JPH10116122A - Controller for powder feeder, and powder feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a powder conveyance amount in a short time with high precision and to improve the operability by utilizing a calibration curve obtained by feeder calibration at the start of supply. SOLUTION: As a duty ratio at the start of supply, a duty ratio to a target supply actual flow rate qT is found from the calibration curve obtained by feeder calibration. Consequently, only a rise response time T1 (<1sec) is needed until the set target supply actual flow rate qT is reached. Therefore, powder supply in a short time (several sec) can be performed with high precision. Further, a momentary supply actual flow rate is calculated in a feedback control area T based on the output from a load cell and the duty ratio to it is found from the calibration curve. Consequently, an error in the momentary supply actual flow rate is within <=2% and powder can be supplied with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a powder feeder, and more particularly, to a method for controlling the amount of powder supplied in a short time with high accuracy, and a powder feeder having such a control means. Things.

[0002]

2. Description of the Related Art Conventionally, a powder feeder using an ultrasonic motor using an ultrasonic vibrator has been known. This powder feeder conveys powder by generating mechanical vibrations in a vibrating body, utilizing the fact that an ultrasonic vibrator causes mechanical deformation of a piezoelectric element due to electric energy at a resonance frequency. . That is, when an AC drive voltage having a resonance frequency is applied to an ultrasonic vibration motor configured to simultaneously generate longitudinal vibration (longitudinal vibration) and bending vibration, elliptical vibration occurs at the tip, and a pipe is placed at the tip. Is attached, powder is supplied into a pipe, and the powder is conveyed in a certain direction by elliptical vibration.

The supply amount of the powder is controlled by the following control. That is, by intermittently applying the drive voltage to the ultrasonic motor, the ratio of the drive voltage per cycle (duty ratio) is changed, thereby changing the output to the ultrasonic motor and supplying the powder. Is controlling. For example, an AND of a resonance frequency oscillating circuit oscillating at a resonance frequency and a clock generator for duty ratio control for changing a duty ratio, for example.
Then, the output is amplified and applied to the vibrating body.

Further, in order to improve the accuracy of the control, feedback control is performed by a control system as shown in a block diagram of FIG. That is, the amount of powder is measured by a load cell, which is a load sensor, and the output signal of the sensor is amplified by a load cell amplifier and fed back to the microcomputer system (duty ratio control means) via an A / D converter. Sample. Then, in the microcomputer system, the drive circuit operates by the calculated duty ratio clock signal based on the output amplification signal. Then, the drive voltage signal is applied to the ultrasonic motor, and the ultrasonic motor operates. At this time, the microcomputer system calculates the optimum duty ratio based on the output signal from the load cell, so that the powder supply amount can be controlled optimally.

[0005]

However, in the above control method, it takes time until the actual flow rate is stabilized by performing feedback control so that the target actual flow rate of the powder is obtained. For example, as shown in FIG. 13, it takes several seconds T2 from the start of powder supply to the target actual supply flow rate qT, including the rise response time of the control system. Therefore, the actual supply flow rate for several seconds from the start of supply is
It was very unstable and could not supply powder at the target actual supply flow rate qT. This is because the flow rate control of the powder until reaching the target actual supply flow rate qT is performed by a method in which the duty ratio is gradually increased.

[0006] Therefore, in the initial stage of powder supply, the actual supply actual flow rate greatly deviates from the target actual supply flow rate qT, and the powder cannot be supplied at a constant flow rate with high accuracy. Therefore, in the powder supply in a short time, for example, for several seconds, there is a large error with respect to the target actual supply flow rate, and there is a problem that the powder supply cannot be performed with high accuracy at a constant flow rate.

Further, since the fluidity of the powder varies depending on the properties of the supplied powder and variations between lots, these factors greatly affect the powder supply accuracy. Therefore, in order to maintain the accuracy of the supply amount, it is necessary to perform the feeder calibration every time the property of the powder or the lot changes, which is troublesome.

Accordingly, the present invention has been made to solve the above-mentioned problems, and a powder capable of controlling the amount of powder conveyed in a short time with higher accuracy and improving workability. It is an object of the present invention to provide a feeder control method and a powder feeder having such control means.

[0009]

According to the first aspect of the present invention, there is provided a vibrating body whose tip portion performs elliptical vibration when a predetermined resonance frequency is applied to a piezoelectric element.
A powder conveying path formed at the tip of the vibrating body, a hopper for storing the powder and feeding the powder into the powder conveying path, and a resonance for a time corresponding to a duty ratio with respect to the vibrating body; In a powder feeder control device comprising a duty ratio control means for giving a frequency and a load cell which is a load sensor for sequentially measuring a weight loss value of the powder in the hopper, a feeder calibration performed before using the powder feeder Feeder calibration storage means for obtaining the actual supply flow rate of each powder per unit time with respect to the duty ratio of two or more points, linearly interpolating the values to obtain and store a calibration curve, and a target actual supply flow rate Is set, a duty ratio calculating means for calculating a duty ratio for the actual supply flow rate from the calibration curve, based on the duty ratio. The drives the vibrator, the supply of the powder starts, after the supply actual flow rate value of the powder becomes a target value,
And a feedback unit that feedbacks an output value from the load cell to the duty ratio control unit.

Since the tip of the vibrating body oscillates elliptically, the powder supply pipe attached to the tip also elliptically vibrates. Then, the powder supplied from the hopper into the pipe is accelerated and moved by the elliptical vibration in a horizontal direction (a direction perpendicular to the vertical vibration of the vibrating body and parallel to the bending vibration of the vibrating body). I do. Therefore, the powder can be transported.

In this case, since the AC drive voltage applied to the piezoelectric element is on / off controlled, the powder is conveyed while the vibrator is driven. On the other hand, during the period in which the vibrating body is not driven, the tip of the vibrating body does not perform elliptical vibration, so that the powder is not transported. Then, from the calibration curve obtained by the feeder calibration and stored in the feeder calibration storage unit, the duty ratio calculation unit calculates the duty ratio with respect to the target actual supply flow rate, and starts supplying the powder based on the duty ratio. Therefore, the powder can be supplied with high accuracy at an instantaneous (within 1 second) actual supply flow rate equal to the target actual supply flow rate.

According to a second aspect of the present invention, in order to solve the above-mentioned problems, a vibrating body whose tip portion performs elliptical vibration when a predetermined resonance frequency is applied to the piezoelectric element, and a vibrating body formed at the front end portion of the vibrating body. Powder conveying path, storing the powder, a hopper for feeding the powder to the powder conveying path, a time corresponding to the duty ratio for the vibrator, a duty ratio control means for giving a resonance frequency, In a powder feeder control device comprising a load cell as a load sensor for sequentially measuring the weight loss value of the powder in the hopper, a feeder calibration performed before use of the powder feeder is performed for a duty ratio of two or more points. Feeder calibration storage means for obtaining the actual supply flow rate of each powder per unit time, linearly interpolating the value to obtain and store a calibration curve, and feedback A learning storage unit for storing a stable value of the actual supply flow rate of the powder in the control area and a duty ratio with respect to the stable value; a duty ratio stored in the learning storage unit; and a duty ratio stored in the feeder calibration storage unit. A correction coefficient calculating unit that calculates a correction coefficient by comparing the duty ratio with the duty ratio, correcting the correction curve each time with the correction coefficient, storing the correction curve in the learning storage unit, and correcting the duty ratio with respect to the target actual supply flow rate. The duty ratio calculating means to be calculated from the calibration curve, and the vibrating body is driven based on the duty ratio to start supplying the powder, and after the actual supply flow rate value of the powder reaches the target value,
Feedback means for feeding back an output value from the load cell to the duty ratio control means.

The duty ratio calculating means calculates the duty ratio with respect to the target actual supply flow rate from the calibration curve obtained by the feeder calibration and stored in the feeder calibration storage means. Based on the stable value of the actual supply flow rate of the powder, the calibration curve is corrected each time for each supply, the duty ratio for the target actual flow rate is calculated from the corrected calibration curve, and the powder is calculated based on the duty ratio. Start supplying the body. Therefore, the target actual supply flow and the actual actual supply flow are instantaneously (within 1 second), and the calibration curve is corrected for each supply. Is smaller than the previous supply, and the powder can be supplied with higher accuracy.

Further, since the calibration curve is corrected each time and the corrected calibration curve is stored, when the properties of the powder or the lot changes, the feeder calibration is automatically performed without performing the feeder calibration. Since the calibration curve is obtained and corrected for each supply, the powder can be supplied with higher accuracy, and the workability is improved.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, a vibrating body whose tip portion performs elliptical vibration when a predetermined resonance frequency is applied to the piezoelectric element, A formed powder conveying path, a hopper for storing the powder and feeding the powder into the powder conveying path, and a duty ratio control means for applying a resonance frequency to the vibrator for a time corresponding to the duty ratio And a load cell as a load sensor for sequentially measuring the weight loss value of the powder in the hopper, and the powder feeder control device according to claim 1.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problems, a vibrator whose tip portion performs elliptical vibration when a predetermined resonance frequency is applied to the piezoelectric element, A formed powder conveying path, a hopper for storing the powder and feeding the powder into the powder conveying path, and a duty ratio control means for applying a resonance frequency to the vibrator for a time corresponding to the duty ratio And a load cell as a load sensor for sequentially measuring the weight loss value of the powder in the hopper, and a powder feeder control device according to claim 2.

According to the powder feeder having the above configuration,
It has a control means for calculating a duty ratio with respect to a target actual supply flow rate from a calibration curve obtained by feeder calibration and starting powder supply based on the duty ratio. The powder can be supplied at the same supply actual flow rate as the actual supply flow rate of the powder, and the powder supply in a short time can be performed with high accuracy.

Further, the calibration curve is corrected based on the stable value of the actual supply flow rate of the powder in the feedback control range in the previous supply, and the duty ratio with respect to the target actual supply flow rate is calculated from the corrected calibration curve. By providing a control means for starting the supply of powder based on the duty ratio, the error between the target actual supply flow and the actual supply actual flow is instantaneously (within 1 second) smaller than the previous one, and It is possible to supply with high accuracy.

Further, since the calibration curve is corrected each time and the corrected calibration curve is stored in the storage device, the feeder calibration when the property of the powder or the lot is changed becomes unnecessary, and the workability is improved.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the structure of the powder feeder according to the first embodiment. The vibrating body 10
This is a so-called linear type ultrasonic motor, in which two flat plate-shaped piezoelectric elements 1 are laminated via an electrode plate (not shown), and both sides thereof are formed into a substantially cylindrical metal horn 2a and a substantially cylindrical metal back horn 2b. It has a structure sandwiched between. The vibrating body 10 includes the back horn 2b and the piezoelectric element 1
And is fixed to a fixing member 4 by a bolt 3 having one end fastened to a horn 2a. The tip 2c of the horn 2a has two chamfers, and a through hole 2d for inserting a pipe to be described later.
Is provided.

A powder supply pipe 20 through which powder flows is inserted and fixed in the through hole 2d. The left end 21 of the powder supply pipe 20 in the figure is slightly bent downward so that the powder P conveyed from the right in the figure can easily fall and move from the end 21 of the pipe 20. ing. On the other hand, the right end portion 22 of the pipe 20 in the drawing is bent slightly upward, so that the powder P supplied from the hopper body 30 can be easily transported to the left side in the drawing.

The hopper body 30 stores the powder P and gradually supplies the powder to the pipe 20, and the bottom 31 has a funnel shape. A tube 32 is connected to the bottom 31, and the other end of the tube 32 is connected to an end 22 of the powder supply pipe 20. Therefore,
The powder P charged into the hopper body 30 is supplied to the pipe 20 via the tube 32. In addition, tube 3
For 2, a flexible material is selected so as not to hinder the vibration of the vibrating body 10, and in this example, a nylon tube is used.

FIG. 2 shows the results of measuring the frequency characteristics of the input impedance of the vibrating body 10 using an impedance analyzer. From this result, the resonance frequency F of the vibrating body 10
It turns out that r is about 29.4 kHz. When driven at this resonance frequency Fr, it vibrates greatly. on the other hand,
When driven at a frequency deviating from the resonance frequency, that is, at a non-resonance frequency, since the driving energy cannot be injected due to an increase in impedance, almost no vibration occurs.
Therefore, in this embodiment, the driving of the vibrating body 10 is turned on / off by alternately applying the resonance frequency and the non-resonance frequency. Incidentally, even if the drive voltage is not applied during the period in which the non-resonant frequency is applied, the drive of the vibrating body 10 can be similarly turned on / off.

Here, the state of vibration when the vibrating body 10 is driven at the resonance frequency will be described. When the piezoelectric element 1 is driven at the resonance frequency, the piezoelectric element expands and contracts, so that the vibrating body 10 bends and vibrates as shown in FIG. This vibration is
This is a composite vibration of vibration of expansion and contraction (vertical vibration) in the vertical direction in the figure and bending vibration (bending vibration) in the horizontal direction of the figure.

To explain in more detail one cycle of the vibration, the vibration occurs as shown in FIG. In addition,
In FIG. 4, a black dot is formed at the center of the tip to make it easy to understand the movement of the tip (the lower end in the figure). First, t = 0
In FIG. 4A, the tip (black dot) is bent so as to be located on the right side. Then, t = π after 1/4 cycle
/ 2 (FIG. 4 (b)), the vibrating body shrinks, and the tip (black dot) is located on the upper side in the figure. Further, t = π (FIG. 4)
In (c)), the tip portion (black dot) is bent so as to be located on the left side. Further, t = 3π / 2 after 1/4 cycle
In FIG. 4D, the vibrating body is elongated, and the tip (black dot) is located on the lower side in the figure. Therefore, when the movement of the sunspot is traced for one cycle, it can be seen that the ellipse moves as shown in FIG.

Therefore, a pipe is attached to this tip,
When the powder is supplied into the pipe, the powder is lifted but is accelerated in the left direction in the figure and is conveyed to the left. Then, the ratio of time for driving at the resonance frequency is adjusted, that is, the duty ratio is changed to adjust the amount of powder transported (cutout amount). At this time, the hopper body 30
The weight of the powder P inside is measured by a load cell, and the output signal is fed back to the microcomputer system. Based on this feedback signal, a duty ratio control signal optimally calculated by the microcomputer system is sent to the drive circuit, and the drive voltage VACT is applied to the vibrating body 10 for a time corresponding to the duty ratio, whereby the powder P The cutting amount and the actual flow rate are controlled. In the present embodiment, the microcomputer system includes a duty ratio control unit, a feeder calibration storage unit, a duty ratio calculation unit, and a feedback unit.

However, in the conventional control method, FIG.
As shown in FIG. 3, several seconds from the start of powder supply (period T
2) Since the actual supply flow rate is not stabilized at the target actual flow rate qT until the time has elapsed, if the supply is performed in a short time, for example, for several seconds, the powder cannot be supplied with high accuracy. This is because in the conventional control method, control is performed such that the duty ratio is gradually increased from the start of supply until the actual supply flow reaches the target actual supply flow qT.

Therefore, in the present invention, the calibration curve obtained by the feeder calibration used in the feedback control area T in the conventional control method is used at the start of the supply, so that the target is instantaneously supplied from the start of the supply. The powder can be supplied at the actual supply flow rate qT. Therefore, powder supply in a short time (several seconds) can be performed with high accuracy.

A method for controlling a powder feeder according to the present embodiment will be described with reference to the drawings. First, the feeder calibration will be described with reference to FIGS. FIG. 6 shows a flowchart of the feeder calibration, and FIG. 7 shows a calibration curve obtained by the feeder calibration. The calibration curve shown in FIG. 7 is stored in the feeder calibration storage unit. This feeder calibration is performed in a similar manner in the prior art. Feeder calibration is an operation for graphing the relationship between the actual flow rate of a given powder and the duty ratio.

In FIG. 6, in step (hereinafter abbreviated as S) 1, the duty ratio of the duty ratio control means is set to 100%, and then in S2, the current powder in the hopper measured by the load cell is measured. The body weight is stored in the duty ratio control means. Here, the storage processing performed in S2 will be outlined with reference to FIG. FIG. 8 shows a weight calibration straight line prepared in advance before using the powder feeder. This straight line shows the relationship between the output values (voltage values) V1, V2,... Of the load cells and the weight values Q1, Q2,. Therefore, when the output value of the load cell is input to the duty ratio control means, the weight value of the powder is calculated from the output value based on the weight calibration straight line and stored.

Then, in S3, the vibrating body is driven at a predetermined duty ratio to supply the powder. At this time, the duty ratio is stored in the duty ratio control means. Here, the predetermined duty ratio is a duty ratio set in advance, and in FIG.
X2,..., Specifically, 20%, 40%,. Thereafter, when 10 seconds have elapsed from the start of supply (S4: Yes), the process directly proceeds to S5. 10se
If c has not elapsed (S4: No), powder supply is continued at the duty ratio in S3.

Next, in step S5, the weight of the powder in the hopper is measured by the load cell, and the value is stored in the duty ratio control means. The process of S5 is performed in the same procedure as the process of S2. Then, in S6, a change in weight per unit time, that is, an actual supply flow rate value (g / sec) is stored in the duty ratio control means from the stored value in S2 and the stored value in S5. That is, S6 corresponds to a feeder calibration storage unit.

Subsequently, when the end is reached in S7 (S
7: Yes), the feeder calibration ends,
A straight line is interpolated between the measurement points to create a calibration curve shown in FIG. If the end is not reached (S7: No),
Proceed directly to S8. In S8, the duty ratio in S3 is reduced by a certain value. Thereafter, the process returns to S2 and the above processing is repeated.

Next, a method of controlling powder supply will be described with reference to FIGS. FIG. 9 shows a powder supply pattern, and FIG. 10 shows a state of actual powder flow control in relation to the actual supply flow rate and time. First, a supply pattern as shown in FIG. 9 is set before supplying the powder. This supply pattern includes a slope-up supply start actual flow rate qT1, a steady supply actual flow rate qT2, a slope-down supply end actual flow rate qT3, a slope-up time t1, and a steady supply time t.
2. It is created by determining the slope down time t3 and inputting it to the duty ratio control means. here,
In FIG. 9, a square wave pattern is obtained when t1 = t3 = 0, and a trapezoidal wave pattern is obtained when t1 = t3> 0. The slope of the supply pattern is
For example, like the seat part of the supply and exhaust valve of the engine,
This is because when the alloy powder is produced by melting, for example, the powder supply start position and the powder supply end position overlap, and the amount of powder in the overlapping portion is made uniform with the other portions. The area surrounded by the supply pattern is the total supply amount of the powder.

Here, focusing on the start of powder supply,
In the conventional control method, as shown in FIG. 13, it takes T2 (> several seconds) until the set actual supply flow rate qT is reached. This is because the flow control from the start of the supply to the target actual supply flow qT is performed by gradually increasing the duty ratio so that the actual supply flow approaches the target actual supply flow qT. On the other hand, in the method for controlling the powder feeder according to the first embodiment, FIG.
As shown by 0, only the rising response time T1 (<1 sec) is required until the set actual supply flow rate qT is reached. This is because the duty ratio at the start of supply is shown in FIG.
This is because the duty ratio with respect to the target actual supply flow rate qT is determined from the calibration curve of (a), and powder supply is started based on the duty ratio.

The symbol T in FIGS. 10 and 13 indicates the period during which the feedback control is being performed on the target actual supply flow rate qT. In this feedback control region, the instantaneous supply actual flow rate calculated based on the output signal from the load cell is obtained, and the duty ratio with respect to the instantaneous supply actual flow rate is obtained from the calibration curve of FIG. The process of supplying the powder is repeated. As a result, the error of the instantaneous supply actual flow rate with respect to the target actual supply flow rate qT in the feedback control range T is ±
It is within 2% and supplies powder with high precision.

The hatched portions in FIGS. 10 and 13 show an error with respect to the target actual supply flow rate qT. Therefore,
The smaller the area of the hatched portion, the more precisely the powder is supplied in a short time.

Further, the control method according to the present embodiment will be described in detail with reference to FIGS. 10 (a), 10 (b) and 10 (c). FIG. 10A shows the actual supply actual flow rate qA at the start of supply, that is, the target actual supply flow rate qT.
This shows the supply state of the powder when the actual supply flow rate obtained from the calibration curve of (a) is larger than the target actual supply flow rate qT. The reason for such a supply state is that the relationship between the target actual supply flow rate qT and the duty ratio is as shown in FIG.
This is when it exists above the calibration curve of (a). Therefore, the duty ratio at the start of supply at this time is larger than the original duty ratio XT with respect to the target actual supply flow rate qT.

FIG. 10 (b) shows the supply state of the powder when the actual actual supply flow rate qB at the start of the supply is smaller than the target actual supply flow rate qT, contrary to FIG. 10 (a). is there. Such a supply state occurs when the relation point between the target actual supply flow rate qT and the duty ratio exists below the calibration curve in FIG. 7A. Therefore, the duty ratio of the supply start at this time is the target supply actual flow rate qT
Is smaller than the original duty ratio XT.

FIG. 10C shows the supply state of the powder when the actual supply actual flow qC at the start of supply is the same as the target actual supply flow qT. Such a supply state occurs when the relation between the target actual supply flow rate qT and the duty ratio exists on the calibration curve of FIG. 7A. Therefore, the supply start duty ratio at this time is the same as the original duty ratio XT with respect to the target actual supply flow rate qT.

Here, in order to make the supply state in FIGS. 10A and 10B closer to the supply state in FIG. The number of duty ratios X1, X2,... Measured in the application may be increased.

As described above, according to the powder feeder according to the first embodiment, the duty ratio XT with respect to the target actual supply flow rate qT is calculated based on the calibration curve obtained from the feeder calibration performed before use. do it,
Since the supply of the powder P is started at the duty ratio XT, the actual supply flow rate reaches the target actual supply flow rate qT instantaneously (within the time T1) from the start of the supply. Therefore, it is possible to supply the powder while controlling the actual flow rate with high accuracy, and further, for several seconds.
The powder can be supplied with high accuracy even in the short-time supply at c.

Next, a powder feeder according to a second embodiment will be described. The structure itself of the powder feeder is the same as in the first embodiment. A feature of the second embodiment is that in the second and subsequent powder supply, the calibration curve obtained from the feeder calibration is corrected each time based on the stable value in the feedback control area in the previous supply. is there.

The control of the flow rate of the powder feeder according to the second embodiment will now be described with reference to FIGS. FIG. 11 shows a flowchart of the correction processing of the calibration curve, and FIG. 12 shows the state of the actual flow rate control of the powder in relation to the actual flow rate of supply and time.

In FIG. 11, in the current supply state, when the actual supply flow is within an error of ± 2 with respect to the target actual supply flow qT (S10: Yes), or the time until the control ends is 0. .5 seconds or less (S11: Y
In es), the supply actual flow rate value is stored, and the process proceeds to S12. When the actual supply flow rate is not within the error of ± 2 from the target actual supply flow rate qT (S10: No), or when the time until the control end is 0.5 sec or more (S10).
11: No), the powder supply is continued while performing feedback control.

In S12, first, the correction coefficient is calculated by comparing the actual supply flow rate value stored in S10 or S11 with the stable value of the actual supply flow rate in the initial supply. Next, based on the correction coefficient, the calibration curve (FIG. 7A) obtained from the feeder calibration is corrected, and the corrected calibration curve (FIG. 7B or 7C) is stored.

Here, in the third and subsequent supply, S
The correction coefficient is calculated by comparing the supply actual flow value stored in step 10 or S11 with the stable value of the supply actual flow in the previous supply, and based on the correction coefficient, the correction calibration curve stored in the previous supply (FIG. 7). (B) or (c)) is further corrected, and the corrected calibration curve is stored. That is, S
Reference numeral 12 corresponds to a correction coefficient calculation unit and a duty ratio calculation unit.

When the process of S12 is completed, the process proceeds to S13, where it is determined whether or not the next supply is to be performed. If there is a next supply instruction (S13: Yes), the process proceeds to S1.
Returning to 0 or S11, the above processing is repeated. If there is no next supply instruction (S13: No), the flow enters the standby state in S13, and the flow control ends in a state of waiting for the input of the supply instruction.

When the powder is supplied under the above control, the actual supply flow rate becomes as shown in FIG. That is, in the initial stage of powder supply, the target actual supply flow rate qT and the actual supply actual flow rate qD always become substantially equal. In addition, as in the first embodiment, the duty ratio at the start of supply is calculated from the calibration curve of FIG. 7A or FIG.
A duty ratio with respect to T is obtained, and powder supply is started at the duty ratio. Therefore, the rising response time T1 (<1) until the set actual supply flow rate qT is reached.
Only 1 sec) is required. Therefore, as shown in FIG. 12, it can be seen that the area of the hatched portion (the error with respect to the target supply amount) is small, and the powder is supplied with high accuracy at the beginning of the supply. After the actual supply flow reaches the target actual supply flow, the same control as in the first embodiment is performed in the feedback control area T, and the error of the instantaneous actual supply flow with respect to the target actual supply flow qT is obtained. It can be seen that the powder was supplied with high accuracy while keeping the temperature within ± 2%.

As described above, according to the powder feeder of the second embodiment, as in the case of the first embodiment, based on the calibration curve obtained from the feeder calibration performed before use, the target The duty ratio XT with respect to the actual supply flow rate qT is calculated, and the supply of the powder P is started at the duty ratio XT. Therefore, the actual supply flow rate instantaneously (within the time T1) from the start of the supply to the target actual supply flow rate qT. Reach. Therefore, the powder P can be supplied with high accuracy by controlling the actual flow rate, and the powder P can be supplied with high precision even in a short time supply within several seconds.

Further, based on the stable value of the actual supply flow rate in the feedback control region T in the previous supply, the calibration curve obtained from the feeder calibration is optimally corrected each time, and based on the corrected calibration curve after the correction. The duty ratio XT with respect to the target actual supply flow rate qT is calculated, and the supply of the powder P is started at the duty ratio XT, so that the target actual supply flow rate qT and the actual actual supply flow rate qD are always obtained.
Are approximately equal. Therefore, the error with respect to the target actual flow rate is always minimized, and the powder P can be supplied with higher accuracy.

Further, since the calibration curve is optimally corrected in each supply, if the feeder calibration is performed only before the powder feeder is used, the flow of the powder may vary depending on the properties of the powder and variations between lots. Even if the degree changes, it is not necessary to perform the feeder calibration every time, and the workability is improved.

In the above embodiment, a powder feeder using an ultrasonic motor using a piezoelectric element as a drive source has been exemplified. However, the control method of the present invention is not limited to this, and the control method is controlled by a duty ratio. It can be widely used as a method for controlling the rising operation of the actuator to be performed with high precision. For example, it can be used for an output control method of an ultrasonic processing machine such as an ultrasonic welder used for welding and processing plastics.

[0054]

As described above, according to the powder feeder of the present invention, the actual supply of each powder per unit time for two or more duty ratios is performed by the feeder calibration performed before the use of the powder feeder. The flow rate is obtained, a calibration curve is obtained by linearly interpolating the value, and when a target actual supply flow rate is set, a duty ratio for the actual supply flow rate is calculated from the calibration curve, and the vibrating body is calculated based on the duty ratio. To start the supply of the powder, and after the actual supply flow rate of the powder reaches the target value, the output value from the load cell is fed back to the duty ratio control means. Instant (1s
Within ec), the target actual supply flow rate is reached. Therefore, it is possible to supply the powder by controlling the actual flow rate with high accuracy from the initial stage of the supply, and to supply the powder with high accuracy in a short time supply within several seconds.

Further, by optimally correcting the calibration curve in each supply, it is possible to supply the powder while controlling the actual flow rate with high precision from the beginning of the supply. Powder can be supplied with higher precision. In addition, if the feeder calibration is performed only before using the powder feeder, even if the fluidity of the powder changes due to the properties of the powder or variations between lots, it is not necessary to perform the feeder calibration every time. , Workability is improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway sectional view showing a structure of a powder feeder according to a first embodiment.

FIG. 2 is a graph showing a frequency characteristic of an input impedance of a vibrating body.

FIG. 3 is a schematic diagram showing a state of vibration at the time of resonance of a vibrating body.

FIG. 4 is a schematic diagram showing a state of vibration at the time of resonance of a vibrating body for each quarter cycle.

FIG. 5 is a block diagram showing a powder feeder system.

FIG. 6 is a flowchart of feeder calibration.

FIG. 7 is a calibration curve showing a relationship between an actual supply flow rate and a duty ratio obtained by feeder calibration.

FIG. 8 is a weight calibration line showing a relationship between an output value (voltage value) of a load cell and a weight value.

FIG. 9 is an explanatory diagram showing a powder supply pattern.

FIGS. 10A and 10B are explanatory diagrams showing flow rate control in the powder feeder according to the first embodiment. FIG. 10A shows that the duty ratio at the start of supply is larger than the original duty ratio with respect to the target actual supply flow rate. (B) shows the case where the duty ratio of the supply start is smaller than the original duty ratio with respect to the target actual supply flow rate,
(C) shows a case where the supply start duty ratio is equal to the original duty ratio with respect to the target actual supply flow rate.

FIG. 11 shows a flowchart of a correction process of a calibration curve in the flow rate control of the powder feeder according to the second embodiment.

FIG. 12 is an explanatory diagram showing flow rate control in a powder feeder according to a second embodiment.

FIG. 13 is an explanatory diagram showing flow rate control in a conventional powder feeder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2a Metal horn 2b Back horn 2c Tip 2d Through hole 3 Bolt 4 Fixing member 20,21 Powder supply pipe 30 Hopper body 31 Bottom 32 Tube P Powder qT Target actual flow rate T Feedback control area

Claims (4)

[Claims] 1. A vibrating body whose tip portion performs an elliptical vibration when a predetermined resonance frequency is applied to a piezoelectric element; a powder conveying path formed at a tip portion of the vibrating body; A hopper for feeding powder to the body transport path; a duty ratio control means for giving a resonance frequency to the vibrator for a time corresponding to the duty ratio; and a load sensor for sequentially measuring a weight loss value of the powder in the hopper. A load cell comprising: a load cell; and a feeder calibration performed before use of the powder feeder, to determine an actual supply flow rate of each powder per unit time for a duty ratio of two or more points. A feeder calibration storage means for linearly interpolating the value to obtain and store a calibration curve; and when a target actual supply flow is set, a data for the actual supply flow is stored. Duty ratio calculating means for calculating a duty ratio from the calibration curve, and driving the vibrating body based on the duty ratio,
Starting the supply of the powder, after the actual supply flow rate of the powder reaches the target value, the feedback means for feeding back the output value from the load cell to the duty ratio control means, Feeder control device. 2. A vibrator whose tip portion performs an elliptical vibration when a predetermined resonance frequency is applied to a piezoelectric element, a powder conveying path formed at a tip portion of the vibrator, and a device for storing powder, A hopper for feeding powder to the body transport path; a duty ratio control means for giving a resonance frequency to the vibrator for a time corresponding to the duty ratio; and a load sensor for sequentially measuring a weight loss value of the powder in the hopper. A load cell comprising: a load cell; and a feeder calibration performed before use of the powder feeder, to determine an actual supply flow rate of each powder per unit time for a duty ratio of two or more points. Feeder calibration storage means for linearly interpolating the value to obtain and store a calibration curve; and a stable value of the actual supply flow rate of the powder in the feedback control area and its value. Learning storage means for storing a duty ratio with respect to a stable value; a correction coefficient for calculating a correction coefficient by comparing the duty ratio stored in the learning storage means with the duty ratio stored in the feeder calibration storage means. Calculating means; correcting the calibration curve with the correction coefficient each time, storing the corrected correction curve in the learning storage means, and calculating the duty ratio with respect to the target actual supply flow rate from the corrected calibration curve; and the duty ratio. Driving the vibrating body based on
Starting the supply of the powder, after the actual supply flow rate of the powder reaches the target value, the feedback means for feeding back the output value from the load cell to the duty ratio control means, Feeder control device. 3. A vibrating body whose tip portion performs an elliptical vibration when a predetermined resonance frequency is applied to the piezoelectric element, a powder conveying path formed at a tip portion of the vibrating body, a powder storage device, and a powder storage device. A hopper for feeding powder to the body transport path; a duty ratio control means for giving a resonance frequency to the vibrator for a time corresponding to the duty ratio; and a load sensor for sequentially measuring a weight loss value of the powder in the hopper. A powder feeder comprising: a load cell according to claim 1; and the control device for a powder feeder according to claim 1. 4. A vibrating body whose tip portion performs an elliptical vibration when a predetermined resonance frequency is applied to the piezoelectric element, a powder conveying path formed at a tip portion of the vibrating body, a powder storage device, and a powder storage device. A hopper for feeding powder to the body transport path; a duty ratio control means for giving a resonance frequency to the vibrator for a time corresponding to the duty ratio; and a load sensor for sequentially measuring a weight loss value of the powder in the hopper. A powder feeder, comprising: a load cell (1); and the powder feeder control device (1) according to claim 2.