JP2013190240A - Acceleration life test system for cooling fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a life of a cooling fan in a short period.SOLUTION: An acceleration life test system comprises: vibration measurement means 100 for measuring bearing vibration of a cooling fan comprising a fan to be estimated; a vibration calculation device 200 for calculating degree of bearing damage of a bearing from the bearing vibration; and a life time calculation device 300 for calculating a life time of the fan to be estimated on the basis of the degree of the bearing damage during a plurality of acceleration life testing times different from each other calculated by the vibration calculation device 200.

Description

  The present invention relates to an accelerated life test system for a cooling fan used for an inverter or a hard disk of a personal computer.

  Electronic components mounted on electronic devices tend to increase in heat generation per unit volume year by year due to miniaturization and high-density mounting, and stabilization and longer life are important. In addition, when selecting a cooling fan for equipment by speeding up the development of new models, a life test to ensure reliability, especially a bearing life test, which is the biggest factor in cooling fan failure, is carried out efficiently in a short period of time. It is hoped to do.

Conventionally, in this type of life test, a required sample (cooling fan) is set in a thermostatic chamber, power is supplied from the outside, and the sample is rotated at a temperature higher than the operating temperature or at a rotational speed higher than the rated speed. Thus, an accelerated life test is performed in which the life is estimated by the time when the rotational speed is reduced to a required ratio.
However, in the case of a cooling fan, the accelerated life test by temperature adopts a 15 ° C. half time instead of the commonly known Arrhenius 10 ° C. half law, and the rotational speed is expressed by the following equation (1). Life estimation is performed based on this (see Non-Patent Document 1).
LogL ₅₀ = −2.02 × 10 ⁻⁶ V (1)
Here, L ₅₀ is the life (h), V is the dmN value [dm: pitch circle diameter of the bearing, N: rotational speed (min ⁻¹ )].

  Further, as a method for obtaining the remaining life of a rolling bearing, in Patent Document 1, the wear particles contained in the lubricating oil in the bearing are measured by a quantitative ferrography method to obtain an abnormal wear index. The bearing deterioration curve and the correlation curve between the abnormal wear index and the vibration acceleration of the bearing are obtained. Thus, in this document, a bearing deterioration curve based on vibration acceleration is obtained, and the life is estimated from vibration acceleration measured at two measurement points.

Japanese Patent No. 4584085

NTN Technical Review No.69 (2001)

  However, many of the cooling fans to be subjected to the life test as described above have a long life and a small fan, miniature bearings and the like are adopted as components of the cooling fan, and there is also a resin housing. For this reason, an accelerated life test cannot be performed at high temperatures. That is, in the conventional life test method, for example, in order to confirm a life of 60,000 hours at 50 ° C., a test time of 1 year or longer is required even for an accelerated life test at 90 ° C. In addition, since the bearing diameter of the miniature bearing is small, even if the number of revolutions is doubled, the acceleration time is only about 10%. Therefore, there is a problem that the life test cannot be completed in a short period of about several months. .

Furthermore, the method for estimating the life from the relationship between the abnormal wear index of the bearing and the bearing vibration acceleration must obtain a correlation with the life curve and vibration acceleration due to the abnormal wear index, and the master curve for estimating the life can be obtained in a short period of time. There was a problem that I could not find it.
Therefore, the present invention has been made paying attention to such problems, and an object thereof is to provide an accelerated life test system capable of estimating the life of a cooling fan in a short period of time.

  In order to solve the above problems, an accelerated life test system for a cooling fan according to an aspect of the present invention is an accelerated life test system that performs an accelerated life test by heating a plurality of cooling fans to a required temperature and rotating them. Vibration measuring means for measuring bearing vibration of a cooling fan including a fan under test, vibration calculating device for calculating a bearing damage degree of the bearing from the bearing vibration, and a plurality of different accelerated life tests calculated by the vibration calculating device And a life time calculating device for calculating the life time of the fan under test based on the degree of bearing damage in time.

  Here, in the accelerated life test system for a cooling fan according to an aspect of the present invention, the vibration arithmetic device passes a required frequency band from a bearing vibration waveform measured by the vibration measuring means, and the band An envelope processor that processes the waveform after passing the pass filter, and a damage degree that calculates a bearing damage level represented by a maximum value or an average value from the envelope waveform processed by the envelope processor It is preferable to have an arithmetic unit.

  Further, in the accelerated life test system for a cooling fan according to an aspect of the present invention, the life time calculation device stores a bearing damage degree calculated by the vibration calculation device and a storage device. An approximate expression calculator that formulates the relationship between the life test time and the bearing damage degree, a life determination value calculator that calculates a life determination value of the bearing damage degree from the approximate expression calculated by the approximate expression calculator, A life time calculator that calculates a life time from the determination value calculated by the life determination value calculator and the approximate expression calculated by the approximate expression calculator, and the life time calculated by the life time calculator are displayed. It is preferable to have an output indicator.

Furthermore, it is preferable that the approximate expression calculator formulates a relationship between a plurality of different life test times and bearing damage levels stored in the storage unit.
Further, it is preferable that the life determination value calculator calculates a life determination value of a bearing damage degree from an approximate expression of a cooling fan that is calculated in advance by the approximate expression calculator and whose life time is known in advance.

  According to the present invention, the bearing vibration of the cooling fan is measured, the bearing damage degree is calculated from the bearing vibration, and the life time is calculated from the bearing damage degrees at a plurality of different accelerated life test times calculated, The lifetime of the cooling fan can be estimated in a short period.

It is a block diagram explaining the system configuration | structure of one Embodiment of the accelerated life test system which concerns on 1 aspect of this invention. It is a flowchart explaining the test procedure in one Embodiment of the accelerated life test system which concerns on 1 aspect of this invention. It is explanatory drawing of the lifetime determination method in one Embodiment of the accelerated lifetime test system which concerns on 1 aspect of this invention. It is an example of the bearing vibration waveform measured at the time of an accelerated life test.

Hereinafter, an accelerated life test system according to an embodiment of the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 1, this accelerated life test system includes a cooling fan currently used as a cooling fan to be tested (hereinafter also referred to as “current fan”) and a cooling fan to be subjected to a life test (hereinafter referred to as “fan”). Vibration measuring means 100 having acceleration sensors 1a and 1b that respectively measure bearing vibrations of “fans under test” and amplifiers 2a and 2b that amplify output signals, and bearings measured by the vibration measuring means 100 The vibration calculation device 200 for determining the bearing damage degree of the bearing from the vibration waveform, and the life judgment value QL (see FIG. 3) of the cooling fan from the test time and the bearing damage degree in an appropriate accelerated life test process are obtained. A lifetime calculating unit 300 for calculating the lifetime Lt (see FIG. 3).

The vibration calculation device 200 includes bandpass filters 3 a and 3 b, envelope processing units 4 a and 4 b, and a damage level calculator 5. Envelope processor 4a, 4b extracts the high frequency vibration component resulting from a bearing from the bearing vibration waveform measured by the vibration measurement means 100, for example, it filters by 1 kHz-10 kHz band pass filters 3a, 3b. Envelope the processed waveform. The damage degree calculator 5 temporarily stores the envelope waveform, and obtains the bearing damage degree of the bearing from the stored envelope waveform. The bearing damage degree is a maximum value or a Q value obtained from the following equation (2) used for bearing diagnosis.
Q = Vrms × Vp [| (Vp / Vrms) −5 | + b] (2)
However, Vrms is the effective value of the vibration envelope waveform, Vp is the maximum value, and b is a constant.

The life time calculation device 300 includes a storage device 6, an approximate expression calculator 7, a life determination value calculator 8, a life time calculator 9, and an output display 10.
The storage device 6 stores the bearing damage degree calculated by the vibration calculation device 200 together with the test time at that time. The approximate expression calculator 7 obtains an approximate expression of the relationship from the bearing damage degree and the test time at an appropriate test time stored in the storage device 6. The life judgment value calculator 8 obtains the bearing damage degree at the life time from the approximate expression obtained by the approximate expression calculator 7. The service life calculator 9 calculates the service life from the service life determination value of the bearing damage obtained by the service life determination value calculator 8 and the approximate expression determined by the approximate expression calculator 7. The output display 10 displays the lifetime calculated by the lifetime calculator 9. The approximate expression calculator 7 is a calculator that approximates the degree of bearing damage from the respective bearing vibration waveforms of the cooling fan and the fan under test whose lifetime is known in advance, such as current fans that are already in use. The lifetime determination value calculator 8 calculates the lifetime determination value from the lifetime of the current fan whose lifetime is known in advance and its approximate expression.

Next, the procedure of the accelerated test in the accelerated life test system of the above embodiment will be described with reference to the flowchart of FIG. 2 and FIG. The life time determination method shown in FIG.
When performing an accelerated test with this accelerated life test system, first, bearing vibration is measured by the vibration measuring means 100 for a current fan and a plurality of fans under test whose lifetimes are known in advance, and the vibration calculation device 200 is measured. Thus, the initial bearing damage degree Q before the acceleration test is obtained and stored in the storage unit 6 of the life time calculation device 300 (step S1).

  Thereafter, the measured current fan and a plurality of fans under test are rotated at the rated rotation speeds at test temperatures of 80 ° C., 90 ° C., and 100 ° C., respectively (steps S2, S3, and S4). When a continuous test time has passed for an appropriate time (here, 1000 hours), each bearing vibration is measured by the vibration measuring means 100 to obtain a Q value at that time, and stored in the storage unit 6 of the lifetime calculation unit 300. Store (step S5). The vibration calculation device 200 includes a counter and a timer (not shown), and automatically obtains the Q value at set intervals. Thereafter, similarly, a Q value after an appropriate time has elapsed (2000 hours and 3000 hours in the example of the present embodiment) is obtained and stored in the storage device 6 (step S5).

  When a tendency change from the initial value appears in the obtained Q value, the acceleration time of each test temperature is converted to 50 ° C. for each of the current fan and the fan under test, and each approximate expression of the test time and the bearing damage degree Q ( The current fan (a): refer to the solid line graph shown in FIG. 3 and the fan under test (b): refer to the broken line graph shown in FIG. 3 are obtained by the approximate expression calculator 7 of the life time calculation device 300 (step S6). ).

  Next, the life judgment value QL and the life time Lt of the fan under test shown in FIG. That is, the life judgment value QL is calculated by the life judgment value calculator 8 from the obtained approximate expression (a) of the current fan and the preset life time Lo of the current fan (step S7), and the calculated life judgment value QL. The life time Lt of the fan under test is calculated by the life time calculator 9 from the approximate expression (b) of the fan under test (step S8). The calculated lifetime Lt is displayed on the output display 10 (step S9).

  FIGS. 4A to 4D show examples of bearing vibration waveforms after 3000 hours have elapsed from before the test when the acceleration test was performed at 100 ° C., respectively. As shown in these figures, it can be seen that the vibration level tends to increase with time. Here, the approximate acceleration time magnification for 50 ° C. is 2 times, 6 times, and 10 times at 80 ° C., 90 ° C., and 100 ° C. Therefore, the Q value at each test temperature (80 ° C., 90 ° C., 100 ° C.) obtained in 1000 hours is the Q value at 2000 hours, 6000 hours, and 10000 hours.

  Therefore, according to this accelerated life test system, the bearing vibration of the current fan and the fan under test is measured, the bearing damage degree (Q value) is calculated from the bearing vibration, and a plurality of different accelerated life test times calculated are calculated. By calculating the life determination value QL based on the bearing damage degree (Q value) at 1000 hours, 2000 hours, 3000 hours in the example of this embodiment and calculating the life time Lt of the fan under test, a short period of time is obtained. Thus, the life of the cooling fan (fan under test) can be estimated.

The configuration of the accelerated life test system according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the test temperature condition may be one condition, but if the test is performed under a plurality of different temperature conditions as in this embodiment, more time-converted data at 50 ° C. will yield more Q value data. improves. Further, although FIG. 3 shows an example in which data from one current fan is compared, if it is used as an example in which data measured by a plurality of units is compared, a lifetime in consideration of the range of variation can be obtained.

In the example of the present embodiment, the approximate expression is obtained from the degree of bearing damage obtained at a required interval. However, the approximate expression may be obtained from the degree of bearing damage obtained continuously, or a bearing obtained for a certain period. An approximate expression may be obtained from the average value of the degree of damage. As a result, a more accurate approximate expression for the test time and the bearing damage degree Q can be obtained.
In addition, when the life judgment value QL is known in advance based on the current fan, it is needless to say that an approximate expression may be obtained only for the fan under test.

1a, 1b... Acceleration sensors 2a, 2b... Amplifiers 3a, 3b... Band pass filters 4a, 4b. ································································································································· ... Vibration measuring means 200 ... Vibration calculation device 300 ... Life time calculation device

Claims (5)

An accelerated life test system for performing an accelerated life test by heating and rotating a plurality of cooling fans to a required temperature,
Vibration measurement means for measuring bearing vibration of a cooling fan including a fan under test, vibration calculation device for calculating a bearing damage degree of the bearing from the bearing vibration, and a plurality of different accelerated life test times calculated by the vibration calculation device An accelerated life test system for a cooling fan, comprising a life time calculation device for calculating the life time of a fan under test based on the degree of bearing damage at   The vibration calculation device includes a bandpass filter that passes a required frequency band from a bearing vibration waveform measured by the vibration measuring unit, an envelope processor that performs an envelope process on the waveform after the bandpass filter, The acceleration of the cooling fan according to claim 1, further comprising a damage degree calculator for calculating a bearing damage degree represented by a maximum value or an average value from an envelope waveform processed by the envelope processor. Life test system.   The life time calculation device is a storage device that stores the bearing damage degree calculated by the vibration operation device, and an approximate expression calculation that formulates the relationship between the life test time and the bearing damage degree stored in the storage device. A life determination value calculator that calculates a life determination value of the bearing damage degree from the approximate expression calculated by the approximate expression calculator, a determination value calculated by the life determination value calculator, and the approximate expression calculator The life time calculator that calculates the life time from the calculated approximate expression, and the output display that displays the life time calculated by the life time calculator are provided. Cooling fan accelerated life test system.   4. The accelerated life test system for a cooling fan according to claim 3, wherein the approximate expression calculator formulates a relationship between a plurality of different life test times stored in the storage device and a degree of bearing damage.   The said life determination value calculator calculates the life determination value of a bearing damage degree from the approximate expression of the cooling fan by which the life time is known beforehand calculated by the said approximate expression calculator. Cooling fan accelerated life test system.

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