Piston metal mold rapid cooling mold

Abstract

The utility model relates to a piston metal type fast cooling mould, including side mould, upper die and inner mould, the inner mould is formed by welding two parts of up and down, and its welding surface separates the inner mould cooling channel and divides into two parts of up and down and the volume of upper part is greater than the volume of lower part, the pin core is formed by welding two parts of left and right, and the welding surface separates the pin core cooling channel and divides into two parts of left and right and the volume of the part close to the inner mould part is greater than the volume of the part far from the inner mould part, the upper die middle ring is formed by welding two parts of up and down, and the welding surface divides the volume of the cooling channel of the upper die middle ring and divides into two parts of up and down, the upper die inner ring is formed by welding two parts of up and down, and the welding surface separates the cooling channel of the upper die inner ring and divides into two parts of up and down and the volume of upper part is less than the volume of small part, the utility model solves the problem that the fast cooling mould cooling structure is limited and the machining difficulty is high currently, has the advantages such as simple structure, high reliability, simple manufacturing process, satisfies the requirement of improving piston comprehensive performance.

Description

Technical Field

[0001] This utility model relates to the field of piston manufacturing technology, specifically to a piston metal mold for rapid cooling. Background Technology

[0002] Chinese patent CN201810101917.9 discloses a conformal cooling mold and its usage method, which includes a top mold, an inner mold, and an outer mold fixed to a casting device. The top mold is provided with heating and cooling channels, and the inner mold is divided into three parts, each with a cooling channel. In this method, the cooling channels of the top mold are sealed by a sealing ring and a pressure cap. The mold temperature is limited by the upper temperature limit of the sealing gasket material, resulting in a short mold life and a single mold material. The cooling channels of the inner mold are machined by drilling, which easily leads to stress concentration at the drilled end, causing the mold to crack and become unusable.

[0003] Chinese patent CN201410633085.7 discloses a rapid cooling mold for gravity casting aluminum pistons, comprising an upper outer mold block and a lower outer mold block assembled together. The upper outer mold block has cooling channels. A top mold, also with cooling channels, is located at the top of the upper outer mold block. A pin is horizontally installed on the lower outer mold block, and each pin has a cooling channel. Between two pins, a tightly fitted inner core has a cooling channel. All cooling channels except the top mold cooling channel contain cooling pipes. This method uses a block seal for the top mold cooling channel, requiring high precision in the fit between the block and the mold, making processing difficult and prone to leakage during use. The cooling channels for the inner core and pins are machined by drilling. Due to process limitations, asymmetrical design cannot be achieved. This machining method results in a small mold cooling area, stress concentration at the drilled end, and poor weld sealing, leading to a lifespan of only 55,000 cycles and a short mold lifespan.

[0004] The existing mold uses gravity casting aluminum piston rapid cooling mold. This technology is limited by the drilling process and cannot achieve asymmetrical, conformal design of the cooling channel. Furthermore, due to the limitations of the existing cooling channel sealing technology, it is impossible to further increase the mold cooling area. Moreover, the mold cooling structure is limited by the size of the inserts. The fit between the inserts and the mold is highly precise, which is difficult to process and prone to leakage during use. The cooling channels of the inner core and pin core are all processed by drilling. This processing method results in a small mold cooling area, and stress concentration is prone to occur at the end of the drilled hole, which reduces the mold life. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model provides a piston metal mold for rapid cooling. By welding and dividing the cooling channels, a conformal cooling path design is achieved. Furthermore, dissimilar materials are used for welding, solving the problems of limited cooling structure, leakage, and high processing difficulty in current rapid cooling molds. The design is simple, reliable, and easier to manufacture, improving mold cooling efficiency, increasing supercooling, refining grains, and enhancing the overall performance of the piston to meet the requirements of high power and low emissions for diesel engine pistons.

[0006] This utility model is achieved through the following technical solution: A piston-type metal rapid cooling mold is provided, comprising a side mold, an upper mold, and an inner mold. The top and bottom surfaces of the side mold have upper openings that connect to the inner cavity of the side mold. The upper part of the side mold has a cooling channel with an asymmetrical uniform wall thickness around the upper opening. Pin holes are opened on both sides of the side mold, and pin cores are installed laterally in the pin holes. The ends of the two pin cores that face each other form a pin core cooling channel with a symmetrical uniform wall thickness. The bottom surface of the side mold has a lower opening that connects to the inner cavity of the side mold. The upper part of the inner mold is connected between the two pins through the lower opening. The inner mold has symmetrical and uniformly thick cooling channels. The middle part of the inner mold and the lower opening of the side mold are closely fitted by a stop ring. The upper mold includes an outer ring, a middle ring, an inner ring, and an insulating riser, which are assembled sequentially from the outside to the inside. The outer ring, the middle ring, and the inner ring each form a separate cooling channel. Among them: the inner mold is formed by welding two parts of materials with different thermal conductivity. The welding surface divides the inner mold cooling channel into two parts with a volume ratio of 2:1 to 3:1, so as to achieve preferential flow and cooling of the cooling medium in the upper part, thereby improving the cooling rate of the thick part at the top of the piston casting. The pin core is formed by welding two parts, left and right. The welded surface divides the pin core cooling channel into two parts, with the volume of the part closer to the inner mold being larger than that of the part farther from the inner mold. The flow rate of the cooling medium on the side closer to the inner mold increases by 20%~30%, the cooling area increases by 30%, and stress concentration at the end of traditional drilling is avoided (weld strength ≥800MPa vs. tensile strength of drilling area 600MPa). The mold life is increased by 58%.

[0007] The upper mold middle ring is formed by welding two parts of materials with different thermal conductivity. The upper part is made of conventional steel, and the dissimilar materials are metallurgically bonded through friction welding to ensure that the weld strength is ≥90% of the base material, avoiding the leakage problem of traditional sealing structures. The weld surface divides the volume of the cooling channel of the upper mold middle ring into two equal parts. The upper mold inner ring is also formed by welding two parts of materials with different thermal conductivity. The weld surface divides the cooling channel of the upper mold inner ring into two parts, with the volume of the upper part being smaller than that of the smaller part. The riser support sleeve is made of mold steel with low thermal conductivity.

[0008] Preferably, the lower part of the upper mold middle ring and the upper mold inner ring, as well as the part of the pin core near the inner mold, are made of high thermal conductivity high strength mold steel or beryllium copper, while the upper part of the upper mold middle ring and the upper mold inner ring, as well as the part of the pin core away from the inner mold, are made of conventional steel.

[0009] Different materials can be used for the upper and lower parts of the mold to meet different heat conduction requirements, resulting in a long mold life, unrestricted mold temperature, large cooling area, and easy achievement of turbulent cooling. Furthermore, it has better adaptability to external environmental temperatures, is not limited by uneven or excessively high temperatures, and requires less frequent replacement of sealing rings, making maintenance easier.

[0010] Preferably, heat insulation grooves are formed on the outer wall of the side mold below the two pins.

[0011] By setting heat insulation grooves on the side mold, the heat storage capacity of the mold is reduced, which is beneficial to the forming of thin-walled parts of the piston casting, and is combined with directional cooling by the water spray pipe of the inner mold.

[0012] Furthermore, a riser support sleeve is installed between the insulating riser and the inner ring of the upper mold.

[0013] The riser support sleeve is fitted over the insulation riser and contacts the inner ring of the upper mold to position and install the insulation riser, ensuring the stability of the connection.

[0014] Furthermore, the inner mold center is connected to an inner mold water spray pipe that extends into the inner cavity of the inner mold and enters the inner mold cooling channel.

[0015] The cooling channels in the upper mold's middle ring are equally divided, forming a 'strong cooling-weak cooling' mold cooling gradient with the heat insulation grooves in the side mold. Combined with the directional cooling of the inner mold's water spray pipes, the cooling volume of the upper part of the inner mold is designed to be larger than that of the lower part, with a volume ratio of 2:1 to 3:1. This allows the cooling medium to form a stronger turbulent state in the upper part, reducing heat accumulation and controlling the temperature gradient in the combustion chamber area of ​​the piston casting to within 15℃ / mm (compared to 30℃ / mm in traditional molds). This significantly reduces shrinkage defects (<0.5% vs 3.2%). By increasing the supercooling, the grain size is refined to below 50μm (compared to 85μm in traditional designs).

[0016] Furthermore, the pin core center is connected to a pin core water spray pipe that extends into the pin core cavity and enters the pin core cooling channel.

[0017] Furthermore, a first annular groove is recessed on the upper part of the inner wall of the outer ring of the upper mold, a first convex ring is protruded on the upper part of the outer wall of the middle ring of the upper mold to match the first annular groove, a second annular groove is recessed on the upper part of the inner wall of the middle ring of the upper mold, a second convex ring is protruded on the upper part of the outer wall of the inner ring of the upper mold to match the second annular groove, and a third convex ring is protruded on the upper part of the inner ring of the upper mold to match the upper edge of the inner ring of the upper mold.

[0018] Furthermore, the insulating riser is circumferentially fitted with an upper mold cover located on the upper inner ring and the upper middle ring of the upper mold, and the inner ring wall of the upper mold cover is recessed to form a cover ring groove that matches the third convex ring.

[0019] The beneficial effects of this utility model are: This invention adopts a split upper mold structure (outer ring + middle ring + inner ring), with each component having an independent cooling channel, forming a three-dimensional cooling network surrounding the combustion chamber. The side mold, inner mold, and pin core are also designed with corresponding cooling channels, increasing the cooling area. In particular, the upper mold middle ring and upper mold inner ring, compared with the conventional technology of integral mold or local cooling, the multi-layer nesting + segmented cooling method of this invention more than doubles the cooling area of ​​the upper mold, enhances the heat transfer effect between the mold and the cooling medium, and improves the mold cooling effect.

[0020] By designing the upper mold as a split mold consisting of an outer ring, a middle ring, an inner ring, and a riser support sleeve, and designing uniform wall thickness cooling channels on the middle and inner rings of the upper mold, the cooling area of ​​the mold is increased, and the cooling efficiency of the upper mold is improved. Each cooling channel is welded and formed, without drilling. It supports asymmetrical or symmetrical arrangement, so that the cross-section of the cooling channel can show different forms.

[0021] In the upper mold's middle and inner rings, where they are closest to the combustion chamber of the casting, mold materials with excellent thermal conductivity and strength are selected. High-strength sealing connections between dissimilar materials are achieved using friction welding, laser welding, and vacuum brazing. This simultaneously improves the cooling effect of the combustion chamber, increases supercooling, and refines the grain microstructure. The riser support sleeve is made of a mold material with low thermal conductivity, and combined with a heat-insulating riser with good insulation properties, it reduces the solidification rate at the top riser area of ​​the casting, greatly improving the feeding effect at the riser and preventing casting shrinkage defects. Through strong cooling of the upper mold's middle / inner rings, low thermal conductivity of the riser support sleeve, and heat-insulating risers, "directional solidification" is achieved.

[0022] The cooling channels are formed by welding different materials to the inner mold, upper mold middle ring, upper mold inner ring, and pin core using methods such as friction welding, laser welding, argon arc welding, brazing, and electron beam welding, replacing the drilling process. This welds the two conformally machined half-molds together to form a closed flow channel. The weld itself possesses metallurgical bonding strength far exceeding that of traditional sealing structures. This avoids stress concentration at the drilling end, extending the mold's lifespan by more than 30% (actual measurement data). It allows for the design of cooling paths with arbitrary directions, approximating ideal conformal cooling. This design overturns the industry's perception that "cooling channels must be pre-drilled," representing a methodological innovation. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of the present invention.

[0024] Figure 2 This is a cross-sectional view of the upper mold in this utility model.

[0025] Figure 3 This is a cross-sectional view of the inner mold in this utility model.

[0026] Figure 4 This is a cross-sectional view of the pin core in this utility model.

[0027] Figure 5 A comparison table showing the improvement in product performance achieved by using the mold of this utility model compared to existing molds.

[0028] As shown in the figure: 1. Side mold; 2. Side mold cooling channel; 3. Upper mold outer ring; 4. Upper mold outer ring cooling channel; 5. Upper mold middle ring; 6. Upper mold middle ring cooling channel; 7. Upper mold inner ring; 8. Upper mold inner ring cooling channel; 9. Riser support sleeve; 10. Insulating riser; 11. Pin; 12. Pin cooling channel; 13. Stop ring; 14. Inner mold; 15. Inner mold cooling channel; 16. Inner mold water spray pipe; 17. Side mold insulation groove; 18. Pin water spray pipe; 19. Upper mold cap; 20. Upper mold middle ring welding surface; 21. Upper mold inner ring welding surface; 22. Inner mold welding surface; 23. Pin welding surface. Detailed Implementation

[0029] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0030] A piston-type metal rapid cooling mold includes a side mold 1, an upper mold and an inner mold 14.

[0031] The top and bottom surfaces of the side mold 1 each have an upper opening that communicates with the inner cavity of the side mold 1. The upper part of the side mold 1 has an asymmetrical cooling channel 2 with uniform wall thickness circumferentially arranged around the upper opening. Pin holes are opened on both sides of the side mold 1, and pin cores 11 are horizontally installed in each pin hole. Symmetrical cooling channels 12 with uniform wall thickness are formed in the opposite ends of the two pin cores 11. A lower opening communicating with the inner cavity of the side mold 1 is opened at the center of the bottom surface of the side mold 1. Heat insulation grooves 17 are respectively formed on the outer wall of the side mold 1 below the two pin cores 11.

[0032] The upper part of the inner mold 14 is connected between the two pins 11 through the lower opening. The inner mold 14 is provided with symmetrical and uniformly thick inner mold cooling channels 15. The middle part of the inner mold 14 and the lower opening peripheral wall of the side mold 1 are closely fitted by a stop ring 13.

[0033] The upper mold includes, from the outside in, an outer ring 3, a middle ring 5, an inner ring 7, and an insulating riser 10, which are assembled sequentially from the outside in. A riser support sleeve 9 is installed between the insulating riser 10 and the inner ring 7. The outer ring 3, the middle ring 5, and the inner ring 7 each form a separate cooling channel.

[0034] Wherein: the inner mold 14 is formed by welding two parts, and its inner mold welding surface 22 divides the inner mold cooling channel 15 into two parts, and the volume of the upper part is larger than that of the lower part.

[0035] The pin 11 is formed by welding two parts, left and right, and the pin welding surface 23 divides the pin cooling channel 12 into two parts, left and right, and the volume of the part closer to the inner mold 14 is larger than the volume of the part farther away from the inner mold 14.

[0036] The upper mold middle ring 5 is formed by welding two parts, and the upper mold middle ring welding surface 20 divides the volume of the upper mold middle ring cooling channel 6 into upper and lower equal parts; the upper mold inner ring 5 is formed by welding two parts, and the upper mold inner ring welding surface 21 divides the upper mold inner ring cooling channel 8 into upper and lower parts, and the volume of the upper part is smaller than the volume of the lower part.

[0037] The lower parts of the upper mold middle ring 5 and the upper mold inner ring 7, as well as the part of the pin core 11 near the inner mold 14, are made of mold materials with high thermal conductivity and high strength, such as high thermal conductivity and high strength mold steel or beryllium copper. The upper parts of the upper mold middle ring 5 and the upper mold inner ring 7, as well as the part of the pin core 11 away from the inner mold 14, are made of low-cost conventional steel mold materials. In this embodiment, the upper mold middle ring 5 and the upper mold inner ring 7 directly face the top of the piston combustion chamber and are made of H13 modified steel (thermal conductivity ≥35 W / m•K), which significantly accelerates heat dissipation. The upper mold outer ring 3 mainly serves a supporting function and is made of ordinary tool steel (cost reduction of about 40%). The riser support sleeve is made of a low thermal conductivity alloy, Inconel 600, which, together with a calcium silicate insulating riser, delays the solidification of the top and ensures smooth feeding. This design achieves "material selection on demand," which not only meets the rapid heat conduction requirements of the combustion chamber area (increasing subcooling) but also reduces material costs by 40%. At the same time, the weld strength (≥800MPa) far exceeds that of traditional sealing structures (≤500MPa), balancing performance and economy. It is a typical functional-oriented design paradigm shift.

[0038] The inner mold 14 is connected to a water spray pipe 16 that extends into the inner cavity of the inner mold 14 and enters the inner mold cooling channel. The pin 11 is connected to a water spray pipe 18 that extends into the inner cavity of the pin 11 and enters the pin cooling channel.

[0039] The upper part of the inner wall of the outer ring 3 of the upper mold is recessed to form a first annular groove. The upper part of the outer wall of the middle ring 5 of the upper mold is protruded to form a first convex ring that matches the first annular groove. The upper part of the inner wall of the middle ring 5 of the upper mold is recessed to form a second annular groove. The upper part of the outer wall of the inner ring 5 of the upper mold is protruded to form a second convex ring that matches the second annular groove. The outer wall of the heat-insulating riser 10 is protruded at the upper part of the inner ring 7 of the upper mold and a third convex ring that matches the upper edge of the inner ring 5 of the upper mold.

[0040] The heat-insulating riser 10 is circumferentially fitted with an upper mold cover 19 located on the upper inner ring 7 and the upper middle ring 5 of the upper mold. The inner ring wall of the upper mold cover 19 is recessed to form a cover ring groove that matches the third convex ring.

[0041] Individual cooling channels are designed on the upper mold middle ring 5, upper mold inner ring 7, pin 11, and inner core 14. Moreover, the upper mold middle ring 5, upper mold inner ring 7, pin 11, and inner core 14 are all formed by welding two parts. The part in contact with the casting is made of mold material with excellent thermal conductivity and strength, while the part connected to the casting machine is made of mold material with lower cost. This can effectively reduce costs and solve the problems of limited mold cooling structure and high processing difficulty. The two parts of the upper mold middle ring 5, upper mold inner ring 7, pin 11, and inner core 14 can be welded together by friction welding, laser welding, argon arc welding, brazing, electron beam welding, etc. to form cooling channels. The welding surface can separate the corresponding cooling channels.

[0042] A heat insulation groove 17 is provided at the lower part of the side mold 1 to reduce the heat storage capacity of the mold, which is beneficial to the forming of thin-walled parts of the piston casting. If friction welding is used, the weld flash further increases the heat dissipation area of ​​the cooling channel. Laser welding or brazing can obtain a smooth cooling channel and accelerate the oscillation of the medium, all of which help the cooling medium achieve a stable turbulent flow state.

[0043] This invention establishes an active temperature field control mechanism, achieving directional solidification through the following combined strategies: enhanced cooling of the area below the combustion chamber (upper mold middle ring 5 and upper mold inner ring 7) → increased supercooling → refined α-Al grains to below 50μm (compared to approximately 80~100μm in the original process); reduced heat dissipation in the riser area → formed a bottom-up temperature gradient → extended the liquid state holding time in the feeding channel by more than 20%; and the side mold heat insulation groove design reduces bottom heat accumulation and prevents cold shuts at thin walls. This synergistic control of "differentiated cooling + differentiated heat preservation + temperature-controlled cooling parameters" reflects the trend of deep integration between casting technology and mold design.

[0044] Actual production verification has shown that the key performance indicators of piston castings are significantly improved after adopting the mold of this utility model, such as... Figure 5 As shown.

[0045] The test sample is a piston for a common rail injection system of a certain type of diesel engine, with a casting temperature of 715-745℃ and a cooling water flow rate of 6-12 L / min for each mold component.

[0046] These data show that this utility model not only improves product quality, but also brings significant economic benefits: the average lifespan of each mold increases, and the production capacity of a single mold increases.

[0047] Of course, the above description is not limited to the examples above. Technical features of this utility model not described can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solution of this utility model and are not intended to limit this utility model. This utility model has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this utility model do not depart from the spirit of this utility model and should also fall within the protection scope of the claims of this utility model.

Claims

1. A piston-type metal rapid cooling mold, comprising a side mold, an upper mold, and an inner mold, characterized in that: The top and bottom surfaces of the side mold have upper openings that connect to the inner cavity of the side mold. The upper part of the side mold has a cooling channel with an asymmetrical uniform wall thickness around the upper opening. Pin holes are opened on both sides of the side mold, and pin cores are installed laterally in the pin holes. The ends of the two pin cores that face each other form a pin core cooling channel with a symmetrical uniform wall thickness. The bottom surface of the side mold has a lower opening that connects to the inner cavity of the side mold. The upper part of the inner mold is connected between the two pins through the lower opening. The inner mold has symmetrical and uniformly thick cooling channels. The middle part of the inner mold and the lower opening of the side mold are closely fitted by a stop ring. The upper mold includes an outer ring, a middle ring, an inner ring, and an insulating riser, which are assembled sequentially from the outside to the inside. The outer ring, the middle ring, and the inner ring each form a separate cooling channel. Among them: the inner mold is formed by welding two parts of materials with different thermal conductivity. The welding surface divides the cooling channel of the inner mold into two parts with a volume ratio of 2:1 to 3:

1. The pin core is formed by welding two parts, left and right, and the welding surface divides the pin core cooling channel into two parts, with the volume of the part closer to the inner mold being larger than the volume of the part farther from the inner mold. The upper mold middle ring is formed by welding two parts of materials with different thermal conductivity, and the welding surface divides the volume of the cooling channel of the upper mold middle ring into two equal parts. The upper mold inner ring is formed by welding two parts of materials with different thermal conductivity, and the welding surface divides the cooling channel of the upper mold inner ring into two parts, with the volume of the upper part being smaller than that of the lower part.

2. The piston metal mold rapid cooling die according to claim 1, characterized in that: The lower part of the upper mold middle ring and the upper mold inner ring, as well as the part of the pin core near the inner mold, are made of high thermal conductivity, high strength mold steel or beryllium copper. The upper part of the upper mold middle ring and the upper mold inner ring, as well as the part of the pin core away from the inner mold, are made of conventional steel. The riser support sleeve is made of low thermal conductivity mold steel.

3. The piston metal mold rapid cooling die according to claim 1, characterized in that: Heat insulation grooves are opened on the outer wall of the side mold below the two pins.

4. The piston metal mold rapid cooling die according to claim 1, characterized in that: A riser support sleeve is installed between the insulating riser and the inner ring of the upper mold.

5. The piston metal mold rapid cooling die according to claim 1, characterized in that: The inner mold is connected to a water spray pipe that extends into the inner cavity of the inner mold and enters the cooling channel of the inner mold.

6. The piston metal mold rapid cooling die according to claim 1, characterized in that: The pin core is connected to a pin core water spray pipe that extends into the pin core cavity and enters the pin core cooling channel.

7. The piston metal mold rapid cooling die according to claim 1, characterized in that: The upper part of the inner wall of the outer ring of the upper mold is recessed to form a first annular groove. The upper part of the outer wall of the middle ring of the upper mold is protruded to form a first convex ring that matches the first annular groove. The upper part of the inner wall of the middle ring of the upper mold is recessed to form a second annular groove. The upper part of the outer wall of the inner ring of the upper mold is protruded to form a second convex ring that matches the second annular groove. The outer wall of the heat-insulating riser is protruded at the upper part of the inner ring of the upper mold and has a third convex ring that matches the upper edge of the inner ring of the upper mold.

8. The piston metal mold rapid cooling die according to claim 7, characterized in that: The heat-insulating riser is circumferentially fitted with an upper mold cover located on the upper inner ring and the upper middle ring of the upper mold. The inner ring wall of the upper mold cover is recessed to form a cover ring groove that matches the third convex ring.

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