JP5679852B2 - Weighing device - Google Patents

Description

  The present invention relates to a weighing apparatus that detects which of the load sensors that support the four corners of the weighing table has an abnormal span.

  When a load sensor (hereinafter referred to as “load cell”), which is the most important element for achieving the function of the weighing device, breaks down, it is necessary to determine the failure state easily, accurately and quickly. If the failure can be detected accurately while the degree of the failure is small, the weighing operation can be continued without interrupting the operation until a new load cell is replaced. Here, in the failure of the load cell, the zero point fluctuation amount may be abnormally large and the span fluctuation amount may be abnormally large. It is required to determine these zero point fluctuation amount and span fluctuation amount without requiring a special operation during normal measurement work, and to issue an alarm if there is an abnormality.

  As for the fluctuation of the zero point among failure factors, the operator checks the zero point by the weight display when there is no object to be weighed on the weighing platform, and if the zero point is shifted, operates the zero adjustment switch. Since the weight display value is used after adjusting the zero point, when the zero point fluctuation is so large that the zero point adjustment is impossible due to the linearity in the load cell usage range, that is, the absolute value of the fluctuation amount is large. An abnormal alarm may be issued. The zero point often fluctuates even if the load cell is normal, such as foreign matter adhering to the weighing platform.

  On the other hand, the abnormality of the span has no function to be corrected in normal work, and the abnormality must be able to be determined even when the absolute value of the fluctuation amount is small. For example, if the accuracy of the weighing device is a specification of 1/2000, and if it is strictly determined that the span is abnormal, the weight measurement value of the object to be weighed at a load substantially corresponding to the rated load is 1 / If the fluctuation amount is 2000 or more, an allowable value is set so as to warn of a span abnormality. However, even if this value is judged as the zero point fluctuation amount, it is small. Therefore, if an abnormality alarm is made by simply judging the magnitude of the fluctuation amount of the weight measurement value, it is unnecessary as described above due to the zero point fluctuation. An abnormal alarm is output, making it difficult to use as a weighing device. On the other hand, if the determination is based on a large allowable value ignoring a small output fluctuation, a span abnormality cannot be accurately detected or alarmed.

  Conventionally, there are devices disclosed in Patent Documents 1 and 2 as devices for diagnosing a failure of a weighing device in which four corners of a weighing table are supported by a load cell.

JP 2006-162252 A JP 2006-226916 A

  In the failure diagnosis apparatus disclosed in Patent Documents 1 and 2, of the four load cells during the weighing operation under the condition that two or more abnormal products do not occur simultaneously in the four load cells. Thus, it is configured to easily and promptly determine that a span abnormality has occurred in any of the load cells. However, as described above, a span abnormality needs to be distinguished from a zero point fluctuation and an alarm for the abnormal state needs to be alarmed. However, in Patent Documents 1 and 2, individual load cells handled for determining a span abnormality are used. If the output signal contains zero fluctuation, the zero fluctuation is judged as a span abnormality, and it is judged that the abnormality is not a span abnormality. There is a problem.

  Further, since the output signal of each load cell includes the zero point fluctuation amount component individually, in order to accurately evaluate the span fluctuation, each load cell needs to be provided with means for removing the zero point movement amount. In Patent Documents 1 and 2, no consideration is given to the removal processing method for the zero point fluctuation of the individual load cell during normal use.

  In addition to the above-described problems, there is a problem that accurate abnormality determination cannot be performed as described below even if the zero-point fluctuation component is removed from the output signal of the load cell.

As shown in FIG. 1A, if load cells 1A, 1B, 1C, and 1D are respectively installed at four corners a, b, c, and d of a weighing platform 5 having a quadrilateral shape, the following formula ( 50) holds. However, in the actual machine, it is difficult to accurately arrange the load cells supporting the weighing platform 5 at the four corners of the quadrilateral according to the dimensions (it is not easy to reduce the installation dimension accuracy to 1/1000). , B, c, d points are arranged as shown in FIG. In this case, for example, when the gravity center position G of the object to be weighed moves along the x axis on the line y = B / 2, the load distributed to the load cells 1A and 1B of the load Wx of the object to be weighed at the gravity center position G The ratio and the ratio of the load distributed to the load cells 1D and 1C differ depending on the value of the x coordinate, that is, the x coordinate value of the gravity center position G of the object to be weighed. Therefore, the ratio W1 / W2 and the ratio W4 / W3 differ depending on the value of the x coordinate, that is, the placement position of the object to be weighed on the weighing platform 5. The same applies to the movement in the y-axis direction.
W1 = {(A−x) · (B−y) / A · B} Wx
W2 = {x · (B−y) / A · B} Wx
W3 = {x · y / A · B} Wx
W4 = {(A−x) · y / A · B} Wx
W1 / W2 = W4 / W3 = (A−x) / x
W1 / W4 = W2 / W3 = (B−y) / y (50)

  Accordingly, as described below in paragraph [0046] of Patent Document 1, an object to be weighed is an arbitrary one on the weighing table with reference to the placement position of the object to be weighed at a certain point on the weighing table at the time of adjustment. When evaluating the abnormality of the span during normal weighing placed at the position, the value of R0 varies depending on the x-coordinate value or the x, y-coordinate value of the center of gravity position on the weighing table of the object to be measured. Even if does not fluctuate, the value of (Rt−R0) / R0 takes various values accurately depending on the position of the center of gravity of the object to be weighed. Each time the object to be weighed is placed so that the position of the center of gravity is substantially the same, it is accurate. However, it is difficult to place it accurately at the same position in each normal weighing operation.

  Further, in the method described in paragraph [0033] and below in Patent Document 1, it is highly accurate (for example, 1/1000 or more) that the position of the object to be weighed on the weighing platform is accurately moved only by the position D. )), It is difficult to perform normal operations because accuracy is required for D, and in each weighing operation, the equation (10) described in the same document 1 is used. It cannot be accurately determined that the span of any load cell is abnormal.

  The present invention has been made in view of the above-described problems, and in a weighing device including a weighing platform whose four corners are supported by a load cell, the load sensor installation position is deviated from the four corner positions of the quadrilateral. However, it is intended to provide a weighing device that can easily and accurately detect at an early stage that the span of any load sensor has become abnormal during normal weighing work. is there.

In order to achieve the above object, the weighing device according to the first invention comprises:
So as to measure the weight of the objects to be weighed four corners of the quadrilateral are placed the objects to be weighed on the weighing platform supported by load sensors, two being arranged at both ends of one side of the quadrilateral the ratio of the load signal calculated based on the output signal of the load sensor, the relative proportions of the ratio of the load signal calculated based on the output signals of the two load sensors which are arranged at both ends of opposite sides of the one side In a weighing device comprising a span abnormality detection means for detecting an abnormality of the span of the load sensor based on the relative ratio ,
Zero point fluctuation component removal means for generating a load signal obtained by individually removing the zero point fluctuation component generated during the operation included in each of the output signals of the plurality of load sensors supporting the four corners during the operation, and removing the zero point fluctuation component The load signals calculated based on the output signals of the two load sensors arranged at both ends of the one side of the quadrilateral by the means, and the output signals of the two load sensors arranged at both ends of the opposite side of the one side The zero point fluctuation component included in each of the load signals calculated based on the above is removed .

In the first invention, the zero point fluctuation component removing means is arranged at both ends of the opposite side of the one side and the load signal calculated based on the output signals of the two load sensors arranged at both ends of the one side of the quadrilateral. It is preferable that the zero point fluctuation component included in each of the load signals calculated based on the output signals of the two load sensors is manually or automatically removed during operation (second invention). .

In the first aspect of the invention, the zero point fluctuation component removing means determines the stability of the load signal output from the load sensor, and generates a stable weight value of the load sensor, and the stable weight value generating means. The difference between the latest stable weight value generated by the weight value generating means and the stable weight value generated at the timing immediately before the latest stable weight value is calculated for each load sensor as a stable load change amount. It is preferable that it is a load change amount calculation means (3rd invention).

In addition, a fourth invention is the method according to any one of the first to third inventions, wherein the origin is set at an arbitrary position on a plane formed by the placement surface of the object to be weighed of the weighing table, and the plane is passed through the origin. One of the two axes orthogonal to each other above is defined as the x-axis, and the center of gravity of the object to be weighed on the x-axis is determined as the x-coordinate value based on the output signal of the load sensor. A span evaluation coefficient that defines the relationship of the relative ratio to the x-coordinate value of the center of gravity position of the object to be weighed placed on the weighing table by calculating the output signals of the position calculating means and all load sensors And an x-coordinate value span evaluation coefficient calculating means.

According to a fifth invention, in the fourth invention, in the adjustment mode of the weighing device, a span corresponding to the x coordinate value based on the x coordinate value of the center of gravity position of the object to be weighed during normal operation of the weighing device. An x-coordinate value span evaluation coefficient reference value calculation formula determining means for determining a calculation formula for calculating the reference value of the evaluation coefficient is provided.

Further, a sixth invention is the calculation formula according to the fifth invention, wherein the x coordinate value based on the load sensor during normal operation of the weighing device is changed to the calculation formula determined by the x coordinate value span evaluation coefficient reference value calculation formula determining means. By applying, a reference value of a span evaluation coefficient corresponding to the x-coordinate value of the gravity center position of the object to be measured is calculated.

According to a seventh aspect of the present invention based on the sixth aspect of the invention, the span abnormality detecting means includes the span evaluation coefficient calculated by the x coordinate value span evaluation coefficient calculating means and the x coordinate during normal operation of the measuring device. A span abnormality of any one of the load sensors is detected by comparing the reference value of the span evaluation coefficient calculated by the value span evaluation coefficient reference value calculation formula determining means.

In addition, in an eighth invention according to any one of the first invention to the third invention, the origin is set at an arbitrary position on a plane formed by the placement surface of the object to be weighed of the weighing table, and the plane is passed through the origin. Two axes orthogonal to each other are defined as an x-axis and a y-axis, respectively, and based on the output signal of the load sensor, the position of the center of gravity of the object to be measured on the x-axis and the y-axis is set to the x coordinate value and the y coordinate By calculating the gravity center position calculation means of the object to be weighed as a value and the output signals of all the load sensors, the x coordinate value and the y coordinate value of the gravity center position of the object to be weighed placed on the weighing table are calculated. It comprises x, y coordinate value span evaluation coefficient calculation means for calculating a span evaluation coefficient that defines the relationship of the relative ratios.

According to a ninth aspect of the present invention based on the eighth aspect , in the adjustment mode of the weighing device, the x coordinate value is based on the x coordinate value and the y coordinate value of the center of gravity position of the weighing object during normal operation of the weighing device. And x, y coordinate value span evaluation coefficient reference value calculation formula determining means for determining a calculation formula for calculating the reference value of the span evaluation coefficient corresponding to the y coordinate value.

The tenth invention is the ninth invention, in which the x-coordinate value and the y-coordinate value based on the load sensor during the normal operation of the weighing device are determined by the span evaluation coefficient reference value calculation formula determining means for the x and y coordinate values. By applying to the determined calculation formula, the reference value of the span evaluation coefficient corresponding to the x-coordinate value and the y-coordinate value of the gravity center position of the object to be measured is calculated.

The eleventh aspect of the invention is the tenth aspect of the invention, wherein the span abnormality detecting means includes a span evaluation coefficient calculated by the x, y coordinate value span evaluation coefficient calculating means during normal operation of the weighing device, An abnormality of the span of any load sensor is detected by comparing the reference value of the span evaluation coefficient calculated by the span evaluation coefficient reference value calculation formula determining means for the x and y coordinate values. is there.

According to each of the inventions described above, even if the load sensor installation position has an error from the four corners of the quadrilateral, the zero point fluctuation is reliably removed during operation from the output signal of the individual load sensor to be handled , and only the span fluctuation is obtained. It is possible to accurately detect, and it is possible to accurately determine whether any of the load sensors has a span abnormality. Moreover, it is possible to easily determine the abnormality of the span while continuing normal measurement work without requiring any special work.

Schematic diagram of a weighing platform in a weighing device according to an embodiment of the present invention. Schematic system configuration diagram of the weighing device of the present embodiment The figure explaining the method of calculating | requiring a span evaluation coefficient by proportional distribution by x, y coordinate

  Next, specific embodiments of the weighing device according to the present invention will be described with reference to the drawings.

  1A and 1B are schematic views of a weighing table in a weighing device according to an embodiment of the present invention. FIG. 2 is a schematic system configuration diagram of the weighing device according to the present embodiment.

As shown in FIG. 1A, the weighing platform 5 has a quadrilateral shape, and the four corners a, b, c, and d are supported by load cells 1A, 1B, 1C, and 1D, respectively. On the plane including the article placement surface of the weighing platform 5, the point a is the origin, the direction of the straight line connecting the points a and b is the x axis, and the direction of the straight line connecting the points a and d is the y axis. Set the xy coordinates. The coordinates of the center of gravity G of the object placed on the weighing platform 5 are (x, y), the load at the center of gravity G of the object to be weighed is Wx, and each load cell 1A, 1B, The output signals of 1C and 1D are W1, W2, W3, and W4. The dimensions of the weighing platform 5 are ab = A and ad = B.
Actually, it is difficult to accurately place the load cells 1A, 1B, 1C, and 1D at the four corners of the quadrilateral, and the points a, b, c, and d that are the positions of the load cells are extremely small. In other words, the arrangement is as shown in FIG.

  As shown in FIG. 2, each of the load cells 1A, 1B, 1C, 1D (LC1, LC2, LC3, LC4) needs to be individually adjusted to take out an output signal of the same magnitude with respect to the same load load. Therefore, the weighing device of the present embodiment amplifies the output voltage of the strain gauge bridge circuit affixed to the load cell body including the strain generating part, A / D converts, and then outputs the individual load cell outputs W1 to W4. An arithmetic circuit 26 for generating and outputting to the weight measuring device is provided.

  The arithmetic circuit 26 includes an input / output circuit (I / O) 51, a central processing unit (CPU) 52, and a memory block (MEM) 53. Thus, the output signal of the A / D converter is read into the memory block 53 from the input / output circuit 51 via the central processing unit 52. Here, the memory block 53 is composed of a storage element (semiconductor element) such as a RAM that primarily stores data for input, output, and computation, an EEPROM that continuously stores setting data, and a PROM that continuously stores predetermined programs. is there. The arithmetic circuit 26 is provided with a display device (DIS) 54, a key switch (KEY) 55, and the like. The weight value and the like are displayed on the display device 54, and the initial load storage operation and zero point adjustment operation are performed by the key switch. 55.

(1) Determination of load cell with abnormal span (1.1) Zero point fluctuation processing of output signal of load cell A zero point adjustment and automatic zero point adjustment function is added to the output of each load cell 1A, 1B, 1C, 1D individually. For example, the outputs W1, W2, W3, and W4 of the load cells 1A to 1D are expressed by the following equations.
W1 = K1. (Wa1-Wi1) -Wz1
W2 = K2 · (Wa2-Wi2) -Wz2
W3 = K3. (Wa3-Wi3) -Wz3
W4 = K4. (Wa4-Wi4) -Wz4 (1)
As described above, in the weighing device including four load cells, the initial weight, zero point weight, and span coefficient of each load cell are managed independently.

  Regarding the adjustment of the load cell 1A (LC1), the zero point memory Wz1 is reset to 0 in the equation (1) and set to the span coefficient K1 = 1 in the single adjustment point in advance. The / D conversion load signal Wa1 is stored in the initial load storage memory as the initial load Wi1. The A / D conversion load signal is smoothed by a filter so as to be sufficiently stable. Subsequently, a reference load (such as a weight) whose weight value is known is applied to the load cell, and the span coefficient K1 is adjusted so that the value of the output W1 is equal to the value of the reference load.

  Next, the load cell adjusted as described above is incorporated into the weighing table 5 of the weighing device, the zero point memory Wz1 is reset to 0 in the adjustment mode as the weighing device, and the initial load storage switch is pressed. Of this load, the portion that supports the load cell 1A is input as the A / D conversion load signal Wa1, and is read into the initial load storage memory Wi1 to update and store the initial load value stored at the time of single unit adjustment.

  The same applies to the load cells 1B to 1D. After the load cells 1A to 1D are incorporated into the weighing platform, it is preferable to store the initial load in the load measuring device by using the initial load storage switch of the weight measuring device at the same time. During use of the weighing device, it is preferable to operate the zero point adjustment switch in the weight measuring device so that the four load cells simultaneously perform the zero point adjustment in common.

  In addition, a stable state near the zero point weight is individually determined for each load cell, and the output is stable, and the weight display value count level is 0, but the count levels representing W1 to W4 deviate from zero. When it is, the zero correction function is automatically executed for each load cell. In this case, W1 to W4 are processed with a high resolution so that they can be represented by a count number that is at least four times larger than one count of the display weight value of the minimum unit as the weight value of the object to be weighed.

  By processing in this way, the zero point fluctuation is removed as the output signal of each load cell at the time of normal weighing work, and what accurately corresponds to the magnitude of the load load can be obtained, so it can handle the detection of span abnormalities It becomes possible to make it. The manual adjustment or automatic adjustment of the load cell zero point is executed by the load sensor individual zero adjustment unit in the central processing unit 52.

(1.2) Reliable Span Abnormality Determination Processing The following load cell span abnormality detection is executed by the span abnormality detection means in the central processing unit 52.
The weight value WT of the object to be weighed is expressed by the following equation with the outputs of the four load cells 1A to 1D.
WT = W1 + W2 + W3 + W4 (2)
The weight display of the weighing device is displayed by converting the value of WT, which is the weight measurement value of the object to be weighed on the weighing platform 5, into the count number of the display level. The operator performs the weighing work while looking at the displayed value. Therefore, for example, even if the zero points of the load cell 1A and the load cell 1B fluctuate by the same large value in the positive and negative directions, the zero point as the added value WT becomes 0, so the display value becomes 0, and the zero point adjustment switch is not pressed.

  When W1 and W2 fluctuate as described above, according to the method described in Japanese Patent Laid-Open No. 2006-162252 (Patent Document 1), zero fluctuation is erroneously calculated as a span fluctuation amount, An alarm will be issued. In view of this point, in order to accurately detect the span abnormality, means capable of recognizing that the zeros of the load cells 1A to 1D are individually adjusted or means capable of individually recognizing the zero fluctuation (in the central processing unit 52) It is necessary to provide a zero point variation identification means provided in

  For this reason, in this embodiment, when relying on an operator's zero point adjustment switch operation, the value of each load cell 1A-1D is also individually converted into the same resolution level as the weight display value of a to-be-measured object, and is used as a measuring device. Display on the weighing device together with the weight of the object to be weighed, or when the zero point of any load cell is fluctuating, that is, the output of any load cell is in the region near the zero point The lower limit value Wzl and the upper limit value Wzu are defined as the boundary weight values for determining whether or not the output W1 to W4 of any of the load cells is within the determined zero point region, and a sign indicating that is displayed (zero point fluctuation sign) Display on the device 54 to allow the operator to recognize the necessity of pressing the zero adjustment switch, or the range of the zero vicinity region where any load cell is defined. If outside, it is to urge the push the zero point adjustment switch. In this case, the upper limit value Wzu and the lower limit value Wzl are set to values in front of which the value of the minimum display amount (minimum scale value) of the weight value display of the object to be measured converted from the WT is displayed. It is preferable.

  Next, countermeasures will be described in the case of a weighing device that cannot rely on the operator's zero adjustment operation or when the operator forgets the zero adjustment operation. As a countermeasure against this, a load fluctuation amount detecting means for calculating only the fluctuation amount due to the load load is provided in the central processing unit 52 for the output signals W1 to W4 of each load cell as follows, thereby automatically and accurately. So that a span error can be detected.

  For example, for the output W1 of the load cell 1A, this W1 is generated at a time interval of, for example, Ta = several 100 msec after smoothing the load signal read from the A / D converter. The number W1 is stored in the prepared M shift registers, and if the maximum value-minimum value in the stored number W1 is within an allowable value of a preset stability limit, the state is in a stable state. Is determined. In this way, the average value of the shift register is calculated and used as the current weight measurement W1, that is, the stable weight value of the load cell. This arithmetic processing is executed in the stable weight value generating means in the central processing unit 52.

  If an object to be weighed is placed on the weighing platform 5, the shift register data may deviate from the allowable value due to the value of W1 read at a certain timing, and the stable condition may not be satisfied. However, since the most recent value that entered the shift register at the timing just before the stability condition is assumed to be the limit value of the allowable range, it is necessary to calculate the value of W1 as the stable weight value. It is appropriate to exclude the most recently entered value and obtain the average value with M-1.

If one stable weight value storage register for storing the stable weight value immediately before becoming unstable (latest stable weight value) is prepared and stable weight values are continuously generated at every time interval Ta, the stable Every time a weight value is generated, the contents of the stable weight value storage register are updated with the latest stable weight value W1 as the previous stable weight value W1u. Thus, the latest stable weight value is always stored in the stable weight value storage register and updated to the latest value with respect to the load signals of all the load cells 1A to 1D, and the respective values are changed to W1u, W2u, W3u. , W4u. Then, when the stable weight values of W1 to W4 are generated for each of the load cells 1A to 1D next to the latest value, the stable load value of all the load cells and the currently stored stable weight value are further loaded. Change amounts W1p to W4p are calculated. This calculation process is executed by the load change amount calculation means in the central processing unit 52.
W1p = | W1-W1u |
W2p = | W2-W2u |
W3p = | W3-W3u |
W4p = | W4-W4u | (3)

When the change width Wh of the stable weight value is determined in advance and the load change amount exceeds the change width Wh in the load signals of all the load cells 1A to 1D, that is, when the following equation is satisfied simultaneously, each load cell has a span error. Assuming that the load change amounts W1p to W4p are large enough to determine the load, the span abnormality of each load cell is determined. Here, as the value of Wh, a load of maximum Ws / 4 is normally applied to each load cell with respect to the rated load Ws of the weighing device, so that Wh = Ws / 16 as 1/4 of the value. Etc. are set.
W1p to W4p> Wh (4)

  As described below, by using W1p to W4p obtained here instead of the output signals W1 to W4 of each load cell, the coordinate value and coordinates of the center of gravity of the object to be weighed newly placed on the weighing table The reference value of the span evaluation coefficient corresponding to the value and the current span evaluation coefficient are calculated. After W1 to W4 make the above-mentioned determination, they are stored and updated in the stable weight value storage registers as W1u to W4u. It should be noted that the load change amount must be sufficiently large in order to determine a span abnormality. If this amount of change in load is small, the so-called S / N ratio becomes small and accurate determination cannot be made.

  According to the span abnormality determination method of the present embodiment, it is possible to determine a span abnormality based on the load change amount from the stability at a certain timing to the stability at the next timing. In addition, not only when there is no object to be weighed on the weighing platform, but also when a new object to be weighed is placed where the object to be weighed is placed and the load signal is stable, the zero point will fluctuate. It is possible to detect and determine a span abnormality using the load change amount for each load cell not included. Therefore, even if the operator forgets the zero point operation, it is possible to prevent the zero point fluctuation portion from being abnormally determined as the span fluctuation portion.

(2) Regarding a coefficient relating each load cell output at an arbitrary position on the weighing platform (see FIG. 1B)
(2.1) Arbitrary position on the x-axis The load change amounts W1 = W1p, W2 = W2p, W3 = W3p, W4 = W4p calculated above are used for the output signals of the load cells 1A to 1D described below. preferable. An artificially zero-adjusted output may be used.
If the load cells are not accurately arranged at the four corners of the quadrilateral, the values of W1 / W2 and W4 / W3 are not equal even if the output signals of all the load cells are normal, and It changes gradually according to the change of the center of gravity position G of the object to be weighed. If the object to be weighed (lorry vehicle) is to be weighed near the center line (CL) at the center of the weighing platform 5 as shown in FIG. / W2 and W4 / W3 are expressed as follows: W1 / W2 = r · (W4 / W3) (5)
Thus, it can be considered that the value of r (referred to as “span evaluation coefficient”) changes depending on the x coordinate of the gravity center position G of the object to be weighed placed on the weighing table 5. However, it is good also as W1 / W4 = r * (W2 / W3). So r is a function of x,
r = f (x) (6)
It is expressed by the following formula.
r = f (x) = (W1 / W2) / (W4 / W3) (7)

<Adjustment mode>
In the adjustment mode, a function r = f (x) relating r (span evaluation coefficient) and x when all the load cells have normal spans is obtained.

The position of the x, y coordinates of the object to be weighed obtained from the output signal of the load cell is as shown in the following equation from FIG.
x = [{W2 / (W1 + W2)} + {W3 / (W3 + W4)}] · A / 2
y = [{W3 / (W2 + W3)} + {W4 / (W1 + W4)}] · B / 2
... (8)

When there is some object to be weighed on the weighing platform 5 and a new object to be weighed is additionally placed, the load change amounts W1p to W4p are calculated and replaced with W1 to W4 as described above. Since the calculation is performed, the position of the center of gravity of the added object to be weighed is obtained.
The positions x and y of the objects to be weighed and the load change amount of each load cell are displayed on the display of the weight measuring device.

  In the adjustment mode of the weight measuring device, in the case of a weight or truck scale, an object to be weighed as a test sample such as a freight car is located near the center of the weighing platform 5 where x is x <(1/2) · A Between the cases where x> (1/2) · A, the display is moved by a small distance around x = (1/2) · A while confirming the display of the x coordinate.

  Here, an arbitrary load can be used as the load of the test sample, but it is preferable to use a load having a large value below the rated load of the weighing device. The display value of the x coordinate is preferably moved so as to change between x = A / 4 to (3/4) · A. Further, it is preferable to measure the test sample while moving it as much as possible along the center line represented by y = B / 2 in FIG. That is, it is preferable to move the y-coordinate so that y = B / 2 is displayed as much as possible.

  Each time the test sample is moved to several places around x = (1/2) · A, the x coordinate value is changed to an appropriate interval, and the stable weight value is obtained each time the position of the test sample is changed. When the load change amount of each of the load cells 1A to 1D is obtained, the display value of the load change amount is confirmed, and the measurement data storage switch provided in the weight measuring device is pushed. Then, each time the measurement data storage switch is pressed, the span evaluation coefficient r is calculated from the load change amount of each of the load cells 1A to 1D by the equation (7), and the memory block 53 of the arithmetic circuit 26 of the weight measuring device together with the x coordinate value. Is remembered.

When span evaluation coefficients corresponding to a plurality of x coordinates are obtained on both sides of x = (1/2) · A as a center, when a span evaluation coefficient reference value setting switch provided in the weight measuring device is pressed, x Is divided into a range of x <(1/2) · A and a range of x ≧ (1/2) · A, and a reference value of a span evaluation coefficient for x is obtained for r by a method such as a method of least squares. As the functions fa (x) and fb (x), a linear expression or a multi-order expression is determined for each range (span evaluation coefficient reference value calculation expression determining means for x coordinate value) and expressed in the form of the following expression, The data is stored in the memory block 53 of the arithmetic circuit 26 as a function related to the x coordinate value of the span evaluation coefficient reference value.
ra = fa (x) (x <(1/2) · A)
rb = fb (x) (x ≧ (1/2) · A) (9)

  If any one of the load cell spans changes by a certain ratio, the span evaluation coefficient obtained directly from the outputs of the four load cells also changes at the same rate as the variation amount of the load cell span. However, when the deviation from the four corner positions of the quadrilateral of the load cell is small, the x coordinate obtained from the output of the load cell that has changed slightly (the x coordinate also changes as much as the change rate of the load cell output) is obtained. Since the amount of change in the span evaluation coefficient is small (if the amount of deviation is 0, the span evaluation coefficient does not change at all no matter how the x-coordinate value of the object to be measured changes), it is obtained from the load cell output during normal operation. By comparing the reference value of the span evaluation coefficient calculated by the x-coordinate and the span evaluation coefficient obtained directly from the output of the load cell at that time, the fluctuation of the span of one load cell output among the four The rate can be determined.

  In the above description, two types of functions are set with x = (1/2) · A as a boundary. However, no range is provided for the value of x, and one type of function is set. Also good. Further, the range of the x coordinate may be subdivided, and the function of the span evaluation coefficient may be set in each range.

  The above is a method for obtaining the span evaluation coefficient as the reference value of the span evaluation coefficient when the load cell output spans at the four corners are all normal and the center of gravity of the object to be measured is at an arbitrary x coordinate position.

<During normal operation>
During normal operation (during normal weighing work), when the objects to be weighed are placed on the weighing platform 5, the load change amounts W1p to W4p can be obtained for all the load cells at the same time. W1 / W2 and W4 / W3 are calculated as W1 to W4, and a span evaluation coefficient rx at the current placement position of the object to be measured is calculated by the following formula (span evaluation coefficient calculation means for x coordinate value) ).
rx = (W1 / W2) / (W4 / W3) (10)

  If the output span is normal in any load cell during normal operation, the span evaluation coefficient rx obtained by (W1 / W2) / (W4 / W3) is the x coordinate of the center of gravity position of the object to be weighed at that time. It is approximately equal to the reference value of the span evaluation coefficient calculated from the load cell output (measurement object gravity center position calculation means) and calculated from the calculated x coordinate by the above equation. If there is an abnormality in the output span of any of the load cells, the span evaluation coefficient rx is calculated with the same rate of change as the rate of change of the span of the load cell, compared to when all the load cells are normal.

  On the other hand, as the span evaluation coefficient reference value at the current placement position of the object to be weighed when the span of any load cell is normal, the x coordinate of the gravity center position of the object to be weighed is obtained from the load change amounts W1 to W4. (Weighing object center-of-gravity position calculation means) Substituted into either fa (x) or fb (x) according to the range of the coordinate value of x as shown in equation (9).

When the displacement of the load cell installation position from the four corners of the quadrilateral is small, the rate of change of the span evaluation coefficient defined above according to the change in the center of gravity of the object to be weighed on the weighing table is small. Even if the x-coordinate changes at the same rate, the span evaluation coefficient reference value calculated based on the x-coordinate value is the reference value of the span evaluation coefficient calculated when there is no load cell span fluctuation. Is almost equal to Therefore, the span change rate of any one load cell can be calculated as follows.
For example, if the x coordinate value is x <(1/2) · A, the x coordinate value is substituted into ra = fa (x), and the span evaluation coefficient reference value ra for the current x coordinate value is calculated. As a result, the rate of change Sx from the span reference value is calculated by comparing rx and ra and using the following equation.
Sx = | rx−ra | / ra (11)

If the permissible value Rh for the span change rate Sx is set in advance, the span change rate Sx is compared with the permissible value Rh, and if the following formula is satisfied, the weighing device has an abnormal span coefficient for one of the load cells. The alarm signal is output to the display, buzzer, external output, etc. by various methods.
Sx> Rh (12)

(2.2) Arbitrary position on the x and y axes (2.2.1) Method of obtaining the span evaluation coefficient from the x and y coordinates In order to obtain more accuracy, the x and y coordinates are the values of x and y. Are divided into four quadrants, and a function for determining the reference value of the span evaluation coefficient corresponding to the x and y coordinates in each quadrant is determined (x, y coordinate value span evaluation coefficient reference value calculation formula determining means). This method can be applied to a weighing device in which an object to be weighed is placed at an arbitrary position on the weighing table 5.

<Adjustment mode>
In the adjustment mode, the weighing table surface is divided into four equal parts by a straight line connecting x = (1/2) · A and y = (1/2) · B, and the center of gravity of the test sample is set to the first quadrant to the fourth quadrant, respectively. The coordinates are positioned in each quadrant, and the span evaluation coefficient reference value corresponding to the x and y coordinate values is obtained for each quadrant. The x and y coordinate values on the weighing platform of the test sample are calculated by the equation (8) by measuring the output signal of each load cell and displayed on the weight measuring device. At the same time, the load change amount is displayed.

First, for the first quadrant: the test sample placement position is changed within the range of x <(1/2) · A, y <(1/2) · B, and the span evaluation coefficient reference value r1 is expressed by the following equation: r1 = (W1 / W2) / (W4 / W3) (13)
And the output signals of the load cells 1A to 1D are measured at a plurality of locations together with the x and y coordinate values. Thus, r1 corresponding to the coordinate values (x, y) at a plurality of measurement points in the first quadrant is obtained.

Next, a span evaluation coefficient reference value calculation formula for the first quadrant is expressed as follows: r1 = a1 · x + b1 · y + c1 (14)
Then, the values of a1, b1, and c1 are obtained by a method such as the least square method, and a calculation formula for the span evaluation coefficient reference value r1 for an arbitrary center of gravity (x, y) in the first quadrant is determined.

  Similarly, for the second quadrant: Formula for calculating the span evaluation coefficient reference value r2 for an arbitrary barycentric position (x, y) within the range of x ≧ (1/2) · A, y <(1/2) · B For the third quadrant: Formula for calculating the span evaluation coefficient reference value r3 for an arbitrary barycentric position (x, y) within the range of x ≧ (1/2) · A, y ≧ (1/2) · B For the fourth quadrant: x <(1/2) · A, y ≧ (1/2) · Calculation formula of span evaluation coefficient reference value r4 for an arbitrary center of gravity (x, y) within the range of B Determine. The formula for calculating the span evaluation coefficient reference value ri in the i quadrant (i = 1, 2, 3, 4) thus determined is stored in the memory block 53 of the arithmetic circuit 26 for each quadrant.

<During normal operation>
During normal operation (during normal weighing work), when an object to be weighed is placed on the weighing platform 5, when the load change amounts W1p to W4p of all the load cells are obtained for all the load cells, these are obtained. Is set to W1 to W4, and the x and y coordinates of the center of gravity position of the object to be weighed are calculated (the object to be weighed center of gravity position calculating means), and the quadrant of which the loading position of the object to be weighed is defined. A function corresponding to the quadrant is selected from r1 to r4, and x and y coordinate values are substituted into the selected function to calculate a span evaluation coefficient reference value corresponding to the placement position of the object to be measured (x, y-coordinate value span evaluation coefficient calculation means). Subsequently, the span evaluation coefficient of the current object to be weighed is calculated from the values of W1 to W4, and it is determined whether or not the span of any load cell is abnormal by the equation (11).

(2.2.2) Method for obtaining span evaluation coefficient by proportional distribution with x, y coordinates When the weighing platform is smaller than a track scale or the like, e, f shown in FIG. , G, h, and p are placed in the vicinity of a point, and a four-corner error is verified. A measurement result of the four-corner verification is used to determine a reference value for a span evaluation coefficient at an arbitrary position.

<Adjustment mode>
In the adjustment mode, the four-corner adjustment opportunity is used, and at the time of adjustment, the four-corner coordinate e point (A / 4, B) is determined by the combined value of the full-bridge output of one specific load cell and the full-bridge outputs of the other three load cells. / 2), f point ((3/4) · A, B / 2), g point (A / 2, (3/4) · B), h point (A / 2, B / 4) and the center As reference points for the span evaluation coefficients corresponding to the p points (A / 2, B / 2), the coefficients re, rf, rg, rh, and rp are obtained and stored in the memory block 53 of the arithmetic circuit 26.

For example, with respect to re, when a weight is placed so that the center of gravity of the object to be weighed is near the point e in FIG. 3A, that is, in the adjustment mode, the x and y coordinate display values are x≈A / 4, y≈ In the vicinity of displaying B / 2, the coefficient storage switch is pressed to measure the load changes W1 to W4 of the load cells 1A to 1D, and re is obtained by the following equation.
re = (W1 / W2) / (W4 / W3) (15)
Similarly, rf, rg, rh, and rp are obtained for the f point, the g point, the h point, and the p point other than the e point. Then, the reference value of the span evaluation coefficient at these reference coordinate values is stored in the memory of the weight measuring device.

<During normal operation>
At the time of normal operation, the x and y coordinates of the center of gravity of the object to be weighed are calculated by the equation (8) when the load change amounts W1 to W4 can be obtained together as described above. Now, assuming that the coordinates of the center of gravity m of the object to be weighed on the weighing platform 5 are m (x, y) in FIG. 3A, the calculated x, y coordinate values and x = A / 2, y = The quadrant in which the m point is in the coordinates is determined by a comparison with B / 2. Then, the coordinates of the reference position and the corresponding reference value of the evaluation coefficient are selected according to the quadrant to which the m point belongs.

For example, as shown in FIG. 3B, when the m point is in the fourth quadrant, the m point span evaluation coefficient reference value is based on the p point, g point, and e point span evaluation coefficient reference values. (Same for other quadrants).
At this time, first, values of k1, k2, q1, and q2 are obtained. The reference value for the e ′ point is obtained from the following equation by using the ratio between k1 and k2 as the reference value for the e and p points.
re ′ = (k1 · rp + k2 · re) / (k1 + k2) (16)
Similarly, the reference value of the point g ′ is obtained by the following equation by using the ratio of q1 and q2 as the reference value of the point g and the point p.
rg ′ = (q2 · rp + q1 · rg) / (q1 + q2) (17)
The reference value rm of the m-point span evaluation coefficient is expressed by the following equation depending on the ratio of k2 and q1.
rm = (q1 · rg ′ + k2 · re ′) / (k2 + q1) (18)
And on the other hand, the span evaluation coefficient by the present to-be-measured object is calculated by W1-W4, and a warning signal will be output if there is a span abnormality based on the above equations (11) and (12).

  As described above, according to the weighing device of the present embodiment, it is not affected by the fluctuation of the zero point, and is not affected by the placement position of the object to be weighed on the weighing table, and is special during normal measurement work. Thus, it is possible to accurately warn when any of the load cell spans is abnormal. Further, if the load signal change amount is used, even if the load signal does not return to the zero point, an alarm can be given by an object to be weighed added on the weighing table. When the abnormality determination is made, a sign that the span of one of the load cells is abnormal is made by the weight measuring device with display contents that can be identified to the operator, and the rate of change of the span is also displayed. As the alarm signal, means such as lamp display, character display, and voice can be used.

  The weighing device of the present invention can be suitably used for detecting an abnormality of a span generated in a strain gauge type load cell used in a weighing instrument such as a conveyor scale, a hopper scale, a track scale, a platform scale, a fee scale, or the like.

1A, 1B, 1C, 1D Load cell 5 Weighing table 26 Arithmetic circuit 52 Central processing unit 53 Memory block 54 Display device

Claims (11)

So as to measure the weight of the objects to be weighed four corners of the quadrilateral are placed the objects to be weighed on the weighing platform supported by load sensors, two being arranged at both ends of one side of the quadrilateral the ratio of the load signal calculated based on the output signal of the load sensor, the relative proportions of the ratio of the load signal calculated based on the output signals of the two load sensors which are arranged at both ends of opposite sides of the one side In a weighing device comprising a span abnormality detection means for detecting an abnormality of the span of the load sensor based on the relative ratio ,
Zero point fluctuation component removal means for generating a load signal obtained by individually removing the zero point fluctuation component generated during the operation included in each of the output signals of the plurality of load sensors supporting the four corners during the operation, and removing the zero point fluctuation component The load signals calculated based on the output signals of the two load sensors arranged at both ends of the one side of the quadrilateral by the means, and the output signals of the two load sensors arranged at both ends of the opposite side of the one side A zeroing component included in each of the load signals calculated based on the above is removed . The zero point fluctuation component removing means includes a load signal calculated based on output signals of two load sensors arranged at both ends of one side of the quadrilateral, and two pieces arranged at both ends of the opposite side of the one side. The weighing apparatus according to claim 1, wherein the zero point fluctuation component included in each of the load signals calculated based on the output signal of the load sensor is individually or automatically removed during operation . The zero point fluctuation component removing means is generated by the stable weight value generating means for generating the stable weight value of the load sensor and the stable weight value generating means while performing stability determination of the load signal output from the load sensor. A load change amount calculating means for calculating, for each load sensor, a difference between the latest stable weight value and the stable weight value generated at a timing immediately before the latest stable weight value as a stable load change amount. The weighing device according to claim 1 . The origin is determined at an arbitrary position on a plane formed by the placement surface of the object to be weighed on the weighing table, and one of two axes passing through the origin and orthogonal to each other on the plane is defined as an x axis, By calculating the gravity center position calculation means for measuring the gravity center position of the measurement object on the x-axis as the x coordinate value based on the output signal of the load sensor, and calculating the output signals of all the load sensors, X-coordinate value span evaluation coefficient calculating means for calculating a span evaluation coefficient that defines the relationship of the relative ratio to the x-coordinate value of the gravity center position of the object to be weighed placed on a weighing table. The measuring device according to any one of claims 1 to 3 . Calculation formula for calculating a reference value of a span evaluation coefficient corresponding to the x-coordinate value based on the x-coordinate value of the center of gravity position of the weighing object during normal operation of the weighing device in the adjustment mode of the weighing device The weighing apparatus according to claim 4 , further comprising: an x-coordinate value span evaluation coefficient reference value calculation formula determining means for determining By applying the x coordinate value based on the load sensor during normal operation of the weighing device to the calculation formula determined by the span evaluation coefficient reference value calculation formula determination means for the x coordinate value, The weighing apparatus according to claim 5 , wherein a reference value of a span evaluation coefficient corresponding to the x coordinate value is calculated. The span abnormality detection means includes a span evaluation coefficient calculated by the x coordinate value span evaluation coefficient calculation means and an x coordinate value span evaluation coefficient reference value calculation formula determination means during normal operation of the weighing device. 7. The weighing apparatus according to claim 6 , wherein an abnormality of the span of any one of the load sensors is detected by comparing with a calculated reference value of the span evaluation coefficient. The origin is determined at an arbitrary position on a plane formed by the placement surface of the object to be weighed on the weighing platform, and two axes passing through the origin and orthogonal to each other on the plane are defined as an x-axis and a y-axis, respectively, and the load A to-be-measured object center-of-gravity position calculating means for determining the center-of-gravity position of the object to be measured on the x-axis and the y-axis as an x-coordinate value and a y-coordinate value based on sensor output signals, and output signals of all load sensors X and y coordinate values for calculating a span evaluation coefficient that defines the relationship of the relative ratio to the x-coordinate value and the y-coordinate value of the center of gravity position of the object to be weighed placed on the weighing table. weighing device according to any of claims 1-3, characterized in that it comprises a use span evaluation coefficient calculating means. In the adjustment mode of the weighing device, the span evaluation coefficient reference corresponding to the x-coordinate value and the y-coordinate value based on the x-coordinate value and the y-coordinate value of the center of gravity position of the weighing object during normal operation of the weighing device 9. The measuring apparatus according to claim 8 , further comprising: x, y coordinate value span evaluation coefficient reference value calculation formula determining means for determining a calculation formula for calculating a value. By applying the x-coordinate value and the y-coordinate value based on the load sensor during normal operation of the weighing device to the calculation formula determined by the span evaluation coefficient reference value calculation formula determination means for the x and y coordinate values, The weighing apparatus according to claim 9 , wherein a reference value of a span evaluation coefficient corresponding to the x-coordinate value and the y-coordinate value of the gravity center position of the weighing object is calculated. The span abnormality detecting means calculates the span evaluation coefficient calculated by the x, y coordinate value span evaluation coefficient calculating means and the x, y coordinate value span evaluation coefficient reference value during normal operation of the weighing device. 11. The weighing apparatus according to claim 10 , wherein an abnormality of the span of any load sensor is detected by comparing with a reference value of a span evaluation coefficient calculated by the formula determining means.

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