A method for manufacturing a hollow aluminum alloy subframe

Abstract

The present invention provides a method for manufacturing a hollow aluminum alloy subframe, comprising the following steps: step 1, manufacturing a sand core (2) structure, wherein the sand core (2) is an integrated sand core (2); step 2, placing the sand core (2) in a mold and closing the mold, wherein the sand core (2) is placed horizontally; step 3, pouring molten aluminum, wherein the temperature of the molten aluminum is greater than 610 degrees Celsius; pressurizing the casting process, and maintaining the pressure after the casting is completed, wherein the casting process is controlled within 2 to 3 minutes; step 4, after the pressure maintenance is completed, the pressure is withdrawn and the cooling is carried out, wherein the cooling time is 2 to 3 minutes; step 5, opening the mold, removing the cast part, and leaking the sand core (2). The aluminum alloy subframe has the advantages of high manufacturing efficiency, simple manufacturing process, and simple bushing press-fitting in the later stage.

Description

Technical Field

[0001] The present invention relates to the field of casting, and in particular to a method for manufacturing a hollow aluminum alloy subframe. Background Art

[0002] With the rapid development of new energy vehicles in China, new energy vehicle manufacturers are increasingly opting for five-link suspensions with improved handling performance to enhance their products' competitive advantages. As a key component of the suspension system, the subframe, carrying the motor, control arms, stabilizer bar, and other components, presents a relatively complex structure. On one-piece cast subframes, the motor mounts are typically located on the front and rear crossmembers (for example, CN202210286360.7 - Aluminum Alloy Hollow Subframe Casting Structure). This results in thinner sand cores at the mounting holes of the front and rear crossmembers, making them susceptible to breakage.

[0003] In order to achieve the feasibility of casting the suspended mounting point, side core pulling is usually arranged on the casting mold. At the same time, in order to ensure that the sand core will not break when lifting the sand core, the sand core is divided into four parts and assembled on the mold.

[0004] This structure has the following disadvantages: arranging side core pulling on the casting mold makes the casting mold complicated and the cost increases, and aluminum is easy to escape from the side core pulling during casting, causing safety risks, and flash is easy to be generated at the joint between the side core pulling mechanism and the mold, resulting in low casting quality and the need for manual removal of flash, which prolongs the product production cycle.

[0005] The subframe sand core adopts segmented sand core, and each segment of the sand core needs to be arranged with positioning and support structure, which makes the mold positioning structure complicated and reduces the casting qualification rate. Summary of the Invention

[0006] The present invention provides a method for manufacturing a hollow aluminum alloy subframe based on the existing technical problems.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for manufacturing a hollow aluminum alloy subframe comprises the following steps:

[0009] Step 1: manufacturing a sand core structure, wherein the sand core is an integrated sand core;

[0010] Step 2: Place the sand core into the mold and close the mold, with the sand core placed horizontally;

[0011] Step 3: pouring molten aluminum, the temperature of which is greater than 610 degrees Celsius; pressurizing during the pouring process, and maintaining the pressure after the pouring is completed, and the pouring process is controlled within 2 to 3 minutes;

[0012] Step 4: After the pressure is maintained, release the pressure and cool down for 2 to 3 minutes.

[0013] Step 5: Open the mold, take out the casting, and leak out the sand core.

[0014] Preferably, in step one, the sand core is an integrated structure, and the sand core includes a beam core, and a hole one is formed on the beam core for forming a motor fixing hole, and the hole one is arranged in the front-to-back direction and passes through the front and rear sides of the beam core; a support core is arranged inside the hole one, and the support core is fixed to the side of the hole one through the support arm core; the support core, the support arm core and the beam core are an integrated molding structure; a guide hole is formed at the support arm position, and the guide hole plays a guiding role in the installation of the bushing and has a sand leakage effect on the sand core.

[0015] Preferably, the connection between the support arm core and the support core is an arc transition; the transition position is a transition zone, and the transition zone is an obtuse angle transition.

[0016] Preferably, the support arm core is provided with at least two support arm cores in the transverse direction, and the two support arm cores are located on both sides of the support core.

[0017] Preferably, the support core is a columnar structure arranged in the front-to-back direction, and the upper surface of the support core is a plane and the other side surfaces are arc surfaces matching the shape of the fixing hole, and the upper surface space is connected to the mold casting port.

[0018] Preferably, the support core and hole 1 are coaxially arranged.

[0019] Preferably, the sand core forms a cavity structure in the middle of the subframe, and the support arm core forms a guide hole on the side wall of the fixing hole; the opening of the guide hole forms a trumpet mouth with an obtuse angle due to the transition zone.

[0020] Preferably, the mold is provided with a body fixing hole, the cast hollow sub-frame has the body fixing hole, and the inner wall of the body fixing hole is formed into a step shape by machining.

[0021] Preferably, the space section reserved in the mold for casting the longitudinal beam has unequal wall thickness, and the thickness of the inner side and lower side of the longitudinal beam is greater than the thickness at other positions.

[0022] This solution has the following beneficial effects:

[0023] The patent of this invention redesigns the structure of the subframe, adds square holes at the front and rear crossbeam core suspension holes, fills the suspension holes with sand cores and connects them to the main sand cores through the square holes, so that the subframe sand cores are connected as a whole, so that the casting mold does not need a side core pulling mechanism, which is also beneficial for sand leakage in the future, improves the overall strength of the sand core, improves the casting quality, and increases the sand core manufacturing qualification rate by 50%. The sand core is a whole and can be placed in one go, saving 20 seconds of manufacturing time for each mold and improving the manufacturing cycle. Adding chamfers to the edges of the square holes can avoid cutting the bushing when pressing it in, and improves the bushing pressing qualification rate by 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of four sand core modules in the prior art.

[0025] Figure 2 Schematic diagram of the sand core of the technical solution of the present invention.

[0026] Figure 3 yes Figure 2 A partial enlarged view of .

[0027] Figure 4 It is a structural diagram of the subframe.

[0028] Among them, 1-beam core, 2-sand core, 3-motor fixing hole, 4-hole one, 5-support core, 6-support arm core, 7-transition area, 8-upper side surface, 9-guide hole, 10-limiting step, 11-bell mouth. DETAILED DESCRIPTION

[0029] Example 1

[0030] A method for manufacturing a hollow aluminum alloy subframe comprises the following steps:

[0031] Step 1: Manufacturing a sand core 2 structure. The sand core 2 is an integrated sand core 2. This sand core 2 structure can eliminate the use of a side core pulling structure in the existing solution, thereby avoiding leakage at the position where the side core pulling matches the motor fixing hole 3 during the manufacturing process. In addition, this structure will not cause burrs at the fixing hole position.

[0032] Step 2: Place the sand core 2 into the mold and close the mold, with the sand core 2 placed horizontally;

[0033] Step 3: pouring molten aluminum, the temperature of which is greater than 610 degrees Celsius; pressurizing during the pouring process, and maintaining the pressure after the pouring is completed, and the pouring process is controlled within 2 to 3 minutes;

[0034] Step 4: After the pressure is maintained, release the pressure and cool down for 2 to 3 minutes.

[0035] Step 5: Open the mold, take out the casting, and leak out the sand core 2.

[0036] The pouring time, pouring pressure, and holding pressure are obtained based on prior simulation calculations combined with experiments.

[0037] The design of the sand core 2 is key in this solution. The sand core 2 is an integrated structure, and the shape of the sand core 2 matches the shape of the subframe. The sand core 2 includes a crossbeam core 1, on which a hole 4 is formed for forming a motor fixing hole 3. The hole 4 is arranged in the front-to-back direction and passes through the front and rear sides of the crossbeam core 1; a support core 5 is arranged inside the hole 4, and the support core 5 is fixed to the side of the hole 4 by a support arm core 6. The design of the support core 5 structure replaces the traditional side core pulling structure, which can realize the integrated design of the sand mold, and the positioning of the sand mold is simpler and more cost-effective. Specifically, in this solution, since the subframe is a quadrilateral hollow structure, the sand mold includes two crossbeam cores 1 and two longitudinal beams, and the mounting holes on the crossbeam core 1 are the motor fixing holes 3. The traditional side core pulling structure makes the sand mold placement complicated and may cause aluminum liquid leakage. In addition, the sand mold and the mold will produce burrs at the matching part, which needs to be polished separately later. This solution adopts an integrated sand mold structure that can match the mold to directly form the motor fixing hole 3.

[0038] In this solution, the support core 5, support arm core 6, and crossbeam core 1 are integrally formed. The support arms support the sand core 2, preventing breakage during transport. Later, guide holes 9 will be formed on the side of the motor mounting hole 3 to match the cross-sectional shape of the support arm core 6.

[0039] The connection between the support arm core 6 and the support core 5 is an arc transition. This arc transition not only plays a smooth transition between the support core 5 and the support arm core 6, but more importantly, this structure can ensure that the hole formed subsequently can facilitate the press-fitting of the bushing.

[0040] For ease of description, the transition position is defined as transition zone 7, which is an obtuse angle transition. The angle of transition zone 7 can be calculated by using the angle formed by the end lines of the two end points of the arc surface of transition zone 7 and the middle point line of transition zone 7.

[0041] The support arm core 6 is provided with at least two support arm cores 6 in the transverse direction, and the two support arm cores 6 are located on both sides of the support core 5. The advantage of arranging the support arm core 6 in the transverse direction is that it has little effect on the strength of the crossbeam core 1, because the thinnest parts of the crossbeam core 1 are above and below the fixing holes.

[0042] The support core 5 is a cylindrical structure arranged in a front-to-back direction. Its upper surface 8 is flat, while the remaining side surfaces are arc-shaped to match the shape of the fixing hole. The purpose of the flat upper surface is to form a feeding channel that connects to the external gate. This can be used to feed shrinkage during cooling and prevent shrinkage defects on the inner wall of the fixing hole.

[0043] In this embodiment, the support core 5 and the hole 1 4 are coaxially arranged.

[0044] The hollow sub-frame designed in this solution is made by casting with a matching mold using the above-mentioned manufacturing method. The sand mold forms the cavity structure in the middle of the sub-frame, and the support arm core 6 forms a guide hole 9 on the side wall of the fixing hole. Since the bushing installed in the mounting hole is made of nylon, the outer diameter of the nylon bushing is larger than the inner diameter of the motor mounting hole in the initial state, and the difference is generally about 1.5mm. Therefore, in the traditional straight hole structure, when the bushing is pressed for the first time, the deformation of the bushing will accumulate elastic force, so rebound will occur, and a second pressing and embedding is generally required. However, when the bushing of the guide hole 9 in this solution reaches this position, a part of it will be squeezed into the hole. Since the edge of the hole is an obtuse-angle structure, the bushing will not be stuck at the edge of the hole when continuing to press down, and a single pressing and embedding can be achieved.

[0045] In this embodiment, the opening of the guide hole 9 forms a bell mouth 11 with an obtuse angle due to the transition zone 7 .

[0046] The fixing hole is provided with a limiting step 10 to increase the friction force of the bushing and improve the bushing press-out force.

[0047] The patent of this invention redesigns the structure of the subframe, adds square holes at the suspension holes of the front and rear crossbeam cores 1, fills the suspension holes with sand cores 2 and connects to the main sand core 2 through the square holes, so that the subframe sand core 2 is connected as a whole, so that the casting mold does not need a side core pulling mechanism, which is also beneficial to sand leakage in the future, improves the overall strength of the sand core 2, improves the casting quality, and increases the manufacturing qualification rate of the sand core 2 by 50%. The sand core 2 is a whole, and it can be completed at one time when the sand core 2 is placed, which saves 20 seconds of manufacturing time for each mold and improves the manufacturing cycle. The chamfered edges of the square holes can avoid cutting the bushing when the bushing is pressed in, and the bushing pressing qualification rate is increased by 30%.

[0048] Example 2

[0049] The difference from Example 1 is that: the support core 5 in the motor mounting hole of one of the beam cores 1 is connected to four support arm cores 6, and the support arm cores 6 are designed to be cross-shaped with each other.

[0050] Example 3

[0051] The difference between this embodiment and embodiment 1 is that the cross section of the support arm core 6 is rectangular.

Claims

1. A method for manufacturing a hollow aluminum alloy subframe, characterized by: The following steps are involved: Step 1: manufacturing a sand core (2) structure, wherein the sand core (2) is an integrated sand core (2); Step 2: Place the sand core (2) into the mold and close the mold, with the sand core (2) placed horizontally; Step 3: Pour molten aluminum. The temperature of the molten aluminum is greater than 610 degrees Celsius. Pressurize the aluminum during the pouring process and maintain the pressure after the pouring is completed. The pouring process is controlled within 2 to 3 minutes. Step 4: After the pressure is maintained, release the pressure and cool down for 2 to 3 minutes. Step 5: Open the mold, take out the casting, and drain out the sand core (2); In step 1, the sand core (2) is an integrated structure, and the sand core (2) includes a crossbeam core (1), and a hole (4) for forming a motor fixing hole (3) is formed on the crossbeam core (1), and the hole (4) is arranged in the front-to-back direction and passes through the front and rear side surfaces of the crossbeam core (1); a support core (5) is arranged inside the hole (4), and the support core (5) is fixed to the side surface of the hole (4) through the support arm core (6); the support core (5), the support arm core (6) and the crossbeam core (1) are an integrated structure; the position of the support arm core (6) forms a guide hole (9) of the aluminum alloy subframe, and the guide hole (9) plays a guiding role in the installation of the bushing and plays a role in leaking sand for the sand core (2).

2. The method for manufacturing a hollow aluminum alloy subframe according to claim 1, characterized in that: The connection between the support arm core (6) and the support core (5) is an arc transition; the transition position is a transition zone (7), and the transition zone (7) is an obtuse angle transition.

3. The method for manufacturing a hollow aluminum alloy subframe according to claim 1, characterized in that: At least two support arm cores (6) are provided in the circumferential direction, and the two support arm cores (6) are located on both sides of the support core (5).

4. The method for manufacturing a hollow aluminum alloy subframe according to claim 1, characterized in that: The support core (5) is a columnar structure arranged in the front-to-back direction, and the upper surface (8) of the support core (5) is a plane, and the other side surfaces are arc surfaces matching the shape of the fixing hole, and the upper surface (8) is spatially connected to the mold casting port.

5. The method for manufacturing a hollow aluminum alloy subframe according to claim 1, characterized in that: The support core (5) and hole one (4) are coaxially arranged.

6. The method for manufacturing a hollow aluminum alloy subframe according to claim 1, characterized in that: The sand core (2) forms a cavity structure in the middle of the subframe, and the support arm core (6) forms a guide hole (9) on the side wall of the fixing hole; the opening of the guide hole (9) forms a trumpet mouth (11) with an obtuse angle at the opening due to the transition zone (7).

7. The method for manufacturing a hollow aluminum alloy subframe according to claim 6, characterized in that: The mold is reserved for processing body fixing holes, and the cast hollow subframe has the body fixing holes, and the inner walls of the body fixing holes are machined to form a step shape.

8. The method for manufacturing a hollow aluminum alloy subframe according to claim 6, characterized in that: The space section reserved in the mold for casting the longitudinal beam has unequal wall thickness, and the thickness of the inner side and lower side of the longitudinal beam is greater than the thickness at other positions.

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