JPH02213402A - Manufacturing method of hollow sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention A. Field of Industrial Application The present invention relates to a method for producing a hollow sintered body, and in particular, a hollow sintered body suitable for producing a high-density hollow sintered body by a powder metallurgy method. This invention relates to a method for producing a solid.

For example, the camshaft of an internal combustion engine is used in the mechanism to open and close intake and exhaust valves through tappets and rocker arms, or through rocker arms, and during operation of the internal combustion engine, the camshaft is Since it slides with the above-mentioned mating parts, wear resistance is required.

Traditionally, cast iron has been widely used as the material for these parts. Taking camshafts as an example, during casting, the cam piece is rapidly solidified using a cold metal, and the surface of the cam piece is coated with hard white cast iron. A so-called chill camshaft, which has a surface layer of tissue to provide wear resistance, is often used.

However, when the above-mentioned chill camshaft is used in a diesel engine where the lubricating oil is contaminated with carbon sludge or a gasoline engine whose fuel is leaded gasoline and where the lubricating oil is contaminated with lead compounds, the cam piece may be damaged by these contaminants. There is a tendency for more wear to occur.

Sintered alloys produced by the powder metallurgy method, unlike alloys produced by the smelting method, can have a uniform structure because there is no solidification segregation. Since it is easy to obtain and the dimensional accuracy of the sintered body is high, the field of its application has been expanding in recent years.

One possible method for imparting wear resistance to a camshaft is to use a cam piece or journal made of a sintered alloy that has excellent wear resistance, and to form the camshaft by a so-called insert molding method. Such cam pieces and journal parts need to be hollow cylindrical bodies so that molten metal can be supplied inside them during casting, and when the cam pieces and journal parts are made of sintered alloy. It is necessary to have high density from the viewpoint of wear resistance and mechanical strength. In sintered alloys, pores are inevitably formed at the boundaries of raw material powder particles.
Make the porosity as small as possible to achieve high density. High-density sintered alloys can be easily produced by so-called liquid-phase sintering, in which the sintering temperature is raised to turn the phase with a relatively low melting point into a liquid phase among the phases that make up the structure of the raw material powder particles. can get.

However, the cam piece and journal portion require a predetermined length in the axial direction, and when forming with a punch that reciprocates in the axial direction, the density of the green compact is not uniform in the axial direction.

Particularly in liquid phase sintering, the density of the green compact is not uniform in the axial direction, so deformation due to sintering becomes large. In the low-density part of the compact, the dimensional shrinkage due to liquid phase sintering is 10%.
reach even. Even in the case of double pressing (compression molding from the upper and lower directions using an upper punch and a lower punch) which can reduce the density difference within the compact, the cylindrical compact shown in Fig. 12(a) is When the phases are sintered, the central region with low density is called the neutral zone. ) is larger than the other parts, resulting in a drum-shaped cylindrical sintered body 50 with a constricted center as shown in FIG. 5(b). Such deformation increases not only dimensional differences within one sintered body but also dimensional variations within manufacturing lots. To obtain such a high-density sintered body without deformation, it is possible to use compression molding using hydraulic pressure or a hot press method that performs molding and sintering at the same time, but these methods increase equipment costs and are not economical. Not the point. Therefore, high-density sintered bodies are limited to those having a relatively small height dimension, making it difficult to apply them to cam pieces and journal parts.

C.1 Purpose of the Invention The present invention aims to provide a method for manufacturing a hollow sintered body with high dimensional accuracy, regardless of density.

21 Structure of the Invention The present invention provides, when manufacturing a hollow sintered body, (1) preparing a molded body having substantially the same external dimensions as the internal dimensions of the hollow sintered body to be manufactured; (2) A step of molding the raw material powder into a hollow green compact with dimensions that take into account shrinkage due to liquid phase sintering; (3) Inserting the green compact into the hollow part of the green compact. The present invention relates to a method for manufacturing a hollow sintered body, which includes a step of liquid-phase sintering to form the green compact into a sintered body, and (4) a step of removing the molded body from the sintered body.

The above-mentioned "molded body" is made of ceramic powder (particle size 0.01 to 1.0 ma+) such as alumina, zirconia, silicon nitride, etc., which does not fuse to the sintered body during sintering, and a thermosetting resin as a binder. Added powder or molded molding sand can be conveniently used. It is also possible to use a metal (having a melting point higher than the sintering temperature) processed into a predetermined shape and size, or a ceramic molded body whose surface is coated with a thin ceramic powder. The former can be easily removed from the sintered body by breaking it up after sintering, and the latter can be easily removed from the sintered body by pulling it out after sintering.

E, Example The present invention will be explained in detail below.

Weight ratio: 2.00% total carbon, 11.5% chromium, 0.9
9% molybdenum, 1.92% vanadium, 0.8% phosphorus,
A raw material powder was prepared by adding 0.7% by weight of zinc stearate powder as a lubricant to an alloy steel powder having a composition in which the remainder was essentially iron and having a particle size below 100 mesh sieve.

This raw material powder was made into a cylindrical cam piece compacted powder by the press shown in FIG.

First, as shown in FIG. 2(a), a cavity formed by the die 1, core rod 2, and lower punch 3 is filled with raw material powder 5A. Next, as shown in the same figure (b), the upper punch 4 is lowered into the die 1, the lower punch 3 is raised, and both punches 4.3 compress the raw material powder at a compression pressure of 6t/cffl. It is compressed and molded into a green compact for 5 days. Next, as shown in the same figure (C), after raising the upper punch 4 above the die 1,
The punch 3 is raised so as to slightly protrude from the upper surface of the die 1, and the green compact is punched out from the die 1 and the core rod 2.

The size of the powder compact for 5 days was set to be 1.11 times the size of the cam piece sintered body in anticipation of shrinkage during liquid phase sintering later.

The above-mentioned cylindrical green compact is placed on a tray so as to surround a previously prepared core, and sintered to form a cylindrical cam piece sintered body. FIG. 1 shows the core, and FIG. 1(a) is a plan view, and FIG. 1(b) is a sectional view taken along line Ib-1b in FIG. 1(a). The core 6 is made of silica sand solidified with resin (same as the shell mold of the shell molding method), and has the same dimensions as the internal dimension of the cam piece sintered body (90 mm with respect to the internal dimension of the green compact 5 days). % dimensions). FIG. 3 shows a state in which the powder compact 5 and the core 6 are set, and FIG. 3(a) is a plan view, and FIG. 3(Φ) is a sectional view taken along the line mb-mb of FIG. A green compact is placed on an alumina tray 18 surrounding the core 6.

Next, the 5-day green compact is sintered to form a cylindrical cam piece sintered body.

The sintering was carried out by conventional vacuum sintering in which the compact was heated to 1130"C for 60 minutes in a vacuum. FIG. ) is a plan view, and FIG.
becomes. Since the core 6 has the dimensions described above, the sintered body 5C embraces the core 6 with almost no gaps. The presence of the core 6 prevents the occurrence of large contraction in the neutral zone as shown in FIG. 12, resulting in a sintered body with good dimensional accuracy.

The core 6 is made of the same material as the shell mold, so it has high mechanical strength and can withstand the force that causes the neutral zone to shrink significantly when the green compact is liquid-phase sintered. It becomes brittle when heated to a high temperature of over 1000°C together with the powder, and is easily broken and removed from the sintered body 6.

FIG. 5 shows a sintered body from which the core has been removed, and FIG. 5(a) is a plan view, and FIG. 5(b) is a sectional view taken along the line vb-vb of FIG. 5(a).

The dimensions of the sintered body 5C are as follows. The inner diameter of the approximately semicircular portion is 25 mm, which is the same as the outer diameter D4 of the core shown in FIG. 1(a). The outer diameter DI of this part, 02, is 3
0 mm, the outer radius R3 is 15 mm, and the wall thickness T is 2.
It is 5an. In addition, the outer diameter R of the tip of the cam nose part 5Ca
2 is 9 nm, and the maximum outer diameter passing through the tip of the cam nose portion 5Ca is 37 mm. The height H is 18 m++a.

The difference between the outer diameter of the end surface and the outer diameter D2 of the center part is 0.05 to 0,
It was 15ma+. In the cylindrical cam piece sintered body 5D manufactured in the same manner as in the above example without using the core 6, the end surface outer diameter d+ and the center outer diameter shown in FIG. 12(b) are used. The difference from d2 was 0.3 to 0.5I+a.

The number of measurements was five in each case. In this example, the difference in the outer diameter is significantly smaller than in the case of the conventional method, and the dimensional accuracy is significantly improved.

FIG. 6 is a front view of a camshaft material manufactured using the cylindrical cam piece sintered body 5C of FIG. 5. The camshaft 9 is manufactured by an insert molding method. That is, the cylindrical cam piece sintered body 5C and the cylindrical journal part sintered body 7 are set at predetermined positions in the mold cavity,
Molten metal was poured into this mold to create an integrated camshaft.

The journal portion 7 is manufactured in the same manner as the cam piece 5C. In the figure, reference numeral 8 indicates a shaft portion into which metal is poured, and its material is FCD60, which is spheroidal graphite cast iron.

Instead of the shell mold material core of FIG. 1, a metal or ceramic core can be used. The core 20 in FIG. 7 is constructed by thinly coating ceramic powder (for example, alumina powder) 22 on the circumferential surface of a metal (for example, steel) or ceramic base material 21 having a melting point higher than the sintering temperature using a binder. It has become. Cast iron is not suitable as a material for the base material 21 because it grows by repeated heating and cooling. The coating of the ceramic powder 22 allows the core 20 to be easily removed from the sintered body after sintering.

In addition to manufacturing the camshaft by casting as described above, the cam shaft is manufactured by inserting a steel pipe into the sintered cylindrical cam piece and the sintered cylindrical journal part, and by enlarging the diameter of the steel pipe and inserting the sintered cam piece into the steel tube. And the journal part can be manufactured by fixing the sintered body. To enlarge the diameter of a steel pipe, press-fit a pipe expander into the steel pipe, which has a tapered tip and a pipe expander with a diameter slightly (0.5 to 1, 0+n) larger than the inner diameter of the steel pipe. , by inserting it. By making the camshaft hollow in this manner, weight reduction can be achieved. In this case, as shown in FIG. 8, it is preferable to form an uneven engagement portion 25a on the inner peripheral surface of the cam piece sintered body (the same applies to the journal portion sintered body). When fixing the cam piece sintered body 50 to the steel pipe by expanding the steel pipe, the meshing portion 50
a bites into the outer circumferential surface of the steel pipe and the two mesh with each other, ensuring that they are fixed.

FIG. 9 is a perspective view of essential parts showing an example of the relationship between the main parts of an internal combustion engine in which the camshaft of FIG. 6 is assembled. The rotation of the camshaft 9 causes the rocker arm 13 in sliding contact with the cam piece 5C to swing, and this swing causes the rocker arm 1 to swing.
A valve 11 connected to 3 reciprocates to perform intake and exhaust. The valve 11 is urged toward the closed state by the coil spring 12, and the tip of the rocker arm 13 is pressed against the cam piece 5C. The tip of the valve 11 is located within a cylinder head (not shown). The valve 11 reciprocates (opens and closes) to cause intake explosion and exhaust,
A piston 14 reciprocates in a cylinder (not shown), and this reciprocation causes a crankshaft 16 connected to the piston 14 via a connecting rod 15 to rotate, thereby generating power. The timing of opening and closing of the valve 11 and the reciprocating movement of the piston 14 is determined by a timing belt (or chain) 17 that is passed between the camshaft 9 and the crankshaft 16. Due to such a mechanism, when the rotational speed of the camshaft 9 increases, or when the pressing force of the rocker arm 13 on the cam piece 5C increases, the cam piece 5C
It will be understood that the sliding movement between the rocker arm 13 and the rocker arm 13 is performed under extremely severe conditions.

Therefore, the cam piece 5C is made of the above-mentioned high-alloy iron-based alloy, and is made to have a high density by liquid phase sintering. As for the material of the cam piece, in addition to using the aforementioned alloy powder as the raw material powder, a mixed powder obtained by blending and mixing metal or alloy powder that has an effect of improving wear resistance with iron powder can be used as the raw material powder.

In addition to vacuum, the atmosphere during sintering is non-oxidizing AX
The atmosphere may be gas (ammonia decomposition gas), argon, or the like. In addition to the above-mentioned materials, the core may be made of any suitable material that can withstand the sintering temperature, does not fuse the sintered body, and can be removed from the sintered body.

Next, an example in which the present invention is applied to manufacturing a cylinder liner for a rotary compressor will be described.

Since rolling compressors are easy to reduce in size and weight, they are widely used as compressors for refrigerators, air conditioners, Kartara, etc., and their types are roughly divided into two types: Bosch type and rolling piston type.

As shown in FIG. 10, the Bosch rotary compressor is housed in a housing 37, and a plurality (four in most cases) of vanes 33 are mounted on a rotor 32 in a cast iron cylinder 34 having an inner peripheral surface with an oval cross section. The rotor 32 fitted into the shaft 31 rotates as the shaft 31 rotates, and the vane 33 presses against the inner circumferential surface of the liner 35 of the cylinder 34 due to centrifugal force and slides thereon. It has become.

The refrigerant gas is supplied to the space 39 between the liner 35 and the rotor 32 via an intake port and a discharge port (both not shown) provided in the side housing 38, and is discharged from the space 40.

As shown in FIG. 11, the rolling piston type rotary compressor rotates the shaft 41.
A rotating piston (rolling piston) 42 eccentrically fitted into the piston 1 rotates eccentrically, and is fitted into a vane groove provided in a cast iron cylinder 44 that accommodates these pistons, and a pressing force is applied from behind by a vane spring 46. The vane 43 is in pressure contact with the outer circumferential surface of the rotary piston 42, and the vanes 43 are configured to slide against each other. Further, the eccentrically rotating rotary piston 42 slides on the inner circumferential surface of a liner 45 fitted into the cylinder 44, and the vane 43
and the vane groove of the liner 45.

Left side space 49 of vane 43, right side space 50 and cylinder 4
A ventilation path (provided in the side housing 48, but not shown) is provided that communicates with the intake port 44a1 and the discharge port 44b provided in the side housing 48, respectively, and the refrigerant gas passes through this ventilation path. Supplied and discharged into the compressor.

Due to the structure described above, the liner 35, 45 is required to have wear resistance.

A sintered metal liner was manufactured in the same manner as in the previous example. The dimensions of the liner 35 are a short axis of 40mm, a long axis of 45mm (all inner diameters), and a width of 30mm, and the dimensions of the liner 45 are an inner diameter of 50m++ and a width of 30mm, and the inner circumferential surface of each is polished. It was finished to a thickness of 1 mm. The difference between the maximum diameter of the end face of the liner before polishing and the minimum diameter in the neutral zone (DI in the above example)
Dz) is 0.05 to 0.15 for liner 35.
m+++, 0.07 to 0.25 m for liner 45
It was m. Other aspects are the same as in the previous example.

For liners manufactured in the same manner as above without using a core (corresponding to core 6 in Figures 3 and 4), the difference between the maximum diameter and minimum diameter before polishing is the first
In the liner shown in FIG. 0, it was 0.3 to 0.5 peng, and in the liner shown in FIG. 11, it was 0.5 to 0.8 peng.

As mentioned above, even in this example, the dimensional accuracy of the material is significantly improved compared to the conventional method, and the finishing allowance can be reduced, resulting in a significant reduction in both material costs and finishing processing costs. .

The above examples relate to the cam piece and journal part of a camshaft, and the cylinder of a rotary compressor, but the present invention can also be applied to the manufacture of bushes, inner rings, outer rings, and other hollow sintered bodies of bearings. is applicable.

1. Effects of the Invention The present invention provides a molded body having substantially the same external dimensions as the internal dimensions of a hollow sintered body to be manufactured, and inserts this molded body into a hollow compacted powder body to form a liquid phase. Since the molded body is sintered, the molded body prevents the generation of distortion in the sintered body based on the difference in shrinkage rate depending on the position within the sintered body, which is characteristic of liquid phase sintering. The bodies come into close contact and the shape of the sintered body follows the shape of the molded body.As a result, the resulting sintered body has the dimensions as designed and has high dimensional accuracy. The liquid phase produced by sintering fills the pores, resulting in high earthquake resistance and excellent mechanical properties.

[Brief explanation of the drawing]

1 to 11 show embodiments of the present invention, in which FIG. 1 shows a core, FIG. 1A is a plan view, and FIG.
is a cross-sectional view taken along line Ib-Ib in Figure (a), Figure 2 shows the procedure for forming a green compact, Figure (a) is a cross-sectional view of the main parts of the press in a state filled with raw material powder, Figure (b) is a cross-sectional view of the main part of the press in a state where the raw material powder is compressed into a green compact, and (C) is a cross-sectional view of the main part of the press with the green compact removed from the mold. Figure 3 shows the state in which the core is inserted into the powder compact, where (a) is a plan view and (b) is a top view (
Figure 4 shows the sintered body immediately after sintering, Figure (a) is a plan view, and Figure (b) is a cross-sectional view taken along the line IVb-IVb in Figure (a). figure,
Figure 5 shows the sintered body after removing the compact;
) is a plan view, and figure (b) is v b −v of figure (a).
6 is a front view of the camshaft, FIG. 7 is a perspective view of a molded body according to another example, FIG. 8 is a plan view of a sintered body according to another example, and FIG. 9 is an internal combustion engine. FIGS. 10 and 11 are sectional views of the rotary compressor, respectively. FIG. 12 shows a conventional example, in which FIG. 12(a) is a sectional view of a green compact, and FIG. 12(a) is a sectional view of a sintered body. In addition, in the symbols shown in the drawings, 1...Gui 2...Core Rondo 3...Lower Punch 4... ...... Upper punch 5A... Raw material powder 5B... Cam piece compacted powder 5C125, 5D... Cam Piece sintered body6.
20... Core (molded body) 7...
...Journal part sintered body 9...Camshaft 13...Rocker arm 31.41...Rotary shaft 32... ...Rotor 33.43 ...Vane 35.45 ...Liner 42 ...Rotating piston.

Claims (1)

[Claims] 1. When manufacturing a hollow sintered body, (1) Internal method of the hollow sintered body to be manufactured.
(2) forming a raw material powder into a hollow green compact with dimensions that allow for shrinkage due to liquid phase sintering; (3) a step of inserting the compact into a hollow portion of the green compact and performing liquid phase sintering to turn the green compact into a sintered body; (4) a step of removing the compact from the sintered body; A method for manufacturing a hollow sintered body, comprising: