JPH0551390B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a cylinder liner used in an internal combustion engine, and more specifically, to a cylinder liner used in an internal combustion engine. This invention relates to improvements in the manufacturing method of cylinder liners made of.

(Prior art) Cylinder liners used in internal combustion engines must maintain airtightness while sliding with the piston cylinder, so their material basically needs to have wear resistance and seizure resistance. Ru. For this purpose, special cast iron castings containing A-type graphite to improve corrosion resistance and dispersing carbides to impart wear resistance have been used exclusively for conventional cylinder liners.

However, such materials have low strength and
Therefore, as the output of internal combustion engines increases, the problem of cracks occurring from the outside has arisen. In other words, the material could no longer withstand the explosion pressure inside the cylinder liner and the thermal stress caused by the difference in heat distribution.

In order to prevent cylinder liner cracks,
The present applicant had previously proposed the development of a new multi-layer cylinder liner in Japanese Patent Application No. 59-26295 (Japanese Unexamined Patent Publication No. 60-169654), but the manufacturing cost was high and depending on the purpose of use, Sometimes there is no need.

In order to reduce the combustion stress among the above two stresses, there is a method of providing a cooling water passage in the part where the combustion stress is large (generally near the top dead center of the piston, that is, the thick end of the liner on the combustion chamber side). It is publicly known. The water holes, which are cooling water passages, are provided by machining or pipe casting, but the casting method is advantageous from a cost standpoint.

(Problems to be Solved by the Invention) Cylinder liners are generally manufactured by a static casting method, in which a pipe insert is cast on top. Problems in this case include: Inclusions and cavities are likely to occur at the boundary between the pipe and cast iron. :Long object (3m
(above), this problem is particularly serious.

Therefore, this results in a reduction in strength.

(Means for Solving the Problems) In order to solve the problems of the prior art, the present invention provides the following steps in manufacturing a cast steel pipe cylinder liner:
The objective is to provide a sound cylinder liner without inclusions or cavities, even if the liner is long, by using a specially constructed cast body and using centrifugal force casting as the casting method. As a means to achieve this objective, we adopted the following configuration.

That is, the present invention is a method for manufacturing a cylinder liner in which a cooling water passage communicating with a cooling water jacket is formed in a thick part of the liner on the combustion chamber side using a steel pipe casting, and the method comprises: At the thick end of the liner combustion chamber, there are band-shaped ring bodies whose width extends in the direction of the mold axis, and at equal intervals on the inner wall there are both base ends of cast pipes bent into a U-shape facing centripetally. A cast body with a fixed mold is inserted into the mold, and then a sand mold or the like is placed at both ends of the mold to form a mold.While this centrifugal casting mold is rotated at a predetermined G _Np , a heat-resistant and resistant material is poured into the mold. A liner material is cast by casting molten cast iron with excellent seizability, and then the outer shape of this liner material is milled as appropriate, and the band-shaped ring body of the cast body is removed to open a hole at the base end of the cast body pipe. It was designed to do so.

(Function) As shown in Figure 1, if a cast body is set in a centrifugal casting mold and centrifugal casting is performed as usual, even if large vibrations are applied to the cast pipe of the cast body, the band-like ring will hold it firmly. Inclusions that are fixed and present near the pipe in the molten metal are centrifuged.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 shows a half sectional view of a centrifugal casting mold for manufacturing the liner material of the cylinder liner of the present invention. The one shown is a horizontal type, but it can be either an inclined type or a rigid type. In the case of long lengths, horizontal type is advantageous. In the mold shown in the figure, 1 is the mold,
In terms of yield, it is better to make the inner surface shape of the mold substantially match the outer surface shape of the liner material to be created, rather than just a cylindrical inner surface shape, in terms of machining in the subsequent machining process. Therefore, the first large-diameter step portion 2 is a portion where the thick end portion of the combustion chamber of the liner is formed. A second large-diameter step 3 is formed at the further outer end of the first large-diameter step 2, and this portion is formed to be slightly larger than the thickness of a band-like ring of the cast body, which will be described later. 4 is a sand mold provided in the second large-diameter stepped portion 3; 5, 6;
are sand molds provided in a metal frame located on both sides of the mold 1, and the mold 1 and the sand molds 4, 5, and 6 constitute a mold.

7 is a cast body used in the present invention, the cross section and plan view of which are shown in FIG. Reference numeral 8 denotes a belt-shaped cylinder body whose outer periphery has a diameter slightly smaller than that of the second large-diameter step 3 of the mold 1, and whose width direction is in the mold axis direction. Both base ends 9', 9' of a cast steel pipe 9 bent in a U-shape facing the centripetal direction are fixed by welding or the like at equally spaced positions of 16 as shown in the figure. Together with the ring body 8, a cast body 7 is constituted.
It should be noted that the shape of the cast pipe 9 is not U-shaped in the strict sense, and the number thereof is of course not limited.

The inner diameter of the cast pipe 9 is determined by the purpose of use, and the wall thickness of the pipe 9 is preferably 3 to 15 mm because if it is too thin, it will be damaged by molten cast iron, and if it is too thick, it will likely cause poor welding. . As mentioned above, steel pipes are used as the pipe material in terms of toughness. However, if there is rust or deposits on the surface of the steel pipe, it is likely to cause poor welding, so the outer surface should be plated with Sn, Cu, etc., or coated with oil. It is necessary to keep it.

Next, the material for the cylinder liner is a special cast iron material containing A-type graphite, for example,
So, C: 2.5 to 4.0, Si: 0.8 to 2.5, Mn: 0.3 to 1.5,
P: 0.05 to 1.5, S: 0.3 or less, and Ni: 2.5 or less, Cr: 1.5 or less, Mo: 0.8 or less, Sn: 0.5 or less,
Cu: 4.0 or less, the total of one or more of B, Ti, V, Nb, Zr is 1.0 or less, Al, Ca, Ba, Sr,
Total of one or more rare earth elements: 0.2 or less,
Contains one or more of the following, and the remainder is substantially
Use one made of Fe. However, it goes without saying that the present invention is not limited to the materials mentioned above.

Next, referring to centrifugal force casting, referring to FIG.
Set and embed the belt-shaped ring 8 of the cast body 7,
Sand molds 5 and 6 are set on both sides of the mold 1, and while the mold is rotated at a predetermined rotation speed, a cast body 7 is formed.
Pour the molten metal from the opposite side 10. Note that in the figure, reference numeral 11 indicates the molten metal surface.

At this time, the higher the rotation speed in centrifugal force casting, the lower the incidence of segregation and defects near the pipe, but the mold needs to be made tougher, which increases costs. If the rotation speed is low, segregation will occur and the floating separation of impurities will not be sufficient.
30G is necessary.

As for the casting temperature, the higher the temperature, the better the welding will be, but if it is too high, the problem of coarsening of the structure will occur.
On the other hand, if it is low, welding will be poor. Therefore, it is necessary to set the solidification start temperature of the material +50 to 200℃,
The temperature is desirably about 100°C.

The mold 1 is usually coated, but from the viewpoint of improving yield, it may also be used as a sand mold by filling the inside of the mold with sand. In the illustrated example, casting is performed from the opposite direction of the cast pipe body 7, but if the length is long, the temperature will drop until the molten metal reaches the cast pipe body 7. Therefore, the so-called gutter casting method, which changes the position where the molten metal falls, is also effective.

After the above-mentioned casting and solidification, the liner material is obtained by dismantling the mold in the usual manner, and the outer surface of this material is cut to an appropriate thickness by appropriate mechanical cutting means, etc., and the cast body 7 is formed.
By removing the strip ring 8, the individual base ends 9', 9' of the cast pipe 9 become open holes 12,
12, and the product shown by diagonal lines in FIG. 1, that is, the cylinder liner product shown in FIG. 3, is obtained.

Next, more specific examples of the present invention will be shown below.

●Mold length: 2900mm ●Mold diameter (maximum part): φ1020mm ●Rotation speed: Gravitational acceleration display, 120G at φ1020 ●Cast pipe: φ32mm, wall thickness 6mm, STKS1
Outer surface Sn electroplating ●Number of cast pipes: 24 (15° pitch) ●Casting amount: 7200Kg ●Casting temperature: 1360℃ ●Casting material (weight percentage shown, remaining practically
Fe) C Si Mn P 3.31 1.21 0.81 0.415 S Ni Cr Mo B 0.051 − 0.20 − 0.41 ●Mold coating: Resin sand 2.8 mm Casting was performed according to the method shown in Figure 1 under the above conditions. When pipe casting is carried out by static casting, the defect rate due to inclusions and cavities near the pipe is about 40%, but in the case of the method of the present invention, inclusions are centrifuged and the riser Since the effect was large, a healthy product was obtained.

Figure 4 shows the hardness distribution in this example (φ1020
Department).

In this example, the tensile strength at 30mm from the surface is 24.5Kg/
mm ² and elongation of 0.41% (φ1020 part).

Two other pieces were cast under the same casting conditions as in this example, but no defects were observed in either of them.

(Effects of the Invention) The present invention utilizes a centrifugal force casting method in manufacturing a pipe cast cylinder liner.
We were able to manufacture a sound cylinder liner with no inclusions or cavities at the thick end of the liner in which the pipe was cast. Because a cast body is used, the fixation to the mold is reliable and stable, despite the large vibrations of the centrifugal cast image.
It was possible to provide an excellent cylinder liner that combines the inclusion centrifugation effect unique to the centrifugal casting and the riser effect.

[Brief explanation of the drawing]

The drawings show an embodiment of the method of the present invention; FIG. 1 is a sectional view of a half of a centrifugal casting mold; FIG. 2 is a side view and a plan view of a half of a cast body used in the present invention; FIG. 3 is a side view of the cylinder liner obtained by the present invention, and FIG. 4 is a hardness distribution graph of the liner obtained by the present invention. 1...Mold, 4,5,6...Sand mold, 7...Cast body, 8...Striped ring body, 9...Cast pipe, 9', 9'...Pipe base end, 12...Open Hole.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a cylinder liner in which a cooling water passage communicating with a cooling water jacket is formed in a thick part of the liner on the combustion chamber side using a steel pipe casting, the method comprising: one end of a centrifugal casting mold; At the thick ends of the liner combustion chamber, there are two bases of cast pipes, which are belt-shaped rings whose width extends in the direction of the mold axis, and which are bent into a U-shape in the centripetal direction at equal intervals on the inner wall. A cast body with fixed ends is fitted inside the mold, and then a sand mold or the like is placed at both ends of the mold to form a mold.While this centrifugal casting mold is rotated at a predetermined G _Np , a heat-resistant material is poured into the mold. A liner material is cast by casting molten cast iron with excellent seizure resistance, and then the outer shape of this liner material is milled as appropriate, and the band-shaped ring body of the cast body is removed to open the base end of the cast pipe. A method for manufacturing a cylinder liner characterized by having holes.