Preparation method of lightweight control arm

Abstract

A preparation method of a lightweight control arm comprises the following steps: heating a sheet of a continuous fiber reinforced thermoplastic composite material with a U-shaped structure, transferring the sheet into an injection mold, carrying out hot press molding to form a skeleton, carrying out injection molding on an on-line mixed long fiber reinforced homologous resin onto the skeleton to form a covered edge and a reinforcing rib, and pressing the covered edge and the reinforcing rib into a spherical hinge after molding to form the control arm. Wherein the U-shaped joint of the sheet adopts a large arc structure, and during injection molding, resin is directly injected into a mold from a buffer cylinder of online mixing equipment in a piston manner. According to the invention, a plate with a large arc structure is subjected to hot pressing to form a framework, and a forming process of integrating online mixing, hot pressing and injection molding is used, and a mode of directly injecting resin into a mold from a buffer cylinder of online mixing equipment in a piston manner is matched, so that the overall performance of the formed control arm is greatly improved.

Description

Technical Field

[0001] The present invention relates to a preparation method of a control arm, and particularly to a preparation method of a lightweight control arm prepared from a composite material. Background Art

[0002] At present, the development of lightweight new energy vehicles is increasingly focused on the hybrid application of multiple materials. Among them, the hybrid application of continuous fiber-reinforced thermoplastic composites as the main load-bearing skeleton and engineering plastics with a high fiber content for connection, cooperation, and reinforcement has the broadest application prospects. As an important part of the vehicle chassis system, the comprehensive mechanical properties of the vehicle control arm play a crucial role in the safety and handling stability of the vehicle. Currently, in order to meet the lightweight requirements, composite materials are also selected for production.

[0003] For example, in the invention patent with the application number CN202110177255.5 and the name "A Control Arm Forming Method and a Control Arm", a V-shaped closed skeleton is first formed by using a strip-shaped thermoplastic continuous fiber-reinforced composite material, and then the V-shaped closed skeleton is placed in an injection mold, and a thermoplastic fiber-reinforced composite material is filled into the V-shaped closed skeleton by high-pressure injection molding to integrally injection mold and form the control arm. This method requires a separate preforming process. The reinforcement skeleton is prepared in advance outside the injection mold, and then the reinforcement skeleton is transferred to the injection mold for secondary injection molding, so the efficiency is relatively low.

[0004] In the invention patent application with the application number CN202110745630.1 and the name "A Vehicle Composite Control Arm and Its Forming Method", a carbon fiber composite board is first prepared, and then the carbon fiber composite board and the bushing are placed in a mold for injection molding together. However, in this method, there is no specific description on how to accurately maintain the relative position of the carbon fiber composite board and the bushing during the injection molding process, so it is impossible to know whether this method can produce a control arm that meets the requirements. Moreover, the cost of carbon fiber is high, making it difficult to popularize and apply.

[0005] In the invention patent application with the application number CN202311089612.8 and the name "A Thermocompression Injection Molding Integrated Forming Method of a Composite Control Arm", as Figure 1 shown, a V-shaped composite board with an opening cut at the ball pin is used as the main load-bearing skeleton, and a composite control arm is formed by thermocompression injection molding in a mold. During the use of this control arm, since an opening is cut at the composite board at the ball pin, which is the main stress point, cracks may occur at the interface of the coated composite structure during the service stress process, resulting in problems such as mechanical property deterioration, premature aging, and delamination of the product during use.

[0006] Therefore, improvement is still needed. Summary of the Invention

[0007] In view of the above problems existing in the current composite control arms, the present invention proposes a preparation method for lightweight control arms. By adopting a forming method that integrates on-line mixing, hot pressing, and injection molding, steps such as mixing and granulation and re-melting are omitted to reduce the manufacturing cost, and at the same time, the thermal oxidation and thermal damage of the material are reduced, thereby improving the performance of the product.

[0008] The technical means adopted by the present invention to solve the above problems is: a preparation method for lightweight control arms. After heating the sheet of continuous fiber-reinforced thermoplastic composite material with a U-shaped structure, it is transferred to an injection mold, hot-pressed into a skeleton, and then on-line mixed long fiber-reinforced homologous resin is injected onto the skeleton to form a wrap and reinforcing ribs. After molding, a ball joint is pressed in to form a control arm; the U-shaped connection of the sheet adopts a large arc structure. During injection molding, the resin is directly injected into the mold in a piston manner from the buffer cylinder of the on-line mixing equipment. The arc structure with a large central angle avoids wrinkles or tears during the hot pressing process, and the piston injection of the resin into the mold avoids the injection machine screw from cutting the long fibers.

[0009] Further, the points A corresponding to the ball pin center, points B and C corresponding to the centers of the two bushings on the sheet form a triangle ABC, and the centers of the outer arc R1 and the inner arc R2 at the U-shaped connection of the sheet are both located on the angular bisector of ∠BAC.

[0010] Further, the outer hypotenuse S1 connecting the two ends of the outer arc R1 on the sheet is tangent to R1; the inner hypotenuse S2 connecting the two ends of the inner arc R2 on the sheet is tangent to R2; S1 is parallel to S2, and the distance between S1 and S2 is L; the radius r1 of the outer arc R1 satisfies: 1 / 2(BC + L) ≥ r1 ≥ 80 mm, and the radius r2 of the inner arc R2 satisfies: 1 / 2(BC - L) ≥ r2 ≥ 35 mm.

[0011] Further, triangle ABC is an isosceles triangle.

[0012] Further, the ends of the two outer hypotenuses S1 far from the outer arc R1 are respectively connected to the straight edges T and T', and T∥T'.

[0013] Further, the length of the long fibers of the wrap and reinforcing ribs is 10 - 50 mm. The length of the long fibers ensures the interpenetration effect.

[0014] Further, the injection mold adopts a multi-point gating method with large channels. To ensure the fluidity of the long fiber resin.

[0015] Further, the inner diameter of the runner at the gating point is 4 - 7 mm.

[0016] Further, the gating points are four symmetrically arranged.

[0017] Further, the gating points adopt a sequential gating method to reduce the influence of the weld line.

[0018] Further, the resin of the composite material includes PA6, PA66, and PP; the continuous fibers include glass fiber, carbon fiber, aramid fiber, and basalt fiber.

[0019] Further, the fiber content in the sheet is 50-75 wt%.

[0020] Further, the fiber content in the homologous composite material used for injection molding is 20-65 wt%.

[0021] Further, a concave shape is formed on one surface after hot pressing the sheet, a wrapped edge is formed at the edge of the concave shape after injection molding, and a reinforcing rib is formed inside the concave shape.

[0022] The beneficial effects of the present invention are as follows: 1. The present invention uses a sheet with an arc structure having a large central angle to be hot pressed into a skeleton, avoiding wrinkles or tears generated during the hot pressing process from affecting the performance of the control arm. The integrated forming process of on-line mixing - hot pressing - injection molding omits steps such as mixing and granulation, and re-melting, thus reducing the manufacturing cost. At the same time, it reduces the thermal oxidation and thermal damage of the material, thereby improving the performance of the product. And the resin is directly injected into the mold in a piston type from the buffer cylinder of the on-line mixing equipment, canceling the screw extrusion feeding of the injection molding machine, avoiding the injection molding machine screw from cutting the long fibers, enabling the homologous long fibers to maintain a relatively large length. With the high temperature and high pressure during injection molding, the fibers in the long fiber reinforced resin will wash into the continuous fiber sheet during high-speed movement, generating fiber interpenetration and improving the mechanical bonding strength. Thus, the overall performance of the control arm is improved.

[0023] 2. The outer periphery of the main body part of the U-shaped sheet of the present invention adopts a structure connected by a straight edge, an outer bevel edge, and a large-radius outer arc, and the inner periphery adopts a structure connected by an inner bevel edge and a large-radius inner arc, avoiding wrinkles or tears generated during the hot pressing process while meeting the size requirements of the control arm and ensuring the overall performance.

[0024] 3. The present invention adopts the method of multi-point sequential injection with large channels, enabling the long fibers to flow in a runner with a relatively large cross-sectional area, ensuring that the long fiber resin can be smoothly and directly injected into the mold without the screw extrusion of the injection molding machine. Description of the Drawings

[0025] Figure 1 It shows an opening at the ball pin of the sheet in the prior art; Figure 2 It is a schematic diagram of the sheet structure of Example 1; Figure 3 It is a schematic diagram of the structure after injection molding of Example 1; In the figure: 1. Sheet, 2. Wrapped edge, 3. Reinforcing rib, 4. Ball pin hole, 5. Bushing, 6. Injection point. Detailed Embodiments

[0026] The present invention is further described below in conjunction with the accompanying drawings. The accompanying drawings are only for illustrative purposes and are only schematic diagrams, not actual pictures, and cannot be understood as limiting the present patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the accompanying drawings may be omitted. Embodiment 1

[0027] A method for preparing a lightweight control arm, using a U-shaped continuous fiber reinforced thermoplastic composite material as the main load-bearing sheet 1, heated to a semi-molten state and then transferred to an injection mold, and hot-pressed into a skeleton with a concave shape on one surface and arc-shaped at two free ends after the mold is closed; then, a long fiber reinforced resin homologous to the sheet 1 is directly piston-injected into the mold from a buffer cylinder of an online mixing device after online mixing, forming an edge 2 at the edge of the sheet 1 and a reinforcing rib 3 inside the concave shape. After demolding and trimming operations, a ball joint is pressed into two bushings 5 ​​to form a control arm.

[0028] With the current Figure 1 There are different ways to dig holes at the ball pins of V-shaped sheets, such as Figure 2 As shown, the main body of the U-shaped sheet 1 of this embodiment located between the two bushings at both ends is a complete whole, and a large arc is used for connection at its U-shaped connection. The outer periphery of the sheet 1 adopts a structure of straight edge T-outer hypotenuse S1-outer arc R1-outer hypotenuse S1-straight edge T' connection, and the inner periphery adopts a structure of inner hypotenuse S2-inner arc R2-inner hypotenuse S2 connection. The corresponding ball pin center A on the sheet 1 and the centers B and C of the two bushings 5 ​​form a triangle. In this embodiment, the triangle ABC is an isosceles triangle. At this time, the sheet and the formed control arm are symmetrical structures. The straight edge T is parallel to the straight edge T', the outer hypotenuse S1 is also parallel to the inner hypotenuse S2, and the radius r1 of the outer arc R1, the radius r2 of the inner arc R2, the distance L between the outer hypotenuse S1 and the inner hypotenuse S2, and the length of the line connecting B and C satisfy the following relationship: 1 / 2 (BC + L) ≥ r1 ≥ 80mm, 1 / 2 (BC-L) ≥ r2 ≥ 35mm. In this way, during the hot pressing process, the main part of the sheet 1 can be pressed into a complete concave structure without wrinkles or cracks, and the molded control arm can meet the assembly requirements and ensure performance.

[0029] In addition, the sheet 1 of continuous fiber-reinforced thermoplastic composite material and the resin for injection molding homologous to sheet 1 include PA6, PA66, and PP. The continuous fibers include glass fiber, carbon fiber, aramid fiber, and basalt fiber. The fiber content in the sheet is 50 - 75 wt%, and the fiber content in the homologous composite material used for injection molding is 20 - 65 wt%. And during injection molding, the composite material does not require the screw of the injection molding machine to extrude the material into the mold, but is directly injected from the buffer cylinder of the on-line mixing, ensuring that the long fibers in the molded product have a length of 10 - 50 mm, which is much longer than the current common length of only 1 - 3 mm for long fibers. After injection molding, a hemming is formed at the edge of sheet 1, and ribs are formed inside the concave structure of the hot-pressed concave structure. Under the high-temperature and high-pressure injection molding process, the long fibers in the injection molding material move at high speed and wash into sheet 1, generating interpenetration, improving the mechanical bonding strength of the homologous material, and thus improving the bonding force between sheet 1 and the hemming and ribs.

[0030] Meanwhile, to ensure that the long fibers can smoothly enter the mold, the mold adopts a large-channel multi-point gating method. The inner diameter of the runner at the gating point 6 is 4 - 7 mm, which is much larger than the current common 2 - 3 mm method. As Figure 3 shown, the product is provided with a total of four gating points 6, which are symmetrically arranged in pairs.

[0031] The following is a comparative description through specific examples 1 - 4 and comparative examples 1 - 3.

[0032] Specific examples 1 - 4 all use the non-opening U-shaped sheet in Example 1, and the injection molding material uses the on-line mixed long fiber composite material in Example 1. The specific operation process of each example is as follows: Turn on the on-line mixing equipment, feed the material for injection molding, adjust the fiber to reach the required weight ratio, and conduct on-line mixing. Place the 3-mm-thick continuous fiber-reinforced thermoplastic composite material sheet 1 in an infrared heating furnace, heat the temperature to the set temperature and balance for 40 seconds (set at 200 °C for polypropylene and 270 °C for polycaprolactam), then the robotic arm quickly transfers it to the injection mold of the injection molding machine, close the mold and hot-press it into a concave shape, and then inject the on-line mixed melt, and cool it to form.

[0033] Comparative example 1 uses the currently common V-shaped sheet with an opening and does not adopt the on-line mixing procedure. The injection molding material is a short fiber-reinforced modified resin, and the others are the same as the specific examples.

[0034] Comparative example 2 also does not adopt the on-line mixing procedure, and the others are the same as the specific examples.

[0035] Comparative example 3 also uses the currently same V-shaped sheet with an opening, and the others are the same as the specific examples.

[0036] The component ratios in each example are shown in the following table:

[0037] The ultimate performance of the products formed in each example is shown in the following table:

[0038] It can be seen from the above table that the in-line mixing process, U-shaped sheet material, and long fiber material can all improve the ultimate compressive performance of the product, thereby enabling the quality of the control arm to be provided.

[0039] The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the relevant technical fields can also make various changes or transformations without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the protection scope of the present invention, and the protection scope of the present invention should be defined by each claim.

Claims

1. A method for preparing a lightweight control arm, characterized in that: The U-shaped continuous fiber reinforced thermoplastic composite sheet is heated and transferred to the injection mold, hot-pressed into a skeleton, and then the online mixed long fiber reinforced homologous resin is injected onto the skeleton to form the edge and reinforcement ribs. After molding, the ball joint is pressed into the control arm. The U-shaped connection of the sheet adopts a large arc structure. During injection molding, the resin is directly piston-injected into the mold from the buffer cylinder of the online mixing equipment.

2. The method for preparing a lightweight control arm according to claim 1, characterized in that: Point A corresponding to the center of the ball pin on the sheet and points B and C corresponding to the centers of the two bushings form a triangle ABC. The centers of the outer arc R1 and the inner arc R2 at the U-shaped connection of the sheet are both located on the angle bisector of ∠BAC.

3. The method for preparing a lightweight control arm according to claim 2, characterized in that: The outer bevel connecting the two ends of the outer arc R1 on the sheet is S1, and R1 is tangent to S1; the inner bevel connecting the two ends of the inner arc R2 on the sheet is S2, and R2 is tangent to S2; S1 is parallel to S2, and the distance between S1 and S2 is L; the radius r1 of the outer arc R1 satisfies: 1 / 2 (BC+L) ≥ r1 ≥ 80 mm, and the radius r2 of the inner arc R2 satisfies: 1 / 2 (BC-L) ≥ r2 ≥ 35 mm.

4. The method for preparing a lightweight control arm according to claim 3, characterized in that: Triangle ABC is an isosceles triangle.

5. The method for preparing a lightweight control arm according to claim 3, characterized in that: The ends of the two outer oblique sides S1 away from the outer arc R1 are respectively connected to the straight sides T and T', and T||T'.

6. The method for preparing a lightweight control arm according to claim 1, characterized in that: The long fiber length of the edging and reinforcement is 10-50mm.

7. The method for preparing a lightweight control arm according to claim 1, characterized in that: The inner diameter of the flow channel at the mold inlet point is 4-7mm.

8. The method for preparing a lightweight control arm according to claim 1, characterized in that: There are four glue feeding points which are symmetrically arranged.

9. The method for preparing a lightweight control arm according to claim 1, characterized in that: The resins of the composite materials include PA6, PA66, and PP; the continuous fibers include glass fiber, carbon fiber, aramid fiber, and basalt fiber.

10. The method for preparing a lightweight control arm according to claim 9, characterized in that: The fiber content in the sheet is 50-75wt%, and the fiber content in the homologous composite material used for injection molding is 20-65wt%.

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