrust opens
To utilize the phenomenon that high-pressure reflected waves are generated at the fuel supply port
So it can be done with effective timing.

(3) In the fuel injection pump of claim 3,
Following a minimum pilot fuel injection during load operation
The main fuel such as coal can be injected.

(4) In the fuel injection pump of claim 4 ,
During engine idling and at start-up
Since I tried to operate only with ilot fuel,
Misfired even if alcohol was injected for load operation
There is no danger of it occurring.

[Brief description of drawings]

FIG. 1 is a vertical cross-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 developed view showing the upper part of the 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.

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

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.

FIG. 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 (4)

(57) [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 integrally connected in the vertical direction, and pilot fuel is injected into the main fuel. It is preceded, as well as configured to prevent ignition miss of the engine, before
Fuel for pilot fuel at the end of small plunger thrust
High-pressure fuel from the passage is connected between the large plunger and the barrel.
A fuel injection pump for a dual fuel engine, which is provided with an oil passage adapted to pass therethrough. 2. Oil is introduced into a sliding portion on the outer circumference of the large plunger.
And the oil from the fuel passage for pilot fuel
Connect the opening of the passage to the oil introduction part at the raised position of the large plunger.
Through the small plunger at the time of communication.
The fuel fuel barrel port to match the enlightenment position
A fuel injection pump for a dual fuel engine according to claim 1. 3. The pilot fuel discharge amount is fully operated.
2. The fuel injection pump for a dual fuel engine according to claim 1 , wherein the total amount of heat is about 5% . 4. The injection amount of the small plunger can be activated.
The injection amount can be increased up to the injection amount, and the injection amount exceeding this amount
The fuel rack is restricted so that it will not occur.
A fuel injection pump for the dual fuel engine described.