Rear fork for two-wheeled vehicle

Abstract

This utility model relates to the field of two-wheeled vehicle rear swingarm technology, specifically to a two-wheeled vehicle rear swingarm, including a support arm and a pivot mounted on the vehicle body. The support arm has a C-shaped cross-section with an opening facing downwards, including an outer support wall, an inner support wall, and an upper support wall. The outer support wall, inner support wall, upper support wall, and pivot are integrally manufactured. The specific manufacturing method includes S1, prefabricating a mold according to the pre-designed dimensions of the two-wheeled vehicle rear swingarm; S2, die casting or injection molding, using magnesium alloy or aluminum alloy materials for die casting or semi-solid molding; S3, demolding, removing the core of the pivot and cooling the entire assembly for demolding. This technical solution aims to simplify the casting process through a truss structure, achieving a high level of unity between aesthetics, rigidity, and lightweight without compromising appearance.

Description

Technical Field

[0001] This utility model relates to the field of rear swingarm technology for two-wheeled vehicles, including fuel-powered two-wheeled vehicles, electric two-wheeled vehicles, and lightweight electric two-wheeled vehicles, specifically to the rear swingarm of two-wheeled vehicles. Background Technology

[0002] The rear swingarm of a two-wheeled vehicle is a component used to support the rear wheel of the vehicle and allow it to move freely up and down. It typically consists of a left support arm, a right support arm, a crossbeam connecting the left and right support arms, and a pivot mounted on the vehicle body.

[0003] Traditional two-wheeled vehicles mainly use a steel tube rear swingarm, which is mostly welded from steel parts, formed by welding a pivot support and a crossbeam to the ends of the tube. Although this structure is simple, the high weight of steel and the structural limitations result in poor appearance design, requiring additional coverings such as resin shells.

[0004] In addition, to improve aesthetics, some manufacturers use stamped iron plates welded together, but this requires welding around the entire circumference, resulting in long welds and increased weight. The combination of painted metal parts and a resin shell not only increases assembly and painting processes but also hinders recycling.

[0005] In recent years, to address these issues, integral die-casting structures for aluminum have been proposed. For example, Japanese Patent Application Publication No. 2008-81107 proposed a rear flat fork with an open outer surface, but it suffers from an uneven appearance and difficulty in cleaning after mud and water splashes. Japanese Patent Application Publication No. 2013-147218 designed the inner surface as an open structure to maintain aesthetics, but the inner surface accumulates mud and requires frequent cleaning. Furthermore, the undercut structure requires the use of a complex sliding mold, leading to reduced production efficiency and design freedom.

[0006] Traditional technologies for integral molding of rear swingarms present numerous limitations in terms of aesthetics, lightweight design, rigidity, and manufacturability. In particular, the challenge lies in simplifying the casting mold while simultaneously ensuring appearance quality, ease of cleaning, resistance to dirt and grime, and high rigidity. Utility Model Content

[0007] The technical problem to be solved by this utility model is to provide a rear horizontal fork for two-wheeled vehicles and its manufacturing method. The aim is to simplify the casting process through a truss structure and achieve a high level of unity between aesthetics, rigidity and lightweight without compromising appearance.

[0008] The above-mentioned technical objective of this utility model is achieved through the following technical solution: A two-wheeled vehicle rear swingarm includes a support arm and a pivot mounted on the vehicle body. The support arm has a downward-opening C-shaped cross-section, which includes an outer support wall, an inner support wall, and an upper support wall. The outer support wall, inner support wall, upper support wall, and pivot are integrally manufactured. This two-wheeled vehicle rear swingarm can be a single-sided swingarm or a double-sided swingarm.

[0009] Furthermore, in terms of manufacturing process, magnesium alloys or aluminum alloys are used for die casting or thixochemical forming.

[0010] Further specifying, this two-wheeled vehicle's rear horizontal fork is a double-sided horizontal fork, that is, it also includes a crossbeam section. The support arm section includes a left support arm section and a right support arm section. The crossbeam section connects the front ends of the left support arm section and the right support arm section. The crossbeam section, the left support arm section, and the right support arm section are manufactured as a single piece. The connection points between the left support arm section and the crossbeam section, and the connection points between the right support arm section and the crossbeam section are all set as curved connection points. The inner wall of the curved connection point is provided with a connection truss reinforcing rib.

[0011] In addition, the outer support wall is longer than the inner support wall, which makes it look more robust and aesthetically pleasing from the outside.

[0012] To ensure a reasonable strength distribution, the distance between the outer support wall and the inner support wall at the bending connection is limited to a greater distance than the distance between the outer support wall and the inner support wall at the middle section of the support arm. This concentrates stress in a targeted manner, reducing the amount of material used while ensuring stable performance.

[0013] In addition, to enhance strength, support arm truss reinforcing ribs are provided within the cavities of the left and right support arms, and these ribs and the connecting truss reinforcing ribs are integrally formed. The support arm truss reinforcing ribs and the connecting truss reinforcing ribs have a grid-like three-dimensional design.

[0014] Furthermore, the manufacturing method of the rear swingarm of the two-wheeled vehicle that limits the above technical solution includes the following steps: S1. Prefabricated mold, a mold manufactured according to the pre-designed dimensions of the rear flat fork of a two-wheeled vehicle, the mold including an upper mold and a lower mold, the upper mold and the lower mold fitting together to form a rear flat fork forming cavity, the mold of the pivot part having a core-pulling structure; S2, die casting or injection molding, using magnesium alloy or aluminum alloy materials for die casting or semi-solid molding; S3. Demolding: After removing the core from the pivot section, the entire part is cooled and demolded.

[0015] The upper mold and the lower mold are fitted together to form a cavity for supporting the truss reinforcement ribs of the support arm.

[0016] The present invention aims to simplify the casting process through a truss structure, and achieve a high level of unity between aesthetics, rigidity and lightweight without compromising appearance.

[0017] The rear swingarm of this utility model has the following structural features: Structural composition: The rear horizontal fork is continuously connected to the outer side (outer wall) and the inner wall by truss-shaped reinforcing ribs, achieving high rigidity and load distribution while maintaining the open cross section of the bottom surface.

[0018] Molding method: The support arm is designed as a truss structure, eliminating the need for a traditional sliding mold; only two molds, upper and lower, are required for molding. This simplifies the mold structure, shortens the molding cycle, improves temperature stability, and facilitates thin-wall molding.

[0019] The technical solution achieves a balance between appearance and cleanliness; the mud and dirt inside the truss structure are not visible and do not affect the aesthetics; the non-open design of the inner side avoids the defect of mud accumulation.

[0020] Stress concentration relief: At the connection between the support arm and the crossbeam, truss stiffeners are configured in three dimensions to target the bending points of the inner wall, thereby effectively relieving local stress concentration.

[0021] Applicable materials and molding methods: Die casting of magnesium alloy or aluminum alloy, or semi-solid molding, is recommended. Truss structures are particularly suitable for semi-solid molding processes with low solidification shrinkage. Attached Figure Description

[0022] Figure 1 This is a three-dimensional schematic diagram of the rear horizontal fork of the two-wheeled vehicle according to this utility model; Figure 2 A top-view diagram of the rear swingarm of a two-wheeled vehicle; Figure 3 A top-down view of the rear swingarm of a two-wheeled vehicle; Figure 4 This is a schematic diagram of the outside. Figure 5 for Figure 3 Enlarged view of point A in the middle; that is, a schematic diagram of the curved connection between the left support arm and the crossbeam. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings.

[0024] A two-wheeled vehicle rear swingarm includes a support arm and a pivot 2 mounted on the vehicle body. The support arm has a downward-opening C-shaped cross-section, which includes an outer support wall 11, an inner support wall 12, and an upper support wall 13. The outer support wall 11, the inner support wall 12, the upper support wall 13, and the pivot 2 are integrally manufactured using magnesium alloy or aluminum alloy through die casting or thixochemical molding.

[0025] This type of two-wheeled vehicle rear swingarm can be a single-sided swingarm, meaning it has only one support arm on one side; or it can be a double-sided swingarm, meaning it has two support arms on the left and right sides, connected in the middle by a crossbeam 3. Specific embodiments are as follows: like Figure 1 — Figure 5 As shown, a two-wheeled vehicle rear swingarm includes a support arm and a pivot 2 mounted on the vehicle body. The support arm has a downward-opening C-shaped cross-section, which includes an outer support wall 11, an inner support wall 12, and an upper support wall 13. The outer support wall 11, inner support wall 12, upper support wall 13, and pivot 2 are integrally manufactured using magnesium alloy or aluminum alloy through die casting or thixotropic molding. The vehicle also includes a crossbeam 3. The support arm includes a left support arm 10 and a right support arm 20. The left side of the crossbeam 3 is connected to the front end of the left support arm 10, and the right side of the crossbeam 3 is connected to the front end of the right support arm 20. The crossbeam 3, left support arm 10, and right support arm 20 are integrally manufactured. The connection points between the left support arm 10 and the crossbeam 3, and between the right support arm 20 and the crossbeam 3 are also integrally manufactured. All connections of 3 are configured as curved connections 31, and the inner wall of the curved connection 31 is provided with connection truss reinforcing ribs 32; the height of the outer support wall 11 is greater than that of the inner support wall 12, and the distance between the outer support wall 11 and the inner support wall 12 at the curved connection 31 is greater than the distance between the outer support wall 11 and the inner support wall 12 at the middle section of the support arm; support arm truss reinforcing ribs 22 are provided in the inner cavity of the left support arm 10 and the right support arm 20, and crossbeam truss reinforcing ribs 42 are provided in the inner cavity of the crossbeam 3. The support arm truss reinforcing ribs 22, the connection truss reinforcing ribs 32 and the crossbeam truss reinforcing ribs 42 are integrally formed; the support arm truss reinforcing ribs 22 and the connection truss reinforcing ribs 32 are grid-like three-dimensional designs.

[0026] In this embodiment, the rear swingarm includes a pivot portion 2, a left support arm portion 10, a right support arm portion 20, and a crossbeam portion 3. The crossbeam portion 3 is arranged close to the tire and together with the pivot portion 2 fixed to the frame, it effectively improves the overall torsional rigidity. In particular, the bolt length of the pivot portion 2 can be shortened to achieve component weight reduction and structural simplification.

[0027] Support arm truss reinforcing ribs 22 are provided in the inner cavities of the left support arm 10 and the right support arm 20 (i.e., between the outer support wall 11 and the inner support wall 12). Crossbeam truss reinforcing ribs are provided in the inner cavity of the crossbeam 3. The connection between the crossbeam 3 and the left support arm 10, and the connection between the crossbeam 3 and the right support arm 20 are both set as curved connection points 31. That is, the connection between the crossbeam 3, the left support arm 10 and the right support arm 20 is completely connected, and the connection point is set as a curved connection point 31. The support arm truss reinforcing ribs 22 and the crossbeam truss reinforcing ribs are integrally formed (including the connection truss reinforcing ribs 32). The support arm truss reinforcing ribs 22 and the connection truss reinforcing ribs 32 are grid-like three-dimensional designs.

[0028] Figure 3 The above structure forms a hollow truss structure that is both lightweight and rigid, achieving stress dispersion and uniform rigidity. Figure 4 The outer wall of the display features a smooth and aesthetically pleasing shape, combining functionality and design. Figure 5 In the displayed cross-sectional structure, the height of the inner support wall 12 is controlled to the minimum required to ensure rigidity, while the overall wall height of the support arm is also optimized to avoid unnecessary material usage. This achieves overall product lightweighting. The structure is preferably manufactured in one piece using magnesium / aluminum alloy die casting or semi-solid molding. Semi-solid molding allows for high-precision filling of deep groove structures such as truss reinforcing ribs, suppressing solidification shrinkage and ensuring dimensional accuracy and molding stability.

[0029] Furthermore, the manufacturing method of the rear swingarm of the two-wheeled vehicle that limits the above technical solution includes the following steps: S1. Prefabricated mold, a mold manufactured according to the pre-designed dimensions of the rear flat fork of a two-wheeled vehicle, the mold including an upper mold and a lower mold, the upper mold and the lower mold fitting together to form a rear flat fork forming cavity, the mold of the pivot part having a core-pulling structure; S2, die casting or injection molding, using magnesium alloy or aluminum alloy materials for die casting or semi-solid molding; S3. Demolding: After removing the core from the pivot section, the entire part is cooled and demolded.

[0030] The upper mold and the lower mold are fitted together to form a cavity for supporting the truss reinforcement ribs of the support arm.

[0031] The present invention aims to simplify the casting process through a truss structure, and achieve a high level of unity between aesthetics, rigidity and lightweight without compromising appearance.

[0032] The rear swingarm of this utility model has the following structural features: Structural composition: The rear horizontal fork is continuously connected to the outer side (outer wall) and the inner wall by truss-shaped reinforcing ribs, achieving high rigidity and load distribution while maintaining the open cross section of the bottom surface.

[0033] Molding method: The support arm is designed as a truss structure, eliminating the need for a traditional sliding mold; only two molds, upper and lower, are required for molding. This simplifies the mold structure, shortens the molding cycle, improves temperature stability, and facilitates thin-wall molding.

[0034] The technical solution achieves a balance between appearance and cleanliness; the mud and dirt inside the truss structure are not visible and do not affect the aesthetics; the non-open design of the inner side avoids the defect of mud accumulation.

[0035] Stress concentration relief: At the connection between the support arm and the crossbeam, truss stiffeners are configured in three dimensions to target the bending points of the inner wall, thereby effectively relieving local stress concentration.

[0036] Applicable materials and molding methods: Die casting of magnesium alloy or aluminum alloy, or semi-solid molding, is recommended. Truss structures are particularly suitable for semi-solid molding processes with low solidification shrinkage.

[0037] The advantages of this technical solution are that it requires only two molds (upper and lower), eliminating the sliding mechanism and greatly simplifying the mold structure. This reduces the movement time of complex sliding molds and the need to stabilize mold temperature, shortening the molding cycle and making it suitable for thin-walled casting. It also reduces the number of parts, significantly simplifying the manufacturing and assembly process. Minimizing the painting process reduces VOC emissions and achieves complete recyclability. It is particularly suitable for large two-wheeled vehicles with a single shock absorber structure, maintaining strength and rigidity under high loads without requiring special strengthening methods such as sand cores as in existing technologies like Japanese Patent Application Laid-Open No. 2013-147218, simultaneously improving production efficiency and reducing costs.

[0038] In summary, this utility model solves many technical problems in the rear flat fork forming structure, and is a high-level innovative process that integrates design freedom, production efficiency, performance, aesthetics and environmental protection.

[0039] In this technical solution, the semi-solid injection molding technology (Thixomolding) was proposed by Flemmings et al. in the 1970s. Initially, by improving the traditional die casting process, using semi-solid rheo-die casting technology to prepare AZ91D magnesium alloy, and borrowing injection molding technology to manufacture magnesium alloy components, the relatively weak affinity between magnesium alloy and iron was utilized, allowing steel screws and barrels to meet the molding requirements of magnesium alloy. Therefore, semi-solid injection molding technology (Thixomolding), also known as thixotropic injection molding technology, emerged and has now become one of the most promising green manufacturing technologies for magnesium alloy components worldwide.

[0040] The semi-solid injection molding process for magnesium alloys falls under the thixocasting technology. First, small, rice-grain-sized magnesium alloy particles are cut from a magnesium alloy ingot as raw material. Under gravity or negative pressure, these particles enter the barrel from the hopper. Inside the barrel, the rotation of the screw, combined with heat provided by an external heater, heats and shears the magnesium alloy particles as they are conveyed forward. In the middle of the barrel, the magnesium alloy undergoes thermoplastic deformation under the compression section of the screw, achieving densification. When it reaches the storage section at the front of the screw, the magnesium alloy particles have transformed into a partially molten semi-solid slurry containing spherical solid phases. This slurry possesses excellent flowability and filling properties. Subsequently, this slurry is injected at high speed into the mold through a nozzle, where it rapidly cools and solidifies under high speed and pressure, forming a part with a specific shape and size. After injection, the tip of the nozzle cools down to form a cold plug for self-sealing, thus completing the continuous molding operation without the need for protective gas or complete melting.

[0041] This specific embodiment is merely an explanation of the present utility model and is not intended to limit the present utility model. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present utility model, they are protected by patent law.

Claims

1. A rear fork for a two-wheeled vehicle comprising a support arm portion and a pivot portion (2) mounted to a vehicle body, characterised in that, The support arm has a downward-opening C-shaped cross section, which includes an outer support wall (11), an inner support wall (12), and an upper support wall (13). The outer support wall (11), the inner support wall (12), the upper support wall (13), and the pivot (2) are integrally manufactured.

2. The two-wheeler rear fork as claimed in claim 1, wherein: The outer support wall (11), inner support wall (12), upper support wall (13) and pivot (2) are integrally formed from magnesium alloy or aluminum alloy by die casting or thixoforming.

3. The two-wheeler rear fork as claimed in claim 1 wherein: It also includes a crossbeam (3), the support arm includes a left support arm (10) and a right support arm (20), the left side of the crossbeam (3) is connected to the front end of the left support arm (10), the right side of the crossbeam (3) is connected to the front end of the right support arm (20), the crossbeam (3), the left support arm (10) and the right support arm (20) are integrally manufactured, the connection between the left support arm (10) and the crossbeam (3) and the connection between the right support arm (20) and the crossbeam (3) are both set as curved connection points (31), and the inner wall of the curved connection point (31) is provided with connection truss reinforcing ribs (32).

4. The two-wheeler rear fork as claimed in claim 1 wherein: The height of the outer support wall (11) is greater than that of the inner support wall (12).

5. The two-wheeler rear fork as claimed in claim 3, wherein: The spacing at the curved connection (31) is greater than the spacing at the middle section of the support arm.

6. The two-wheeler rear fork as claimed in claim 3, wherein: The inner cavities of the left support arm (10) and the right support arm (20) are provided with support arm truss reinforcing ribs (22), and the support arm truss reinforcing ribs (22) and the connecting truss reinforcing ribs (32) are integrally formed.

7. The two-wheeler rear fork as claimed in claim 6, wherein: The supporting arm truss reinforcing rib (22) and the connecting truss reinforcing rib (32) are grid-shaped three-dimensional designs.

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