Threshold value conversion test device and method for internal leakage detection of hydraulic element

Abstract

The invention belongs to the technical field of hydraulic element internal leakage detection, and discloses a threshold conversion test device and method for hydraulic element internal leakage detection, and the device comprises a test loop and a tested hydraulic element. The test loop comprises an oil tank, a hydraulic pump, an overflow valve, a second stop valve and a pressure sensor, a temperature control module is arranged in the oil tank, one end of the hydraulic pump is connected with the oil tank, the other end is connected with the overflow valve and the second stop valve, and one end of the second stop valve away from the hydraulic pump is connected with a tested hydraulic element; a gas cylinder is connected in a connecting pipeline between the hydraulic pump and the second stop valve, a gas content detector is connected in a connecting pipeline between the gas cylinder and the second stop valve, and a pressure sensor is arranged in a connecting pipeline between the second stop valve and the tested hydraulic element. According to the threshold conversion technical scheme provided by the invention, whether the internal leakage test of the tested hydraulic element is qualified or not can be intuitively judged, the time cost can be greatly saved, and the test error is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic component internal leakage detection, and in particular relates to a threshold conversion test device and method for hydraulic component internal leakage detection. Background Art

[0002] Hydraulic transmission systems are widely used in various fields of manufacturing due to their unique advantages. Hydraulic cylinders, hydraulic valves and other key components are the "lifeline" of the entire hydraulic system, and their reliability directly affects the working performance of the entire system. Internal leakage is one of the common faults of hydraulic components, which will cause the system working pressure to drop, the actuator to malfunction, and even fail to work properly, resulting in downtime and increasing maintenance costs. Therefore, the detection of internal leakage faults is particularly important.

[0003] Internal leakage detection is a mandatory test item in the factory test items of key hydraulic components such as hydraulic cylinders and hydraulic valves. According to relevant standards, the test method adopts the measuring cup test method. The detection process of this method is cumbersome and inefficient. When the internal leakage is small, the oil will adhere to the wall surface, seriously affecting the accuracy of the measurement results. The data-driven method mainly uses various monitoring signals such as pressure, displacement, vibration, acoustic emission, etc. to further obtain feature quantities, and input these features into the classifier to identify each type of leakage fault. This method has high detection accuracy but requires a large amount of fault data and complex optimization calculations. It is not suitable for rapid screening of internal leakage faults of hydraulic components. The pressure signal is simple and easy to measure during the test, and a small internal leakage will cause a change in pressure. Therefore, it is feasible to use the pressure drop signal to judge whether the internal leakage of the test component is qualified or not. This method is also mentioned and allowed in relevant industry standards, but it does not specify how to convert the standard threshold of internal leakage to the pressure drop threshold, and lacks theoretical verification of effectiveness. Summary of the invention

[0004] The purpose of the present invention is to provide a threshold conversion test device and method for detecting internal leakage of hydraulic components, so as to solve the problems existing in the above-mentioned prior art.

[0005] On the one hand, to achieve the above-mentioned object, the present invention provides a threshold conversion test device for detecting internal leakage of a hydraulic component, comprising a test circuit and a tested hydraulic component;

[0006] The test circuit includes an oil tank, a hydraulic pump, an overflow valve, a second stop valve and a pressure sensor. A temperature control module is arranged in the oil tank. One end of the hydraulic pump is connected to the oil tank, and the other end is respectively connected to the overflow valve and the second stop valve. The end of the second stop valve away from the hydraulic pump is connected to the tested hydraulic element. A gas cylinder is connected to the connecting pipeline between the hydraulic pump and the second stop valve, a gas content detector is connected to the connecting pipeline between the gas cylinder and the second stop valve, and a pressure sensor is arranged in the connecting pipeline between the second stop valve and the tested hydraulic element.

[0007] Optionally, a motor is also included, and the hydraulic pump is drivingly connected to the motor.

[0008] Optionally, the hydraulic pump is a plunger pump.

[0009] Optionally, a first stop valve is installed at the gas outlet of the gas cylinder.

[0010] Optionally, a measuring cup is placed below the oil outlet of the tested hydraulic component.

[0011] Optionally, the gas content detector adopts a CGS gas concentration detection system.

[0012] On the other hand, in order to achieve the above-mentioned purpose, the present invention provides a threshold conversion method for detecting internal leakage of a hydraulic component, which is applied to a threshold conversion test device for detecting internal leakage of a hydraulic component, comprising:

[0013] Step 1: Conduct internal leakage detection on the test circuit;

[0014] Step 2: setting the test scheme under different working conditions, the working conditions including pressure, temperature and gas content;

[0015] Step 3: Install the tested hydraulic component into the test circuit, perform a pressure holding test based on each of the test schemes, and record the test change curve data corresponding to each of the test schemes, wherein the test change curve data includes pressure-time change curve data and internal leakage volume-time change curve data;

[0016] Step 4: performing rate processing on the test change curve data corresponding to each of the test schemes to obtain rate curve data, wherein the rate curve data includes pressure drop rate-time change curve data and internal leakage amount-time change curve data;

[0017] Step 5: Combining the pressure drop rate-time change curve data and the internal leakage amount-time change curve data and performing polynomial fitting to obtain a pressure drop rate-internal leakage amount polynomial equation;

[0018] Step 6: Substitute the standard internal leakage threshold corresponding to each of the test schemes into the pressure drop rate-internal leakage polynomial equation to obtain the pressure drop threshold corresponding to each of the test schemes.

[0019] Optionally, a pressure holding test is performed, including:

[0020] The temperature control module controls the oil in the oil tank to reach the preset temperature based on the PID control algorithm;

[0021] The hydraulic pump driven by the motor provides power oil to the test circuit;

[0022] Based on the preset gas content, the first stop valve is opened to allow the gas cylinder to inflate the test circuit;

[0023] The pressure in the test circuit is collected in real time through the pressure sensor;

[0024] When the pressure reaches the preset pressure threshold, the second stop valve is closed, the test time is set, and the pressure holding test is performed;

[0025] The pressure-time variation curve data of the oil inlet of the tested hydraulic component within the set test time is measured by a pressure sensor, and the internal leakage volume at different times is recorded by a measuring cup. The internal leakage volume-time variation curve data is obtained based on the recorded internal leakage volume.

[0026] The technical effects of the present invention are:

[0027] The present invention designs a test device for detecting pressure changes and internal leakage volumes under different working conditions, which can simultaneously collect real-time data of pressure and internal leakage volume, and can simulate different working conditions through the gas content control module and the temperature control module, and can be applied to various types of tested hydraulic components, with strong versatility. Further, the pressure and internal leakage volume data are rate-calculated by the proposed method, and the corresponding mapping relationship between the internal leakage threshold and the pressure drop threshold is identified by setting a standard internal leakage threshold and performing conversion calculation, and the pressure drop threshold under different working conditions is further obtained. The pressure drop threshold can be used to intuitively judge whether the internal leakage test of the tested hydraulic component is qualified, which can greatly save time cost and reduce test errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1 This is a schematic diagram of a multi-operating-condition internal leakage simulation test bench in an embodiment of the present invention;

[0031] Figure 2 It is a flow chart of the internal leakage threshold-pressure drop threshold conversion steps in an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the internal leakage simulation test pressure-time and internal leakage volume-time variation curves in the embodiment of the present invention; wherein, Figure 3 (a) is a schematic diagram of a pressure-time variation curve in an embodiment of the present invention, Figure 3 (b) is a schematic diagram of the internal leakage volume-time variation curve in an embodiment of the present invention;

[0033] Figure 4 It is a schematic diagram of the pressure drop rate-time and internal leakage amount-time variation curves of the internal leakage simulation test in the embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of a pressure drop rate-time variation curve in an embodiment of the present invention, Figure 4 (b) is a schematic diagram of the internal leakage amount-time variation curve in an embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the internal leakage threshold-pressure drop threshold conversion process in an embodiment of the present invention;

[0035] Explanation of reference numerals: 1. Overflow valve; 2. Hydraulic pump; 3. Motor; 4. First stop valve; 5. Gas cylinder; 6. Gas content detector; 7. Temperature control module; 8. Second stop valve; 9. Pressure sensor; 10. Tested hydraulic element; 11. Measuring cup. DETAILED DESCRIPTION

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0039] The words “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0040] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] Embodiment 1

[0042] like Figure 1 - Figure 5 As shown, in this embodiment, a threshold conversion test device for detecting internal leakage of a hydraulic component is provided, comprising a test circuit and a hydraulic component 10 to be tested; the test circuit comprises an oil tank, a hydraulic pump 2, an overflow valve 1, a second stop valve 8 and a pressure sensor 9, a temperature control module 7 is arranged in the oil tank, one end of the hydraulic pump 2 is connected to the oil tank, and the other end is respectively connected to the overflow valve 1 and the second stop valve 8, and the end of the second stop valve 8 away from the hydraulic pump 2 is connected to the hydraulic component 10 to be tested; a gas cylinder 5 is connected to the connecting pipeline between the hydraulic pump 2 and the second stop valve 8, a gas content detector 6 is connected to the connecting pipeline between the gas cylinder 5 and the second stop valve 8, and a pressure sensor 9 is arranged in the connecting pipeline between the second stop valve 8 and the hydraulic component 10 to be tested.

[0043] On the other hand, a threshold conversion method for detecting internal leakage of a hydraulic component is provided, which is applied to a threshold conversion test device for detecting internal leakage of a hydraulic component, and comprises:

[0044] Conduct leak detection on the test circuit;

[0045] Setting test plans under different working conditions, including pressure, temperature and gas content;

[0046] The tested hydraulic element 10 is installed in the test circuit, and a pressure holding test is performed based on each of the test schemes, and the test change curve data corresponding to each of the test schemes is recorded, wherein the test change curve data includes pressure-time change curve data and internal leakage volume-time change curve data;

[0047] Performing rate processing on the test change curve data corresponding to each of the test schemes to obtain rate-based curve data, wherein the rate-based curve data includes pressure drop rate-time change curve data and internal leakage amount-time change curve data;

[0048] The pressure drop rate-time variation curve data and the internal leakage amount-time variation curve data are combined and polynomially fitted to obtain a pressure drop rate-internal leakage amount polynomial equation;

[0049] The standard internal leakage threshold corresponding to each of the test schemes is substituted into the pressure drop rate-internal leakage polynomial equation to obtain the pressure drop threshold corresponding to each of the test schemes.

[0050] The purpose of this embodiment is to address the shortcomings of the current commonly used hydraulic component internal leakage detection technology, and to propose a threshold conversion method and test device for hydraulic component internal leakage detection. The method designs a test device for detecting pressure changes and internal leakage under different working conditions, which can simultaneously collect real-time data of pressure and internal leakage. Further, the pressure and internal leakage data are calculated at a rate by the proposed method, and the corresponding mapping relationship from the internal leakage threshold to the pressure drop threshold is identified by setting a standard internal leakage threshold and performing a conversion calculation, and the pressure drop threshold under different working conditions is further obtained. The pressure drop threshold can be used to intuitively determine whether the internal leakage test of the tested hydraulic component 10 is qualified, which can greatly save time cost and reduce test errors.

[0051] like Figure 1 As shown, this embodiment provides a multi-condition internal leakage simulation test bench for a threshold conversion method suitable for hydraulic component internal leakage detection, comprising:

[0052] Oil tank, overflow valve 1, hydraulic pump 2, motor 3, first stop valve 4, gas cylinder 5, gas content detector 6, temperature control module 7, second stop valve 8, pressure sensor 9, tested hydraulic element 10, measuring cup 11.

[0053] The oil tank is used to provide the hydraulic oil required for work and also serves as a storage container for the return oil;

[0054] A first stop valve 4, one end of which is connected to the oil outlet of the hydraulic pump 2 and the other end of which is connected to the gas cylinder 5, for controlling the gas content in the oil;

[0055] The gas content detector 6 is connected to the main oil circuit through a pipeline connector and is used to measure the gas content in the oil.

[0056] The temperature control module 7 is connected to the outlet of the oil tank through a pipeline connector, wherein a temperature sensor is arranged in the oil tank for measuring the temperature of the oil.

[0057] A second stop valve 8, one end of which forms a passage with the main oil circuit, and the other end of which is connected to a pressure sensor 9;

[0058] The pressure sensor 9 is installed on the circuit formed by the oil outlet of the second stop valve 8 and the oil inlet of the tested hydraulic element 10, and is used to detect the pressure of the tested hydraulic element 10 during the test;

[0059] One end of the hydraulic pump 2 is connected to the oil tank, and the other end is coaxially connected to the motor 3. The oil inlets of the second stop valve 8 and the first stop valve 4 are connected to the oil outlet of the hydraulic pump 2. At the same time, the oil outlet of the hydraulic pump 2 is connected to the overflow valve 1, and the inlet of the first stop valve 4 is connected to the outlet of the gas cylinder 5. The gas content detector 6 is connected to the passage formed by the hydraulic pump 2 and the second stop valve 8 through a pipe joint. The temperature control module 7 is connected to the oil tank. The temperature control module 7 may specifically include a high-precision temperature sensor, a controller, and a heat sink, wherein the temperature sensor is arranged in the oil tank. The pressure sensor 9 is arranged on the passage formed by the oil outlet of the second stop valve 8 and the oil inlet of the tested hydraulic element 10, and a measuring cup 11 is placed below the oil outlet of the tested hydraulic element 10.

[0060] In this specific embodiment, the hydraulic pump 2 may preferably be a plunger pump, the motor 3 may be a servo motor 3, the gas content detector 6 may preferably be a CGS gas concentration detection system, and the controller in the temperature control module 7 may adopt PID control.

[0061] PID control forms a control deviation based on the oil temperature value and the actual oil temperature value, and forms a control amount through linear combination of the deviation in proportion, integration and differentiation to control the oil temperature. Among them, proportional control reacts quickly and can respond to the deviation immediately, but using it alone may cause steady-state errors in the system. Integral control can eliminate steady-state errors and improve accuracy. When the temperature approaches the set value, the differential control will adjust the control amount according to the rate of temperature change. If the temperature rises too quickly, the differential control will generate a negative control amount to reduce the power of the heating equipment to prevent the temperature from rising excessively and exceeding the set value.

[0062] The hydraulic pump 2 is driven by the motor 3 to provide power oil to the tested hydraulic component 10 when performing the test items.

[0063] When the first stop valve 4 is in an open state, the gas cylinder 5 can inflate the test circuit to change the gas content in the hydraulic oil. When the first stop valve 4 is closed, the gas source is cut off.

[0064] In the temperature control module 7, the temperature sensor is used to monitor the temperature of the hydraulic oil in real time. When the temperature is lower than the target temperature, the oil is heated by the heater. When the temperature is higher than the target temperature, the radiator is activated to lower the oil temperature. The heat dissipation method can be air convection heat dissipation.

[0065] When the main oil circuit reaches the specified test pressure, the second stop valve 8 closes the main oil circuit to achieve the pressure-maintaining test process for the tested hydraulic component 10 .

[0066] The measuring cup 11 is used to collect the oil generated by the leakage in the tested hydraulic element 10 .

[0067] The threshold conversion method for detecting internal leakage of hydraulic components, the conversion step flow chart is as follows Figure 2 As shown, the specific steps include:

[0068] Step 1: In order to eliminate the interference of internal leakage of other components in the system, it is necessary to conduct a visual inspection before conducting the hydraulic cylinder internal leakage test to eliminate external and internal leakage at each component and pipe joint. The internal leakage simulation test can be carried out only if there is no obvious external or internal leakage after inspection.

[0069] Step 2: Determine the test plan and set the test levels for different working conditions (pressure, temperature and gas content).

[0070] Step 3: Install the tested hydraulic element 10 into the test circuit, pressurize the test circuit to the predetermined test pressure level in turn, and start the pressure holding test. The duration of the pressure holding test is T. The internal leakage volume data corresponding to the pressure change within the time T is measured and recorded by the oil drop method. Specifically, the pressure change curve of the working chamber within the time T is measured by the pressure sensor 9, and the internal leakage volume at different times is recorded by the measuring cup 11. For the collected data, the data points of the internal leakage volume are relatively sparse, so the polynomial fitting and interpolation methods are used to expand the data points. After expansion, the internal leakage volume-time change curve is constructed. The pressure-time and internal leakage volume-time change curves are as follows: Figure 3 shown.

[0071] Step 4: Change different operating conditions (pressure, temperature, gas content, etc.) and repeat the test multiple times.

[0072] Step 5: After all the tests are completed, data processing is performed to convert the pressure-time and internal leakage volume-time change curves into rate curves, as shown below: Figure 4 The pressure drop rate-time and internal leakage volume-time curves are shown. For the data heterogeneity problem faced by high-frequency pressure data and low-frequency internal leakage volume data, the frequency of the internal leakage volume data is increased by using polynomial fitting and interpolation methods.

[0073] Step 6: Figure 4 The pressure drop rate and internal leakage are combined to obtain Figure 5The pressure drop rate-internal leakage rate relationship curve shown in the figure is fitted to obtain a polynomial equation of pressure drop rate-internal leakage. Substituting the internal leakage threshold determined by the relevant standards into the above pressure drop rate-internal leakage rate equation, the pressure drop threshold under the corresponding working condition can be obtained in the form shown in Table 1, which can be used intuitively to judge whether the internal leakage test under different working conditions is qualified.

[0074] Table 1 Pressure drop thresholds under different working conditions

[0075]

[0076]

[0077] The multi-working condition internal leakage simulation test bench proposed in this embodiment can simultaneously complete the measurement of the pressure and internal leakage volume of the tested hydraulic component during the pressure holding test, improve the efficiency and accuracy of the test, and can simulate different working conditions through the gas content control module and the temperature control module. The pressure drop threshold under all working conditions can be obtained through the conversion method and test bench involved in this embodiment, which can be applied to various types of tested hydraulic components and has strong versatility.

[0078] The internal leakage amount-pressure drop threshold conversion method involved in this embodiment is not only applicable to the threshold conversion between internal leakage amount and pressure drop, but also can be applied to the conversion process of other difficult-to-measure-easy-to-measure key parameters. It is simple, intuitive and practical. Further, the method can be extended to the internal leakage detection process of other liquid medium components, enriching and developing the internal leakage detection method of hydraulic / hydraulic component equipment, and improving the reliability and intelligent operation and maintenance capabilities of hydraulic / hydraulic component equipment.

[0079] This embodiment proposes a polynomial fitting and interpolation method to solve the heterogeneous problem of time series mismatch between high-frequency pressure data and low-frequency internal leakage volume data, which can make up for the defect of sparse internal leakage volume data and improve the accuracy of the test.

[0080] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A threshold conversion test device for detecting internal leakage of hydraulic components, characterized in that: It includes a test circuit and a hydraulic component to be tested (10); The test circuit comprises an oil tank, a hydraulic pump (2), a relief valve (1), a second stop valve (8) and a pressure sensor (9); a temperature control module (7) is arranged in the oil tank; one end of the hydraulic pump (2) is connected to the oil tank, and the other end is respectively connected to the relief valve (1) and the second stop valve (8); the end of the second stop valve (8) away from the hydraulic pump (2) is connected to the tested hydraulic element (10); a gas cylinder (5) is connected to the connecting pipeline between the hydraulic pump (2) and the second stop valve (8); a gas content detector (6) is connected to the connecting pipeline between the gas cylinder (5) and the second stop valve (8); and a pressure sensor (9) is arranged in the connecting pipeline between the second stop valve (8) and the tested hydraulic element (10).

2. A threshold conversion test device for detecting internal leakage of hydraulic components according to claim 1, characterized in that: It also includes a motor (3), and the hydraulic pump (2) is drivingly connected to the motor (3).

3. A threshold conversion test device for detecting internal leakage of hydraulic components according to claim 1, characterized in that: The hydraulic pump (2) is a plunger pump.

4. A threshold conversion test device for detecting internal leakage of hydraulic components according to claim 1, characterized in that: A first stop valve (4) is installed at the gas outlet of the gas cylinder (5).

5. A threshold conversion test device for detecting internal leakage of hydraulic components according to claim 1, characterized in that: A measuring cup (11) is placed below the oil outlet of the tested hydraulic element (10).

6. A threshold conversion test device for detecting internal leakage of hydraulic components according to claim 1, characterized in that: The gas content detector (6) adopts a CGS gas concentration content detection system.

7. A threshold conversion method for detecting internal leakage of a hydraulic component, applied to a threshold conversion test device for detecting internal leakage of a hydraulic component as claimed in any one of claims 1 to 6, characterized in that: include: Step 1: Conduct internal leakage detection on the test circuit; Step 2: setting the test scheme under different working conditions, the working conditions including pressure, temperature and gas content; Step 3: installing the tested hydraulic element (10) into the test circuit, performing a pressure holding test based on each of the test schemes, and recording test change curve data corresponding to each of the test schemes, wherein the test change curve data includes pressure-time change curve data and internal leakage volume-time change curve data; Step 4: performing rate processing on the test change curve data corresponding to each of the test schemes to obtain rate curve data, wherein the rate curve data includes pressure drop rate-time change curve data and internal leakage amount-time change curve data; Step 5: Combining the pressure drop rate-time change curve data and the internal leakage amount-time change curve data and performing polynomial fitting to obtain a pressure drop rate-internal leakage amount polynomial equation; Step 6: Substitute the standard internal leakage threshold corresponding to each of the test schemes into the pressure drop rate-internal leakage polynomial equation to obtain the pressure drop threshold corresponding to each of the test schemes.

8. A threshold conversion method for detecting internal leakage of hydraulic components according to claim 7, characterized in that: Carry out pressure holding test, including: The temperature control module (7) controls the oil in the oil tank to reach a preset temperature based on a PID control algorithm; The hydraulic pump (2) is driven by the motor (3) to supply power oil to the test circuit; Based on the preset gas content, the first stop valve (4) is opened to allow the gas cylinder (5) to inflate the test circuit; The pressure in the test circuit is collected in real time by means of a pressure sensor (9); When the pressure reaches a preset pressure threshold, the second stop valve (8) is closed, the test time is set, and a pressure holding test is performed; The pressure-time variation curve data of the oil inlet of the tested hydraulic element (10) within the set test time is measured by a pressure sensor (9), and the internal leakage volume at different times is recorded by a measuring cup (11), and the internal leakage volume-time variation curve data is constructed based on the recorded internal leakage volume.

Images