Die for forming crowned teeth

Abstract

The present invention discloses a concave die for forming a drum-shaped gear, comprising a concave die body, the concave die body having a central inner hole, an inner wall of the central inner hole being provided with a mold core of an annular structure, the mold core comprising an upper forming section, a middle forming section and a lower forming section arranged in sequence along its axial direction, wherein the elastic modulus of the middle forming section is smaller than the elastic modulus of the upper forming section and the lower forming section, and the inner ring of the mold core has a forming gear. The present invention has the beneficial effect that the drum-shaped gear can be quickly formed by extrusion means, thereby improving the production efficiency of the drum-shaped gear.

Description

Technical Field

[0001] The invention relates to a gear processing die, in particular to a concave die for forming a drum-shaped gear. Background Art

[0002] The tooth profile of a gear has many forms. In order to improve the meshing accuracy of the gear and reduce the meshing noise, some gears have a drum-shaped tooth profile, that is, the tooth has a curved tooth profile in the working circle section, such as the drum-shaped tooth in the planetary reducer. In the tooth width direction, the middle part of the tooth is higher than the two ends of the tooth, that is, the tooth thickness in the middle part of the tooth is greater than the tooth thickness at both ends of the tooth.

[0003] In the prior art, the crown gear can be processed by cutting or grinding, but these processing methods have low material utilization and low processing efficiency. For this reason, it is necessary to design a mold that can quickly form a crown gear. Summary of the invention

[0004] In view of this, the present invention provides a concave die for forming a drum-shaped tooth, which can quickly extrude and form the drum-shaped tooth by extrusion means, thereby improving the production efficiency of the drum-shaped tooth gear.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A die for forming drum-shaped teeth, the key of which is: comprising a die body, the die body having a central inner hole, a die core with an annular structure on the hole wall of the central inner hole, the die core comprising an upper forming section, a middle forming section and a lower forming section arranged in sequence along its axial direction, wherein the elastic modulus of the middle forming section is smaller than the elastic modulus of the upper forming section and the lower forming section, and the inner ring of the die core has forming teeth.

[0007] With the above structure, the mold core is composed of three sections, and the elastic modulus of the middle section is smaller than that of the two end sections, that is, the material hardness of the middle molding section is lower than that of the upper and lower ends. When the gear is extruded on the inner ring of the mold core, the metal material expands under pressure, and the deformation of the middle molding section will be higher than the deformation of the upper molding section and the lower molding section, so that the middle part of the gear tooth shape is higher than the two ends of the tooth shape, thereby completing the extrusion of the drum-shaped tooth, and the gear extrusion molding has high precision and efficiency, and the drum shape is better.

[0008] As a preferred embodiment, the upper forming section, the middle forming section and the lower forming section are installed in the central inner hole in an interference fit manner and are formed into one body. The above structure is convenient for using the die and forming the drum-shaped gear.

[0009] Preferably, the central inner hole is a tapered hole, the circumference of the mold core is a tapered annular surface adapted to the tapered hole, and the taper of the tapered hole and the tapered annular surface is 1 to 2 degrees. The above structure can ensure that the axis of the mold core and the central inner hole have a high degree of coincidence, and can also ensure that after assembly, the tapered annular surface and the tapered hole have a larger effective contact area, so that the reliability of the mold is better.

[0010] Preferably, the upper forming section, the middle forming section and the lower forming section are all made of metal materials, wherein the Rockwell hardness of the upper forming section and the lower forming section is greater than the Rockwell hardness of the middle forming section. The above structure can ensure smooth forming of the drum-shaped teeth.

[0011] Preferably, the compressive strength of the material of the middle forming section is less than that of the material of the upper forming section and the lower forming section. With the above structure, when extruding the gear, the deformation of the middle forming section can be ensured to be higher than that of the upper forming section and the lower forming section, so that the drum gear can be formed smoothly.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] When the die provided by the present invention is used to extrude a gear internally on the die body, the deformation of the middle area of ​​the die core is higher than that of the two end areas, so that the deformation of the middle part of the tooth shape during the forming process is higher than that of the two ends of the tooth shape, thereby achieving one-time extrusion to complete the forming of the drum-shaped tooth, and the extrusion forming of the drum-shaped tooth has high precision and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A top view of the present invention;

[0015] Figure 2 is a cross-sectional view of the present invention;

[0016] Figure 3 It is a cross-sectional view of the die body;

[0017] Figure 4 It is a structural schematic diagram of the drum gear. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with embodiments and drawings.

[0019] like Figure 1 and 2As shown, a die for forming drum-shaped teeth, whose main structure includes a die body 1, the die body 1 has a central inner hole 1a, a core 2 with an annular structure is arranged on the hole wall of the central inner hole 1a, the inner ring of the core 2 has a forming tooth 21, and the core 2 is composed of three parts in its axial direction, namely an upper forming section 2a, a middle forming section 2b and a lower forming section 2c, which are arranged in sequence. The elastic modulus of the middle forming section 2b is smaller than the elastic modulus of the upper forming section 2a and the lower forming section 2c. In this embodiment, the material of the middle forming section 2b is Cr12MoV (cold working die steel), and its compressive strength is 3.4GPa. The materials of the upper forming section 2a and the lower forming section 2c are both YG15 (hard alloy), and their compressive strength is 4GPa.

[0020] like Figure 2 and 4 As shown, during the extrusion molding process of the gear 3 in the mold core 2, the deformation of the middle molding section 2b will be higher than the deformation of the upper molding section 2a and the lower molding section 2c, so that the middle part b of the tooth shape of the gear 3 is higher than the upper end a and the lower end c of the tooth shape during the molding process. The molding of the drum-shaped gear 3 can be completed with only one extrusion, which can effectively improve the processing efficiency of the drum-shaped gear 3.

[0021] For example Figure 2 and 3 As shown, in order to ensure that the axis lines of the mold core 2 and the central inner hole 1a have a high degree of coincidence, the central inner hole 1a is a tapered hole, and the circumference of the mold core 2 is a tapered annular surface matching the tapered hole. The taper of the tapered hole and the tapered annular surface is equal to 1 to 2 degrees. In this embodiment, the taper is preferably set to 1.5 degrees. After the mold core 2 is assembled in the central inner hole 1a, it is necessary to ensure that the effective contact area of ​​the inner and outer cones exceeds 75%.

[0022] The upper molding section 2a, the middle molding section 2b and the lower molding section 2c are integrally molded on the inner wall of the central inner hole 1a in the following manner:

[0023] The upper forming section 2a, the middle forming section 2b and the lower forming section 2c are first fastened together with bolts to form the above-mentioned core 2. The core 2 is integrally processed with a conical annular surface. After the conical annular surface processing is completed, the central inner hole 1a of the die body 1 is heated to expand the conical hole, and then the core 2 is placed in the conical hole as a whole. After the temperature cools naturally and the conical hole shrinks, the core 2 can be tightened. At this time, the bolts are loosened. Due to the large tightening force, the upper forming section 2a, the middle forming section 2b and the lower forming section 2c have become an integral one-piece interference connection on the hole wall of the central inner hole 1a, and then the teeth and other processing are performed on this assembled mold.

[0024] In this embodiment, in order to ensure smooth forming of the drum-shaped teeth, the upper forming section 2a, the middle forming section 2b and the lower forming section 2c are all made of metal materials, wherein the Rockwell hardness of the upper forming section 2a and the lower forming section 2c is greater than the Rockwell hardness of the middle forming section 2b. Specifically, the Rockwell hardness of the upper forming section 2a and the lower forming section 2c is HRC68-70, and the Rockwell hardness of the middle forming section 2b is HRC60-62. The lower the hardness of the middle forming section 2b, the higher the hardness of the upper forming section 2a and the lower forming section 2c, and the more obvious the drum-shaped amount of the drum-shaped teeth.

[0025] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A concave die for forming a drum-shaped tooth, characterized in that: The die body (1) comprises a die body having a central inner hole (1a), a die core (2) having an annular structure being arranged on the hole wall of the central inner hole (1a), the die core (2) comprising an upper molding section (2a), a middle molding section (2b) and a lower molding section (2c) arranged in sequence along its axial direction, wherein the elastic modulus of the middle molding section (2b) is smaller than the elastic modulus of the upper molding section (2a) and the lower molding section (2c), and the inner ring of the die core (2) has molding teeth (21); The central inner hole (1a) is a tapered hole, and the circumference of the mold core (2) is a tapered annular surface adapted to the tapered hole; The upper molding section (2a), the middle molding section (2b) and the lower molding section (2c) are all made of metal materials, wherein the Rockwell hardness of the upper molding section (2a) and the lower molding section (2c) is greater than the Rockwell hardness of the middle molding section (2b).

2. The concave die for forming a drum-shaped tooth according to claim 1, characterized in that: The upper molding section (2a), the middle molding section (2b) and the lower molding section (2c) are installed in the central inner hole (1a) in an interference fit manner and are formed into one piece.

3. The concave die for forming a crown-shaped tooth according to claim 1 or 2, characterized in that: The taper of the tapered hole and the tapered annular surface is equal to 1 to 2 degrees.

4. The concave die for forming a crown-shaped tooth according to claim 3, characterized in that: The taper is equal to 1.5 degrees.

5. The concave die for forming a crown-shaped tooth according to claim 1, characterized in that: The Rockwell hardness of the upper molding section (2a) and the lower molding section (2c) is HRC68-70, and the Rockwell hardness of the middle molding section (2b) is HRC60-62.

6. The concave die for forming a crown-shaped tooth according to claim 1, characterized in that: The compressive strength of the material of the middle forming section (2b) is less than the compressive strength of the materials of the upper forming section (2a) and the lower forming section (2c).

7. The concave die for forming a crown-shaped tooth according to claim 6, characterized in that: The material of the middle forming section (2b) is Cr12MoV, and its compressive strength is 3.4 GPa; the material of the upper forming section (2a) and the lower forming section (2c) is YG15, and its compressive strength is 4 GPa.

Images