JP4191173B2 - Sterilization operation method and sterilization apparatus. - Google Patents

Description

  The present invention relates to a sterilization operation method and a sterilization apparatus when sterilizing using a flash lamp, and can be used for sterilizing foods, lunch boxes, food trays, food bats and the like.

As a non-heating sterilization method for food containers, daily necessities, medical / care products, etc., a method of spraying a disinfectant is widely used. For example, in a lunch center, in order to prevent food corruption and prevent food poisoning, a lunch box is sprayed with a disinfectant and the lunch box is placed in the sterilized tray container.
However, the disinfection method using the disinfectant has a problem that the disinfectant is affected by the human body and the operation cost is considerably high.
As a non-heating type sterilization method, a method of irradiating radiation light of a low-pressure mercury lamp (sterilization lamp) is also known. This is a method for preventing bacterial growth by damaging bacterial DNA by ultraviolet irradiation, and irradiates light having a dominant wavelength of 254 nm. On the other hand, the flash of the xenon flash lamp has a wavelength distribution from 200 nm to 2000 nm and includes an abundant ultraviolet wavelength range of 220 nm to 300 nm as shown in FIG.
Xenon flash lamps have higher illuminance than germicidal lamps, and recently, conversion from germicidal lamps to xenon flash lamps has been attempted.

According to the result of earnest study by the present inventor, food can be sterilized with a power supply energy per flash pulse of the flash lamp of 0.5 J to 25 J, 30 to 120 flash pulses per second, and in an open system. Even if the irradiation is performed, the amount of ultraviolet rays exposed to the worker can be suppressed to the permissible value of JIS sterilized processed material 8812-1987 (30 J / m ² or less at a wavelength of 270 nm), and the influence on the human body can be eliminated.

In addition to sterilization, xenon flash lamps are also used for heat fixing of toner images and heat treatment of semiconductor wafer surface films in copiers, printers, facsimiles, etc., but these use the infrared region of xenon flash. is there.
As an apparatus used for fixing a toner image such as a printer, “to charge and discharge two xenon flash lamps to fix a toner image formed on recording paper by irradiating flash pulses from two xenon flash lamps” It is proposed that “the drive circuit is shared by one” (Patent Document 1).
JP 2000-47517 A

  4 (a) is a flash pulse generation circuit described in Patent Document 1, and FIG. 4 (b) is a trigger pulse and a capacitor voltage during charging / discharging, and the operation of the flash pulse generation circuit is explained using these. Then, the flash lamp 12a is discharged by the trigger pulse (b) to generate a flash pulse at the time interval T, and the flash lamp 12b is discharged by the trigger pulse (c) to generate a flash pulse at the time interval T. The trigger pulse (c) is shifted by the time T / 2 with respect to the trigger pulse (b), and charging / discharging of the capacitor 19 is repeated every time the flash lamps 12a and 12b are flashed. In this case, ta ≦ T / 2 is satisfied with respect to time ta when the capacitor voltage reaches the dischargeable voltage of the flash lamp.

The flash lamps 12a and 12b generate flash light having the radiation spectrum distribution shown in FIG. 3 by discharge of xenon gas.
The illuminance of this spectral distribution decreases as the cumulative number of flash pulses increases. For example, the supply power energy 1J per flash pulse and the flash pulse number 60 (60 Hz) per second. Between the relative irradiance S% and the cumulative number N of flash pulses,
S = 100-1.4 × 10 ⁻⁷ N
There is a relationship.
As the trigger pulse switches SW ₃ and SW ₄ in FIG. 4A, thyristors are usually used, and a gate pulse of a shift time T / 2 is applied to both thyristors at a time interval T, and each flash lamp 12a, The accumulated flash pulse number 12b is obtained by accumulating the gate pulse of the thyristor, and when this accumulated number reaches a limit value (for example, the accumulated number in which the relative irradiance S decreases to 80%), both flash lamps 12a. , 12b are replaced.

  In order to perform sterilization by irradiating flash light pulses, it is necessary to irradiate flash light from both the upper side and back side of the object to be sterilized, and it is usually required to install flash lamps above and below the object to be sterilized. Is done. In this case, if the sterilization device is a light shielding case type or a roll conveyor type, the interval between the object to be sterilized and the lower flash lamp must be shorter than the interval between the object to be sterilized and the upper flash lamp ( The height of the upper flash lamp must be increased so that the height of the object to be sterilized varies, and it can be adapted to any height), as shown in FIG. When two flash lamps 12a and 12b sharing the discharge capacitor 19 are used, both flash lamps generate flash pulses of the same energy and frequency, so that the back side illuminance is higher than the top side illuminance of the object to be sterilized. Since both the flash lamps 12a and 12b are replaced with the same limit cumulative flash pulse number as described above, the lower flash lamp has the side to be sterilized. Capacity despite remains considerably, so that the replacement of the flash lamp is performed.

This can also be explained as follows.
When the supply power energy per flash pulse is E, the distance from one flash lamp to the irradiation surface is r, and the relative irradiance with respect to the cumulative flash pulse number N is 100-kN as described above, the article to be sterilized The illuminance X is X = AE (100-kN) / (2πr)
(A is a constant).
When the critical illuminance on sterilization and X _0, the limit cumulative flash pulse number of articles N ₀ is
N ₀ = [100− (2πr · X ₀ / AE)] / k
Can be expressed as
The limit cumulative flash pulse number of articles N _{0 "for} the lower flash lamp and limits cumulative flash pulse number of articles N _{0 'relative} to the upper flash lamp, the distance r to the sterilization product is different for different from the flash lamp, the lower The limit cumulative flash pulse number N ₀ ″ for the side flash lamp is larger than the limit cumulative flash pulse number N ₀ ′ for the upper flash lamp. However, in the operation method of the flash lamp as described in Patent Document 1, both The number of accumulated flash pulses for the flash lamp cannot be grasped individually, it is impossible to grasp the individual sterilization remaining capacity of both flash lamps and replace both flash lamps individually, and sufficient sterilization remaining in the lower flash lamp Despite being capable, the lower flashlamp was replaced with the upper flashlamp. It will be.

  An object of the present invention is to arrange a xenon flash lamp above and below the object to be sterilized, share a charge / discharge capacitor for both flash lamps, and shift the trigger pulse of the same frequency in time to shift these lamps. When the flash lamp is applied to the flash lamp to generate a flash pulse, and the flash light pulse is irradiated to the object to be sterilized, the flash lamp is replaced from the sterilization limit based on the accumulated flash pulse generated by each flash lamp. However, it is to be able to replace the flash lamp after it has been used up effectively.

The sterilization operation method according to claim 1 is provided with a flash lamp that irradiates a flash pulse from the upper side to an object to be sterilized, and the lower flash lamp that similarly irradiates a flash pulse from the lower side with the flash lamp and the sterilization process. A trigger pulse having a frequency f that is shifted in time by arranging the flash lamp at a distance shorter than that of the upper flash lamp and connecting both flash lamps in parallel to a common charge / discharge capacitor. Is added to both flash lamps to generate a flash pulse of frequency f in each flash lamp, the cumulative number of trigger pulses in each flash lamp is counted, and the lower flash is compared with the cumulative limit number of trigger pulses in the upper flash lamp. Set the lamp usage limit cumulative trigger pulse to a large number and replace both flash lamps with new ones. And wherein the Ukoto.
The sterilization apparatus according to claim 2 includes an upper flash lamp connected in parallel and a charge / discharge capacitor connected in parallel to the lower flash lamp, and an individual trigger pulse generating circuit for applying a trigger pulse to each of the flash lamps. A separate counter for counting the cumulative number of each trigger pulse is provided.
The sterilization apparatus according to claim 3 is the sterilization apparatus according to claim 2, wherein the upper flash lamp is provided in the middle upper part of the roll conveyor, the lower flash lamp is provided in the middle lower part of the roll conveyor, the lower flash lamp and the roll. The distance from the conveyor surface is shorter than the distance between the upper flash lamp and the roll conveyor surface.
The sterilizer according to claim 4 is the sterilizer according to claim 2, wherein a lattice shelf is provided in the light shielding case, an upper flash lamp is provided above the lattice shelf, and a lower flash lamp is provided below the lattice shelf. The distance between the lower flash lamp and the lattice shelf is shorter than the distance between the upper flash lamp and the lattice shelf.
The sterilization operation method according to claim 5 is characterized in that, in the sterilization operation method of claim 1, a preliminary flash lamp is installed, and the old flash lamp is automatically switched to the preliminary flash lamp.
The sterilization apparatus according to claim 6 is the sterilization apparatus according to any one of claims 2 to 4, comprising a preliminary flash lamp for the upper flash lamp and a preliminary flash lamp for the lower flash lamp, and the cumulative number of trigger pulses is the use limit trigger pulse. It is characterized in that a change-over switch that automatically detects the cumulative number and switches to the preliminary flash lamp is provided.
The sterilization operation method according to claim 7 is the sterilization operation method according to claim 1 or 5, wherein the supplied power energy per one flash pulse of the flash lamp is 0.5 J to 25 J, and the number of flash pulses per second is 30. It is characterized by being -120 pieces.
The sterilizing apparatus according to an eighth aspect is the sterilizing apparatus according to any one of the second to fourth and sixth aspects, wherein the flash lamp is a xenon flash lamp.

Assuming that the power supply energy per flash pulse is E, the distance from one flash lamp to the irradiation surface is r, and the relative irradiance with respect to the cumulative flash pulse number N is 100-kN, the illuminance X of the object to be sterilized is X = AE (100−kN) / (2πr)
(A is a constant), and the limit illuminance on sterilization is X ₀ , the limit cumulative flash pulse number N ₀ is
N ₀ = [100− (2πr · X ₀ / AE)] / k
Can be expressed as
The limit cumulative flash pulse number of articles N _{0 "for} the lower flash lamp and limits cumulative flash pulse number of articles N _{0 'relative} to the upper flash lamp, the distance r to the sterilization product is different for different from the flash lamp, the lower The limit cumulative flash pulse number N ₀ ″ for the side flash lamp is larger than the limit cumulative flash pulse number N ₀ ′ for the upper flash lamp.
In the present invention, since the cumulative number of trigger pulses of the upper flash lamp and the cumulative number of trigger pulses of the lower flash lamp can be individually counted, the cumulative number of flash pulses of the upper flash lamp and the cumulative flash of the lower flash lamp can be counted. a pulse number of articles can be grasped individually, their cumulative flash pulse number of articles has become marginal cumulative flash pulse number of articles N _{0 "for} limiting the accumulated flash pulse number of articles N _{0 'or} the lower flash lamp relative to the upper flash lamp Sometimes you can replace the flash lamp.
Therefore, the lower flash lamp can be replaced after its sterilization residual capacity is exhausted.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1-1 (a) is a cross-sectional view showing an example of a sterilizer used in the present invention, and (b) in FIG. 1-1 is a cross-sectional view in FIG. 1-1 (b). .
In FIG. 1, reference numeral 2 denotes a light shielding case, for example, a steel case or an aluminum case, and the front wall is freely opened and closed by a lower end hinge support lid 21. Reference numeral 3 denotes a lattice shelf provided in the case 2 and can be constituted by a quartz bar, a metal bar or the like. M is an object to be sterilized placed on the lattice shelf 3. 1a is an upper xenon flash lamp, 1b is a lower xenon flash lamp, and a distance rb between the lower xenon flash lamp 1b and the lattice shelf 3 is shorter than a distance ra between the upper xenon flash lamp 1a and the lattice shelf 3. (The object to be sterilized is usually not a flat surface, and the distance between the surface to be sterilized and the flash lamp is substantially equal to the distance between the conveyor surface and the flash lamp in consideration of the lunch box bottom wall of the lunch box, for example. ). These xenon flash lamps 1a and 1b can be operated by the drive circuit shown in FIG.

1-2 (a) is a longitudinal sectional view showing an example of a sterilizing apparatus used in the present invention, and (b) in FIG. 1-2 is a cross-sectional view in FIG. 1-2 (b). .
1-2, 4 is a gantry, 5 is a roll conveyor provided on the gantry 4, 6 is an irradiation chamber provided in the middle upper part of the roll conveyor 5, and light-shielding curtains 61 and 62 are attached to the entrance and the exit. . 1a is an upper xenon flash lamp provided on the upper side in the light shielding chamber 6, and 1b is a lower xenon flash lamp provided on the lower side of the roll conveyor 5 at the same position as the upper xenon flash lamp 1a. lamp 1b and the distance r _b is shorter than the distance r _a between the upper xenon flash lamp 1a and the roll conveyor surface 5 (the sterilization of the roll conveyor surface 5 is not a normal flat surface, for example, lunch box lunch In consideration of the box bottom wall, the distance between the surface to be sterilized and the flash lamp is substantially equal to the distance between the shelf surface and the flash lamp). These xenon flash lamps 1a and 1b can be operated by the drive circuit shown in FIG.

1-3 shows an example of a flash lamp driving circuit used in the present invention, where C is a main charging / discharging capacitor, 1a is an upper flash lamp, 1b is a lower flash lamp, C _t is a trigger capacitor, T _ta (T _tb ) is a trigger step-up transformer, and SCR _a (SCR _b ) is a thyristor that is turned on by a gate pulse P _Ga (P _Gb ). K _a (K _b ) is a trigger pulse counter.

1-4, (a) to (e) show the output waveforms of the respective parts used to explain the operating state of the flash lamp driving circuit.
In the circuit of FIG. 1-3, the thyristor SCR _a (SCR _b ) is turned on by the gate pulse P _Ga (P _Gb ) to discharge the charging voltage of the trigger capacitor C _t , and the trigger step-up transformer T _ta (T A trigger pulse P _Ta (P _Tb ) boosted (about 5 to 20 kv) is generated on the secondary side of _tb ).
At this time, the xenon flash lamp 1a (1b) to which the charging voltage of the main charging / discharging capacitor C is applied generates an arc by applying the trigger pulse P _Ta (P _Tb ), and the main charging / discharging is generated by this arc generation. The voltage of the capacitor C drops, the arc is stopped, and the main charge / discharge capacitor C is charged again. Therefore, the voltage Vc of the main charging / discharging capacitor C has a waveform with a cycle in which both trigger pulses P _Ta and P _Tb are overlapped, as shown in FIG.

In the above, since the supplied power energy per one flash pulse of the upper flash lamp 1a and the lower flash lamp 1b is equal and the number of flash pulses per second is equal, the radiation of the upper flash lamp 1a and the lower flash lamp 1b. The energy is equal.
Assuming that the distance between the flash lamp and the object to be sterilized is r and there is no influence of reflection or the like, since the flash lamp is a linear light source, the illuminance on the surface of the object to be sterilized is inversely proportional to 2πr.
The而Ru, structural distance r _b sterilization apparatus and the back surface of said the lower flash lamp 1b be sterilized product M, than the distance r _a between the upper flash lamp 1a and the upper surface of the object to be sterilized product M Since it is shortened, the irradiation illuminance on the back surface of the object to be sterilized becomes higher than the irradiation illuminance on the upper surface of the flash lamp.
In the flash lamp, the radiation ability is reduced over time due to fogging of the glass tube, deterioration of the discharge electrode, etc., and the radiation ability S (%) is N, where N is the cumulative number of flash pulses.
S = 100-kN
For example, when the supplied power energy per flash pulse is 1 J and the flash pulse frequency (trigger pulse frequency) is 60 Hz,
S = 100-1.4 × 10 ⁻⁷ N
Given in.

In order to perform sterilization according to the present invention, in the case of the roll conveyor type shown in FIG. 1-2, when the object to be sterilized M enters the irradiation chamber 6, the power switch SW of the drive circuit shown in FIG. The power switch SW is turned off when exiting the irradiation chamber 6, and in the case of the light shielding case type shown in FIG. 1-1, the power switch SW is operated as a timer, and is described with reference to FIG. As described above, the upper flash lamp 1a and the lower flash lamp 1b are flashed to sterilize the object to be sterilized.
During this time, the flash pulse cumulative number of articles of the upper flash lamp 1a counted by a counter K _a, will the flash pulse cumulative number of articles in the lower flash lamp 1b counted by a counter K _b.
The initial irradiance of the upper flash lamp 1a _{S a, t = 0,} when the sterilizing limit irradiance and _{S 0,} the limit cumulative flash pulse number of articles _{N a} of the upper flash lamp 1a N _a = [1- _(S 0 / _{Sa, t = 0} )] 100 / k
For example, the sterilization limit irradiation illuminance S _{0 is set} to 80% of the initial irradiation illuminance S _{a, t = 0} , and k is 1.4 × 10 ⁻⁷ (supplied power energy per flash pulse is 1 J, flash pulse When the frequency is 60 Hz), Na = 1.43 × 10 ⁸ , and when the count value of the counter Ka becomes 1.43 × 10 ⁸ , the upper flash lamp 1a is replaced with a new flash lamp, and the counter K _The sterilization process is continued after resetting _a to 0.

As described above, since the distance r _b between the lower flash lamp 1b and the object to be sterilized treated back surface is smaller than a distance r _a between the upper flash lamp 1a and the object to be sterilized was top, the lower flash The initial irradiation illuminance S _{b, t = 0} on the rear surface of the object to be sterilized by the lamp 1b is higher than the initial irradiation illuminance S _{a, t = 0} on the upper surface of the object to be sterilized by the upper flash lamp 1a.
S _{b, t = 0} = eS _{a, t = 0} , e> 1
Can be expressed by (e.g., when the distance r _b between the lower flash lamp and the object to be sterilized treated back surface is 1/2 of the distance r _a between the upper flash lamp and the object to be sterilized product top surface, Assuming there is no reflection effect, e = 2).
Therefore, the limit cumulative flash pulse number of articles in the lower flash lamp 1b _{N b} is N _b = _{[1- (S 0 / S b,} t = 0) ] 100 / k = _{[1- (S 0 / eS a,} t _{= 0} )] 100 / k
N _b / N _a = [1- (S ₀ / eS _{a, t = 0} )] / [1- (S ₀ / S _{a, t = 0} )]
For example, under the same conditions as described above, the sterilization limit irradiation illuminance S ₀ is 80% of the initial irradiation illuminance S _{a, t = 0} , and k is 1.4 × 10 ^−7, that is, one flash pulse. When the supplied power energy per unit is 1 J and the flash pulse frequency is 60 Hz], when N _b / N _a = 3 and the count value of the counter Kb becomes 1.43 × 3 × 10 ⁸ , the lower flash lamp 1b is newly installed. The flash lamp is replaced, the counter _Kb is reset to 0, and then the sterilization process by the above operation is continued.

As shown in FIG. 2, the upper flash lamp 1a (lower flash lamp 1b) is replaced with a new flash lamp by replacing the upper flash lamp 1a (lower flash lamp 1b) with a spare upper flash lamp 1a '(lower 1b). ') Are arranged adjacent to each other, and a changeover switch SW _a (SW _b ) is provided between the old upper flash lamp 1a (old lower flash lamp 1b) and the spare upper flash lamp 1a' (lower 1b '). When the counter Ka (Kb) counts the limit cumulative flash pulse number N _a (N _b ), the changeover switch SW _a (SW _b ) may be automatically operated.

In the present invention, a flash pulse is generated under a supply power energy per flash pulse of 0.5 to 25 J, preferably 4 to 18 J, and a half-value width of the supply power waveform per flash pulse is set to 10 to 40 μs. It is desirable that the number of flash pulses per second is 30 to 120, preferably 30 to 70. The distance between the xenon flash lamp and the irradiation surface is set to a range of ± 20 mm with respect to 100 mm on the upper side and a range of ± 20 mm with reference to 30 mm on the lower side.
The reason why the supplied power energy per one flash pulse is 0.5 to 25 J is that if it is less than 0.5 J, the illuminance is too low to avoid incomplete sterilization, and if it exceeds 25 J, the discharge gap becomes large. As a result, an increase in the cooling means of the xenon flash lamp is invited, making it difficult to reduce the size of the xenon flash lamp and increasing the ultraviolet illuminance that the worker receives by reflecting the irradiated surface, thereby hindering the safety of the worker. is there.

Capacity C _m of the main charging and discharging the capacitor C of _the, when a DC voltage voltage application to the capacitor to is V, the stored energy of the capacitor is given by C _{m V} ^2/2, the supply power of the energy per flash pulse By setting the energy to 0.5 to 25 J, the capacitor can be reduced in size or the DC voltage can be reduced, and the energy supply device can be reduced in size and cost.

  The reason for setting the number of flash pulses per second to 30 to 120 is that if the number is less than 30, the cumulative ultraviolet ray irradiation amount per unit time is too small and effective sterilization becomes difficult. This is because the cumulative ultraviolet ray irradiation amount becomes too large, and the flash lamp generates a significant amount of heat, requiring a large cooling means, making it difficult to ensure a substantial downsizing of the flash lamp.

  In the present invention, in addition to a xenon flash lamp, a rare gas flash lamp such as a krypton flash lamp or an argon flash lamp can be used as the flash lamp.

It is drawing which shows an example of the sterilizer used in this invention. It is drawing which shows an example different from the above of the sterilizer used in this invention. It is a circuit diagram which shows an example of the drive circuit of the flash lamp in the said sterilizer. It is drawing which shows the output waveform of each site | part of the flash lamp drive circuit of FIGS. 1-3. It is a circuit diagram which shows the principal part of another example of the drive circuit of the flash lamp used in this invention. It is drawing which shows the spectrum distribution of a xenon flash. It is drawing which shows a prior art example.

Explanation of symbols

1a Upper flash lamp 1a 'Preliminary upper flash lamp 1b Lower flash lamp 1b' Preliminary lower flash lamp 2 Shading case 3 Lattice shelf 5 Roll conveyor 6 Irradiation chamber M Object to be sterilized C Main charge / discharge capacitor C _t Trigger capacitor T transformer _ta trigger the step-up transformer _{T tb} trigger boosting _{K a} trigger pulse counter _{K b} trigger pulse counter

Claims (8)

A flash lamp for irradiating a flash pulse from the upper side to the object to be sterilized is disposed, and the lower flash lamp for irradiating the flash pulse from the lower side is set to the distance between the flash lamp and the object to be sterilized in the upper flash lamp. The flash lamps are arranged to be shorter than the same distance, and both the flash lamps are connected in parallel to a common charging / discharging capacitor, and a trigger pulse of a frequency f shifted in time is added to both the flash lamps. The number of trigger pulses in each flash lamp is counted, the number of trigger pulses accumulated in each flash lamp is counted, and the number of use limit cumulative trigger pulses in the lower flash lamp is compared to the number of use limit accumulated trigger pulses in the upper flash lamp. Sterilization operation method characterized by performing a new replacement for both flash lamps set to large . The upper and lower flash lamps connected in parallel, the charge / discharge capacitors connected in parallel to the lower flash lamp, individual trigger pulse generation circuits that apply trigger pulses to these flash lamps, and the cumulative number of trigger pulses A sterilizing apparatus comprising an individual counter for counting. An upper flash lamp is provided in the middle upper part of the roll conveyor, and a lower flash lamp is provided in the middle lower part of the roll conveyor, and the distance between the lower flash lamp and the roll conveyor surface is greater than the distance between the upper flash lamp and the roll conveyor surface. The sterilizer according to claim 2, wherein the sterilizer is also shortened. A lattice shelf is provided in the light shielding case, an upper flash lamp is provided above the lattice shelf, a lower flash lamp is provided below the lattice shelf, and the distance between the lower flash lamp and the lattice shelf is the upper flash lamp. The sterilizer according to claim 2, wherein the sterilizer is shorter than a distance from the lattice shelf. 2. The sterilization operation method according to claim 1, wherein a preliminary flash lamp is installed and the old flash lamp is automatically switched to the preliminary flash lamp. A spare flash lamp for the upper flash lamp and a spare flash lamp for the lower flash lamp are provided, and when the cumulative number of trigger pulses reaches the limit of use limit trigger pulses, it automatically switches to the preliminary flash lamp. The sterilizer according to any one of claims 2 to 4, further comprising a changeover switch circuit. 6. The sterilizing operation method according to claim 1 or 5, wherein the power supply energy per flash pulse of the flash lamp is 0.5 J to 25 J, and the flash pulse number per second is 30 to 120. The sterilizer according to any one of claims 2 to 4, wherein the flash lamp is a xenon flash lamp.

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