Double-layer sliding bearing powder metallurgy forming device and forming process

Abstract

The application discloses a double-layer sliding bearing powder metallurgy forming device, which comprises a pressing die and a positioning device; the pressing die comprises an upper die punch, a die core, a lower inner die punch, a lower outer die punch, a female die, a lower blocking cylinder and an elastic positioning sheet; the positioning device comprises an upper positioning plate, a lower supporting plate and multiple positioning units; the lower blocking cylinder is placed on the upper end surface of the lower supporting plate; the lower part of the small-diameter section and the large-diameter section of the die core are located in the lower blocking cylinder; the inner hole of the lower inner die punch is matched with the outer circle of the small-diameter section of the die core; the lower outer die punch is located on the upper part of the lower blocking cylinder; the upper section of the outer circle of the female die is matched with the inner hole of the upper positioning plate, and the inner hole is matched with the outer circle of the upper middle part of the small-diameter section of the lower outer die punch. The application can press two different metal powders into the inner layer and the outer layer of the sliding bearing respectively, and press the inner layer and the outer layer with different physical properties into an integrated body, so that a dense and uniform double-layer sliding bearing blank is formed.

Description

Technical Field

[0001] This invention relates to the fields of metal forming and powder metallurgy, specifically to a powder metallurgy forming device and forming process for a double-layer sliding bearing. Background Technology

[0002] Sliding bearings are mostly manufactured using powder metallurgy. Due to their simple structure, high load-bearing capacity, stable operation, and wide applicability, they are widely used in transmission machinery in automobiles, construction machinery, and precision machinery. When sliding bearings operate under complex conditions or boundary lubrication, the bearing material often exhibits insufficient hardness and strength, resulting in poor load-bearing capacity. This inevitably leads to severe wear on the inner surface of the sliding bearing, thus shortening its service life. To improve the inner surface strength of sliding bearings, reduce friction between the shaft and the inner surface of the sliding bearing, and minimize wear, the main measures currently adopted include: using materials with superior performance for the entire sliding bearing, or electroplating a layer of harder alloy on its inner surface. Both of these methods effectively improve the inner surface strength of sliding bearings, reduce wear, and extend their service life. However, using high-performance materials for the entire bearing is costly, and the process of electroplating the inner surface with alloys is relatively complex, costly, and causes significant environmental pollution. Sliding bearings have a ring-shaped structure. Powder metallurgy technology can easily fabricate single-layer sliding bearings. Although the academic community believes that double-layer sliding bearings have significant performance advantages, the complexity of the pressing molds and forming processes makes powder metallurgy forming technology for double-layer sliding bearings a technological bottleneck in the industry. In the past, the inner and outer bearing materials were often prepared separately and then mechanically joined together to form a double-layer sliding bearing. However, the poor bonding strength between the two layers limits the improvement of double-layer sliding bearing performance. Therefore, there is an urgent need to develop a relatively simple and low-cost powder metallurgy forming technology to manufacture double-layer sliding bearings to meet the higher performance requirements of mechanical transmission equipment under complex working conditions. Summary of the Invention

[0003] The problem this invention aims to solve is to provide a powder metallurgy forming apparatus for double-layer sliding bearings. This apparatus can press two different metal powders separately into the inner and outer layers of a sliding bearing, and then press the two layers with different physical properties into a single unit, forming a dense and uniform double-layer sliding bearing blank. Simultaneously, this invention provides a forming process for double-layer sliding bearing powder metallurgy.

[0004] This invention discloses a powder metallurgy forming device for a double-layer sliding bearing, comprising a pressing mold and a positioning device. The pressing mold includes an upper die punch, a die core, a lower inner die punch, a lower outer die punch, a female die, a lower stop cylinder, and an elastic positioning plate. The positioning device includes an upper positioning plate, a lower support plate, and multiple positioning units. The upper positioning plate and the lower support plate have multiple positioning holes at corresponding positions on their upper and lower sides, and are connected by these multiple positioning units. The lower stop cylinder is placed on the upper end face of the lower support plate. The lower part of the small-diameter section and the large-diameter section of the die core are both located inside the lower stop cylinder, with the lower end face of the large-diameter section contacting the upper end face of the lower support plate. The lower inner die... The inner hole of the die punch mates with the outer circle of the small diameter section of the die core. The lower part of the small diameter section and the large diameter section of the lower inner die punch are both located inside the lower stop cylinder. The lower outer die punch is located at the upper part of the lower stop cylinder, and its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower inner die punch. The upper section of the outer circle of the female die mates with the inner hole of the upper positioning plate, and its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower outer die punch. The outer circles of the die core and the lower inner die punch each have two circumferentially symmetrically distributed grooves. The elastic positioning piece is fixedly installed in the groove. The movable section on the outer side of the elastic positioning piece has an outward wedge-shaped protrusion. The axes of the die core, the lower inner die punch, the lower outer die punch, the female die, and the lower stop cylinder coincide.

[0005] Furthermore, the mold core, lower inner mold punch, lower outer mold punch, and female mold can move relative to each other in the axial direction; the relative positions of the lower inner mold punch, lower outer mold punch, female mold, and mold core allow the four components to form the required powder loading space; the upper mold punch performs stamping to press and shape the bearing.

[0006] Furthermore, the outer circle of the lower straight section of the upper die punches fits with the inner hole of the female die, and its inner hole fits with the outer circle of the small diameter section of the die core.

[0007] Furthermore, the lower baffle is composed of two symmetrical semi-cylindrical cylinders.

[0008] Furthermore, the outer circle of the large-diameter section of the mold core fits into the inner hole of the lower stop cylinder.

[0009] Furthermore, the outer diameter of the lower inner die punch is slightly smaller than the inner hole of the lower stop cylinder.

[0010] Furthermore, each positioning unit includes a guide post and a spring, and multiple positioning holes are evenly distributed at corresponding positions on the upper and lower positioning plates; the guide post passes through the positioning holes of the lower support plate, the spring, and the positioning holes of the upper positioning plate, and its threaded end is locked by a nut.

[0011] Furthermore, the positioning device also includes a clamping mechanism, which includes a ring, a lead screw driving mechanism, and multiple clamping units. The lead screw driving mechanism includes a lead screw, a pushing block, a fixing block, a handle, and an anti-detachment pin. Each clamping unit includes a threaded pin, a slider, a strip block, and a contact block. The pushing block is connected to a small mounting block on the outer circle of the ring via a pin. The anti-detachment pin passes through the upper end of the pin. The fixing block is fixed on the lower end face of the upper positioning plate. One end of the lead screw is screwed into the threaded hole of the pushing block and extends out, while the other end is engaged with the inner hole of the fixing block and extends out to connect with the handle. Several grooves are evenly opened circumferentially between the upper and lower end faces of the ring. The slider is located in the groove and is hinged to the ring via a pin. The strip block passes through the slider, its inner end is connected to the contact block via a pin, and its outer end is connected to the pin at the lower end of the threaded pin. The upper end of the threaded pin is threadedly connected to a small mounting block on the lower end face of the upper positioning plate.

[0012] The present invention discloses a forming process for powder metallurgy of double-layer sliding bearings: the pressing of the blank is divided into three processes: filling and pre-pressing of outer layer metal powder, filling and pre-pressing of inner layer metal powder, and mixing and pressing of inner and outer layer metal layers.

[0013] Furthermore, the molding process is specifically divided into five steps: ① Filling the outer layer powder: First, the lower end face of the lower outer die punch contacts the upper end face of the lower stop cylinder. At this time, the distance between the upper end face of the lower outer die punch and the upper end face of the female die is d1; then, the upper end face of the lower inner die punch is flush with the upper end face of the female die. At this time, the elastic positioning piece installed in the mold core groove pops out and supports the bottom of the lower inner die punch to prevent it from sliding down; then, the outer layer metal powder is filled into the gap formed by the lower outer die punch, the lower inner die punch and the female die until the powder is flush with the upper end face of the female die; ② Outer layer powder Pre-compression: The external press drives the upper die punch to move vertically downwards, pre-compressing the outer layer powder. During this process, the lower inner die punch moves downwards a distance d2 following the upper die punch. When the lower inner die punch is pressed down by external force, the elastic positioning piece in the die core groove is squeezed and retracts into the groove, ensuring the smooth downward movement of the lower inner die punch. ③ Filling the inner layer powder: First, remove the upper die punch above the pre-compressed outer layer powder from the female mold. Then, move the lower outer die punch upwards until the upper end face of the pre-compressed outer layer blank is flush with the upper end face of the female mold. Then, disassemble and remove the lower stop cylinder to expose the lower inner mold. The lower inner die punch is moved down so that its lower end face contacts the upper end face of the large diameter section of the die core. At this time, the upper end face of the lower inner die punch forms a distance d1 with the upper end face of the female die. At the same time, the elastic positioning piece installed in the groove of the lower inner die punch pops out and supports the bottom of the lower outer die punch to prevent it from sliding down. Then, the lower stop is reassembled into a whole in the initial position. Finally, the inner layer metal powder is filled into the gap formed by the lower outer die punch, the lower inner die punch, the die core and the outer blank until the powder is flush with the upper end face of the female die. ④ Inner layer powder pre-pressing: The external press drives the upper die punch in the vertical direction. The lower outer die punch and the pre-pressed outer blank move downwards by a distance d2. When the lower outer die punch moves downwards under external force, the elastic positioning piece in the groove of the lower inner die punch is pressed and retracts into the groove to ensure the smooth downward movement of the lower outer die punch. When the lower end face of the lower outer die punch just contacts the upper end face of the lower baffle, the inner powder is pre-pressed. ⑤ Double-layer sliding bearing pressing: Continue to increase the pressure of the external press to make the upper die punch continue to move downwards, so that the outer blank and the inner blank are squeezed into one piece to form a dense and uniform double-layer blank.

[0014] The advantages of the double-layer sliding bearing powder metallurgy forming device and forming process of this invention are as follows: First, by cooperating and changing the relative positions of the lower outer die punch, lower inner die punch, female die, and die core in the mold, two different metal powders can be pressed into the inner and outer layers of the sliding bearing respectively, and the two inner and outer layers with different physical properties can be pressed into one piece to form a dense and uniform double-layer sliding bearing blank; Second, the clamping mechanism improves the adaptability of clamping and positioning female dies with different outer diameters, reducing the manufacturing cost while ensuring the stability of pressing; Third, by adding elastic positioning plates to the die core and lower inner die punch, the lower inner die punch and lower outer die punch are positioned quickly and accurately at the required specific position without affecting the relative movement between the die core, lower inner die punch, lower outer die punch, and female die. Attached Figure Description

[0015] Figure 1 This is a perspective view of the powder metallurgy forming apparatus of the present invention.

[0016] Figure 2 This diagram shows the positional relationship between the various components of the pressing mold when loading the outer layer powder (excluding the upper mold punch).

[0017] Figure 3 This is a diagram showing the positional relationship between the various components of the pressing mold during the pre-pressing of the outer layer powder (excluding the upper die punch).

[0018] Figure 4 This is a sectional view showing the positional relationship between the various components of the pressing mold when loading the inner layer powder (excluding the upper mold punch).

[0019] Figure 5 This is a diagram showing the positional relationship between the components of the pressing mold during the pre-pressing of the inner layer powder (excluding the upper die punch).

[0020] Figure 6 For the three-dimensional clamping mechanism Figure 1 (Remove the upper positioning plate).

[0021] Figure 7 For the three-dimensional clamping mechanism Figure 2 .

[0022] Figure 8 This is a partially enlarged sectional view of the elastic positioning piece installed in the lower inner die punch when it pops out.

[0023] Figure 9 This is a partially enlarged sectional view of the elastic positioning piece installed in the lower inner die punch when it retracts. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0025] from Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As can be seen, the present invention provides a double-layer sliding bearing powder metallurgy forming device, which includes a pressing mold 1 and a positioning device 2; the pressing mold 1 includes an upper die punch 11, a die core 12, a lower inner die punch 13, a lower outer die punch 14, a female die 15, a lower stop cylinder 16, and an elastic positioning piece 17; the positioning device 2 includes an upper positioning plate 21, a lower support plate 22, and multiple positioning units; the upper positioning plate 21 and the lower support plate 22 have multiple positioning holes at corresponding positions, and the upper positioning plate 21 and the lower support plate 22 are connected by multiple positioning units; the lower stop cylinder 16 is placed on the upper end surface of the lower support plate 22; the lower part of the small diameter section and the large diameter section of the die core 12 are both located inside the lower stop cylinder 16, and the lower end surface of the large diameter section is in contact with the upper end surface of the lower support plate 22. The inner hole of the lower inner die punch 13 mates with the outer circle of the small diameter section of the die core 12. The lower part and the large diameter section of the small diameter section of the lower inner die punch 13 are both located inside the lower stop cylinder 16. The lower outer die punch 14 is located on the upper part of the lower stop cylinder 16, and its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower inner die punch 13. The upper section of the outer circle of the female die 15 mates with the inner hole of the upper positioning plate 21, and its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower outer die punch 14. The outer circles of the die core 12 and the lower inner die punch 13 each have two circumferentially symmetrically distributed grooves. The elastic positioning piece 17 is fixedly installed in the groove. The movable section on the outer side of the elastic positioning piece 17 has an outward wedge-shaped protrusion. The axes of the die core 12, the lower inner die punch 13, the lower outer die punch 14, the female die 15, and the lower stop cylinder 16 coincide.

[0026] The present invention discloses a double-layer sliding bearing powder metallurgy forming device: the mold core 12, the lower inner mold punch 13, the lower outer mold punch 14, and the female mold 15 can move relative to each other in the axial position; the relative positions of the lower inner mold punch 13, the lower outer mold punch 14, the female mold 15, and the mold core 12 enable the four components to form the required powder loading space; the upper mold punch 11 performs stamping to press and form the bearing.

[0027] Among them, the elastic positioning piece 17 has a good elastic deformation capacity and can be completely pressed into the groove under the action of external force: when the lower inner die punch 13 moves up relative to the die core 12 and the lower outer die punch 14 moves up relative to the lower inner die punch 13 to the required position, the elastic positioning piece 17 pops out, and the wedge-shaped protrusion on the elastic positioning piece 17 just supports the bottom of the lower inner die punch 13 or the lower outer die punch 14, which facilitates the accurate and rapid positioning of the lower inner die punch 13 and the lower outer die punch 14 and prevents them from sliding down; when the lower inner die punch 13 moves down relative to the die core 12 and the lower outer die punch 14 moves down relative to the lower inner die punch 13 under the action of external force, the elastic positioning piece 17 is squeezed by its own supporting component and then retracts into the groove, so that its own supporting component slides down smoothly.

[0028] To reduce frictional resistance when the supporting component moves downward and ensure that the supporting component can slide smoothly, an appropriate amount of grease can be applied to the tip of the wedge-shaped protrusion of the elastic positioning plate 17. When the elastic positioning plate 17 loses elasticity or becomes inaccurate in positioning the supporting component during long-term use, simply remove the original elastic positioning plate and replace it with a new one. Example 2

[0029] from Figure 2 , Figure 3 , Figure 4 , Figure 5 It can be seen that the present invention provides a double-layer sliding bearing powder metallurgy forming device: the outer circle of the lower small straight section of the upper die punch 11 is matched with the inner hole of the female die 15, and its inner hole is matched with the outer circle of the small diameter section of the die core 12.

[0030] The upper die punch 11 presses out the bearing during the pressing process by cooperating with the female die 15 and the die core 12 through its outer circle and inner hole. Example 3

[0031] from Figure 2 , Figure 3 , Figure 4 , Figure 5 It can be seen that the present invention provides a double-layer sliding bearing powder metallurgy forming device: the lower baffle 16 is composed of two symmetrical semi-cylindrical cylinders.

[0032] The functions of the lower stop cylinder 16 are as follows: First, when the upper die punch 11 presses the outer layer of metal powder, the lower end face of the large diameter section of the lower outer die punch 14 will not move downward after contacting the upper end face of the lower stop cylinder 16, thus supporting the lower outer die punch 14 and ensuring that the relative position of the lower outer die punch 14 with respect to the die core 12 and the female die 15 does not change; Second, when it is necessary to install the inner layer of metal powder, the lower stop cylinder 16 can be easily disassembled and removed from the positioning device 2 to expose the lower outer die punch 13, thereby facilitating the adjustment of the relative position of the lower inner die punch 13 with respect to the female die 15 and the die core 12. After adjusting the position of the lower inner die punch 13, the lower stop cylinder 16 can be reinstalled. Example 4

[0033] from Figure 2 , Figure 3 , Figure 4 , Figure 5 It can be seen that in the present invention, a double-layer sliding bearing powder metallurgy forming device is provided: the outer circle of the large diameter section of the mold core 12 is matched with the inner hole of the lower stop cylinder 16.

[0034] The outer circle of the large diameter section of the mold core 12 contacts the inner hole of the lower stop cylinder 16, and the lower end face of the large diameter section of the mold core 12 contacts the upper end face of the lower support plate 22, which ensures the stability of the mold core 12, and thus ensures the stability during the pressing process. Example 5

[0035] from Figure 2 , Figure 3 , Figure 4 , Figure 5 It can be seen that in the present invention, a double-layer sliding bearing powder metallurgy forming device, the outer diameter of the lower inner die punch 13 is slightly smaller than the inner hole of the lower baffle 16.

[0036] The outer diameter of the lower inner die punch 13 is slightly smaller than the inner hole of the lower stop cylinder 16, which facilitates the up and down movement of the lower inner die punch 13. Example 6

[0037] from Figure 1 As can be seen, the present invention provides a double-layer sliding bearing powder metallurgy forming device: each positioning unit includes a guide post 23 and a spring 24, and multiple positioning holes are evenly distributed on the upper positioning plate 21 and the lower support plate 22 at corresponding positions; the guide post 23 passes through the positioning hole of the lower support plate 22, the spring 24, and the positioning hole of the upper positioning plate 21, and its threaded section at the tail is locked by a nut.

[0038] The nut is tightened into the thread at the tail of the guide post 23, which forms a certain preload on the spring 24 to ensure the stability of the overall positioning device. When the upper positioning plate 21 moves downward along the guide post 23 under the push of external force, the spring 24 installed on the guide post 23 is compressed to generate a greater elastic force. When the external force acting on the upper positioning plate 21 is released, the upper positioning plate 21 can return to the initial position along the guide post 23 under the action of the elastic force of the spring 24. Example 7

[0039] from Figure 1 , Figure 6 , Figure 7 It is understood that the present invention provides a double-layer sliding bearing powder metallurgy forming device: the positioning device 2 further includes a clamping mechanism, which includes a ring 251, a lead screw pushing mechanism, and multiple clamping units. The lead screw pushing mechanism includes a lead screw 255, a pushing block 256, a fixing block 257, a handle 258, and an anti-detachment pin 259. Each clamping unit includes a threaded pin 250, a slider 252, a strip block 253, and a contact block 254. The pushing block 256 is connected to a small mounting block on the outer circle of the ring 251 by a pin. The anti-detachment pin 259 passes through the upper end of the pin, and the fixing block 257 is fixed to the ring. On the lower end face of the upper positioning plate 21, one end of the lead screw 255 is screwed into the threaded hole of the push block 256 and extends out, while the other end is fitted into the inner hole of the fixing block 257 and extends out to connect with the handle 258. Several grooves are evenly opened in the circumferential direction between the upper and lower end faces of the ring 251. The slider 252 is located in the groove and is hinged to the ring by a pin. The strip block 253 passes through the slider 252, its inner end is connected to the contact block 254 by a pin, and its outer end is connected to the pin at the lower end of the threaded pin 250. The upper end of the threaded pin 250 is threadedly connected to the small mounting block on the lower end face of the upper positioning plate 21.

[0040] Different specifications of the double-layer sliding bearing will cause changes in the outer diameter of the female mold 15, which in turn will change the hole diameter of the upper positioning plate 21. Replacing the upper positioning plate would increase manufacturing costs. Therefore, the device of the present invention improves the adaptability to different outer diameters of the female mold 15 by adding a clamping mechanism, thereby reducing manufacturing costs.

[0041] The clamping mechanism works as follows: Rotating the handle 258 causes the lead screw 255 to rotate, which in turn drives the ring 251 to rotate via the push block 256. The slider 252 rotates with the ring 251 and simultaneously drives the strip block 253 to rotate towards the center of the ring 251, causing the contact block 254 to contact the outer circle of the female mold 15, thus positioning and clamping the female mold 15 and ensuring the stability of the mold throughout the pressing process. When it is necessary to replace the female mold 15 or the mold itself, simply rotate the handle 258 in the opposite direction to separate the contact block 254 from the female mold 15.

[0042] The preferred number of clamping units is three clamping units evenly distributed along the circumference of the ring, which realizes the three-jaw clamping of the female mold 15 by the three contact blocks 254, ensuring the stability of the clamping and preventing the female mold 15 from deforming due to uneven force. The contact surfaces between the contact blocks 254 and the outer circle of the female mold 15 are preferably two planes with a specific obtuse angle. Example 8

[0043] The forming process of powder metallurgy for double-layer metal sliding bearings of this invention: the pressing of the blank is divided into three processes: filling and pre-pressing of outer layer metal powder, filling and pre-pressing of inner layer metal powder, and mixing and pressing of inner and outer metal layers.

[0044] It should be noted that there is no restriction on the order of the filling and pre-pressing process of the inner layer metal powder and the outer layer metal powder. The outer layer metal powder can be filled and pre-pressed first, followed by the inner layer; or the inner layer metal powder can be filled and pre-pressed first, followed by the outer layer. The only difference between the two pressing methods is the order in which the inner and outer layers are pre-pressed. Example 9

[0045] The powder metallurgical forming method for double-layer sliding bearings of this invention specifically consists of 5 steps:

[0046] ① Filling with outer layer powder: First, bring the lower end face of the lower outer die punch 14 into contact with the upper end face of the lower stop cylinder 16. At this time, the distance between the upper end face of the lower outer die punch 14 and the upper end face of the female die 15 is d1. Next, align the upper end face of the lower inner die punch 13 with the upper end face of the female die 15. At this time, the elastic positioning piece 17 installed in the groove of the mold core 12 pops out, supporting the bottom of the lower inner die punch 13 to prevent it from sliding down. Then, fill the gap formed by the lower outer die punch 14, the lower inner die punch 13, and the female die 15 with outer layer metal powder until the powder is level with the upper end face of the female die 15. The distance d1 is determined by the height h of the female die 15, d1 = h * (2 / 3 ~ 3 / 4). Figure 2 As shown,

[0047] ② Outer layer powder pre-compression: An external press drives the upper die punch 11 to move vertically downwards, pre-compressing the filled outer layer powder. During this process, the lower inner die punch 13 moves downwards a distance d2 following the upper die punch 11. When the lower inner die punch 13 is pressed down by external force, the elastic positioning piece 17 in the groove of the die core 12 is squeezed and retracted into the groove, ensuring the smooth downward movement of the lower inner die punch 13. The distance d2 is determined by the height h of the female die 15, d2 = h * (1 / 4 ~ 2 / 5). Figure 3 As shown,

[0048] ③ Filling the inner layer powder: First, remove the upper die punch 11 above the pre-pressed outer layer powder from the female mold 15; then move the lower outer die punch 14 upward until the upper end face of the pre-pressed outer layer blank is flush with the upper end face of the female mold 15; then disassemble and remove the lower stop cylinder 16 to expose the lower inner die punch 13, and move the lower inner die punch 13 downward so that its lower end face contacts the upper end face of the large diameter section of the mold core 12. At this time, the upper end face of the lower inner die punch 13 forms a distance d1 with the upper end face of the female mold 15; at the same time, the elastic positioning piece installed in the groove of the lower inner die punch 13 pops out and supports the bottom of the lower outer die punch 14 to prevent it from sliding down; then, reassemble the lower stop cylinder 16 into the original position, and finally fill the gap formed by the lower outer die punch 14, the lower inner die punch 13, the mold core 12 and the outer layer blank with inner layer metal powder until the powder is filled to the same level as the upper end face of the female mold 15; Figure 4 As shown,

[0049] ④ Inner layer powder pre-compression: The external press drives the upper die punch 11 to move vertically downwards, pre-compressing the filled inner layer powder. During this process, the lower outer die punch 14 and the pre-compressed outer layer blank move downwards by a distance d2. When the lower outer die punch 14 moves downwards under external force, the elastic positioning piece 17 in the groove of the lower inner die punch 13 is pressed and retracts into the groove, ensuring the smooth downward movement of the lower outer die punch. When the lower end face of the lower outer die punch 14 just contacts the upper end face of the lower baffle 16, the inner layer powder is pre-compressed. Figure 5 As shown,

[0050] ⑤ Double-layer sliding bearing pressing: Continue to increase the pressure of the external press, so that the upper die punch 11 continues to move down, so that the outer blank and the inner blank are squeezed into one piece, forming a dense and uniform double-layer blank.

[0051] After the pressing die has pressed the double-layer sliding bearing blank, the upper die punch 11 is first pulled upward from the female die 15; then an external force is applied to press down the upper positioning plate 21, causing the female die 15 to move downward in the vertical direction relative to the die core 12, the lower inner die punch 13, and the lower outer die punch 14, until the double-layer blank is completely exposed, and the pressed blank is extracted from the die core 12; the external force acting on the upper positioning plate 21 is removed, so that the upper positioning plate 21 and the female die 15 return to their initial positions under the action of the spring force 24, preparing for the pressing of the next double-layer metal sliding bearing blank.

[0052] The advantages of the double-layer sliding bearing powder metallurgy forming device and forming process of this invention are as follows: First, by cooperating and changing the relative positions of the lower outer die punch, lower inner die punch, female die, and die core in the mold, two different metal powders can be pressed into the inner and outer layers of the sliding bearing respectively, and the two inner and outer layers with different physical properties can be pressed into one piece to form a dense and uniform double-layer sliding bearing blank; Second, the clamping mechanism improves the adaptability of clamping and positioning female dies with different outer diameters, reducing the manufacturing cost while ensuring the stability of pressing; Third, by adding elastic positioning plates to the die core and lower inner die punch, the lower inner die punch and lower outer die punch are positioned quickly and accurately at the required specific position without affecting the relative movement between the die core, lower inner die punch, lower outer die punch, and female die.

[0053] The molding apparatus and process of this invention can flexibly combine different powders in the gap between the inner and outer powder layers according to actual working conditions, thereby pressing out double-layer sliding bearing blanks with different physical properties to meet the requirements of different application conditions. The powders can be metal powders or non-metal powders. For example, ordinary metal powder can be pressed into the outer layer of the sliding bearing, while high-strength, oil-impregnating, and lubricating metal powder can be pressed into the inner layer, ultimately resulting in a double-layer sliding bearing blank with excellent inner surface wear resistance, longer service life, and low manufacturing cost. Furthermore, this invention is not limited to pressing double-layer sliding bearing blanks; any double-layered sleeve-type parts can be pressed using the apparatus and process of this invention.

[0054] The double-layer sliding bearing powder metallurgy forming device of the present invention has a simple structure, convenient operation process, low manufacturing cost, low energy consumption and no pollution to the environment during use.

Claims

1. A powder metallurgy forming apparatus for a double-layer sliding bearing, characterized in that: It includes a pressing mold (1) and a positioning device (2); the pressing mold (1) includes an upper die punch (11), a die core (12), a lower inner die punch (13), a lower outer die punch (14), a female die (15), a lower stop (16), and an elastic positioning piece (17); the positioning device (2) includes an upper positioning plate (21), a lower support plate (22), and multiple positioning units; the upper positioning plate (21) and the lower support plate (22) have multiple positioning holes at corresponding positions on the upper and lower parts, and the upper positioning plate (21) and the lower support plate (22) have multiple positioning holes at corresponding positions on the upper and lower parts. The support plates (22) are connected by multiple positioning units; the lower stop cylinder (16) is placed on the upper end face of the lower support plate (22); the lower part of the small diameter section and the large diameter section of the die core (12) are both located inside the lower stop cylinder (16), and the lower end face of its large diameter section is in contact with the upper end face of the lower support plate (22); the inner hole of the lower inner die punch (13) fits with the outer circle of the small diameter section of the die core (12), and the lower part of the small diameter section and the large diameter section of the lower inner die punch (13) are both located inside the lower stop cylinder (16); the lower outer die punch (14) Located at the upper part of the lower stop (16), its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower inner die punch (13); the upper section of the outer circle of the female die (15) mates with the inner hole of the upper positioning plate (21), and its inner hole mates with the outer circle of the upper middle part of the small diameter section of the lower outer die punch (14); the outer circles of the die core (12) and the lower inner die punch (13) are each provided with two circumferentially symmetrically distributed grooves, and the elastic positioning piece (17) is fixedly installed in the groove. The movable section on the outer side of the elastic positioning piece (17) has an outward wedge-shaped protrusion. The axes of the mold core (12), lower inner mold punch (13), lower outer mold punch (14), female mold (15), and lower stop cylinder (16) coincide; the axial positions of the mold core (12), lower inner mold punch (13), lower outer mold punch (14), and female mold (15) can be moved relative to each other; the relative positions of the lower inner mold punch (13), lower outer mold punch (14), female mold (15), and mold core (12) form the required powder filling space between the four components; the upper mold punch (11) performs stamping to press and form the bearing.

2. The molding apparatus according to claim 1, characterized in that: The outer circle of the lower straight section of the upper die punch (11) fits with the inner hole of the female die (15), and its inner hole fits with the outer circle of the small diameter section of the die core (12).

3. The molding apparatus according to claim 1, characterized in that: The lower baffle (16) is composed of two symmetrical semi-cylindrical tubes.

4. The molding apparatus according to claim 1, characterized in that: The outer circle of the large diameter section of the mold core (12) fits with the inner hole of the lower stop cylinder (16).

5. The molding apparatus according to claim 1, characterized in that: The outer diameter of the lower inner die punch (13) is slightly smaller than the inner hole of the lower stop cylinder (16).

6. The molding apparatus according to claim 1, characterized in that: Each positioning unit includes a guide post (23) and a spring (24). Multiple positioning holes are evenly distributed on the upper positioning plate (21) and the lower support plate (22) at corresponding positions. The guide post (23) passes through the positioning holes of the lower support plate (22), the spring (24), and the upper positioning plate (21), and its threaded section is locked by a nut.

7. The molding apparatus according to claim 6, characterized in that: The positioning device (2) also includes a clamping mechanism, which includes a ring (251), a lead screw drive mechanism, and multiple clamping units. The lead screw drive mechanism includes a lead screw (255), a drive block (256), a fixing block (257), a handle (258), and an anti-detachment pin (259). Each clamping unit includes a threaded pin (250), a slider (252), a strip block (253), and a contact block (254). The drive block (256) is connected to a small mounting block on the outer circle of the ring (251) by a pin. The anti-detachment pin (259) passes through the upper end of the pin. The fixing block (257) is fixed to the upper positioning plate (21). On the lower end face, one end of the lead screw (255) is screwed into the threaded hole of the push block (256) and extends out, and the other end is engaged with the inner hole of the fixing block (257) and extends out to connect with the handle (258); several grooves are evenly opened in the circumferential direction between the upper and lower end faces of the ring (251), the slider (252) is located in the groove and is hinged to the ring by a pin, the strip block (253) passes through the slider (252), its inner end is connected to the contact block (254) by a pin, its outer end is connected to the pin at the lower end of the threaded pin (250), and the upper end of the threaded pin (250) is threaded to the small mounting block on the lower end face of the upper positioning plate (21).

8. A forming process for powder metallurgy of a double-layer sliding bearing, characterized by: The pressing of the blank is divided into three processes: filling and pre-pressing the outer layer of metal powder, filling and pre-pressing the inner layer of metal powder, and mixing and pressing the inner and outer metal layers; specifically, it consists of five steps: ① Filling the outer layer powder: First, bring the lower end face of the lower outer die punch into contact with the upper end face of the lower stop cylinder. At this time, the distance between the upper end face of the lower outer die punch and the upper end face of the female die is d1. Then, align the upper end face of the lower inner die punch with the upper end face of the female die. At this time, the elastic positioning piece installed in the mold core groove pops out and supports the bottom of the lower inner die punch to prevent it from sliding down. Then, fill the gap formed by the lower outer die punch, the lower inner die punch and the female die with outer metal powder until the powder is flush with the upper surface of the female die. ② Outer layer powder pre-compression: The external press drives the upper die punch to move downward in the vertical direction to pre-compress the filled outer layer powder. During this process, the lower inner die punch moves downward a distance d2 along with the upper die punch. When the lower inner die punch is pressed down by external force, the elastic positioning piece in the die core groove is squeezed and retracted into the groove to ensure the smooth downward movement of the lower inner die punch. ③ Filling the inner layer powder: First, remove the upper die punch above the pre-pressed outer layer powder from the female mold; then move the lower outer die punch upward until the upper end face of the pre-pressed outer layer blank is flush with the upper end face of the female mold; then disassemble and remove the lower stop cylinder to expose the lower inner die punch, and move the lower inner die punch downward so that its lower end face contacts the upper end face of the large diameter section of the mold core. At this time, the upper end face of the lower inner die punch forms a distance d1 with the upper end face of the female mold; at the same time, the elastic positioning piece installed in the groove of the lower inner die punch pops out and supports the bottom of the lower outer die punch to prevent it from sliding down; Subsequently, the lower stop cylinder is reassembled into a whole in its original position. Finally, the inner metal powder is filled into the gap formed by the lower outer die punch, the lower inner die punch, the die core and the outer blank until the powder is flush with the upper end face of the female die. ④ Inner layer powder pre-compression: The external press drives the upper die punch to move vertically downwards to pre-compress the filled inner layer powder. During this process, the lower outer die punch and the pre-compressed outer layer blank move downwards by a distance d2. When the lower outer die punch moves downwards under external force, the elastic positioning in the groove of the lower inner die punch is compressed and retracts into the groove, ensuring the smooth downward movement of the lower outer die punch. When the lower end face of the lower outer die punch just contacts the upper end face of the lower baffle, the inner layer powder is pre-compressed. ⑤ Double-layer sliding bearing pressing: Continue to increase the pressure of the external press, so that the upper die punch continues to move downward, so that the outer blank and the inner blank are squeezed into one, forming a dense and uniform double-layer blank.

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