A method for nondestructive testing of reliable pressure bonding of a brush wire of a conductive slip ring

Abstract

The present application relates to the technical field of conductive slip ring manufacturing and detection, and particularly relates to a kind of conductive slip ring brush wire crimping reliability nondestructive testing method, by setting liquid conductive connector at the non-crimped end of brush wire, setting conductive connector at the crimping end of brush wire, using four-wire measurement method to measure the conductor resistance of brush wire;And by measuring the resistance of crimping sleeve and the resistance of conductive rod and conductive liquid in advance, a double compensation calculation model is established to accurately calculate the equivalent resistance value of the metal wire inserted into the crimping sleeve;Then according to the principle that the conductor resistance is inversely proportional to the cross-sectional area, whether the crimping of brush wire meets the reliability requirements is judged by calculating the cross-sectional area ratio.The present application realizes nondestructive testing and full coverage detection of brush wire crimping reliability, overcomes the defects of traditional destructive detection method, and has the advantages of high detection precision, batch detection, and no damage to the measured piece.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing and detection of conductive slip rings, in particular to a non-destructive detection method for crimping reliability of bundled brush wires of conductive slip rings. Background Art

[0002] A conductive slip ring is a key component for realizing transmission of electrical signals and electric power between two relatively rotating mechanisms, and one of its core components is a brush assembly. The brush assembly is usually composed of multiple bundles of brush wires, each bundle of brush wires is composed of several or tens of metal wires, and the manufacturing of bundled brush wires mostly adopts two processes: welding and crimping. The crimping process is a method of crimping and fixing one end of metal wires in a metal crimping sleeve by mechanical force. The crimping reliability between the bundled brush wires and the crimping sleeve directly determines the contact resistance stability, service life and overall reliability of the conductive slip ring.

[0003] At present, the mainstream detection method for crimping reliability of bundled brush wires in the industry is destructive sampling inspection. The specific operation is: randomly sampling samples from each batch of bundled brush wires, slicing and grinding the crimping part, then measuring the crimping cross-sectional area under a microscope, and calculating the porosity, that is, the proportion of void area not filled by metal wires. When the porosity is lower than a certain threshold, the crimping is considered qualified. However, this method has limitations: for example, the detected bundled brush wires are damaged and can no longer be used as products, so only sampling inspection can be adopted, and full inspection of each bundle of brush wires cannot be achieved, resulting in a risk of missed detection; secondly, due to batch fluctuations in crimping quality, the sampling results cannot fully represent the reliability of the whole batch of products; in addition, if there is a slight deviation in the cutting position, the measured porosity may not match the actual crimping quality, which directly affects the judgment of crimping reliability.

[0004] In summary, there is an urgent need for a non-destructive, rapid, full-inspection detection method for crimping reliability of bundled brush wires, so as to realize accurate assessment of the crimping quality of each bundle of brush wires. Summary of the Invention

[0005] Aiming at the technical defects of destructiveness, low coverage and uncertain cutting position in the detection of crimping reliability of bundled brush wires in the prior art, the present invention provides a non-destructive detection method for crimping reliability of bundled brush wires of conductive slip rings, which realizes non-destructive detection and full-coverage detection of crimping reliability of bundled brush wires.

[0006] To achieve the above objective, the present invention provides the following technical solution: a non-destructive detection method for crimping reliability of bundled brush wires of conductive slip rings, comprising the following steps:

[0007] Step 1: Measure the resistance value R of the crimping sleeve 套 .

[0008] Before inserting the metal wires into the crimping sleeve, the four-wire measurement method is used to measure the conductor resistance value R of the crimping sleeve 套Specifically, two measuring probes are placed close to the two end faces of the crimping sleeve, and the measuring probes are connected in series with a low-resistance tester to measure the resistance value R of the crimping sleeve. 套 Because the crimp sleeve is a hollow tubular structure, it is necessary to ensure good contact between the measuring probe and the end face of the crimp sleeve during measurement.

[0009] Step 2: Measure the resistance R between the conductive rod and the conductive liquid. 测 .

[0010] The resistance R between the conductive rod and the conductive liquid was measured using a four-wire method. 测 Specifically, the resistance R between the conductive rod and the conductive liquid is measured using a four-wire low-resistance tester—one clamping a conductive rod immersed in a conductive liquid, and the other immersed at a horizontal distance L from the conductive rod. 测 The purpose of this step is to pre-calibrate the resistance value of the conductive liquid path in the test circuit, providing a reference for subsequent series compensation.

[0011] Step 3: Measure the total resistance R of the brush ribbon crimp sleeve, conductive rod, and conductive liquid. 总 .

[0012] After crimping, the non-crimped ends of the brush filaments are immersed in a conductive liquid to ensure that each wire is in the test circuit. The two current terminals and two voltage terminals of a four-wire low-resistance tester are connected to the conductive rod and the crimping sleeve, respectively. While maintaining a constant horizontal distance L between the conductive rod and the brush filaments, the total resistance value R is measured. 总 .

[0013] Step 4: Calculate the equivalent resistance R of the metal wire inserted into the crimp sleeve.

[0014] The crimping sleeve and the metal wire inserted into the crimping sleeve are connected in parallel, while the brush bristles, conductive rod, and conductive liquid are connected in series. Based on the principles of parallel and series circuits, the equivalent resistance R of the metal wire inserted into the crimping sleeve is calculated using the following formula:

[0015] R = [R 套 × (R 总 - R 测 )] / [R 套 - R 总 + R 测 If the calculated R value is negative or physically unreasonable (e.g., much smaller than the theoretical resistance of a single metal wire), then the brush filament crimping is directly deemed unqualified. The physical meaning of this formula is: firstly, from the total measured value R... 总 Subtract the known liquid path resistance R 测The true resistance of the parallel section of the crimping sleeve and the metal wire is obtained; then, using the parallel circuit formula, the net resistance R of the metal wire is deduced from the parallel resistance, thereby eliminating the current shunting effect of the crimping sleeve.

[0016] Step 5: Calculate the effective cross-sectional area S of the multiple metal wires and calculate the cross-sectional area ratio η.

[0017] Calculate the total effective cross-sectional area S of the multiple metal wires in the brush bundle using the conductor resistance formula R = ρ·L' / S, and calculate the cross-sectional area ratio η = S / (N × S) 单 ), where L' is the distance from the conductive liquid surface to the far end face of the crimping sleeve, ρ is the resistivity of the metal wire, N is the number of metal wires in a single bundle of brush filaments, and S 单 This is the nominal cross-sectional area of ​​a single metal wire.

[0018] Step 6: Determine the crimping reliability. When the cross-sectional area ratio η is greater than the preset threshold, the crimping reliability of the bristle bundle is determined to be qualified.

[0019] Preferably, a three-level judgment standard is adopted: η > 0.95 is judged as qualified; η < 0.90 is judged as unqualified; 0.90 ≤ η ≤ 0.95 is judged as critical, requiring re-inspection or other methods to assist in the judgment.

[0020] When the equivalent resistance of the brush filaments approaches the theoretical resistance of the multiple metal wires inserted into the crimping sleeve in complete parallel, it indicates that each fiber filament has achieved good electrical contact within the crimping sleeve, meaning the crimping reliability meets the requirements. This judgment criterion is quantified by the cross-sectional area ratio η, making it operable and repeatable.

[0021] Preferably, in step one, two measuring probes are used to press against both ends of the crimp sleeve, and the measuring probes are connected in series with a four-wire low-resistance tester to measure the resistance value R of the crimp sleeve. 套 .

[0022] Preferably, the conductive liquid is a dispersion of graphene-coated liquid metal droplets.

[0023] Preferably, the preset threshold in step six is ​​0.95; when η > 0.95, it is determined to be qualified, and when η ≤ 0.95, it is determined to be unqualified.

[0024] Preferably, step six employs a ratio method for rapid batch detection, including the following steps:

[0025] During the calibration phase, a bundle of brush filaments is selected as the standard bundle of brush filaments, and its equivalent resistance R0 and cross-sectional area ratio η0 are recorded.

[0026] During the testing phase, for the same batch of brush filaments to be tested, their total resistance R is measured according to step three.总 Then, according to the simplified formula R'=R 总 '-R 标 Calculate the equivalent resistance R' of the brush filaments to be tested, where R 标 The constant value of the resistance between the conductive rod and the conductive liquid, measured during the calibration phase of the standard bundle of brush filaments;

[0027] The cross-sectional area ratio of the brush filaments to be tested, η', is calculated using the formula η' = (R0 × η0) / R'. When η' > 0.95, it is considered qualified; when η' < 0.90, it is considered unqualified; and when 0.90 ≤ η' ≤ 0.95, it is considered critical and requires re-inspection.

[0028] Preferably, a preset qualified resistance threshold R is used. 限 =(R0×η0) / 0.95, when the equivalent resistance R' of the brush filament under test is ≤R 限 If R' > R, it is directly judged as qualified. 限 It is judged as unqualified or borderline at that time.

[0029] Preferably, the four-wire tester uses a Kelvin clamp, and its current terminal and voltage terminal are independently set on the conductive rod and the crimping sleeve.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention combines liquid conductive connectors with four-wire measurement to achieve non-destructive testing and full-coverage testing of the reliability of brush wire crimping; the dual compensation model simultaneously eliminates the current shunting effect of the crimping sleeve and the interference of conductive liquid path resistance, and the detection accuracy is highly consistent with the slicing method; the horizontal distance L is precisely controlled by the insulating limit block to ensure the effectiveness of compensation; and a simplified ratio method is further provided, which only requires a single total resistance measurement to complete the judgment, shortening the single-brush detection time and increasing the detection efficiency. Attached Figure Description

[0031] Figure 1 The total resistance R of the brush ribbon crimp sleeve, conductive rod and conductive liquid 总 Measurement principle diagram;

[0032] Figure 2 The resistance R of the conductive rod and the conductive liquid 测 Measurement principle diagram;

[0033] Figure 3 This is a schematic diagram of the structure of the conductive slip ring bundle brush filaments;

[0034] Figure 4 For the crimp sleeve resistor R 套 Measurement principle diagram.

[0035] In the diagram: 1. Brush bristles, 2. Conductive liquid cylinder, 3. First conductive clamp, 4. Low resistance tester, 5. Second conductive clamp, 6. Conductive rod, 7. First insulating limit block, 8. Second insulating limit block, 9. Measuring needle, 11. Crimping sleeve, 12. Metal wire. Detailed Implementation

[0036] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of the invention.

[0037] See Figure 1-4 An embodiment of the present invention provides a non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping. The method relies on a testing device to perform non-destructive testing on the bundle brush wire 1.

[0038] The testing device includes a conductive liquid cylinder 2, a first conductive clamp 3, a low resistance tester 4, a second conductive clamp 5, a conductive rod 6, a first insulating limit block 7, a second insulating limit block 8, and two measuring needles 9.

[0039] The conductive liquid cylinder 2 is made of insulating material and is used to contain the conductive liquid. The conductive liquid is highly conductive, non-corrosive, and leaves no residue; preferably, it is a graphene-coated liquid metal droplet with a room temperature conductivity of approximately 1.2 × 10⁻⁶. 4 S / m, while the conductive liquid will not leave residue on the brush filaments, thus maintaining the material properties of the brush filaments themselves; the conductive rod 6 is fixed in the conductive liquid cylinder 2 by the second insulating limiting block 8, with its lower end immersed in the conductive liquid and its upper end protruding above the liquid surface, facilitating connection with the second conductive clamp 5; the first insulating limiting block 7 is used to support the first conductive clamp 3 and limit the horizontal distance L between the brush filaments 1 and the conductive rod 6; the second insulating limiting block 8 is used to fix the conductive rod 6 and limit the connection position between the second conductive clamp 5 and the conductive rod 6; two measuring needles 9 are used to measure the resistance value R of the crimping sleeve by closely contacting both ends of the crimping sleeve before the metal wire is inserted. 套 The four-wire low resistance tester 4 has two current terminals and two voltage terminals that can be connected to conductive rods 6, first conductive clamps 3, second conductive clamps 5, measuring needles 9 or crimping sleeves 12, depending on the testing requirements.

[0040] The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping provided by this invention includes the following six steps:

[0041] Step 1: Measure the resistance R of the crimp sleeve 套

[0042] See Figure 4Before inserting the metal wire into the crimp sleeve, the conductor resistance R of the crimp sleeve 11 is measured individually using a four-wire measurement method. 套 The specific procedure involves placing two measuring probes 9 against the two end faces of the crimping sleeve 11, with the measuring probes 9 connected in series with the low-resistance tester 4. Since the crimping sleeve is a hollow tubular structure, it is essential to ensure good contact between the measuring probes 9 and the end faces of the crimping sleeve 11 during measurement. To improve measurement accuracy, each crimping sleeve can be measured three times, and the average value taken. The ambient temperature should be recorded for subsequent temperature compensation correction.

[0043] Step 2: Measure the resistance R between the conductive rod 6 and the conductive liquid. 测

[0044] The purpose of this step is to pre-calibrate the resistance value of the conductive liquid path in the test circuit, providing a reference for subsequent series compensation. See also... Figure 2 After the conductive liquid is injected into the conductive liquid cylinder 2, the lower end of the conductive rod 6 is immersed in the conductive liquid for a length of not less than 20 mm. Then, the second conductive clamp 5 connected to the low resistance tester 4 clamps the upper end of the conductive rod 6, and the first conductive clamp 3 connected to the low resistance tester 4 is immersed at a horizontal distance L from the conductive rod 6. After the first conductive clamp 3 is immersed below the liquid surface, the low resistance tester 4 is started to measure the resistance R between the conductive rod 6 and the conductive liquid. 测 .

[0045] Step 3: Measure the total resistance R of the brush ribbon crimp sleeve, conductive rod, and conductive liquid. 总

[0046] See Figure 1 After crimping, the non-crimped ends of the brush filaments 1 are immersed in the conductive liquid in the conductive liquid tank 2. The conductive liquid ensures that each metal wire is in the test circuit. During operation, the second conductive clamp 5 connected to the low resistance tester 4 clamps the conductive rod 6 immersed in the conductive liquid, and the first conductive clamp 3 connected to the low resistance tester 4 clamps the crimping sleeve 11 of the brush filaments 1. The low resistance tester 4 is then started to measure the total resistance R of the brush filaments, the crimping sleeve, the conductive rod 6, and the conductive liquid. 总 .

[0047] It is important to clarify that in this embodiment, the first conductive clamp 3 must be clamped at the far end of the crimping sleeve 11, away from the non-crimping end of the brush filaments. If it is clamped at the near end of the crimping sleeve, the contact state of the metal wires in the area near the far end inside the crimping sleeve will be excluded from the test circuit, and the true crimping reliability cannot be reflected. Based on this, the first conductive clamp 3 adopts a Kelvin clamp. When clamped on the outer wall of the far end of the crimping sleeve, its voltage sensing end should be located on the side of the current injection end near the end face of the crimping sleeve to ensure that the voltage drop measurement accurately covers the crimping area of ​​the entire length of the crimping sleeve.

[0048] The mechanical limiting by the first insulating limiting block 7 and the second insulating limiting block 8 ensures that the horizontal distance between the conductive rod 6 and the brush filament 1 in this step remains consistent with the distance L in step two. This also ensures that R... 测 This is a prerequisite for accurately representing the liquid path resistance in R_total.

[0049] Step 4: Calculate the equivalent resistance R of the metal wire inserted into the crimp sleeve.

[0050] The core of this step lies in establishing a dual-compensation calculation model, sequentially eliminating the current shunting effect of the crimp sleeve 11 and the liquid path resistance from the total resistance, thereby obtaining the net resistance of the metal wire. The crimp sleeve 11 and the metal wire inserted into the crimp sleeve form a parallel relationship because they share the same starting and ending points, resulting in two current paths; the brush wire 1, the conductive rod 6, and the conductive liquid form a series relationship. Based on the principles of parallel and series circuits, the equivalent resistance R of the metal wire inserted into the crimp sleeve is calculated using the following formula:

[0051] R 总 =R 测 +(R) 套 × R) / (R 套 + R)

[0052] By rearranging the terms and solving for R, we get:

[0053] R = [R 套 × (R 总 - R 测 )] / [R 套 - R 总 + R 测 ]

[0054] The physical meaning of this formula is: firstly, from the total measured value R 总 Subtract the known liquid path resistance R 测 The true resistance of the parallel section of the crimping sleeve and the metal wire is obtained; then, using the parallel circuit formula, the net resistance R of the metal wire is deduced from the parallel resistance, thereby eliminating the current shunting effect of the crimping sleeve.

[0055] If the calculated R value is negative or physically unreasonable (e.g., much smaller than the theoretical resistance of a single metal wire), it indicates that there is a serious defect in the crimping of the brush filament bundle. The metal wire and the crimping sleeve have failed to form an effective parallel electrical contact, causing the current to mainly flow through the crimping sleeve while the metal wire branch is almost open-circuited. The sample should be directly judged as unqualified.

[0056] Step 5: Calculate the effective cross-sectional area S of the multiple metal wires and calculate the cross-sectional area ratio η.

[0057] Based on the formula for calculating conductor resistance R = ρ·L' / S, calculate the total effective cross-sectional area S of the multiple metal wires in the brush bundle:

[0058] S = ρ·L' / R

[0059] Where R is the equivalent conductor resistance of the metal wire, ρ is the resistivity of the metal wire, L' is the distance from the surface of the conductive liquid to the far end face of the crimping sleeve, and S is the effective cross-sectional area of ​​the metal wire. It should be clarified that the effective cross-sectional area S calculated in this step does not refer to the physical cross-sectional area of ​​a single metal wire, but rather to the sum of the cross-sectional areas of the effective conductive paths of all metal wires in the bundle of brush filaments after crimping, i.e., the total effective cross-sectional area.

[0060] Further calculate the cross-sectional area ratio η:

[0061] η = S / (N × S 单 )

[0062] Where N is the number of metal wires in a single bundle of brush filaments, S 单 This represents the nominal cross-sectional area of ​​a single metal wire. The η value directly reflects the proportion of the effective conductive cross-sectional area of ​​each metal wire to the theoretically complete contact cross-sectional area after crimping. The closer the η value is to 1, the more metal wires achieve effective electrical contact within the crimp sleeve.

[0063] Step Six: Determine the reliability of the crimping

[0064] The preset threshold is preferably 0.95. When η is greater than the preset threshold, the crimping reliability of the bristle bundle is determined to be qualified.

[0065] Alternatively, a three-level judgment standard can be used: η > 0.95 is judged as qualified; η < 0.90 is judged as unqualified; 0.90 ≤ η ≤ 0.95 is judged as critical, requiring re-inspection or other methods to assist in the judgment.

[0066] When the equivalent resistance of the brush filament 1 is close to the theoretical resistance of the multiple metal fibers inserted into the crimping sleeve in complete parallel connection, it indicates that each fiber has achieved good electrical contact within the crimping sleeve, meaning the crimping reliability meets the requirements. This judgment criterion is quantified by the cross-sectional area ratio η, making it operable and repeatable.

[0067] This embodiment also provides a calibration method for a threshold of 0.95: At least 30 press-fit samples are prepared, covering the complete quality range from good to poor; for each sample, the cross-sectional area ratio η is first measured and calculated using the method of this invention; then, the porosity of the same batch of samples is tested by slicing; a correspondence between η value and porosity is established; according to GJB5020, a porosity ≤10% is the acceptable standard, and the corresponding lower limit of the η value is the judgment threshold. Statistical calibration shows that the η values ​​of acceptable samples are all between 0.96 and 0.99, and 0.95 is taken as the judgment threshold.

[0068] In one embodiment, to accommodate batch inspection of brush filaments of the same batch and specification, the present invention also provides a simplified inspection method based on a ratio method. This simplified ratio method is applicable to the crimp sleeve resistor R. 套 When the resistance is much greater than the equivalent resistance R of the metal wire, the shunt effect of the crimp sleeve can be ignored, and the total resistance is approximately equal to the sum of the liquid path resistance and the metal wire resistance, i.e., R. 总 ≈R 测 +R. If the sample to be tested does not meet this condition, the resistance of the metal wire should be calculated using the complete formula in step four before making a judgment to ensure detection accuracy.

[0069] In the foregoing embodiments, a measurement R needs to be performed on each bundle of brush filaments to be tested. 套 Measure R 测 Measure R 总 While this method offers high accuracy, performing full-process testing on each item individually is too inefficient in mass production scenarios.

[0070] For mass-produced brush filaments of the same specification, the material and dimensions of the crimping sleeve are identical, the conductive liquid and testing fixtures are identical, and the resistivity ρ and effective length L' of a single filament are also the same. Under these constant conditions, the total resistance R of the brush filaments is... 总 There is a monotonic correspondence between R and the equivalent resistance R of the metal wire inserted into the crimp sleeve, i.e., R 总 The smaller the value, the more fully the parallel conduction of the metal wires inside the crimp sleeve is achieved, the smaller the equivalent resistance R is, and the better the crimping quality.

[0071] Based on the above principles, this embodiment pre-calibrates a standard bundle of brush filaments that has passed the crimping test through a complete testing process, and uses its total resistance as the judgment criterion; for subsequent products in the same batch, only the total resistance R needs to be measured. 总 The equivalent resistance R can be used to determine whether a value is qualified or not by comparing it with the standard value.

[0072] First, select a bundle that has been verified as qualified through the complete testing process of the aforementioned embodiments and confirmed by the slicing method, or take the average value of multiple qualified bundles, and calculate its cross-sectional area ratio η0, and record its equivalent resistance R0.

[0073] That is, according to the foregoing steps S1 to S4, the equivalent resistance R0 of the standard bundle of brush wires is measured and calculated, and the cross-sectional area ratio η0 (η0> 0.95) is calculated according to step S5. This bundle of brush wires is calibrated as a standard bundle of brush wires, its equivalent resistance value is denoted as R0, and its cross-sectional area ratio is denoted as η0.

[0074] For subsequent bundles of brush wires to be tested of the same batch, the following simplified steps are adopted:

[0075] In the first step, the non-crimping end of the bundle of brush wires to be tested is immersed in a conductive liquid, and the four-wire measurement method is used to directly measure R 总 ', without repeatedly measuring R 套 and R 测 , the far end of the crimping sleeve is clamped by a first conductive chuck, and the conductive rod is clamped by a second conductive chuck, the measured total resistance value is denoted as R 总 ';

[0076] In the second step, the equivalent resistance R' of the bundle of brush wires to be tested is calculated according to a simplified formula:

[0077] R'= R 总 '-R 标 , wherein R 标 is a constant value of the resistance of the conductive rod and the conductive liquid measured by the standard bundle of brush wires in the calibration stage.

[0078] In the third step, the cross-sectional area ratio η' of the bundle of brush wires to be tested is calculated:

[0079] η' = (R0 × η0) / R', wherein R0 is the equivalent resistance of the standard bundle of brush wires, η0 is the cross-sectional area ratio of the standard bundle of brush wires, and R' is the equivalent resistance of the bundle of brush wires to be tested.

[0080] In the fourth step, the judgment standard is the same as the foregoing: when η' > 0.95, it is judged as qualified; when η' < 0.90, it is judged as unqualified; when 0.90 ≤ η' ≤ 0.95, it is judged as critical and requires re-inspection.

[0081] Formula derivation: From the conductor resistance formula S = ρ·L' / R, it can be obtained that for bundles of brush wires of the same batch and the same specification, ρ and L' are the same, so the cross-sectional area S is inversely proportional to the equivalent resistance R.

[0082] For the standard bundle of brush wires: S0= ρ·L' / R0, η0 = S0 / (N·S 单 )

[0083] For the bundle of brush wires to be tested: S'= ρ·L' / R', η'= S' / (N·S 单 )

[0084] Comparing the two equations: η' / η0 = (ρ·L' / R') / (ρ·L' / R0) = R0 / R', therefore: η'= (R0 × η0) / R', where η0 is the cross-sectional area ratio of the standard bundle of brush filaments, R0 is the equivalent resistance of the standard bundle of brush filaments, and R' is the equivalent resistance of the bundle of brush filaments to be tested.

[0085] In more mass production, there is no need to calculate η'; a qualified reference resistance threshold R can be preset directly. 限 Given that η is ≥ 0.95 and η = (R0 × η0) / R, the qualification condition is: R ≤ (R0 × η0) / 0.95, i.e., a threshold R is set. 限 = (R0 × η0) / 0.95, when the equivalent resistance R' of the brush filament under test is ≤ R 限 When R' > R, it is directly judged as qualified; 限 If the condition is met, it is judged as unqualified or borderline.

[0086] The advantage of this embodiment is that after the standard bundle brush filaments are calibrated, only one total resistance measurement is needed to complete the judgment for the same batch of products, reducing the single bundle detection time from minutes to seconds, meeting the batch detection requirements of the production line; it eliminates the need to repeatedly measure R for each bundle. 套 and R 测 This eliminates the need for repetitive calibration of the resistance of the crimp sleeve and the conductive liquid path, and also eliminates the need to measure the absolute length L' and resistivity ρ: the influence of L' and ρ is offset by the ratio method, which reduces the complexity of operation and the accuracy requirements of tooling.

[0087] In summary, the present invention provides a non-destructive testing method for the reliability of conductive slip ring brush filament crimping. This method can be widely applied to the quality inspection of brush filament crimping in the field of conductive slip ring manufacturing. It has the advantages of high detection accuracy, batch testing capability, and no damage to the tested parts, and can significantly improve the product quality inspection efficiency and reliability control level of conductive slip rings.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping, characterized in that, Includes the following steps: Step 1: Measure the resistance of the crimp sleeve: Before inserting the metal wire into the crimp sleeve, measure the resistance R of the crimp sleeve individually using the four-wire method. 套 ; Step 2: Calibrate the liquid path resistance: Immerse a conductive rod in a conductive liquid; connect one of the two conductive clamps of a four-wire low-resistance tester to the upper end of the conductive rod, and guide the other clamp into the conductive liquid via an insulating limiting block, ensuring that the horizontal distance between the immersed conductive rod and the conductive clamp is maintained at L. Measure the resistance R using the low-resistance tester. 测 ; Step 3: Measure the total resistance: Immerse the non-crimped end of the crimped brush filaments into the conductive liquid. Connect the two conductive clamps of the four-wire tester to the conductive rod and the far end of the crimping sleeve away from the non-crimped end of the brush filaments, respectively. While maintaining the horizontal distance between the conductive rod and the brush filaments as L described in step S2, measure the total resistance value R. 总 ; Step 4: Calculate the equivalent resistance of the metal wires: Based on the principles of parallel and series circuits, calculate the equivalent resistance R of the multiple metal wires inserted into the crimp sleeve using the following formula: R = [R 套 × (R 总 - R 测 )] / [R 套 - R 总 + R 测 If the calculated R value is negative, the brush filaments are directly judged to be unqualified for crimping. Step 5: Calculate the effective cross-sectional area ratio: Calculate the total effective cross-sectional area S of the multiple metal wires in the brush bundle according to the conductor resistance formula R = ρ·L' / S, and calculate the cross-sectional area ratio η = S / (N × S) 单 ), where L' is the distance from the conductive liquid surface to the far end face of the crimping sleeve, ρ is the resistivity of the metal wire, N is the number of metal wires in a single bundle of brush filaments, and S 单 This is the nominal cross-sectional area of ​​a single metal wire; Step 6: Crimping reliability determination: When the cross-sectional area ratio η is greater than the preset threshold, the crimping reliability of the bristle bundle is determined to be qualified.

2. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 1, characterized in that: In step one, two measuring probes are placed close to both ends of the crimp sleeve, and the measuring probes are connected in series with a four-wire low-resistance tester to measure the resistance value R of the crimp sleeve. 套 .

3. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 1, characterized in that: The conductive liquid is a dispersion of graphene-coated liquid metal droplets.

4. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 1, characterized in that: The preset threshold mentioned in step six is ​​0.95; when η > 0.95, it is judged as qualified, and when η ≤ 0.95, it is judged as unqualified.

5. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 1, characterized in that, Step six employs the ratio method for rapid batch detection, including the following steps: During the calibration phase, a bundle of brush filaments is selected as the standard bundle of brush filaments, and its equivalent resistance R0 and cross-sectional area ratio η0 are recorded. During the testing phase, for the same batch of brush filaments to be tested, their total resistance R is measured according to step three. 总 Then, according to the simplified formula R'=R 总 '-R 标 Calculate the equivalent resistance R' of the brush filaments to be tested, where R 标 The constant value of the resistance between the conductive rod and the conductive liquid, measured during the calibration phase of the standard bundle of brush filaments; The cross-sectional area ratio of the brush filaments to be tested, η', is calculated using the formula η' = (R0 × η0) / R'. When η' > 0.95, it is considered qualified; when η' < 0.90, it is considered unqualified; and when 0.90 ≤ η' ≤ 0.95, it is considered critical and requires re-inspection.

6. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 6, characterized in that: Preset qualified resistance threshold R 限 =(R0×η0) / 0.95, when the equivalent resistance R' of the brush filament under test is ≤R 限 If R' > R, it is directly judged as qualified. 限 It is judged as unqualified or borderline at that time.

7. The non-destructive testing method for the reliability of conductive slip ring bundle brush wire crimping according to claim 1, characterized in that: The four-wire tester uses a Kelvin clamp, and its current and voltage terminals are independently set on the conductive rod and the crimping sleeve.

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