JPH0441244Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a nozzle holder for a diesel engine, and particularly to a plain injection type nozzle holder.

[Conventional technology and its problems]

One of the nozzle holders for diesel engines is a plane extension type (with a double plunger). This plain injection type nozzle holder is designed to improve combustion efficiency by first injecting a small amount of fuel as a pilot according to the rotation angle of the crankshaft, and then performing the main injection when this is combusted in the piston bore. Generally, as in JP-A-57-159954, the needle valve inserted into the nozzle is urged toward the valve closing side by a spring inserted in the nozzle holder body, and a piston is connected in series with this spring. It has a structure that incorporates.

Therefore, this nozzle holder requires a supply system for the fuel pumped from the fuel injection pump to the nozzle side (oil reservoir on the outer periphery of the needle valve) and a supply system for increasing the pressure of the piston. As for its structure, in the prior art, a fuel supply port to the nozzle side is provided on the side of the nozzle holder main body, since one or more pump cylinders are used in excess of the number of engine cylinders to control the piston operation. Separately, a supply port communicating with the piston head is provided at the rear end of the nozzle holder body. For this reason, in addition to the disadvantage of having to install an extra pump cylinder, since the fuel inlet is provided above the piston, there is little flexibility in connecting it to the injection pump when it is attached to the cylinder block of the engine body, and various types of engine Cylinder arrangement (in-line type, V
There was a problem that it was difficult to adapt freely to various types (type, horizontal type).

As a countermeasure for this, a fuel supply port was provided at the rear end of the nozzle holder body in the axial direction, an oil passage was bored from there to the nozzle, and a part of the oil passage was branched to lead to the upper part of the piston. In this case, the pressure oil from the pump acts on the nozzle side and the piston push side chamber, and the piston, which has a larger pressure-receiving area than the needle valve, moves immediately, so the spring is compressed and the valve opening pressure is set higher than the intended one. Pilot injection cannot be realized, and disadvantages due to the fact that the fuel inlet is provided above the piston cannot be avoided.

[Means for solving problems]

Therefore, the present invention solves the problems of the plain injection type nozzle holder as described above, and can perform the functions of pilot injection and main injection, and also allows the fuel inlet to be provided on the rear side of the nozzle holder body. We aim to provide this type of nozzle holder that has a large degree of freedom in connection to the injection pump, can supply fuel from any angle desired by the engine on the cylinder head, and has a small number of parts and is compact. It is.

To achieve this purpose, the present invention includes a spring that biases the needle valve in the opening direction, which is inserted into the nozzle so that it can move forward and backward, and a piston that supports the spring. In the second stage, only the needle valve opens and injection occurs, and then the piston moves from the seated position and presses the needle valve toward the closing side to reduce the injection amount.In the second stage, the injection amount is reduced by the displacement of the piston. In a nozzle holder of the type in which the needle valve lifts at a set high valve opening pressure and main injection is performed, the nozzle holder body has a cylindrical hole with an enlarged stepped hole at the upper end, and the piston slides into this cylindrical hole. The piston is movably inserted, and the piston has an enlarged head that is freely mounted in the stepped hole so that the pressure receiving area can be switched by moving from the seated position in contact with the member that closes the stepped hole. The blind hole has a blind hole with a required depth from At the same time, it communicates with the stepped hole through a relief hole provided under the head, and the blind hole is configured so that its upper end is closed by a member that closes the stepped hole when the piston is in the seated position. It is something.

〔Example〕

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

Figures 1 and 2 show an embodiment of a nozzle holder for a diesel engine according to the present invention.
is the nozzle holder body, 2 is the nozzle holder body 1
The nozzle is arranged on the front side of the nozzle holder and is integrally connected to the nozzle holder main body 1 by a cap nut 12.

A needle valve 3 whose tip end approaches and separates from the nozzle valve seat is inserted into the nozzle 2, and a spring chamber 13 formed in the nozzle holder body 1 is provided in the shaft portion of the rear end of the needle valve 3.
A push rod 11 is fitted therein.

Reference numeral 4 denotes a cylindrical hole for a piston formed from the top surface of the rear end of the nozzle holder main body 1 on the same axis as the spring chamber 13, and an enlarged stepped hole 14 is provided at the end of the hole, and an annular groove is formed on the tip side. It communicates with the spring chamber 13 via 15.

Reference numeral 5 designates an oil passage for fuel supply, which is bored on the upper side of the nozzle holder main body 1 in a relationship that intersects with the axial direction of the nozzle holder main body 1. A fuel inlet 17 is formed on the rear end side by a connecting pipe 16, and a fuel inlet 17 is formed by a connecting pipe 16, and a fuel inlet 17 is formed on the rear end side. It is designed to be connected to the fuel injection pump through
The distal end side extends to the side of the spring chamber 13 to reach the distal end surface of the nozzle holder body 1, and communicates with an oil reservoir on the outer periphery of the needle valve via an oil passage 18 formed in the nozzle 2.

A piston 6 has a head 19 that fits loosely into the stepped hole 14 at its upper part, and a shaft part 21 which fits into the spring chamber 13 at its lower end. A spring 23 for biasing the needle valve 3 is interposed between the valve opening pressure adjusting shims 22.

Furthermore, a blind hole 7 is bored in the center of the piston 6 to a required depth from the end surface of the head 19. This blind hole 7 constitutes a pressure receiving surface that displaces the piston 6 in the axial direction in the present invention, and the blind hole 7 diameter (pressure receiving surface diameter) D ₁ acts on the needle valve 3 through the oil passage 5. The dimensions are such that it applies a smaller force to the piston 6 than the force exerted by the piston 6.

Furthermore, a shim 24 for setting the piston lift amount is provided at the bottom of the stepped hole 14 facing the lower surface of the piston head.
is installed, and a relief hole 25 communicating with the blind hole 7 is bored in the main body part corresponding to this shim 24, and the top surface of the piston head is formed at a required angle with a flat part 190 having a diameter D equal to the piston diameter d. A slope 191 is provided which slopes downward at a slope of .

Reference numeral 8 denotes a piston operating oil passage branched from the oil passage 5 leading to the nozzle side, the tip of which opens in the cylindrical hole 4, and the piston 6 has a hole at a position corresponding to this opening. A through hole 26 reaching the blind hole 7 is bored.

Reference numeral 9 denotes a cap nut that is screwed onto the outer periphery of the rear end of the nozzle holder main body 1. Inside the cap nut 9 is a bush 1 that contacts the flat head portion 190 of the piston 6 and provides a high-pressure seal with the stopper of the piston 6.
0 is attached.

In other drawings, reference numeral 27 denotes a mounting flange provided on the outer periphery of the intermediate portion of the nozzle holder main body 1.

[Effect of the embodiment]

The nozzle holder for a diesel engine according to the invention is fixed to a cylinder head by a mounting flange (not shown) and connected to a supply pipe from a fuel injection pump by a connecting pipe 16. In this case, in the present invention, the fuel supply port 17 is provided not at the axial end of the nozzle holder main body 1 but at a position intersecting this, and the supply of fuel essential for the operation of the piston 6 is provided through the oil passage 5 to the nozzle. Since the oil passage 8 branched from the oil passage 8 and inside the piston is carried out, the rear end of the nozzle holder body 1 in the axial direction may have a closed structure, and therefore there is a large degree of freedom in connection with the fuel injection pump.

That is, in the present invention, when pressure feeding of fuel from the fuel injection pump is started, fuel is supplied to the oil sump of the nozzle 2 through the oil passages 5 and 18, and the pressure in the oil sump exceeds the residual pressure. begins to increase. Since the oil passage 5 is branched off from the oil passage 8 for piston operation, the fuel simultaneously passes through this oil passage 8 and reaches the cylindrical hole 4. A piston 6 is provided in this cylindrical hole 4.
Since the blind hole 7 at the center of the cylinder is in communication through the through hole 26, the fuel is press-fitted into the blind hole 7, and the piston 6 is pressed toward the nozzle side.

However, at this time, the piston 6 is
Opening pressure is applied to the needle valve 3 through the relief hole 2.
Since the fuel pressure passing through 5 acts as a pushing force from the lower surface of the head 19, the head flat portion 190 comes into close contact with the bush 10. Moreover, since the diameter D ₁ of the blind hole 7 is configured to be smaller than the pressure receiving area of the needle valve 3,
Piston 6 is held in the seated position shown in FIG. In this state, when the nozzle opening pressure applied by the spring 23 is exceeded, the needle valve 3 lifts against the pressing force of the spring 23, and pilot injection is started. When the needle valve 3 is fully lifted and the amount of fuel pumped further increases, the pressure in the sealed chamber between the blind hole 7 of the piston 6 and the bush 10 increases, so that the flat head portion 190 separates from the bush 10. As a result, the head flat portion 190 is added to the pressure receiving surface, and the pressure receiving area becomes larger than the pressure receiving area of the needle valve, so that the piston 6 moves until it comes into contact with the shim 24. At this time, the fuel on the lower surface side of the head 19 flows into the blind hole 7 from the relief hole 25, so that the piston 6 operates smoothly.

Due to this displacement of the piston 6, fuel flows into the stepped hole by the amount of displacement, increasing the volume of the oil passage system and lowering the internal pressure. 3 is moved to the valve closing side, the fuel injection amount decreases, and pilot injection ends.

When fuel is subsequently supplied, the needle valve 3 overcomes the spring force and opens again, and main injection begins. At this time, the piston 6 has already received fuel pressure over its entire cross-sectional area and has undergone a full stroke displacement, and the spring 23 has been compressed by this amount of displacement, so the valve opening pressure at the start of main injection is equal to that at the time of pilot injection. , and main injection continues for a predetermined crank rotation angle. Then, when the crankshaft reaches a predetermined angle and pressure feeding of fuel from the fuel supply pump ends, the needle valve 3 is moved in the valve closing direction and the main injection ends.

At the end of the main injection, the piston 6 is moved by the spring 23
It is moved to the state shown in FIG. 1 by the force of the spring. Even during this movement, the fuel in the chamber above the piston head flows into the blind hole 7 from the relief hole 25, so that the operation is smooth.

[Effect of idea]

According to the present invention described above, the nozzle holder body 1 is provided with the cylindrical hole 4 having the stepped hole 14 enlarged at the upper end, and the cylindrical hole receives pressure by moving from the seating position in contact with a member that closes the stepped hole 14. A piston 6 with an enlarged head 19 loosely installed in the stepped hole 14 is inserted so that the area can be switched, a blind hole 7 of a required depth is provided from the head 19 of the piston 6, and the blind hole 7 is inserted into the stepped hole 14. 7 is constantly communicated via a through hole 26 with a piston operating oil passage 8 branched from an oil passage 5 extending toward the nozzle side extending in a direction intersecting the axis of the nozzle holder body 1, and a piston provided under the head. Relief hole 2
5 communicates with the stepped hole 14, and the blind hole 7 is closed at its upper end by a member that closes the stepped hole 14 when the piston 6 is in the seated position. Therefore, even if fuel is introduced into the nozzle side oil passage 5 and the piston operation oil passage 8 at the same time, the piston 6 is held in the seated position in the first stage, and under relatively low valve opening pressure. Injection starts at , and when the fuel pressure increases and the pressure in the sealed chamber from the blind hole 7 to the stepped hole 14 rises, the head 19 moves away from the seating position and joins the pressure receiving area, causing the piston 6 to move. Since the volume of the fuel passage increases and the pressure inside the pipe decreases, the needle valve 3, which had been open, is forcibly moved to the closed side, and the pilot injection ends. Even if fuel continues to be sent, at this time the piston 6 remains down the entire stroke, and the spring 23 is compressed by the displacement of this piston, so the valve opening pressure is set high, and this valve opening pressure The main injection will be performed based on this.

Therefore, while achieving the appropriate injection characteristics of pilot injection and main injection, it is sufficient to provide only one fuel supply port not at the rear end of the nozzle holder body but on the side where there is a high degree of freedom in connection to the injection pump. The fuel can be injected from any desired angle on the engine side, it is easy to assemble, and the length of the nozzle holder can be shortened because the piston internal passage is used.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a nozzle holder for a diesel engine according to the present invention, and FIG. 2 is a front view thereof. 1... Nozzle holder body, 2... Nozzle, 3...
... Needle valve, 4... Cylindrical hole, 5... Oil passage to the nozzle side, 6... Piston, 7... Blind hole, 8... Piston hydraulic oil passage, 14... Stepped hole, 19 ...Head, 25...Escape hole, 26...Through hole.

Claims (1)

[Claims for Utility Model Registration] A needle valve inserted into a nozzle so as to be freely advanced and retracted is provided with a spring that biases the needle valve in the valve closing direction, and a piston that supports the spring. In the nozzle holder of the type, a small amount of injection is performed by opening and closing the needle valve, and in the second stage, the needle valve is lifted again at a high valve opening pressure set by the movement of the piston, and the main injection is performed. Stepped hole 1 with 1 enlarged at the top end
4, and a piston 6 is slidably inserted into this cylinder hole, and the pressure receiving area of the piston 6 can be switched by moving from a seated position where it contacts a member that closes the stepped hole 14. Stepped hole 14
The piston 6 has a blind hole 7 of a required depth from the head 19, and the blind hole 7 extends in a direction intersecting the axis of the nozzle holder body 1. It constantly communicates with the piston operating oil passage 8 branched from the oil passage 5 to the side via the through hole 26, and communicates with the stepped hole 14 through the relief hole 25 provided under the head, and also communicates with the blind hole 7. A nozzle holder for a diesel engine, characterized in that the upper end is closed by a member that closes the stepped hole 14 when the piston 6 is in the seated position.