JPH0674933U - Weight measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] To eliminate the influence of gain drift so that the weight of a sample can be measured accurately. [Structure] A reference body 5 having a known weight WR * is arranged on a mounting table 2 at a position where it can be lifted by a probe 3 alone or together with a sample A, and a measurement value WR of the reference body 5 by a detection means 4 is provided.
The drift rate WR / WR * is determined from the ratio of the known value WR * to the measured value W of the sample A by the drift rate WR / WR *.
S was compensated to obtain the true value WS *.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a weight measuring device applicable to a sample placed in a special atmosphere such as a furnace, and more particularly to a weight measuring device with improved measurement accuracy.

[0002]

[Prior art]

 For example, a press-molded body is a sample placed in a furnace. This press-molded body is finished into a final product by first dewaxing a green body, which is obtained by kneading a raw material with wax and pressing it into a desired shape, in a furnace, and then sintering it. The dewaxing process is a process in which the green body is heated in a vacuum-exhausted furnace to gradually evaporate and remove the wax contained in the green body. At this time, if the temperature control or pressure control is passed too quickly, the wax will escape quickly, and therefore degreasing and sintering shrinkage of the molded body will progress faster than expected, causing deformation and cracking of the molded body. . However, in the past, it was difficult to actually monitor changes in the compact in the furnace.Therefore, after the completion of sintering or interruption of degreasing, the condition of the compact taken out from the furnace was inspected. However, I have tried to evaluate how temperature control and pressure control should be based on experience and feeling. Therefore, the evaluation was not very objective and it took a long time to establish the treatment process. There was also the problem that it was difficult to improve the quality of products.

Therefore, the present inventor has developed a weight / dimension measuring device capable of measuring the dimensions and weight of a compact with high accuracy while suppressing adverse effects on the furnace to a minimum. Proposed in No. 3-63590. As shown in FIG. 5, this can contact the saucer 1 holding the sample A on the upward surface 1 a, the installation base 2 on which the saucer 1 is installed, and the saucer 1 and the sample A alternately. A probe 3 which is arranged at a position so that the supporting surface 3b is attached to the lower surface 1b of the saucer 1 and the saucer 1 can be lifted together with the sample A and separated from the installation base 2, and the probe 3 of the sample A and the saucer 1. And a detection means 4 for detecting the movement amount X of the upper end of the probe 3 when the probe 3 is relatively displaced between the probe 3 and the load W applied to the upper end. Then, for example, the weight change and dimensional change of the sample A are measured based on the following measurement principle. First, the probe 3 is lowered to the position P1 where the protrusion 3a contacts the sample A, and then the probe 3 is raised, and the probe 3 contacts the lower surface 1b of the tray 1 at the position P2. 1 is lifted together with the sample A and separated from the installation base 2. During this time, the relationship between the displacement X and the load W detected by the detecting means 4 is as shown in FIG. The probe movement amount ΔX from the P1 position to the P2 position corresponds to the dimension L of the sample A and the pan 1, and the dimensional change of the sample A can be measured as the change of ΔX. The probe load difference ΔW detected by the detecting means 4 before and after the P2 position corresponds to the weight of the sample A and the pan 1, and the weight change of the sample A can be measured as the change of ΔW. Thus, the device exhibits the function of obtaining the dimensional change and the weight change of the sample A almost at the same time.

[0004]

[Problems to be solved by the device]

 However, such devices always require accurate calibration for weighing. More specifically, the detection means 4 such as the load cell outputs the detection value Y in a form in which the actual load W is multiplied by the gain as shown in FIG. When the detecting means 4 is used, as shown by the solid line in the figure, accurate setting of the gain (slope) and zero adjustment for outputting 0 when no load is applied are required. Done. However, the detecting means 4 causes a null drift and a gain drift as shown by the imaginary line in the figure due to a change over time. Then, in the configuration described above, null drift is canceled when the difference between the measured values is taken, but gain drift is not compensated at all. Therefore, the device requires regular calibration.

The present invention has been made in view of such a problem, and an object thereof is to provide a weight measuring device which does not require calibration of the weight measuring accuracy even if a gain drift occurs.

[0006]

[Means for Solving the Problems] The present invention adopts the following configuration in order to achieve such an object.

That is, the weight measuring apparatus according to the present invention comprises an installation table for supporting the sample, a probe for lifting the sample and separating it from the installation table, and a detection means for detecting the load applied to the upper end of the probe. A reference body having a known weight is provided on the installation table, at a position where it can be lifted by the probe alone or together with the sample. It is characterized in that the drift rate is determined from a ratio with a known value, and the measured value of the sample by the detecting means can be compensated by the drift rate.

[0008]

[Action]

 With such a configuration, when there is no gain drift, the measured value of the sample is detected as the true value through the detection means. At this time, since the drift rate is 1, the weight value of the sample after compensation becomes the same value as when the compensation is not performed. On the other hand, when gained lift occurs and the measured value of the sample fluctuates from the true value, the measured value of the reference body also fluctuates at the same ratio. Therefore, the ratio can be obtained from the drift rate of the reference body. Therefore, if the measured value of the sample is compensated by the drift rate (multiplication / division calculation), the true value of the sample can be obtained by removing the influence of gain drift.

[0009]

【Example】

 Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The parts common to those in FIG. 5 are designated by the same reference numerals.

As shown in FIG. 1, this weight measuring device is provided with an annular reference body 5 on a stepped portion 2a provided near the upper end of an installation table 2 for supporting a sample A. The sample A is set on the upper end of the installation table 2 protruding upward from the body 5 via the saucer 1. The reference body 5 is preferably made of the same graphite as the furnace material or molybdenum. The probe 3 is carried by an elevating mechanism (not shown), and when its protrusion 3a is lowered to the position Pa (see FIG. 1) in contact with the sample A, the ascending / descending mechanism switches it to an ascending operation. Then, first, the supporting surface 3b is brought into contact with the lower surface 5a of the reference body 5 at the Pb position shown in FIG. 5 is brought into contact with the lower surface 1b of the saucer 1, and then the saucer 1 and the sample A are lifted via the reference body 5 to be separated from the installation base 2. A detection means 4 for detecting the load W applied to the upper end of the probe 3 together with the displacement X of the probe 3 is provided around the drive mechanism described above. Then, when the probe 3 is displaced from the position Pa in FIG. 1 to the position Pc in FIG. 3, the XW signal as shown in FIG. 4 detected by the detecting means 4 is inputted to the signal processing means 6. There is.

The signal processing means 6 is composed of, for example, a microcomputer system having a normal function, and the known weight value WR * of the reference body 5 and the weight value W 1 of the pan 1 are given in advance. . Then, first, the weight WR of the reference body 5 is calculated from the load change before and after the Pb position, and the weight W S of the sample A including the saucer 1 is calculated from the load change before and after the Pc position. Next, the ratio of the above-mentioned known value WR * and the measured value WR, that is, the lift ratio WR / WR * is obtained. Then, from the drift rate WR / WR * and the weight WS of the sample A including the saucer 1, the true weight value of the sample A including the saucer 1 is expressed as WS * = WS / (WR / WR *). Ask for WS *. Finally, the weight value W1 of the saucer 1 is subtracted from the weight value WS * to calculate the weight of the sample A.

With such a configuration, the measured value Ws of the sample A including the saucer 1 becomes the true value WS * itself when there is no gain drift. At this time, the drift rate (WR / WR *) also becomes 1, so the value compensated by the formula matches the value not compensated, and the compensation does not have any adverse effect. On the other hand, when a gain drift occurs and the measured value WS of the sample A fluctuates from the true value WS * by a ratio (WS / WS *), the measured value WR of the reference object 5 also fluctuates at the same ratio, and the ratio is It is obtained from the drift rate (WR / WR *) of the reference body 5. Therefore, by calculating the formula from the drift rate (WR / WR *) and the measured value WS of the sample A, the true value WS * of the sample A including the saucer 1 when there is no gain drift can be obtained. Therefore, it becomes possible to obtain the true weight of the sample A.

The shape and installation structure of the reference body are not limited to the illustrated examples, and various modifications can be made without departing from the spirit of the present invention. The vertical dimension of the sample A is, as shown in FIGS. 3 and 4, the displacement δ of the probe 3 between the position Pa at which the probe protrusion 3 contacts the sample A and the position Pc at which the reference body 5 contacts the saucer 1. It can be measured from the length L of the space in which the sample A is placed, but by appropriately adjusting the expansion coefficients αL ₁ and αL ₂ of the frame portion of the probe 3 and the reference body 5, the length of the space in which the sample A is placed can be measured. It is also possible to keep the length L constant regardless of the temperature and obtain a dimension compensated by L-δ. In this case, when the temperature of the frame portion can be easily measured, the reference body 5 may be used only for weight compensation, and the dimensional compensation may be calculated.

[0014]

[Effect of device]

 As described above, the weight measuring device according to the present invention is provided with a reference body of known weight at a position where it can be lifted by the probe alone or together with the sample. The drift rate is determined from the ratio of the, and the measured value of the weight of the sample is compensated by the drift rate. Therefore, even if a gain drift occurs in the detection means for detecting the weight, it is possible to eliminate the influence of the drift and perform accurate weight measurement.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention.

FIG. 2 is an operation explanatory view corresponding to FIG.

FIG. 3 is an operation explanatory view corresponding to FIG.

FIG. 4 is a graph showing the relationship between the displacement X and the load W detected by the detection means when the probe moves in the embodiment.

FIG. 5 is a front view corresponding to FIG. 1 showing a conventional example.

FIG. 6 is a graph showing the relationship between the displacement X and the load W detected by the detection means when the probe moves in the conventional example.

FIG. 7 is a graph for explaining gain drift.

[Explanation of symbols]

 1 ... saucer 1a ... upward surface 2 ... installation stand 3 ... probe 4 ... detection means 5 ... reference body A ... sample WR / WR * ... drift rate WS ... measured value of sample

Claims (1)

[Scope of utility model registration request] 1. A weight measuring apparatus comprising: a mounting table for supporting a sample; a probe for lifting the sample and separating it from the mounting table; and a detection means for detecting a load applied to an upper end portion of the probe, A reference body having a known weight is disposed on the installation table alone or at a position where it is lifted up together with the sample by the probe, and the drift rate is determined from the ratio between the measured value of the reference body by the detection means and the known value. A weight measuring device characterized in that the measured value of the sample by the detecting means can be compensated by the drift rate.