JPH0686032U - Quantitative balance - Google Patents

Abstract

(57) [Summary] [Purpose] High-precision quantitative measurement in a short supply time. [Structure] While the weighing signal of the weighing unit 4 is smaller than the first set weight, the comparison means 6 does not generate a passing signal,
A control signal is supplied from the first control signal generation means 8 to the supply device 2. In response to this, the supply device 2 continuously controls the supply amount based on the function signal of the difference between the second set weight and the weighing signal, and supplies it to the weighing unit 4. Weighing signal is first
When the weight exceeds the set weight, the comparison means 6 generates a passage signal, the second control signal generation means 10 supplies a control signal having a constant value to the supply device 2, and the supply device 2 supplies the articles at a constant supply amount. Supply to the measuring unit 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a quantitative scale for supplying a container with an amount of a predetermined weight, and more particularly to controlling the supply amount.

[0002]

[Prior art]

 Conventionally, in the above-mentioned quantitative weighing machine, a screw feeder is used to feed articles to a weighing hopper equipped with a weighing section, and in proportion to a deviation between a weighing signal from the weighing section and a target weight (supply remaining amount), There was one that controlled the supply amount of the screw feeder. (Jpn. Pat. Appl. Pub.

[0003]

[Problems to be solved by the device]

 However, since this quantitative balance controls the supply amount in proportion to the remaining supply amount (target weight-weighing signal), if the remaining supply amount becomes extremely small, the supply amount also decreases. The time it takes to deliver an item increases. Certainly, this quantitative scale improves the weighing accuracy, but it increases the supply time. In order to shorten the supply time, it is necessary to increase the proportional coefficient by which the remaining supply amount is multiplied when the remaining supply amount (target weight-weighing signal) is supplied to the screw feeder. However, if this is large, the amount of supply will be large when the remaining amount of supply is large, so vibration will be applied to the weighing unit. As a result, the measurement accuracy is reduced. In this way, the proportional coefficient exerts a contradictory effect on both the supply time and the measurement accuracy, so it was not possible to shorten the supply time and improve the measurement accuracy.

Furthermore, since the weighing unit is a secondary vibration system and is also affected by the basic vibration of the floor on which the weighing unit is provided and the wind, the weighing signal always contains vibrational noise. Therefore, since the remaining supply amount also has vibrational noise, the supply amount of the screw feeder controlled in proportion to the remaining supply amount is also affected by the vibrational noise. When supplying near the target weight, it is necessary to have a highly reproducible and stable supply in order to obtain high accuracy, but in this quantitative balance, the supply is affected by noise as described above. Therefore, the value of the remaining supply amount was particularly small, and the influence of vibrational noise on the weighing signal was large, and high-accuracy weighing could not be performed.

In this quantitative weighing machine, even when a stop signal is supplied to the screw feeder at the moment when the target weight is reached, a certain amount of articles (so-called drop difference) is supplied to the weighing hopper. To reduce this drop difference, the supply amount immediately before the stop may be made extremely small. However, since the supply time becomes long as described above, the supply is generally stopped when the supply amount reaches a predetermined value. This drop difference changes when the density of the articles contained in the screw feeder is constant and the supply amount immediately before the stop is constant, when the density changes. Therefore, it is necessary to adjust the drop difference by increasing the target weight when the density of the article tends to increase and decreasing the target weight when the density of the article tends to decrease. However, if the target weight is adjusted, the supply amount changes, so the supply amount at the time when the goods are supplied to the vicinity of the target weight, that is, what is considered to be a constant value, also changes. Therefore, the drop difference could not be controlled accurately.

[0006]

[Means for Solving the Problems]

 As shown in FIG. 1, the present invention is directed to a supply device 2 for controlling the supply amount of articles according to the magnitude of a control signal, a weighing section 4 for weighing the articles to be supplied, and a weighing signal from the weighing section 4. And a predetermined first set weight, comparing means 6 for generating a passage signal when the weighing signal passes the first set weight, and the first set weight until the passage signal is generated. The first control signal generating means 8 for supplying a function signal of the difference between the predetermined second set weight and the weighing signal to the supply device 2 as the control signal, and the passage after the passage signal is generated. The second control signal generation means 10 supplies a signal having a magnitude equal to or smaller than the function signal at the time of signal generation and having a constant magnitude to the supply device 2 as the control signal.

[0007]

In the quantitative balance configured as described above, since the comparison unit 6 does not initially generate the passage signal, the control signal is supplied from the first control signal generation unit 8 to the supply device 2. Therefore, since the supply device 2 continuously controls the supply amount based on the function signal of the difference between the second set weight and the weighing signal, a large change in the supply amount does not occur, and the meter caused by the change does not occur. No oscillation of the quantity signal occurs. Further, after the comparison means 6 generates the passage signal, the second control signal generation means 10 supplies the second control signal having a constant value to the supply device 2. Therefore, since the supply device 2 supplies the articles at a constant supply amount irrelevant to the function signal, the weighing accuracy is not deteriorated without being affected by the vibration noise.

[0008]

【Example】

 Hereinafter, the present invention will be described in detail based on four embodiments shown in FIGS. The first embodiment is shown in FIGS. The first embodiment has a reservoir hopper 12 as a supply device as shown in FIG. The storage hopper 12 has a discharge port at the bottom, and a discharge gate 14 is provided to open and close the discharge port. The discharge gate 14 is connected to a rotary shaft of a servomotor 18 via a transmission gear 16. A potentiometer 20 is also coupled to this rotary shaft, and its output is supplied to the servo amplifier 22. The output of the other D / A converter 24 is also supplied to the servo amplifier 22 so that the deviation between the output of the potentiometer 20 and the output of the D / A converter 24 becomes zero. The rotation of the servo motor 18 is controlled to maintain the state when the deviation becomes zero. As a result, the discharge gate 14 is controlled to have an opening degree according to the magnitude of the output of the D / A converter 24. A control signal is supplied to the D / A converter 24 from a microcomputer 36 described later.

Below the storage hopper 12, a weighing hopper 26 is provided so as to receive articles from this. The weighing hopper 26 is provided with two load cells 28, 28 as a weighing unit. The analog weighing signals of the load cells 28, 28 are added by the adder 30, amplified by the amplifier 32, converted into the digital weighing signal WI by the A / D converter 34, and supplied to the microcomputer 36. A discharge port is also provided below the weighing hopper 26, and a discharge gate 38 is provided so that the discharge port can be opened and closed. The discharge gate 38 is driven by an air cylinder 40, and the air cylinder 40 is controlled by the microcomputer 36.

The microcomputer 36 functions not only as a comparison means and a first and second control signal generation means, but also as a control means for the air cylinder 40. In the microcomputer 36, the weight Wa for switching the means for generating the control signal to be supplied to the D / A converter 24 from the first control signal generating means to the second control signal generating means, the target weight W, and the discharge The weight Wf that is the weight for closing the gate 14 and is smaller than the target weight W by only the difference ΔW is set by the setting unit 42. This setting is performed while watching the displayed value on the display unit 44.

The microcomputer 36 achieves each of the above functions based on these set values and preset programs. That is, as shown in FIG. 3, in step 46, the digital weighing signal WI is read. Next, in step 48, the digital weighing signal WI is subtracted from the set weight W, and the subtracted value is multiplied by the proportional coefficient K to calculate the control signal Po, and this Po is output to the D / A converter 24. As a result, as described above, the discharge gate 14 opens to the opening degree according to the control signal Po, and the articles are supplied to the weighing hopper 26 at the supply amount according to the opening degree. Then, in step 50, it is judged whether or not the digital weighing signal WI is equal to or larger than the set weight Wa, and if it is not equal to or larger than Wa, steps 46, 48 and 50 are repeated until WI becomes equal to or larger than Wa. During this period, the digital measurement signal WI is gradually increasing as shown in FIG. 4, so that the opening of the discharge gate 14 which is initially the maximum opening GI is gradually decreased as shown in FIG. Becomes gradually smaller, and the digital weighing signal WI does not vibrate due to changes in the supply amount.

If it is determined in step 50 that the digital weighing signal WI has become equal to or greater than the set weight Wa, in step 52 the predetermined gate opening data Pox is output to the D / A converter 24. As a result, the opening degree of the discharge gate 14 is fixed to G2 as shown in FIG. 5, and the articles are supplied at the supply amount according to G2. Then, in step 54, the digital weighing signal WI is read, and in step 56, it is judged whether or not the digital weighing signal WI is not less than the set weight Wf. If it is not more than Wf, then steps 54 and 56 are repeated until it becomes not less than Wf. . During this time, the opening degree of the discharge gate 14 is fixed to G2, and the supply amount becomes a predetermined constant value. Therefore, even if the digital weighing signal WI contains an impact due to a product drop or a vibration due to a basic vibration, it has no influence on the flow rate control.

When it is determined in step 56 that the digital weighing signal WI has exceeded the set weight Wf, in step 58, predetermined gate opening data P c is output to the D / A converter 24. As a result, the discharge gate 14 is completely closed, and at this time, the articles are loaded into the weighing hopper 26 by the drop difference ΔW already discharged from the storage hopper 14, and the articles of the target weight W are loaded into the weighing hopper 26. Complete. After this, the microcomputer 36 supplies a control signal to the air cylinder 40 to eject the articles in the weighing hopper 26. As is clear from the comparison of steps 48 and 52, Po and Pox are independent, and changing one has no effect on the other.

In the second embodiment, as shown in FIG. 6, a logic circuit is used instead of the microcomputer. That is, the subtractor 60 and the multiplier 62 are provided as the first control signal generating means. The subtractor 60 subtracts the digital weighing signal WI from the A / D converter 34 from the set weight W set in the W setter 64. The multiplier 62 multiplies the subtracted value by K and supplies the output side to the AND gate 66 connected to the D / A converter 24. A control signal Pox generator 68 is provided as a second control signal generating means, and the control signal Pox generated by the control signal Pox generator 68 is supplied to an AND gate 70 whose output side is connected to the D / A converter 24. Further, a control signal Pc generator 72 for generating a gate fully closed control signal is provided, and the control signal Pc generated by this is supplied to an AND gate 74 whose output side is connected to the D / A converter 24.

Comparators 76 and 78 are provided as comparison means. The comparator 76 sets the output signal to H level when the digital weighing signal WI exceeds the set weight Wa set in the Wa setter 80. This output signal is supplied to the AND gate 70. The comparator 78 sets the output signal to the H level when the digital weighing signal WI exceeds the set weight Wf set in the Wf setter 82. This output signal is supplied to the AND gate 74. The output signals of the comparators 76 and 78 are inverted by the inverters 84 and 86 and supplied to the AND gate 66.

Therefore, since the output signals of the comparators 76 and 78 are both at the L level at the beginning of turning on, the AND gate 66 is opened and the output of the multiplier 62 is supplied to the D / A converter 24 as a control signal. It When the output signal of the comparator 76 becomes H level, the AND gate 70 is opened instead of closing the AND gate 66, and the control signal Pox is supplied to the D / A converter 24. Further, when the output signal of the comparator 78 becomes H level, the AND gate 74 is opened instead of closing the AND gate 70, and the control signal Pc is supplied to the D / A converter 24. The other points are similar to those of the first embodiment, and the description thereof will be omitted.

FIG. 7 shows a third embodiment, in which the second embodiment processes digital signals, whereas this embodiment processes analog signals. As the first control signal generation signal generation means, an operational amplifier 88 configured to subtract the analog target weight VW from the analog weighing signal VWI and multiply the subtracted value by K is provided. A VPcx generator 90 for generating an analog control signal VPcx is provided as a second control signal generating means. Also provided is a V Pc generator 92 which generates a gate fully closed analog control signal VPc. The output of the operational amplifier 88, the output of the VPcx generator 90 and the output of the VPc generator 92 are supplied to the amplifier 100 via analog switches 94, 96 and 98, respectively. The output signal of the amplifier 100 is supplied to the servo amplifier 22.

Comparators 102 and 104 are provided as comparison means. The comparator 102 sets the output signal to the H level when the analog weighing signal VWI exceeds the analog set weight VWa. This output signal is supplied to the analog switch 96, and this analog switch 96 is closed when the supplied output signal is at the H level. Similarly, the comparator 104 sets the output signal to the H level when the analog weighing signal VWI exceeds the analog set weight VWf. This output signal is supplied to the analog switch 98, and this analog switch 98 is closed when the supplied output signal is at the H level. The output signals of the comparators 102 and 104 are supplied to the two-input negation AND gate 106, and the output signal of the AND gate 106 is supplied to the analog switch 94. The analog switch 94 is closed when this output signal is at the H level. Since the operation of the third embodiment is similar to that of the second embodiment, its explanation is omitted.

FIG. 8 shows a fourth embodiment. In this embodiment, a screw feeder 108 is used instead of the reservoir hopper 12, and a servo motor 18 controls a screw 110. Others are the same as those in the first embodiment, and detailed description thereof will be omitted.

In the first embodiment, the load cells 28, 28 are provided on the weighing hopper 26, but they may be provided on the reservoir hopper 12 side. However, in that case, it is necessary to set Wa> Wf. Further, although Wf and W are set, ΔW and W may be set, and Wf may be set by calculating W−ΔW in the microcomputer 36. Although the servomotor 18 is used, a pulse motor, a cylinder having a positioner, or the like may be used instead. Further, although the control signal Pox is preset, the control signal when WI becomes Wa or more may be supplied as it is without changing. Further, in each of the above embodiments, the supply flow rate was gradually changed from the start of charging, but as shown in FIG. 9, a fixed time t from the start of charging or a constant weight Wb preset from the start of charging was set. Until it is supplied, the supply amount is controlled to a constant amount with a preset gate opening G1 as shown in FIG. 10, and then the supply amount is gradually changed until the weight becomes Wa, as in the above embodiment. , Wa, the gate opening degree may be switched to a predetermined amount set as G2, and the gate may be closed when the weight becomes Wf. Further, in each of the above-described embodiments, the value obtained by multiplying (W-WI) by K is used as Po, but it is also possible to use a value obtained by adding an appropriate value to (W-WI) depending on the situation. .

[0021]

[Effect of device]

 As described above, according to the present invention, until the weighing signal from the weighing unit reaches the first set weight, the supply amount is controlled based on the function signal of the difference between the second set weight and the weighing signal. When the weighing signal exceeds the first set weight, the articles are supplied at a fixed supply amount that is determined regardless of the function signal. Since the feedback control and the constant value control are combined in this way, even if the supply time is shortened by properly adjusting the function of the function signal in the feedback control state, it is fixed at the final measurement. Since the value is controlled, the supply time is shortened, and even if vibration occurs, it is not affected by the vibration, and high-precision weighing is possible. Similarly, since the constant value control is performed after the weighing signal exceeds the second set weight, even if the weighing signal of the weighing unit vibrates due to the fundamental vibration of the floor or the influence of wind, it is not affected. Instead, it can be weighed with high accuracy. Moreover, since the feedback control and the constant value control can be controlled independently of each other, for example, even if the second set weight is changed according to the fluctuation of the density of the article, the constant value control is not affected, and the constant value control can be reversed. Adjustment does not affect feedback control. That is, since the feedback control and the constant value control can be adjusted independently of each other, the drop difference can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a block diagram of a first embodiment of the present invention.

FIG. 3 is a flowchart of the first embodiment.

FIG. 4 is a diagram showing a change state of the weighing signal according to the first embodiment over time.

FIG. 5 is a diagram showing a relationship between a weighing signal and a gate opening degree in the first embodiment.

FIG. 6 is a block diagram of a main part of the second embodiment.

FIG. 7 is a block diagram of a main part of the third embodiment.

FIG. 8 is a schematic view of a main part of the fourth embodiment.

FIG. 9 is a diagram showing a change state of a weighing signal in the modified example of the first embodiment with time.

FIG. 10 is a diagram showing a relationship between a metering signal and a gate opening degree in a modification of the first embodiment.

[Explanation of symbols]

 2 supplying device 4 measuring section 6 comparing means 8 first control signal generating means 10 second control signal generating means

Claims (1)

[Scope of utility model registration request] 1. A supply device for controlling a supply amount of an article according to a magnitude of a control signal, a weighing section for weighing the supplied article, a weighing signal from the weighing section, and a predetermined first set weight. And comparing means for generating a passage signal when the weighing signal passes the first set weight, and a second set weight which is larger than the first set weight and is predetermined until the passage signal is generated. First control signal generating means for supplying a function signal of a difference from the weighing signal as the control signal to the supply device, and a magnitude equal to or smaller than the control signal when the passage signal is generated after the passage signal is generated. A quantitative balance comprising: a second control signal generating means for supplying a signal of a constant magnitude to the supply device as the control signal.