JP5052119B2 - Mold for elastic roller and method for producing elastic roller - Google Patents

Description

  The present invention comprises a cylindrical mold and a resin cap that closes both ends of the mold, and forms an elastic layer by curing the material injected around the shaft disposed inside the mold. The present invention relates to a mold for an elastic roller.

  In an image forming apparatus using an electrophotographic system such as a copying machine or a printer, various elastic rollers such as a developing roller and a charging roller are used in each step of image formation. These elastic rollers are shown in FIG. As shown in the sectional view, an elastic layer 22 is formed around the shaft 21. As a method for forming such an elastic roller 20, as shown in a cross-sectional view in FIG. 2, a mold 90 including a cylindrical mold 93 and a pair of resin caps 94 is used. After the shaft 21 is disposed therein, both ends of the hollow portion of the mold 93 are closed with a resin cap 94, and the material is injected into a cavity 99 surrounded by the mold 93 and both caps 94 and cured to be elastic. A method of forming the layer 22 is known (see, for example, Patent Document 1).

  And as such a cap 94, as shown in sectional drawing in FIG. 3, while having the outer peripheral surface 94a fitted by the inner peripheral surface 93w of the metal mold | die 93, the end part of the said shaft 21 is accommodated and fixed. It is known that the concave portion 95 includes a cylindrical wall surface portion 95 a and a bottom surface portion 95 b that faces the end surface of the shaft 21 inserted into the concave portion 95 and positions the end surface. Yes.

Japanese Patent Laid-Open No. 2005-354977

However, since the cylindrical wall surface portion 95a is composed of only a single cylindrical wall surface parallel to the central axis L of the concave portion 95 as shown in FIG. When pressing and fixing until it comes into contact with 95b, as shown in the sectional view of the concave portion 95 in FIG. in the end-side portion 96b, a gap d, the material injected into the cavity, and enters the space 99a made around the shaft 21 in the recess 95, as a result, to be exposed, the length L _z shaft The elastic material adhered to the surface of the part, and it took extra time to scrape off the adhered material.

  As a measure for coping with this problem, the material enters the recess 95 by making the inner diameter of the opening end portion 96 in a state where the shaft 21 is not inserted into the recess 95 smaller than the inner diameter of the rear portion 96a. It was confirmed by the inventor that this can be prevented. However, in this measure, when inserting the shaft 21 into the recess 95, first, after passing the portion 96 on the opening end side through the shaft 21, and then trying to insert the shaft 21 further, the wall surface of the back side portion 96a and the shaft The air between the end portion 21 and the end portion of the opening 21 is compressed by losing the clearance by eliminating the gap between the portion 96 on the opening end side and the shaft 21, and as a result, the end surface of the shaft 21 is compressed with the bottom surface portion of the recess 95. It becomes impossible to insert until it contacts 99.

  This means that the protruding length of the shaft 21 from the elastic layer 22 in the completed elastic roller 20 is shorter than a predetermined protruding length determined on the assumption that the end surface of the shaft 21 contacts the bottom surface portion 95b. . In this case, when the elastic roller 20 is attached to the apparatus, there is a problem that the elastic layer 22 interferes with the surrounding apparatus part. Therefore, in order to ensure a predetermined shaft protrusion length, the elastic roller 22 is elastic after molding of the elastic roller. An operation of cutting and removing the end portion of the layer is necessary, and a wasteful process is generated.

  The present invention has been made in view of such a problem, and it is possible to prevent the elastic layer material from adhering to the shaft portion to be exposed, and without providing a step of cutting the end portion of the elastic layer. It is an object of the present invention to provide a mold that can secure a protruding length of the shaft from the elastic layer, and a method of manufacturing an elastic roller using the same.

<1> consists of a cylindrical mold and a resin cap that closes both ends of the mold. An elastic layer is formed by injecting and curing a material around the shaft disposed inside the mold. In the elastic roller mold used to
The resin cap has an outer peripheral surface that is fitted to the inner peripheral surface of the mold, and includes a concave portion that receives and fixes the end portion of the shaft. The concave portion is inserted into the cylindrical wall surface portion. was opposed to the peripheral surface of the shaft is composed of a bottom portion for positioning the end face, the cylindrical wall is made of a different wall parts of the inner diameter, at a position corresponding wall portion minimum inner diameter distant from the bottom portion Arranged,
At least one of the bottom surfaces of the resin cap is provided with an air vent hole for discharging air confined between the shaft and the recess to the atmosphere side in a state where the end of the shaft is accommodated in the recess. Do Ri,
The air-removal holes, from the bottom side, an elastic roller mold ing is formed in a shape expanding in a tapered shape on the atmosphere side.

< 2 > is an elastic roller molding die according to <1 > , wherein a wall surface portion corresponding to the minimum inner diameter has a finite width.

< 3 > is a molding die for an elastic roller in which the wall surface portion corresponding to the minimum inner diameter is connected to the wall surface portion on the bottom surface side through a step in <1> or <2> .

< 4 > is for an elastic roller according to any one of <1> to < 3 >, wherein a radial direction portion from the opening end of the concave portion to the outer peripheral surface of the resin cap is formed by a tapered surface extending in a tapered shape. It is a mold.

<5>, in <4>, of the tapered surface, an elastic roller mold ing as a 45 to 60 ° angle of inclination with respect to the recess center line.

< 6 > is an elastic roller manufacturing method for forming an elastic roller using the molding die according to any one of <1> to < 5 >.
In the elastic roller manufacturing method, the resin cap having an inner diameter of a wall portion corresponding to the minimum inner diameter is smaller than an outer diameter of the shaft and a difference with respect to the outer diameter of the shaft is within 0.1 mm.

<7> is have you to <6>, until the material injected around the shaft to complete the curing, elastic roller that presses the cap, at the end face in pairs towards and over 30N and the force of the shaft It is a manufacturing method.

  According to <1>, the resin cap includes a concave portion that accommodates and fixes the end portion of the shaft, and the concave portion is a cylindrical wall surface portion and a bottom surface that positions the end surface facing the end surface of the shaft. The cylindrical wall surface portion is composed of wall surface portions having different inner diameters, and the wall surface portion corresponding to the minimum inner diameter is disposed at a position away from the bottom surface portion. Even if it is inserted to the position where it abuts against the bottom surface, the wall portion corresponding to the minimum inner diameter abuts on the outer periphery of the shaft, so that it is possible to prevent the material from entering deeper than this wall portion. By disposing the wall surface portion corresponding to the inner diameter near the opening end of the recess, the elastic layer material can be prevented from adhering to the shaft portion to be exposed from the end portion of the elastic layer.

  In this case, when the shaft is inserted into the recess, the wall surface portion corresponding to the minimum inner diameter is closed by the shaft, so that a sealed space surrounded by the shaft and the wall surface of the recess is formed behind the wall surface portion. Even if it is going to be inserted deeply, it becomes difficult to insert until the shaft end surface comes into contact with the bottom surface of the recess due to the increase in pressure in the sealed space, and the elasticity of the shaft is determined according to the length of the recess. As a result, there is a possibility that the projecting length dimension from the layer end face is insufficient, and as a result, in order to secure this projecting length, there is a useless process for cutting the end of the elastic layer after forming the elastic roller. It will occur.

However, according to the present invention, the bottom surface portion of the concave portion of the cap is provided with an air vent hole for discharging air from the sealed space in the bottom surface portion, so that an increase in pressure in this space is suppressed, The protruding length dimension from the end face of the elastic layer can be made constant and uniform.
Further, since the air vent hole is formed in a shape that expands in a tapered shape from the bottom surface side to the atmosphere side, it relates to a cap disposed on the material injection side among both caps inserted into the mold, The material that has entered the recess from the atmosphere side through the air vent hole and has adhered to the shaft end can be peeled off by the taper surface of the air vent hole by simply removing the shaft from the cap after molding. .

According to < 2 >, since the wall surface portion corresponding to the minimum inner diameter has a finite width, it is possible to further reliably prevent the material injected into the cavity from entering from the back side.

According to < 3 >, the wall surface portion corresponding to the minimum inner diameter is connected to the wall surface portion closer to the bottom surface portion via a step, so that only the wall surface portion corresponding to the minimum inner diameter is reliably attached to the outer peripheral surface of the shaft. It can be made to contact | abut, and the approach to the recessed part back side of a material can be suppressed still more reliably.

< 4 > According to < 4 >, since the radial direction part from the opening end of the said recessed part to the outer peripheral surface of the said resin cap was comprised by the taper surface which spreads in a taper shape, there exists misalignment at the time of inserting a shaft in a recessed part However, it is possible to absorb the misalignment by guiding the corner of the end surface of the shaft with this tapered surface, and to facilitate the insertion into the concave portion of the shaft.

According to < 5 >, since the inclination angle of the tapered surface with respect to the center line of the recess is set to 45 to 60 °, the shaft can be more easily inserted into the recess, and the inclination angle is set to 45 °. If it is less than the height, the height of the frustoconical portion formed at the end of the elastic layer in the elastic roller as a product increases, and the length of the outer peripheral surface of the elastic layer with respect to the predetermined shaft length. It becomes difficult to ensure the effective length of the so-called elastic roller.On the other hand, when this inclination angle exceeds 60 °, even if the angle of the shaft end face is applied to the taper surface, It becomes impossible to guide the shaft end smoothly in the center direction.

According to < 6 >, since the inner diameter of the wall surface portion corresponding to the minimum inner diameter is smaller than the outer diameter of the shaft as the resin cap, the state in which the wall surface portion corresponding to the minimum inner diameter is compressed is maintained. The material can be prevented from entering the interior, and the difference between the outer diameter of the shaft and the outer diameter is within 0.1 mm, so that the insertion into the concave portion of the shaft can be facilitated.

According to <7>, until the material injected around the shaft to complete the cure, the cap, since the pressing on the end face in pairs towards and over 30N and the force of the shaft, until the material is cured Even if there is thermal expansion of the air confined in the sealed space, the shaft end surface can be kept in contact with the bottom surface of the recess, whereby the shaft portion protruding from the elastic layer end surface The length of can be stabilized.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a cross-sectional view showing a mold according to an embodiment of the present invention. The mold 10 includes a cylindrical mold 3 and a pair of resin caps 4A and 4B. 4B is inserted into the inner peripheral surface 3w of the mold 3 to form a cavity 9 that closes both sides of the hollow portion of the mold 3 and is filled with the elastic layer material, and is disposed inside the mold 3 Both ends of the shaft 21 are fixed.

  FIG. 6 is a cross-sectional view showing the caps 4A and 4B. The caps 4A and 4B include the outer cylinder 7 having the outer peripheral surface 14 fitted to the inner peripheral surface 3w of the mold 3 and the end portion of the shaft 21. A plurality of ribs 8 including an inner cylinder 6 having a cylindrical recess 5 to be accommodated and fixed, and connecting the inner cylinder 6 and the outer cylinder 7 are arranged at intervals in the circumferential direction. And the recessed part 5 consists of the cylindrical wall surface part 15 and the bottom face part 16 which opposes the end surface of the shaft 21, and positions this end surface.

  In order to manufacture an elastic roller using such a mold 10, first, the shaft 21 is disposed inside the mold 3, and then the caps 4 </ b> A and 4 </ b> B are respectively attached to the hollow portion inside the mold 3 from both sides. The both ends of the hollow portion are inserted and the ends of the shaft 21 are inserted into the recesses 5 of the caps 4A and 4B to fix the shaft 21. Next, the elastic layer material is injected from the gap between the outer cylinder 7 and the inner cylinder 6 of the cap 4A, and the cavity 9 is filled with this material. At this time, the gap between the outer cylinder 7 and the inner cylinder 6 of the cap 4B functions as a gas vent for discharging the air in the cavity 9.

  Next, with the mold 10 closed, heat is applied for a predetermined time to cure the elastic layer material, and then both caps 4A and 4B are removed from the mold 3, and then an elastic layer 21 is formed around the cap. The formed shaft 21 is taken out and the molding process is finished.

Here, the cap 4A of the present invention, in 4B, as shown in cross-section the recesses 5 in FIG. 7, the cylindrical wall portion 15 has an inner diameter different wall portions 15a, 15b, made of 15c, corresponding to the minimum inner diameter d ₁ The wall surface portion 15a to be performed is characterized by being disposed at a position away from the bottom surface portion 16. That is, the inner diameter d ₂ of the wall portion adjacent to the bottom portion 16 is larger than the minimum inner diameter d _1, also the wall portion 15c is an inner diameter is continuously changed, that where the very inner diameter, the minimum larger than the inner diameter d _1.

Then, the wall surface portion 15a corresponding to the minimum inner diameter d ₁ while positioned near the open end 17, is only slightly greater than the wall portion 15a which corresponds to the outer diameter D of the shaft 21 to be inserted into the recess 5 to the minimum inside diameter d ₁ Thus, as shown in the sectional view of the concave portion 5 in a state where the shaft 21 is inserted in FIG. 8, the wall surface portion 15a can be brought into a state in which the outer peripheral surface of the shaft 21 is tightened over the entire surface 21b. Further, the elastic layer material can be prevented from entering from the wall surface portion 15a to the back side, and the material can be prevented from adhering to the shaft portion (length L ₀ ) to be exposed. To satisfy this condition, the distance L _y from the open end of the wall portion 15a to the bottom surface portion 16 may be greater than the length L _z of the shaft portion to be exposed.

Here, as shown in cross-section the recesses 5 in FIG. 9, in the vicinity of the wall surface portion 15f corresponding to the minimum inner diameter d ₁ constituted by a surface cross-section is curved, i.e., the wall portion corresponding to the minimum inner diameter d ₁ Although 15f may be a composed of those infinitesimal width, first, as shown in FIG. 7, to constitute the wall portions 15a corresponding to the minimum inner diameter d ₁ in having a width l ₃ of the finite In this way, it is possible to more reliably prevent the material injected into the cavity 9 from going deeper than the wall surface portion 15a.

  Further, for example, as shown in FIG. 9, the wall surface portion 15f corresponding to the minimum inner diameter can be connected to the wall surface portion 15g on the bottom surface portion 16 side so that the inclination φ continuously changes. As in the example shown in FIG. 7, it is preferable that the slope φ is discontinuously changed, that is, the step 25 is formed and connected so that only the wall surface portion corresponding to the minimum inner diameter is reliably connected to the outer periphery of the shaft. It can make it contact | abut to a surface, and can approach more reliably the approach to the back of the recessed part 5 of a material.

Further, the wall portion 15b located on the bottom portion 16 side of the wall surface portion 15a corresponding to the minimum inner diameter d ₁ constituted by a cylindrical surface having a constant inner diameter d _2, 0.01 to the difference 2.delta. ₁ of the inner diameter of these wall portions 0.1 mm is preferable.

When the inner diameter difference 2δ ₁ is smaller than 0.01 mm, when the shaft is inserted all the way into the recess 5, a gap is generated between the wall surface portion 15a corresponding to the minimum inner diameter d ₁ and the outer peripheral surface of the shaft 21, and the material This is because it becomes difficult to prevent the wall portion 15a from entering the interior.

On the other hand, if the inner diameter difference 2δ ₁ becomes too large, as shown in FIG. 10, the volume of the sealed space 23 formed at the back of the wall surface portion 15a corresponding to the minimum inner diameter d ₁ becomes too large, and the shaft 21 is recessed. 5, the pressure of the air confined in the sealed space 23 increases, and it becomes difficult to insert the shaft 21 until the end surface 21 a abuts against the bottom surface portion 16.

Thus, the length L ₁ of the shaft portion protruding from the end F of the elastic layer is a predetermined protrusion by an amount corresponding to the gap δ ₃ formed between the end surface 21a and the bottom surface portion 16 of the shaft 21. The protrusion length L ₁ is not constant because it is shorter than the length L ₀ and the Δ ₃ cannot be controlled to be a constant value. If the projecting length L ₁ varies, it is not preferable that the elastic roller 20 is set in the apparatus, and the position of the end F of the elastic layer varies and may interfere with surrounding mechanisms. In general, it is required that the variation in the protruding length be within a tolerance of ± 0.1 mm.

In order to satisfy this requirement, the cap 4B according to the present invention is characterized in that the bottom surface portion 16 is provided with a hole 18 of an air inlet, and in this case, the shaft 21 is in contact with the bottom surface portion 16a of the end surface 21a. be inserted until it is, because the air in the recess 5 to be discharged from the air vent hole 18, never the pressure rises, the length L ₁ of the predetermined tolerance ± shaft portion projecting from the elastic layer end surface F Can fit in 0.1mm.

  Here, when the air vent hole 18 is provided in the cap 4A on the material injection side, if the hole diameter is large, the material enters the recess 5 from the atmosphere side through the air vent hole 18 when the material is injected. For this reason, it is preferable to form the air vent hole 18 in a tapered shape so as to be narrow on the bottom surface portion 16 side of the recess 5 and wide on the atmosphere side. This is because the material that has entered the recess 5 through the air vent hole 18 from the atmosphere side, cured by the molding process, and adhered to the end of the shaft 21 is simply pulled out of the cap 21A from the cap 21A. This is because the material portion cured in the air vent hole 18 can be separated from the shaft.

Further, as shown in FIG. 6, it is preferable that the radial direction portion from the opening end 17 of the concave portion 5 to the outer peripheral surface 14 of the cap 4 is constituted by a tapered surface that spreads out in a tapered shape. Even if there is a misalignment δ ₂ when the shaft is inserted into the recess 5, the corner 24 of the end surface 21 a of the shaft 21 can be guided by the tapered surface 15 c to absorb the misalignment δ _2. 5 can be easily inserted.

  In this case, it is preferable that the inclination angle θ of the wall surface portion 15c having the tapered surface with respect to the center line C of the recess 5 is 45 to 60 °.

However, by using such a mold 10, to form an elastic layer 22, as a method for producing the elastic roller 20, the inner diameter d ₁ of the wall portion 15a is preferably smaller than the outer diameter D of the shaft 21, the Accordingly, the material coming from the cavity 9 can be prevented from entering from the wall surface portion 15a to the back, and the recess of the shaft 21 can be obtained by using the cap 4 having a difference with respect to the outer diameter D of the shaft 21 within 0.1 mm. 5 can be easily inserted.

Furthermore, in such a manufacturing method of the elastic roller 20, the caps 4A and 4B are pressed against the end surface 21a of the shaft 21 with a force of 30 N or more until the material injected around the shaft 21 is completely cured. In this way, the end surface 21a of the shaft 21 can be kept in contact with the bottom surface portion 16 even if there is thermal expansion of the air confined in the sealed space 23 until the elastic layer material is cured. As a result, the protruding length L ₁ of the shaft 21 from the elastic layer end face F can be stabilized.

Here, as materials for the caps 4A and 4B, resins such as polypropylene, polyacetal, polyethylene, and polycarbonate can be used.

  In forming a conductive roller using the elastic roller molding die of the present invention, the shaft 21 of the conductive roller may be, for example, a cored bar made of a solid metal such as iron, stainless steel, or aluminum, It is possible to use a metal shaft such as a metal cylinder that is hollowed in a hollow or a highly conductive plastic shaft. Here, the outer diameter of the shaft 21 is preferably in the range of 4 to 8 mm.

  On the other hand, as the material of the elastic layer 22 of the elastic roller 20, it is preferable to use a urethane foam obtained by mechanical stirring and foaming of a urethane raw material, that is, a mechanical floss foamed urethane. This urethane foam is manufactured by a method in which bubbles are mixed by mechanically stirring a urethane raw material without using a foaming agent. Here, examples of the urethane raw material include a polyol and a polyisocyanate, or a urethane prepolymer and a chain extender synthesized from a polyol and a polyisocyanate. Further, a catalyst, a foam stabilizer and a conductive agent are added to the urethane raw material. can do.

It is sectional drawing which shows the elastic roller formed with the shaping | molding die of this invention. It is sectional drawing which shows the conventional shaping | molding die. It is sectional drawing of the cap which comprises the conventional shaping | molding die. It is sectional drawing which shows the recessed part of the conventional cap in the state which inserted the shaft. It is sectional drawing which shows the shaping | molding die concerning this invention. It is sectional drawing which shows the cap which comprises the shaping | molding die concerning this invention. It is sectional drawing which shows the recessed part of a cap under the state which does not insert a shaft. It is sectional drawing which shows the recessed part of a cap under the state which inserted the shaft. It is sectional drawing which shows the recessed part of the cap of another aspect. It is sectional drawing which shows the recessed part of a cap under the state which inserted the shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Mold 3w Inner peripheral surface of a mold 4 Cap 5 Recessed part 6 Inner cylinder 7 Outer cylinder 8 Rib 9 Cavity 10 Elastic roller forming die 14 Cap outer peripheral surface 15a Wall portion corresponding to the minimum inner diameter 15b, 15f, 15g Wall portion 15c Tapered surface 16 Bottom surface portion 17 Open end of recess 18 Air vent hole 20 Elastic roller 21 Shaft 21a End surface of shaft 22 Elastic layer 23 Sealed space 25 Step C Center axis of recess F End of elastic layer

Claims (7)

It consists of a cylindrical mold and a resin cap that closes both ends of the mold, and is used to form an elastic layer by injecting and curing a material around a shaft disposed inside the mold. In the mold for elastic rollers,
The resin cap has an outer peripheral surface that is fitted to the inner peripheral surface of the mold, and includes a concave portion that receives and fixes the end portion of the shaft. The concave portion is inserted into the cylindrical wall surface portion. was opposed to the peripheral surface of the shaft is composed of a bottom portion for positioning the end face, the cylindrical wall is made of a different wall parts of the inner diameter, at a position corresponding wall portion minimum inner diameter distant from the bottom portion Arranged,
At least one of the bottom surfaces of the resin cap is provided with an air vent hole for discharging air confined between the shaft and the recess to the atmosphere side in a state where the end of the shaft is accommodated in the recess. Do Ri,
The air-removal holes, from the bottom side, the elastic roller mold ing is formed in a shape expanding in a tapered shape on the atmosphere side. The mold for an elastic roller according to claim 1 , wherein the wall surface portion corresponding to the minimum inner diameter has a finite width. The elastic roller molding die according to claim 1 or 2 , wherein the wall surface portion corresponding to the minimum inner diameter is connected to the wall surface portion on the bottom surface side through a step. The elastic roller molding die according to any one of claims 1 to 3 , wherein a radial direction portion from an opening end of the concave portion to an outer peripheral surface of the resin cap is configured by a tapered surface that expands in a tapered shape. The elastic roller molding die according to claim 4 , wherein an inclination angle of the tapered surface with respect to the center line of the recess is 45 to 60 °. In the manufacturing method of the elastic roller which forms an elastic roller using the shaping | molding die in any one of Claims 1-5 ,
A method for producing an elastic roller, wherein the resin cap has an inner diameter corresponding to the minimum inner diameter that is smaller than an outer diameter of the shaft, and a difference with respect to the outer diameter of the shaft is within 0.1 mm. Until the material injected around the shaft to complete the curing, the cap, the manufacturing method of the elastic roller according to claim 6 that presses on the end face in pairs towards and over 30N and the force of the shaft.

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