JP6433235B2 - Combination scale - Google Patents

Description

  The present invention relates to an automatic or semi-automatic combination weigher, and more specifically, by supplying an object to be weighed from a supply hopper to a weighing hopper, a load signal of a weight sensor corresponding to the weighing hopper is used. The present invention relates to a combination weigher configured to obtain a weight value.

  Conventionally, as an automatic or semi-automatic combination weigher, a structure having a supply hopper above a plurality of weighing hoppers for combining and weighing objects to be weighed is known. In this type of combination weigher, an object to be weighed is once stored in a supply hopper, automatically dropped from the supply hopper to the weighing hopper, and the weight is measured by the weighing hopper.

  When measuring the weight of an object to be weighed into the weighing hopper using the combination weigher, the load signal obtained from a weight sensor such as a load cell is not limited to the vibrations inherent to the balance and vibrations due to external factors. Contains vibration components. Therefore, in order to perform accurate weighing, it is necessary to wait for the load signal to converge to a steady value. However, if waiting for convergence, high-speed weighing cannot be performed. Therefore, the weight signal of the weighing hopper in the weighing hopper is read by a digital signal processing algorithm (dynamic weighing method) such as digital filtering so that the load signal contains vibration components so that high-speed weighing is possible. A technology has been developed to enable quick reading.

  As digital filtering, a technique using multiple moving average filters or FIR filters is known. For example, Patent Document 1 proposes an FIR filter that attenuates a vibration component included in a digital load signal based on a predetermined filter transfer function as a technique using an FIR filter.

  The weight value is acquired from the load signal in which the vibration component is attenuated by the digital filtering. As a method for determining the acquisition timing of the weight value, there are a stability determination method and a stable waiting time method.

  In the stability determination method, it is determined whether the load signal satisfies the stability determination condition, and the time when the load signal is satisfied is determined as the time when the load signal is stabilized, and that time is determined as the weight value acquisition timing. To do. As this stability determination method, for example, in Patent Document 2, for time-series load signal data a1, a2, a3, a4,..., First, the average value A1 of the data a1, a2, a3, and then the data a2, a3. , A4 average value A2, then the average value A3 of the data a3, a4, a5, and so on, the average value at several points in time series data is obtained, and the difference between these average values (A1-A2), (A2- A3),... Is determined to be stable when the load signal becomes equal to or less than the variation width allowable value C1, and the weight value is acquired at this time. In other words, a stability determination section is provided to evaluate the vibration state of the load signal at a certain time interval, and it is determined whether or not the load signal in this stability determination section has reached the allowable value. Assuming that the signal is stable, that time is set as the weight value acquisition timing.

  On the other hand, the stable waiting time method is determined in advance by operating a timer or the like when supply of articles to the weighing hopper is started, as described in, for example, [Prior Art] of Patent Document 3. The weight value is acquired when the load signal is stabilized at the time when the stabilization waiting time, which is a long time, has elapsed.

  Further, Patent Document 4 measures the stabilization waiting time and determines whether or not the load signal at the time when the stabilization waiting time is completed is in a stable state using the load signal before the stabilization waiting time is completed. The weight value is acquired when the stable state is determined.

JP-A-7-134057 JP-A-9-113348 JP-A-3-259720 JP 2011-43369 A

  In the stability determination method in which weight determination is performed by performing stability determination as in Patent Document 2, if the number of data used for stability determination is too small, in other words, if the time of the stability determination section is too short, the load signal converges. In spite of this, there is a possibility of misjudging that it is stable. Therefore, it is usually necessary to evaluate a load signal in a longer stability determination section, and the weight value acquisition timing is delayed.

  For this reason, it is difficult to apply the stability determination method to an automatic or semi-automatic combination weigher for which high-capacity weighing processing is expected, and it is applied to a track scale or the like.

  A stable waiting time method for obtaining a weight value when a predetermined stabilization waiting time elapses without performing stability determination is applied to a combination weigher or the like, but has the following problems.

  That is, when the object to be weighed is, for example, an elastic object to be weighed such as a winner or a bell pepper, the object to be weighed supplied from the supply hopper to the weighing hopper jumps in the weighing hopper, An abnormal supply state sometimes occurs such that the objects to be weighed that are supplied to the weighing hopper and are piled up in an unstable manner fall afterwards.

  Such an abnormal supply state is a normal supply in which the object to be weighed does not jump in the weighing hopper as described above, or the object to be weighed that is unstablely overlapped by being supplied to the weighing hopper does not fall down after that. Compared to the state, it takes time until the load signal is stabilized after the supply of the object to be weighed to the weighing hopper is started.

  Conventionally, an operator performs a test to supply an object to be weighed during adjustment operation, observes the waveform of the load signal, and sets the time until the load signal is stabilized as the stabilization wait time. The stable waiting time is set to be long so that a measurement error does not occur even in the abnormal supply state as described above. That is, the time until the load signal in the abnormal supply state is stabilized is set as the stabilization wait time.

  For this reason, in a normal supply state in which the object to be weighed does not jump in the weighing hopper or overlap and fall down, the load signal is already stable, but it is set in consideration of the abnormal supply state. There is a problem that the weighing capacity is lowered because it is necessary to wait for the weight value to be acquired until the longer stable waiting time has elapsed.

  On the other hand, in Patent Document 3, it is described that the time when the load signal is maximum is detected, and the load signal at the time when the reading time has elapsed from that time is read to obtain the weight value. When the load signal is maximized, it is necessary to detect the time point, and when the setting of the reading time is not appropriate, the stability determination is not performed, so that there is a problem that a measurement error occurs.

  In Patent Document 4, which measures the stabilization waiting time and determines whether or not the load signal at the time when the stabilization waiting time is completed is determined using a load signal before the stabilization waiting time is completed, In this case, the object to be weighed must be weighed a plurality of times, and the standard deviation of the variation in the error of the load signal must be calculated to determine the stable waiting time, which is troublesome.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a combination weigher that can prevent the occurrence of poor measurement without lowering the weighing ability.

  In order to achieve the above object, the present invention is configured as follows.

(1) The present invention corresponds to a plurality of supply hoppers, a plurality of weighing hoppers arranged corresponding to the respective supply hoppers, holding and discharging the objects to be weighed supplied from the supply hoppers, and the respective weighing hoppers. A plurality of weight sensors that detect the weight of the objects to be weighed held by the weighing hoppers, and a combination calculation unit that performs a combination calculation based on a load signal from the weight sensors. A scale,
A setting operation display unit that is operated to set, as a stable waiting time, a fixed time starting from the time when the object to be weighed is supplied from the supply hopper to the weighing hopper, and displays the waveform of the load signal. When,
Stability determining means for determining whether or not the load signal is stable based on the load signal in a predetermined period including a time point when the stability waiting time elapses or a predetermined period near the time point elapses.
When it is determined by the stability determining means that the load signal is stable, the combination calculation unit causes the weight value based on the load signal to participate in the combination calculation, and determines that the load signal is not stable. When the weight value based on the load signal is not included in the combination calculation,
The stabilization waiting time is a predicted time from the starting point until the load signal is stabilized when the supply of the object to be weighed from the supply hopper to the weighing hopper is in a normal state. This is the predicted time from the starting point to the stabilization of the load signal when it is not less than the predicted time and the supply of the object to be weighed from the supply hopper to the weighing hopper is not normal. A predetermined time less than the second predicted time is preset by the setting operation display unit ,
The first predicted time and the second predicted time are determined in advance based on the waveform of the load signal displayed on the setting operation display unit .

  The “predetermined period” in the “predetermined period including the time point at which the stable waiting time elapses or a predetermined period in the vicinity of the elapse time point” refers to the period required for stability determination. It may be a period including the time point to be performed, or may be a period in the vicinity thereof without including the time point when the stable waiting time elapses.

  “The supply of the object to be weighed from the supply hopper to the weighing hopper is in a normal state” means that, for example, the supply timing of the object to be weighed from the supply hopper to the weighing hopper is delayed, or the supply hopper In this state, the object to be weighed supplied to the weighing hopper does not jump in the weighing hopper, and the object to be weighed supplied to the weighing hopper and unstably overlapped does not fall down.

  “The supply of the object to be weighed from the supply hopper to the weighing hopper is in an abnormal state” means that the timing of the object to be weighed from the supply hopper to the weighing hopper is delayed, or the weighing from the supply hopper is It means a state in which an object to be weighed supplied to the hopper jumps in the weighing hopper, or an object to be weighed that is supplied to the weighing hopper and piled up in an unstable manner falls down afterwards.

  The first prediction time and the second prediction time are predicted by performing an adjustment operation in advance and observing the waveform of the load signal.

  According to the present invention, as the stable waiting time, when the supply of the object to be weighed from the supply hopper to the weighing hopper is in a normal state, the estimated time until the load signal is stabilized from the starting point of the supply of the object to be weighed Is the estimated time from the starting point until the load signal is stabilized when the supply of the object to be weighed from the supply hopper to the weighing hopper is not normal. A certain time less than a certain second prediction time can be set. That is, when the supply of the weighing object is in a normal state as the stabilization waiting time, it is longer than the first predicted time until the load signal is stabilized, and the supply of the weighing object is not normal. At some time, a time less than the second predicted time until the load signal becomes stable can be set.

  Therefore, as in the conventional example, when the supply of the object to be weighed is not normal as in the conventional example, a longer time than the second predicted time that is the predicted time until the load signal is stabilized is set. When there is no need and the supply of the weighing object is in a normal state, it is sufficient to set a shorter time than the first predicted time which is the predicted time until the load signal is stabilized. When the supply signal is normal and the load signal is stable, the weight value can be acquired if the set short waiting time has elapsed, so that it is possible to suppress a decrease in the weighing capacity. it can.

  On the other hand, when the supply of the object to be weighed is not normal, a stabilization waiting time shorter than the second prediction time during which the load signal is stabilized is set, so that the load signal is not stabilized by the stability determination means. Since the weight value based on the load signal is excluded from the combination calculation, it is possible to prevent a measurement error from occurring.

  Further, the stability determination means determines whether or not the load signal is stable based on the load signal in a predetermined period including a time point at which the stabilization waiting time elapses or in a predetermined period near the time point elapses. At the time when the waiting time elapses, the time equal to or longer than the first predicted time has elapsed. Therefore, when the supply of the object to be weighed is in a normal state, the load signal has substantially converged. The required predetermined period can be a short period.

  (2) In a preferred embodiment of the present invention, the first predicted time or a time close to the first predicted time is set as the stable waiting time.

  The “time close to the first predicted time” is preferably a time as close as possible to the first predicted time.

  According to this embodiment, as the stabilization waiting time, when the supply of the weighing object is in a normal state, the first prediction time until the load signal is stabilized or a time close to the first prediction time is set. Therefore, when the supply of the object to be weighed is in a normal state, the weight value is immediately obtained from the stable load signal when the first predicted time which is the stable waiting time or a time close to the first predicted time has elapsed. Can participate in combination calculations.

  (3) In another embodiment of the present invention, the stability determining means is configured to stabilize the load signal based on at least three sampling signals obtained by sampling the load signal in the predetermined period at a constant sampling period. It is determined whether or not.

  According to this embodiment, the predetermined period is a period including a time point at which the stabilization waiting time elapses or a period in the vicinity of the time point elapses. Therefore, when the supply of the weighing object is in a normal state, the load signal Is substantially converged, it is possible to determine whether or not the load signal is stable based on at least three sampling signals.

  (4) In still another embodiment of the present invention, the at least three sampling signals include sampling signals obtained by sampling the load signals at the time when the stabilization waiting time has elapsed from the starting point and before and after that point. You may make it.

  According to this embodiment, the load signal is stabilized based on at least three sampling signals at the time before the stabilization waiting time elapses, the time at which the stabilization waiting time elapses, and the time after the stabilization waiting time elapses. It can be determined whether or not.

  (5) In a preferred embodiment of the present invention, the stability determining means determines whether or not the load signal is stable based on a difference between the at least three sampling signals.

  According to this embodiment, the stability determination is performed based on the difference between at least three sampling signals, so that the stability determination can be performed with simple arithmetic processing.

  (6) In another embodiment of the present invention, when the stability determining means determines that the load signal is not stable, it is determined that the load signal is stable within a predetermined limit period. Until then, an additional determination process for determining whether or not the load signal is stable is repeated based on at least three sampling signals delayed by one sampling period.

  According to this embodiment, when the supply of the object to be weighed is not in a normal state and is not determined to be stable by the stability determining means, based on at least three sampling signals delayed by one sampling period. Since the additional determination process for determining whether or not the load signal is stable is repeated, when it is determined that the load signal is stable by this repeated determination process, the weight value can be obtained from the load signal at that time. it can.

  (7) In a preferred embodiment of the present invention, when the combination calculation unit is in time for a combination calculation when it is determined that the load signal is stable by the additional determination processing by the stability determination unit, A weight value based on the load signal is included in the combination calculation.

  According to this embodiment, when the load signal is determined to be stable by the additional determination process after it is determined that the load signal is not stable by the stability determination means, the load signal is stable when the combination calculation is in time. Since the weight value based on the load signal determined to be present is included in the combination calculation, it is possible to prevent the combination accuracy from being lowered.

  As described above, according to the present invention, the stable waiting time is equal to or longer than the first predicted time until the load signal is stabilized when the supply of the object to be measured is in a normal state, and the object to be weighed. When the supply of objects is not normal, a time shorter than the second predicted time until the load signal is stabilized can be set.

  Therefore, as in the conventional example, when the supply of the object to be weighed is not normal as in the conventional example, a longer time than the second predicted time that is the predicted time until the load signal is stabilized is set. When there is no need and the supply of the weighing object is in a normal state, it is sufficient to set a shorter time than the first predicted time which is the predicted time until the load signal is stabilized. When the supply signal is normal and the load signal is stable, the weight value can be acquired if the set short waiting time has elapsed, so that it is possible to suppress a decrease in the weighing capacity. it can.

  On the other hand, when the supply of the object to be weighed is not normal, a stabilization waiting time shorter than the second prediction time during which the load signal is stabilized is set, so that the load signal is not stabilized by the stability determination means. Since the weight value based on the load signal is not allowed to participate in the combination calculation, it is possible to prevent a measurement error from occurring.

  Further, the stability determination means determines whether or not the load signal is stable based on the load signal in a predetermined period including a time point at which the stabilization waiting time elapses or in a predetermined period near the time point elapses. At the time when the waiting time elapses, the time equal to or longer than the first predicted time has elapsed. Therefore, when the supply of the object to be weighed is in a normal state, the load signal has substantially converged. The required predetermined period can be a short period.

It is a schematic diagram of the combination scale which concerns on embodiment of this invention. It is a block diagram of the combination weigher of FIG. It is a wave form diagram of a load signal when supply of an object to be measured is in a normal state. It is an enlarged view of the principal part of FIG. It is a wave form diagram of a load signal when supply of a to-be-measured object is in the state where it is not normal. It is an enlarged view of the principal part of FIG. It is a wave form chart of a load signal near the stability waiting time for explaining stability discrimination processing. It is a flowchart which shows a stability discrimination | determination process. It is a time chart of the measurement cycle of a combination scale.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing a schematic configuration of a combination weigher according to an embodiment of the present invention. The combination weigher of this embodiment has a conical top cone 3 that disperses an object to be weighed (not shown) supplied from the supply device 1 radially by vibration, and a top cone 3 in the center of the upper part of the device. A main feeder (distributed feeder) 4 to be vibrated is provided.

  The object to be weighed is not particularly limited, but the object to be weighed supplied from the supply hopper 12 to the weighing hopper 13 jumps in the weighing hopper 13 or is fed to the weighing hopper 13 to be unstablely overlapped. Then, it is suitable for an object to be weighed, such as a winner, a bell pepper, or a wrap candy, in which an abnormal supply state such as falling after that occurs occasionally.

  The supply device 1 conveys an object to be weighed supplied from a belt conveyor (not shown) by vibration and supplies it to the central portion of the top cone 3. In the top cone 3, the object to be weighed supplied from the supply device 1 to the central portion thereof is conveyed toward the peripheral portion by vibration. In the vicinity of the top cone 3, a plurality of linear feeder pans 6 for conveying the objects to be weighed sent from the top cone 3 to the plurality of supply hoppers 12, and a plurality of linear feeders for vibrating the linear feeder pans 6 respectively. 8 are provided radially. A plurality of supply hoppers 12 are provided below the peripheral edge of the linear feeder pan 6, a weighing hopper 13 is provided below the supply hopper 12, and both hoppers 12 and 13 are arranged in a circumferential shape. .

  Under the supply hopper 12 and the weighing hopper 13, discharge gates 12a and 13a that can be opened and closed are respectively provided.

  The supply hopper 12 receives an object to be weighed which is conveyed by the linear feeder pan 6 and dropped and discharged from the conveyance end 6a which is the leading end thereof. When the weighing hopper 13 disposed below the empty hopper 13 becomes empty, a discharge gate 12a is provided. Open, drop and discharge the object to be weighed, and put it into the weighing hopper 13. Each weighing hopper 13 is connected to a weight sensor 10 such as a load cell that measures the weight of an object to be weighed in the weighing hopper 13, and a load signal from each weight sensor 10 is given to the control device 9.

  The objects to be weighed are conveyed to the corresponding supply hoppers 12 by the plurality of linear feeder pans 6 and the plurality of linear feeders 8 that respectively vibrate the respective linear feeder pans 6.

  The weighing hopper 13 can discharge the objects to be weighed to the collecting chute 14. The control device 9 having a function as a combination calculation unit calculates a weight value of an object to be weighed held in each weighing hopper 13, that is, a weight value based on a load signal from each weight sensor 10 corresponding to each weighing hopper 13. The combination calculation is performed to select a combination in which the variously combined weight values are equal to the combination target weight value or the weight value within the allowable weight range closest to the combination target weight value. The control device 9 selects a combination of the weighing hoppers 13 from which the objects to be weighed are to be discharged from the plurality of weighing hoppers 13 by combination calculation, and if a discharge command signal is input from the packaging machine 15, the combination is applicable. The objects to be weighed are discharged from the weighing hopper 13 to the collecting chute 14 and further discharged to the lower packaging machine 15.

  The amount of the object to be weighed supplied from the supply device 1 to the top cone 3 is measured by the top cone weight sensor 5 supporting the top cone 3 and the main feeder 4, and the measured value is given to the control device 9. . In the control device 9, based on the weight of the weighing object on the top cone 3 measured by the top cone weight sensor 5, the supply device 1 keeps the amount of the weighing object on the top cone 3 constant. To control.

The operation setting display unit 11 is configured using, for example, a touch panel or the like, and performs operation of the combination weigher, setting of operation parameters thereof, and the like, and displays an operation speed, a combination measurement value, and the like on a screen. As will be described later, the operation setting display unit 11 displays a waveform of a load signal obtained in a supply test of an object to be weighed during an adjustment operation, and is used for determining a timing for acquiring a weight value from the load signal. It has a function as a setting operation display unit for setting a waiting time.

  The control device 9 performs operation control of the supply device 1 and overall operation control of the combination weigher, and also performs stability determination of the load signal as described later, and based on the result, obtains a weight value obtained from the load signal. Based on this, the above combination calculation is performed.

  FIG. 2 is a block diagram showing a schematic configuration of the control system of the combination weigher in this embodiment, and the same reference numerals are given to the portions corresponding to FIG.

  As shown in FIG. 2, the control device 9 is connected to the CPU unit 16, the memory unit 17, the A / D conversion circuit unit 18, the gate drive circuit unit 19, the vibration control circuit unit 21, and the packaging machine 15. The I / O circuit unit 22 is provided.

  The CPU unit 16 controls each unit and performs combination calculation and stability determination described later. The memory unit 17 stores an operation program for the combination weigher, operation parameters to be set, and the like, and serves as a work area for operations on the CPU unit 16. The A / D conversion circuit section 18 is an analog signal from the weight sensor 5 for detecting the weight of the weighing object on the top cone 3 and the weight sensor 10 for detecting the weight of the weighing object of each weighing hopper 13. Is converted into a digital signal and output to the CPU unit 16.

  The CPU unit 16 and the memory unit 17 constitute a filter operation circuit that digitally filters the A / D converted load signal from the A / D conversion circuit unit 18 and an arithmetic circuit that performs a combination operation. Stability determining means for determining whether or not the applied load signal is stable is configured.

  The gate drive circuit unit 19 controls the opening and closing of the discharge gates 12 a and 13 a of the supply hopper 12 and the weighing hopper 13 based on a control signal from the CPU unit 16. The vibration control circuit unit 21 controls each vibration operation of the supply device 1, the main feeder 4, and each linear feeder 8 based on a control signal from the CPU unit 16. The CPU unit 16 is connected so as to be able to communicate with the operation setting display unit 11.

  The control device 9 controls the operation of the supply device 1 and the entire combination weigher by the CPU unit 16 executing the operation program stored in the memory unit 17.

  In the combination weigher, it is necessary to set a large number of operation parameters for performing the operation as described above, and the setting is performed by the operator using the operation setting display unit 11, and the value of the set operation parameter is the CPU unit. 16 and stored in the memory unit 17. The operation parameters include a combination target weight, which is a target value in the combination calculation, and an allowable weight range with respect thereto, vibration amplitude and driving time of each feeder 4 and 8 (one vibration continuation time), a stable waiting time, and the like.

  In this embodiment, the stable waiting time for determining the timing for acquiring the weight value from the load signal subjected to the digital filter processing is set as follows.

  That is, the operator operates the operation setting display unit 11 to perform an adjustment operation prior to the operation operation, and performs a supply test of the object to be weighed.

  In the supply test, an object to be weighed is supplied from the supply hopper 12 with respect to a certain weighing hopper 13, and the waveform of the load signal which has been A / D converted by the A / D conversion circuit unit 18 and subjected to digital filter processing is displayed on the operation setting display unit. 11 is displayed. This supply test is repeated a plurality of times, and the operator sets a stable waiting time based on the waveform of the load signal.

  FIG. 3 is a diagram showing a waveform of the load signal S1 displayed on the operation setting display unit 11 in this supply test, and FIG. 4 is an enlarged view of a main part of FIG. 3, 4, 5, and 6, the vertical display bar 25 indicates the set time point of the stable waiting time set by operating the operation setting display unit 11.

  In FIG. 3, the horizontal axis indicates the elapsed time from the starting point of supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13, specifically, from the time when the discharge gate 12 a of the opened supply hopper 12 is closed. The vertical axis indicates a value (hereinafter referred to as “AD value”) obtained by subjecting the load signal to A / D conversion and digital filtering.

  As shown in FIG. 3, the load signal S1 initially exceeds the upper and lower display ranges, and after oscillating up and down, converges to a constant value.

  The load signal S1 shows a signal waveform when the supply of the object to be weighed is in a normal state.

  5 and 6 are waveform diagrams of the load signal S2 corresponding to FIGS. 3 and 4 and show signal waveforms when the supply of the object to be weighed is not normal.

  When the supply of the object to be weighed is in a normal state, as shown in FIG. 3, the elapsed time t starting from when the discharge gate 12a of the opened supply hopper 12 is closed is the load signal S1 at the time t3. Is convergent and stable.

  On the other hand, the object to be weighed supplied from the supply hopper 12 to the weighing hopper 13 jumps in the weighing hopper 13, or the object to be weighed supplied to the weighing hopper 13 and unstably overlapped then falls down. When the supply is not normal, as shown in FIG. 5, the load signal S2 does not converge at time t3.

  For this reason, in the case of the conventional stable waiting time method, the load signal S2 shown in FIG. 5 is used as a stable waiting time in order to prevent a measurement defect from occurring in a state where the supply of the object to be weighed is not normal. A time equal to or longer than the second predicted time, which is the predicted time until convergence and stabilization, is set. Specifically, the time is set longer, for example, set near the time point t4.

  For this reason, in the conventional stable waiting time method, taking into account that there is a state in which the supply of the object to be weighed is not normal, the stabilization waiting time is lengthened, for example, set near the time point t4. In the normal state, as shown in FIG. 3, although the load signal S1 converges and stabilizes at the time point t3, the weight value cannot be obtained until the time point t4, and the weighing capacity is reduced. Was.

  In order to prevent such a decrease in weighing capacity, in this embodiment, the supply hopper that is opened when the supply of the objects to be weighed from the supply hopper 12 to the weighing hopper 13 is in a normal state as a stable waiting time. The first estimated time, which is the estimated time until the load signal is stabilized, starting from the time point when the 12 discharge gates 12a are closed, and the objects to be weighed from the supply hopper 12 to the weighing hopper 13 When it is assumed that the supply is not normal, a fixed time less than a second predicted time, which is a predicted time from the starting point until the load signal is stabilized, is set.

  When the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is in a normal state, the load signal is stabilized from the time when the discharge gate 12a of the opened supply hopper 12 is closed. The first predicted time, which is the predicted time, is the time until the vicinity of the time t3 according to the supply test shown in FIG.

  FIG. 5 shows the second predicted time, which is the predicted time from the starting point until the load signal is stabilized when the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is not normal. According to the supply test shown, it is the time to the vicinity of the time point t4 ′.

  Since the first and second prediction times are prediction times, a slight deviation is allowed and the load signal only needs to be stable.

  In this embodiment, as the stabilization waiting time, any time point after the time point t3 and before the time point t4 ′ can be set. However, in order to suppress a decrease in the weighing capacity, the time t3 It is preferable that the time point is as close as possible to the time point t3.

  In this embodiment, based on the result of the supply test, the stabilization waiting time is set to the time t3 which is the first predicted time, and the vertical display bar 25 is displayed at the setting time.

  In this embodiment, when the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is in a normal state, the load starts from the time when the discharge gate 12a of the opened supply hopper 12 is closed. The first prediction time, which is the prediction time until the signal is stabilized, is set as the stable waiting time as described above.

  Therefore, when the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is in a normal state, the load signal S1 converges and stabilizes at time t3 when the stabilization waiting time has elapsed, as shown in FIG. Therefore, an accurate weight measurement value can be obtained. However, when the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is not normal, as shown in FIG. Since it has not converged, an accurate weight value cannot be obtained, resulting in a measurement error.

  Therefore, in this embodiment, the stability determination is performed based on the load signal in a predetermined period including the time t3 when the stabilization waiting time elapses.

  Next, the stability determination process will be described in detail.

  FIG. 7 is a waveform diagram of a load signal before and after time t3, which is the elapsed time of the stabilization wait time, and shows a signal waveform when the supply of the object to be weighed corresponding to FIG. 3 is in a normal state.

  In this embodiment, the A / D conversion circuit unit 18 samples the load signal from the weight sensor 10 at an interval of, for example, 5 ms and performs A / D conversion, and performs A / D conversion and digital filter processing. The load signal is sampled, and stability determination is performed based on the sampling signal.

  In the vicinity of the stable waiting time, it is considered that the balance vibrates due to the natural vibration of the balance, and the load signal is sampled with a time of 1/4 period of the natural vibration of the balance as a sampling interval.

  Specifically, assuming that the natural vibration frequency of the balance is 30 Hz, the cycle is 1000 ms / 30 = 33.33 ms, and the sampling interval is 33.33 ms / 4 = 8.33 ms. In this embodiment, Since the sampling interval of the A / D conversion circuit unit 18 is 5 ms, 8.33 msec is rounded up to 10 ms.

  That is, the stability determination is performed based on the sampling signal obtained by sampling the load signal which has been A / D converted by the A / D conversion circuit unit 18 and subjected to digital filter processing at a sampling interval ts of 10 msec.

  In this embodiment, as shown in FIG. 7, based on the three sampling signals obtained by sampling the load signal at the time t3 when the stabilization waiting time elapses, and the sampling times (t3−ts) and (t3 + ts) before and after that. Then, stability determination processing is performed as follows.

  In the following description, the load signal from the weight sensor 10 is A / D converted, and the value of the signal obtained by sampling the digitally filtered load signal at the sampling time (t3-ts) is used as the AD value addata1 at the first sampling point. The value of the signal sampled at the sampling time t3 is taken as the AD value addata2 at the second sampling point, and the value of the signal sampled at the sampling time (t3 + ts) is taken as the AD value addata3 at the third sampling point.

  In this embodiment, the stability determination is performed based on the difference between the values of the three sampling signals addata1, addata2, and addata3.

  Specifically, the first difference diff1, which is the absolute value of the difference between the AD value addata2 at the second sampling point and the AD value addata1 at the first sampling point, the AD value addata3 at the third sampling point, and the second sampling point A second difference diff2 that is an absolute value of a difference from the AD value addata2 of the second sampling point, a third difference diff3 that is an absolute value of a difference between the AD value addata3 of the third sampling point and the AD value addata1 of the first sampling point, Are calculated as follows.

diff1 = | addata2-addata1 |
diff2 = | addata3-addata2 |
diff3 = | addata3-addata1 |
The following determination is made for each difference diff1, diff2, and diff3.

  (1) The first difference diff1 is less than or equal to the first threshold diff thrs1 (diff1 ≦ diff thrs1), and the second difference diff2 is less than or equal to the first threshold diff thrs1 (diff2 ≦ diff thrs1) And the third difference diff3 is less than or equal to the second threshold diff thrs2 (diff3 ≦ diff thrs2), and the second difference diff2 is less than the first difference diff1 (diff2 <diff1) At some point, it is determined that the load signal is stable.

  (2) Otherwise, it is determined that the load signal is not stable.

  Each determination condition of the above (1) will be described.

  The first threshold value diff thrs1 is a threshold value for determining whether or not the first difference diff1 and the second difference diff2 are small. In this embodiment, for example, the minimum scale of the combination weigher If the value of twice the sm, for example, the minimum scale sm is 0.1 g, the first threshold value diff thrs1 is 0.2 g.

  If the first difference diff1 and the second difference diff2 are both less than or equal to the first threshold value diff thrs1 (diff1 ≦ diff thrs1), (diff2 ≦ diff thrs1), the first sampling time (t3− ts) to the second sampling time point t3, the change of the load signal at one sampling interval ts, and the change of the load signal at the one sampling interval ts from the second sampling time point t3 to the third sampling time point (t3 + ts). Both are small and stable.

  In other words, since the sampling interval is constant, the slope of the straight line connecting the first sampling point (t3-ts) of the load signal and the second sampling point t3, and the second sampling point t3 of the load signal It shows that the slope of the straight line connecting the third sampling time point (t3 + ts) is small below the first threshold value diff thrs1.

  The second threshold diff thrs2 determines whether or not the third difference diff3 is small, that is, in a two sampling interval from the first sampling time point (t3-ts) to the third sampling time point (t3 + ts). This is a threshold value for determining whether or not the change in the load signal is small. The third difference diff3 is a change in the load signal at two sampling intervals 2ts, whereas the first difference diff1 and the second difference diff2 are both changes at one sampling interval ts of the load signal. It is.

  As described above, the third difference diff3 is a change in the load signal in a period twice as long as the first and second differences diff1 and diff2, but the second threshold diff thrs2 that is the threshold of the third difference diff3. Is less than twice the first threshold diff thrs1, that is, less than four times the minimum scale sm in the above example. Specifically, for example, a value that is three times the minimum scale sm, and therefore, in the above example, the second threshold value diff thrs2 is 0.3 g.

  If the third difference diff3 is equal to or less than the second threshold value diff thrs2 (diff3 ≦ diff thrs2), the change in the load signal over two sampling periods is the threshold value for the change in the load signal in one sampling period. It is less than twice the threshold value diff thrs1, indicating that the change in the load signal over two sampling periods is small and stable.

  Whether or not the second difference diff2 is less than the first difference diff1 (diff2 <diff1) is determined based on the second difference diff2, that is, the second sampling time t3 to the third sampling time (t3 + ts). It is determined whether or not the change in the load signal is smaller than the first difference diff1, that is, the change in the load signal from the first sampling time point (t3-ts) to the second sampling time point t3. is there.

  If the second difference diff2 is less than the first difference diff1 (diff2 <diff1), the change in the load signal in the subsequent sampling period is smaller than the change in the load signal in the previous sampling period, that is, the load signal Indicates a tendency to converge.

  The first and second threshold values diff thrs1 and diff thrs2 can be changed by operating the operation setting display unit 11 based on the supply test.

  When the condition (1) is satisfied and it is determined that the load signal is stable, the AD value addata3 of the third sampling point is acquired as a weight value and is included in the combination calculation.

  In this way, stability can be determined by simple arithmetic processing based on the differences diff1, diff2, and diff3 of the three sampling signals, so that the burden on the CPU unit 16 that performs filter arithmetic and other processing is reduced. It can be.

  When it is determined that the condition (1) is not satisfied and the load signal is not stable, three sampling signals including a signal sampled by delaying one sampling interval without acquiring a weight value; That is, based on the three sampling signals sampled at the sampling time points t3, (t3 + ts), and (t3 + 2ts), the same stability determination processing as described above is performed, and when it is determined that the load signal is not stable, Based on three sampling signals including a signal sampled by delaying the sampling interval, that is, three sampling signals sampled at the sampling time points (t3 + ts), (t3 + 2ts), and (t3 + 3ts), respectively, the same stability as above Perform discriminating process, and then add additional until it is determined to be stable. Repeating the constant determination process.

  By this additional stability determination process, when it is determined that the load signal is stable and the acquisition of the weight value is in time for the combination calculation, it is allowed to participate in the combination calculation, thereby preventing a reduction in the combination accuracy. .

  With this additional stability determination process, the weight value of the weighing hopper 13 that is in a state where the supply of the object to be weighed from the supply hopper 12 to the weighing hopper 13 is not normal can be acquired when the load signal is stabilized. it can.

  Further, this additional stability determination processing is performed within a limited time, in this embodiment, until the set stabilization waiting time elapses, that is, twice the stabilization time has elapsed from the supply of the object to be weighed. If it is not determined that the load signal is stable within the limited time, the load signal at the final point in time is acquired as the weight value.

  In this embodiment, although the stability determination is performed based on the sampling signals before and after the time t3 including the time t3 when the stabilization waiting time elapses, as another embodiment of the present invention, at the time t3 and the previous two times The stability determination may be performed based on three sampling signals, or three sampling signals at time t3 and two subsequent time points.

  In this embodiment, the stability determination is performed based on the load signal for a predetermined period including the time t3 when the stabilization waiting time elapses. However, as another embodiment of the present invention, the time t3 when the stabilization waiting time elapses. The stability determination may be performed based on the vicinity of the time point t3 that does not include, for example, the three sampling signals before the time point t3 or the three sampling signals after the time point t3.

  The predetermined period is a period in which the load signal can be sampled three times. However, as another embodiment of the present invention, a period in which the load signal can be sampled four times or more may be used, and may be four or more, for example, four or five sampling signals. Based on this, stability determination may be performed.

  FIG. 8 is a flowchart for explaining the operation of the stability determination process.

  The process of FIG. 8 is started by an interrupt process for each sampling period. First, it is determined whether or not the status is idle (step n1), and when it is in the idle state, it is determined whether or not the measurement is started. (Step n2). Specifically, it is determined whether or not the discharge gate 12a of the opened supply hopper 12 is closed (step n24). When the measurement is not started, the process proceeds to step n4. When the measurement is started, a timer time obtained by subtracting the sampling interval ts from the stable waiting time is set in the first timer of the CPU unit 16 (step n25). The status is awaited by the timer and the process proceeds to step n4 (step n26). In step n4, the first timer is decremented, and then the second timer is decremented and returned (step n5).

  If the status is not idle in step n1, it is determined whether the status is waiting for a timer (step n2). If the status is waiting for a timer, the process proceeds to step n17. In step n17, it is determined whether or not the first timer has timed up, that is, whether or not the sampling time (t3-ts) one sampling before the stabilization wait time is reached. The process moves to n4, and when the sampling time comes, the process moves to step n18.

  In step n18, the register for storing the AD value adddata1 at the first sampling time is reset to “0”, the register for storing the AD value adddata2 at the second sampling time is reset to “0” (step n19), The current AD value is taken in as the AD value at the third sampling time (step n20), the sampling interval ts is set as the timer time of the first timer (step n21), and the timer time of the second timer of the CPU unit 16 is set. As described above, a stabilization waiting time for limiting the additional determination process is set (step n22), the status is set as stable detection (step n23), and the first timer and the second timer are decremented and returned (step n4). , N5).

  If the status is not waiting for the timer in step n2, it is determined whether the status is being detected for stability (step n3). If the status is not being detected, the process proceeds to step n4. It is determined whether or not the timer has expired, that is, whether or not the sampling interval ts has elapsed. If the sampling interval ts has not elapsed, the process proceeds to step n4, and if the sampling interval ts has elapsed, the first The value of the register that stores the AD value adddata1 at the sampling time is replaced with the value of the register that stores the AD value adddata2 at the second sampling time (step n7), and the register value that stores the AD value adddata2 at the second sampling time Value is the AD value addat at the third sampling time Replacing 3 to the value of the store register (step n8), takes in a current AD value as the AD value of the third sampling point, it proceeds to the step n10 (step n9).

  In step n10, the first difference | diff1 | is calculated and the process proceeds to step n11. In step n11, the second difference | diff2 | is calculated and the process proceeds to step n12. In step n12, the third difference | diff3 is calculated. | Is calculated, and the process proceeds to Step n13. In step n13, based on each difference, it is determined whether or not the conditions for stability determination are satisfied (step n13). When the conditions for stability determination are satisfied, the status is set to idle and the weight value is determined. Is transferred to Step n4 (Step n16).

  When the stability determination condition is not satisfied in step n13, it is determined whether or not the second timer has expired, that is, whether or not the stability determination time limit has been reached (step n14), and the time limit has been reached. If not, the sampling interval ts is set as the timer time of the first timer and the process proceeds to step n4 (step n15). When the time limit is reached, the weight value is acquired and the process proceeds to step n16.

  FIG. 9 is a time chart of the combination weigher. FIG. 9A is a discharge gate 13a of the weighing hopper 13, FIG. 9B is a discharge gate 12a of the supply hopper 12, and FIG. The timing of the linear feeder 8 is shown respectively.

  A discharge command signal is given to the combination weigher from the packaging machine 15, and the combination weigher opens the discharge gate 13a of the weighing hopper 13 selected by the combination calculation as shown in FIG. Discharge the object to be weighed to the machine.

  The discharge gate 12a of the supply hopper 12 corresponding to the weighing hopper 13 that has been emptied by discharging the object to be measured is opened as shown in FIG. To do.

  The stable waiting time is measured from the start of supply of the objects to be weighed from the supply hopper 12 to the weighing hopper 13, specifically, the discharge gate 12a of the supply hopper 12 is fully opened. Be started.

  The linear feeder 8 corresponding to the supply hopper 12 that has been emptied by supplying the object to be weighed to the weighing hopper 13 is driven as shown in FIG. .

  Based on the sampling signal at the time when the stabilization waiting time elapses and before and after that time, the stability determination is performed as described above, the weight measurement value is obtained from the load signal determined to be stable, the combination calculation is performed, and the measurement is performed. The weighing hopper 13 for discharging the object is selected, and the same processing as described above is repeated.

  When it is determined that the state is not stable by the stability determination, the additional stability determination process is repeated while shifting by one sampling interval ts as described above. When the stability is determined, the weight value is acquired. When it is in time for the combination calculation when the weight value is acquired, it is allowed to participate in the combination calculation, and when it is not in time, it is allowed to participate in the combination calculation of the next measurement cycle.

  In the above embodiment, the time when the object to be weighed is supplied from the supply hopper 12 to the weighing hopper 13, that is, the time when the discharge gate 12 a of the opened supply hopper 12 is closed as the starting point of the stable waiting time. However, the present invention is not limited to this, and may be the time when the discharge gate 12a of the supply hopper 12 is opened or other time.

  Although the above embodiment has been described as applied to an automatic combination weigher, as another embodiment of the present invention, it may be applied to a semi-automatic combination weigher in which an operator puts an object to be weighed into a supply hopper. .

DESCRIPTION OF SYMBOLS 1 Supply apparatus 4 Main feeder 8 Linear feeder 9 Control apparatus 10 Weight sensor 11 Memory 12 Supply hopper 13 Weighing hopper 15 Packaging machine 16 CPU part 17 Memory part 18 A / D conversion circuit part

Claims (7)

A plurality of supply hoppers;
A plurality of weighing hoppers arranged corresponding to the respective supply hoppers, holding and discharging the objects to be weighed supplied from the supply hoppers;
A plurality of weight sensors provided corresponding to each weighing hopper and detecting the weight of the object to be weighed held by each weighing hopper;
A combination weigher comprising a combination calculation unit for performing a combination calculation based on a load signal from the weight sensor,
A setting operation display unit that is operated to set, as a stable waiting time, a fixed time starting from the time when the object to be weighed is supplied from the supply hopper to the weighing hopper, and displays the waveform of the load signal. When,
Stability determining means for determining whether or not the load signal is stable based on the load signal in a predetermined period including a time point when the stability waiting time elapses or a predetermined period near the time point elapses.
When it is determined by the stability determining means that the load signal is stable, the combination calculation unit causes the weight value based on the load signal to participate in the combination calculation, and determines that the load signal is not stable. When the weight value based on the load signal is not included in the combination calculation,
The stabilization waiting time is a predicted time from the starting point until the load signal is stabilized when the supply of the object to be weighed from the supply hopper to the weighing hopper is in a normal state. This is the predicted time from the starting point to the stabilization of the load signal when it is not less than the predicted time and the supply of the object to be weighed from the supply hopper to the weighing hopper is not normal. A predetermined time less than the second predicted time is preset by the setting operation display unit ,
The first predicted time and the second predicted time are determined in advance based on a waveform of a load signal displayed on the setting operation display unit.
A combination weigher characterized by that. As the stabilization waiting time, the first predicted time or a time close to the first predicted time is set.
The combination weigher according to claim 1. The stability determining means determines whether or not the load signal is stable based on at least three sampling signals obtained by sampling the load signal in the predetermined period at a constant sampling period.
The combination weigher according to claim 1 or 2. The at least three sampling signals include a sampling signal obtained by sampling a load signal at a time when the stabilization waiting time elapses from the starting point, and before and after the time point.
The combination weigher according to claim 3. The stability determining means determines whether the load signal is stable based on a difference between the at least three sampling signals.
The combination weigher according to claim 3 or 4. When it is determined that the load signal is not stable, the stability determination means is at least three samplings delayed by one sampling period until it is determined that the load signal is stable within a predetermined limit period. Repeating an additional determination process for determining whether or not the load signal is stable based on the signal;
The combination weigher according to any one of claims 3 to 5. The combination calculation unit, when it is determined that the load signal is stable by the additional determination processing by the stability determination means, and when the combination calculation is in time, the combination calculation unit calculates the weight value based on the load signal. To join,
The combination weigher according to claim 6.

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