JPS6380064A - Jet nozzle structure - Google Patents

Abstract

PURPOSE:To prevent impact force from being exerted to the ceramic front end part of an injection nozzle upon a needle valve being seated, so as to greatly enhance the durability of the injection nozzle, by forming a seat part in an intermediate metal member connecting between a nozzle body and the ceramic front end part of the nozzle. CONSTITUTION:An intermediate metal member 3 formed therein with a seat part 3a on which a needle valve 2 is adapted to be seated, and having a wear- resistant ability and a low thermal expansion coefficient, is connected to the front end of a nozzle body 1 in which the needle valve 2 is elevatably disposed. Further, a nozzle front end part 4 made of ceramic and having fuel jet ports 5 is connected to the other end of the intermediate metal member 3. Further, a slight clearance may be obtained between the inner peripheral surface of the nozzle front end part 4 and the outer peripheral surface of the forward end part of the needle valve 2 upon the needle valve 2 being seated. With this arrangement, it is possible to prevent impact force produced upon the needle valve 2 being seated, from being exerted to the connecting section between the ceramic nozzle front end part 4 and the intermediate metal member 3.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an injection nozzle that atomizes fuel and supplies it to an internal combustion engine, and particularly relates to an injection nozzle structure in which the nozzle body is made of metal and the nozzle tip is made of ceramics. .

[Prior Art] An injection nozzle disposed with its nozzle tip facing the combustion chamber of an internal combustion engine is required to have high-temperature strength because it is constantly exposed to combustion gas. For this reason, the applicant has filed a patent application for Japanese Patent Application Laid-Open No.
Japanese Patent No. 16 proposes a fuel injection nozzle for an engine in which at least the injection port, which is the tip of the nozzle body, is formed of ceramics such as Si3N4 or M2O3.

[Problem to be Solved by the Invention 1 Ceramics have superior advantages compared to metal materials, such as: 1) a low coefficient of thermal expansion, 2) high heat resistance to VJI shock, and 2) low thermal conductivity.

The nozzle part was made of ceramics, the nozzle body was made of Kanazawa, and the technology of connecting them together left room for improvement in terms of structure and cost.

[Means to solve the problem 1 The present invention aims to solve the above problems.

The present invention connects a ring-shaped intermediate metal member having a low coefficient of thermal expansion and having a seat portion on the tip side on which the needle valve is seated, to a metal nozzle body that accommodates a ceramic needle valve so as to be able to move up and down. A nozzle tip made of ceramics and provided with an injection port is connected to the tip of this metal member to form an injection nozzle structure.

[Function] When the needle valve housed in the nozzle body so as to be able to move up and down is seated on the seat part, the tip of the needle valve does not come into contact with the ceramic nozzle tip. Therefore, the impact force generated when the needle valve is seated is not applied to the nozzle tip and the joint between the intermediate metal member and the nozzle tip, and the durability and connection strength of the nozzle tip are greatly improved. Become.

Further, since the intermediate metal member has wear resistance and a low coefficient of thermal expansion, there is little wear and tear, and thermal expansion is suppressed as much as possible, so the connection strength of the connection portion is maintained constant.

Furthermore, forming the needle valve with ceramics reduces wear on the seat surface of the needle valve, and has a thermal expansion coefficient equivalent to that of the intermediate metal member, so it always sits airtight against the seat and controls the fuel flow rate. Fluctuations can be suppressed.

[Embodiment] A preferred embodiment of the injection nozzle structure of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, inside the cylindrical nozzle body 1,
The needle valve 2 is housed with an appropriate clearance in the radial direction so as to be able to move up and down. This nozzle body 1 is made of iron or iron-based metal. A ring-shaped intermediate metal member 3 is integrally connected to the tip of the nozzle body 1, and the seat surface 2a of the needle valve 2 is airtightly seated on the tip side of the inner peripheral surface of the intermediate metal member 3. A sheet portion 3a is formed.

In this embodiment, the intermediate metal member 3 is made of a metal material having wear resistance and a low coefficient of thermal expansion, such as Niresist cast iron. A nozzle tip 4 fired from ceramics is integrally connected to the other end of the intermediate metal member 3, and the nozzle tip 4 has a V-shaped cross section so as to follow the outer peripheral surface of the tip of the needle valve 2. It is formed. Further, when the seat surface 2a of the needle valve 2 is seated on the seat portion 3a, a slight clearance is maintained between the inner circumferential surface 4a of the nozzle tip 4 and the outer circumferential surface of the tip of the needle valve 2. It is set as follows. By the way, the nozzle body 1 is made of iron or iron-based metal, and the needle valve 2
is made of ceramics, the nozzle body 1 extends in the axial direction relative to the needle valve 2 due to the large difference in coefficient of thermal expansion between the two, increasing the clearance with the ceramic needle valve 2, which reduces the fuel flow rate. will change. For this reason, in this embodiment, a cylindrical portion 3b is formed above the seat portion 3a of the intermediate metal member 3 to surround a part of the stem portion 2b of the needle valve 2. The length of this cylindrical portion 3b in the axial direction is determined by the ceramic (
For example, it can be appropriately set based on the difference in thermal expansion coefficient between 5i3Na) and steel. Furthermore, the nozzle tip 4 is formed with a nozzle 5 that is opened in a direction crossing the inclination direction of the nozzle tip 4, and in the embodiment, the nozzle 5 is spaced apart in the inclination direction. Multiple formations.

A groove 6 connecting the plurality of nozzles 5 is formed in the inner peripheral surface 4a of the nozzle tip 4, and this groove 6 guides the fuel to each nozzle 5. In other words, the grooves 6 form fuel pools to improve fuel drainage, thereby preventing carbon from clogging the nozzles 5, and also ensure that fuel is evenly injected from each nozzle 5.

By the way, the nozzle body 1 and the intermediate metal member 3 are welded together by friction welding in this embodiment, and the intermediate metal member 3
and the ceramic nozzle tip 4 are connected by brazing welding or diffusion welding.

Furthermore, since the nozzle 5 can be formed at the same time as the ceramic is fired, the nozzle 5 can have an irregular shape and the nozzle 5 can be formed with high precision. 7 is a fuel chamber, and 8 is a fuel passage.

[Effects of the Invention] As is clear from the above explanation, the injection nozzle structure of the present invention can exhibit the following excellent effects.

(1) A metal nozzle body and a ceramic nozzle tip are connected to each other, and an intermediate metal member having a seat portion on which a ceramic needle valve is seated is interposed; Since the member is made of a metal material with wear resistance and a low coefficient of thermal expansion, the impact force generated when the needle valve is seated can be applied to the nozzle tip, the intermediate metal member, and the nozzle tip, without applying it to the nozzle tip. This will greatly improve durability.

(D) Since the intermediate metal member that connects the nozzle body and the nozzle tip is formed with a seat and a cylindrical part surrounding the needle valve on this seat, the clearance relationship between these parts is kept constant and the fuel flow rate is constant. It can be done.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a preferred embodiment of the injection nozzle structure of the present invention. In the figure, 1 is the nozzle body, 2 is the needle valve, 3 is the intermediate metal member,
3a is a seat portion, 4 is a nozzle tip, and 5 is a spout.

Claims (5)

[Claims] (1) A ring-shaped intermediate metal member having a low coefficient of thermal expansion and having a seat portion on the tip side on which the needle valve is seated is connected to a metal nozzle body that accommodates a ceramic needle valve so as to be able to move up and down; An injection nozzle structure characterized in that a nozzle tip made of ceramics and provided with an injection port is connected to the tip of the metal member. (2) The injection nozzle structure according to claim 1, wherein the intermediate metal member is made of Niresist cast iron and includes a cylindrical portion surrounding the stem portion of the needle valve above the seat portion. (3) The injection nozzle structure according to claim 1, wherein the intermediate metal member and the nozzle body are joined by pressure contact. (4) The injection nozzle structure according to claim 1, wherein the intermediate metal member and the nozzle tip are joined by brazing welding. (5) The nozzle tip is formed with a slight clearance between the outer circumferential surface of the tip of the needle valve and the inner circumferential surface of the nozzle tip when the needle valve is seated on the seat portion. The injection nozzle structure according to claim 1 above.