JP4454331B2 - Roller mold - Google Patents

Description

  The present invention relates to a mold for molding a roller having a roller main body formed by injecting resin or rubber around a core metal, and in particular, a roller having high accuracy of outer diameter deflection without polishing finish. It relates to what can be molded.

  Various resin rollers or rubber rollers are used in image forming apparatuses such as laser printers, copiers, and fax machines. These include, for example, a charging roller that charges the surface of the photosensitive drum, a developing roller that transfers toner onto the photosensitive drum to develop a latent image, a toner supply roller that supplies toner to the developing roller, and a toner on the photosensitive drum that is paper A transfer roller for transferring to a recording medium such as a cleaning roller, a cleaning roller for wiping off toner remaining on the photosensitive drum, a paper feed roller for feeding paper, and the like. Most of these rollers form a roller main body around the cored bar. It is formed by injecting resin or rubber.

  As a mold used for molding such a roller, a mold 90 shown in a sectional view in FIG. 1A is known (for example, see Patent Document 1). A left and right shaft end metal that has a main body mold 92 having a cavity space 91 corresponding to the main body and a hole 93 for fixing the end of the core metal, and that specifies the core metal extending direction region of the cavity space 91. An opening space 95 that accommodates at least one of the shaft end molds 94 in a core metal extending direction, and at least one of the shaft end molds 94 includes the mold 94. A gate portion 96 for injecting material is provided.

Such a mold 90 is formed by injecting resin or rubber material from the gate portion 96 into the cavity space 91 around the core metal, which is fixed by inserting both ends into the hole portion 93 of the shaft end die 94. The part can be formed, but has the following problems. That is, in the conventional mold 90, the shaft end mold 94 is made of metal such as iron, and therefore has high rigidity. Therefore, in order to efficiently insert and remove the core metal into the hole 93 of the shaft end mold 94, , as shown in cross section in FIG. 1 (b), the inner diameter D ₁ of the hole 93, the diameter of the core S than D _2, must be increased by a predetermined clearance d, this means that the hole The core S supported by 93 may be eccentric depending on the size of the clearance d with respect to the cavity space 91 arranged on the same central axis as the shaft end mold 92 when the mold is closed. As a result, the roller main body rotating around the central axis of the core metal generates a shake equivalent to this clearance, and the required image quality cannot be obtained. Polish the outer circumference of the roller body to Must be kept to within the range has been a problem.
JP-A-11-320569

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a roller molding die that can mold a roller with high accuracy of outer diameter runout without polishing finish. And

(1) The present invention is a gold used for molding a roller having a cylindrical roller main body formed by injecting a resin or a rubber material around an axial central portion of a core metal having both ends fixed. In the mold,
A main body mold having a cavity space corresponding to the roller main body section, and left and right shaft end molds each having a hole portion for fixing an end of the core metal and specifying a core metal extending direction region of the cavity space. The main body mold is provided with an opening space for accommodating at least one of the shaft end molds in the core metal extending direction, and a gate portion for injecting the material is provided on at least one of the shaft end molds. ,
Each of the shaft end dies is integrally formed of resin, and is arranged around the partition wall portion that specifies the core metal extending direction region of the cavity space, the hole wall portion surrounding the hole portion, and the hole wall portion. And a roller molding die that includes a plurality of rib portions that connect the hole wall portion and the partition wall portion .

(2) In the present invention, in (1), the shaft end mold is provided with an outer wall portion in surface contact with the wall surface of the opening space of the main body mold when the mold is closed, and the rib portion is formed on the outer wall portion. It is a die for roller molding formed by coupling.

(3) The present invention (2), the walls of the open space, from the cavity to the core extending outwardly configured to include a part of the conical surface as a diverging, the axis chicken feed type This is a roller molding die in which the outer wall portion is configured to come into surface contact with the conical surface when the die is closed.

(4) The present invention is the roller molding die according to any one of (1) to (3) , wherein the shaft end die is configured to have rotational symmetry around the hole center axis.

(5) The present invention is the roller molding die according to (4), wherein the rotational symmetry is established with respect to a rotationally symmetric operation of at least 120 degrees.

According to the invention of (1), since each of the shaft end dies is formed of a resin having flexibility instead of metal, the inner diameter of the hole and the outer diameter of the core metal are made substantially the same. The cored bar can be easily inserted into and removed from the hole part, so that the clearance between the hole part and the cored bar can be made almost zero, and the deflection of the roller main body part caused by this clearance can be suppressed. .

In addition, since the shaft end mold has a structure in which the hole wall portion and the partition wall portion are connected by the rib portion, the hole portion into which the core end portion is inserted can be prevented from falling down, and the hole portion and the roller body By maintaining a high degree of coaxiality with the cavity space corresponding to the portion, it is possible to further suppress roller runout.

According to the invention of (2), the shaft end mold is provided with the outer wall portion in surface contact with the wall surface of the opening space of the main body mold when the mold is closed. That is, the radial position with respect to the cavity space can be specified, the deterioration of the deflection of the roller main body due to the misalignment between the shaft end mold and the main body mold can be prevented. Since the rib portion is connected to the outer wall portion, deformation of the outer wall portion can be suppressed, and misalignment between the shaft end mold and the main body mold can be prevented more reliably.

According to the invention of (3), the outer wall of the shaft chicken feed type, under the mold closure, since it is configured to contact the conical surface and the surface forming the wall surface of the open space, the axes chicken feed type, the mold closure The position accuracy of the main body mold, that is, the core metal extending direction with respect to the cavity space can be increased, and variations in the length of the roller main body can be suppressed.

According to the invention of (4), since the shaft end mold has rotational symmetry around the hole center axis, the coaxiality of the hole wall part with respect to the outer wall part can be further increased.

According to the invention of (5), since the shaft end mold has rotational symmetry about the hole center axis with respect to 120 degree rotational symmetry operation, the hole wall portion is eccentric in a specific direction with respect to the outer wall portion. The possibility of this can be eliminated, and the coaxiality can be further increased.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing the structure of a roller molded by the roller molding die of the present invention. The roller 30 includes a cored bar 31 and an axially central part of the cored bar 31 excluding an axial end. And a roller main body portion 32 formed by injection molding of a resin or rubber material. Examples of the roller having such a structure include a charging roller, a developing roller, a toner supply roller, a transfer roller, a cleaning roller, and a paper feed roller used in an image forming apparatus such as a laser printer, a copying machine, and a fax machine. Can do.

FIG. 3 is a cross-sectional view showing a roller molding die for molding the roller 30. The roller molding die 10 includes a main body die 2 having a cavity space 1 corresponding to the roller main body portion 32, and a core metal 31. Left and right shaft end molds 4 having holes 3 for fixing the end portions of the hollow space 1 and specifying the region of the cavity space 1 in the core metal extending direction, that is, the region between the illustrated virtual planes P ₁ and P ₂ , The main body mold 2 is provided with an opening space 5 in which at least one of the shaft end molds 4 is accommodated in a core metal extending direction, and the material is injected into at least one of the shaft end molds 4. The gate portion 6 is provided. In FIG. 3, one of the shaft end molds 4 is shown in a sectional view and the other is shown in a side view.

4 is an arrow view corresponding to the IV-IV arrow view of FIG. 3, and the shaft end mold 4 is integrally formed of resin, and specifies the core metal extending direction region of the cavity space 1. A partition wall 11 that surrounds the hole 3, a wall 12 that surrounds the hole 3, an outer wall 13 that is in surface contact with the wall surface 5 A of the opening space 5 of the main body mold 2 when the mold is closed, and a hole disposed around the hole wall 12. A plurality of rib portions 15 that connect the wall portion 12, the partition wall portion 11, and the outer wall portion 13, and a proximal end plate 14 that continues to the proximal end of the outer wall portion 13 are provided. In addition, the gate portion 6 is provided to be opened in the partition wall portion 11. In the example shown in the drawing, a plurality of circular hole-shaped gate portions 6 are arranged at a predetermined pitch in the circumferential direction, but the gate portions 6 are composed of openings of various shapes and sizes. It is sufficient if it has a total opening area necessary for injecting the material and is evenly arranged in the circumferential direction.
The injected material passes through the opening of the base end plate 14, passes through the outer wall portion 13, and is guided to each gate portion 6.

In the axial chicken feed type 4 which is integrally formed of resin, the inner diameter D ₁ of the hole wall portion 12, even when approximately equal to the outer diameter D ₂ at both ends of the core metal 31, an end portion of the core metal 31 It is possible to easily put in and out of the hole portion 3, and therefore, by making D ₁ substantially equal to D ₂ , the end portion of the core metal is connected to the shaft end die 4 and thus the shaft end die when the die is closed. The cavity space 1 of the main body mold 2 arranged concentrically with the mold 4 can be matched with the center thereof, and as a result, the deflection of the roller main body portion 32 rotating around the central axis of the core metal 31 can be reduced. It can be minimized.

  Examples of the resin material forming the shaft end mold 4 include polypropylene, polyacetal, polyamide, polyester, polycarbonate, and the like. These materials have excellent dimensional stability by injection molding and are relatively inexpensive. It is.

Here, the opening space 5 that accommodates the shaft end mold 4 of the main body mold 2 is located outward from the virtual planes P ₁ and P _{2 that} are the ends of the cavity space 1 as shown in FIG. The wall surface 5 </ b> A of the opening space 5 is configured to include a part of a conical surface that widens toward the outer side in the core metal extending direction, while the outer wall portion of the shaft end mold 4. 13 is also provided with a tapered portion so as to come into surface contact with the conical surface when the die is closed, and the shaft end die 4 is moved to the main body die 2 by mutual surface contact at the tapered portion. Positioning can be performed with high accuracy in both the core metal extending direction and the radial direction.

Further, the rib portion 12 is composed of, for example, twelve ribs 15a having the same size, which is a multiple of 3 and arranged at equal intervals in the circumferential direction on the outer side of the hole wall portion 12. By configuring the mold 4 to have rotational symmetry about the central axis of the hole portion 3, in particular, rotational symmetry with respect to a rotational symmetry operation of 120 degrees, the coaxiality between the outer wall portion 13 and the hole wall portion 12. In addition, the flow of the resin can be made uniform in the circumferential direction, and the deflection of the roller 30 can be suppressed.
Further, the resin mold forming gate 8 for forming the shaft end mold 4 also affects the uniformity in the circumferential direction of the shaft end mold 4. In the case shown in FIG. Since the gate position 8 is provided, the shaft end mold 4 has rotational symmetry with respect to 120-degree rotational symmetry operation, and can carry circumferential uniformity.

FIG. 5 shows another example of a shaft end mold having a rotational symmetry with respect to a rotationally symmetric operation of 120 degrees. FIG. 5A is an axial sectional view, and FIG. FIG. 5A is an arrow view corresponding to the arrow bb shown in FIG. 5A, and the shaft end mold 4 </ b> A is formed integrally with resin in the same manner as the shaft end mold 4, and is a cavity space. A partition wall portion 11A that identifies the core metal extending direction region of 1A, a hole wall portion 12A that surrounds the hole portion 3A, an outer wall portion 13A that is in surface contact with the wall surface 5A of the opening space 5 of the main body mold 2 when the mold is closed, A plurality of rib portions 15A arranged around the hole wall portion 12A and connecting the hole wall portion 12A, the partition wall portion 11A and the outer wall portion 13A, and a base end plate 14A connected to the base end of the outer wall portion 13A are provided.
Further, the gate portion 16A is provided so as to make a round around the outer side in the radial direction of the hole wall portion 12A except for a portion blocked by the rib portion 15A. Further, the resin mold forming gates 18 for forming the shaft end mold 4A are respectively provided on three ribs 15b separated by 120 degrees in the circumferential direction. It can have rotational symmetry for 120 degree rotational symmetry operation.

  Using the roller molding die 10 of the embodiment shown in FIGS. 3 and 4, a urethane foam made of urethane foam having a diameter of 16 mm and a length of 240 mm around a core metal having a diameter of 8 mm and a length of 260 mm is used. A roller main body was formed, and then a uniform coating film made of acrylic urethane with a thickness of 20 μm was formed on the outer peripheral surface of the roller main body, and 60 developing rollers were prototyped. Each of these developing rollers was used as an example, and each of the developing rollers was measured for shake and mounted on a printer for image evaluation. In addition, using the conventional roller molding die 90 shown in FIG. 1, the same number of developing rollers having the same structure, dimensions, and materials as in the embodiment are made as prototypes, and they are used as conventional examples. The measurement of shake and image evaluation were performed and compared with those of Examples. The evaluation results are shown in Table 1.

Here, in the roller mold 10 embodiment, the difference between the outer diameter D ₂ of the inner diameter D ₁ and the core end portion of the hole portion 3 of the shaft chicken feed type 4, i.e., to the clearance between 9.6μm . In addition, the shaft end die 94 in the roller molding die 30 of the conventional example is formed by cutting out from a steel bar, but the same ease as in the embodiment is ensured in and out of the hole of the cored bar. This was set to 0.1 mm as the minimum clearance for this. The outer dimensions of the conventional roller molding die 30 other than the clearance are the same as those of the example.

  For the runout measured for each roller, an average value, a maximum value, and a minimum value were obtained for each of the examples and the conventional examples, and these were compared. For image evaluation, 5 samples were randomly extracted from each of the 60 examples and the conventional example, and these rollers were mounted on the printer cartridge as developing rollers, and a laser beam manufactured by Hewlett-Packard Company was used. An image printing test was performed with a printer Laserjet 4050, and the image unevenness was evaluated to determine whether it was acceptable or not visually.

  As is apparent from Table 1, the developing roller of the example can greatly improve the accuracy of the shake as compared with the conventional one, and as a result, it can provide a good result also in the image evaluation. it can.

  This roller molding die is used for molding a charging roller, a developing roller, a toner supply roller, a transfer roller, a cleaning roller, a paper feeding roller and the like used in an image forming apparatus such as a laser printer, a copying machine, and a fax machine. it can.

It is sectional drawing which shows the conventional metal mold | die for roller molding. It is sectional drawing which shows the roller shape | molded with the metal mold | die for roller molding of embodiment which concerns on this invention. It is sectional drawing which shows the metal mold | die for roller molding of embodiment. It is an arrow view corresponding to the IV-IV arrow view of FIG. It is sectional drawing and arrow view which show the shaft end metal mold | die of another aspect.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cavity space 2 Main body metal mold | die 3, 3A Hole part 4, 4A Shaft end metal mold | die 5 Opening space 5A Wall of opening space 6 Gate part 8 Gate for resin mold formation 10 Die 11 for roller molding 11, 11A Partition part 12, 12A Hole wall part 13, 13A Outer wall part 14, 14A Base end plate 15, 15A Rib part 15a, 15b Rib 16A Gate part 18 Resin mold forming gate 30 Roller 31 Core metal 32 Roller body part

Claims (5)

In a mold used for molding a roller having a cylindrical roller body formed by injecting a resin or rubber material around the axial center of a core metal fixed at both ends,
A main body mold having a cavity space corresponding to the roller main body section, and left and right shaft end molds each having a hole portion for fixing an end of the core metal and specifying a core metal extending direction region of the cavity space. The main body mold is provided with an opening space for accommodating at least one of the shaft end molds in the core metal extending direction, and a gate portion for injecting the material is provided on at least one of the shaft end molds. ,
Each of the shaft end dies is integrally formed of resin, and is arranged around the partition wall portion that specifies the core metal extending direction region of the cavity space, the hole wall portion surrounding the hole portion, and the hole wall portion. A roller molding die comprising a plurality of rib portions for connecting the hole wall portion and the partition wall portion . Said shaft chicken feed type, an outer wall portion for contacting the wall surface and the surface of the opening space of the body mold provided under the mold closure, the roller molding according to the ribs to claim 1, formed by connecting the outer wall portion Mold. The wall surface of the opening space is configured to include a part of a conical surface that extends from the cavity space toward the outside in the core metal extending direction, and the outer wall portion of the shaft end mold is closed when the mold is closed. roller mold according to claim 2 ing configured to contact face-to-face. The roller mold according to any one of claims 1 to 3, wherein the shaft end mold is configured to have rotational symmetry about the center axis of the hole. The roller molding die according to claim 4 , wherein the rotational symmetry is established for a rotationally symmetric operation of at least 120 degrees.

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