Powder metallurgy drive hub high density compaction apparatus and compaction process

Abstract

This invention relates to the field of powder metallurgy mold technology, specifically to a high-density pressing device and process for powder metallurgy active wheel hubs. The device forms a multi-step cavity through an integral female mold body, mandrel, upper punch assembly, and lower punch assembly. Multiple circumferentially variable-volume powder replenishing components are arranged around the fixed mold base, and a powder replenishing piston changes the volume of the powder storage cavity. After pre-pressing, powder is replenished to the root of the step, and the gate is closed after replenishment. Multiple powder replenishing pistons are synchronously driven by an annular piston, a conical pressure ring, and a driven block. An axial differential compensation component is set between the pressing main slide and the upper punch assembly, allowing different forming areas to compensate for displacement based on the forming resistance during the final pressing stage. This invention can improve the problem of localized powder shortage at the root and outer periphery of the multi-step active wheel hub steps, and is beneficial for improving the compaction consistency of each area of ​​the pressed blank and reducing demolding damage.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy mold technology, specifically to a high-density pressing device and pressing process for powder metallurgy active wheel hubs. Background Technology

[0002] Powder metallurgy drive hubs are typically not simple disc components with uniform thickness and cross-section; Figure 11 , Figure 12 Taking the structure shown as an example, the active hub has a central hub section, a radial disk section and an outer peripheral drive section. The axial height, cross-sectional area and contact length with the mold wall are different at different positions. When conventional one-time powder filling and axial pressing are used, after the powder enters the multi-step cavity from the feeding position, it will be affected by step obstruction, particle bridging and mold wall friction. The initial filling amount is prone to be insufficient at the root of the step, the outer peripheral drive section and other positions.

[0003] For example, patent publication number CN206732128U discloses a powder metallurgy mold for a high-pressure pump toothed wheel hub with a keyway conical hole, including a middle mold, an upper punch assembly, and a lower punch assembly. The middle mold has a mold cavity with a shape structure consistent with the high-pressure pump toothed wheel hub. The upper punch assembly includes an upper first punch and an upper second punch. The lower punch assembly includes a lower first punch, a lower second punch, a stepped mandrel, a process spring, and a floating mandrel. In use, both the upper punch assembly and the lower punch assembly fit with the mold cavity. This utility model optimizes and adjusts the mold structure, using a combination of the middle mold, upper punch assembly, and lower punch assembly to press the high-pressure pump toothed wheel hub in one step. Analysis of the above metallurgical mold reveals that existing multi-step pressing usually adjusts the axial compression of each region through layered punches. This method can improve the compression difference caused by different powder column heights, but its premise is still that each region has a suitable initial powder quality. In some cases, if there is insufficient powder in a local area, simply increasing the axial stroke can easily transfer the density difference to adjacent areas. If pressure is applied directly from the side during the final pressing stage, problems such as powder backflow, reaction force on the lateral actuator, and local overpressure can easily occur. Secondly, the clamping force of the high-density blank in the die is relatively large. If the radial mechanism is not completely withdrawn before ejection, the edge of the step may also be subjected to a large shear load.

[0004] In view of the above-mentioned problems, the present invention designs a powder metallurgy active wheel hub high-density pressing device and pressing process. Summary of the Invention

[0005] The purpose of this invention is to provide a high-density pressing device and pressing process for powder metallurgy active wheel hubs, so as to solve the problems mentioned in the background art.

[0006] In a first aspect, to achieve the above objectives, the present invention provides the following technical solution: a powder metallurgy active wheel hub high-density pressing device, comprising a frame, a pressing main slider disposed above the frame and capable of moving axially, a mold assembly, an upper punch assembly and a lower punch assembly, characterized in that the mold assembly comprises a fixed mold base, an integral female mold body disposed inside the fixed mold base and capable of floating axially relative to the fixed mold base, and a mandrel disposed along the central axis of the device, wherein the integral female mold body, the mandrel, the upper punch assembly and the lower punch assembly together form a multi-step cavity; A circumferential variable volume powder replenishing assembly is provided on the outer side of the fixed mold base. The circumferential variable volume powder replenishing assembly includes multiple powder replenishing boxes. Each powder replenishing box is provided with a powder storage cavity, a powder replenishing throat communicating with a multi-step cavity, and a powder replenishing piston that can move radially. A gate sleeve that can switch between a connected position and a closed position is provided at the powder replenishing throat. A compaction nose is provided at the end of the powder replenishing piston near the multi-step cavity. The annular pressure equalization drive locking assembly is provided around the circumferential variable volume powder replenishing assembly. The annular pressure equalization drive locking assembly includes an annular piston, a conical pressure ring, multiple driven blocks corresponding to the powder replenishing piston, a self-locking element for limiting the radial outward retraction of the driven blocks, and a release piston for releasing the locking state of the self-locking element. The annular piston can push the conical pressure ring to move axially, and push the multiple driven blocks to move radially through the conical pressure ring. An axial differential compensation assembly is provided between the main pressing slider and the upper punch assembly. The axial differential compensation assembly includes a main pressure plate, a closed pressure medium cavity, a first output piston and a second output piston. The pressure-bearing sides of the first output piston and the second output piston are both connected to the closed pressure medium cavity and are respectively connected to the upper inner punch and the upper outer punch in the upper punch assembly.

[0007] As a further aspect of the present invention: a floating demolding assembly is provided below the overall female mold body, the floating demolding assembly including a floating support member for supporting the overall female mold body and allowing the overall female mold body to float axially.

[0008] As a further aspect of the present invention: the multi-step cavity is formed sequentially from the inside to the outside into a central hub forming area, a radial disc forming area, and an outer peripheral driving forming area; the central hub forming area is located on the outside of the mandrel, the radial disc forming area is located on the radial outside of the central hub forming area, the outer peripheral driving forming area is located on the radial outside of the radial disc forming area, and an exhaust micro-groove is provided at the step transition position between adjacent forming areas, and the exhaust micro-groove is connected to the exhaust manifold.

[0009] As a further aspect of the present invention: multiple powder replenishing boxes are arranged circumferentially along the fixed mold base and facing the multi-step cavity, and the powder replenishing piston slides in cooperation with the inner wall of the powder replenishing box; when the powder replenishing piston moves away from the multi-step cavity, it expands the effective volume of the powder storage cavity; when the powder replenishing piston moves towards the multi-step cavity, it reduces the effective volume of the powder storage cavity, and pushes the powder in the powder storage cavity into the multi-step cavity through the powder replenishing throat. When the gate sleeve is in the connected position, the powder storage chamber is connected to the multi-step cavity through the powder replenishment throat; after the powder replenishment is completed, the gate sleeve switches to the closed position, which separates the powder storage chamber from the multi-step cavity. The powder replenishment piston continues to move toward the multi-step cavity and performs radial micro-compaction on the powder replenished into the multi-step cavity through the compaction nose.

[0010] As a further aspect of the present invention: the conical pressure ring has a circumferentially continuous conical force transmission surface, and multiple driven blocks are arranged along the circumference of the conical pressure ring. One side of the driven block contacts or cooperates with the conical force transmission surface of the conical pressure ring, and the other side is connected to or abuts against the corresponding powder replenishing piston for force transmission. When the conical pressure ring moves axially, it simultaneously pushes multiple driven blocks to move radially inward through the conical force transmission surface, and the multiple driven blocks push the corresponding powder replenishing piston respectively.

[0011] As a further aspect of the present invention: the self-locking component is disposed between the radial outward retraction path of the driven block and the fixed support seat, and restricts the radial outward retraction of the driven block after the driven block reaches the powder replenishment endpoint or the radial micro-compaction endpoint. The release piston is disposed on the side of the self-locking component facing away from the wedge tightening direction. The output end of the release piston directly abuts against the release end of the self-locking component or is connected to the self-locking component through a short push rod, and can push the self-locking component out of the locking position.

[0012] As a further aspect of the present invention: the axial differential compensation assembly further includes a first mechanical limiting member and a second mechanical limiting member; the first mechanical limiting member is disposed at the stroke limiting position of the first output piston, and the second mechanical limiting member is disposed at the stroke limiting position of the second output piston; when the forming resistance of the forming area corresponding to one of the first and second output pistons increases, the pressure medium chamber is closed to allow the other output piston to continue to generate compensation displacement, and the first or second mechanical limiting member restricts the corresponding output piston from continuing to move.

[0013] As a further aspect of the present invention: the pressing device further includes a detection and control component, which is used to identify or control the pressing, holding and return states of the pressing main slider, and coordinate the action sequence of circumferential powder replenishment, gate sleeve opening and closing, self-locking component holding, release piston release and lower punch assembly ejection; the floating support component is arranged around the mold axis and jointly supports the overall female mold body, so that the overall female mold body can generate axial floating during the pressing process, and moves downward relative to the pressed blank before the lower punch assembly ejects the pressed blank during the unloading process.

[0014] Secondly, the high-density pressing process for powder metallurgy drive hubs is applicable to the aforementioned high-density pressing device for powder metallurgy drive hubs. The pressing process includes the following steps: Step 1: Set the powder filling box around the circumference of the fixed mold base so that the powder filling throat faces the multi-step cavity. The powder filling piston retracts to the powder storage position, the gate sleeve remains connected, and powder is filled into the multi-step cavity, and some powder enters the powder storage cavity through the powder filling throat. Step 2: Pressing the main slider drives the upper inner punch and upper outer punch to perform axial pre-compression on the powder in the multi-step cavity. During the pre-compression process, the air between the powder particles enters the exhaust manifold through the exhaust micro-groove and is discharged. Step 3: After pre-compression is completed, the annular piston pushes the conical pressure ring to move axially, the conical pressure ring pushes multiple driven blocks to move radially inward, and the driven blocks push the corresponding powder replenishing piston to move toward the multi-step cavity, so that the powder in the powder storage cavity is replenished into the multi-step cavity through the powder replenishing throat. Step 4: After the powder replenishment is completed, switch the gate sleeve to the closed position. The conical pressure ring continues to push the powder replenishment piston to move through the driven block, so that the compaction nose performs radial micro-compaction on the replenished powder. After the radial micro-compaction is completed, the self-locking component maintains the radial position of the driven block and the powder replenishment piston. Step 5: Press the main slider to continue to descend, the main pressure plate loads the closed pressure medium cavity, and the closed pressure medium cavity simultaneously transmits pressure to the first output piston and the second output piston. The first output piston and the second output piston respectively drive the upper inner punch and the upper outer punch to perform final pressing, and perform displacement compensation according to the forming resistance of the corresponding forming area. Step 6: After the final pressing is completed, the main slide block is pressed back, the piston is released and pushes the self-locking part out of the locked position, so that the driven block and the powder replenishing piston retract radially outward. Then, the floating support part makes the whole female mold body move downward relative to the blank, and finally the lower inner punch and the lower outer punch work together to push out the blank.

[0015] As a further aspect of the present invention: during the circumferential powder replenishment process, the effective volume of the powder storage cavity is reduced by moving the powder replenishment piston, and the powder in the powder storage cavity is replenished into the root of the step through the powder replenishment throat; during the radial micro-compaction process, the gate sleeve is first used to separate the powder storage cavity from the multi-step cavity, and then the powder replenishment piston continues to move and the replenished powder is radially micro-compacted through the compaction nose; during the unloading process, the pressing main slider returns, the release piston releases the self-locking component, the powder replenishment piston retracts, the overall female mold body moves downward relative to the blank, and the lower punch assembly ejects the blank in sequence.

[0016] Compared with the prior art, the beneficial effects of the present invention are: After normal powder filling and pre-compression, powder is added to the step root and other places where powder is prone to shortage by using the circumferential variable volume powder filling component. This allows the local powder quality deficiency to be compensated before final compression. After the powder filling is completed, the powder filling passage is closed first, and then the compaction nose is used to radially micro-compact the powder that has just been added, so that the powder filling and local compaction are completed in sequence. By forming a common driving relationship through an annular piston, a conical pressure ring, and multiple driven blocks, multiple powder replenishing pistons can move synchronously based on the same driving structure. The self-locking component maintains the position after powder replenishment and radial micro-compaction, thereby reducing the powder reaction force generated by the subsequent final compaction that causes the powder replenishing piston to retract. By coordinating the closed pressure medium cavity with different output pistons, the upper inner and outer punches can compensate for displacement based on the forming resistance of different forming areas at the final pressing stage. This allows for seamless integration of local powder filling and overall axial compaction. During the demolding stage, loads in different directions are released in stages according to the sequence of reducing axial load, releasing radial lock, retracting the powder filling piston, moving the overall female mold body downward, and ejecting the lower punch. This helps reduce the mold wall friction of the high-density compact and the concentrated shearing action on the steps and outer periphery, thereby improving the consistency of local filling and compaction of the multi-step active hub and reducing the possibility of damage during demolding. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of the powder metallurgy active hub high-density pressing device of the present invention. Figure 2 for Figure 1 A magnified view of part A in the diagram; Figure 3 This is a schematic diagram of the circumferential arrangement of the circumferential variable volume powder replenishment component and the annular pressure equalization drive locking component; Figure 4 A three-dimensional structural diagram of a circumferential variable volume powder replenishment assembly installed on a fixed mold base; Figure 5 The diagram shows the three working states of the powder replenishment box, where a is the powder storage state, b is the powder replenishment state after pre-compression, and c is the radial micro-compaction state after the gate is closed. Figure 6 This is a partial cross-sectional view of the overall annular equalizing pressure drive locking assembly. Figure 7 This is a partial cross-sectional view of the self-locking component and the driven block in two different working positions, where a and b represent the two mating states, respectively. Figure 8 This is a partially enlarged and three-dimensional structural schematic diagram of the annular equalizing pressure drive locking assembly; Figure 9 This is a schematic diagram showing the connection between the axial differential compensation component and the upper punch component; Figure 10 This diagram illustrates the graded unloading and low-damage demolding process, where a, b, and c represent the axial unloading, release of radial locking, and ejection of the blank after the female mold retracts, respectively. Figure 11 A schematic diagram of the functional segmentation of the drive hub; Figure 12 This is a three-dimensional structural diagram of the active hub. In the diagram: frame 100, pressing main slide block 110. Mold assembly 200, fixed mold base 210, integral female mold body 220, central hub forming area 221, radial disc forming area 222, outer peripheral drive forming area 223, venting micro-groove 224, venting manifold 225, mandrel 230. Upper punch assembly 240, upper inner punch 241, upper outer punch 242, lower punch assembly 250, lower inner punch 251, lower outer punch 252; Circumferential variable volume powder replenishing assembly 300, powder replenishing box 310, powder storage chamber 311, powder replenishing throat 312, powder replenishing piston 313, gate sleeve 314, compaction nose 315; The annular equalizing pressure drive locking assembly 400 includes an annular piston 410, a conical pressure ring 420, a driven block 430, a self-locking component 450, and a release piston 460. Axial differential compensation assembly 500, main pressure plate 511, closed pressure medium chamber 512, first output piston 513, second output piston 514, first mechanical limiter 515, second mechanical limiter 516; Detection and control component 600; Floating demolding assembly 700, floating support component 710; Central hub section 11, radial disc section 12, outer peripheral drive section 13. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To facilitate differentiation from the further improved disclosure, the following supplementary explanations are provided regarding the structural form, material selection, processing and manufacturing, preferred size range, connection and sealing methods, and assembly and debugging relationships of key components. These parameters serve as preferred examples for directly implementing this solution. Without altering the structure and force transmission relationship shown in the attached drawings, they can be adjusted proportionally or through technological means based on the specifications of the drive hub and the tonnage of the press.

[0023] First of all, it should be noted that, Figures 11-12 As shown, the active hub pressed in this embodiment is formed radially from the inside to the outside as follows: a central hub section 11, a radial disk section 12, and an outer peripheral drive section 13. The central hub section 11 is located at the center of the hub and is used to form the central shaft hole and the axial protrusion around it. The radial disk section 12 extends outward from the central hub section 11 and forms the main disk surface of the active hub. The outer peripheral drive section 13 is located at the outer edge of the radial disk section 12 and is used to form the thicker outer periphery or the part with the drive structure. The three parts are continuous with each other, but their axial height and cross-sectional thickness are different. Therefore, the corresponding powder column height, mold wall contact length, and compression resistance are also different during pressing. It should be emphasized that the junction of the central hub section 11 and the radial disc section 12, as well as the junction of the radial disc section 12 and the outer peripheral drive section 13, form a stepped transition position. The subsequent powder replenishment and pressure equalization in this embodiment are mainly aimed at these parts that are prone to powder shortage. Example

[0024] like Figure 1 As shown, a powder metallurgy active wheel hub high-density pressing device includes a frame 100; the entire pressing device is installed on the frame 100, the frame 100 constitutes the fixed support foundation of the device, the upper part of which leaves a pressing space, and the lower part is used to bear the reaction force generated during the pressing and demolding process. A pressing main slide 110 is provided above the frame 100 and moves up and down along the axis. The pressing main slide 110 corresponds to the main drive end of the press. During operation, it provides the main pressing stroke downward. During the return stroke, it drives the upper pressing mechanism away from the mold. In this way, the frame 100 provides a fixed reference and the pressing main slide 110 provides the axial driving force. The two work together to form the basis for the subsequent mold pressing action.

[0025] As a directly manufacturable structure, the frame 100 can be welded from Q355B steel plates into a closed or four-column load-bearing frame. After welding, stress-relief annealing or vibration aging is performed, and then the reference surface in contact with the fixed mold base 210 and guide parts is milled and ground as a whole. For medium and small-sized devices, HT300 or QT500-7 can also be integrally cast.

[0026] The pressing main slide block 110 is preferably made of 45 steel, 40Cr or 42CrMo forgings, which are then heat-treated and precision-machined. It is axially guided with the frame 100 by one of the following: guide post and guide sleeve, rectangular slide rail or rolling linear guide. Taking the active wheel hub with an outer diameter of about 150 to 250 mm as an example, the effective working stroke of the pressing main slide block 110 can be set to 80 to 250 mm. The clearance on one side of the guide pair is preferably controlled at 0.01 to 0.05 mm to balance the load-bearing capacity and repeatability.

[0027] The frame 100 and the fixed mold base 210 are preferably connected by high-strength bolts and at least two cylindrical locating pins, wherein the bolts bear the clamping force and the locating pins bear the radial positioning during repeated assembly; the perpendicularity of the mounting reference surface of the fixed mold base 210 to the motion axis of the pressing main slide block 110 is preferably no greater than 0.03mm / 100mm. The above connection method allows the mold assembly 200 to return to its original center position after disassembly and assembly, and reduces the cumulative coaxiality error caused by multiple mold changes.

[0028] Furthermore, a mold assembly 200 is provided in the middle of the frame 100. The mold assembly 200 includes a fixed mold base 210, an integral female mold body 220, and a mandrel 230. The fixed mold base 210 is installed in the pressing working area of ​​the frame 100 to determine the radial position of the entire forming mold and to provide a base for the circumferentially arranged powder replenishment mechanism. The integral female mold body 220 is disposed inside the fixed mold base 210, and its outer periphery forms a guiding and supporting relationship with the fixed mold base 210. The mandrel 230 is arranged along the central axis of the device and extends into the central area of ​​the integral female mold body 220 to define the shape and position of the central hole of the drive hub. The fixed mold base 210 provides a fixed reference, the integral female mold body 220 provides the outer periphery and stepped forming surface, and the mandrel 230 provides the center hole forming surface. The positional relationship of the three together determines the basic outline of the active hub cavity. It should be noted that the integral female mold body 220 and the fixed mold base 210 are not completely locked in the axial direction, but the integral female mold body 220 is allowed to float axially with a small stroke within a set range.

[0029] The fixed mold base 210 is preferably made of 40Cr, 42CrMo or equivalent quenched and tempered alloy steel, and the quenching and tempering hardness can be controlled at HRC28~36. Its inner hole and end face are ground to form the installation and guiding reference of the integral female mold body 220. The integral female mold body 220 is in direct contact with the powder and bears the radial expansion pressure under the pressing conditions of 650~850MPa. Its working insert can be made of Cr12MoV, DC53, SKD11 type cold work die steel, or YG15, YG20 type cemented carbide. When using die steel, it is preferred to vacuum quench and temper to make the hardness of the working area reach HRC58~62, and the cavity surface is finely ground, polished or PVD wear-resistant treated. The mandrel 230 is preferably made of high speed tool steel, powder high speed steel, DC53 or cemented carbide. Its outer working surface is preferably Ra0.2~0.8μm after grinding.

[0030] The integral female mold body 220 and the fixed mold base 210 adopt an axial sliding guide fit. The radial clearance is designed to prevent significant swaying and allow for smooth floating. H7 / g6 or equivalent fit is preferred. When converted to the diameter of commonly used molds, the working clearance on one side can be 0.01 to 0.04 mm. A guide section with a length of 15 to 50 mm can be set on the outer periphery of the integral female mold body 220. The surface hardness and roughness of the guide section should meet the requirements for repeated floating.

[0031] Furthermore, an upper punch assembly 240 is provided above the overall female mold body 220. The upper punch assembly 240 includes an upper inner punch 241 arranged near the central axis of the device and an upper outer punch 242 located outside the upper inner punch 241. Both the upper inner punch 241 and the upper outer punch 242 can move along the axial direction and correspond to the axial forming area of ​​the active wheel hub respectively. The overall female mold body 220 is provided with a lower punch assembly 250 opposite to the upper punch assembly 240. The lower punch assembly 250 includes a lower inner punch 251 and a lower outer punch 252. The lower inner punch 251 is matched with the upper inner punch 241, and the lower outer punch 252 is matched with the upper outer punch 242. That is, the inner wall of the overall female mold body 220, the outer wall of the mandrel 230, the lower forming surface of the upper punch assembly 240, and the upper forming surface of the lower punch assembly 250 together form a multi-step cavity. By utilizing the relative movement and change of the upper inner punch 241, upper outer punch 242, lower inner punch 251, and lower outer punch 252 in the axial position, the height of the powder column in each forming area is changed, thereby achieving axial compaction of the powder.

[0032] The upper inner punch 241, upper outer punch 242, lower inner punch 251, and lower outer punch 252 are preferably made of Cr12MoV, DC53, SKH51, powder high-speed steel, or cemented carbide. After grinding and polishing, the Ra of the working end of the punch is preferably no greater than 0.8μm. The non-working end of each punch can be equipped with a stepped flange, T-head, or threaded connection. It is detachably connected to the corresponding output piston or press punch seat by a pressure plate, nut, or pin. After connection, the coaxiality of the punch axis and the mandrel 230 axis is preferably no greater than 0.03mm.

[0033] Furthermore, participation Figure 1 , Figure 12 Based on the three functional areas of the active hub, namely the central hub section 11, the radial disk section 12, and the outer peripheral drive section 13, the multi-step cavity is formed with the central hub forming area 221, the radial disk forming area 222, and the outer peripheral drive forming area 223 respectively. Specifically, the central hub forming area 221 is located outside the mandrel 230, corresponding to the central hub section 11 of the drive hub. The radial disc forming area 222 is located radially outside the central hub forming area 221, corresponding to the radial disc 12. The outer peripheral driving area 223 is located outside the radial disc forming area 222, corresponding to the outer peripheral driving section 13. The central hub forming area 221, the radial disc forming area 222, and the outer peripheral driving forming area 223 are continuously transitioned by a stepped surface. After powder filling, when the powder crosses the step and enters a deeper position, it will be blocked, which is also the reason for the technical problem that this technical solution aims to solve.

[0034] like Figure 1 , Figure 2As shown, an exhaust micro-groove 224 is provided at the transition position of the adjacent steps between the central hub forming area 221, the radial disc forming area 222 and the outer peripheral drive forming area 223. One end of the exhaust micro-groove 224 extends toward the root of the step in the multi-step cavity, and the other end is connected to an exhaust manifold 225. The exhaust manifold 225 is used to collect the gas from multiple local exhaust positions and then export it to the external area of ​​the mold. During pre-compression, the compressed air between the powder particles first enters the exhaust micro-groove 224 and then enters the exhaust manifold 225, thereby reducing the possibility of forming a closed airbag at the root of the step. Among them, the exhaust micro-groove 224 only needs to meet the exhaust requirements, and its cross-section should not be too large to avoid a large amount of powder entering the exhaust channel.

[0035] Preferably, the exhaust manifold 225 is disposed on the outer peripheral surface or end face of the integral female mold body 220 near the fixed mold base 210, and forms a continuous or segmented continuous annular groove around the multi-step cavity. The outer ends of each exhaust micro-groove 224 are respectively connected to the annular groove. The exhaust manifold 225 is then connected to the external atmosphere or negative pressure exhaust pipe of the mold through one or more radial exhaust holes.

[0036] For example, based on the particle size of commonly used iron-based powder, the groove depth of the venting microgroove 224 can preferably be 0.02-0.08 mm and the groove width can be 0.10-0.50 mm. The width of the venting manifold 225 can be 1-4 mm and the depth can be 0.5-2 mm. The diameter of the radial venting hole can be 1-4 mm. The end of the venting microgroove 224 near the cavity should preferably have a smooth transition and be deburred so that air can pass through while large particles of powder do not easily enter the manifold in large quantities.

[0037] Furthermore, such as Figure 1 , Figures 3-5 As shown, a circumferential variable volume powder replenishing component 300 is provided on the outer circumferential side of the fixed mold base 210; the circumferential variable volume powder replenishing component 300 is arranged around the multi-step cavity, and is used to replenish powder to the local short powder positions such as the root of the step after normal powder filling and pre-compression. Preferably, eight sets of circumferential variable volume powder filling components 300 are provided, and all of them are distributed towards the multi-step cavity. By utilizing the full powder filling of the eight sets of circumferential variable volume powder filling components 300, the powder can be directly applied to the step transition area that is not easy to be fully filled by conventional feeding.

[0038] Specifically, the circumferential variable volume powder replenishing assembly 300 includes a powder replenishing box 310; the powder replenishing box 310 is installed on the periphery of the fixed mold base 210 and is arranged approximately radially along its length direction. The powder replenishing box 310 has a powder storage cavity 311 for temporarily storing compensation powder. A powder replenishing throat 312 is formed or connected to the side of the powder storage cavity 311 near the multi-step cavity. The powder replenishing throat 312 passes through the corresponding area of ​​the fixed mold base 210 and communicates with the radial disk forming area 222 or the adjacent step transition area, thereby forming an openable and closable local powder replenishing path between the powder storage cavity 311 and the multi-step cavity. Through this powder replenishing path, the powder can reach the position that needs compensation through a shorter radial path. The powder replenishing box 310 is equipped with a powder replenishing piston 313 that can move radially back and forth. The powder replenishing piston 313 slides in fit with the inner wall of the powder replenishing box 310. When the powder replenishing piston 313 moves away from the multi-step cavity, it expands the effective volume of the powder storage cavity 311, so that the powder storage cavity 311 can receive and store powder during the normal powder filling stage. When it moves towards the cavity, it compresses the powder storage cavity 311, so that the powder stored therein is forced to move towards the powder replenishing throat 312. In this way, the radial displacement of the powder replenishing piston 313 can be converted into a change in the volume of the powder storage cavity 311, thereby pushing a certain amount of pre-stored powder into the multi-step cavity. Preferably, a gate sleeve 314 is provided at the powder replenishment throat 312 to open and close the powder replenishment passage. The gate sleeve 314 corresponds to the powder replenishment throat 312 and can switch between the connected position and the closed position with a small stroke. For example, when in the connected position, the powder storage cavity 311 can communicate with the multi-step cavity through the powder replenishment throat 312. After switching to the closed position, the powder storage cavity 311 and the multi-step cavity are separated, which can prevent the powder in the multi-step cavity from flowing back to the powder storage cavity 311 during the subsequent pressing process.

[0039] The powder replenishing piston 313 has a compaction nose 315 at one end near the cavity. The compaction nose 315 corresponds to the powder replenishing throat 312 and the local position of the multi-step cavity. After the gate sleeve 314 is closed, it can continue to move inward with the powder replenishing piston 313 to perform short-stroke radial compaction on the powder that has just been replenished to the root of the step.

[0040] Preferably, the powder replenishing box 310 is made of 40Cr, 42CrMo or 38CrMoAl alloy steel and machined into a rectangular or cylindrical shell, and is fixed to the periphery of the fixed mold base 210 by bolts and positioning pins. For occasions that require frequent disassembly and cleaning, a replaceable sealing gasket or metal contact surface can be provided between the powder replenishing box 310 and the fixed mold base 210. The guide hole in the powder replenishing box 310 that mates with the powder replenishing piston 313 is preferably honed or internally ground, and the surface roughness Ra can be controlled within 0.4 to 0.8 μm.

[0041] The gate sleeve 314 can be a plate-type sliding gate, a sleeve-type sliding gate, or a small wedge-shaped gate. The structure shown in the figure is preferably a plate-type or sleeve-type gate that slides laterally along the powder filling throat 312. The gate sleeve 314 can be driven by a small hydraulic cylinder, pneumatic cylinder, electromagnetic push rod, or mechanical cam. Its opening and closing stroke is usually 1 to 6 mm. The gate sleeve 314 is preferably made of 40Cr, Cr12MoV, or stainless wear-resistant steel. The sliding surface can be nitrided or hard chrome treated. When the gate sleeve 314 is in the closed position, its closed surface forms a surface contact or small clearance fit with the periphery of the powder filling throat 312, so that the powder is not easy to backflow into the powder storage chamber 311 during the final pressing process.

[0042] The compaction nose 315 and the powder filling piston 313 are machined as a single unit, or a replaceable wear-resistant head can be fixed by threads, dovetail grooves, or pressure plates. Furthermore, such as Figure 5 As shown, it illustrates three consecutive operating states of the toner cartridge 310, such as... Figure 5 a is the powder storage state: At this time, the powder replenishing piston 313 is in the retracted position, the powder storage chamber 311 has a large effective volume, the gate sleeve 314 remains connected, and some powder can enter the powder storage chamber 311 during normal feeding. Figure 5 b is the powder replenishment state after pre-compression: At this time, the gate sleeve 314 remains connected, the powder replenishment piston 313 moves toward the cavity, the volume of the powder storage cavity 311 gradually decreases, and the stored powder is pushed into the root of the step through the powder replenishment throat 312. Figure 5 c represents the radial micro-compacted state after powder replenishment: at this time, the gate sleeve 314 is first switched to the closed position, and then the powder replenishment piston 313 continues to move inward, so that the compaction nose 315 exceeds the multi-step cavity reference surface and is directly pressed on the powder replenishment area.

[0043] These three states continuously complete the powder storage, powder replenishment, and gate-closing micro-compaction, so that the quality of the replenished powder and the local compaction after powder replenishment are completed in two separate actions.

[0044] Specifically, during the operation of the above three states, it should be noted that the powder replenishing piston 313 can continue to move inward by 0.03 to 0.30 mm after the gate sleeve 314 is closed; within the trial molding range of this embodiment, the stroke of the compaction nose 315 across the multi-step cavity reference surface can preferably be controlled within 0.08 to 0.18 mm; the first part of the powder replenishing stroke is mainly used to change the volume of the powder storage cavity 311 and replenish the powder in place, while the second part of the shorter stroke is mainly used to organize and compact the powder that has just entered the root of the step, rather than relying on a larger lateral stroke to replace the axial final pressure, so as to avoid directly increasing the lateral pressure when there is originally insufficient powder in a local area.

[0045] The initial powder replenishment amount of the powder replenishment box 310 can be calibrated by the initial effective volume of the powder storage cavity 311. During specific assembly, a threaded limit can be set at the end of the powder replenishment piston 313 away from the multi-step cavity, or limit shims of different thicknesses can be used to change the retraction endpoint of the powder replenishment piston 313, thereby changing the effective volume of the powder storage cavity 311 in the powder storage state. At the same time, the above-mentioned multiple powder replenishment boxes 310 can be initially calibrated according to the same benchmark to keep the preset powder replenishment amount of each circumferential position consistent as much as possible. For products with different local requirements, the initial volume of the corresponding powder replenishment box 310 can also be adjusted separately.

[0046] When quantitative replenishment by mass is required, the target replenishment mass can be determined first based on the theoretical volume V0 of the pressed blank and the set replenishment ratio η. Then, the effective volume of the powder storage chamber 311 can be calculated by combining the loose packing density ρa of the powder used. That is, the target powder storage volume of a single replenishment box 310 is approximately set as ΔV=m / ρa, where m is the target replenishment mass allocated to the replenishment box 310. For example, for the case of replenishing powder in eight replenishment boxes 310 with equal amounts, the total replenishment amount can be set into eight equal parts first, and then the powder mass discharged from a single box can be weighed for secondary calibration. If the powder shortage is more obvious in a certain circumferential position, the retraction stroke of the replenishment box 310 can be increased accordingly without changing the structure of the other replenishment boxes.

[0047] like Figure 3 , Figures 6-8 As shown, in order to further maintain a unified driving reference for multiple powder replenishing pistons 313, an annular pressure equalization drive locking component 400 is provided around the annular variable volume powder replenishing component 300. The annular pressure equalization drive locking component 400 transmits radial driving force to multiple powder replenishing pistons 313 simultaneously through a single annular drive structure. Compared with multiple independent drive ends, it can effectively reduce the synchronization deviation that occurs during control. Preferably, the annular drive structure adopts the form of an annular hydraulic cylinder. An annular cylinder cavity is machined in the annular support housing that is fixedly connected to the fixed mold base 210 or outside the fixed mold base 210. The annular piston 410 can be axially slidably installed in the annular cylinder cavity. The outer circle and inner circle of the annular piston 410 are respectively sealed with the annular cylinder cavity through high-pressure resistant sealing rings. The annular cylinder cavity is connected to the hydraulic source through the inlet and outlet oil ports. When hydraulic oil enters the working cavity, the annular piston 410 moves axially as a whole and pushes the conical pressure ring 420. In addition to hydraulic drive, in specifications with smaller loads, an annular cylinder or multiple circumferentially uniformly braced rods can also be used to push the annular piston 410. However, all driving points ultimately act on the same annular piston 410, so that the conical pressure ring 420 still maintains a uniform axial displacement reference.

[0048] Specifically, the annular pressure equalization drive locking assembly 400 includes an annular piston 410 that moves along the axial direction under force. The annular piston 410 is arranged coaxially with the central axis of the device and forms an annular drive end around the working area of ​​the mold. A conical pressure ring 420 is provided on the force transmission side of the annular piston 410. When the annular piston 410 moves, it applies an axial thrust to the conical pressure ring 420, causing the conical pressure ring 420 to move along the axial direction. Preferably, the conical pressure ring 420 has a circumferentially continuous conical force transmission surface, so that its axial displacement can be converted into a radial component force through the conical surface; The annular piston 410 is preferably made of 42CrMo or 40Cr quenched and tempered steel. After grinding, its mating surface with the annular cylinder cavity can be sealed with polyurethane U-shaped seals, Glyd rings or high-pressure combination seals. Preferably, the cone angle of the conical pressure ring 420 is 10° to 30°. When the cone angle is small, the amplification effect of axial thrust to radial thrust is more obvious, but the required axial stroke increases relatively. When the cone angle is large, the radial response is faster, but the driving force requirement increases. Therefore, it can be selected by combining the powder replenishing stroke of the powder replenishing piston 313 and the auxiliary hydraulic pressure that the press can provide. The driven block 430 is made of 40Cr, 42CrMo, or GCr15 steel and slides radially within a fixed guide groove. The end in contact with the tapered pressure ring 420 can be directly formed with an inclined surface, or rollers or rollers can be installed to reduce friction. When a sliding inclined surface is used, the contact surface can be coated with molybdenum disulfide grease or treated with wear-resistant surfaces such as DLC or nitriding. When rolling contact is used, the rollers or rollers are preferably made of GCr15 bearing steel. Each driven block 430 can transmit force to the powder-replenishing piston 313 via a threaded joint, pin, or end face contact.

[0049] Multiple driven blocks 430, each corresponding to a powder replenishing box 310, are arranged circumferentially along the conical pressure ring 420. One side of each driven block 430 contacts or engages with the conical force transmission surface of the conical pressure ring 420, while the other side connects to or abuts against the corresponding powder replenishing piston 313. When the conical pressure ring 420 moves axially, the same conical force transmission surface simultaneously pushes each driven block 430 to move radially inward, and each driven block 430 then pushes the corresponding powder replenishing piston 313 to compress the powder storage chamber 311. Since multiple driven blocks 430 share the same conical pressure ring 420, their displacement reference comes from the same annular component, which helps to keep multiple circumferential powder replenishing actions consistent.

[0050] Furthermore, a self-locking element 450 for maintaining position is provided near the movement path of each driven block 430; the self-locking element 450 is provided between the driven block 430 and the relatively fixed support part, and enters the locking state after the driven block 430 reaches the powder filling end point or the radial micro-compaction end point, thereby restricting the driven block 430 from retracting radially outward.

[0051] like Figure 7 a, Figure 7 As shown in b, the self-locking component 450 and the driven block 430 are in two working positions; the self-locking relationship shown above can be a rolling element wedge type, or a small cone angle self-locking cone sleeve, roller wedge assembly or split retaining ring can be used according to specific manufacturing conditions. That is, as long as it can withstand the reverse force transmitted from the cavity powder in the final pressing stage and maintain the position of the powder replenishing piston 313. Specifically, the self-locking element 450 is positioned between the radial outward retraction path of the driven block 430 and the fixed support seat, while the release piston 460 is positioned on the side of the self-locking element 450 facing away from the wedging direction. Its output end directly abuts against the release end of the self-locking element 450 or is connected to the self-locking element 450 through a short push rod. When the release piston 460 is not in motion, the self-locking element 450 presses against the driven block 430 under the preload of the spring or the action of the wedge surface, preventing the driven block 430 from retracting radially. When the release piston 460 is extended under pressure, its output end pushes the self-locking element 450 away from the wedging position, creating a release gap between the self-locking element 450 and the driven block 430, allowing the driven block 430 and the powder-replenishing piston 313 to retract outward.

[0052] Preferably, the self-locking component 450 adopts a roller wedge type, with the rollers made of GCr15 bearing steel and hardened. The wedge or raceway can be made of 42CrMo or 20CrMnTi, and used after surface hardening. The wedge angle is preferably 3° to 8° so that the locking effect is enhanced when the reverse load increases. The release piston 460 can be a small hydraulic piston or pneumatic piston with a diameter of 8 to 25 mm, and the actual release stroke is usually only 0.5 to 3 mm. The reset of the release piston 460 can be completed by a compression spring. It should be noted that the above dimensions are based on the principle of reliably releasing the wedge without interfering with the normal stroke of the driven block 430.

[0053] The release piston 460 can move before demolding and disengage the self-locking member 450 from the locked position, so that the driven block 430 and the powder replenishing piston 313 can return to the retractable state. The self-locking member 450 is responsible for "holding" after powder replenishment is completed, and the release piston 460 is responsible for "releasing" when demolding is required. The two work together to separate the force holding of the circumferential powder replenishing mechanism from the subsequent retraction action, so as to avoid the powder reaction force during final pressing directly pushing back to the annular piston 410.

[0054] like Figure 1 , Figure 9 As shown, an axial differential compensation component 500 is provided between the pressing main slider 110 and the upper punch assembly 240; the axial differential compensation component 500 is located on the path through which the main pressing force is transmitted to the upper punch assembly 240. Its function is to passively redistribute the small displacements of the upper inner punch 241 and the upper outer punch 242 at the end of the final pressing stage, based on the overall downward pressure provided by the pressing main slider 110, so that different forming areas can still obtain a relatively suitable compaction stroke under different resistance conditions. The axial differential compensation component 500 includes a main pressure plate 511, which receives the downward pressure of the main slider 110. The main pressure plate 511 moves downward with the main slider 110 and constitutes the main force-bearing component of the differential compensation component. A closed pressure medium cavity 512 is formed within the main pressure plate 511. The closed pressure medium cavity 512 is filled with a pressure medium capable of transmitting pressure and maintains a common pressure space. The function of the closed pressure medium cavity 512 is to convert the overall axial load input by the main slider 110 into a common pressure on multiple output ends, rather than setting completely independent pressure sources for each output end. The lower side of 512 is provided with a first output piston 513 and a second output piston 514 respectively; the first output piston 513 is located at a position corresponding to the upper inner punch 241, and its lower end is connected to the upper inner punch 241 and transmits axial pressure to the upper inner punch 241; the second output piston 514 is located at a position corresponding to the upper outer punch 242, and its lower end is connected to the upper outer punch 242 and transmits axial pressure to the upper outer punch 242; the pressure-bearing sides of the first output piston 513 and the second output piston 514 are both connected to the same closed pressure medium cavity 512, so they work under the same pressure reference, but their actual displacements can vary slightly based on the forming resistance experienced by the connected punches.

[0055] The main pressure plate 511 is preferably machined as a whole using 42CrMo or equivalent high-strength alloy steel. The closed pressure medium cavity 512 can be formed by boring or milling and then sealing it with a cover plate, or an annular or partitioned cavity can be directly machined inside the main pressure plate 511. The cavity is preferably filled with low-compressibility anti-wear hydraulic oil. Preferably, in order to limit the range of differential compensation, a first mechanical limiter 515 is provided at the stroke limit position of the first output piston 513, and a second mechanical limiter 516 is provided at the stroke limit position of the second output piston 514; the first mechanical limiter 515 is used to limit the maximum compensation stroke of the first output piston 513 relative to the main pressure plate 511, and the second mechanical limiter 516 is used to limit the maximum compensation stroke of the second output piston 514; the function of the two mechanical limiters is to set the boundary for the differential action, and prevent one punch from obtaining too much additional displacement when the other punch is blocked, thus causing local overpressure; Preferably, the first mechanical limiting member 515 and the second mechanical limiting member 516 adopt an adjustable mechanical stop structure, which is specifically one of a fine-tooth limiting screw with a locking nut, a limiting washer with replaceable thickness, a threaded limiting ring, or a fixed step shoulder.

[0056] Among them, with Figure 9Taking the structure shown as an example, limiting steps are respectively set on the outer periphery or below of the first output piston 513 and the second output piston 514, and adjustable limiting screws or limiting rings are installed at the corresponding positions on the main pressure plate 511. When the output piston completes the set compensation stroke, the shoulder on the piston contacts the stop surface of the corresponding mechanical limiting component, and the subsequent load is directly transmitted through the main pressure plate 511 and the stop surface, thereby mechanically preventing the output piston from continuing to generate compensation displacement.

[0057] For example, for a drive hub with an outer diameter of 150-250mm, the differential compensation stroke of a single output piston defined by the first mechanical limiter 515 and the second mechanical limiter 516 can preferably be 0.05-0.80mm, more preferably 0.10-0.50mm; when using fine-pitch limit screws, the pitch can be selected as 0.5-1.0mm, and a locking nut or anti-loosening pressure plate is provided; during trial molding, the two limiters are first set at a small compensation amount, and then gradually fine-tuned according to the density measurement results of different forming areas. After adjustment, they are locked to prevent production vibration from changing the limit position.

[0058] When the axial differential compensation component 500 is working, the main slider 110 first compresses the pressure medium in the closed pressure medium cavity 512 through the main pressure plate 511, and the pressure is simultaneously transmitted to the first output piston 513 and the second output piston 514. In the initial stage of final pressure, the upper inner punch 241 and the upper outer punch 242 move down together with the main pressure plate 511. After entering the final stage of final pressure, if the central hub forming area 221 enters a high rigidity state first due to the high powder column or large internal friction, the resistance encountered by the first output piston 513 connected to the upper inner punch 241 as it continues to move down increases. The pressure in the closed pressure medium cavity 512 will cause the second output piston 514 to continue to obtain the remaining small displacement, so that the radial disk forming area 222 and the outer peripheral drive forming area 223 corresponding to the upper outer punch 242 continue to be compacted. Conversely, if the outer forming area enters a high rigidity state first, the remaining compensation displacement can also be more distributed to the first output piston 513. After reaching the corresponding limit, the first mechanical limit member 515 or the second mechanical limit member 516 prevents the compensation from increasing further.

[0059] Furthermore, such as Figure 1 As shown, a detection and control component 600 is also provided on one side of this device; the detection and control component 600 works in conjunction with the execution end and detection point that need to participate in the action sequence control to identify or control the pressing, holding and return states of the pressing main slider 110, and coordinate the sequence of circumferential powder replenishment, gate sleeve opening and closing, self-locking holding, release and retraction and demolding actions. Preferably, the detection and control component 600 can be implemented by combining a controller, pressure detection element and displacement detection element commonly used in presses. This embodiment does not limit the specific sensor model or controller model; its main function is to ensure that the following actions are completed in a predetermined order and to avoid mutual interference. Details will not be elaborated here.

[0060] Preferably, the detection and control component 600 consists of a PLC or industrial controller, a main pressure sensor, a displacement encoder for the pressing main slide block 110, a limit switch for the annular piston 410, a position switch for the brake sleeve 314, a position switch for the release piston 460, and a floating displacement detection component for the overall female mold body 220. The pressure sensor measurement accuracy is preferably not less than ±0.5%FS, and the key displacement detection resolution is preferably at the 0.01mm level. The control logic shall at least set the following interlocks: radial micro-compaction is not allowed when the brake sleeve 314 is not in the closed position; final pressure is not allowed when the self-locking component 450 is not confirmed to be locked; and the lower punch component 250 is not allowed to be ejected when the release piston 460 has not been unlocked and the powder replenishing piston 313 has not retracted.

[0061] The detection and control component 600 uses a conventional electrical connection with hydraulic valve assemblies, pneumatic valve assemblies, or servo actuators, such as... Figure 1 The dashed lines in the diagram only indicate the relationship between control signals and do not restrict the specific laying path of the cable. Control parameters can be saved by product number when changing models, including pre-compression pressure, powder replenishment stroke, micro-compaction stroke, final pressure, holding time, and demolding retraction amount, so that they can be directly called up when producing the same specification repeatedly.

[0062] like Figure 1 , Figure 10 As shown, a floating demolding assembly 700 is provided in the lower support chain of the integral female mold body 220; the floating demolding assembly 700 is located between the mold assembly 200 and the lower support of the frame 100, and is used to provide controlled axial floating and unloading retraction conditions for the integral female mold body 220. The floating demolding assembly 700 is provided with at least two sets of floating support members 710. Multiple floating support members 710 are arranged around the mold axis and jointly support the overall female mold body 220, so that it maintains the required support preload during normal pressing, while allowing the overall female mold body 220 to generate a set small stroke displacement in the axial direction.

[0063] During the main pressing stage, friction exists between the powder and the pressed blank and the inner wall of the integral female mold body 220. Supported by the floating support 710, the integral female mold body 220 can float axially with a small stroke due to this friction, thereby shortening the sliding distance of the powder relative to the mold wall. During the unloading stage, the floating support 710 provides a condition for the integral female mold body 220 to retract earlier, allowing it to move downwards relative to the pressed blank before the lower punch assembly 250 formally ejects it, releasing some of the mold wall clamping force. Therefore, the floating demolding assembly 700 participates in both the friction path adjustment during the pressing stage and the staged unloading during the demolding stage.

[0064] like Figure 1 , Figure 10 As shown, preferably, the floating support 710 adopts a compression helical spring support structure evenly distributed along the circumference, consistent with the spring form shown in the figure; the spring is made of 60Si2Mn or 50CrVA spring steel and placed in the guide hole or spring seat to avoid lateral bending when subjected to eccentric load.

[0065] For larger tonnage devices, disc spring assemblies or small hydraulic floating cylinders can be used instead without changing the support positions shown in the figure. The number of floating support components 710 is preferably 4 to 8 sets, which are symmetrically arranged circumferentially along the mold axis to make the overall female mold body 220 more uniformly stressed. When assembling the floating support components 710, an initial pre-compression amount should be set so that the overall female mold body 220 can be stably supported and returned to its initial height when there is no pressing load. The total spring preload should be greater than the self-weight of the overall female mold body 220 and its connecting parts, and less than the axial force that can be overcome by the friction of the mold wall during the normal pressing stage. Example

[0066] This embodiment provides a high-density pressing process for powder metallurgy active wheel hubs, applicable to the high-density pressing device for powder metallurgy active wheel hubs described in Embodiment 1 above. The specific process includes the following steps: Taking iron-based powder metallurgy active wheel hub as an example, the powder can be pre-alloyed iron powder, diffusion alloyed iron powder or mixed alloyed iron powder, and graphite and lubricant can be added according to the actual material system; the specific grade and ratio of powder are not necessary limitations on the structure of the device of this invention, and can be selected according to the material compressibility and sintering requirements during actual production.

[0067] As a set of powder conditions that facilitate the reproduction of experiments, the bulk particle size of the iron-based powder can preferably be selected in the range of approximately 45–180 μm, and the loose packing density and flowability should meet the requirements for stable filling of the feed shoe; the amount of graphite added can be selected according to the target carbon content, and the commonly used reference range is 0.2%–0.8% (mass fraction); the internal lubricant can be stearate, amide wax or special temperature and pressure lubricant, and the reference addition amount is 0.4%–1.0% (mass fraction); the above ratio is only an optional condition for process verification of this device and does not restrict the use of this device for other copper-based, iron-copper-based or diffusion alloy powder systems.

[0068] Step 1, Mold loading and powder storage preparation: Powder replenishment box 310 according to... Figure 3 , Figure 4 The powder filling throats 312 are installed around the fixed mold base 210 at circumferential intervals, so that each powder filling throat 312 is preferentially aligned with the root of the step between the radial disc forming area 222 and the central hub forming area 221. Each powder filling piston 313 first retracts outward to the pre-marked powder storage position, and the gate sleeve 314 remains connected. When the feeding shoe fills the multi-step cavity formed by the integral female mold body 220, the mandrel 230, the upper punch assembly 240 and the lower punch assembly 250 with powder, the main powder enters each forming area, and at the same time, a part of the powder enters the powder storage cavity 311 through the powder filling throat 312. Since the retraction endpoint of the powder filling piston 313 has been pre-defined, a relatively certain amount of compensation powder can be retained in the powder storage cavity 311.

[0069] Step 2, Pre-compression and venting: After the initial powder filling, the pressing main slider 110 drives the upper punch downwards. The upper inner punch 241 and upper outer punch 242 respectively perform the first axial pre-compression on the powder in the corresponding area. The pre-compression pressure can be 100-180 MPa, so that the loose powder first forms a relatively stable free surface and stepped profile, but still retains space for rearrangement after subsequent powder replenishment. In this stage, the compressed air at the root of the step enters the exhaust manifold 225 along the exhaust micro-groove 224 and is discharged, reducing the impact of local trapped air on subsequent powder replenishment and final compression.

[0070] Step 3, circumferential powder replenishment after pre-compression: After the pre-compression reaches the set state, the pressing main slider 110 maintains its current position or only undergoes a small increase in pressure. The detection and control component 600 causes the annular pressure equalization drive locking component 400 to enter the powder replenishment action. The annular piston 410 pushes the conical pressure ring 420 to move axially. The conical pressure ring 420 uses the circumferential continuous conical surface to synchronously push each driven block 430 radially inward. Each driven block 430 then pushes the corresponding powder replenishment piston 313 to move towards the cavity. As the volume of the powder storage cavity 311 decreases, the powder stored therein enters the root of the step through the powder replenishment throat 312, which is still in a connected state. The amount of powder replenishment can be controlled to be 0.8% to 2.5% of the theoretical volume of the final pressed blank. For the active hub with a large volume of the outer peripheral drive section 13 or a deep tooth root, the amount of powder replenishment can be appropriately increased, but preferably not exceeding 4.0%.

[0071] Step 4, Gate Closure and Radial Micro-compaction: After the powder replenishing piston 313 completes the set volume transfer, the gate sleeve 314 is first switched from the connected position to the closed position, isolating the powder storage chamber 311 from the multi-step cavity. Then, the annular piston 410 continues to cause a small axial displacement of the conical pressure ring 420. The conical pressure ring 420 continues to push the powder replenishing piston 313 inward through the driven block 430. The compaction nose 315 changes from its original state of retreating from the cavity reference surface to crossing the reference surface, performing short-stroke radial micro-compaction on the powder that has just been replenished into the root of the step. After micro-compaction is completed, the self-locking member 450 enters the locking state and maintains the radial position of the driven block 430 and the powder replenishing piston 313, so that the powder reaction force generated by the subsequent final pressure does not push the powder replenishing piston 313 outward.

[0072] Step 5, Final Pressure and Axial Differential Compensation: After the circumferential powder replenishment position is locked, the pressing main slider 110 continues to descend, and the main pressure plate 511 is subsequently loaded downwards. The pressure medium in the closed pressure medium cavity 512 simultaneously applies pressure to the first output piston 513 and the second output piston 514. The first output piston 513 drives the upper inner punch 241 to continue compacting the central hub forming area 221, and the second output piston 514 drives the upper outer punch 242 to continue compacting the radial disc forming area 222 and the corresponding outer area. In the final pressure stage, according to the actual resistance of different areas, the two output pistons automatically distribute a small amount of remaining stroke within the range limited by the first mechanical limiter 515 and the second mechanical limiter 516. For iron-based powders, the final peak pressure can be 650–850 MPa, and the holding time can be 0.3–1.0 s. When using warm pressing, the mold working area can be maintained at 80–140℃. The above parameters serve as a process window for trial molding, and the specific values ​​can be adjusted according to the powder compressibility, lubrication system, and hub size.

[0073] During the process debugging phase, the average green density of 7.25–7.55 g / cm³ in the key load-bearing area of ​​the active hub can be used as a reference target, and the density range between different key measuring points of the same compact should be checked. When specific material and dimensional conditions permit, the density range can be controlled within 0.05–0.10 g / cm³ as a debugging direction. It should be noted that the above values ​​are used to illustrate the goal of improving density consistency through "powder replenishment—micro-compaction—axial differential compensation" in this solution, and do not constitute an absolute performance guarantee for all powder systems and all product sizes.

[0074] Step 6, graded unloading and low-damage demolding: its process is similar to... Figure 10 a~ Figure 10Corresponding to c, after the final pressing is completed, the pressing main slide 110 first returns, reducing the axial pressure to about 30% of the final pressing peak, releasing most of the axial pressing load. Then, the release piston 460 actuates, causing the self-locking member 450 to exit the locked position, and the driven block 430 and the powder replenishing piston 313 to return to the retractable state. The powder replenishing piston 313 retracts to a position where the compaction nose 315 no longer interferes with the cavity. After confirming that the radial powder replenishing mechanism has exited, the floating support member 710 is used to move the overall female mold body 220 downward relative to the pressed blank by 0.5-1.5mm, first weakening the clamping effect of the overall female mold body 220 on the high-density pressed blank. Finally, the lower inner punch 251 and the lower outer punch 252 work together to push the pressed blank upward. This sequence releases the axial pressure, radial locking force, and mold wall clamping force in stages, reducing the concentrated shear load borne by the pressed blank steps or outer peripheral parts during ejection.

[0075] The unloading sequence described above corresponds to the structure of this device. If the powder-replenishing piston 313 and the compaction nose 315 have not fully retracted, and the blank is directly ejected by the lower punch assembly 250, the outer periphery or step position of the blank may interfere with the radial powder-replenishing components. If the overall female mold body 220 has not retracted first, and the lower inner punch 251 and lower outer punch 252 directly bear the entire ejection load, the high-density blank will be subjected to greater mold wall friction resistance. Therefore, the action chain of first reducing pressure, then releasing the self-locking and retracting the powder-replenishing piston 313, then retracting the overall female mold body 220, and finally ejecting it by the lower punch assembly 250 is determined by the positional and functional relationships of each mechanism.

[0076] In another embodiment, when the main powder shortage location of a certain type of active hub is concentrated in the outer peripheral drive forming area 223, it is not required that all multiple powder replenishing boxes 310 correspond to the root of the step. Instead, powder replenishing boxes 310 are only set at the corresponding positions of the tooth root or lug root of the outer peripheral drive forming area 223, and the powder replenishing throat 312 is directly facing these local areas. For cases where it is necessary to further reduce the fluctuation of circumferential powder replenishment, pressure equalization holes can also be set between the powder storage chambers 311 of two adjacent powder replenishing boxes 310, so that the adjacent powder storage chambers 311 have a certain powder or pressure equalization capability during the powder storage stage. The above adjustment does not change the basic relationship of the powder replenishing piston 313 replenishing powder through volume change, and the radial micro-compaction by the compaction nose 315 after the brake sleeve 314 is closed.

[0077] When the drive hub has three or four steps along the axial direction, the upper punch assembly 240 and the lower punch assembly 250 can add corresponding intermediate punches to the upper inner punch 241, upper outer punch 242, and lower inner punch 251 and lower outer punch 252. Corresponding to the increase in the number of punches, the axial differential compensation assembly 500 can be equipped with multiple concentric or partitioned output pistons in a common closed pressure medium chamber 512, so that each output piston corresponds to a different axial forming area. Its working principle is still that the common pressure medium chamber provides a pressure reference, and according to the difference in the order in which each forming area enters the high stiffness state, the small amount of stroke in the final pressure stage is redistributed within the mechanical limit range.

[0078] Finally, in this embodiment, the specific materials, sealing forms, conventional fastening methods, and drive sources of each component can be selected according to the press structure and powder system, as long as the basic positions and force transmission relationships shown in the attached drawings are maintained, namely: the fixed mold base 210 supports the overall female mold body 220, the mandrel 230 and the upper and lower punches together form a multi-step cavity; the powder replenishing box 310 replenishes powder to the local cavity through the powder storage cavity 311 and the powder replenishing throat 312, and the powder replenishing piston 313, the gate sleeve 314, and the compaction nose 315 sequentially complete the powder replenishment and micro-compaction; the annular piston 410, the conical pressure ring 420, and the driven block 430 synchronously drive multiple powder replenishing pistons 313, and the self-locking component 450 and the release piston 460 complete the holding and unlocking; the main pressure plate 511, the closed pressure medium cavity 512, and each output piston complete the axial differential compensation; the floating support component 710 enables the overall female mold body 220 to have controlled floating and first downward retraction capabilities; the pressing device and pressing process described in this invention can be implemented according to the above relationships.

[0079] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A powder metallurgy active wheel hub high-density pressing device, characterized in that, The device includes a frame (100), a pressing main slide (110) disposed above the frame (100) and capable of moving axially, a mold assembly (200), an upper punch assembly (240), and a lower punch assembly (250). The mold assembly (200) includes a fixed mold base (210), an integral female mold body (220) disposed inside the fixed mold base (210) and capable of floating axially relative to the fixed mold base (210), and a mandrel (230) disposed along the central axis of the device. The integral female mold body (220), the mandrel (230), the upper punch assembly (240), and the lower punch assembly (250) together form a multi-step cavity. A circumferential variable volume powder replenishing assembly (300) is provided on the outer side of the fixed mold base (210). The circumferential variable volume powder replenishing assembly (300) includes multiple powder replenishing boxes (310). Each powder replenishing box (310) is provided with a powder storage cavity (311), a powder replenishing throat (312) communicating with a multi-step cavity, and a powder replenishing piston (313) that can move radially. A gate sleeve (314) that can switch between a connected position and a closed position is provided at the powder replenishing throat (312). A compaction nose (315) is provided at one end of the powder replenishing piston (313) near the multi-step cavity. The annular variable volume powder replenishing assembly (300) is surrounded by an annular pressure equalization drive locking assembly (400). The annular pressure equalization drive locking assembly (400) includes an annular piston (410), a conical pressure ring (420), a plurality of driven blocks (430) corresponding to the powder replenishing piston (313), a self-locking member (450) for limiting the radial outward retraction of the driven blocks (430), and a release piston (460) for releasing the locking state of the self-locking member (450). The annular piston (410) can push the conical pressure ring (420) to move axially, and push the plurality of driven blocks (430) to move radially through the conical pressure ring (420). An axial differential compensation assembly (500) is provided between the pressing main slider (110) and the upper punch assembly (240). The axial differential compensation assembly (500) includes a main pressure plate (511), a closed pressure medium cavity (512), a first output piston (513) and a second output piston (514). The pressure-bearing sides of the first output piston (513) and the second output piston (514) are both connected to the closed pressure medium cavity (512) and are respectively connected to the upper inner punch (241) and the upper outer punch (242) in the upper punch assembly (240).

2. The powder metallurgy active hub high-density pressing device according to claim 1, characterized in that, A floating demolding assembly (700) is provided below the integral female mold body (220), the floating demolding assembly (700) including a floating support (710) for supporting the integral female mold body (220) and allowing the integral female mold body (220) to float axially.

3. The powder metallurgy active hub high-density pressing device according to claim 2, characterized in that, The multi-step cavity forms a central hub forming area (221), a radial disc forming area (222), and an outer peripheral driving forming area (223) from the inside to the outside. The central hub forming area (221) is located on the outside of the mandrel (230), the radial disc forming area (222) is located on the radial outside of the central hub forming area (221), and the outer peripheral driving forming area (223) is located on the radial outside of the radial disc forming area (222). An exhaust micro-groove (224) is provided at the step transition position between adjacent forming areas, and the exhaust micro-groove (224) is connected to the exhaust manifold (225).

4. The powder metallurgy active hub high-density pressing device according to claim 3, characterized in that, Multiple powder replenishing boxes (310) are arranged circumferentially along the fixed mold base (210) and facing the multi-step cavity. The powder replenishing piston (313) slides with the inner wall of the powder replenishing box (310). When the powder replenishing piston (313) moves away from the multi-step cavity, it expands the effective volume of the powder storage cavity (311). When the powder replenishing piston (313) moves towards the multi-step cavity, it reduces the effective volume of the powder storage cavity (311) and pushes the powder in the powder storage cavity (311) into the multi-step cavity through the powder replenishing throat (312). When the gate sleeve (314) is in the connected position, the powder storage chamber (311) is connected to the multi-step cavity through the powder replenishment throat (312); after the powder replenishment is completed, the gate sleeve (314) switches to the closed position, so that the powder storage chamber (311) is separated from the multi-step cavity, and the powder replenishment piston (313) continues to move toward the multi-step cavity, and performs radial micro-compaction on the powder replenished into the multi-step cavity through the compaction nose (315).

5. The powder metallurgy active wheel hub high-density pressing device according to claim 4, characterized in that, The conical pressure ring (420) has a circumferentially continuous conical force transmission surface. Multiple driven blocks (430) are arranged along the circumference of the conical pressure ring (420). One side of the driven block (430) contacts or cooperates with the conical force transmission surface of the conical pressure ring (420), and the other side is connected to or abuts against the corresponding powder-filling piston (313) for force transmission. When the conical pressure ring (420) moves axially, it simultaneously pushes multiple driven blocks (430) to move radially inward through the conical force transmission surface, and the multiple driven blocks (430) push the corresponding powder-filling piston (313) respectively.

6. The powder metallurgy active wheel hub high-density pressing device according to claim 5, characterized in that, The self-locking element (450) is located between the radial outward retraction path of the driven block (430) and the fixed support seat. After the driven block (430) reaches the powder filling endpoint or the radial micro-compaction endpoint, it restricts the radial outward retraction of the driven block (430). The release piston (460) is located on the side of the self-locking element (450) facing away from the wedge tightening direction. The output end of the release piston (460) directly abuts against the release end of the self-locking element (450) or is connected to the self-locking element (450) through a short push rod, and can push the self-locking element (450) out of the locking position.

7. The powder metallurgy active wheel hub high-density pressing device according to claim 6, characterized in that, The axial differential compensation assembly (500) further includes a first mechanical limiting member (515) and a second mechanical limiting member (516); the first mechanical limiting member (515) is disposed at the stroke limiting position of the first output piston (513), and the second mechanical limiting member (516) is disposed at the stroke limiting position of the second output piston (514); when the forming resistance of the forming area corresponding to one of the first output pistons (513) and the second output piston (514) increases, the closed pressure medium chamber (512) causes the other output piston to continue to generate compensation displacement, and the first mechanical limiting member (515) or the second mechanical limiting member (516) restricts the corresponding output piston from continuing to move.

8. The powder metallurgy active wheel hub high-density pressing device according to claim 7, characterized in that, The pressing device also includes a detection and control component (600), which is used to identify or control the pressing, holding and return states of the pressing main slider (110), and coordinate the action sequence of circumferential powder replenishment, opening and closing of the gate sleeve (314), holding of the self-locking component (450), release of the release piston (460) and ejection of the lower punch component (250); the floating support component (710) is set around the mold axis and jointly supports the overall female mold body (220), so that the overall female mold body (220) can generate axial floating during the pressing process, and eject the pressed blank before the lower punch component (250) during the unloading process and move downward relative to the pressed blank.

9. A high-density pressing process for powder metallurgy active wheel hubs, characterized in that, The powder metallurgy active wheel hub high-density pressing device according to any one of claims 1-8, wherein the pressing process includes the following steps: Step 1: Set the powder filling box (310) around the circumference of the fixed mold base (210), so that the powder filling throat (312) faces the multi-step cavity, the powder filling piston (313) retracts to the powder storage position, the gate sleeve (314) remains connected, fills the multi-step cavity with powder, and allows some powder to enter the powder storage cavity (311) through the powder filling throat (312). Step 2: Pressing the main slider (110) drives the upper inner punch (241) and the upper outer punch (242) to perform axial pre-compression on the powder in the multi-step cavity. During the pre-compression process, the air between the powder particles enters the exhaust manifold (225) through the exhaust micro-groove (224) and is discharged. Step 3: After the pre-compression is completed, the annular piston (410) pushes the conical pressure ring (420) to move axially. The conical pressure ring (420) pushes multiple driven blocks (430) to move radially inward. The driven blocks (430) push the corresponding powder replenishing piston (313) to move toward the multi-step cavity, so that the powder in the powder storage cavity (311) is replenished into the multi-step cavity through the powder replenishing throat (312). Step 4: After the powder replenishment is completed, switch the gate sleeve (314) to the closed position. The conical pressure ring (420) continues to push the powder replenishment piston (313) to move through the driven block (430), so that the compaction nose (315) performs radial micro-compaction on the replenished powder. After the radial micro-compaction is completed, the self-locking part (450) maintains the radial position of the driven block (430) and the powder replenishment piston (313). Step 5: Press the main slider (110) to continue to descend, the main pressure plate (511) loads the closed pressure medium cavity (512), the closed pressure medium cavity (512) transmits pressure to the first output piston (513) and the second output piston (514) at the same time, the first output piston (513) and the second output piston (514) drive the upper inner punch (241) and the upper outer punch (242) to perform final pressing, and perform displacement compensation according to the forming resistance of the corresponding forming area; Step 6: After the final pressing is completed, the main slide block (110) is pressed back, the piston (460) is released and pushes the self-locking part (450) out of the locked position, so that the driven block (430) and the powder filling piston (313) retract radially outward. Then, the floating support part (710) moves the entire female mold body (220) downward relative to the blank, and finally the lower inner punch (251) and the lower outer punch (252) work together to eject the blank.

10. The powder metallurgy high-density pressing process for active wheel hubs according to claim 9, characterized in that: During the circumferential powder replenishment process, the effective volume of the powder storage chamber (311) is reduced by moving the powder replenishment piston (313), and the powder in the powder storage chamber (311) is replenished into the root of the step through the powder replenishment throat (312); During the radial micro-compaction process, the gate sleeve (314) first separates the powder storage cavity (311) from the multi-step cavity, and then the powder replenishing piston (313) continues to move and performs radial micro-compaction on the replenished powder through the compaction nose (315). During the unloading process, the pressing main slider (110) returns, the release piston (460) releases the self-locking part (450) from locking, the powder replenishing piston (313) retracts, the overall female mold body (220) moves down relative to the blank, and the lower punch assembly (250) ejects the blank.

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