Measuring device

Abstract

To provide a weighing device that weighs articles during conveyance while conveying the articles, and can accurately estimate a defect element.SOLUTION: A weighing device 100 weighs a weight of a product P while conveying the product. The weighing device comprises: a second conveyor 14 that conveys the product; a load cell 28; and a control unit 84. The second conveyer has a conveyance speed that is variable. The load cell is configured to detect a weight of the second conveyer or, when conveying the product by the second conveyor, the weight of the second conveyor and a weight of the product on the second conveyor, and then outputs a weighing signal. The control unit is configured to generate statistic information on each of a plurality of conveyance speeds from the weighing signal to be output from the load cell in a state where the product is not on the second conveyor. The control unit is configured to determine and output a candidate of a defect factor on the basis of the statistic information for each conveyance speed.SELECTED DRAWING: Figure 7A

Description

[Technical Field]

[0001] The present invention relates to a weighing device. [Background technology]

[0002] For example, as disclosed in Patent Document 1 (JP 2020-148589 A), a weighing device is known that weighs an object while transporting the object.

[0003] In such weighing devices, malfunctions in weighing may occur due to factors such as deterioration of the components over time. Because there are multiple factors that can cause malfunctions, identifying the cause generally takes a long time. In response to this, Patent Document 1 (JP 2020-148589 A) discloses a method for acquiring a weighing signal output by a detection unit when a conveying unit is driven with no items on the conveying unit at a single conveying speed, calculating the amount of variation for each vibration component, and identifying malfunctioning parts of the rotating parts based on the calculation results. Summary of the Invention [Problem to be solved by the invention]

[0004] However, since there are many factors that can cause problems in weighing, it may be difficult to accurately estimate the cause of the problem from among the various factors using the method of Patent Document 1 (JP 2020-148589 A).

[0005] An object of the present invention is to provide a weighing device that weighs items while transporting the items, and that is capable of accurately estimating the cause of a malfunction. [Means for solving the problem]

[0006] A weighing device according to a first aspect weighs the weight of an item while transporting the item. The weighing device includes a transport unit that transports the item, a detection unit, and a control unit. The transport unit has a variable transport speed. The detection unit detects the weight of the transport unit, or, if an item is being transported to the transport unit, the weight of the transport unit and the weight of the item on the transport unit, and outputs a weighing signal. The control unit generates statistical information for each of a plurality of transport speeds from the weighing signal output by the detection unit when no item is on the transport unit. The control unit determines and outputs candidate malfunction causes based on the statistical information for each transport speed.

[0007] In the weighing device of the first aspect, since candidate causes of the malfunction are determined based on statistical information obtained for multiple conveying speeds, when a malfunction occurs in weighing, candidate causes of the malfunction can be estimated with high accuracy, allowing a maintenance worker for the weighing device to resolve the malfunction in a short time.

[0008] A weighing device of a second aspect is a weighing device of the first aspect, wherein the statistical information generated by the control unit includes statistical information generated from a weighing signal output by the detection unit when the conveying speed is zero and there are no items on the conveying unit.

[0009] In the weighing device of the second aspect, candidate causes of the malfunction of the weighing device are determined based on statistical information obtained when the conveying speed is zero, i.e., when the conveying unit is stopped, so that candidate causes of the malfunction can be estimated with particularly high accuracy when a malfunction occurs in weighing, allowing the maintenance worker for the weighing device to resolve the malfunction in a short time.

[0010] A weighing device according to a third aspect is the weighing device according to the second aspect, wherein the defect factors include at least one of defect factors related to the installation state of the weighing device and defect factors related to the installation environment of the weighing device.

[0011] The weighing device of the third aspect can detect not only malfunctions in the components of the weighing device, but also the possibility of other types of malfunctions, thereby reducing the time required for a maintenance worker to identify the cause of the malfunction.

[0012] A fourth aspect of the weighing device is the weighing device of any one of the first to third aspects, wherein the control unit has a plurality of filters with different characteristics used to filter the weighing signal. The control unit generates statistical information from signals obtained by filtering the weighing signal output by the detection unit with each of the plurality of filters when no items are on the conveying unit for each of a plurality of conveying speeds. The control unit determines and outputs candidate malfunction causes based on the statistical information for each conveying speed and each filter.

[0013] In the weighing device of the fourth aspect, since candidate causes of the malfunction are determined using statistical information obtained from signals processed by different filters, when a malfunction occurs in the weighing, candidate causes of the malfunction can be estimated with high accuracy, allowing a maintenance worker for the weighing device to resolve the malfunction in a short time.

[0014] A fifth aspect of the present invention relates to the weighing device of the fourth aspect, and further includes a storage unit. The storage unit stores statistical information criteria for each conveying speed and each filter. The control unit compares the generated statistical information for each conveying speed and each filter with the corresponding conveying speed and filter criteria stored in the storage unit, and determines and outputs candidate malfunction causes based on the results.

[0015] In the weighing device of the fifth aspect, the generated statistical information can be compared with a standard to accurately estimate possible causes of the malfunction.

[0016] A weighing device of a sixth aspect is the weighing device of the fifth aspect, wherein the memory unit stores, as a standard, statistical information generated from signals obtained by filtering, with each of a plurality of filters, the weighing signals output by the detection unit when there are no articles on the conveying unit for each of a plurality of conveying speeds during a trial run of the weighing device.

[0017] In the weighing device of the sixth aspect, statistical information obtained during the test run of the weighing device is used as a standard, so that possible causes of malfunction can be estimated based on the characteristics unique to each weighing device.

[0018] A seventh aspect of the weighing device is the weighing device of any one of the first to sixth aspects, wherein the statistical information includes at least one of standard deviation, variance, difference between maximum and minimum values, maximum value, and minimum value. [Effects of the Invention]

[0019] The weighing device of the present invention determines potential causes of a malfunction based on statistical information obtained for multiple conveying speeds, so when a weighing malfunction occurs, it can accurately estimate potential causes of the malfunction, allowing the maintenance worker for the weighing device to resolve the malfunction in a short amount of time. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic front view of a weighing device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram of the weighing device of FIG. 1. [Figure 3] 2 is a schematic plan view of the main part of the weighing device of FIG. 1 as seen from above. [Figure 4] 2 is a schematic diagram of the weighing device and a second conveyor of the transport device of the weighing device of FIG. 1. FIG. [Figure 5] 2 is a block diagram of a configuration for weight calculation processing of a control device of the weighing device of FIG. 1. FIG. [Figure 6] 2 is a diagram showing a schematic diagram of a weighing signal from a load cell of the weighing device of FIG. 1 and a weighing signal after filtering. FIG. [Figure 7A] 2 is an example of a flowchart of a diagnostic process performed by a control device of the weighing device of FIG. [Figure 7B] 10 is another example of a flowchart of the diagnostic process performed by the control device of the weighing device of FIG. [Figure 8A] FIG. 10 is a diagram showing the tendency of abnormalities that appear in filtered signals when there is a problem with the installation environment of the weighing device or when the installation state of the weighing device is poor. [Figure 8B]This is a diagram showing the normal / abnormal trends that appear in the filtered signal when there is a problem with the second conveyor belt of the second conveyor. [Figure 8C] This is a diagram showing the normal / abnormal trends that appear in the filtered signal when there is a problem with the rollers of the second conveyor. DETAILED DESCRIPTION OF THE INVENTION

[0021] A weighing device 100 according to one embodiment of the present invention will be described with reference to the drawings. Note that the embodiment of the weighing device 100 described below is merely an example, and various modifications in form and details are possible without departing from the spirit and scope of the present disclosure as set forth in the claims.

[0022] (1) Overall structure The overall configuration of the weighing device 100 will be described with reference to Figures 1 to 3. Figure 1 is a schematic front view of the weighing device 100. Figure 2 is a block diagram of the weighing device 100. Figure 3 is a schematic plan view of the main parts of the weighing device 100 as seen from above.

[0023] The weighing device 100 is a weighing device that weighs the item P while transporting the item P.

[0024] 1, the weighing device 100 mainly includes a conveying device 10 and a detecting device 20. The weighing device 100 also includes a control device 80 (see FIG. 2) that controls the operations of the conveying device 10 and the detecting device 20.

[0025] In addition to the function of controlling the operation of the conveying device 10 and the detection device 20, the control device 80 has the function of determining whether there is a malfunction in the weighing of the weighing device 100. Furthermore, if there is a malfunction in the weighing of the weighing device 100, the control device 80 has the function of determining candidate causes of the malfunction of the weighing device 100 and outputting the determined candidate causes of the malfunction of the weighing device 100.

[0026] The conveying device 10 receives and conveys the article P supplied from an upstream process (not shown, for example, a manufacturing process of the article P). Specifically, the conveying device 10 conveys the article P to a location where the weight is detected by the detection device 20.

[0027] The detection device 20 detects the weight of the item P being transported by the conveying device 10 and outputs a weighing signal corresponding to the detected weight to the control device 80. The control device 80 calculates the weight W of the item P based on the weighing signal output by the detection device 20 when detecting the weight of the item P. Furthermore, the control device 80 determines whether the calculated weight W of the item P is within the allowable weight range. When the weight W of the item P is within the allowable weight range, it means that the weight of the item P is equal to or greater than the allowable minimum weight and equal to or less than the allowable maximum weight.

[0028] It should be noted that, for example, a sorting device (not shown) is arranged downstream of the weighing device 100. The sorting device sorts the items P based on the weight W of the items P calculated by the control device 80. For example, if the weight W of the items P is within the allowable weight range, the sorting device removes the items P from the conveying line for the items P.

[0029] (2) Detailed configuration The details of the weighing device 100 will be described in detail below.

[0030] In the following, expressions such as "front," "rear," "up," "down," "left," and "right" may be used when describing directions and positional relationships, but these expressions are for the convenience of explanation and do not limit the content of the present invention. Expressions such as "front," "rear," "up," "down," "left," and "right" refer to the directions indicated by the arrows in the drawings unless otherwise specified.

[0031] (2-1) Conveyor The conveying device 10 conveys the article P along a conveying direction A1 (see FIGS. 1 and 3).

[0032] The transport device 10 includes a first conveyor 12, a second conveyor 14, a first drive unit 18a, and a second drive unit 18b. The first drive unit 18a and the second drive unit 18b are, for example, motors.

[0033] As shown in FIGS. 1 and 3, in the conveying device 10, a first conveyor 12 and a second conveyor 14 are arranged in this order from the upstream side in a conveying direction A1 of the articles P.

[0034] 3, the first conveyor 12 is disposed upstream in the conveying direction A1 of the first conveyor 12 and the second conveyor 14. The first conveyor 12 functions as an intake conveyor that takes in the items P conveyed from a process upstream of the weighing device 100 into the weighing device 100. The first conveyor 12 conveys the items P in the conveying direction A1 and hands over the items P to the second conveyor 14.

[0035] The first conveyor 12 includes a first conveyor belt 12a (see FIG. 1). The first conveyor belt 12a is, for example, a flat belt. The first driving unit 18a drives the driving roller 122a of the driving roller 122a and the driven roller 122b around which the first conveyor belt 12a is wound, thereby causing the first conveyor 12 to convey articles P on the first conveyor belt 12a in the conveying direction A1.

[0036] As shown in Figure 3, the second conveyor 14 is disposed downstream in the conveying direction A1 of the first conveyor 12 and the second conveyor 14. The second conveyor 14 receives and conveys the items P conveyed by the first conveyor 12. The detection device 20 detects the weight of the items P being conveyed by the second conveyor 14 and outputs a weighing signal. The second conveyor 14 conveys the items P in the conveying direction A1 and delivers the items P to a subsequent process of the weighing device 100 (for example, a sorting device not shown).

[0037] The second conveyor 14 includes a second conveyor belt 14a (see FIG. 1). The second conveyor belt 14a is, for example, a flat belt. The second drive unit 18b drives the roller (drive roller) 144a of the rollers 144a, 144b around which the second conveyor belt 14a is wound, causing the second conveyor 14 to convey the articles P on the second conveyor belt 14a in the conveying direction A1.

[0038] The conveying speed of the first conveyor 12 and the second conveyor 14 is variable. In other words, the rotation speed of the motors of the first drive unit 18a and the second drive unit 18b is variable.

[0039] (2-2) Detection device The detection device 20 will be described with further reference to Fig. 4. Fig. 4 is a schematic diagram of the second conveyor 14 of the transport device 10 and the detection device 20.

[0040] As shown in FIGS. 3 and 4, the detection device 20 mainly includes a sensor 25 and a load cell 28 as an example of a detection unit (weight sensor).

[0041] The sensor 25 detects that an article P conveyed by the first conveyor 12 has reached the second conveyor 14. The sensor 25 is, for example, a photoelectric sensor. However, the type of the sensor 25 is not limited to a photoelectric sensor, and any type of sensor 25 can be used as long as it is a sensor that can detect that an article P has reached the second conveyor 14.

[0042] The control device 80 detects the timing when the entire item P is present on the second conveyor belt 14a based on the detection result of the sensor 25, the conveying speed V of the conveying device 10, and the length L1 in the conveying direction A1 of the item P. The control device 80 calculates the weight W of the item P based on the weighing signal output by the load cell 28 while the entire item P is present on the second conveyor belt 14a.

[0043] The load cell 28 includes a strain element 28a that distorts in proportion to the force acting on it, and a strain gauge (not shown) that is attached to the strain element 28a and converts the strain into an electrical signal (called a measurement signal) and outputs it. In short, the load cell 28 transmits a measurement signal that corresponds to the force acting on it. The load cell 28 is housed inside a case 26 disposed below the second conveyor 14 (see FIG. 4).

[0044] The detection of weight by the load cell 28 will be described below. Before describing the detection of weight by the load cell 28, the structure of the second conveyor 14 of the transport device 10 will first be described in detail.

[0045] In addition to the second conveyor belt 14a described above, the second conveyor 14 mainly includes a frame 142, a driving roller 144a, and a driven roller 144b (see FIG. 4).

[0046] The frame 142 of the second conveyor 14 is supported by brackets 24 that extend upward from the case 26. The case 26 is fixed to the frame 50 of the weighing device 100, as shown in FIG.

[0047] As shown in Figure 4, the drive roller 144a and the driven roller 144b are provided at both ends of the frame 142. The drive roller 144a and the driven roller 144b are rotatably supported by the frame 142. The second conveyor belt 14a is wound around the drive roller 144a and the driven roller 144b. When the second drive unit 18b drives the drive roller 144a, the second conveyor belt 14a rotates, and the second conveyor 14 conveys articles P on the second conveyor belt 14a in the conveying direction A1.

[0048] Due to the above structure, when no article P is present on the second conveyor belt 14a, the load cell 28 detects the weight of the second conveyor 14 as a transport unit (the force that the second conveyor 14 applies to the load cell 28) and outputs a weighing signal. Note that the weight of the second conveyor 14 here is roughly the total weight of the frame 142, the drive roller 144a, the driven roller 144b, and the second conveyor belt 14a. Furthermore, when the second conveyor belt 14a is transporting an article P, the load cell 28 detects the weight of the second conveyor 14 and the weight of the article P on the second conveyor 14 and outputs a weighing signal.

[0049] (2-3) Control device The control device 80 controls the operation of each part of the weighing device 100. The control device 80 also performs a process of calculating the weight W of the item P based on the weighing signal transmitted by the detection device 20.

[0050] The control device 80 also has a function to determine whether there is a malfunction in the weighing of the weighing device 100. Furthermore, if there is a malfunction in the weighing of the weighing device 100, the control device 80 has a function to determine candidate causes of the malfunction of the weighing device 100 and output the determined candidate causes of the malfunction of the weighing device 100.

[0051] Although the placement of the control device 80 is not limited, the control device 80 is mounted on the main body 100a of the weighing device 100, which is provided with the input device 60 and output device 70 described below and is placed to the side of the conveying device 10.

[0052] The control device 80 of this embodiment mainly includes a CPU, memory consisting of ROM, RAM, auxiliary storage device (e.g., flash memory), etc., various electronic circuits, etc. The control device 80 controls the operation of each part of the weighing device 100 and performs various processes by the CPU reading and executing programs stored in the memory.

[0053] Note that the configuration of the control device 80 described here is merely one example of the configuration of the control device 80, and functions similar to those of the control device 80 of this embodiment may be realized by hardware such as a logic circuit, or by a combination of hardware and software.

[0054] Furthermore, the control device 80 may be realized by a single device or multiple devices. For example, the control device 80 may have a control device mounted on the main body 100a and a device located at a different location from the main body 100a that is communicatively connected to the control device. The control device mounted on the main body 100a and a device outside the main body 100a may cooperate to function as the control device 80 described herein.

[0055] The control device 80 is electrically connected to the first driving unit 18a and the second driving unit 18b of the transport device 10, and the sensor 25 and the load cell 28 of the detection device 20.

[0056] The control device 80 is also electrically connected to an input device 60 and an output device 70 provided in the main body 100a (see FIG. 2). The input device 60 receives various commands and information input by the operator of the weighing device 100. For example, the input device 60 is a touch panel display. The commands and information input to the input device 60 are transmitted to the control device 80. The output device 70 is controlled by the control device 80 to output various information. For example, the output device 70 is a display that displays various information. In other words, in this embodiment, a touch panel display functions as the input device 60 and the output device 70.

[0057] The input device and output device are not limited to the devices exemplified here. For example, the input device may be a portable terminal (not shown) operated by an operator of the weighing device 100, a device that receives commands and information transmitted from a central control device (not shown) that is higher than the weighing device 100, or a switch provided on the weighing device 100. The output device may be a portable terminal (not shown) held by an operator of the weighing device 100, or a device that outputs (transmits) various information to a central control device (not shown) that is higher than the weighing device 100.

[0058] The memory of the control device 80 includes a storage unit 82 that stores various types of information. Examples of information stored in the storage unit 82 will be described later.

[0059] The CPU of the control device 80 functions as a control unit 84 and an acquisition unit 86 by reading and executing a program stored in the memory.

[0060] (2-4-1) Acquisition department The acquisition unit 86 acquires various pieces of information input to the input device 60. The various pieces of information acquired by the acquisition unit 86 are stored in the storage unit .

[0061] The information acquired by the acquisition unit 86 includes, for example, the specified weight Wt of the item P to be transported by the transport device 10. In other words, the specified weight Wt is the weight that the item P should originally be (the target weight of the item P).

[0062] The information acquired by the acquisition unit 86 also includes the length L1 of the item P transported by the second conveyor 14. Here, the length L1 of the item P transported by the second conveyor 14 is the length of the item P in the transport direction A1 when the item P is transported by the second conveyor 14.

[0063] Note that, here, the specified weight Wt of the item P and the length L1 of the item P are input to the input device 60, but this is not limited to this. For example, the memory unit 82 may store information on the specified weight Wt of the item P and the length L1 of the item P for each type of item P, and the acquisition unit 86 may acquire an identifier that identifies the type of item P input to the input device 60. Even in this configuration, the acquisition unit 86 can acquire the specified weight Wt of the item P and the length L1 of the item P by referring to the memory unit 82.

[0064] The information acquired by the acquisition unit 86 also includes the conveying speed V of the item P by the conveying device 10 when the item P is weighed by the weighing device 100. Note that the acquisition unit 86 may acquire information that can identify the conveying speed V of the item P (for example, the rotation speed of the motor of the second drive unit 18b) as information on the conveying speed V of the item P by the conveying device 10.

[0065] (2-4-2) Control Unit When the weighing device 100 weighs an item P, the control unit 84 controls the operation of the weighing device 100 based on commands input to the input device 60, and the specified weight Wt of the item P, the length L1 of the item P, and the conveying speed V of the item P by the conveying device 10, etc., acquired by the acquisition unit 86.

[0066] For example, when an operating command is input to the input device 60, the control unit 84 controls the operation of the first drive unit 18a and the second drive unit 18b so that the conveying speed of the item P by the first conveyor 12 and the second conveyor 14 becomes the conveying speed V acquired by the acquisition unit 86.

[0067] Furthermore, for example, the control unit 84 calculates the weight W of a certain item P based on the weighing signal output by the load cell 28 while the item P is being transported by the second conveyor 14. Specifically, the control unit 84 detects the timing when the entire item P is present on the second conveyor belt 14a based on the detection result of the sensor 25, the transport speed V of the transport device 10, and the length L1 of the item P. The control unit 84 calculates the weight W of the item P based on the weighing signal output by the load cell 28 while the entire item P is present on the second conveyor belt 14a. The calculation of the weight W of the item P by the control unit 84 will be described later.

[0068] Furthermore, for example, the control unit 84 determines whether the calculated weight of the item P is within the allowable weight range. For example, the control unit 84 determines whether the calculated weight W of the item P is a value between the allowable minimum weight (specified weight Wt of the item - α) and the allowable maximum weight (specified weight Wt of the item + β) (α and β are preset numerical values). If the calculated weight W of the item P is within the allowable weight range, the control unit 84 determines that the item P is an acceptable item, and if the calculated weight W of the item P is outside the allowable weight range, the control unit 84 determines that the item P is an unacceptable item.

[0069] Also, for example, the control unit 84 determines whether there is a malfunction in the weighing of the weighing device 100. Furthermore, if there is a malfunction in the weighing of the weighing device 100, the control unit 84 determines candidate causes of the malfunction of the weighing device 100 and outputs the determined candidate causes of the malfunction of the weighing device 100.

[0070] (A) Calculation of the weight of the item The calculation process of the weight W of the item P by the control unit 84 will be described. First, the configuration of the control device 80 for the weight calculation process will be described with reference to Fig. 5. Fig. 5 is a block diagram of the configuration of the control device 80 for the weight calculation process.

[0071] The control device 80 includes an amplifier 182, an analog filter 184, and an A / D converter 186. The control unit 84 also includes a signal processing unit 188 as a functional unit for processing the calculation of the weight of the item P.

[0072] The amplifier 182 amplifies the weighing signal input from the load cell 28 and outputs it as an amplified signal to the analog filter 184. The analog filter 184 removes unnecessary high-frequency components from the amplified signal and outputs it as an analog signal. The A / D converter 186 converts the analog signal output from the analog filter 184 into a digital signal and outputs it to the signal processing unit 188. The signal processing unit 188 filters the digital signal using a predetermined finite impulse response (FIR) filter (hereinafter simply referred to as a filter). In short, the signal processing unit 188 uses a predetermined filter to filter the weighing signal that has been preprocessed by the amplifier 182, analog filter 184, and A / D converter 186 (hereinafter the preprocessed weighing signal is referred to as the weighing signal of the load cell 28). The control unit 84 calculates the weight W of the item P based on the weighing signal of the load cell 28 filtered by the signal processing unit 188.

[0073] As described above, when the second conveyor belt 14a is transporting an item P, the load cell 28 detects the weight of the second conveyor 14 and the weight of the item P on the second conveyor 14 and outputs a weighing signal. Therefore, if the control unit 84 directly calculates the weight based on the weighing signal from the load cell 28 when the second conveyor belt 14a is transporting an item P, the control unit 84 will calculate the total weight of the second conveyor 14 and the item P. Therefore, before actually starting to measure the weight of the item P, the control unit 84 performs a process to derive a zero point based on the weighing signal output by the load cell 28 when no item P is present on the second conveyor belt 14a. In other words, before actually starting to measure the weight of the item P, the control unit 84 previously performs a process to calculate the weight of the second conveyor 14 to be subtracted from the total weight of the second conveyor 14 and the item P on the second conveyor 14.

[0074] The reason why the signal processing unit 188 filters the weighing signal of the load cell 28 is that the weighing signal of the load cell 28 contains noise caused by the inherent vibration of the weighing device 100 (vibration caused by the impact when the item P is transferred to the second conveyor 14) and rotational vibration of the motor (e.g., the motor used as the second drive unit 18b) and rollers (e.g., the drive roller 144a and driven roller 144b of the second conveyor 14) used by the weighing device 100.

[0075] Explaining this with reference to Fig. 6, the weighing signal of the load cell 28 is a signal that contains vibration components (noise) with a relatively large amplitude, as shown by the dashed line in Fig. 6. The weight of the item P cannot be calculated with high accuracy from a weighing signal that contains such vibration components. Therefore, the signal processing unit 188 uses a predetermined filter to filter the weighing signal of the load cell 28 (to reduce noise) and extracts a signal with less noise (a signal that generally indicates only the force that the item P applies to the load cell 28), as shown by the solid line in Fig. 6.

[0076] The control unit 84 calculates the weight W of the item P based on the difference between the weighing signal after filtering by the signal processing unit 188 and the zero point. Specifically, the control unit 84 calculates the weight W of the item P based on the difference between the weighing signal during the period when the entire item P is present on the second conveyor belt 14a (the weighing signal of the plateau portion of the solid line in FIG. 6) and the weighing signal during the period when the item P is not present on the second conveyor belt 14a.

[0077] The frequency of the noise contained in the weighing signal of the load cell 28 changes depending on various conditions.

[0078] For example, the natural vibration frequency of the weighing device 100 is a relatively large frequency of about 20 to 100 Hz. The natural vibration frequency varies depending on, for example, the length Lc1 of the second conveyor 14 in the conveying direction A1 of the conveying device 10, the length Lc2 of the second conveyor 14 in a direction perpendicular to the conveying direction A1 of the conveying device 10 (see FIG. 3), the specified weight Wt of the item P, and the length L1 of the item P in the conveying direction A1.

[0079] The frequency of the rotational vibration of the motor and roller is about 10 to 30 Hz. The frequency of the rotational vibration varies depending on, for example, the conveying speed V of the article P (the conveying speed of the second conveyor belt 14a), the length Lc1 of the second conveyor 14 in the conveying direction A1 of the conveying device 10, the length Lc2 of the second conveyor 14 in a direction perpendicular to the conveying direction A1 of the conveying device 10, the diameters of the drive roller 144a and the driven roller 144b, the number of teeth of the drive roller 144a, the number of teeth of the motor used as the second drive unit 18b, the number of teeth of the timing belt 144c of the second conveyor 14, the circumferential length of the second conveyor belt 14a, etc.

[0080] For example, the vibration frequency of the roller is calculated by the conveying speed of the second conveyor belt 14a [m / s] / roller diameter [m] × π. For example, the vibration frequency of the motor is calculated by the vibration frequency of the roller × number of roller teeth / number of motor teeth. For example, the vibration frequency of the timing belt is calculated by the vibration frequency of the roller × number of roller teeth / number of timing belt teeth. For example, the vibration frequency of the second conveyor belt 14a (flat belt) is calculated by the conveying speed of the second conveyor belt 14a [m / s] / circumferential length of the second conveyor belt 14a [m].

[0081] Furthermore, disturbance frequencies such as floor vibrations in factories may be relatively low, at 10 Hz or less.

[0082] As described above, since the frequency of noise contained in the weighing signal of the load cell 28 can change depending on various conditions, the signal processing unit 188 is configured to have a variable setting for the filter used for filtering. In other words, the control device 80 of the weighing device 100 has a plurality of filters with different characteristics that the signal processing unit 188 uses to filter the weighing signal. The reason why the setting for the filter used by the signal processing unit 188 for filtering is variable is that there is no single filter that can sufficiently reduce noise in all frequency ranges among the filters used by the signal processing unit 188.

[0083] The filters that can be set by the control device 80 include filters that can sufficiently reduce noise above a predetermined frequency. Although not limited to these, the multiple filters that the control device 80 has include, for example, filter A that can sufficiently reduce noise above 5 Hz from the measurement signal, filter B that can sufficiently reduce noise above 10 Hz, filter C that can sufficiently reduce noise above 15 Hz, and filter D that can sufficiently reduce noise above 20 Hz. Here, being able to sufficiently reduce noise above a predetermined frequency means, for example, a filter that can reduce the amplitude of signals above a predetermined frequency to a predetermined reduction rate or less.

[0084] Furthermore, the filters that can be set by the signal processing unit 188 include a combination filter. Here, a combination filter is a filter created by multiplying multiple base filters. By performing filtering using a combination filter, noise at frequencies equal to or higher than a certain frequency can be sufficiently reduced (for example, to 1 / 10,000 or less), and even for frequencies lower than that frequency, it is possible to reduce the amplitude of a predetermined frequency by a relatively large amount.

[0085] The filter used by the signal processing unit 188 when weighing an item P with the weighing device 100 is set (selected) by, for example, an engineer during a trial run so as to suppress noise contained in the weighing signal. Alternatively, the filter used by the signal processing unit 188 when weighing an item P with the weighing device 100 may be automatically set by the control unit 84 based on the results of the trial run, etc.

[0086] (B) Diagnostic Processing (B-1) Overview The control device 80 acquires the weighing signal output by the load cell 28, determines whether a weighing malfunction has occurred in the weighing device 100, and determines and outputs candidate causes of the malfunction. This series of processes is called diagnostic processing.

[0087] The diagnostic processing performed by the control device 80 will now be described.

[0088] The main processes in the diagnostic process include determining whether a weighing malfunction has occurred in the weighing device 100, and, if a weighing malfunction has occurred, determining and outputting candidate malfunction causes. In the control device 80, the control unit 84 in particular determines whether a weighing malfunction has occurred in the weighing device 100. Specifically, the control unit 84 determines whether there is vibration in the weighing device 100 that has / may have an adverse effect on the weighing accuracy of the weighing device 100. Furthermore, in the control device 80, if the control unit 84 determines that a malfunction has occurred in the weighing device 100, it determines candidate malfunction causes. Then, if the control unit 84 determines that a malfunction has occurred in the weighing device 100, it outputs the determined candidate malfunction causes to the output device 70.

[0089] The malfunction causes that the control unit 84 can determine as candidates include malfunctions of the weighing device 100 (breakdown, deterioration over time, poor maintenance, etc.). Malfunctions of the weighing device 100 include, for example, breakage of the rollers 144a, 144b of the second conveyor 14. Deterioration over time of the weighing device 100 includes, for example, wear of the second conveyor belt 14a. Poor maintenance of the weighing device 100 includes, for example, improper tension adjustment of the second conveyor belt 14a and adhesion of dirt to the second conveyor belt 14a.

[0090] Furthermore, the malfunction causes that the control unit 84 can determine as candidates may include a fault in the installation state of the weighing device 100. A fault in the installation state of the weighing device 100 includes, for example, a state in which one or more of the legs 52 (see FIG. 1 ) of the frame 50 that supports the conveying device 10 and the detection device 20 are floating above the installation surface of the weighing device 100. In other words, a fault in the installation state of the weighing device 100 includes a state in which any of the legs 52 of the frame 50 does not support the conveying device 10 and the detection device 20.

[0091] Furthermore, the malfunction causes that the control unit 84 can determine as candidates may include malfunctions related to the installation environment of the weighing device 100. Malfunctions related to the installation environment of the weighing device 100 include, for example, vibrations on the floor where the weighing device 100 is installed. Malfunctions related to the installation environment of the weighing device 100 also include, for example, air currents in the installation location of the weighing device 100 (for example, strong air conditioning).

[0092] The control device 80 executes the diagnostic process, for example, when a diagnostic command for the weighing device 100 is input to the input device 60. Furthermore, in addition to or instead of the condition that a diagnostic command for the weighing device 100 is input to the input device 60, the control device 80 may execute the diagnostic process at a predetermined timing. For example, the control device 80 may execute the diagnostic process every time the power to the weighing device 100 is turned on. Furthermore, for example, the control device 80 may execute the diagnostic process every time an operation command for the weighing device 100 is input to the input device 60.

[0093] (B-2) Specific examples of diagnostic processing A specific example of the diagnostic processing executed by the control device 80 will be described with reference to the flowchart of FIG. 7A.

[0094] When a predetermined condition as described above (for example, a condition that a diagnostic command for the weighing device 100 has been input) is met, the control device 80 executes diagnostic processing based on the flowchart of FIG. 7A, for example.

[0095] In step S1, the control device 80 acquires a weighing signal output by the load cell 28 for a predetermined time (e.g., several tens of seconds) when there are no articles P on the second conveyor 14 and the conveying speed of the second conveyor 14 is zero (i.e., when the second conveyor 14 is stopped). More specifically, the control device 80 acquires the weighing signal output by the load cell 28 for a predetermined time when the conveying speed of the second conveyor 14 is zero and there are no articles on the second conveyor 14, amplifies the signal by an amplifier 182, and processes the signal by an analog filter 184 and an A / D converter 186 (to avoid redundant explanation, this signal may be referred to as the weighing signal of the load cell 28 below). The weighing signal of the load cell 28 acquired by the control device 80 is stored in the memory unit 82.

[0096] At this time, the conveying device 10 is not operating and does not generate vibrations, so the load cell 28 detects disturbances such as factory floor vibrations and air currents blowing onto the second conveyor 14. In particular, if the weighing device 100 is poorly installed, with one of the legs 52 of the frame 50 floating above the floor and the weighing device 100 easily shaking, the load cell 28 will likely detect vibrations even if they are relatively small disturbances such as factory floor vibrations.

[0097] Next, in step S2, the control device 80 operates the second conveyor 14 at a conveying speed Va [m / s] when there are no articles on the second conveyor 14 (no articles P are supplied to the second conveyor 14). In other words, the control device 80 controls the operation of the second conveyor 14 so that the second conveyor 14 does not convey any articles and operates only the second conveyor belt 14a at the conveying speed Va. At this time, the control device 80 may also operate the first conveyor 12 at the same time, for example, at the conveying speed Va.

[0098] Next, in step S3, the control device 80 acquires a weighing signal output by the load cell 28 for a predetermined time (e.g., several tens of seconds) when there is no article P on the second conveyor 14 and the second conveyor 14 is operating at a conveying speed Va. More specifically, the control device 80 acquires the weighing signal output by the load cell 28 for a predetermined time when the second conveyor 14 is operating at a conveying speed Va without conveying any article P, amplifies the weighing signal by an amplifier 182, and processes it by an analog filter 184 and an A / D converter 186 (to avoid redundant explanation, this may be referred to as the weighing signal of the load cell 28 below). The weighing signal of the load cell 28 acquired by the control device 80 is stored in the memory unit 82.

[0099] Next, in step S4, the control device 80 operates the second conveyor 14 at a conveying speed Vb [m / s] when there are no articles on the second conveyor 14 (no articles P are supplied to the second conveyor 14). The conveying speed Vb is faster than the conveying speed Va. For example, but not limited to, the conveying speed Vb is twice the conveying speed Va. In other words, the control device 80 controls the operation of the second conveyor 14 so that the second conveyor 14 does not convey any articles, and only the second conveyor belt 14a operates at the conveying speed Va. At this time, the control device 80 may also operate the first conveyor 12 at the same time, for example, at the conveying speed Vb.

[0100] Next, in step S5, the control device 80 acquires a weighing signal output by the load cell 28 for a predetermined time (e.g., several tens of seconds) when there is no article P on the second conveyor 14 and the second conveyor 14 is operating at the conveying speed Vb. More specifically, the control device 80 acquires the weighing signal output by the load cell 28 for a predetermined time when the second conveyor 14 is operating at the conveying speed Vb without conveying any article P, amplifies the weighing signal by the amplifier 182, and processes it by the analog filter 184 and the A / D converter 186 (hereinafter, to avoid redundant explanation, this may be referred to as the weighing signal of the load cell 28). The weighing signal of the load cell 28 acquired by the control device 80 is stored in the memory unit 82.

[0101] In steps S3 and S5, the second conveyor 14 is not transporting any articles, so ideally the load cell 28 would not detect anything. However, in reality, the load cell 28 detects external disturbances such as factory floor vibrations and air currents blowing onto the second conveyor 14, as well as vibrations generated by the transport device 10.

[0102] Next, in step S6, the signal processing unit 188 of the control device 80 filters each of the weighing signals of the load cells 28 acquired in steps S1, S3, and S5 using multiple filters. For example, in step S6, the signal processing unit 188 filters each of the weighing signals of the load cells 28 acquired in steps S1, S3, and S5 (the weighing signals of the three load cells 28) using four filters A to D. While not limited to these filters, for example, filter A is a filter capable of sufficiently reducing noise of 5 Hz or higher, filter B is a filter capable of sufficiently reducing noise of 10 Hz or higher, filter C is a filter capable of sufficiently reducing noise of 15 Hz or higher, and filter D is a filter capable of sufficiently reducing noise of 20 Hz or higher. Therefore, the weighing signal of the load cells 28 processed by filter A generally includes only signals with frequencies lower than 5 Hz. The weighing signal of the load cells 28 processed by filter B generally includes only signals with frequencies lower than 10 Hz. The weighing signal of the load cell 28 processed by filter C contains approximately only signals with frequencies lower than 15 Hz. The weighing signal of the load cell 28 processed by filter D contains approximately only signals with frequencies lower than 20 Hz. Here, the signal processing unit 188 processes each of the weighing signals of the three load cells 28 with four filters A to D, resulting in a total of 12 filtered signals. The filtered signals are stored in the memory unit 82.

[0103] Next, in step S7, the control unit 84 generates statistical information for each of the multiple signals (in this embodiment, signals for a conveying speed of zero (conveying stopped), conveying speed Va, and conveying speed Vb) stored in the memory unit 82 and filtered by each of the multiple filters A to D. The statistical information here is, for example, at least one (one type) of standard deviation, variance, difference between the maximum and minimum values, maximum value, and minimum value of each filtered signal. Preferably, the statistical information includes at least one of the standard deviation, variance, and difference between the maximum and minimum values ​​of each filtered measurement signal. Note that the control unit 84 may generate only one type of statistical information or multiple types of statistical information for each of the multiple measurement signals stored in the memory unit 82 and filtered by each of the multiple filters A to D.

[0104] Next, in step S8, the control unit 84 compares the statistical information generated for each of the multiple signals filtered by each of the multiple filters A to D with the statistical information standards stored in the memory unit 82 for each conveying speed and each filter.

[0105] A specific example will be given to explain the process of comparing statistical information with the standard statistical information, which is executed by the control unit 84. Here, it is assumed that the control unit 84 generates the variance and the difference between the maximum and minimum values ​​as statistical information, and compares this with the standard statistical information.

[0106] As a prerequisite for performing step S8, the memory unit 82 stores combinations of reference values ​​for variance and reference values ​​for the difference between the maximum and minimum values ​​for each combination of three types of conveying speeds, namely, conveying speed zero, conveying speed Va, and conveying speed Vb, and four filters, filter A to filter D.

[0107] The information stored in the storage unit 82 may be, for example, the variance and the difference between the maximum and minimum values ​​for each conveying speed and each filter calculated from computer simulations or theoretical calculations. Also, the information stored in the storage unit 82 may be, for example, the variance and the difference between the maximum and minimum values ​​for each conveying speed and each filter obtained by a method similar to steps S1 to S7 above using a test machine for the weighing device 100 that is known to be free of defects (a machine different from the weighing device 100 to be diagnosed).

[0108] Alternatively, the information stored in the memory unit 82 may be, for example, the variance and the difference between the maximum and minimum values ​​for each conveying speed and for each filter generated from a signal obtained by filtering the weighing signal output by the load cell 28 with each of multiple filters A to D when no item P is on the second conveyor 14, for each of multiple conveying speeds, during a trial run of the weighing device 100 (the weighing device 100 itself that is known to have no malfunctions).

[0109] Furthermore, for example, the storage unit 82 may store as default the variance and the difference between the maximum and minimum values ​​of the weighing signal, obtained in a manner similar to steps S1 to S7 above using, for example, a test machine for the weighing device 100. After the test run, the storage unit 82 may store the variance and the difference between the maximum and minimum values ​​of the weighing signal, obtained in a manner similar to steps S1 to S7 above during the test run of the weighing device 100 to be diagnosed.

[0110] In step S7, the control unit 84 compares the variance and the difference between the maximum and minimum values ​​generated from the signals filtered by each filter for each conveying speed with a combination of a reference value for variance and a reference value for the difference between the maximum and minimum values ​​stored in the storage unit 82 and associated with the same conveying speed and the same filter. The control unit 84 then determines that the statistical information is abnormal (that the statistical information deviates from normal values) if the variance generated from the signals filtered by each filter for each conveying speed is greater than the reference value for variance by a predetermined value or more, or if the difference between the maximum and minimum values ​​generated from the signals filtered by each filter for each conveying speed is greater than the reference value for the difference between the maximum and minimum values ​​by a predetermined value or more. Note that the control unit 84 may also determine that the statistical information is abnormal if the variance generated from the signals filtered by each filter for each conveying speed is greater than the reference value for variance by a predetermined value or more, and if the difference between the maximum and minimum values ​​generated from the signals filtered by each filter for each conveying speed is greater than the reference value for the difference between the maximum and minimum values ​​by a predetermined value or more.

[0111] For example, if the statistical information is a maximum value, the control unit 84 may determine that there is an abnormality in the statistical information if the maximum value is greater than the reference value by a predetermined value or more. Also, for example, if the statistical information is a minimum value, the control unit 84 may determine that there is an abnormality in the statistical information if the minimum value is smaller than the reference value by a predetermined value or more.

[0112] In step S8, the control unit 84 compares such statistical information with the statistical information standard for each combination of three types of conveying speed, i.e., conveying speed zero, conveying speed Va, and conveying speed Vb, and four filters, i.e., filters A to D. In this embodiment, the control unit 84 compares the statistical information with the statistical information standard for each of the 12 combinations of conveying speed and filter type.

[0113] Next, in step S9, the control unit 84 determines whether any of the multiple pieces of statistical information (12 pieces of statistical information in this embodiment) generated for each combination of conveying speed and filter type contains an abnormality. If any of the statistical information contains an abnormality, the diagnostic process proceeds to step S10; if no such statistical information contains an abnormality, the diagnostic process proceeds to step S20.

[0114] In step S10, the control unit 84 determines candidates for the cause of the malfunction based on a plurality of pieces of statistical information generated for each combination of the transport speed and the filter type. A specific example will be described with reference to Figs. 8A to 8C.

[0115] For example, as shown in FIG. 8A, if the control unit 84 determines that the statistical information generated from the weighing signal of the load cell 28 filtered by filters B, C, and D when the conveying speed is at least zero (when the second conveyor 14 is stopped) is abnormal, the control unit 84 determines that problems related to the installation environment of the weighing device 100 and poor installation conditions of the weighing device 100 are possible causes of the malfunction of the weighing device 100.

[0116] For example, as shown in FIG. 8B, the control unit 84 determines that the statistical information generated from the weighing signal of the load cell 28 when the conveying speed is zero, filtered by filter B, filter C, and filter D, is normal. On the other hand, the control unit 84 determines that the statistical information generated from the weighing signal of the load cell 28 when the conveying speed is Va or Vb, filtered by filter A, is abnormal. In this case, the control unit 84 determines that aging or poor maintenance of the second conveyor belt 14a is a candidate cause of the malfunction of the weighing device 100. The reason for this determination is that, since there is no abnormality in the statistical information when the conveying speed is zero, it is assumed that there is no problem with the installation environment or the installation state of the weighing device 100, and that a malfunction in the second conveyor belt 14a (flat belt) is likely to generate relatively low-frequency vibrations.

[0117] 8C , the control unit 84 determines that the statistical information generated from the signal obtained by filtering the weighing signal of the load cell 28 with filter B, filter C, and filter D when the conveying speed is zero is normal. Furthermore, the control unit 84 determines that the statistical information generated from the signal obtained by filtering the weighing signal of the load cell 28 with filter D when the conveying speed is Va is abnormal. Furthermore, the control unit 84 determines that the statistical information generated from the signal obtained by filtering the weighing signal of the load cell 28 with filter C and filter D when the conveying speed is Vb is abnormal. In this case, the control unit 84 determines that a failure of the rollers 144a, 144b or the second drive unit 18b is a candidate cause of the malfunction of the weighing device 100. The reason for making such a judgment is that, since there are no abnormalities in the statistical information when the conveying speed is zero, it is assumed that there are no problems with the installation environment or installation state of the weighing device 100, and that if there is a problem with the rollers 144a, 144b or the second drive unit 18b, vibrations of a relatively low frequency are likely to occur.

[0118] The motor serving as the second drive unit 18b may have a function of detecting its own damage and outputting the detection result to the control device 80. In such a case, if there is a problem with the second drive unit 18b, an abnormality in the second drive unit 18b will be reported to the control device 80. Therefore, in such a case, even if a result such as that shown in FIG. 8C is obtained, the control unit 84 may exclude a failure of the second drive unit 18b from the list of possible causes of the malfunction of the weighing device 100 if no abnormality is reported from the second drive unit 18b.

[0119] When the determination of the cause of the malfunction is completed in step S10, the control unit 84 outputs the candidate cause of the malfunction of the weighing device 100 determined in step S10 to the output device 70 (step S11). For example, the control unit 84 displays the candidate cause of the malfunction of the weighing device 100 determined in step S10 on a display serving as the output device 70. In another example, the control unit 84 may transmit information on the candidate cause of the malfunction of the weighing device 100 determined in step S10 to a mobile terminal or the like operated by an operator of the weighing device 100 or the like.

[0120] In step S20, the control unit 84 determines that there is no malfunction in the weighing device 100. Then, in step S21, the control unit 84 outputs to the output device 70 that there is no malfunction in the weighing device 100.

[0121] The diagnostic process described above is merely an example and can be modified as appropriate.

[0122] For example, the order of steps S1 to S5 can be changed as appropriate. For example, steps S2 and S3 may be performed first, followed by steps S4 and S5, and step S1 may be performed last, or steps S4 and S5 may be performed first, followed by steps S2 and S3, and step S1 may be performed last.

[0123] 7A, the filtering of the measurement signal of the load cell 28 acquired in steps S1, S3, and S5 is performed all at once in step S6, but this is not limited to this. For example, once the measurement signal of the load cell 28 is acquired in each of steps S1, S3, and S5, the signal processing unit 188 may subsequently perform filtering. Furthermore, the process of acquiring statistical information in step S7 may also be performed subsequent to the filtering of the measurement signal of the load cell 28.

[0124] Furthermore, in the above embodiment, even if there is no malfunction in the weighing device 100, the determination result that there is no malfunction is output to the output device 70 in step S21, but this is not limited to such an embodiment. For example, the processes of steps S20 and S21 may be omitted.

[0125] 7A, the weighing device 100 changes the conveying speed in only three stages: zero, Va, and Vb. However, this is not limited to this, and the weighing device 100 may change the conveying speed in four or more stages. By changing the conveying speed in multiple stages, it becomes easier to more accurately determine candidate malfunction causes from the many possible malfunction causes.

[0126] Furthermore, in the above description, the weighing device 100 uses four types of filters in the diagnostic process, but this is not limited to this, and the weighing device 100 may use two, three, or five or more types of filters to filter the weighing signal of the load cell 28.

[0127] Furthermore, in the flowchart described with reference to FIG. 7A, the control device 80 filters one weighing signal at zero conveyance through multiple filters A to D, one weighing signal at conveyance speed Va through multiple filters A to D, and one weighing signal at conveyance speed Vb through multiple filters A to D. However, this is not limited to this, and the control device 80 may directly filter the weighing signals of the load cell 28 acquired at zero conveyance, conveyance speed Va, and conveyance speed Vb through one of multiple filters A to D, as shown in FIG. 7B. In other words, the control device 80 may simultaneously perform steps S1 and S6 in FIG. 7A as step S1a, simultaneously perform steps S2, S3, and S6 in FIG. 7A as step S2a, and simultaneously perform steps S4, S5, and S6 in FIG. 7A as step S3a. Note that the processing from step S7 onward in FIG. 7B is the same as in FIG. 7A, and therefore will not be described here.

[0128] (3) Features (3-1) The weighing device 100 of the above embodiment weighs the weight of the item P while transporting the item P. The weighing device 100 includes a second conveyor 14 as an example of a transport unit that transports the item P, a load cell 28 as an example of a detection unit, and a control unit 84. The second conveyor 14 has a variable transport speed. The load cell 28 detects the weight of the second conveyor 14, or, if an item P is being transported on the second conveyor 14, the weight of the second conveyor 14 and the weight of the item P on the second conveyor 14, and outputs a weighing signal. The control unit 84 of the control unit 84 generates statistical information from the weighing signal output by the load cell 28 when no item is on the second conveyor 14, for each of multiple transport speeds (in the above embodiment, transport speed zero, transport speed Va, and transport speed Vb). The control unit 84 of the control unit 84 determines and outputs candidate malfunction causes based on the statistical information for each transport speed.

[0129] In this weighing device 100, candidate causes of the malfunction are determined based on statistical information obtained for multiple conveying speeds Va and Vb, so that when a malfunction occurs in weighing, candidate causes of the malfunction can be estimated with high accuracy. This allows the maintenance worker for the weighing device 100 to resolve the malfunction in a short time.

[0130] (3-2) In the weighing device 100 of the above embodiment, the statistical information generated by the control unit 84 includes statistical information generated from the weighing signal output by the load cell 28 when the conveying speed is zero and no items are on the second conveyor 14.

[0131] In this weighing device 100, candidate causes of a malfunction of the weighing device 100 are determined based on statistical information obtained when the conveying speed is zero, i.e., when the second conveyor 14 is stopped, so candidate causes of the malfunction can be estimated with particularly high accuracy when a malfunction occurs in weighing. This allows the maintenance worker for the weighing device 100 to resolve the malfunction in a short time.

[0132] (3-3) In the weighing device 100 of the above embodiment, the defect factors include at least one of defect factors related to the installation state of the weighing device 100 and defect factors related to the installation environment of the weighing device 100.

[0133] This weighing device 100 can detect not only malfunctions in the components of the weighing device 100, but also the possibility of other types of malfunctions, thereby reducing the time required for maintenance workers of the weighing device 100 to identify the cause of the malfunction.

[0134] (3-4) In the weighing device 100 of the above embodiment, the control unit 84 has multiple filters with different characteristics that are used to filter the weighing signal. The control unit 84 generates statistical information from signals obtained by filtering, with each of the multiple filters, the weighing signal output by the load cell 28 when no items are on the second conveyor 14, for each of multiple conveying speeds (in this embodiment, a conveying speed of zero, a conveying speed Va, and a conveying speed Vb). For example, in the above embodiment, the control unit 84 generates statistical information from signals obtained by filtering, with each of four types of filters A to D, the weighing signal output by the load cell 28 when no items are on the second conveyor 14, for each of multiple conveying speeds. The control unit 84 determines and outputs candidate malfunction causes based on the statistical information for each conveying speed and each filter.

[0135] In this weighing device 100, candidate causes of the malfunction are determined using statistical information obtained from signals processed with different filters, so that when a malfunction occurs in weighing, candidate causes of the malfunction can be estimated with high accuracy. This allows maintenance workers for the weighing device 100 to resolve the malfunction in a short time.

[0136] (3-5) The weighing device 100 of the above embodiment has a memory unit 82. The memory unit 82 stores statistical information standards for each conveying speed and each filter. The control unit 84 compares the generated statistical information for each conveying speed and each filter with the standards for the corresponding conveying speed and filter stored in the memory unit 82, and determines and outputs candidate malfunction causes based on the results.

[0137] In this weighing device 100, by comparing the generated statistical information with a standard, it is possible to accurately estimate possible causes of the malfunction.

[0138] (3-6) In the weighing device 100 of the above embodiment, the memory unit 82 may store, as a standard, statistical information generated from signals obtained by filtering the weighing signal output by the load cell 28 with each of a plurality of filters when no items are on the second conveyor 14, for each of a plurality of conveying speeds during a trial run of the weighing device 100.

[0139] In this weighing device 100, statistical information obtained during a test run of the weighing device 100 is used as a reference, so that possible causes of malfunctions can be estimated based on the characteristics unique to each weighing device 100.

[0140] (3-7) In the weighing device 100 of the above embodiment, the statistical information includes at least one of the standard deviation, the variance, the difference between the maximum value and the minimum value, and the difference between the maximum value and the minimum value.

[0141] (4) Variations Modifications of the above embodiment are shown below. The contents of the modifications may be combined with part or all of other modifications as long as they are not contradictory to each other.

[0142] (4-1) Variation A In the above embodiment, the diagnostic process utilizes statistical information generated from the weighing signal output by the load cell 28 when the conveying speed is zero (in other words, the second conveyor 14 is stopped) and there are no items on the second conveyor 14, but this is not limited to this.

[0143] In other words, the statistical information used in the diagnostic process may be only statistical information generated from the weighing signal output by the load cell 28 when the second conveyor 14 is operating and there are no items on the second conveyor 14.

[0144] Note that if a weighing problem occurs due to a problem with the installation environment of the weighing device 100 or a poor installation condition of the weighing device 100, changing the conveying speed will not result in a significant change in the vibration components that affect the weighing. Therefore, by observing this phenomenon, it is possible to determine that a problem with the installation environment of the weighing device 100 or a poor installation condition of the weighing device 100 is a possible cause of the problem, even without using statistical information generated from the weighing signal output by the load cell 28 when the conveying speed is zero and there are no items on the second conveyor 14.

[0145] (4-2) Variation B In the above embodiment, during the diagnostic process, the conveying speed of the second conveyor 14 is changed between conveying speed Va and conveying speed Vb, and statistical information generated from the weighing signal output by the load cell 28 when no items are on the second conveyor 14 is used for each of the conveying speeds Va and Vb. However, this is not limited to this, and the diagnostic process may use only statistical information generated from the weighing signal of the load cell 28 when the conveying speed of the second conveyor 14 is zero and statistical information generated from the weighing signal of the load cell 28 when the conveying speed of the second conveyor 14 is conveying speed Va. However, in order to accurately determine candidate malfunction causes, it is preferable to change the conveying speed of the second conveyor 14 during operation in two or more stages and use statistical information generated from the weighing signal output by the load cell 28 when no items are on the second conveyor 14 for each conveying speed.

[0146] (4-3) Variation C In the above embodiment, an example in which multiple filters are used during the diagnostic process is described, but this is not limited to this, and only one filter may be used during the diagnostic process. Even in such a case, statistical information can be generated for each of multiple conveying speeds from the weighing signal output by the load cell 28 when no items are on the second conveyor 14, and candidate malfunction causes can be determined based on the statistical information for each conveying speed.

[0147] For example, the vibration frequency of the rollers 144a, 144b of the second conveyor 14 and the vibration frequency of the second conveyor belt 14a change depending on the conveying speed of the second conveyor 14. Therefore, if a malfunction occurs in the rollers 144a, 144b of the second conveyor 14 or the second conveyor belt 14a, even when only one filter is used, the vibration may be detected strongly or hardly at all in the filtered signal depending on the conveying speed of the second conveyor 14. By observing such phenomena, it is possible to determine possible causes of the malfunction even when only one type of filter is used.

[0148] Furthermore, the control unit 84 does not need to use a filter for the diagnostic process. For example, the control unit 84 may perform frequency analysis on the weighing signal output by the load cell 28 when the article is not on the second conveyor 14 for each of a plurality of conveying speeds, generate statistical information for each frequency band, and determine and output candidate malfunction causes based on the generated statistical information.

[0149] (4-4) Variation D The weighing device 100 in the above embodiment includes the conveying device 10, the detecting device 20, and the control device 80, but the weighing device 100 may be a device having other configurations. For example, the above embodiment describes an example in which a sorting device separate from the weighing device 100 is placed downstream of the weighing device 100, but the weighing device 100 may also include a sorting mechanism that sorts the items P based on the results of weighing the items P.

[0150] (4-5) Variation E In the above embodiment, an FIR filter is used as an example of a filter, but the type of filter is not limited to an FIR filter, and other types of filters capable of filtering a measurement signal may be used.

[0151] (4-6) Variation F In the above embodiment, a weighing device 100 is described that includes a load cell 28 having a strain gauge as a detection unit (weight sensor). However, the type of detection unit of the weighing device is not limited to a load cell that uses a strain gauge. For example, the load cell 28 may be a hydraulic load cell or a pneumatic load cell. Furthermore, the detection unit may be a weight sensor other than a load cell type, such as a tuning fork vibrating weight sensor, an electromagnetic balance weight sensor, or a capacitance weight sensor. [Industrial Applicability]

[0152] The present invention is widely applicable and useful to weighing devices that weigh items while being transported. [Explanation of symbols]

[0153] 14 Second conveyor (transport section) 28 Load cell (detection part) 82 Memory section 84 Control Unit 100 Weighing device A 1st filter (filter) B Second filter (filter) C Third filter (filter) D 4th filter (filter) V Conveying speed [Prior art documents] [Patent documents]

[0154] [Patent Document 1] Japanese Patent Application Publication No. 2020-148589

Claims

1. A weighing device that weighs an item while transporting the item, a conveying unit that conveys an article and has a variable conveying speed; a detection unit that detects the weight of the conveying unit, or, when the item is being conveyed to the conveying unit, the weight of the conveying unit and the weight of the item on the conveying unit, and outputs a weighing signal; a control unit that generates statistical information for each of the plurality of conveying speeds from the weighing signal output by the detection unit when no article is on the conveying unit, and determines and outputs candidate malfunction causes based on the statistical information for each of the conveying speeds; Equipped with The statistical information generated by the control unit includes statistical information generated from the weighing signal output by the detection unit when the conveying speed is zero and no article is on the conveying unit. Weighing device.

2. The defect factors include at least one of defect factors related to the installation state of the weighing device and defect factors related to the installation environment of the weighing device. The weighing device according to claim 1 .

3. the control unit has a plurality of filters with different characteristics used for filtering the weighing signal, the control unit generates the statistical information from signals obtained by filtering the weighing signal output by the detection unit with each of the plurality of filters when no article is on the conveying unit for each of the plurality of conveying speeds, and determines and outputs candidates for the malfunction cause based on the statistical information for each of the conveying speeds and each of the filters.

3. A weighing device according to claim 1 or 2.

4. a storage unit in which a standard of the statistical information is stored for each of the conveying speeds and each of the filters; the control unit determines and outputs candidates for the defect cause based on a result of comparing the generated statistical information for each of the conveying speeds and each of the filters with the criteria for the corresponding conveying speeds and the corresponding filters stored in the storage unit.

4. The weighing device according to claim 3.

5. The storage unit stores, as the standard, the statistical information generated from signals obtained by filtering the weighing signal output by the detection unit with each of the plurality of filters when no article is on the conveying unit, for each of the plurality of conveying speeds during a test run of the weighing device.

5. The weighing device according to claim 4.

6. The statistical information includes at least one of a standard deviation, a variance, a difference between a maximum value and a minimum value, a maximum value, and a minimum value. A weighing device according to any one of claims 1 to 5.

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