CN117161287A - Hot precision forging forming die, system and method for spur gear - Google Patents

Abstract

The invention discloses a spur gear hot precision forging forming mold, system and method in the technical field of spur gear production. The spur gear hot precision forging forming mold includes an upper cover plate, a punch mold, a concave mold, a bottom plate and an ejector rod. ; The concave mold is provided with a spur gear cavity; the lower end surface of the upper cover plate can be connected with the upper end surface of the concave mold; the upper end surface of the bottom plate is fixedly connected to the lower end surface of the concave mold; the upper cover plate is provided with a There is a first through hole; the punch is slidably connected to the first through hole, and the shape of its lower end is adapted to the shape of the inner ring of the workpiece to be processed; the bottom plate is provided with a core coaxial with the spur gear cavity A second through hole; the upper end of the push rod is slidably connected to the second through hole. The spur gear hot precision forging forming mold provided by the present invention is integrated and has high production efficiency; the spur gear hot precision forging forming system is simple to operate and has efficient collaboration; the spur gear hot precision forging forming method using this mold is simple and convenient, and the gear forming is high quality.

Description

A spur gear hot precision forging mold, system and method

Technical field

The invention relates to a spur gear hot precision forging mold, system and method, and belongs to the technical field of spur gear production.

Background technique

Spur gears have the characteristics of "high load and large transmission ratio" and are widely used as drive axle planetary gears and sun gears. The spur gear used in the drive axle of engineering machinery has a large module and is difficult to be directly forged. Currently, the industry mainly relies on cutting processing. Precision forging is a new process that has emerged in recent years. Compared with traditional cutting and forming spur gears, precision forging spur gears have the advantages of high material utilization, high production efficiency, simple process and low production cost, and the tooth root is Has good bending strength and fatigue resistance.

The mold is an indispensable tool in the precision forging process of spur gears. Good mold structural design can make the forging process more efficient, the mold life longer, and the product quality better.

However, most of the existing forging molds are multi-process molds, such as pre-forging dies, final forging dies or split forging dies. During the tooling transfer process, the surface temperature of the blanks decreases, the surface oxidation increases, and the production efficiency is low, etc.; it is complex; The machining process reduces the fluidity of the blank metal, making it difficult to fill the upper and lower corner tooth shapes, requiring a higher forming load. It also leads to a larger tonnage selection for the press, seriously affecting the service life of the final forging die and indirectly affecting the service life of the final forging die. Increased production costs.

Contents of the invention

The purpose of the present invention is to provide a spur gear hot precision forging forming mold, system and method, which can realize the integration of hot precision forging forming of spur gears, improve the efficiency of the forging process and improve the forming quality.

In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

On the one hand, the invention provides a spur gear hot precision forging mold, which includes an upper cover plate, a male die, a female die, a bottom plate and a ejector pin;

The concave mold is provided with a spur gear cavity; the upper cover plate is located above the concave mold, and the lower end surface of the upper cover plate can be connected with the upper end face of the concave mold; the upper end surface of the bottom plate is fixedly connected to the concave mold. End surface of mold;

A first through hole is provided in the upper cover plate; the punch is slidably connected to the first through hole, and the shape of its lower end is adapted to the shape of the inner ring of the workpiece to be processed;

The bottom plate is provided with a second through hole coaxial with the spur gear cavity; the upper end of the ejector rod is slidingly connected to the second through hole, and the axial projection of the outer contour of the upper end of the ejector rod is located on the The axial projection of the root circle of the spur gear cavity is inside.

The spur gear hot precision forging forming mold of the present invention is designed as an integrated molding method, and one set of molds can simultaneously realize the processing processes of upsetting, punching and tooth profile filling. The integrated forming mold not only reduces heat loss during the forging process and refines the gear structure, but also ensures the fluidity of the blank metal, reduces the mold stress of the die, and increases the service life accordingly.

Optionally, the middle part of the top of the ejector pin is provided with a positioning pin for tightly matching the bottom of the workpiece to be processed. The design of the positioning pin on the ejector can not only effectively ensure the uniformity of tooth filling of the blank during the forging process, but also facilitate the demoulding operation of the later forged gear.

Optionally, the positioning pin is a conical protrusion integrally formed with the push rod. The design of the conical protrusion enables the blank before the pier to be positioned more accurately, ensuring the coaxiality accuracy during the inner hole forming.

Optionally, the peripheral portion of the spur gear cavity has an internal tooth cavity corresponding to the module, number of teeth, and indexing circle of the spur gear to be processed, and the internal gear has an inner tooth cavity on each side in the tooth width direction and on the gear profile. There is a processing allowance. The machining allowance with a certain gap ensures further precision machining in the later stage.

Optionally, pressure relief grooves are provided on both sides of the bottom end of the upper cover plate toward the tip circle of the inner tooth cavity. In the final stage of tooth filling, the design of the pressure relief groove can not only reduce the effective stress of metal flow, making it easier to completely fill the upper corners, but at the same time, it can also effectively reduce the mold stress of the die and extend the use of the die. life.

Optionally, the base plate and the female mold are detachably fixed. The removable fixed connection can facilitate the replacement of the corresponding die according to the gear specifications.

Optionally, the contact surface between the bottom plate and the ejector pin is provided with a draft angle of 1°. The design of the draft angle makes it easier for the ejector pin to eject the processed workpiece upward after the gear precision forging is completed.

Optionally, there is a transition fit between the punch and the first through hole, and between the upper end of the ejector pin and the second through hole. The transition-fit connection method makes the punch and ejector easier to disassemble and install.

Optionally, the convex mold, concave mold, bottom plate and ejector pin are all made of stainless steel, with a surface hardness of 62HRC and above. Since the forming mold operates under high temperature and high pressure conditions for a long time, the hot precision forging forming mold made of quenched mold steel has stronger strength, hardness and thermal stability, as well as higher thermal fatigue, endurance and wear resistance.

Optionally, during the spur gear forming process, the upper cover plate, punch mold, concave mold, bottom plate and ejector pin are coaxial. The coaxiality of the mold components during the molding process maximizes the machining accuracy of the workpiece during processing to achieve high-quality finished products.

In a second aspect, the present invention also provides a system for hot precision forging of spur gears, including a box furnace, a press, a mold temperature controller, a manipulator, a demoulding drive structure, and a mold for hot precision forging of spur gears. ;

Specifically, the box-type furnace can be used to heat the billet, and the manipulator can be used to transfer the heated billet to the spur gear cavity of the spur gear hot precision forging mold;

The press has a driving mechanism respectively used to drive the upper cover plate and the punch to move in a vertical direction;

The mold temperature machine can be used to control the temperature of the spur gear forming mold;

The ejection driving mechanism can be used to drive the ejector pin to move in the vertical direction to eject the workpiece in the spur gear cavity.

In the spur gear hot precision forging forming system provided by the invention, the box furnace heats the blank to the required temperature, the manipulator quickly transfers the blank into the processing cavity, the press provides a power source for the processing of the forming gear, and the mold temperature machine is in The constant temperature control of the mold during the processing also allows the blank to avoid various defects such as a rapid drop in deformation temperature and poor metal fluidity. The demoulding drive mechanism quickly demolds and makes the entire production process quick and simple, and the production efficiency is also significantly improved. further improvement.

In a third aspect, the present invention also provides a spur gear hot precision forging forming method using the spur gear hot precision forging mold, including the following steps:

S1: Heating and keeping the mold warm;

Machine a certain positioning hole on one of the end faces of the blank, then heat it to the set temperature and keep it warm;

S2: Transfer the heated and heat-insulated blank into the spur gear cavity so that the positioning hole closely matches the positioning pin on the ejector pin;

S3: Use the press to drive the upper cover plate and the punch to simultaneously squeeze the blank downward along the axial direction of the spur gear cavity until the lower end surface of the upper cover plate contacts the upper end surface of the concave mold to complete the pier. If rough, the upper cover plate is controlled to stop moving;

Control the punch to continue to squeeze the blank downward until it reaches a preset depth in the spur gear cavity, so that the blank fills the internal tooth cavity and completes punching;

S4: Remove the upper cover plate and the punch, and control the ejector pin to push the workpiece in the spur gear cavity upward through the demoulding drive mechanism to complete demolding.

The invention provides a spur gear hot precision forging forming method. Under this method step, the upper cover plate and the punch in the integrated forming mold move together during the upsetting process; during the punching process, the punch continues to move in the axial direction. , punched into holes, and the upper cover restricts the reverse flow of the blank metal, forming a closed reverse extrusion molding of the gear blank, forming a metal streamline perpendicular to the force direction at the tooth root, so that its mechanical properties are improved further improvement.

At the same time, the heat preservation control of the blank and the mold not only avoids the problem of poor metal fluidity of the workpiece caused by the rapid drop in temperature of the replacement mold, but also solves the problem of mold life due to the rapid drop in blank temperature causing the mold to bear greater deformation load. A series of shortcomings that shorten and result in poor economic efficiency.

Optionally, before step S1, spray a release agent on the side wall of the spur gear cavity of the concave mold. The selection of release agent is more conducive to the completion of demoulding.

Optionally, in step S1, heat the mold to 300°C and then keep it warm, use a box furnace to heat the billet to 1000°C and then keep it warm for 1 hour. During the heating process of the billet, the temperature rise rate is set to 30°C/min.

Optionally, in step S3, a 1000-ton closed precision forging press is used to drive and control the upper cover plate and punch. The safety factor is set to 0.8. The movement speed of the upper cover plate is controlled to 20mm/s during the roughening process. The movement speed of the punch is controlled to 20mm/s in the entire process from pier roughening to completion of punching.

According to actual production needs, the selection of specific parameters in steps S1 and S3 further improves the overall performance of the forgings during the hot precision forging of spur gears by the forming mold, and maximizes quality and accuracy.

Further, the method also includes air-cooling the demolded workpiece, and when the temperature of the workpiece drops to room temperature, heat treatment and machining are performed to obtain the finished precision forged gear. After the forged hollow spur gear undergoes machining processes, such as gear shaving or grinding, the roughness and dimensional accuracy required by the technology can be achieved.

Among them, the demolded workpiece has a punched and integrated skin, which is beneficial to protecting the mold from damage; the heat treatment and thermomechanical processing are at least used for finishing the inner hole and the upper and lower end surfaces of the gear.

Compared with the prior art, the beneficial effects achieved by the present invention are:

(1) The spur gear hot precision forging forming mold of the present invention is an integrated forming mold. The upper cover plate and the punch work together to complete the upsetting process, and the punch independently completes the punching process. One set of molds can complete the complex processes of upsetting and punching at the same time. The integrated design not only reduces mold development and costs; it also avoids low yields and low mold life caused by heat loss during mold replacement. question;

(2) The system used for hot precision forging of spur gears makes the entire production process fast and simple, and the production efficiency has been significantly further improved.

(3) The hot precision forging forming method using spur gear hot precision forging molds is simple to operate, which not only improves the tooth quality and fatigue strength at the tooth root; it also effectively reduces the die stress of the die and extends the service life of the die; It also effectively ensures the uniformity of tooth filling of the blank during the forging process.

Description of drawings

Figure 1 is a three-dimensional schematic diagram of a hot precision forging spur gear mold according to an embodiment of the present invention;

Figure 2 is a schematic axial cross-sectional structural diagram of the hot precision forging spur gear mold shown in Figure 1.

Implementation

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention, but cannot be used to limit the scope of the present invention.

Example 1

As shown in Figures 1 and 2, the present invention provides a spur gear hot precision forging mold, which includes a male die 1, an upper cover plate 2, a female die 4, a bottom plate 5 and a ejector pin 6;

The concave mold 4 is provided with a spur gear cavity; the upper cover plate 2 is located above the concave mold 4, and the lower end surface of the upper cover plate 2 can be connected with the upper end face of the concave mold 4; the bottom plate 5 is The end face is fixedly connected to the lower end face of the concave mold 4;

The upper cover plate 2 is provided with a first through hole; the punch 1 is slidably connected to the first through hole, and the shape of its lower end is adapted to the shape of the inner ring of the workpiece to be processed;

The bottom plate 5 is provided with a second through hole coaxial with the spur gear cavity; the upper end of the ejector rod 6 is slidingly connected to the second through hole, and the axial projection of the outer contour of the upper end of the ejector rod 6 Located inside the axial projection of the tooth root circle of the spur gear cavity.

When this embodiment is applied, due to the integrated molding of the forging mold, blank pre-forging, upsetting and punching operations can be realized without the need to change the mold midway, and the operation is simple. First, the bar blank is heated and kept warm in a box furnace to achieve consistent internal and external temperatures. Then it is transferred to the complete set of forming molds. This process should be as fast as possible to reduce the loss of external surface temperature. Under the action of the press, the upper cover plate 2 and the punch 1 move together during the upsetting process; during the punching process, the punch 1 continues to move along the axial direction to punch the hole, and the upper cover plate 2 restrains the blank metal The reverse flow of the gear blank forms a closed reverse extrusion molding of the gear blank, forming a metal streamline perpendicular to the force direction at the tooth root. The forged hollow spur gear then undergoes a machining process, such as gear shaving or By grinding the teeth, the roughness and dimensional accuracy required by the technology can be achieved.

Example 2

On the basis of Embodiment 1, this embodiment also has the following design:

The middle part of the top of the ejector pin 6 is provided with a positioning pin 7 for tightly matching the bottom of the workpiece to be processed. The position of the positioning pin 7 on the ejector rod is preferably the center position of the top of the ejector rod 6, and the positioning pin 7 is A conical protrusion formed integrally with the ejector pin 6 .

The peripheral portion of the spur gear cavity has an internal tooth cavity corresponding to the module, number of teeth and indexing circle of the spur gear to be processed, and the internal gear is provided with machining allowances on each side in the tooth width direction and on the gear profile. quantity. Specifically, a machining allowance of 2 mm is left on one side in the tooth width direction, and a machining allowance of 1 mm is left on the tooth profile. A certain gap machining allowance is retained to facilitate later machining to improve the dimensional accuracy and roughness of the hole. Spend.

The two sides of the bottom end of the upper cover plate 2 are provided with pressure relief grooves 3 facing the tip circle of the inner tooth cavity. In the late stage of tooth filling, the forming load rises rapidly, but always remains within the safety limit of the press. The pressure relief groove at the lower end of the upper cover plate 2 not only reduces the effective stress of the metal flow, making it easier to completely fill the upper corner , at the same time, it also effectively reduces the mold stress of the die 4 and extends the service life of the die 4.

The base plate 5 and the concave mold 4 are detachably fixed. The detachable connection method makes it easier to replace the corresponding concave mold 4 according to the gear specifications. Specifically, bolts and nuts can be used to fix the base plate. 5 and die 4.

The contact surface between the bottom plate 5 and the ejector pin 6 is provided with a draft angle of 1°, and the contact surface between the bottom plate 5 and the ejector pin 6 has a draft angle of 1°, which facilitates the upward movement of the ejector pin 6 after precision forging is completed. Eject the workpiece.

There is a transition fit between the punch 1 and the first through hole, and between the upper end of the ejector pin 6 and the second through hole. The male mold 1 passes through the first through hole of the upper cover plate 2 and is connected with the upper end of the female mold 4, and the upper end of the ejector pin 6 passes through the second through hole of the bottom plate 5 and is connected with the female mold 4. Fixed connection, in which the transition-fit connection method makes it easier to disassemble the components.

The male mold 1, the female mold 4, the bottom plate 5 and the ejector pin 6 are all cylinders made of quenched mold steel, with a surface hardness of 62HRC and above. Since the forming mold operates under high temperature and high pressure conditions for a long time, the hot precision forging forming mold made of quenched mold steel has stronger strength, hardness and thermal stability, as well as higher thermal fatigue, endurance and wear resistance.

In the spur gear forming process, the upper cover plate 2, the punch 1, the concave die 4, the bottom plate 5 and the ejector 6 are coaxially arranged, so that the processing accuracy of the workpiece can reach a high standard, and the finished product can be processed to achieve high quality. .

Example 3

This embodiment introduces a system for hot precision forging of spur gears, which includes a box furnace, a press, a mold temperature controller, a manipulator, a demoulding drive structure, and the hot precision forging of spur gears described in Embodiment 1 or 2. Forming mold.

Among them, it is worth mentioning that the box-type furnace is used to heat the billet; the manipulator is used to transfer the heated billet to the spur gear cavity of the spur gear hot precision forging mold; the pressure The machine has driving mechanisms respectively used to drive the upper cover plate 2 and the punch 1 to move in the vertical direction; the mold temperature machine is used to control the temperature of the spur gear forming mold; the demoulding driving mechanism It is used to drive the ejector pin 6 to move in the vertical direction to eject the workpiece in the spur gear cavity.

When the spur gear hot precision forging forming system of this embodiment is applied, the blank is heated and insulated in the box furnace to achieve consistency of internal and external temperatures. The mold temperature machine also controls the forming mold to achieve constant temperature maintenance, and then the blank is quickly moved by the robot. Transferred to the complete set of forming molds, this process should be as fast as possible to reduce the loss of outer surface temperature. Then, under the action of the press, the heated blank is forged into a semi-finished hollow spur gear, and then the demoulding drive mechanism drives the ejector 6 It moves in the vertical direction to eject the workpiece, and finally goes through a machining process, such as gear shaving or grinding, to obtain a finished spur gear that meets the technical requirements of roughness and dimensional accuracy.

Example 4

This embodiment introduces a hot precision forging gear forming method using the spur gear hot precision forging forming mold of Embodiment 1, which specifically includes the following steps:

S1: Heat and keep the mold warm; machine a tapered positioning hole on one end of the blank, then heat it to the set temperature and keep it warm.

First machine a Φ8mm×8mm conical notch on one end face of the Φ90mm×120mm bar, then put the blank into a box furnace and heat it to 1000°C. Set the heating rate of the heating furnace to 30°C/min and keep it warm. 60min to ensure the consistency of the core and surface temperatures of the blank. At the same time, a mold temperature machine is used to control the constant temperature of all molds at 300°C, and lubricant is applied to the surface of the mold to reduce the friction between the blank and the mold.

Specifically, the box-type furnace is a muffle furnace, the heating element is a silicon carbon rod, the temperature is controllable (room temperature -1500°C), the heating rate is controllable (3-50°C/min), and the temperature control accuracy is ±1 ℃. During use, protective gas is introduced, and the structural state of the billet at the initial forging temperature is determined by adjusting the heating rate, heating temperature, and holding time of the heating furnace.

Among them, before step S1, the oil circuit can be designed in advance inside the mold and a release agent can be sprayed on the side wall of the spur gear cavity of the concave mold. The selection of the release agent is more conducive to the completion of demoulding.

S2: Transfer the heated and heat-insulated blank into the spur gear cavity, so that the positioning hole closely matches the positioning pin 7 on the ejector pin 6 .

Use the robot to quickly transfer to the concave mold 4, closely match the notched end surface with the positioning pin 7 on the ejector pin 6, and the upper end surface of the blank is in contact with the upper cover plate 2 and the punch 1 to ensure that the heated blank is located in the center of the concave mold 4 , ensuring the uniformity of tooth profile forming and the coaxiality accuracy during inner hole forming.

Specifically, a positioning pin 7 is provided at the center of the top of the ejector pin 6. The selection of the conical positioning pin effectively ensures the uniformity of the tooth filling of the blank during the forging process, and on the other hand is more helpful for later forging. Gear demoulding operation.

S3: Use a press to drive the upper cover plate 2 and the punch 1 to squeeze the blank downward along the axial direction of the spur gear cavity until the lower end surface of the upper cover plate 2 is in contact with the upper end surface of the female mold 4 After contact and the thickening of the pier is completed, the upper cover plate 2 is controlled to stop moving; the punch 1 is controlled to continue to squeeze the blank downward until it reaches the preset depth in the spur gear cavity, so that the blank fills the inner cavity. Tooth cavity and complete punching.

In the upsetting stage, ensure that the forging end face is flat and perpendicular to the axis of the billet. By controlling the rotation of the bottom plate and ejector pin, the die and the billet inside are driven to rotate, preferably uniformly, to straighten and bend in time. The press drives the upper cover plate 2 and the punch 1 to squeeze the blank downward at the same time. The movement speed is 20mm/s. The height of the blank gradually shortens and increases radially. The outer surface begins to be constrained by the inner wall tooth profile of the die 4 until the upper When the cover plate 2 touches the upper surface of the concave die 4, the upper cover plate 2 stops moving, but the punch 1 still maintains the same speed and continues to squeeze the blank downward.

In the punching stage, the punch 1 serves as a power die to continue to squeeze the blank downwards. The material extruded from the inner hole will flow to the tooth profile and the upper end. Under the anti-extrusion constraint of the upper cover plate 2, it will eventually flow to the tooth. The profile parts are gradually filled with tooth shapes, forming a tooth shape filling sequence of first middle - then lower - then upper, forming a directional metal forging streamline. In the late stage of tooth filling, the forming load rises rapidly, but always remains within the safety limit of the press. The pressure reduction groove 3 at the lower end of the upper cover plate 2 plays a certain pressure reduction and buffering role.

It is worth mentioning that in step S3, a 1000-ton closed-mode precision forging press is used to drive and control the upper cover plate and punch 1. The safety factor is set to 0.8, and the movement speed of the upper cover plate 2 is controlled during the roughening process. is 20mm/s, and the movement speed of punch 1 is controlled to be 20mm/s during the entire process from piercing to completion of punching.

According to actual production needs, the selection of specific parameters in steps S1 and S3 further improves the overall performance of the forgings during the hot precision forging of spur gears by the forming mold, and maximizes quality and accuracy.

S4: Remove the upper cover plate and punch 1, and control the ejector pin 6 to push the workpiece in the spur gear cavity upward through the demoulding drive mechanism to complete demolding.

After step S4, the demolded workpiece is air-cooled. When the temperature of the workpiece drops to room temperature, heat treatment and machining are performed to obtain the finished precision forged gear. After the forged hollow spur gear undergoes machining processes, such as gear shaving or grinding, the roughness and dimensional accuracy required by the technology can be achieved.

Specifically, the demoulded workpiece is provided with punched and integrated skins, which can prevent the mold from hitting and being damaged; at the same time, the heat treatment and thermomechanical processing are at least used for finishing the inner hole and the upper and lower end faces of the gear.

In summary, the spur gear hot precision forging forming mold, system and method of the present invention not only reduce the heat loss during the forging process, but also reduce the initial forging temperature by realizing the processes of upsetting, punching and tooth profile filling. The structure of the gear to be processed is improved; at the same time, the fluidity of the blank metal is ensured, the mold stress of the concave mold 4 is appropriately reduced, and the service life of the mold is improved.

The above are only preferred embodiments of the present invention. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. The hot precision forging forming die for the spur gear is characterized by comprising an upper cover plate, a male die, a female die, a bottom plate and a push rod;

a spur gear cavity is arranged in the female die; the upper cover plate is positioned above the female die, and the lower end surface of the upper cover plate can be in butt joint with the upper end surface of the female die; the upper end face of the bottom plate is fixedly connected with the lower end face of the female die;

a first through hole is formed in the upper cover plate; the male die is connected with the first through hole in a sliding manner, and the shape of the lower end of the male die is matched with the shape of an inner ring of a workpiece to be processed;

a second through hole coaxial with the spur gear cavity is formed in the bottom plate; the upper end of the ejector rod is connected with the second through hole in a sliding mode, and the axial projection of the outer contour of the upper end of the ejector rod is located in the tooth root circular axial projection of the spur gear cavity.

2. The straight gear hot precision forging forming die according to claim 1, wherein a locating pin which is used for being tightly matched with the bottom of a workpiece to be processed is arranged in the middle of the top end of the ejector rod;

the locating pin is a conical bulge integrally formed with the ejector rod.

3. The spur gear hot precision forging forming die as set forth in claim 1, wherein the spur gear cavity peripheral portion has an internal tooth cavity corresponding to a modulus, a number of teeth and a reference circle of a spur gear to be processed, and the internal gear is provided with machining allowance on each side in a tooth width direction and on a gear profile, respectively;

and the two sides of the bottom end of the upper cover plate are provided with pressure reducing grooves facing to the tooth top circle part of the internal tooth cavity.

4. The spur gear hot precision forging forming die as set forth in claim 1, wherein a detachable fixedly connection is provided between the bottom plate and the female die;

the contact surface of the bottom plate and the ejector rod is provided with a draft angle of 1 degree.

5. The hot precision forging forming die for a spur gear according to claim 1, wherein transition fit is respectively provided between the male die and the first through hole, and between the upper end of the ejector rod and the second through hole.

6. The hot precision forging forming die for straight gears according to claim 1, wherein the male die, the female die, the bottom plate and the ejector rod are all cylinders made of quenched die steel, and the surface hardness is 62HRC or more;

in the spur gear forming process, the upper cover plate, the male die, the female die, the bottom plate and the ejector rod are coaxial.

7. A spur gear hot precision forging forming system, which is characterized by comprising a box-type furnace, a press, a mold temperature machine, a mechanical arm, a demolding driving structure and the spur gear hot precision forging forming mold according to any one of claims 1-6;

the box-type furnace is used for heating the blank, and the manipulator is used for transferring the heated blank into a spur gear cavity of the spur gear hot precision forging forming die;

the press is provided with a driving mechanism for driving the upper cover plate and the male die to move along the vertical direction respectively;

the die temperature machine is used for controlling the temperature of the spur gear forming die;

the demolding driving mechanism is used for driving the ejector rod to move along the vertical direction so as to eject the workpiece in the spur gear cavity.

8. A method for hot precision forging of a spur gear by using the hot precision forging die for a spur gear according to any one of claims 1 to 6, wherein a positioning pin is arranged in the middle of the top end of the ejector rod;

the hot precision forging forming method of the spur gear comprises the following steps:

s1: heating and preserving heat of the die;

machining a positioning hole on one end face of the blank, heating to a set temperature, and preserving heat;

s2: transferring the heated and insulated blank into the spur gear cavity to enable the positioning hole to be tightly matched with the positioning pin on the ejector rod;

s3: the upper cover plate and the male die are driven by a press machine to simultaneously axially extrude blanks downwards along the straight gear cavity until the lower end surface of the upper cover plate contacts with the upper end surface of the female die, upsetting is completed, and then the upper cover plate is controlled to stop moving;

controlling the male die to continuously extrude the blank downwards until reaching the preset depth in the spur gear cavity, so that the blank fills the internal tooth cavity and completes punching;

s4: and removing the upper cover plate and the male die, and controlling the ejector rod to push the workpiece in the spur gear cavity upwards through the demolding driving mechanism to finish demolding.

9. The method of hot precision forging a spur gear as recited in claim 8, further comprising:

before the step S1, spraying a release agent on the side wall of the straight gear cavity of the female die;

air cooling the demoulded workpiece, and performing heat treatment and machining treatment after the temperature of the workpiece is reduced to room temperature to obtain a finished product precision forging gear;

the workpiece after demoulding is provided with a punching connecting skin, and the heat treatment and the thermal engine processing treatment are at least used for finishing an inner hole and the upper end face and the lower end face of the gear.

10. The hot precision forging forming method for a spur gear as recited in claim 9, wherein,

in the step S1, heating the die to 300 ℃ and then preserving heat, heating the blank to 1000 ℃ by adopting a box-type furnace and then preserving heat for 1h, wherein the heating rate is set to be 30 ℃/min in the blank heating process;

in the step S3, a 1000 ton blocking precision forging press is adopted to drive and control the upper cover plate and the male die, the safety coefficient is set to be 0.8, the movement speed of the upper cover plate is controlled to be 20mm/S in the upsetting process, and the movement speed of the male die is controlled to be 20mm/S in the whole process from upsetting to punching.