JP5944232B2 - Non-automatic scale - Google Patents

Description

  The present invention relates to a non-automatic scale, and more particularly, to a non-automatic scale having a structure in which a placing body on which an object to be weighed is placed is supported by a plurality of load sensors.

  As this type of non-automatic scale, there is a conventional one disclosed in Patent Document 1, for example. According to this prior art, a rectangular mounting table as a mounting body is supported by four digital load cells as a plurality of load sensors arranged at four corners. When an object to be weighed is placed on the platform, a load due to the weight of the object to be weighed is distributed and applied to each digital load cell via the platform. Each digital load cell generates a digital load signal corresponding to the magnitude of the load applied to itself through the mounting table. Based on the total value of each digital load signal obtained from each of these digital load cells, the weight of the object to be weighed is obtained, and more specifically, a display weight value (display weight value) which is a display weight value is obtained.

  Furthermore, according to this prior art, each digital load cell is provided with an automatic zero point correction function, so-called zero tracking function, for automatically correcting the fluctuation of the zero point of the digital load signal due to drift. Strictly speaking, the above-described display weight value is obtained based on the total value of each digital load signal after the zero point correction by the zero tracking function for each digital load cell, that is, the individual zero tracking function. Accordingly, as a result, the zero correction for the displayed weight value representing the weight of the object to be weighed is performed by the individual zero tracking function. The individual zero tracking function is also used for evaluating whether or not an abnormality such as a failure has occurred in each digital load cell, so-called abnormality diagnosis. Specifically, the zero point correction amount (drift amount) by the individual zero tracking function is accumulated for each digital load cell. When the accumulated value (absolute value thereof) becomes equal to or greater than a predetermined reference value (second reference value), it is diagnosed that the corresponding digital load cell is abnormal. As described above, in the non-automatic scale, a function for automatically correcting the zero point of the display weight value is necessary, and at the same time, an abnormality is detected in each digital load cell based on the zero point correction amount for each digital load cell. There is also a need for the ability to diagnose whether it has occurred.

JP 2003-35592 A

  Incidentally, in the Japanese Industrial Standard (B7611-2), the performance and the like of the non-automatic scale are specified in detail. In particular, with regard to the zero tracking function (zero tracking device), it operates when the zero correction does not exceed 1/2 of the scale within one second, in other words, a load load exceeding 1/2 of the scale is applied. It is stipulated that it should not operate if That is, when the output of the load cell fluctuates, a standard for determining whether this fluctuation is due to drift or due to application of a load is defined.

  Here, for example, in the above-described conventional technology, an object to be weighed having a weight exceeding 1/2 of the scale (in other words, the individual zero tracking function should not be activated) is placed on the platform. It is assumed that the placement position of the object to be weighed on the platform is extremely biased. In this case, the load load (the load due to the weight of the object to be weighed) is applied only to some of the digital load cells, and the load load is hardly applied to the other digital load cells. obtain. Then, the digital load signal from the digital load cell to which the load load is applied fluctuates relatively greatly. Although this change is correctly determined to be due to the application of the load load, it is almost the load load. The digital load signal from the digital load cell to which no voltage is applied fluctuates only slightly, and there is a possibility that the slight fluctuation is erroneously determined to be caused by drift. Then, the individual zero tracking function malfunctions to correct the erroneously determined fluctuation of the digital load signal. If the individual zero tracking function malfunctions in this way, an error appears in the displayed weight value based on the total value of each digital load detection signal including the digital load signal that has been erroneously corrected by this malfunction. There is a disadvantage that the displayed weight value is smaller than the original value. That is, in the conventional technique in which the display weight value is automatically corrected by the individual zero tracking function, the automatic zero correction of the display weight value may not be accurately performed.

  Accordingly, the present invention is capable of always accurately and accurately realizing automatic zero correction of the displayed weight value representing the weight of the object to be weighed while realizing whether or not each load sensor is normal. The purpose is to provide a scale.

  In order to achieve this object, the present invention provides a display weight calculation means, a total zero tracking means, a non-automatic scale having a structure in which a placing body on which an object to be weighed is placed is supported by a plurality of load sensors, Individual load calculation means, individual zero tracking means, accumulation means, and evaluation means are provided. Of these, the display weight calculation means obtains a display weight value representing the weight of the object to be weighed based on the total load detection signal that is the sum of the load detection signals obtained from the load sensors. The total zero tracking means monitors the zero point of the displayed weight value and corrects it when the zero point of the displayed weight value fluctuates. Further, the individual load calculation means obtains an individual load value representing a component due to the weight of the object to be weighed among the loads applied to the respective load sensors based on the corresponding load detection signal. The individual zero tracking means monitors the zero point of the individual load value corresponding to each load sensor, and corrects the zero point of the fluctuating individual load value when any zero point of the individual load value fluctuates. To do. In addition, the accumulating means accumulates the zero point correction amount by the individual zero tracking means for the individual load values corresponding to the respective load sensors for each corresponding to the respective load sensors. Then, the evaluation means evaluates whether or not each load sensor is normal based on the accumulated value by the accumulation means for the individual load value corresponding to each load sensor.

  In this configuration, for example, when an object to be weighed is placed on the mounting body, a load due to the weight of the object to be weighed is distributedly applied to each load sensor via the mounting body. Each load sensor generates a load detection signal corresponding to the magnitude of the load applied to the load sensor itself. Based on the total load detection signal that is the sum of the load detection signals obtained from the load sensors, a display weight value representing the weight of the object to be weighed is obtained by the display weight calculation means. In addition, an individual load value representing a component due to the weight of an object to be weighed among loads applied to each load sensor, that is, a load load component, is individually determined based on a load detection signal corresponding to each load sensor. It is obtained by the load calculation means. On the other hand, the display weight value is ideally zero when the object to be weighed is not placed on the placing body, that is, in a so-called hanging state. Also, each individual load value is ideally zero. However, when the load detection signal of a certain load sensor fluctuates due to drift, the individual load value corresponding to the certain load sensor is not zero, that is, the zero point fluctuates. Further, the display weight value obtained based on the total load detection signal including the load detection signal of the certain load sensor is not zero, that is, the zero point fluctuates (in addition, each load detection signal of two or more load sensors is changed to each load detection signal). When fluctuation due to drift occurs, the fluctuation due to drift is canceled between these load detection signals, and as a result, the displayed weight value may remain zero). Therefore, the total zero tracking means monitors the zero point of the display weight value and corrects it when the zero point of the display weight value fluctuates. In addition, the individual zero tracking means monitors the zero point of the individual load value corresponding to each load sensor, and when any zero point of the individual load value fluctuates, the individual zero value of the fluctuating individual load value is detected. to correct. That is, according to the present invention, the total zero tracking function for automatically correcting the zero point of the displayed weight value and the individual zero tracking function for automatically correcting the zero point of each individual load value are provided. A kind of zero tracking function is provided. Since these two types of zero tracking functions correct different objects independently of each other, they do not affect each other. Therefore, for example, the total zero tracking function can correct the zero of the displayed weight value without being affected by the individual zero tracking function. In addition, the individual zero tracking function can correct the zero of each individual load value without being affected by the total zero tracking function.

  In addition, the accumulating means accumulates the zero point correction amount by the individual zero tracking function for the individual load values corresponding to the respective load sensors for each corresponding to the respective load sensors. Here, for example, when an abnormality such as a failure occurs in a certain load sensor, the accumulated value by the accumulating means for the individual load value corresponding to the load sensor becomes an abnormal value. Specifically, the absolute value of the accumulated value is excessively large. Become. Using this, the evaluation means evaluates whether or not each load sensor is normal based on the accumulated value by the accumulation means for the individual load value corresponding to each load sensor. Specifically, for example, the absolute value of each cumulative value is compared with a predetermined threshold value, and the load sensor whose absolute value is less than or equal to the threshold value is normal. Evaluate as abnormal.

  The total zero tracking function determines whether or not the vehicle is in the above-described hung state based on the total load detection signal and monitors the zero point of the displayed weight value when it is determined that the hung state is in the hung state. It may be a thing. In this case, the individual zero tracking function may monitor the zero point of the individual load value corresponding to each load sensor when it is determined by the total zero tracking function that the individual zero tracking function is in the idle state.

  That is, the total zero tracking function automatically corrects the zero point of the displayed weight value as described above. The zero point of the displayed weight value referred to here is the value of the displayed weight value in the empty state. Ideal value. Therefore, the total zero tracking function can monitor the zero point of the displayed weight value only when it is in the idle state, and thus can correct the zero point of the displayed weight value. In other words, in order to realize the total zero tracking function, it is necessary to determine whether or not it is in an idle state. Therefore, the total zero tracking function determines whether or not the vehicle is in the idle state based on the total load detection signal. Since the total load detection signal is the sum of all the load detection signals, for example, it basically does not change (except for fluctuation due to drift) when in an idle state, and when it is not in the empty state, When an object to be weighed is placed on the body, it always shows a variation according to the weight of the object to be weighed. Based on such a total load detection signal, the total zero tracking function can accurately determine whether or not it is in an idle state. If it is determined that the display is in the idle state, the total zero tracking function monitors the zero point of the display weight value, and corrects this when the zero point of the display weight value fluctuates.

  On the other hand, the individual zero tracking function automatically corrects the zero point of the individual load value corresponding to each load sensor. The zero point of the individual load value referred to here is the load load ( This is an ideal value of the individual load value when the load due to the weight of the object to be weighed) is not applied. Therefore, the individual zero tracking function can monitor the zero point of the individual load value corresponding to each load sensor only when no load is applied to each load sensor. The zero value of the load value can be corrected. In other words, in order to realize the individual zero tracking function, it is necessary to determine whether or not a load is applied to each load sensor. The state in which no load is applied to each load sensor includes an empty state. Therefore, the individual zero tracking function recognizes whether or not a load load is applied to each load sensor by using the determination result of whether or not it is in an empty state by the total zero tracking function. . That is, the individual zero tracking function recognizes that no load is applied to each load sensor when it is determined by the total zero tracking function that the load is in the idle state. Only after recognizing that, the individual zero tracking function monitors the zero point of the individual load value corresponding to each load sensor, and when that zero point of any individual load value fluctuates, Correct. In other words, the individual zero tracking function becomes operable on the condition that it has been determined that it is in the idle state by the total zero tracking function.

  Separately from this, the individual zero tracking function, for example, determines whether or not a load load is applied to each load sensor, and determines that the load load is not applied. In this case, the zero point of the corresponding individual load value may be monitored, and consequently the zero point of the individual load value may be corrected. Specifically, the load detection signal of each load sensor is individually observed. For a load sensor in which the load detection signal shows a relatively large variation, it is determined that the load load is being applied, and the load detection signal does not vary or shows a very slight variation. It is determined that the sensor is in a state where no load is applied. For the load sensor determined to be in a state where no load is applied, the zero point of the corresponding individual load value is monitored, and when the zero point of the individual load value fluctuates, the correction is made. May be.

  However, in this configuration, although the object to be weighed is mounted on the mounting body, the zero point correction by the individual zero tracking function is performed for some load sensors, that is, the individual zero tracking function is activated. There are things to do. For example, the mounting body is a substantially rectangular plate-shaped body, and the four corners of the mounting body are supported by each load sensor, and the mounting position of the object to be weighed on the mounting body is extremely biased. If that is the case. That is, in this case, a situation can occur in which a load is applied only to some of the load sensors and almost no load is applied to other load sensors. In such a situation, for a load sensor to which a load is applied, the load detection signal fluctuates relatively greatly, so that the individual zero tracking function does not operate. On the other hand, for a load sensor to which almost no load is applied, the load detection signal does not change or shows only a slight change, so that the individual zero tracking function may be activated. However, there is no particular inconvenience due to this.

  That is, the individual zero tracking function according to the present invention is used for evaluating whether or not each load sensor is normal, but does not affect the total zero tracking function at all and does not affect the displayed weight value. Therefore, even if the object to be weighed is mounted on the mounting body as described above, even if the individual zero tracking function is activated for some load sensors, the total zero tracking is completely independent of this. The zero point correction of the display weight value by the function is performed, so that the accurate display weight value can be obtained. When the object to be weighed is lowered from the mounting body, the individual zero tracking function is activated again for the part of load sensors. Therefore, there is no influence in the evaluation of each load sensor using this individual zero tracking function.

  In addition, according to the above-described configuration that the individual zero tracking function can be operated on the condition that it is determined to be in the idle state by the total zero tracking function, the object to be weighed is placed on the mounting body. When this is done, the individual zero tracking function will not be activated.

  In addition, the individual load value that is the zero point correction target by the individual zero tracking function in the present invention is smaller than the display weight value that is the zero point correction target by the total zero tracking function. Therefore, it is desirable that the correction resolution by the individual zero tracking function is higher (finer) than the correction resolution by the total zero tracking function.

  In the present invention, the zero point setting function (zero point setting device: a device for setting the display to zero when idling) specified in Japanese Industrial Standards, especially the semi-automatic zero point setting function (semi-automatic zero point setting device: manually operated) A device for automatically setting the display to zero may be further provided. Specifically, total zero setting means for setting the zero of the displayed weight value in response to a zero setting command arbitrarily given by manual operation from the outside, and corresponding to each load sensor in response to the zero setting command Individual zero point setting means for setting the zero point of the individual load value may be provided. In short, there are two types of zero setting functions: a comprehensive zero setting function for forcibly setting the zero of the displayed weight value, and an individual zero setting function for forcibly setting the zero of each individual load value. It may be provided. It is desirable that these zero point setting functions operate simultaneously in response to mutually common zero point setting commands.

  As described above, according to the present invention, whether or not each load sensor is normal is evaluated using the individual zero tracking function. The automatic zero correction of the displayed weight value representing the weight of the object to be weighed is always accurately performed by the total zero tracking function without being affected by the individual zero tracking function. That is, automatic zero point correction of the displayed weight value can always be realized accurately while realizing whether or not each load sensor is normal.

It is an illustration figure which shows schematically the whole structure of one Embodiment of this invention. It is an illustration figure which shows schematically the external appearance of the measurement part in the embodiment. 3 is a block diagram schematically showing an electrical configuration of each load cell in the same embodiment. FIG. It is an illustration figure which shows notionally the digital load detection signal output from the load cell. It is an illustration figure which shows the structure of the digital load detection signal generation circuit formed notionally by CPU in the load cell. It is an illustration figure for demonstrating the process sequence by CPU in the data processor in the embodiment. It is an illustration figure which shows the structure of the comprehensive arithmetic circuit conceptually formed by CPU in the data processor. It is an illustration figure for demonstrating the process procedure different from FIG. 6 by CPU in the same data processor. It is an illustration figure which shows the structure of the separate arithmetic circuit formed notionally by CPU in the data processor. It is an illustration figure for demonstrating the process procedure further different from FIG. 8 by CPU in the same data processor. It is an illustration figure which shows the structure of the left side arithmetic circuit formed notionally by CPU in the data processor. It is an illustration figure for demonstrating the process procedure replaced with FIG. It is an illustration figure for demonstrating the process procedure replaced with FIG.

  An embodiment of the present invention will be described by taking a track scale 10 shown in FIG. 1 as an example.

  As shown in the figure, the track scale 10 according to the present embodiment includes, for example, a weighing unit 30 installed outdoors, and a data processor 50 installed indoors where the weighing unit 30 can be visually recognized. ing. The weighing unit 30 includes a weighing table 32 as a mounting body on which a track 100 as an object to be weighed is placed, and four digitals of the same standard as a plurality of load sensors that support the weighing table 32. Formula load cells (hereinafter simply referred to as “load cells”) 34, 34,.

  Specifically, as shown in FIG. 2, the weighing table 32 is a substantially rectangular plate-like body, which is made of a substantially rectangular metal whose rigidity is reinforced by an appropriate reinforcing member such as a rib (not shown). It is a flat plate. The four corners of the weighing table 32 are supported by the load cells 34, 34,... So that the upper and lower surfaces of the weighing table 32 are horizontal. Each load cell 34 is of a so-called double convex type having a structure in which both ends (of the columnar strain body) protrude in an approximately hemispherical shape toward the outside, and one of the both ends is connected to the lower surface of the weighing table 32. It is in a state where it abuts and the other abuts on the ground surface 36 such as the ground, so to speak, it is in an upright posture.

  The truck 100 travels slowly along the longitudinal direction of the weighing table 32, so that the truck 100 gets on the weighing table 32 or is lowered from the weighing table 32. Further, individual identification codes “LC1”, “LC2”, “LC3” and “LC4” are attached to the load cells 34, 34,. For example, an identification code “LC1” is attached to the load cell 34 arranged at the left corner (upper left corner in FIG. 2A) of the weighing platform 32 on the entrance side, and the left corner of the weighing platform 32 on the exit side. An identification code “LC2” is attached to the load cell 34 arranged in (the upper right corner in FIG. 2A). An identification code “LC3” is attached to the load cell 34 arranged at the right corner (the lower left corner in FIG. 2A) of the weighing platform 32 on the entrance side. An identification code “LC4” is attached to the load cell 34 arranged at the right corner (the lower right corner in FIG. 2A). Thereafter, the load cells 34, 34,... May be expressed using the identification codes “LC1”, “LC2”, “LC3”, and “LC4”. Further, the unspecified load cell 34 may be expressed by using a symbol “LCn” (n = 1, 2, 3, and 4).

When the truck 100 gets on the weighing table 32, that is, is placed, a load corresponding to the weight of the truck 100 is distributed and applied to the load cells 34, 34,. Each load cell 34 (LCn) generates a digital load detection signal wa [n] corresponding to the magnitude of the load applied to itself. Referring to FIG. 3 in detail, each load cell LCn has four or more strain gauges 36, 36,... Attached to a strain generating body (not shown) connected in a bridge shape. A Wheatstone bridge circuit 38 having the above-described configuration is provided. The Wheatstone bridge circuit 38 has a voltage value of an excitation power supply voltage supplied from an excitation power supply circuit (not shown) for driving the Wheatstone bridge circuit 38 and distortions generated in the strain gauges 36, 36,. And an analog load detection signal wa indicating a voltage value corresponding to the magnitude of. The analog load detection signal wa is appropriately amplified by the amplification circuit 40 and then input to the A / D conversion circuit 42. Note that an analog filter (not shown) for removing a noise component included in the analog load detection signal wa, particularly a noise component mainly having an electrical factor with a frequency of 100 Hz or more, is provided on the input side or the output side of the amplifier circuit 40. A circuit is provided. The A / D conversion circuit 42 digitizes the analog load detection signal wa after amplification by the amplifier circuit 40, and converts it into a digitized signal wad [n]. Further, the digitized signal wad [n] after conversion by the A / D conversion circuit 42 is a CPU (Central
Processing Unit) 44.

  The CPU 44 obtains the digital load detection signal wa [n] by substituting the digitized signal wad [n] input from the A / D conversion circuit 42 into Equation 1 described later. The digital load detection signal wa [n] is sent to the data processor 50 via the input / output interface (I / O) circuit 46, and strictly, in response to a request from the data processor 50. The operation of the CPU 44 including the calculation of the digital load detection signal wa [n] follows an individual control program stored in the memory circuit 48 as individual storage means attached to the CPU 44.

  Returning to FIG. 1, the data processor 50 receives the digital load detection signals wa [1], wa [2], wa [3] and wa [4] sent from the load cells LC1, LC2, LC3 and LC4. An input / output interface (I / O) circuit 52 for receiving input is provided. Each of the digital load detection signals wa [1], wa [2], wa [3] and wa [4] input to the input / output interface circuit 52 is further input to the CPU 54 as a comprehensive calculation means. The CPU 54 represents the weight of the track 100 as will be described later based on the respective digital load detection signals wa [1], wa [2], wa [3] and wa [4] input via the input / output interface circuit 52. The display weight value Wd is obtained. The display weight value Wd is displayed on a digital display 56 as display means connected to the CPU 54 via the input / output interface circuit 52. Although not shown, the display weight value Wd is also output to the outside via the input / output interface circuit 52 and sent to an external device such as a printing device, for example.

  In parallel with this, the CPU 54 applies to the load cells LC1, LC2, LC3 and LC4 based on the respective digital load detection signals wa [1], wa [2], wa [3] and wa [4]. The individual load values wd [1], wd [2], wd [3] and wd [4] representing the components due to the weight of the truck 100, that is, the load components, are calculated. These individual load values wd [1], wd [2], wd [3] and wd [4] are also displayed on the digital display 56 and output to the outside. Note that these individual load values wd [1], wd [2], wd [3] and wd [4] are used to evaluate whether the load cells LC1, LC2, LC3 and LC4 are operating normally, for example. In other words, it is used for diagnosing whether or not an abnormality such as a failure has occurred in each of the load cells LC1, LC2, LC3 and LC4. However, this so-called abnormality diagnosis is also realized by an abnormality diagnosis function described later.

  Further in parallel, the CPU 54 determines the two load cells LC1 on the left side based on the digital load detection signals wa [1] and wa [2] from the two load cells LC1 and LC2 supporting the left side of the weighing platform 32. A so-called left load value Wd12 representing a component due to the load load among the loads applied to LC2 is obtained. Similarly, the CPU 54, based on the digital load detection signals wa [3] and wa [4] from the two load cells LC3 and LC4 that support the right side of the weighing platform 32, A right-side load value Wd34 representing a component due to the load load among the loads applied to the LC4 is obtained. These left load value Wd12 and right load value Wd34 are also displayed on the digital display 56 and output to the outside. The left side load value Wd12 and the right side load value Wd34 are particularly used to determine the left and right weight balance of the truck 100, that is, a so-called uneven load. Since the procedure for calculating the unbalanced load is well known, detailed description thereof is omitted here.

  The operation of the CPU 54 is controlled by a comprehensive control program stored in a memory circuit 58 as general storage means attached to the CPU 54. Further, for example, an operation key 60 as command input means for inputting various commands such as a zero setting command and a reset command, which will be described later, is connected to the CPU 54 via an input / output interface circuit 52.

  On the other hand, when the truck 100 descends from the weighing platform 32 and enters an empty state in which no object is placed on the weighing platform 32, the display weight value Wd is ideally zero. Also, the individual load values wd [1], wd [2], wd [3] and wd [4] are ideally zero. Further, the left load value Wd12 and the right load value Wd34 are ideally zero. However, when the analog load detection signal wa of any load cell LCn fluctuates due to a drift such as temperature drift, and this fluctuation appears in the digital load detection signal wa [n], the individual load value wd [n corresponding to the load cell LCn. ] Is no longer zero, that is, the zero point fluctuates. The displayed weight value Wd is also no longer zero, that is, the zero point fluctuates (in the case where drift occurs in the plurality of load cells LCn, the fluctuation due to the drift is canceled between the plurality of load cells LCn. As a result, the display weight value Wd may remain zero). Further, when the load cell LCn in which the drift occurs is at least one of the left load cells LC1 and LC2, the zero point of the left load value Wd12 varies (the drift occurs in both the left load cells LC1 and LC2). In the case where there is a difference, the fluctuation due to the drift is canceled between these LC1 and LC2, and as a result, the left load value Wd12 may remain zero). Similarly, when the load cell LCn in which the drift occurs is at least one of the right load cells LC3 and LC4, the zero point of the right load value Wd34 fluctuates (note that both the right load cells LC3 and LC4 are drifted). In the case where the fluctuation occurs due to the drift between the LC3 and LC4, the right load value Wd34 may remain zero as a result).

Therefore, the track scale 10 according to the present embodiment has a total zero tracking function for automatically correcting the zero point of the display weight value Wd. In addition, an individual zero tracking function for automatically correcting the zero point of each individual load value wd [n] is provided. Furthermore, a left zero tracking function for automatically correcting the zero point of the left load value Wd12 and a right zero tracking function for automatically correcting the zero point of the right load value Wd34 are also provided. These zero tracking functions will be described in detail below. Here, the weighing Mc of the track scale 10 is 50 t (= 50 × 10 ³ kg), and the scale (actual scale) Sd is 10 kg. In other words, the measurement resolution Rs (= Sd / Mc) is 1/5000. In addition, the track scale 10 according to the present embodiment has a zero point setting function defined by Japanese Industrial Standards, particularly an initial zero point setting function (initial zero point setting device: automatically zeroing the display before using the scale after turning on the power. And a semi-automatic zero point setting function. In addition, a zero point display function (zero point display device: a device that displays a special signal when the deviation from the zero point is within ¼ of the scale value) defined in the Japanese Industrial Standard is provided. In addition, an abnormality diagnosis function for diagnosing whether or not an abnormality such as a failure has occurred in each load cell LCn is provided. These functions will also be described as appropriate.

  First, the total zero tracking function will be described. This total zero tracking function automatically corrects the zero point of the display weight value Wd as described above. According to the Japanese Industrial Standard, the accuracy of the zero point of the display weight value Wd is 1 / of the scale value. It is stipulated that it must not exceed 4, in other words, it must be 1/4 or less of the scale. In accordance with this rule, in the present embodiment, for example, the zero correction of the display weight value Wd is performed with the accuracy of 1/4 of the scale Sd, that is, with the correction resolution Sb of 2.5 kg (= 10 kg / 4). Shall be.

  Under this premise, in each load cell LCn, in detail, the CPU 44 in the load cell LCn performs an operation based on the following equation 1 to obtain the digital load detection signal wa [n].

<< Formula 1 >>
wa [n] = k [n] (wad [n] −wis [n])

  In Equation 1, wad [n] is a digitized signal after conversion by the A / D conversion circuit 42 described above. Wis [n] is an initial load value of the load cell LCn alone representing an initial load component of the load cell LCn itself. The initial load value wis [n] of the single load cell LCn is in a single state before the load cell LCn is incorporated as a component of the measuring unit 30, and no load is applied to the load cell LCn. This is the stored value of the digitized signal wad [n] when there is no load. K [n] is a span coefficient (gain) of the load cell LCn alone. The span coefficient k [n] of the load cell LCn alone is a known reference load that is equal to or less than the rated capacity (preferably equivalent to the rated capacity) of the load cell LCn. 4, the width sa of one count value (digital value) of the digital load detection signal wa [n] is 0.625 kg (= Sd / {N / (Sb / Sd)} is set to correspond to a weight value of 10 kg / 16). Here, N is the number of load cells LCn, that is, N = 4. The span coefficient k [n] is obtained together with the initial load value wis [n] when the load cell LCn is adjusted (at the time of assembly in a factory or at the site) and stored in the memory circuit 48.

  The calculation based on Equation 1 can be expressed by a digital load detection signal generation circuit 200 as shown in FIG. 5, for example. That is, the digital load signal generation circuit 200 has an adder 202 to which the digitized signal wad [n] after being converted by the A / D conversion circuit 42 is input. The adder 202 subtracts the initial load value wis [n] of the load cell LCn alone stored in the memory circuit 48 from the digitized signal wad [n]. The signal (= wad [n] −wis [n]) after the subtraction processing by the adder 202 is input to the multiplier 204. The multiplier 204 multiplies the signal after the subtraction processing by the span coefficient k [n] of the load cell LCn alone stored in the memory circuit 48. Thereby, the digital load detection signal wa [n] is generated, that is, the calculation based on Expression 1 is realized.

  In Formula 1 (FIG. 5), although the initial load value wis [n] of the load cell LCn alone is considered, the initial load component of the entire weighing unit 30 including the weight of the weighing table 30 is not considered. . Therefore, in the digital load detection signal wa [n] based on the equation 1, the zero point is not fixed, and is indefinite. Then, the digital load detection signal wa [n] is input to the data processor 50 and further input to the CPU 54 with the zero point being indefinite.

  The CPU 54 in the data processor 50 sums up the digital load detection signals wa [1], wa [2], wa [3] and wa [4] from the load cells LC1, LC2, LC3 and LC4, that is, Based on the following equation 2, the total digital load detection signal Wa is obtained.

<< Formula 2 >>
Wa = wa [1] + wa [2] + wa [3] + wa [4]

  As shown in FIG. 6 (a), the total digital load detection signal Wa has a width Sa of one count value of each digital load detection signal wa [1], wa [2], wa [3] and wa [4]. ] Is equivalent to each one count value width sa (Sa = sa), that is, the one count value width Sa is a signal corresponding to a weight value of 0.625 kg. Also in this total digital load detection signal Wa, the zero point is uncertain.

  Further, the CPU 54 divides the total digital load detection signal Wa by the number N (= 4) of the load cells LCn, that is, based on the following expression 3, the 1 count value width Sa of the total digital load detection signal Wa is calculated. In other words, the count value width change signal Wa ′ is obtained. In the calculation based on Equation 3, the decimal part is rounded down.

<< Formula 3 >>
Wa ′ = Wa / N = Wa / 4 Ｎ N = 4

  As shown in FIG. 6B, the count value width change signal Wa ′ based on this equation 3 is N times the one count value width Sa of the total digital load detection signal Wa (Sa ′ = Sa · N). That is, the 1 count value width Sa ′ corresponds to 2.5 kg (= 0.625 kg × 4), that is, corresponds to the correction resolution Sb described above. Also in the count value width change signal Wa ', the zero point is uncertain. After obtaining the count value width change signal Wa ′, the CPU 54 performs an operation based on the following equation 4 to determine the zero point of the count value width change signal Wa ′, in other words, to obtain such an internal signal Wb. Run.

<< Formula 4 >>
Wb = K · (Wa′−Wi) −Wf−Wz

  In Equation 4, Wi is an initial load value of the entire weighing unit 30, and more specifically, a stored value of the count value width change signal Wa ′ when there is an empty state in which no object is placed on the weighing table 32. It is. K is a span coefficient of the entire weighing unit 30. As shown in FIG. 6 (c), the span coefficient K is expressed by the equation 4 when a reference weight having a known weight equal to or less than the weighing Mc (preferably equivalent to the weighing Mc) is placed on the weighing table 32. The 1 count value width Sb of the internal signal Wb based is set to correspond to 2.5 kg. However, if the span coefficient k [n] of each load cell LCn in Equation 1 is adjusted accurately, the span coefficient K of the entire weighing unit 30 is basically 1. As can be seen from the sign of the 1 count value width Sb of the internal signal Wb, the 1 count value width Sb of the internal signal Wb determines the correction resolution Sb. Further, Wf is a cumulative value of the fluctuation amount due to the zero point drift of the internal signal Wb, in other words, a cumulative value of the zero point correction amount of the internal signal Wb by the total zero tracking function. The zero point correction amount accumulated value Wf of the internal signal Wb will be described in detail later. Wz is a zero adjustment value for forcibly setting the zero of the internal signal Wb. This zero point adjustment value Wz will also be described in detail later. The initial load value Wi and the span coefficient K in Expression 4 are obtained at the time of prior adjustment as the entire track scale 10 according to the present embodiment (at the time of installation in a factory or field), and are stored in the memory circuit 58. Also, the zero point correction amount accumulated value Wf and the zero point adjustment value Wz are also stored in the memory circuit 58, and in particular, the zero point correction amount accumulated value Wf is stored in a non-illustrated non-volatile memory constituting the memory circuit 58. The zero point correction amount accumulated value Wf and the zero point adjustment value Wz are appropriately updated as will be described later.

  In addition, the CPU 54 obtains the display level signal Wc based on the following formula 5. In the calculation based on Equation 5, the decimal part is rounded down.

<< Formula 5 >>
Wc = {Wb · (Sb / Sd)} + 0.5 = (Wb / 4) +0.5
∵ Sb / Sd = 1/4

  As shown in FIG. 6D, the display level signal Wc based on this equation 5 has a 1 count value width Sc that is Sd / Sb times the 1 count value width Sb of the internal signal Wb, that is, 4 times (Sc = 4 · Sb). ). That is, the 1 count value width Sc corresponds to 10 kg, which is the same as the scale amount Sd (Sc = Sd).

  After that, the CPU 54 multiplies the display level signal Wc based on Expression 5 by the scale factor Sd (= 10 kg) as a conversion coefficient, that is, based on the following Expression 6, the display level signal Wc is displayed as the display weight value. Convert to Wd.

<< Formula 6 >>
Wd = Sd · Wc = 10 · Wc ∵ Sd = 10 [unit: kg]

  The displayed weight value Wd based on the equation 6 is a value having the scale Sd (= 10 kg) as a minimum unit, as shown in FIG. Here, for example, if the zero point of the displayed weight value Wd is accurate, the displayed weight value Wd is greater than −5 kg when the load applied to the weighing platform 32 is 0 kg. Indicates less than 5 kg. For example, when the displayed weight value Wd is 10 kg, it indicates that the magnitude of the load applied to the weighing platform 32 is 5 kg or more and less than 15 kg. Similarly, the larger (positive) display weight value Wd represents the magnitude of the load applied to the weighing table 32 in units of scale Sd. On the other hand, when the displayed weight value Wd is, for example, −10 kg, it indicates that the magnitude of the load applied to the weighing platform 32 is more than −15 kg and not more than −5 kg. Similarly, for the display weight value Wd smaller (negative), the magnitude of the load applied to the weighing table 32 is expressed in units of scale Sd. The displayed weight value Wd is displayed on the digital display 56 and output to the outside.

  Here, for example, it is assumed that the track scale 10 according to the present embodiment is in a power-off state and transitions from the power-off state to the power-on state, that is, is activated. At the time of activation, the activation is performed after confirming that the object is in an empty state in which no object is placed on the weighing table 32.

  Then, the CPU 54 sets the zero adjustment value Wz in the above equation 4 to zero. At this time, the zero point correction amount accumulated value Wf in the equation 4 is in a state where 0 or an appropriately updated value is set as will be described later. Then, the CPU 54 obtains the internal signal Wb based on the equation 4. Then, the value of the internal signal Wb is recognized as the zero point of the internal signal Wb at the time of start-up, and this is substituted for the zero point adjustment value Wz in Equation 4. Then, the internal signal Wb is obtained based on Formula 4 and the display weight value Wd is obtained based on Formula 6. As a result, the value of the internal signal Wb becomes 0, and consequently the display weight value Wd becomes 0. In this way, the initial zero point setting of the internal signal Wb is performed by appropriately updating the zero point adjustment value Wz so as to absorb the value of the internal signal Wb at the time of start-up (so-called zero point deviation). The initial zero point of the weight value Wd is set. That is, an initial zero setting function is realized.

  After setting the initial zero point, the CPU 54 obtains the internal signal Wb at a time interval much shorter than 1 second, for example, a cycle of a positive fraction of 1 second, more specifically, a cycle of several ms to several tens of ms. As a result, the display weight value Wd is obtained. At the same time, the CPU 54 monitors the internal signal Wb one by one to determine whether it is in an empty state. Specifically, whether or not the value of the internal signal Wb is not less than −1 and not more than 1 (−1 ≦ Wb ≦ 1) over a predetermined period of 1 second or more, that is, in the above-described FIG. Check if it is within the range shown. Then, when the value of the internal signal Wb is within the range A, the CPU 54 determines that it is in an empty state. In other words, when the value of the internal signal Wb is within a range A of −1 or more and 1 or less for a predetermined period of 1 second or more, it is defined as being in an idle state. Here, the predetermined period of 1 second or longer is, for example, 1 second to 10 seconds, and preferably 1 second. Although not shown, the CPU 54 configures a digital filter circuit for removing noise components included in the internal signal Wb, particularly noise components mainly having mechanical factors (vibration) having a frequency of 100 Hz or less. The internal signal Wb after the filtering process by the digital filter circuit is monitored.

  Further, when the CPU 54 is in an idle state, and particularly when the value of the internal signal Wb is 0, that is, within the range indicated by the symbol B in FIG. It is recognized that the zero point is accurate, in other words, the zero point of the displayed weight value Wd is accurate. Then, a zero point instruction signal indicating that is generated. In response to the zero indication signal, the digital display 56 performs a special display called zero display. That is, a zero display function is realized.

  When the internal signal Wb is -1 or 1, that is, within the range indicated by the symbol C in FIG. It is recognized that the zero point of the internal signal Wb has changed. Then, in order to correct the zero point fluctuation of the internal signal Wb, the value of the internal signal Wb is added to or subtracted from the zero point correction amount accumulated value Wf in Expression 4. For example, when the value of the internal signal Wb is −1, 1 is added to the zero point correction amount accumulated value Wf in Equation 4. On the other hand, when the value of the internal signal Wb is 1, 1 is subtracted from the zero point correction amount accumulated value Wf in Equation 4. Then, the internal signal Wb is obtained based on Formula 4 and the display weight value Wd is obtained based on Formula 6. As a result, the value of the internal signal Wb becomes 0, and consequently the display weight value Wd becomes 0. Thus, the zero point fluctuation amount accumulated value Wf is appropriately updated to absorb the fluctuation of the zero point of the internal signal Wb due to drift, so that the zero point fluctuation of the internal signal Wb due to the drift is corrected, and consequently the display weight The zero point fluctuation of the value Wd is corrected. That is, the total zero tracking function is realized.

  Note that when not in the idle state, that is, when the value of the internal signal Wb is smaller than −1 or larger than 1, the CPU 54 recognizes that the fluctuation of the internal signal Wb is caused by a load. In this case, the CPU 54 obtains the display weight value Wd without correcting the zero point of the internal signal Wb.

  Further, when the zero point setting operation for forcibly setting the display weight value Wd to zero is performed by the operation key 60, and the zero point setting command described above is input to the CPU 54, the CPU 54 The value of the internal signal Wb is added to or subtracted from the zero adjustment value Wz in Equation 4. For example, when the value of the internal signal Wb is a negative value, the absolute value | Wb | of the value of the internal signal Wb is added to the zero point adjustment value Wz in Equation 4. On the other hand, when the value of the internal signal Wb is a positive value, the absolute value | Wb | of the value of the internal signal Wb is subtracted from the zero point adjustment value Wz in Expression 4. Then, the internal signal Wb is obtained again, and consequently the display weight value Wd is obtained. As a result, the value of the internal signal Wb becomes 0, and consequently the display weight value Wd becomes 0. In this way, the zero point adjustment value Wz is appropriately updated to absorb the value of the internal signal Wb when the zero point setting operation is performed, so that the zero point of the internal signal Wb is forcibly reset. As a result, the zero point of the display weight value Wd is forcibly reset. That is, a semi-automatic zero point setting function is realized. The zero point setting operation is basically performed when the zero point of the display weight value Wd is relatively largely deviated, that is, the display weight value Wd is relatively far from 0 even though the display weight value is in an empty state. When you are done. Therefore, when the zero point setting operation is performed, basically, it is essential to be in the empty state. However, so-called taring can be performed using a semi-automatic zero point setting function by the zero point setting operation. In this case, the zero point setting operation is performed in a state where a tare equivalent is placed on the weighing table 32.

  In addition, when the reset operation for returning the track scale 10 to the initial state is performed by the operation key 60, and the reset command described above is input to the CPU 54, the CPU 54 performs a reset operation. Specifically, the CPU 54 sets each of the zero point correction amount accumulated value Wf and the zero point adjustment value Wz in Equation 4 to zero. After that, the CPU 54 obtains the internal signal Wb based on the equation 4, and substitutes the value of the internal signal Wb into the zero adjustment value Wz in the equation 4. Then, the internal signal Wb is obtained based on Formula 4 and the display weight value Wd is obtained based on Formula 6. As a result, the value of the internal signal Wb becomes 0, and consequently the display weight value Wd becomes 0. At the same time, as described above, the zero point correction amount accumulated value Wf is returned to its initial value of 0, that is, reset. The reset operation is basically performed immediately after the installation of the track scale 10 or immediately after repair or replacement of the load cell LCn diagnosed as abnormal by an abnormality diagnosis function described later. It is executed only when 10 needs to be returned to the initial state. Therefore, the reset operation can be executed only by a person with special qualifications such as an installer of the truck scale 10, and for this purpose, for example, input of a predetermined password by the operation key 60 is required. Also, when this reset operation is performed, it is essential to be in an empty state.

  The calculations based on the above-described Expressions 2 to 6 can be expressed by, for example, a general arithmetic circuit 300 as shown in FIG. That is, the total arithmetic circuit 300 is an adder to which the digital load detection signals wa [1], wa [2], wa [3] and wa [4] from the load cells LC1, LC2, LC3 and LC4 are input. 302. The adder 302 sums these digital load detection signals wa [1], wa [2], wa [3] and wa [4]. Thereby, the calculation based on Expression 2 is realized, that is, the total digital load detection signal Wa is generated. The total digital load detection signal Wa is input to the multiplier 304.

  The multiplier 304 multiplies the total digital load detection signal Wa input from the adder 302 by the inverse of the number N of load cells LCn (1 / N = 1/4). Thereby, the calculation based on Expression 3 is realized, that is, the count value width change signal Wa ′ is generated. In addition, in the multiplication process (calculation based on Expression 3) by the multiplier 304, the decimal part is truncated as described above. The number N of load cells LCn is stored in the memory circuit 58.

  Further, the count value width change signal Wa ′ is input to another adder 306. The adder 306 subtracts the initial load value Wi of the entire weighing unit 30 stored in the memory circuit 58 from the count value width change signal Wa ′. Then, the signal (= Wa′−Wi) after the subtraction processing by the adder 306 is input to the multiplier 308. The multiplier 308 multiplies the signal after the subtraction processing by the span coefficient K of the entire measuring unit 30 stored in the memory circuit 58. The signal (= K · (Wa′−Wi)) after the multiplication processing by the multiplier 308 is input to another adder 310. The adder 310 subtracts the zero correction amount accumulated value Wf stored in the memory circuit 58 from the signal after the multiplication process. The signal (= K · (Wa′−Wi) −Wf) after the subtraction process by the adder 310 is further input to another adder 312. The adder 312 subtracts the zero point adjustment value Wz stored in the memory circuit 58 from the signal after the subtraction process by the adder 310 in the preceding stage. Thus, the internal signal generation circuit 314 including the adder 306, the multiplier 308, another adder 310, and yet another adder 312 realizes the calculation based on Expression 4 and generates the internal signal Wb. . As described above, the zero point correction amount accumulated value Wf is appropriately updated when a drift occurs. The zero-point correction amount accumulated value Wf is reset (Wf = 0) only when a reset operation including the input of a password is performed by the operation key 60, and is reset otherwise (including at the time of activation). Instead, the previous stored value (0 or a value updated as appropriate) is maintained. In other words, the zero point correction amount accumulated value Wf is continuously updated unless a reset operation is performed. Further, as the zero point correction amount accumulated value Wf is reset during the reset operation, the zero point correction amount accumulated value Wf immediately before the reset operation is added to the zero point adjustment value Wz, that is, the zero point adjustment value Wz is updated. . The zero point adjustment value Wz is updated also when the zero point setting operation is performed by the operation key 60, and is also updated at the time of activation.

  The internal signal Wb generated by the internal signal generation circuit 314 is input to another multiplier 316. The multiplier 316 has a mutual ratio Sb / Sd (= 1/4) between the internal signal Wb and the count value width Sb of the internal signal Wb (in other words, the zero point correction resolution Sb of the display weight value Wd) and the scale Sd. Multiply The mutual ratio Sb / Sd is stored in the memory circuit 58 in advance. Further, the signal (= Wb · (Sb / Sd)) after the multiplication processing by the multiplier 316 is input to the adder 318. The adder 318 adds a constant of 0.5 to the signal after the multiplication process. This constant of 0.5 is also stored in the memory circuit 58 in advance. Thus, the display level signal generation circuit 320 including the multiplier 316 and the adder 318 implements the calculation based on the above-described equation 5, that is, the display level signal Wc is generated. In the calculation processing (calculation based on Expression 5) by the display level signal generation circuit 320, the decimal part is truncated as described above.

  The display level signal Wc generated by the display level signal generation circuit 320 is input to another multiplier 322. The multiplier 322 multiplies the display level signal Wc by a scale amount Sd (= 10 kg) as a conversion coefficient. This scale Sd is also stored in the memory circuit 58 in advance. Thereby, the calculation based on Expression 6 is realized, that is, the display weight value Wd is obtained.

  In this way, the display weight value Wd representing the weight of the truck 10 as the object to be weighed is obtained by the general arithmetic circuit 300 of FIG. When the value of the internal signal Wb (see FIG. 6C) that is the basis of the display weight value Wd is within the range A of −1 or more and 1 or less over a predetermined period of 1 second or more, the empty state It is determined that In particular, when the value of the internal signal Wb is within the range B where the value is 0, the zero point of the internal signal Wb is regarded as accurate, in other words, the zero point of the display weight value Wd is regarded as accurate. A zero display indicating that effect is made, that is, the zero display function is activated. On the other hand, when the value of the internal signal Wb is within the range C of −1 or 1, the zero point of the internal signal Wb is corrected, and the zero point of the display weight value Wd is corrected, that is, the total zero tracking function is activated. . In addition, when the zero setting operation is performed by the operation key 60, the zero point of the internal signal Wb is forcibly reset, and the zero point of the display weight value Wd is forcibly reset, that is, semi-automatic zero point. The setting function is activated. At the time of start-up, the zero point of the internal signal Wb is set, and consequently the zero point of the display weight value Wd is set, that is, the initial zero point setting function is activated. When the reset operation including the input of the password is performed by the operation key 60, the track scale 10 is initialized, including the fact that the zero point correction amount accumulated value Wf in the above equation 4 is reset to its initial value 0. Reset to state.

  Next, the individual zero tracking function will be described. This individual zero tracking function automatically corrects the zero point of the individual load value wd [n] corresponding to each load cell LCn as described above. The individual load value wd [n] that is the zero point correction target by the individual zero tracking function is smaller than the display weight value Wd that is the zero point correction target by the above-described total zero tracking function, and is approximately equal to the display weight value Wd of the load cell LCn. It is close to the value divided by the number N (= 4). Therefore, in the individual zero tracking function, the individual load value wd [[[2.5 kg / 4 = 0.625 kg) and 1 / N resolution sb (= 2.5 kg / 4 = 0.625 kg) of the zero point correction resolution Sb of the display weight value Wd by the total zero tracking function. n] is corrected. Further, the scale of the individual load value wd [n] (hereinafter referred to as “individual scale”) sd is 1 / N (= 10 kg / 4 = 2.5 kg) of the scale Sd of the display weight value Wd. Is done.

  In order to realize this individual zero tracking function, the CPU 54 in the data processor 50 determines the zero point for each digital load detection signal wa [n] obtained from each load cell LCn, in other words, such an individual zero tracking function. In order to obtain the internal signal wb [n], an operation based on the following Expression 7 is executed.

<< Formula 7 >>
wb [n] = wa [n] −wi [n] −wf [n] −wz [n]

  In Equation 7, wi [n] is an initial load value for the corresponding load cell LCn, and more specifically, a stored value of the digital load detection signal wa [n] when in an empty state. Then, wf [n] is the accumulated value of the fluctuation amount due to the drift of the zero point of the individual internal signal wb [n] based on this equation 7, in other words, the zero point of the individual internal signal wb [n] by the individual zero tracking function. This is the cumulative value of the correction amount. In other words, the individual zero correction amount accumulated value wf [n] will be described in detail later. Furthermore, wz [n] is an individual zero adjustment value for forcibly setting the zero of the individual internal signal wb [n]. The individual zero adjustment value wz [n] will also be described in detail later. Note that the initial load value wi [n] in Equation 7 is obtained at the time of prior adjustment as the entire track scale 10 described above, and is stored in the memory circuit 58. The individual zero correction amount accumulated value wf [n] and the individual zero adjustment value wz [n] are also stored in the memory circuit 58. In particular, the individual zero correction amount accumulated value wf [n] is stored in the above-described nonvolatile memory. Remembered. The individual zero correction amount accumulated value wf [n] and the individual zero adjustment value wz [n] are appropriately updated as will be described later.

  As shown in FIG. 8A, the individual internal signal wb [n] based on Equation 7 has the same 1 count value width sb as the 1 count value width sa of the digital load detection signal wa [n] shown in FIG. (Sb = sa = 0.625 kg) signal.

  Further, the CPU 54 obtains the individual display level signal wc based on the following equation 8 that conforms to the above equation 5. In the calculation based on the equation 8, the decimal part is truncated as in the equation 5.

<< Formula 8 >>
wc [n] = {wb [n] · (sb / sd)} + 0.5 = (wb [n] / 4) +0.5
∵ sb / sd = 1/4

  As shown in FIG. 8B, the individual display level signal wc [n] based on the equation 8 has a 1 count value width sc that is sd / sb times the 1 count value width sb of the individual internal signal wb [n], that is, The signal is four times (sc = 4 · sb). That is, the one count value width sc corresponds to 2.5 kg which is the same as the individual eye amount sd (sc = sd).

  After that, the CPU 54 converts the individual display level signal wc [n] into the individual load value wd [n] based on the following Expression 9 based on the above Expression 6.

<< Formula 9 >>
wd [n] = sd · wc [n] = 2.5 · wc [n]
∵ sa = 2.5 [Unit: kg]

  As shown in FIG. 8C, the individual load value wd [n] based on the equation 9 is a value having the individual eye amount sd (= 2.5 kg) as a minimum unit. Here, for example, if the zero point of the individual load value wd [n] is accurate, the individual load value wd [n] is the load load applied to the corresponding load cell LCn when the individual load value wd [n] is 0 kg. It represents that the size is more than -1.25 kg and less than 1.25 kg. For example, when the individual load value wd [n] is 2.5 kg, it indicates that the magnitude of the load applied to the load cell LCn is 1.25 kg or more and less than 3.75 kg. Similarly, the larger (positive) individual load value wd [n] represents the magnitude of the load applied to the load cell LCn in units of individual scale sd. On the other hand, when the individual load value wd [n] is, for example, −2.5 kg, it indicates that the magnitude of the load applied to the load cell LCn is more than −3.75 kg and −1.25 kg or less. Similarly, the smaller (negative) individual load value wd [n] represents the magnitude of the load applied to the load cell LCn in units of individual scale sd. The individual load value wd [n] is displayed on the digital display 56 and output to the outside.

  Although description will be made before and after, for example, when the track scale 10 is activated, the CPU 54 sets the individual zero adjustment value wz [n] in the above equation 7 to 0 for each load cell LCn. At this time, the individual zero correction amount accumulated value wf [n] in Expression 7 is in a state where 0 or a value appropriately updated as described later is set. Then, the CPU 54 obtains the individual internal signal wb [n] based on Equation 7. Then, the value of the individual internal signal wb [n] is recognized as the zero point of the individual internal signal wb [n] at the time of startup (initial), and this is substituted for the individual zero point adjustment value wz [n] in Equation 7. Then, the individual internal signal wb [n] is obtained based on the equation 7 again, and the individual load value wd [n] is obtained based on the equation 9. As a result, the value of the individual internal signal wb [n] becomes 0, and thus the individual load value wd [n] becomes 0. In this way, the initial zero point setting of the individual internal signal wb [n] is performed by appropriately updating the individual zero adjustment value wz [n] so as to absorb the value of the individual internal signal wb [n] at the time of activation. As a result, the initial zero point of the individual load value wd [n] is set. That is, an initial zero setting function for each load cell LCn, that is, an individual initial zero setting function is realized.

  After the setting of the individual initial zero point, the CPU 54 outputs the individual internal signal wb [n] for each corresponding to each load cell LCn in accordance with the calculation cycle (timing) of the internal signal Wb shown in FIG. The individual load value wd [n] is obtained. The individual internal signal wb [n] is subjected to filtering processing by a digital filter circuit similar to that for the internal signal Wb in order to remove a noise component mainly included due to mechanical factors. For example, when the CPU 54 is in an idle state, that is, when the value of the internal signal Wb is within a range A of −1 or more and 1 or less for a predetermined period of 1 second or more, the individual internal signal wb [n] Whether or not the value of the individual internal signal wb [n] is preferably 0 over a predetermined period of 1 second or longer. Here, for example, when the value of the individual internal signal wb [n] is 0, that is, within the range indicated by the symbol B ′ in FIG. 8A, the CPU 54 determines the value of the individual internal signal wb [n]. It is recognized that the zero point is accurate, in other words, the zero point of the individual load value wd [n] is accurate. Then, an individual zero indicating signal indicating that is generated. In response to the individual zero indication signal, the digital display 56 displays the individual zero. That is, a zero display function for each load cell LCn, that is, an individual zero display function is realized.

  On the other hand, when the value is in the idle state and the value of the individual internal signal wb [n] is not within the range B ′ of 0, in other words, the value of the individual internal signal wb [n] is −1 or less or 1 When this is the case, the CPU 54 recognizes that the zero point of the individual internal signal wb [n] has fluctuated due to drift. Then, in order to correct the zero point fluctuation of the individual internal signal wb [n], the value of the individual internal signal wb [n] is added to or subtracted from the individual zero point correction amount accumulated value wf [n] in Expression 7. For example, when the value of the individual internal signal wb [n] is a negative value, the absolute value | wb [n] of the value of the individual internal signal wb [n] is added to the individual zero correction amount accumulated value wf [n] in Equation 7. ] Is added. On the contrary, when the value of the individual internal signal wb [n] is a positive value, the absolute value of the value of the individual internal signal wb [n] is calculated from the individual zero correction amount accumulated value wf [n] in Expression 7. | Wb [n] | Then, the individual internal signal wb [n] is obtained based on the equation 7 again, and the individual load value wd [n] is obtained based on the equation 9. As a result, the value of the individual internal signal wb [n] becomes 0, and thus the individual load value wd [n] becomes 0. In this way, the individual zero point correction amount accumulated value wf [n] is appropriately updated to absorb the fluctuation of the zero point of the individual internal signal wb [n] due to drift, whereby the individual internal signal wb [ n] is corrected, and the zero value fluctuation of the individual weight value wd [n] is corrected. That is, an individual zero tracking function is realized.

  Here, when this individual zero tracking function is compared with the above-described total zero tracking function, for example, it is determined that the total zero tracking function is in an idle state based on the internal signal Wb shown in FIG. Only when the value of the internal signal Wb is in the range C of -1 or 1. This is because it conforms to the above-mentioned regulations regarding the zero tracking function in the Japanese Industrial Standard (that it should not operate when a load exceeding 1/2 of the scale is applied).

  On the other hand, the individual zero tracking function is in an empty state, and the value of the individual internal signal wb [n] shown in FIG. 8A is other than 0 for each load cell LCn. In other words, if there is a fluctuation in the value of the individual internal signal wb [n], it operates regardless of the magnitude of the fluctuation. That is, the individual zero tracking function is not restricted by Japanese Industrial Standards. Therefore, for example, even if the zero point of the individual internal signal wb [n] corresponding to a certain load cell LCn greatly fluctuates due to drift, the fluctuation of the zero point is appropriately corrected. Extremely speaking, even if an abnormality such as a failure occurs in a certain load cell LCn and the zero of the individual internal signal wb [n] corresponding to the load cell LCn fluctuates excessively, this excessive zero fluctuation is also corrected. Is done. Then, the zero point correction amount of the individual internal signal wb [n] is accumulated as the individual zero point correction amount accumulation value wf [n] in Equation 7 described above. This greatly contributes to the realization of an accurate abnormality diagnosis function as will be described later.

  Note that the individual zero tracking function does not operate when not in the idle state. In this case, the individual internal signal wb [n] is obtained in the manner described above for each of the cells corresponding to each load cell LCn, and the individual load value wd [n] is thus obtained.

  When the above-described zero setting operation is performed by the operation key 60, the CPU 54 adjusts the value of the individual internal signal wb [n] at that time for each corresponding to each load cell LCn in the individual zero adjustment in Expression 7. Addition and subtraction to the value wz [n]. For example, when the value of the individual internal signal wb [n] is a negative value, the absolute value | wb [n] | of the value of the individual internal signal wb [n] is added to the individual zero adjustment value wz [n] in Equation 7. Add On the other hand, when the value of the individual internal signal wb [n] is a positive value, the absolute value | wb [n] | of the value of the individual internal signal wb [n] is calculated from the individual zero adjustment value wz [n] in Equation 7. Reduce. Then, the individual internal signal wb [n] is obtained again, and as a result, the individual load value wd [n] is obtained. As a result, the value of the individual internal signal wb [n] becomes 0, and thus the individual load value wd [n] becomes 0. In this way, the individual zero adjustment value wz [n] is appropriately updated to absorb the value of the individual internal signal wb [n] when the zero setting operation is performed, so that the individual internal signal wb [ The zero point of n] is forcibly reset, and consequently the zero point of the individual load value wd [n] is forcibly reset. That is, a semi-automatic zero point setting function for each load cell LCn, that is, an individual semi-automatic zero point setting function is realized. This individual semi-automatic zero point setting function can also be used for the above-described taring.

  In addition, when the above-described reset operation is performed by the operation key 60, the CPU 54 sets each of the individual zero adjustment value wz [n] and the individual zero correction amount accumulated value wf [n] in Expression 7 to zero. After that, the CPU 54 obtains the individual internal signal wb [n] based on the equation 7, and substitutes the value of the individual internal signal wb [n] into the individual zero adjustment value wz [n] in the equation 7. Then, the individual internal signal wb [n] is obtained based on the equation 7 again, and the individual load value wd [n] is obtained based on the equation 9. As a result, the value of the individual internal signal wb [n] becomes 0, and thus the individual load value wd [n] becomes 0. At the same time, as described above, the individual zero correction amount accumulated value wf [n] is returned to its initial value of 0, that is, reset.

  The calculations based on the above-described Expressions 7 to 9 can be expressed by an individual calculation circuit 400 as shown in FIG. 9, for example. That is, the individual arithmetic circuit 400 is provided corresponding to each load cell LCn, that is, four individual arithmetic circuits 400 are provided in total. Each individual arithmetic circuit 400 includes an adder 402 to which the digital load detection signal wa [n] from the corresponding load cell LCn is input. The adder 402 subtracts the initial load value wi [n] stored in the memory circuit 58 from the digital load detection signal wa [n]. Then, the signal (= wa [n] −wi [n]) after the subtraction processing by the adder 402 is input to another adder 404. The adder 404 subtracts the individual zero point correction amount accumulated value wf [n] stored in the memory circuit 58 from the signal after the subtraction process by the adder 402 in the previous stage. The signal after subtraction processing by the adder 404 (= wa [n] −wi [n] −wf [n]) is further input to another adder 406. The adder 406 further subtracts the individual zero adjustment value wz [n] stored in the memory circuit 58 from the signal after the subtraction processing by the adder 404 in the previous stage. As a result, the individual internal signal generation circuit 408 including the three adders 402, 404, and 406 realizes the calculation based on Expression 7 and generates the individual internal signal wb [n]. As described above, the individual zero correction amount accumulated value wf [n] is appropriately updated when a drift occurs. The individual zero correction amount accumulated value wf [n] is reset (wf [n] = 0) only at the time of reset operation by the operation key 60, and is not reset at any other time (including at the time of activation). The stored value up to is maintained. In other words, the individual zero point correction amount accumulated value wf [n] is continuously updated unless a reset operation is performed. This is for the convenience of an abnormality diagnosis function described later. Further, when the individual zero correction amount accumulated value wf [n] is reset by the reset operation, the individual zero correction amount accumulated value wf [n] immediately before the reset operation is accordingly changed to the individual zero adjustment value wz [n]. In other words, the individual zero adjustment value wz [n] is updated. The individual zero adjustment value wz [n] is updated also when the zero point is set by the operation key 60, and is also updated at the time of activation.

  The individual internal signal wb [n] generated by the individual internal signal generation circuit 408 is further input to the multiplier 410. For the individual internal signal wb [n], the multiplier 410 has a count value width sb of the individual internal signal wb [n] (in other words, a zero point correction resolution sb of the individual load value wd [n]) and the individual scale sd. Is multiplied by the mutual ratio sb / sd (= 1/4). The mutual ratio sb / sd is stored in the memory circuit 58 in advance. Further, the signal (= wb [n] · (sb / sd)) after the multiplication processing by the multiplier 410 is input to the adder 412. The adder 412 adds a constant of 0.5 to the signal after the multiplication process. This constant of 0.5 is also stored in the memory circuit 58 in advance. As a result, the individual display level signal generation circuit 414 including the multiplier 410 and the adder 412 realizes the calculation based on the above equation 8, that is, the individual display level signal wc [n] is generated. In the arithmetic processing (calculation based on Expression 8) by the individual display level signal generation circuit 412, the decimal part is truncated as described above.

  The individual display level signal wc [n] generated by the individual display level signal generation circuit 414 is input to another multiplier 416. The multiplier 416 multiplies the individual display level signal wc [n] by an individual eye amount sd (= 2.5 kg) as a conversion coefficient. The individual scale sd is also stored in the memory circuit 58 in advance. Thereby, the calculation based on Formula 9 is realized, that is, the individual load value wd [n] is obtained.

  As described above, the individual load value indicating the load applied to the load cell LCn for each load cell LCn by the individual arithmetic circuit 400 of FIG. wd [n] is determined. Then, in the determination of whether or not the vehicle is in the idle state based on the internal signal Wb shown in FIG. 6C, it is determined that the vehicle is in the idle state. Then, the element of the individual load value wd [n] is determined. Is within the range B ′ where the value of the individual internal signal wb [n] is 0, the zero point of the individual internal signal wb [n] is accurate, that is, the zero point of the individual load value wd [n] is It is regarded as accurate, and an individual zero display indicating that effect is made, that is, the individual zero display function is activated. On the other hand, when the value of the individual internal signal wb [n] is not 0, the zero point of the individual internal signal wb [n] is corrected, and hence the zero point of the individual load value wd [n] is corrected, that is, the individual zero tracking function is performed. Operate. In addition, when the zero point setting operation is performed by the operation key 60, the zero point of the individual internal signal wb [n] is forcibly reset, and consequently the zero point of the individual load value wd [n] is forcibly set. In other words, the individual semi-automatic zero setting function is activated. At the time of activation, the zero point of the individual internal signal wb [n] is set, and thus the zero point of the individual load value wd [n] is set, that is, the individual initial zero point setting function operates. When the reset operation is performed by the operation key 60, the individual zero correction amount accumulated value wf [n] in the above-described equation 7 is reset to 0, which is its initial value.

  Further, an abnormality diagnosis function is realized using the individual zero tracking function. That is, the CPU 54 monitors the individual zero point correction amount accumulated value wf [n] in the above-described equation 7 for each load cell LCn. Then, based on this individual zero correction amount accumulated value wf [n], it is diagnosed whether or not an abnormality such as a failure has occurred in the corresponding load cell LCn. Specifically, the absolute value | wf [n] | of the individual zero correction amount accumulated value wf [n] is compared with a predetermined threshold value α. When the absolute value | wf [n] | of the individual zero correction amount accumulated value wf [n] is equal to or less than the threshold value α (| wf [n] | ≦ α), the corresponding load cell LCn is diagnosed as normal. To do. On the other hand, when the absolute value | wf [n] | of the individual zero correction amount accumulated value wf [n] is larger than the threshold value α (| wf [n] |> α), an abnormality such as a failure occurs in the corresponding load cell LCn. Is diagnosed. The diagnosis result is displayed on the digital display 56 and output to the outside. In particular, when an abnormality occurs, an alarm is issued. In order to realize such an abnormality diagnosis function using the individual zero tracking function, in order to realize a particularly accurate abnormality diagnosis function, as described above, the individual internal tracking function corresponding to each load cell LCn can be realized by the individual zero tracking function. The fact that the zero point fluctuation of the signal wb [n] (and hence the individual load value wd [n]) is corrected regardless of its magnitude (that is, without being restricted by Japanese Industrial Standards) greatly contributes. Further, the individual zero correction amount is accumulated unless the zero correction amount of the individual internal signal wb [n] is continuously accumulated as the individual zero correction amount accumulated value wf [n], that is, unless the reset operation by the operation key 60 is performed. The fact that the value wf [n] is not reset greatly contributes to the realization of an accurate abnormality diagnosis function.

  Note that the threshold α is stored in the memory circuit 58 and may be changed as appropriate. The individual zero correction amount accumulated value wf [n] may be displayed on the digital display 56 or may be output to an external device. Since the individual zero correction amount accumulated value wf [n] is accumulated continuously (that is, over a long period of time) unless the reset operation is performed as described above, the individual zero point correction amount accumulated value wf [n] is observed. Thus, in particular, by observing the history (record), it is possible to appropriately grasp the operating state of the corresponding load cell LCn. In turn, when the individual zero correction amount accumulated value wf [n] is reset, the individual zero correction amount accumulated value wf [n] until then is shifted to the individual zero adjustment value wz [n] in Equation 7. By observing the individual zero adjustment value wz [n], it is possible to perform abnormality diagnosis of each load cell LCn, and such a configuration may be adopted. Further, by comparing the absolute values | wf [n] | of the individual zero-point correction amount accumulated values wf [n] between the load cells LCn (that is, the magnitude of the comparison difference), the abnormality diagnosis of the load cells LCn can be performed. Such a configuration may be adopted (however, in this case, it is assumed that no abnormality has occurred in the plurality of load cells LCn). Incidentally, when it is found that an abnormality has occurred in one of the load cells LCn, the load cell LCn is repaired or replaced. Thereafter, a reset operation is performed by the operation key 60, whereby the entire track scale 10 is reset to the initial state including resetting the individual zero correction amount accumulated value wf [n] for all the load cells LCn.

Next, the left zero tracking function will be described. This left-side zero tracking function automatically corrects the zero point of the left-side load value Wd12 as described above. The left load value Wd12 that is the zero point correction target by the left zero tracking function is smaller than the display weight value Wd that is the zero point correction target by the total zero tracking function, and is approximately half the number N of the load cells LCn. It is close to the value divided by N / 2 (= 2). Therefore, in this left-side zero tracking function, the left-side load value Wd12 is obtained with a resolution Sb12 (= 2.5 kg / 2 = 1.25 kg) of the zero point correction resolution Sb of the display weight value Wd by the total zero tracking function. Zero correction is performed. Further, the scale value of the left load value Wd12 (hereinafter referred to as “left scale value”) Sd12 is 2 / N (= 10 kg / 2 = 5 kg) of the scale value Sd of the display weight value Wd.

  In order to realize this left-side zero tracking function, the CPU 54 in the data processor 50 adds up the two digital load detection signals wa [1] and wa [2] obtained from the two left load cells LC1 and LC2n. That is, the left digital load detection signal Wa12 is obtained based on the following equation (10).

<< Formula 10 >>
Wa12 = wa [1] + wa [2]

  As shown in FIG. 10A, the left digital load detection signal Wa12 has a 1-count value width Sa12 of the digital load detection signals wa [1] and wa [2] from the left load cells LC1 and LC2n. This signal is equivalent to one count value width sa (Sa12 = sa), in other words, equivalent to one count value width Sb of the total digital load detection signal Wa (based on Expression 7) shown in FIG. 6A (Sa12 = Sa). That is, the 1 count value width Sa12 corresponds to a weight value of 0.625 kg. In the left digital load detection signal Wa12, the zero point is uncertain as in the case of the total digital load detection signal Wa.

  Further, the CPU 54 divides the left digital load detection signal Wa12 by a half N / 2 (= 2) of the number N of load cells LCn, that is, based on the following equation 11, the left digital load detection signal Wa12 One count value width Sa12 is changed, that is, a left count value width change signal Wa12 ′ is obtained. In the calculation based on Equation 11, the decimal part is rounded down.

<< Formula 11 >>
Wa12 ′ = Wa12 / (N / 2) = Wa12 / 4 Ｎ N / 2 = 2

As shown in FIG. 10 (b), the left count value width change signal Wa12 ′ based on this equation 11 has a 1 count value width Sa12 ′ that is N / 2 times (Sa12 ′) the 1 count value width Sa12 of the left digital load detection signal Wa12. = Sa12 · N / 2). That is, the 1 count value width Sa12 ′ corresponds to 1.25 kg (= 0.625 kg × 2), that is, corresponds to the zero point correction resolution Sb12 for the left load value Wd12. In the left count value width change signal Wa12 ′, the zero point is uncertain. After obtaining the left count value width change signal Wa12 ′, the CPU 54 determines the zero point of the left count value width change signal Wa12 ′, in other words, in order to obtain such a left internal signal Wb12, Perform a calculation based on it.

<< Formula 12 >>
Wb12 = Wa12′−Wi12−Wf12−Wz12

In Equation 12, Wi12 is an initial load value for the left load cells LC1 and LC2, and more specifically, a stored value of the left count value width change signal Wa12 ′ when in the empty state. Wf12 is the accumulated value of the fluctuation amount due to the zero point drift of the left internal signal Wb12 based on this equation 12, in other words, the accumulated value of the zero point correction amount of the left internal signal Wb12 by the left zero tracking function. In other words, the left-side zero correction amount cumulative value Wf12 will be described in detail later. Further, Wz12 is a left zero adjustment value for forcibly setting the zero of the left internal signal Wb12. The left zero adjustment value Wz12 will also be described in detail later. The initial load value Wi12 in Expression 12 is obtained at the time of prior adjustment for the entire track scale 10 described above, and is stored in the memory circuit 58. Further, the left-side zero correction amount accumulated value Wf12 and the left-side zero adjustment value Wz12 are also stored in the memory circuit 58. In particular, the left-side zero correction amount accumulated value Wf12 is stored in the above-described nonvolatile memory. The left-side zero correction amount accumulated value Wf12 and the left-side zero adjustment value Wz are appropriately updated as will be described later.

  As shown in FIG. 10C, the left internal signal Wb12 based on Expression 12 is a signal whose 1 count value width Sb12 is 1/4 of the left eye amount Sd12 (Sb12 = Sd12 / 4 = 1.25 kg). . As can be seen from the sign of the 1 count value width Sb12 of the left internal signal Wb12, the 1 count value width Sb12 of the left internal signal Wb12 determines the zero point correction resolution Sb12 for the left load value Wd12.

  In addition, the CPU 54 obtains the left display level signal Wc12 based on the following equation 13 based on the above equation 5 (and equation 8). In the calculation based on the equation 13, the decimal part is truncated as in the equation 5 (and the equation 8).

<< Formula 13 >>
Wc12 = {Wb12 · (Sb12 / Sd12)} + 0.5 = (Wb12 / 4) +0.5
∵ Sb12 / Sd12 = 1/4

As shown in FIG. 10D, the left display level signal Wc12 based on the equation 13 has a 1 count value width Sc12 that is Sd12 / Sb12 times the 1 count value width Sb12 of the left internal signal Wb12, that is, 4 times (Sc12 = 4). -The signal of Sb12). That is, the one count value width Sc12 corresponds to 5 kg which is the same as the left eye amount Sd12 (Sc12 = Sd12).

  After that, the CPU 54 converts the left display level signal Wc12 into the left load value Wd12 based on the following equation 14 based on the above equation 6 (and equation 9).

<< Formula 14 >>
Wd12 = Sd12 · Wc12 = 5 · Wc12
∵ Sd12 = 5 [Unit: kg]

  As shown in FIG. 10E, the left load value Wd12 based on the equation 14 is a value having the left eye amount Sd12 (= 5 kg) as a minimum unit. Here, for example, assuming that the zero point of the left load value Wd12 is accurate, when the left load value Wd12 is 0 kg, the magnitude of the load applied to the left load cells LC1 and LC2 is -2. .5 kg and less than 2.5 kg. For example, when the left load value Wd12 is 5 kg, it indicates that the magnitude of the load applied to the left load cells LC1 and LC2 is 2.5 kg or more and less than 7.5 kg. Similarly, the larger (positive) left load value Wd12 represents the magnitude of the load applied to the left load cells LC1 and LC2 in units of the left eye amount Sd12. On the other hand, when the left load value Wd12 is, for example, -5 kg, it indicates that the load applied to the left load cells LC1 and LC2 is greater than -7.5 kg and less than -2.5 kg. Similarly, the smaller (negative) left load value Wd12 represents the magnitude of the load applied to the left load cells LC1 and LC2 in units of the left eye amount Sd12. The left load value Wd12 is displayed on the digital display 56 and output to the outside.

  Although the description will be omitted here, for example, when the track scale 10 is activated, the CPU 54 sets the left-side zero adjustment value Wz12 in the above equation 12 to zero. At this time, the left-side zero correction amount accumulated value Wf12 in Expression 12 is set to 0 or an appropriately updated value as will be described later. Then, the CPU 54 obtains the left internal signal Wb12 based on the equation 12. Then, the value of the left internal signal Wb12 is recognized as the zero point of the left internal signal Wb12 at the time of startup, and this is substituted for the left zero adjustment value Wz12 in Equation 12. Then, the left internal signal Wb12 is obtained based on the equation 12 and the left load value W12 is obtained based on the equation 14. As a result, the value of the left internal signal Wb12 becomes 0, and consequently the left load value Wd12 becomes 0. Thus, the left zero adjustment value Wz12 is appropriately updated in order to absorb the value of the left internal signal Wb12 at the time of activation, whereby the initial zero setting of the left internal signal Wb12 is made, and consequently the left load value Wd12. The initial zero point is set. That is, the initial zero setting function for the left load cells LC1 and LC2, that is, the left initial zero setting function is realized.

  After setting the left initial zero point, the CPU 54 obtains the left internal signal Wb12 in accordance with the calculation cycle of the internal signal Wb shown in FIG. 6C, and thus obtains the left load value Wd12. It should be noted that the left internal signal Wb12 is for the internal signal Wb (and the individual internal signals wb [n] shown in FIG. 6A) so as to remove noise components mainly due to mechanical factors. It is filtered by a digital filter circuit similar to the above. For example, when the CPU 54 is in an idle state, that is, when the value of the internal signal Wb is within a range A of −1 or more and 1 or less over a predetermined period of 1 second or more, the value of the left internal signal Wb12 is further increased. It is determined whether or not it is 0. Preferably, it is determined whether or not the value of the left internal signal Wb12 is 0 over a predetermined period of 1 second or more. Here, for example, when the value of the left internal signal Wb12 is 0, that is, within the range indicated by the symbol B ″ in FIG. 10C, the CPU 54 has an accurate zero point of the left internal signal Wb12. In other words, it recognizes that the zero point of the left side load value Wd12 is accurate, and generates a left side zero point indicating signal to that effect, and in response to this left side zero point indicating signal, the digital display 56 displays the left side zero point. That is, the zero point display function for the left load cells LC1 and LC2, that is, the left zero point display function is realized.

  On the other hand, when the left internal signal Wb12 is not in the range B ″ of 0, that is, when the value of the left internal signal Wb12 is −1 or less or 1 or more, the CPU 54 is in the idle state. Recognizes that the zero point of the left internal signal Wb12 has fluctuated due to drift, and the value of the left internal signal W12 is accumulated in the left zero correction amount in Expression 12 in order to correct the zero point fluctuation of the left internal signal Wb12. For example, when the value of the left internal signal Wb12 is a negative value, the absolute value | Wb12 | of the value of the left internal signal Wb12 is added to the left zero correction amount accumulated value Wf12 in Expression 12. On the contrary, when the value of the left internal signal Wb12 is a positive value, the left zero correction amount accumulated value Wf12 in Expression 12 The absolute value | W12 | of the value of the internal signal Wb12 is subtracted, and the left internal signal Wb12 is obtained again based on the equation 12, and the left load value Wd12 is obtained based on the equation 14. Thus, the left internal signal Wb12 is calculated. As a result, the left-side load value Wd12 becomes 0. Thus, the left-side zero correction amount accumulated value Wf12 is appropriately updated to absorb the fluctuation of the zero point of the left-side internal signal Wb12 due to drift. Then, the zero point fluctuation of the left internal signal Wb12 due to the drift is corrected, and hence the zero point fluctuation of the left weight value Wd12 is corrected, that is, the left zero tracking function is realized.

  This left-side zero tracking function is also not subject to the restrictions of the Japanese Industrial Standard, like the individual zero tracking function described above. That is, this left-side zero tracking function is in the idle state, and when the left-side internal signal Wb12 shown in FIG. 10C is not 0, that is, If there is a fluctuation in the value, it operates regardless of the magnitude of the fluctuation. Therefore, for example, even if the zero point of the left internal signal Wb12 greatly fluctuates due to drift, the greatly fluctuating zero point is appropriately corrected.

  Note that the left-side zero tracking function does not operate when not in the idle state. In this case, the CPU 54 obtains the left load value Wd12 without correcting the zero point of the left internal signal Wb12.

  When the above-described zero setting operation is performed by the operation key 60, the CPU 54 adds or subtracts the value of the left internal signal Wb12 at that time to the left zero adjustment value Wz12 in Equation 12. For example, when the value of the left internal signal Wb12 is a negative value, the absolute value | Wb12 | of the value of the left internal signal Wb12 is added to the left zero adjustment value Wz12 in Expression 12. On the other hand, when the value of the left internal signal Wb12 is a positive value, the absolute value | Wb12 | of the value of the left internal signal Wb12 is subtracted from the left zero adjustment value Wz12 in Expression 12. Then, the left internal signal Wb12 is obtained again, and the left load value Wd12 is obtained. As a result, the value of the left internal signal Wb12 becomes 0, and consequently the left load value Wd12 becomes 0. As described above, the left zero adjustment value Wz12 is appropriately updated to absorb the value of the left internal signal Wb12 when the zero setting operation is performed, so that the zero of the left internal signal Wb12 is forcibly set. Then, the zero point of the left load value Wd12 is forcibly reset. That is, the semi-automatic zero point setting function for the left load cells LC1 and LC2, that is, the left semi-automatic zero point setting function is realized. This left-side semi-automatic zero point setting function can also be used for the above-described taring.

  In addition, when the above-described reset operation is performed by the operation key 60, the CPU 54 sets each of the left zero correction amount accumulated value Wf12 and the left zero adjustment value Wz12 in Expression 12 to zero. Then, the CPU 54 obtains the left internal signal Wb12 based on Expression 12, and substitutes the value of the left internal signal Wb12 into the left zero adjustment value Wz12 in Expression 12. Then, the left internal signal Wb12 is obtained based on the equation 12 and the left load value Wd12 is obtained based on the equation 14. As a result, the value of the left internal signal Wb12 becomes 0, and consequently the left load value Wd12 becomes 0. At the same time, as described above, the left zero correction amount accumulated value Wf12 is returned to its initial value of 0, that is, reset.

  The calculations based on the above-described Expressions 10 to 14 can be expressed by a left-side arithmetic circuit 500 as shown in FIG. 11, for example. That is, the left arithmetic circuit 500 includes an adder 502 to which two digital load detection signals wa [1] and wa [2] from the left load cells LC1 and LC2 are input. The adder 502 adds these two digital load detection signals wa [1] and wa [2]. Thereby, the calculation based on Expression 10 is realized, that is, the left digital load detection signal Wa12 is generated. The left digital load detection signal Wa12 is input to the multiplier 504.

  The multiplier 504 multiplies the left digital load detection signal Wa12 input from the adder 502 by a reciprocal (2 / N = 1/2) of a half N / 2 of the number N of load cells LCn. Thereby, the calculation based on Expression 11 is realized, that is, the left count value width change signal Wa12 'is generated. In addition, in the multiplication process (calculation based on Expression 11) by the multiplier 504, the decimal part is truncated as described above.

  Further, the left count value width change signal Wa <b> 12 ′ is input to another adder 506. The adder 506 subtracts the initial load value Wi12 for the left load cells LC1 and LC2 stored in the memory circuit 58 from the left count value width change signal Wa12 '. The signal (= Wa12′−Wi12) after the subtraction processing by the adder 506 is input to another adder 508. The adder 508 subtracts the left-side zero correction amount accumulated value Wf12 stored in the memory circuit 58 from the signal after the subtraction process by the adder 506 in the previous stage. Then, the signal (= Wa12′−Wi12−Wf12) after the subtraction processing by the adder 508 is input to another adder 510. The adder 510 further subtracts the left zero adjustment value Wz12 stored in the memory circuit 58 from the signal after the subtraction processing by the adder 508 in the preceding stage. Thus, the left internal signal generation circuit 512 including the three adders 506, 508, and 510 realizes the calculation based on Expression 12, and generates the left internal signal Wb12. As described above, the left-side zero correction amount accumulated value Wf12 is appropriately updated when a drift occurs. The left zero correction amount accumulated value Wf12 is reset (Wf12 = 0) only at the time of the reset operation by the operation key 60, and is not reset at any other time (including at the time of start-up) and maintains the stored value up to that time. To do. In other words, the left zero correction amount accumulated value Wf12 is continuously updated unless a reset operation is performed. As the left zero correction amount accumulated value Wf12 is reset during the reset operation, the left zero correction amount accumulated value Wf12 immediately before the reset operation is added to the left zero adjustment value Wz12, that is, the left zero adjustment value. Wz12 is updated. This left-side zero adjustment value Wz12 is updated also when the zero point setting operation is performed by the operation key 60, and is also updated at the time of activation.

  The left internal signal Wb12 generated by the left internal signal generation circuit 512 is input to another multiplier 514. The multiplier 514 has a mutual ratio Sb12 / Sd12 (= 1) between the left internal signal Wb12 and the 1 count value width Sb12 of the left internal signal Wb12 (in other words, the zero point correction resolution Sb12 of the left load value Wd12) and the left eye amount Sd12. / 4) Multiply. The mutual ratio Sb12 / Sd12 is stored in the memory circuit 58 in advance. Further, the signal (= Wb12 · (Sb12 / Sd12)) after the multiplication processing by the multiplier 514 is input to the adder 516. The adder 516 adds a constant of 0.5 to the signal after the multiplication process. This constant of 0.5 is also stored in the memory circuit 58 in advance. Thus, the left display level signal generation circuit 518 including the multiplier 514 and the adder 516 implements the calculation based on the above-described equation 13, that is, the left display level signal Wc12 is generated. In the calculation process (calculation based on Expression 13) by the left display level signal generation circuit 518, the decimal part is truncated as described above.

  The left display level signal Wc12 generated by the left display level signal generation circuit 518 is input to another multiplier 520. The multiplier 520 multiplies the left display level signal Wc12 by a left eye amount Sd (= 5 kg) as a conversion coefficient. The left eye amount Sd is also stored in the memory circuit 58 in advance. Thereby, the calculation based on Expression 14 is realized, that is, the left side load value Wd12 is obtained.

  As described above, the left side load value Wd12 is obtained by the left side arithmetic circuit 500 of FIG. Then, in the determination as to whether or not the vehicle is in the idle state based on the internal signal Wb shown in FIG. 6C, it is determined that the vehicle is in the idle state, and then the left side that is the origin of the left load value Wd12. When the value of the internal signal Wb12 is within the range B ″ where the value is 0, the zero point of the left internal signal Wb12 is regarded as accurate, that is, the zero point of the left load value Wd12 is regarded as accurate, and this is indicated. On the other hand, when the value of the left internal signal Wb12 is not 0, the zero of the left internal signal Wb12 is corrected, and hence the zero of the left load value Wd12 is corrected. In other words, the left-side zero tracking function operates.In addition, when the zero-point setting operation is performed by the operation key 60, the zero point of the left-side internal signal Wb12 is forcibly reset and In this case, the zero point of the left side load value Wd12 is forcibly reset, that is, the left side semi-automatic zero point setting function operates. Is set, that is, the left-side initial zero setting function is activated, and when the reset operation is performed by the operation key 60, the left-side zero correction amount accumulated value Wf12 in the above equation 12 is reset to 0, which is its initial value. The

  The right-side zero tracking function is the same as the left-side zero tracking function, and thus the description thereof is omitted. Also, the right-side zero display function, right-side semi-automatic zero-point setting function, and right-side initial zero-point setting function are the same as those on the left side, and thus description thereof is omitted.

  As described above, according to the present embodiment, four types of zero tracking functions, that is, the total zero tracking function, the individual zero tracking function, the left side zero tracking function, and the right side zero tracking function are provided. These zero tracking functions correct different objects independently of each other. In other words, these zero tracking functions are realized by the separate circuits 300, 400, and 500 shown in FIGS. There is no impact. Therefore, in particular, the total zero tracking function can appropriately correct the zero point of the display weight value Wd representing the weight of the track 100 as the object to be measured without being affected by the other zero tracking functions. The displayed weight value Wd can be obtained. At the same time, abnormality diagnosis is performed to determine whether or not each load cell LCn is normal using the individual zero tracking function, and this abnormality diagnosis is also not affected by other zero tracking functions. That is, according to the present embodiment, it is possible to always obtain an accurate display weight value Wd while performing abnormality diagnosis of each load cell LCn.

  The contents described in the present embodiment are specific examples for realizing the present invention, and do not limit the scope of the present invention.

  In particular, paying attention to the individual zero tracking function, the individual zero tracking function in this embodiment is determined to be in an idle state based on the internal signal Wb shown in FIG. It operates when the value of the individual internal signal wb [n] shown in FIG. In other words, the individual zero tracking function in the present embodiment can be operated on the condition that it is determined by the total zero tracking function that the vehicle is in the idle state. However, it is not limited to this configuration. For example, for each load cell LCn, a determination is made as to whether or not the load cell LCn is in an empty state, strictly speaking, whether or not a load load is applied, and the load load is not applied. When the determination is made, the zero point correction of the corresponding individual internal signal wb [n] may be performed, and thus the zero point correction of the individual load value wd [n] may be performed. Specifically, for each load cell LCn, the value of the corresponding individual internal signal wb [n] is −1 or more and 1 or less (−1 ≦ wb [n] ≦ 1) over a predetermined period of 1 second or more. Whether it is within the range indicated by the symbol A ′ in FIG. 12A instead of FIG. 8A is confirmed. Then, when the value of the individual internal signal wb [n] is within the range A ′, it is determined that a load is not applied to the corresponding load cell LCn. In addition, when the value of the individual internal signal wb [n] corresponding to the load cell LCn is −1 or 1, that is, within the range indicated by the symbol C ′ in FIG. In order to correct, the individual zero tracking function may be activated.

  However, in this configuration, the individual zero tracking is performed for some of the load cells LCn even though the truck (strictly speaking, a relatively small and light object to be weighed other than the truck) 100 is placed on the weighing platform 32. The function may be activated. For example, there is a possibility that the placement position of the object to be weighed 100 on the weighing platform 32 is extremely biased. That is, when the placement position of the object 100 to be weighed on the weighing platform 32 is extremely deviated, it is only for a part of the load cells (in this case, it is tentatively expressed by using the symbol “LCn ′”). A situation may occur in which a load is applied, and the load is not applied to other load cells (herein, it is tentatively represented by using the symbol “LCn”). In such a situation, for the load cell LCn ′ to which a load is applied, the individual internal signal wb [n] ′ corresponding to the load cell LCn ′ fluctuates relatively greatly, that is, the individual internal signal wb [n]. Since “value” is out of the range A, it is determined that a load is applied. On the other hand, for the load cell LCn ″ to which almost no load is applied, the corresponding individual internal signal wb [n] ″ does not change or only slightly changes, and particularly the individual internal signal wb [n] ″. May be within the range A ′, and if so, it is determined that no load is applied. In addition, the value of the individual internal signal wb [n] ″ is in the range of −1 or 1. If within C ′, an individual zero tracking function is activated to correct this.

  On the other hand, according to the individual zero tracking function described in the present embodiment, as shown in FIG. 6A, on the condition that it is determined to be in the idle state by the total zero tracking function as described above. The internal signal Wb can be operated on condition that the value of the internal signal Wb is within a range A of −1 or more and 1 or less for a predetermined period of 1 second or more, and the object 100 is placed on the weighing table 32. The individual zero tracking function does not operate when That is, the internal signal Wb is a signal based on the total digital load detection signal Wa, which is the sum of the digital load detection signals wa [n] from all the load cells LCn. When the weighing object 100 is not placed in the hung state (ie, when the weighing object 100 is placed on the weighing table 32), the fluctuation according to the weight of the weighing object 100 is always indicated. Therefore, based on such an internal signal Wb, the total zero tracking function can accurately determine whether or not it is in an idle state. When the object to be weighed 100 is placed on the weighing platform 32, the individual zero tracking function can be activated on the condition that the total zero tracking function is determined to be in the empty state. The operation of the individual zero tracking function is surely limited.

  On the other hand, by adopting the configuration described with reference to FIG. 12, even when the object 100 is placed on the weighing table 32, the individual zero tracking function is provided for some load cells LCn. Even if is activated, there is no particular inconvenience. That is, as described above, the individual zero tracking function has no effect on other zero tracking functions, particularly the total zero tracking function. Therefore, the total zero tracking function can appropriately correct the zero point of the display weight value Wd without being affected by the individual zero tracking function at all, and can always obtain the display weight value Wd that is accurate. Of course, the left-side zero tracking function can also appropriately correct the zero point of the left-side load value Wd12 without being affected by the individual zero-tracking function at all, thereby obtaining the accurate left-side load value Wd12. The right-side zero tracking function can also appropriately correct the zero point of the right-side load value Wd34 without being affected by the individual zero-tracking function at all, and thus the accurate right-side load value Wd34 can be obtained. When the object to be weighed 100 is lowered from the weighing platform 32, the individual zero tracking function is activated again (continuously) for some load cells LCn for which the individual zero tracking function has been activated. Therefore, the above-described abnormality diagnosis function using the individual zero tracking function has no influence as a result.

  However, when the weighing object 100 is placed on the weighing table 32 as described above, if the individual zero tracking function is activated for some load cells LCn, the weighing object 100 is removed from the weighing table 32. Until it gets off, the zero point of the individual internal signal wb [n] corresponding to the part of the load cells LCn is corrected, so that the finally obtained individual load value wd [n] is originally obtained. It becomes a value different from the value of, and in detail becomes smaller than the original value. Therefore, when it is desired to always obtain the individual load value wd [n] corresponding to each load cell LCn accurately, the individual zero tracking function having the configuration described in this embodiment (with reference to FIG. 8) is employed. It is desirable.

  Similarly, for the left zero tracking function, for example, it is determined whether or not a load is applied to the left load cells LC1 and LC2, and it is determined that the load is not applied. Sometimes, the zero point correction of the left internal signal Wb12 may be performed, and thus the zero point correction of the left load value Wd12 may be performed. Specifically, whether the value of the left internal signal Wb12 is −1 or more and 1 or less (−1 ≦ Wb12 ≦ 1) over a predetermined period of 1 second or more, that is, a diagram in place of the above-described FIG. 13 (c), it is confirmed whether or not it is within the range indicated by the symbol A ″. When the value of the left internal signal wb [n] is within the range A ″, the left load cell LC1 and It is determined that no load is applied to LC2. In addition, when the value of the left internal signal Wb12 is −1 or 1, that is, when it is within the range indicated by the symbol C ″ in FIG. 13C, the left zero tracking function is corrected. May be activated.

  However, in this configuration, as in the other example of the individual zero tracking function described with reference to FIG. 12 described above, the left-side zero tracking function is provided despite the object 100 being placed on the weighing table 32. As a result, the left load value Wd12 may be different from the original value (although temporarily). Therefore, when it is desired to always obtain an accurate left side load value Wd12, it is desirable to employ the left side zero tracking function having the configuration described in this embodiment (with reference to FIG. 10). The same applies to the right zero tracking function.

  Furthermore, in the present embodiment, the track scale 10 has been described as an example, but the present invention can also be applied to non-automatic scales other than the track scale 10 such as platform scales and fee scales. Of course, the weighing Mc, the scale Sd, the zero point correction resolution Sd, and the like are not limited to the above-described values.

  The number N of load cells LCn is four, but it may be other than four, that is, it may be plural.

  In addition, as the load cell LCn, a so-called strain gauge type is given as an example, but a load cell LCn other than the strain gauge type such as a magnetostrictive type or a capacitance type may be adopted.

  In particular, each individual load value wd [n] that is a zero correction target by the individual zero tracking function is determined in the data processor 50 (by the CPU 54), but in the corresponding load cell LCn (by the CPU 44). ) You may be asked. In this case, it is appropriate that the zero point correction of the individual load value wd [n] is performed in each load cell LCn, that is, the individual zero tracking function is realized.

  Furthermore, one of the load cells LCn is set as a parent device, and the digital load detection signals wa [n] of all the load cells LCn are collected in this parent device, and all or one of the above-described operations by the data processor 50 is performed by this parent device. Department may be performed.

10 Track Scale 30 Weighing Section 32 Weighing Platform 34 Load Cell 50 Data Processor 54 CPU
56 digital display 100 tracks

Claims (3)

In a non-automatic scale having a structure in which a placing body on which an object to be weighed is placed is supported by a plurality of load sensors,
Display weight calculating means for obtaining a display weight value representing the weight of the object to be weighed based on a total load detection signal that is a sum of a plurality of load detection signals obtained from the plurality of load sensors;
Total zero tracking means for monitoring the zero point of the display weight value obtained by the display weight calculation means and correcting the zero point of the display weight value when the zero point of the display weight value fluctuates;
Individual load calculation means for obtaining an individual load value representing a component due to the weight of the object to be weighed among the loads applied to each of the plurality of load sensors based on the corresponding load detection signal;
Individual zero tracking means for monitoring the zero point of the individual load value corresponding to each of the plurality of load sensors and correcting the zero point of the individual load value that has changed when any zero point of the individual load value fluctuates; ,
Accumulating means for accumulating a zero correction amount by the individual zero tracking means for each individual load value corresponding to each of the plurality of load sensors for each of the plurality of load sensors;
Evaluation means for evaluating whether each of the plurality of load sensors is normal based on a cumulative value by the cumulative means for the individual load values corresponding to each of the plurality of load sensors;
Equipped with,
The correction resolution by the individual zero tracking means is higher than the correction resolution by the total zero tracking means,
A non-automatic scale characterized by When the total zero tracking means determines whether or not the object to be weighed is in an empty state in which the object is not placed on the above-mentioned object based on the total load detection signal and determines that the object is in the empty state To monitor the zero point of the displayed weight value,
The individual zero tracking means monitors the zero point of the individual load value corresponding to each of the plurality of load sensors when it is determined by the total zero tracking means that the idle state is in the idle state.
The non-automatic balance according to claim 1. Total zero setting means for setting the zero of the displayed weight value in response to a zero setting command arbitrarily given from the outside;
Individual zero point setting means for setting a zero point of the individual load value corresponding to each of the plurality of load sensors in response to the zero point setting command;
Further comprising weighing non-automatic according to claim 1 or 2.

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