JPH0547366U - Pre-combustion chamber structure of diesel engine - Google Patents

Abstract

(57) [Abstract] [Purpose] Effectively prevent cracks from occurring in the die, especially around the nozzle, in a diesel engine in which a die made of heat-resistant steel is press-fitted into the opening end of the pre-combustion chamber in the cylinder head. And improve durability. [Structure] The heat-resistant steel die has a planar shape that is a polygon, such as a regular octagon, or an elliptical or rice ball type non-circular curved shape, and the maximum outer diameter is required to be larger than the inner diameter of the press-fitting hole on the cylinder head side. The press-fitting margin is made large and press-fitted into the same press-fitting hole. The base contacts the inner peripheral surface of the press-fitting hole only in the part of the maximum outer diameter, and in other parts, a gap is formed between the inner peripheral surface of the press-fitting hole and the outer peripheral surface of the base, so that the center of the cap from the outside. When a compressive force is applied toward, the deformation of the die is allowed in the gap portion, and stress concentration is relieved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pre-combustion chamber structure of a diesel engine.

[0002]

[Prior Art]

 A typical structure of a conventional pre-combustion chamber type diesel engine will be described with reference to FIG. 1 showing an embodiment of the present invention for the sake of convenience. Reference numeral 10 in the drawing denotes a crank part of which is shown. A case, 12 is a cylinder head made of a metal material such as cast iron mounted above the crank case 10, 14 is a bell-shaped or dome-shaped pre-combustion chamber formed in the cylinder head 12, and 16 is the crank. A cylinder formed in the case 10, 18 is slidably fitted in the cylinder, and only a part of the piston is shown in the figure. 20 is an opening end of the pre-combustion chamber 14 on the cylinder side. A mouthpiece made of heat-resistant steel (including heat-resistant stainless steel, of course) that is press-fitted into the press-fitting hole 22 that has been formed, 24 is an injection port provided in the substantially central portion of the mouthpiece 20, and 26 is the ceiling of the pre-combustion chamber 14. Arranged in part Fuel injection nozzle, 28 is a gasket interposed between the cylinder head 12 and the crankcase 10.

In the conventional pre-combustion chamber structure, the inner peripheral surface of the press-fitting hole 22 formed in the cylinder head 12 and the outer peripheral surface of the mouthpiece 20 are both formed into a cylindrical surface, that is, the plane shape is circular. The outer diameter of the mouthpiece 20 is larger than the inner diameter of the press-fitting hole 22 by the amount of the press-fitting margin.

In the diesel engine having the above-mentioned pre-combustion chamber structure, during operation, a temperature difference occurs between the cylinder head 12 forming the pre-combustion chamber 14 and the base 20, and the thermal expansion coefficients of the two differ. Therefore, a large stress is generated in the die 20, and there is a drawback that cracks are likely to occur around the nozzle hole 24 where the stress is concentrated, especially in the corner portions.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the conventional pre-combustion chamber structure, and cracks caused by stress concentration in the die, especially the injection hole portion, which is press-fitted into the opening end of the pre-combustion chamber. It is an object of the present invention to provide an improved structure capable of effectively preventing the occurrence of

[0006]

[Means for Solving the Problems]

 The present invention was devised to achieve the above object, in which a heat-resistant steel die is press-fitted and fixed to the cylinder-side opening end of the pre-combustion chamber formed inside the cylinder head. A first invention, characterized in that the mouthpiece has a polygonal plane shape, and an outer diameter of the die is larger than an inner diameter of the press-fitting hole at the opening end of the cylinder head; In the pre-combustion chamber, in which a heat-resistant steel die is press-fitted and fixed to the cylinder-side opening end of the pre-combustion chamber, the die is the same as the major diameter larger than the inner diameter of the press-fitting hole at the opening end of the cylinder head. A second invention is proposed, which is characterized by comprising a non-circular curved plane shape such as an ellipse having a minor axis smaller than the inner diameter of the hole and a rice ball type.

[0007]

【Example】

 Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. (Note that the re-description is omitted for the matters already described with reference to FIG. 1 in relation to the conventional pre-combustion chamber structure.) First, the embodiment of the first invention shown in FIGS. 1 and 2 2 is a partial plan view taken along line II-II in FIG. 1, the base 20 has a polygonal (regular octagonal) planar shape. The diameter of the outer circumferential circle connecting the vertexes of the polygon is larger than the inner diameter of the press-fitting hole 22 of the cylinder head 12 by the press-fitting margin. Therefore, when the mouthpiece 20 is press-fitted into the press-fitting hole 22, a notched circular gap 30 is formed between the apexes of the polygon.

According to this configuration, a temperature difference occurs between the cylinder head 12 made of cast iron and the mouthpiece 20 made of heat-resistant steel (including heat-resistant stainless steel as described above) during operation of the engine, Further, due to the difference in the thermal expansion coefficient between the two, when a large compressive stress acts from the outer peripheral apex of the die 20 toward the center side, deformation of the die 20 is allowed due to the presence of the notched circular gap 30. The stress concentration around the nozzle hole 24, especially at the corners thereof, is effectively relieved. As a result, it is possible to effectively prevent the occurrence of cracks in the peripheral portion of the nozzle 20 of the die 20, and to improve its durability and reliability. Further, the inner peripheral surface of the press-fitting hole 22 of the cylinder head 12 and the outer periphery of the die 20 contact each other near the apex of the polygon, and a gap 30 is formed between the two, so that the die 20 is transmitted to the cylinder head 12. Moreover, there is an advantage that the amount of heat that is carried away by the cooling water is reduced and the thermal efficiency of the engine is correspondingly improved.

In the illustrated embodiment, the base 20 has a regular octagonal shape in plan view, but of course a polygon having an octagon or more sides, such as a decagon or an octagon, is less than the polygonal shape. It is obvious that a polygon having a number of sides such as a heptagon can be appropriately adopted.

Next, in the second invention shown in FIG. 3, the die 20 has a substantially elliptical plan shape, and its major axis is formed larger than the inner diameter of the circular press-fitting hole 22 by a necessary press-fitting margin. In addition, the minor diameter is formed sufficiently smaller than the inner diameter of the press-fitting hole 22 so that a crescent-shaped gap 32 is formed between the press-fitting hole 22 and the press-fitting hole 22.

Also in this configuration, when a compressive force acting from the outer peripheral surface toward the center is applied to the mouthpiece 20 during operation of the engine, the presence of the gap 32 allows the mouthpiece 20 to be deformed, so that the injection port 24 The concentration of stress on the periphery, especially at the corners, is effectively moderated and cracks are prevented. Therefore, the durability and reliability of the base 20 can be effectively improved. Further, the presence of the gap 32 reduces the amount of heat that is transferred from the base 20 to the cylinder head 12 and is further absorbed by the cooling water, so that the thermal efficiency of the engine is correspondingly improved.

Although FIG. 3 illustrates the die 20 having a substantially elliptical planar shape, a rice ball 20 having three major diameter portions and the like, which has a non-circular curved shape in a planar shape, may be appropriately adopted. The same effect as described above can be obtained.

[0013]

[Effect of the device]

 As described above, the structure of the pre-combustion chamber of the diesel engine according to the present invention is formed by pressing the heat-resistant steel die into the cylinder-side opening end of the pre-combustion chamber formed inside the cylinder head. A first invention, characterized in that the mouthpiece has a polygonal plane shape, and the outer diameter of the die is larger than the inner diameter of the press-fitting hole at the opening end of the cylinder head, and the inside of the cylinder head. In the pre-combustion chamber with the heat-resistant steel mouthpiece press-fitted into the cylinder-side opening end of the pre-combustion chamber, the mouthpiece has the same major diameter as the inner diameter of the press-fitting hole at the cylinder head opening end. The gist of the second invention is characterized in that it has a non-circular curved plane shape such as an ellipse and a rice ball type having a shorter diameter smaller than the inner diameter of the press-fitting hole. Cracks occur Preparative effectively prevented, it is possible to improve the durability and reliability, is practically useful.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of the first invention.

FIG. 2 is a plan view taken along line II-II of FIG.

FIG. 3 is a plan view similar to FIG. 2, showing a second invention.

[Explanation of symbols]

10 ... Crank case, 12 ... Cylinder head, 20 ...
Mouth, 22 ... Press fit hole.

Claims (2)

[Scope of utility model registration request] 1. A heat-resistant steel die is press-fitted and fixed to an opening end of a pre-combustion chamber formed inside a cylinder head on the cylinder side, wherein the die has a polygonal planar shape, A pre-combustion chamber structure for a diesel engine, the outer diameter of which is formed larger than the inner diameter of the press-fitting hole at the opening end of the cylinder head. 2. A heat-resistant steel die is press-fitted and fixed to an opening end of a pre-combustion chamber formed in the cylinder head on the cylinder side, wherein the die is a press-fitting hole at the opening end of the cylinder head. A pre-combustion chamber structure for a diesel engine, characterized in that it has a non-circular curved plane shape such as an ellipse or a rice ball type having a major axis larger than the inner diameter of the above and a minor axis smaller than the inner diameter of the same press-fitting hole.