Measuring device

Abstract

To provide a weighing device that allows for the selection of a suitable digital filter. [Solution] The weighing device is a weighing device for weighing an article, and comprises a transport unit for transporting the article, a weighing unit, and a control unit. The weighing unit outputs a raw signal corresponding to the force acting on the transport unit. The control unit controls the transport unit and applies a digital filter to the raw signal. The control unit performs a selection process (S4-S6) to select one digital filter from among a plurality of digital filters. The control unit performs the selection process based on the result of applying the plurality of digital filters to the raw signal during the period from when a stop instruction is sent to the transport unit until the transport unit stops.

Description

Technical Field

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

Background Art

[0002] As disclosed in Patent Document 1 (republication patent WO2015 - 141670), a weighing device that applies a plurality of digital filters to an original signal output from a weighing unit is known.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In a weighing device that performs processing using a plurality of digital filters, the setting of the digital filter according to the article to be weighed and the surrounding situation is often performed by a skilled person.

[0004] However, in the manual setting of the digital filter, if the proficiency of the person setting it is low, an appropriate setting may not be made, and accurate weighing may not be possible.

[0005] An object of the present invention is to provide a weighing device in which a suitable digital filter is selected.

Means for Solving the Problems

[0006] The weighing device according to the first aspect is a weighing device for weighing an article. The weighing device includes a conveying unit that conveys the article, a weighing unit, and a control unit. The weighing unit outputs an original signal corresponding to the force acting on the conveying unit. The control unit controls the conveying unit and applies a digital filter to the original signal. The control unit executes a selection process of selecting one digital filter from a plurality of digital filters. The control unit executes the selection process based on the results of applying a plurality of digital filters to the original signal during the period from when a stop instruction is sent to the conveying unit until the conveying unit stops.

[0007] In the weighing device relating to the first aspect, after a stop command is sent to the conveying unit, the selection process is executed by the control unit while the conveying unit is in motion. This ensures that the digital filter is appropriately and automatically selected according to the item being weighed and the surrounding conditions.

[0008] Furthermore, in the weighing device relating to the first viewpoint, the period from when the control unit sends a stop command to the transport unit until the transport unit stops is used for the selection process. As a result, in the weighing device relating to the first viewpoint, it is not necessary to allocate extra time for the selection process, or the time after the transport unit stops that is used for the selection process can be shortened.

[0009] The weighing device relating to the second perspective is the weighing device relating to the first perspective, and the control unit performs a selection process during the initial setting before weighing the items.

[0010] In the weighing device relating to the second aspect, the selection process by the control unit is performed not after the actual production of goods has started on the production line including the weighing device, but during the initial setting stage before production. As described above, the present invention makes effective use of the above period, thus shortening the time required for initial setting.

[0011] The weighing device relating to the third perspective is a weighing device relating to the first or second perspective, and the control unit determines the number of digital filters to apply to the original signal in the selection process according to the length of the time limit when applying the digital filters.

[0012] In weighing devices, the time required to weigh each item varies depending on parameters such as the conveying speed of the item, the length of the item, and the size of the conveying unit. These parameters also affect the time limit for applying digital filters. In light of this, the weighing device relating to the third aspect determines the number of digital filters applied to the original signal according to the length of the time limit for applying the digital filters. This ensures adherence to the time limit.

[0013] The weighing device relating to the fourth perspective is a weighing device relating to the first or second perspective, and the control unit performs the selection process based on the result of applying a predetermined group of digital filters to the original signal during the selection process.

[0014] In the weighing device relating to the fourth aspect, the control unit performs a selection process based on the result of applying a predetermined group of digital filters to the original signal. This selects a suitable digital filter.

[0015] The weighing device relating to the fifth perspective is the weighing device relating to the fourth perspective, and the group of digital filters is a digital filter for removing vibration components generated when the conveying unit is conveying an item.

[0016] In the weighing device relating to the fifth aspect, a group of digital filters is used to eliminate vibration components of the original signal that are several tens of Hz or higher, such as vibration components associated with the transfer of goods on the conveyor in the transport section, or vibration components generated when goods in transport come into contact with guide members, etc.

[0017] The weighing device relating to the sixth viewpoint is a weighing device relating to the first or second viewpoint, and the control unit acquires the original signal from the weighing unit when another device adjacent to the upstream or downstream of the weighing device is operating.

[0018] In the weighing device related to the sixth perspective, the raw signal is acquired while the goods being transported and adjacent devices that physically affect the transport section are in operation when the production line is actually running. Therefore, the selection process reflects the actual conditions when the production line is running.

[0019] The weighing device relating to the seventh perspective is a weighing device relating to any of the first to sixth perspectives, further comprising a display unit. The display unit displays the result of applying multiple digital filters to the original signal.

[0020] The measuring device according to the eighth aspect is any one of the measuring devices from the first aspect to the seventh aspect, and during the period from when the control unit sends a stop instruction to the transport unit until the transport unit stops, the operating speed of the transport unit gradually decreases.

[0021] The measuring device according to the ninth aspect is any one of the measuring devices from the first aspect to the seventh aspect, and the period from when the control unit sends a stop instruction to the transport unit until the transport unit stops is the period from when the control unit sends a stop instruction to the transport unit until the transport unit naturally stops.

[0022] The measuring device according to the tenth aspect is any one of the measuring devices from the first aspect to the seventh aspect, and further includes a brake. The brake is provided to stop the operation of the transport unit. The control unit executes a selection process based on the result of applying a plurality of digital filters to the original signal during the period from when the control unit sends a stop instruction to the transport unit and an operation instruction to the brake until the transport unit stops.

Advantages of the Invention

[0023] According to the present invention, the selection of the digital filter according to the article to be measured and the surrounding situation is appropriately and automatically performed. In addition, it is not necessary to secure extra time for the selection process, or the time after the transport unit stops dedicated to the selection process can be shortened.

Brief Description of the Drawings

[0024] [Figure 1] It is a diagram showing a schematic configuration of a measuring device according to an embodiment of the present invention. [Figure 2] It is a diagram showing a functional configuration of a control unit of a measuring device. [Figure 3] It is a flowchart for explaining a method of selecting a digital filter in an initial setting. [Figure 4A] It is a diagram showing a waveform included in an original signal. [Figure 4B] It is a diagram showing a waveform after filtering the waveform shown in FIG. 4A. [Figure 5A] An enlarged view showing a plurality of measurement results obtained by applying a default digital filter. [Figure 5B] An enlarged view showing a plurality of measurement results obtained by applying a digital filter different from the default digital filter.

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention. Also, in each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0026] (1) Overall Configuration of the Measuring Device FIG. 1 is a diagram schematically showing a measuring device 10 according to the present embodiment. The measuring device 10 shown in FIG. 1 is a device that measures while conveying a measurement object in the direction of the white arrow A in FIG. 1 (hereinafter simply referred to as the "conveying direction"). The measuring device 10 is a device arranged on a product production line. The measurement object is an article P (product) extending along the conveying direction. The measuring device 10 includes a frame 20, a conveying unit 30, a measuring unit 50, an operation unit 70 having a touch panel 72, and a control unit 80.

[0027] (2) Configuration of the Conveying Unit The conveying unit 30 is a conveying device that transports articles P along the transport direction, and is, for example, a conveyor. The conveying unit 30 transports articles P at a transport speed specified via the touch panel 72 of the operation unit 70. The transport speed is specified by the user via the touch panel 72. The conveying unit 30 has a first conveyor 31, a second conveyor 32, and a third conveyor 33. The first conveyor 31, the second conveyor 32, and the third conveyor 33 each have rotating bodies such as rollers and motors, a transport belt, etc. The first conveyor 31, the second conveyor 32, and the third conveyor 33 are arranged in order from the upstream side in the transport direction. That is, the second conveyor 32 is located between the first conveyor 31 and the third conveyor 33 in the transport direction. The first conveyor 31 is a conveyor that loads articles P into the second conveyor 32. The first conveyor 31 may have, for example, a metal detector (not shown). The second conveyor 32 is a conveyor that transports items P from the first conveyor 31 to the third conveyor 33. The third conveyor 33 is a conveyor that unloads items P from the second conveyor 32. The third conveyor 33 has, for example, a sorting machine (not shown) that sorts out items P whose weight deviates from the appropriate range.

[0028] The second conveyor 32 is equipped with a weighing unit 50. The items P being transported by the transport unit 30 are weighed by the weighing unit 50 while they are on the second conveyor 32.

[0029] (3) Structure of the mounting frame The frame 20 is a member that supports the weighing unit 50 and is fixed to the floor F below the second conveyor 32.

[0030] (4) Configuration of the weighing section The weighing unit 50 is a unit that weighs the weight of the item P on the second conveyor 32 and is located in the center of the transport unit 30. The weighing unit 50 mainly consists of a load cell 51 and an A / D converter (not shown). The weighing unit 50 outputs a raw signal corresponding to the force acting on the transport unit 30.

[0031] In the load cell 51, multiple strain gauges attached to a strain generating element are connected to a Wheatstone bridge circuit. The load cell 51 also extracts an electrical signal corresponding to the load transmitted from the strain gauges from the Wheatstone bridge circuit. This electrical signal is an analog source signal indicating the weighing result of the load cell 51 for item P. This analog source signal is converted into a digital source signal by an A / D converter. The weighing unit 50 uses this digital source signal as the source signal and outputs it externally.

[0032] The strain-generating body of the load cell 51 is fixed to the frame 20 at one end (right end in Figure 1) and to the lower part of the rigid member 34 at the other end (left end in Figure 1). The rigid member 34 is a member that supports the second conveyor 32, and its upper part is fixed to the second conveyor 32.

[0033] (5) Configuration of the control panel The control unit 70 is provided for operating the transport unit 30 and the weighing unit 50, and is erected near the second conveyor 32. The control unit 70 mainly consists of a touch panel 72 and a control unit 80.

[0034] (5-1) Touch panel The touch panel 72 is a display unit that displays images based on display information output from the control unit 80, and also a reception unit that receives input from the user. The touch panel 72 displays the weighing signal obtained by filtering the original signal, the weighing value indicating the weighing result of the weight of the item P, accuracy information for evaluating the accuracy of the weighing value, the transport speed of the transport unit 30, the dimensions of the item P along the transport direction, the transport frequency of the item P, the weighing pitch of the item P, and so on. When the touch panel 72 receives input from the user, input information indicating the input content is output from the touch panel 72 to the control unit 80. The input information is data related to the transport speed of the transport unit 30, the dimensions of the item P along the transport direction, the type of item P, the transport frequency of the item P, and so on. The transport frequency of the item P is set based on the capacity of the production machine located upstream of the weighing device 10.

[0035] The weighing value and accuracy information of item P are data obtained based on the raw signal transmitted from the weighing unit 50 to the operation unit 70. The weighing value is calculated by a known method. The weighing pitch of item P is calculated by the control unit 80 based on the transport speed of the transport unit 30, the dimensions of item P, and the transport frequency of item P. The transport frequency of item P is set based on the capacity of the production machine located upstream of the weighing device 10.

[0036] (5-2) Control Unit The control unit 80 is a controller that controls each part of the weighing device 10 and is built into the operation unit 70. The control unit 80 is a computer composed of a CPU, RAM, ROM, etc. The control unit 80 sends an operation signal to the transport unit 30 via the touch panel 72 so that the transport speed of the transport unit 30 is set to the specified speed. In addition, if a sorting machine is provided on the third conveyor 33 and the control unit 80 determines that the weight of the item P deviates from a preset appropriate range, the control unit 80 sends an operation signal to the sorting machine to sort the item P (remove it from the production line).

[0037] Furthermore, the control unit 80 functions not only to control each part of the weighing device 10, but also as a processing unit that performs tasks such as receiving, calculating, and transmitting various signals, and recording and reading various signals.

[0038] An example of the calculation of various signals by the control unit 80 is the derivation of the weighing result of item P. The control unit 80 includes, for example, a drive circuit for outputting a control signal for the transport unit 30, a drive circuit for calculating the weighing value of item P from the original signal generated by the weighing unit 50, a drive circuit for calculating the above-mentioned precision information from the original signal, and a storage circuit for storing each signal and each piece of information.

[0039] Figure 2 shows the functional configuration of the control unit. As shown in Figure 2, the control unit 80 has a receiving unit 81, a filtering unit 82, a calculation unit 83, an output unit 84, and a storage unit 85 as its functional units.

[0040] (5-2-1) Receiving section The receiving unit 81 is the part that receives the raw signal transmitted from the weighing unit 50 and the input information transmitted from the touch panel 72. The transmission of the raw signal from the weighing unit 50 to the receiving unit 81 and the transmission of the input information from the touch panel 72 to the receiving unit 81 may be carried out via a wired connection or via a wireless connection.

[0041] (5-2-2) Filter section The filter unit 82 is the part that filters the original signal output from the metering unit 50 using a plurality of pre-set digital filters. In other words, the filter unit 82 applies digital filters to the original signal. Each of the plurality of digital filters consists of a low-pass filter that attenuates frequency components exceeding a predetermined frequency, a notch filter (bandstop filter) that attenuates noise at the frequency of the rotating body included in the carrier unit 30, and so on. When at least some of the plurality of digital filters are selected, the filter unit 82 performs multi-stage filtering on the original signal. Each digital filter includes one or more low-pass filters and one or more notch filters. Each of the plurality of digital filters may include low-pass filters with different attenuation amounts for different frequency bands, or may include notch filters that attenuate different frequency bands. The plurality of low-pass filters may be known variable filters, such as those described in Japanese Patent No. 5901126.

[0042] The filter unit 82 filters the original signal using one digital filter pre-selected from a plurality of digital filters while the transport unit 30 is operating and while the item P is being transported. The filter unit 82 then outputs a signal (weighing signal) obtained by filtering the original signal. The obtained weighing signal is output to the calculation unit 83, storage unit 85, etc., included in the control unit 80 shown in Figure 1. The weighing signal has a waveform that is prepared for calculating the weight of the item P.

[0043] The filter unit 82 obtains the raw signal during the initial setting of the weighing device 10 (setting process before weighing the item P) when the transport unit 30 is in operation but the item P is not being transported by the transport unit 30 (hereinafter also referred to as "during idle operation of the transport unit 30"). Then, it applies each of the multiple digital filters to the raw signal. In other words, the filter unit 82 performs filtering by applying each of the multiple digital filters to the raw signal obtained during the idle operation of the transport unit 30. As a result, the filter unit 82 generates multiple weighing signals, which are the result of applying each of the multiple digital filters to the raw signal obtained during the idle operation of the transport unit 30. The filter unit 82 then outputs the multiple weighing signals to the calculation unit 83, the storage unit 85, etc. As will be described later, the filtering process and the generation of multiple weighing signals are performed during the period from when a stop instruction is sent to the transport unit 30 until the transport unit 30 stops.

[0044] In this embodiment, the information output from the weighing unit 50 when the transport unit 30 is run empty at a transport speed specified via the touch panel 72 corresponds to the original signal obtained when the transport unit 30 is operating but no item P is being transported by the transport unit 30. For example, if the multiple digital filters consist of a first filter to a third filter, the filter unit 82 performs filtering on the original signal using each of the first to third filters. As a result, the filter unit 82 generates a first weighing signal obtained by applying the first filter, a second weighing signal obtained by applying the second filter, and a third weighing signal obtained by applying the third filter.

[0045] (5-2-3) Arithmetic section The calculation unit 83 processes the various input information. During normal operation (production mode), while the transport unit 30 is operating and while the item P is being transported, the calculation unit 83 calculates the weight of item P based on the weighing signal output from the filter unit 82. As a result, the calculation unit 83 generates a weighed value for item P. The calculation unit 83 sends the generated weighed value to the output unit 84. The calculation unit 83 calculates the weighing pitch (weighing interval) for item P based on the input transport speed of the transport unit 30, the dimensions of item P, and the transport frequency. Based on the generated weighed value for item P, the calculation unit 83 determines whether the weight of item P deviates from a preset appropriate range. Depending on the result of this determination, the calculation unit 83 outputs an operation signal to, for example, a sorting machine.

[0046] Furthermore, the calculation unit 83 selects one of the multiple digital filters based on the results of applying each of the multiple digital filters to the original signal obtained when the transport unit 30 is operating but the item P is not being transported by the transport unit 30. This digital filter selection process is performed during the initial setting of the weighing device 10, from the time a stop instruction is sent to the transport unit 30 until the transport unit 30 stops.

[0047] In this embodiment, the calculation unit 83 first generates multiple accuracy information based on multiple metering signals obtained during the idle operation of the transport unit 30. Next, the calculation unit 83 compares the multiple accuracy information and determines the most appropriate accuracy information and / or metering signal. Subsequently, the calculation unit 83 selects a digital filter corresponding to the determined accuracy information and / or metering signal. Then, the calculation unit 83 outputs the determined accuracy information and / or metering signal, along with information regarding the selected digital filter, to the storage unit 85.

[0048] The accuracy information is calculated, for example, based on the standard deviation of the amplitude of the waveform contained in the metering signal. This calculation result may be the standard deviation of the waveform amplitude itself, or a parameter based on the standard deviation. In this embodiment, the accuracy information is the standard deviation of the amplitude of the waveform contained in the metering signal. The calculation unit 83 compares the standard deviations of the amplitude of each waveform obtained by applying each of the multiple digital filters to the original signal, and selects the digital filter that yields the smallest standard deviation. If the multiple digital filters consist of a first filter to a third filter, the calculation unit 83 obtains the first standard deviation of the amplitude of the waveform contained in the first metering signal, the second standard deviation of the amplitude of the waveform contained in the second metering signal, and the third standard deviation of the amplitude of the waveform contained in the third metering signal from the filter unit 82. Subsequently, the calculation unit 83 identifies the metering signal that yields the smallest value among the first standard deviation, second standard deviation, and third standard deviation. Then, the calculation unit 83 selects the digital filter applied to the identified metering signal.

[0049] Furthermore, the calculation unit 83 determines the number of digital filters to be selected in the selection process described above, according to the length of the time limit when applying the digital filters. The time limit when applying the digital filters is the time that can be multiplied for one item P, and is determined by various parameters such as the transport speed of the item P by the transport unit 30, the length of the transport direction of the item P, and the length of the transport direction of the transport unit 30. Within this time limit, for example, multiple digital filters are extracted from the variable filters, and the standard deviation of each digital filter is calculated as described above.

[0050] The waveform included in the weighing signal contains vibrations generated by the weighing device 10 and its surroundings. These vibrations become noise in the weighing of the item P. Therefore, the smaller the standard deviation of the waveform amplitude, the less noise is considered to be in the weighing of the item P. Vibrations generated by the weighing device 10 include vibrations associated with the operation of the conveying unit 30, vibrations that occur when the item P is placed on the conveying unit 30, etc. For example, vibrations that occur when the item P is placed on the conveying unit 30 are noises of several tens of Hz or higher that we want to eliminate by applying a filter. Vibrations generated by the surroundings of the weighing device 10 include, for example, vibrations transmitted from the floor F on which the weighing device 10 is placed (vibrations of the floor F). Vibrations of the floor F are caused by, for example, multiple devices installed on the production line of the item P including the weighing device 10, other devices not included in the production line, etc.

[0051] (5-2-4) Output section The output unit 84 outputs various information and signals generated by the control unit 80, as well as various information and signals stored in the storage unit 85, to the outside. The output unit 84 outputs the weighed value, accuracy information, weighing pitch, etc. of the item P as display information to the touch panel 72. The output unit 84 outputs an operation signal to the transport unit 30 for controlling the transport speed of the transport unit 30. The output unit 84 outputs an operation signal to the sorter.

[0052] The digital filter selected during the initial setup of the weighing device 10 is output to the touch panel 72 as display information.

[0053] (5-2-5) Storage section The memory unit 85 stores input information received via the touch panel 72, as well as various information and signals generated by the control unit 80. The memory unit 85 stores a plurality of pre-set digital filters. The memory unit 85 stores the date and time when one of the plurality of digital filters was selected based on the result of applying each of the plurality of digital filters to the raw signal obtained during the idle operation of the transport unit 30. In addition, the memory unit 85 stores the single digital filter selected at that date and time, the raw signal itself, and the metering signal, metering value, and accuracy information based on that raw signal.

[0054] (6) Automatic selection function of digital filters in initial settings Next, with reference to Figure 3, the method for automatically selecting the digital filter during initial setting by the weighing device 10 according to this embodiment will be described. Initial setting is one of the functions of the reservation setting mode selected during trial operation, etc.

[0055] First, the control unit 80 determines the transport speed of the transport unit 30 (step S1). In step S1, the transport speed of the transport unit 30 is specified via the touch panel 72. At this time, the user may input the transport speed of the transport unit 30 itself via the touch panel 72, or they may input the transport frequency of the items P. In the latter case, the control unit 80 calculates the transport speed of the transport unit 30. The control unit 80 may also use a value obtained by multiplying the input speed or the calculated speed by a predetermined value (margin value) as the transport speed. In this case, it is possible to correct the timing discrepancy of the supply of items P that occurs upstream of the weighing device 10.

[0056] Next, the raw signal is acquired when the transport unit 30 is operated without any items P being transported (i.e., when the transport unit 30 is run empty) (step S2). In step S2, for example, the weighing unit 50 acquires the raw signal when the transport unit 30 is run empty for about 5 seconds at a specified transport speed before weighing the items P. The acquired raw signal is output to the control unit 80.

[0057] Next, the control unit 80 sends a command to the transport unit 30 to stop transporting (step S3). Specifically, the control unit 80 sends a command to stop operation to the motors driving the first conveyor 31, second conveyor 32, and third conveyor 33 of the transport unit 30. The first conveyor 31, second conveyor 32, and third conveyor 33 of the transport unit 30 continue to move due to inertia even after the motors receive the stop command, but the transport speed naturally decreases and they come to a complete stop after about 1 second. During this period of about 1 second (the period from when the stop command is sent to the transport unit 30 until the transport unit 30 stops), the following steps S4 to S6 are performed. The process in steps S4 to S6 is a selection process in which one digital filter is selected from among multiple digital filters based on the result of applying multiple digital filters to the original signal. The multiple digital filters are selected so that the filtering process can be completed within a time limit determined by the transport speed of the item P, the length of the item P in the transport direction, the length of the transport unit 30 in the transport direction, etc., as described above.

[0058] In step S4, the filter unit 82 of the control unit 80 applies each of the multiple digital filters to the original signal acquired in step S2. That is, the filter unit 82 performs filtering by applying each of the multiple digital filters to the original signal. As a result, the filter unit 82 generates multiple metering signals.

[0059] In step S5, the calculation unit 83 of the control unit 80 compares the standard deviations of the amplitudes of each waveform after filtering. In step S5, first, the calculation unit 83 calculates the standard deviation of the amplitudes of the waveforms contained in each of the multiple metering signals. Next, the calculation unit 83 compares the magnitudes of each standard deviation. Here, the calculation unit 83 determines the waveform that yields the smallest standard deviation among the multiple standard deviations.

[0060] Next, the calculation unit 83 selects one digital filter from among the multiple digital filters (step S6). In step S6, the calculation unit 83 selects the digital filter used to generate the metric signal having a waveform that yields the smallest standard deviation. The selected digital filter may be the digital filter used in the standard settings (default digital filter) from among the multiple digital filters, or it may be a digital filter different from the default digital filter.

[0061] By following the steps S1 to S6 described above, before weighing item P, the digital filters used when weighing item P at the specified conveying speed are automatically set and reserved. The set and reserved digital filters, as well as the results of applying multiple digital filters, are displayed on the touch panel 72.

[0062] Furthermore, step S7 in Figure 3, although not a direct process by the control unit 80, shows that the transport speed of the transport unit 30 naturally becomes zero after a certain period of time has elapsed since the instruction to stop transport in step S3 was sent. Here, after the control unit 80 sends a stop instruction to the transport unit 30, the transport speed of the transport unit 30 gradually decreases, and after a certain period of time, the transport unit 30 naturally stops.

[0063] (7) Characteristics of the weighing device (7-1) First, the basic effects and benefits of the weighing device 10 will be explained with reference to Figures 4A, 4B, 5A, and 5B. Figure 4A(a) shows the waveform contained in the original signal. Figure 4B shows the waveform after filtering the waveform shown in Figure 4A.

[0064] Figure 4A shows a waveform WF1 used to calculate the weight of an item P acquired by the weighing unit 50 of the weighing device 10 when the transport unit 30 is transported at a predetermined speed. This waveform WF1 includes noise originating from the weighing device 10 and its surroundings. Therefore, the above noise is usually removed by applying a filtering process to the waveform WF1.

[0065] Figure 4B shows waveforms WF2 and WF3 after filtering waveform WF1. Waveform WF2 is obtained by applying the digital filter used in the standard settings (the default digital filter) from among several digital filters. Waveform WF3 is obtained by applying one digital filter different from the default digital filter from among several digital filters. According to Figure 4B, the noise in waveform WF3 tends to be removed more effectively than that in waveform WF2. Therefore, it is estimated that when the weighing device 10 weighs the weight of item P at the predetermined speed described above, the weight of item P is weighed more accurately by applying the one digital filter described above rather than the default digital filter.

[0066] To confirm the above estimation, the weighing results of multiple items P are compared and examined below. Figure 5A is an enlarged view showing multiple weighing results obtained by applying the default digital filter. Figure 5B is an enlarged view showing multiple weighing results obtained by applying a digital filter different from the default digital filter. As shown in Figures 5A and 5B, the amplitude of the multiple waveforms is smaller when the above-mentioned digital filter is applied than when the default digital filter is applied. Therefore, the standard deviation of the waveform amplitude is also smaller when the above-mentioned digital filter is applied. Thus, when the weighing device 10 weighs the weight of item P at the above-mentioned predetermined speed, it can be seen that the weighing performance of the weighing device 10 can be fully demonstrated when the above-mentioned digital filter is applied than when the default digital filter is applied.

[0067] In this embodiment of the weighing device 10, the calculation unit 83 of the control unit 80 selects one of several digital filters in the initial setting based on the results of applying each of the multiple digital filters to the raw signal obtained during the idle operation of the transport unit 30. This allows for the automatic selection of a digital filter suitable for the weighing device 10 and its surroundings (for example, vibrations of the weighing device 10 itself, vibrations transmitted to the weighing device 10 from the outside, etc.). In other words, a digital filter that can appropriately remove noise generated by the weighing device 10 and its surroundings can be automatically selected. Therefore, even if the designer of the weighing device 10 does not set it based on the results of applying each of the multiple digital filters, the weighing device 10 can accurately weigh the item P using a digital filter that has appropriately removed the above-mentioned noise. Thus, the weighing device 10 can fully demonstrate its weighing performance while improving work efficiency.

[0068] (7-2) In the weighing device 10, after a stop command is sent to the transport unit 30, the selection process is executed by the control unit 80 while the transport unit 30 is in motion. In other words, the selection process is executed by the control unit 80 while the transport unit 30 is naturally decelerating after the stop command. This ensures that the digital filter is appropriately and automatically selected according to the item P to be weighed and the surrounding conditions.

[0069] Furthermore, the weighing device 10 effectively utilizes the period between the stop instruction and the stopping of the transport unit 30, allocating that time to the selection process. This eliminates the need for the weighing device 10 to allocate extra time for the selection process.

[0070] (7-3) In the weighing device 10, the digital filter selection process by the control unit 80 is performed not after the actual production of item P has started on the production line including the weighing device 10, but during the initial setting stage before production. As described above, the weighing device 10 effectively utilizes the time until the transport unit 30 stops, thus shortening the time required for initial setting.

[0071] (7-4) Generally, in weighing devices, the time required to weigh each item varies depending on parameters such as the conveying speed of the item, the length of the item, and the size of the conveying unit. These parameters also affect the time limit for applying a digital filter.

[0072] In light of this, the weighing device 10 according to this embodiment determines the number of digital filters to be applied to the original signal according to the length of the time limit when applying the digital filters. Therefore, all digital filters subject to the selection process are matched to the time limit. As a result, a suitable digital filter is selected in the selection process.

[0073] (7-5) In the weighing device 10 according to this embodiment, the group of digital filters subject to selection processing are digital filters for removing vibration components generated when the conveying unit 30 is conveying the item P. In the weighing device 10, a group of digital filters is selected for eliminating vibration components of the original signal with a frequency of several tens of Hz or higher as noise. As a result, vibration components associated with the transfer of item P from the conveyor in the conveying unit 30, and vibration components generated when the item P in transit comes into contact with a guide member positioned on the side of the conveyor, can be removed as noise.

[0074] (7-6) In the weighing device 10 according to this embodiment, the control unit 80 acquires the raw signal from the weighing unit 50 when other devices adjacent to the weighing device 10, both upstream and downstream, are in operation. In this way, the raw signal is acquired while adjacent devices that physically affect the transported goods P and the transport unit 30 are in operation when the production line is actually running, so that the selection process reflects the actual conditions when the production line is running.

[0075] The adjacent devices mentioned above include a supply device for goods P, another weighing device, an inspection device for checking the weight and presence of foreign matter in goods P, a receiving conveyor, a sorting device, a boxing device, and so on.

[0076] (8) Variations (8-1) In the weighing device 10 described above, multiple digital filters that complete the filtering process within a time limit determined by factors such as the transport speed of the item P, the length of the item P in the transport direction, and the length of the transport section 30 in the transport direction are selected by the control unit 80 and are subject to automatic selection of digital filters during initial setup. Alternatively, a group of digital filters predetermined and manually entered may be stored in the storage unit 85, and this group of digital filters may be subject to selection processing.

[0077] (8-2) In the weighing device 10 described above, after a stop command is sent to the transport unit 30, the selection process is executed by the control unit 80 while the transport unit 30 is in motion. This period, that is, the time from receiving the stop command until the transport unit 30 decelerates and comes to a natural stop, is, for example, 1 second. On the other hand, the calculation time required for the digital filter selection process is, for example, 300 to 400 mmsec. In such a case, the weighing device 10 may be equipped with a brake to further reduce the time required for initial setting.

[0078] The brake is provided to stop the operation of the transport unit 30. When the control unit 80 sends a stop command to the transport unit 30, it activates, shortening the time until the transport unit 30 stops. This shortens the time required for initial setup.

[0079] (8-3) In the weighing device 10 described above, the digital filter selection process, which is performed during the period from when a stop instruction is sent to the conveying unit 30 until the conveying unit 30 stops, is performed during the initial setting. Alternatively, or in addition to this, the digital filter selection process may be performed during normal operation (production mode) after a stop instruction is sent to the conveying unit 30.

[0080] (8-4) In the weighing device 10 described above, the selection process by the control unit 80 is completed while the transport unit 30 is in operation, after a stop instruction has been sent to the transport unit 30. However, the selection process does not necessarily have to be completed within that period. For example, half of the selection process may be performed within that period, and the remaining selection process may be performed after the transport unit 30 has stopped. In this case, the present invention offers the advantage of reducing the time after the transport unit 30 has stopped that is used for the selection process.

[0081] (8-5) The weighing device 10 described above is equipped with one weighing unit 50, but the present invention can also be applied to a weighing device equipped with two weighing units for weighing long items. In this case, one digital filter is selected from among a plurality of digital filters for each of the two raw signals output from each weighing unit.

[0082] (8-6) In the weighing device 10 described above, the accuracy information is calculated based on the standard deviation of the amplitude of the waveform obtained by applying a digital filter to the original signal, but is not limited to this. For example, the accuracy information may be calculated based on the standard deviation of the derivative of the amplitude of the waveform obtained by applying a digital filter to the original signal. This calculation result may be the standard deviation of the derivative of the amplitude of the waveform itself. Alternatively, the accuracy information may be calculated based on the standard deviation of the second derivative of the amplitude of the waveform obtained by applying a digital filter to the original signal. This calculation result may be the standard deviation of the second derivative of the amplitude of the waveform itself. Alternatively, the accuracy information may be calculated by subtracting the minimum value of the amplitude from the maximum value of the amplitude of the waveform.

[0083] (8-7) In the weighing device 10 described above, the weighing unit 50 outputs the digital source signal to the outside as the source signal, but is not limited to this. The weighing unit 50 may also output the acquired analog source signal to the outside as the source signal. In this case, the control unit 80 converts the analog source signal to digital. [Explanation of symbols]

[0084] 10 Weighing device 30 Conveying section 50 Measuring part 72 Touch panel (display unit) 80 Control Unit [Prior art documents] [Patent Documents]

[0085] [Patent Document 1] Republished Patent Publication WO2015-141670

Claims

1. A weighing device for weighing goods, A conveying unit for transporting the aforementioned articles, A metering unit that outputs a raw signal corresponding to the force acting on the transport unit, A control unit that controls the transport unit and applies a digital filter to the original signal, Equipped with, The control unit, A selection process is performed to select one of the multiple digital filters. During the period from when a stop instruction is sent to the transport unit until the transport unit stops, the selection process is executed based on the result of applying the multiple digital filters to the original signal. Weighing device.

2. The control unit performs the selection process during the initial setting before weighing the items. The weighing device according to claim 1.

3. The control unit determines, in the selection process, the number of digital filters to be applied to the original signal according to the length of the time limit for applying the digital filters. The weighing device according to claim 1 or 2.

4. The control unit performs the selection process based on the result of applying a predetermined group of digital filters to the original signal. The weighing device according to claim 1 or 2.

5. The aforementioned group of digital filters are digital filters for removing vibration components generated when the transport unit is transporting the article. The weighing device according to claim 4.

6. The control unit acquires the original signal from the metering unit when another device adjacent to the upstream or downstream of the metering device is operating. The weighing device according to claim 1 or 2.

7. A display unit that displays the result of applying a plurality of digital filters to the original signal. The weighing device according to claim 1 or 2, further comprising the above.

8. During the aforementioned period, the operating speed of the transport unit gradually slows down. The weighing device according to claim 1 or 2.

9. The aforementioned period is the period from when the control unit sends a stop command to the transport unit until the transport unit stops naturally. The weighing device according to claim 1 or 2.

10. A brake for stopping the operation of the transport unit, Furthermore, The control unit, during the period from when it sends a stop command to the transport unit and an activation command to the brake until the transport unit stops, executes the selection process based on the result of applying a plurality of digital filters to the original signal. The weighing device according to claim 1 or 2.

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