JP2013026201A - Binding force inspection method of battery stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binding force inspection method which allows for accurate measurement of the binding force of a restraint band without disassembling a battery stack (nondestructively).SOLUTION: The binding force inspection method of a battery stack inspecting the binding force of a restraint band in a battery stack including a laminate of a plurality of electric cells, a pair of end plates located at both ends of the laminate, and a restraint band which is attached to the pair of end plates in order to restrain the laminate, includes an acquisition step for acquiring a vibration frequency by vibrating the laminate, and a step for determining the binding force by the restraint band based on the acquisition results in the acquisition step.

Description

  The present invention relates to a restraint force inspection method for inspecting a restraint force of a restraint band in a battery stack obtained by restraining a stacked body in which a plurality of unit cells are stacked by restraint bands.

  Conventionally, for example, in an electric vehicle, a battery stack is used as a power source for driving a motor. This battery stack is configured by alternately laminating a plurality of single cells and spacer members, and arranging a pair of end plates at both ends of the laminate. The laminate is restrained by a restraining band attached to the end plate. Since a single battery as a lithium ion battery can obtain a desired output by pressurizing at a certain pressure or higher, it is very important to inspect the restraint force by the restraint band.

  Patent Document 1 discloses a technique for measuring and inspecting a restraining force by a restraining band in a non-destructive manner by simply applying vibration to the restraining band and measuring the vibration state.

JP 2007-305320 A

  However, in the measurement method of Patent Document 1, in order to measure the restraining force of the restraining band based on the vibration frequency obtained by exciting the restraining band, other components, that is, the single cell, the spacer member, and the end plate are used. As a result, the restraining force of the restraining band could not be measured accurately. Specifically, when the present applicant conducted an experiment, the relationship between the frequency and the restraining force indicates that the restraining force curve of the restraining band according to the measurement method of Patent Document 1 is different from the actual restraining force curve of the restraining band. It was largely off. In particular, regarding the measurement of a large restraint force, the relation of the restraint force with respect to the frequency was measured higher than the actual restraint force in the measurement method described in Patent Document 1. Thus, when the measured value is higher than the actual restraining force, the restraining force may actually be smaller than the predetermined restraining force even when it is determined that the measured value is higher than the predetermined restraining force.

  Accordingly, the present invention provides a restraint force inspection method capable of accurately measuring the restraint force by the restraint band without disassembling the battery stack (by nondestructive).

In order to solve the above-mentioned problem, a binding force inspection method according to the present invention includes a laminate formed by laminating a plurality of single cells, a pair of end plates located at both ends of the laminate, and the pair of end plates. A battery stack restraint force inspection method for inspecting the restraint force of the restraint band in a battery stack provided with a restraint band restraining the laminate by being attached,
The method includes an acquisition step of vibrating the laminate to acquire a vibration frequency, and a determination step of determining a binding force by the binding band based on an acquisition result of the acquisition step.

  According to the present invention, it is possible to accurately measure the restraining force by the restraining band without disassembling the battery stack (by nondestructive).

It is a perspective view of a battery stack. It is a disassembled perspective view of a battery stack. It is the schematic of the inspection method in 1st Embodiment of this invention. It is a control flowchart in the restraint force inspection method of the present invention. It is the relationship figure which showed the relationship between a load and a frequency. It is a modeling figure in a battery stack. It is the relationship figure which showed the relationship between the load in a restraint band and a laminated body, and a frequency.

(First embodiment)
Hereinafter, an embodiment of a restraint force inspection method for restraint bands in the battery stack of the present invention will be described. Here, FIG. 1 is a perspective view of the battery stack, and FIG. 2 is an exploded perspective view of the battery stack. The arrows in FIG. 1 indicate the intake direction and the exhaust direction. In FIG. 2, the intake chamber, the exhaust chamber, and the restraining band are omitted.

  As shown in FIG. 1, the battery stack 1 includes a bottom plate 11, a stacked body 12 placed on the bottom plate 11 in two rows, an intake chamber 13 that sucks air from one side surface of the stacked body 12, The exhaust chamber 14 exhausts the air sucked into the laminate 12 by the intake chamber 13 from the side facing the mounting surface of the intake chamber 13, and the restraining band 15 that restrains the upper and lower peripheries of each laminate 12.

  As shown in FIG. 2, the stacked body 12 is formed by alternately stacking a plurality of single cells 121 and a plurality of spacer members 122 in the x-axis direction and sandwiching the end portions in the stacking direction by end plates 123. Here, the unit cell 121 is a lithium ion battery and houses a power generation element therein. On the upper end surface side of the unit cell 121, a positive electrode terminal and a negative electrode terminal are provided side by side in the Y-axis direction. The unit cells 121 adjacent in the X-axis direction are connected in series via a bus bar (not shown).

  The restraint band 15 extends in the X-axis direction along the upper end surface and the lower end surface of the battery stack 1, and both end portions thereof are bent downward. By fixing the bent portion to the end plate 123, the pair of end plates 123 are pressurized in a direction approaching each other. The restraint bands 15 are attached to a total of four places at four corners in the YZ section of the end plate 123. Thus, the laminated body 12 is compressed by restraining the four corners of the end plate 123 with the restraining band 15. Thereby, the performance in the stacked unit cells 121 can be maintained. Here, the restraining force of each restraining band 15 on the battery stack 1 is set so as to have a necessary and sufficient restraining force (design value) for the laminate 12 by a restraining band tightening device (not shown).

  If the laminate 12 is restrained with a restraining force lower than the necessary and sufficient restraining force, there is a possibility that desired input / output characteristics of the unit cell 121 cannot be obtained. Therefore, it is necessary to confirm whether the laminated body 12 is restrained with a predetermined restraining force.

  Therefore, a measurement method for inspecting the restraining force of the restraining band 15 will be described below.

  In FIG. 3, the conceptual diagram about the measuring method of 1st Embodiment is shown. This measuring apparatus is an apparatus based on a measuring method using a hammering method, and includes an impact hammer 2 for hammering (striking) the laminated body 12 and an actuator driving device (not used) for driving the impact hammer 2. And an acceleration pick 3 for measuring the frequency of the vibration waveform indicating the vibration state of the laminated body 12, and a frequency analysis device 4 for analyzing the frequency based on the measurement result of the acceleration pick 3. In addition, by driving the impact hammer 2 with an actuator driving device, it is possible to always hit the laminate 12 with a predetermined force.

  FIG. 4 is a flowchart showing the binding force inspection method. First, in the vibration measurement process of step S101, hammering is performed and the vibration waveform of the restraining band 15 is measured by the acceleration pick 3. That is, the impact hammer 2 is driven by the actuator driving device, and the laminated body 12 is struck to vibrate the laminated body 12. Here, the position where the laminate 12 is hit with the impact hammer 2 may be anywhere, but the center in the X-axis direction of the laminate 12 is effective in terms of the ease of vibration. By hitting the laminated body 12 with the impact hammer 2 in this manner, it is possible to make the laminated body 12 have the same state as vibrations of various frequencies at a time. The frequency of the vibration waveform generated in the vibrated laminate 12 is measured by the acceleration pick 3.

  Next, the measurement result measured by the acceleration pick 3 is sent to the frequency analyzer 4. In this analysis determination step S102 (determination step), the frequency measured by the acceleration pick 3 is subjected to FFT analysis to analyze the frequency in the laminate 12. It is determined whether or not the analyzed frequency (f) is within a predetermined range (A ≦ f ≦ B). The predetermined range is set to a frequency corresponding to the lower limit value from the upper limit value of the design load (design constraint force) based on the relationship between the constraint force (load) and the frequency as shown in FIG.

  In this analysis determination step, when it is determined that the frequency measured by the acceleration pick 3 is within a predetermined range, OK is displayed on the frequency analysis device 4 and designed for the operator of the frequency analysis device 4. The battery stack 1 that satisfies the standard is notified. On the other hand, if it is determined in the analysis determination step that the frequency measured by the acceleration pick 3 is not within the predetermined range, NG is displayed in the frequency analysis device 4.

  By the way, the measurement of the restraining force of the restraining band 15 in the present invention is not the vibration waveform of the restraining band 15 but the vibration waveform of the laminate 12. This is because when the restraint band 15 itself is measured, it is affected by the vibration of the laminated body 12 (unit cell 121, spacer member 122, end plate 123, etc.) and the bottom plate 11 which are other members. For this reason, simply measuring the vibration waveform of the restraint band 15 with the acceleration pick 3 cannot measure the restraint force of the restraint band 15 accurately.

  On the other hand, since the laminated body 12 is pressed so as to be close to each other by the restraining band 15 via the end plate 123, it is not easily influenced by other members, for example, the restraining band 15 and the bottom plate 11. For this reason, when measuring the frequency in the vibration waveform of the laminated body 12, it can measure, without considering the vibration of members other than the laminated body 12 in particular.

  In addition, since the bulging output of the laminate 12 is always in balance with the restraining force of the restraining band 15, the restraining force of the restraining band 15 can be calculated by measuring the swelling output of the laminate 12. . In order to explain this specifically, the modeling will be described assuming that the restraint band 15 and the laminate 12 are assumed to be springs. The expansion output of the laminate 12 is a spring constant k1, and the restraining force of the restraining band 15 is a spring constant k2. The displacement amount of the laminated body 12 and the displacement amount of the restraining band 15 are x1 and x2, respectively.

積層体１２は、Ｘ−Ｚ断面における４隅の計４カ所において拘束バンド１５で拘束されている。そして、この積層体１２の膨出力と拘束バンド１５の拘束力は釣り合っており、この関係は式（３）のように表す。さらに、この式（３）に式（１）および（２）の関係を考慮して整理すると、式（４）のようになる。

このように、拘束バンド１５の拘束力は、積層体１２の膨出力の１／４に相当することが分かる。この関係から、単に積層体１２の膨出力を算出するだけで、拘束バンド１５の拘束力も算出することができる。 Since the upper and lower portions of the laminate 12 are constrained by the restraint band 15, the restraint bands 15 are positioned vertically in the XZ cross section with the laminate 12 at the center as shown in FIG. Here, when the restraining force of the restraining band 15 is F2, and the swollen output of the laminate 12 is F1, these forces (F1, F2) are expressed by the following equations (1) and (2).

The laminated body 12 is restrained by restraint bands 15 at a total of four places in four corners in the XZ cross section. And the expansion | swelling output of this laminated body 12 and the restraint force of the restraint band 15 balance, and this relationship is represented like Formula (3). Further, when this equation (3) is arranged in consideration of the relationship of equations (1) and (2), equation (4) is obtained.

Thus, it can be seen that the restraining force of the restraining band 15 corresponds to ¼ of the expansion output of the laminate 12. From this relationship, the restraining force of the restraining band 15 can also be calculated simply by calculating the expansion output of the laminate 12.

  Furthermore, as a result of experiments conducted by the present applicant, the curve regarding the relationship between the frequency and the load in the laminated body 12 is a gentle curve as compared with the curve regarding the relationship between the frequency and the load in the restraint band 15. Thus, if the slope of the curve of the relationship between the frequency and the load is gentle, the frequency analyzer 4 even when the frequency measured by the acceleration pick 3 is shifted from the frequency of the actual laminate 12. The load calculated by (3) does not deviate significantly from the load (binding force) that actually acts on the laminate 12. That is, even if the frequency measurement in the laminated body 12 is shifted due to the influence of vibration of other members as compared with the frequency measurement in the restraint band 15, the actual load (constraint force) in the laminated body 12 is measured. A load (restraint force) greatly deviated is not calculated by the frequency analyzer 4.

  As described above, the measuring method of the present embodiment can accurately calculate the restraining force of the restraining band 15 only by measuring the frequency in the laminate 12 vibrated by the impact hammer 2. Further, since the laminated body 12 is simply vibrated with the impact hammer 2 and the vibration of the vibrated laminated body 12 is simply measured with the acceleration pick 3, the battery stack 1 is not particularly disassembled (nondestructively). The restraining force of the restraining band 15 can be measured.

  Furthermore, since the measurement method of the present embodiment can measure the restraining force of the restraining band 15 without damaging the battery stack 1, the restraining force of the restraining band 15 can be easily obtained even when the battery stack 1 is mounted on a vehicle. Can be measured. Thereby, the battery stack 1 can also confirm correctly also about the grade of aged deterioration accompanying the prolongation of a use period.

(Second Embodiment)
In the first embodiment, it has been described that the battery stack 1 is vibrated with the impact hammer 2 by the actuator driving device. However, the present invention is not limited to this. For example, as shown in FIG. It is good also as a structure which vibrates by 5. By using the vibration exciter 5 in this way, the restraining force of the restraining band 15 can be measured only by bringing the acceleration pick 3 into contact with the laminate 12.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Battery stack 11 Bottom plate 12 Laminated body 121 Cell 122 Spacer member 123 End plate 13 Intake chamber 14 Exhaust chamber 15 Restraint band 2 Impact hammer 3 Acceleration pick 4 Frequency analyzer 5 Exciter

Claims (1)

A laminate comprising a plurality of unit cells laminated, a pair of end plates positioned at both ends of the laminate, and a restraining band that restrains the laminate by being attached to the pair of end plates. A battery stack restraint force inspection method for inspecting a restraint force of the restraint band in a battery stack,
Obtaining the vibration frequency by vibrating the laminate, and
A determination step of determining a binding force by the binding band based on an acquisition result by the acquisition step;
A method for inspecting a binding force of a battery stack, comprising:

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