JPH0925501A - Powder metallurgical product and its production and powder metallurgy method as well as powder molding device for powder metallurgy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce powder metallurgical products with which the occurrence of crack in high-temp. holding parts, etc., is prevented by loading the first powder material which is charged with a second powder material at a prescribed charging speed and is agitated into a powder mold at a prescribed speed and subjecting these materials to pressurizing and sintering. SOLUTION: The prescribed amt. of the first powder material 2 which is a base material is stored in a first storage means 3. The second powder material 4 which is a compounding material is continuously or intermittently transferred therein at a predetermined charging speed from a second storage means 5 and both materials are agitated and mixed by an agitating means 7. The powder material in the first storage means 3 is continuously or intermittently charged from above simultaneously therewith into the powder mold 8 at a prescribed charging speed via a powder charging means 9. The powder materials loaded into the powder mold 8 are thereafter pressurized in a vertical direction and are sintered, by which the powder metallurgical products reinforced by compounding the compounding material with the base material are obtd. As a result, the thermal stresses generated in the high-temp. holding parts are relieved, the occurrence of the trouble, such as crack, is prevented and the increase in the volumetric rate of the compounding material is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder metallurgical product in which a base material is blended with a compounding material and reinforced, a manufacturing method thereof, a powder metallurgical method, and a powder molding apparatus for powder metallurgy.

[0002]

2. Description of the Related Art As is well known, a base material is blended with a compounding material such as a reinforcing fiber to improve wear resistance, a composite material having a reduced thermal expansion amount, or a portion to be strengthened. The products used or the method of compounding only the part to be strengthened is already known. For example, JP-A-61-1669
In Japanese Patent Laid-Open No. 34-34, a molded body called a preform, which is molded into a desired shape in advance only with a compounding material, is placed inside a mold, and a molten base material is injected into the mold to form a composite of only the molded body. A modified piston is disclosed. Here, the part of the molded body that corresponds to the part that is not processed after cutting, such as cutting, is pressed to form a difference in the density of the molded body itself and integrate it with the base material, improving the machinability at the low density part. The high density part is given strength. Also, when using a composite material partially, set the composite material in advance in the part of the mold corresponding to the top ring groove and top land part of the piston after casting, pour molten metal and integrate it, top ring The groove and top land are strengthened. In this way, by arranging the composite material only in the part to be reinforced, or in the composite product, if the volume ratio of the compound material in the composite material or the part to be composited (molded body) is increased in the expectation of further performance improvement, It can be improved in terms of strength.

[0003]

However, when the volume ratio of the compounded material is increased in this way, the coefficient of thermal expansion of the composite material or the composited part is lowered, and the part without the composite material or the composite material is not composited. The difference in the coefficient of thermal expansion between the part and the part becomes large, and high thermal stress occurs during high temperature holding. In the worst case, this high thermal stress causes defects such as cracks at the boundary. Further, in consideration of the problem caused by the generation of this high thermal stress, the volume ratio of the compounding material must be limited, and the thermal expansion coefficient cannot be lowered as expected. When a piston is manufactured with such a material, the gap between the cylinder inner peripheral surface and the pinton land outer peripheral surface, that is, the further reduction of the clearance is limited, and the gap between the cylinder inner peripheral surface and the piston land outer peripheral surface ( There is a problem that the clevis cannot be set narrow and the reduction of HC in the exhaust gas by the unburned gas accumulated in the (clevis) is limited. A first object of the present invention is to alleviate the thermal stress generated in the high temperature holding portion and prevent the occurrence of defects such as cracks, and the second object is to provide a composite portion or a composite material. The thermal expansion coefficient is reduced by increasing the volume ratio of the compounding material contained.

[0004]

Therefore, in the invention described in claim 1, the first storage means for storing a prescribed amount of the first powder material, the second storage means for storing the second powder material, and the second storage means. Transfer means for transferring the second powder material in the first storage means, stirring means for stirring the powder material in the first storage means, and charging the powder material in the first storage means into a powder molding die. The second powder material is continuously or intermittently transferred into the first storage means at a predetermined charging speed, and the powder material in the first storage means is predetermined. The powder material is continuously or intermittently charged from above from above at a charging speed, the powder material in the first storage means is loaded into the powder molding die, and the loaded powder material is vertically applied. It is pressed and sintered to produce powder metallurgy products.

According to a second aspect of the invention, a first step of transferring a desired amount of the second powder material to the first storage means, and a second step of stirring and mixing the powder material in the first storage means. And a third step of charging a part of the powder material in the first storage means into the powder molding die is repeatedly performed, and the powder material of the first storage means is added to the powder molding die. Is loaded from above, and the loaded powder material is pressed in the vertical direction and sintered to manufacture a powder metallurgical product.

Aluminum alloy is used as the first powder material in the present invention, and ceramics or carbon such as alumina, mullite, silicon carbide, silica or cordierite, or both are used as the second powder material.

In a sixth aspect of the present invention, the first storage means in which the first powder material and the second powder material are stored in a predetermined mixing ratio and the first powder material or the first powder material are mixed. A second stored mixture of a first powder material and a second powder material, the ratio of which is higher than the mixing ratio in the first storage means.
Storage means, stirring means provided in the first storage means for stirring the powder material in the first storage means, and transfer means for transferring the powder material in the second storage means to the one storage means The powder material in the second storage means is continuously or intermittently transferred into the first storage means at a predetermined charging rate, and the powder material in the first storage means is defined in advance. The powder metallurgical product is manufactured by continuously or intermittently charging the powder material into the powder molding die from above from above, pressurizing the powder material charged in the powder molding die in the vertical direction, and sintering the powder material.

In a seventh aspect of the invention, a predetermined amount of the first powder material is charged into a container equipped with a stirring means at a substantially constant speed at a desired time, and a predetermined amount of the second powder material is accelerated or While decelerating, put it in the container at the desired time,
The first powder material and the second powder material are agitated by the agitating means, and the agitated powder material is continuously or intermittently charged into a mold for molding at a desired timing and speed, and then pressured and baked. I'm tied.

According to the present invention, the first powder material and the second powder material are stored in desired amounts, respectively, the first storage means and the second storage means, and the powder in the second storage means at a desired time. Powder charging means for charging the powder in the first storage means at a substantially constant speed, stirring means for stirring the powder in the first storage means, and powder molding in the first storage means at a desired time. A first powder charging means for charging the mold at a substantially constant speed is provided.

According to the ninth aspect of the invention, the mixing ratio of the second powder material to the first powder material is continuously changed from 0% to a predetermined ratio, and sintering is performed under high temperature and pressure.

According to the tenth aspect of the invention, the base material made of aluminum alloy powder and the compound material made of at least one of ceramic powder and carbon powder are mixed and sintered. Therefore, according to the invention described in this specification, the second powder material (compounding material) stored in the second storage means.
The second powder material is continuously or intermittently transferred at a predetermined charging rate to the first storage means in which a specified amount of the first powder material is stored.
The amount of powdered material supplied changes. In the first storage means, while being stirred by the stirring means, the powder material therein is continuously or intermittently charged into the powder molding die by the charging means at a predetermined charging speed. At this time, if the powder material in the first storage means is only the first powder material (base material), only the first member is put into the powder molding die, and the powder material is mixed with the first powder material (base material). If the powder material is composed of two powder materials (compounding material), the powder material obtained by mixing the first and second powder materials is put into a powder molding die. Further, when the powder material from the first storage means is charged into the powder molding die, the powder material is continuously or intermittently supplied at a predetermined charging speed, so that the first powder material and the second powder material are continuously mixed. The powder material, which has changed over time, is filled in the powder mold. The powder material loaded is
Since the powder metallurgical product is obtained by pressing and sintering, the powder metallurgical product in which the compounding ratio of the first powder material and the second powder material is continuously or stepwise changed is formed (claim 1).

A first step of transferring a desired amount of the second powder material to the first storage means, a second step of stirring and mixing the powder material in the first storage means, and a powder material in the first storage means. A series of steps including the third step of charging a part of the powder into the powder molding die is repeated, the powder material in the first storage means is loaded into the powder molding die, and the loaded mixed powder end material is heated. -Since it manufactures a powder metallurgy product by sintering, the second step in the first step is performed as the series of processes progresses.
By changing the desired amount of the powder material, the powder material having different mixing ratios of the first powder material and the second powder material is supplied to the powder molding die in the third step (claim 2).

Since the first powder material is an aluminum alloy and the second powder material is ceramics or carbon, it is supplied to the powder molding die while changing the compounding ratio of the ceramics to the aluminum alloy charged into the powder molding die. A powder metallurgical product having different blending amounts of aluminum alloy and ceramics is formed continuously or intermittently (claims 3 and 4).

When the first powder material is stored in the second storage means, the first powder material is transferred into the first storage means by the transfer means and the powder material in the first storage means is stirred by the stirring means. Stirring and mixing change the mixing ratio of the first powder material in the powder material in the first storage means. Also, the second
When the mixture of the first powder material and the second powder material in which the mixing ratio of the first powder material is higher than the mixing ratio in the first storing means is stored in the storage means, the mixture having the high mixing ratio is The powder material having a constant mixing ratio is transferred to the first storage means by the transfer means, and is agitated and mixed with the powder material having a constant mixing ratio stored in the first storage means, and the mixing ratio of the powder material having the constant mixing ratio is changed. The powder material in the first storage means is
The powder material is continuously or intermittently charged from above at a prescribed charging speed from above, so that the powder material in which the composition of the first powder material and the second powder material is continuously changed is filled in the powder molding die. It Since the powder material with the changed mixing ratio is pressed and sintered in this way, the powder metallurgy is formed in which the first powder material and the second powder material are continuously and gradually changed (claim 6).

A predetermined amount of the first powder material is charged at a substantially constant speed into a container equipped with a stirring means at a desired time, and a predetermined amount of the second powder material is speeded or decelerated while the above is performed at the desired time. It is charged into a container, the first powder material and the second powder material are stirred by the stirring means, and the stirred powder material is continuously or intermittently charged into a molding die at a desired timing and speed. After that, it is pressed and sintered, so the first powder material and the second powder material
The powder metallurgy has a different blending ratio with the powder material (claim 7).

The second powder material in the second storage means is charged into the first storage means at a substantially constant speed by the second powder charging means at a desired time. The powder material in the first storage means is charged into the powder molding die at a substantially constant speed by the first powder charging means at a desired time. At this time, if the timing of charging the second powder material into the first storage means by the second powder charging means is later than the timing of charging the powder material into the powder molding die by the first powder charging means, When only the first powder material is charged and the second powder material is charged into the first storage means earlier than the powder material is charged into the powder molding die, the powder molding die is first moved by the stirring means. The powder material and the second powder material, which are agitated at a constant mixing ratio, are charged (claim 8).

Since the compounding ratio of the second powder material with respect to the first powder material in the powder metallurgy product is continuously changing from 0% or the compounding ratio to a predetermined ratio, the second powder material with respect to the first powder material is changed. The blending ratio does not change rapidly but changes gently (claim 9).

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the powder molding apparatus indicated by reference numeral 1 in FIG. 1, a first tank 3 as a first storage means in which a desired amount of a first powder material 2 serving as a base material is stored, and a desired amount of a second powder material 4 serving as a compounding material are provided. A second tank 5 with the stored second storage means, a second powder charging means 6 for charging the second powder material 4 from the second tank 5 into the first tank 3 at a substantially constant speed at a desired time,
A screw 7 as a stirring means for stirring the powder material in the first tank 3, and a first powder charging means for charging the powder material in the first tank 3 into the powder molding die 8 at a substantially constant speed at a desired time. 9 and 9.

The second powder feeding means 6 comprises a passage 61 communicating with the second tank 5 and an opening / closing member 62 for opening / closing a tip opening 61a of the passage 61. The passage 61 is made of a pipe material, and serves as a transfer means of the second powder material to the first tank 3 here. Opening / closing member 6
As shown in FIG. 2, reference numeral 2 denotes a circular plate having a diameter smaller than that of the front end opening 61a, and a lever 6 extending outward from a part thereof.
2a is rotatably supported by a pin 64 on a boss 63 fixed to the outer periphery of the passage 61. End face 61 of the tip opening 61a
A stopper 65 for placing the opening / closing member 62 in the closed position shown by the solid line is provided at b.

As shown in FIG. 1, the first powder feeding means 9 comprises a passage 91 communicating with the first tank 3 and an opening / closing member 92 for opening / closing a tip opening 91a of the passage 91. The passage 91 is made of a pipe material having a larger diameter than the passage 61. As shown in FIG. 3, the opening / closing member 92 is a circular plate having a diameter smaller than that of the front end opening 91a, and a lever 92a extending outward from a part of the opening / closing member 92 is attached to a boss portion 93 fixed to the outer periphery of the passage 91. It is rotatably supported by a pin 94. A stopper 65 for placing the opening / closing member 92 at the closed position shown by the solid line is provided on the end surface 91b of the tip opening 91a. The opening / closing members 62 and 92 are here the levers 62a and 92a.
The distal end openings 61a and 91a are opened and closed by operating each by computer control or the like. That is, the opening / closing member 92
Constitutes a charging means for charging the powder material in the first tank into the powder molding die 8. Screw 7 shown in FIG.
Is connected to a drive source such as a motor (not shown),
It is rotationally driven in the tank 3. The opening / closing members 62, 9
2 is not limited to the illustrated shape and structure,
It may be a slide type or a butterfly type, or may have another configuration.

A method of manufacturing the powder metallurgical product 10 using the powder molding apparatus 1 having such a configuration will be described. Here, as the powder metallurgy product 10, a piston used in an internal combustion engine is metallurgically formed. Further, aluminum alloy powder is used as the first powder material 2, and alumina powder is used as the second powder material 4.

First, the opening / closing member 6 for continuously transferring the alumina powder into the first tank 3 at a predetermined charging speed.
2 is operated to open the tip opening 61a. Next, the powder material in the first tank 3 is continuously fed into the powder molding die 8 at the feeding speed.
The opening / closing member 92 is operated so that the tip opening 91a
Open. At this time, the opening / closing members 62 and 92 are adjusted so that the feeding speed of the alumina powder into the first tank 3 is faster than the feeding speed of the powder material charged into the powder molding die 8. Then, the powder material charged into the powder molding die 8 from the first tank 3 is initially only the aluminum alloy powder in the passage 91, and the alumina powder is mixed with the aluminum alloy powder by the screw 7 with the passage of time. It becomes a powdered material. Then, the blending ratio of the alumina powder blended in the aluminum alloy powder gradually increases due to the relationship between the insertion speed into the first tank 3 and the powder molding die 8.

Therefore, the powder layer A of only the aluminum alloy powder is formed below the molding space 8a of the powder molding die 8, and the composite layer in which the alumina powder is blended into the aluminum alloy powder gradually as it goes above the molding space 8a. B is formed, forming space 8
In the uppermost part a, the compounding ratio of the alumina powder with respect to the aluminum alloy powder becomes high and the aluminum powder is loaded.

Next, the powder molding die 8 in which the mixing ratio of the alumina powder to the aluminum alloy powder is continuously high is pressed and sintered. Here, as shown in FIG. 4, a powder molding die 8 loaded with a powder material is arranged in a case 11 provided with a heater 12 as a heating means and discharged in a vacuum, and a pressing member is pressed from above the powder material. While pressurizing at 14, it is heated by the heater 12 and sintered. The powder molding die 8 is composed of a fixed mold 8b and two extruding members 9a and 9b. When the powdered metallurgy 101 after sintering is taken out from the powder molding die 8, first, the pressing portion 14 is removed,
The extruding members 9a and 9b simultaneously push out the powder metallurgy 101 above the powder molding die 8. The powder metallurgy 101 strongly extruded from the powder molding die 8 still has the pushing members 9a, 9a.
Since it is firmly fixed to b, only the pushing member 9b is further pushed outward in the mold. Then, the powder metallurgy 101 is supported by the extruding member 9b, and the powder metallurgy 10
The contact between 1 and the extruding member 9a is cut off, the powder metallurgy 101 is released from the powder molding die 8 in this state, and the powder metallurgy (piston before processing) 101 shown in FIG. 5 is molded.

The sintered powder metallurgy 101 is used as a tool 1
5, using a plurality of ring grooves 102, in which the rings 15, 16 and 17 are inserted and fitted, as shown in FIG.
The powder metallurgy product 10 (completed piston) is formed by forming 103 and 104 and using various tools not shown. As shown in FIG. 7, the cross section of the powder metallurgy product 10 has a non-composite portion A made of only aluminum alloy powder toward the piston upper surface 10A and a composite portion B in which the alumina mixing ratio gradually increases. It will be. That is, the powder metallurgical product has a mixture ratio of the second powder material 4 with respect to the first powder material 2 continuously changing from 0% to a predetermined ratio. Here, it changes continuously in the vertical direction. Therefore, the non-composite part A and the composite part B continuously change, and the non-composite part A and the composite part B in the vicinity of the boundary part D between the non-composite part A and the composite part B. The difference in thermal expansion coefficient between Therefore, the thermal stress generated at the time of holding at high temperature is reduced, and the occurrence of cracks and the like is reduced.

Further, the piston upper surface 10A rather than the boundary portion D
As the blending ratio of alumina in the composite portion B increases, the thermal expansion coefficient on the upper surface 10A side decreases from that on the boundary portion D side. Therefore, the width L (clearance) of the clevis C formed between the pinton upper end outer peripheral surface 10a and the inner peripheral surface 18a of the cylinder 18 has the same alumina compounding amount shown in FIG. 10, and the alumina compounding range is uniform. It can be made narrower than the piston 100 having the composite layer B ′.

In this embodiment, the alumina powder and the powder material are continuously charged into the first tank 3 and the powder molding die 8 at a predetermined charging speed. Alternatively, the alumina powder and the powder material may be intermittently charged into the powder molding die 8. For example, first
Opening / closing member 9 to put only the aluminum alloy into the powder molding die 8
The tip opening 91a is opened by operating only 2 and once the fixed amount can be charged, the tip opening 91a is once closed. And
By operating only the opening / closing member 62, the alumina powder is put into the first tank 3 through the tip opening 61a, stirred and mixed, and the tip opening 91a is opened again to fill the powder molding die 8 with the aluminum alloy and the alumina powder. You may throw in the powder material which mixed.

That is, a desired amount of the second powder material 4 is transferred to the first tank 3 in the first step, and the first powder is transferred in the first step in the second step.
The first powder material 2 in the tank and the transferred second powder material 4
The powder material composed of and is mixed by stirring with the screw 7,
In the third step, a part of the powder material in the first tank 3 is put into the powder molding die 8. Then, while repeating the series of steps from the first step to the third step, the powder material mixed with stirring in the first tank 3 is loaded into the powder molding die 8, and the loaded powder end material is shown in FIG. Heat and sinter in vacuum to produce a powder metallurgy product as shown.

When the series of steps from the first step to the third step are repeated, the blending ratio of the second powder material 4 (alumina powder) to the first powder material 2 (aluminum alloy powder) is set in each series. The non-composite portion A and the composite layer B are gradually changed by gradually increasing each step. Therefore, the difference in the coefficient of thermal expansion between the non-composite portion A and the composite portion B in the vicinity of the boundary portion D between the non-composite portion A and the composite portion B becomes small, and the thermal stress generated during high temperature holding becomes small. Occurrence of cracks is reduced.

In the above-described embodiment, the first tank 3 is previously provided with the first tank.
Although the aluminum alloy powder as the powder material 2 and the alumina powder as the second powder material 4 are stored in the second tank 5 as an example, the description has been given, but the present invention is not limited to this. For example, a desired amount of a mixture of aluminum alloy powder and alumina powder having a predetermined mixing ratio is stored in the first tank 3, and the mixing ratio of the alumina powder in the second tank 5 is the mixing ratio of the alumina powder in the first tank 3. It may be configured to store a higher mixture of aluminum alloy powder and alumina powder. In this case, below the forming space 8a of the powder molding die 8, a composite layer A of aluminum alloy powder and alumina powder having a predetermined mixing ratio is formed.
Is formed and the blending ratio of the alumina powder continuously increases as it goes above the molding space 8a. At the upper part of the molding space 8a, the blending ratio of the alumina powder to the aluminum alloy powder becomes higher and the aluminum powder is loaded. Thereafter, as in the above-mentioned embodiment, the powder molding die 8 is pressed and terminated to obtain a piston as a powder metallurgy product.

Although the powder metallurgy method of the piston has been described above, when other products are obtained by the powder metallurgical method, the first powder material having a predetermined mixing ratio is used as the first powder material in the first tank 3 contrary to the case of the piston. A desired amount of a mixture of the compounding material (for example, ceramic powder) and the base material (for example, aluminum alloy powder) as the second powder material is stored in the second tank 5, and only the base material or the mixing ratio of the compounding material is the first tank A mixture of the base material and the compounding material having a higher mixing ratio than the above may be used. In this way, in the molding space 8a, the mixing ratio of the compounding material can be changed while continuously decreasing in the vertical direction as time passes. Specifically, the powder metallurgical product is obtained in which the compounding amount of the compounding material decreases as it goes upward in the molding space 8a.

Next, another embodiment of the present invention will be described. In this embodiment, as shown in FIG.
The powder material 2 is charged into a container 21 equipped with a screw 20 as a stirring means, and a predetermined amount of the second powder material 4 is charged into the container 21 at a desired time while speeding or decelerating the first powder material. 2 and the second powder material 4 are agitated by a screw 20, and the agitated powder material 22 is continuously or intermittently charged into a molding die 80 at a desired timing and speed, and then, as shown in FIG. It is characterized by pressurizing and sintering.

The powder molding apparatus 50 used in this embodiment is
A tank 23 for storing the first powder material 2 and a second powder material 4
Tank 24 for storing the above, screw 20, container 21 and first powder material 2 from tank 23, 24 to container 21
And a shutter 25 as a means for charging the second powder material 4,
26, and a shutter 27 as a means for charging the powder material from the container 21 into the mold 80. Also in this case, aluminum alloy powder is used as the first powder material 2 and alumina powder is used as the second powder material.

The tanks 23 and 24 have shutters 25,
The charging passages 28 and 29 communicate with each other via 26. First powder material 2 and second from tank 23, 24 to container 21
The supply speed of the powder material 4 is determined by the opening area of the charging passages 28 and 29 by the operation of the shutters 25 and 26. The input passage 28 is set to have a constant opening area by the shutter 25, and is input at a constant input speed. The input passage 29 is configured such that its opening area is changed by the shutter 26 that is opened and closed at a desired time.

As shown in FIG. 9, the shutter 26 is supported by a shaft 32 of a motor 31 mounted on a bracket 30 provided on the outer periphery of the closing passage 29, and the closing passage 2
9 can be opened and closed freely. The motor 31 is a step motor, is connected to a controller (not shown), and the drive timing and the amount of rotation are controlled by a drive signal from the controller. Since the shutter 27 has the same configuration as the shutter 26, the description thereof is omitted here.

The controller, as time goes by, the second controller
The feeding rate of the powder material 4 is set to be high. That is, the shutter 26 is opened a lot so that the input amount of the second powder material 4 increases with the passage of time. Further, these devices 50 are covered with an outer case 51 fixed to the container 21 and can be horizontally swiveled in a molding space 80a of a mold 80, and the powder material 22 is evenly distributed in the molding space 80a. Can be input.

According to such a device 50, when the power source (not shown) of the device is turned on, the screw 20 rotates and the entire device 50 rotates. Then, first, the shutter 25 is opened by a certain amount and the first powder material 2 is charged into the container 21 at a substantially constant speed, and the shutter 27 is opened by the controller by a certain amount so that only the first powder material 2 is formed in the molding space. It is put into 80a to form the non-composite section A.

When a certain amount of the non-composite section A is formed in the molding space 80a, the controller 26 opens and closes a certain amount of the shutter 26 to put the second powder material 4 into the container 21. Then, the second powder material 4 is agitated and mixed with the first powder material 2 by the screw 20, and is charged into the molding space 80a in which the non-composite section A is formed to form the composite lower part B. At this time, the feeding rate of the first powder material 2 into the container 21 is substantially constant, and the feeding rate of the second powder material 4 increases with the passage of time, so that the compounding ratio of the second powder material 4 in the composite section B is Will increase.

As shown in FIG. 4, the mold 80 having the non-composite portion A and the composite lower portion B formed as described above is disposed in the case 11 provided with the heater 12 and is added from above the composite portion B. The powder metallurgy (piston before processing) 10 shown in FIG. 5 is heated and sintered by the heater 12 while being pressed by the pressure member 14.
Mold 1. Then, the powder metallurgy 101 is used as a tool 15
To produce a powder metallurgy product 10 (completed piston).

Therefore, looking at the cross section of the powder metallurgy product 10, as shown in FIG. 7, the compounding ratio of the second powder material 4 from the non-compositing part A consisting of the aluminum alloy powder alone toward the piston upper surface 10A is shown. It has a composite part B which becomes higher gradually. That is, the powder metallurgical product 10 is obtained in which the mixing ratio of the second powder material 4 to the first powder material 2 continuously changes from 0% to a predetermined ratio in the pressing direction. Therefore, the non-composite part A and the composite part B gradually change, and the non-composite part A and the composite part B in the vicinity of the boundary part D between the non-composite part A and the composite part B are separated. The difference in the coefficient of thermal expansion is reduced, the thermal stress generated in the high temperature holding portion is reduced, and the occurrence of cracks is reduced.

Further, the piston upper surface 10A rather than the boundary portion D
As the blending ratio of the second powder material 4 (alumina) in the composite portion B becomes higher as it goes to, the coefficient of thermal expansion on the upper surface 10A side decreases from that on the boundary portion D side. Therefore, the width L (clearance) of the clevis C formed between the outer peripheral surface 10a of the Pinton land portion and the inner peripheral surface 18a of the cylinder 18 is shown in FIG.
Piston 1 having composite part B1 in which the alumina blending amount shown in 0 is equal and the alumina blending range is uniform
It can be narrower than 00.

In each of the above-mentioned embodiments, a piston is taken as an example of the powder metallurgy product 10, but the present invention is not limited to this. For example, a severe thermal condition such as a cylinder runner or a brake rotor to which thermal stress is applied. Of course, the parts used below may be used. In addition, the second which becomes the compounding material
Although the powder metallurgical product 10 was molded using alumina as the powder material, the present invention is not limited to this. For example, ceramic powder or carbon represented by mullite, silicon carbide, silica or cordierite, or the first powder. Material 2
On the other hand, any powder of a material having a small coefficient of thermal expansion may be used.
Although an aluminum alloy is used as the first powder material as the base material, other materials such as aluminum, magnesium, magnesium alloy, or other appropriate metal may be used.

[0043]

According to the present invention, it is possible to eliminate a portion where the blending ratio of the second powder material to the first powder material changes rapidly, so that the thermal expansion at the boundary between the composite and non-composite parts can be eliminated. The coefficient difference can be reduced. Therefore, the thermal stress generated in the high temperature holding portion is reduced, and defects such as cracks can be prevented. In addition, since the thermal stress at the boundary is reduced, the thermal expansion amount at the boundary is large, and thus the second powder material, which has been limited in the amount to be mixed with the first powder material, is added to the first powder material. Can be added in a relatively large amount. Therefore, the coefficient of thermal expansion decreases, so when a piston is manufactured from such a material, the gap between the cylinder inner peripheral surface and the pinton land outer peripheral surface (the gap between the cylinder inner peripheral surface and the piston ring portion) can be set narrow. , (Clevis), the amount of unburned gas accumulated in the exhaust gas can be reduced to reduce the emission of HC in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing one step of a powder molding apparatus and a powder metallurgy manufacturing process showing an embodiment of the present invention.

FIG. 2 is a plan view showing an opening / closing member in the configuration of a first powder feeding means.

FIG. 3 is a plan view showing a configuration of a first powder charging means.

FIG. 4 is a side view showing a pressing / sintering step in the present invention.

FIG. 5 is a side view showing a processing step in the present invention.

FIG. 6 is a cross-sectional view showing the relationship between a piston and a cylinder, which is an example of a powder metallurgy product.

FIG. 7 is a cross-sectional view showing a state of a composite part and a non-composite part in the powder metallurgy product of the present invention.

FIG. 8 is a configuration diagram showing one step of a powder molding apparatus and a powder metallurgy manufacturing step showing another embodiment of the present invention.

FIG. 9 is a plan view showing a configuration of first and second charging means in another embodiment.

FIG. 10 is a cross-sectional view showing a state of a compounding portion and a non-compounding portion of a conventional compounding piston.

[Explanation of symbols]

 1, 50 Powder molding device 2 First powder material 3, 23 First storage means 4 Second powder material 5, 24 Second storage means 6 Second powder charging means 61 Transfer means 7, 20 Stirring means 8 Powder molding die 9th 1 powder feeding means 92 feeding means 10 powder metallurgy product 21 container

Claims (10)

[Claims] 1. A first storage means for storing a prescribed amount of a first powder material, a second storage means for storing a second powder material, and a second powder material in the second storage means transferred to the first storage means. And a charging means for charging the powder material in the first storage means into a powder molding die, and the second powder material in advance. The powder material in the first storage means is continuously or intermittently transferred into the first storage means at a predetermined charging speed, and the powder material in the first storage means is continuously or intermittently transferred to the powder molding die at a predetermined charging speed. The powder material in the first storage means is loaded into the powder molding die from above, and the loaded powder material is vertically pressed,
A method of manufacturing a powder metallurgical product, which comprises sintering to produce a powder metallurgical product. 2. A first storage means for storing a prescribed amount of a first powder material, a second storage means for storing a second powder material, and a second powder material in the second storage means transferred to the first storage means. And a feeding means for feeding the powder material in the first storage means into a powder molding die, wherein the second powder material is desired. A first step of transferring an amount of the powder material to the first storage means, a second step of stirring and mixing the powder material in the first storage means, and a part of the powder material in the first storage means to the powder molding die. The powder material of the first storage means is loaded into the powder molding die from above, and the loaded powder material is pressed in the vertical direction by repeating a series of processes including the third step of charging , Sintering to produce powder metallurgy products A method for manufacturing a powder metallurgical product, comprising: 3. The powder metallurgy product is a piston for an internal combustion engine, the first powder material is an aluminum alloy, and the second powder material is a second alloy.
3. The method for producing a powder metallurgy product according to claim 1, wherein the powder material is either ceramic or carbon, or both. 4. The method for producing a powder metallurgy product according to claim 3, wherein the second powder material is a ceramic such as alumina, mullite, silicon carbide, silica, or cordierite, or carbon. 5. The first powder material is a base material, the second powder material is a compounding material, only the first powder material is stored in the first storage means, and the second storage means is stored in the second storage means. Only two powder materials are stored, characterized in that
A method for producing the powder metallurgy product described. 6. A first storage means in which a first powder material and a second powder material are stored in a predetermined mixing ratio, and a mixing ratio of the first powder material or the first powder material is the first storage means. Second storage means for storing a mixture of the first powder material and the second powder material having a higher mixing ratio than the above, and the powder material in the first storage means is agitated. A stirring means and a transfer means for transferring the powder material in the second storage means to the first storage means are provided, and the powder material in the second storage means is continuously or intermittently supplied at a predetermined charging rate. While being transferred into the first storage means, the powder material in the first storage means is continuously or intermittently charged from above into the powder molding die at a predetermined charging speed to form the same powder molding die. The input powder material is pressed in the vertical direction and sintered to produce powder. A method for producing a powder metallurgy product, which comprises producing a powder metallurgy product. 7. A predetermined amount of the first powder material is charged at a substantially constant speed into a container equipped with a stirring means at a desired time, and a predetermined amount of the second powder material is accelerated or decelerated at a desired time. Into the container, the first powder material and the second powder material are stirred by the stirring means, and the stirred powder material is continuously or intermittently molded at a desired timing and speed. A powder metallurgical method, which comprises pressurizing and sintering after charging into 8. A first storage means in which a desired amount of the first powder material is stored, a second storage means in which a desired amount of the second powder material is stored, and a second storage means in the second storage means at a desired time. 2 Second powder charging means for charging the powder material into the first storage means at a substantially constant speed, stirring means for stirring the powder material in the first storage means, and powder in the first storage means A powder molding machine for powder metallurgy, comprising: a first powder charging means for charging a material into a powder molding die at a substantially constant speed at a desired time. 9. A powder metallurgical product, wherein the compounding ratio of the second powder material to the first powder material continuously changes from 0% to a predetermined ratio. 10. A piston for an internal combustion engine, which is obtained by sintering a mixture of a base material made of aluminum alloy powder and a compounding material made of at least one of ceramic powder and carbon powder, the compounding of the compounding material. A piston for an internal combustion engine made of powder metallurgy, characterized in that the rate increases as it approaches the top surface of the piston.