Hybrid battery pack structure and integrated low-pressure salt core casting forming method thereof

Abstract

The invention relates to the field of mechanical equipment and casting, in particular to a hybrid power battery pack structure and an integrated low-pressure salt core casting forming method thereof.The hybrid power battery pack structure comprises an upper cover and a lower shell, a sealing gasket is arranged between the upper cover and the lower shell, and the upper cover and the lower shell are each a box body which is formed by sequentially connecting a flange, a side plate and a bottom plate and provided with an opening in the top; the low-pressure salt core heat exchanger is characterized in that the upper cover and / or the lower shell are / is a low-pressure salt core casting part of an integrated structure, a built-in cooling flow channel is formed in the bottom plate, a liquid inlet and a liquid outlet of the cooling flow channel are opened in the side plates respectively, and internal threads or external threads matched with the quick-change connectors are arranged on the liquid inlet and the liquid outlet respectively. The invention has the following advantages: the whole structure of the battery pack adopts a low-pressure salt core casting forming method, so that the built-in cooling channel is formed in the bottom plate, the high-precision internal cooling water channel is cast in the bottom support shell of the battery pack, the cooling function and the integrated forming of the battery pack are synchronously realized, the forming process is advanced, and the cost is low. And the overall strength of the battery pack is improved.

Description

Technical Field

[0001] The present invention relates to the fields of mechanical equipment and casting, and in particular to a hybrid battery pack structure and an integrated low-pressure salt core casting method thereof. Background Art

[0002] At present, new energy vehicles generally include two types: plug-in hybrid vehicles and pure electric vehicles. Among the preparation methods of battery packs, welding forming method and low-pressure casting method are commonly used methods for preparing hybrid battery packs. The battery pack shell made by welding forming method is generally produced by sheet metal welding, which uses stamping sheet metal and then forms the battery pack shell by welding. This scheme has the following shortcomings: heavy weight, complex processing technology, precision cannot be guaranteed, poor consistency, long production cycle, poor strength, poor sealing and other defects. These defects cause great inconvenience to the manufacture of products and pose hidden dangers to the safety performance of electric vehicles. For battery pack products with complex cooling channels, welded pipes will deform or crack during use due to temperature stress, load changes, corrosion and other reasons, causing battery pack failure.

[0003] The low-pressure casting method generally uses gravity casting to form the battery tray skeleton of the entire chassis battery installation part, and then uses glue to screw or rivet the template. It uses cast aluminum 102 as the casting material, and gravity casting to form the blank of the battery box 100. The wall thickness of the blank is at least 6 mm, and a processing allowance is left. This solution also has some shortcomings: its wall thickness is thicker (greater than 6mm), heavy weight, low production efficiency (6-8 minutes / piece), poor dimensional accuracy, and poor sealing. For battery pack shells without complex cooling water, when the output is large, die casting is the preferred casting process. However, when the battery pack has complex cooling channels, gravity casting becomes difficult to adapt.

[0004] The Chinese utility model patent application number 202320149307.2 discloses a battery pack case and a battery pack having the same, including a case having a first cooling channel and a first inlet and a first outlet connected to the first cooling channel; a case cover connected to the case and defining an installation space together, and having a second cooling channel and a second inlet and a second outlet connected to the second cooling channel. The battery pack case of the utility model integrates the liquid cooling system into the case cover and the case, but in essence it is still a welded cooling channel, which has common problems with welded structures.

[0005] The Chinese utility model patent with application number 202420019109.9 discloses a battery pack shell assembly and a battery pack, including a lower shell and a liquid cooling joint. The lower shell includes a side beam and an end plate. A cooling channel is provided in the side beam. The side beam is located on the inner side of the end plate. An interface that penetrates the end plate and communicates with the cooling channel is provided on the outer wall of the end plate. The liquid cooling joint is suitable for being plugged and fixed at the interface from the outside of the lower shell and is sealed and connected with the cooling channel. A cooling channel is provided in the side beam, and an interface that communicates with the cooling channel is provided on the end plate, so that the liquid cooling joint can be directly connected to the interface on the end plate from the outside of the lower shell to achieve communication with the cooling channel in the side beam.

[0006] In summary, there is no application of built-in cooling water channels at the bottom of the battery pack in the prior art, mainly due to the limitations of the casting process. The processing technology of welding cooling water channels has the problems of cumbersome production and welding point leakage. Although the cooling effect of the built-in cooling water channel at the bottom of the battery pack is better, it has not been applied. Summary of the invention

[0007] The purpose of the present invention is to provide a hybrid battery pack structure and an integrated low-pressure salt core casting method thereof, to overcome the shortcomings of the prior art, the battery pack as a whole adopts a low-pressure salt core casting method, so that a built-in cooling channel is formed inside the bottom plate, and the cooling function and integrated forming of the battery pack are simultaneously realized, the problem of welding cooling channel opening and leakage is solved, the overall strength of the battery pack is improved, and the safety performance of hybrid vehicles and pure electric vehicles is ensured.

[0008] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions:

[0009] One of the technical solutions: A hybrid battery pack structure, including an upper cover and a lower shell, a sealing gasket is provided between the upper cover and the lower shell, wherein the upper cover and the lower shell are both top-opening boxes composed of a flange, a side panel and a bottom panel connected in sequence, the upper cover and / or the lower shell are integrated low-pressure salt core castings, a built-in cooling channel is formed inside the bottom panel, the liquid inlet and the liquid outlet of the cooling channel are respectively opened on the side panels, and the liquid inlet and the liquid outlet are respectively provided with internal or external threads matching the quick-change connector.

[0010] Furthermore, the cross section of the cooling channel is any one of a circle, an oblate circle, a rounded rectangle or a rounded square, and the maximum dimension of the cross section is 6-8 mm.

[0011] Furthermore, the thickness of the flange is 5-6 mm, the thickness of the side is 3-4 mm, and the thickness of the bottom plate is 20-30 mm.

[0012] Furthermore, the cooling channel is any one of an M-shape, an Ω-shape, a Z-shape, a X-shape, and a zigzag line shape.

[0013] Furthermore, the side panels have a draft angle of 1-2°, and adjacent side panels are connected by concave curved surfaces.

[0014] Technical solution 2: Integrated low-pressure salt core casting forming method, using low-pressure salt core casting to complete the integrated forming of the upper cover or lower shell, with multiple gates distributed to meet the shrinkage flow balance during the casting process, specifically including the following steps:

[0015] 1) Design and manufacture the salt core according to the structure and size of the bottom plate of the upper cover or lower shell and the cooling channel inside it;

[0016] 2) Design and manufacture a casting upper mold and a casting lower mold according to the outer contour structural dimensions of the upper cover or the lower shell, wherein the bottom of the casting lower mold is provided with a positioning step for fixing the salt core; the bottom of the casting lower mold is connected with a plurality of pouring gates, which are connected to a low-pressure casting machine through a diverter cone and a liquid riser;

[0017] 3) The casting upper mold and the casting lower mold are closed, and the low-pressure casting machine is started to pour the molten liquid into the mold. When the upper surface of the molten liquid exceeds the corresponding liquid level of the flange by 3-5mm, the pouring is stopped, and the mold temperature is lowered to room temperature before opening the mold;

[0018] 4) Clean the castings, remove the gates, remove the salt core protruding from the side panels, post-process the salt core, plug the outlet of the support core, process the threads of the liquid inlet and outlet, process the upper surface of the flange, and obtain a qualified battery pack cover or lower shell.

[0019] Furthermore, before pouring in step 3), graphite powder is evenly applied to the inner wall of the cavity.

[0020] Furthermore, the molten liquid is any one of high-strength stainless steel, aluminum alloy, and titanium alloy.

[0021] Furthermore, the casting lower mold is also provided with a core block corresponding to the groove structure on the surface of the lower shell.

[0022] Furthermore, the gate is in the form of a sprue, or a composite structure consisting of a sprue and a horizontal extension of the sprue, wherein the ratio of the outlet area of ​​the horizontal extension of the sprue to the cross-sectional area of ​​the sprue is 3-5:1.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The overall structure of the battery pack is formed by low-pressure salt core casting, so that a built-in cooling channel is formed inside the bottom plate, and a high-precision internal cooling water channel is cast in the bottom support shell of the battery pack, which simultaneously realizes the cooling function and integrated forming of the battery pack. The forming process is advanced and the overall strength of the battery pack is improved;

[0025] 2) The battery pack has good forming quality, high forming efficiency, simple process and low cost, which solves the problems of complicated processing technology of welding battery pack cooling channel and welding leakage of welds. Compared with the existing welding forming process, it has higher efficiency, lower cost, firm and stable structure, and is more applicable and safer.

[0026] 3) The temperature inside the battery pack can be managed (heat dissipated) through rapid cooling, which effectively reduces the internal temperature of the battery pack, improves the cooling effect of the battery pack, and ensures the safety performance of hybrid vehicles and pure electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a lower shell embodiment of a hybrid battery pack structure of the present invention;

[0028] Figure 2 This is a schematic diagram of a perspective state of the cooling channel inside the bottom plate in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the salt core structure in an embodiment of the present invention;

[0030] Figure 4 A bottom view of the integrated low-pressure salt core casting mold in an embodiment of the present invention;

[0031] Figure 5 This is a flow chart of the integrated low-pressure salt core casting system in an embodiment of the present invention.

[0032] In the figure: 1-lower shell, 2-bottom plate, 3-side plate, 4-flange, 5-cooling channel, 6-liquid inlet, 7-liquid outlet, 8-main channel core, 9-support core, 10-port core, 11-casting upper mold, 12-casting lower mold, 13-gate, 14-sprue, 15-sprue horizontal extension section, 16-core block. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the specific embodiments required to be used in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some implementation methods of the present invention. For ordinary technicians in this field, other specific embodiments can be obtained based on these specific embodiments without paying creative work.

[0035] The components of the embodiments of the present invention generally described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific embodiments is not intended to limit the scope of the invention claimed, but merely represents selected embodiments of the present invention.

[0036] See Figure 1-2 , is a schematic diagram of the structure of a hybrid battery pack of the present invention. The hybrid battery pack generally includes an upper cover and a lower shell 1, and a sealing gasket is provided between the upper cover and the lower shell 1, wherein the upper cover and the lower shell 1 are both boxes with a top opening formed by connecting a flange 4, a side plate 3 and a bottom plate 2 in sequence. After the upper cover, the sealing gasket and the lower shell 1 are combined, their internal volume is used to carry the battery pack and the battery management system (BMS). The shell 1 of the hybrid battery pack is fixed to the bottom of the new energy vehicle through the bottom plate 2.

[0037] The embodiment takes the lower shell 1 as an example. The lower shell 1 is an integrated low-pressure salt core casting. The side panels 3 have a draft angle of 1-2°, and the adjacent side panels 3 are connected by a concave arc surface. A built-in cooling channel 5 is formed inside the bottom plate 2. The liquid inlet 6 and the liquid outlet 7 of the cooling channel 5 are opened on the side panel 3 respectively. The liquid inlet 6 and the liquid outlet 7 are respectively provided with internal or external threads matching the quick-change connector. The liquid inlet 6 and the liquid outlet 7 are connected to the cooling water pump through a quick-change connector and a pipeline to provide cooling and heat dissipation for the battery pack.

[0038] In the embodiment, the thickness of the flange 4 is 5-6 mm, the thickness of the side is 3-4 mm, and the thickness of the bottom plate 2 is 20-30 mm. The cross section of the cooling channel 5 is circular, or can be any one of an oblate circle, a rounded rectangle or a rounded square, and the maximum cross section size is 6-8 mm. The cooling channel 5 is M-shaped, or can be any one of an Ω shape, a Z shape, a zigzag shape, and a zigzag line shape, and is arranged according to the size of the bottom plate.

[0039] The integrated low-pressure salt core casting forming method of the present invention adopts a low-pressure salt core casting method to complete the integrated forming of the lower shell 1, and utilizes multiple gate distribution to meet the shrinkage flow balance during the casting process. Figure 5 , specifically including the following steps:

[0040] 1) The salt core is designed and manufactured according to the structural dimensions of the bottom plate 2 of the lower shell 1 and the cooling channel 5 inside it, see Figure 3 The salt core is M-shaped, including a main channel core 8, a support core 9 and a port core 10. The support core 9 is used to support the main channel core 8, enhance the structural strength of the shape, and avoid brittle fracture during the pouring process. The port core 10 is used to connect and position with the casting lower mold to maintain the position and posture of the salt core in the cavity.

[0041] The method for making the salt core includes mixing a water-soluble metal halide (such as sodium chloride) and a powder (including at least one of graphite powder and talcum powder) to obtain a pre-treated mixture, and then spraying an aqueous solution of sodium silicate to obtain a mixture to be processed. Then, pressing, turning, and curing are performed to obtain a salt core to be used.

[0042] 2) Design and manufacture the casting upper mold 11 and the casting lower mold 12 according to the outer contour structural dimensions of the lower shell 1. The bottom of the casting lower mold 12 is provided with a positioning step for fixing the salt core. According to conventional design principles, the casting upper mold 11 forms the inner contour of the lower shell, and the casting lower mold 12 forms the outer contour of the lower shell; the bottom of the casting lower mold 12 is connected with a plurality of pouring gates 13, and the pouring gates 13 are connected to the low-pressure casting machine through a diverter cone and a riser pipe; the pouring gates 13 are in the form of a sprue 14, and also a composite structure consisting of a sprue 14 and a horizontal extension section 15 of the sprue, wherein the outlet area of ​​the horizontal extension section 15 of the sprue is 3-5:1 compared with the cross-sectional area of ​​the sprue 14, in order to reduce the resistance to the replenishment of molten metal.

[0043] 3) The upper casting mold 11 and the lower casting mold 12 are molded together. Figure 4 Before pouring, the inner wall of the cavity is evenly coated with graphite powder to prevent adhesion when the mold is opened. The low-pressure casting machine is started to pour molten metal into the model. The molten metal enters the casting cavity through the sprue 14 and the horizontal extension section 15 of the sprue to fill the mold. When the upper surface of the molten liquid exceeds the corresponding liquid level of the flange 4 by 3-5mm, the pouring is stopped. At this time, the main channel core 8, the support core 9 and the port core 10 are all covered in the metal liquid. When the temperature of the model drops to room temperature, the mold is opened to obtain the lower shell rough blank. At this time, the salt core has been embedded in the bottom plate.

[0044] During the pouring process, the mold temperature needs to be maintained at 200-250℃. The speed control of low-pressure casting mainly includes the liquid rising speed, the filling speed and the pressurization speed. The liquid rising speed refers to the speed at which the molten metal rises in the liquid rising tube. In order to facilitate the discharge of the gas in the cavity, the liquid rising speed should be slow, usually controlled between 50 and 150 mm / s. For aluminum alloys, the liquid rising speed is generally 50-100 mm / s. The filling speed refers to the speed at which the molten metal rises in the cavity. The filling speed is faster than the liquid rising speed, usually controlled within the range of 50-100 mm / s to avoid eddy currents in the molten metal. The pressurization speed refers to the speed at which the pressure is added to the mold after the filling is completed. The range of the low-pressure casting pressurization rate is usually 0.2-0.5 bar / s.

[0045] 4) Clean the casting, remove the gates, remove the support core 9 and the port core 10 protruding from the side plate 3, post-process the salt core, block the outlet of the support core 9, process the threads of the liquid inlet 6 and the liquid outlet 7, process the upper surface of the flange, and obtain a qualified battery pack upper cover or lower shell 1.

[0046] 5) The post-treatment is to boil the lower shell blank in hot water with dilute hydrochloric acid for one hour, take it out after the salt core is dissolved, and wash and dry it to obtain a qualified casting. The concentration of dilute hydrochloric acid is 4-5 mol / L, and the ratio of hot water to dilute hydrochloric acid is 1500:1-2000:1.

[0047] The molten liquid used for casting the lower shell 1 of the present invention is any one of high-strength stainless steel, aluminum alloy, and titanium alloy. High-strength stainless steel has extremely high strength and corrosion resistance, and is suitable for scenarios with extremely high safety requirements for battery packs. The stainless steel shell can effectively resist external impact and extrusion, and protect the internal structure of the battery from damage. However, the weight of stainless steel is relatively large, which may affect the energy efficiency of the vehicle to a certain extent. Aluminum alloy has become the preferred material for the battery pack shell of electric vehicles due to its light weight, high strength and good corrosion resistance. The aluminum alloy shell can effectively reduce the overall weight of the battery pack and improve the energy efficiency of the vehicle. At the same time, its excellent thermal conductivity also helps the battery maintain a good heat dissipation effect during operation. Titanium alloy is favored for its higher strength and toughness, despite its higher cost.

[0048] In the above embodiment, the casting lower mold 12 may also be provided with a core block 16 corresponding to the groove structure on the surface of the lower shell 1 according to the functional structure of the battery pack. This part is of conventional design and will not be described in detail.

[0049] It should be noted that the above implementation methods are only used to illustrate the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should all be included in the scope of the claims of the present invention.

Claims

1. A hybrid battery pack structure, comprising an upper cover and a lower shell, a sealing gasket is provided between the upper cover and the lower shell, wherein the upper cover and the lower shell are both a box body with a top opening composed of a flange, a side plate and a bottom plate connected in sequence, characterized in that: The upper cover and / or lower shell are integrated low-pressure salt core castings, and a built-in cooling channel is formed inside the bottom plate. The liquid inlet and outlet of the cooling channel are opened on the side plates respectively, and the liquid inlet and outlet are respectively provided with internal or external threads matching the quick-change connector.

2. A hybrid battery pack structure according to claim 1, characterized in that: The cross section of the cooling channel is any one of a circle, an oblate circle, a rounded rectangle or a rounded square, and the maximum size of the cross section is 6-8 mm.

3. A hybrid battery pack structure according to claim 1, characterized in that: The thickness of the flange is 5-6 mm, the thickness of the side is 3-4 mm, and the thickness of the bottom plate is 20-30 mm.

4. A hybrid battery pack structure according to claim 1, characterized in that: The cooling channel is in any one of an M-shape, an Ω-shape, a Z-shape, a X-shape, and a zigzag line shape.

5. The hybrid battery pack structure according to claim 1, characterized in that: The side panels have a draft angle of 1-2°, and adjacent side panels are connected by concave curved surfaces.

6. The integrated low-pressure salt core casting method for a hybrid battery pack structure according to claims 1-5, characterized in that: The low-pressure salt core casting method is used to complete the integrated forming of the upper cover or lower shell, with multiple gates distributed to meet the shrinkage flow balance during the casting process. The specific steps include: 1) Design and manufacture the salt core according to the structure and size of the bottom plate of the upper cover or lower shell and the cooling channel inside it; 2) Design and manufacture a casting upper mold and a casting lower mold according to the outer contour structural dimensions of the upper cover or the lower shell, wherein the bottom of the casting lower mold is provided with a positioning step for fixing the salt core; the bottom of the casting lower mold is connected with a plurality of pouring gates, which are connected to a low-pressure casting machine through a diverter cone and a liquid riser; 3) The casting upper mold and the casting lower mold are closed, and the low-pressure casting machine is started to pour the molten liquid into the mold. When the upper surface of the molten liquid exceeds the corresponding liquid level of the flange by 3-5mm, the pouring is stopped, and the mold temperature is lowered to room temperature before opening the mold; 4) Clean the castings, remove the gates, remove the salt core protruding from the side panels, post-process the salt core, plug the outlet of the support core, process the threads of the liquid inlet and outlet, process the upper surface of the flange, and obtain a qualified battery pack cover or lower shell.

7. The integrated low-pressure salt core casting method according to claim 6, characterized in that: In the step 3), before pouring, the inner wall of the cavity is evenly coated with graphite powder.

8. The integrated low-pressure salt core casting method according to claim 6, characterized in that: The molten liquid is any one of high-strength stainless steel, aluminum alloy and titanium alloy.

9. The integrated low-pressure salt core casting method according to claim 6, characterized in that: The casting lower mold is also provided with a core block corresponding to the groove structure on the surface of the lower shell.

10. The integrated low-pressure salt core casting method according to claim 6, characterized in that: The gate is in the form of a sprue, or a composite structure consisting of a sprue and a horizontal extension of the sprue, wherein the outlet area of ​​the horizontal extension of the sprue is 3-5:1 compared to the cross-sectional area of ​​the sprue.

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