JP2002180834A - Diesel engine auxiliary combustion chamber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subsidiary chamber capable of preventing the occurrence of a misfire and pale smoke by reducing the wetness of the subsidiary chamber wall surface due to the adhesion of an atomized fuel. SOLUTION: This subsidiary chamber 2 is intrusively formed in a cylinder head 1, and an injection part 5a of a fuel injector 5 is so faced to the subsidiary chamber 2 as to inject the atomized fuel (q) into the subsidiary chamber 2. A heat-resistant oil-repellent film 4 is so overlaid and formed on the inside wall surface 3 of the subsidiary chamber 2 that the contact angle θ of each oil droplet Q of the atomized fuel (q) stuck to the oil-repellent film 4 is set larger than that of each oil droplet of the atomized fuel stuck to the surface of the subsidiary chamber forming material 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sub-combustion chamber of a diesel engine, and more particularly to a technique for making the inner wall surface of the sub-combustion chamber hardly wet with spray fuel.

[0002]

2. Description of the Related Art As a sub-combustion chamber of a diesel engine, there is a sub-combustion chamber in which a sub-combustion chamber is formed in a cylinder head so that an injection portion of a fuel injector faces the sub-combustion chamber. It is configured to inject the spray fuel into the fuel. The spray fuel is promoted to mix with the air by the compressed vortex formed in the sub-combustion chamber. In addition,
A bare skin of a material forming the sub-combustion chamber appears on the inner wall surface of the sub-combustion chamber.

[0003]

According to this prior art, at the time of a low-temperature start or the like, the sprayed fuel rides on the above-mentioned compressed vortex and wets the inner wall surface of the sub-combustion chamber, causing poor ignition and blue-white smoke. The present invention has been made in order to improve such inconvenience, and an object of the present invention is to reduce the wetting of the inner wall of the sub-combustion chamber due to the adhesion of the spray fuel, thereby preventing poor ignition and generation of blue-white smoke. Is to provide.

[0004]

In order to solve the above-mentioned problems, the present invention is configured as follows. That is, claim 1
The sub-combustion chamber 2 is recessed and formed in the cylinder head 1, the injection portion 5a of the fuel injector 5 faces the combustion chamber 2, and the spray fuel q is injected into the sub-combustion chamber 2. In a sub-combustion chamber of a diesel engine configured as described above (hereinafter referred to as a “basic configuration” of the present invention), for example, FIG.
As shown in (A), a heat-resistant oil-repellent film 4 is formed on the inner wall surface 3 of the sub-combustion chamber 2 by skin, and the contact angle θ of the oil droplet Q of the spray fuel q adhered to the oil-repellent film 4. However, it is characterized in that the contact angle is larger than the contact angle of the oil droplets of the spray fuel adhered to the surface of the auxiliary combustion chamber forming material 2a.

According to a second aspect of the present invention, in the direct injection combustion chamber of the diesel engine according to the first aspect, the oil-repellent film 4 is formed of a fluororesin.

[0006]

According to the present invention, the following functions and effects are obtained. According to the first aspect of the invention, in the auxiliary combustion chamber of the diesel engine having the basic configuration, for example, as shown in FIGS. An oil film 4 is formed, and the oil-repellent film 4
Is configured such that the contact angle θ of the oil droplet Q of the sprayed fuel q adhered to the surface of the auxiliary combustion chamber forming material 2a is larger than the contact angle θ of the oil droplet of the sprayed fuel adhered to the surface of the auxiliary combustion chamber forming material 2a. This can reduce the wetting of the wall surface 3 of the sub-combustion chamber, thereby preventing poor ignition and generation of blue-white smoke.

That is, as shown in FIG. 1B, when an oil droplet Q of the spray fuel q adheres to the oil-repellent film 4, a point O
There are three boundary surfaces intersecting with each other, and the interface tension T
₁ , T ₂ and T ₃ act. In the equilibrium state, the following equation is established between the contact angle θ of the oil droplet Q and each of the interfacial tensions T ₁ , T ₂ , and T ₃ . Here, T ₁ is the interfacial tension between the oil repellent film 4 and the gaseous phase, T ₂ is the interfacial tension between the oil repellent film 4 and the oil droplet Q, and T ₃ is the interfacial tension between the gaseous phase and the oil drop Q. Is the interfacial tension of T ₁
= T ₂ + T ₃ COS θ and whether or not the oil droplet Q wets the film 4 depends on the magnitude of the contact angle θ of the oil droplet Q attached to the film 4.

In the present invention, the contact angle θ of the oil droplet Q on the film 4
However, since the heat-resistant oil-repellent film 4 was formed on the inner wall surface 3 of the sub-combustion chamber 2 so as to be larger than the contact angle of the oil droplet attached to the surface of the sub-combustion chamber forming material 2a, The contact area between the oil-repellent film 4 and the oil droplet Q is reduced, and the wetting of the wall surface 3 of the sub-combustion chamber due to the adhesion of the spray fuel q is smaller than in the related art. Thereby, the inner wall surface 3 of the sub-combustion chamber 2
As a result, the amount of heat released is reduced, and the combustion of the air-fuel mixture is promoted, whereby poor ignition and generation of blue-white smoke can be prevented.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1A is a longitudinal sectional view of a sub-combustion chamber of a diesel engine according to an embodiment of the present invention.
(B) is a schematic diagram showing a relationship between the contact angle θ of the oil droplet Q of the spray fuel q attached to the oil-repellent film and the surface tension. This sub-combustion chamber has the same basic configuration as the conventional example. That is,
The upper half 2a of the sub-combustion chamber 2 is recessed in the cylinder head 1, and the lower half 2b of the sub-combustion chamber 2 is
The fuel injection device 5 is configured such that the injection portion 5 a of the fuel injector 5 faces the sub-combustion chamber 2 and the spray fuel q is injected into the sub-combustion chamber 2. Note that reference numeral 6 in FIG. 1A indicates a piston, and at the end of the compression stroke, the piston 6
Compressed air A ₁ pressed into the auxiliary combustion chamber 2 through the injection hole 7 becomes a compressed vortex A ₂ in the auxiliary combustion chamber 2,
Promotes the mixing of air and atomized fuel q.

As described above, whether or not the oil droplet Q of the sprayed fuel q wets the inner wall surface 3 of the combustion chamber 2 depends on the magnitude of the contact angle θ of the oil droplet Q attached to the film 4. In the present invention, the contact angle θ of the oil droplet Q on the film 4 is attached to the surface of the material forming the sub-combustion chamber 2 (specifically, the material 2a forming the cylinder head 1 and the nozzle hole base 1a). A heat-resistant oil-repellent film 4 was formed on the inner wall surface 3 of the sub-combustion chamber 2 so as to be larger than the contact angle of the oil droplet. This is intended to reduce the wetting of the wall surface 3 of the sub-combustion chamber due to the attachment of the spray fuel q as described above, thereby preventing poor ignition and generation of blue-white smoke. The heat-resistant oil-repellent film 4
, A fluorine resin (for example, “polytetrafluoroethylene”) is used.

The heat-resistant oil-repellent film 4 is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. It is conceivable to use chrome plating as the film 4.

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of a sub-combustion chamber of a diesel engine according to an embodiment of the present invention, and FIG. 1B is a view showing a contact angle and a surface tension of a fuel oil droplet adhering to an oil-repellent coating. It is a schematic diagram which shows the relationship with.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 2 ... Sub combustion chamber, 2a ... Sub combustion chamber forming material, 3 ... Inner wall surface of sub combustion chamber, 4 ... Oil repellent coating, 5 ... Fuel injector, 5a ... Injection part of fuel injector, Q ... oil droplets of sprayed fuel, q: sprayed fuel, θ: contact angle of oil droplets.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Setsuo Yamada 3-8 Chikushinmachi, Sakai City, Osaka Inside Kubota Sakai Rinkai Plant (72) Inventor Takashi Hanada 3-8 Chikushinmachi, Sakai City, Osaka Stock Kubota Sakai Rinkai Plant (72) Inventor Yuhiko Fujiwara 3-8 Chikushinmachi Shinmachi, Sakai City, Osaka Prefecture (72) Inventor Hiroshi Sasaki 3-8 Chikushinmachi Shinmachi, Sakai City, Osaka Stock (72) Inventor Kozo Yoshida 3-8 Chikushinmachi, Sakai City, Osaka Prefecture F-term (reference) 3G023 AA02 AA04 AA07 AB05 AC04 AD03 AD09 AD22 AE06 3G024 AA03 DA02 EA01 GA18 HA15

Claims (2)

[Claims] An auxiliary combustion chamber (2) is provided in a cylinder head (1).
Is formed so that the injection part (5a) of the fuel injector (5) faces the sub-combustion chamber (2), and the spray fuel (q) is injected into the sub-combustion chamber (2). In the sub-combustion chamber of the diesel engine, a heat-resistant oil-repellent film (4) is formed on the inner wall surface (3) of the sub-combustion chamber (2), and the spray fuel adhered to the oil-repellent film (4) is formed. The contact angle (θ) of the oil droplet (Q) of (q) is configured to be larger than the contact angle of the oil droplet of the spray fuel adhered to the surface of the auxiliary combustion chamber forming material (2a). The auxiliary combustion chamber of the diesel engine. 2. The direct injection combustion chamber for a diesel engine according to claim 1, wherein the oil-repellent film (4) is formed of a fluorine resin.