JP4184213B2 - Ion generation amount control method and ionizer - Google Patents

Description

  The present invention relates to an ionizer used in a static eliminator and the like, and in particular, adjusts the positive / negative ion balance around a static elimination object affected by temperature and humidity, thereby reducing the potential of the static elimination object as much as possible. The present invention relates to an ion generation amount control method for controlling the generation amount of positive and negative ions to be blown, and an ionizer using this control method.

  Electrostatic discharge (ESD) causes various obstacles in the manufacturing process and mounting process of precision electronic devices. With the miniaturization of semiconductor circuits, the permissible charge amount is reduced, and even with a slight charge, the silicon circuit and the oxide insulating layer are destroyed by ESD. Another problem is that the adhesion of dust is promoted by charging. In order to achieve high integration of semiconductor circuits, antistatic measures are indispensable. Generally, positive and negative ions generated by a discharge device are sprayed onto a static elimination object by a gas jet to neutralize the charge. Yes. Such a device is called a static elimination device or an ionizer for static elimination (hereinafter referred to as an ionizer).

  Many of these ionizers generate a corona discharge localized at the tip by applying a high voltage to the discharge electrode. These ionizers generate positive and negative bipolar ions, so that an AC voltage is applied to the discharge electrode, a positive or negative DC voltage is applied to each of the electrodes, and the same discharge electrode is pulsed. There are various types such as one in which positive and negative voltages are alternately applied. In either case, if there is an imbalance in the amount of positive and negative ions sprayed by the ionizer, there is a problem that even if the charge is once removed, it is charged by excessive ions. For this reason, various proposals have conventionally been made for means for ensuring the ion balance of the ionizer and means for ensuring the neutrality of the charge of the object to be neutralized.

  For example, a current detection electrode grounded via an ammeter is placed in the space near the discharge electrode, and the positive and negative currents flowing through this current detection electrode can be used to balance the positive and negative ions in the gas near the discharge electrode. Many methods for detecting and adjusting either positive or negative discharge voltage (or discharge time) have been proposed (Patent Document 1 below).

In the case of an AC ionizer, a vibration type surface potential sensor is arranged in the ionized air flow, and the counter electrode (discharge) is set so that the detected value of the charged potential of the surface potential sensor is within a predetermined range. There has been proposed a method for securing an ion balance by controlling a DC voltage applied from an electrode to a counter electrode where corona discharge is performed (Patent Document 2).
In addition, a surface potential meter that continuously measures the surface potential of the object to be discharged and an arithmetic processing means that calculates a voltage applied to the discharge electrode in accordance with the surface potential are fed back and the measurement result of the surface potential meter is fed back A method for controlling the discharge voltage has been proposed (Patent Document 3).

JP-A-3-266398 Japanese Patent Application Laid-Open No. 6-209933 Japanese Patent Laid-Open No. 11-345697

  In recent years, ultra-miniaturization and diversification of electronic devices have progressed without knowing a limit. Along with this, the demand for antistatics has become increasingly severe. For this reason, when discharging an air stream containing positive and negative ions, it is necessary to minimize the residual potential due to the unbalance of positive and negative ions near the spray point, and the level of control required for ionizer ion balance control accuracy is increasing. It has become.

  All of the conventional ion balance control methods as described above have advantages and disadvantages, and it cannot be said that they sufficiently satisfy the above-described demand for advanced ion balance control. For example, in the method as described in Patent Document 1, even if the ion balance near the current detection electrode (and therefore near the discharge electrode) is taken, positive and negative ions are applied before the ions are placed on the air current and sprayed on the static elimination object. There is a decrease in each amount, and there is no guarantee that the ion balance is in the vicinity of the spray point.

  According to the findings of the present inventors, it cannot be said that the decrease in the amount of positive and negative ions necessarily occurs at the same rate, and may be preceded by the decrease in the amount of either one of the ions such as the temperature and humidity of the atmosphere. Depending on the complexity. Therefore, in the method as described above, even if the ion balance near the discharge electrode is accurately controlled, a positive or negative potential exceeding the allowable range may remain in the static elimination object. The same applies to the method as disclosed in Patent Document 2, and the residual potential of the static elimination object is within the allowable range even though the ion balance can be controlled at the position of the surface potential sensor arranged in the air flow. There is no guarantee that

  On the other hand, the method as described in Patent Document 3 can be said to be a more direct control method in terms of measuring the surface potential of the static elimination object. However, when processing various types of static elimination objects, it is often difficult to measure the surface potential. Also, when the static elimination object is large or when multiple objects are subjected to static elimination treatment at the same time, the surface potential of the object may vary greatly depending on the part, and how to obtain the average value of the surface potential The issue is whether to perform control.

Accordingly, the present invention grasps the influence of atmospheric conditions such as temperature and humidity on the decrease in the amount of generated positive and negative ions in an ionizer that discharges positive and negative ions generated by corona discharge to an object to be neutralized by an air flow. On the other hand, two ion sensors are provided between the discharge electrode and the object to be neutralized, and the voltage applied to the discharge electrode so that the potential of the object to be neutralized approaches zero due to the ground potential of the two ion sensors. It is an object to provide a method for controlling and controlling the amount of ions generated.

To solve the above problems, the present invention is, in a direction positive and / or negative ion discharge electrodes occurs is blown, provided the two ion sensors at intervals of a distance X, the ground of the two ion sensors A potential difference per unit length (hereinafter referred to as potential gradient V _d ) is obtained from the charging potential and the distance X, and the ground charging potential V of the ion sensor on the downstream side of the blower and the desired point in the downstream direction of the blower from the ion sensor. The potential V _o at the desired point is obtained from the distance Y and the potential gradient V _d , the voltage applied to the discharge electrode is controlled so that the potential V _o approaches zero potential, and the amount of ions generated is determined. It is characterized by controlling.

The two ion sensors are rod-shaped conductors provided at a substantially right angle to the blowing direction and separated from each other by a predetermined horizontal distance , and the ground potential is provided between the two ion sensors and the ground. It is preferable that the potential be generated in the resistor . This sensor is charged by ions sent from the discharge electrode, whereby a current flows and a voltage is induced.

The ionizer according to the present invention includes a discharge means including a discharge electrode for generating positive and / or negative ions, an ion generation amount control means for controlling the amount of positive and / or negative ions generated by the discharge means, and the discharge means. Air blowing means for transporting ions generated by the air current, two ion sensors arranged at different distances from the discharge electrode at a distance X, and a ground potential of the two ion sensors , said distance X and obtains the potential gradient V _d from the the ground charge potential V of the ion sensor of the air downstream side, the distance Y from the ion sensor to a desired point of the air downstream direction, and the potential gradient V _d , Means for obtaining the potential V _o at the desired point, and means for adjusting the ion generation amount control means so that the potential V _o approaches zero potential .

In the above ionizer, it is preferable that a resistance is provided between the two ion sensors and the ground, and a means for calculating the ground charging potential from a potential generated in the resistance is provided. Moreover, it is preferable that the two ion sensors are arranged on approximately the same stream line of the airflow in which the generated ions are blown. Further, the discharge means may apply an AC voltage to the discharge electrode. Furthermore, a certain level of bias DC voltage may be applied to the discharge electrode in addition to the AC voltage, and the ion generation amount control means may control the level of the bias DC voltage. Further, it is preferable that a pulsed DC voltage is applied to the discharge electrode, and the ion generation amount control means controls the pulse width and application cycle of the DC voltage, or the applied voltage.
The ion balance control method according to the present invention controls the ion balance by adjusting the amount of positive and / or negative ions generated by corona discharge by applying a high voltage to the discharge electrode by controlling the value of the high voltage. In the method, two ion sensors are arranged at an interval of a distance X in the air flow in which the ions are blown, and a potential gradient V is calculated from the ground charging potential of these ion sensors and the distance X. seek _d, and ground the charge potential V of the ion sensor of the air downstream side, the distance Y from the ion sensor to a desired point of the air downstream from said potential gradient V _d, the potential V _o of the desired location determined, wherein the potential V _o to regulate the high voltage to approach zero potential. The ground charging potential is preferably a potential generated in a resistor provided between the two ion sensors and the ground.

  Since this invention is comprised as mentioned above, it can control so that the amount of positive / negative ions in the airflow in the arbitrary positions of the downstream of airflow may become substantially the same. As a result, it is possible to reliably prevent unbalance of positive and negative charges from occurring in the static elimination object. In other words, in the conventional control method for detecting the ion balance in the vicinity of the discharge electrode or only in one location in the airflow, even if the ion balance in the measurement location can be controlled, the rate of decrease of positive and negative ions in the airflow flow process is reduced. Since a difference arises, the amount of positive and negative ions at the position of the static elimination object may become unbalanced.

According to the present invention, on the other hand, since information corresponding to a reduction rate of deviation of the positive and negative ions in the two airflow streams process by ion sensor is obtained, extrapolating the measured values of the two ion sensors By controlling the amount of positive and negative ions generated at the discharge electrode so that the amount of positive and negative ions at this position can be approximately the same, the ion balance at the position of the static elimination object can be estimated. The residual potential of the static elimination object can be brought close to zero with significantly high accuracy.

  According to the present invention, taking into account the amount of positive and negative ions generated at the discharge electrode and 2) the amount of decrease in the amount of positive and negative ions until reaching the object to be neutralized, which varies depending on atmospheric conditions such as temperature and humidity, The amount of positive and negative ions generated can be controlled so that the amount of positive and negative ions sprayed on the object is minimized. According to the present invention, it is possible to stably bring the potential of the static elimination object close to zero level regardless of the atmospheric conditions.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples. FIG. 1 is a schematic cross-sectional view of an ionizer that is an embodiment of the present invention. This ionizer causes corona discharge by a large number of electrodes arranged in parallel in a direction perpendicular to the paper surface, and blows an air stream containing positive and negative ions to the static elimination object. FIG. 1 shows a vertical cross section near the center of a rectangular ionizer body. This apparatus includes an ionizer body 1, an ion sensor 2, a power supply circuit and a control circuit (not shown), and the like. The ionizer body 1 includes a discharge electrode 3, a grid 4 as a counter electrode, a blower fan 5 that forms an air flow, a filter 6, a duct 7 that forms an air flow channel, and the like.

  FIG. 2 is an explanatory view showing the structure of the ionizer body and the ion sensor in an exploded manner. Many acicular discharge electrodes 3 are attached to an electrode attachment member 8 made of an insulating material at substantially equal intervals in the horizontal direction. The ionizer of the present embodiment applies an alternating high voltage to the discharge electrode 3, and one end on the secondary side of the transformer 9 is connected to each discharge electrode 3 via a conducting wire 10 that conducts the center of the insulating member 8. Yes. Commercial power AC power is supplied to the primary side of the transformer 9.

  In general, in AC corona discharge, there is often a bias in the amount of positive and negative ions generated. Therefore, a method of correcting this bias by applying a DC bias voltage to the AC is taken. In this embodiment, the grid 4 that is the counter electrode is grounded, and the other terminal (on the side that is not connected to the discharge electrode) of the transformer 8 is grounded via the DC bias power supply 11. . By making the voltage of the DC bias power supply 11 variable, the positive and negative levels of the AC voltage applied to the discharge electrode 3 with respect to the ground potential can be made variable, thereby adjusting the amount of positive and negative ions generated. it can.

  In this ionizer, a horizontally long line flow fan is used in order to make the air flow uniform over the entire width of the duct 7. That is, the blower fan 5 has a horizontal rotating shaft attached with swirl vanes having a length that covers almost the entire width of the duct 7, and the air blowing port is also formed in the entire width of the duct. It is configured to reduce as much as possible the bias. In addition, a filter 6 is disposed at the air intake port of the blower fan 5 to clean the air flow to be neutralized. Further, the duct 7 is made of a conductive material and grounded so as not to be charged by corona discharge.

  The two ion sensors 2a and 2b are made of the same metal rod and are supported by a sensor support member 12 made of an insulating material so as to be substantially horizontal and perpendicular to the air flow. Further, the two sensors are arranged so as to be substantially parallel with being separated by a predetermined interval. Both sensors are grounded through a resistor 13, and ions in the air current collide to receive positive or negative charges, and a minute current flows to the ground. Therefore, a potential is applied to a point P before the resistor 13. Will occur. By amplifying this potential with the amplifier 14 and taking out it as a signal converted into the amount of ions, the amount of ions at two locations of the ion sensors 2a and 2b can be measured.

  The potential at the point P is proportional to the difference between the positive charge and the negative charge received by the ion sensor, but the voltage waveform is generally the same as the AC voltage applied to the discharge electrode. Therefore, integrating the voltage waveform at point P, interpreting that the integral value of the positive part is proportional to the amount of positive ions received by each ion sensor, and the integral value of the negative part is proportional to the amount of negative ions. You can also. The distance d between the two sensors does not need to be strictly limited, but is usually preferably about 1 to 5 cm.

  FIG. 3 is a diagram showing a power supply circuit and a control circuit of the ionizer of this embodiment. The voltage signals of the ion sensors 2a and 2b are amplified by the amplifiers 14a and 14b, respectively, converted into digital signals by the AD converters 15a and 15b, and input to the arithmetic circuit 16. The arithmetic circuit 16 outputs a control signal for controlling the bias voltage value of the DC bias power supply 11 based on a control logic as will be described later.

  AC power having a commercial frequency of 100 V is supplied to the primary side of the transformer 9, boosted to about 6 kV on the secondary side, and applied to the discharge electrode 3. As already described, one end of the secondary side of the transformer 9 is grounded via the DC bias power supply 11, and the bias voltage is changed in a range of about -100 to 350V by the control signal described above. As a result, the positive / negative voltage between the grid 4 of the counter electrode at the ground potential and the discharge electrode 3 changes, and the generation amount of positive / negative ions is controlled accordingly.

  FIG. 4 is an explanatory diagram showing the basic concept of the ion balance control method according to the present invention. As shown in the figure, the position of the discharge electrode 3 is point A, the positions of the upstream and downstream ion sensors 2a and 2b are point B and C, respectively, and the position of the charge removal object 17 is point D. Taking the case where the signal of the ion sensor 2a (potential at point P in FIG. 2) is positive as an example, the conventional control method determines that the ion balance is biased to the positive side only by this information, and negative ions Control was carried out to increase the amount of generation.

  On the other hand, in the present invention, since there are two measured values of the ion sensors 2a and 2b, it is possible to obtain not only the ion balance at the point B but also information regarding the change in the amount of ions between the BCs. For example, in the case A of FIG. 4, even if it is positively biased at the point B, the bias is small at the point C, and when this is extended to the point D, it is estimated that the potential is almost zero. That is, although the amount of positive ions is large at the position of the discharge electrode 3, and the rate of decrease is large, it is presumed that the position of the neutralization target 17 is almost in an ion balanced state, and positive and negative ions are generated. It is not necessary to perform control to change the amount.

  On the other hand, in case B, it is positively biased at point B, and at point C, it is equally positively biased. That is, the amount of positive ions is large at the position of the discharge electrode, and the rate of decrease of positive ions and negative ions is considered to be approximately the same. In this case, control is performed to increase the amount of negative ions generated. In case C, it is biased positively at point B, but it is close to zero potential at point C, and if it is extended as it is, it is assumed that it becomes negative potential at point D. That is, even if the amount of positive ions is large at the position of the discharge electrode, the rate of decrease of positive ions is significantly large, so it is rather necessary to increase the amount of positive ions generated.

  The above description describes the basic concept. Actually, the ion balance at the point D is measured by the method shown in the examples described later and information on the ion sensors at the points B and C. Based on the measured information or the like, data is accumulated and learning control or AI control is also introduced to perform optimal control. In any case, the decrease in the amount of positive ions and the amount of negative ions changes depending on the humidity and temperature of the atmosphere, so that the residual potential of the static elimination object can be accurately controlled only by the ion balance at the position of the discharge electrode. It was found that it was difficult. Actually, as shown in the examples described later, it was confirmed that the control accuracy of the latter is remarkably improved when the number of ion sensors is one or two.

  The ionizer of the present invention is not limited to the configuration of the apparatus of the above embodiment. For example, the voltage applied to the discharge electrode is not limited to alternating current but may be direct current. In the case of direct current, the positive electrode and the negative electrode may be separately used for corona discharge, or a positive potential and a negative potential may be alternately applied to one electrode in a pulse shape. In the case of DC, the means to control the amount of positive and negative ions generated is basically by changing the potential difference between the discharge electrode and the counter electrode, but the amount of ions generated can also be changed by changing the application time of the pulsed applied voltage. Can be controlled.

  Further, in this embodiment, the amount of positive and negative ions generated is controlled by changing the bias voltage applied to the secondary ground terminal of the transformer, but the bias voltage is applied to the grid as the counter electrode, The generation amount of positive and negative ions may be controlled by making this bias voltage variable. In the present invention, there are no particular limitations on the shape, material, mounting method and number of discharge electrodes. Further, the shape of the grid as the counter electrode, the positional relationship with the discharge electrode, etc. are not particularly limited.

  Further, the type of the ion sensor is not necessarily limited to that used in the present embodiment. For example, the ion detection electrode may be grounded via an ammeter and a minute current flowing through the ammeter may be measured. Alternatively, a charged body may be disposed in the air flow, and a means for receiving the positive and negative ions and measuring the charge generated on the surface with various surface potentiometers may be used. Furthermore, an ion sensor by a method (so-called Ebelt method) in which air containing positive and negative ions is sucked to neutralize charges of positively or negatively charged electrodes may be used. In the case of the Ebelt method, the amount of positive ions and the amount of negative ions can be measured independently. The ion sensor used in the present invention may be one that detects an imbalance in the balance between the positive ion amount and the negative ion amount, or may measure the positive ion amount and the negative ion amount independently.

By using an ionizer as shown in FIGS. 1 to 3, control was performed based on information of two ion sensors according to the present invention . As the discharge electrode, eight needle-like tungsten electrodes arranged at equal intervals in the horizontal direction were used, and an AC voltage of about 6 kV was applied at a commercial frequency (60 kHz) to cause corona discharge between the counter electrode grid. I did it. The flow rate of the air flow by the blower fan was about 4 m / sec at the ionizer outlet. Alternatively, the ionizer outlet cross-sectional area was about 62.1 cm ² and the air flow rate was about 0.31 / sec.

In this embodiment , a stainless steel (metal) round bar having a diameter of 3 mm and a length of 128 mm is used as the two ion sensors, the upstream sensor is separated from the grid by 27 mm, and the downstream sensor is separated by 37 mm. It arrange | positioned so that it might become a right angle with this at the approximate center. The control of the ion balance is performed using the control circuit shown in FIG. 3, and based on the basic principle as described above, automatic control of the AC voltage is performed based on the difference information from the two ion sensors (empirical accumulated data). AI control was taken into consideration).

The evaluation of the ion balance, downstream of the sensor using a charge plate monitor commercially available for the purpose of performance evaluation of ionizers (MONROE ELECTRIC Co. Model288), the charge plate of 0.99 × 150 mm square, ion sensor (in this example - ) Was placed 30 cm away from the center of the air flow at a right angle to the center, and the potential of this plate was continuously measured to obtain the average ion balance. At the same time, the temperature and humidity of the atmosphere were also measured with this measuring device. The measurement result of this example is shown in FIG. In addition, although the display scale of ion balance is a relative value and does not have a unit, it indicates that the ion balance is good at zero level.

As shown in FIG. 5a, it can be seen that the fluctuation of the ion balance is greatly reduced by only a slight fluctuation around the zero level. It was confirmed that the effect of the present invention was great in keeping the ion balance around the static elimination object near zero level and reducing the residual potential.

It is a cross-sectional schematic diagram of the ionizer which is an Example of this invention. It is explanatory drawing which decomposed | disassembled and showed the structure of the ionizer main body and ion sensor of a present Example. It is a figure which shows the power supply circuit and control circuit of the ionizer of a present Example. It is explanatory drawing which shows the fundamental view of the control method of the ion balance in this invention. It is a figure which shows the measurement result of the ion balance in the example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ionizer main body 2, 2a, 2b Ion sensor 3 Discharge electrode 4 Grid 5 Blower fan 6 Filter 7 Duct 8 Electrode attachment member 9 Transformer 10 Conducting wire 11 DC bias power supply 12 Sensor support member 13 Resistance 14, 14a, 14b Amplifier 15a, 15b A / D converter 16 arithmetic circuit 17 static elimination object

Claims (10)

Two ion sensors are provided at intervals of a distance X in the direction in which positive and / or negative ions generated by the discharge electrode are blown, and a unit length is obtained from the ground charging potential of the two ion sensors and the distance X. A potential difference (hereinafter, potential gradient V _d )
A ground charging potential V of the ion sensor of the air downstream side, the distance Y from the ion sensor to a desired point of the air downstream from said potential gradient V _d, obtains the potential V _o in the desired location,
The potential V _o controls the voltage applied to the discharge electrode to approach zero potential, the ion generation amount control method characterized by controlling the amount of generated ions. The two ion sensors are rod-shaped conductors that are substantially perpendicular to the air blowing direction and separated from each other by a predetermined horizontal distance, and the ground potential is provided between the two ion sensors and the ground. The ion generation amount control method according to claim 1, wherein the potential is a potential generated in a resistor . A discharge means including a discharge electrode for generating positive and / or negative ions;
Ion generation amount control means for controlling the amount of positive and / or negative ions generated by the discharge means;
An air blowing means for conveying ions generated by the discharging means by an air current;
Two ion sensors arranged at a distance X from the discharge electrodes at different positions from each other;
A potential gradient _Vd is obtained from the ground charging potential of the two ion sensors and the distance X, and the ground charging potential V of the ion sensor on the downstream side of the air blowing and the desired point in the downstream direction of the air blowing from the ion sensor. a distance Y, from said potential gradient V _d, and means for determining the potential V _o in the desired location,
Ionizer, characterized in that the potential V _o has a means for adjusting the ion generation amount control means so as to approach the zero potential. 4. The ionizer according to claim 3, further comprising a resistor provided between the two ion sensors and the ground, and means for calculating the ground charging potential from a potential generated in the resistor. 5. The ionizer according to claim 4, wherein the two ion sensors are arranged on substantially the same stream line of an air flow through which generated ions are blown. 6. The ionizer according to claim 3, wherein the discharge means applies an AC voltage to the discharge electrode. 7. The bias DC voltage of a certain level is applied to the discharge electrode in addition to the AC voltage, and the ion generation amount control means controls the level of the bias DC voltage. Ionizer. 8. The pulsed DC voltage is applied to the discharge electrode, and the ion generation amount control means controls the pulse width and application cycle of the DC voltage, or the applied voltage. Ionizer. In the ion balance control method of adjusting the amount of positive and / or negative ions generated by corona discharge by applying a high voltage to the discharge electrode by controlling the value of the high voltage,
Two ion sensors are arranged at an interval of a distance X in the air flow in which the ions are blown, and a potential gradient V is obtained from the ground charging potential of these ion sensors and the distance X. _d Seeking
The ground charging potential V of the ion sensor on the downstream side of the blower, the distance Y from the ion sensor to a desired point in the blower downstream direction, and the potential gradient V _d From the potential V at the desired point. _o Seeking
The potential V _o The method of controlling ion balance, wherein the high voltage is adjusted so that the voltage approaches zero potential. 10. The ion balance control method according to claim 9, wherein the ground potential is a potential generated in a resistance provided between the two ion sensors and ground.

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