Enveloping forming method for an arc tooth conical gear based on local forming-global setting

Abstract

The present application relates to a kind of based on local shaping-global shaping arc tooth conical gear envelope forming method, comprising the following steps: S1, preform initial position determination;S2, local shaping-stage one;S3, local shaping-stage two;S4, local shaping-stage three;S5, global shaping;S6, demoulding shape retention;S7, ejection.The upper die of tooth profile cavity in local shaping process is inclined and contacted with the local blank, not only can reduce forming force, and the upper die makes multiple degrees of freedom envelope movement, can improve metal fluidity, tooth profile filling is full;Global shaping process, the upper die is returned to normal and vertically fed down, can greatly improve the forming accuracy of arc tooth conical gear;Demoulding shape retention process, the upper die makes multiple degrees of freedom demoulding movement, avoids the interference of upper die and the tooth profile of the formed arc tooth conical gear in demoulding process, can guarantee the forming accuracy of arc tooth conical gear.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic forming manufacturing of arc tooth bevel gear, and more particularly to an arc tooth bevel gear envelope forming method based on local forming-global setting. BACKGROUND

[0002] The arc tooth bevel gear is widely used in aerospace, ship, automobile and many other industrial fields because it can transmit the motion and power between two intersecting shafts, has high load capacity, stable transmission and large overlap coefficient. However, the arc tooth bevel gear has a complex structure and a tooth shape with an inverted cone structure, which makes it extremely difficult to manufacture. At present, the main machining method of the arc tooth bevel gear is milling, which has low material utilization, long processing cycle and destroys metal flow lines, and cannot meet the requirements of high performance and high efficiency manufacturing of the arc tooth bevel gear. Metal plastic forming is a high performance and high efficiency manufacturing technology for gear parts. However, if the arc tooth bevel gear is formed by using the global plastic forming process, it is easy to form a deformation dead zone, and the inverted tooth shape of the arc tooth bevel gear cannot be demolded after the forming is completed, thereby making it difficult to form the arc tooth bevel gear by using the global plastic forming process. SUMMARY

[0003] The technical problem to be solved by the present application is to provide an arc tooth bevel gear envelope forming method based on local forming-global setting, which can not only reduce the forming force, improve the metal flowability, improve and ensure the forming precision of the arc tooth bevel gear, but also improve the mechanical properties and fatigue strength of the arc tooth bevel gear, and finally obtain an arc tooth bevel gear with full tooth shape filling, high precision, good mechanical properties and high fatigue strength.

[0004] The technical solution adopted by the present application to solve the technical problem is to construct an arc tooth bevel gear envelope forming method based on local forming-global setting, which comprises the following steps:

[0005] S1, a preform with a hole shaft rod is placed into the annular hole of the lower model cavity of the envelope forming die, and the large end lower end surface of the preform is ensured to be in contact with the upper horizontal surface in the lower model cavity; the envelope forming die comprises an upper die and a lower die, the upper die with a tooth-shaped cavity forms the tooth shape of the forged piece, and the lower die forms the hole shaft rod and the lower surface of the web of the forged piece;

[0006] S2, the included angle between the upper die axis and the vertical axis of the forming equipment is adjusted to γ1, the upper die with the tooth-shaped cavity performs envelope motion around the envelope center, that is, the inclination angle of the upper die during the envelope motion is γ1, and at the same time, the upper die performs feeding motion along the vertical axis of the forming equipment, the preform metal flows in multiple directions and gradually fills the tooth-shaped cavity of the upper die, and when the feeding amount of the upper die along the vertical axis of the forming equipment reaches the preset value h1, the envelope motion and the feeding motion of the upper die are stopped;

[0007] S3, after the upper die completely stops moving, the angle between the upper die axis and the vertical axis of the forming equipment is adjusted to γ2, where γ2<γ1, the upper die with the tooth-shaped cavity continues to make envelope motion around the envelope center of rotation, that is, the inclination angle of the envelope motion of the upper die in this process is γ2, at the same time, the upper die makes feeding motion along the vertical axis of the forming equipment, the metal of the preform formed in S2 continues to flow in multiple directions and gradually fills the tooth-shaped cavity of the upper die, when the feeding amount of the upper die along the vertical axis of the forming equipment reaches the preset value h2, the envelope motion and the feeding motion of the upper die are stopped, at this time, the shape of the preform formed is closer to the shape of the forged arc-tooth conical gear than that of the preform formed in S2;

[0008] S4, after the upper die completely stops moving, the angle between the upper die axis and the vertical axis of the forming equipment is adjusted to γ3, where γ3<γ2<γ1, the upper die with the tooth-shaped cavity continues to make envelope motion around the envelope center of rotation, that is, the inclination angle of the envelope motion of the upper die in this process is γ3, at the same time, the upper die makes feeding motion along the vertical axis of the forming equipment, the metal of the preform formed in S3 continues to flow in multiple directions and gradually fills the tooth-shaped cavity of the upper die, when the feeding amount of the upper die along the vertical axis of the forming equipment reaches the preset value h3, the envelope motion and the feeding motion of the upper die are stopped, at this time, the shape of the preform formed is closer to the shape of the forged arc-tooth conical gear than that of the preform formed in S3;

[0009] S5, after the upper die completely stops moving, the upper die is returned to the normal position, that is, the upper die axis is adjusted to coincide with the vertical axis of the forming equipment, the upper die only makes feeding motion along the vertical axis of the forming equipment downward, when the feeding amount of the upper die along the vertical axis of the forming equipment reaches the preset value h4, the feeding motion of the upper die is stopped, the overall shaping process is completed, at this time, the forged arc-tooth conical gear is in complete contact with the upper die and the lower die, the profile of the forged arc-tooth conical gear is consistent with the geometric shape of the upper die and the lower die;

[0010] S6, after the overall shaping process is completed, the upper die axis is still in the coinciding state with the vertical axis of the forming equipment, the upper die is driven to make circumferential rotation motion along the tooth shape rotation direction of the forged arc-tooth conical gear and linear motion upward along the vertical axis of the forming equipment according to the motion path planning of the upper die, so as to realize the demolding and shape preservation of the forged arc-tooth conical gear;

[0011] S7, the top ring makes linear motion upward to eject the forged arc-tooth conical gear from the lower die.

[0012] In the scheme, the design method of the forged arc tooth bevel gear is: in order to prevent the tooth shape small end corner from being too narrow at the corresponding die cavity, resulting in large metal flow resistance and tooth shape small end corner filling defect, the tooth shape small end of the forged arc tooth bevel gear is extended to the intersection with the horizontal plane where the tooth shape minimum end tooth top is located; in order to improve the die life and avoid part of the tooth shape large end of the tooth die exposed outside the die base, the tooth shape large end of the gear is extended to the intersection with the horizontal plane where the maximum tooth root diameter is located; the draft slope is arranged on the inner and outer surfaces of the gear hole shaft, and part of the upper end of the outer surface of the gear hole shaft is kept without slope to prevent the forging from sticking to the upper die during demolding; the horizontal flash is designed on the horizontal plane where the maximum diameter of the tooth root of the forged arc tooth bevel gear is located, and the thickness of the horizontal flash is a.

[0013] In the scheme, the design method of the preform is: the preform lower part hole shaft is reduced by b on the basis of the size of the forged arc tooth bevel gear hole shaft designed in step S2 to ensure that the preform can be smoothly put into the lower die; the shape of the upper part of the preform is shaped with the shape of the upper part of the forged arc tooth bevel gear, and the geometric shape is determined by finite element simulation.

[0014] In the scheme, the design method of the upper die is: the intersection part of the upper surface of the designed forged arc tooth bevel gear flash above the entity and the upper die base is obtained according to Boolean operation, and the intersection part is cut off on the upper die base to obtain the upper die with tooth shape cavity; in order to avoid the contact between the upper die and the lower die during local forming, a circle of horizontal plane is reserved outside the upper die cavity, assuming that the maximum radius of the horizontal plane is r, and the slope is set outside the maximum horizontal plane radius r upwards to obtain the envelope forming upper die.

[0015] The design method of the lower die is: the intersection part of the lower surface of the forged arc tooth bevel gear flash below the entity and the lower die base is obtained according to Boolean operation, and the intersection part is cut off on the lower die base to obtain the lower die with shaft and web cavity.

[0016] In the scheme, the envelope motion design method in steps S2-S4 is: the envelope rotation center is always at the center of the upper die intermediate boss surface; in step S2, the upper die axis and the vertical axis of the forming equipment always maintain a γ1 angle; in step S3, the upper die axis and the vertical axis of the forming equipment always maintain a γ2 angle; in step S4, the upper die axis and the vertical axis of the forming equipment always maintain a γ3 angle; the upper die rotates around its own axis while revolving around the vertical axis of the forming equipment, the two rotation speeds are equal and constant, and the rotation directions are opposite, which ensures that the upper die with tooth shape cavity and the tooth shape of the forged arc tooth bevel gear always satisfy the envelope geometric motion relationship; the lower die is fixed and immovable.

[0017] In the above scheme, in the steps S2-S5, the feed amount determination method is as follows: in step S2, the upper die is fed to a position where the minimum distance from the lower die is the flash thickness a in the state that the upper die is inclined by γ1, and the vertical distance from this position to the initial position of the upper die is the feed amount h1; the determination method of the feed amount h2 in step S3 is as follows:

[0018] h2=r(sinγ1-sinγ2) (4)

[0019] The determination method of the feed amount h3 in step S4 is as follows:

[0020] h3=r(sinγ2-sinγ3) (5)

[0021] The determination method of the feed amount h4 in the overall setting stage in step S5 is as follows:

[0022] h4=rsinγ3 (6).

[0023] In the above scheme, in the step S6, the upper die demolding movement design method is as follows: the upper die is moved out of the die in a multi-degree-of-freedom movement, that is, the upper die is moved vertically upward while being rotated circumferentially in the direction of the tooth profile of the gear forging of the spiral bevel gear; assuming that the angular velocity of the circumferential rotation of the upper die is w and the vertical upward movement speed of the upper die is v, the relationship p=w / v is satisfied, and the value range of p is obtained through geometric movement simulation.

[0024] The spiral bevel gear envelope forming method based on local forming and overall setting according to the present application has the following beneficial effects:

[0025] 1. In the local forming process of the method, the upper die with a tooth profile cavity is inclined and locally contacted with the blank, which can not only reduce the forming force, but also improve the metal fluidity and tooth profile filling through multi-degree-of-freedom envelope movement of the upper die;

[0026] 2. In the overall setting process of the method, the upper die is returned to the normal position and fed vertically downward, which can greatly improve the forming precision of the spiral bevel gear;

[0027] 3. In the demolding and shape preserving process of the method, the upper die is moved out of the die in a multi-degree-of-freedom movement, which avoids the interference between the upper die and the tooth profile of the formed spiral bevel gear in the demolding process, and can ensure the forming precision of the spiral bevel gear.

[0028] 4. The method has high material utilization rate and manufacturing efficiency, and can obtain continuous metal flow lines under repeated rolling of the upper die and the lower die, thereby greatly improving the mechanical properties and fatigue strength of the spiral bevel gear. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present application will be further described below in combination with the drawings and examples, and the drawings are as follows:

[0030] Figure 1 is a part drawing of an arc tooth bevel gear;

[0031] Figure 2 is a top view of an arc tooth bevel gear;

[0032] Figure 3 is a local forming-global setting-drawing shape flow chart of an arc tooth bevel gear;

[0033] Figure 4 is a local forming-global setting process of an arc tooth bevel gear;

[0034] Figure 5 is a local forming-global setting process (contact area) of an arc tooth bevel gear;

[0035] Figure 6 is a schematic diagram of a narrow mold cavity and exposed tooth profile outside the mold when the tooth profile is not extended;

[0036] Figure 7 is a schematic diagram of tooth profile extension of an arc tooth bevel gear;

[0037] Figure 8 is a forging drawing of an arc tooth bevel gear;

[0038] Figure 9 is a preform drawing of an arc tooth bevel gear;

[0039] Figure 10 is a schematic diagram of an upper die of an arc tooth bevel gear;

[0040] Figure 11 is a schematic diagram of a comparison between a tooth profile of a simulation result and a standard tooth profile. DETAILED DESCRIPTION

[0041] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the drawings.

[0042] The arc tooth bevel gear is composed of an upper part of a web and an inverted cone structure tooth profile and a lower part of a hole shaft, as shown in Figure 1 , the hole shaft has a height of 60 mm, an inner diameter of 104 mm, an outer diameter of 133.4 mm, the web and the tooth profile have a height of 27 mm, the maximum diameter is 200 mm, and the tooth profile has an inverted cone structure, as shown in Figure 2 .

[0043] The present application is based on a local forming-global setting arc tooth bevel gear envelope forming method, which comprises the following steps:

[0044] S1, the multi-degree-of-freedom envelope forming manufacturing process of the high-performance arc tooth bevel gear of local forming-global setting-drawing shape is:

[0045] S11, initial position determination of the preform: as shown in Figure 3 (a), the preform 1 with a hole shaft is put into the annular hole of the lower die 2 cavity, ensuring that the lower end surface of the large end of the preform 1 is in contact with the upper horizontal surface in the cavity of the lower die 2;

[0046] S12, partial forming-stage 1: adjust the angle between the axis of the upper die 3 and the vertical axis of the forming equipment to γ1=1.5°, the upper die 3 with a tooth-shaped cavity makes envelope motion around the envelope center of rotation, that is, the inclination angle of the envelope motion of the upper die 3 in this process is 1.5°, at the same time, the upper die 3 makes a feeding motion along the vertical axis of the forming equipment at a speed of 2mm / s, the metal of the preform 1 flows in multiple directions and gradually fills the tooth-shaped cavity of the upper die 3, when the feeding amount of the upper die 3 along the vertical axis of the forming equipment reaches the preset value h1=11.6mm, stop the envelope motion and feeding motion of the upper die 3, as shown in Figure 3 (b);

[0047] S13, partial forming-stage 2: after the upper die 3 completely stops moving, adjust the angle between the axis of the upper die 3 and the vertical axis of the forming equipment to γ2=1°, the upper die 3 with a tooth-shaped cavity continues to make envelope motion around the envelope center of rotation, that is, the inclination angle of the envelope motion of the upper die 3 in this process is 1°, at the same time, the upper die 3 makes a feeding motion along the vertical axis of the forming equipment at a speed of 2mm / s, the metal of the preform 4 after S12 forming continues to flow in multiple directions and gradually fills the tooth-shaped cavity of the upper die 3, when the feeding amount of the upper die 3 along the vertical axis of the forming equipment reaches the preset value h2=0.982mm, stop the envelope motion and feeding motion of the upper die 3, at this time, the shape 5 of the preform formed is closer to the shape of the arc tooth bevel gear forging than the preform 4 after S12 forming, as shown in Figure 3 (c);

[0048] S14, partial forming-stage 3: after the upper die 3 completely stops moving, adjust the angle between the axis of the upper die 3 and the vertical axis of the forming equipment to γ3=0.5°, the upper die 3 with a tooth-shaped cavity continues to make multi-degree-of-freedom envelope motion around the envelope center of rotation, that is, the inclination angle of the envelope motion of the upper die 3 in this process is 0.5°, at the same time, the upper die 3 makes a feeding motion along the vertical axis of the forming equipment at a speed of 2mm / s, the metal of the preform 5 after S13 forming continues to flow in multiple directions and gradually fills the tooth-shaped cavity of the upper die 3, when the feeding amount of the upper die 3 along the vertical axis of the forming equipment reaches the preset value h3=0.983mm, stop the envelope motion and feeding motion of the upper die 3, at this time, the shape 6 of the preform formed is closer to the shape of the arc tooth bevel gear forging than the preform 5 after S13 forming, as shown in Figure 3 (d);

[0049] S15, overall setting: after the upper die 3 completely stops moving, the upper die 3 is adjusted to be coincident with the vertical axis of the forming equipment, and the upper die 3 is fed along the vertical axis of the forming equipment at a speed of 2 mm / s, when the feeding amount of the upper die 3 along the vertical axis of the forming equipment reaches a preset value h4=0.983 mm, the feeding movement of the upper die 3 is stopped, and the overall setting process is completed, at this time, the arc tooth bevel gear forging 7 is in complete contact with the upper die 3 and the lower die 2, the profile of the arc tooth bevel gear forging 7 is consistent with the geometric shape of the upper die 3 and the lower die 2, and the forming geometric precision is high, as shown in Figure 3 (e) shown; the arc tooth bevel gear local forming-overall setting forming process is as shown in Figure 4 and Figure 5 ;

[0050] S16, demolding and shaping: after the overall setting process is completed, the axis of the upper die 3 is still coincident with the vertical axis of the envelope forming equipment, the upper die 3 is driven to rotate circumferentially along the tooth shape rotation direction of the arc tooth bevel gear forging 7 while moving linearly upward along the vertical axis of the forming equipment according to the movement path planning of the upper die 3, and the demolding and shaping of the arc tooth bevel gear forging 7 is realized, as shown in Figure 3 (f) shown;

[0051] S17, ejection: the top ring moves linearly upward to eject the arc tooth bevel gear forging from the lower die;

[0052] S2, in step S1, the arc tooth bevel gear forging design method is: in order to prevent the tooth shape small end corner from being too narrow at the corresponding die cavity, as shown in Figure 6 , resulting in large metal flow resistance and defects such as tooth shape small end corner underfilling, the arc tooth bevel gear tooth shape small end is extended to the intersection with the horizontal plane where the tooth shape minimum end tooth tip is located, as shown in Figure 7 ; in order to improve the die life and avoid part of the tooth shape large end of the tooth die being exposed outside the die base, as shown in Figure 6 , the gear tooth shape large end is extended to the intersection with the horizontal plane where the maximum tooth root diameter is located, as shown in Figure 7 ; the 1° draft angle is arranged on the inner and outer surfaces of the gear hole shaft, and a 20 mm high non-inclination section is reserved on the upper end of the outer surface of the gear hole shaft to prevent the forging from sticking to the upper die during demolding; the inner and outer horizontal flash is designed on the horizontal plane where the maximum diameter of the tooth root of the arc tooth bevel gear is located, and the thickness a is 2 mm, as shown in Figure 8 ;

[0053] S3, in step S11, the preform design method is: as shown in Figure 9As shown, the lower part of the preform with hole shaft is reduced by 0.5mm on the basis of the shaft size of the forged piece of the involute splined bevel gear designed in step S2 to ensure that the preform can be smoothly put into the lower die; the shape of the upper part of the preform is profiled with the shape of the upper part of the forged piece of the involute splined bevel gear, and the geometric shape is determined to be 187.2mm in diameter and 38.75mm in height through finite element simulation;

[0054] S4, in step S1, the envelope forming die includes an upper die and a lower die, the upper die with tooth-shaped cavity forms the tooth shape of the forged piece, and the lower die forms the hole shaft and the lower surface of the web of the forged piece;

[0055] The design method of the upper die is as follows: the intersection part of the entity above the flash upper surface of the forged piece of the involute splined bevel gear designed in step S2 and the upper die base body is obtained according to Boolean operation, and the intersection part is cut off on the upper die base body, so that the upper die with tooth-shaped cavity is obtained; in order to avoid the contact between the upper die and the lower die in the local forming process, a circle of horizontal surface is reserved outside the upper die cavity, the maximum radius of the horizontal surface is r is 112.6mm, and a slope of 5° is arranged outside the maximum horizontal surface radius upwards, so that the final upper die of envelope forming is obtained, as shown in Figure 10 ;

[0056] The design method of the lower die is as follows: the intersection part of the entity below the flash lower surface of the forged piece of the involute splined bevel gear designed in step S2 and the lower die base body is obtained according to Boolean operation, and the intersection part is cut off on the lower die base body, so that the lower die with shaft and web cavity is obtained;

[0057] S5, in steps S12-S14, the envelope motion design method is as follows: the envelope rotation center is always at the center of the surface of the middle boss in the upper die; in stage 1 of local forming in step S12, the upper die axis and the equipped vertical axis always keep a γ1=1.5° angle; in stage 2 of local forming in step S13, the upper die axis and the equipped vertical axis always keep a γ2=1° angle; in stage 3 of local forming in step S14, the upper die axis and the equipped vertical axis always keep a γ3=0.5° angle; the upper die revolves around its own axis while revolving around the equipped vertical axis, the two rotation speeds are equal, both are 1r / s, the rotation directions are opposite, and it is ensured that the upper die with tooth-shaped cavity and the tooth shape of the forged piece of the involute splined bevel gear always satisfy the envelope geometric motion relationship; the lower die is fixed and immovable;

[0058] S6, in steps S12-S15, the feed amount determination method of each stage is as follows: in stage 1 of local forming in step S12, the upper die is fed to a distance of 2mm from the lower die minimum distance, which is the flash thickness, and then the feeding is stopped, the vertical distance from this position to the initial position of the upper die is the feed amount h1=11.6mm; the feed amount h2 of stage 2 of local forming in step S13 is determined as 0.982mm by formula (1),

[0059] h2 = r · (sin γ1 - sin γ2) (1)

[0060] The local forming stage 3 feed amount h3 in step S14 is determined as 0.983 mm by formula (2),

[0061] h3 = r · (sin γ2 - sin γ3) (2)

[0062] The overall shaping stage feed amount h4 in step S15 is determined as 0.983 mm by formula (3),

[0063] h4 = r · sin γ3 (3)

[0064] S7, in step S16, if the upper die single degree of freedom vertically upward movement demolding, the upper die will remove the S15 formed arc tooth bevel gear forging with inverted tooth shape, thereby causing the arc tooth bevel gear forging to be scrapped;

[0065] The upper die demolding movement design method is that the upper die makes multi-degree of freedom movement demolding, that is, the upper die makes circumferential rotation movement along the tooth shape rotation direction of the arc tooth bevel gear forging while vertically upward movement. Assuming that the circumferential rotation angular velocity of the upper die is w and the vertically upward movement velocity of the upper die is v, then the relationship p = w / v is met. The value range of p is obtained through geometric motion simulation as 0.075 ≤ p ≤ 0.45.

[0066] Preferably, the swing angles γ1, γ2, γ3 of the local forming different stages in steps S12-S14 meet γ3 < γ2 < γ1, because the smaller the swing angle before overall shaping, the closer the formed forging tooth shape to the designed forging tooth shape, thereby the forming force of the overall shaping stage can be reduced; and the local forming stages are not limited to the three stages listed in the present application, and there can be i (i ≥ 1) stages, and the swing angles γ i (i ≥ 1) meet the relationship: γ i < γ i-1 < … < γ1.

[0067] The tooth profile of a certain section parallel to the shaft section in the finite element simulation result is extracted, which is compared with the tooth profile of the standard arc tooth bevel gear at this section, as shown in Figure 11 The black profile in the figure is the standard tooth profile at this section, and the red profile is the simulation result tooth profile at this section. The simulation result tooth profile is coincided with the standard tooth profile, proving that the high-performance arc tooth bevel gear envelope forming manufacturing method based on local forming-overall shaping-demolding shaping proposed in the present application can manufacture high-precision arc tooth bevel gears.

[0068] The present application is based on the local forming process of the local forming-global setting enveloping forming method of the curved-tooth conical gear, the upper die of the toothed cavity is inclined and locally contacted with the blank, which can not only reduce the forming force, but also make the upper die move in multiple degrees of freedom, improve the metal flowability, and fill the tooth profile fully; in the global setting process, the upper die is returned to normal and vertically fed downward, which can greatly improve the forming precision of the curved-tooth conical gear; in the demolding and shaping process, the upper die moves in multiple degrees of freedom, avoids the interference between the upper die and the tooth profile of the formed curved-tooth conical gear in the demolding process, and can ensure the forming precision of the curved-tooth conical gear.

[0069] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative but not restrictive. Those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which are all within the protection of the present application.

Claims

1. A method for envelope forming of arc-tooth bevel gears based on local forming and overall shaping, characterized in that, Includes the following steps: S1. Place the preformed shaft with holes into the annular hole of the lower mold cavity of the enveloping forming mold, ensuring that the lower end face of the large end of the preformed shaft is in contact with the upper horizontal surface in the lower mold cavity; the enveloping forming mold includes an upper mold and a lower mold, the upper mold with toothed cavity forms the toothed shape of the forging, and the lower mold forms the perforated shaft and the lower surface of the web of the forging; S2. Adjust the angle between the upper mold axis and the vertical axis of the forming equipment to... The upper mold with a toothed cavity undergoes an envelope motion around its envelope rotation center; that is, the tilt angle of the upper mold during this envelope motion is... Simultaneously, the upper die moves downward along the vertical axis of the forming equipment, and the preform metal flows in multiple directions and gradually fills the toothed cavity of the upper die. When the feed amount of the upper die along the vertical axis of the forming equipment reaches the preset value... h After step 1, stop the envelope motion and feed motion of the upper mold; S3. After the upper mold has completely stopped moving, adjust the angle between the upper mold axis and the vertical axis of the forming equipment to... ,in The upper mold with the toothed cavity continues to perform an envelope motion around the envelope rotation center; that is, the tilt angle of the upper mold's envelope motion during this process is... Simultaneously, the upper die moves downward along the vertical axis of the forming equipment. The preform metal formed by S2 continues to flow in multiple directions and gradually fills the toothed cavity of the upper die. When the feed amount of the upper die along the vertical axis of the forming equipment reaches the preset value... h After step 2, the enveloping motion and feeding motion of the upper die are stopped. At this time, the shape of the preform formed is closer to the shape of the arc tooth bevel gear forging than the preform formed after step S2. S4. After the upper mold has completely stopped moving, adjust the angle between the upper mold axis and the vertical axis of the forming equipment to... ,in The upper mold with the toothed cavity continues to perform an envelope motion around the envelope rotation center; that is, the tilt angle of the upper mold's envelope motion during this process is... Simultaneously, the upper die moves downward along the vertical axis of the forming equipment. The preformed metal after S3 forming continues to flow in multiple directions and gradually fills the toothed cavity of the upper die. When the feed amount of the upper die along the vertical axis of the equipment reaches the preset value... h After step 3, the enveloping motion and feed motion of the upper die are stopped. At this time, the shape of the preform formed is closer to the shape of the arc tooth bevel gear forging than the preform formed after step S3. S5. After the upper die has completely stopped moving, return the upper die to its original position, that is, adjust the upper die axis to coincide with the vertical axis of the forming equipment. The upper die will only perform a downward feed movement along the vertical axis of the forming equipment. When the feed amount of the upper die along the vertical axis of the forming equipment reaches the preset value... h After step 4, stop the upper die feeding motion to complete the overall shaping process. At this time, the arc-tooth bevel gear forging is in complete contact with the upper and lower dies, and the outline of the arc-tooth bevel gear forging is consistent with the geometry of the upper and lower dies. S6. After the overall shaping process is completed, the upper die axis and the vertical axis of the forming equipment are still in the same state. According to the upper die motion path planning, the upper die is driven to rotate circumferentially along the tooth direction of the arc tooth bevel gear forging while moving linearly upward along the vertical axis of the forming equipment to achieve demolding and shape retention of the arc tooth bevel gear forging. S7. The top ring moves upward in a straight line, ejecting the arc-tooth bevel gear forging from the lower die; The envelope motion design method in steps S2-S4 is as follows: the envelope rotation center is always at the center of the surface of the upper die's middle boss; in step S2, the upper die axis and the vertical axis of the forming equipment are always kept in the same position. Angle; in step S3, the upper die axis and the vertical axis of the forming equipment are always kept at the same angle. Angle; in step S4, the upper die axis and the vertical axis of the forming equipment are always kept at the same angle. The included angle; the upper die rotates around its own axis while revolving around the vertical axis of the forming equipment. The two rotational speeds are equal and constant, and the rotation directions are opposite, ensuring that the upper die with the toothed cavity and the toothed bevel gear forging always satisfy the envelope geometric motion relationship; the lower die is fixed. In steps S2-S5, the method for determining the feed rate is as follows: In step S2, the upper die is tilted... In this state, the upper die is fed to the minimum distance from the lower die, which is equal to the flash thickness. a Stop feeding when the flash thickness is reached. a The thickness of the horizontal flash on the inner and outer sides of the plane where the maximum diameter of the tooth root is located is the feed rate. The vertical distance from this position to the initial position of the upper die is the feed rate. h 1; Feed rate in step S3 h The method for determining 2 is as follows: (1) Feed rate in step S4 h The method for determining 3 is as follows: (2) Feed rate during the overall shaping stage in step S5 h The method for determining 4 is as follows: (3) 2. The method for envelope forming of arc-tooth bevel gears based on local forming and overall shaping according to claim 1, characterized in that, The design method for the arc-tooth bevel gear forging is as follows: To prevent the mold cavity corresponding to the corner of the small end of the tooth profile from being too narrow, resulting in high metal flow resistance and incomplete filling at the corner of the small end of the tooth profile, the small end of the arc-tooth bevel gear tooth profile is extended to the intersection with the horizontal plane where the tooth tip of the smallest end of the tooth profile is located; to improve the mold life and avoid a part of the large end of the tooth profile on the mold being exposed on the outside of the mold base, the large end of the gear tooth profile is extended to the intersection with the horizontal plane where the maximum tooth root diameter is located; draft angles are set on both the inner and outer surfaces of the gear shaft with holes, and a section without draft angle is retained at the upper part of the outer surface of the gear shaft with holes to prevent the forging from sticking to the upper mold during demolding; inner and outer horizontal flashes are designed on the horizontal plane where the maximum diameter of the arc-tooth bevel gear tooth root is located, and the thickness of the horizontal flashes is [missing information]. a .

3. The method for envelope forming of arc-tooth bevel gears based on local forming and overall shaping according to claim 2, characterized in that, The design method of the preform is as follows: the lower part of the preform with a hole shaft is reduced by b on one side based on the size of the perforated shaft of the arc-tooth bevel gear forging designed in step S2, so as to ensure that the preform can be smoothly placed into the lower mold; the shape of the upper part of the preform is similar to the shape of the upper part of the arc-tooth bevel gear forging, and its geometry is determined by finite element simulation.

4. The method for envelope forming of arc-tooth bevel gears based on local forming and overall shaping according to claim 3, characterized in that, The design method of the upper mold is as follows: the intersection of the solid above the flash surface of the designed arc-tooth bevel gear forging and the upper mold base is obtained according to Boolean operation, and the intersection is cut off on the upper mold base to obtain an upper mold with toothed cavity. In order to avoid the upper mold and the lower mold from contacting each other during the local forming process, a horizontal surface is retained on the outside of the upper mold cavity. Assuming that the maximum radius of the horizontal surface is r, an upward slope is set on the outside of the maximum horizontal surface radius r to obtain the envelope forming upper mold. The design method of the lower die is as follows: based on the intersection of the solid below the flash of the arc-tooth bevel gear forging and the lower die base obtained by Boolean operation, the intersection is cut off on the lower die base to obtain a lower die with a shaft and web cavity.

5. The method for envelope forming of arc-tooth bevel gears based on local forming and overall shaping according to claim 1, characterized in that, In step S6, the upper die demolding motion design method is as follows: the upper die performs multi-degree-of-freedom demolding motion, that is, the upper die rotates circumferentially along the helical direction of the spiral tooth profile of the arc-tooth bevel gear forging while simultaneously moving vertically upward; assuming the angular velocity of the upper die's circumferential rotation is... w， The speed at which the upper mold moves vertically upward is v Then the following relationship is satisfied: p = w / v , p The range of values ​​is obtained through geometric motion simulation.

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