JPS62255571A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To prevent fuel leakage, by inserting an elastic ring between a nozzle tip and a nozzle body to ensure a sufficient jointing strength to an engaged portion even if they are exposed to a high temperature in use. CONSTITUTION:An elastic steel ring 3 is inserted into the outer periphery of a nozzle tip 2 in the condition that it is heated and thermally expanded and then it is integrally and fixedly attached to the nozzle tip 2 because its diameter is reduced after it is cooled. The nozzle tip 2 is integrally engaged with a nozzle body 1 in such a way that its dimensional variation is small even if they are exposed to a high temperature in operation and no space is caused between the elastic ring 3 and the nozzle body 1. Further, since it is possible to make the thermal expansion ratios of the elastic ring 3 and the nozzle body 1 substantially identical because both of them are made of metal, a difference between the dimensional variations caused in them is also small with a result that no gap is made between the elastic ring 3 and the nozzle body 1, whereby fuel leakage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection nozzle for an internal combustion engine, and particularly to a structure in which a nozzle tip made of a heat-resistant material (ceramic, etc.) is fitted into a nozzle body.

[Conventional technology]

For the purpose of improving heat resistance, corrosion resistance, etc., a part of the nozzle body is made of a nozzle tip made of a heat-resistant material such as ceramic, and this nozzle tip is fitted to the nozzle body. has been proposed in "Utility Model Application Publication No. 161417/1983".

The fuel injection nozzle disclosed in this publication has an injection hole and a valve seat made of a ceramic nozzle tip.

[Problem that the invention seeks to solve]

However, when such a TF4 fuel injection nozzle is exposed to high temperatures during combustion, dimensional changes occur due to the difference in coefficient of thermal expansion between the ceramic tip and the metal nozzle body, causing a difference in the fitting part. There was a problem in which the fuel separated and fuel leaked.

In addition, since the needle is lifted by sliding on the nozzle body, if the valve seat is eccentric with respect to this sliding part, the needle will not come into close contact with the valve seat, making it difficult to securely connect the nozzle hole. cannot be closed.

For this reason, after fitting the tip into the nozzle body, it is necessary to rework the valve seat part based on the sliding part, but processing ceramics after firing is difficult, and precision processing is especially expensive and extremely troublesome. Therefore, in reality, it has been extremely difficult to suppress the eccentricity to a tolerance value required to ensure performance.

The present invention solves the above-mentioned problems, and provides a fuel injection system that can ensure sufficient joint strength at the fitting part even when exposed to high temperatures during use, prevent leakage, and reduce the number of machining steps. The aim is to provide a nozzle.

[Means for Solving the Problems] In order to solve the above problems, the present invention is characterized in that an elastic ring is inserted between a nozzle tip and a nozzle body made of a heat-resistant material such as ceramic.

[Function] With this configuration, the difference in dimensional change due to the difference in coefficient of thermal expansion when the injection nozzle is exposed to high temperatures is absorbed by the elastic action of the elastic ring, so that the fit between the nozzle tip and the nozzle body is improved. Sufficient joint strength is ensured at the parts to prevent fuel leakage.

Furthermore, after fitting the elastic ring into the nozzle tip, the eccentricity can be corrected by processing the outer periphery of the elastic ring, which is easy to process, using the valve seat as a reference, and then fitting it into the nozzle body. It is possible to reduce the number of processing steps.

[Embodiments of the invention]

The present invention will be described below based on a first embodiment shown in FIG.

In the figure, 1 is a nozzle body, 4 is a needle,
The needle 4 is slidably accommodated in the nozzle body 1 in a sliding portion 4a formed in the nozzle body 1.

Reference numeral 2 denotes a nozzle chip in which a part of the nozzle body (nozzle hole part) is manufactured as a separate structural part, and is made of a heat insulating material such as ceramic.

Reference numeral 5 denotes a valve seat portion formed on the nozzle tip 2, on which the needle 4 abuts in a movable manner.

Reference numeral 3 denotes an elastic ring made of steel, which is fitted between the nozzle tip 2 and the nozzle body 1.

The elastic ring 3 is fitted onto the outer periphery of the nozzle tip 2 in a thermally expanded state after being heated to a high temperature, and then the diameter of the elastic ring 3 is reduced by cooling, so that it is integrally fastened to the nozzle tip 2. The nozzle body 1 is fitted into the nozzle body 1 as an integral structure.

Reference numeral 6 denotes a fuel passage provided in the nozzle body, which communicates with an oil reservoir 7 provided in the same nozzle body 1, and is supplied with high-pressure fuel pumped by an injection pump (not shown).

8 is a nozzle hole provided in the nozzle chip.

The operation of the fuel injection nozzle having such a configuration will be explained.

Fuel sent from an injection pump (not shown) reaches an oil reservoir 7 through a fuel passage 6, but when this fuel pressure overcomes the force of a spring (not shown) pushing down the needle 4, the needle 4 is lifted by this fuel pressure. Therefore, the needle 4 is separated from the valve seat portion 5, and the nozzle hole 8 is opened. Therefore, the fuel in the oil reservoir 7 is injected from the injection hole 8.

When the fuel pressure in the oil reservoir 7 decreases, the needle 4 seats on the valve seat 5 due to the downward force of the spring, and the nozzle hole 8
Close. Therefore, fuel injection ends.

This operation is similar to that of a conventional injection nozzle.

In this embodiment, the elastic ring 3 is fitted onto the outer periphery of the nozzle tip 2 at a high temperature (a temperature higher than the temperature normally used in actual use), and is then integrated into the nozzle tip 2 by reducing the diameter of the elastic ring 3 by cooling. Since the nozzle body 1 is fitted into the nozzle body 1 with such an integral structure, when the entire nozzle is exposed to high temperatures during operation, the elastic ring 3 is attached to the nozzle tip 2 in a high temperature state in advance. By being fitted into the elastic ring 3 and the nozzle tip 2, there is little difference in dimensional change even when exposed to high temperatures during operation.
There will be no gap between the two.

In addition, since the thermal expansion coefficients of the elastic ring 3 and the nozzle body 1 can be made almost the same between metals, the difference in dimension between them is small, and therefore the difference between the elastic ring 3 and the nozzle body 1 is also small. No gaps are created. Therefore, fuel leakage is prevented.

On the other hand, in the case of the conventional configuration without the elastic ring 3, the outer metal nozzle body 1 has a larger coefficient of thermal expansion than the inner ceramic nozzle tip 2, so the nozzle body 1 expands significantly. , there will be differences in dimensional changes, and the joint surfaces will separate, creating gaps and easily causing problems such as leaks.

In addition, the elastic ring 3 is fitted onto the outer periphery of the nozzle tip 2 while being heated to a high temperature, and after that, the elastic ring 3 and the nozzle tip 2 are fitted into the nozzle body 1 as one body. At low temperatures, a large tensile stress is exerted on the nozzle tip 2 due to the difference in thermal expansion coefficient with the nozzle tip 2.
Therefore, a large compressive stress is exerted on the nozzle tip 2. Note that the thickness of the nozzle tip 2 is determined so that the compressive stress is sufficiently small below the elastic limit.

Therefore, the tensile stress generated by the impact force when the needle 4 is seated on the valve seat part 5 can be canceled out, and the drawback of being weak against impact force, which conventional ceramic chips had, can be improved.

Furthermore, in the case of this configuration, the elastic ring 3 is attached to the nozzle tip 2.
After fitting, the outer periphery of the elastic ring 3, which is easy to process, can be corrected for eccentricity by using the valve seat part 5 of the nozzle tip 2 as a reference, and then it can be fitted to the body 1, making it easy to process. This can reduce eccentricity.

2 and 3 are the second and third embodiments of the present invention, respectively.
FIG. 3 is a cross-sectional view of each main part showing an example of the embodiment.

In the case of FIG. 1, the nozzle tip 2 and the elastic ring 3 are integrated and then fitted into the nozzle body 1 from the sliding part 4a side, whereas in the examples of FIGS. 2 and 3, too,
A case is shown in which the nozzle tip 2 and the elastic ring 3 are fitted and joined to the nozzle body 1 from the bottom side of the figure.

In FIG. 2, the elastic ring 3 and the nozzle tip 2 are held by a cap 8, and the cap 8 is fixed to the nozzle body 1 by means such as welding or brazing (shown as a joint 9).
has been done.

In the case of FIG. 3, the elastic ring 3 is directly fixed to the nozzle body 1 at a joint 9 by welding or the like.

〔Effect of the invention〕

As explained above, according to the present invention, since the elastic ring is inserted between the nozzle tip and the nozzle body made of a heat-resistant material such as ceramic, the difference in thermal expansion coefficient when the injection nozzle is exposed to high temperatures is Differences in dimensional changes are absorbed by the elastic action of the elastic ring, ensuring sufficient joint strength at the fitting portion between the nozzle tip and the nozzle body, and preventing fuel leakage. In addition, after fitting the elastic ring into the nozzle tip, the eccentricity can be corrected by processing the outer periphery of the elastic ring, which is easy to process, using the valve seat as a reference, and then fitting it into the nozzle body. It is possible to reduce the number of man-hours, and it can also be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional views of essential parts showing second and third embodiments of the present invention, respectively. 1... Nozzle body, 2... Nozzle tip made of heat insulating material such as ceramic, 3... Elastic ring made of steel,
4... Needle, 5... Valve seat part. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (2)

[Claims] (1) In a fuel injection nozzle in which a part of the nozzle body is composed of a nozzle tip made of a heat-resistant material such as ceramic, and this nozzle tip is fitted into the nozzle body, an elastic ring is fitted between the nozzle tip and the nozzle body. A fuel injection nozzle characterized by the fact that it is inserted into the fuel injection nozzle. (2) The elastic ring is fitted onto the outer periphery of the nozzle tip while being heated to a higher temperature than when the injection nozzle is in use, and is tightened to the tip by contraction of the elastic ring as it cools, thereby forming the nozzle body. The fuel injection nozzle according to claim 1, wherein the fuel injection nozzle is fitted into a fuel injection nozzle.