A fixture for testing the flexibility and bending force of automotive cables

Abstract

The present invention discloses a testing fixture for the bending force of automotive cable flexibility, which belongs to the technical field of cable testing equipment. The fixture comprises an upper frame and a lower frame. The lower portion of the upper frame is mounted with a horizontal lower reel, and the upper portion of the upper frame is mounted with an upper reel whose axis is parallel to the lower reel. The upper and lower reels are formed by winding the same reel. The upper frame is mounted with an upper positioning pin for limiting the rotation of the upper reel and a lower positioning pin for limiting the rotation of the lower reel. The lower frame is mounted with two pulleys whose axes are parallel to the axes of the upper and lower reels and located on the same horizontal plane. The two pulleys are located on both sides below the lower reel, and the pulleys are mounted on the lower frame in a laterally adjustable manner. This fixture can more accurately test the bending force of a cable in a certain bending state and obtain a more accurate bending force value, which is helpful for the research and development or comparison of cable flexibility.

Description

Technical Field

[0001] The invention belongs to the technical field of cable testing equipment, and in particular relates to a fixture for testing the flexibility and bending force of automobile cables. Background Art

[0002] As a specialty cable, automotive cables are primarily used inside cars, connecting various electrical components. Because the space in which automotive cables are installed and operated is limited, they require high cable flexibility.

[0003] Although the flexibility of automotive cables is an important indicator for measuring their performance and quality, how to quantitatively test the strength of automotive cable flexibility is still a difficult problem in the automotive industry. The factors that make testing difficult are the wide variety of automotive cable models, which are mainly manifested in the following aspects:

[0004] 1. The diameter of automotive cables varies greatly, with commonly used specifications ranging from 1mm to 30mm;

[0005] 2. The nominal cross-sectional area size of automotive cables is varied, ranging from 0.13mm 2 ~120mm 2 ;

[0006] 3. Cables with the same nominal cross-section have very different conductor compositions, which are usually divided into 2 to 4 categories. For example, 2 Cables with nominal cross-sections include single-filament diameters of 0.2mm, 0.4mm, and 0.8mm, etc.

[0007] 4. According to the requirements of the application, the selected insulation materials and insulation thickness are also different. For example, there are silicone rubber materials with a Shore hardness of A65, polyolefin and polyvinyl chloride materials with a Shore hardness of 90A, and high-hardness fluoroplastics;

[0008] 5. The bending radius varies greatly depending on the characteristics of the cable, ranging from 5 times to 10 times.

[0009] The different characteristics of the above cables result in the inconsistency of the bending force (flexibility) of automotive cables and also restrict the quantitative measurement of the bending force of the cables.

[0010] At present, there are two main methods for measuring the flexibility of automotive cables at home and abroad: 5.3.5 flexibility test in ISO 19642.2 standard and 9.3.4 cable bending strength test in VW 60306-1 of Volkswagen Group.

[0011] The 5.3.5 flexibility test apparatus and method in ISO 19642.2 standard are:

[0012] The test device includes two sets of optional fixtures, the fixture structure is as follows Figure 5 As shown, each fixture consists of three main parts: a lower bracket, three pulley blocks, and an upper bracket. The lower bracket is symmetrically mounted with two lower pulleys with adjustable center distances. The upper bracket is equipped with an upper pulley located above and between the two lower pulleys. The upper bracket is mounted on the upper fixture of the electronic tensile testing machine, and the lower bracket is mounted on the lower fixture of the electronic tensile testing machine. During the test, a certain length of cable is cut as the test cable and placed on the two lower pulleys. The cable is subjected to a bending force test by bending the cable downward with the upper pulley. The following table shows the test data for different cable outer diameters:

[0013]

[0014] This test divides cables into eight ranges based on their outer diameter and also specifies the diameter and center distance of the pulleys required in the fixture. Data calculations show that the tested cables require bending force measurements at a bend radius of approximately 3.33D to 4.4D. However, within the same outer diameter range, the bending radius of cables with different diameters can vary by as much as 0.8 to 0.9D, making it impossible to precisely select the bending radius ratio based on the cable's outer diameter or nominal maximum outer diameter. Furthermore, in actual use, many cables, due to their rigid insulation materials, simply cannot meet the 3.33 to 4.4D requirement. Even if this could be measured, it would be meaningless. Furthermore, our actual tests have shown that the bending force of the same cable varies at different bend radii.

[0015] 9.3.4 Cable bending strength test in Volkswagen Group's VW 60306-1 standard: Test equipment such as Figure 6 As mentioned above, this standard specifies the maximum angle limit based on the actual angle of cable use and years of automotive manufacturing experience. It cannot compare cable flexibility or conduct flexibility tests on the cable itself.

[0016] In summary, the above two mainstream cable bending force test schemes have inaccurate bending radius ratios and poor test accuracy, and cannot meet the test requirements of cable production. Summary of the Invention

[0017] In view of the problems existing in the prior art, the present invention provides a flexible bending force testing fixture for automotive cables, which solves the problem of inaccurate cable bending force testing.

[0018] The present invention is realized in this way: a fixture for testing the flexibility and bending force of automobile cables is characterized by comprising an upper frame and a lower frame.

[0019] The lower mounting axis of the upper frame is horizontal, the upper mounting axis of the upper frame is parallel to the lower mounting axis of the lower tape reel, the upper and lower tape reels are formed by winding the same tape, and the upper frame is installed with an upper positioning pin for limiting the rotation of the upper tape reel and a lower positioning pin for limiting the rotation of the lower tape reel.

[0020] The lower frame is installed with two pulleys whose axes are parallel to the axes of the upper and lower belt reels and located on the same horizontal plane. The two pulleys are respectively located on both sides below the lower belt reel, and the pulleys are installed on the lower frame in a laterally adjustable manner.

[0021] The fixture disclosed in this invention is mounted on electronic tensile testing equipment. The cable's test bend radius is determined by the radius of the lower reel, which can be adjusted using the reel's thickness as the minimum unit. This allows the fixture to precisely control the cable's bend radius and accurately measure the bending force of automotive cables at a specific bend radius. This provides more accurate results than the eight-pulley test results in the traditional test standard (ISO 19642), meeting the quantitative cable flexibility requirements of automotive and cable manufacturers. Cable manufacturers can analyze the test data and improve cable flexibility by adjusting material hardness, extrusion tightness, copper wire annealing, and stranding processes.

[0022] In the above technical solution, preferably, the upper frame body is installed with an upper crank that can drive the upper belt reel to rotate, and the upper frame body is installed with a lower crank that can drive the lower belt reel to rotate.

[0023] In the above technical solution, preferably, the pulley is a V-groove pulley.

[0024] In the above technical solution, preferably, the lower frame has a transverse slide groove, two sliders that can be moved along the transverse slide groove are installed in the transverse slide groove, the two pulleys are respectively installed on the two sliders, and the lower frame is installed with two transverse adjustment screws for adjusting the transverse positions of the two sliders.

[0025] In the above technical solution, preferably, the upper frame body is provided with a vertical guide portion, and the lower frame body is provided with a vertical guide groove combined with the vertical guide portion.

[0026] In the above technical solution, preferably, the coil is a stainless steel strip with a thickness of 0.25 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the present invention;

[0028] Figure 2 It is a structural schematic diagram of the upper frame in the present invention;

[0029] Figure 3 It is a structural schematic diagram of the lower frame in the present invention;

[0030] Figure 4 Schematic diagram of the installation structure of the transverse adjustment screw in the present invention;

[0031] Figure 5 This is a schematic diagram of the structure of the test device in the ISO 19642.2 standard;

[0032] Figure 6 This is a schematic diagram of the structure of the test device in the VW 60306-1 standard.

[0033] In the figure, 1, upper frame; 2, lower frame; 2-1, horizontal slide; 2-2, vertical guide groove; 3, lower belt reel; 4, upper belt reel; 5, upper positioning pin; 6, lower positioning pin; 7, upper crank; 8, lower crank; 9, pulley; 10, slider; 11, horizontal adjustment screw; 12, positioning block. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] To address the issue of inaccurate cable bending force testing, the present invention provides a flexible bending force test fixture for automotive cables. This fixture can more accurately test the bending force of cables in a certain bending state and obtain more accurate bending force values, which is helpful for the research and development or comparison of cable flexibility. To further illustrate the structure of the present invention, a detailed description is provided below with reference to the accompanying drawings:

[0036] See also Figures 1-4 A fixture for testing the flexibility and bending force of automobile cables comprises an upper frame 1 and a lower frame 2.

[0037] The lower portion of the upper frame 1 is mounted with a lower tape reel 3 having a horizontal axis. The upper portion of the upper frame 1 is mounted with an upper tape reel 4 having an axis parallel to the lower tape reel 3. The upper tape reel 4 and the lower tape reel 3 are wound from the same tape. The upper frame 1 is mounted with an upper locating pin 5 for limiting the rotation of the upper tape reel 4 and a lower locating pin 6 for limiting the rotation of the lower tape reel 3.

[0038] In this embodiment, the upper frame 1 is a vertically extending stainless steel frame with a slot extending laterally through it and open at the bottom. A lower shaft, rotatable about its own axis, is mounted on the lower portion of the slot of the upper frame 1 via a bearing, while an upper shaft, rotatable about its own axis, is mounted on the upper portion of the slot of the upper frame 1 via a bearing. The tape is a 0.25 mm thick stainless steel tape, the ends of which are fixed to the upper and lower shafts, respectively, by screws. The upper and lower shafts are wound around the upper and lower shafts into disc-shaped upper and lower reels 4 and 3, respectively. By rotating the upper and lower shafts, the number of layers of tape wound around the two shafts can be adjusted, thereby adjusting the diameter of the lower reel 3. The lower reel 3 serves as a disc that presses the cable downward during testing, while the upper reel 4 serves as a reserve tape. In this embodiment, the tape is wound in an S-shaped pattern between the upper and lower shafts. The upper end of the upper frame 1 has a mounting hole for connecting to the upper fixture of a gantry-type electronic tensile testing machine.

[0039] To facilitate the rotation and adjustment of the lower reel 3, the upper frame 1 is equipped with an upper crank handle 7 that drives the upper reel 4, and a lower crank handle 8 that drives the lower reel 3. The upper crank handle 7 is directly connected to the end of the upper shaft, while the lower crank handle 8 is directly connected to the end of the lower shaft. In this embodiment, the upper and lower locating pins 5 and 6 are isosceles triangular blocks with circumferential teeth at the ends of the upper and lower shafts. The upper and lower locating pins 5 and 6 are positioned near the ends of the respective upper and lower shafts and are removably inserted into the upper frame 1 through sockets. The bottom end surfaces of the upper and lower locating pins 5 and 6 have teeth. Taking the connection between the upper locating pins 5 and the upper shaft as an example, after the top side of the upper locating pin 5 is inserted into the upper frame 1 via an integrated pin rod, the center of the bottom end surface of the upper locating pin 5 engages with the outer circumferential surface of the upper shaft end through teeth, thereby locking the upper shaft circumferentially. The cross-section of the upper locating pin 5 and the socket connecting the upper frame 1 to the pin can be designed to be non-circular, which can also provide a locking function. Conventional technology has various forms of circumferential locking structures for rotating shafts. The above is only an example of a structural method for circumferentially locking the upper and lower rotating shafts, but is not limited to this.

[0040] The lower frame 2 is installed with two pulleys 9 whose axes are parallel to the axes of the upper belt reel 4 and the lower belt reel 3, and the axes of the two pulleys 9 are located in the same horizontal plane. The two pulleys 9 are respectively located on both sides below the lower belt reel 3, and the pulleys 9 are installed on the lower frame 2 in a transversely adjustable manner. Specifically, in this embodiment, the lower frame 2 is a T-shaped stainless steel frame, and the upper part of the lower frame 2 has a transverse groove 2-1, and two sliders 10 that can be moved along the transverse groove are installed in the transverse groove 2-1. The two pulleys 9 are respectively installed on the two sliders 10, and the transverse position and center distance of the two pulleys 9 can be adjusted by the movable movement of the sliders 10 in the transverse groove 2-1. The lower frame 2 is installed with two transverse adjustment screws 11 for adjusting the transverse positions of the two sliders 10. Positioning blocks 12 are fixed to both sides of the lower frame 2. These blocks 12 are screwed into the transverse chute 2-1. These blocks 12 have transverse through-holes, through which transverse adjustment screws 11 extend. Transverse adjustment screws 11 also have stop flanges that restrict axial movement relative to the positioning blocks 12. The slider 10 is threadedly mounted on the transverse adjustment screws 11. Because the transverse chute 2-1 and slider 10 have non-circular cross-sections, the position of the slider 10 within the transverse chute 2-1 can be adjusted by rotating the knob of the transverse adjustment screw 11.

[0041] The specific usage of this fixture is as follows:

[0042] The fixture is installed on a gantry-type universal tensile testing machine.

[0043] 70mm 2 Take the cable as an example, and measure the bending force when its bending radius is 5D:

[0044] 1. The diameter of the measuring cable is 20mm.

[0045] 2. Calculate the bending radius of 5 times the cable diameter to be 100mm and the bending diameter to be 200mm.

[0046] 3. Rotate the upper crank handle to adjust the diameter of the upper reel. Use a 0-300mm caliper to measure the diameter of the upper reel. When it is 200mm, fix the upper and lower reels.

[0047] 4. Control the upper frame to move downward, and move the lower belt plate to the same level as the pulley center (such as Figure 6 (as shown), place the cable under test between the side of the lower reel and the pulley. Position the cable vertically and adjust the knob of the transverse adjustment screw until the lower reel and pulley make contact with the cable. Vertical movement of the cable gently rotates the pulley. Similarly, adjust the pulley on the other side of the lower reel. Once adjustments are complete, move the upper frame upward, positioning the lower reel above the two pulleys.

[0048] 5. Cut the cable to a length 1.5 times the bending diameter as the test cable, i.e. 300mm (200mm*150%). Place the cable horizontally and centered on the two pulleys, with both ends supported on the pulleys.

[0049] 6. Start the tensile testing machine, and the upper frame moves downward at a speed of 100 mm / min and presses the cable. The cable is squeezed and bent, and the bending radius is consistent with the lower reel until both ends of the cable are completely vertical and pressed down from the two pulleys. The maximum bending force of the measured cable can be obtained by the tensile testing machine.

[0050] The clamp described in this invention allows for precise setting and control of the cable's bending radius. Even if the cable diameter changes by 0.1mm, resulting in a 0.5mm change in bending radius, the tape can be adjusted to match the diameter, ensuring accurate test results. The rotatable pulley eliminates test errors caused by sliding friction during cable compression.

[0051] In this embodiment, the pulley 9 is a V-groove pulley. A "V"-shaped groove structure is adopted to embed the cable into the pulley, ensuring the vertical bending of the cable during the bending process. The upper frame 1 is provided with a vertical guide portion, and the lower frame is provided with a vertical guide groove 2-2 combined with the vertical guide portion. The vertical guide portion is the rear side of the upper frame, and the vertical guide groove 2-2 is a vertically extending long groove with a width slightly larger than the width of the rear side of the upper frame. This structure can ensure the relative stability between the upper frame and the lower frame during the downward movement, making the vertical measurement more accurate.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fixture for testing the flexibility and bending strength of automotive cables, characterized by: It comprises an upper frame (1) and a lower frame (2); The lower portion of the upper frame (1) is provided with a lower tape reel (3) with a horizontal axis, and the upper portion of the upper frame (1) is provided with an upper tape reel (4) with an axis parallel to the lower tape reel (3). The upper tape reel (4) and the lower tape reel (3) are formed by winding a same tape, and the upper frame (1) is provided with an upper positioning pin (5) for limiting the rotation of the upper tape reel (4) and a lower positioning pin (6) for limiting the rotation of the lower tape reel (3); The lower frame (2) is installed with two pulleys (9) whose axes are parallel to the axes of the upper belt reel (4) and the lower belt reel (3) and are located on the same horizontal plane. The two pulleys (9) are respectively located on both sides below the lower belt reel (3). The pulleys (9) are installed on the lower frame (2) in a transversely adjustable manner.

2. The automotive cable flexibility bending force testing fixture according to claim 1, characterized in that: The upper frame (1) is provided with an upper crank (7) capable of driving the upper belt reel (4) to rotate, and the upper frame (1) is provided with a lower crank (8) capable of driving the lower belt reel (3) to rotate.

3. The automotive cable flexibility bending force testing fixture according to claim 1, characterized in that: The pulley (9) is a V-groove pulley.

4. The automotive cable flexibility bending force testing fixture according to claim 1, characterized in that: The lower frame (2) has a transverse slide groove (2-1), two sliders (10) that can move along the transverse slide groove are installed in the transverse slide groove (2-1), the two pulleys (9) are respectively installed on the two sliders (10), and the lower frame (2) is installed with two transverse adjustment screws (11) for adjusting the transverse positions of the two sliders (10).

5. The automotive cable flexibility bending force testing fixture according to claim 4, characterized in that: The upper frame (1) is provided with a vertical guide portion, and the lower frame (2) is provided with a vertical guide groove (2-2) combined with the vertical guide portion.

6. The automotive cable flexibility bending force testing fixture according to claim 1, characterized in that: The coil is a stainless steel strip with a thickness of 0.25 mm.

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