Hollow connecting rod

Abstract

The connecting rod (3) according to the invention comprises: a hollow body (30) having a ring (31) at each end (36) and a center (35); and a thickness wall e (34) defining an outer perimeter p. e and inner circumference p i The surface section s is included between the outer perimeter and the inner perimeter, and the link is characterized in that the outer perimeter p e The thickness e increases from the end (36) of the hollow body (30) toward the center (35) of the connecting rod (3), while the hollow body (30) maintains a constant cross section s, and the thickness e decreases from the end (36) of the connecting rod (3) toward the center (35).

Description

Technical Field

[0001] The technical field of this invention is the technical field of double ball joint connecting rods, and more particularly those double ball joint connecting rods used in aero engines, or any other products including connecting rods and requiring quality control. Background Technology

[0002] Today, these links are made of metal or solid composite materials (circular or non-circular, constant or non-constant cross-section).

[0003] These links are available and inexpensive, can withstand fairly high temperatures (>300°C), are typically made of metal (steel, stainless steel), and have a simple geometry (a round bar with a constant solid cross-section), but are relatively heavy, especially when the dimensions between the two joints become greater. In fact, as Euler's formula shows, under equal resistance (buckling / compression, tension), the mass of a solid circular link increases with the cube of the distance between the joints.

[0004] However, as attachment points become increasingly distant (e.g., from 331mm to 440mm), one of these goals is to find a connecting rod that can be manufactured at a lower cost and is lighter, in order to limit the weight of engines or products that include the connecting rod.

[0005] To address these issues, there are tubular connecting rods made of metal or composite materials, as described in patents EP 2 643 600 and EP 1 864 027.

[0006] However, the weight of the link remains significant, and it is impossible to reduce the wall size without compromising the performance of these links. Summary of the Invention

[0007] This invention provides a solution to the problems previously discussed by reducing the amount of material, which makes it possible to lighten the linkage while increasing its inertia, thus increasing buckling stiffness, especially in the central region.

[0008] The connecting rod according to the invention comprises a hollow body having bushings at each end and a center; and a wall having a thickness e that defines an outer perimeter p. e and inner circumference p i The cross-sectional area s is included between the outer perimeter and the inner perimeter, characterized in that the outer perimeter p e The thickness e increases from the end of the hollow body toward the center of the connecting rod, while the hollow body maintains a constant cross-sectional area s and the thickness e decreases from the end toward the center of the connecting rod.

[0009] The new connecting rod has a hollow geometry and an increasing perimeter from the edges towards the center. The wall thickness is also adjusted to balance the working cross-section throughout the hollow body, so that the minimum thickness is at the center of the connecting rod. Maintaining a constant cross-section allows for the preservation of some stiffness in the connecting rod. This results in a reduction in mass, an increase in buckling resistance, and an increase in frequency in the first vibration mode. This profile provides a significant gain in mass (approximately -40%) and twice the resistance. The gain in resistance allows for further enhancement of the mass gain by reducing the wall thickness or by switching to a lighter and / or less rigid material.

[0010] According to the first alternative, the hollow body is a rotating cylindrical shape, which allows for the symmetry and balance of the linkage.

[0011] According to the second alternative, the hollow body is elliptical or rectangular. Therefore, this can reduce the overall size in a given direction, for example, if the connecting rod passes through a gas or liquid flow.

[0012] It is also possible to deviate from the "track" or deform the line or axis of the link to make it easier to avoid (hot) areas or objects than in a solid case, because the hollow profile has better inertia and stiffness for the same mass.

[0013] Advantageously, the reinforcing ring is positioned on the inner side of the hollow body at the center of the connecting rod. This reduces or even eliminates the risk of local buckling because the wall is thinner at the center of the connecting rod, which would otherwise risk collapsing on its own or being damaged during handling, as the central area is the most "exposed".

[0014] Advantageously, holes are provided at the joints of each bushing, serving as extensions of the hollow body. The presence of these holes at the edges of the joints is specifically designed to make the connecting rod "powder-removable," i.e., allowing powder to be expelled from the central cavity without weakening it at the end of additive manufacturing via laser beam melting (LBM) or laser powder bed fusion (LPBF). This also allows for the lightening of the connecting rod.

[0015] Advantageously, the length of the connecting rod is greater than or equal to 440 mm. This profile is particularly suitable for long connecting rods.

[0016] The present invention also relates to a method for manufacturing a connecting rod having at least one of the aforementioned features, characterized in that the connecting rod is manufactured by additive manufacturing. This manufacturing method allows for approximately -20% cost savings compared to conventional profiles. Additive manufacturing can be performed via laser powder bed fusion or via DED (direct energy deposition).

[0017] The connecting rod is manufactured in casting according to an alternative manufacturing method.

[0018] According to an alternative manufacturing method, the connecting rod is manufactured by machining. Casting and machining can be combined.

[0019] Advantageously, the manufacturing method includes the following steps:

[0020] - Manufacture the first half-link.

[0021] - Manufacture the second half-link.

[0022] - Assemble the two half-links.

[0023] Two half-links can be assembled by welding, brazing, screwing, or any other assembly method. Attached Figure Description

[0024] These figures are illustrated for the purpose of indicating rather than limiting the invention.

[0025] Figure 1 These are perspective views of connecting rods of different sizes and shapes;

[0026] Figure 2 This is a perspective view of the connecting rod according to the present invention;

[0027] Figure 3 yes Figure 2 Cross-sectional view of the connecting rod;

[0028] Figure 4 This is a cross-sectional view of the half-link according to the present invention;

[0029] Figure 5 Details of the joint between the hollow body and the bushing according to an alternative embodiment of the invention are shown.

[0030] Figure 6 The center of the link is shown in detail;

[0031] Figure 7 It is a cross-sectional view of the hollow body;

[0032] Figure 8 The results of a finite element simulation of buckling of a link with a conventional profile are shown.

[0033] Figure 9 The results of a finite element simulation of buckling of a link having a hollow profile according to the invention are shown. Detailed Implementation

[0034] These figures are illustrated for the purpose of indicating rather than limiting the invention.

[0035] Unless otherwise stated, the same element appearing in different figures has a single reference numeral.

[0036] exist Figure 1As can be seen, conventional connecting rods 1 and 2 in the prior art become increasingly longer, resulting in an increase in the diameter of the bodies 10 and 20, and therefore their weight, which are connected to two bushings 11 and 21 arranged at one end 36. They are typically made of metal, steel, or stainless steel. Unlike connecting rods 1 and 2 in the prior art, connecting rod 3 according to the invention does not have a constant diameter. All of these connecting rods 1, 2, and 3 have a longitudinal axis X.

[0037] exist Figure 2 The connecting rod 3, which is visible in more detail, has a hollow body 30 that forms two half-links 300 and 301 in two parts, but may also be a single part without departing from the scope of the invention. The body 30 has two bushings 31 at its ends, each bushing 31 connecting to a component and serving as a hinge to the component. A joint 310 connects each end 36 of the hollow body 30 to the bushing 31.

[0038] like Figure 3 As can be seen, the hollow body 30 defines the internal space 32. The two half-links 300 and 301 are connected to each other by a connector 33 made by welding, brazing, or any other connection method. Figure 6 As seen in the image, the reinforcing ring 4 is arranged in the center 35 of the connecting rod 3, that is, on the connector 33 between the two half-links 300 and 301. This reinforcing ring 4 is located inside the hollow body 30 on the inner portion 340 of the wall 34. This allows for a reduction or even elimination of the risk of local buckling of the wall 34, which is thinner at the center 35.

[0039] The wall 34 of the hollow body 30 has a thickness e. For example, in... Figure 4 As can be seen, the thickness decreases from the joint 310 to the center 35 of the connecting rod 3, while the distance between the axis X and the wall 34 increases. The surface of the cross-section s is circular here, and for a given cross-section, it is the difference between the surface defined by the outer wall 341 and the surface defined by the inner wall 340, that is, the outer perimeter p of the wall 34. e The inner perimeter p of wall 34 i The surface area of ​​the cross section s remains constant along the entire hollow body 30; therefore, the greater the increase in the distance between the axis X and the wall 34, the greater the decrease in thickness e. The cross section of the wall 34 can also be elliptical or rectangular, or even change shape from the joint 310 to the center 35 of the link 3 while still remaining closed. The axis X is straight here, but it can be deformed to avoid areas (e.g., hot zones) or objects.

[0040] Therefore, the wall thickness is adjusted to balance the entire working section along the hollow body 30, with the minimum thickness at the center of the connecting rod.

[0041] The joint 310 between the bushing 31 and the hollow body 30 has a hole 320, which is arranged as an extension of the internal space 32. During the additive manufacturing process, it is necessary to allow the powder remaining in the hollow body 30 to be discharged.

[0042] Indeed, link 3 can be manufactured using additive manufacturing with laser powder bed fusion. It can also be manufactured using direct energy deposition. These manufacturing methods allow for the achievement of desired wall thicknesses. The manufacturing of link 3 is then performed vertically.

[0043] Link 3 can also be built as a single component or as two half-links assembled by welding, brazing, or screwing. This is especially true if it is manufactured by casting or machining.

[0044] Finite element simulations have been performed to evaluate link 3 ( Figure 9 Compared to a regular profile of the same length ( Figure 8 Buckling of the link. Three types of buckling are defined:

[0045] -Buckling A,

[0046] - B-bending

[0047] - Bending C.

[0048] The load multiplier (MC in Tables 8 and 9) has been calculated for each type of buckling, where the load multiplier corresponds to the load applied to the link that must be multiplied to obtain the factor of the buckling under consideration.

[0049] For buckling A, it was found that the load applied to link 3 was more than twice that of a conventional link, 2.354, instead of 1.0985.

[0050] For buckling B, the difference between the two links is greater than 50%, which is 6.7314 for 4.351.

[0051] For buckling C, the difference is also greater than 50%: 7.0982 for link 3 and 4.6821 for the conventional link.

[0052] It is thus noted that, far removed from reducing the characteristics of the link, especially its inertia, the profile of the link according to the invention improves its characteristics while significantly reducing its weight by up to 40%. The gain in resistance allows for further enhancement of the mass gain by reducing the wall thickness or by switching to a lighter, less rigid material (e.g., a titanium alloy like TA6V).

Claims

1. A connecting rod (3), comprising: Hollow body (30), the hollow body having a bushing (31) at each end (36) and a center (35), and a wall (34) having a thickness e, the wall (34) defining an outer perimeter p e and inner circumference p i The cross-sectional area s is included between the outer perimeter and the inner perimeter, characterized in that the outer perimeter p e The thickness e increases from the end (36) of the hollow body (30) toward the center (35) of the connecting rod (3), while the hollow body (30) maintains a constant cross-sectional area s along the entire hollow body (30), and the thickness e decreases from the end (36) toward the center (35) of the connecting rod (3).

2. The connecting rod (3) according to claim 1, characterized in that, The hollow body (30) is a rotating cylindrical shape.

3. The connecting rod (3) according to claim 1, characterized in that, The hollow body (30) is elliptical or rectangular.

4. The connecting rod (3) according to any one of claims 1 to 3, characterized in that, The reinforcing ring (4) is located in the center (35) of the connecting rod (3) on the inner side of the hollow body (30).

5. The connecting rod (3) according to any one of claims 1 to 3, characterized in that, The hole (320) is configured as an extension of the hollow body (30) at the joint (32) having each bushing (31).

6. The connecting rod (3) according to any one of claims 1 to 3, characterized in that, The length of the connecting rod is greater than or equal to 440 mm.

7. A method for manufacturing a connecting rod (3) according to any one of claims 1 to 6, characterized in that, The connecting rod is manufactured by additive manufacturing (3).

8. A method for manufacturing a connecting rod (3) according to any one of claims 1 to 6, characterized in that, The connecting rod (3) is manufactured in casting.

9. A method for manufacturing a connecting rod (3) according to any one of claims 1 to 6, characterized in that, The connecting rod is manufactured by machining.

10. The method for manufacturing a connecting rod (3) according to any one of claims 7 to 9, characterized in that, The method includes the following steps: - Manufacture the first half-link (300, 301). - Manufacture the second half-link (301, 300). - Assemble the two half-links (300, 301).

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