Low pressure casting mold for a magnetic levitation compressor housing and method of use thereof

Abstract

The application relates to the technical field of casting molds and forming processes, in particular to a low-pressure casting mold for a magnetic suspension compressor shell and a use method thereof. The mold comprises a bottom mold and three opening and closing molds matched with the bottom mold; the bottom mold and the three opening and closing molds are combined with a sand core to form a casting blank cavity of the magnetic suspension compressor shell, the blank cavity is in a horizontal layout and only one sprue is arranged at a cylindrical outer center position of the blank cavity; the mold further comprises a point cooling mechanism, the point cooling mechanism comprises a plurality of interval-arranged point cooling units, the point cooling units are arranged at each slow cooling point position close to the casting and away from the sprue and at a local thick position of the casting, each point cooling unit is respectively connected with cooling liquid, each cooling position is cooled through the cooling liquid, and the metal liquid realizes sequential solidification from top to bottom and from both ends to the center after entering the blank cavity. The sequential solidification is realized through the multi-point cooling, and the forming quality and process yield of the magnetic suspension compressor shell are improved.

Description

Technical Field

[0001] This application relates to the field of casting mold and molding process technology, and in particular to a low-pressure casting mold for a magnetic levitation compressor housing and its method of use. Background Technology

[0002] The magnetic levitation compressor housing refers to the main housing of an oil-free magnetic bearing compressor in the HVAC industry, and is the main structural component of the magnetic levitation compressor. The compressor shaft passes through the interior of the motor and is fixed within the compressor housing by three bearings, radially and axially respectively. These bearings are magnetic and have no moving parts, thus eliminating friction and the need for oil. They generate a strong electromagnetic field that levitates the compressor shaft, forcing it to rotate under the magnetic force of the motor stator shaft and the permanent magnet rotor, thereby achieving power output. Besides supporting and protecting the main power and transmission components of the compressor, the external structure of the compressor housing also serves to secure the electrical and electronic control modules and dissipate heat generated by the compressor's output to prevent it from affecting the operation of the electrical and electronic equipment. Therefore, the molding, internal quality, and sealing of the magnetic levitation compressor housing have strict requirements.

[0003] Gravity casting is a standard casting process for producing the housing of this magnetic levitation compressor and similar products, and it is also the method long used by overseas suppliers of this product. The main process is as follows: the compressor housing is vertically arranged, with a separate gating system on one side of the casting to guide molten metal into the bottom of the casting; as the filling height of the casting increases, multiple transverse runners can be arranged on the gating system and the sides of the casting to continuously inject high-temperature molten metal; a ring of risers with a large modulus is arranged on the top flange face of the casting for feeding the molten metal during the solidification process. The mold structure corresponding to this process is typically: a metal bottom mold combined with four opening and closing side molds (front, rear, left, and right); due to equipment limitations and demolding constraints, sand cores are used to shape the inner cavity of the casting and the top risers. The limitations of the above-mentioned processes and mold structures are as follows: the casting process has a low yield, with a large amount of material used for the forming gating and riser system, and subsequent sawing processes are cumbersome and have long cycle times; the casting process has a long cycle time and low production efficiency; the mold requires high precision, and after long-term use, the mold gap of the front, back, left, and right molds is greatly affected by mold deformation; the casting qualification rate is low, and riser feeding can easily cause internal quality defects in the corresponding positions of the casting, requiring high process control.

[0004] It should be noted that the information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of the prior art by providing a low-pressure casting mold for a magnetic levitation compressor housing and its usage method. The mold has a single gate design and does not have other complex gating and filling systems or riser feeding systems. Through the mold structure design and multi-point cooling system, the casting achieves sequential solidification "from top to bottom and from both ends to the center". This can greatly improve the molding quality and process yield of the housing casting while simplifying the gating system.

[0006] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a low-pressure casting mold for a magnetic levitation compressor housing, comprising: a bottom mold and three opening and closing side molds that cooperate with it: an upper mold, a first side mold, and a second side mold. The bottom mold and the three opening and closing side molds enclose and combine with a sand core to form a casting blank cavity for the magnetic levitation compressor housing. The blank cavity is horizontally arranged, and a unique gate is set at the center of the bottom of the outer cylinder of the blank cavity. The mold has no other gating filling system or riser feeding system. The mold also includes a spot cooling mechanism, which comprises multiple spaced spot cooling units. These units are located near the casting and away from the gate, at various slow cooling points and at locally thick areas of the casting. Each spot cooling unit is connected to a coolant, which cools the slow cooling points and locally thick areas, allowing the molten metal to solidify sequentially from top to bottom and from both ends to the center after entering the blank cavity.

[0007] Furthermore, the method for determining the slow cooling point is as follows: the low-pressure casting process is simulated and analyzed using casting process simulation analysis software on the digital model of the magnetic levitation compressor housing. Based on the simulation analysis, the solid fraction change of the casting during the solidification process is determined, and the local area in the casting whose cooling rate is significantly lagging behind the surrounding structure is identified as the slow cooling point. The point cooling unit is arranged at the corresponding position of the mold at a distance of 15-20mm from the area.

[0008] Furthermore, multiple point cooling units are detachably and spaced apart on the upper mold, with the liquid outlet of each point cooling unit extending into the interior of the upper mold and arranged close to the blank cavity.

[0009] Furthermore, the cooling unit integrates a liquid inlet, a liquid inlet channel, a liquid outlet, a liquid return channel, and a liquid return port. The liquid inlet and the liquid return port are respectively connected to the coolant pipeline. The coolant flows in from the liquid inlet, passes through the liquid inlet channel to the liquid outlet to cool the upper mold, and then flows back to the liquid outlet through the liquid return channel. The interior of the upper mold forms a liquid storage cavity that connects the liquid outlet and the liquid return channel.

[0010] Furthermore, the cooling mechanism further includes a coolant management module, which is used to centrally connect all coolant pipelines and set an identifier for each coolant pipeline.

[0011] Furthermore, the mold further includes: an auxiliary mold opening mechanism arranged horizontally on both sides of the blank cavity, the auxiliary mold opening mechanism including a clamping block and a driving component, the clamping block locking the casting to the upper mold under the drive of the driving component, or releasing the casting under the action of the driving component so that it can be separated from the upper mold.

[0012] Furthermore, the two ends of the blank cavity along the horizontal direction are sealed with molten metal through the cooperation of the sand core with the bottom mold and / or the upper mold.

[0013] Furthermore, the upper mold is provided with multiple vent holes at positions on the casting where there is a risk of venting. A venting rod is movably installed in the vent hole. One end of the venting rod is connected to the blank cavity, and the other end extends out of the vent hole. A venting gap is formed between the venting rod and the vent hole to allow gas in the blank cavity to overflow.

[0014] Furthermore, an exhaust line is provided in the area of ​​the casting where there is a risk of venting, and the lower end of the exhaust rod forms a mating structure with the exhaust line.

[0015] Secondly, this application provides a method for using the low-pressure casting mold of the first aspect mentioned above, comprising the following steps: 1) Fix the bottom mold on the mold base plate, place the sand core, and then drive the upper mold through the main oil cylinder of the equipment, and drive the first side mold and the second side mold through the side oil cylinder to move, so that the bottom mold, the upper mold, the first side mold, the second side mold and the sand core surround and form the blank cavity. 2) Turn on the low-pressure casting equipment to allow the molten metal to be filled into the blank cavity through the gate; 3) Activate the cooling mechanism and introduce coolant to cool the mold at multiple points, so that the molten metal in the blank cavity can be cooled sequentially "from top to bottom and from both ends to the center"; 4) After the casting solidifies, the first side mold and the second side mold move forward and backward in two directions under the drive of the side oil cylinder, leaving the surface of the casting; after the first side mold and the second side mold are in place, the upper mold moves upward under the drive of the main oil cylinder of the equipment, and the locking block locks the casting under the action of the driving component, so that the casting moves with the upper mold and takes the casting and the internal sand core out of the lower mold. 5) After the upper mold is raised, the locking block is released from the casting by the drive component, and the ejector mechanism pushes the casting and sand core out of the upper mold.

[0016] The beneficial effects of this application are as follows: Compared with the traditional gravity casting process, the low-pressure casting mold of this application greatly improves the casting quality and process yield of the magnetic levitation compressor housing, simplifies the structure of the gating system, shortens the subsequent processing steps of the casting, reduces the operating difficulty of the equipment, and improves the production efficiency of the magnetic levitation compressor housing. This is of great significance for realizing high-precision and mass production of the magnetic levitation compressor housing. Attached Figure Description

[0017] Figure 1 According to some embodiments of this application, a structural schematic diagram of a low-pressure casting mold for a magnetic levitation compressor housing is shown; Figure 2 According to some embodiments of this application, a cross-sectional view of the mold in the XZ plane is shown; Figure 3 According to some embodiments of this application, a schematic cross-sectional view of the mold in the YZ plane is shown; Figure 4 According to some embodiments of this application, it is shown that Figure 3 A magnified view of part A in the middle; Figure 5 According to some embodiments of this application, a schematic diagram of the internal structure of the mold is shown; Figure 6 According to some embodiments of this application, it is shown that Figure 5 Top view; Figure 7 According to some embodiments of this application, a schematic diagram of the cooperation between the cooling unit and the upper mold is shown; Figure 8 According to some embodiments of this application, a schematic diagram of the fit between the exhaust push rod and the casting is shown. Detailed Implementation

[0018] The technical features and advantages of this application will be described in more detail below with reference to the accompanying drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of this invention.

[0019] It should be noted that in the description of this application, the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention.

[0020] The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly indicating the importance of the technical features shown.

[0021] Furthermore, it should be noted that, in the description of this application, 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] The magnetic levitation compressor housing part in this embodiment is characterized by its hollow, thin-walled structure, complex structure, and high installation precision requirements. Such housing parts are typically manufactured using gravity mold casting in traditional processes. In this process, the blank cavity is vertically arranged within the mold, and molten metal is filled into the cavity through the gating gate under gravity. Due to the complex structure of the housing, a complex gating and filling system and a riser feeding system need to be designed in the mold to ensure the filling rate. This results in multiple sprues and a large number of risers to feed the molten metal, leading to a large mold size. The equipment operation during casting is also complex. After demolding, the casting requires multiple sawing and grinding processes to remove the gating and riser structures, resulting in low production efficiency. More importantly, even with this process, the casting yield is still not ideal, only about 50%.

[0023] In view of this, the purpose of this application is to design a low-pressure casting mold for the aforementioned magnetic levitation compressor housing. Low-pressure casting is a casting method in which liquid alloy is pressed from bottom to top into the mold cavity under pressure, and then solidified under pressure to obtain the casting. Compared with gravity casting, this casting method has better feeding, a denser casting structure, and is easier to cast large, thin-walled, and complex castings. Based on the low-pressure casting process, this application improves the casting quality and process yield of the magnetic levitation compressor housing by designing the mold structure and cooling system, and simplifies the operation of the equipment and the design of the gating system. This is of great significance for improving the casting quality and production efficiency of the magnetic levitation compressor housing.

[0024] To achieve the above objectives, the basic idea of ​​the embodiments of this application is as follows: Please see Figures 1 to 8 This is a schematic diagram of the low-pressure casting mold used for the housing of a magnetic levitation compressor in an embodiment of this application. For ease of explanation, the directions of the coordinate system are set as follows: Figure 1 As shown, where, Figure 2 This is a cross-sectional view of the mold in the XZ plane. Figure 3This is a sectional view of the mold in the YZ plane. The mold as a whole includes: a bottom mold 102 and three cooperating opening and closing side molds, namely: an upper mold 101, a first side mold 103, and a second side mold 104. The bottom mold 102 and the three opening and closing side molds together form a four-opening mold structure. The bottom mold 102 is fixed on the mold base plate 108. The upper mold 101 can move upward under the drive of the main hydraulic cylinder of the equipment. The first side mold 103 and the second side mold 104 can move forward and backward along the Y direction under the drive of the side hydraulic cylinders. The hollow inner cavity of the shell is connected by a sand core 10. 6. Forming: The upper mold 101, bottom mold 102, first side mold 103, and second side mold 104 are combined with the sand core 106 to form the casting blank cavity 107 of the magnetic levitation compressor housing. The blank cavity 107 is horizontally laid out. The only gate 105 of the mold is arranged at the center of the bottom of the outer cylinder of the blank cavity 107. Apart from the gate 105, the entire mold does not have any other gates or runners, nor does it have a riser design, which greatly simplifies the structure of the gating system and reduces the overall size of the mold.

[0025] At both ends of the blank cavity 107 in the X direction, the molten metal inside is sealed by the cooperation of the two ends of the sand core 106 with the bottom mold 102 and the upper mold 101. This avoids the need to arrange side molds on both sides in the X direction, reduces the number of side molds, and lowers the difficulty of equipment operation. For some embodiments, please refer to... Figure 4 The aforementioned sealing structure 1061 may include stepped groove structures designed at both ends of the sand core 106, and utilizes the stepped groove structure to form a slotted fit structure with the bottom mold 102 / upper mold 101 to achieve sealing of the molten metal in the blank cavity 107.

[0026] Because no gating system or riser feeding structure is designed, in order to obtain good casting quality and process yield in the low-pressure casting process, the magnetic levitation compressor housing mold of this application embodiment is equipped with a point cooling mechanism 110 to achieve cooling and solidification of the molten metal in the cavity. Please refer to... Figures 5-6 The aforementioned spot cooling mechanism 110 includes multiple spot cooling units 1101 spaced apart on the upper mold 101. Each spot cooling unit 1101 is individually connected to a corresponding coolant pipe 1103. Coolant is circulated into the spot cooling unit 1101 through the coolant pipe 1103. The outlet cooling position of the spot cooling unit 1101 is arranged inside the mold near the blank cavity 107. Through the layout of each spot cooling unit 1101 on the mold, the molten metal in the cavity is cooled, and the casting 114 is solidified sequentially "from top to bottom and from both ends to the center", thereby improving the casting quality of the casting 114.

[0027] Specifically, the arrangement of the aforementioned point cooling units 1101 on the mold is determined in the following way: After completing the structural design of the magnetic levitation compressor housing, the digital model is imported into the casting process simulation software for simulation analysis of the low-pressure casting process. Based on the simulation analysis of the solid fraction change during the solidification process of the casting 114, several local areas in the casting 114 with significantly slower cooling rates than the surrounding structure are identified as slow cooling points. Point cooling units 1101 are arranged at corresponding positions on the upper mold 101 at a distance of 15-20 mm from these points. At the same time, the start and end times of solidification in these areas are determined using the same simulation results. These times are used as the time points for the point cooling units 1101 to turn on and off the coolant through equipment control. The flow rate of the coolant can also be adjusted by measuring the temperature of the coolant entering and exiting the point cooling units 1101.

[0028] Please see Figure 6 Based on the simulation analysis results of the software, the applicant determined the layout positions of each point cooling unit 1101 (cooling points 1-16 marked in the figure). After the point cooling units 1101 were installed at intervals at various positions on the upper mold 101, since the liquid outlet cooling position of the point cooling unit 1101 is close to the blank cavity 107, coolant is circulated into each point cooling unit 1101 through the coolant pipe 1103. The coolant cools the corresponding position on the upper mold 101, and further cools the molten metal in the blank cavity 107 through the upper mold 101. Since each point cooling unit 1101 is equipped with a separate coolant pipe 1103, the flow rate / velocity of each coolant can be controlled individually. This allows for more precise and targeted control of each cooling position, greatly improving the controllability of the casting cooling system. As a result, good casting forming quality can be obtained, meeting the high-precision quality requirements of the magnetic levitation compressor housing.

[0029] This embodiment replaces the traditional method of arranging local inserts for cooling by using multiple local spot cooling methods. This can effectively avoid the problem of the gap between the insert and the mold affecting the service life of the mold. The gap will increasingly affect the surface quality of the casting, such as flash, burrs, and missing material, thereby increasing the time required for subsequent casting grinding.

[0030] Please see Figure 7This is a schematic diagram of the cooperation structure between a single point cooling unit 1101 and the upper mold 101. Each point cooling unit 1101 integrates a liquid inlet 11011, a liquid inlet channel 11012, a liquid outlet 11013, a liquid return channel 11014, and a liquid return port 11015. The coolant pipeline 1103 includes a liquid inlet pipeline and a liquid outlet pipeline. The liquid inlet 11011 and the liquid return port 11015 are respectively connected to the aforementioned liquid inlet pipeline and liquid outlet pipeline. The coolant enters through the liquid inlet 11011, flows through the liquid inlet channel 11012 to the liquid outlet 11013 and is sprayed out, and then flows back to the liquid return port 11015 through the liquid return channel 11014, realizing circulation. In this embodiment, the point cooling unit 1101 integrates the liquid inlet and outlet into one structure, which can simplify the structure of the cooling system and make its cooling more targeted to specific locations.

[0031] To facilitate the detachable installation between the cooling unit 1101 and the upper mold 101, a pipe thread connection structure can be provided between the cooling unit 1101 and the upper mold 101. The upper mold 101 has a threaded mounting hole 1011, and the cooling unit 1101 is inserted into the mounting hole 1011 and fixed by the pipe thread connection structure. Furthermore, in order to achieve the sealing of the coolant, a tapered pipe thread connection structure 11016 can be provided between the cooling unit 1101 and the mounting hole 1011, and the sealing effect can be further improved by wrapping Teflon tape or applying sealant at the tapered pipe thread during assembly.

[0032] To further improve the cooling effect, a liquid storage chamber 1012 is formed on the side of the mounting hole 1011 near the cavity. After the coolant is sprayed out through the outlet 11013, it fills the liquid storage chamber 1012. After the liquid storage chamber 1012 is full, it is returned through the return channel 11014 connected to it. To avoid blockage of the outlet 11013, the outlet 11013 can be designed as an angled opening.

[0033] In some preferred embodiments, a coolant management module 1102 can be provided on one side of the mold, and all coolant pipes 1103 can be centrally connected to the coolant pipe module 1102 to centrally manage all coolant pipes 1103. The coolant management module 1102 is marked with a number corresponding to each cooling unit 1101 to avoid misconnection or omission of coolant pipes 1103.

[0034] In the process layout of this embodiment, since the venting requirements of the casting are concentrated in the upper mold 101, which has a large area, and some areas are difficult for operators to observe and handle in a timely manner during actual production, this embodiment uses a venting ejector rod to replace the traditional venting plug to achieve venting. Please refer to... Figures 5-6Multiple vent holes are formed on the upper mold 101, and vent ejector rods 111 (E1 to E10 in the figure) are movably installed in the vent holes. One end of the vent ejector rod 111 passes through the vent hole and contacts the casting, while the other end extends out of the upper mold 101, forming a venting gap between the vent ejector rod 111 and the vent hole; in some embodiments, please refer to Figure 8 The venting ejector rod 111 can be obtained by machining a standard ejector rod. The end of the standard ejector rod near the casting is machined into a polygonal prism-shaped venting structure 1111, with gaps formed between the facets of the polygonal prism and the circular vent holes for venting the molten metal. Furthermore, venting lines 202 can be designed at high-risk locations on the casting. A corresponding mating structure 1112 is provided between the bottom end of the venting ejector rod 111 and the venting line 202. Through connection with the venting line 202, the venting channel can be expanded, further improving the venting effect. The installation position of each venting ejector rod 111 can be determined based on the filling results in the casting process simulation analysis. In the simulation analysis, the area where the molten metal is last filled is prone to air stagnation; therefore, venting structures must be set at corresponding positions on the mold. For example, if the last filled area is a planar structure, venting lines 202 are designed on this planar structure to increase the venting channel.

[0035] In this embodiment, because the casting is horizontally oriented, the shape of the casting involved in the upper mold 101 is relatively limited, and the overall weight of the casting and sand core is large. Therefore, the clamping force of the upper mold 101 is insufficient when the mold is opened. To prevent the casting from remaining in the lower mold 102 during mold opening, an auxiliary mold opening mechanism is added to the mold. Please refer to [link to relevant documentation]. Figure 2 The auxiliary mold opening mechanism includes a first auxiliary mold opening mechanism 112 and a second auxiliary mold opening mechanism 113 respectively located at both ends of the mold along the X direction. Both the first auxiliary mold opening mechanism 112 and the second auxiliary mold opening mechanism 113 are mounted on the upper mold 101 and respectively include a locking cylinder 1121 and a locking block 1122; please refer to [link / reference]. Figure 5 The locking block 1122 can slide along the guide rail 1123 under the drive of the locking cylinder 1121 to press the casting 114, locking the casting 114 onto the upper mold 101. At this time, the casting 114 is in a "locked" state and can move upward together with the upper mold 101 under the drive of the main cylinder, exiting the mold and preventing the casting 114 from remaining in the lower mold, thus ensuring continuous production. For example, the locking block 1122 can achieve locking by clamping the flanges on both ends of the magnetic levitation compressor housing.

[0036] The specific method of using the low-pressure casting mold of the magnetic levitation compressor in this embodiment is as follows: With the mold open or closed, the sand core 106 is placed in the corresponding position of the lower mold 102. The first side mold 103 and the second side mold 104, pushed by the side cylinders of the equipment, move along the guide rails on the mold base plate 108 to close with the lower mold 102. The upper mold 101, driven by the main cylinder of the equipment, moves downwards to close with the first side mold 103 and the second side mold 104. After confirming that the molds are in place, the pressure inside the equipment crucible is increased through the equipment pressure system, causing the molten metal in the crucible to enter the mold gate 105 through the riser pipe. Under continuous pressure, it fills the blank cavity upwards, completing the casting process of the casting 114.

[0037] After the casting solidifies, the first side mold 103 and the second side mold 104 move along both sides in the Y direction under the drive of the side cylinder of the equipment and leave the surface of the casting. After the two molds are in place, the upper mold 101 moves upward under the drive of the main oil cylinder of the equipment. At this time, the locking block 1122, driven by the locking oil cylinder 1121, puts the casting 114 in a "locked" state. The casting 114 and the sand core 106 move upward together with the upper mold 101, leave the lower mold 102, and rise to the height where the equipment receiving device can enter below the casting 114. Under the control of the equipment's oil circuit, the locking cylinder 1121 drives the locking block 1122 to move to both sides, loosening the casting. The mold's ejection mechanism then ejects the casting 114 and the sand core 106, which fall into the receiving device.

[0038] The mold structure and process scheme of this embodiment can achieve a process yield of over 94% for the magnetic levitation compressor housing product. In addition, due to the simple structure of the gating system, the time required for cutting, grinding and other processing after casting can be greatly reduced, thereby improving the production efficiency of the magnetic levitation compressor housing.

[0039] In the description of this specification, references to terms such as "some embodiments," "some examples," "exemplarily," "example," "preferred," or "further" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made based on the content of this specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A low-pressure casting mold for a magnetic levitation compressor housing, characterized in that, include: The bottom mold and three opening and closing side molds that cooperate with it: the top mold, the first side mold and the second side mold. The bottom mold and the three opening and closing side molds together and combined with the sand core form the casting blank cavity of the magnetic levitation compressor housing. The blank cavity is horizontally arranged. A unique gate is set at the center of the bottom of the outer cylinder of the blank cavity. The mold has no other gating filling system or riser feeding system. The mold also includes a point cooling mechanism, which includes multiple point cooling units arranged at intervals. The point cooling units are located near the casting and away from the gate, at various slow cooling points and at local thick areas of the casting. Each point cooling unit is connected to a coolant, which cools the various slow cooling points and local thick areas, so that the molten metal enters the blank cavity and solidifies sequentially "from top to bottom and from both ends to the center". The upper mold is provided with multiple vent holes at the locations of the casting where there is a risk of venting. A venting rod is movably installed in the vent hole. One end of the venting rod is connected to the blank cavity, and the other end extends out of the vent hole. A venting gap is formed between the venting rod and the vent hole to allow gas in the blank cavity to overflow. The casting is designed with vent lines at locations where there is a risk of venting, and a mating structure is provided between the lower end of the venting rod and the vent lines.

2. The low-pressure casting mold according to claim 1, characterized in that, The method for determining the slow cooling point is as follows: the low-pressure casting process is simulated and analyzed by the digital model of the magnetic levitation compressor housing using casting process simulation analysis software. Based on the simulation analysis, the solid fraction change of the casting during the solidification process is determined, and the local area in the casting where the cooling rate lags behind the surrounding structure is identified as the slow cooling point. The point cooling unit is arranged at the corresponding position of the mold at a distance of 15-20mm from the area.

3. The low-pressure casting mold according to claim 2, characterized in that, Multiple point cooling units are detachably and spaced apart on the upper mold, with the liquid outlet of each point cooling unit extending into the interior of the upper mold and arranged close to the blank cavity.

4. The low-pressure casting mold according to claim 3, characterized in that, The cooling unit integrates a liquid inlet, a liquid inlet channel, a liquid outlet, a liquid return channel, and a liquid return port. The liquid inlet and the liquid return port are respectively connected to the coolant pipeline. The coolant flows in from the liquid inlet, passes through the liquid inlet channel to the liquid outlet to cool the upper mold, and then flows back to the liquid outlet through the liquid return channel. The interior of the upper mold forms a liquid storage cavity that connects the liquid outlet and the liquid return channel.

5. The low-pressure casting mold according to claim 4, characterized in that, The cooling mechanism further includes a coolant management module, which is used to centrally connect all coolant pipelines and set an identifier for each coolant pipeline.

6. The low-pressure casting mold according to claim 1, characterized in that, The mold further includes: an auxiliary mold opening mechanism arranged horizontally on both sides of the blank cavity, the auxiliary mold opening mechanism including a clamping block and a driving component, the clamping block locking the casting to the upper mold under the drive of the driving component, or releasing the casting under the drive of the driving component so that it can be separated from the upper mold.

7. The low-pressure casting mold according to claim 1, characterized in that, The blank cavity is sealed at both ends along the horizontal direction by the sand core and the bottom mold and / or the upper mold to achieve the sealing of the molten metal inside the cavity.

8. The method of using the low-pressure casting mold according to claim 6, characterized in that, Includes the following steps: 1) Fix the bottom mold on the mold base plate, place the sand core, and then drive the upper mold and the side mold through the main oil cylinder of the equipment to drive the first side mold and the second side mold to move, so that the bottom mold, the upper mold, the first side mold, the second side mold and the sand core surround to form the blank cavity; 2) Turn on the low-pressure casting equipment to allow the molten metal to fill the blank cavity through the gate; 3) Activate the point cooling mechanism and introduce coolant to cool the mold at multiple points, so that the molten metal in the blank cavity can be cooled sequentially "from top to bottom and from both ends to the center"; 4) After the casting solidifies, the first side mold and the second side mold move forward and backward in two directions under the drive of the side cylinder, leaving the surface of the casting; after the first side mold and the second side mold are in place, the upper mold moves upward under the drive of the main cylinder of the equipment, and the locking block locks the casting under the action of the driving component, so that the casting moves together with the upper mold and takes the casting and the internal sand core out of the lower mold. 5) After the upper mold is raised, the locking block releases the casting under the drive of the drive component, and the ejector mechanism ejects the casting and sand core out of the upper mold.

Images