JPS61214907A - Piston combustion chamber forming method for diesel engine - Google Patents

Abstract

PURPOSE:To make it possible to quickly and readily form a special twisted petal shaped combution chamber at a low cost by forming the combution cham ber of a piston into a plurality of partial circular petal shape by cutting. CONSTITUTION:In order to form the cavity of a combution chamber 14, a cut ting tool 16 composed of a shank 18 an a cutting section is used. The cutting of the partial circular petal shaped section 14a of the cavity to the depth of H1 is performed by rotating the cutting tool 16 with the center of the partial circular petal shaped section and the rotary axis of the cutting tool aligned. In the next step, the cutting tool 16 is rotated and lowered by a desired depth of H2 moving the rotary axis of the tool up to a position B1 in the circumferen tial direction to perform the cutting. The cuttings of partial circular petal shaped section 14b through 14d are performed in the completely same manner as mentioned above. The combution chamber obtained in such cavity forming can restrain the generation of black smoke and can diminish noises.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a combustion chamber cavity that is recessed from the upper surface of a piston into the interior of a diesel engine, particularly a direct injection diesel engine.

The present applicant previously proposed that the planar shape of the opening edge on the upper surface of the piston has a multi-petal shape with a plurality of partially circular petals, and that the multi-petal shape is rotated around a center line parallel to the piston axis. Diesel engine whose basic shape is a twisted petal-shaped cavity that is formed by moving downward along the concentric line.
Invented a combustion chamber for a piston for gin, and applied for utility model registration No. 180419 of 1982 (filed on November 22, 1988).
proposed in. According to this previously proposed device, by associating the above-mentioned specially shaped twisted petal-shaped cavity with the direction of the swirl flow, it is possible to improve combustion by improving the mixing of fuel spray and air, thereby improving fuel efficiency and exhaust gas performance. improved,
Although it was possible to further reduce noise, there was a problem with the processing of the combustion chamber.

In other words, conventionally, the combustion chamber was formed by electric discharge machining using an electrode that had the same shape as the multi-petal planar shape of the combustion chamber at the opening edge of the upper surface of the piston, but the machining time was long and productivity was extremely high. Due to the low price, the manufacturing cost was extremely high and there were defects that made it unsuitable for mass production.

Therefore, the present invention does not rely on the conventional electrical discharge machining method, but utilizes a highly productive turning machine to create a combustion chamber that has the above-mentioned twisted, multi-petaled basic shape and has undergone useful modifications thereto. It is an object of the present invention to provide a method for forming a combustion chamber of a piston for a diesel engine, which can significantly reduce manufacturing costs and meet large-scale demand by making molding possible. In order to achieve the above object, the method of the present invention provides a method for forming a combustion chamber comprising a cavity whose opening edge on the upper surface of the piston has a multi-petal shape with a plurality of partially circular petals. A shaft handle that is gripped and rotated by the device, and a disc-shaped shaft fixed to the coaxial handle and having substantially the same diameter as the above-mentioned partial circular petal portion, and whose lower surface outer circumferential portion corresponds to the outer circumferential curved surface portion of the bottom of the combustion chamber. (1) A cutting tool consisting of a cutting part forming a curved surface is lowered to a desired depth along a straight line passing through the center An of the partial circular petal part and parallel to the piston axis, and then cutting is performed (2). ) The center O of the combustion chamber and the center An of the partial circular petal portion
The desired point is a circular arc that forms an acute angle θ with respect to the straight line OAn connecting the above, and has its center at one point 01 on the straight line a An Os that passes through the center An, and that passes through the center An of the partial circular petal portion. The combustion chamber is cut by moving the rut in the circumferential direction at the center angle α and lowering it further to a desired depth, and repeating the above blank cutting process for the number of partial petals. It is characterized by:

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. First, in FIG. 1, reference numeral 10 generally indicates a piston of a diesel engine (not shown), and the piston is provided with a cavity 14 opening at its upper surface 12, and the cavity constitutes a combustion chamber. The cavity 14 has a plurality of partially circular petal portions 14 a , 14 b L having a plurality of opening edges on the piston upper surface 12 (four in the illustrated embodiment, but may be three, five, or six). 1
It has a multi-petal shape with 4 c and 14 d, and each petal part of this multi-petal shape is aligned with an axis 0) parallel to the center line O of the combustion chamber.
1 (This axis 06 will be explained in detail later.

Note that the suffix n is l in this four-petal-shaped embodiment.
It is 4 to 4. ) is rotated at an angular velocity equal to the desired center angle α around the periphery of the coaxial line and moved downward to the desired depth. With the advantageous modifications detailed below.

In order to form the cavity 14, a shaft handle 18 shown in FIG. 2 is held and rotated by a turning device (not shown).
and a cutting part 20, the cutting part 20 having a diameter substantially equal to the diameter 2r of the partially circular petal part.
It has a disc shape, and has a rotational curved surface having a radius ρ corresponding to the bottom outer peripheral curved surface of the combustion chamber cavity 14 on the outer circumferential portion continuous with the lower surface thereof, and has a cutting edge 22 on the lower surface and the outer circumferential curved surface, respectively. There is. Such a tool 16
When molding the cavity 14 using a combustion chamber, first align the center line of the stem 18 with the center A of the arbitrary partially circular petal part 14a, and then Cutting is performed by rotating the tool 16 while lowering it by a depth indicated by Hl in FIG. Next, the tool 16 is moved between the combustion chamber center 0 and the center A1 of the partial circular petal portion 14a.
makes an acute angle θ with respect to the straight line OA connecting the lines OA, and the center A,
The center is at one point o1 on a straight line passing through the circle, and extends along a circular arc of radius R passing through the center A8 of the partial circular petal portion to a desired central angle α (that is, up to point B1 in the figure) on the circumferential surface. Cutting is performed by lowering the old IF of 100 l/r to the desired depth indicated by the arrow Δiro.

As a result, one partial circular petal portion 14a is first lowered linearly by a depth Hl parallel to the center line O of the combustion chamber, and then lowered by a depth H2 while being rotated around the center 01. , a twisted partial cavity is formed, and a curved surface with a radius ρ is formed on the outer circumferential surface of the bottom thereof. Then, the tool 16 is moved in the opposite direction to the above and extracted from the already cut partial cavity, and the partial circular petal parts 14b to 14d are processed in exactly the same manner. That is, the tool 16
First, the center An of each partial circular petal part (n is 1 to 4 and corresponds to the partial circular petal parts 14a to 14d, respectively,
= 1 has already been explained, in this case n is 2 to 4), and parallel to the combustion chamber center line O to a depth Hl.
Then, the angle θ is lowered with respect to the straight line OAn.
One point on (here n
are 1 to 4 and correspond to the partial circular petal parts 14a to 14d, respectively, but since n=1 has already been mentioned, here n is 2 to 4), and passes through the above center An. Cutting is performed by moving the cylinder along an arc of radius R in the circumferential direction by a center angle α and lowering it parallel to the center line 0 of the combustion chamber by a depth H2. When all the partial circular petal parts 14a to 14d have been processed in this way, there is a deep eave-like bulge having a roughly triangular planar shape between the adjacent partial circular petal parts as shown in FIG. A reentrant section 24 is formed. Then, without first lowering the tool 16 by a depth Hl parallel to the combustion chamber center line O, the tool 16 is moved circumferentially from the beginning along an arc AB with the same center angle α to the same depth H=H, - If the basic shape of the twisted petal-shaped combustion chamber is formed by lowering the combustion chamber by 1-H2, a reentrant combustion chamber with a small protrusion amount as shown by the two-dot chain line 26 in FIG. part is formed. Therefore, according to the method of the present invention, the symbol S in FIG.
A combustion chamber 14 having an end runt portion 24 that is thicker by the dimension shown in is formed. By expanding the end runt portion 24 in this manner, it is possible to more effectively prevent fuel spray and people injected into the combustion chamber 14 from being ejected onto the upper surface of the piston 10, thereby suppressing the generation of black smoke. In addition, the twisted petal-shaped combustion chamber has the advantage of reducing noise.

In addition, in the previously proposed device, as mentioned in the specification, the partial petals 141 to 14d do not necessarily need to be provided at equal intervals, but may be provided at unequal intervals in relation to the nozzle holes of the fuel injection nozzle. Although it may be arranged at intervals,
In this case as well, there is no change in the method of forming the combustion chamber itself. In the case of an automobile diesel engine, the four-petal combustion chamber shown in the diagram is usually appropriate, but depending on the size of the piston diameter and the number of injection holes in the injection nozzle, it may be possible to use a three-petal, five-petal, or It is also clear that multi-hole valve shaped combustion chambers, such as six petals, can be fabricated in a manner similar to that described above. In any of the above cases, the machining time required to shape the combustion chamber 14 inside the piston 10 using the mushroom-shaped cutting tool 16 is longer than the conventional electrical discharge machining method If? L-Makushibo Bay a)
Raku λ-ju between V Dankyoku. It has the advantage of low production costs and the ability to easily meet large-scale demand.

As described above, the method for forming a combustion chamber of a piston for a diesel engine according to the present invention is a combustion chamber consisting of a cavity in which the planar shape of the opening edge on the upper surface of the piston is in the shape of a multi-hole valve with a plurality of partially circular petals. A method for forming a chamber, comprising: a shaft handle that is gripped and rotated by a turning device; A cutting tool consisting of a cutting part with a curved surface corresponding to the outer peripheral curved part of the bottom of the combustion chamber is
1) After cutting down to the desired depth along a straight line passing through the center An of the partial circular petal and parallel to the piston axis, (2) cutting between the combustion chamber center O and the center An of the partial circular petal.
It forms an acute angle θ with respect to the straight line OAn connecting the above, and has a center at a point On on the straight line AnOn passing through the center An,
Cutting is performed by moving the circumferential direction to a desired center angle α along an arc passing through the center An of the partial circular petal portion, and further descending to a desired depth to cut the partial circular petal. The combustion chamber is cut by repeating the number of times, using a normal turning device and a simple and inexpensive tool,
It has the advantage of being able to produce a special twisted petal-shaped combustion chamber quickly, easily, and at low cost.The combustion chamber made by this method also effectively suppresses the generation of black smoke and reduces noise. It has the effect of reducing

[Brief explanation of drawings]

FIG. 1 is a plan view of a piston showing an embodiment of the molding method of the present invention, and FIG. 2 is a side view of a cutting tool used for molding the combustion chamber of FIG. 1, and a developed trajectory of the tool. 10...Piston 141-14d...
・Partial circular petal part 12...Piston top surface 16・
... Cutting tool 14 ... Combustion chamber Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] A method for forming a combustion chamber comprising a cavity whose opening edge on the upper surface of a piston has a multi-petal shape with a plurality of partially circular petals, the cavity being gripped by a turning device and rotated. a shaft handle, and a cutting part fixed to the coaxial handle and having a disc shape having substantially the same diameter as the partial circular petal part and having a curved surface corresponding to the outer peripheral curved surface of the bottom of the combustion chamber on the outer peripheral part of the lower surface thereof; After (1) lowering the cutting tool to a desired depth along a straight line passing through the center An of the partial circular petal portion and parallel to the piston axis to perform cutting, (2) cutting between the center O of the combustion chamber and the above Partial circle center of petal part An
A desired central angle α is formed along a circular arc that forms an acute angle θ with respect to the straight line OAn connecting the above, and has its center at one point O_1 on the straight line AnO_1 passing through the above-mentioned center An, and passes through the center An of the above-mentioned partial circular petal portion. The diesel engine is characterized in that the combustion chamber is cut by cutting the combustion chamber by moving it in the circumferential direction and lowering it to a desired depth, and repeating the cutting process by the number of partial petals. Combustion chamber forming method for pistons.