JP2013007596A - Combination weigher - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combination weigher capable of precisely obtaining the weight of an article on an article placing part of a vibration feeder and improving the yield of a combined product by control of a driving signal based on the weight of an article.SOLUTION: In a combination weigher 1 including a forward-moving vibration feeder (forward-moving feeder) 5 for conveying an article downstream by vibrating a trough 5a serving as an article placing part, article weight calculation means 43 calculates the weight of the article on the trough 5a on the basis of a natural vibration cycle or a frequency of the trough 5a with the article placed thereon and equivalent mass and an equivalent spring constant of a feeder vibration system, and feeder main control means 41 controls the supply operation of the forward-moving feeder 5 so that the supply weight of the article supplied from the forward-moving feeder 5 matches a target supply weight by controlling the number of pulses (supply time period) of a driving signal and the amplitude of the driving signal, for example, on the basis of the calculated weight of the article.

Description

  In the present invention, for example, the article placement unit is vibrated by using an attractive force of an electromagnet and a restoring force of a spring, and articles on the article placement unit are supplied to a supply hopper provided downstream by a predetermined amount. The present invention relates to a combination weigher using a vibration feeder.

For example, as a combination weigher for performing a combination calculation, a conical distributed feeder and a plurality of linearly-vibrating vibratory feeders (hereinafter referred to as “straight-forward feeders”) disposed along the circumference of the distributed feeder. There are things that are equipped with.
On the downstream side of each linear feeder, a supply hopper and a weighing hopper are sequentially arranged, and a collecting chute is arranged below the weighing hopper.

For example, the article is supplied from an external supply device to the central portion of the dispersion feeder, and the dispersion feeder conveys the article to the linear feeder by sending the article toward the peripheral portion by vibration.
Each linear feeder conveys an article by vibrating a trough, which is an article placement unit, and supplies the article to a supply hopper.

  The article is temporarily held in the supply hopper, and then the article is supplied to a weighing hopper disposed below the supply hopper, and the article is weighed by the weighing hopper to obtain a measured value. Then, by performing a combination calculation based on the measurement value, the closest combination of the measurement hoppers in which the total of the measurement values matches the target combination weight is obtained, and the article is discharged from the measurement hopper selected for the combination. . The articles discharged from the weighing hopper slide down on the collecting chute and are gathered together, and are put into a packaging machine as one product.

The supply hopper is installed in order to immediately prepare an appropriate amount of articles in which a combination to be supplied to the weighing hopper is easily established, and the installation purpose is to increase the combination processing capability.
If an appropriate amount of articles is supplied directly from the linear feeder to the weighing hopper, it takes a long time to supply the appropriate amount. In addition, a long waiting time is required for obtaining a stable weighing value of the supplied article.
In order to supply goods with appropriate weight instead of weighing with the supply hopper, it takes a long time to accumulate the articles, and the weighing hopper requires little time to receive the articles from the supply hopper, but expects a long time to wait for stability This balances the time distribution of both hoppers.

  By the way, improving the yield of combination products is a very important issue. In order to improve the yield of the combination product, it is necessary to increase the number of combinations to be selected for combination selection. For this purpose, it is necessary to align the individual article weight supplied to the weighing hopper near the target weight of the individual article. .

In the supply by the linear feeder, when the linear feeder is driven at a constant condition of a predetermined amplitude for a predetermined time, the weight of the supplied article is greatly affected by the amount of articles on the trough.
In the combination weigher, it is necessary to more accurately control the weight of articles supplied from the linear feeder to the supply hopper in order to improve the combination accuracy (improve the yield of the combination product).

Conventionally, there is a proposal to measure the weight of an article directly on the trough, not the weight of the article conveyed by the feeder, with a strain sensor attached to a leaf spring that elastically supports the trough (see, for example, Patent Document 1).
In addition, paying attention to the fact that the gap between the iron core of the feeder driving magnet and the armature changes according to the weight of the article on the trough, the change in the gap dimension is measured as the change in self-inductance, and the weight of the article on the trough There is also a proposal for requesting (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2000-97752 JP 2010-83615 A

  The combination weigher provided with the feeders according to Patent Documents 1 and 2 has the following problems.

That is, in the feeder according to Patent Document 1, the leaf spring is configured for trough vibration, and the leaf spring is not provided with a concentrated portion of strain stress due to load load. Since the strain stress concentration portion is varied and the bending is in accordance with the bending moment, it is difficult to obtain the output linearity with respect to the load on the trough, and the weight of the article on the trough cannot be detected accurately.
The plate spring is usually made of resin, but since the resin is porous, it swells due to moisture absorption and does not stabilize due to drift of the DC level output, and is based on a strain sensor due to span variation due to thickness variation. The weight and amplitude detection value fluctuate.

  On the other hand, in the feeder according to Patent Document 2, the gap displacement amount between the iron core of the feeder driving electromagnet and the armature is basically determined by the amount of bending due to the bending moment of the leaf spring. The weight of the article on the trough cannot be detected accurately.

Further, in the feeders according to each of the above patent documents, even if an attempt is made to detect the amplitude of the trough while the article is loaded on the trough, the article moves up and down on the trough. The state of over and under is repeatedly acting according to the vibration, and the amplitude cannot be measured accurately.
In the vibration system consisting of mass and spring, the ratio of the amplitude of the feeder signal to the magnitude of the drive signal amplitude is determined by the ratio of the frequency of the drive signal and the natural vibration. For example, the output amplitude of the vibration feeder is measured during operation. Even if the optimum drive vibration cycle and frequency are determined, the optimum drive signal cycle cannot be accurately determined unless the output amplitude is accurately obtained.

  The present invention has been made in view of the above-described problems, and accurately determines and obtains the natural vibration period or frequency of the vibration feeder according to the weight of the article placed on the vibration feeder during operation. Provided is a combination weigher that can accurately determine the weight of the article on the article placement portion in the vibration feeder by the natural vibration period or frequency, and can improve the yield of the combination by controlling the drive signal based on the weight of the article It is intended to do.

In order to achieve the above object, the combination weigher according to the present invention comprises:
A plurality of weighing hoppers participating in the combination calculation, and provided on the upstream side corresponding to each weighing hopper, the article placement unit is vibrated according to the drive signal, and the article on the article placement unit is moved downstream. And a combination weigher comprising a vibrating feeder for conveying,
Vibration period detecting means for detecting a vibration period of the vibration feeder;
The natural vibration period measuring means for determining the current natural vibration period of the vibration feeder by measuring the output of the vibration period detecting means for the vibration period remaining in the vibration feeder after the application of the drive signal applied to the vibration feeder is stopped. When,
(First invention).
Since the frequency is represented by the reciprocal of the vibration period, the natural frequency (natural frequency) of the vibration feeder may be measured instead of the measurement of the natural vibration period of the vibration feeder by the natural vibration period measuring means. Good.

In the present invention,
Vibration characteristic calculation means for calculating an equivalent mass and an equivalent spring constant of a feeder vibration system including an article placement portion in the vibration feeder in advance;
Articles in the vibration feeder based on the current natural vibration period of the vibration feeder measured by the natural vibration period measuring means and the equivalent mass and equivalent spring constant of the feeder vibration system calculated by the vibration characteristic calculating means An article weight calculating means for calculating an article weight on the placement unit;
(2nd invention).

In the present invention,
Drive signal frequency determining means for determining the frequency of the drive signal in the next article supply to be given to the vibration feeder based on the current natural vibration period of the vibration feeder measured by the natural vibration period measuring means;
The vibration feeder is driven with a drive signal having a frequency determined by the drive signal frequency determination means, and the supply weight of the article supplied from the vibration feeder is a target supply based on the article weight calculated by the article weight calculation means. Feeder main control means for controlling the feeding operation of the vibratory feeder to match the weight;
(3rd invention).

In the present invention,
Based on the weight of the article on the article placement section and the number of applied voltage pulses of the drive signal, or on the basis of the weight of the article on the article placement section and the operation time of the vibration feeder, or the article It is preferable that a predicted supply weight calculating means for calculating a predicted value of the supply weight is provided based on the weight of the article on the mounting portion and the time value indicating the applied voltage pulse width of the drive signal (fourth invention).

In the present invention,
The feeder main control means may perform feed forward control of the supply weight so that the predicted supply weight calculated by the predicted supply weight calculation means matches the target supply weight (fifth invention). .

In the present invention,
The feeder main control means may perform feed weight feedback control so that the predicted supply weight calculated by the predicted supply weight calculation means matches the actually supplied supply weight (first). 6 invention).

In the present invention,
The feeder main control unit is configured to perform feed-forward control of a supply weight that matches a predicted supply weight calculated by the predicted supply weight calculation unit with a target supply weight, and an actual predicted supply weight calculated by the predicted supply weight calculation unit. It is possible to simultaneously perform feedback control of the supply weight to be matched with the supply weight supplied to (Seventh invention).

  In the present invention, the vibration period (frequency, frequency) of the free vibration (= representing the natural vibration at the time of the next supply) still remaining in the vibration feeder while stopping the application of the drive signal applied to the vibration feeder is measured. Thus, the natural vibration period (natural frequency, natural frequency) of the vibration feeder at the time of the next supply is obtained. Thereby, the natural vibration period of the vibration feeder can be accurately determined according to the weight of the article placed on the vibration feeder during the operation. Then, the weight of the article on the article placement portion in the vibration feeder can be accurately obtained from the obtained natural vibration period, and the yield of the combination product can be improved by controlling the drive signal based on the weight of the article.

By adopting the configuration of the second invention, the weight of the article supplied onto the article placement portion of the vibration feeder can be determined more accurately.
By adopting the configuration of the third invention, it is possible to accurately match the supply weight of the articles supplied from the vibration feeder with the target supply weight.

By adopting the configuration of the fourth aspect of the invention, it is possible to appropriately determine the control amount at the time of feedforward control and feedback control of the supply weight by the vibration feeder.
By adopting the configuration of the fifth invention, even when an external factor that disturbs the control of the feeding operation of the vibration feeder occurs, the influence can be suppressed in advance.
By adopting the configuration of the sixth aspect of the invention, even when an external factor that disturbs the control of the feeding operation of the vibration feeder occurs, if the effect appears as a change in the feeding weight, it is immediately fed back and the feeding operation is appropriately performed Can be corrected.
By adopting the configuration of the seventh aspect of the invention, it is possible to more reliably suppress disturbance in the control of the supply operation by the vibration feeder.

1 is a schematic system configuration diagram of a combination weigher according to an embodiment of the present invention. Overall perspective view (a) and side view (b) of a linear vibration feeder equipped in the combination weigher of this embodiment Block diagram explaining the configuration of the control system of the linear vibration feeder Diagram showing drive voltage waveform applied to linear vibration feeder and vibration displacement of trough at that time The figure showing the relationship between the drive pulse Ps during the application period of the drive pulse Ps, the current (excitation current) I flowing through the coil of the electromagnet during that period, and the vibration displacement Aw of the trough. Diagram showing drive stop voltage waveform applied to linear vibration feeder and vibration displacement of trough at that time Explanatory diagram of the period detection method

  Next, specific embodiments of the combination weigher according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic system configuration diagram of a combination weigher according to an embodiment of the present invention.

<Description of composition of combination weigher>
As shown in FIG. 1, in the combination weigher 1 of the present embodiment, a cone that disperses articles supplied from an external supply device 3 radially by vibration on an upper portion of a center base 2 disposed in the center of the device. In the form of a distributed feeder 4 is provided.
The dispersion feeder 4 includes a conical dispersion table 4a on which an article is placed, and a vibration device 4b that vibrates the dispersion table 4a. The article supplied from the supply device 3 to the central portion thereof is vibrated toward the periphery. Send it out.

Around the dispersion feeder 4, a plurality of rectilinear vibration feeders 5 (hereinafter referred to as “straight advance feeders 5”) are provided radially, and each rectilinear feeder 5 vibrates an article sent from the dispersion feeder 4. Are fed to each supply hopper 6.
The combination weigher 1 includes a linear feeder 5, a weighing hopper 6 and a weighing hopper 7 which are arranged downstream from the linear feeder 5, and a weighing unit 8 attached to the weighing hopper 7. A plurality of sets are provided.

  The supply hopper 6 receives the articles sent from the linear feeder 5 and opens the discharge gate 6g when the weighing hopper 7 disposed below the empty hopper 7 becomes empty, and puts the articles into the weighing hopper 7.

  The weight of the article put into the weighing hopper 7 is measured by the weight sensor 8. This measured value is output to the control device 9. Below the measuring hoppers 7 arranged in a circle, a substantially inverted frustoconical collective chute 10 is disposed, and below the collective chute 10 a funnel-shaped discharge chute 11 is provided.

  Among the plurality of weighing hoppers 7, in the weighing hopper 7 selected by the control device 9, the discharge gate 7g is opened to discharge the articles, and the discharged articles are then collected on the collecting chute 10 And is inserted into a packaging machine (not shown) through the discharge chute 11, for example.

Further, a level detector 12 for detecting the amount of articles on the dispersion feeder 4 is provided above the dispersion feeder 4. For example, an ultrasonic sensor is used as the level detector 12, the layer thickness of the article on the dispersion feeder 4 is detected, and the detection signal is output to the control device 9.
The control device 9 controls the supply device 3 so that the amount of articles on the dispersion feeder 4 is always kept constant based on the layer thickness of the articles on the dispersion feeder 4.

The control device 9 is configured by, for example, a microcomputer having an arithmetic control unit 9a and a storage unit 9b.
The storage unit 9b stores a control program, various setting values, and the like.
The calculation control unit 9a executes combination operation control, combination calculation, and the like based on the control program and various set values.
The operation indicator 13 attached to the control device 9 includes, for example, a touch screen screen, and also includes input means for operating the combination weigher and setting operation parameters.

  Next, the configuration of the linear feeder equipped in the combination weigher of the present embodiment will be described more specifically with reference to FIG.

  The rectilinear feeder 5 includes a trough 5a as an article placement unit for placing and conveying an article, and a vibration device 5b that vibrates the trough 5a. The article is supplied from the peripheral part of the dispersion feeder 4 (see FIG. 1) to the rear part of the trough 5a, and the article is conveyed to the front part by vibrating the trough 5a and discharged from the front end of the trough 5a to the supply hopper 6. .

The vibration device 5b includes a fixed frame 21, and a movable plate 22 is swingably attached to the fixed frame 21 via elastic members 23a and 23b made of, for example, a carbon resin plate spring.
The elastic members 23a and 23b are attached between the fixed frame 21 and the movable plate 22 so that the upper end side thereof is inclined rearward.
An electromagnet 24 is fixed to the fixed frame 21 so as to have a predetermined angle with respect to a horizontal plane, and a member to be attracted (armature) 25 is opposed to the movable plate 22 with a predetermined interval. Is attached.
The fixed frame 21 is attached to the center base 2 (see FIG. 1) via a vibration-proof spring 26.

  An attachment portion 27 is fixed to the upper surface of the movable plate 22 of the vibration device 5b, and the trough 5a is detachably attached to the attachment portion 27 by an attachment fitting 28 provided on the lower surface thereof.

In the vibration mechanism of the linear feeder 5, when a voltage is applied to the electromagnet 24, the attracted member 25 fixed to the movable plate 22 is attracted to the electromagnet 24. At this time, the movable plate 22 moves to the electromagnet 24 side, that is, rearward and obliquely downward, due to elastic deformation of the elastic members 23a and 23b connecting the movable plate 22 and the fixed frame 21.
Next, when the application of voltage to the electromagnet 24 is stopped, the attractive force generated in the electromagnet 24 is released, and the movable plate 22 moves obliquely upward in the forward direction by the elastic repulsive force of the elastic members 23a and 23b. Since the trough 5a moves together with the movable plate 22, by repeating the above operation, the trough 5a vibrates and the articles on the trough 5a are conveyed forward.
Note that the material, structure, and configuration of the members constituting the vibration mechanism are not limited to this example.

In this embodiment, the vibration period detection means 29 is provided in either one of the elastic members 23a and 23b (in this case, the elastic member 23a).
The vibration period detecting means 29 is constituted by, for example, a piezoelectric element such as a piezo film attached to the elastic member 23a in order to detect distortion of the elastic portion.
The vibration period detection unit 29 distorts according to the elastic deformation of the elastic member 23a, and outputs an output corresponding to the distortion to the control device 9 (see FIG. 1).

The strain detection sensor may be a strain gauge.
Further, since the strain detection is for detecting the vibration period of the linear feeder 5, an acceleration sensor is attached to the movable plate 22 that swings at a predetermined period so as to detect the acceleration in the swing direction, and the vibration of the swinging vibration is detected. A signal corresponding to the acceleration may be output to the control device 9 (see FIG. 1).
Moreover, you may make it provide a displacement sensor so that the period of a displacement between the elastic members 23a and 23b and the base 30 in which the movable plate 22 is installed may be measured.

Next, the configuration of the control system related to the linear feeder will be described with reference to FIG.
The configuration of the control system shown in FIG. 3 is the same for the individual linear feeders 5 provided in the combination weigher 1.

  That is, the linear feeder control means 40 is provided corresponding to each of the plurality of linear feeders 5. The plurality of linear feeder control means 40 are realized by the function of the control device 9 in the present embodiment, but may be provided separately from the control device 9.

The scale control means 39 shown in FIG. 3 is means for realizing functions other than the plurality of linear feeder control means 40 in the control device 9.
That is, the control device 9 has a scale control means 39 and a plurality of linear feeder control means 40.

  The straight feeder control means 40 includes a feeder main control means 41, a vibration period calculation means 42, an article weight calculation means 43, a drive signal frequency determination means 44, a vibration characteristic calculation means 45, and a predicted supply weight calculation means 46. have.

<Description of feeder main control means>
The feeder main control means 41 has a function as a voltage application control means for controlling the supply operation of the vibration feeder. During the drive period, the initial attracting pulse Po shown in FIG. A rectangular voltage such as a drive voltage pulse Ps (Ps1, Ps2,...) Is applied. The feeder main control means 41 controls the pulse width (T1 to T4) of the drive pulse Ps so that the trough 5a has the target amplitude.

<Description of natural vibration period measuring means>
The vibration period calculation unit 42 has a function of calculating the vibration period of the linear feeder 5 based on the detection signal from the vibration period detection unit 29. The configuration including the vibration period detecting means 29 and the vibration period calculating means 42 corresponds to the “natural vibration period measuring means” of the present invention.

<Description of article weight calculation means>
The article weight calculation means 43 has a function of calculating the article weight on the trough 5a based on the natural vibration period or frequency of the trough 5a and the equivalent mass and equivalent spring constant of the feeder vibration system.

<Description of drive signal frequency determining means>
The drive signal frequency determination means 44 has a function of determining the frequency of the drive signal in the next article supply to be given to the linear feeder 5 based on the natural vibration period or frequency of the article placement section.

<Description of vibration characteristic calculation means>
The vibration characteristic calculation unit 45 has a function of calculating an equivalent mass and an equivalent spring constant of the feeder vibration system including the article placement portion in the linear feeder 5.

<Description of predicted supply weight calculation means>
The predicted supply weight calculation means 46 has a function of calculating a predicted value of the supply weight of the articles by the linear feeder 5.

<Explanation of linear feeder drive signal and setting method>
In the present embodiment, during the drive signal stop period during the operation of the combination weigher 1, the vibration mechanism determined by the weight of the article on the trough 5 a, that is, the period of the drive signal corresponding to the value of the natural vibration period of the linear feeder 5. In this way, the drive pulse cycle Tv is changed.

  FIG. 4 is a diagram showing a drive voltage waveform applied to the linear feeder and the vibration displacement of the trough at that time.

  In the present embodiment, an initial suction pulse Po having a voltage Va and a pulse width Tp is applied at the start of driving, and thereafter, driving pulses Ps (Ps1, Ps2,. ... Is applied at a cycle Tv (drive frequency fv = 1 / Tv).

Here, the application time Tp is set so that the trough 5a has a vibration displacement corresponding to the target amplitude At by applying the initial attraction pulse Po to the electromagnet 24.
That is, by applying the initial suction pulse Po having the pulse width Tp, the position of the trough 5a becomes a position corresponding to the target amplitude At, and very excellent rising characteristics are obtained.
The position corresponding to the target amplitude At corresponds to the lower end position of vibration when the trough 5a vibrates with the target amplitude At.
The target amplitude At is a standard value of the vibration amplitude of the trough 5a, and is set in consideration of the type of transport article, the transport amount, and the like.

  Here, the voltage Va is a predetermined voltage set in advance as a drive voltage, and may be, for example, a rated voltage of the electromagnet 24. Further, the initial pulse Po, times To and Ts, the frequency fv and period Tv of the drive pulse Ps, and the standard pulse width Ta of the drive pulse Ps are determined as follows from the experimental results.

<Description of determination of time width Tp of initial pulse Po>
A sample article (solid) corresponding to the average weight and weight distribution expected to be placed during operation is placed on the trough 5a, so that the amplitude detection value does not vary. It is preferable to measure in a state of being fixed on the trough 5a so as not to move up and down during vibration. Note that the test may be performed in a no-load state.

  For each of a predetermined number of voltage application times (time for applying voltage Va) Tpx, an experiment of applying voltage Va to electromagnet 24 is performed, and amplitude Atx of trough 5a is measured using, for example, a laser displacement meter. Here, the difference between the highest position and the lowest position of the trough 5a when the trough 5a vibrates due to voltage application is defined as the amplitude of the trough 5a. Based on this measurement result, a relational expression Atx = f (Tpx) between the voltage application time Tpx and the amplitude Atx is obtained, and the voltage application time Tp at the amplitude standard value At is determined using this relational expression.

<Description of Determination of Frequency fv and Period T of Drive Pulse Ps>
For the frequency fv of the drive pulse Ps, the natural vibration period fc of the trough 5a is obtained and is set to fv = k · fc.
Here, k is set to 1 or a value close to 1 in advance. That is, the frequency fv of the drive pulse Ps is set to a value that is equal to or close to the natural frequency of the trough 5a.

For this purpose, for example, the voltage Va is applied to the electromagnet 24 only during the application voltage time Tp determined above to cause free vibration in the trough 5a, and the vibration period is detected by the method described later (method also used during operation). The natural vibration period fc of the trough 5a is obtained from the output of the means 29, the frequency fv is determined from the value of this fc, and the period Tv is also determined.
In addition, the time change of the vibration displacement may be measured by the output of the laser displacement meter and obtained by FFT (Fast Fourier Transform) analysis.

  Further, during the measurement, the time from the end of application of the voltage Va to the time when the vibration displacement of the trough 5a becomes 0 for the second time is measured, and the time is defined as To.

<Description of Determination of Standard Pulse Width Ta of Drive Pulse Ps>
For example, for each of a predetermined number of pulse widths Tax, vibrations were given at a driving cycle of this cycle Tv while measuring the natural vibration cycle fc according to the weight of the article on the trough 5a at each time to determine the cycle Tv. When the amplitude Atx of the trough 5a is measured with a laser displacement meter and the pulse width Tax is changed, a relational expression Atx = f (Tax) between Tax and the vibration amplitude Atx is obtained, and the standard amplitude At is obtained using the relational expression. The corresponding pulse width Ta is obtained, and this value is set as the standard pulse width of the drive pulse Ps.

  As a method not using a laser displacement meter, an article having a weight corresponding to an average article weight during operation is fixedly placed on the trough 5a to cause free vibration, and a natural vibration is obtained by a method described later or FFT analysis. After obtaining the period, the frequency and period of the driving signal are determined by a predetermined coefficient k set in advance, and the vibration obtained from the strain sensor, the displacement sensor, and the acceleration sensor is forcibly driven by the driving signal having the determined period. The pulse width Ta may be determined by obtaining the amplitude Atx from the signal output.

If an acceleration sensor is used as the vibration period detection means 29, the displacement amplitude can be obtained from the acceleration detection signal. When the vibration period is ωv, the relationship between the displacement vibration and the acceleration vibration is A Since sin (ωv · t) and -A · ωv ² · sin (ωv · t), the drive signal frequency ωv (= 2π · fv) is used and the measured acceleration amplitude is multiplied by 1 / ωv ^2. Evaluate the magnitude of the output amplitude.

<Description of determination of time Ts>
The time Ts from the end of voltage application of the initial suction pulse Po to the start of application of the first drive pulse Ps1 is determined as Ts by subtracting the standard pulse width Ta from the previously obtained time To.

  A voltage is applied at each time determined as described above as shown in FIG.

  In this embodiment, the trough 5a is displaced to a position corresponding to the standard amplitude At by applying one initial suction pulse Po at the start of driving. If a voltage is applied to the electromagnet 24 so as to move from the position (that is, the stationary position where the vibration displacement is 0) to the position corresponding to the standard amplitude At without returning to the position before the start of the vibration operation, Good. For example, as indicated by a one-dot chain line in FIG. 4, two initial suction pulses Po1 and Po2 may be applied instead of one initial suction pulse.

  Further, in the present embodiment, as shown in FIG. 4, the time point when the drive pulse Ps falls (the time point when the application ends) coincides with the time point when the vibration displacement becomes 0 (position when stationary). This is the same even when the pulse width of the drive pulse Ps is changed, and the drive pulse Ps is applied so that the falling point thereof becomes a constant interval (cycle Tv). This will be described below with reference to FIG.

As shown in FIG. 5, it is desirable that the drive pulse Ps is applied so that the attraction force of the electromagnet 24 is most efficiently reflected in the amplitude. That is, in order to reduce the power consumption, it is desirable to apply the drive pulse Ps so that the attractive force of the electromagnet 24 is generated before the vibration displacement Aw reaches the minimum value AL from the maximum value AH.
Furthermore, it is desirable to apply the drive pulse Ps so that the maximum attraction force of the electromagnet 24 occurs before the vibration displacement Aw becomes 0 to the minimum value AL.

The attractive force F of the electromagnet 24 is proportional to the square of the current I, and increases as the current I increases. As shown in FIG. 5, the current I starts to flow from the rising point of the driving pulse Ps, and becomes maximum after a predetermined time from the falling point of the driving pulse Ps.
In the present embodiment, the time point when the drive pulse Ps falls is set to coincide with the time point when the vibration displacement Aw becomes zero.
That is, here, the drive pulse Ps is driven so that the trough 5a passes the stationary position from the vibration upper end position (vibration displacement Aw is the maximum value AH) so that the drive pulse Ps falls (application end time). Ps is applied.
In this way, the attractive force of the electromagnet 24 can be generated until the vibration displacement Aw changes from the maximum value AH to the minimum value AL.

  A counter Ct is provided for detecting the number of outputs of the drive pulse Ps. It is noted that a stop pulse having the same time width as Ps is applied in the vicinity of the middle of the periodically repeated drive pulse Ps shown in FIG. 4 so that the force acts in the opposite phase in the amplitude direction of the trough 5a. In such a manner, the vibration of the straight feeder 5 is stopped. Assuming that the driving time is used instead of the driving pulse Ps, the time from 0 to the application of the stop pulse in FIG. 6 may be counted by the counter Ct.

After setting the respective parameters as described above, the voltage Vai for causing free vibration in the linear feeder 5 is set.
First, without placing an article on the trough 5a, the voltage Vai is applied to the electromagnet 24 only during the applied voltage time Tp determined above to cause free vibration in the linear feeder 5 and the vibration period detecting means 29. From the output, the natural frequency To of the linear feeder 5 is obtained.
This operation is necessary only at the time of adjustment and only when obtaining the natural period when there is no article placed on the trough 5a.

<Description of a method for determining the relationship between the article weight on the trough, the number of drive signal pulses, the drive signal pulse width and the supplied article weight>
Next, the average amount of articles actually used during operation is placed on the trough 5a.
The voltage Vai is applied to the electromagnet 24 only for the applied voltage time Tp determined above, and free vibration is caused in the linear feeder 5.
This operation is also necessary only when the article is first placed on the trough 5a. If the driving operation is continued intermittently during adjustment or during operation, the linear feeder 5 Since free vibration remains in the rectilinear feeder 5 after the end of driving (after the drive pulse Ps is stopped), the free vibration (natural vibration period) in the state where the article to be conveyed and supplied next exists on the trough 5a is expressed by the voltage Vai. Can be measured without supplying.
In this way, the natural period Tc (natural vibration period fc) in a state where the article is placed on the trough 5a is measured, and the article on the trough 5a is measured by the method described later with the natural period To value at the time of no load. The mass Wcx is obtained.

The drive frequency fv (drive cycle Tv) is set to fv = k · fc in accordance with the natural vibration cycle fc obtained above, and a drive signal of frequency fv (cycle Tv) is given.
Since the period Tv of the drive signal is determined so that fv / fc = k = constant always, the ratio of the amplitude of the linear feeder 5 (amplitude transmission rate) to the amplitude of the drive signal is constant, and the drive pulse width Ta is If constant, the output amplitude At of the linear feeder 5 becomes constant even if the weight of the article on the linear feeder 5 changes. That is, the drive signal frequency is determined so that At に な る Ta.

For each type of article, the article weight Wx supplied from the linear feeder 5 to the supply hopper 6 is approximately proportional to the article weight Wcx on the trough 5a and is also approximately proportional to the drive signal pulse number Nx, so the amplitude At of the linear feeder 5 That is, if the pulse time Ta is constant and Wcx and Nx are within a certain range with a standard value as the center, the supply weight value Wx can be expressed by the following equation (1):
Wx = f (Wcx, Nx) (1)
It can be predicted that it is expressed as a function of the article weight value Wcx on the trough 5a and the drive signal pulse number Nx.

Further, assuming that a constant value N is always given as the number of pulses of the drive signal Ps, the article weight Wy supplied from the trough 5a to the supply hopper 6 for each type of article is the output amplitude Aty of the trough 5a, that is, the pulse width Tay. Is substantially proportional to the article weight Wcy on the trough 5a, so that the relationship between the drive signal frequency fv and the current natural vibration period fc is fv / fc = k = constant relation. If Wcy and Tay are within a certain range with a standard value at the center, the supply weight Wy is expressed by the following equation (2):
Wy = f (Wcy, Tay) (2)
It can be predicted that it is expressed as a function of the article weight value Wcy on the trough 5a and the drive signal pulse width Tay.

As prediction functions, coefficients k11, k21, and k31 with respect to the above equation (1),
Wx = k11 · Wcx + k21 · Nx + k31 (3)
For the above equation (2),
Wy = k12 · Wcy + k22 · Tay + k32 (4)
Each coefficient is determined by experimental values.

For example, in order to determine the coefficient of the above equation (3), the drive signal parameters are set by the above method, assuming that the pulse width Ta of the drive signal is constant and the target supply weight supplied from the linear feeder 5 to the supply hopper 6 is Wq. Then, an average amount, a larger amount or a smaller amount of a predetermined article is placed on the trough 5a, and the drive signal pulse number N is set to various values centering on a standard value. Each time the natural vibration period fc and the natural period Tc are measured and the article weight Wcx is calculated by the method described later, the frequency fv and the period Tv of the drive signal are calculated and set, the linear feeder 5 is driven, and the supply hopper 6 is driven. The actually supplied weight Wx is measured.
The calculated Wcx is preferably displayed on the operation indicator 13 during the experiment.

  Drive signal by measuring the natural frequency and natural period in advance of each supply while changing the drive signal pulse number N little by little and increasing / decreasing the amount of articles on the trough 5a from the average amount. The supply operation is executed while determining the frequency of the operation so that the electromagnet 24 is not heated with a slight time interval for each operation.

A set of data (W1, Wc1, N1), (W2, Wc2) of (weight measurement value of actually supplied article, calculated article weight on trough 5a, set value of the number of driving pulses) by n supply tests , N2),..., (Wn, Wcn, Nn) is obtained.

W1 = k11 · Wc1 + k21 · N1 + k31
W2 = k11 · Wc2 + k21 · N2 + k31
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
Wn = k11 · Wcn + k21 · Nn + k31

Therefore, the errors E1, E2,.

E1 = W1- (k11 · Wc1 + k21 · N1 + k31)
E2 = W2- (k11 · Wc2 + k21 · N1 + k31)
...
En = Wn− (k11 · Wcn + k21 · Nn + k31)

Therefore, the function f (Wcx, Nx) is determined by determining the coefficients k11, k21, k31 that minimize the square sum of errors R = E1 ² + E2 ² +... + En ² .

Wx = f (Wcx, Nx) = k11 · Wcx + k21 · Nx + k31

And determine. (K11, k21, and k31 that satisfy ∂R / ∂k11 = 0, ∂R / ∂k21 = 0, and ∂R / ∂k31 = 0 may be obtained as solutions of simultaneous equations.)

<Description of supply control method>
Control during operation is performed as follows. The number of pulses of the drive signal to be applied is changed in accordance with the size of the article weight on the trough 5a, and control is performed so that an article having a predetermined weight Wq is supplied from the rectilinear feeder 5.

Each time the drive signal is stopped at the time when the previous supply is completed, the vibration period detecting means 29 measures the natural vibration period fc and the natural period Tc.
From the natural vibration period fc, the article weight Wcx on the trough 5a and the next drive signal frequency fv are calculated.
If the predetermined supply weight is Wq,

Wq = k11 · Wcx + k21 · Nx + k31

The number of signal pulses Nx given to the next supply

Nx = {Wq− (k11 · Wcx + k31)} / k21
(Nx rounds the calculated value and selects it as an integer)

And supply the next time.
The same applies when the drive time is used as a parameter instead of the number of drive pulses.

<Description of another supply control method>
As another method, the driving signal pulse numbers N1, N2,..., Nn and N1 to Nn are gradually increased, and the article weight value Wcx on the trough 5a is also Wc1, Wc2,. , Wcn and gradually increasing values, the supply operation is performed under the conditions of each set (Wc1, N1), (Wc2, N2),..., (Wcn, Nn), If W1, W2,..., Wn are obtained by measuring the weight values,
X1 = Wc1 · N1
X2 = Wc2 · N2
...
Xn = Wcn · Nn
Where X = X1, X2,..., Xn is a function representing the relationship of W1, W2,..., Wn, X = (weight of article on trough 5a) × (number of drive signal pulses or drive Time) by least squares method

Wx = f (X)

May be determined.

Similarly, when the supply weight is controlled by changing the amplitude At of the linear feeder 5 by changing the weight of the article on the trough 5a and changing the pulse width Ta of the drive signal while keeping the number of drive pulses constant, (2) While changing the setting of the drive signal pulse number Ta little by little in equation (4) and increasing or decreasing the amount of articles on the trough 5a from the average amount, the natural frequency in advance of each supply, The supply operation is executed while measuring the natural period and determining the frequency of the drive signal, and the coefficients k12, k22, and k32 are determined from the measurement data in the same manner as described above.
In addition, Y = ((weight of article on trough 5a) × (driving signal pulse width)), and a function that expresses supply weight value Wy with a value of Y,

Wy = f (Y)

May be determined.

<Explanation of combined feedback control>
In the above, the value of the pulse width Ta of the drive signal is constant, and the frequency of forced vibration given to the linear feeder 5 is kept at a constant ratio with respect to the natural vibration frequency of the linear feeder 5 in a state where an article is placed. The vibration amplitude appearing in the linear feeder 5 is premised on a constant relationship with the vibration amplitude of the drive signal. However, if there is a change in ambient temperature or a temperature increase of the electromagnet 24 due to continuous and continuous operation of the electromagnet 24, A phenomenon occurs in which the attractive force of the electromagnet 24 is weakened and the output amplitude At of the linear feeder 5 becomes smaller than a predetermined pulse width Ta.
Therefore, when articles having the same weight exist on the trough 5a, even if a predetermined amplitude is given as a drive signal, the amplitude generated in the trough 5a changes and the supply weight changes, so a countermeasure is required.

Articles supplied to the supply hopper 6 are temporarily stored in the supply hopper 6, and are supplied to the weighing hopper 7 when the discharge gate 6 g of the supply hopper 6 is opened. . This measured value is the weight value of the article actually supplied.
When the obtained measured value is Wqx, an error rate rex of the target supply weight Wq of Wqx is

rex = (Wqx / Wq) -1

And calculate. When the supplied weight is smaller than the target value, rex <0 is calculated.

Preferably, the average value of the error rate or the moving average value rea is calculated using a plurality of measurement values Wqxa,

reax = (Wqxa / wq) -1
rea + reax → rea (initial value of rea 1)

The target supply weight is replaced with Wq / rea instead of Wq, and tracking correction is performed.
In other words, if the supply weight changes in a direction smaller (larger) than the target supply weight for the change from the target value that appears in the actual supply weight, the target weight is corrected to be larger (smaller) according to the amount of change at that time. To increase the number of pulses of the drive signal by

Nx = {(Wq / rea) − (k11 · Wcx + k31)} / k21

And follow-up correction by feedback so that the actual supply weight matches the target supply weight.

<Explanation of measurement of natural vibration period and determination of spring constant and initial mass of linear feeder>
At the time of adjustment, the spring constant and initial mass of the linear feeder 5 are determined.
The frequency (period) of the natural vibration may be obtained by performing FFT (Fast Fourier Transform) on the output of the strain sensor or the acceleration sensor, but the following method for measuring on the time axis is used.

First, a test for determining the initial mass M0 and the spring constant Kq of the linear feeder 5 at the time of adjustment, and a natural vibration period when the linear feeder 5 is unloaded and a natural vibration period when the article is placed at the maximum are obtained. .
At the time of test adjustment, only one pulse of time Tp in FIG. 4 is added as a drive signal to give free vibration to the linear feeder 5.
A test is performed for a case where there is no load on the trough 5a and a known weight Wq (= Mq · g: Mq; mass, g: gravitational acceleration) corresponding to the case of the maximum load.

A vibration is applied to the linear feeder 5, and the vibration signal output of the strain sensor (displacement vibration signal = Asin ωt) and the acceleration signal of the acceleration sensor (acceleration signal = −A · ω ² · sin ωt) are output freely in the control device 9 (inherent (Vibration) The time in free vibration of the linear feeder 5 after a predetermined time when a vibration waveform appears stably after applying a drive signal Tp after sampling at a time interval sufficiently short (for example, about 0.5 msec) compared to the period. Measurement values between t0 and te are stored in the storage unit 9b in time series (in order of acquisition).

  The time interval between t0 and te is set to be long so as to include a sufficiently large number of vibration periods even when the free vibration (natural vibration) period is the longest, that is, even when an article of Wq is placed.

  In order to obtain the period from the oscillating A / D sampling data, the natural vibration period Tmin when the trough 5a is unloaded is calculated from the A / D sampling data between t0 and te by the same method as described later. Then, the natural vibration period Tmax when the maximum load Mq is placed on the trough 5a is obtained.

here,
Tmin = 2π · (M0 / Kq) ^1/2
Tmax = 2π · {(M0 + Mq) / Kq} ^1/2
Therefore, the simultaneous load equation 2 is solved to determine the initial load M0 and the spring constant Kq of the linear feeder 5.
The initial mass M0 and the spring constant Kq are stored, T1 and T2 are set as follows based on Tmin and Tmax, and the operation operation is started.

<Explanation of natural vibration period measurement during operation>
During the operation operation, the vibration of the linear feeder 5 is stopped, and the period of free vibration (natural vibration) that occurs in the state where the next conveyance supply article is present on the trough 5a until the next forced drive is started. taking measurement.

  When the linear feeder 5 is driven by a predetermined number of pulses in the drive signal, the time T ′ elapses as shown in FIG. 6 in order to stop the conveyance of the article, that is, to stop the vibration of the trough 5a. The vibration stop pulse signal Ps ′ is given at the timing when the spring force acts in the increased vibration direction.

  The linear feeder 5 is stopped from a large amplitude vibration by the vibration stop pulse Ps', but a small amplitude free vibration remains. This is a natural vibration based on the mass and spring constant of the rectilinear feeder 5 in a state where an article to be supplied next to the supply hopper 6 is placed on the trough 5a.

  The conveyance and supply operation of the articles in the linear feeder 5 needs to be stopped after the completion of the supply of the articles to the supply hopper 6 at least during the time when the article discharge operation to the weighing hopper 7 positioned below the supply hopper 6 is expected. is there.

  That is, at least, the article supplied into the supply hopper 6 from the timing at which the drive signal of the linear feeder 5 stops (for example, the timing at which the counter for counting the number of drive signal pulses reaches a predetermined value) is supplied to the weighing hopper 7. The drive signal is stopped during the time Tw until the discharge is completed. While the drive signal is stopped, free vibration remains due to the reaction force of the spring due to the excitation energy so far.

Therefore, after the stop command of the drive signal, the time T "required for shifting from the forced vibration to the free vibration so far is expected, and the A / D sampling value of the output of the strain sensor or the acceleration sensor is calculated during the Ti time. Are stored in the storage unit 9b.
Ti is
Tw> Ti + T "
The natural frequency (natural period) is measured for the next conveyance and feeding that occurs based on the weight of the article on the trough 5a at the time of Ti, and the drive signal frequency is calculated.

Accurate measurement of the natural period is performed as follows.
Based on the previously obtained values of Tmin and Tmax, the first data test section T1 is selected to be slightly shorter than (Tmin / 2) (shorter than a plurality of A / D sampling time intervals).
In addition, the second data verification section T2 is

(Tmax / 2) <T2 <Tmin

Select and set the length. The reason for the set value range will be described later.

In order to be able to select such T2, (Tmax / 2) <Tmin must be satisfied.
When the natural vibration period Tcx of the rectilinear feeder 5 is a spring constant Kq, the mass when no load is applied by the trough 5a or the attached parts is M0, and the mass of the article on the trough 5a is Mx,

Tcx = 2π · {(M0 + Mx) / Kq} ^1/2

Therefore, if the mass M0 of the linear feeder 5 is 0, if the maximum mass of articles on the trough 5a is more than four times the minimum, (Tmax / 2) ≧ Tmin and T2 Can't decide.
However, since M0 is often a value close to the mass of the article or more, it is always (Tmax / 2) <Tmin in a normal use state.

<Explanation of period detection method>
Next, the period detection method will be described with the example shown in FIG.
The A / D sampling data of the Ti section is stored in the storage unit 9b of the control device 9 in the order of time series t0 to tn.
A counter is provided for counting the number of extreme values.
The first test range is set to a time interval T1 starting at time t0 and ending at time tr, and the maximum value and minimum value of the sampling values existing at the interval T1 and the corresponding time are obtained.
In the case shown in FIG. 7A, the value at time tm0 is the maximum value and the value at tr is the minimum value.

  If the time at which the maximum value or the minimum value appears is at least a predetermined time interval tw that is at least one interval time of A / D sampling from the start and end, if the time is the maximum value The appearance time of the maximum value is determined as the appearance time of the minimum value if it is the minimum value. Each time an extreme value is obtained, the counter is incremented by one. The counter is reset before the count starts.

When the maximum value or the minimum value does not satisfy the above condition, for example, as shown in FIG. 7B, the time when the maximum value appears is around t0 (the maximum value is just the time t0 due to the influence of the noise signal). (Although it may not be), it is near the time tr where the minimum value appears, and neither of them is more than the predetermined time interval tw from the start and end.
In that case, the start end of T1 is shifted in the direction in which the time elapses by one sampling interval of the A / D dump ring. Then, the maximum value and the minimum value in T1 and the time of occurrence thereof are detected again, and the difference from the time at both ends representing the range of T1 is examined to determine whether it is the 0th local maximum or local minimum.

When the zeroth extreme value is detected in this way, the end time td of the second test range is determined with a time interval T2 starting from the first occurrence time of the maximum or minimum value.
In the case shown in FIG. 7A, the 0th extremum time tm0 is the start of T2.

T2 is shorter than one period when T2 <Tmin and the vibration period appears at the shortest, but (Tmax / 2) <T2, and is longer than a half period when the vibration period is the longest, so the first time has a maximum value ( If it is a minimum value, one minimum value (maximum value) is always included between T2 (until the end time).
Therefore, when the minimum value (maximum value) of all the sampling values included in T2 is obtained, the time tm1 when the minimum value (maximum value) is acquired is the minimum value (maximum value). At this time, the counter is incremented by one.

Next, T2 is set in the same manner as described above starting from time tm1, and time tm2 at which the maximum value appears is obtained.
The time at which the maximum value and the minimum value appear is sequentially obtained, and when the time width of T2 includes tn which is the end of the sampling data acquisition range, the process of searching for the appearance time of the extreme value is terminated.

Let p be the number of extreme values that appear in each half cycle counted by the counter.
When the number of times the extrema is obtained is p at the 0th extremum appearance time tm0, the last round = Nth extremum appearance time tmp, the natural vibration period included between the times tm0 and tmp The number is
p / 2
Therefore, the natural vibration period Tcx depends on the time difference between the extreme values,
Tcx = (tmp−tm0) / {p / 2}
And calculate.

<Explanation of calculation of article weight on trough by natural period measurement value>
As previously mentioned,

Tcx = 2π · {(M0 + Mx) / Kq} ^1/2

Therefore, the article mass Mx is calculated using the measured value Tcx, the initial mass M0 of the vibration system obtained at the time of adjustment and stored in the storage unit 19, and the spring constant Kq.
The weight value Wcx is calculated by converting Wcx = Mx · g (g: gravitational acceleration).

  Even during the operation operation, the measurement timing of the natural vibration is during the stop of the drive signal, so the article placed on the trough 5a is stationary. Therefore, the natural vibration of the vibration system of the rectilinear feeder 5 including the weight of the article accurately appears in the strain sensor and the acceleration sensor as the vibration period detecting unit 29 in a state where the article to be supplied next is loaded on the rectilinear feeder 5. Therefore, a value capable of accurately calculating the weight of the article to be supplied next can be obtained.

Moreover, the following can be dealt with when the nonlinearity cannot be ignored as the characteristic of the vibration system.
For example, masses Ms1 and Ms2 (Ms1 <Ms2) having known values are prepared in advance.
At the time of adjustment, the natural period Tc0 when there is no load and the natural periods Tc1 and Tc2 when the mass Ms1 and the mass Ms2 are placed on the trough 5a of the linear feeder 5 are measured.
Inevitably, Tc0 <Tc1 <Tc2.

Further, the equivalent initial load M01 and the equivalent spring constant Kq1 are obtained by the natural vibration periods Tc0 and Tc1 measured when no load is applied and when the known mass Ms1 is loaded.

Tc0 = 2π · (M01 / Kq1) ^1/2
Tc1 = 2π · {(M01 + Ms1) / Kq1} ^1/2

From the simultaneous equations of

Next, the equivalent initial mass M02 and the equivalent spring constant Kq2 are determined by the natural vibration periods Tc1 and Tc2 measured when the known mass Ms1 and the mass Ms2 are loaded.

Tc1 = 2π · {(M02 + Ms1) / Kq2} ^1/2
Tc2 = 2π · {(M02 + Ms2) / Kq2} ^1/2

From the simultaneous equations of
It is assumed that the natural frequency of the vibration system changes linearly between small mass changes.

  Then, M01 and Kq1 are paired with Tc1, and M02 and Kq2 are paired with Tc2 and stored in the storage unit 9b.

If the value of the natural species vibration period Tcx measured when the drive signal is stopped during operation is close to Tc1, select the equivalent initial load of the vibration system as M01 and the equivalent spring constant as Kq1,

Tcx = 2π · {(M01 + Mx) / Kq1} ^1/2

To obtain the article mass Mx.

Further, when the value of the natural vibration period Tcx measured when the drive signal is stopped during the operation is close to Tc2, the equivalent initial load of the vibration system is selected as M02, and the equivalent spring constant is selected as Kq2.

Tcx = 2π · {(M02 + Mx) / Kq2} ^1/2

To obtain the article mass Mx.

  More masses may be used and stored with more natural vibration period stages and corresponding parameters. By doing this, that is, if the equivalent initial mass and the equivalent spring constant of the vibration system at each stage are obtained using the relationship between the small mass difference and the natural frequency difference, it will be accurate even if the vibration system is nonlinear. The article weight can be calculated.

<Determination of Determination of Drive Signal Frequency (Period) and Determination of Drive Pulse Number or Drive Signal Pulse Width Ta>
As described above, when the natural vibration period Tc is obtained, the drive signal frequency fv for forced vibration for the next article transportation and supply is determined by a preset ratio k.

From fc = 1 / Tc, fv = k · fc, Tv = 1 / fv

The period Tv of the drive signal is determined so that

  If the drive signal frequency is determined in this way, the gain of the amplitude appearing in the vibration system with respect to the drive signal (forced vibration signal) is always constant.

That is, when the frequency of the drive signal is ωv = 2π · fv, the natural frequency of the vibration system with one degree of freedom is ωc, and the damping ratio is ζ, the gain G of the output amplitude with respect to the input amplitude is

G = 1 / [{1- (ωv / ωc) ² } ² + {2ζ · (ωv / ωc)}] ²

Since ωv / ωc = fv / fc = k = constant, G = constant.
However, since the vibration system output with respect to the input drive signal fluctuates even when the environment changes as described above, it is preferable to use compensation by feedback control together.

The article mass Wcx on the trough is

Tc = 2π · {(M0 + Mcx) / Kq} ^1/2

The article mass Mcx is calculated from Tc obtained this time and M0 and Kq obtained in advance, and obtained as Wcx = (Mcx / g).

  When Wcx is obtained in this way and the target supply weight Wq is set for the linear feeder 5, the drive pulse number Nx or the drive signal pulse width Tax is set as described above, and it matches the set value. The drive signal is supplied to carry out the next conveyance.

  According to the combination weigher of this embodiment, since the natural period is measured when the vibration feeder vibrates with free vibration during operation, the disturbance is not mixed in the measured value, and the article to be supplied next Can be accurately measured, and the trough 5a can be measured on the basis of the accurately measured natural period or frequency and the equivalent mass and equivalent spring constant of the feeder vibration system. Therefore, the weight of the article on the trough 5a can be obtained accurately. Further, since the vibration signal detects the AC level, the drift of the DC level signal is not related. Further, based on the calculated article weight, for example, by controlling the number of pulses of the drive signal (supply time), the amplitude of the drive signal, etc., the supply weight of the article supplied from the linear feeder 5 matches the target supply weight. Thus, since the feeding operation of the linear feeder 5 is controlled, the weight of articles supplied from the linear feeder 5 to the weighing hopper 7 via the supply hopper 6 can be accurately controlled, and the yield of the combined product is improved. be able to.

  The combination weigher of the present invention has been described above based on one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the configuration is appropriately changed without departing from the spirit of the present invention. It is something that can be done.

  The present invention is capable of accurately obtaining the weight of an article on the article placement portion in the vibration feeder and improving the yield of the combined product by controlling the driving signal based on the weight of the article. Therefore, it can be suitably used for a combination weigher having a configuration in which a vibration feeder is provided corresponding to each of a plurality of weighing hoppers participating in the combination calculation.

1 Combination Weigher 5 Linear Feeder (Vibration Feeder)
5a trough (article placement section)
7 Weighing hopper 29 Vibration period detecting means 41 Feeder main control means 42 Vibration period calculating means 43 Article weight calculating means 44 Drive signal frequency determining means 45 Vibration characteristic calculating means 46 Predicted supply weight calculating means

Claims (7)

A plurality of weighing hoppers participating in the combination calculation, and provided on the upstream side corresponding to each weighing hopper, the article placement unit is vibrated according to the drive signal, and the article on the article placement unit is moved downstream. And a combination weigher comprising a vibrating feeder for conveying,
Vibration period detecting means for detecting a vibration period of the vibration feeder;
The natural vibration period measuring means for determining the current natural vibration period of the vibration feeder by measuring the output of the vibration period detecting means for the vibration period remaining in the vibration feeder after the application of the drive signal applied to the vibration feeder is stopped. When,
A combination weigher comprising: Vibration characteristic calculation means for calculating an equivalent mass and an equivalent spring constant of a feeder vibration system including an article placement portion in the vibration feeder in advance;
Articles in the vibration feeder based on the current natural vibration period of the vibration feeder measured by the natural vibration period measuring means and the equivalent mass and equivalent spring constant of the feeder vibration system calculated by the vibration characteristic calculating means An article weight calculating means for calculating an article weight on the placement unit;
The combination weigher according to claim 1, comprising: Drive signal frequency determining means for determining the frequency of the drive signal in the next article supply to be given to the vibration feeder based on the current natural vibration period of the vibration feeder measured by the natural vibration period measuring means;
The vibration feeder is driven with a drive signal having a frequency determined by the drive signal frequency determination means, and the supply weight of the article supplied from the vibration feeder is a target supply based on the article weight calculated by the article weight calculation means. Feeder main control means for controlling the feeding operation of the vibratory feeder to match the weight;
The combination weigher according to claim 2, comprising:   Based on the weight of the article on the article placement section and the number of applied voltage pulses of the drive signal, or on the basis of the weight of the article on the article placement section and the operation time of the vibration feeder, or the article 4. The combination weigher according to claim 3, further comprising a predicted supply weight calculating means for calculating a predicted value of the supply weight based on the weight of the article on the mounting portion and a time value representing the applied voltage pulse width of the drive signal.   5. The combination weigher according to claim 4, wherein the feeder main control unit performs feed-forward control of the supply weight so that the predicted supply weight calculated by the predicted supply weight calculation unit coincides with the target supply weight.   5. The combination weigher according to claim 4, wherein the feeder main control unit executes feedback control of supply weight so that the predicted supply weight calculated by the predicted supply weight calculation unit coincides with the actually supplied supply weight. .   The feeder main control unit is configured to perform feed-forward control of a supply weight that matches a predicted supply weight calculated by the predicted supply weight calculation unit with a target supply weight, and an actual predicted supply weight calculated by the predicted supply weight calculation unit. The combination weigher according to claim 4, wherein feedback control of the supply weight to coincide with the supply weight supplied to is simultaneously performed.

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