JP2013044287A - Method and apparatus for manufacturing hollow engine valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture a hollow valve with a hollow axis part in an extremely easy manner at a low cost.SOLUTION: This method for manufacturing a hollow engine valve includes steps for forming material that has an upward-open bottomed hole at the center part; and pushing out the material inserted in a mold hole 8 of a die 9 downward by a punch 12, lowering the lower part of a pin 17 down to the upper part of a small diameter hole part 8c of the mold hole, and allowing the material to plastically flow downward through a clearance between the lower part of the pin 17 and the small diameter hole part 8c to mold a primary intermediate product 2 having a diameter-enlarged head part 2b at the upper end of the axis part 2a and formed with hollow holes 25, 26 therein.

Description

  The present invention relates to a method and apparatus for manufacturing a hollow engine valve used in an internal combustion engine.

Among engine valves (hereinafter abbreviated as valves) used in internal combustion engines, particularly automobile engines, in order to reduce the weight and improve engine performance, to make the valve hollow or to reduce the thermal load, Some of them have metal sodium sealed in a hollow shaft.
As a conventional manufacturing method of such a hollow valve, for example, as described in Patent Document 1, a valve material in which a core material is inserted into a hole provided in the center is formed by hot squeezing forging or the like. As described in Patent Document 2, after forming a valve shape having an umbrella portion at one end of the shaft, the core member is pulled out to make the shaft portion hollow, and the opening end of the hollow hole is closed by a closing member. After the valve material with the core inserted in the hole provided in the center is heated and contracted, it is formed into a valve shape with an umbrella at one end of the shaft, and the core is pulled out to make the shaft hollow. In this hollow hole, metal sodium is inserted, and the opening end of the shaft portion is closed with a shaft end sealing portion. Similarly, as described in Patent Document 2, the hole provided in the center is machinable. To heat and stretch the valve material with a rich core material inserted The shaft is molded into a valve shape having an umbrella at one end, and the core material is drilled with a gun drill to make the shaft hollow, and after inserting metallic sodium into the hollow hole, the shaft A shaft end sealing portion is fixed to the opening end by welding, and as described in Patent Document 3, a hole is drilled by a gun drill from the end face side at the center of the shaft portion of the valve. There are some that are hollow.

JP-A-63-109205 Japanese Patent Laid-Open No. 7-119421 JP-A-4-334708

  In the method for manufacturing a hollow valve described in Patent Documents 1 and 2, a process for producing a core material, a process for forming a hole for inserting a core material in the valve material, and a method for making the shaft portion hollow, Since at least four steps of inserting the core material into the hole and extracting the inserted core material are required, there is a problem that productivity is low and manufacturing cost is high.

On the other hand, when the shaft portion is made hollow by punching with a gun drill as in the method of manufacturing a hollow valve described in Patent Documents 2 and 3, the machining time required for this is long, the productivity is lowered, and the life of the drill is also reduced. Since it is short, the manufacturing cost becomes large.
In particular, austenitic heat-resistant steel, which is frequently used as a material for exhaust valves, is hard and inferior in machinability. Therefore, drilling the material further shortens the life of the drill.

  The present invention has been made in view of the above-mentioned problems, and a hollow engine valve manufacturing method and manufacturing apparatus capable of manufacturing a hollow valve having a hollow shaft portion very easily and efficiently at low cost. The purpose is to provide.

According to the method for manufacturing a hollow valve of the present invention, the above-described problems are solved as follows.
(1) A step of forming a material having a bottomed hole that opens upward in the center, and the material inserted into the die hole of the die is strongly pressed with a punch, so that the diameter gradually decreases downward in the die hole. The bottom of the pin inserted into the bottomed hole is lowered until it enters the upper part of the small-diameter hole, The lower end of the pin has an enlarged head at the upper end of the shaft portion by plastically flowing downward through an annular gap formed between the outer peripheral surface of the small diameter hole portion and And forming a first intermediate product in which a hollow hole opening upward is formed.

According to such a configuration, in order to make the valve shaft hollow, it is not necessary to pull it out using a core material or to drill a hole with a gun drill as in the past, but to extrude the material. At the same time as forming the first intermediate product, a hollow hole can be easily formed in the shaft portion, so that a hollow valve can be manufactured very easily and efficiently at a low cost.
Moreover, since the hollow hole formed in the shaft part of the primary intermediate product can also be used as a pilot hole (guide hole) of the drill, a hollow hole is formed in the shaft part from the beginning by a gun drill as in the prior art. Compared to the case, the drilling can be easily performed in a short time, the productivity is improved, and the load applied to the drill is reduced, so that the life thereof is extended.

(2) In the above item (1), before the material is strongly pressed by the punch, the lower end of the pin is lowered to the lower end of the bottomed hole of the material.

  According to such a configuration, when the material is strongly pressed by the punch, the lower portion of the pin can be quickly lowered to the small diameter hole portion of the mold hole, so that the hollow hole can be reliably formed in the shaft portion.

(3) The upper surface of the cylindrical material inserted into the die hole of the die is strongly pressed with a pin, and the material is plastically deformed so that the lower part of the pin enters the inside of the material. A process of forming a bottomed hole to be opened, and by pressing the material with a punch, the squeeze hole part gradually reducing in diameter toward the lower part of the mold hole is passed through to the small-diameter hole part below the part. The lower part of the pin is lowered until it enters the upper part of the small-diameter hole, and the material is formed into an annular shape formed between the outer peripheral surface of the lower part of the pin and the inner peripheral surface of the small-diameter hole part. Forming a primary intermediate product having a diameter-enlarged head at the upper end of the shaft portion and having a hollow hole opened upward in the inside by plastically flowing downward through a gap; and Shall be provided.

  According to such a configuration, not only the same effect as the configuration described in the above item (1) is obtained, but also the step of providing the bottomed hole in the material in advance is unnecessary because the bottomed hole is formed in the material by the pin. Thus, the manufacturing cost can be reduced.

(4) In any one of the above (1) to (3), after forming the primary intermediate product, the pin is raised while the upper end thereof is pressed by the punch.

  According to such a configuration, after molding the first intermediate product, the lower end portion of the pin can be easily pulled out from the hollow hole formed therein.

(5) In any one of the above items (1) to (4), by forging the diameter-enlarged head portion of the first intermediate product, an umbrella portion is connected to the upper end of the shaft portion, and the umbrella portion A step of forming a secondary intermediate product having a hollow hole opening upward therein and a step of closing the opening of the hollow hole of the umbrella portion with a closing member are provided.

  According to such a configuration, a hollow engine valve having an umbrella portion at the upper end of the shaft portion and having a sealed hollow hole formed therein can be easily manufactured with a small number of steps.

(6) In the above item (5), after inserting metallic sodium into the hollow hole of the shaft part from the opening of the hollow hole of the umbrella part in the secondary intermediate product, the opening part of the hollow hole of the umbrella part is closed. It closes with a member.

  According to such a configuration, a hollow valve in which metallic sodium is sealed in the hollow hole of the shaft portion can be easily manufactured.

(7) In the above item (5) or (6), the hollow hole of the umbrella part in the secondary intermediate product is formed into a trumpet shape that gradually increases in diameter upward.

According to such a configuration, the overall weight of the valve can be reduced, and the heat radiation area when metal sodium is sealed in the hollow hole is increased, whereby the umbrella portion is effectively cooled.
Moreover, since the hollow hole of the umbrella part is expanded in a trumpet shape, it is easy to insert metal sodium into the hollow hole of the shaft part.

According to the apparatus for manufacturing a hollow valve of the present invention, the above problems are solved as follows.
(8) A large-diameter hole portion into which the material can be inserted from above, an extraction hole portion that gradually decreases in diameter toward the lower end continuous to the lower end of the large-diameter hole portion, and a shaft portion continuous to the lower end of the extraction hole portion A die having a mold hole composed of a small-diameter hole for forming; a ram that moves up and down above the die; and a punch that is attached to the ram so that a lower part can enter into a large-diameter hole part of the mold hole in the die; In the vertical guide hole provided in the center of the punch, the ram or other lifting means is linked so as to be able to move up and down, and when lowered, the diameter is smaller than the small diameter hole of the mold hole. The lower small-diameter shaft portion protrudes below the punch, and the lower end is formed of a pressing device including a pin that enters and stops at the upper portion of the small-diameter hole portion.

  According to such a configuration, the material inserted into the die hole of the press device is pushed out by the punch mounted on the ram in one press operation, and at the same time, the small-diameter shaft below the pin accommodated in the center portion of the punch A hollow valve having a hollow hole in the shaft portion can be easily manufactured by lowering the portion to the upper portion of the small-diameter hole portion of the die hole of the die.

 (9) In the above item (8), the ram is provided with a pressing means for pressing the punched downward to press the formed first intermediate product downward until the pin starts to rise.

  According to such a configuration, after molding the first intermediate product, the lower part of the pin can be easily pulled out from the hollow hole formed therein.

 (10) In the above item (9), the pressing means is a compression coil spring.

  According to such a configuration, there is no need to provide another pressing means such as a hydraulic press, so that the cost of the hollow valve manufacturing apparatus can be reduced.

(11) In any one of the above items (8) to (10), in the vicinity of the press device, the shaft hole into which the shaft portion of the first intermediate product can be inserted and the diameter-enlarged head portion can be gradually inserted upward. A second die having a second die hole that expands in a trumpet shape, a second ram that moves up and down above the second die, and a lower portion of the second ram that is attached to the lower end. A second press device is provided that includes a second punch that plastically deforms the enlarged-diameter head inserted into the second mold hole into an umbrella shape so as to form a hollow hole that opens upward.

  According to such a configuration, the first intermediate product and the second intermediate product having hollow holes inside can be continuously and efficiently manufactured by the two pressing devices.

  According to the present invention, a hollow valve having a hollow shaft portion can be manufactured very easily and efficiently at low cost.

It is process drawing which shows one Embodiment of the manufacturing method of the hollow valve of this invention. It is a center longitudinal front view of the principal part of the 1st press apparatus which shape | molds the 1st intermediate product of a hollow valve. Similarly, it is a center longitudinal front view in a state where the ram is lowered and the lower end of the punch is in contact with the upper end of the material. Similarly, the ram is further lowered, and the center pin is a central longitudinal front view in a state where the lower end portion of the center pin enters the lower portion of the bottomed hole of the material. Similarly, it is a center longitudinal front view of the state where the ram has been lowered to the lower limit position and the material has been forged. Similarly, the ram is slightly raised, and the lower end portion of the center pin is a central longitudinal front view in a state in which it is detached from the hollow hole of the primary intermediate product. It is a center vertical front view of the principal part of the 2nd press apparatus which forges a 1st intermediate product and shape | molds a 2nd intermediate product.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIGS. 1A to 1E show a method for manufacturing a hollow valve according to the present invention in the order of steps. FIG. 1A shows a material 1 for manufacturing a hollow valve, and FIG. The molding process of the secondary intermediate product 2, (c) is the molding process of the secondary intermediate product 3, (d) is the process of inserting the metallic sodium 4 into the secondary intermediate product 3, (e) The process of closing the opening of the secondary intermediate product 3 with the closing member 5 is shown.

  The raw material 1 is formed by, for example, forming a bottomed hole 6 in the center by using a drill or the like after cutting a long round bar-like steel material of martensite or austenite to a predetermined size. The bottomed hole 6 includes a lowermost small-diameter hole 6a and a large-diameter hole 6c that is continuous with the small-diameter hole 6a via a tapered hole 6b, for example, approximately twice the inner diameter of the small-diameter hole 6a. It has become.

  The primary intermediate product 2 shown in FIG. 1 (b) is obtained by extruding the raw material 1 with a manufacturing apparatus shown in FIG. 2, for example, a first press device 7 (only the main part is shown) made of a friction press. It can be formed by hot forging.

  The 1st press apparatus 7 is equipped with the die | dye 9 which was hold | maintained by the die holder which is not shown in figure in the center part which has the type | mold hole 8, and the cylindrical ram 10 which can be raised-lowered upwards. The mold hole 8 is open above the die 9 and is continuous with the large diameter hole portion 8a having the same diameter as the outer diameter of the material 1, and the lower end thereof, and gradually decreases in a funnel shape downward. The squeezing hole 8b is continuous with the lower end of the squeezing hole 8b and includes a small-diameter hole 8c that opens below the die 9.

A cylindrical punch holder 11 that is coaxial with the axis of the die hole 8 of the die 9 is fitted in the lower part of the ram 10 so as to be relatively movable in the vertical direction. The large-diameter shaft portion 12a in the upper half is fitted so as not to move up and down. The small-diameter shaft portion 12b of the lower half portion of the punch 12 has an outer diameter that can enter the large-diameter hole portion 8a of the die 9 and is substantially equal to the inner diameter.
A large-diameter guide hole 13a and a small-diameter guide hole 13b for slidably guiding a center pin 17 (described later) are provided in the center of the punch 12 so as to communicate with each other vertically.

In the ram 10 at the upper part of the punch holder 11, a bottomed cylindrical spring receiver 14 that opens upward is fitted so that the lower surface is in contact with the upper surface of the punch holder 11 slidably up and down. A compression coil spring 15 having a large compression load is accommodated in the spring receiver 14. The lower surface of the spring retainer 16 fitted and fixed to the upper end portion of the ram 10 is in contact with the upper surface of the compression coil spring 15, and the compression coil spring 15 is prevented from coming off upward.
The opposing surfaces of the spring receiver 14 and the spring retainer 16 are separated so that the spring coil 16 can compress the compression coil spring 15 by a required amount.

  The large-diameter guide hole 13a and the small-diameter guide hole 13b of the punch 12 are fitted with a large-diameter shaft portion 17a at the upper part of the center pin 17 and a lower-diameter shaft part 17b at the lower part thereof slidably up and down. Are combined. The outer diameter of the small-diameter shaft portion 17b is approximately equal to the inner diameter so that the large-diameter hole 6c of the material 1 and the large-diameter portion 8c of the die 9 can be fitted.

  The lower end portion of the small diameter shaft portion 17b protrudes from the lower end of the punch 12 when the ram 10 is positioned, and the center pin 17 of the large diameter shaft portion 17a extends in the vertical direction of the required stroke with respect to the punch 12. The large-diameter guide hole 13a is spaced above the lower end of the large-diameter guide hole 13a.

An upper end portion of the large-diameter shaft portion 17a of the center pin 17 is fitted in a guide hole 18 provided at the center of the bottom wall 14a of the spring receiver 14 so as to be slidable in the vertical direction.
A cylindrical spacer 19 is accommodated in the compression coil spring 15 such that the upper end is fitted into the upward concave hole 20 on the lower surface of the spring retainer 16 and the lower end is in contact with the upper end of the center pin 17. ing.
The upper end portion of the center pin 17 is fixed to the spring retainer 16 by forming the lower end portion of the bolt 21 inserted from above the spring retainer 16 into the upper end portion of the large diameter shaft portion 17a and screwing it into the screw hole 22. Has been.

  The tip end portion (lower end portion) protruding from the lower end of the punch 12 in the small diameter shaft portion 17 b of the center pin 17 is tapered by connecting a straight small diameter shaft portion 24 to the lower end of the tapered small diameter shaft portion 23. It is as. The lower end of the small-diameter shaft portion 24 is a spherical surface in order to prevent breakage.

  The outer diameters of the tapered small diameter shaft portion 23 and the straight small diameter shaft portion 24 are slightly smaller than the inner diameters of the extraction hole portion 8b and the small diameter hole portion 8c of the mold hole 8 provided in the die 9, respectively. When the ram 10 and the center pin 17 are lowered to the lower limit position, the outer peripheral surfaces of the small-diameter shaft portions 23 and 24 and the inner peripheral surface of the extraction hole portion 8b and the upper peripheral portion of the small-diameter hole portion 8c An annular gap is formed between them (see FIG. 5).

2-6 shows the process of shape | molding the 1st intermediate product 2 with the said 1st press apparatus 7. FIG.
As shown in FIG. 2, when the ram 10 is lowered after the material 1 heated to a predetermined temperature is inserted into the large-diameter hole portion 8 a of the die hole 8 of the die 9 with the ram 10 raised. As shown in FIG. 3, the lower end portion of the punch 12 abuts on the upper end of the material 1, and the small-diameter shaft portions 23 and 24 at the lower end portion of the center pin 17 protrude into the upper portion of the bottomed hole 6 of the material 1. .

  When the ram 10 is further lowered in this state, the spring retainer 16 is also lowered by compressing the compression coil spring 15 as shown in FIG. At this time, the material 1 is not pushed out by the punch 12 until the compression coil spring 15 is compressed, and only the center pin 17 substantially integrated with the ram 10 is further lowered, and its lower end is The material 1 enters to the vicinity of the lower end of the bottomed hole 6 of the material 1. During this time, the spring force of the compression coil spring 15 is applied to the punch 12 so that the material 1 is strongly pressed by the lower end of the punch 12.

  From this state, when the ram 10 is further lowered to the lower limit position, as shown in FIG. 5, the material 1 is pushed downward by the punch 12, and at the same time, the tapered small-diameter shaft portion 23 at the lower end portion of the center pin 17 is While descending to the vicinity of the squeezing hole 8b in the die hole 8 of the die 9, the straight small-diameter shaft portion 24 extends from the upper portion of the small-diameter hole portion 8c of the die hole 8, that is, from the upper end of the small-diameter hole portion 8c. It stops when it descends to the position where it enters downward by the length of the portion 24.

  As a result, the lower portion of the shaft portion 2a is solid when the solid portion of the material 1 first passes through the extraction hole portion 8b of the mold hole 8 and plastically flows into the small diameter hole portion 8c. It becomes the shaft portion 2c. Subsequently, while the upper portion of the material 1 is blocked by the lower end portion of the center pin 17 from the flow of meat to the center portion, the outer peripheral surfaces of the small diameter shaft portions 23 and 24, the inner peripheral surface of the extraction hole portion 8b, and By passing through an annular gap formed between the inner peripheral surface of the upper end portion of the small diameter hole portion 8c and being pushed out toward the small diameter hole portion 8c of the mold hole 8, the solid shaft portion 2c is located above the solid shaft portion 2c. A hollow hole 25 is formed in the shaft portion 2a.

  By this series of extrusion processes, the primary intermediate product 2 having the enlarged head portion 2b is formed at the upper end portion of the shaft portion 2a as shown in FIG. 1B, and the small diameter shaft portion 17b of the center pin 17 is formed. A projecting end portion from the lower end of the punch 12 forms a large-diameter hollow hole 26 that is continuous with the hollow hole 25 and opens upward. The thickness of the shaft portion 2 a in the portion where the hollow hole 25 is formed is formed between the outer peripheral surface of the small diameter shaft portion 24 of the center pin 17 and the inner peripheral surface of the small diameter hole portion 8 c in the mold hole 8. The uniform thickness is almost equal to the gap.

  As shown in FIG. 6, when the center pin 17 is raised together with the ram 10 after the first intermediate product 2 is molded, the downward biasing force of the compression coil spring 15 is applied to the punch 12 until they rise slightly. Therefore, the primary intermediate product 2 is pressed downward by the lower end of the punch 12. Accordingly, at the same time when the ram 10 starts to rise, the small-diameter shaft portions 23 and 24 at the lower end portion of the center pin 17 are moved away from the enlarged-diameter head portion 2b and the hollow holes 26 and 25 in the shaft portion 2b. It can be easily pulled out.

  In this state, if the ram 10 is raised to the upper limit position and the lower end of the shaft portion 2a of the primary intermediate product 2 is pushed up with an eject pin (not shown), the molded primary intermediate product 2 is taken out from the die 9. be able to.

  FIG. 7 shows a main part of the second press device 27 which is a manufacturing apparatus for forming the secondary intermediate product 3 shown in FIG. 1 (c), with the shaft portion 2 a of the primary intermediate product 2 at the center. A second die 31 is fitted into the concave hole 30 at the upper end of the die holder 29 in which the through-hole 28 having a large diameter is formed. The second die 31 expands in a trumpet shape upward. A second mold hole 32 having a diameter and a shaft hole 33 communicating with the through hole 28 of the die holder 29 are formed. The second press device 27 is arranged in the vicinity of the first press device 7, and the first intermediate product 2 and the second intermediate product are converted into the first and second presses by one friction press. The devices 7 and 27 can be molded simultaneously.

  A second punch 37 having a protrusion 36 that is substantially complementary to the mold hole 32 of the second die 31 on the lower surface is fitted in the upward concave hole 35 of the lower end portion of the second ram 34. When the second ram 34 is lowered to the lower limit position and the lower surface of the second punch 37 comes into contact with the upper surface of the second die 31, a hollow valve is provided between the second mold hole 32 and the protrusion 36. A space for forming the umbrella part is formed.

  In order to mold the secondary intermediate product 3, the primary intermediate product 2 immediately after being removed from the die 9 in FIG. 6 in the state where the second ram 34 is raised to the upper limit position is used as the second die 31. The second ram 34 is lowered to the lower limit position. Then, the diameter-enlarged head 2b of the primary intermediate product 2 is plastically deformed by the lower surface of the second punch 37 and the projections 36, whereby the upper end of the shaft 3a as shown in FIG. The hollow valve secondary intermediate product 3 having the umbrella portion 3b is formed in the portion, and the umbrella portion 3b has a hollow hole 38 that opens upward and gradually expands in a trumpet shape upward. It is formed so as to communicate with the hollow hole 25 of the shaft portion 3a.

  After subjecting the secondary intermediate product 3 taken out from the second press device 27 to a predetermined heat treatment, as shown in FIG. 1 (d), the metallic sodium 4 for cooling the valve is placed in the hollow hole 25 of the shaft portion 3a. insert.

  After the metallic sodium 4 is inserted into the hollow hole 25 of the shaft portion 3a, the closing member 5 is fitted into the opening of the hollow hole 38 of the umbrella portion 3b in the secondary intermediate product 3 as shown in FIG. The closing member 5 is fixed by a welding device (not shown) to close the opening of the hollow hole 38. Thereby, the hollow valve 39 in which the inside of the shaft portion 3a excluding the lower portion and the inside of the umbrella portion 3b are hollow is obtained. The manufactured hollow valve 39 is subjected to finishing processing or processing of a cotter groove or the like at the shaft end.

  As described above, according to the method for manufacturing the hollow valve of the above embodiment, the shaft portion 2a is made hollow by using a core material as in the past or by drilling with a gun drill. Since the hollow hole 25 can be easily formed in the shaft portion 2a at the same time as the material 1 is extruded to form the first intermediate product 2, the hollow valve can be formed very easily and It can be manufactured efficiently at low cost.

  Moreover, since the hollow hole 25 formed in the primary intermediate product 2 can also be used as a pilot hole (guide hole) of the drill, when forming a hollow hole in the shaft portion from the beginning with a gun drill as in the prior art, Compared to the above, drilling can be easily performed in a short time, productivity is improved, and the load on the drill is reduced, so that the life is extended.

  Further, when the secondary intermediate product 3 is formed by forging the enlarged diameter head 2b of the primary intermediate product 2, the umbrella portion 3b is also formed with a hollow hole 38 that expands upward in a trumpet shape. Therefore, the overall weight of the bulb can be reduced, and the heat radiation area when metal sodium is sealed in the bulb increases, so that the umbrella portion 3b is effectively cooled.

  Since the hollow hole 38 of the umbrella part 3b is gradually expanded in a trumpet shape upward, the work for inserting the metal sodium 4 into the hollow hole 25 is also facilitated.

The present invention is not limited to the above embodiment.
In the above manufacturing method, a bottomed hole 6 is provided in the material 1 in advance, and the material 1 is strongly pressed by the punch 12 and plastically flows downward while the lower portion of the center pin 17 is inserted into the bottomed hole 6. However, the material 1 can also be solid, that is, cylindrical.
At this time, when the ram 10 is initially lowered, the upper surface of the columnar material 1 is plastically deformed by being strongly pressed by the lower part of the center pin 17 having a larger projecting dimension than the above-described embodiment. After the bottom part of the material 1 is made to enter the inside of the material 1, a bottomed hole that opens upward is formed at the center of the material 1, and then the upper surface of the material 1 is strongly pressed by the punch 12, and the lower part of the pin 17 is further The first intermediate product similar to the above can be formed by lowering until it enters the upper part of the small diameter hole 8c.
If it does in this way, the process of forming the bottomed hole 6 in the raw material 1 beforehand can be omitted.

  Further, in the above manufacturing method, after the secondary intermediate product 3 is formed, the metal sodium 4 for cooling the valve is inserted into the hollow hole 25 of the shaft portion 3a, but only for the purpose of reducing the weight of the valve. In doing so, the insertion process of the metal sodium 4 may be omitted.

  In the manufacturing apparatus described above, the first press device 7 is a friction press, and the punch 12 and the center pin 17 are moved up and down together with the ram 10. For example, the punch 12 and the center pin are moved by two hydraulic presses. 17 can be moved up and down independently with a time difference, or only the punch 12 can be moved up and down by a friction press, and the center pin 17 can be moved up and down by a hydraulic press with a time difference. In this way, the compression coil spring 15 can be omitted, and the timing of entering the small-diameter shaft portion 24 into the small-diameter hole portion 8c of the mold hole 8 can be set by appropriately setting the raising / lowering timing of the center pin 17 with respect to the punch 12. The lower portion of the center pin 17 can be easily pulled out from the hollow holes 25 and 26 of the primary intermediate product 2.

DESCRIPTION OF SYMBOLS 1 Material 2 Primary intermediate product 2a Shaft part 2b Expanded head 2c Solid shaft part 3 Secondary intermediate product 3a Shaft part 3b Umbrella part 4 Metal sodium 5 Closure member 6 Bottomed hole 6a Small diameter hole 6b Tapered hole 6c Large diameter hole 7 First press device 8 Mold hole 8a Large diameter hole 8b Extraction hole 8c Small diameter hole 9 Die 10 Ram 11 Punch holder 12 Punch 12a Large diameter shaft 12b Small diameter shaft 13a Large diameter guide hole 13b Small diameter Guide hole
14 Spring receiver 14a Bottom wall 15 Compression coil spring 16 Spring retainer 17 Center pin 17a Large diameter shaft portion 17b Small diameter shaft portion 18 Guide hole 19 Spacer 20 Upward concave hole 21 Bolt 22 Female screw hole 23 Small diameter shaft portion 24 Small diameter shaft portion 25 Hollow hole 26 Hollow hole 27 Second press device 28 Through hole 29 Die holder 30 Recessed hole 31 Second die 32 Second mold hole 33 Axle hole 34 Second ram 35 Upward recessed hole 36 Projection 37 Second punch 38 Hollow hole 39 Hollow valve

Claims (11)

Forming a material having a bottomed hole opening upward in the center; and
By pressing the material inserted into the die hole of the die with a punch, passing through the squeezing hole part gradually reducing the diameter toward the lower part of the die hole, and extruding it toward the small-diameter hole part below, The lower part of the pin inserted into the bottomed hole is lowered until entering the upper part of the small diameter hole part, and the material is formed between the outer peripheral surface of the lower part of the pin and the inner peripheral surface of the small diameter hole part. By plastically flowing downward through an annular gap, a primary intermediate product having a diameter-increased head at the upper end of the shaft portion and having a hollow hole opened upward inside thereof is formed. And a process for producing a hollow engine valve.   2. The method of manufacturing a hollow engine valve according to claim 1, wherein the lower end of the pin is lowered to the lower end portion of the bottomed hole of the material before the material is strongly pressed by the punch. The upper surface of the cylindrical material inserted into the die hole is strongly pressed with a pin, and the material is plastically deformed so that the lower part of the pin enters the material to open upward at the center of the material. Forming a bottom hole;
By pressing the material with a punch strongly, it passes through the squeezing hole part gradually reducing the diameter in the mold hole, and extrudes it toward the small-diameter hole part below, and the lower part of the pin is By lowering until it enters the upper part of the small-diameter hole, the material is plastically flowed downward through an annular gap formed between the outer peripheral surface of the lower part of the pin and the inner peripheral surface of the small-diameter hole. And a step of forming a primary intermediate product having a diameter-enlarged head at the upper end of the shaft part and having a hollow hole opened upward in the inside thereof. Production method.   The method for manufacturing a hollow engine valve according to any one of claims 1 to 3, wherein after the first intermediate product is formed, the pin is raised while the upper end thereof is pressed by a punch.   By forging the diameter-enlarged head of the primary intermediate product, a secondary intermediate product having an umbrella portion connected to the upper end of the shaft portion and having a hollow hole opened upward is provided inside the umbrella portion. The method for manufacturing a hollow engine valve according to any one of claims 1 to 4, further comprising: a step of forming and a step of closing the opening of the hollow hole of the umbrella portion with a closing member.   The metallic intermediate is inserted into the hollow hole of the shaft part from the opening of the hollow hole of the umbrella part in the secondary intermediate product, and then the opening part of the hollow hole of the umbrella part is closed with a closing member. Item 6. A method for producing a hollow engine valve according to Item 5.   The hollow engine valve manufacturing method according to claim 5 or 6, wherein the hollow hole of the umbrella portion in the second intermediate product is formed into a trumpet shape that gradually increases in diameter upward. A large-diameter hole that can be inserted from above, a squeeze hole that gradually decreases in diameter toward the lower end continuous to the lower end of the large-diameter hole, and a shaft part that continues to the lower end of the squeeze hole. A die having a mold hole composed of a small-diameter hole,
A ram that moves up and down above the die;
A punch that is attached to the ram and into which a lower part can enter into a large-diameter hole of a die hole in the die;
In the vertical guide hole provided in the center of the punch, the ram or other lifting means is linked so as to be able to move up and down, and when lowered, the diameter is smaller than the small diameter hole of the mold hole. A hollow engine valve manufacturing apparatus comprising: a pressing device having a lower small-diameter shaft portion protruding below the punch and a pin having a lower end entering the upper portion of the small-diameter hole portion and stopping. .   9. The hollow engine valve according to claim 8, wherein the ram is provided with pressing means for pressing the first intermediate product after molding downward by urging the punch downward until the pin starts to rise. manufacturing device.   The apparatus for manufacturing a hollow engine valve according to claim 9, wherein the pressing means is a compression coil spring.   A second die having a shaft hole in which the shaft portion of the first intermediate product can be inserted and a second die hole that gradually expands in a trumpet shape toward the upper side in which the enlarged diameter head can be inserted in the vicinity of the press device. A second ram that moves up and down above the second die, and an enlarged head that is attached to the lower part of the second ram and inserted into the second mold hole at the lower end. The hollow engine according to any one of claims 8 to 10, further comprising a second press device including a second punch that is plastically deformed in an umbrella shape so that a hollow hole that opens upward is formed in the hollow engine. Valve manufacturing equipment.

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