JP5809825B2 - Mold and roller manufacturing method - Google Patents

Description

  The present invention relates to a molding die and a roller manufacturing method, and more particularly to a molding die and a roller manufacturing method capable of forming an elastic layer substantially free of weld lines around a shaft body.

  Image forming apparatuses such as printers such as laser printers and video printers, copiers, facsimiles, and multi-function machines thereof include various rollers. As such a roller, for example, a developing roller for carrying and conveying the developer, a developer supplying roller for supplying the developer to the developing roller, a conveying roller for conveying the recording body, a transfer roller for transferring the developer to the recording body, and recording Examples thereof include a fixing roller for fixing the developer on the body to the recording body, and a pressure roller for pressing the fixing roller. These rollers usually include a shaft body and an elastic layer formed on the outer periphery thereof.

  One method of manufacturing a roller including a shaft body and an elastic layer is to form an elastic layer on the outer peripheral surface of the shaft body using a molding die. As a molding die used in this manufacturing method, for example, as shown in FIG. 6, a cylindrical die 101 and an injection hole 104 which is attached to one end portion of the cylindrical die 101 and formed through the cylindrical die 101 are provided. A molding die 100 including a first end die 103 and a second end die 102 attached to the other end of the cylindrical die 101 is exemplified.

  As another example of the molding die, “a molding die having a through-hole cylindrical hole and a lid body that is attached to the opening of the cylindrical hole and seals the cylindrical hole has a concentric shape on the outer periphery thereof. And a wall on the end side of the roller of the groove is a leading beam (Patent Document 1). In addition, as another example, a molding die having “an upper cap 3 and a lower cap 4 that fix a core metal 2 coaxially in a cylindrical die 1” is described as a prior art ( FIG. 3 of Patent Document 2).

  By the way, Patent Document 3 includes “a mold having a penetrating cylindrical hole and a lid attached to both ends of the cylindrical hole in order to hold a shaft-shaped metal core member concentrically with the cylindrical hole. In addition, a “roller molding die” is described in which at least one of the lids is a movable lid provided with a molding material injection port and a ring gate (for example, claim 1 and FIG. 4).

JP-A-1-174423 FIG. 3 of Japanese Patent No. 2820742 JP 2000-289053 A

  By the way, when an elastic layer is molded around a shaft body using a molding die, a merged trace due to non-uniform injection or insufficient mixing in the molding material injected into the cavity formed by the molding die and the shaft body. In some cases, the molding material hardens with so-called “weld lines” in the elastic layer. In particular, in the molding die of Patent Document 1 and the molding die as the prior art of Patent Document 2, a weld line may be remarkably generated. Thus, the elastic layer in which the weld line is generated does not have a uniform circular shape in a cross section cut by a plane perpendicular to the axis, and the intended function as a roller cannot be exhibited.

  Patent Document 3 describes that the roller molding die of Patent Document 3 can prevent the occurrence of such a weld (Patent Document 3, column 0012, etc.), but it still cannot effectively prevent the occurrence of weld. In addition, it has been desired to further suppress the occurrence of weld lines.

  It is an object of the present invention to provide a molding die and a roller manufacturing method capable of forming an elastic layer substantially free of weld lines around a shaft body.

According to a first aspect of the present invention, there is provided a cylindrical mold in which a shaft body is disposed, and an injection hole through which a molding material circulates. A first end mold mounted on the end, and a second end mold having a discharge hole and mounted on the other end of the cylindrical mold, The inner diameter is constant and the outer diameter in the vicinity of the end decreases toward the end, and the first end mold extends along the axis from the disk-shaped base and the periphery of the disk-shaped base. and an annular peripheral wall standing, the peripheral wall is the inner diameter in the vicinity of the end portion is increased towards the end, and the end outer surface of the cylindrical mold and the end inner surface of the peripheral wall is fitted An annular runner portion is formed downstream of the injection hole, and the annular runner portion is a flat annular space and has a blocking surface facing the opening of the injection hole. And does not have a throttle portion for inhibiting the flow of the molding material, a molding die gate width of the ring gate is characterized in that it is a 0.2 to 1.5 mm,
A second aspect of the present invention is the molding die according to the first aspect, wherein the annular runner portion is concentrically formed with a cavity into which a molding material is injected and is disposed outside the cavity.
Claim 3 is the molding die according to claim 1 or 2, wherein the annular runner portion has the same height as the gate width.
Claim 4 is the molding die according to any one of claims 1 to 3, wherein the damming surface is a concentric annular flat surface extending to a cavity into which a molding material is injected.
Claim 5 is the molding die according to any one of claims 1 to 4, wherein the damming surface is an end face of the cylindrical die.
Claim 6 is the molding die according to any one of claims 1 to 5, wherein the damming surface has an annular groove.
A seventh aspect of the present invention is the molding die according to any one of the first to sixth aspects, wherein the molding material has a viscosity of 5 to 500 Pa · s when injected into the cavity.

As a second means for solving the above-mentioned problem, according to claim 8 , in the molding die according to claim 1 , a molding material is passed through the annular runner portion in a cavity defined around the shaft body. A method of manufacturing a roller, characterized by having a step of injecting
According to a ninth aspect of the present invention, in the injecting step, the molding material is circulated in the axial direction of the cavity, and then the circulatory direction is changed and circulated toward the shaft body, whereby the annular runner portion is passed into the cavity. The roller manufacturing method according to claim 8 , wherein the roller manufacturing method is an injection step.

The molding die according to the present invention includes the cylindrical mold and the first end mold having the injection hole and the second end mold, and is a flat annular space and has an opening in the injection hole. Has a damming surface facing the surface, does not have a throttle portion that hinders the flow of the molding material, and has an annular runner portion having a gate width of 0.2 to 1.5 mm on the downstream side of the injection hole. Then, the molding material that has passed through the injection hole is once merged and mixed in the annular runner portion, filled into the annular runner portion, and then passed through the ring gate having the gate width to substantially enter the cavity. The cavity can be injected without a weld line. Further, the roller manufacturing method according to the present invention comprises a molding material in a cavity, a flat annular space and a damming surface facing the opening of the injection hole, and a throttle portion that hinders the flow of the molding material And having a step of injecting via an annular runner having a gate width of 0.2 to 1.5 mm, the molding material can be injected into the cavity substantially without a weld line. Can do. Therefore, according to the present invention, it is possible to provide a molding die and a roller manufacturing method capable of forming an elastic layer substantially free of weld lines around the shaft body.

FIG. 1 is a schematic view showing a molding die as an example of a molding die according to the present invention, and FIG. 1 (a) is a schematic cross-sectional view showing a molding die as an example of a molding die according to the present invention. FIG. 1B is a schematic enlarged cross-sectional view showing the vicinity of a ring gate portion of a molding die which is an example of the molding die according to the invention. FIG. 2 is a schematic enlarged sectional view showing the vicinity of a ring gate portion of a molding die which is another example of the molding die according to the present invention. Figure 3 is a schematic enlarged sectional view showing the vicinity re Ngugeto portion of the mold is a reference example. FIG. 4 is a schematic cross-sectional view showing a state in which a shaft body is arranged in a molding die that is an example of a molding die according to the present invention. FIG. 5 is a schematic perspective view showing an example of a roller manufactured by the molding die and the roller manufacturing method according to the present invention. FIG. 6 is a schematic cross-sectional view showing an example of a conventional molding die.

  First, a description will be given of a roller manufactured by a molding die and a roller manufacturing method according to the present invention (hereinafter sometimes referred to as a roller according to the present invention). The roller according to the present invention may be a roller in which an elastic layer is disposed on the outer peripheral surface of the shaft body, and may include, for example, an adhesive layer, a primer layer, a surface layer, or the like in addition to the shaft body and the elastic layer. .

  In the roller according to the present invention, the elastic layer formed on the outer peripheral surface of the shaft body has substantially no weld line and high shape uniformity. For example, the shape of the cross section in a cross section obtained by cutting the elastic layer along a plane perpendicular to its axis (sometimes referred to as a cross sectional shape) is almost a perfect circle, and specifically, a perfect circle of 2.0 μm or less. When the occurrence of weld lines is further suppressed, the roundness (arithmetic average value) is 1.0 μm or less. Here, according to JIS B0621: 1984, the roundness refers to the magnitude of a deviation from a geometrically correct circle of a circular shape (hereinafter referred to as a geometric circle). When the distance between two concentric circles is the smallest when they are sandwiched between concentric geometric circles, they are expressed as the difference between the radii of the two circles and expressed as roundness μm ”. In short, the roundness is a value indicating how much the cross-sectional shape is displaced with respect to the perfect circle. This roundness is measured by using a roundness measuring instrument (for example, trade name “RONDCOM44DX (manufactured by Tokyo Seimitsu Co., Ltd.)”) and a 2RC filter (position compensation digital filter), and the least square center method (LSC) in the center method. (The least squares center method)) is calculated by the radial difference between the center calculated by the concentric inscribed circle and circumscribed circle, and can be an arithmetic average value calculated using several points of the elastic layer as measurement points. .

  An example of the roller according to the present invention will be described with reference to the drawings. The roller 70 as an example includes a shaft body 71 and an elastic layer 72 as shown in FIG.

  The shaft body 71 is basically the same as a shaft body in a conventionally known roller. The shaft body 71 is a so-called “core metal” made of iron, aluminum, stainless steel, brass, or the like, and has good conductive characteristics. The shaft body 71 may be a shaft body that is made conductive by plating an insulating core body such as a thermoplastic resin or a thermosetting resin.

  The elastic layer 72 is basically the same as the elastic layer in a conventionally known roller except that the shape uniformity is high. That is, the elastic layer 72 has a high shape uniformity with substantially no weld line and a roundness (arithmetic average value) of 2.0 μm or less. The elastic layer 72 is an elastic layer formed by curing a rubber composition described later on the outer peripheral surface of the shaft body 5 by the molding die and the roller manufacturing method according to the present invention. The elastic layer 72 is adjusted to an appropriate hardness, electrical resistance, thickness, etc. according to the application. The thickness of the elastic layer 72 is usually preferably 1 to 30 mm, and more preferably 5 to 20 mm.

  The molding die according to the present invention is a type of injection molding die for molding an elastic layer on the outer peripheral surface of a shaft body, and is mounted on both ends of the cylindrical die and the cylindrical die. An annular mold having an end mold and having a ring width of 0.2 to 1.5 mm along the axial direction of the ring mold that opens to a cavity formed by the mold and the shaft A runner portion is provided downstream of the injection hole drilled in one end mold, that is, between the injection hole and the cavity. In the molding die according to the present invention, the gate width is preferably 0.2 to 1.0 mm, particularly preferably 0.3 to 0.8 mm, in that generation of weld lines can be highly prevented. For example, it can be more than 0.5 mm.

  An example of the molding die according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 (a) and 1 (b), a molding die 1 as an example of a molding die according to the present invention includes a cylindrical die 11 in which a shaft body is disposed, and a cylinder. A first end mold 15 attached to one end 21 of the mold 11 and a second end mold 18 attached to the other end 22 of the cylindrical mold 11, The gate width G of the ring gate 51 formed in the mold 11, the first end mold 15 and the second end mold 18 and opening into the cavity 5 (see FIG. 4) into which the molding material is injected is 0. An annular runner 6 having a diameter of 2 to 1.5 mm is provided on the downstream side of the injection hole 31 of the first end mold 15.

  As shown in FIGS. 1 (a) and 1 (b), the cylindrical mold 11 is a hollow cylindrical body in which both end portions 21 and 22 are open and is also referred to as a tubular mold. The cylindrical mold 11 has a shaft hole 23 having a constant inner diameter, and a shaft body 71 is disposed in the shaft hole 23 along the axial direction (see FIG. 4). The cylindrical mold 11 has a constant outer diameter at the center, and the outer diameter in the vicinity of the end portions 21 and 22 gradually decreases toward the end portions 21 and 22. Has annular end faces 24 and 25 perpendicular to the axis. The cylindrical mold 11 is preferably adjusted to have a surface roughness on its inner surface, and is particularly preferably a mirror surface. The cylindrical mold 11 is adjusted in outer diameter, inner diameter, axial length and the like according to the elastic layer 72 to be molded.

As shown in FIGS. 1A and 1B, the first end mold 15 includes a disc-shaped base 33 and an annular peripheral wall 32 extending along the axis from the periphery of the disc-shaped base 33. The lid body has a bottomed tubular shape. The first end portion mold 15 has a flat area on the bottom surface of the disc-shaped substrate 33 that faces at least the annular end face 24, and in this example, an area excluding a holding hole 34 and an injection hole 31 described later is flat. The peripheral wall 32 is formed so that the inner diameter in the vicinity of the opening end gradually increases toward the opening end. The gradually increasing inner diameter of the peripheral wall 32 coincides with the gradually decreasing outer diameter of the end 21, and an annular space between the annular end surface 24 of the cylindrical mold 11 and the first end mold 15, that is, an annular runner described later. It is adjusted so that part 6 may be formed. Therefore, the first end mold 15 is attached to one end 21 of the cylindrical mold 11 such that the annular runner 6 is formed by fitting the peripheral wall 32 and the end 21. Thus, the first end mold 15 closes one end 21 of the cylindrical mold 11.

  The first end mold 15 has a plurality of, specifically, eight injection holes (also referred to as sprues) 31 that are arranged at equal intervals on a concentric circle and through which the molding material flows when the molding material is injected. Have. The concentric circle in which the injection hole 31 is arranged is configured so that the injection hole 31 faces the annular end surface 24 of the cylindrical mold 11 as described later. The injection holes 31 preferably have the same shape and the same dimensions, and the shape and inner diameter are appropriately set. In this first end mold 15, the injection hole 31 has a constant inner diameter R along its axis, for example, an inner diameter of 0.3 to 3.0 mm, preferably 0.3 to 2.0 mm. . The first end mold 15 has a bottomed holding hole 34 for holding the shaft body on its axis.

  As shown in FIGS. 1A and 1B, the second end mold 18 is equidistantly arranged on a concentric circle instead of the injection holes 31 functioning as a passage when the molding material is injected. 4 discharge holes (also referred to as vents) 41 functioning as gas or molding material discharge paths when the molding material is injected or the molding material is hardened. Except for this, it is basically the same as the first end mold 15. Therefore, the second end mold 18 is a lid body having the discharge hole 41, the peripheral wall 42, the disc-shaped base body 43, and the holding hole 44, and closes the other end 22 of the cylindrical mold 11.

  As shown in FIG. 1A and FIG. 1B, when the cylindrical mold 11 and the first end part mold 15 are assembled, the molding mold 1 is formed with an annular end surface 24 of the cylindrical mold 11. And the first end mold 15, that is, on the downstream side of the injection hole 31 and on the shaft hole 23, that is, on the upstream side of the cavity 5 (see FIG. 4), along the inner surface of the peripheral wall 32. An annular space surrounded by the annular end surface 24 and the bottom surface of the disk-shaped base 33 of the first end mold 15, that is, an annular runner portion 6 is defined. The annular runner portion 6 has the same distance, that is, the height between the annular end surface 24 and the bottom surface of the disc-shaped substrate 33 in the radial direction, which is the same as the gate width G described later, and is flat in the axial direction of the cylindrical mold 11. An annular space. An injection hole 31 communicates with the annular runner portion 6, and an annular end face 24 arranged on the axial extension line of the injection hole 31 facing the opening of the injection hole 31 extends to the axial hole 23, that is, the cavity 5. An annular flat surface that is concentric with the shaft hole 23 and that once blocks the molding material injected from the injection hole 31 and changes the injection direction from the axial direction of the cylindrical mold 11 to its circumferential direction. Function as. Thus, as shown in FIGS. 1 (a) and 1 (b), the annular runner portion 6 is provided with a protruding portion that restricts the flow of the molding material both in the height direction and in the radial direction, such as a throttle portion. I don't have it. The annular runner portion 6 casts the molding material that has passed through the injection hole 31 before flowing into the cavity 5 to join and mix. This blocking surface 24 is preferably perpendicular to the axis of the injection hole 31 and the axis of the cylindrical mold 11.

  As shown in FIGS. 1A and 1B and FIG. 4, the annular runner portion 6 is concentric with the axial hole 23, that is, the cavity 5, and is disposed radially outward from the cavity 5. A ring gate 51 is opened on the end peripheral surface of the first end mold 15 side. The ring gate 51 includes a gate width G, that is, an opening width G to the cavity 5, and a separation distance between the cylindrical mold 11 and the first end mold 15 is 0.2 to 1.5 mm. Here, the gate width G is normally constant in the circumferential direction and is a length along the axial direction of the cylindrical mold 11 in the ring gate 51. In the present invention, the gate width G may be an average value. If the gate width G is less than 0.2 mm, it is difficult for the molding material to flow into the cavity 5 and the elastic layer cannot be molded. Also, if the molding material injection pressure is increased in order to flow the molding material into the cavity 5, In some cases, a weld line is likely to occur in the flowed molding material. On the other hand, when the gate width G exceeds 1.5 mm, the molding material that has flowed into the annular runner portion 6 does not merge and mix in the annular runner portion 6 without the molding material that has passed through the injection hole 31 annularly. In some cases, it is not possible to prevent the generation of the weld line by passing through the ring gate 51 and flowing into the cavity 5 without filling the portion 6. In the present invention, the gate width G is 0.2 to 1 in that an elastic layer having substantially no weld line can be formed by highly preventing a weld line that may be generated when the molding material flows into the cavity 5. 0.0 mm is preferable, and 0.3 to 0.8 mm is particularly preferable. Here, “substantially no weld line” means that the desired function as a roller can be exhibited when used as a roller in an image forming apparatus, in addition to the case where there is no weld line. This includes the case where a large weld line is generated.

  Another example of the molding die according to the present invention will be described. As shown in FIG. 2, the molding die 2 is basically the same as the molding die 1 except that the cylindrical die 12 is different. That is, the molding die 2 includes a cylindrical die 12, a first end die 15, and a second end die 18 (not shown in FIG. 2), and a ring gate 55 that opens into the cavity 5. An annular runner portion 7 having a gate width G of 0.2 to 1.5 mm is provided downstream of the injection hole 31 of the first end mold 15.

  As shown in FIG. 2, the cylindrical mold 12 has an annular groove 27 concentric with the annular runner portion 7 on the blocking surface 26 which is the annular end surface 26 on the first end mold 15 side. Except this, it is basically the same as the cylindrical mold 1. The annular groove 27 is concentric with the shaft hole 23, that is, the cavity 5, and is formed in an annular shape on the annular end surface 26 so that the bottom surface thereof faces the opening of the injection hole 31. Accordingly, the annular groove 27 has an annular damming bottom surface 28 that is disposed on the axial extension line of the injection hole 31 with a space therebetween. The first end mold 15 and the second end mold 18 are as described above.

  As shown in FIG. 2, when the cylindrical mold 12 and the first end mold 15 are assembled, the molding mold 2 is configured such that the annular end face 26 and the first end mold 15 of the cylindrical mold 12 are assembled. A flat annular shape surrounded by the circumferential wall 32, the annular end surface 26, the damming bottom surface 28, and the bottom surface of the disk-shaped substrate 33 of the first end mold 15 along the inner surface of the circumferential wall 32. A space or annular runner portion 7 is defined. The annular runner portion 7 has an annular groove 27 formed in the annular end surface 26. Like the annular runner part 6, the annular runner part 7 is filled with the molding material that has passed through the injection hole 31 by casting it into the annular runner part 7 before flowing into the cavity 5, and joining and mixing.

  As shown in FIGS. 1 and 2, the annular runner portion 7 is basically the same as the annular runner portion 6 except for the presence or absence of the annular groove 27. That is, the annular runner portion 7 is concentric with the shaft hole 23, that is, the cavity 5, and is disposed radially outward from the cavity 5, and the ring gate 55 opens in the cavity 5 with a gate width G of 0.2 to 1.5 mm. . The space between the opening of the injection hole 31 in the annular runner portion 7 and the weir bottom surface 28 of the annular groove 27 and the width of the annular groove 27 are not particularly limited as long as the molding material can be filled in the annular runner portion 7. For example, it can be set to 0.5 to 2.0 mm and 0.3 to 3.0 mm, respectively.

A molding die as a reference example will be described. As shown in FIG. 3, the molding die 3 is basically the same as the molding die 1 except that the formation mode of the annular runner portion 8 is different. That is, in the molding die 1, the annular runner portion 6 is formed by the cylindrical die 11 and the first end portion die 15, but the molding die 1 has the first end portion die 16 having the annular runner portion 8. The cylindrical mold 13 is not involved in the formation of the annular runner portion 8. Therefore, the molding die 3 includes a cylindrical die 13, a first end die 16, and a second end die (not shown in FIG. 3), and the first end die 16 is formed in the cavity 5. An annular runner portion 8 having an opening ring gate 57 with a gate width G of 0.2 to 1.5 mm is provided on the downstream side of the injection hole 31.

  As shown in FIG. 3, the cylindrical mold 13 is basically the same as the cylindrical mold 11 except that both the inner diameter and the outer diameter are tubular bodies.

  As shown in FIG. 3, the first end mold 16 includes a disc-like base 35, a peripheral wall 36 extending along the axis from the periphery of the disc-like base 35, and an edge from the peripheral wall 36 to the axis. A flat annular runner portion 8 is defined by the disc-shaped base body 35, the inner surface of the peripheral wall 36, and the inner side surface of the annular dam portion 37. ing. The peripheral wall 36 has a constant inner diameter and outer diameter, and the axial length is the same as the gate width G of the annular runner portion 8 described later. The annular dam 37 has the same outer diameter as the peripheral wall 36, and has the same inner diameter as the inner diameter of the cylindrical mold 13. The top surface of the annular dam 37 is flat, and is attached to one end 21 of the cylindrical mold 13 by contacting the flat annular end surface 29 of the cylindrical mold 13. The injection hole 31 of the first end mold 16 is arranged concentrically so as to face the inner surface of the annular dam 37 and is basically the same as the injection hole 31 of the first end mold 15. Is formed. In the first end mold 16, the annular runner portion 8 communicates with the injection hole 31, and faces the opening of the injection hole 31, and the inside of the annular dam portion 37 disposed on the axial extension line of the injection hole 31. The side surface is an annular flat surface concentric with the shaft hole 23, that is, the shaft hole 23 extending to the cavity 5, and functions as a blocking surface 38.

  Although not shown in FIG. 3, the second end mold of the molding mold 3 is basically the same as the first end mold 16 except that it has a discharge hole instead of the injection hole 31. .

  As shown in FIGS. 1 and 3, the annular runner portion 8 is basically the same as the annular runner portion 6 except that it is formed by the first end mold 16. That is, the annular runner portion 8 is concentric with the axial hole 23, that is, the cavity 5, and is disposed radially outward from the cavity 5, and the ring gate 57 opens in the cavity 5 with a gate width G of 0.2 to 1.5 mm. .

  The cylindrical molds 11, 12 and 13, the first end molds 15 and 16, and the second end mold 18 and the second end mold of the molding mold 3 have a certain degree of strength and molding material, respectively. It is made of a material having heat resistance at the temperature when heat-curing. Examples of such materials include copper, copper alloy, brass, bronze, aluminum, aluminum alloy, steel, various types of plated iron, iron alloy, stainless steel, and the like. The cylindrical mold, the first end mold and the second end mold are preferably formed of the same material.

  As described above, since the molding dies 1, 2 and 3 all have the annular runner portions 6, 7 and 8 having the gate width G of 0.2 to 1.5 mm, the molding material which has passed through the injection hole 31. Is flown to the annular runner portions 6, 7 and 8 before being blocked by the blocking surfaces 24, 26 and 28 and 38 and flowing into the cavity 5. As described above, the molding dies 1, 2, and 3 have the gate width after the molding material is once merged and mixed in the annular runner portions 6, 7, and 8 to fill the annular runner portions 6, 7, and 8. The G ring gates 51, 55 and 57 are passed through the cavity 5. Therefore, the molding dies 1, 2, and 3 can flow or inject the molding material into the cavity 5 with substantially no weld line. Therefore, according to the molding dies 1, 2, and 3 as examples of the molding dies according to the present invention, a highly uniform elastic layer substantially free of weld lines can be molded around the shaft body.

  The molding die according to the present invention is not limited to the above-described example, and various modifications can be made within a range in which the object of the present invention can be achieved. That is, each of the molding dies 1, 2 and 3 includes the first end mold 15 or 16 and the second end mold 18 having the same structure. The mold need not have the same structure for the first end mold and the second end mold, and may have different structures.

  In the molding dies 1, 2 and 3, the first end molds 15 and 16 have eight injection holes 31, and the second end mold 18 has four discharge holes 41. However, in the present invention, the number of injection holes that the first end mold has and the number of discharge holes that the second end mold have are not particularly limited, and may be one or more, and the shape thereof may also be It is not specifically limited, A ring shape may be sufficient.

  In the molding dies 1, 2 and 3, the injection hole 31 and the discharge hole 41 all have a constant inner diameter along the axis. In this invention, the injection hole and the discharge hole are dammed along the axis. You may have the internal diameter which expands or reduces in diameter toward a surface. In this case, the inner diameter R of the injection hole is the opening diameter.

  Next, a roller manufacturing method according to the present invention for manufacturing a roller having an elastic layer disposed on the outer peripheral surface of the shaft body will be described. The roller manufacturing method according to the present invention includes a step of injecting a molding material into a cavity defined around a shaft body via an annular runner having a gate width of 0.2 to 1.5 mm. When the molding material is injected into the cavity through the annular runner portion in this way, the molding material is once merged and mixed in the annular runner portion and filled into the annular runner portion before being injected into the cavity 5. Then, it flows or injects into the cavity 5 with substantially no weld line. The step of injecting in the roller manufacturing method according to the present invention is performed from a ring gate having a gate width G of 0.2 to 1.5 mm via a flat annular runner portion having no protrusion or the like having the same height as the gate width. The molding material is preferably injected into the cavity. The roller manufacturing method according to the present invention is preferably carried out using the molding die according to the present invention.

  As an example of the roller manufacturing method according to the present invention, a roller manufacturing method (sometimes referred to as a one-roller manufacturing method) for manufacturing the roller 70 shown in FIG.

  In this one-roller manufacturing method, first, the shaft body 71 is prepared. The shaft body 71 is made of, for example, a metal such as iron, aluminum, stainless steel, brass, or an alloy thereof, a resin such as a thermoplastic resin or a curable resin, and carbon black or metal powder as a conductivity imparting agent for the resin. Using a material such as a conductive resin blended with the above, a desired shape is produced by a known method. When the shaft body 71 is required to have conductivity, the shaft body 71 is manufactured by plating the surface of an insulating core formed of the resin or the like in addition to the metal and the conductive resin by a conventional method. be able to. Among the above materials, a metal is preferable and aluminum or stainless steel is particularly preferable from the viewpoint that conductivity can be easily imparted. The shaft body 71 may be coated with an adhesive or a primer on its outer peripheral surface as desired.

  Next, in the one-roller manufacturing method, as shown in FIG. 4, the molding die 1 is assembled, and the shaft body 71 is disposed in the molding die 1. Specifically, the end portions of the shaft body 71 inserted into the shaft hole 23 (see FIG. 1) of the cylindrical mold 11 are respectively connected to the holding hole 34 of the first end mold 15 and the second end mold. 18 are inserted into the holding holes 44 and held.

  In the one-roller manufacturing method, a molding material is then injected into the molding die 1 through the injection hole 31. The molding material is injected using a known injection molding machine or a casting machine. When the molding material is injected from the injection hole 31 in this manner, the molding material can flow into or be injected into the cavity 5 with substantially no weld line. Specifically, the molding material injected from the injection hole 31 passes through the injection hole 31 and abuts against the blocking surface 24 to block the flow in the same direction, along the blocking surface 24 and the peripheral wall 32. It is cast and filled into the annular runner portion 6 to be joined and mixed into a uniform state. The molding material filled in the annular runner portion 6 in this way then passes through the ring gate 51 having the gate width G and enters the cavity 5. In this way, the molding material that has entered the cavity 5 has substantially no weld line due to merging or the like. Therefore, the cavity 5 is filled with the molding material injected substantially without a weld line.

  In the one-roller manufacturing method, the molding material is thus injected into the cavity 5 via the annular runner portion 6 having a gate width of 0.2 to 1.5 mm. Is circulated in the injection hole 31 in the axial direction of the cavity 5, that is, in the width direction of the ring gate 51, and then is circulated in the annular runner portion 6 by changing the flow direction in the horizontal direction of the axial direction. That is, it is a step of injecting into the cavity 5 from the annular runner portion 6 by flowing toward the shaft body 51 or the cavity 5.

  In the one-roller manufacturing method, it is preferable that the temperature of the molding material when the molding material is injected is 20 ° C. or more in that a weld line is less likely to occur. That is, in one-roller manufacturing method, it is preferable that the molding material is heated or kept warm so as to be in the temperature range when the molding material is injected. For example, the mold preheating temperature when the molding material is injected is It is preferable that the molding material is heated or kept warm by being heated in the range of 100 to 150 ° C.

  In the one-roller manufacturing method, the molding material for forming the elastic layer 72 may be a rubber composition containing rubber that is liquid at room temperature. Examples of liquid rubber include silicone or silicone-modified rubber, nitrile rubber, and ethylene propylene. Examples thereof include liquid rubbers such as rubber (including ethylene propylene diene rubber), styrene butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, acrylic rubber, chloroprene rubber, butyl rubber, epichlorohydrin rubber, urethane rubber, and fluorine rubber. These rubbers are preferably an addition-curing type because they are excellent in dimensional accuracy during heat molding.

  The rubber composition may contain various additives usually contained in the rubber composition in addition to rubber. Examples of the various additives include vulcanizing agents, vulcanization accelerators, and vulcanization accelerators. Auxiliary agent, vulcanization retarder, conductivity imparting agent, dispersant, foaming agent, anti-aging agent, antioxidant, filler, pigment, colorant, processing aid, softener, plasticizer, emulsifier, curing agent, Examples thereof include a heat resistance improver, a flame retardant improver, an acid acceptor, a heat conductivity improver, a release agent, and a solvent. These various additives may be commonly used additives or may be specially used additives depending on applications.

  The rubber composition may have a viscosity of 5 to 500 Pa · s at 25 ° C., for example, at a temperature of 10 to 200 Pa · s. It is particularly good to have a viscosity.

As such a rubber composition, for example, an addition-curable millable conductive silicone rubber composition and an addition-curable liquid conductive silicone rubber composition can be preferably exemplified. Addition-curable millable conductive silicone rubber composition: (A) Average composition formula: R _n SiO _{(4-n) / 2} (R may be the same or different, substituted or unsubstituted monovalent hydrocarbon Group, preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and n is a positive number of 1.95 to 2.05). An addition-curable millable conductive silicone rubber composition containing siloxane, (B) a filler, and (C) a conductive material other than those belonging to the component (B). Each of these components (A) to (C) is basically the same as, for example, each component in “The following silicone rubber composition that is a millable type” described in JP-A-2008-058622. Further, as an addition curable liquid conductive silicone rubber composition, (D) organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule, and (E) bonded to silicon atoms in one molecule. An organohydrogenpolysiloxane containing at least two hydrogen atoms, (F) an inorganic filler having an average particle size of 1 to 30 μm and a bulk density of 0.1 to 0.5 g / cm ³ , (G And an addition-curable liquid conductive silicone rubber composition containing a conductivity imparting agent and (H) an addition reaction catalyst. These components (D) to (H) are basically the same as the components in the “liquid silicone composition” described in, for example, JP-A-2008-058622.

  Moreover, the foamed rubber composition containing a foaming agent can also be used as a rubber composition, For example, an addition reaction type foaming silicone rubber composition can be mentioned suitably as such a foamed rubber composition. As the addition reaction type foamed silicone rubber composition, a vinyl group-containing silicone raw rubber, a silica-based filler, a foaming agent, an addition reaction crosslinking agent, an addition reaction catalyst, a reaction control agent, and a conductivity imparting agent are included. An addition reaction type foamed silicone rubber composition containing an organic peroxide cross-linking agent and various additives as desired. These components are basically the same as those in the “addition reaction type foamed silicone rubber composition” described in, for example, Japanese Patent Application Laid-Open No. 2008-076751.

  In the one-roller manufacturing method, the elastic material 72 is then molded by heat-curing the molding material injected into the cavity 5. The heating condition of the molding material may be any heating condition that allows the molding material to be cured, and is determined according to the molding material. For example, when an addition curable liquid conductive silicone rubber composition is used as the molding material, the heating temperature can be set to 100 to 150 ° C., and the heating time can be set to 10 seconds to 1 hour. In order to heat the molding material to the above range in this one-roller manufacturing method, for example, it is preferable to set the hot platen temperature around the molding die to 100 to 150 ° C.

  Thus, the roller 70 shown in FIG. 5 can be manufactured by forming the elastic layer 72 on the outer peripheral surface of the shaft 71. In the case where a surface layer or the like is formed on the outer peripheral surface of the elastic layer 72, a thin-layer tube that is cured after the material for forming the surface layer or the like is applied to the outer peripheral surface of the elastic layer 72, or becomes a surface layer or the like The surface layer and the like can be formed by covering the elastic layer 72 with the like.

  Thus, in the one-roller manufacturing method, the molding material that has passed through the injection hole 31 is once merged and mixed in the annular runner portion 6 to fill the annular runner portion 6, and then the ring gate 51 having the gate width G. Can be allowed to enter the cavity 5. Therefore, according to the one-roller manufacturing method, the molding material can be injected into the cavity 5 with substantially no weld line. Thus, the elastic layer formed by heat-curing the molding material injected into the cavity 5 with substantially no weld line has substantially no weld line and has a highly uniform shape having a roundness of 2.0 μm or less. It has sex.

  In the roller manufacturing method according to the present invention, even if the molding dies 2 and 3 are used, the molding material is once filled in the annular runner portion 7 or 8 as in the one-roller manufacturing method using the molding die 1. Since the ring gate 55 or 57 having the gate width G can be passed through the cavity 5 later, the molding material can be injected into the cavity 5 substantially without a weld line. Therefore, the elastic layer formed by heat-curing the molding material injected into the cavity 5 in a state substantially free of weld lines is substantially free of weld lines and has a roundness (arithmetic average value) of 2.0 μm or less. High shape uniformity.

  The roller manufacturing method according to the present invention is not limited to the above-described example, and various modifications can be made within a range in which the object of the present invention can be achieved. For example, the roller manufacturing method according to the present invention may have a step of heating the molding material again (secondary heating) after the step of curing the molding material, if desired. The step of cutting the end portion of the molded elastic layer and / or the step of adjusting the outer diameter of the molded elastic layer may be included after the step of curing.

(Example 1)
A molding die 1 having the following dimensions was made of NAK steel.
Cylindrical mold 11: Axis length 237 mm, outer diameter 26 mm, inner diameter (mirror finished) 12 mm, flat annular end surface (damming surface) 24 width 3 mm,
First end mold 15: outer diameter 26mm, holding hole 34 inner diameter 6mm, peripheral wall 32 tip thickness 1mm, peripheral wall 32 axial length 14mm, disc-shaped base 33 axial length 22mm, disc-shaped base 33 18 mm in diameter of the flat bottom surface, inner diameter R1.5 mm of the injection hole 31, 22 mm of the axial length of the injection hole 31, 16 mm in diameter of a virtual circle in which the axes of the eight injection holes 31 are arranged,
Second end mold 18: outer diameter 26 mm, holding hole 43 inner diameter 6 mm, peripheral wall 42 tip thickness 1 mm, peripheral wall 42 axial length 14 mm, disc-shaped base 43 axial length 18 mm, disc-shaped base 43 18 mm in diameter of the flat bottom surface, an inner diameter R1.5 mm of the discharge hole 41, an axial length of the discharge hole 41 of 18 mm, a diameter of a virtual circle 16 mm in which the axes of the four discharge holes 41 are arranged,
The gate width G and the distance between the annular end face 25 and the disc-shaped substrate 43 are 0.5 mm.

  Shaft body 71 (made by SUM22, diameter 6 mm, length 281.5 mm) subjected to electroless nickel plating was washed with toluene, and a silicone primer (trade name “Primer No. 16”, Shin-Etsu Chemical Co., Ltd.) was formed on the surface. Co., Ltd.) was applied. The primer-treated shaft body 71 was fired at a temperature of 150 ° C. for 10 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer on the surface of the shaft body 71.

Next, 100 parts by mass of dimethylpolysiloxane (D) (degree of polymerization 300) blocked at both ends with dimethylvinylsiloxy groups, and hydrophobized fumed silica having a BET specific surface area of 110 m ² / g (Nippon Aerosil Co., Ltd.) Made by company, R-972) 10 parts by mass, average particle size 6 μm, diatomaceous earth (F) (Oplite W-3005S, manufactured by Hokuaki Diatomite Co., Ltd.) having a bulk density of 0.25 g / cm ³ , and 5 parts by mass of acetylene black (G) (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) was placed in a planetary mixer, stirred for 30 minutes, and then passed once through three rolls. This is returned to the planetary mixer again, and as a crosslinking agent, methyl hydrogen polysiloxane (E) having Si—H groups at both ends and side chains (polymerization degree 17, Si—H amount 0.0060 mol / g) 2. 1 part by mass, 0.1 part by mass of ethynylcyclohexanol and 0.1 part by mass of platinum catalyst (H) (Pt concentration 1%) are added as reaction control agents, and the mixture is stirred for 15 minutes and added. A curable liquid conductive silicone rubber composition was prepared. The viscosity of this addition curable liquid conductive silicone rubber composition was 50 Pa · s.

  Next, a release agent (trade name “Die Free”, manufactured by Daikin Industries, Ltd.) is applied to the inner surface of the prepared mold 1, and the holding hole 34 and the second end of the first end mold 15 are applied. The shaft body 71 is arranged in the cylindrical mold 11 with the holding hole 44 of the mold 18 to assemble the molding mold 1, and prepared from the injection hole 31 of the first end mold 15 in an environment of 23 ° C. Molding material was injected. Next, the molding material was heated from the outside of the molding die 1 to 150 ° C. and held at the same temperature for 15 minutes to heat the molding material. The molding die 1 was allowed to cool and the molded body was taken out from the molding die 1. The roller 70 provided with the elastic layer 72 was manufactured by cutting and removing 4 mm from both ends along the axial direction of the cured product of the addition curable liquid conductive silicone rubber composition.

(Example 2)
Basically the same as Example 1, except that the axial length 22 mm of the disc-shaped substrate 33 in the first end mold 15 in Example 1 is changed to 22.3 mm and the gate width G is set to 0.2 mm. The roller was manufactured.

(Example 3)
Basically the same as Example 1, except that the axial length 22 mm of the disc-shaped substrate 33 in the first end mold 15 in Example 1 is changed to 21.0 mm and the gate width G is changed to 1.5 mm. A roller was manufactured.

Example 4
Example except that the addition amount of fumed silica in the addition-curable liquid conductive silicone rubber composition was changed to 1 part by mass and the viscosity of the addition-curable liquid conductive silicone rubber composition was adjusted to 5 Pa · s. A roller was manufactured basically in the same manner as in Example 1.

(Example 5)
Example except that the addition amount of fumed silica in the addition curable liquid conductive silicone rubber composition was changed to 60 parts by mass and the viscosity of the addition curable liquid conductive silicone rubber composition was adjusted to 500 Pa · s. A roller was manufactured basically in the same manner as in Example 1.

(Comparative Example 1)
A roller is manufactured basically in the same manner as in Example 1 except that the axial length 22 mm of the disc-shaped substrate 33 in the first end mold 15 is changed to 20.5 mm and the gate width G is set to 2.0 mm. did.

(Evaluation of elastic layer uniformity)
The uniformity of the elastic layer was evaluated using each of the rollers thus produced. Specifically, the elastic layer of each roller is subjected to the above-described method using the aforementioned roundness measuring device “RONDCOM44DX (manufactured by Tokyo Seimitsu Co., Ltd.)” for each of cross-sectional shapes in a plurality of planes perpendicular to the axial direction of the roller. The roundness (arithmetic mean value) was calculated according to As a result, each of the rollers of Examples 1 to 5 had a roundness of 2.0 μm or less and a cross-sectional shape, that is, a cross-sectional outline was substantially circular, whereas Comparative Example 1 had a roundness of 4.0 μm. The cross-sectional shape in which the convex part and the concave part exist was largely off the circle. In this way, when the roundness (arithmetic mean value) of the roller is 2.0 μm or less and the cross-sectional shape is almost circular, there is substantially no weld line in the elastic layer. When the image forming apparatus is mounted on the apparatus, it is easy to contribute to the formation of a high-quality image, for example, an image having a substantially uniform print density when such a roller is mounted on the image forming apparatus as a developing roller. Guessed.

1, 2, 3 Mold 5 Cavity 6, 7, 8 Annular runner part 11, 12, 13 Cylindrical mold 15, 16 First end mold 18 Second end mold 21 One end 22 The other End 23 of shaft 24, 25 annular end surface (damming surface)
26 Annular end face (damming face)
27, 53 Annular groove 28 Damping bottom surface 29 Annular end surface 31 Injection hole (sprue)
32, 36, 42 Peripheral walls 33, 35, 43 Disk-shaped base bodies 34, 44 Holding hole 37 Annular damming portion 38 Inner side surface (damming surface)
41 Discharge hole (vent)
51, 55, 57 Ring gate 52 Damming surface 70 Roller 71 Shaft body 72 Elastic layer 100 Molding die 101 Cylindrical die 102 Second end die 103 First end die 104 Injection hole

Claims (9)

A cylindrical mold in which the shaft body is disposed, a first end mold having an injection hole through which a molding material flows, and mounted on one end of the cylindrical mold, and a discharge hole A second end mold attached to the other end of the cylindrical mold,
The cylindrical mold has a constant inner diameter, and the outer diameter near the end portion decreases toward the end portion,
The first end mold includes a disk-shaped base and an annular peripheral wall extending along the axis from the periphery of the disk-shaped base, and the peripheral wall has an inner diameter near the end that increases toward the end. And
The end inner surface and then fitting the end portion outer surface of the tubular mold wall, annular runner portion is formed on a downstream side of said injection hole,
The annular runner portion is a flat annular space, has a blocking surface facing the opening of the injection hole, does not have a throttle portion that hinders the flow of the molding material, and the gate width of the ring gate is 0 A molding die having a thickness of 2 to 1.5 mm.   The molding die according to claim 1, wherein the annular runner portion is concentric with a cavity into which a molding material is injected and is disposed outside the cavity.   The molding die according to claim 1, wherein the annular runner portion has the same height as the gate width.   The molding die according to any one of claims 1 to 3, wherein the blocking surface is a concentric annular flat surface extending to a cavity into which a molding material is injected.   The molding die according to any one of claims 1 to 4, wherein the blocking surface is an end surface of the cylindrical mold.   The molding die according to claim 1, wherein the blocking surface has an annular groove.   The molding die according to any one of claims 1 to 6, wherein the molding material has a viscosity of 5 to 500 Pa · s when injected into the cavity.   The roller manufacturing method according to claim 1, further comprising a step of injecting a molding material into the cavity defined around the shaft body through the annular runner portion.   The step of injecting is a step of injecting the molding material from the annular runner portion into the cavity by flowing in the axial direction of the cavity and then flowing toward the shaft body while changing the flow direction. The roller manufacturing method according to claim 8.

Images