KR20170059374A - Parking gear having invonlute spline for transmission forging method and apparatus - Google Patents

Abstract

The present invention relates to a method and a device to forge a transmission parking gear having an involute spline. More specifically, a pre-molding product of a parking gear is molded to have a plurality of first involute spline teeth separated at regular intervals along an outer circumferential surface by means of a hot forging process; and a final molding product of the parking gear is molded to have a more elaborate second involute spline teeth formed along an outer circumferential surface by pressing the pre-molding product by means of a cold forging process. Involute spline teeth are formed without cutting and processing a tooth, and a flow of metal is not cut off, thus preventing a spline tooth strength from being degraded. Moreover, the final molding product is formed by means of the cold forging process, thus improving dimension precision.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for forging a parking gear for a transmission having an involute spline,

The present invention relates to a method of forging a parking gear for a transmission having an involute spline, and more particularly to a method of forging a parking gear for a transmission having an involute spline, in which a plurality of first involute splines spaced apart along the outer circumferential surface are formed by a hot forging process The preform is molded and the preform is pressed by a cold forging process to form a final molded product of a parking gear in which a more elaborate second involute spline is formed along the outer circumferential surface to form an involute spline value without tooth cutting, To a method of forging a parking gear for a transmission having an involute spline in which precision of dimensions is improved by forming a final molded product by a cold forging process and preventing the lowering of the strength of the spline teeth.

The transmission is a device that reciprocates between a parking mode in which the vehicle is parked, a reverse mode, and a neutral mode and an auto driving mode. Generally, in an automotive transmission, in a parking structure for parking, when the driver places the conversion lever in the parking mode position, the lever on the transmission side is moved to fix the parking gear 1 to perform parking.

The gear 1 is machined by machining to form a body and gear teeth for forming a gear tooth during the manufacture of the conventional parking gear 1 so that the accuracy of the spline teeth is not uniform, There has been a problem that the accuracy of the workpiece is determined according to the skill of the worker who cuts the workpiece. Further, there is also a problem that the flow of the metal material due to the tooth cutting process is cut off, and the strength of the spline tooth due to the change of the physical properties is lowered. Therefore, the durability of the gear 1 is relatively low during manufacture of the parking gear 1 by the conventional method, and the gear 1 can not be used for a long period of time. Further, in order to manufacture the gear 1 having the involute spline by the cutting process, the time spent in the cutting process relatively increases, thereby increasing the machining cost and increasing the loss of the material.

The present invention relates to a method of manufacturing a parking gear, and more particularly, to a method of manufacturing a parking gear, in which a preliminary assembly gear, which is a preliminary gear of the assembly gear at the time of performing a warm forging process, The present invention relates to a method of manufacturing a parking gear in which tooth surfaces of corner portions and parking gear teeth facing the parking gear teeth are smooth and tooth surface shapes and dimensions of the corner portions and the parking gear teeth of each parking gear tooth are uniform.

However, since the above-mentioned patent passes through a warm-forging step after one warm forging process, the above-mentioned flow of the metal material is cut off, and the problem of the lowering of the tooth strength and the problem of the precision of the tooth are inevitable.

Therefore, it is possible to maintain the tooth strength without preforming the final forming by cutting the flow of the metal material, and forming the involute spline by other processes than the turning process. Thus, the transmission for the transmission having the involute spline There is a need to provide a gear forging method and apparatus therefor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

There is provided a method of forging a parking gear for a transmission having an involute spline for producing a parking gear having an improved accuracy of a second involute spline formed on the outer circumferential surface by forming a final formed product by a cold forging process, It has its purpose.

The present invention also relates to a method for forming a preformed product by a hot forging process and forming a final formed product by a cold forging process to prevent a decrease in the strength of the second involute spline due to a change in physical properties due to flow- And an object of the present invention is to provide a method of forging a parking gear for a transmission having an involute spline capable of preventing an increase in maintenance cost and thus an increase in maintenance cost.

The present invention also relates to a method for forming a preformed article by a hot forging process and molding a final formed article by a cold forging process, thereby preventing an increase in consumption time due to tooth cutting, And an object thereof is to provide a parking gear forging method for a transmission having an involute spline and an apparatus therefor.

The present invention also provides a method for forging a parking gear for a transmission having an involute spline having a further improved precision by further finely machining a first involute spline formed on an outer circumferential surface of a preform by a cold forging process with a second involute spline And an object thereof is to provide such a device.

Further, the present invention is characterized in that the groove forming portion protruding surface defining the second involute spline groove forming portion by the upper second spline groove forming portion and the lower second spline groove forming portion is formed, and the upper second spline groove forming portion When the molded part is worn out, the third lower mold is released from the body part and then inserted again to fix the lower groove forming part to the upper side by changing the upper and lower parts to relatively increase the service life of the third lower mold, And an object of the present invention is to provide a parking gear forging method for a transmission having an involute spline capable of preventing an overvoltage.

The present invention is also directed to a method of manufacturing a molded product, comprising the steps of: after completion of final molding by pressurization of a third upper mold through a first lower knockout having a cylindrical through-hole formed in a hollow portion of the lower through- And an involute spline capable of easily taking out the molded article from the third lower mold by being lifted up, and an object thereof is to provide a method for forging a parking gear for a transmission.

Further, according to the present invention, a spring device positioned below the first lower knockout supports the lower knockout, a space is formed between the third upper and lower molds and the third preform, the volume of the molded product moves toward the space, And an object of the present invention is to provide a method of forging a parking gear for a transmission having an involute spline for preventing the breakage of the mold.

The present invention also provides a parking gear forging method for a transmission having an involute spline for securing a spring device by a fixing portion formed at one side of a bottom surface of a first lower knockout to prevent lateral movement of the spring device, And the like.

In order to achieve the above object, the present invention is implemented by the following embodiments.

According to one embodiment of the present invention, a parking gear forging method for a transmission having involunt splines according to the present invention includes positioning a third preform having a first involute spline along an outer circumferential surface thereof on a first lower knockout surface of a body portion The third upper mold is lowered toward the third lower mold fixed to the upper side of the body portion so that the fourth pressing surface of the first upper punch presses and lowers the third preliminarily molded article to form the through holes of the third lower mold, And a final forming step of forming a final involute spline having a second involute spline spaced apart from the circumferential surface by a second involute spline forming part spaced at regular intervals in the circumferential direction and spaced apart at regular intervals along the outer circumferential surface, And a cold forging process capable of increasing the accuracy of the tooth profile of the first involute spline The.

According to another embodiment of the present invention, there is provided a method for forging a parking gear for a transmission having an involute spline according to the present invention, wherein in the final molding step, a spring device is located in the lower fixed portion of the lower knockout, A space is formed between the three preliminarily molded products to move the volume of the third preliminarily molded product toward the space to prevent twisting phenomenon and thus damage of the mold.

According to another embodiment of the present invention, a method of forging a parking gear for a transmission having involunt splines according to the present invention is characterized in that the final forming step is a step in which the spring device pushes up the first lower knockout Accordingly, the first lower knockout pushes up the final molded product, so that the operator can easily take out the molded product from the third lower mold.

According to another embodiment of the present invention, in the method for forging a parking gear for a transmission having involunt splines according to the present invention, in the final molding step, the third upper mold is lowered and inserted into the hollow portions of the lower through- The first guide portion is inserted into the upper through-hole of the first upper punch so as to guide the downward movement of the third base metal mold.

According to another embodiment of the present invention, in the parking gear forging method for a transmission having involunt splines according to the present invention, in the cold forging process, when the upper second spline groove forming portion is worn by the repeated final process, Further comprising a mold resetting step of interrupting the operation of the third lower mold, separating the lower mold from the body part, and changing the vertical direction so that the lower second spline groove forming part is fixed to the upper side of the body part, Can be relatively extended to prevent the cost increase and waste of resources.

According to another embodiment of the present invention, a parking gear forging method for a transmission having involunt splines according to the present invention is characterized in that the parking gear forging method includes a step of positioning a first preform between a second upper mold and a second lower mold The second upper mold is lowered to form a first involute spline which is spaced apart at regular intervals along one side of the second preform by the second upper pressing surface and the first involute spline forming portion, A second preliminary step of forming a second preliminarily molded product by the third recessed part and the third recessed part, and a third preliminary step of cutting the third protruded surface of the second preliminarily molded product to form a third preliminary molded product, A hot forging step including a third preliminary step of forming a molded article is further carried out so that the metal flow of the molded article can be maintained while increasing the tooth strength And that is characterized.

According to an embodiment of the present invention, a parking gear forging apparatus for a transmission having an involute spline according to the present invention comprises a cylindrical third upper body, a shaft having a reduced diameter at a bottom surface of the third upper body, And a third upper mold including a first upper punch having a through hole having a predetermined diameter on its bottom surface, a third lower body having a cylindrical shape, an outer peripheral surface of a lower through-hole formed on an upper surface of the third lower body, And a third lower mold including a second involute spline forming part having a projection shape spaced apart at regular intervals along a circumferential direction of the final molded product to form a second involute spline along an outer circumferential surface of the final molded product, .

According to another embodiment of the present invention, in the parking gear forging apparatus for a transmission having an involute spline according to the present invention, the second spline forming portion is formed by machining a first involute spline value of the preliminary molded product to form a more elaborate second spline tooth A second spline forming portion formed in a shape complementary to the second involute spline along the circumferential direction of the outer circumferential surface of the lower through hole; a second spline forming portion projecting outward along the circumferential direction of the outer circumferential surface of the lower through- And a second spline groove forming part formed in a shape complementary to the second involute spline groove so as to form a second spline groove between the involute spline teeth.

According to another embodiment of the present invention, in the parking gear forging apparatus for a transmission having involunt splines according to the present invention, the second spline forming portion is protruded outward from one side of the second spline groove forming portion, And a groove forming part protruding surface for defining the groove forming part as an upper groove forming part and a lower groove forming part. When the second spline groove forming part is worn, the third lower mold is separated from the body part, So that the third lower mold can be continuously used.

According to another embodiment of the present invention, the parking gear forging apparatus for a transmission having an involute spline according to the present invention further comprises a body portion for inserting and fixing the third lower mold on the upper side thereof, A first lower knockout for allowing the operator to easily take out the molded article from the third lower mold by pushing up the molded article after the final molded article is molded in a cylindrical shape having a through hole having a predetermined diameter; A space is formed between the third upper and lower molds and the preliminarily molded article by supporting the first lower knockout, and the volume of the molded article is moved toward the space to prevent twisting phenomenon and damage to the mold And a spring device roll.

According to another embodiment of the present invention, there is provided a parking gear forging apparatus for a transmission having an involute spline, wherein the first lower knockout includes a ring-shaped outer fixed ring having a predetermined height at one side of the bottom surface, And a ring-shaped inner fixed stationary ring having a predetermined height to fix the spring device in the space between the rings, thereby limiting lateral movement of the spring device.

According to still another embodiment of the present invention, there is provided a parking gear forging apparatus for a transmission having an involute spline, wherein the body is located in the hollow portion of the lower through-hole and the body portion, And a first guide portion inserted into the upper through-hole to guide the lowering of the first upper punch accurately.

According to another embodiment of the present invention, a parking gear forging apparatus for a transmission having involunt splines according to the present invention is characterized in that the parking gear forging apparatus comprises a cylindrical second upper body and a lower body formed on the lower surface of the second upper body A second lower mold having a cylindrical lower body and a second lower portion formed by being inserted into the upper surface of the second lower body and pressing the preliminarily molded article by hot forging molding, a second upper mold including an upper pressing surface for pressing the preliminarily molded article, And a second involute spline for forming a first involute spline having a predetermined shape on one side of the preform as the second upper mold is lowered to press the preform, And a hot forging mold including a forming part is additionally provided so that the preliminarily molded product is heated by hot forging before forging by the cold forging mold By type it is characterized in that to increase the strength values obtained by molding while keeping the metal flow of the molded article.

The present invention can obtain the following effects according to the above-described embodiment, the constitution described below, the combination and use relationship.

The present invention has the effect of producing a parking gear in which the precision of the second involute spline formed on the outer peripheral surface is improved by molding the final molded product by the cold forging process.

The present invention also relates to a method for forming a preformed product by a hot forging process and forming a final formed product by a cold forging process to prevent a decrease in the strength of the second involute spline due to a change in physical properties due to flow- And an increase in maintenance cost can be prevented.

The present invention also relates to a method for forming a preformed article by a hot forging process and molding a final formed article by a cold forging process, thereby preventing an increase in consumption time due to tooth cutting, It is effective.

Further, according to the present invention, the first involute spline formed on the outer circumferential surface of the preliminarily molded article by the cold forging process is further finely processed by the second involute spline, so that the accuracy of the precision can be further improved.

Further, the present invention is characterized in that the groove forming portion protruding surface defining the second involute spline groove forming portion by the upper second spline groove forming portion and the lower second spline groove forming portion is formed, and the upper second spline groove forming portion When the molded part is worn out, the third lower mold is released from the body part, and the lower groove forming part is inserted again to be fixed on the upper side by changing the upper and lower parts to relatively increase the service life of the third lower mold, Can be prevented.

The present invention is also directed to a method of manufacturing a molded product, comprising the steps of: after completion of final molding by pressurization of a third upper mold through a first lower knockout having a cylindrical through-hole formed in a hollow portion of the lower through- So that the worker can easily take out the molded article from the third lower mold.

Further, according to the present invention, a spring device positioned below the first lower knockout supports the lower knockout, a space is formed between the third upper and lower molds and the third preform, the volume of the molded product moves toward the space, There is an effect that it is possible to prevent the breakage of the mold caused thereby.

Further, the present invention has the effect of preventing lateral movement of the spring device by fixing the spring device by the fixing part formed at one side of the bottom surface of the first lower knockout.

1 is an exploded perspective view of a first mold used in a first preliminary process according to an embodiment of the present invention;
2 is a cross-sectional view showing a state before molding of the first upper mold and the first lower mold according to the present invention
3 is a cross-sectional view showing a state in which the first preformed article of the first upper mold and the first lower mold according to the present invention is hot forged;
4 is a cross-sectional view showing a state after molding of the first upper mold and the first lower mold according to the present invention
Fig. 5 is a perspective view of the first pre-
6 is an exploded perspective view of a second mold used in a second preliminary process according to an embodiment of the present invention.
7 is a cross-sectional view showing a state before molding of the second upper mold and the second lower mold according to the present invention
8 is a cross-sectional view showing a state in which the first preformed article of the second upper mold and the second lower mold according to the present invention is hot forged;
9 is a cross-sectional view showing a state after molding of the second upper mold and the second lower mold according to the present invention
10 is a perspective view of a second preform
11 is a perspective view of the third preliminarily molded article
12 is an exploded perspective view of a third mold used in the final molding process according to an embodiment of the present invention.
13 is a cross-sectional view showing the state before molding of the third upper mold and the third lower mold according to the present invention
14 is a cross-sectional view showing a state in which a final molded product of a third upper mold and a third lower mold according to the present invention is subjected to cold forging molding
15 is a cross-sectional view showing a state after molding of the third upper mold and the third lower mold according to the present invention
16 is an enlarged view of a second involute spline forming portion of a third lower mold according to the present invention
17 is a perspective view of a final molded product
18 is a comparative reference diagram of Involute splines of the third preform and the final molded article
19 is a block diagram of a parking gear forging method for a transmission having an involute spline according to an embodiment of the present invention
Fig. 20 is a block diagram of a hot forging process according to Fig. 19
Fig. 21 is a block diagram of a cold forging process according to Fig. 19

Hereinafter, a method for forging a parking gear for a transmission having an involute spline according to the present invention and its apparatus will be described in detail with reference to the accompanying drawings. It is to be noted that the same elements among the drawings are denoted by the same reference numerals whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs and, if conflict with the meaning of the terms used herein, It follows the definition used in the specification.

FIG. 1 is an exploded perspective view of a first mold used in a first preliminary process according to an embodiment of the present invention, FIG. 2 is a sectional view showing a state before molding of a first upper mold and a first lower mold according to the present invention And FIG. 3 is a cross-sectional view illustrating a state in which the first preform of the first upper mold and the first lower mold according to the present invention is hot forged, FIG. 4 is a cross-sectional view of the first upper mold and the first lower mold according to the present invention, 5 is a perspective view of the first preform, FIG. 6 is an exploded perspective view of a second mold used in a second preliminary process according to an embodiment of the present invention, and FIG. 7 is a cross- 8 is a view illustrating a state where a first preform of a second upper mold and a second lower mold according to the present invention is hot forged; FIG. 8 is a view showing a state in which a first preform of a second upper mold and a second lower mold according to the present invention are hot forged; Sectional view, and Fig. 9 FIG. 10 is a perspective view of the second preform, FIG. 11 is a perspective view of the third preform, and FIG. 12 is a perspective view of the second preform according to the present invention. 13 is an exploded perspective view of a third mold used in a final forming process according to an embodiment, FIG. 13 is a sectional view showing a state before molding of a third upper mold and a third lower mold according to the present invention, and FIG. 14 is a cross- FIG. 15 is a cross-sectional view showing a state after molding of the third upper mold and the third lower mold according to the present invention, and FIG. 15 is a cross-sectional view showing a state after molding of the third upper mold and the third lower mold according to the present invention. 16 is an enlarged view of the second involute spline forming portion of the third lower mold according to the present invention, FIG. 17 is a perspective view of the final molded product, and FIG. 18 is a cross sectional view of the involute spline of the third preform and the final molded product A bridge note.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, preferred embodiments of a hot forging apparatus and a cold forging apparatus used in respective steps of a parking gear forging method for a transmission having involunt splines according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It is obvious that the parking gear according to the present invention can be used not only for an automatic transmission but also for a manual transmission.

1 to 4, in a parking gear forging apparatus for a transmission having involunt splines according to an embodiment of the present invention, in a hot forging step (S1) of a parking gear forging method for a transmission having involute splines The hot forging die used in the first preliminary process S11 includes a first mold 2 and the first mold 2 includes a first upper mold 21 and a first lower mold 23 .

The first upper mold 21 includes a cylindrical first upper body 211 and a first upper pressing surface 213 for pressing a molding material 8 seated on a first lower seating surface 233 And the first lower mold 21 is lowered and the molding material 8 is pressed by positioning the cylindrical molding material 8 in the first lower mold 23, The first preliminarily molded article 11 to be described later is hot forged.

The first upper body 211 is formed in a cylindrical shape having a predetermined height and diameter.

The first upper pressing surface 213 is formed on the lower surface of the first upper body 211 to contact the cylindrical molding material 8 and press the material 8 to form a first preform 1, Is formed by hot forging. The shape of the first upper pressing surface 213 is not limited, but is preferably formed in a horizontal plane on the lower surface of the first upper body 211.

The first lower mold 23 includes a cylindrical first lower body 231 and a molding material 8 seated on a first lower seating surface 233 formed on the upper surface of the body 231, 1 upper pressing surface 213 so that the rear surface of the first preliminarily molded product 11 to be described later together with the first upper mold 21 is hot forged.

The first lower body 231 is formed in a cylindrical shape having a predetermined height and diameter.

The first lower seating surface 233 is formed by placing the cylindrical molding material 8 on the upper surface of the first lower body 231 and then lowering the first upper mold 21, The first preforming part 11 having a predetermined shape on the rear surface thereof is hot forged and molded so that the first seating part 233a and the first recessed part 233b and the second recessed part 233c ).

The first seating part 233a is formed in a ring shape having a predetermined width inward from the end of the first lower seating surface 233, and when the upper body 21 is lowered, 1 upper pressing surface 213 so as to limit the lowering of the upper body 21.

The first recessed portion 233b is formed in a ring shape having a predetermined width by being inserted in a predetermined length downward from the inner circumferential surface of the first seat portion 233a and the first upper mold 21 is lowered, The body of the final molded product 14 of the parking gear 1, which will be described later, is formed by hot forging the rear surface of the first preliminarily molded article 11 except for the first projecting surface 111, .

The second recessed portion 233c is formed in a cylindrical shape having a predetermined diameter by being inserted into the first recessed portion 233b from the inner circumferential surface of the first recessed portion 233 downward for a predetermined length and the first upper mold 2 is lowered, The first protruding surface 111 of the back surface of the first preliminarily molded product 11 to be described later is hot-forged by pressurizing the first protruding surface 8.

Referring to FIG. 5, the first preform 11 formed by the hot forging die used in the first preliminary process S11 will be described. As the first upper pressure surface 213 is formed in a horizontal plane, The front surface of the first preform 11 is formed into a horizontal circular shape having a predetermined diameter. The rear surface of the first preform 11 is formed in a ring shape having a predetermined width complementary to the first recess 233c and is formed in the inner peripheral surface of the first recess 233c, A first protruding surface 111 protruding in a cylindrical shape having a predetermined diameter complementary to the protruding portion 233c is formed.

6 to 9, in a parking gear forging apparatus for a transmission having involunt splines according to an embodiment of the present invention, in a method for forging a parking gear for a transmission having involute splines, a hot forging step (S1) The hot forging die used in the second preliminary process S13 includes the second mold 3 and the second mold 3 includes the second upper mold 31 and the second lower mold 33 do.

The second upper mold 31 has a cylindrical second upper body 311 and a second lower mold 311 formed on the lower surface of the second upper body 311 to press the first preliminarily molded article 11 to form a second preliminary mold The second preliminarily molded article 12 to be described later including the material 2 upper pressing surface 313 forming a predetermined shape on the front surface of the molded article 12 is subjected to hot forging molding.

The second upper body 311 is formed in a cylindrical shape having a height and a diameter downward.

The second upper pressurizing surface 313 presses the first preliminarily molded product 11 seated on the second lower seating surface 333 to be described later according to the descent of the second upper mold 4, A second pressing surface 313b, and a third pressing surface 313c in order to achieve this purpose. The first pressing surface 313a, the second pressing surface 313b, and the third pressing surface 313c may be formed.

The first pressing surface 313a is formed in a ring shape having a predetermined width inward from the distal end of the second upper pressing surface 313 so that the second upper mold 31 presses the second lower mold 33 The first preformed part 11 positioned on the upper surface of the second lower mold 33 is pressed together with the second seating part 333a and the first spline forming part 333b to be described later The first outer surface 121 of the second preform 12 and the first involute spline 122 are formed.

The second pressing surface 313b is formed in a ring shape protruding downward from the inside of the first pressing surface 313a and having a predetermined width so that the second upper mold 31 is pressed against the second lower mold 33, The first preliminarily molded article 11 located on the upper surface of the second lower mold 33 is pressed together with the third recessed portion 333c to be described later so that the second preliminarily molded article And the second projecting surface 123 is formed. The second projection surface 123 to be described below is a configuration for forming the body of the final molded product 14 of the parking gear 1 to be described later.

The third pressing surface 313c protrudes downward in a cylindrical shape having a predetermined diameter from the inner circumferential surface of the second pressing surface 313b so that the second upper mold 31 is pressed against the second lower mold 33, The first preliminarily molded product 11 located on the upper surface of the second lower mold 33 is pressed together with the fourth recessed portion 333d to be described later so that the second preliminarily molded product 12 And the third projecting surface 124 is formed. The third projecting surface 124 to be described below is configured to form the penetration portion 131 in the third preliminarily molded product 13 by cutting in the third preliminary process S13.

The second lower mold 33 includes a cylindrical second lower body 331 and a first preform 11 positioned on a second lower seating surface 333 formed on the upper surface of the lower body 331. [ Is pressed through the second upper pressing surface 313 to form a second preliminary molded product 12 to be described later having a predetermined shape together with the second upper mold 31 by hot forging, The second upper mold 31 is formed of a cylindrical second upper body 311 and a second upper mold 311 formed on the lower surface of the second upper body 311 to press the first pre- The second preliminarily molded article 12 to be described later including the second upper pressing surface 313 forming a predetermined shape on the front surface of the second preliminarily molded article 12 to be subjected to hot forging.

The second upper body 311 is formed in a cylindrical shape having a predetermined height and diameter downward.

The second upper pressurizing surface 313 presses the first preliminarily molded product 11 seated on the second lower seating surface 333 to be described later according to the descent of the second upper mold 4, A second pressing surface 313b, and a third pressing surface 313c in order to achieve this purpose. The first pressing surface 313a, the second pressing surface 313b, and the third pressing surface 313c may be formed.

The first pressing surface 313a is formed in a ring shape having a predetermined width inwardly from both ends of the second upper pressing surface 313 so that the second upper mold 31 is inserted into the second lower mold 33, The first preformed part 11 positioned on the upper surface of the second lower mold 33 is pressed together with the second seating part 333a and the first spline forming part 333b to be described later, The first outer surface 121 of the second preform 12 and the first involute spline 122 are formed.

The second pressing surface 313b is formed in a ring shape protruding downward from an inner circumferential surface of the first pressing surface 313a and having a predetermined width so that the second upper mold 31 is pressed against the second lower mold 33 The first preliminarily molded product 11 located on the upper surface of the second lower mold 33 is pressed together with the third recessed portion 333c to be described later so that the second preliminarily molded product 12, And the second protruding surface 123 of the protruding portion 123 is formed.

The third pressing surface 313c protrudes downward in a cylindrical shape having a predetermined diameter from the inner circumferential surface of the second pressing surface 313b so that the second upper mold 31 is pressed against the second lower mold 33, The first preliminarily molded product 11 located on the upper surface of the second lower mold 33 is pressed together with the fourth recessed portion 333d to be described later so that the second preliminarily molded product 12 And the third projecting surface 124 is formed. The third projecting surface 124 to be described below is configured to form the penetration portion 131 in the third preliminarily molded product 13 by cutting in the third preliminary process S13.

The second lower mold 33 includes a cylindrical second lower body 331 and a first preform 11 positioned on a second lower seating surface 333 formed on the upper surface of the lower body 331. [ Is pressed through the second upper pressing surface 313 to form a second preliminary molded product 12 to be described later having a predetermined shape together with the second upper mold 31 by hot forging, 12 to form a first involute spline 122 to be described later.

The second lower body 331 is formed in a cylindrical shape having a predetermined height and diameter.

The second lower seating surface 333 is formed in a predetermined shape on the upper surface of the second lower body 331 to position the first preform 11 on the second lower seating surface 333 The second preliminarily molded article 12 having a predetermined shape is subjected to hot forging and the second preliminarily molded article 31 is lowered to press the first preliminarily molded article 11, A first spline forming portion 333b, a third recessing portion 333c and a fourth recessing portion 333d are formed in order to form the first involute spline 122, .

The second seating portion 333a is formed in a ring shape having a predetermined width from both ends of the second lower seating surface 333 so that the second upper mold 31 is directed toward the second lower mold 33 The first preliminarily molded article 11 located on the upper surface of the second lower mold 33 is pressed together with the first pressing surface 313a so that the first preliminarily molded article 12, The side surface 121 is formed.

The first spline forming part 333b is formed by pressing the first preliminarily molded product 11 downward by the second upper mold 31 to form a second preliminarily molded product The first involute splines 122 are formed in a repetitive protrusion shape that is complementary to the first involute splines 122 downward along the inner circumferential surface of the second seating portion 333a in order to form the one involute spline 122, The first involute spline tooth forming section 333b-1 and the first involute spline groove forming section 333b-2.

The first involute spline forming portion 333b-1 is formed with a first involute spline tooth 122a to form a plurality of first involute spline teeth 122a spaced apart from each other at regular intervals. And is formed repeatedly along the circumferential direction of the inner peripheral surface of the second seat portion 333a in a complementary shape.

The first involute spline groove forming section 333b-2 is formed in a shape complementary to the spline groove 122b to form a spline groove 122b between the involute spline teeth 122a, which will be described later, And is formed so as to protrude repeatedly along the circumferential direction of the inner peripheral surface of the seat portion 333b. That is, the first involute spline forming portion 333b-1 protrudes outward from the first involute spline forming portion 333b-1. The first spline forming portion and the groove forming portions 333b-1 and 333b-2 are repeatedly formed.

The third inclined portion 333c is formed in a ring shape having a predetermined width from the lower side of the inner peripheral surface of the first involute spline forming portion 333b, The second pressing surface 313b pressurizes the first preliminarily molded article 11 as it descends toward the lower mold 33 to form the second protruding surface 123 to be described later on the rear surface. As described above, the second protruding surface 123 to be described later is a configuration for forming the body of the final molded product 14 of the parking gear 1 to be described later.

The fourth recessed portion 333d is formed into a cylindrical shape having a predetermined diameter by being inserted downward from the inner peripheral surface of the third recessed portion 333c, The third pressing surface 313c pressurizes the first preliminarily molded article 11 as it descends toward the mold 33 to form a third protruding surface 124 to be described later on the rear surface. As described above, the third protruding surface 124, which will be described later, is configured to form the penetrating portion 131 in the third preliminarily molded product 13 by cutting in the third preliminary step S15.

Referring to FIG. 10, the second preform 12 molded by the hot forging die used in the second preliminary process S13 will be described. As shown in FIG. 10, the second upper mold 31 is inserted into the second lower mold 33, And presses the first preliminarily molded product 11 positioned on the second lower seating surface 333 of the second lower mold 33 so as to press the first pressing surface 313a and the second seating portion 333a And the first involute spline forming portion 333b forms a predetermined shape from the inner side to the upper side of the first outer side surface 121 by the first involute spline forming portion 333b, A plurality of first involutes splines 122 spaced apart from each other by a predetermined distance are formed on the inner circumferential surface of the spline 122. The spline 122 is formed by a ring- Shaped second protruding surface 123 is formed and the third pressing surface 313c and the fourth recessed portion 333d are formed A third protruding surface 124 protruding from the inner circumferential surface of the second protruding surface 123 is formed. The diameter of the third projecting surface 124 is not limited, but is preferably smaller than the diameter of the first projecting surface 111 of the first preform 11.

11, in the parking gear forging apparatus for a transmission having involunt splines according to an embodiment of the present invention, in the third preliminary step (S15) in the hot forging step (S1), the second preliminary molded product 12 The first outer surface 121 and the third protruding surface 124 of the first outer surface 121 and the third protruding surface 124 are trimmed so that the penetration portion 131 having a predetermined diameter at the center and the involute spline 122 having a predetermined shape on the outer circumferential surface A formed third preform 13 is formed. After the third preform 13 is formed, the final formed article 14 may be formed according to the cold forging process to complete the parking gear 1, which will be described below.

As described above, in order to perform the cold forging of the parking gear 1 for the transmission having the involute spline, the third preform 13 is formed by hot forging by dividing the third preform 13 by a single hot forging, 1), it is not easy to form the first spline teeth 122 having a high forming volume because of the large forming volume, and it is not possible to improve the tooth strength and durability by maintaining the flow of the metal material of the metal material forming the molding Because. Therefore, it is possible to minimize the above-mentioned problems by molding the final third preform 13 by a plurality of processes according to the present invention.

12 to 16, in the parking gear forging apparatus for a transmission having involunt splines according to an embodiment of the present invention, the cold forging mold used in the cold forging step S2 is formed of a third metal mold 4, The third mold 4 includes a third upper mold 41, a third lower mold 43, and a body 45.

The third upper mold 41 has a cylindrical third upper body 411 and a third lower mold 411. The third upper mold 411 has a cylindrical shape and is formed by extending downward at a lower surface of the third upper body 411 and having a predetermined length, And a first upper punch 413 in which a hole 413b is formed. As the third upper mold 41 descends toward the third lower mold 43 to be described later, the third preform 13 is pressed and the final molded product 14 having a predetermined shape is subjected to the cold forging process And the details will be described below.

The third upper body 411 is formed in a cylindrical shape having a predetermined height and diameter.

The first upper punch 413 is formed by extending downward from the bottom surface of the third upper body 411 by a predetermined length downward and has a through hole 413b having a predetermined diameter formed on the bottom surface thereof. As the third upper body 411 descends, the first upper punch 413 presses the third preform 13 to form a final molded product 14 having a predetermined shape. For this, the first upper punch 413 may include a fourth pressing surface 413a and a first upper through hole 413b.

The fourth pressing surface 413a presses the third preform 13 located on the first lower knockout 453 to be described later to form a final molded product 14 to be described later and presses the third preform 13 The molded article 13 is lowered by a certain distance. The first upper punch 413 including the fourth pressing surface 413a is inserted into the lower through hole 433 of the third lower mold 43 to be described later so that the third pre- A more involute second involute spline 141 can be formed along the outer peripheral surface of the final molded product 14 by the second involute spline forming portion 435 to be described later.

The first upper through hole 413b is guided by the first guide portion 451 inserted into the lower through hole 433 of the third lower mold 43, The first pressing surface 413a and the second pressing surface 413a are formed with a predetermined diameter through the bottom surface of the fourth pressing surface 413a. The diameter of the first upper through hole 413b may be substantially the same as or slightly larger than the diameter of the first guide portion 451 to be described later so that the first upper punch 433 It is easy to guide.

The third lower mold 43 includes a cylindrical lower body 431 and a lower protrusion 433 formed on the upper surface of the lower body 431 in a circumferential direction along the outer circumferential surface of the lower through- The second involute spline 141 is formed on the outer peripheral surface of the final molded product 14 through the second involute spline forming portion 435. [ For this, the third lower mold 43 may include a third lower body 431, a lower through hole 433, and a second spline forming unit 435.

The third lower body 431 is formed in a cylindrical shape having a predetermined height and diameter and is inserted and fixed on the upper side of the body portion 8 to be described later.

The lower through-hole 433 is formed on one side of the third lower mold 43, and is preferably formed in a cylindrical shape downward from the upper surface of the third lower mold 43, The first upper punch 413 is inserted into the lower through hole 433 and the first guide portion 451 to be described later is inserted into the first upper through hole 413b, The lower portion of the first upper punch 413 is guided by the first guide portion 451 and the first upper punch 413 is guided by the third preliminarily molded article 453 located on the first lower knockout 453, (13) is pressed to form a final molded product (14) having a predetermined shape.

The second involute spline forming section 435 has a protruding shape spaced apart at regular intervals along the circumferential direction of the outer circumferential surface of the lower through hole 433 to form a second involute spline 141 to be described later So that the first involute splines 122 formed on the second preform 12 and the third preform 13 are formed more precisely. To this end, the second involute spline forming section 435 includes a second involute spline forming section 435a, a second involute spline groove forming section 435b, and a dentiform projecting surface 435c .

The second involute spline forming section 435a is formed by forming a plurality of first involute spline teeth 122a spaced apart from each other at a predetermined interval to form a more elaborate second involute spline tooth 141a, And is formed in a shape complementary to the second involute spline 141a.

The second involute spline groove forming part 435b is formed by the second involute spline teeth 141a protruding outward along the circumferential direction of the outer circumferential surface of the lower through hole 433, And the second involute spline groove 141b is formed in a shape complementary to the second involute spline groove 141b to form the two involute spline groove 141b. The second involute spline groove forming portion 435b is formed by the upper second involute spline groove forming portion 435b-1 and the lower second involute spline groove forming portion 435b-1 by the groove forming part protruding surface 435c The first lower spline groove forming portion 435b-1 is defined as a lower portion 435b-2 of the lower spline groove forming portion 435b-1. Accordingly, when the upper second spline groove forming portion 435b- The third lower mold 43 can be continuously used by inserting the lower groove forming portion 435b-2 into the body portion by fixing the upper groove forming portion 435b-2 after the mold 43 is taken out. Therefore, the lifetime of the third lower mold 43 can be relatively extended to prevent the cost increase and waste of resources.

The groove forming part protruding surface 435c protrudes outward from one side of the second spline groove forming part 435b so that the second spline groove forming part 435b is formed on the upper groove forming part 435b- And a groove forming section 435b-2. As described above, when the upper second spline groove forming part 435b-1 is worn by long-term use, the lower mold 43 is pressed from the body part 45 supporting the third lower mold 43, The second lower mold 43 can be continuously used by inserting the lower groove forming part 435b-2 while fixing the lower groove forming part 435b-2 by changing the upper and lower directions. The longitudinal width of the groove forming part protruding surface 435c is larger than the width of the upper groove forming part 435b-1 from the upper end of the groove forming part 435b-2 to the lower end of the lower groove forming part 435b- .

The body portion 45 is formed in a cylindrical shape having a predetermined height and diameter, and is inserted and fixed on the upper side of the third lower mold 43, and has a first guide portion 451, (453), and a spring device (455).

The first guide portion 451 is positioned in the hollow portion of the lower through hole 433 and the body portion 45 and inserted into the first upper through hole 413b of the first upper punch 413, 1 is a cylindrical configuration guiding the accurate lowering of the upper punch 413. The diameter of the cylindrical portion constituting the first guide portion 451 is smaller than the diameter of the first upper through hole 413b and the lower through hole 433 and is smaller than the diameter of the first guide portion 451 and the lower through hole 433. [ A first lower knockout 453 to be described later is inserted into the space defined between the first lower knockout 453 and the second lower knockout 453,

The first lower knockout 453 has a cylindrical shape having a predetermined diameter and a through hole having a predetermined diameter formed in the hollow portion of the lower through hole 433 and the body portion 45, And a fixing portion 453a for limiting the lateral movement of the spring device 455 is formed so that the spring device 455 is inserted and not tilted. The diameter of the cylindrical shape of the lower knockout 453 is formed to be substantially the same as the diameter of the lower through hole 433 and the diameter of the through hole formed in the first lower knockout 453 is smaller than the diameter of the first lower knockout 453, Is formed to have a diameter substantially coinciding with the diameter of the portion (451). The first lower knockout 453 flows upward and downward in the space defined by the lower through hole 433 and the first guide 451 so that the third upper mold 43 is lowered, The operator presses the third preform 13 placed on the lower knockout 453 and pushes up the final molded article 14 after raising again so that the operator can easily take the molded article out of the third lower mold 43. [

The fixing portion 453a includes a ring-shaped outer fixed ring 453a-1 having a predetermined height at one side of the cylindrical bottom surface of the first lower knockout 453, and a ring- And a ring 453a-2. There is no limitation on the shape of the rings 453a-1 and 453a-2, but preferably the inner and outer fixed stationary rings 453a-1 and 453a-2 are fixed in a space between the rings by a spring device 455 And has a predetermined height and width.

The spring device 455 is positioned below the first lower knockout 453 to support the first lower knockout 453 and the third upper mold 41 and the third lower mold 43, A space is formed between the preforms 13 and the volume of the molded article 13 is moved toward the space to prevent the occurrence of the twisting phenomenon and the breakage of the mold, So that the workpiece can be easily taken out from the third lower mold 43 by pushing it up through the knockout 453. The spring device 455 is installed at the lower end of the first lower knockout 453 to keep the third preform 13 and the upper and lower molds 41 and 43 in contact with each other continuously during the molding of the final molded product 14 .

Referring to FIG. 17, in the parking gear forging apparatus for a transmission having involunt splines according to an embodiment of the present invention, a final molded product 14 formed by a cold forging mold used in the cold forging step S2 A plurality of second involutes splines 141 are formed on the outer circumferential surface of the final molded product 14 and are spaced apart from each other by a predetermined distance. The second involute splines 141 are smaller in height and width than the first involute splines 122 of the second and third preforms 12 and 13 and are processed more finely. Therefore, the parking gear 1 in which the second involute spline 141a and the second involute spline groove 141b are formed with more elaborate can be formed. In the same way as the third preliminarily molded product 13 described above, there is a penetration portion 142 having a predetermined diameter inside the final molded product 14. [

After the final molded product 14 is molded, a surface heat treatment for strengthening the involute spline 141a of the final molded product 14 is performed through a high-frequency heat treatment, and an inner spline is formed in the inner diameter of the penetrating portion 141 So that the final parking gear 1 is formed.

19 is a block diagram of a method for forging a parking gear for a transmission having an involute spline according to an embodiment of the present invention, Fig. 20 is a block diagram of a hot forging process according to Fig. 19, Fig. 21 is a cross- Fig.

Hereinafter, with reference to Figs. 19 to 21, a method for forging the parking gear 1 for a transmission having an involute spline will be described. The method for forging the parking gear 1 includes a hot forging step S1 for forming the preforms 11, 12 and 13, a cold forming step for forming the molded third preform 13, A high frequency heat treatment step S3 for performing a surface heat treatment for strengthening the involute spline 141a; a step of forming an inner spline on the inner diameter of the through part 142 of the final molded product 14; And a broaching step (S4). The hot forging step S1 includes a first preliminary step S11, a second preliminary step S13 and a third preliminary step S15, and the details thereof will be described later.

In the first preliminary process S11, the molding material 8 is first positioned between the first upper mold 21 and the first lower mold 23. The first upper mold 21 is lowered and the molding material 8 in which the first upper pressing surface 213 is seated on the first lower seating surface 233 is inserted into the first seating portion 233a Lt; / RTI > Accordingly, the front surface of the first preform is formed into a horizontal circular shape having a predetermined diameter, and the rear surface is formed with a ring shape having a predetermined width complementary to the first recessed portion 233b, A cylindrical first protruding surface 111 having a predetermined diameter which is complementary to the second recessed portion 233c protruding from the inner circumferential surface of the first protruded surface 111 is formed. Therefore, the first preliminarily molded article 11 having the first protruding surface 111 formed on the rear surface thereof can be formed by the first preliminary step S11. After the first preform (11) is formed, the first upper mold (2) rises again.

In the second preliminary process (S13), the first preliminarily molded product (11) is positioned between the second upper mold (31) and the second lower mold (33). The second upper mold 31 is lowered toward the second lower mold 33 so that the second upper pressing surface 313 is pressed against the second lower seating surface 333 of the second lower mold 33, The first preliminarily molded article 11 is pressed. Specifically, a ring-shaped first outer surface 121 is formed on the outer side by the first pressing surface 313a and the second seating portion 333a, and the first pressing surface 313a and the first spline- A plurality of first involute splines 122 having a predetermined shape from the inner peripheral surface of the first outer side surface 121 to the upper side are spaced apart from each other by a predetermined distance. A ring-shaped second protruding surface 123 is formed at one side by the second pressing surface 313b and the third recessed portion 333c and the third pressing surface 313c and the fourth recessed portion 333d A third protruding surface 124 protruding upward from the inner circumferential surface of the second protruding surface 123 is formed. As described above, the diameter of the third projecting surface 124 is not limited, but is preferably smaller than the diameter of the first projecting surface 111 of the first preform 11.

In the third preliminary process S15, the first outer surface 121 and the third protruding surface 124 of the second preform 12 are cut to form a through-hole 131 having a predetermined diameter at the center, A third preform 13 is formed on which an involute spline 122 having a predetermined shape is formed on the outer circumferential surface.

The cold forging step (S2) includes a final forming step (S21) and a mold resetting step (S23), the details of which will be described below.

 The third preform 13 is positioned on the upper surface of the first lower knockout 453 of the body portion 45. In the final molding step S21, The third upper mold 41 is then lowered toward the third lower mold 43 inserted and fixed to the body portion 45 so that the lower through hole of the third lower mold 43 The first guide portion 451 inserted into the first upper punch 413 is inserted into the first upper through hole 413b of the first upper punch 413 to guide the lowering of the third upper mold 41, The fourth pressurizing surface 413a presses the third preform 13 and the third preform 13 is lowered so that the second involute spline forming portion 435 separates the third preform 13 The final molded product 14 having the second involute splines 141 is molded. At this time, the spring device 455 located below the first lower knockout 453 generates a space between the third upper and lower molds 41, 43 and the third preform 13, The volume of the mold 13 is shifted to prevent the occurrence of the twist phenomenon and the breakage of the mold. The third upper mold 41 is then lifted and the spring device 455 pushes up the first lower knockout 453 so that the first lower knockout 453 presses the final molded article 14 So that the worker can easily take out the molding from the third lower mold 43.

When the upper second spline groove forming part 435b-1 of the second involute spline forming part 435 is worn by the last step S21, which is repeated, the mold resetting step (S23) The operation of the final step S21 is temporarily stopped and the lower mold 43 is released from the body portion 45 and then the upper and lower grooves are formed in the lower groove forming portion 435b- And then the second lower mold 43 is continuously used by inserting the second lower mold 43 fixedly on the upper side of the body part. Therefore, as described above, the lifetime of the third lower mold 43 can be relatively extended to prevent the cost increase and waste of resources.

As described above, in order to perform the cold forging of the parking gear 1 for the transmission having the involute spline, the hot forging and cold forging are performed separately for the steps (S1, S2) for forming the third preform 13 It is not easy to form the first spline teeth 122 having a high precision when the parking gear 1 is molded by a single forging, and the flow of the metal material of the metal material forming the molding is maintained It is impossible to improve the tooth strength and durability.

The high-frequency heat treatment step S3 is a step of subjecting the final molded product 14 to a high-frequency heat treatment and performing a surface heat treatment for strengthening the involute spline 141a.

The broaching step S4 is a step of forming a final parking gear 1 by advancing a cutting process for forming an inner spline on the inner diameter of the penetrating portion 141 of the final molded product 14. [

The method for forging a parking gear 1 for a transmission having an involute spline according to the present invention as described above forms a basic outer shape of the gear 1 by hot forging and forms a basic shape of a gear 1 of the gear 1 through a cold forging process. The accuracy of the dimension of the lute spline 14 can be improved. In addition, unlike the prior art, the shaping of the final molded product 14 can improve the strength of the teeth 141a by forming the spline teeth 141a only in the cold forging process without machining the precision parts. Accordingly, the disadvantage that the flow of the material is cut off and the strength due to property change is reduced is solved, and the durability of the gear 1 is improved, so that the gear 1 can be used for a long time and the maintenance cost can be reduced .

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Should be interpreted as falling within the scope of.

1: Parking gear
11: First preform
111: first protruding surface
12: Second preform
121: first outer surface 122: first involute spline
122a: first involute spline value 122b: first involute spline groove
123: second protruding surface 124: third protruding surface
13: Third preform
131:
14: Finished product
141: 2nd involute spline
141a: second involute spline 141b: second involute spline groove
142:
15: Finished product
151: hole 152:
2: first mold
21: first upper mold
211: first upper body 213: first upper pressing surface
23: a first lower mold
231: first lower body 233: first lower seating surface
233a: first seat portion 233b: first penetration portion 233c: second penetration portion
3: second mold
31: second upper mold
311: second upper body 313: second upper pressing surface
313a: first pressing surface 313b: second pressing surface 313c: third pressing surface
33: second lower mold
331: second lower body 333: second lower seating surface
333a: second seat portion 333b: first involute spline forming portion
333b-1: First involute spline value forming section
333b-2: First involute spline groove forming part
333c: third penetration portion 333d: fourth penetration portion
4: Third mold
41: third upper mold
411: third upper body 413: first upper punch
413a: fourth pressing surface 413b: first upper through hole
43: third lower mold
431: third lower body 433: lower through hole
435: second involute spline forming part
435a: second involute spline tooth forming section
435b: second involute spline groove forming part
435b-1: upper second involute spline groove forming part
435b-2: Lower second involute spline groove forming part
435c: projecting surface of the groove forming part
45:
451: first guide portion
453: First lower knockout
453a:
453a-1: outer fixed ring 453a-2: inner fixed ring
455: Spring device
S1: Hot forging process
S11: First preliminary process S13: Second preliminary process S15: Third preliminary process
S2: Cold forging process
S21: final forming step S23: mold resetting step
S3: High-frequency heat treatment process
S4: Broaching process

Claims (13)

The third preform having the first involute spline formed along the outer circumferential surface thereof is positioned on the first lower knockout surface of the body portion and the third upper mold is lowered toward the third lower mold fixed on the upper side of the body portion, And the fourth pressing surface presses the third preform to lower the third preform to form a second involute spline forming portion having a protruding shape spaced at regular intervals along the circumferential direction of the outer circumferential surface of the lower through- And a cold forging process capable of increasing the precision of the tooth profile of the first involute spline, including a final forming process of molding a final involute spline having a second involute spline spaced at regular intervals. Of the parking gear. The method according to claim 1,
The method for forging the parking gear further comprises a hot forging step including a third preliminary step of cutting a third projecting surface of the second preliminary molded product to form a third preliminary molded product having a penetrating portion formed at the center thereof, Is formed while maintaining the metal flow of the bolt, so that the tooth strength can be increased. The forging method for a parking gear for a transmission having a involute spline. 3. The method of claim 2,
The hot forging process is performed by positioning the first preliminarily molded article between the second upper mold and the second lower mold and then lowering the second upper mold to press the first upper mold and the second involute spline by the first upper pressing surface and the first involute spline forming portion, Molding a first involute spline which is spaced apart at regular intervals along one side of the preliminarily molded product and molding a second preliminarily molded product forming a ring-shaped second protruding surface on one side by the second pressing surface and the third recessed portion Further comprising a second preliminary process. ≪ RTI ID = 0.0 > 11. < / RTI > A method of forging a parking gear for a transmission having a involute spline. The method according to claim 2 or 3,
In the final molding step, a spring device is located in the lower fixed portion of the first lower knockout, and a space is formed between the third upper and lower molds and the third preform to move the volume of the third preform to the space, Thereby preventing occurrence of a phenomenon and consequent breakage of the mold. [Claim 2] A method for forging a parking gear for a transmission having an involute spline. 5. The method of claim 4,
The final molding process is such that the spring device pushes up the first lower knockout after the final molded article has been molded so that the lower knock pushes up the finished molded article so that the operator can easily remove the molded article from the third lower mold Wherein the method comprises the steps of: The method according to claim 2 or 3,
In the final forming step, a first guide portion inserted into the hollow portion of the lower through-hole and the body while the third upper mold is lowered is inserted into the upper through-hole of the upper punch to guide the lowering of the third upper mold Wherein the spline shaft has an involute spline. The method according to claim 2 or 3,
In the cold forging step, when the upper second spline groove forming part is worn by the repeated final molding step, the operation of the final molding step is stopped, the lower mold is separated from the body part, And further includes a mold resetting step of re-inserting the molding part so as to be fixed on the upper side of the body part, thereby extending the service life of the third lower mold relatively to prevent the cost increase and waste of resources. A method for forging a parking gear for a transmission having a spline. A third upper mold including a third upper body having a cylindrical shape and a first upper punch having a through hole having a predetermined diameter formed on a bottom surface of the third upper body, ,
And a second involute spline forming unit having a cylindrical third lower body and a protrusion shape spaced apart from the outer circumferential surface of the lower through-hole formed on the upper surface of the third lower body at regular intervals along the circumferential direction, And a third lower mold for forming a second involute spline along an outer circumferential surface of the third lower mold. The forging gear forging device for a transmission having the involute spline includes: 9. The method of claim 8,
The parking gear forging apparatus includes a cylindrical second upper body, a second upper mold formed on a bottom surface of the second upper body and including an upper pressing surface for pressing the first preform,
And a second lower seating surface formed on the upper surface of the second lower body for hot forging by pressing the first preliminarily molded article,
And the second lower body includes a first involute spline forming unit for forming a first involute spline having a predetermined shape on one side of the first preform as the second upper mold descends to press the preform, The second preform is further formed by molding the second preliminarily molded product by forging hot forging with the third mold so as to increase the tooth strength by molding while maintaining the metal flow of the second preliminarily molded article. Fork gear for a transmission having a lute spline. 10. The method of claim 9,
The second spline forming portion is formed in a shape complementary to the second involute spline along the circumferential direction of the outer circumferential surface of the lower through hole so as to form a more elaborate second spline tooth by machining the first involute spline of the pre- A second spline tooth forming portion and a second involute spline groove formed on the outer circumferential surface of the lower through hole so as to protrude outward along a circumferential direction of the outer circumferential surface of the lower through hole and spaced apart at regular intervals to form a second spline groove between the involute spline teeth. Wherein the second spline groove forming part is formed in a shape of a second spline groove. 11. The method according to claim 9 or 10,
The third mold further includes a body for inserting and fixing the third lower mold on the upper side,
A first lower knockout for allowing a worker to easily take out a molded product from a third lower mold by pushing up the molded product after the final molded product is molded in a cylindrical shape having a through hole having a predetermined diameter; A space is formed between the third upper and lower molds and the third preform to support the first lower knockout, and the volume of the third preform is moved toward the space, thereby generating a twist phenomenon, And a spring device for preventing breakage of the mold. The forging gear for fork gear for a transmission having an involute spline. 12. The method of claim 11,
The first lower knockout includes a ring-shaped outer fixed ring having a predetermined height on one side of the bottom surface and a ring-shaped inner fixed ring having a predetermined height on the other side to fix the spring device in the space between the rings Wherein the spring device is capable of restricting lateral movement of the spring device. 12. The method of claim 11,
Wherein the body portion further includes a first guide portion which is positioned in the hollow portion of the lower through hole and the body portion and is inserted into the upper through hole as the upper punch descends to guide the lowering of the upper punch accurately. A parking gear forging device for a transmission having a spline.

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