JP2012173270A - Hopper type weighing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hopper type weighing apparatus capable of easily and accurately detecting which load cell generates span abnormality in normal weighing work in the hopper type weighing apparatus including a hopper whose several positions are supported by a plurality of load cells.SOLUTION: The hopper type weighing apparatus storing an object M to be weighed in a hopper 2 whose several positions are supported by load cells 1A, 1B and 1C to measure the weight of the object M to be weighed includes: a half bridge load signal operation unit 52a for performing arithmetic processing so that respective half bridge load signals to loads applied to the load cells 1A, 1B and 1C are load signals of the same size; and a span abnormality detection unit 52b for detecting a load cell generating span abnormality out of the plurality of load cells 1A, 1B and 1C by mutually comparing half bridge load signals outputted from the half bridge load signal operation unit 52a.

Description

  The present invention relates to a hopper type weighing device that determines which one of load cell spans is abnormal among a plurality of load cells that support a plurality of locations of a weighing container such as a hopper, and recovers from a failure. Is.

  When the load cell, which is the core part of the weighing device, fails, the function to easily and accurately determine the failure state and easily return it to the normal state is the time until replacement with a new load cell. It can be said that this is an important function in that the weighing operation can be continued. Here, the factors that cause the load cell output to fluctuate from the normal value are that the zero point fluctuation amount becomes abnormally large and the span fluctuation amount becomes abnormally large. These zero point variation and span variation abnormalities can be determined without the need for special operations during normal weighing work, and it is required to issue an alarm if there is an abnormality. It is required to return the weighing device to a normal state without requiring any special operation.

  Among the above failure factors, the variation of the zero point is not due to the failure of the load cell itself, but also due to foreign matter adhering to the weighing table. Since it can be easily returned to the normal state by operating the adjustment switch or the like, it is not considered to be in an abnormal state and no special alarm is given. In other words, if a zero point abnormality alarm is issued with a small zero point variation that can be easily restored to a normal state, it becomes difficult to use as a weighing device. Therefore, when the zero point continuously fluctuates in one direction, it can be returned to normal by repeating the zero point adjustment operation, but the zero point abnormality is abnormal when the accumulated zero point fluctuation amount becomes a large value. Be alerted as.

  On the other hand, the abnormality of the span cannot be easily corrected during normal work, and the abnormality must be determined even if the absolute value of the load cell output fluctuation amount is small. For example, if the accuracy of the weighing device is 1/2000, and if it is strictly determined that the span is abnormal, the weight measurement value of the object to be weighed even if the object to be weighed is a load substantially corresponding to the rated load. If the fluctuation amount is 1/2000 or more, an allowable value is set so as to warn of a span abnormality. However, since this value is small, if an abnormal alarm is issued simply by determining the amount of fluctuation of the weight measurement value, an unnecessary abnormal alarm due to zero fluctuation is output as described above, and the weighing It becomes difficult to use as a 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, as a device for diagnosing a failure of a weighing device in which a plurality of portions of a weighing container are supported by a plurality of load cells, there are devices disclosed in Patent Documents 1 and 2, for example. In most cases, failure occurs from one of a plurality of load cells, and the probability that the failure proceeds simultaneously to the same extent is extremely small.

JP-A-5-264375 JP-A-9-280939

  The failure diagnosis apparatuses disclosed in Patent Documents 1 and 2 are configured to detect a failure based on the magnitude of fluctuation of the output signal of the individual load cell during use. However, the fluctuation factor is zero fluctuation. Even if there is a span fluctuation, failure detection is performed without distinction, so if an allowable value of an alarm for a small fluctuation amount is set to accurately determine a span abnormality, each individual load cell An alarm is issued immediately by the changing zero point, which makes the weighing device difficult to use. On the other hand, if a large allowable value is set, a span abnormality cannot be accurately detected.

Usually, in a weighing device, a weight measurement value is obtained from the sum of outputs from a plurality of load cells that support a weighing container, and the weight measurement value is displayed on a display. If some weight measurement value is displayed on the display despite no load, zero adjustment is performed by zero adjustment means such as a zero adjustment switch provided in the weighing device.
This zero point adjusting means is means for adjusting the zero point by confirming the case where the output sum of the load cells is not 0 with the display value. However, even if the zero points of a plurality of load cells move, the output sum of these load cells may cancel out and be zero.
Each load cell output signal includes a zero point fluctuation component individually. Therefore, in order to accurately evaluate the span fluctuation, means for enabling the operator to check the zero point movement amount for each load cell, and for each load cell, A means for adjusting the zero point for each output is required. However, Patent Documents 1 and 2 do not disclose a recognition means or a zero-point adjusting means for a zero-point variation of an individual load cell during normal use.
If an attempt is made to detect a span abnormality accurately, a zero point variation that occurs in each load cell will be detected as a load cell span abnormality and an alarm will be issued.

  In addition to the above-mentioned problems, even if the zero point fluctuation component is removed from the output signal of the load cell, accurate abnormality determination cannot be performed as described in (1) to (3) below. There are also problems.

(1) In an actual weighing device, a load cell that supports a weighing container (hereinafter referred to as a “hopper”) cannot be disposed so as to receive the load of an object to be weighed in the hopper accurately and evenly. Also, the hopper cannot be made symmetrical in every cross section. As described above, even if the liquid is accommodated, the outputs of the plurality of load cells are different from each other.
(2) From the positional relationship between the weighing device supply device (hopper feeding port) to the hopper and the hopper, if the fluidity of the weighing object is not as good as the liquid, the supplied weighing object is There is a tendency to be biased to either side of the hopper, in other words, to one of the load cells.
Due to these factors, a fixed deviation peculiar to the structure of the weighing device and the properties of the object to be weighed occurs between the output signals of the load cells in each weighing.
(3) If the object to be weighed is not liquid, it is rarely accommodated in the hopper completely uniformly in each weighing. The distribution of the apparent specific gravity of the object to be weighed is not completely uniform in each weighing. Therefore, in each measurement, the difference between the output signals of the load cells varies depending on the property of the object to be weighed.
In the above-mentioned Patent Documents 1 and 2, measures for these problems are not clear, and no specific measures are taken.

  The present invention has been made in view of the above-described problems. In a hopper type weighing device including a hopper supported by a plurality of load cells at a plurality of locations, any load cell can be used in a normal weighing operation. It is an object of the present invention to provide a hopper type weighing device that can easily and accurately detect whether a span is abnormal.

In order to achieve the above object, a hopper type weighing device according to the present invention comprises:
A half bridge load signal is generated based on output signals from two terminals in a Wheatstone bridge circuit composed of at least four strain gauges affixed to the strain generating portion of the load cell. In a hopper type weighing device that accommodates an object to be weighed in a hopper supported by the load cell and measures the weight of the object to be weighed,
Half-bridge load signal calculation means for calculating the load load on the load cell so that each half-bridge load signal becomes a load signal of the same magnitude,
A span abnormality detecting means for detecting a load cell having an abnormal span among the plurality of load cells by comparing the half bridge load signals output from the half bridge load signal calculating means;
(First invention).

In the present invention,
It is preferable to provide zero point adjusting means for manually or automatically adjusting the zero points of the two half bridge load signals output from the half bridge load signal calculating means (second invention).

In the present invention,
It is identified that at least one half bridge load signal of two half bridge load signals output from the half bridge load signal calculating means varies from a zero point individually set by the zero point adjusting means. It is preferable that a zero point variation identification means is provided (third invention).

In the present invention,
Stable weight value generation means for performing stability determination of two half bridge load signals output from the half bridge load signal calculation means, and for generating a stable weight value of the load cell;
The difference between the latest stable weight value generated by the stable 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 cell as a stable load change amount. And a stable load change amount calculating means for providing,
The span abnormality detection means may detect an abnormality in the span of the load cell by comparing the stable load change amounts of the two half bridges calculated by the stable load change amount calculation means (first). 4 invention).

In the present invention,
Preferably, there is provided a span abnormality half-bridge specifying means for specifying which half bridge of the two half bridges in the load cell in which a span abnormality is detected by the span abnormality detection means (fifth). invention).

In the present invention,
A span change detecting means for comparing two half-bridge load signals in a load cell in which a span abnormality is detected by the span abnormality detecting means;
Two half-bridge load signals in the load cell in which the span abnormality is detected by the span abnormality detection means, and two half-bridge load signals in load cells other than the load cell in which the span abnormality is detected by the span abnormality detection means And a relative comparison means for comparing
The span abnormal half-bridge specifying unit may specify a half bridge having an abnormal span based on a comparison result by the span change detecting unit and a comparison result by the relative comparing unit (Sixth Invention). ).

In the present invention,
It is preferable that an allowable value for specifying a half bridge having an abnormal span in the span abnormal half-bridge specifying means is set based on the magnitude of the comparison result of the relative comparing means (seventh invention).

In the present invention,
The span abnormality half-bridge specifying means totals the comparison results of the relative comparison means in correspondence with the magnitude of the change of the comparison result by the span change detection means being near zero, and the span change detection means By summing up the comparison results of the relative comparison means at the time when the magnitude of the change in the comparison result according to is in the vicinity of the allowable value of the span change, the span of any half bridge of the load cell is in a normal state. By calculating the magnitude of the change, it is possible to identify a half bridge whose span change is abnormal (eighth invention).

In the present invention,
It is preferable that a span correcting means for correcting the span of the half bridge load signal in the half bridge identified as abnormal by the span abnormal half bridge specifying means is provided (ninth invention).

In the present invention,
The half bridge load that replaces the half bridge load signal of the half bridge identified as having an abnormal span by the span abnormal half bridge specifying means with the half bridge load signal of the half bridge that is not identified as having an abnormal span. It is preferable to provide a signal alternative calculation means (10th invention).

In the present invention,
The span abnormality half-bridge specifying means, when the load cell having an abnormal span is specified based on the comparison result of the span change detection means and the comparison result of the relative comparison means, the span in the specified load cell is It is possible to identify the half bridge that is abnormal (the eleventh invention).

In the present invention,
It is preferable that there is provided a variation attenuation calculating means for attenuating the magnitude of the comparison result of the relative comparison means (the twelfth aspect).

In the present invention,
The variation attenuation calculating means can reduce the variation of the relative ratio by calculating an average value of the relative ratio based on the comparison result of the relative comparing means obtained by a plurality of predetermined measurements. (13th invention).

In the present invention, for each half bridge, a load signal having a magnitude corresponding to the magnitude of the load load is output, and calculation processing is performed so that each zero point movement amount can be managed and adjusted. Thereby, the zero point fluctuation | variation part for every half bridge load signal is removed reliably. Then, by comparing the half bridge load signals output from the half bridge load signal calculation means, a load cell having an abnormal span is detected from among the plurality of load cells.
According to the present invention, it is possible to accurately detect only the span fluctuation by removing the zero fluctuation from the output of each half bridge, and the span of which load cell of the plurality of load cells is abnormal. Abnormality can be easily and accurately determined. In addition, this span abnormality determination can be performed while continuing normal measurement work without requiring any special work.

BRIEF DESCRIPTION OF THE DRAWINGS It is structure explanatory drawing of the hopper type | mold measuring apparatus which concerns on one Embodiment of this invention, a top view (a) and a longitudinal cross-sectional view (b) The load cell used state diagram applied to the hopper type weighing device of the present embodiment, the state diagram used for the Robert load cell Schematic system configuration diagram of a failure diagnosis device in the hopper type weighing device of the present embodiment Block diagram showing the configuration of the arithmetic circuit Explanation of relationship between display count of display weight value and internal count Explanatory diagram of variation in variation of half-bridge output comparison ratio Illustration of classification summary calculation Schematic system configuration diagram of a failure diagnosis apparatus according to another embodiment of the present invention

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

  1 (a) and 1 (b) are structural explanatory views of a hopper type weighing device according to an embodiment of the present invention, and a plan view (a) and a longitudinal sectional view (b) are respectively shown. FIG. 2 is a use state diagram of a load cell applied to the hopper type weighing device of the present embodiment, and a state diagram used for a robust load cell is shown. FIG. 3 shows a hopper type weighing of the present embodiment. A schematic system configuration diagram of a failure diagnosis apparatus in the apparatus is shown.

The hopper type weighing device shown in FIGS. 1 (a) and 1 (b) is used as a weighing container in which a plurality of points (three points: points a, b, and c) are suspended and supported by a plurality of load cells 1A, 1B, and 1C. A hopper 2 is provided.
When the discharge gates 3 and 3 provided in the lower part are in a closed state, the hopper 2 can accommodate and measure the object M supplied from the supply device 4 provided above. It is possible to open the discharge gates 3 and 3 after the weighing is completed so that the internal weighing object M can be dropped and discharged.
Three load cells 1A, 1B, 1C, as shown in FIG. 1 (a), with respect to the center of the cylindrical hopper 2, so that the load cell 1A and the load cell 1B is an angle theta _1, load cell 1A and load cell 1C is to form an angle theta _2, the load cell 1B and the load cell 1C is to form an angle theta _3, are arranged respectively. These load cells 1A, 1B, and 1C are arranged so as to divide the hopper 2 into approximately three equal parts with respect to the center point of the hopper 2 in plan view (θ ₁ ≈θ ₂ ≈θ ₃ ).

  As shown in FIG. 2, each of the load cells 1A, 1B, 1C is a Robert load cell, that is, a parallelogram load cell in which two strain generating portions are provided on two beams. In the present embodiment, a portion in which a strain generating body is covered with a metal bellows 5 (see FIG. 1) is applied for waterproofing and dustproofing.

  Each load cell 1 </ b> A, 1 </ b> B, 1 </ b> C includes a strain generating portion 8 having two beams (beams) 6, 7. In the strain generating portion 8, strain gauges 11 and 12 are attached to the beam 6, and strain gauges 13 and 14 are attached to the beam 7 along the longitudinal direction of the beam. A suspension fitting 9 (see FIG. 1B) for suspending and supporting the hopper 2 is coupled to the strain generating portion 8. When the object to be weighed M is accommodated in the hopper 2, a load corresponding to the weight of the object to be weighed M acts on the strain generating portion 8, and the strain gauges 12 and 14 are in the direction in which the gauge adhesion surface extends. Upon receiving the bending stress, the strain gauges 11 and 13 are subjected to bending stress in a direction in which the gauge bonding surface contracts.

  As shown in FIG. 3, the strain gauges 11, 12, 13, and 14 are connected to each other so as to constitute a full bridge circuit (corresponding to a “Wheatstone bridge circuit” in the present invention) 15. Here, in the full bridge circuit 15, if both the strain gauges 12 and 14 constituting the opposite sides are tensile forces, the tensile force is obtained, and both the strain gauges 11 and 13 constituting the opposite sides are both compressive forces. Then, it is wired to receive the same type of force as compression force.

  In the full bridge circuit 15, excitation direct current voltage is applied to two opposing connection points 16 and 17, and force or load is detected from the connection points 18 and 19 positioned at right angles to these connection points 16 and 17. The voltage is taken out.

  A fault diagnosis device 20 is provided for the above-described full bridge circuit 15. The fault diagnosis apparatus 20 includes two voltage reference fixed resistors 21 and 22, an analog adder circuit 23, and two analog-digital converters (hereinafter referred to as “A / D converters”) 24, 25 and an arithmetic circuit 26. Here, the fixed resistors 21 and 22 are connected in series to each other and are connected to connection points 16 and 17 of the full bridge circuit 15. The fixed resistors 21 and 22 and the strain gauges 12 and 13 form a half bridge circuit 15a, and the fixed resistors 21 and 22 and the strain gauges 11 and 14 form a half bridge circuit 15b.

The analog adder circuit 23 includes a first operational amplifier 31, a second operational amplifier 32, a third operational amplifier 33, and a fourth operational amplifier 34.
In the first operational amplifier 31, the input positive terminal 31 a is connected to the connection point 18 of the full bridge circuit 15, the input negative terminal 31 b is connected to the output terminal 31 c, and the output terminal 31 c is connected to the resistor 40.
In the second operational amplifier 32, the input positive terminal 32a is connected to the connection point 41 of the two fixed resistors 21 and 22, the input negative terminal 32b is connected to the output terminal 32c, and the output terminal 32c is connected to the resistors 42 and 43. It is connected.
In the third operational amplifier 33, the input positive terminal 33a is connected to the circuit ground 44, the input negative terminal 33b is connected to the resistors 40 and 42, and is connected to the output terminal 33c via the resistor 45, The output terminal 33c is connected to the A / D converter 24.
In the fourth operational amplifier 34, the input positive terminal 34 a is connected to the connection point 19 of the full bridge circuit 15, and the input negative terminal 34 b is connected to the resistor 43 and connected to the output terminal 34 c via the resistor 46. The output terminal 34 c is connected to the A / D converter 25.

  The A / D converters 24 and 25 convert the analog load signal from the analog adder circuit 23 into a digital load signal. The analog load signals eoa and eob output from the two sets of half-bridge circuits 15a and 15b are converted into analog load signals eoa 'and eob' through the analog adder circuit 23. These analog load signals eoa 'and eob' are represented by A / D converters 24 and 25 convert the signals into digital load signals. These digital load signals are input to the arithmetic circuit 26 to become digital load signals.

  The output signals Wa1 and Wa2 from the A / D converters 24 and 25 shown in FIG. 3 are digital signals obtained by A / D sampling the analog load signals eoa ′ and eob ′ with a relatively short time interval (for example, 5 msec). Thus, the natural vibration signal or the like of the hopper type weighing device is subjected to smooth filtering processing in the arithmetic circuit 26, and is given to equation (1) described later, for example, every several hundred msec time intervals. The output signals Wa1 and Wa2 corresponding to the half-bridge outputs of the load cells 1A, 1B, and 1C are expressed as Wa11, Wa21; Wa12, Wa22; Wa13, Wa23, respectively.

  As shown in FIG. 4, each of the load cells 1A, 1B, 1C (LC1, LC2, LC3) is for the strain generating body including the strain generating section 8 (see FIG. 2) and the A / D conversion circuit shown in FIG. Is constructed as a digital load cell built in a case (metal bellows 5: see FIG. 1B) surrounding the strain generating body, and is connected to the arithmetic circuit 26 of the hopper type weighing device of this embodiment. Yes. Although the A / D conversion circuit can be provided on the hopper type weighing device side, it is more preferable to adopt a configuration of a digital load cell integrated with the strain generating body.

  As shown in FIG. 4, 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 signals of the A / D converters 24 and 25 are read from the input / output circuit 51 into the memory block 53 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 operations such as data setting and zero adjustment are performed by the key. Implemented by switch 55.

<Description of adjustment and processing of half-bridge load signal of load cell>
Output signals (half-bridge load signals) of two sets of half-bridge circuits 15a and 15b (hereinafter referred to as “half-bridge 1” and “half-bridge 2”, respectively, see FIG. 3) in the load cells 1A, 1B, and 1C are respectively W11, W21; W12, W22; W13, W23. The processing of these output signals is independently provided with a span coefficient, a zero point weight storage memory, and an initial weight storage memory.

First, the load cell alone is adjusted. In this adjustment, a weight measuring device similar to that shown in FIG. 4 is connected to the digital load cell. Here, the load measuring device for weight adjustment is provided with an initial load storage switch and a span coefficient setting switch.
For example, when adjusting the half bridge 1 of the load cell 1A, first, set the span coefficient K11 = 1, set the load cell to no load, press the initial load storage switch, and apply the digital load signal Wa11 obtained from the half bridge 1 to the initial load. The initial load storage memory is set as Wi11.

The output of the half bridge 1 is calculated by the following processing expression in the calculation circuit 26.
W11 = K11 · (Wa11−Wi11)
At this time, since K11 = 1 and Wa11 = Wi11, W11 = 0 is displayed on the adjustment weight measuring device. The half bridge 2 is similarly adjusted. Note that W11 is set so as to have, for example, four times the resolution of the display value as the weight measurement value of the object M in the weighing instrument.

  Next, a load rating is applied to the load cells 1A, 1B, and 1C, and a value WM obtained by converting the load rating with high resolution is set. When the span coefficient adjustment switch is pressed, the span coefficient K11 is determined so that the weight display indicates the value of WM. The span coefficient K21 of the half bridge 2 is determined in the same manner, and these span coefficients K11 and K21 are stored in the nonvolatile memory, and the adjustment of the single load cell is completed. In this way, the span coefficient of each half bridge in the single load cell is adjusted so as to have the same output change for the same load.

  Next, the load cells 1A, 1B, 1C adjusted as described above are incorporated into the hopper 2 of the hopper type weighing device, and the output is connected to the weight measuring device for the hopper type weighing device. When the initial load storage switch of the weight measuring device is pressed in this state, for example, the load signal Wa11 which has been A / D converted and smoothed into the half bridge 1 of the load cell 1A enters the initial load storage memory and is stored at the time of single adjustment. The initial load value is changed.

During use as a hopper type weighing device, adjustment for the zero point fluctuation (adjustment for setting the output to 0 when there is no object to be weighed M in the hopper 2) is required, and therefore, a zero point weight storage memory Wz11 is provided. Is set by the following processing equation (1). Similar processing formulas are set for the half bridge 2 and the other load cells 1B and 1C.
-About load cell 1A W11 = K11 * (Wa11-Wi11) -Wz11
W21 = K21 · (Wa21−Wi21) −Wz21
W1 = (W11 + W21) / 2
-About load cell 1B W12 = K12- (Wa12-Wi12) -Wz12
W22 = K22 · (Wa22−Wi22) −Wz22
W2 = (W12 + W22) / 2
-About the load cell 1C W13 = K13- (Wa13-Wi13) -Wz13
W23 = K23 · (Wa23−Wi23) −Wz23
W3 = (W13 + W23) / 2 (1)
In the measurement circuit shown in FIG. 3, only the half-bridge output is provided. Therefore, the full-bridge output used for obtaining the weight measurement value of the object M during normal weighing is half-bridge 1, It is expressed by adding two outputs.
The weight value WT of the object to be weighed M is expressed by the following equation with the outputs of the three load cells 1A, 1B, and 1C.
WT = W1 + W2 + W3 (2)

<Description of zero point adjustment means>
As a manual zero adjustment operation during use of the hopper type weighing device, if the zero adjustment switch 55a (refer to FIG. 4: corresponding to “zero adjustment means” in the present invention) is operated in the weight measurement device during use, three operations are performed. It is preferable if the outputs of the half bridges 1 and 2 of the load cells 1A, 1B, and 1C are simultaneously adjusted to zero. Here, the zero point adjustment is a process for adding W11 at the time of zero point adjustment to Wz11 for W11, for example, so that W11 = 0.

Also, as an automatic zero correction function, the stable state of each load cell 1A, 1B, 1C near the zero point weight of the half bridge output is individually determined, and the output is stable and the weight display value count level is 0 display. However, as shown in FIG. 5, when the display count is 0 but the internal count level is not zero, the zero point correction function is automatically performed for each half bridge of each load cell 1A, 1B, 1C. To do. In this case, as described above, each half bridge output signal can be expressed with a high resolution so that it can be expressed 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 M. Process with.
The zero adjustment operation is executed in a zero adjustment unit 52c (corresponding to “zero adjustment means” in the present invention) in the central processing unit 52.

  By performing signal processing for each half bridge in this way, the zero point fluctuation for each half bridge output of each load cell 1A, 1B, 1C at the time of normal weighing work is removed, and the magnitude of the load load is accurately handled. As a result, it is possible to cope with the detection of a span abnormality.

<Description of half-bridge load signal calculation means and span abnormality detection means>
As described above, in the present embodiment, the arithmetic processing in which the half bridges 1 and 2 become output signals having the same magnitude with respect to the load applied to the load cells 1A, 1B, and 1C is performed by the central processing unit 52. It is executed in the half bridge load signal calculation unit 52a (corresponding to “half bridge load signal calculation means” in the present invention). The arithmetic processing for detecting the load cell having an abnormal span among the three load cells 1A, 1B, 1C by comparing the output signals from the two half bridges 1, 2 is performed in the central processing unit 52. Span abnormality detection unit 52b (corresponding to “span abnormality detection means” in the present invention).

<Description of reliable span abnormality determination processing>
The weight display of the hopper type weighing device is displayed by converting the WT value, which is the weight value of the object M in the hopper 2, into the display level resolution. The operator performs the weighing work while looking at the displayed value. Therefore, for example, when the zero points of the half bridges 1 and 2 of the load cell 1A fluctuate in the positive and negative directions by the same large value, the output as the load cell 1A becomes zero. If the outputs of the other load cells 1B and 1C are also 0, the zero value as the added value WT becomes 0, so the display value becomes 0, and the zero adjustment switch 55a is not pushed.

  Since the abnormality detection of the span of the load cells 1A, 1B, and 1C according to the present embodiment is performed by comparing the outputs of two half bridges in the same load cell, if the zeros are different from each other, Even if the signal change due to load is the same, the difference remains and it is determined that the span is abnormal. For example, when foreign matter is attached to the hopper 2, the zero point of both half bridge outputs fluctuates by the same amount, so the comparison result is not affected, but the ambient temperature is changing. The two half bridges are affected by different temperatures and a difference occurs between the zero points of both half bridge outputs.

<Explanation of zero variation identification means>
In view of this point, in order to accurately detect the span abnormality, it is necessary to provide means capable of recognizing that the zero points of the half bridge outputs are individually adjusted or individually recognizing zero point fluctuations. For this reason, in the present embodiment, a zero point variation identifying unit 52d (corresponding to the “zero point variation identifying means” in the present invention) is provided in the central processing unit 52, and the zero point variation identifying unit 52d has a half bridge output. To vary from individually set zeros. Further, in the present embodiment, when any one of the half bridge outputs is not zero, or when all the half bridge outputs of all the load cells 1A, 1B, 1C are zero, the display device 54 is notified to that effect. A half-bridge zero point display signal generating unit 52m (half-bridge zero point display signal generating means) for generating a display signal for display or character display is provided in the central processing unit 52. In this way, when any one of the zero points of the half bridge output is moving, the operator can easily recognize this by the display device 54, and by pressing the zero adjustment switch 55a, Zero adjustment of all half bridge outputs can be performed simultaneously. Here, it is preferable that the zero adjustment switch 55a is also used as a normal weight display zero adjustment switch.

  Regarding the sign display by the half-bridge zero-point display signal generating unit 52m, the lower limit value Wzl and the upper limit value Wzu are determined as boundary weight values for determining that the half-bridge output is in the region near the zero point, and all the load cells 1A, 1B, In case of any one half bridge output in 1C, the case where the weight measurement value represented by the resolution higher than the displayed weight value, for example, four times higher than the display weight value is not in the near zero region, is detected. A sign to that effect (zero point fluctuation sign) is displayed so that the operator can recognize whether or not the zero point adjustment switch 55a needs to be pressed, and in some cases, the user can be prompted to press the zero point adjustment switch 55a. 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 M converted from the WT is displayed. Preferably it is done.

However, the operator may forget the zero adjustment operation for the half-bridge output. When zero point adjustment is not performed on the half-bridge output and measurement is performed while there is a difference between the half-bridge outputs, it is necessary to prevent the span abnormality from being detected.
As a countermeasure, when the stable weight value described below is in the range between the lower limit value Wzl and the upper limit value Wzu shown in FIG. 5, the half-bridge output is in the zero point range and the zero flag is set to 1.
In addition, a weight value Wzz that is slightly away from the zero point in the positive direction is set in advance for detection of load removal. If the stable weight value (described below) of the half-bridge output returns to Wzz or less but is not within the range defined by the lower limit value Wzl and the upper limit value Wzu, the zero flag is reset.
In the measurement in which the zero flag is not set for all the half bridges, the classification and aggregation calculation for detecting the span abnormality described below is not performed (not adopted as the classification and aggregation data).

  Next, a countermeasure in the case of a hopper type weighing device that cannot rely on the operator's zero adjustment operation or when the operator forgets the zero adjustment operation for the half-bridge output will be described. As a countermeasure, by providing load change amount calculation means for calculating only the fluctuation amount due to the load load with respect to the half bridge output signals of the load cells 1A, 1B, and 1C as follows, a span abnormality is automatically and accurately performed. Can be detected.

<Description of stable weight value generation means>
For example, for the output W11 of the half bridge 1 of the load cell 1A, this W11 is generated at a time interval of, for example, Ta = several 100 msec after smoothing the load signal read from the A / D converter 24. The latest M W11s are always stored in the prepared M shift registers in order, and the maximum value-minimum value in the stored M W11s is within the preset allowable limit of the stability limit. Is determined to be in a stable state. In this way, stability determination is sequentially performed for each time interval Ta for the half-bridge outputs of all the load cells 1A, 1B, and 1C, and the average value of the shift register is calculated to determine the current weight measurement W11, that is, the load cell. The stable weight values are 1A, 1B, and 1C. This calculation process is executed in a stable weight value generation unit 52e (corresponding to "stable weight value generation means" in the present invention) in the central processing unit 52.

<Description of means for calculating stable load change amount>
In order to detect a span abnormality automatically and accurately, it is necessary to calculate only the fluctuation amount due to the load load as follows for the half-bridge outputs of all the load cells. For this reason, a stable load change amount calculation unit 52f (corresponding to the “stable load change amount calculation means” in the present invention) is provided in the central processing unit 52, and the stable load change amount calculation unit 52f has the latest information. A calculation is performed to calculate the difference between the stable weight value and the stable weight value generated at the timing immediately before the latest stable weight value for each load cell 1A, 1B, 1C as a stable load change amount.
In addition, if the value of M pieces of W11 is within a range representing the allowable value, it is determined that the value is stable. Further, the stability determination is sequentially performed at the Ta time interval for the half bridge outputs of all the load cells 1A, 1B, and 1C.

  Assuming that the object to be weighed M is accommodated in the hopper 2, the value of W11 read after a certain timing becomes larger than the allowable value, so that the shift register data deviates from the allowable value and the stable condition is not satisfied. It is assumed that the latest value that entered the shift register at the timing one time before the deviation has already reached the limit value of the allowable range. Therefore, to calculate the value of W11 as the stable weight value, the latest value is entered. It is appropriate to obtain the average value with M−1 values.

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 Each time the weight value is generated, the contents of the stable weight value storage register are updated with the latest stable weight value W11 as the previous stable weight value W1u. In this way, the latest stable weight value is always stored in the stable weight value storage register and updated to the latest value for the half bridge outputs of all the load cells 1A, 1B, and 1C. W21u; W12u, W22u; W13u, W23u. When the stable weight values of the half bridge outputs W11 to W23 of the load cells 1A, 1B, and 1C are generated together, the stable weight values of all the load cells 1A, 1B, and 1C and the currently stored stable weight values are obtained. Further, load change amounts W11p to W23p represented by the following equation (3) are calculated.
W11p = | W11−W11u |
W21p = | W21−W21u |
W12p = | W12−W12u |
W22p = | W22-W22u |
W13p = | W13-W13u |
W23p = | W23−W23u | (3)

When the change width Wh of the stable weight value is set in advance and all the load change amounts are larger than the change width Wh, that is, when the following equation (4) is satisfied simultaneously, each load cell 1A, 1B, 1C has a span error. Span abnormality between the half bridges 1 and 2 of the load cells 1A, 1B, and 1C is determined by assuming that the load change amounts W11p to W23p are large enough to determine the load. Here, as the value of Wh, since each load cell 1A, 1B, 1C is normally loaded with a maximum load of Ws / 4 with respect to the rated load Ws of the hopper type weighing device, it is 1/4 of that value. As such, a value such as Wh = Ws / 16 is set.
W11p-W23p> Wh (4)

For example, for the load cell 1A, the span change rate R1 is expressed by the following equation (5) based on the difference in load change between the half bridge 1 and the half bridge 2.
R1 = 1- (W21p / W11p) (5)
This parameter is defined as the half-bridge output comparison ratio.
The change rates R2 to R4 of other load cells can be obtained in the same manner.

For example, if the span of W11p changes by e from the state of W11p = W21p,

R1 = 1−W21p / {W11p · (1 + e)}
= 1- {1 / (1 + e)} ≈1- (1-e)
= E (e << 1)
When the span of W21p changes by e, R1 = −e
When the span of W11p changes by -e, R1 = -e
When the span of W21p changes by -e, R1 = e

It becomes the relationship.
R1 = W11p / W21p-1 and R2 = W12p / W22p-1 may be used.
If the zero point is adjusted for each half bridge, the fluctuation of the zero point of each half bridge output is not included, and it is accurately expressed as the rate of change of the half bridge span on either side to the half bridge span on the other side. be able to. The same applies to the rate of change R2 to R3 for the other load cells 1B and 1C.

Thus, in each load cell LCn (n = 1 to 3), the inequality (6) with respect to the allowable value Rh in which the span change rate Rn is set.
Rn> Rh (6)
If there is one that satisfies the condition, it is determined that the span of the load cell LCn is abnormal. In other words, it is possible to automatically and accurately specify which load cell span is abnormal among the load cells 1A, 1B, and 1C supporting the three portions of the hopper 2 in a normal weighing operation.

In this judgment method, all the half-bridge output zero point fluctuations are removed, so the load change difference is due to span fluctuations, so it is possible to accurately judge the span abnormality of a specific load cell. A signal processing means for doing this is constructed.
Since the half-bridge outputs with respect to the load applied to the strain body of one load cell are compared with each other, how the load cells 1A, 1B, 1C are arranged and the shape of the hopper 2 is asymmetric. Regardless of the distribution of the objects to be weighed M in the hopper 2 in every weighing, it is not affected by them, and the normal weighing operation is performed accurately to determine which load cell span is abnormal. Judgment can be made while continuing.

  However, when comparing the left and right half-bridge outputs, a difference may occur even if there is no failure due to the influence of vibration noise or electrical noise. It is preferable to have a half-bridge output comparison ratio with

  When an abnormality is determined, a sign that the span is abnormal, the number of the load cell that has failed, the content of the failure, etc. are displayed on the display device 54 so that the operator can identify them, and the rate of change of the span is also displayed. . The alarm signal is output by means such as lamp display, character display, and voice.

  By the way, in the above determination method, when it is detected that R1> Rh, it is only found that the span of W11p is increased or the span of W21p is decreased, and it is detected that R1 <−Rh. In this case, it is only determined that the span of W11p is decreased or the span of W21p is increased, and one of the half bridge outputs W11p and W21p of the load cells 1A, 1B, 1C is increased or decreased. It cannot be determined whether or not.

<Explanation of Span Abnormal Half Bridge Identification Unit, Span Change Detection Unit, Relative Comparison Unit>
In order to return to a state in which normal measurement can be performed, it is necessary to detect any span increase / decrease state in which half bridge is abnormal.
In the present embodiment, in the central processing unit 52, a span abnormality half-bridge specifying unit 52g (corresponding to “span abnormality half-bridge specifying means” in the present invention) and a span change detecting unit 52h (in the present invention “ And a relative comparison unit 52i (corresponding to "relative comparison means" in the present invention).
The span change detection unit 52h compares the two half-bridge load signals in the load cell where the span abnormality is detected.
The relative comparison means 52i compares the two half-bridge load signals in the load cell in which the span abnormality is detected with the two half-bridge load signals in load cells other than the load cell in which the span abnormality is detected.
Then, the span abnormality half-bridge specifying unit 52g, based on the comparison result by the span change detection unit 52h and the comparison result by the relative comparison unit 52i, out of the two half bridges in the load cell in which the span abnormality is detected. Identify which half-bridge is abnormal.

Which half-bridge span is changed in the increasing direction or the decreasing direction is defined by defining the relationship between the half-bridge output of a specific load cell and the outputs of the remaining load cells as follows. That is, the half-bridge output of the load cell identified as abnormal is compared with the half-bridge or full-bridge output of another normal load cell, and the determination is made based on the change state of the comparison result. In this case, the following relative ratios r11, r21; r12, r22; r13, r23 are defined as in the following equation (7) as compared with the full bridge output of a normal load cell.

・ About load cell 1A (LC1)
r11 = W11p / {(W2p + W3p) / 2} -1
r21 = W21p / {(W2p + W3p) / 2} -1
・ About load cell 1B (LC2)
r12 = W12p / {(W3p + W1p) / 2} -1
r22 = W22p / {(W3p + W1p) / 2} -1
・ About load cell 1C (LC3)
r13 = W13p / {(W1p + W2p) / 2} -1
r23 = W23p / {(W1p + W2p) / 2} -1 (7)

  When a load cell with an abnormal span is identified by comparison of half-bridge outputs (output comparison ratio), the determination of which half-bridge span is abnormal and the span is increasing or decreasing is the above relative ratio. This is done by determining the increase or decrease.

For example, the load cell 1A (LC1) is implemented according to the following theory.
That is, at the time of adjusting the load cell 1A as a single unit, the respective spans are adjusted and set so that the full bridge output of each load cell 1A, 1B, 1C and the two half-bridge output changes are equal to the reference load. Therefore, if the spans of the half bridge outputs of all the load cells 1A, 1B, and 1C are normal, r11 = r21 =... = R13 = r23 = 0 for an arbitrary load.
Here, for example, in the equation (7), when the span of the half bridge W11p changes by e, the relative ratio r11 also changes by e.

As mentioned in the description of the above equation (5),
(1) When there is an abnormality detected by R1> Rh,
(1.1) The span of W11 increases beyond e, and the span of W21 is normal. (1.2) The span of W11 is normal, and the span of W21 exceeds either e.
If the value of r11 increases and changes, it is a failure due to (1.1),
If the value of r21 is decreasing, it is determined that the failure is due to (1.2).
(2) When there is an abnormality detected by R1 <−Rh = −e,
(2.1) The span of W11 decreases beyond e, the span of W21 is normal (2.2) The span of W11 is normal, and the span of W21 increases beyond e,
If the value of r11 decreases, it is a failure according to (2.1),
If the value of r21 is increased, it is determined that the failure is due to (2.2).
Hereinafter, the same determination is made for the half bridges of the other load cells 1B and 1C.

  Therefore, while continuing normal metering, the output comparison ratios (moving average values) of R1, R2 and R3 are calculated (and their relative ratios are increased or decreased), and any load cell 1A, 1B, 1C is detected. When the output comparison ratio is larger than the allowable value and it is determined that the span is abnormal, it is detected whether the relative ratio has changed or not, and the abnormal half-bridge and the span increase / decrease are identified. I do.

  By the way, all the output spans of the three load cells 1A, 1B, 1C are normal and accurately adjusted to the zero point, and the hopper 2 is accurately and symmetrically manufactured for any cross section, and the load on the load cells 1A, 1B, 1C If the distribution is equal, the objects to be weighed M are accommodated in the hopper 2 without deviation, the distribution of the apparent specific gravity of the objects to be weighed M is equal, and the above equation (1) is adjusted, As long as the spans of the load cells 1A, 1B, and 1C are normal, all relative ratios are always 0 with respect to the accommodation of the object M to be weighed in an arbitrary load into the hopper 2.

However, even if the spans of all the load cells 1A, 1B, and 1C are normal, in the actual hopper type weighing device as described above, the relative ratios r11 to r23 are caused by the following factors (1) to (3), for example. Includes an inherent deviation and variation.
(1) Due to the positional relationship between the hopper 2 and the supply device, there is a fixed bias in the accommodation state of the object M to be weighed in the hopper 2.
(2) Shape error of the hopper 2 and displacement of the load cells 1A, 1B, 1C (in FIG. 1, the fixed distribution ratio between the load cells due to the disposition angles θ ₁ , θ ₂ , θ ₃ being not equal to each other)
(3) The distribution of the accommodation state of the objects to be weighed M in the hopper 2 naturally varies every time (refer to the one-dot chain line, two-dot chain line, and dotted line in FIG. 1B). Further, the distribution of the apparent specific gravity of the object M accommodated in the hopper 2 is not uniform every time.

  Due to the factors (1) and (2) above, the output ratios r11 to r23 of the half-bridge output of the specific load cell and the remaining load cells have a non-zero fixed deviation.

For example, suppose that the weighing object M with the load Wx can be uniformly accommodated in the hopper 2, and the distribution ratio of the loading load Wx to the load cells 1A, 1B, 1C is even if the weighing object M has a uniform apparent specific gravity distribution. k1: k2: k3 ≠ 1: 1: 1.
In addition, a bias load due to a fixed supply bias of the weighing object M due to a shift in the position of the feeding device 4 and the hopper 2 when the weighing object M is supplied to the hopper 2 also affects the distribution ratio.
When the load distribution ratio to the load cells 1A, 1B, and 1C when the object M of the load Wx is uniformly accommodated in the hopper 2 is k1: k2: k3, the relative ratios r11 to r23 are the above ( From equation (7), a fixed deviation such as the following equation (8) appears.

r11 = r21 = {(k1 · Wx) / {(k2 · Wx + k3 · Wx) / 2}} k1 / {(k2 + k3) / 2} = k1 / {(k2 + k3) / 2} −1
Similarly,
r12 = r22 = k2 / {(k3 + k1) / 2} -1
r13 = r23 = k3 / {(k1 + k2) / 2} -1 (8)
These are not 0, and the values of k1 to k3 are not easily obtained. Further, r11 to r13 vary depending on the accommodation state of the object to be weighed M in the hopper 2 and the variation in apparent specific gravity.

Therefore, the weighing operation was carried out while checking the size of the half-bridge output comparison ratios R1, R2, and R3 in the same load cell that is not affected by bias or variation, and the half-bridge of any load cell 1A, 1B, or 1C was normal. The span of r11 to r13 at the time when the values of R1, R2, and R3 are small and any of the half bridges of any of the load cells 1A, 1B, and 1C becomes abnormal, and any of R1, R2, and R3 is changed from 0 to Rh. R11 to r13 at the time when they are separated from each other are obtained, and the magnitude of the amount of change between them is evaluated. Since the amount of change is a difference, the fixed deviation is canceled out.
However, since the variation includes a variation, the variation cannot be accurately determined directly by the variation.

<Explanation of classification summary calculation>
For this reason, after the start of measurement, the output comparison ratio and the relative ratio are obtained for each of the load cells 1A, 1B, and 1C based on the half-bridge output measured for each measurement, and the classification and aggregation calculation is performed as follows.
The reason why the classification and aggregation calculation is necessary is that the variation in the span is reduced by reducing the variation in the relative ratio due to the variation in the accommodation state of the object to be weighed M in the hopper 2 that occurs during each measurement by obtaining the average value in a plurality of measurements. This is to accurately extract only the change due to.
As described above, when the load change amount is not used, that is, when relying on the operator's zero adjustment, the classification and aggregation calculation is performed only for the weighings for which the zero flag is set for all the half bridge outputs. The same applies to the case where the totalizing calculation is performed only when all the half bridge outputs have a value greater than or equal to a predetermined value, including the case where the load change amount is used.

  In the state where the load cell is close to normal, that is, in the range of the output change rate in the following (1) (3), and in the state where the load cell is close to abnormal, ie, in the range of the output change rate in the following (2) and (4) The relative ratio is classified according to the range of the output change rate and aggregated to obtain statistical data. Here, an allowable value for determining that the half-bridge output is a span abnormality is Rh (= e). This value is preset.

<(1) 0 <range of R1 ≦ (Rh / 4)>
The load cell 1A will be described.
When the value of the half-bridge output change rate R1 in the equation (5) is in the range of (1) 0 <R1 ≦ (Rh / 4),
The register R11a adds r11, adds r11 ² to register R11a'.
The register R21a adds r21, adds r21 ² to register R21a'.
Then, the number counter CA1a is incremented.
In the range of (1), the value of r11, r21 at the time when R1 is as close to 0 as possible, that is, the value at the time when the change of r11, r21 is as small as possible is different from the aggregate value of the range of (2) below. (D11, D21 below) becomes large and the determination becomes accurate. Therefore, when R1 is close to 0, v · Q ₀ are counted, and when R1> Rh / 4 is satisfied, the following r11ai, r21ai and standard deviations σ11ai and σ21ai are calculated.
If the load cell 1A changes rapidly and the number of counts does not reach v · Q ₀ , a warning is given that self-recovery is not possible. At the same time, an alarm / sign is displayed for the span abnormality of the load cell 1A.

<(2) R1> (3/4) · Rh range>
In the range of (2) R1> (3/4) · Rh, the value of the half-bridge output change rate R1 in the equation (5) is:
Adds the value of r11 to register R11b, adds r11 ² to register R11b'.
Adds the value of r21 to register R21b, adds r21 ² to register R21b'.
Then, the number counter CA1b is incremented.
In the range of (2), the value of r11, r21 at the time when R1 is as close to Rh as possible, that is, the value when r11, r21 changes as much as possible is handled with the aggregate value of the range of (1) above. Since the difference (D11, D21 below) becomes large and the determination becomes accurate, v shift registers are prepared, and the added values of r11, 21 and r11 ² , r21 ² are added every basic count Q ₀ . discard the oldest aggregate value and aggregate to complete the added value to store a new aggregate value in the shift register, the shift register is always as the aggregate value of the latest number of v Q ₀ times units are stored (Fig. 7), when R1> Rh is satisfied, the following r11av and r21av are preferably obtained using the total value of the shift register. The standard deviations σ11av and σ21av are also calculated based on the value of the shift register.

<(3)-(Rh / 4) <Range of R1 ≦ 0>
When the value of the half-bridge output change rate R1 in the equation (5) is in the range of (3) − (Rh / 4) <R1 ≦ 0,
Adds the value of r11 to register R11c, adds r11 ² to register R11c'.
Adds the value of r21 to register R21c, adds r21 ² to register R21c'.
Then, the number counter CA1c is incremented.
The calculation of the range (3) is performed in the same manner as the calculation of the range (1).

<(4) R1 <-(3/4) <Rh range>
In the range of (4) R1 <− (3/4) <Rh, the value of the half-bridge output change rate R1 in the equation (5) is:
Adds the value of r11 to register R11d, adds r11 ² to register R11d'.
Adds the value of r21 to register R21d, adds r21 ² to register R21d'.
Then, the number counter CA1d is incremented.
The calculation of the range (4) is performed in the same manner as the calculation of the range (2).

In this way, the calculations in the ranges (1) to (4) are performed.
For the half-bridge outputs of the other load cells 1B and 1C, a register is provided for the same operation in parallel.

  Then, when the value of R1 becomes R2> Rh or R1 <−Rh, an abnormality of the load cell 1A is alarmed, and which half bridge span is abnormal is determined by using aggregate data. .

In the aggregation, a basic aggregation count Q ₀ and a total aggregation count v · Q ₀ (value of v) are set for the R1 aggregation ranges of (1) to (4).
Aggregation in the range of any of the R1 of the above (1) to (4), the aggregate number reaches Q _0, it calculates a provisional average value and the standard deviation of the time of the number Q _0. From this point onward, counting of v · Q ₀ is started again.
Input range of relative ratio

Input range = average value ± standard deviation

When the relative ratio exceeds the above input range, it is not allowed to participate in the aggregation calculation, and the variation in the average value of the aggregation results is reduced. As a result, data having a large variation belonging to a range of about ± 32% or more around the average value is excluded.

While continuing weighing each time, the value of R1 is
(A) Assuming that R1> Rh is established, a comparison determination is made based on the total results of (1) and (2) above.
Also,
(B) Assuming that R1 <−Rh is established, a comparison determination is made based on the total results of (3) and (4) above.

If the above (a) is established, it is either an increase in the span of W11 (W21 is normal) or a decrease in the span of W21 (W11 is normal), so either check the change in the relative ratio r11 and the change in r21. Determine.
Further, the average value r11ai and standard deviation σ11ai of r11 and the average value r21ai and standard deviation σ21ai of r21 are obtained using the data in the total register in the range of 0 <R1 ≦ (Rh / 4) in (1).
Further, the average value r11av and standard deviation σ11av of r11 and the average value r21av and standard deviation σ21av of r21 are obtained using the data of the total register in the range of R1> (3/4) · Rh in (2) above, and r11 , R21 change amounts D11, D21 are calculated by the following equation (9).

D11 = r11av−r11ai
D21 = r21av−r21ai (9)

Here, K1 ′ = k1 / {(k2 + k3) / 2} is set.
If it is due to the increase in the span of W11, when the value of R1 is in the range of (1), the value of r11 is almost totaled from K1 ′ to K1 ′ · (1 + Rh / 4).
On the other hand, since r21 has a small change in W21p, values of K1 ′ · (1−Rh / 4) to K1 ′ · (1 + Rh / 4) are almost totaled.
When the value of R1 is in the above range (2), r11 is almost the sum of the values of K1 ′ · {1+ (3/4) · Rh} to K1 ′ · Rh.
On the other hand, since the change of W21p is also small for r21, almost the values of −K1 ′ · ((1−Rh / 4 to K1 ′ · (1 + Rh / 4)) are collected.

When the total value is averaged, r11av≈K1 ′ · {1+ (7/8) · Rh}, and since r11ai is within the range of (1) above, r11ai≈K1 ′ · {1+ (1/8) · Rh}.
On the other hand, the average value of R21 is closer to K1 ′.
K1 ′ is a value due to the arrangement of the load cells 1A, 1B, 1C and the asymmetry of the hopper 2 and is not exactly 1 but is close to 1 in a normal configuration, so if K1′≈1,
If it is due to the increase in the span of W11, the detection range of the change amount is about (7/8) .Rh- (1/8) .Rh = (3/4) .Rh. ).

D11≈ (3/4) · Rh
D21≈0 (10)

If it is due to the span decrease of W21, D11 and D21 are calculated by the following equation (11).
D11 ≒ 0
D21≈− (3/4) · Rh (11)

As described above, by calculating D11 and D21 corresponding to the range of R1, the output change rate R1 for the load cell 1A increases and the span of the half bridge 1 exceeds Rh if R1> Rh is satisfied. Alternatively, it is reliably determined that the span of the half bridge 2 is decreasing and exceeding Rh.
Therefore, when R1> Rh is satisfied, when the span of the half bridge 1 is increasing, D21 may be increasing simultaneously with D11 due to variation, or the span of the half bridge 2 may be decreasing. Even if D11 may decrease and change at the same time as D21 due to variations, it is determined whether D11 is increasing or decreasing and D21 is surely decreasing and changing. can do.

  Since the average values r11av, r11ai, r21av, and r21ai of the relative ratio vary, it is determined whether D11 is increasing or decreasing when R1> Rh is satisfied even if there is a variation. It is necessary to set an allowable value Rh of a size that can be obtained.

When examining the increasing change of D11, the condition for identifying that D11 is increasing is determined as follows.
The variation amount of r11av and r11ai in the change amount D11 = r11av−r11ai is examined.
Unless there is a special change in operating conditions, the standard deviations σ11ai and σ11abv of variation in v · Q ₀ measurement after the start of operation and v · Q ₀ measurement during operation are considered to be almost equal. The variation σd1 of D11 is determined as the following equation (12) by measuring v · Q ₀ times after the start of operation.

σd1 = (σ11ai ² + σ11av ² ) ^1/2 ≈2 ^1/2 · σ11ai
(12)

Similarly to the standard deviation σ11ai obtained above, the variation σd2 of D21 is calculated as shown in the following equation (13).

^{σd2 ≒ 2 1/2 · σ21ai ··· (} 13)

If the size of variation is evaluated with 2 sigma (or 3 sigma) as follows:

2 · σd1 <(3/4) · Rh

Then, as shown in FIG. 6, it is possible to identify that D11 has an increased variation from 0 in D11 almost certainly in a state in which D21 has variations similar to D11.
That is, it is possible to effectively carry out the determination for identifying an abnormal half bridge.
Therefore, when the span abnormality of the load cell 1A is determined in R1> Rh by setting the allowable value Rh for the determination, D11, which of the half bridge outputs of W11 and W21 is abnormal at the same time In order to be able to determine by D21, the allowable value Rh needs to be set as shown by the following equation (14).

Rh> (8/3) · σd1 (14)

That is,
If D11> 0 and D11> Rh, W11 is a span increase,
If D21 <0 and | D21 |> Rh, it can be determined that W21 is a span decrease.
As the variation amount, a value farthest from the average value may be used in the total data of v · Q ₀ times instead of using the standard deviation.

<Description of allowable value setting means according to accommodation variation>
From the formula (14), the allowable value Rh is Rh> (8/3) · σd1
Since the abnormal half-bridge cannot be specified unless the value is set to σ11av = Σ11ai in the above equation (12), the allowable value Rh is determined as the accommodation variation is always the same during measurement. It is necessary to set so as to satisfy the following expression (15).

σd1 = 2 ^1/2 · σ11ai
∴Rh> (8/3) · 2 ^1/2 · σ11ai (15)

(A) to (D) below regarding the setting of the allowable value Rh, the alarm output, and the sign display for determining whether the load cell is abnormal, and whether an abnormal half-bridge is specified and whether self-recovery operation is possible Arrange to do.
(A) First, the allowable value Rh is set before the operation operation.
(B) After the operation, the data is totalized in the register based on the range of R1 to R3 defined in (1) and (3) in the above-mentioned classification totaling calculation.
(C) When v · Q ₀ is added to the shift register, σ11ai and σ21ai are calculated for r11 and r21 at that time.
Since R2 and R3 are also calculated in parallel with R1, Rh ′ is also obtained for these.
Since the variation conditions for the load cells 1A, 1B, and 1C in one hopper 2 are substantially the same, all the standard deviations have substantially the same value.
However, since the timing of counting v · Q ₀ is different between R1 to R3, the value of Rh ′ is determined based on the earliest one of r11 to r23. Rh ′ may be selected by selecting the maximum standard deviation after all of r11 to r23 are aggregated.
If this is the standard deviation for r11, Rh ′ can be expressed as:

Rh ′ = (8/3) · 2 ^1/2 · σ11ai

(D)
(A) When the set value Rh is Rh> Rh ′ compared to the above Rh ′ Rh in the ranges (2) and (4) relating to R1 to R3 is used as it is in the classification and aggregation calculation.
When any of R1 to R3 exceeds Rh (when | Rn |> Rh), a load cell span abnormality is warned and a sign is displayed. At the same time, a self-recovery operable sign is displayed.
(B) When the set value of Rh is Rh ≦ Rh ′ In the above-described classification and aggregation calculation, Rh in the ranges (2) and (4) regarding R1 to R3 is replaced with Rh ′. However, load cell abnormality determination is performed based on Rh set in advance.
When any of R1 to R3 exceeds Rh (when | Rn |> Rh), a load cell abnormality is warned. At the same time, a self-return operation standby sign is displayed.
Further, when any of R1 to R3 exceeds Rh ′, a self-recovery operable sign is displayed.

  In doing so, either the Rh (or Rh ′) exceeds Rh (or Rh ′) or less than −Rh (or Rh ′) while calculating the moving average values of R1, R2 and R3 which are the comparison ratios of the half bridges by load cell during weighing. While calculating whether the values of r11 to r23 are determined in parallel, one of R1, R2, and R3 exceeds Rh (or Rh ′) or less than −Rh (or Rh ′). If an error is detected, an abnormal load cell is identified. Therefore, for the identified load cell, the load cell in which the span abnormality is detected at the time when the self-recovery operation possible sign is displayed, two half bridges, and other normal cells. Select the result of calculating the relative ratio with the output of the correct load cell, specify which half bridge is in span error, and perform self-reset operation If ability sign is displayed in reduced or span or increased connexion also determined to correct the abnormal span as described below.

<Explanation of variation attenuation calculation means>
In the present embodiment, the variation attenuation calculation unit 52l (corresponding to the “variation attenuation calculation means” in the present invention) in the central processing unit 52 obtains the average value of the variations in r11 to r23 due to the accommodation variation. Although the example which attenuates variation was shown, it is not limited to this.
For example, a median value is obtained for each basic number Q ₀ and used as a representative value, and an average value and standard deviation based on v representative values are obtained, or a linear equation is obtained by the least squares method every basic number Q ₀ and a straight line is obtained. Various variation attenuation calculation means may be used, such as obtaining an average value and standard deviation based on v representative values, using a value corresponding to the central number of times (Q _0/2 ) as a representative value from the equation.

Inhomogeneous arrangement of the load cells 1A, 1B, 1C, asymmetry of the hopper 2, and deviation of the supply device 4 can be ignored from the viewpoint of the accuracy of warning the span abnormality of the load cells 1A, 1B, 1C, and only the accommodation variation cannot be ignored. In the case of R1 in the above, the range of 0 <R1 ≦ (Rh / 4) of (1) and the range of − (Rh / 4) <R1 ≦ 0 of (3) above for r11 and r21 In the same manner, R2 and R3 are also performed in parallel, and Rh ′ is calculated by Rh ′ = (8/3) · σ11ai.
Since load cells 1A, 1B, and 1C are regarded as r11 to r23 = 0 at the normal time, for example, D11 and D21,
D11 = r11av
D21 = r21av
And the equations (12) and (13) are
σd1 = σ11ai = σ11av
σd2 = σ21ai = σ21av
It becomes. Therefore, Rh ′ = σ11ai is calculated.
Rh in the range of R1> (3/4) · Rh in the above (2) and R1 <− (3/4) · Rh in the above (4) In the same manner as described above, replacement of the load cell, display of the failure of the load cell, and display of the sign indicating that the self-recovery operation can be performed.

<Explanation about self-recovery method>
When it is determined that the return can be made, automatic return and manual return selection means are provided for returning to the normal weighing operation so that automatic return or manual return can be selected.

<Explanation of span correction>
When the automatic return is selected based on the determination that the return operation is possible, if the span increase of W11 is determined by the determination, the span increase of W11 of the half bridge output is reduced. ) Instead of K11 in equation (11), set K11 · (1-Rh) or K11 · (1-q · Rh), 0 <q <1 as a new K11 in anticipation of safety. continue. If the span of W21 is decreased, K21 · (1 + Rh) is set as a new K21 instead of K21.
Such correction is executed in a span correction unit 52j (corresponding to “span correction means” in the present invention) in the central processing unit 52.

  When manual return is selected, the alarm display span return switch is pressed only when the return is possible, and the operation works effectively, and the span correction calculation for the return is performed.

Regardless of whether it is automatic or manual, when the return process is completed, a sign indicating that the return process has been completed is displayed.
Even after the return processing, the load cell abnormality determination display remains, and is prepared for replacement of the failed load cell.

Conventionally, if the output of a faulty load cell is replaced using the output signal of another load cell, the fixed deviation or variation of the load applied to the faulty load cell cannot be detected, and each time the measurement is performed There arises a problem that the weight measurement value of the object M becomes a large error.
In the present embodiment, since the half bridge output of the load cell having an abnormal span is corrected by the span, even if there is the above-mentioned fixed deviation or variation in each measurement, an accurate output reflecting these is accurate. A weight measurement can be obtained.

<Full bridge output replacement, half bridge load signal alternative calculation means>
Here, when the abnormality of the span of W11 of the half bridge output is specified, the half bridge output W21 is used instead of the full bridge output W1 in W1 = (W11 + W21) / 2 in the above equation (1). , W1 = W21 may be obtained. Such an alternative calculation is executed in the half-bridge load signal alternative calculation unit 52k (corresponding to the “half-bridge load signal alternative calculation means” in the present invention) in the central processing unit 52.
In a measurement circuit in which a full bridge output exists independently, the full bridge output may be replaced with a half bridge output having a normal span.

<Description of Failure Diagnosis Device According to Other Embodiment>
In the failure diagnosis apparatus 20 according to the present embodiment, as shown in FIG. 3, the load signal for each half bridge is obtained and the full bridge output is obtained by adding two half bridge outputs. Instead of such a system configuration, as shown in FIG. 8, a system configuration in which the full bridge output is detected independently of the half bridge output may be adopted. In the failure diagnosis apparatus 20A, the same or similar parts as those of the failure diagnosis apparatus 20 of the previous embodiment are given the same reference numerals in the drawing, and detailed description thereof is omitted. The description will focus on differences from the failure diagnosis apparatus 20 of the embodiment.

The failure diagnosis apparatus 20A of the present embodiment includes an analog adder circuit 57, an A / D converter 58, and an arithmetic circuit 26 that are provided for the full bridge circuit 15.
Here, the full bridge circuit 15 and the arithmetic circuit 26 are the same as those used in the failure diagnosis apparatus 20 of the previous embodiment.
In the failure diagnosis apparatus 20 of the previous embodiment, two A / D converters 24 and 25 are used, but in the failure diagnosis apparatus 20A of this embodiment, one A / D converter 58 is used. In the failure diagnosis apparatus 20A, three A / D converters may be used for each of two half-bridge outputs and one full-bridge output.
In the fault diagnosis apparatus 20 of the previous embodiment, a DC voltage is applied in which the potential at the connection point 16 in the full bridge circuit 15 is + V and the potential at the connection point 17 is zero. A DC voltage is applied such that the potential at the connection point 16 is + V and the potential at the connection point 17 is −V. In this case, the half-bridge circuits 15a and 15b using the voltage reference fixed resistors 21 and 22 that are required in the failure diagnosis apparatus 20 of the previous embodiment are not necessary.

The analog adder circuit 57 includes a first operational amplifier 61, a second operational amplifier 62, a third operational amplifier 63, a fourth operational amplifier 64, and a fifth operational amplifier 65.
In the first operational amplifier 61, the input positive terminal 61a is connected to the connection point 18 of the full bridge circuit 15, the input negative terminal 61b is connected to the output terminal 61c, and the output terminal 61c is connected to the resistors 66 and 67. .
In the second operational amplifier 62, the input positive terminal 62 a is connected to the connection point 19 of the full bridge circuit 15, the input negative terminal 62 b is connected to the output terminal 62 c, and the output terminal 62 c is the resistor 68 and the fourth operational amplifier 64. Each is connected to the input positive terminal 64a.
In the third operational amplifier 63, the input positive terminal 63a is connected to the resistor 68, and is connected to the circuit ground 70 via the resistor 69, and the input negative terminal 63b is connected to the resistor 66. The output terminal 63 c is connected to the A / D converter 58 via the analog switch 72.
In the fourth operational amplifier 64, the input positive terminal 64 a is connected to the output terminal 62 c of the second operational amplifier 62, and the input negative terminal 64 b is connected to the circuit ground 70 via the resistor 73 and the resistor 74. The output terminal 64 c is connected to the A / D converter 58 via the analog switch 75.
In the fifth operational amplifier 65, the input positive terminal 65 a is connected to the circuit ground 70 via a resistor 76, and the input negative terminal 65 b is connected to a resistor 67, and is also connected to a output terminal 65 c via a resistor 77. The output terminal 65 c is connected to the A / D converter 58 via the analog switch 78.

  In the failure diagnosis apparatus 20A of the present embodiment, the analog load signal for the weighing instrument is synthesized by the third operational amplifier 63. The output load signal of the half-bridge circuit 15a on the connection point 18 side is eob, the load signal of the half-bridge circuit 15b on the connection point 19 side is eoa, and only one A / D converter 58 is used for all signals. The input is switched by analog switches 72, 75, 78. Thus, the number of A / D converters used may be selected as appropriate.

If the full-bridge output exists independently as in the failure diagnosis apparatus 20A, the full-bridge output and the two half-bridge outputs have the same value for the same load when the load cell is adjusted. That is, the span coefficient is set so that Wn = Wan = Wbn, and an initial weight storage memory and a zero point weight storage memory are provided.
Independent of the half-bridge output, W1 to W4 are processed by the following equations.
W1 = K1. (Wa1-Wi1) -Wz1
W2 = K2 · (Wa2-Wi2) -Wz2
W3 = K3. (Wa3-Wi3) -Wz3
W4 = K4. (Wa4-Wi4) -Wz4

  As mentioned above, although the hopper type | mold measuring device of this invention was demonstrated based on several embodiment, this invention is not limited to the structure described in the said embodiment, The structure suitably in the range which does not deviate from the meaning. Can be changed.

  The hopper type weighing device of the present invention is suitable for use in detecting an abnormality of a span generated in a strain gauge type load cell used in a weighing instrument in which a weighing object M is accommodated in a weighing container such as the hopper 2. Can be used.

1A ~ 1C Load cell 2 Hopper (weighing container)
8 Strain section 11-14 Strain gauge 15 Full bridge circuit (Wheatstone bridge circuit)
15a, 15b Half bridge circuit 52 Central processing unit 52a Half bridge load signal calculation part (half bridge load signal calculation means)
52b Span abnormality detection unit (span abnormality detection means)
52c Zero adjustment section (zero adjustment means)
52d Zero variation identifying unit (zero variation identifying means)
52e Stable weight value generation unit (stable weight value generation means)
52f Stable load change calculation unit (stable load change calculation means)
52g Span Abnormal Half Bridge Identification Unit (Span Abnormal Half Bridge Identification Method)
52h Span change detector (span change detector)
52i Relative comparison part (relative comparison means)
52j Span correction unit (span correction means)
52k half bridge load signal alternative calculation unit (half bridge load signal alternative calculation means)
52l Variation attenuation calculation unit (Variation attenuation calculation means)
55a Zero adjustment switch (zero adjustment means)

Claims (13)

A half bridge load signal is generated based on output signals from two terminals in a Wheatstone bridge circuit composed of at least four strain gauges affixed to the strain generating portion of the load cell. In a hopper type weighing device that accommodates an object to be weighed in a hopper supported by the load cell and measures the weight of the object to be weighed,
Half-bridge load signal calculation means for calculating the load load on the load cell so that each half-bridge load signal becomes a load signal of the same magnitude,
A span abnormality detecting means for detecting a load cell having an abnormal span among the plurality of load cells by comparing the half bridge load signals output from the half bridge load signal calculating means;
A hopper type weighing device comprising:   2. The hopper type weighing device according to claim 1, further comprising a zero point adjusting unit that manually or automatically adjusts the zero points of the two half bridge load signals output from the half bridge load signal calculating unit.   It is identified that at least one half bridge load signal of two half bridge load signals output from the half bridge load signal calculating means varies from a zero point individually set by the zero point adjusting means. The hopper type weighing device according to claim 2, further comprising a zero point variation identification means. Stable weight value generation means for performing stability determination of two half bridge load signals output from the half bridge load signal calculation means, and for generating a stable weight value of the load cell;
The difference between the latest stable weight value generated by the stable 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 cell as a stable load change amount. And a stable load change amount calculating means for providing,
2. The hopper type according to claim 1, wherein the span abnormality detection means detects an abnormality of the span of the load cell by comparing the stable load change amounts of the two half bridges calculated by the stable load change amount calculation means. Weighing device.   The span abnormality half-bridge specifying means for specifying which half bridge of the two half bridges in the load cell in which a span abnormality is detected by the span abnormality detection means is provided. Hopper type weighing device. A span change detecting means for comparing two half-bridge load signals in a load cell in which a span abnormality is detected by the span abnormality detecting means;
Two half-bridge load signals in the load cell in which the span abnormality is detected by the span abnormality detection means, and two half-bridge load signals in load cells other than the load cell in which the span abnormality is detected by the span abnormality detection means And a relative comparison means for comparing
6. The hopper type weighing device according to claim 5, wherein the span abnormality half-bridge specifying unit specifies a half bridge having an abnormal span based on a comparison result by the span change detection unit and a comparison result by the relative comparison unit. .   7. The hopper type weighing according to claim 6, wherein an allowable value for specifying a half bridge having an abnormal span in said span abnormal half bridge specifying means is set based on a magnitude of variation in a comparison result by said relative comparison means. apparatus.   The span abnormality half-bridge specifying means totals the comparison results of the relative comparison means in correspondence with the magnitude of the change of the comparison result by the span change detection means being near zero, and the span change detection means By summing up the comparison results of the relative comparison means at the time when the magnitude of the change in the comparison result according to is in the vicinity of the allowable value of the span change, the span of any half bridge of the load cell is in a normal state. The hopper type weighing device according to claim 6, wherein a half bridge whose span change is abnormal is specified by calculating a magnitude of the change.   6. The hopper type weighing device according to claim 5, further comprising a span correcting means for correcting a span of a half bridge load signal in a half bridge identified as having an abnormal span by the span abnormal half bridge identifying means.   The half bridge load that replaces the half bridge load signal of the half bridge identified as having an abnormal span by the span abnormal half bridge specifying means with the half bridge load signal of the half bridge that is not identified as having an abnormal span. 6. The hopper type weighing device according to claim 5, wherein a signal alternative calculation means is provided.   The span abnormality half-bridge specifying means, when the load cell having an abnormal span is specified based on the comparison result of the span change detection means and the comparison result of the relative comparison means, the span in the specified load cell is 7. The hopper type weighing device according to claim 6, wherein an abnormal half bridge is specified.   The hopper type weighing device according to claim 6, further comprising a variation attenuation calculation unit that attenuates a variation in a comparison result obtained by the relative comparison unit.   13. The variation attenuation calculating unit according to claim 12, wherein the variation attenuation calculating unit reduces the variation of the relative ratio by calculating an average value of the relative ratio based on a comparison result of the relative comparing unit obtained by a plurality of predetermined measurements. Hopper type weighing device.

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