JPS5886325A - Glow plug - Google Patents

Abstract

PURPOSE:To keep the tip surface of the glow plug at high temperature at all times and consequently solve the problem of considerable ignition lag at low speed and light load of an engine by a structure wherein the tip surface of the glow plug employed in diesel engine is specifically processed. CONSTITUTION:Because the surface of the tip part 32 of the glow plug 33 is coated with oxidized catalyst 34, even when the energizing of the glow plug 33 is stopped after starting the engine, said oxidized catalyst 34 is kept at its activation temperature at all times due to the combustion heat of the engine and as well as due to reaction heat of oxidation reaction between fuel mists and the oxidized catalyst 34, the surface of the tip part 32 of the glow plug 33 is kept at high temperature. Accordingly, the fuel injected from a fuel injection nozzle 31 during compression stroke ignites and burns itself without causing considerable ignition lag even at low speed and light load of the engine. As a result, the combustion noise and vibration of the engine can sharply be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glow plug used in a diesel engine.

As a conventional diesel engine, for example,
There is one as described in Japanese Patent No.-117019.

This diesel engine is constructed as shown in Fig. 1. In Fig. 1, (1) is a cylinder block (3) in which a cylinder hole (2) is formed, and a cylinder block (3) in which a cylinder hole (2) is formed.
a main combustion chamber defined by a piston (4) slidably housed within the cylinder head (5) fixed to the cylinder block (3) so as to keep the cylinder hole (2) quiet; , and (6) is a swirl chamber defined by the cylinder head (5) and the mouthpiece (7) fitted in the cylinder head (5). These main combustion chamber (1) and swirl chamber (6)
They are communicated with each other by a communication passage (8) formed in the cap (7), and constitute a combustion chamber (9) as a whole.

In addition, the cylinder head (5) has its nozzle hole in the swirl chamber (6).
), and the fuel injection nozzle (10) is installed so as to face the glow plug (11) or its tip (12).
is attached so as to protrude into the fringe flow chamber (6), that is, the combustion chamber (9).

In such a diesel engine, only air is taken into the combustion chamber (9) during the intake stroke, and when the intake air is compressed by the rise of the piston (4) during the compression stroke and its temperature becomes high. , fuel is injected from the fuel injection nozzle (10) into the swirl chamber (6) in the form of a mist. This sprayed fuel is self-ignited by the compression heat of the intake air and the pancreatic ambient temperature, and is first explosively combusted in the swirl chamber (6), and then combustion is continued in the main combustion chamber (1). The period from the start of fuel injection to ignition, that is, the period of ignition delay, is long;
This tendency is particularly noticeable when starting the engine when the cylinder block (3) and cylinder head (5) are cold, or when the engine is running at low speed and under low load. As a result, the injected fuel accumulated up to the point of ignition is combusted all at once, which increases the explosion pressure within the combustion chamber (9) and increases mid-high frequency noise and vibrations associated with combustion. This tendency is remarkable when the engine is started or when the engine is running at low speed and low load.

Therefore, when starting a diesel engine,
By energizing the glow plug (11) and heating it, engine startability in cold conditions is improved.

However, in order to prevent the so-called battery from dying and to prevent the glow plug from overheating due to the large power consumption of the glow plug, it is necessary to stop supplying electricity to the glow plug after starting the engine. Therefore, even after the engine has been started, the ignition performance deteriorates when the engine is running at low speed and low load, causing a delay in ignition and causing combustion noise and vibrations.

This invention was made in view of these conventional problems, and aims to solve the above problems by coating the surface of the part of the glow plug that protrudes into the combustion chamber with an oxidation catalyst. .

The present invention will be explained below based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

First, to explain the configuration, (21) is the cylinder hole (22).
) is formed in the cylinder block, and the cylinder hole (
A piston (23) is slidably housed inside the piston (22). A cylinder head (25) is fixed to the upper end of the cylinder block (21) via a gasket (24) so as to close the cylinder hole (22), and the inner wall of the cylinder block (21) and the piston (23) ) and the cylinder head (25) define a main combustion chamber (26). The cylinder head (25) has a substantially hemispherical shape into which a cap (27) having a substantially hemispherical concave portion is fitted, and which defines a substantially spherical swirl chamber (28) together with the concave portion of the cap (27). A recess is formed. Base (27
) is formed with a communication passage (29) that communicates the main combustion chamber (26) and the swirl chamber (28), and these constitute a combustion chamber (30) as a whole. Cylinder head (25
) is equipped with a fuel injection nozzle (31) so that its injection hole faces the swirl chamber (28), and a glow plug (33) is attached so that its tip (32) protrudes into the swirl chamber (28). ) is installed. This glow plug (
The tip (32) protruding from the combustion chamber mark (33) is coated with an oxidation catalyst (34), such as platinum.

Next, the effect will be explained.

First, when starting the engine, use the glow plug (33
) to heat the glow plug.

During the intake stroke, the air sucked into the combustion chamber (30) is compressed during the compression stroke, and its temperature increases. Fuel is injected from the fuel injection nozzle (3I) into the heated air, and while the sprayed fuel mixes with the air in the swirl chamber (28), it is ignited by the heat generated by the glow plug and the heat of compression. Burn. Furthermore, this combustion continues in the main combustion chamber (26) via the communication passage 29).

In the past, when starting the engine, the glow plug (33)
The heat of the fuel ignites and burns without significant ignition delay, making it possible to reduce combustion noise and vibration.

Next, after the engine is started, the power supply to the glow plug [331 is stopped. However, in this invention,
The surface of the tip (32) of the glow plug (33) is coated with an oxidation catalyst (34). The surface of the tip (32) of the glow plug (33) is kept at a high temperature due to the reaction heat caused by the oxidation reaction between the spray and the oxidation catalyst.Therefore, during the compression stroke, the fuel injected from the fuel injection nozzle (31) ignites and burns without significant ignition delay even when the engine is running at low speeds and under low load.As a result, engine combustion noise and vibration can be significantly reduced.

In the above embodiment, the entire tip of the glow plug protruding into the combustion chamber is coated with the oxidation catalyst, but the coated area or portion may be limited depending on the heating temperature required by the engine, etc. .

Furthermore, if the surface of the glow plug is made of a bolus material, such as ceramics, and an oxidation catalyst is placed on the surface, the catalytic effect is further improved.

As explained above, according to the present invention, in a glow plug that is provided so that its tip protrudes into the combustion chamber of a diesel engine, the surface of the tip is coated with an oxidation catalyst. Even if the power to the glow plug is stopped after starting, the surface of the tip of the glow plug can be kept at a high temperature at all times, and even when the engine is sluggish and under low load, there will be no significant ignition delay.
It is possible to burn fuel. As a result, the effect of significantly reducing engine combustion noise and vibration is obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a conventional glow plug installed in a diesel engine, and FIG. 2 is a schematic sectional view showing an embodiment of the glow plug of the present invention installed in a diesel engine. (30)...Combustion chamber (32)...Tip (33)
... Glow Plaque (34) ... Oxidation Catalyst Leopard License Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Yugagun-Department

Claims (1)

[Claims] 1. A glow plug provided with a tip thereof protruding into a combustion chamber of a diesel engine, characterized in that the surface of the tip is coated with an oxidation catalyst.