JPS591102Y2 - nozzle holder - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a nozzle spring that presses a nozzle needle valve and a bushing rod in a fuel injection device for an internal combustion engine. A drop in the opening pressure of the needle valve is prevented by inserting a second spunong with a smaller setting force.

Conventionally, as shown in FIG. 1, a fuel injection nozzle 3 is attached to the end of a nozzle holder 1 by a nozzle nut 2, and a spring chamber 5 for accommodating a nozzle spring 4 is provided in the nozzle holder 1. In the lower opening 5a of the spring chamber 5, the small diameter portion 3b of the needle valve 3a of the nozzle 3 is fitted into a recess 6a at the lower end of the bushing rod 6.

A spring seat 6b is formed at the upper end of the bushing rod 6, and a spring seat 7a formed at one end of the nozzle valve opening pressure adjustment screw 7 screwed into the opening 5b above the spring chamber and the spring seat 6b of the bushing rod are formed. A nozzle spring 4 is held between them.

A hole 7b for discharging leakage fuel is formed in the axial direction of the adjustment screw 7, and a pipe joint (not shown) is screwed into the extension of the hole 7b.

Further, a fuel passage 1 is provided in the side part of the nozzle holder 1 in the longitudinal direction.
A is provided on the upstream side and connected to a fuel injection pump (not shown) via an injection pipe joint 8.

The downstream side is connected to the fuel introduction hole 3C of the nozzle 3.

However, in the nozzle holder, initial fitting and wear of the bushing rod to the spring seat that occurs at the beginning of fuel injection and along the injection path occur, leading to a decrease in valve opening pressure over the course of operating time. .

As a countermeasure, efforts have been made to correct the setting force of the nozzle spring, or to heat-treat the parts that receive the spring force, and to improve the surface roughness, but none of these measures have been perfect in preventing the drop in valve opening pressure.

The present invention is intended to eliminate the above-mentioned drawbacks, and embodiments of the present invention will be described below with reference to the drawings.

Note that the same parts in FIG. 1 and FIG. 2 are denoted by the same reference numerals.

As shown in FIG. 2, the bushing rod is separated from a spring seat 6b that supports the nozzle spring 4 and a shaft portion 6C, and the shaft portion 6C is press-fitted into the spring seat 6b.

Further, a second spring chamber 10 having a smaller diameter than the large diameter portion of the spring seat is provided in the nozzle holder main body 1 near the spring seat contact portion of the shaft portion 6C, and the second spring chamber 10 has a diameter smaller than that of the spring seat large diameter portion. A second spring 9 with a smaller set force than the spring 4 is inserted.

Moreover, since the second spring 9 is given a stress greater than the setting limit, the stress exceeding the setting limit is constantly repeated during engine operation. The spring 9 is set, and the setting force F2
becomes smaller than the initial value, and as a result, the force F that generates the nozzle opening pressure is equal to the setting force F1 of the nozzle spring 4.
This appears as a difference F1-F2 between the set force F2 of the second spring 9 and the set force F2 of the second spring 9. By reducing the set force of the second spring 9, a decrease in valve opening pressure can be avoided.

The present invention, configured as described above, can compensate for the decrease caused by the wear and initial break-in of the nozzle spring on the spring seat surface of the bushing rod, which was the problem mentioned above, and thus greatly contributes to preventing the drop in valve opening pressure. It has excellent effects such as:

[Brief explanation of the drawing]

Figure 1 shows a conventional nozzle holder.1. FIG. 2 shows an embodiment of the nozzle holder of the present invention. DESCRIPTION OF SYMBOLS 1... Nozzle holder, 3... Nozzle, 4... Nozzle spring, 5... Spring chamber, 6... Bush rod, 6b... Spring seat, 9... Second spring, 1
0...Second spring chamber.

Claims (1)

[Scope of utility model registration request] In a nozzle holder in which the needle valve of a nozzle is pressed by a nozzle spring via a bushing rod, a second force smaller than the setting force of the nozzle spring is placed on the side opposite to the nozzle spring of the spring seat of the bushing rod that is pressed by the nozzle spring. A nozzle holder characterized in that a spring is inserted with a stress exceeding the stress limit.