JP2005088030A - Powder molding method for compound valve seat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a stable laminated molding by surely holding a mortar shape even if the inclination of the mortar-shaped slope of first powder becomes larger and maintaining the mortar-shaped slope even when second powder is filled, as the powder molding of a compound valve seat. <P>SOLUTION: In the powder molding of the compound valve seat for which the molding of the first powder is laminated with that of the second powder in an inclined state, the method is characterized in that a liquid is soaked in the first powder filled in a die cavity of a mold or the surface of the preliminary molding of the first powder, with the second powder filled in thereafter for compression molding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a powder molding method particularly for producing a composite valve seat among sintered alloy valve seats used in internal combustion engines.

  Valve seats for automobile engines and the like are made of an iron-based sintered alloy in which intermetallic compounds and carbides are dispersed because high temperature wear resistance is required. This valve seat adds many elements (Ni, Cr, etc.) that contribute to high temperature wear resistance properties such as heat resistance and high temperature strength to iron powder in order to meet the higher wear resistance associated with higher engine performance. Need to be expensive. As a countermeasure, there is a composite valve seat (see FIG. 7) in which a high-grade sintered alloy is used for the seat portion in contact with the valve and a low-grade iron-based sintered alloy is used for the other main body. In the powder molding for manufacturing the composite valve seat, for example, as described in Patent Document 1, the first powder is filled by filling the die cavity with the first powder and lowering the inner lower punch with respect to the die. There is a method in which the upper surface is made into a mortar shape, the second powder is filled into the mortar shape, and compression molding is performed using a lower punch and an upper punch that forms a tapered surface of the valve seat (see FIG. 4). According to this forming method, there is an advantage that the object can be achieved by reducing the above-mentioned high-quality sintered metal portions. As another molding method, as described in Patent Document 2, after filling the die cavity with the first powder and pressing the punch into the upper surface of the first powder, the upper surface of the first powder is shaped into a mortar shape. There is a method in which a second powder is filled in the mortar shape of the shaped preform, and compression molding is performed using a lower punch and an upper punch (see FIG. 5).

JP-A-57-140802 (FIG. 5) JP 58-215299 A (FIGS. 5 to 10)

  In the above prior art, in the molding method of Patent Document 1, it is difficult to increase the inclination angle of the mortar-shaped inclined surface when the powder flowability is the first powder that is usually used, and it is formed in the mortar shape. The tilted surface collapses due to the vibration of the press machine and the tilt becomes gentle, or while filling the second powder, the mortar part of the first powder flows, and the tilt is further reduced and The inclined surface collapses. Due to this, for example, the manufactured composite valve seat has a mortar-shaped inclination that differs from front to back and from side to side with respect to the feeder movement direction of the second powder, and undulates the opposing surface. In the method described in Patent Document 2, when the powder is compressed at a high pressure to form a mortar shape, the density of the preform is increased, and when the second powder is filled and compression molded, Cracks occur at the boundary. On the other hand, if the pressing force for forming the mortar shape is too low, when filling the second powder, the mortar portion formed of the first powder is attacked by the load at the time of filling the second powder. The inclined surface of the shape collapses, and an irregular boundary surface is formed as in the case described above. The object of the present invention is to solve the above-mentioned problems, and as a powder molding of a valve seat, for example, even when a mortar-shaped inclination angle of the first powder is set large, an inclined surface that can withstand the attack of the second powder. In order to obtain a stable laminated molded body.

  In order to achieve the above object, the present invention provides a composite valve seat in which a molded body of a first powder and a molded body of a second powder are laminated in an inclined state in the powder molding of a composite valve seat, wherein It is characterized in that a liquid is infiltrated into the surface portion of one powder or the preform of the first powder and then compression-molded. In this powder molding method, the liquid is any one of oil, water, and alcohol.

  The above-mentioned method of the present invention remarkably deteriorates the powder flowability of the powder surface layer by moistening the surface of the first powder or its preform with a liquid, and the inclined surface of the first powder or its preform is reduced. Since it is formed into a strong mortar shape, the mortar portion will not inadvertently collapse due to an attack such as a load received when filling with the second powder, so that the shape can be reliably maintained, and the valve seat The powder facing surface in the circumferential direction of the green compact for use can be homogenized. As a result, the quality of the composite valve seat can be stably maintained as designed, and a thinner seat portion can be formed using high-grade sintered metal or the like.

  FIG. 7 is a longitudinal sectional view of a sintered alloy valve seat. This valve seat 15 is made of a sintered body having a substantially similar shape, and each surface is finished to a predetermined size and shape by sizing or cutting as necessary. The slanted seat portion 17 is made of a high-grade sintered alloy and abuts against a valve (not shown). The present invention is directed to a powder molding method for producing a generally cylindrical valve seat 15 as shown in FIG. A contrivance is that the raw material powder or the preform is soaked with liquid at the initial stage of molding. In the following embodiments, the device will be clarified by comparing with Patent Documents 1 and 2. In addition, the apparatus basics of the powder mold used are the same as before. For this reason, in each figure, only the principal part of the apparatus is shown, and the same reference numerals are given to the same members and parts in the apparatus of each figure.

  1 to 6 are longitudinal sectional views schematically showing a powder molding method. Among these, FIGS. 1-3 are the powder forming methods of the invention, FIG. 4 is the method described in Patent Document 1, and FIG. 5 is the method described in Patent Document 2. Here, the mold apparatus of FIG. 1, FIG. 2, FIG. 4 and FIG. 6 is slid in a state in which the die 1 having the step portion 1a in the hole is fitted into the hole of the die 1 from below. A lower punch 3, a core 2 that is slid in a state of being fitted to the lower punch 3, an upper punch 4 that can be moved up and down on the die 1, and a feeder for supplying powder are provided. The upper punch 4 has a protrusion with a tapered surface that is provided on the lower end side and forms the seat surface portion of the valve seat, and powder is placed between the upper punch 4 and the lower punch 3 while being fitted to the hole of the die 1 and the core 2. Compress. Each of these members is operated by a press mechanism as described in Patent Document 2. As for the mode of operation, there are cases where the die 1 is fixed or the lower punch 3 is fixed and the core 2 and the die 1 are moved up and down as in the withdrawal system. The feeder for powder supply stands by at a position away from the die cavity, and the first feeder for the first powder (not shown) that advances during the powder filling, the second feeder for the second powder, It is composed of 3 and 5 is different from the above-described apparatus in that the die 1 does not have the step portion 1a and is formed as a straight hole.

(Conventional method) In the powder molding method of FIG. 4, FIG. 4 (a) shows a state in which the first powder 5 is filled in the die cavity defined by the hole of the die 1 and the core 2 and the lower punch 3 and is rubbed off. ing. Next, FIG. 4B shows a state in which the lower punch 3 is lowered by a predetermined amount so that the upper surface of the first powder 5 becomes a mortar shape and an inclined surface S is formed that approaches the core side from top to bottom. It is. The inclined surface S becomes a curved surface due to powder friction or powder flowability, and is collapsed when the lowering amount of the lower punch 3 is increased or a load is applied. FIG. 4C shows a state where the second powder 6 is filled in the mortar portion with a second feeder. In this state, the powder facing surface is illustrated in a clear state, but in actuality, the mortar portion is partially collapsed by the load of the second powder 6 and the inclined surface S changes and becomes irregular. . FIG. 4D shows a state in which the upper punch 4 is lowered and the first powder 5 and the second powder 6 are compressed with the lower punch 3. FIG. 4E shows a state where the upper punch 4 is raised and the molded body 10 is pushed up by the lower punch 3 and extracted from the mold. The molded body 10 is a molding material of the valve seat 15, and the green compact 6 a of the second powder 6 is integrated in a layered manner on the inclined portion of the green compact 5 a of the first powder 5 or the sheet corresponding portion.

  In the powder molding method of FIG. 5, FIG. 5 (a) shows a state in which the first powder 5 is filled in the die cavity and rubbed off as in FIG. 4 (a). Next, FIG. 5 (b) shows that the upper powder 4 is lowered and lightly compressed, whereby the first powder 5 is preformed, and the upper surface of the preform 5b is the lower punch shape of the upper punch, which is a mortar shape, that is, an inclined surface. In this state, S is formed. FIG. 5C shows a state in which the second powder 6 is filled in the mortar portion with a second feeder as in FIG. 4C. Thereafter, compression molding and die extraction are performed as in (d) and (e) of FIG.

  6 uses a mold apparatus in which the die 1 shown in FIG. 4 has a stepped portion 1a, and pre-forms the first powder 5 with the upper punch 4 in the same manner as in FIG. Shows how. FIG. 6A shows a state in which the die powder is filled with the first powder 5 and rubbed off as in FIG. 4A. Next, in FIG. 6 (b), the first powder 5 is preformed by lowering the upper punch 4 and lightly compressing similarly to FIG. 5 (b), and the upper surface of the preform 5b has a mortar shape. It is a formed state. FIG. 6C shows a state in which the second powder 6 is filled in the mortar portion with a second feeder as in FIG. 4C. Thereafter, compression molding and die extraction are performed as in (d) and (e) of FIG.

  In the above prior art, as described above, the opposed surfaces of the first powder 5 and the second powder 6 are irregular, and the characteristics of the composite valve seat 15 vary accordingly. The present invention solves such a problem by the method shown in FIGS.

(Invention Method) The compacting method of the present invention will be described with reference to FIGS. Each drawing shows the steps from the step of forming the upper surface of the first powder 5 in a mortar shape to the filling of the second powder 6 in the molding procedure shown in FIGS. The filling of the powder 5, the compression molding after filling the second powder 6, and the die extraction of the molded body are performed in the same manner as in the past. For this reason, the process similar to the conventional process is omitted in the drawing.

  The powder molding method of FIG. 1 is a filling step of the first powder 5, a step of forming a mortar shape in the filled first powder 5, and a step of filling the second powder 6 with respect to the conventional method of FIG. 4. Only the differences are shown because they are the same in that they undergo a compression forming step and a step of extracting the molded body 10. That is, in this method, first, as in FIG. 4A, the first powder 5 is filled in the die cavity defined by the hole of the die 1, the core 2, and the lower punch 3 and is rubbed. Next, the lower punch 3 is lowered similarly to FIG. 4B to form a mortar-shaped inclined surface S on the upper surface of the first powder 5 as shown in FIG. Is sprayed or sprayed. Specifically, as schematically shown in FIG. 1A, the upper surface portion of the first powder 5 is wetted with the liquid suitable 7a as shown in the enlarged view while the lower punch 3 is being lowered or when the lowering is completed. As described above, an appropriate amount of liquid 7 such as water, spindle oil, or alcohol is sprayed or sprayed from above the die cavity. In this case, it is preferable to spray or spray the liquid 7 in a mist form through a cylindrical jig or the like. FIG.1 (c) has shown the state which filled the 2nd powder 6 in the mortar part of the 1st powder 5 which soaked the liquid suitable 7a in the surface layer part. Thus, in this compacting method, the surface of the first powder 5 is wetted with the liquid, so that the powder fluidity is deteriorated and the inclination of the inclined surface S is stabilized in a large state. Therefore, it becomes strong against an attack such as a load received when the second powder 6 is filled, and the mortar portion or the inclined surface S is less likely to collapse compared to the conventional method. The liquid 7a attached to the surface of the first powder 5 is removed from the compact 10 by volatilization or combustion at a relatively low temperature in the initial stage of heating by heating in the sintering process.

  Table 1 is an example when the above-mentioned first powder 5 is examined how the repose angle changes depending on the wetness degree. The mold used was the same as that shown in FIG. 1 and the like, and in the test, a normal mixed powder containing graphite powder and a molding lubricant was used as iron powder. The repose angle θ of the mixed powder was about 38 degrees. When this mixed powder is soaked with spindle oil, the angle of repose θ of the mixed powder increases in proportion to the oil content. The present invention applies the effect to increase the powder friction by appropriately moistening at least the surface layer portion of the first powder 5 (or its preform 5b) filled in the gap. Even if the inclination angle forming the mortar shape of the powder 5 (or its preform 5b) is made larger than before, the inclination angle can be maintained or the strength of the inclined surface S is increased.

  Next, the molding method of FIG. 2 uses a mold apparatus similar to that of FIG. 6 showing the prior art, and forms a mortar-shaped inclined surface S on the first powder 5 by preliminary formation via the upper punch 4 or the like. Is the case. FIG. 2A is the same as FIG. 6B and shows a state where the upper surface of the first powder 5 is pressed by the upper punch 4. FIG. 2B shows a state where an appropriate amount of liquid 7 is sprayed or sprayed on the inclined surface S of the formed preform 5b. Thus, after wetting the inclined surface S (upper surface portion including the inclined surface) to make it difficult to flow, the second powder 6 is filled as shown in FIG. Thereafter, compression molding and die extraction are performed as shown in FIGS. 4D and 4E. The liquid suitability attached to the surface of the preform 5b is removed from the compact 10 by volatilization or combustion at a relatively low temperature by heating in the sintering process. In this compacting method, instead of the upper punch 4, a temporary pressing punch device for forming a mortar-shaped inclined surface S provided separately from the molding device may be used. The temporary press punching device has a structure in which a tip-shaped punch that forms a mortar-shaped inclined surface S is moved up and down with an air cylinder or the like on the surface of the filling powder, and is installed at a location away from the die cavity for supplying powder. Like the feeder, it moves forward and backward toward the die cavity when necessary.

  The molding method of FIG. 3 is the same procedure as the molding method of FIG. 5 showing the prior art. FIG. 3A shows a state where an appropriate amount of liquid 7 is sprayed or sprayed on the powder surface after the first powder 5 is filled. From the state in which the powder surface is wet with the liquid 7, as shown in FIG. 3B, the upper punch 4 is lowered to lightly press the first powder 5, and the pre-form 5b and its surface are formed into a mortar shape by the pressing. The inclined surface S is formed. The inclined surface S that presses the wet powder surface is strong although the density is low, and even if the second powder 6 is filled in the mortar portion as shown in FIG.

  As described above, the liquid supply method of moistening the surface portion of the first powder 5 or its preform 5b with the liquid 7 can be configured as follows. That is, as shown in FIGS. 2 (b) and 3 (b), a mortar-shaped inclined surface S is formed on the upper surface of the first powder 5 by the upper punch 4 of the mold device or the temporary press punch device provided. In this case, while the upper punch 4 or the attached temporary pressing punch is waiting upward, a liquid is applied to the punch surface, and the first powder 5 or the preform 5b in the die cavity is applied. In this method, the liquid is soaked into the powder surface during the pressing process. In addition, a liquid supply hole is provided in the temporary pressing punch and connected to a liquid pressure feeding device so that the liquid can be discharged from a plurality of orifices communicating with the umbrella-shaped surface on the lower surface of the temporary pressing punch, and the first powder 5 in the die cavity or This is a method of injecting liquid onto the powder surface in the process of pressing the preform 5b.

  The present invention uses these liquid supply methods to moisten the mortar-shaped inclined surface S of the first powder 5 and its preform 5b, so that the mortar-inclination that is likely to occur when the mechanical powder or the second powder 6 is filled. Since the collapse of the surface can be prevented, the composite valve seat can be manufactured with the quality as designed, and the mortar inclination angle of the high-end side seat portion 17 of the valve seat 15 can be made more acute or thin. .

It is a schematic cross section which shows the powder molding procedure principal part of invention composite valve seat. It is a schematic cross section which shows the powder molding procedure principal part by another method of this invention. FIG. 6 is a schematic cross-sectional view showing a main part of a powder molding procedure according to still another method of the present invention. 6 is a schematic cross-sectional view showing a powder molding procedure described in Patent Document 1. FIG. 10 is a schematic cross-sectional view showing the main part of the powder molding procedure described in Patent Document 2. FIG. It is a schematic cross section which shows the other conventional powder shaping | molding procedure principal part. It is a longitudinal cross-sectional view which shows the composite valve seat made from the sintered alloy of invention object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Die 2 ... Core 3 ... Lower punch 4 ... Upper punch 5 ... First powder (5a is green compact, 5b is a preform)
6 ... second powder (6a is green compact)
S ... inclined surface 7 ... liquid (7a is suitable for liquid)
DESCRIPTION OF SYMBOLS 10 ... Molded body for composite valve seats 15 ... Composite valve seat (16 is a main body part, 17 is a mortar-shaped seat part)

Claims (2)

  In powder molding of a composite valve seat in which a molded body of the second powder is laminated in an inclined state on the molded body of the first powder, the first powder filled in the die cavity of the mold or the preformed body of the first powder A powder molding method for a composite valve seat, comprising: impregnating a liquid into the surface portion of the material, filling the second powder, and performing compression molding. The method for powder molding a composite valve seat according to claim 1, wherein the liquid is one of oil, water, and alcohol.

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