JPH0828403A - Fuel injection device for direct injection diesel engine - Google Patents

Abstract

PURPOSE:To always make fuel injection to the optimum position in a combustion chamber possible even when revolving speed varies. CONSTITUTION:A nozzle holder 1 is fixed to a cylinder head 2, and a nozzle 4 is movably attached to the nozzle holder 1, and a spring 14 is accommodated in the lower end of the nozzle holder 1, and one end of a locker arm 15 oscillated by a cam 19 is engaged in the side opposite to the spring of the nozzle 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a direct injection diesel engine, and more particularly to a variable nozzle position device.

[0002]

2. Description of the Related Art In a direct injection type (hereinafter referred to as direct injection) diesel engine having no auxiliary combustion chamber, a fuel injection nozzle is directly fixed to a cylinder head, and the combustion chamber is a recess formed at the top of a piston. The technology being constructed is known.

Therefore, the combustion chamber and the piston are constantly moved in the axial direction of the cylinder, and the nozzle is fixed to the cylinder head, so that the relative position of the nozzle and the combustion chamber is constantly changing. In the prior art, fuel injection was started before the piston reached the top dead center according to the number of revolutions, so fuel rarely came out of the combustion chamber, and there was no problem.

[0004]

However, in recent years,
Reduction of exhaust gas is a social requirement, and exhaust gas (for example, No
In order to reduce x), it is effective to delay the fuel injection timing, increase the injection pressure and reduce the injection hole diameter. The distance that the piston moves becomes large,
Since the fuel injection nozzle is fixed, even if the fuel spray is injected outside the combustion chamber, or even if it is injected into the combustion chamber, the fuel spray is not injected to the optimum position inside the combustion chamber, so the effect of combustion improvement is canceled out. May be.

Therefore, an object of the present invention is to provide a fuel injection device for a direct injection engine which always injects fuel to an optimum position in the combustion chamber even if the rotational speed or the like changes.

[0006]

According to the present invention, the nozzle holder is fixed to the cylinder head, the nozzle is movably mounted on the nozzle holder, and the spring is housed at the lower end of the nozzle holder. One end of a rocker arm that is rocked by a cam is engaged with.

[0007]

Since the present invention is configured as described above, the nozzle can move in the axial direction of the cylinder along the nozzle holder fixed to the cylinder head, and follows the movement near the upper fulcrum of the piston. Since the cam shape is formed so that the nozzle moves, the nozzle moves following the movement of the piston at the top dead center, and fuel is always injected to the optimum position of the combustion chamber installed at the top of the piston. Is
Combustion can be performed under the best conditions in response to changes in rotation speed, and changes in injection timing are not affected. Therefore, the injection timing can be set to the optimum timing for reducing exhaust gas such as Nox.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of a fuel injection device according to the present invention, in which a nozzle mounting hole 2 provided in a cylinder head 2 is shown.
The nozzle holder 1 is fixed to a by a fixing device (not shown), and the nozzle 4 is mounted inside the nozzle holder 1 so as to be movable in the axial direction. A return spring 14 for urging the nozzle upward is provided at the tip of the nozzle, and the other end is prevented from coming off by a nut 1a. The injection hole 9 provided at the tip of the nozzle is a hole at the tip of the nozzle holder 1. 1
It goes out into the cylinder through b and the hole 3 provided in the cylinder head.

The nozzle 4 is provided with a first passage 5 to which fuel is supplied and a second passage 6 to which fuel is returned. A spring 7 biasing in the direction is provided, and the first passage extends around the needle to reach the tip of the needle.

Further, enlarged portions 5a and 6a are respectively provided at the portions where the first passage and the second passage are connected to the oil supply hole 10a and the return hole 11a of the nozzle holder 1, and these enlarged portions 5a are provided. , 6a are provided outside the upper and lower nozzles, respectively, and a plurality of seals 12 and 13 are provided, and an oil supply pipe 10 and a return pipe 11 are connected to the oil supply hole 10a and the return hole 11a, respectively.

Further, one end of the rocker arm 16 provided on the rocker arm shaft 16 attached to the cylinder head 2 contacts the end 4a of the nozzle, and the other end contacts the cam via the push rod 17 and the cam follower 18. ing.

FIG. 2 is a diagram for explaining the operation of the fuel injection device of FIG. 1, in which the vertical axis represents the piston and nozzle tip positions in the piston stroke direction near the top dead center, and the horizontal axis represents the crank angle. There is.

The position P of the piston reaches the top at the top dead center T according to the crank angle, and as the position P lowers, the nozzle tip position N also drops along the position P of the piston during the fuel injection period F. Since the cam 19 is configured, the fuel spray is always injected at the optimum position in the combustion chamber.

Therefore, in order to reduce the exhaust gas, the fuel injection timing is delayed, and as shown in FIG. 3, even if the piston 20 is lowered to the position of the chain line, the nozzle 4 is likewise lowered to the position of the chain line, and is denoted by reference numeral 22. As shown, the fuel spray does not leave the combustion chamber and combustion does not deteriorate. Note that reference numeral 2
Reference numeral 3 indicates a piston pin.

Therefore, the combustion efficiency does not decrease.

[0017]

Since the present invention is constructed as described above, it has the following excellent effects. (1) Even if there is a change in the engine speed or injection timing, fuel can always be injected to the optimum position in the combustion chamber. (2) Therefore, even if the injection timing is delayed to reduce the exhaust gas, the combustion efficiency does not decrease, and the optimal exhaust gas reduction can be implemented.

[Brief description of drawings]

FIG. 1 is a side sectional view of a fuel injection device for a direct injection diesel engine showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the fuel injection device in FIG.

FIG. 3 is a diagram showing a relationship between fuel spray and a direct injection type combustion chamber.

[Explanation of symbols]

 1 ... Nozzle holder 2 ... Cylinder head 4 ... Nozzle 5 ... First passage 6 ... Second passage 7, 14 ... Spring 8 ... Needle 9 ... Injection hole 12, 13 ... Seal 15 ... Rocker arm 19 ... Cam

Claims (1)

[Claims] 1. A nozzle holder is fixed to a cylinder head, a nozzle is movably mounted on the nozzle holder, a spring is housed at the lower end of the nozzle holder, and one end of a rocker arm swinging by a cam is provided on the side opposite to the spring of the nozzle. A fuel injection device for a direct injection diesel engine, characterized by being engaged.