JP2020186983A - Hose deterioration determination method - Google Patents

Abstract

To provide a hose deterioration determination method that can readily determine a deterioration degree of inner surface rubber of a hose with high accuracy.SOLUTION: A hose deterioration determination method is configured to: set a time required until an elongation Eb when inner surface rubber 4 fractures in a prescribed temperature condition drops to a reference elongation Ex as a life of the inner surface rubber 4 in the prescribed temperature condition; perform advance testing, grasp a correlation relationship R between lives in a plurality of temperature conditions and the temperature condition, and input the correlation relationship R to a computation unit 10; segment temperature data on a fluid F in a fluid passage 3 detected by a temperature sensor 9 into a plurality of prescribed temperature ranges; integrate a use time of the hose 2 every each temperature range by the computation unit 10; calculate a thermal aging life of the inner surface rubber 4 on the basis of each representative temperature with the representative temperature in each temperature range as the temperature condition, and the correlation relationship R; and determine a deterioration degree of the inner surface rubber 4 on the basis of a comparison of an integration use time of the hose 2 in each temperature range with a length of the thermal aging life of the inner surface rubber 4.SELECTED DRAWING: Figure 8

Description

The present invention relates to a method for determining deterioration of a hose, and more particularly to a method for determining deterioration of a hose, which can easily and accurately determine the degree of deterioration of the rubber on the inner surface of the hose.

The degree of deterioration of the outer layer of the hose can be easily determined from the outside of the hose based on its appearance and the like. However, it is difficult to grasp the degree of deterioration of the rubber on the inner surface of the hose. Therefore, a method of predicting the life of a hose by using the reference elongation at the time of the life of the hose and the estimated equivalent load temperature of the inner rubber layer of the hose at that time has been proposed (see Patent Document 1).

The estimated equivalent load temperature of the inner rubber layer used in the method proposed in Patent Document 1 is obtained from the estimated equivalent load temperature of the outer rubber layer, and the hardness data of the outer rubber layer is used to obtain this. Will be done. That is, the life is predicted by utilizing the characteristic that the rubber hardness increases according to the operating temperature and the operating time of the hose (paragraphs 0021, 0030, etc.).

However, since the rubber hardness is an index in which the measurement results are likely to vary, it is disadvantageous for improving the accuracy of life prediction. It is also difficult to accurately estimate the operating temperature from the rubber hardness and the operating time of the hose. Therefore, there is room for improvement in easily and accurately determining the degree of deterioration of the rubber on the inner surface of the hose.

Japanese Unexamined Patent Publication No. 2003-215023

An object of the present invention is to provide a method for determining deterioration of a hose, which can easily and accurately determine the degree of deterioration of the rubber on the inner surface of the hose.

In order to achieve the above object, the hose deterioration determination method of the present invention is a hose deterioration determination method using the thermal aging life of the inner rubber forming the fluid flow path of the hose and the temperature data of the fluid flowing through the fluid flow path. The time required for the elongation at break of the inner surface rubber to become equal to or less than the reference value under a predetermined temperature condition is set as the life of the inner surface rubber under the predetermined temperature condition, and the life and the said life are obtained by a preliminary test. The correlation with the temperature condition is grasped, the temperature data is divided into a plurality of predetermined temperature ranges, the usage time of the hose for each of the temperature ranges is integrated, and the representative in each of the temperature ranges. With the temperature as the temperature condition, the life calculated by each of the representative temperatures and the correlation is defined as the heat aging life at each of the representative temperatures, and the integrated usage time in each of the temperature ranges is integrated. It is characterized in that the degree of deterioration of the inner surface rubber is determined based on the calculated heat aging life in each of the temperature ranges.

According to the present invention, the correlation between the life and the temperature condition using the elongation of the inner rubber as an index is grasped by performing a preliminary test. Then, when determining the deterioration of the hose, by detecting the temperature of the fluid flowing through the fluid flow path of the hose, the detected temperature data is divided into a plurality of predetermined temperature ranges and the hose in each temperature range is determined. The lengths of the cumulative usage time of the above and the heat aging life of the inner surface rubber calculated by the representative temperature in each temperature range and the above correlation are compared. By directly using the temperature data of the fluid that greatly affects the deterioration of the inner rubber and using the life indexed by the elongation at which the deterioration state of the inner rubber directly appears, the degree of deterioration of the inner rubber can be easily and accurately determined. It becomes possible to do.

It is explanatory drawing which illustrates by cutting out a part of a hose. It is a cross-sectional view of the hose of FIG. It is explanatory drawing which illustrates the determination apparatus used in this invention. It is a graph which illustrates the relationship between the elongation of the inner surface rubber under a plurality of temperature conditions, and the elapsed time of a test. It is a graph which illustrates the correlation (heat aging life of an inner rubber) with a temperature condition (heat aging life of an inner rubber). It is a graph which illustrates the time-dependent change of the temperature data of the fluid flowing through a fluid flow path. It is a graph which illustrates the integrated use time of a hose in each temperature range. It is a graph which illustrates the cumulative use time of the hose in each temperature range, and the heat aging life of the inner rubber.

Hereinafter, a method for determining deterioration of the hose will be described based on the embodiment shown in the figure.

As illustrated in FIGS. 1 and 2, the hose 2 to be determined for deterioration according to the present invention is formed by laminating the inner surface rubber 4, the reinforcing layer 5, and the outer surface layer 6 coaxially in this order from the inner peripheral side. There is. In this embodiment, two reinforcing layers 5 are laminated, and an intermediate rubber layer 5b is laminated between the reinforcing layers 5. The inner surface rubber 4 is located on the innermost peripheral side and forms the fluid flow path 3. Since the fluid F comes into direct contact with the inner surface rubber 4, an appropriate rubber type is adopted in consideration of durability against the fluid F and the like. Examples of the fluid F include hydraulic oil, air conditioner refrigerant, and water, but are not particularly limited.

The reinforcing layer 5 is formed of a reinforcing wire 5a such as a metal wire or a fiber. In this embodiment, the reinforcing layer 5 is a blade layer formed by braiding the reinforcing wire 5a, but it may be a spiral layer in which the reinforcing wire 5a is spirally wound. The material of the reinforcing wire 5a and the number of layers of the reinforcing layer 5 are determined in consideration of the pressure resistance required for the hose 2.

The outer surface layer 6 is formed of, for example, rubber, resin, or the like. An appropriate material is adopted for the outer surface layer 6 in consideration of trauma resistance, weather resistance and the like. Other members (layers) are provided on the hose 2 as needed.

In order to determine the deterioration of the hose according to the present invention, the determination device 8 illustrated in FIG. 3 is used. The determination device 8 includes a temperature sensor 9 and a calculation unit 10. The temperature sensor 9 sequentially detects the temperature K _{f of the} fluid F flowing through the fluid flow path 3 of the hose 2. In this embodiment, the temperature sensor 9 is installed on the upstream side of the hose fitting 7.

The temperature data of the fluid F detected by the temperature sensor 9 is input to the calculation unit 10 one by one. A computer or the like is used as the calculation unit 10. The temperature sensor 9 and the calculation unit 10 are communicably connected by wire or wirelessly. By connecting the temperature sensor 9 and the calculation unit 10 in a communicable manner via a communication network such as the Internet, the temperature data of the fluid F of the hose 2 in use can be obtained regardless of the place where the hose 2 is used (installation place). It can be easily sequentially input to the calculation unit 10. In addition, various data indicating the correlation R and the like, which will be described later, are input to the calculation unit 10, and the calculation unit 10 performs various data processing. The calculation unit 10 can also be mounted on an automobile or a construction vehicle in which the hose 2 is used.

The hose assembly 1 to which the hose metal fitting 7 is attached to the end of the hose 2 is used by being attached to, for example, a part mounted on an automobile or a construction vehicle, or a part of various other devices. The hose 2 is mounted in various states depending on the space of the place of use, and may be mounted not only in a bent state as in this embodiment but also in a linear state. Further, the hose 2 is not only fixed in a constant state, but may also be attached in a movable state.

In the present invention, the deterioration state of the hose 2 is determined by paying attention to the deterioration degree of the inner surface rubber 4. Therefore, the heat aging life of the inner rubber 4 and the temperature data of the fluid F are used.

Inner rubber 4 can be regarded as the elongation E under the influence of heat changes, elongation at break Eb is when it becomes less than the reference value E _X becomes life aged impaired elasticity. Therefore, the time required for the elongation at break Eb of inner rubber 4 which is maintained at a predetermined temperature condition is less than the reference value E _X can be set as the life of the inner rubber 4 at the predetermined temperature condition.

Reference value E _X is set to a suitable value, for example, elongation at break Eb is the predetermined value between 100% or less than 30%. Specifically when setting the reference value E _X in elongation at break Eb50%, inner rubber 4 is generally appropriate to the determined elastic is impaired by life.

Therefore, in the present invention, a heat aging test of the inner surface rubber 4 is performed as a preliminary test to grasp the correlation R between the life of the inner surface rubber 4 and the temperature condition. In the preliminary test, as illustrated in FIG. 4, the elongation Eb at break of the inner surface rubber 4 is measured over time under a plurality of temperature conditions K (K1, K2, K3) to acquire data. In order to accurately grasp the heat aging life of the inner rubber 4, this temperature condition K may be set within the operating temperature range of the hose 2. The elongation Eb at break is measured according to the provisions of JIS K 6251. It is advantageous to set the temperature condition to 3 levels or more in order to accurately grasp the thermal deterioration life of the inner surface rubber 4. The acquired data is input to and stored in the calculation unit 10.

For the preliminary test, a sample of the hose 2 can be used, or a sheet sample of the inner rubber 4 can be used. When the sample of the hose 2 is used, for example, the fluid L that actually flows in the fluid flow path 3 when the hose 2 is used is heated to a predetermined temperature condition and flows through the fluid flow path 3 of the sample of the hose 2. The inner surface rubber 4 may be maintained at a predetermined temperature condition. The pressure of the fluid L flowing through the fluid flow path 3 (internal pressure of the hose) may be set to the maximum value of the specified working pressure of the hose 2. When measuring the elongation Eb at break, the measuring piece of the inner surface rubber 4 is cut out from the hose 2.

When the sheet sample of the inner surface rubber 4 is used for the preliminary test, for example, when the hose 2 is used, the fluid L actually flowing in the fluid flow path 3 is heated to a predetermined temperature condition, and the sheet sample of the inner surface rubber 4 is brought into contact with the sheet sample. It is preferable to maintain the inner surface rubber 4 at a predetermined temperature condition by (immersing). When the hose 2 is used, not only the fluid L that actually flows through the fluid flow path 3 but also a fluid equivalent to this fluid L can be used, but if this fluid L is used, the thermal deterioration life of the inner surface rubber 4 can be accurately shortened. It will be advantageous to grasp.

The data illustrated in FIG. 4 is not limited to be acquired tested until elongation at break Eb of inner rubber 4 is less than the reference value E _X. For example, it is also possible to use a calculation value data of previous short test data was accelerated deterioration in a known analysis method elongation at break Eb of inner rubber 4 becomes the reference value E _X.

In Figure 4, respectively in the conditions of temperature K1, K2, K3, time required for the elongation at break Eb of inner rubber 4 becomes the reference value E _X is in t1, t2, t3. Therefore, the life of the inner surface rubber 4 under the conditions of temperatures K1, K2, and K3 is regarded as t1, t2, and t3, respectively.

Next, the correlation R between the lifetimes t1, t2, t3 and the temperature condition K (K1, K2, K3) is grasped. Therefore, as illustrated in FIG. 5, the calculation unit 10 calculates the data illustrated in FIG. 5 by processing the data in FIG. In FIG. 5, the vertical axis is the logarithm ln (time t) of the life (t1, t2, t3) of the inner rubber 4 under each temperature condition (K1, K2, K3), and the horizontal axis is the temperature condition K (K1, K2, K1). It is plotted as the reciprocal of K3) (1 / K). Then, a straight line C connecting each plot is drawn. That is, the straight line C is acquired by the Arrhenius plot. This straight line C shows the correlation R between the life of the inner surface rubber 4 and the temperature condition K, and is data showing the heat aging life of the inner surface rubber 4. This correlation R is input to the calculation unit 10 and stored.

If the rubber type of the inner surface rubber 4, the type of the compounding agent, the compounding ratio of the rubber and each compounding agent, the manufacturing conditions (kneading conditions, vulcanization conditions, etc.) are different, the heat aging life also differs. That is, if the specifications of the inner rubber 4 are different, the heat aging life will be different. Therefore, the heat aging life is calculated by grasping the correlation R illustrated in FIG. 5 for each specification of the inner surface rubber 4.

Next, an example of the procedure for determining the deterioration of the hose 2 will be described.

As illustrated in FIG. 3, the temperature K _{f of the} fluid F flowing in the fluid flow path 3 of the hose 2 actually used is sequentially detected by the temperature sensor 9. As illustrated in FIG. 6, the detected temperature data is sequentially input and stored in the calculation unit 10. The vertical axis of FIG. 6 shows the temperature K _{f of the} fluid F, and the horizontal axis shows the usage time t of the hose 2.

The temperature K _{X in} FIG. 6 indicates the lower limit temperature to be considered when determining the deterioration of the inner surface rubber 4. If the temperature K _{f of the} fluid F is not so high, the influence on the deterioration of the inner surface rubber 4 can be ignored. Therefore, the lower limit temperature K _X is set in this way, and the temperature data lower than the lower limit temperature K _X is the deterioration of the inner surface rubber 4. It may not be used for the judgment of. The lower limit temperature K _X is set to, for example, 50 ° C., and the data of 50 ° C. or higher is used for determining the deterioration of the inner surface rubber 4. It is arbitrary to set the lower limit temperature Kx, and deterioration can be determined using all the temperature data.

Next, as illustrated in FIG. 7, the calculation unit 10 divides the input temperature data into a plurality of predetermined temperature ranges, and integrates the usage time of the hose 2 for each of the divided temperature ranges. That is, the data illustrated in FIG. 7 is calculated by processing the data in FIG. In FIG. 7, the vertical axis is the logarithm ln (time t) of the cumulative usage time t of the hose 2, and the horizontal axis is the reciprocal of the temperature K _f of the fluid F (1 / K _f ).

In FIG. 7, the temperature data is divided into n temperature ranges, and the magnitude of the temperature range of each division is the same. That is, k ₂ −k ₁ ＝ k ₃ −k ₂ ＝ ・ ・ ・ ＝ k _{n + 1} −k _n ＝ is constant. In the leftmost temperature range, the cumulative usage time t of the hose 2 is t _w1 , and in the adjacent temperature ranges, the cumulative usage time is t _w2 , t _w3 , ... t _wn . ..

The difference between the upper limit temperature and the lower limit temperature of each temperature range may be set to 2 ° C. or higher and 20 ° C. or higher. That is, the values of k ₂ −k ₁ , k ₃ −k ₂ , ..., K _{n + 1} −k _n = should be 2 ° C. or higher and 20 ° C. or lower. If this difference is less than 2 ° C, data processing becomes complicated, but improvement in the accuracy of deterioration determination of the inner rubber 4 cannot be expected so much, and if it exceeds 20 ° C, it becomes difficult to improve the accuracy of deterioration determination. ..

Next, using the correlation R grasped in advance, the representative temperature in each temperature range is set as the temperature condition K, and the heat aging life of the inner rubber 4 is determined by the calculation unit 10 by the respective representative temperatures and the correlation R. calculate. Specifically, as illustrated in FIG. 8, the heat aging life in each temperature range (representative temperature) is calculated by superimposing the data illustrated in FIG. 5 and the data illustrated in FIG.

In FIG. 8, the upper limit temperatures (k ₁ , k ₂ , k ₃ , k ₄ ... k _n ) in each temperature range are used as representative temperatures in each temperature range. In the leftmost temperature range, the heat aging life of the inner rubber 4 is t _L1 , and in the adjacent temperature ranges, the heat aging life is t _L2 , t _L3 , ... T _Ln . ..

The calculation unit 10 determines the degree of deterioration of the inner surface rubber 4 based on the cumulative usage time t of the hose 2 in each temperature range and the heat aging life in each temperature range. That is, the degree of deterioration of the inner surface rubber 4 is determined by comparing the lengths of the cumulative usage time t and the heat aging life and the length ratio of the two. Specifically, the determination life L is calculated based on the following equation (1) to determine the degree of deterioration.
Judgment life L = t _w1 / t _L1 + t _w2 / t _L2 + t _w3 / t _L3 + ... + t _wn / t _Ln (1)

Here, when the determined life L ≧ 1, it is determined that it is inappropriate to continuously use the hose 2 because the inner surface rubber 4 has already reached the end of its life due to the progress of thermal deterioration. On the other hand, when the determined life L <1, it is determined that the hose 2 can be continuously used because the inner rubber 4 has not reached the end of its life in a state where the thermal deterioration has not progressed to the allowable limit. .. That is, in each temperature range (range shown by the bar graph) in FIG. 8, it is determined that the degree of deterioration progresses as the proportion of the heat aging life indicated by the diagonal line increases.

As the representative temperature of each temperature range, not only the upper limit temperature in each temperature range but also the lower limit temperature and the intermediate temperature between the upper limit temperature and the lower limit temperature can be used. When the upper limit temperature in each temperature range is used as the representative temperature in each temperature range, the judgment life L becomes larger, so that it is considered that the thermal deterioration of the inner surface rubber 4 is further progressing. As a result, the deteriorated state of the inner surface rubber 4 is determined more severely, which is advantageous in avoiding the problem that the hose 2 in use is thermally deteriorated and becomes unusable.

As described above, if there is a device that can grasp the above-mentioned correlation R in advance by performing a preliminary test and detect the temperature K _{f of the} fluid F flowing through the fluid flow path 3 of the hose 2 to be determined. Therefore, the determination device 8 can have a very simple configuration. When determining the degree of deterioration of the hose 2, the calculation unit 10 may perform data processing using the correlation R previously grasped and the temperature data of the fluid F sequentially detected. As data processing, the length of the integrated usage time t of the hose 2 in each of the divided temperature ranges and the heat aging life of the inner surface rubber 4 calculated by the representative temperature in each temperature range and the correlation R is calculated. Just compare.

Then, in the deterioration determination, the temperature data of the fluid F, which greatly affects the deterioration of the inner surface rubber 4, is directly used, and the life with the elongation E at which the deterioration state of the inner surface rubber 4 directly appears is used as an index. Therefore, it is advantageous to easily and accurately determine the degree of deterioration of the inner surface rubber 4.

1 Hose assembly 2 Hose 3 Fluid flow path 4 Inner surface rubber 5 Reinforcing layer 5a Reinforcing wire 5b Intermediate rubber layer 6 Outer surface layer 7 Hose metal fittings 8 Judgment device 9 Temperature sensor 10 Calculation unit F Fluid

Claims (6)

A method for determining deterioration of a hose using the heat aging life of the inner rubber forming the fluid flow path of the hose and the temperature data of the fluid flowing through the fluid flow path.
The time required for the elongation at break of the inner surface rubber to fall below the reference value under a predetermined temperature condition is set as the life of the inner surface rubber under the predetermined temperature condition, and the life and the temperature condition are determined by a preliminary test. Know the correlation,
The temperature data is divided into a plurality of predetermined temperature ranges, the usage time of the hose for each temperature range is integrated, and the representative temperature in each temperature range is used as the temperature condition, and each representative temperature is used. The life calculated by the above correlation is defined as the heat aging life at each of the representative temperatures, and the integrated usage time in each of the integrated temperature ranges and the calculated heat aging in each of the temperature ranges are calculated. A method for determining deterioration of a hose, which comprises determining the degree of deterioration of the inner surface rubber based on the life. The method for determining deterioration of a hose according to claim 1, wherein the reference value is set to a predetermined value of 30% or more and 100% or less. The method for determining deterioration of a hose according to claim 1 or 2, wherein the temperature condition of the preliminary test is set within the operating temperature range of the hose. The method for determining deterioration of a hose according to any one of claims 1 to 3, wherein data of 50 ° C. or higher is used as the temperature data. The method for determining deterioration of a hose according to any one of claims 1 to 4, wherein the difference between the upper limit temperature and the lower limit temperature of each of the above temperature ranges is set to 2 ° C. or higher and 20 ° C. or lower. The method for determining deterioration of a hose according to any one of claims 1 to 5, wherein the upper limit temperature of each of the above temperature ranges is used as the representative temperature.

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