JPH08294921A - Cleaning method for vulcanizing mold - Google Patents

Abstract

PURPOSE: To provide a method for cleaning a vulcanizing mold in which uniform residue ashing is realized in a short time by operating a local high-density plasma at the entire periphery of the inner surface of the mold stuck with vulcanizing residue. CONSTITUTION: A method for cleaning a vulcanizing mold comprises the steps of disposing an annular vulcanizing mold 7 as the other electrode at the periphery of one electrode 7 protruding into a treating tank, disposing the one electrode surface at the position deviated to the vicinity position of the inner surface of the mold, generating a local high-density plasma between both the electrode surfaces approaching to each other, rotatably holding at least the electrode of one side at the deviated position, and operating the plasma at the entire periphery of the inner surface of the mold upon rotating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a molding surface on the inside of a mold repeatedly used for vulcanization molding of rubber products such as rubber tires and vibration-proof rubber and other plastic products as elastomers, and in the case of split molds A method for cleaning a vulcanization mold for advantageously removing elastomer residues that are unavoidably formed on the surface including the surface and in the recesses and holes, particularly without accompanying disadvantageous deterioration and damage to the vulcanization mold, Further, the present invention relates to a method for cleaning a vulcanization mold, which enables uniform residue treatment in a short time without being involved in forming a non-uniform region of plasma distribution.

[0002]

2. Description of the Related Art JP-A-6-2858 already filed by the present applicant.
As described in detail in Japanese Patent Publication No. 68, elastomer products, particularly rubber tire products (hereinafter simply referred to as tires), anti-vibration rubber products, and the like satisfy the required performance, and therefore natural rubber, synthetic rubber or blended rubbers thereof are cross-linked. In addition to blending sulfur as a component and carbon black as a reinforcing material, it is necessary to blend a vulcanization accelerator and various chemicals for maintaining various durability.

When the unvulcanized rubber composition thus prepared is vulcanized and molded, a chemical reaction such as a crosslinking reaction generally occurs at a high temperature close to 200 ° C., so that the rubber composition has fluidity. Not only does it increase, but it also partially gasifies, and as a result, not only the molding surface of the vulcanizing mold, but also the extremely narrow gaps in the mating surface of the mold and holes such as so-called vent holes for venting the rubber composition and its chemical composition. It is unavoidable that the reaction product adheres strongly as a residue, although it is a small amount, each time it is vulcanized and molded. By repeating this vulcanization molding a number of times, the residue is deposited in a thickness that cannot be overlooked. This applies not only to the rubber composition but also to other elastomers in the same manner and in different sizes.

The thick vulcanization residue firmly adhered and deposited on the vulcanization mold not only impairs the appearance of the tire, but also adversely affects the excellent quality maintenance of the entire tire. Therefore, it is necessary to clean the vulcanization mold that has been vulcanized and molded a predetermined number of times as if it was a new product.As this work method, a shot blast cleaning method in which granules such as plastic beads and glass beads are sprayed with high pressure gas, Alternatively, a liquid cleaning method of immersing in a solution of acid, alkali, amine or the like has predominantly been used. Since the various disadvantages of these cleaning methods are remarkably improved, the applicant of the present invention has described the above-mentioned JP-A-6- 285868
The method for cleaning a vulcanization mold by plasma described in Japanese Patent Publication has been proposed, and a remarkably excellent result has been obtained.

[0005]

However, upon examining this result, it was found that there is room for further improvement in the following points. That is, the first point is that the plasma region is excessively large with respect to the clean surface of the vulcanization mold, and as a result, a large amount of electric power and an excessive amount of reaction gas are required, resulting in high processing cost.

The second point is that, on the mold forming surface of the vulcanizing mold that needs to be cleaned, apart from special tire types, generally, the large grooves and fine grooves that are indispensable for sufficiently exhibiting the required characteristics of the tire are required. A large number of ribs and protrusions such as sipes (strips) for forming grooves and slits on the tread portion are provided, and the plasma is blocked by these protrusions and vulcanized over the entire area of the clean surface. This is because the uniform ashing (ashing) of the residue is impaired and tends to occur.

The third point is that the cleaning efficiency is lowered because a lot of processing time is required in relation to the second point, and the fourth point is that the surface not to be cleaned is exposed to plasma. This surface part is apt to cause deterioration and damage, and the fifth point is that the plasma density distribution is made uniform over the entire region to be cleaned, so that processing conditions that are unfavorable to the ashing process such as reaction Further reduction of gas pressure and halide gas (especially CF ₄ gas)
That is, the adoption of conditions such as a decrease in the amount of

Therefore, an object of the present invention is to improve all of the above-mentioned disadvantages, and it is advantageous to provide uniform ashing at a low cost and a short processing time without restricting the mold forming surface of the vulcanization mold. An object of the present invention is to provide a method of cleaning a vulcanization mold that can be realized.

[0009]

In order to achieve the above object, a method for cleaning a vulcanizing mold of the present invention is to apply a plasma generated in a dilute reaction gas in a vacuum treatment tank to the vulcanizing mold, When removing the elastomer residue formed on the inner surface of the mold by repeated vulcanization molding of the elastomer by ashing, one electrode is projected into the processing tank, and the annular vulcanization mold is surrounded by the protruding electrode. In addition to being positioned as an electrode, the surface of one of the electrodes is biased near the inner surface of the mold to generate high-density plasma locally between the electrode surfaces that are close to each other by applying power to both electrodes. At the same time, at least one of the two electrodes should be able to rotate while maintaining the above bias, and the local high-density plasma should be made to act over the entire circumference of the inner surface of the mold along with this rotating operation. And butterflies.

In practicing the present invention, the one electrode is arranged at the tip of the arm-shaped member, and the center axis of the inner surface of the mold passes through the end opposite to the tip of the member. The electrode is composed of a plate-shaped member having a surface curved in the same direction as the inner peripheral surface of the inner surface of the mold, the one electrode is composed of a cylindrical plate member, and the central axis of the member is the inner surface of the mold. Being deviated from the central axis, the one electrode is provided with a large number of holes, the one electrode is provided with a plurality of fins on the surface facing the mold, the vulcanizing mold has its inner surface Be rotatable about the central axis of
It is desirable that the one electrode can rotate while maintaining a predetermined distance from the inner surface of the mold.

As a reaction gas, oxygen gas (O ₂ ,
A mixed gas of O ₃ ) and a halide gas is preferable, and as the halide gas, any gas containing F (fluorine), Cl (chlorine), Br (bromine), I (iodine), etc. can be used. it can. Moreover, since it only needs to be supplied as a gas to the vacuum processing tank, the standard condition (25
It is not necessarily a gas at 1 ° C. and 1 ° C., and may be in a liquid state, for example. Especially Freon, NF ₃ , SF
₆ is preferably used, among which CF ₄ (carbon tetrafluoride)
Is effective.

[0012]

Operation: First, one electrode is projected into the processing tank, and an annular vulcanizing die is positioned around this electrode as the other electrode at a predetermined distance from the former electrode, so that cleaning is required. It is only necessary to generate the plasma in the area between the surface of the metal mold and the electrode surface, and as a result, the plasma area can be optimized to the minimum required, and therefore, the extra power and the extra reaction gas consumption are required. And the processing cost can be reduced.

Next, by disposing one electrode surface protruding into the processing tank in a position near the inner surface of the mold so as to be biased between the two electrode surfaces which are close to each other when electric power is applied to both electrodes. Thus, it becomes possible to locally generate high-density plasma. This is nothing but the intentional formation of a non-uniform plasma region over the entire peripheral region of the inner surface of the mold. This state is shown in FIG. 2 which shows a plane of a main part of an embodiment according to the present invention.

In FIG. 2, reference numeral 1 is one electrode protruding into the processing tank, reference numeral 7 is a vulcanization mold as the other electrode, and the electrode 1 is fixed to the tip of the arm-shaped member 5. Power is supplied to the electrode 1 via the arm-shaped member 5. When a predetermined electric power is applied to both electrodes, a plasma region is formed only between the adjacent surfaces of the electrodes 1 and 7 in a local portion having a lattice pattern shown in the figure. Of course, the highest density plasma is formed in the vicinity of the distance D where the electrodes 1 and 7 are closest to each other, and the plasma density decreases as the distance between them increases.

Moreover, since at least one of the electrodes 1 and 7 can rotate while maintaining the deviation distance D, for example, the electrode 1 can be stationary and the electrode 7 (vulcanization mold) can be rotated. The local high-density plasma region acts on the entire inner surface of the mold along with this rotation. Therefore, it is not necessary to reduce the pressure of the reaction gas and the inflow amount of the halide gas, and it is possible to reduce the processing time at low cost, and also to cause deterioration and damage to the surface of the vulcanization mold 7 that is not the cleaning target. It has the advantage that problems can be avoided.
Further, the plasma region optimized for the tire tread pattern forming surface having a considerably complicated and various shape provides a uniform ashing effect.

Further, conventionally, it has been difficult to optimize the ashing progress degree by power control because the applied power amount and the ashing progress degree are not proportional to each other, whereas the occurrence of local plasma is Since the plasma density is in a narrow region, it is easy to control the plasma density, and since the plasma density is proportional to the ashing progress degree, the control of this degree is facilitated. This effect is common to each embodiment described below.

In another embodiment, as shown in FIGS. 3 (a) and 3 (b), a plate member having a surface in which the one electrode 2 is curved in the same direction as the inner peripheral surface of the inner surface of the mold 7. In this example, it is advantageous in controlling the distribution of the high-density plasma region and contributes to further shortening of the ashing processing time.

In another embodiment, as shown in FIGS. 4 (a) and 4 (b), the one electrode 3 is formed as a cylindrical plate member, and the central axis Z ₃ of the member is formed on the inner surface of the mold 7. It is possible to easily control the plasma distribution region by locating the position so as to deviate from the central axis line Z by a distance δ.

Further, if the plate-like portion of the electrode 2 is provided with a large number of holes 2h as shown in FIGS. 3 (a) and 3 (b), the so-called hollow cathode effect makes it possible to achieve higher density with the same power. Plasma can be generated, which contributes to further shortening of the ashing processing time and cost reduction. The size of the hole may be any size as long as the hollow cathode effect is suitable. At a pressure of around 1 Torr, a diameter of about 5 mm,
A depth of 10 mm or more is preferable.

Further, as in the example shown in FIGS. 4A and 4B and the modified examples of FIGS. 5A and 5B, the outer peripheral surface of the electrode 3 and the electrode 4 are made of gold. If a large number of fins 3f, 4f extending in the central axis Z direction of the inner surface of the die 7 are provided on the surface close to the die 7, the fins 3 adjacent to each other can be provided.
Since the plasma of the troughs formed by f and 4f becomes even higher in density, it also contributes to further shortening of the ashing process time and cost reduction, as in the above.

If the vulcanization mold 7 is rotatable about the central axis Z of the inner surface of the vulcanization mold 7, power is transmitted to the electrodes 1, 2, 3, 4 on the voltage application side with the mold 7 as the ground side. Helps to be easy.

[0022]

The present invention will be described in more detail below with reference to Examples 1 to 4. [Embodiment 1] FIG. 1 is a simplified vulcanization mold 7 showing a cross section of a main part of a side surface of a vacuum processing tank 10 used for cleaning the vulcanization mold 7.
2 is an explanatory view also showing the cross section of FIG. 2, and FIG. 2 is a plan view showing only the vulcanization mold 7 and the electrode 1 shown in FIG. The additional electrode 1 and the sulphate mold 7 shown in FIG. 1 are sectional views taken along the line II-II in FIG.

In FIG. 1, the vacuum processing tank 10 comprises a container 11 having a container upper part 11-1 and a container lower part 11-2 which are vertically separable from each other and can be sealed at a lower position. One side is detachably attached to the lower part 11-2 of the container so as to be attachable and detachable, and the lower part 11-2 of the container is provided with a suction part 12 connected to a vacuum pump (not shown). Before starting the cleaning operation of the vulcanization mold 7, the vacuum pump is operated to adjust the pressure inside the container 11 to, for example, 10 ⁻¹ to 10 ⁻⁵ T.
The so-called medium vacuum to high vacuum of orr is used. In the illustrated vacuum processing tank 10, the container lower part 11-2 side is fixed to the floor surface Fs or the like by, for example, a plurality of columns 13 (only one is shown in the figure).

As shown in FIG. 1, the electrode 1 on one side is arranged so as to project from the upper side into the container 11 in a suspended state. As shown in FIGS. 1 and 2, the electrode 1 is arranged at the tip of the arm-like member 5 on the side closer to the inner surface of the vulcanization mold 7, and the arm-like member 5 has an end opposite to the tip. Is fixed to a pipe 6 that suspends the electrode 1 and accommodates a power transmission conductor (not shown). The central axis Z ₁ of the pipe 6 is aligned with the central axis Z of the inner surface of the vulcanization mold 7. In the illustrated example, the electrode 1 is on the voltage application side, and the container 11 and the vulcanization mold 7 are on the ground side.

Although the power supply power supply is not shown in the figure, in this example, high frequency power called radio wave having a frequency of 13.56 MHz is transmitted to both electrodes 1 and 7. Plasma can be generated by either a DC power supply or an AC power supply,
An AC power source is more preferable. The power supply frequency in alternating current is
A high frequency of several Hz to several hundreds of MHz is preferably used, but discharge at a higher frequency (microwave) is also possible.

The position of the electrode 1 may be vertically movable in FIG. 1 or may be fixed on the upper side 11-1 of the container, and may be further rotatable. The example shown in FIG. 1 is a vacuum processing tank 10 when the electrode 1 is rotated and the vulcanization mold 7 is stationary. Conversely, when the vulcanization mold 7 is rotated, illustration is omitted. , The platen 14 on which the mold 7 is placed and the wheel conveyor 15 supporting the platen 14 are rotated around the central axis of the mold 7.

Although the vulcanization mold 7 is shown as one body,
In this example, a large number, for example, 3 to 20, of the so-called split mold, which is formed on the outer peripheral side, are formed on the upper surface of the supporting and transporting platen 14 which is also made of metal, for example, steel and which also serves as an electric conductor when actually used. The figure shows a temporary assembly in the same state as.

Further, an aluminum alloy is generally applied to the tread portion of the tire where treads and various grooves and slits are formed. When actually used, this alloy portion is attached to a steel holding member to form the above-mentioned segment. In the present invention, both the case of only the alloy portion and the case of the segment are referred to as a vulcanization mold.

When the vulcanization mold 7 is a split mold, a pair of side molds are combined above and below the illustrated segment mold to form a mold body. This mold body can be used as a vulcanization mold 7 for plasma cleaning, and the present invention can also be applied to a so-called two-piece mold having a divided surface on the circumference.

Although not shown in the drawings, the surface plate 14 is a mechanism for setting a group of segments or a set of these molds at a predetermined position when temporarily assembling a large number of segments or when placing a split mold body or a split mold. Furthermore, the surface plate 14 is provided with a mechanism for centering the vulcanization mold 7 as an assembly or the vulcanization mold 7 as these molds with respect to the pipe 6. The latter mechanism is a vulcanization mold 7 and a platen 14.
Centering engagement with a centering device provided on the wheel conveyor 15 supporting the.

The vulcanization mold 7 is introduced into the processing tank 10 by preliminarily assembling it on the surface plate 14 outside the processing tank 10 with the container upper part 11-1 and the electrode 1 being moved upward. The stationary vulcanization mold 7 is conveyed together with the surface plate 14 on another similar wheel conveyor (not shown) to the position shown, and at the same time, centering is performed. This centering accuracy is the amount of misalignment, and is preferably 3
cm or less, more preferably 5 mm or less.

After the surface plate 14 is conveyed to a predetermined position, the surface plate 14 is temporarily fixed by a fixing means (not shown) provided on the wheel conveyor 15. After fixing, the electrical contact 16 provided on the upper end of the rod 17 connected to the elevating means 18 is raised to make contact with the surface plate 14. The electrical contact 16 is connected to the ground side of the power supply for power supply via the rod 17. That is, in this example, the vulcanization mold 7 is on the ground side, but in another example, it can be on the voltage application side.

After that, the container upper part 11-1 and the electrode 1 are lowered and brought into contact with and engage with the container lower part 11-2.
1 and 11-2 are fixed in a hermetically sealed state, and then a vacuum pump (not shown) is operated to bring the inside of the container 11 into the predetermined medium to high vacuum state through the suction unit 12. Then, the reaction gas is guided from above the container 11 by means not shown in the figure and allowed to flow between the electrodes 1 and 7. In order to smooth the balance between the air discharge and the inflow and outflow of the reaction gas, a plurality of through holes are preferably provided at the position of the surface plate 14 corresponding to the position of the suction port of the suction portion 12. The position for measuring the pressure of the reaction gas may be any position except the suction port of the suction unit 12 and its vicinity.

Two examples, Example 1A according to FIG. 1 and Example 1B in which the electrode 1 is stationary and the vulcanization mold 7 is rotated,
Vulcanization 7 having a large amount of vulcanization residue adhered thereto was subjected to plasma ashing treatment as follows. The vulcanization mold 7 has eight segments and a maximum inner diameter of 550 mm. The minimum distance D between the electrode 1 and the mold 7 was set to 10 mm. A mixed gas of O ₂ gas and CF ₄ gas was used as the reaction gas, and the ratio of the inflow amounts of these gases was set to O ₂ : CF ₄ = 2: 1.
Specifically, O ₂ is 500 SCCM and CF ₄ is 250 SCC.
It is M. The pressure of the reaction gas is kept at 1.5 Torr,
High-frequency power having a frequency of 13.56 MHz was supplied at 8 kW, and the processing time was 60 minutes. In each of Examples 1A and 1B, the rotation speed was 1 rotation per minute.

In order to confirm the effects of these embodiments, as a method closest to the embodiments, the electrode has a cylindrical shape with an outer diameter of 480 mm and a height of 220 mm, and the center axis of the cylinder is aligned with the center axis of the mold 7. The plasma ashing process was also applied to the comparative example in which both the electrode and the mold 7 were stationary. The conditions of the reaction gas, the power supply, and the processing time were all adjusted to the examples.

As a result of observing the inner peripheral surface of the vulcanization mold 7 after the treatment, both Examples 1A and 1B had a white appearance, while the Comparative Example had a gray color. Therefore, Example 1A,
When 1B was washed with water, the white substance easily flowed off, and the metallic surface of the mold like a new one appeared. As a precaution, when the white substance was analyzed, it was found to be inorganic metal salts Z _n SO ₄ and Z _n F ₂ which were not adhesive to metals. On the other hand, in the comparative example, it was confirmed that the organic matter in the vulcanization residue remained in a considerable amount and thus was gray.

Further, when the temperature distribution of the vulcanizing mold immediately after the treatment was measured, it was found that Examples 1A and 1B were within a suitable range of 130 to 135 ° C., whereas Comparative Examples were 70 to 2
It was found to be in the range of 10 ° C., and particularly high temperature (200 ° C. or higher) has a significant adverse effect on the vulcanization mold.

[Embodiment 2] The vacuum processing tank 10 of Embodiment 1 is applied, and the electrode 2 and the vulcanization mold 7 are shown in plan view in FIG.
In FIG. 3A, a cross-sectional view taken along line III-III of FIG. 3A is shown in FIG. Electrode 2 is mold 7
The connecting member 5 is a plate-shaped member having a curved surface in the same direction as the inner peripheral surface of the inner surface of the pipe, and is attached to the tip of the pipe 6.
The electrode 2 is fixed to the tip of a. The plate-shaped member of the electrode 2 has a large number of through holes 2h, and these holes 2h are arranged in the vertical direction (line Z ₂
It is preferable to arrange a large number of columns in a vertical direction and to arrange in a zigzag pattern in the curved horizontal direction.

The shortest distance D between the inner peripheral surface of the mold 7 and the electrode 2 is on the vertical line of the curved surface of the plate-shaped member including the line III-III in the figure, or along the curved surface. It may be uniform. The central axis Z ₂ of the pipe 6 is aligned with the central axis Z of the mold 7. Also in this embodiment, it is possible to make the electrode 2 stand still and rotate the mold 7, and conversely, make the mold 7 stand still and rotate the electrode 2. It is also possible to rotate both electrodes 2, 7 in opposite directions.

Under the same treatment conditions as in Examples 1A and 1B, the ashing treatment was carried out for Example 2A in which the mold 7 was stationary and the electrode was rotated twice and Example 2B in which the electrode 2 was stationary and the mold was rotated 7 times.
The same method as in Example 1 was used for the comparative example. As a result, almost the same effect as in Examples 1A and 1B was obtained.

[Embodiment 3] The vacuum treatment tank 10 of Embodiment 1 is applied, and the electrode 3 and the vulcanization mold 7 are shown in plan view in FIG.
FIG. 4A is a sectional view taken along line IV-IV in FIG.
Those shown in (b) were used. The electrode 3 is composed of a cylindrical member having a large number of fins 3f arranged on its outer peripheral surface, and the electrode 2 is attached to the tip of a connecting member 5b attached to the tip of a pipe 6a.
To fix. The multiple fins 3f of the electrode 3 are pipes 6a
It is preferable to extend in the direction of the central axis Z ₃ and be arranged at substantially equal intervals along the outer circumference of the cylindrical member.

The center axis Z ₃ of the pipe 6a is positioned so as to be offset from the center axis Z of the mold 7 by a distance δ. The shortest distance D between the inner peripheral surface of the mold 7 and the electrode 3 is determined by the two central axis lines Z, Z.
_It is determined by the tip of the fin 3f on or near a plane including ₃ . Also in this embodiment, it is possible to make the electrode 3 stand still and rotate the mold 7, and conversely, make the mold 7 stand still and rotate the electrode 3. It is also possible to rotate both electrodes 3, 7 in opposite directions. Note that electrode 3
4A, the left half part of the fin 3f can be removed as seen in FIG. 4A.

Under the same treatment conditions as in Examples 1A and 1B, the ashing treatment was carried out for Example 3A in which the mold 7 was stationary and the electrode was rotated 3 times and Example 3B in which the electrode 3 was stationary and the mold was rotated 7 times.
The same method as in Example 1 was used for the comparative example. As a result, an effect similar to that of Examples 1A and 1B was obtained.

[Embodiment 4] The vacuum treatment tank 10 of Embodiment 1 is applied, and the electrode 4 and the vulcanization mold 7 are shown in plan view in FIG.
FIG. 5A is a sectional view taken along line V-V of FIG.
Those shown in (b) were used. The fourth embodiment is a modification of the second embodiment, and instead of arranging a large number of through holes in the electrode of the curved plate-shaped member, the third embodiment is provided on the outer peripheral surface of the plate-shaped member.
The electrode 4 is formed by arranging the fins 4f similar to the above. Of course, the central axis Z ₄ of the pipe 6 coincides with the axis Z.

Under the same processing conditions as in Examples 1A and 1B, the ashing treatment was performed for Example 4A in which the mold 7 was stationary and the electrode was rotated 4 times and Example 4B in which the electrode 4 was stationary and the mold was rotated 7 times.
The same method as in Example 1 was used for the comparative example. As a result, an effect similar to that of Examples 1A and 1B was obtained.

[0046]

According to the present invention, the elastomer residue formed on the surface of the mold by the repeated vulcanization molding of the elastomer is not accompanied by a disadvantage such as damage to the vulcanization mold and the vulcanization mold. Without any restrictions on the mold forming surface of
It is possible to provide a method for cleaning a vulcanization mold that can ash uniformly and effectively at low cost in a short processing time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a side surface of a vacuum processing tank and a side surface of a vulcanizing mold used for cleaning according to an embodiment of the present invention.

FIG. 2 is a plan view of the electrode shown in FIG. 1, a holding member thereof, and a vulcanization mold.

3A and 3B are a plan view and a sectional view of an electrode, a holding member thereof, and a vulcanization mold of another embodiment according to the present invention.

FIG. 4 is a plan view and a cross-sectional view of an electrode, a holding member thereof and a vulcanization mold according to another embodiment of the present invention.

5A and 5B are a plan view and a sectional view of an electrode, a holding member therefor, and a vulcanization mold according to still another embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3, 4 One electrode 2h Hole 3f, 4f Fin 5 Arm-shaped member 5a, 5b Connection member 6 Pipe 7 Vulcanization mold 10 Vacuum treatment tank 11 Container 12 Suction part 13 Strut 14 Surface plate 15 Wheel conveyor 16 Electrical contact 17 Rod 18 Lifting means

Claims (8)

[Claims] 1. A vulcanization mold is acted on by plasma generated in a dilute reaction gas in a vacuum processing tank, and the elastomer residue formed on the inner surface of the mold by vulcanization molding of the elastomer is removed by ashing. In doing so, one of the electrodes is projected into the treatment tank, and the annular vulcanizing mold is positioned as the other electrode around the projected electrode,
The above-mentioned one electrode surface is arranged so as to be biased to a position near the inner surface of the mold, and a high-density plasma is locally generated between both electrode surfaces that are close to each other by applying electric power to both electrodes. A method for cleaning a vulcanization mold, characterized in that at least one of the electrodes is rotatable while maintaining the above-mentioned deviation, and a local high-density plasma is caused to act over the entire circumference of the inner surface of the mold in accordance with this rotation operation. . 2. The cleaning method according to claim 1, wherein the one electrode is arranged at the tip of the arm member, and the central axis of the inner surface of the mold passes through the end opposite to the tip of the member. 3. The cleaning method according to claim 2, wherein the one electrode is a plate-shaped member having a surface that curves in the same direction as the inner peripheral surface of the inner surface of the mold. 4. The cleaning method according to claim 1, wherein the one electrode is made of a cylindrical plate member, and the central axis of the member is located deviated from the central axis of the inner surface of the mold. 5. The cleaning method according to claim 3, wherein the one electrode has a plurality of holes. 6. The cleaning method according to claim 2, wherein the one electrode has a large number of fins on the surface facing the mold. 7. The cleaning method according to claim 1, wherein the vulcanizing mold is rotatable about the central axis of the inner surface thereof. 8. The cleaning method according to claim 1, wherein the one electrode is rotatable while maintaining a predetermined distance from the inner surface of the mold.