Method for Detecting Oil Level of Hydraulic Damper and Method for Evaluating Its Remaining Life

Abstract

The present invention discloses a method for detecting the oil level of a hydraulic damper. The outer cylinder piston of the hydraulic damper includes an outer fitting portion that fits against the inner wall of the outer cylinder, an inner fitting portion that fits against the outer wall of the inner cylinder, and a ring portion that is suspended. The detection method includes the following steps: The outer cylinder cavity is sequentially divided into a first region, a second region, and a third region along its axial direction according to the position of the outer cylinder piston of the hydraulic damper. The first region extends from the end of the outer oil cavity with an elastic member to the end of the outer fitting portion away from the elastic member. The second region is the position corresponding to the ring portion. The third region extends from the end of the ring portion away from the elastic member to the end of the outer oil cavity away from the elastic member. An ultrasonic detection device is used to sequentially detect the first region, the second region, and the third region, and the position of the outer cylinder piston is judged according to the detected echo signal, and then the oil level is judged.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic dampers for nuclear power plants, and particularly relates to a method for detecting the oil level of a hydraulic damper and a method for evaluating the remaining service life of a hydraulic damper. Background Art

[0002] Hangers are the general term for the structural support and protection devices of steam-water pipelines and equipment in the power and chemical industries. Hangers can be classified into three categories according to their functions: bearing the weight of the pipeline, restricting the displacement of the pipeline, and controlling the vibration of the pipeline. Among them, the hanger device for controlling the vibration of the pipeline mainly has two functions: one is to control the steady-state vibration of the pipeline, including fixed supports, limit supports, sliding supports, guiding supports, etc. Different forms of hangers all have a certain restrictive effect on the vibration of the pipeline and equipment; the other is a transient vibration control device for preventing large displacements of the pipeline and equipment, including hydraulic dampers, anti-fall devices, etc. Among them, hydraulic dampers are the most widely used.

[0003] Hydraulic dampers are widely used as safety protection devices for steam-water pipelines and equipment in the power and chemical industries. The hydraulic damper is designed not to affect its normal thermal displacement when the pipeline and equipment slowly expand and contract due to temperature changes. However, when the pipeline and equipment are subjected to seismic waves or other transient shock conditions and produce rapid displacements, the hydraulic damper automatically locks and becomes an approximate rigid part, preventing the pipeline and equipment from causing damage to themselves or surrounding equipment due to large displacements, thereby playing a role in protecting the pipeline and equipment. Currently, the commonly used forms of hydraulic dampers are similar, and all use hydraulic oil sealed in a stainless steel cavity as the power transmission medium. The external transient impact load is transmitted through the piston and interacts with the hydraulic oil.

[0004] Common hydraulic damper structures are as Figure 1As shown in the figure, it mainly consists of an inner oil cylinder 3, an inner oil cylinder piston 4, an outer oil cylinder 7, an outer oil cylinder piston 8, a spring 10, a needle valve, a dust cover 2, a stroke indicator, a connector 1, etc. The first needle valve 61 communicates with the oil cavities on both sides of the inner oil cylinder piston 4, and the second needle valve 62 communicates with the inner oil cylinder 3 and the outer oil cylinder 7. The two connectors 1 are respectively connected to pipelines, equipment and on-site steel structures. When the pipeline or equipment undergoes slow free displacement due to temperature changes, the pressure difference on both sides of the needle valve is relatively small, and the flow rate of the hydraulic oil does not reach the locking limit value of the needle valve, so the needle valve is in the normally open state, and the oil pressure on both sides of the inner oil cylinder and between the inner oil cylinder and the outer oil cylinder is automatically balanced under the action of the spring. When the pipeline generates impact vibration, the movement of the inner oil cylinder piston causes the pressure difference between both sides of the inner oil cylinder piston and between the inner oil cylinder and the outer oil cylinder to increase. When the flow rate of the hydraulic oil flowing through the needle valve exceeds the set value, most of the needle valve passage is automatically locked, and only a very small needle hole allows the hydraulic oil to flow through, and the inner oil cylinder piston generates a strong braking force to limit the impact vibration displacement of the pipeline or equipment. When the pipeline or equipment stops vibrating, the oil pressure on both sides of the inner oil cylinder piston and between the inner oil cylinder and the outer oil cylinder slowly balances through the needle holes on the needle valve to return to the normal standby state.

[0005] The parameters of the steam-water pipelines in the power industry are relatively high, and the phenomenon of transient impact vibration occurs very frequently. Therefore, hydraulic dampers have been widely used in the steam-water pipeline systems and equipment in the power industry. When the hydraulic damper fails or its function deteriorates due to various reasons and cannot provide a strong impedance effect when the pipeline and equipment generate impact vibration, it is very likely to cause malignant accidents such as large-amplitude vibration cracking, leakage and bursting of the pipeline, and serious damage to the equipment.

[0006] Multiple seals are designed between the moving parts and non-moving parts of the hydraulic damper to prevent hydraulic oil leakage. However, after long-term operation, due to seal material aging, component wear, dust action, etc., hydraulic oil leakage often occurs. The hydraulic oil is sealed in the metal cylinder body and the internal structure is relatively complex. For the hydraulic damper in service, it is impossible to directly observe the internal oil level position and determine whether the hydraulic oil leakage has affected its anti-impact performance.

[0007] According to the design concept of the hydraulic damper, when the hydraulic damper leaks oil, the hydraulic oil in the outer oil cylinder is replenished into the inner oil cylinder at any time under the thrust of the spring. Therefore, whether it is the seal leakage of the inner oil cylinder or the outer oil cylinder, it will first ensure that the inner oil cylinder is filled with hydraulic oil until the hydraulic oil in the outer oil cylinder is replenished, so as to ensure the anti-impact performance of the hydraulic damper. Therefore, the oil level in the outer oil cylinder is the main indicator for determining whether the leaking oil damper still maintains its anti-impact performance and how long its anti-impact performance can be maintained.

[0008] According to the on-site situation, to a greater or lesser extent, there will be a certain degree of steady-state vibration in the steam-water pipeline system or equipment of the power industry during normal operation. The long-term relative movement between the moving parts and non-moving parts of the hydraulic damper, the aging and wear of seals, etc. are inevitable. Whether in a thermal power plant or a nuclear power plant, the situation of oil leakage in the hydraulic damper after long-term use is very common. In view of the situation of oil leakage in the hydraulic damper found on-site, how to know its specific oil level to evaluate whether its anti-shock performance is affected and how to estimate the remaining maintenance time of its performance have become crucial and urgent problems to be solved.

[0009] At present, there is no effective method to measure the oil level of the hydraulic damper online. Previously, some technical personnel proposed the idea of collecting the leaked hydraulic oil and then combining it with the total amount of oil injected at the initial stage of the production of the hydraulic damper to calculate the remaining oil volume inside the hydraulic damper. However, due to the harsh on-site conditions, the leaked hydraulic oil is often absorbed by dust, part of the hydraulic oil still accumulates in the dust cover after leakage, and the leakage position of the hydraulic oil cannot be accurately predicted, etc., it is impossible to accurately obtain the remaining oil volume of the hydraulic damper, nor can the oil level of the hydraulic damper be accurately inferred. Summary of the Invention

[0010] In view of this, in order to overcome the defects of the prior art and achieve the above purposes, the purpose of the present invention is to provide a method for detecting the oil level of a hydraulic damper and a method for evaluating its remaining life, which can determine the position of the piston of the outer cylinder, effectively calculate the oil leakage speed of the hydraulic damper, and then estimate the remaining life of the hydraulic damper.

[0011] To achieve the above purposes, the present invention adopts the following technical solutions:

[0012] A method for detecting the oil level of a hydraulic damper, the piston of the outer cylinder of the hydraulic damper includes an outer fitting portion that fits against the inner wall of the outer cylinder, an inner fitting portion that fits against the outer wall of the inner cylinder, and a ring portion that is suspended;

[0013] The detection method includes the following steps:

[0014] The outer cylinder cavity is sequentially divided into a first region, a second region, and a third region along its axial direction according to the position of the piston of the outer cylinder of the hydraulic damper; the first region extends from the end of the outer oil cavity with an elastic member to the end of the outer fitting portion away from the elastic member, the second region is the position corresponding to the ring portion, and the third region extends from the end of the ring portion away from the elastic member to the end of the outer oil cavity away from the elastic member;

[0015] An ultrasonic detection device is used to sequentially detect the first region, the second region, and the third region, and the position of the piston of the outer cylinder is judged according to the detected echo signal, and then the oil level in the outer cylinder cavity of the hydraulic damper is judged.

[0016] According to some preferred implementation aspects of the present invention, the echo signals corresponding to the first region are a group of equally spaced echo signals with gradually decreasing amplitudes, and the time intervals between the echoes are equal.

[0017] According to some preferred implementation aspects of the present invention, the time interval between the echoes in the echo signals corresponding to the first region is calculated by the following formula:

[0018] t1 = 2d1 / v1 (1)

[0019] Wherein, t1 is the time interval between the echo signals reflected by the inner wall surface of the outer oil cylinder, d1 is the wall thickness of the outer oil cylinder wall of the hydraulic damper, and v1 is the propagation speed of ultrasonic waves in the material of the outer oil cylinder wall.

[0020] According to some preferred implementation aspects of the present invention, the echo signals corresponding to the second region are multiple groups of equally spaced echo signals with gradually decreasing amplitudes.

[0021] According to some preferred implementation aspects of the present invention, the time interval between two groups of echo signals in the second region is calculated by the following formula:

[0022] t 12 = 2d2 / v2 (2)

[0023] Wherein, t 12 is the time interval between two groups of echo signals respectively reflected by the inner wall surface of the outer oil cylinder and the outer surface of the ring part of the outer oil cylinder piston, d2 is the distance between the inner wall surface of the outer oil cylinder and the outer surface of the ring part of the outer oil cylinder piston, and v2 is the propagation speed of ultrasonic waves in the hydraulic oil.

[0024] According to some preferred implementation aspects of the present invention, the echo signals corresponding to the third region are multiple groups of equally spaced echo signals with gradually decreasing amplitudes.

[0025] According to some preferred implementation aspects of the present invention, the time interval between two groups of echo signals in the third region is calculated by the following formula:

[0026] t 13 = 2d3 / v2 (3)

[0027] Wherein, t 13 is the time interval between two groups of echo signals respectively reflected by the inner wall surface of the outer oil cylinder and the outer surface of the inner oil cylinder wall, d3 is the distance between the inner wall surface of the outer oil cylinder and the outer surface of the inner oil cylinder wall, and v2 is the propagation speed of ultrasonic waves in the hydraulic oil.

[0028] According to some preferred implementation aspects of the present invention, the form and time interval of the ultrasonic echo signals corresponding to different regions will change to detect the specific position of the piston of the outer cylinder of the hydraulic damper, and further monitor the oil level in the outer cylinder cavity of the hydraulic damper.

[0029] The present invention also provides a method for evaluating the remaining life of a hydraulic damper, including the following steps:

[0030] 1) Establish a relationship between the total length of the outer cylinder cavity and the lengths of the first region, the second region, and the third region:

[0031] L 外 = L1 + L2 + L3 (4)

[0032] Wherein, L 外 is the total length of the outer cylinder cavity, and L1, L2, and L3 are the lengths of the first region, the second region, and the third region respectively;

[0033] 2) Divide the inner cylinder cavity into a fourth region, a fifth region, and a sixth region. Among them, the fourth region is the position corresponding to the first inner oil cavity, the fifth region is the position corresponding to the inner cylinder piston, and the sixth region is the position corresponding to the second inner oil cavity; the first inner oil cavity and the second inner oil cavity are respectively located on both sides of the inner cylinder piston, and the second inner oil cavity is communicated with the outer oil cavity;

[0034] 3) Establish a relationship between the total length of the inner cylinder cavity and the lengths of the fourth region, the fifth region, and the sixth region:

[0035] L4 = L 内 -(L5 + L6) (5)

[0036] Wherein, L 内 is the total length of the inner cylinder cavity, and L4, L5, and L6 are the lengths of the fourth region, the fifth region, and the sixth region respectively;

[0037] 4) Establish an expression for the leakage rate of the hydraulic damper:

[0038]

[0039] In the formula, V is the leakage rate of the hydraulic oil of the hydraulic damper, and the unit is mm 3 / day; S 内 is the cross-sectional area of the inner cylinder piston, and S 外 is the cross-sectional area of the outer cylinder cavity;

[0040] is the stroke indication position of the hydraulic damper at the first detection, is the position of the piston of the outer and inner cylinders of the hydraulic damper during the first detection; L26 is the stroke indication position of the hydraulic damper during the second detection, is the position of the piston of the outer and inner cylinders of the hydraulic damper during the second detection; n is the time interval between the two detections, in days;

[0041] 5) The calculation formula for the remaining life H is as follows:

[0042]

[0043] According to some preferred implementation aspects of the present invention, when the calculation result of formula (7) is positive, this value represents the remaining life days of the corresponding hydraulic damper; when the calculation result of formula (7) is zero or negative, it means that the piston of the outer cylinder of the corresponding hydraulic damper has reached the limit position at this stroke indication position, air has entered the inner cylinder, the damper has failed, and the remaining life is zero.

[0044] Due to the adoption of the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows: The detection method of the oil level of the hydraulic damper of the present invention is based on the remaining oil volume inside the damper, avoiding the situation where the measurement result cannot be accurately obtained due to harsh on-site conditions. This method detects the specific position of the piston of the outer cylinder of the hydraulic damper, and combines with the structural dimensions of the hydraulic damper to accurately calculate the remaining oil volume inside the hydraulic damper; according to the severity of the oil leakage of the hydraulic damper, multiple detections are carried out at appropriate time intervals to determine the change amount of the position of the piston of the outer cylinder, and the oil leakage speed of the hydraulic damper can be effectively calculated, and then the remaining life of the hydraulic damper can be estimated, so as to provide a reference for the online evaluation of the oil-leaking hydraulic damper, and at the same time provide a basis for the maintenance personnel to prepare a maintenance plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 is a schematic structural diagram of the hydraulic damper;

[0047] Figure 2 is a schematic diagram of the division of the first region, the second region, the third region, the fourth region, the fifth region and the sixth region in the detection method of the oil level of the hydraulic damper and the evaluation method of its remaining life in the preferred embodiment of the present invention;

[0048] Figure 3Schematic diagram of echo signals corresponding to the first region detected by the oil level detection method of the hydraulic damper in the preferred embodiment of the present invention;

[0049] Figure 4 Schematic diagram of echo signals corresponding to the second region detected by the oil level detection method of the hydraulic damper in the preferred embodiment of the present invention;

[0050] In the drawings, connector - 1, dust cover - 2, inner cylinder - 3, inner cylinder piston - 4, first inner oil cavity - 51, second inner oil cavity - 52, first needle valve - 61, second needle valve - 62, outer cylinder - 7, outer cylinder piston - 8, outer fitting part - 81, inner fitting part - 82, ring part - 83, first region - 91, second region - 92, third region - 93, fourth region - 94, fifth region - 95, sixth region - 96, spring - 10, outer oil cavity - 11. Detailed implementation manners

[0051] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] According to the Figure 1 hydraulic damper structure shown, normally, both the inner cylinder 3 and the outer cylinder 7 of the hydraulic damper are filled with hydraulic oil. When there is leakage in the hydraulic damper, the total internal oil volume decreases. Under the thrust of the spring 10, the outer cylinder piston 8 moves forward to compress the space of the outer cylinder 7, so as to ensure that the inner cylinder 3 and the outer cylinder 7 cavities are always filled with hydraulic oil until the outer cylinder piston 8 is pushed to the limit and the space of the outer cylinder 7 cannot be further compressed. If the hydraulic damper leaks further, air will enter the outer cylinder 7, resulting in a horizontal interface of the hydraulic oil in the outer cylinder 7.

[0053] Embodiment 1 Detection of the position of the outer cylinder piston of the hydraulic damper

[0054] Schematic diagram of using ultrasonic waves to detect the position of the outer cylinder piston 8 of the hydraulic damper is as Figure 2 shown. The outer cylinder piston 8 includes an outer fitting part 81 that fits with the inner wall of the outer cylinder 7, an inner fitting part 82 that fits with the outer wall of the inner cylinder 3, and a ring part 83 that is suspended.

[0055] The detection principle is as follows: The ultrasonic signal emitted by the ultrasonic probe enters the outer wall of the outer oil cylinder 7 of the hydraulic damper through the coupling agent. When the ultrasonic wave encounters the interface of different materials, part of the ultrasonic wave transmits into the next layer of material, and part of the ultrasonic wave is reflected back to the outer wall of the outer oil cylinder 7 by the interface and received by the ultrasonic probe. When the ultrasonic probe switches between Figure 2 the different regions (the first region 91, the second region 92, and the third region 93) shown, since the main reflection interface of the ultrasonic wave changes, the finally received ultrasonic waveform will also change significantly. According to the ultrasonic return time and waveform, combined with the internal component structure size of the hydraulic damper and the propagation speed of the ultrasonic wave in different materials, the specific position of the piston 8 of the outer oil cylinder of the hydraulic damper can be effectively identified, and then the oil level in the outer oil cavity 11 can be judged.

[0056] Based on the above principle, the method for detecting the oil level of the hydraulic damper in this embodiment specifically includes the following steps:

[0057] The cavity of the outer oil cylinder 7 is sequentially divided into a first region 91, a second region 92, and a third region 93 along its axial direction according to the position of the piston 8 of the outer oil cylinder of the hydraulic damper; the first region 91 extends from the end of the outer oil cavity 11 with the elastic member to the end of the outer fitting portion 81 away from the elastic member, the second region 92 is the position corresponding to the ring portion 83, and the third region 93 extends from the end of the ring portion 83 away from the elastic member to the end of the outer oil cavity 11 away from the elastic member; the ultrasonic detection device is used to detect the first region 91, the second region 92, and the third region 93 in sequence, and the position of the piston 8 of the outer oil cylinder is judged according to the detected echo signal, and then the oil level in the cavity of the outer oil cylinder 7 in the hydraulic damper is judged.

[0058] The detections in the first region 91, the second region 92, and the third region 93 are described in detail as follows:

[0059] 1) When the ultrasonic probe is located in the first region 91, since there is no hydraulic oil in this region, the ultrasonic signal cannot transmit into the air on the inner wall surface of the outer oil cylinder 7. Therefore, almost all the ultrasonic energy returns at this interface. When returning to the outer surface of the outer oil cylinder 7, part of the ultrasonic energy is received by the probe through the coupling agent, and another part of the ultrasonic energy returns from the interface between the outer surface of the outer oil cylinder 7 and the coupling agent to the inside of the outer oil cylinder 7 and generates multiple back-and-forth reflections therein until the ultrasonic energy is exhausted.

[0060] Therefore, when the ultrasonic probe is located in the first region 91, the ultrasonic probe will receive a group of gradually decaying ultrasonic echoes, and the time intervals between the echoes are equal. This time interval is the time for the ultrasonic wave to travel back and forth once in the outer oil cylinder 7 wall, and its calculation formula is shown in Equation (1).

[0061] t1 = 2d1 / v1 (1)

[0062] Among them, t1 is the time interval between the echo signals reflected by the inner wall surface of the outer oil cylinder 7, d1 is the wall thickness of the outer oil cylinder 7 of the hydraulic damper, and v1 is the propagation speed of the ultrasonic wave in the material of the outer oil cylinder 7 wall.

[0063] When the ultrasonic probe is located in the first region 91, the received echo signal is similar to Figure 3 a group of equally spaced echo signals that gradually decay as shown, and the time interval between each echo is t1.

[0064] 2) When the ultrasonic probe is located in the second region 92, since there is hydraulic oil in this region, the hydraulic oil can act as a couplant to transmit most of the ultrasonic energy into the hydraulic oil and further propagate forward. Part of the ultrasonic energy is reflected back to the outer oil cylinder 7 wall at the interface between the inner surface of the outer oil cylinder 7 wall and the hydraulic oil and dissipated after multiple reflections in it. The ultrasonic wave that enters the hydraulic oil continues to propagate forward, and part of it is reflected and part is transmitted again at the interface between the hydraulic oil and the outer surface of the outer oil cylinder piston 8 (the outer wall of the ring part 83). When the reflected part returns to the interface between the hydraulic oil and the inner surface of the outer oil cylinder 7 wall, reflection and transmission occur again, and the transmitted part enters the outer oil cylinder 7 wall and undergoes the same behavior as the part reflected at this interface for the first time and is received by the ultrasonic probe. Since the propagation speed of the ultrasonic wave in the metal medium is several times or even more than a dozen times that in the liquid medium, the ultrasonic wave reflected by the inner surface of the outer oil cylinder 7 wall has undergone multiple reflections back and forth in the outer oil cylinder 7 wall before the ultrasonic wave signal reflected by the outer surface of the outer oil cylinder piston 8 is received by the probe. Therefore, when the ultrasonic probe is located in the second region 92, in addition to the first group of equally spaced and gradually decaying echoes similar to those in the first region 91, a second group of equally spaced and gradually decaying echoes reflected by the outer surface of the outer oil cylinder piston 8 and undergoing multiple reflections in the outer oil cylinder 7 wall will be received again. The time interval calculation formula for the two groups of echoes is shown in Equation (2).

[0065] t 12 = 2d2 / v2 (2)

[0066] Among them, t 12 is the time interval between the two groups of echo signals reflected by the inner surface of the outer oil cylinder 7 wall and the outer surface of the outer oil cylinder piston 8 (the outer wall of the ring part 83) respectively, d2 is the distance between the inner surface of the outer oil cylinder 7 wall and the outer surface of the outer oil cylinder piston 8, and v2 is the propagation speed of the ultrasonic wave in the hydraulic oil.

[0067] When the ultrasonic probe is located in the second region 92, the received echo signal is similar to Figure 4 multiple groups of equally spaced and gradually decaying echoes as shown, the time interval between each echo is t2, and the time interval between each echo in the same group is t1.

[0068] 3) When the ultrasonic probe is located in the third region 93, the ultrasonic waves entering the hydraulic oil will return on the outer surface of the inner cylinder 3 wall. At this time, the propagation distance of the ultrasonic waves in the hydraulic oil is greatly increased, and the time interval between the two groups of ultrasonic echo signals is significantly increased. Its calculation formula is shown in Equation (3).

[0069] t 13 = 2d3 / v2 (3)

[0070] Where, t 13 is the time interval between the two groups of echo signals reflected by the inner surface of the outer cylinder 7 wall and the outer surface of the inner cylinder 3 wall respectively. d3 is the distance between the inner surface of the outer cylinder 7 wall and the outer surface of the inner cylinder 3 wall. v2 is the propagation speed of the ultrasonic waves in the hydraulic oil.

[0071] When the ultrasonic probe is located in the third region 93, the received echo signals are similar to those in the second region 92, and are also multiple groups of equally spaced echo signals that gradually decay. The time interval between each echo is t3, and the time interval between each echo within the same group is t1.

[0072] Through the above analysis, it can be known that the specific position of the piston 8 of the outer cylinder of the hydraulic damper can be effectively detected by the phenomenon that the form and time interval of the ultrasonic echo signals change significantly when passing through different regions, and then the oil level in the cavity of the outer cylinder 7 in the hydraulic damper can be monitored.

[0073] Example 2 Estimation of the remaining life of a leaking oil damper

[0074] In this embodiment, the method for evaluating the remaining life of the hydraulic damper includes the following steps:

[0075] 1) Establish a relational expression between the total length of the cavity of the outer cylinder 7 and the lengths of the first region 91, the second region 92, and the third region 93

[0076] According to Figure 1-2 the structural form of the hydraulic damper shown, the total length L 外 of the cavity of the outer cylinder 7 of different models of hydraulic dampers is specific, and this value can be obtained from the manufacturer. According to the position of the outer cylinder piston 8, the cavity of the outer cylinder 7 is divided into the first region 91, the second region 92, and the third region 93. The lengths of each region are respectively denoted as L1, L2, and L3. Among them, L2 is the structural dimension of the outer cylinder piston 8 and can be obtained from the manufacturer. The values of L1 and L3 change with the movement of the outer cylinder piston 8 and can be detected by the above method for detecting the position of the outer cylinder piston 8 of the hydraulic damper, and there is the following relational expression:

[0077] L 外 = L1 + L2 + L3 (4)

[0078] 2) Divide the cavity of the inner oil cylinder 3 into a fourth region 94, a fifth region 95, and a sixth region 96. Among them, the fourth region 94 corresponds to the position of the first inner oil cavity 51, the fifth region 95 corresponds to the position of the inner oil cylinder piston 4, and the sixth region 96 corresponds to the position of the second inner oil cavity 52; the first inner oil cavity 51 and the second inner oil cavity 52 are respectively located on both sides of the inner oil cylinder piston 4, and the second inner oil cavity 52 is communicated with the outer oil cavity 11. The first needle valve 61 is located in the first inner oil cavity 51 for communicating the first inner oil cavity 51 with the second inner oil cavity 52, and the second needle valve 62 is located in the second inner oil cavity 52 for communicating the second inner oil cavity 52 and the outer oil cavity 11.

[0079] According to the structural design of the hydraulic damper, the oil level of the outer oil cylinder 7 is also related to the position of the damper inner oil cylinder piston 4, that is, related to the stroke of the damper in the current state. The stroke of the hydraulic damper is indicated by the scale marks (stroke indication) on the outer surface of the outer oil cylinder 7 wall and the end face of the dust cover 2. After complete assembly, the end face of the dust cover 2 is flush with the end face of the inner oil cylinder piston 4 close to the first inner oil cavity 51, and the scale marks on the outer surface of the outer oil cylinder 7 correspond to the moving space of the piston in the inner oil cylinder 3.

[0080] When the end face of the dust cover 2 is respectively aligned with the last scale marks at both ends of the scale marks, the inner oil cylinder piston 4 also just moves to the limit positions at both ends of the inner oil cylinder 3. As Figure 2 shown, divide the cavity of the inner oil cylinder 3 into three regions: a fourth region 94, a fifth region 95, and a sixth region 96. The lengths of each region are L4, L5, and L6 respectively. Among them, L5 is the structural dimension of the inner oil cylinder piston 4 and can be obtained from the manufacturer. The values of L4 and L6 change with the movement of the inner oil cylinder piston 4 and can be obtained through the stroke indication.

[0081] 3) Establish a relational expression between the total length of the cavity of the inner oil cylinder 3 and the lengths of the fourth region 94, the fifth region 95, and the sixth region 96:

[0082] L4 = L 内 -(L5 + L6) (5)

[0083] where L 内 is the total length of the inner oil cylinder 3, which can be obtained from the manufacturer or by measuring the length of the scale marks. L6 is the stroke of the hydraulic damper.

[0084] 4) Establish an expression for the leakage oil rate of the hydraulic damper

[0085] According to the design concept of the hydraulic damper, when the inner oil cylinder 3 is filled with hydraulic oil, the impact resistance of the hydraulic damper can be ensured as long as the functions of other components do not fail. However, whether the inner oil cylinder 3 can be filled with hydraulic oil is not only related to the remaining oil volume but also related to the position of the inner oil cylinder piston 4. When the position of the inner oil cylinder piston 4 changes, L4 and L6 change. Since there is an inner oil cylinder piston rod in the fourth region 94, when L4 increases and L6 decreases, the volume of the oil storage cavity of the inner oil cylinder 3 becomes smaller, and the excess hydraulic oil is discharged to the outer oil cylinder 7. When L4 decreases and L6 increases, the volume of the oil storage cavity of the inner oil cylinder 3 becomes larger, and the hydraulic oil in the outer oil cylinder 7 is supplemented to the inner oil cylinder 3 under the thrust of the spring 10.

[0086] Based on the above analysis, estimating the remaining life of a hydraulic damper with leakage not only requires detecting the change in the position of the outer oil cylinder piston 8 but also determining the change amount of the damper stroke and the current stroke. That is, the remaining life of a leaking oil hydraulic damper is a function of the hydraulic oil leakage rate and the stroke.

[0087] Let L6 represent the stroke of the hydraulic damper, and the length L3 of the third region 93 represents the position of the outer oil cylinder piston 8. Assume that when the hydraulic damper stroke is indicated as the position of the outer oil cylinder piston 8 is at the first detection, and when the hydraulic damper stroke is indicated as the position of the outer oil cylinder piston 8 is at the second detection. If the time interval between the two detections is n days, then the expression for the hydraulic oil leakage rate of the hydraulic damper is as shown in Equation (6):

[0088]

[0089] where V is the hydraulic oil leakage rate of the hydraulic damper, with the unit of mm 3 / day. S 内 is the cross-sectional area of the inner oil cylinder piston 4 rod, and S 外 is the cross-sectional area of the cavity of the outer oil cylinder 7.

[0090] 5) The calculation formula for the remaining life H is as shown in the following formula:

[0091] When the hydraulic damper operates under the L6 stroke condition, the calculation formula for the remaining life H is as shown in Equation (7).

[0092]

[0093] When the calculation result of Equation (7) is positive, this value represents the remaining life days of the damper. When the calculation result of Equation (7) is zero or negative, it indicates that the outer oil cylinder piston 8 of the hydraulic damper has reached the limit position at this stroke, and air has entered the inner oil cylinder 3, and the damper is considered to have failed, and the remaining life is zero.

[0094] The present invention provides a method for detecting the position of the internal piston of a hydraulic damper by using ultrasonic waves, so as to assist in online analysis of whether a damper with hydraulic oil leakage still has the required shock resistance function and how long its function can be maintained. The method of the present invention is based on the remaining oil volume inside the damper, avoiding the situation where accurate measurement results cannot be obtained due to harsh on-site conditions. By detecting the specific position of the piston in the outer cylinder of the hydraulic damper and combining the structural dimensions of the hydraulic damper, the remaining oil volume inside the hydraulic damper can be accurately calculated; according to the severity of the oil leakage of the hydraulic damper, multiple detections are carried out at appropriate time intervals to determine the change amount of the position of the piston in the outer cylinder, and the oil leakage speed of the hydraulic damper can be effectively calculated, and then the remaining life of the hydraulic damper can be estimated, so as to provide a reference for online evaluation of the oil-leaking hydraulic damper and provide a basis for the maintenance personnel to prepare a maintenance plan.

[0095] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. An evaluation method for the remaining life of a hydraulic damper, characterized in that, The outer cylinder piston of the hydraulic damper includes an outer fitting portion that fits against the inner wall of the outer cylinder, an inner fitting portion that fits against the outer wall of the inner cylinder, and a ring portion that is suspended; The outer cylinder cavity is sequentially divided into a first region, a second region, and a third region along its axial direction according to the position of the outer cylinder piston of the hydraulic damper; the first region extends from the end of the outer oil cavity with the elastic member to the end of the outer fitting portion away from the elastic member, the second region is the position corresponding to the ring portion, and the third region extends from the end of the ring portion away from the elastic member to the end of the outer oil cavity away from the elastic member; An ultrasonic detection device is used to sequentially detect the first region, the second region, and the third region, and the position of the outer cylinder piston is judged according to the form and the change of the time interval of the detected echo signals, and then the oil level in the outer cylinder cavity in the hydraulic damper is judged; The evaluation method includes the following steps: 1) Establish a relational expression between the total length of the outer cylinder cavity and the lengths of the first region, the second region, and the third region: L 外 = L1 + L2 + L3 where, L 外 is the total length of the outer oil cylinder cavity, and L1, L2, and L3 are the lengths of the first region, the second region, and the third region, respectively; 2) Divide the inner cylinder cavity into a fourth region, a fifth region, and a sixth region. Among them, the fourth region is the position corresponding to the first inner oil cavity, the fifth region is the position corresponding to the inner cylinder piston, and the sixth region is the position corresponding to the second inner oil cavity; the first inner oil cavity and the second inner oil cavity are respectively located on both sides of the inner cylinder piston, and the second inner oil cavity is communicated with the outer oil cavity; 3) Establish a relational expression between the total length of the inner cylinder cavity and the lengths of the fourth region, the fifth region, and the sixth region: L4 = L 内 -(L5 + L6) Among them, L 内 is the total length of the inner oil cylinder cavity, and L4, L5, and L6 are the lengths of the fourth region, the fifth region, and the sixth region, respectively; 4) Establish an expression for the leakage oil rate of the hydraulic damper: Wherein, V is the hydraulic oil leakage rate of the hydraulic damper, with the unit of mm 3 / day; S 内 is the cross-sectional area of the piston of the inner oil cylinder, and S 外 is the cross-sectional area of the cavity of the outer oil cylinder; is the stroke indication position of the hydraulic damper during the first detection, is the position of the piston of the outer cylinder in the hydraulic damper during the first detection; is the stroke indication position of the hydraulic damper during the second detection, is the position of the piston of the outer cylinder in the hydraulic damper during the second detection; n is the time interval between the two detections, in days; 5) The calculation formula for the remaining life H is shown as follows:

2. The evaluation method according to claim 1, wherein The echo signal corresponding to the first region is a group of equally spaced echo signals that gradually decay, and the time intervals between the echoes are equal.

3. The evaluation method according to claim 2, characterized in that The time interval between the echoes in the echo signal corresponding to the first region is calculated by the following formula: t1 = 2d1 / v1 Where, t1 is the time interval between the echo signals reflected by the inner wall surface of the outer cylinder of the ultrasonic wave, d1 is the wall thickness of the outer cylinder wall of the hydraulic damper, and v1 is the propagation speed of the ultrasonic wave in the material of the outer cylinder wall.

4. The evaluation method according to claim 1, characterized in that, The echo signal corresponding to the second region is multiple groups of equally spaced echo signals that gradually decay.

5. The evaluation method according to claim 4, characterized in that The time interval between two groups of echo signals in the second region is calculated by the following formula: t 12 = 2d2 / v2 where t 12 is the time interval between two groups of echo signals respectively reflected by the inner wall surface of the outer oil cylinder and the outer surface of the ring part of the outer oil cylinder piston, d2 is the distance between the inner wall surface of the outer oil cylinder and the outer surface of the ring part of the outer oil cylinder piston, and v2 is the propagation speed of ultrasonic waves in hydraulic oil.

6. The evaluation method according to claim 1, wherein The echo signal corresponding to the third region is multiple groups of equally spaced echo signals that gradually decay.

7. The evaluation method according to claim 6, wherein The time interval between two groups of echo signals in the third region is calculated by the following formula: t 13 = 2d3 / v2 where t 13 is the time interval between two groups of echo signals reflected by the inner wall surface of the outer oil cylinder and the outer surface of the inner oil cylinder wall respectively, d3 is the distance between the inner wall surface of the outer oil cylinder and the outer surface of the inner oil cylinder wall, and v2 is the propagation speed of ultrasonic waves in hydraulic oil.

8. The evaluation method according to claim 1, characterized in that When the calculation result of the remaining life H is a positive value, this value represents the remaining life days of the corresponding hydraulic damper; when the calculation result of the remaining life H is zero or a negative value, it means that the outer cylinder piston of the corresponding hydraulic damper has reached the limit position at this stroke indication position, air has entered the inner cylinder, and the damper has failed, and the remaining life is zero.

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