Automobile precision part airtightness detection method

Abstract

The invention discloses an automobile precision part airtightness detection method. The method comprises the steps that a to-be-detected part is clamped in an airtightness detection tool in a sealed mode to form a detection cavity; the detection cavity is pre-filled with detection gas until the initial detection pressure is reached and the pressure is stabilized, so that pressure drift caused by sealing springback, clamping elastic deformation and gas separation is weakened; applying pressure disturbance with a preset amplitude under the same clamping state, collecting pressure change data, and calculating to obtain an equivalent volume parameter of the detection system; collecting pressure change data within a preset detection time, and performing adaptive compensation on the airtightness detection result based on the equivalent volume parameter to obtain a compensation result; and completing qualification judgment according to a compensation result, and analyzing detection abnormity in combination with an equivalent volume parameter so as to distinguish tool leakage and part body leakage. According to the invention, the stability and consistency of airtightness detection of the aluminum casting can be improved, the misjudgment rate is reduced, and the batch detection requirement of an automatic production line is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automobile part detection, and particularly relates to a precision automobile part air tightness detection method. BACKGROUND

[0002] Automobile precision parts (such as valve bodies, pump bodies, housings, etc.) are usually subjected to the cyclic action of oil, coolant or gas medium pressure and temperature during use, and their sealing performance directly affects the safety, reliability and emission compliance of the vehicle. For aluminum cast precision parts, they often have complex flow channels, thin-walled cavities and multi-interface structures. Once there is a slight leakage, it will not only cause medium leakage, insufficient pressure, increased noise and vibration, but also may cause heat management failure, insufficient lubrication or increased corrosion. Therefore, stable, fast and highly consistent air tightness detection of aluminum cast precision parts at the manufacturing stage is an important process to ensure product quality and batch delivery.

[0003] The existing air tightness detection methods mostly use pressure drop or differential pressure methods, that is, after the parts are clamped and sealed by the tooling, gas is filled into the inner cavity, and after pressure stabilization, the pressure change is collected within a set time to determine whether there is leakage by whether the pressure drop exceeds the threshold. This method is mature, fast and suitable for batch detection on the production line. However, in the application scenario of aluminum cast precision parts, the traditional pressure drop / differential pressure detection is easily affected by multiple factors: first, the equivalent volume of the detection system is not only determined by the volume of the part cavity, but also includes the tooling pipeline, valve cavity, joint cavity, etc., and the compression amount of the sealing ring, clamping force fluctuation and elastic deformation of the clamp structure will all cause changes in the equivalent volume; second, the surface and micro-porous structure of the aluminum cast may produce gas adsorption / desorption or slight leakage non-linear characteristics during pressurization, causing additional drift in the initial pressure curve; third, temperature fluctuations in the workshop will cause changes in the state of the gas, thereby amplifying the defects sensitive to temperature and volume in the pressure drop method. After the above factors are superimposed, it is easy to misjudge that "the part does not leak but is judged to leak" or "the part slightly leaks but is judged to be qualified", especially when different types of parts are switched, the inner cavity volume differs greatly, or the tooling sealing state deteriorates over time, the consistency of the detection results decreases, making it difficult to meet the requirements of high-precision quality control.

[0004] In addition, the existing method usually refers to detection abnormalities as part leakage, and lacks effective means to distinguish between tooling sealing leakage and part body leakage. In actual production, factors such as sealing ring wear, valve leakage, loose pipeline joints, etc. will also cause pressure drop. If the tooling problem cannot be identified and located in time, it will lead to batch misjudgment, rework and line stoppage, increasing the quality cost and management difficulty. SUMMARY

[0005] To solve the above problems, the application provides a kind of automobile precision parts air tightness detection method, can complete equivalent volume identification under the same clamping condition, and the air tightness detection result is self-adaptive compensation.

[0006] The technical scheme provided by the application is as follows: A kind of automobile precision parts air tightness detection method, comprising the following steps: S1: the automobile precision parts to be detected is clamped in air tightness detection tool, the detection interface of the part is sealed and clamped, and a closed detection cavity is formed; S2: detection gas is introduced into the detection cavity, the pressure in the detection cavity is raised to a preset initial detection pressure, and the pressure is kept stable for a preset time, to eliminate the influence of seal compression rebound, clamping structure elastic deformation and part surface gas emission on the detection result; S3: after the stable pressure is completed, a preset amplitude of pressure disturbance is applied to the detection cavity, the pressure change data in the detection cavity before and after the pressure disturbance is collected, and the equivalent volume parameter of the detection system under the current clamping state is calculated according to the pressure change data; S4: after the equivalent volume parameter is determined, the air tightness of the detection cavity is detected, the pressure change data during the detection time is collected, and the pressure change result obtained by the detection is compensated based on the equivalent volume parameter, to obtain the compensated air tightness detection result; S5: the air tightness performance of the part to be detected is qualified according to the compensated air tightness detection result, and the detection abnormality is analyzed in combination with the equivalent volume parameter, to distinguish the abnormality caused by detection tool sealing leakage from the abnormality caused by part body leakage.

[0007] In some embodiments, the detection gas is air or nitrogen.

[0008] In some embodiments, the preset initial detection pressure is higher than the normal working pressure of the part.

[0009] In some embodiments, the pressure disturbance is a small step pressure change applied on the basis of the initial detection pressure, the amplitude of the step pressure change is controlled within the range of 1% to 10% of the initial detection pressure, and the application and removal of the pressure disturbance are completed under the same clamping and sealing state, to avoid the influence of repeated clamping on the equivalent volume identification result.

[0010] In some embodiments, the equivalent volume parameter is an integrated equivalent volume in the current clamping state, which includes the internal cavity volume of the part to be detected, the internal pipeline and valve cavity volume of the detection tool, and the equivalent volume change corresponding to the elastic deformation of the sealing structure and clamping structure under pressure. The equivalent volume parameter is obtained by calculating the pressure change before and after the pressure disturbance and the corresponding gas state parameter.

[0011] In some embodiments, the compensation process includes converting the pressure change data collected during the detection time into an equivalent leakage amount under standard conditions based on the equivalent volume parameter, or performing equivalent volume normalization processing on the original pressure drop data to eliminate the influence of the internal cavity volume difference of different parts and the clamping state change on the airtightness detection result.

[0012] In some embodiments, when the compensated airtightness detection result is abnormal, and the abnormality is synchronous or related to the change of the equivalent volume parameter, the clamping force change or the sealing element compression state change, it is determined that the abnormality is a tool leakage abnormality caused by leakage of the sealing structure, pipeline or valve of the detection tool.

[0013] In some embodiments, when the compensated airtightness detection result is stable and exceeds the preset qualified threshold in multiple repeated detections, and the detection result has no significant correlation with the clamping state and the change of the equivalent volume parameter, it is determined that the abnormality is a part leakage abnormality caused by the existence of micro-leakage or defects in the part to be detected.

[0014] In summary, the beneficial effects of the present application are: (1) The present application identifies the equivalent volume parameter of the detection system under the same clamping state, and performs self-adaptive compensation on the pressure drop / differential pressure result, which can significantly reduce the influence of the internal cavity volume difference of the part, the tool pipeline volume and the elastic deformation of the clamping on the detection result, and make the detection results of different batches and different types of aluminum cast parts more consistent. (2) The present application can more accurately reflect the real leakage trend of the part and improve the identification ability of micro-leakage by weakening the initial drift caused by the rebound of the sealing ring, the stress relaxation of the clamp and the gas precipitation on the surface of the aluminum casting through the pre-charge pressure stabilization process. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The flowchart of the method of the present application. DETAILED DESCRIPTION

[0016] In order to deepen the understanding of the present application, the present application will be further described in combination with the embodiments below, and the following embodiments are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0017] AsFigure 1 As shown, the present application is suitable for air tightness detection of precision parts for automobiles, and the parts are aluminum cast parts, such as housings, valve bodies, pump bodies or other parts with closed or semi-closed internal cavity structures.

[0018] Since aluminum cast parts are prone to form micro-holes, shrinkage holes or micro-cracks during casting, and the detection process is easily affected by factors such as clamping sealing structure, tool elastic deformation and temperature change, the traditional air tightness detection method is prone to misjudgment or insufficient stability.

[0019] During detection, the automobile precision parts to be detected are clamped in the air tightness detection tool, and the detection tool includes a sealing structure for cooperating with the part detection interface.

[0020] By sealing and clamping the detection hole, interface or channel of the part, the internal part and the detection tool form a closed detection cavity. The detection cavity not only includes the internal cavity space of the part, but also includes the space surrounded by the internal pipeline, valve cavity and sealing structure of the detection tool.

[0021] In this embodiment, the clamping process is completed in the same clamping state, and the clamping state is maintained unchanged in the subsequent detection step, so as to avoid the influence of repeated clamping on the detection result.

[0022] After completing the sealing and clamping, detection gas is introduced into the detection cavity, which can be air or nitrogen.

[0023] The pressure in the detection cavity is raised to a preset initial detection pressure, which is determined according to the design working pressure of the part to be detected, and is usually higher than the normal working pressure of the part.

[0024] After reaching the initial detection pressure, the pressure is maintained for a preset time. Through this pressure maintaining process, the sealing element of the detection tool completes compression and rebound, the elastic deformation of the clamping structure tends to be stable, and the gas adsorbed or precipitated on the surface of the aluminum cast part is reduced, thereby providing a stable initial state for subsequent detection.

[0025] After the pressure stabilizing is completed, a pressure disturbance of a preset amplitude is applied to the detection cavity in the same clamping and sealing state.

[0026] The pressure disturbance is a small step pressure change based on the initial detection pressure, and the amplitude is preferably controlled within 1% to 10% of the initial detection pressure, and the application and removal of the pressure disturbance are completed without releasing the clamping.

[0027] The equivalent volume parameter of the detection system under the current clamping state is calculated by collecting pressure change data in the detection cavity before and after pressure disturbance and combining with state parameters of the detection gas.

[0028] The equivalent volume parameter is a comprehensive equivalent volume, which includes the internal cavity volume of the part to be detected, the internal pipeline and valve cavity volume of the detection tool, and the equivalent volume change corresponding to the elastic deformation of the sealing structure and clamping structure under pressure.

[0029] In the above manner, the equivalent volume is no longer dependent on the design theoretical value or empirical estimate of the part, but is identified based on the current actual clamping state.

[0030] In the specific implementation of the present application, the identification of the equivalent volume parameter and the compensation processing of the air tightness detection result are both realized by engineering calculation based on the pressure change data of the detection cavity during pressure disturbance and detection. It should be understood that the present application does not limit the specific mathematical model or calculation formula, and those skilled in the art can use linear calculation, piecewise calculation or other equivalent data processing methods to complete the identification of the equivalent volume and the compensation of the detection result according to the structure of the detection system, the accuracy of the sensor and the condition of the control system, without affecting the implementation effect of the technical scheme of the present application.

[0031] After the equivalent volume parameter is determined, the detection cavity is subjected to air tightness detection.

[0032] During the preset detection time, the pressure change data in the detection cavity is continuously collected to obtain the original pressure change result.

[0033] Subsequently, the original pressure change result is compensated based on the equivalent volume parameter. The compensation processing can include: Converting the pressure change data during the detection time into equivalent leakage under standard state, or performing equivalent volume normalization processing on the original pressure drop data.

[0034] Through the above compensation method, the influence of the volume difference of the internal cavity of different parts, the change of clamping state and the elastic deformation of the tool on the detection result can be effectively eliminated, thereby improving the consistency and comparability of the air tightness detection result.

[0035] According to the compensated air tightness detection result, the air tightness performance of the part to be detected is judged as qualified or unqualified by comparing with the preset qualified threshold.

[0036] When the compensated air tightness detection result is abnormal, and the abnormality is synchronous or related to the change of the equivalent volume parameter, the change of clamping force or the change of compression state of the sealing element, it is determined that the abnormality is caused by the leakage of the sealing structure, pipeline or valve of the detection tool, which is a tool leakage abnormality.

[0037] When the compensated air tightness detection result exceeds the preset qualified threshold stably in multiple repeated detections, and the detection result has no significant correlation with the clamping state and the equivalent volume parameter change, it is determined that the abnormality is caused by the micro leakage or structural defect of the body of the part to be detected, which is a leakage abnormality of the body of the part.

[0038] Through the above separation and identification method, the leakage of the tool and the leakage of the body of the part are distinguished and determined, and the reliability of the detection result is improved.

[0039] The air tightness detection method can complete the equivalent volume identification and compensation detection under the same clamping condition, can improve the stability and repeatability of the air tightness detection of aluminum cast automobile precision parts, can effectively avoid misjudgment caused by changes in tool sealing or clamping state, and is suitable for batch detection application of automatic production line.

[0040] The technical effects of the present application are further illustrated by the following examples.

[0041] Example 1, air tightness detection of aluminum casting valve body.

[0042] In this embodiment, an aluminum casting valve body for a certain automobile is taken as the object to be detected. The valve body has a closed flow channel structure inside, and the design working pressure is 300 kPa.

[0043] During detection, the valve body is clamped in the air tightness detection tool, the end face of the valve detection interface is sealed and clamped to form a closed detection cavity. Dry air is selected as the detection gas.

[0044] Air is filled into the detection cavity, the cavity pressure is raised to 350 kPa, and the pressure is kept stable for 5s to eliminate the influence of the compression rebound of the sealing ring and the elastic deformation of the clamping structure.

[0045] After the pressure stabilization is completed, the pressure disturbance is applied to the detection cavity under the same clamping state, so that the cavity pressure is stepped up from 350 kPa to 370 kPa, and the pressure disturbance amplitude is about 5% of the initial detection pressure. The cavity pressure change data before and after the pressure disturbance is collected, and the equivalent volume parameter under the current clamping state is calculated as 420 mL according to the pressure change.

[0046] Then enter the air tightness detection phase, and continuously collect the cavity pressure change data within 10s detection time. The original detection result shows that the pressure drop value is 1.8 kPa. Based on the equivalent volume parameter 420 mL, the equivalent volume normalization processing is performed on the original pressure drop data, and the compensated equivalent pressure drop value is 1.1 kPa.

[0047] The compensated detection result is compared with the preset qualified threshold (1.5 kPa), and it is determined that the air tightness performance of the valve body is qualified.

[0048] Example 2, tooling leakage separation determination of aluminum casting pump body.

[0049] This example takes an aluminum casting pump body for automobiles as the detection object, and the detection method is the same as in Example 1.

[0050] After the pump body is clamped, the detection cavity is pressurized to 400 kPa and stabilized for 6 s. Then, pressure disturbance is applied to raise the pressure from 400 kPa to 430 kPa, and the equivalent volume parameter is calculated to be 610 mL.

[0051] During the 8 s air tightness detection, the original pressure drop is 2.5 kPa, and the compensated pressure drop after equivalent volume compensation is 2.2 kPa, which exceeds the qualified threshold.

[0052] Under the same detection conditions, the detection is performed again after replacing the sealing ring of the detection tool, and the identified equivalent volume parameter decreases to 560 mL, and the compensated pressure drop decreases to 1.3 kPa, meeting the qualified requirements.

[0053] Through comparative analysis, it is found that the detection abnormality is obviously related to the change of equivalent volume parameter and sealing structure state, and it is determined that the abnormality is caused by the sealing leakage of the detection tool, rather than the leakage of the pump body.

[0054] Example 3, aluminum casting shell body micro-leakage identification This example takes an aluminum casting shell for automobiles as the detection object, and the shell has multiple casting cavities.

[0055] After the shell is clamped, the detection cavity is pressurized to 300 kPa and stabilized for 5 s, and pressure disturbance is applied to raise the pressure from 300 kPa to 330 kPa, and the equivalent volume parameter is identified to be 780 mL.

[0056] The pressure change data is collected within 10 s of detection time, the original pressure drop is 3.2 kPa, and the compensated pressure drop after equivalent volume compensation is 2.9 kPa, which is obviously beyond the qualified threshold.

[0057] Under the same detection conditions, the shell is detected three times repeatedly, and the equivalent volume parameters obtained by the three detections are 775 mL, 782 mL and 778 mL respectively, and the compensated pressure drops are 2.8 kPa, 2.9 kPa and 2.8 kPa respectively, and the detection results are stable and have no obvious correlation with the change of clamping state.

[0058] Accordingly, it is determined that the detection abnormality is caused by the micro-leakage or casting defects of the aluminum casting shell body.

[0059] As can be seen from the above examples, the air tightness detection method can complete equivalent volume identification under the same clamping condition, and self-adaptively compensate the air tightness detection result, thereby improving the stability of the air tightness detection result of the aluminum casting type automobile precision part, and effectively distinguishing the detection tool leakage from the part body micro leakage, and improving the accuracy and reliability of the detection determination.

[0060] The above description shows and describes preferred embodiments of the present application, as previously described, it is to be understood that the application is not limited to the disclosed forms and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the inventive concept described herein, by the above teaching or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the application shall be within the protection scope of the claims of the present application.

Claims

1. A method for airtightness testing of precision automotive parts, characterized in that, Includes the following steps: S1: The precision automotive parts to be tested are clamped in an airtight testing fixture, and the testing interface of the parts is sealed and clamped to form a closed testing cavity; S2: Introduce detection gas into the detection chamber to raise the pressure inside the detection chamber to a preset initial detection pressure and maintain the pressure for a preset time to eliminate the influence of seal compression rebound, clamping structure elastic deformation and gas evolution on the surface of components on the detection results. S3: After the pressure stabilization is completed, a pressure disturbance of a preset amplitude is applied to the detection cavity, and pressure change data in the detection cavity before and after the pressure disturbance is collected. The equivalent volume parameters of the detection system under the current clamping state are calculated based on the pressure change data. S4: After the equivalent volume parameters are determined, the airtightness of the detection cavity is tested, the pressure change data during the detection time is collected, and the pressure change results obtained by the test are compensated based on the equivalent volume parameters to obtain the compensated airtightness test results. S5: Based on the compensated airtightness test results, determine the airtightness performance of the component to be tested to be qualified, and analyze the test anomalies in conjunction with the equivalent volume parameters to distinguish between anomalies caused by leakage of the test tooling seal and anomalies caused by leakage of the component body.

2. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, The detection gas is air or nitrogen.

3. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, The preset initial detection pressure is higher than the normal operating pressure of the component.

4. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, The pressure disturbance is a small step pressure change applied based on the initial detection pressure. The amplitude of the step pressure change is controlled within the range of 1% to 10% of the initial detection pressure. The application and removal of the pressure disturbance are completed in the same clamping and sealing state to avoid repeated clamping affecting the equivalent volume identification result.

5. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, The equivalent volume parameter is the comprehensive equivalent volume under the current clamping state, which includes the internal cavity volume of the component to be tested, the internal pipeline and valve cavity volume of the testing fixture, and the equivalent volume change corresponding to the elastic deformation of the sealing structure and clamping structure under pressure. The equivalent volume parameter is calculated by the pressure change before and after the pressure disturbance and the corresponding gas state parameters.

6. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, The compensation process includes converting the pressure change data collected during the detection time into the equivalent leakage under standard conditions based on the equivalent volume parameter, or performing equivalent volume normalization processing on the original pressure drop data to eliminate the influence of differences in the internal cavity volume of different components and changes in clamping status on the airtightness test results.

7. The method for airtightness testing of precision automotive parts according to claim 1, characterized in that, When the compensated airtightness test result is abnormal, and the abnormality is synchronous or related to the change in the equivalent volume parameter, the change in clamping force, or the change in the compression state of the seal, the abnormality is determined to be a tooling leakage abnormality caused by leakage of the sealing structure, pipeline, or valve of the testing tooling.

8. The method for airtightness testing of precision automotive parts according to claim 7, characterized in that, When the compensated airtightness test result consistently exceeds the preset qualified threshold in multiple repeated tests, and the test result is not significantly correlated with the clamping state and the change of the equivalent volume parameter, the abnormality is determined to be a component leakage abnormality caused by micro-leakage or defects in the body of the component to be tested.

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