JP3516583B2 - Diesel engine fuel injection system - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection device for a diesel engine.

[0002]

2. Description of the Related Art As a conventional technique of a fuel injection device for a diesel engine, there is one which is configured to perform a preliminary injection and a main injection. This is because the preliminary injection is performed before the main injection to improve combustion by the main injection. In this type of fuel injection device, the maximum lift dimension by which the plunger of the fuel injection pump is lifted by the preliminary injection projection is set shorter than the maximum lift dimension by the main injection projection, and the preliminary injection For example, the amount is larger than the main injection amount.

[0003]

Problems to be Solved by the Invention The above-mentioned prior art has the following problems. If the maximum lift size for lifting the plunger of the fuel injection pump by the preliminary injection projection is set shorter than the maximum lift size for lifting by the main injection projection, the pre-injection and main injection end conditions are Because of the difference, the conditions for sucking back the fuel by the suction return valve performed at the end of the preliminary injection and the main injection are different, and the residual pressure of the fuel injection pipe may decrease at the end of the preliminary injection.
Therefore, the injection may be lost or the injection timing may be misaligned, and smooth operation cannot be performed.

If the preliminary injection amount is larger than the main injection amount, pre-ignition occurs and an appropriate output cannot be obtained. In addition, a large amount of pre-injected fuel spontaneously ignites at one time, which may cause severe knocking.

An object of the present invention is to solve the above problems.

[0006]

The main constitution of the invention of claim 1 is as follows (see FIGS. 3 and 4 ). In a fuel injection device for a diesel engine configured to perform a preliminary injection (1) and a main injection (2) as fuel injection, one fuel injection cam (3) has one preliminary injection protrusion (4). And a main injection projection (5) for the fuel injection pump
(7) the plunger (21) of maximum lift dimensioned to be lifted by the projections for preinjection (4), the maximum lift dimension substantially the same, which is lifted by a main injection projections (5)
Is, projections for preinjection (4) and the projection for the main injection (5) is different from
The plunger (2
The lift speed of 1) is the plunger due to the main injection projection (5)
It is set slower than the lift speed of (21).

[0007]

Action and Effect of the Invention (Invention of Claim 1) The invention of Claim 1 has the following action and effect ( FIGS. 3 and 4).
reference). Since the maximum lift dimension by which the plunger (21) of the fuel injection pump (7) is lifted by the preliminary injection projection (4) is substantially the same as the maximum lift dimension by the main injection projection (5), The end conditions for injection (1) and main injection (2) are substantially the same or very close to each other, and the conditions for sucking back fuel by the suction return valve performed at the end of pre-injection and main injection are substantially the same. Therefore, it is possible to prevent the deficiency that the residual pressure of the fuel injection pipe decreases at the end of the preliminary injection. Therefore, it is possible to prevent the missing of the injection and the deviation of the injection timing due to this, and it is possible to perform the smooth operation.

Pre-injection of the required injection amount in one cycle (1)
And the main injection (2) can be divided into two injections.
Compared to the case where only one injection is performed during a cycle, the amount of fuel discharged per injection is small, and a small-sized and low-capacity fuel injection pump (7) can be used. In addition,
Lift speed of the plunger (21) by the projection (4) for injection
Lift speed of the plunger (21) by collision force for the main injection (5)
Since it is set later than
It is less than the amount, and it is possible to suppress premature ignition and knocking.
More effectively.

[0009]

[0010]

[0011]

(Invention of Claim 2 ) The invention of Claim 2 has the function and effect of the invention of Claim 1 ,
The following operational effects are achieved (see FIGS. 3 and 4 ). Since the pre-injection protrusion (4) and the main-injection protrusion (5) are arranged on the opposite sides, they can be arranged sufficiently apart from each other, and the cam profile of the fuel injection cam (3) It can be designed and manufactured easily.

(Invention of Claim 3 ) The invention of claim 3 has the following effect in addition to the effect of the invention of claim 1 or claim 2 (see FIGS. 3 and 4 ). Since the preliminary injection (1) is started in the first half of the intake stroke and the main injection (2) is started in the latter half of the compression stroke, the preliminary injection is performed.
The period from (1) to the main injection (2) is long, and the main injection (2) is performed after the vaporized preliminary injection fuel has spread to the entire combustion chamber (6). Therefore, the combustion flame generated by the main injection (2) propagates to the entire combustion chamber (6), the utilization rate of air is increased, and the generation of black smoke due to incomplete combustion is suppressed.

(Invention of Claim 4 ) The invention of claim 4 has the following effect in addition to the effect of any one of claims 1 to 3 ( Fig. 3 ) .
( See FIG. 4 ). Since the preliminary injection (1) and the main injection (2) are performed via a single injection path, the structure of the fuel injection device is simplified, the manufacturing cost thereof is reduced, and the failure thereof is unlikely to occur.

Since the pre-injection (1) is directly performed in the combustion chamber (6), the vaporized fuel-free air can be sucked into the combustion chamber (6). Therefore, the efficiency of filling air is increased, and the generation of black smoke due to incomplete combustion can be suppressed.

(Invention of Claim 5 ) The invention of Claim 5 has, in addition to the function and effect of the invention of Claim 4 ,
The following operational effects are achieved (see FIG. 3 ). The combustion chamber (6) is a direct injection type, and the preliminary injection (1) and the main injection (2) are pistons.
Since it is carried out into the cavity (12) of (11), the washing out of the lubricating oil on the inner peripheral surface of the cylinder (17) by the injected fuel is suppressed, and the seizure of the piston (11) is suppressed.

(Invention of Claim 6 ) According to the invention of Claim 6 , in addition to the function and effect of the invention of Claim 4 ,
The following operational effects are obtained (see FIG. 4 ). The combustion chamber (6) is of a sub-chamber type, and the preliminary injection (1) and the main injection (2) are the sub-combustion chamber (1).
3), and during the preliminary injection (1) and the main injection (2), the communication hole (15) between the auxiliary combustion chamber (13) and the main combustion chamber (14) forms the piston.
Since it is directed to the top surface (16) of (11), the washing out of the lubricating oil on the inner peripheral surface of the cylinder (17) by the injected fuel is suppressed, and the seizure of the piston (11) is suppressed.

[0018]

Reference Example A reference example of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a first reference example of the present invention. This ginseng
In the example , a direct injection multi-cylinder engine is used.

This engine is constructed as follows. As shown in FIG. 1A, a piston (11) is fitted in a cylinder (17), and a cavity (12) is provided on a top surface (16) of the piston (11).
The inside is a combustion chamber (6). The cylinder head (18) is assembled to the cylinder (17).
A fuel injection nozzle (9) is attached to (18). Reference numeral (19) in the drawing is an intake valve.

The fuel injection system of this engine is constructed as follows. As shown in FIG. 1A, a fuel injection pipe (8) is connected to the fuel injection pump (7), and a fuel injection nozzle (9) is connected to the tip of this fuel injection pipe (8).
The fuel injection pump (7) is driven by the fuel injection cam (3). As shown in FIG. 1B, a preliminary injection (1) and a main injection (2) are performed as fuel injection.

As shown in FIG. 1A, one fuel injection cam (3) has one preliminary injection protrusion (4) and one main injection protrusion.
(5) and are provided, and the plunger of the fuel injection pump (7)
The maximum lift dimension by which (21) is lifted by the preliminary injection projection (4) is substantially the same as the maximum lift dimension by which the main injection projection (5) is lifted. The preliminary injection protrusion (4) and the main injection protrusion (5) have substantially the same shape.

The preliminary injection projection (4) and the main injection projection (5) sandwich the rotation center (10) of the fuel injection cam (3) between them,
Located on opposite sides of each other. As shown in FIG. 1 (B), the preliminary injection (1) is started in the first half of the intake stroke, and the main injection is performed.
(2) is started in the latter half of the compression process. The preliminary injection (1) starts immediately after the exhaust valve (not shown) is closed and ends in the first half of the intake stroke. The main injection (2) starts before the top dead center where the compression process ends and ends after the top dead center. Figure 1
As shown in (A), preliminary injection (1) into the combustion chamber (6) of 1
And one main injection (2) are connected to the fuel injection pump (7) and one fuel injection pipe (8) and one connected to this fuel injection pipe (8)
Directly into the combustion chamber (6) via the fuel injection nozzle (9). The preliminary injection (1) and the main injection (2) are
It is performed toward the inside of the cavity (12) of 1).

The fuel injection pump (7) is constructed as follows. As shown in FIG. 1 (A), the fuel injection pump
(7) is an escape hole type row pump. A plunger (21) is fitted in the barrel (20). The plunger (21) is lifted by the fuel injection cam (3) and the return spring (22)
Returned by A plunger chamber (23) is provided on the lift side of the plunger (21). A fuel storage chamber (24) is provided around the barrel (20). Barrel (20)
A fuel inlet (25) and an escape hole (26) are provided on the peripheral wall of the
Through these, the plunger chamber (23) and the fuel storage chamber (24)
And are in communication. Diagonal groove (27) on the plunger (21)
Is provided. The oblique groove (27) communicates with the plunger chamber (23) by a vertical groove (28). The plunger (21) is interlockingly connected to the governor section (not shown) via a fuel metering rack (29). A suction return valve (30) is provided at the discharge port of the plunger chamber (23), and the plunger chamber (23) communicates with the fuel injection pipe (8) through the suction return valve (30).

The preliminary injection (1) and the main injection (2) are performed as follows. Plunger (21) is the fuel injection cam (3)
After being lifted by the main injection protrusion (5) of the return spring (22)
Plunger chamber in barrel (20) when returned by
(23) becomes negative pressure, and the fuel in the fuel storage chamber (24) is sucked into the plunger chamber (23) from the fuel inlet (25). When the plunger (21) is lifted from the bottom dead center by the preliminary injection projection (4) and the fuel inlet (25) and the escape hole (26) are closed on the peripheral surface of the plunger (21), the plunger chamber (23) The fuel oil pressure increases, the suction return valve (30) is opened, the fuel is discharged from the plunger chamber (23) to the fuel injection pipe (8), and the preliminary injection (1) is started. When the plunger (21) is further lifted and the escape hole (26) is opened in the oblique groove (27), the fuel in the plunger chamber (23) is fed into the vertical groove (28), the oblique groove (27) and the escape hole (26). Escape from the fuel sump (24) through the and
The fuel pressure in the plunger chamber (23) has dropped and the suction valve
The valve (30) is closed, and when the valve is closed, part of the fuel in the fuel injection pipe (8) is sucked back into the plunger chamber (23) and the preliminary injection (1) is ended. By the same operation, the main injection projection
The main injection (2) is performed at (5). The preliminary injection amount and the main injection amount are substantially the same.

In the second reference example shown in FIG. 2, the combustion chamber (6) is of the auxiliary chamber type, and the preliminary injection (1) and the main injection (2) are the auxiliary combustion chamber.
(13), during the pre-injection (1) and the main injection (2), the communication hole (15) between the auxiliary combustion chamber (13) and the main combustion chamber (14) forms the top surface of the piston (11) ( 16). Other structures and functions are the same as those in the first embodiment. 2, the same elements as those in the first embodiment are designated by the same reference numerals as those in FIG.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION In the first embodiment shown in FIG. 3, the preliminary injection projection (4) and the main injection projection (5) have different shapes. That is, the lift surface of the preliminary injection projection (4) used for lifting the plunger (21) is the main injection projection.
It rises more slowly from the base circle than the lift surface in (5). Therefore, the plunger with the preliminary injection projection (4)
The lift speed of (21) is set slower than the lift speed of the plunger (21) by the main injection projection (5). Therefore, in the pre-injection (1), the rising speed of the fuel oil pressure in the plunger chamber (23) due to the lift of the plunger chamber (21) decreases, the start of the pre-injection (1) is delayed, and the pre-injection amount is the main injection amount. Less than the amount. For other structures and functions, refer to the first reference
Same as the example . 3, the same elements as those of the first reference example are designated by the same reference numerals as those of FIG.

[0027] In the second embodiment shown in FIG. 4, first in Fig 2
As in the reference example , the combustion chamber (6) is of the sub-chamber type, and the preliminary
(1) and the main injection (2) are performed in the auxiliary combustion chamber (13), and during the preliminary injection (1) and the main injection (2), the auxiliary combustion chamber (13) and the main combustion chamber
The communication hole (15) with (14) is the top surface (16) of the piston (11).
Is directed to. Further, similar to the first embodiment of FIG.
The preliminary injection protrusion (4) and the main injection protrusion (5) have different shapes. That is, the lift surface of the preliminary injection projection (4) used for lifting the plunger (21) is the main injection projection.
It rises more slowly from the base circle than the lift surface in (5). Other structures and functions are the same as those of the first and second reference examples and the first actual example.
It is the same as the embodiment . In FIG. 4, the same elements as these are denoted by the same reference numerals as those in FIGS.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first reference example of the present invention.
1A is a vertical cross-sectional view of a fuel injection device, and FIG. 1B is a diagram illustrating injection timing and injection rate during one cycle.

FIG. 2 is a diagram illustrating a second reference example of the present invention.
1A is a view corresponding to FIG. 1A, and FIG. 2B is a view corresponding to FIG.

FIG. 3 is a diagram for explaining the first embodiment of the present invention, and FIG.
1A is a view corresponding to FIG. 1A, and FIG. 3B is a view corresponding to FIG.

FIG. 4 is a diagram for explaining the second embodiment of the present invention.
1A is a view corresponding to FIG. 1A, and FIG. 4B is a view corresponding to FIG.

[Explanation of symbols]

(1) ... Preliminary injection, (2) ... Main injection, (3) ... Fuel injection cam,
(4) ... Projection for preliminary injection, (5) ... Projection for main injection, (6) ... Combustion chamber, (7) ... Fuel injection pump, (8) ... Fuel injection pipe, (9)
... Fuel injection nozzle, (10) ... Center of rotation, (11) ... Piston, (12) ... Cavity, (13) ... Sub-combustion chamber, (14) ...
Main combustion chamber, (15) ... communication hole, (16) ... top surface, (21) ... plunger.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02M 61/14 F02M 61/14 310P (56) References JP 10-18940 (JP, A) JP 9-158810 ( JP, A) JP 61-112724 (JP, A) Actually developed 63-121772 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 45/06 F02B 19/08 F02D 1/02 301 F02M 59/10 F02M 59/20 F02M 59/26 310 F02M 61/14 310

Claims (6)

(57) [Claims] 1. A pre-injection (1) and a main injection as fuel injection
In a fuel injection device for a diesel engine configured so that (2) and (2) are performed, one fuel injection cam (3) has one preliminary injection protrusion (4) and one main injection protrusion (5). The maximum lift dimension of the plunger (21) of the fuel injection pump (7) lifted by the preliminary injection projection (4) is substantially the same as the maximum lift dimension of the main injection projection (5). And the preliminary injection projection (4) and the main injection projection (5) have different shapes.
And the plunger (21) by the preliminary injection projection (4)
Plunger (21) with lift speed due to the main injection projection (5)
It is set to be slower than the lift speed of. 2. The fuel injection device for a diesel engine according to claim 1 , wherein the pre-injection projection (4) and the main-injection projection (5) define a rotation center (10) of the fuel injection cam (3). Those placed on opposite sides of each other, sandwiched between them. 3. A fuel injection device for a diesel engine according to claim 1 or 2 , wherein preliminary injection (1)
Is started in the first half of the intake stroke, and main injection (2) is started in the second half of the compression stroke. 4. The fuel injection device for a diesel engine according to claim 3 , wherein preliminary injection into one combustion chamber (6).
One fuel injection pipe (8) in which (1) and main injection (2) are connected to a fuel injection pump (7), and one fuel injection nozzle (9) connected to this fuel injection pipe (8) It is designed to be directly conducted to the combustion chamber (6) via and. 5. The fuel injection device for a diesel engine according to claim 4 , wherein the combustion chamber (6) is of a direct injection type, and the preliminary injection (1) and the main injection (2) are cavities of a piston (11). (12) Things to be done inward. 6. The fuel injection device for a diesel engine according to claim 4 , wherein the combustion chamber (6) is of a sub chamber type,
The preliminary injection (1) and the main injection (2) are performed in the auxiliary combustion chamber (13), and during the auxiliary injection (1) and the main injection (2), the auxiliary combustion chamber (13) and the main combustion chamber (14) The communication hole (15) with is directed to the top surface (16) of the piston (11).