A screw-rotor powder metallurgy green compact forming machine and a forming method

Abstract

The present application relates to the field of powder metallurgy, and more particularly to a screw rotor powder metallurgy green compact forming machine and a forming method. The forming machine comprises a rack, a female die, a pressure head, a ejector rod and a driving assembly arranged on the rack; the female die is internally provided with a spiral cavity; the pressure head is arranged above the female die, and the ejector rod is arranged below the female die; the pressure head is provided with a first spiral outer surface matched with the spiral cavity, the ejector rod is provided with a second spiral outer surface matched with the spiral cavity, and the first spiral outer surface and the second spiral outer surface are respectively matched with the inner wall of the spiral cavity to form a spiral pair; the driving assembly is configured to drive the pressure head and / or the ejector rod to rotate and linearly move along a spiral path, so that the pressure head and the ejector rod jointly press the powder in the spiral cavity. The present application enables the powder to be axially pressed while being subjected to bidirectional circumferential shearing and compaction, effectively improves the density uniformity of the blank, and reduces the generation of defects such as cracks.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and more specifically, to a spiral rotor powder metallurgy green blank forming machine and forming method. Background Technology

[0002] Currently, the manufacturing of helical rotors mainly employs casting or machining methods. Casting suffers from drawbacks such as high melting temperatures, high defect density, and low strength and hardness; while machining involves numerous steps, low material utilization, and long processing cycles, and is particularly difficult for the complex blade profiles of helical rotors. To address these issues, some existing technologies attempt to use powder metallurgy to prepare rotor-like parts. However, existing powder metallurgy forming equipment is mostly designed for general-purpose parts and lacks specialized forming equipment for the complex cross-sectional shapes of helical rotors. During the pressing process, the traditional straight-up-down flat pressing method makes it difficult for the press head and ejector pin to adapt to the complex shape of the helical cavity, resulting in uneven powder filling, insufficient pressure transmission, and consequently, uneven density distribution of the blank. Furthermore, during demolding, the green blank is prone to interference and jamming with the inner wall of the cavity, causing demolding damage. Summary of the Invention

[0003] To address the problems of uneven green blank density distribution and easy demolding damage caused by the existing powder metallurgy flat pressing method being unable to adapt to the spiral cavity, the present invention provides a spiral rotor powder metallurgy green blank forming machine and forming method to achieve near-net-shape forming of the spiral rotor in powder metallurgy, which is beneficial to improve the uniformity of green blank density and reduce demolding damage.

[0004] To at least partially solve the above problems, the present invention provides a spiral rotor powder metallurgy green forming machine, comprising: a frame, and a female mold, a pressure head, an ejector rod, and a drive assembly disposed on the frame; the female mold has a spiral cavity inside; the pressure head is located above the female mold, and the ejector rod is located below the female mold; the pressure head has a first spiral outer surface adapted to the spiral cavity, and the ejector rod has a second spiral outer surface adapted to the spiral cavity, the first spiral outer surface and the second spiral outer surface respectively forming a spiral pair with the inner wall of the spiral cavity; the drive assembly is configured to drive the pressure head and / or the ejector rod to perform a combined rotational and linear motion along a spiral path, so that the pressure head and the ejector rod jointly press the powder in the spiral cavity.

[0005] Furthermore, the pressure head includes: a connecting section and a spiral pressing section; the connecting section is a straight rod structure or a stepped shaft structure, connected to the output end of the drive assembly; the spiral pressing section is a rod-shaped structure with spiral teeth or spiral protrusions, the spiral teeth or spiral protrusions forming a first spiral outer surface, the spiral parameters of the first spiral outer surface being consistent with the spiral groove parameters of the inner wall of the spiral cavity; the lower end face of the pressure head is a forming end face, the contour of the forming end face being adapted to the upper end face of the workpiece to be pressed.

[0006] Furthermore, the push rod includes a helical pressing section and a support section. The helical pressing section is a rod-shaped structure with a second helical outer surface, and the support section is a straight rod structure or a stepped shaft structure. The drive assembly includes a push rod hydraulic cylinder, which is fixed on the frame. The piston rod of the push rod hydraulic cylinder is connected to a bearing housing, a deep groove ball bearing is installed in the bearing housing, a bearing end cap is fixed on the bearing housing and limits the deep groove ball bearing, and the push rod passes through the inner hole of the deep groove ball bearing and can rotate. The push rod hydraulic cylinder drives the bearing housing and the push rod as a whole to move in the vertical direction.

[0007] Furthermore, when the hydraulic cylinder drives the push rod to move linearly in the vertical direction, the helical pair between the outer surface of the second helix and the inner wall of the helical cavity converts the axial force into rotational torque, thereby passively driving the push rod to rotate.

[0008] Furthermore, the drive assembly also includes: a first variable frequency motor, a second variable frequency motor, a steering box, and a worm gear screw jack; the first variable frequency motor is connected to the input end of the steering box, the output end of the steering box is connected to the worm gear screw jack, and the worm gear screw jack is configured to drive the pressure head to move up and down in the vertical direction; the second variable frequency motor is configured to drive the pressure head to rotate.

[0009] Furthermore, the frame includes: a top plate, a support plate, a worktable, and a base; multiple vertical support shafts are fixed on the base, and the worktable is fixedly connected to the middle of the multiple vertical support shafts, with the female mold fixed in the through vertical hole of the worktable; the support plate is slidably fitted above the multiple vertical support shafts, and the top of the support plate is fixedly connected to the top plate through a column; a second variable frequency motor is fixed on the top plate, and the output shaft of the second variable frequency motor is fixedly connected to the connecting section of the pressure head; the support plate is fixedly connected to the support frame of the lifting end of the worm gear screw jack, so that the pressure head can be driven to move up and down along the vertical support shafts under the drive of the worm gear screw jack.

[0010] Furthermore, the spiral rotor powder metallurgy green billet forming machine further includes: a feeding mechanism; the feeding mechanism includes a feeding box, a feeding pipe and a feeding hydraulic cylinder; a slide rail is provided on the worktable, the feeding box is set on the slide rail, the feeding hydraulic cylinder is configured to drive the feeding box to reciprocate along the slide rail, and the feeding pipe is connected to the feeding box and extends to the top of the female mold.

[0011] The present invention also provides a method for forming a spiral rotor powder metallurgy green billet, applicable to the spiral rotor powder metallurgy green billet forming machine described in any of the above claims, the method comprising: Powder filling stage: The drive rod is rotated along the spiral path into the spiral cavity to seal the bottom end of the spiral cavity and fill the spiral cavity with powder; Pressing stage: The driving head and push rod rotate along the spiral path to press the powder in the spiral cavity in both directions. Demolding stage: Drive the pressure head to continue rotating downward to push the green blank out along the spiral path, and drive the ejector pin to rotate in the opposite direction and exit the spiral cavity downward.

[0012] During the pressing stage: the pressure head is actively driven to rotate and feed by the drive assembly; the push rod is passively driven to rotate and feed by the helical pair between the outer surface of the second spiral and the inner wall of the spiral cavity under linear drive; the pressure head and the push rod move towards each other, so that the powder is subjected to bidirectional circumferential shearing and compaction while being axially compressed.

[0013] During the demolding stage: the outer surface of the first spiral of the pressure head always maintains a spiral pair engagement with the inner wall of the spiral cavity, pushing the green blank out from the bottom of the spiral cavity along the spiral path; the ejector rod rotates in the opposite direction and exits the spiral cavity downward to make way; the green blank naturally rotates out under the guidance of the spiral cavity.

[0014] The beneficial effects of this invention are as follows: This invention provides a spiral rotor powder metallurgy green billet forming machine and forming method. By having both the pressure head and the ejector rod have spiral outer surfaces adapted to the spiral cavity of the female mold to form a spiral pair, the pressure head and ejector rod are driven to rotate and feed along the spiral path and perform bidirectional pressing. This allows the powder to be subjected to axial pressure while also experiencing bidirectional circumferential shearing and compaction, effectively improving the density uniformity of the billet and reducing defects such as cracks. During the demolding stage, the pressure head and ejector rod rotate smoothly out along the spiral path, and the green billet naturally rotates out under the guidance of the spiral cavity, avoiding the jamming and extrusion damage caused by traditional direct-push demolding, and significantly reducing demolding resistance and billet damage. At the same time, the rotational movement of the ejector rod can be passively achieved by the linear driving force of the hydraulic cylinder through the spiral pair, without the need for a separate rotary motor and synchronous control system. The structure is simple, the control is simple, and the operation is reliable.

[0015] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is an overall schematic diagram of the spiral rotor powder metallurgy green billet forming machine of the present invention; Figure 2 This is a partial schematic diagram of the feeding mechanism and worktable of the present invention; Figure 3 This is a partial schematic diagram of the push rod and push rod hydraulic cylinder of the present invention; Figure 4 This is a schematic diagram of the pressure head structure of the present invention; Figure 5 This is a partial top view of the demolding and part removal stage of the spiral rotor powder metallurgy green billet forming machine of the present invention; Figure 6 This is a partial schematic diagram of the push rod reset device, push rod, and push rod hydraulic cylinder of the present invention; Figure 7 This is a top view of the push rod reset device of the present invention; Figure 8 This is a partial schematic diagram of the push rod reset device of the present invention; Figure 9 This is a partial cross-sectional view of the push rod reset device of the present invention.

[0017] Icons: 1-Top plate; 2-Support plate; 3-Support frame; 4-Female mold; 5-Slide rail; 6-Worm gear screw jack; 7-Swivel box; 8-Base; 9-Second variable frequency motor; 10-Pressure head; 11-Feeding pipe; 12-Feeding box; 13-Feeding hydraulic cylinder; 14-Top rod; 15-First variable frequency motor; 16-Top rod hydraulic cylinder; 17-Workbench; 18-Bearing end cover; 19-Deep groove ball bearing; 20-Top rod reset device; 21-U-shaped bracket; 22-Guide crossbar; 23-Reset rack; 24-Reset gear; 25-Initial locking block; 26-Limiting locking block; 27-End seat; 28-Restricting guide tube; 29-Reset spring; 30-Lifting control screw; 31-Control rotating block; 32-Lifting distance limiting slider; 33-Distance limiting groove. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] Example 1:

[0020] like Figures 1-5As shown, this embodiment provides a spiral rotor powder metallurgy green billet forming machine. The forming machine includes a frame, and a female mold 4, a pressure head 10, a push rod 14, and a drive assembly mounted on the frame. The frame serves as the overall load-bearing skeleton, providing the mounting base for each component. The female mold 4 is fixedly positioned in the middle working position of the frame, and its interior has a spiral cavity extending vertically. The inner wall of the spiral cavity has a spiral groove structure that matches the outer contour of the target spiral rotor. The pressure head 10 is located above the female mold 4, and the push rod 14 is located below the female mold 4; the three are arranged coaxially. The pressure head 10 has a first spiral outer surface adapted to the spiral cavity, and the push rod 14 has a second spiral outer surface adapted to the spiral cavity. The first and second spiral outer surfaces respectively form a spiral pair with the inner wall of the spiral cavity. Specifically, the helical parameters of the first helical outer surface of the pressure head 10 and the second helical outer surface of the ejector rod 14, including lead, helical angle, tooth profile, and direction of rotation, need to be consistent with the helical groove parameters of the inner wall of the helical cavity of the female mold 4. This parameter consistency helps the external helical teeth of the pressure head 10 and the ejector rod 14 to slide into the helical groove of the inner wall of the cavity when they enter the helical cavity, forming a motion constraint relationship similar to that of a lead screw and a nut. It should be understood that although this embodiment and the accompanying drawings show a symmetrical structure in which both the pressure head 10 and the ejector rod 14 have helical outer surfaces, in other embodiments, as long as the functional requirement of being able to make a combined rotational and linear motion along the helical path is met, the specific fit clearance and tooth profile of the helical pair can be adaptively adjusted according to the characteristics of the powder material, for example, a small gap fit can be used to prevent powder overflow. This helical pair fit not only provides precise rotational motion guidance for the pressure head 10 and the ejector rod 14, but also plays a circumferential limiting role during the pressing process, preventing the green body from twisting or misaligning during the forming process. The drive assembly is configured to drive the pressure head 10 and / or the push rod 14 to perform a combined rotational and linear motion along a helical path, so that the pressure head 10 and the push rod 14 jointly press the powder within the helical cavity. Specifically, the combined rotational and linear motion means that the pressure head 10 or the push rod 14 simultaneously rotates around its own axis while making a linear feed along the axis, and its motion trajectory is strictly constrained by the helical path of the helical cavity. The drive assembly can independently drive the pressure head 10 downward, independently drive the push rod 14 upward, or simultaneously drive them to move towards each other. This embodiment achieves bidirectional rotational pressing of the powder through the above-mentioned combined motion. From a microscopic mechanism perspective, when the pressure head 10 and the push rod 14 move towards each other under the action of the drive assembly, the powder is not only subjected to compression from both ends in the axial direction, but also subjected to bidirectional circumferential shear forces due to the rotation of the pressure head 10 and the push rod 14 under the cooperation of the helical pair. This combined effect of axial compression and circumferential shearing breaks the frictional self-locking effect between powder particles during traditional unidirectional flat pressing, causing powder particles to rearrange and fill micropores in the cavity, thereby significantly improving the density uniformity of the green body and effectively reducing the generation of defects such as cracks.At the same time, the screw pair makes the demolding process a rotational exit along the screw path, avoiding the jamming and squeezing damage caused by traditional direct push demolding.

[0021] Example 2:

[0022] like Figures 1-5 As shown, based on Embodiment 1, this embodiment further defines the specific structure of the pressure head 10, the push rod 14, and the active power configuration of the drive assembly. The pressure head 10 includes a connecting section and a spiral pressing section. The connecting section is a straight rod structure or a stepped shaft structure, coaxially driven and connected to the output end of the drive assembly. The spiral pressing section is a rod-shaped structure with spiral teeth or spiral protrusions. The spiral teeth or spiral protrusions form the first spiral outer surface, and the spiral parameters of the first spiral outer surface are consistent with the spiral groove parameters of the inner wall of the spiral cavity. The lower end face of the pressure head 10 is the forming end face, and the contour of the forming end face is adapted to the upper end face of the workpiece to be pressed and formed. Specifically, the main function of the connecting section is to transmit torque and bear axial thrust, so its structural form needs to match the output end of the drive assembly. For example, when a key connection is used to transmit torque, the connecting section can be designed as a straight rod structure with a keyway; when it needs to bear a large axial load and is easy to disassemble, the connecting section can be designed as a multi-stage stepped shaft structure. The helical parameters of the first helical outer surface of the helical pressing section, including lead, helical angle, tooth profile, and direction of rotation, need to be consistent with the helical groove parameters of the inner wall of the helical cavity of the female mold 4. This parameter consistency is a geometric prerequisite for the fit of the helical pair, which helps the helical teeth of the press head 10 to slide into the helical grooves of the cavity wall when rotating downwards, reducing interference and jamming. The lower end face of the press head 10 directly contacts the powder, and its contour shape determines the final forming shape of the upper end face of the green body. For example, when the upper end face of the target helical rotor is flat, the forming end face can be designed as a flat circular surface; when the upper end face of the target helical rotor has a groove or a boss, the forming end face needs to be designed as a corresponding protrusion or groove structure to achieve near-net-shape forming and reduce subsequent machining allowance.

[0023] The push rod 14 includes a helical pressing section and a support section. The helical pressing section is a rod-shaped structure with a second helical outer surface, and the support section is a straight rod structure or a stepped shaft structure. The drive assembly includes a push rod hydraulic cylinder 16, which is fixed to the frame. The piston rod of the push rod hydraulic cylinder 16 is connected to a bearing housing. A deep groove ball bearing 19 is installed in the bearing housing. A bearing end cap 18 is fixed to the bearing housing and limits the deep groove ball bearing 19. The push rod 14 passes through the inner hole of the deep groove ball bearing 19 and is rotatable. The push rod hydraulic cylinder 16 drives the bearing housing and the push rod 14 to move vertically as a whole. Specifically, the structure of the helical pressing section is similar to that of the helical pressing section of the pressure head 10, and it also needs to meet the condition of being consistent with the helical groove parameters of the inner wall of the helical cavity. The main function of the support section is to cooperate with the bearing assembly to achieve rotational support. The design of its straight rod or stepped shaft structure depends on the inner diameter and assembly tolerance of the deep groove ball bearing 19. In terms of assembly, the push rod hydraulic cylinder 16 serves as a linear power source, with its cylinder body fixed to the base 8 of the frame. The piston rod extends vertically and is fixedly connected to the bearing housing. The outer ring of the deep groove ball bearing 19 is fixed in the inner hole of the bearing housing, axially limited by the bearing end cover 18 to prevent it from moving during operation. The support section of the push rod 14 passes through the inner hole of the deep groove ball bearing 19, with an interference fit to the inner ring, allowing the push rod 14 to rotate freely within the bearing housing while simultaneously moving vertically with the bearing housing. This assembly design effectively decouples the degrees of freedom of linear and rotational motion, allowing the push rod hydraulic cylinder 16 to provide only axial pushing and pulling force without bearing rotational torque, thus extending the service life of the push rod hydraulic cylinder 16. The push rod 14 can rotate freely within the deep groove ball bearing 19. When the hydraulic cylinder 16 drives the push rod 14 to move linearly in the vertical direction, the helical pair between the outer surface of the second helix and the inner wall of the helical cavity converts the axial force into a rotational torque, passively driving the push rod 14 to rotate. The passive rotation mechanism of the push rod 14 is based on the mechanical transmission characteristics of the helical pair. When the hydraulic cylinder 16 pushes the push rod 14 upward in a linear motion, the linear motion is blocked by the helical groove sidewall due to the engagement between the outer surface of the second helix and the helical groove of the inner wall of the helical cavity, thus generating a normal reaction force on the contact surface. This normal reaction force can be decomposed into an axial component and a circumferential component, where the circumferential component forms a rotational torque relative to the axis of the push rod 14, driving the push rod 14 to rotate. The realization of this passive rotation mechanism requires that the helical pair not be self-locking, that is, the lead angle of the helical surface is greater than the friction angle. If the lead angle is less than or equal to the friction angle, the helical pair will be in a self-locking state, the axial force cannot be converted into rotational motion, and the push rod 14 may jam. To meet the non-locking requirement, the helical mating surfaces of the ejector pin 14 and the female mold 4 are typically precision ground and surface treated, such as nitriding or hard chrome plating, to reduce surface roughness. After surface treatment, the coefficient of friction can usually be reduced to 0.05–0.10, corresponding to a friction angle of approximately 3°–6°.Since the lead angle of a helical rotor is typically much greater than 6°, the helical pair can usually transmit power smoothly, and axial force can be converted into rotational motion. This passive rotation design eliminates the need for a separate rotary motor for the push rod 14. It utilizes the linear drive force of the hydraulic cylinder to naturally generate rotational motion, and the rotation direction automatically reverses with the axial motion direction, eliminating the need for an additional reversing mechanism. The structure is simple and the control is reliable.

[0024] The drive assembly also includes a first variable frequency motor 15, a second variable frequency motor 9, a steering box 7, and a worm gear screw jack 6. The first variable frequency motor 15 is connected to the input end of the steering box 7, and the output end of the steering box 7 is connected to the worm gear screw jack 6. The worm gear screw jack 6 is configured to drive the pressure head 10 to move vertically. The second variable frequency motor 9 is configured to drive the pressure head 10 to rotate. The active part of the drive assembly adopts a control architecture that independently decouples rotational power and linear power. The first variable frequency motor 15 serves as the main power source for linear feed, and its output shaft is connected to the input end of the steering box 7. The steering box 7 outputs the power to the worm gear screw jack 6 after changing the direction of power transmission. The worm gear screw jack 6 uses the worm gear transmission principle to convert rotational motion into linear lifting motion of the screw, thereby driving the pressure head 10 to feed vertically. The second variable frequency motor 9 serves as an independent source of rotational power, directly or through a drive shaft connected to the connection section of the pressure head 10, driving the pressure head 10 to rotate around its axis. This invention allows for precise adjustment of the rotational speed and linear feed speed of the pressure head 10, matching them to the helical parameters of the helical cavity. This helps avoid interference or scratching caused by speed mismatch. For example, when pressing helical rotors with different leads, the speeds of the first variable frequency motor 15 and the second variable frequency motor 9 can be set separately via frequency converters, enabling flexible adjustment of motion parameters and improving the adaptability and molding accuracy of the equipment.

[0025] Example 3:

[0026] like Figures 1-5As shown, based on the above embodiments, this embodiment further defines the spatial layout of the frame layer structure and power components. The frame includes a top plate 1, a support plate 2, a worktable 17, and a base 8. Multiple vertical support shafts are fixed on the base 8, and the worktable 17 is fixedly connected to the middle of the multiple vertical support shafts. The female mold 4 is fixed in the through vertical hole of the worktable 17. The support plate 2 is slidably fitted above the multiple vertical support shafts, and the top of the support plate 2 is fixedly connected to the top plate 1 through a column. A second variable frequency motor 9 is fixed on the top plate 1, and the output shaft of the second variable frequency motor 9 is fixedly connected to the connecting section of the pressure head 10. The support plate 2 is fixedly connected to the support frame 3 of the lifting end of the worm gear screw jack 6, so that the pressure head 10 can be driven to move up and down along the vertical support shaft under the drive of the worm gear screw jack 6. In this invention, the frame adopts a frame structure combining multi-layer boards and columns to provide a stable load-bearing foundation. The base 8 is located at the bottom layer, with multiple vertical support shafts fixed vertically at the edges. The worktable 17 is fixedly inserted through the middle of the vertical support shafts, and the female mold 4 is tightly installed in the through vertical hole in the middle of the worktable 17, thus stabilizing the molding area in the middle of the frame. The support plate 2 is located above the worktable 17, with through holes at its four corners and slidably fitted onto the vertical support shafts, allowing the support plate 2 to slide smoothly up and down along the vertical support shafts. The top plate 1 is fixed above the support plate 2 by outer columns, forming a rigid upper frame. The second variable frequency motor 9 is fixed upside down on the top plate 1, and its output shaft passes downward through the top plate 1 and is coaxially fixedly connected to the connecting section of the pressure head 10, thus realizing the direct transmission of rotational power. The worm gear screw jack 6 serves as a linear feed power source, and its lifting end is fixedly connected to the support plate 2 through the support frame 3. When the worm gear screw jack 6 is started, its screw extends and retracts, pushing the support frame 3 and the support plate 2 as a whole to rise and fall along the vertical support shaft. Since the pressure head 10 and the support plate 2 rotate relatively independently but move axially, the vertical guiding motion of the support plate 2 directly drives the pressure head 10 to move stably downwards or upwards. This spatial layout guides the support plate 2 at multiple points through multiple vertical support shafts, effectively resisting the lateral load moment generated by the pressure head 10 during rotational pressing, which helps to ensure the coaxiality of the pressure head 10 and the cavity of the female mold 4 and reduces motion interference. It should be understood that although this embodiment shows a four-column frame structure, in other embodiments, the frame can also adopt a portal frame structure or a single-column guide structure, as long as it can provide stable vertical guidance for the support plate 2 and withstand the pressing reaction force.

[0027] Example 4:

[0028] like Figures 1-5As shown, based on the above embodiments, this embodiment further defines the automated feeding structure of the molding machine. The molding machine also includes a feeding mechanism, with a slide rail 5 on the worktable 17. The feeding mechanism includes a feeding box 12, a feeding pipe 11, and a feeding hydraulic cylinder 13. The feeding box 12 is mounted on the slide rail 5, and the feeding hydraulic cylinder 13 is configured to drive the feeding box 12 to reciprocate along the slide rail 5. The feeding pipe 11 communicates with the feeding box 12 and extends above the female mold 4. The slide rail 5 is fixed horizontally to the upper surface of the worktable 17 and is arranged on one side of the female mold 4. The bottom of the feeding box 12 has a guide groove adapted to the slide rail 5, allowing the feeding box 12 to slide smoothly in a straight line along the slide rail 5. The cylinder body of the feeding hydraulic cylinder 13 is fixed to the side wall of the worktable 17 or the frame, and the end of its piston rod is hinged or rigidly connected to the outer side wall of the feeding box 12, thereby converting the linear extension and retraction motion of the hydraulic cylinder into the reciprocating translational motion of the feeding box 12. One end of the feeding pipe 11 communicates with the internal cavity of the feeding box 12, and the other end extends directly above the female mold 4, used to guide the metal powder in the feeding box 12 into the spiral cavity. It should be understood that although the feeding hydraulic cylinder 13 is used as the driving source in this embodiment, in other embodiments, a cylinder, electric push rod, or screw and nut mechanism can also be used as an equivalent linear driving member, as long as sufficient thrust can be provided to make the feeding box 12 reciprocate along the slide rail 5.

[0029] This embodiment achieves synchronized automatic powder filling and pressing actions through the cooperation of the feeding hydraulic cylinder 13 and the slide rail 5. During the powder filling stage, the feeding hydraulic cylinder 13 extends, pushing the feeding box 12 to slide along the slide rail 5 above the female mold 4, and the powder is filled into the cavity via the feeding pipe 11. After filling, the feeding hydraulic cylinder 13 retracts, causing the feeding box 12 to return to its original position, thus avoiding the downward movement path of the pressing head 10. This synchronized design avoids spatial interference between the pressing head 10 and the feeding mechanism during downward pressing, while the rigid guiding effect of the slide rail 5 ensures that the feeding pipe 11 is always aligned with the cavity opening, preventing powder spillage and improving the continuity and stability of automated production.

[0030] Example 5:

[0031] like Figures 6-9As shown, based on the above embodiments, the spiral rotor powder metallurgy green billet forming machine of the present invention further includes a push rod reset device 20. In the present invention, the rotation drive methods of the pressure head 10 and the push rod 14 are different, and their angular position reset capabilities after exiting the spiral cavity are fundamentally different. Therefore, a separate push rod reset device 20 needs to be set for the push rod 14. The specific reasons are as follows: The pressure head 10 is actively driven to rotate by the second variable frequency motor 9, and its rotational motion is controlled by a closed-loop motor position control. During reset, the second variable frequency motor 9 can control the pressure head 10 to rotate in the opposite direction to a preset initial angular position, so that the first spiral outer surface of the lower section of the pressure head 10 returns to a fixed position aligned with the spiral groove of the spiral cavity of the female mold 4. Therefore, when the pressure head 10 descends again to insert into the cavity, it can stably enter the spiral cavity without an additional alignment mechanism, and the spiral teeth on the first spiral outer surface and the spiral groove of the spiral cavity always maintain correct engagement. The ejector pin 14 employs a passive rotation method. Its rotational motion is passively achieved by the linear driving force of the ejector pin hydraulic cylinder 16 through a helical pair. The rotational constraint originates from the helical pair between the outer surface of the second helix of the ejector pin 14 and the inner wall of the helical cavity. During the ejector pin 14's exit from the helical cavity, as long as the outer surface of the second helix remains within the cavity, the helical pair constraint remains in effect. The rotation angle of the ejector pin 14 is determined by the relationship between the axial displacement and the helical lead of the helical cavity, and the angle change is predictable. However, when the upper end of the ejector pin 14 is completely withdrawn from the lower end face of the helical cavity of the female mold 4, and the outer surface of the second helix is ​​freed from the constraint of the inner wall of the helical cavity, the ejector pin 14 is in a free rotational state within the inner hole of the deep groove ball bearing 19. Its angular position is no longer subject to any constraint but is determined by random factors such as inertia, bearing friction resistance, and equipment vibration, exhibiting uncertainty. When the push rod 14 rises again under the drive of the push rod hydraulic cylinder 16, preparing to re-insert into the helical cavity, due to the random angular position of the outer surface of the second helix, the phase of its helical teeth and the helical groove of the helical cavity cannot be guaranteed to be aligned. This can result in the helical teeth facing the top of the helical teeth of the helical cavity, causing the push rod to fail to insert into the cavity, or even damaging the helical cavity or the helical surface of the push rod. Therefore, a push rod reset device 20 must be installed on the push rod 14 to allow it to return to a fixed angular position after disengaging from the helical cavity, ensuring that the helical teeth of the outer surface of the second helix correctly mesh with the helical groove of the helical cavity upon re-insertion.

[0032] The push rod reset device 20 includes a U-shaped bracket 21, which is fixedly connected to the piston rod of the push rod hydraulic cylinder 16 in the middle and moves up and down with the piston rod. Two guide crossbeams 22 are fixedly connected to the upper end of the U-shaped bracket 21. A reset rack 23 is slidably connected to both ends of each guide crossbeam 22, meaning the two reset racks 23 are arranged in parallel, guided by the two guide crossbeams 22, and can slide along the guide crossbeams 22. The inner sides of the two reset racks 23 mesh with a reset gear 24 fixed to the lower end of the push rod 14, and the reset gear 24 rotates synchronously with the push rod 14. An initial locking block 25 is fixed to one end of each of the two reset racks 23. The two initial locking blocks 25 are respectively locked onto the outer surfaces of the two guide crossbeams 22, with the two guide crossbeams 22 located between the two initial locking blocks 25, forming a mechanical hard positioning of the initial position. The other ends of the two reset racks 23 are fixed with limit blocks 26, and the two limit blocks 26 are connected to the outer sides of the two guide crossbars 22 by a reset elastic structure.

[0033] The reset elastic structure includes an end seat 27 fixed to the outer side of the guide crossbar 22. A limiting guide tube 28 is coaxially fixedly connected to the end seat 27. A reset spring 29 is sleeved on the limiting guide tube 28, with its two ends fixed to the end seat 27 and the limiting block 26, respectively. A lifting control screw 30 is coaxially rotatably connected inside the limiting guide tube 28. A control rotating block 31 is fixed to the outer end of the lifting control screw 30. A lifting limiting slider 32 is threadedly connected to the lifting control screw 30. The middle part of the lifting limiting slider 32 is slidably fitted within a limiting groove 33 opened on the surface of the limiting guide tube 28, allowing the lifting limiting slider 32 to slide axially along the limiting guide tube 28 but not to rotate. One end of the lifting limiting slider 32 extending outside the limiting guide tube 28 is located between the end seat 27 and the limiting block 26. A locking screw is also threaded onto the guide tube 28. The inner end of the locking screw abuts against the lifting control screw 30 to lock the adjustment position of the lifting control screw 30.

[0034] In this invention, when the hydraulic cylinder 16 drives the push rod 14 to rise into the spiral cavity, the push rod 14 is passively rotated by the spiral pair, which drives the reset gear 24 to rotate synchronously. When the reset gear 24 rotates, it meshes with two reset racks 23, causing the two reset racks 23 to move in different directions along the guide crossbeam 22. The initial locking block 25 disengages from the outer side of the guide crossbeam 22, and the limiting locking block 26 slides towards the outer side of the guide crossbeam 22. At this time, the limiting locking block 26 slides on the limiting guide tube 28 and compresses the reset spring 29, which stores elastic potential energy. When the limiting locking block 26 moves to contact the lifting distance limiting slider 32, it is blocked by the lifting distance limiting slider 32. The limiting locking block 26, the reset racks 23, the reset gear 24, and the push rod 14 stop rotating further, and the maximum rotation angle of the push rod 14 is limited.

[0035] Since the rotation angle and axial displacement of the push rod 14 satisfy the relationship of a screw pair: Δx = Δθ·P / (2π) (where Δx is the axial displacement, Δθ is the rotational angular displacement, and P is the helical lead of the helical cavity); The maximum rotation angle of the push rod 14 is limited, which means the maximum axial upward displacement of the push rod 14 is limited, thereby limiting the maximum depth of the push rod 14 inserted into the spiral groove of the spiral cavity, that is, controlling the pressing distance of the push rod 14.

[0036] When the hydraulic cylinder 16 drives the push rod 14 to descend and disengage from the helical cavity, the helical pair constraint is released. The two return springs 29 release their elastic potential energy, driving the two limit blocks 26 to reset, which in turn drives the two return racks 23 to move in the opposite direction. The return racks 23 drive the return gear 24 to rotate in the opposite direction, thereby causing the push rod 14 to rotate in the opposite direction and return to its initial angular position. At this time, the two initial blocks 25 are re-locked onto the outer sides of the two guide crossbars 22, forming a mechanical hard positioning, so that the second helical outer surface of the push rod 14 returns to a fixed position aligned with the helical groove of the helical cavity, ensuring the accuracy of subsequent re-insertion.

[0037] The adjustment principle of the lifting control screw 30 is as follows: rotating the control block 31 drives the lifting control screw 30 to rotate, and the lifting control screw 30 drives the lifting distance slider 32 to slide along the distance groove 33 through the thread, changing the position of the lifting distance slider 32 between the end seat 27 and the limit block 26, thereby changing the maximum allowable displacement of the limit block 26, which in turn changes the maximum displacement of the reset rack 23, the maximum rotation angle of the reset gear 24, and the maximum rotation angle of the push rod 14, ultimately changing the maximum pressing depth of the push rod 14. After adjustment, the locking screw is tightened against the lifting control screw 30 to lock the adjustment position.

[0038] The push rod reset device 20 of the present invention has the following technical effects: First, precise angular reset of the push rod 14: After the push rod 14 is released from the constraint of the helical cavity, the elastic force of the reset spring 29 drives the mechanism composed of the reset gear 24 and two reset racks 23 to precisely pull the push rod 14 back to the initial angular position, and the initial locking block 25 locks the outer side of the guide crossbar 22 to form a mechanical hard positioning. This dual positioning method of elastic reset and mechanical hard positioning ensures high repeatability of the angular position after the push rod 14 is withdrawn each time. When it is reinserted, the helical teeth on the outer surface of the second helix are accurately aligned with the helical groove of the helical cavity, avoiding the top of the helical teeth and the helical groove of the helical cavity, and solving the unique technical problem of phase loss after the passively rotating push rod 14 is released from the constraint.

[0039] Second, the reset energy is self-consistent: the kinetic energy of the passive rotation of the push rod 14 when it rises and inserts into the spiral cavity is converted into the elastic potential energy of the reset spring 29 through the mechanism composed of the reset gear 24 and two reset racks 23 and stored therein; after the push rod 14 exits the spiral cavity, the spring potential energy is released and drives the push rod 14 to reset. The energy storage and release cycle is self-consistent, and there is no need to configure a separate power source for reset, which is consistent with the design concept that the passive rotation of the push rod 14 does not require a separate rotating motor.

[0040] Third, the pressing distance is adjustable: by rotating the control block 31 to adjust the position of the lifting limit slider 32, the maximum displacement of the limit block 26, the maximum displacement of the reset rack 23, the maximum rotation angle of the reset gear 24, the maximum rotation angle of the push rod 14, and the maximum pressing depth of the push rod 14 can be adjusted steplessly. The adjustment is intuitive and can be adjusted online.

[0041] Fourth, mechanical linkage control with rotation angle limiting displacement: axial displacement control is transformed into rotation angle control by utilizing the screw pair relationship. The axial pressing depth is limited by limiting the rotation angle of the push rod 14. It is a pure mechanical linkage control, which does not require electrical limit switches, displacement sensors or controllers. It avoids the risk of failure of electrical components under powder metallurgy dust and vibration conditions. It has high reliability and simple maintenance.

[0042] Fifth, limiting the maximum insertion depth of the push rod 14: When the push rod 14 rises to the maximum angle and is limited by the lifting distance slider 32, the push rod 14 stops rotating and moving upward, providing a mechanical end limit for the pressing stroke, limiting the maximum depth of the push rod 14 inserted into the spiral groove of the spiral cavity, and avoiding over-stroke pressing; in conjunction with the hydraulic system to unload or stop applying force when the limit is reached, it can avoid overload of the spiral surface and protect the spiral cavity and the spiral surface of the push rod 14.

[0043] Sixth, symmetrical force balance of double racks: Two reset racks 23 are symmetrically arranged on both sides of the reset gear 24. When the reset gear 24 rotates, the reset racks 23 on both sides are subjected to forces simultaneously and in opposite directions. The bearings of the reset gear 24 are subjected to symmetrical force balance, which reduces off-center load and lateral force, improves the rotational smoothness of the reset gear 24 and the push rod 14, and extends the life of the bearings and gears.

[0044] Furthermore, the limiting guide tube 28 simultaneously serves as a guide rod for the return spring 29 to prevent it from bending and becoming unstable when compressed; it also acts as a receiving tube for the lifting control screw 30 and the lifting distance limiting slider 32, protecting their internal mechanisms from dust intrusion; and it serves as a carrier for the distance limiting groove 33, providing sliding guidance for the lifting distance limiting slider 32. This single tube serves three purposes, resulting in a simple structure and good protection. Moreover, the reset endpoint is mechanically hard-positioned by the initial locking block 25 engaging the outer side of the guide crossbeam 22, rather than relying solely on spring force for balancing. Spring force may change due to fatigue, temperature, and friction fluctuations, causing the equilibrium position to drift. However, the mechanical hard-positioning is determined by the geometric fit between the locking block and the guide crossbeam, unaffected by spring force fluctuations. This ensures a stable reset position over a long period without drifting, guaranteeing repeatability accuracy during repeated cycles. By adjusting the position of the lifting limit slider 32, different pressing depths can be adapted to different spiral rotor models. The same device can be used for forming spiral rotors of various specifications without the need to replace the reset device, thus improving the equipment's versatility and changeover efficiency. For rotors with different cavity spiral leads, the relationship between rotation angle and displacement can be calculated according to the lead during adjustment.

[0045] This invention, through the aforementioned push rod reset device 20, ensures that the push rod 14 is precisely reset to a fixed angular position each time it exits the helical cavity. This guarantees phase consistency as the outer surface of the second helix of the push rod 14 repeatedly inserts into the helical cavity during continuous automated production cycles, preventing damage from impact between the outer surface of the second helix and the helical cavity, and improving the reliability and service life of the equipment. Furthermore, because the reset device employs a purely mechanical structure, without the introduction of an additional rotary motor and synchronous control system, it complements the simple drive method of the passive rotation of the push rod 14, maintaining the advantages of a compact overall structure and simple control.

[0046] Example 6:

[0047] like Figures 1-5 As shown, based on the above embodiments, this embodiment provides a method for forming a spiral rotor powder metallurgy green billet, using the spiral rotor powder metallurgy green billet forming machine as described in the above embodiments. The method includes a powder loading stage, a pressing stage, and a demolding stage.

[0048] Step S100, powder loading stage: drive the push rod 14 to rotate into the spiral cavity along the spiral path to seal the bottom end of the spiral cavity and fill the spiral cavity with powder.

[0049] During the powder loading stage, the ejector hydraulic cylinder 16 provides linear driving force, pushing the ejector rod 14 upward in a linear motion. Due to the engagement of the outer surface of the second spiral with the spiral pair of the inner wall of the spiral cavity, the linear motion is passively converted into rotational motion, causing the ejector rod 14 to spiral into the bottom of the spiral cavity along the spiral path. The upper end face of the ejector rod 14 moves to a preset position, closing the bottom end of the spiral cavity and forming a molding chamber to accommodate the powder. Subsequently, the feeding hydraulic cylinder 13 drives the feeding box 12 to move along the slide rail 5 to above the female mold 4, and the powder is filled into the spiral cavity through the feeding pipe 11. After the powder filling is completed, the feeding box 12 retracts to avoid the movement path of the pressure head 10. By spiraling in along the spiral path, while the ejector rod 14 closes the bottom end of the cavity, the spiral teeth on its outer surface engage with the spiral grooves on the inner wall of the cavity, providing an accurate initial phase reference for the subsequent pressing stage.

[0050] Step S200, pressing stage: drive the pressure head 10 and the push rod 14 to rotate and feed along the spiral path to perform bidirectional rotational pressing of the powder in the spiral cavity.

[0051] During the pressing stage, the pressing head 10 is actively driven to rotate and feed by the drive assembly. The push rod 14 is passively driven to rotate and feed by the helical pair between the outer surface of the second spiral and the inner wall of the spiral cavity under linear drive. The pressing head 10 and the push rod 14 move towards each other, so that the powder is subjected to bidirectional circumferential shearing and compaction while being axially compressed.

[0052] The rotary feed of the pressure head 10 is powered by the second variable frequency motor 9 and the linear lifting power is provided by the worm gear screw jack 6. These two are independently decoupled and controlled, actively driving the pressure head 10 downwards along a spiral path. The push rod 14 is powered by the push rod hydraulic cylinder 16 and passively rotates upwards in the cooperation of the screw pair. When the pressure head 10 and the push rod 14 move towards each other, the powder is compressed axially from both ends. Simultaneously, since both the pressure head 10 and the push rod 14 rotate, and their rotation directions are opposite during the opposite feed, the powder is subjected to both axial compression and bidirectional circumferential shear forces. From a microscopic perspective, this combined effect of axial compression and circumferential shear breaks the frictional self-locking effect between powder particles, causing the powder particles to rearrange within the cavity and fill micropores, thereby significantly improving the density uniformity of the green body and effectively reducing defects such as cracks.

[0053] Step S300, demolding stage: drive the pressure head 10 to continue rotating downward to push the green blank out along the spiral path, and drive the ejector pin 14 to rotate in the opposite direction and exit the spiral cavity downward.

[0054] During the demolding stage, the outer surface of the first spiral of the pressure head 10 always maintains a spiral pair engagement with the inner wall of the spiral cavity, pushing the green blank out from the bottom of the spiral cavity along the spiral path. The ejector pin 14 rotates in the opposite direction and exits downward from the spiral cavity to make way, and the green blank naturally rotates out under the guidance of the spiral cavity.

[0055] Specifically, after the pressing and holding pressure is completed, the press head 10 does not immediately move upward and retract, but continues to rotate downward under the action of the drive assembly. The push rod 14, pulled downward linearly by the push rod hydraulic cylinder 16, passively drives the push rod 14 to rotate in the opposite direction and exit the spiral cavity, opening a channel for the green billet to exit. The green billet moves downward under the push of the press head 10. Because the spiral teeth on the outer surface of the green billet and the spiral grooves on the inner wall of the spiral cavity form a spiral pair motion constraint, the green billet rotates naturally under the spiral guidance of the cavity, smoothly exiting the lower end of the cavity along the spiral path. During this process, the rotational angular velocity and linear feed speed of the press head 10 need to match the lead of the spiral cavity, so that the press head 10 rotates along the spiral path.

[0056] When the motion parameters of the pressure head 10 are matched with the helical parameters of the helical cavity, the relative sliding between the lower end face of the pressure head 10 and the upper end face of the green blank is small, which helps to avoid scratching the upper end face of the green blank. At the same time, the green blank naturally rotates out along the helical path, which helps to avoid sidewall jamming. This demolding method transforms the direct push friction in the traditional flat pressing process into rotational sliding under the guidance of the helical, significantly reducing demolding resistance and green blank damage.

[0057] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A spiral rotor powder metallurgy green billet forming machine, characterized in that, include: The frame, and the female mold, pressure head, ejector pin and drive assembly mounted on the frame; the female mold has a spiral cavity inside; The pressure head is located above the female mold, and the ejector pin is located below the female mold. The pressure head has a first helical outer surface adapted to the helical cavity, and the ejector pin has a second helical outer surface adapted to the helical cavity. The first and second helical outer surfaces respectively form a helical pair with the inner wall of the helical cavity. The driving assembly is configured to drive the pressure head and / or the ejector pin to perform a combined rotational and linear motion along the helical path, so that the pressure head and the ejector pin together press the powder in the helical cavity.

2. The spiral rotor powder metallurgy green billet forming machine according to claim 1, characterized in that, The pressure head includes a connecting section and a spiral pressing section; the connecting section is a straight rod structure or a stepped shaft structure, which is connected to the output end of the drive assembly; the spiral pressing section is a rod-shaped structure with spiral teeth or spiral protrusions, the spiral teeth or spiral protrusions forming the first spiral outer surface, and the spiral parameters of the first spiral outer surface are consistent with the spiral groove parameters of the inner wall of the spiral cavity; the lower end face of the pressure head is the forming end face, and the contour of the forming end face is adapted to the upper end face of the workpiece to be pressed.

3. The spiral rotor powder metallurgy green billet forming machine according to claim 1, characterized in that the push rod... include: The machine comprises a spiral pressing section and a support section. The spiral pressing section is a rod-shaped structure with a second spiral outer surface, and the support section is a straight rod structure or a stepped shaft structure. The drive assembly includes a push rod hydraulic cylinder, which is fixed on the frame. The piston rod of the push rod hydraulic cylinder is connected to a bearing housing, a deep groove ball bearing is installed in the bearing housing, a bearing end cover is fixed on the bearing housing and limits the deep groove ball bearing, and the push rod passes through the inner hole of the deep groove ball bearing and can rotate. The push rod hydraulic cylinder drives the bearing housing and the push rod as a whole to move in the vertical direction.

4. The spiral rotor powder metallurgy green billet forming machine according to claim 1, characterized in that, When the hydraulic cylinder drives the push rod to move linearly in the vertical direction, the helical pair between the outer surface of the second helix and the inner wall of the helical cavity converts the axial force into rotational torque, thereby passively driving the push rod to rotate.

5. The spiral rotor powder metallurgy green billet forming machine according to claim 1, characterized in that, The drive assembly also includes: a first variable frequency motor, a second variable frequency motor, a steering box, and a worm gear screw jack; the first variable frequency motor is connected to the input end of the steering box, the output end of the steering box is connected to the worm gear screw jack, and the worm gear screw jack is configured to drive the pressure head to move up and down in the vertical direction; the second variable frequency motor is configured to drive the pressure head to rotate.

6. The spiral rotor powder metallurgy green billet forming machine according to claim 5, characterized in that, The rack includes: The system comprises a top plate, a support plate, a worktable, and a base. Multiple vertical support shafts are fixed to the base, with the worktable fixedly connected to the middle of each shaft. The female mold is fixed within a through-hole in the worktable. The support plate is slidably fitted above the multiple vertical support shafts, and its top is fixedly connected to the top plate via a column. A second variable frequency motor is fixed to the top plate, and its output shaft is fixedly connected to the connecting section of the pressure head. The support plate is fixedly connected to the support frame at the lifting end of the worm gear screw jack, so that the pressure head can move up and down along the vertical support shafts under the drive of the worm gear screw jack.

7. The spiral rotor powder metallurgy green billet forming machine according to claim 6, characterized in that, Also includes: Feeding mechanism; The feeding mechanism includes a feeding box, a feeding pipe, and a feeding hydraulic cylinder; a slide rail is provided on the worktable, the feeding box is set on the slide rail, the feeding hydraulic cylinder is configured to drive the feeding box to reciprocate along the slide rail, and the feeding pipe is connected to the feeding box and extends to the top of the female mold.

8. A method for forming green billets of powder metallurgy using a spiral rotor, applicable to the spiral rotor powder metallurgy green billet forming machine as described in any one of claims 1-7, characterized in that, The method includes: Powder filling stage: The drive rod is rotated along the spiral path into the spiral cavity to seal the bottom end of the spiral cavity and fill the spiral cavity with powder; Pressing stage: The driving head and push rod rotate along the spiral path to press the powder in the spiral cavity in both directions. Demolding stage: Drive the pressure head to continue rotating downward to push the green blank out along the spiral path, and drive the ejector pin to rotate in the opposite direction and exit the spiral cavity downward.

9. The method for forming a spiral rotor powder metallurgy green billet according to claim 8, characterized in that, During the suppression phase: The pressure head is actively driven to rotate and be fed by the drive assembly; Under linear drive, the push rod is passively driven to rotate and feed through the helical pair between the outer surface of the second helix and the inner wall of the helical cavity; The pressure head and the push rod move in opposite directions, causing the powder to be subjected to bidirectional circumferential shearing and compaction while being compressed axially.

10. The method for forming a spiral rotor powder metallurgy green billet according to claim 9, characterized in that, During the demolding stage: The outer surface of the first spiral of the pressure head always maintains a spiral pair engagement with the inner wall of the spiral cavity, pushing the green billet out from the bottom of the spiral cavity along the spiral path; The push rod rotates in the opposite direction and moves downward to exit the spiral cavity to make way; The green blank rotates and exits naturally under the guidance of the spiral cavity.

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