JP4547660B2 - Resin gear, fixing device, image forming apparatus, and resin gear molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin gear, a fixing device, an image forming apparatus, and a resin gear molding method.
[0002]
[Prior art]
As a fixing device of an image forming apparatus, a thermal pressure type having a pair of rotating bodies pressed against each other is well known. In this type of fixing device, there is one in which a heating roll is driven by a resin gear. If the welded gear is formed when the resin gear is molded, the strength of the welded gear becomes low. In addition, the resin gear that drives the heating roll may be deteriorated by heat received from the heater, and may crack.
By the way, it is known that the accuracy of meshing of the resin gear is improved by making the weld of the resin gear present on the tooth bottom surface or the tooth root surface (see Patent Document 1).
In addition, it is known that a heat shield is provided on a gear key fixed to a heating roll of a copying machine to prevent the gear from being carbonized and deteriorated by the heat of the heater (see Patent Document 2).
[0003]
[Patent Document 1]
JP-A-6-280969 [Patent Document 2]
Japanese Patent Application Laid-Open No. 7-44048
[Problems to be solved by the invention]
However, when a resin gear having a weld is used, for example, for driving a heating roll or the like, the weld may crack due to the heat received from the heater and the magnitude of the rotational load.
[0005]
Accordingly, an object of the present invention is to provide a resin gear that can prevent the resin gear from being broken by a weld and can stably transmit a driving force.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is characterized in that a gear body, a shaft hole formed inside the gear body, into which a rotating body is inserted, formed outside the gear body, and a tooth for receiving a driving force from the gear, the gear main body includes a connecting portion connected to the rotating body, and one of the weld formed during the molding of the gear body, the weld, the a rotating direction upstream side from the connecting portion, in the resin gear formed by and formed in a range from the connection part of 90 degrees or less.
In this specification, the upstream side in the rotational direction is the direction opposite to the rotational direction. Further, in this specification, the weld is a portion where the flow of the molten resin is merged when the resin gear is formed.
[0008]
Further, it is more preferable that the weld is formed on the upstream side in the rotation direction from the connecting portion and within a range of 60 degrees or less from the connecting portion.
In another aspect, the characteristic of the present invention is a resin gear having a gate mark formed at a position of about 180 degrees in the rotation direction from the weld. This is because the resin gear of the present invention is manufactured by the following method.
The resin gear is formed by injecting molten resin into the mold from the position of the gate. The mold has a ring-shaped flow path that matches the shape of the gear, and can form a weld, for example, at a position facing the gate.
If the gear is formed by the one-point gate method, the weld can be formed in one place, and the position of the weld can be set by the arrangement of the gate. For example, molten resin injected from the gate flows separately in opposite directions according to the shape of the mold, and merges in the vicinity of the position facing the gate. A weld is formed in the portion where the molten resin has joined.
[0009]
According to a second aspect of the present invention, there is provided a fixing device for fixing a developer on a sheet, the fixing device having the resin gear described above.
[0010]
A third feature of the present invention resides in an image forming apparatus having the above-described fixing device.
[0011]
A fourth feature of the present invention is a method of forming a gear by injecting molten resin from one place, and injecting the molten resin into a mold from a flow path, In the molding method of the resin gear, the gear is molded so that one weld is formed on the upstream side in the rotation direction from the coupling portion to be coupled and within a range of 90 degrees or less from the coupling portion .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 described later is provided on the upper portion of the image forming apparatus main body 12. In addition, for example, two-stage sheet feeding units 18 and 18 are disposed below the image forming apparatus main body 12. Further, a plurality of paper feeding units can be optionally arranged below the image forming apparatus main body 12.
[0013]
Each paper feed unit 18 has a paper feed unit main body 20 and a paper feed cassette 22 in which paper is stored. A pickup roll 24 is disposed in the upper part near the rear end of the paper feed cassette 22, and a retard roll 26 and a feed roll 28 are disposed behind the pickup roll 24.
[0014]
The main conveyance path 32 is a sheet path from the feed roll 28 to the discharge port 34, and the main conveyance path 32 is in the vicinity of the back side (the left side surface in FIG. 1) of the image forming apparatus main body 12, and the lowermost supply path. A portion formed substantially vertically from the paper unit 18 to a fixing device 36 described later is included. A transfer device 42 and an image carrier 44, which will be described later, are disposed on the upstream side of the fixing device 36 in the main transport path 32, and a registration roll 38 is disposed on the upstream side of the transfer device 42 and the image carrier 44. Further, a discharge roll 40 is disposed in the vicinity of the discharge port 34 of the main conveyance path 32.
[0015]
Therefore, the sheet fed from the sheet feeding cassette 22 of the sheet feeding unit 18 by the pickup roll 24 is turned by the cooperation of the retard roll 26 and the feed roll 28, and only the uppermost sheet is guided to the main transport path 32. The developer image is temporarily stopped by the roll 38, and the developer image is transferred between a transfer device 42 and an image carrier 44, which will be described later, and the transferred developer image is fixed by the fixing device 36 and discharged. The paper is discharged from the discharge port 34 to the discharge unit 16 by the roll 40.
[0016]
However, in the case of duplex printing, it is returned to the reverse path. That is, the front side of the discharge roll 40 in the main conveyance path 32 is divided into two forks, a switching device 46 is provided in the divided part, and a reverse path 48 is formed from the divided part to the registration roll 38. . The reversing path 48 is provided with transport rolls 50a to 50c. In the case of double-sided printing, the switching device 46 is switched to the side that opens the reversing path 48 and the discharge roll 40 is in front of the rear end of the sheet. Thus, the discharge roll 40 is reversed, the paper is guided to the reverse path 48, and is discharged from the discharge port 34 to the discharge unit 16 through the registration roll 38, the transfer device 42, the image carrier 44 and the fixing device 36. .
[0017]
The discharge unit 16 includes an inclined portion 52 that is rotatable with respect to the image forming apparatus main body 12. The inclined portion 52 has a lower discharge port portion and is inclined so as to gradually increase in the front direction (right direction in FIG. 1), with the discharge port portion as a lower end and a higher tip as an upper end. The inclined portion 52 is supported by the image forming apparatus main body 12 so as to be rotatable around the lower end. As shown by a two-dot chain line in FIG. 1, when the inclined portion 52 is rotated upward and opened, an opening portion 54 is formed, and a process cartridge 64 described later can be attached and detached through the opening portion 54. .
[0018]
The image forming unit 14 is, for example, of an electrophotographic type, and is charged by an image carrier 44 made of a photosensitive member, a charging device 56 made of, for example, a charging roll that uniformly charges the image carrier 44, and a charging device 56. An optical writing device 58 that writes a latent image on the image carrier 44 with light, a developing device 60 that visualizes the latent image of the image carrier 44 formed by the optical writing device 58 with a developer, and the developing device 60. A transfer device 42 composed of, for example, a transfer roll for transferring the developer image produced by the toner onto the paper, a cleaning device 62 composed of, for example, a blade for cleaning the developer remaining on the image carrier 44, and the paper transferred by the transfer device 42 The image forming apparatus includes a fixing device 36 that fixes a developer image on a sheet. The optical writing device 58 is composed of, for example, a scanning type laser exposure device, and is arranged in the vicinity of the front surface of the image forming apparatus main body 12 in parallel with the paper feeding unit 18 described above, and exposes the image carrier 44 across the developing device 60. . The exposure position of the image carrier 44 is the latent image writing position P.
In this embodiment, a scanning laser exposure apparatus is used as the optical writing device 58, but an LED, a surface emitting laser, or the like can be used as another embodiment.
[0019]
The process cartridge 64 is obtained by integrating the image carrier 44, the charging device 56, the developing device 60, and the cleaning device 62. The process cartridge 64 is disposed immediately below the inclined portion 52 of the discharge portion 16 and is attached and detached via the opening portion 54 formed when the inclined portion 52 is opened as described above.
[0020]
2 to 5, the configuration of the fixing device 36 is shown. The fixing device 36 is unitized and has a unit main body 66, and the unit main body 66 is configured by combining a first casing 68 and a second casing 70. That is, the first casing 68 and the second casing 70 are connected via a fulcrum (not shown), and the heating roll 72 is rotatably supported by the first casing 68, A pressure roll 74 is rotatably supported on the housing 70. The pressure roll 74 is pressed against the heating roll 72 by two elastic bodies 76 formed of a coil spring or the like, and a nip portion 78 is formed. Each elastic body 76 has one end fixed to a bracket (not shown) provided on the second housing 70 side, and the other end hooked on a groove provided in the first housing 68. ing.
[0021]
A heater 80 made of a lamp is disposed in the heating roll 72 to heat the heating roll 72. The above-described conveyance path 32 is configured in the vertical direction across the nip portion 78, and the sheet is conveyed from the bottom to the top. An inlet side chute 82 is disposed on the upstream side of the nip portion 78, and outlet side chutes 84 a and 84 b are disposed on the downstream side of the nip portion 78. The outlet side chutes 84a and 84b are provided in the first casing 68 and the second casing 70, and the outlet side chute 84a of the second casing 70 rotates upward to pass the paper. It is supposed to let you.
[0022]
A thermostat 86 is provided in the first casing 68 in the vicinity of the heating roll 72, and the thermostat 86 prevents a failure due to overheating of the heating roll 72. Further, a plurality of peeling claws 88 are provided in the first casing 68 in the vicinity of the downstream side of the nip portion 78 in the axial direction of the heating roll 72 (paper width direction). The peeling claw 88 is urged toward the heating roll 72 with a weak force that does not damage the surface of the heating roll 72, the tip of the peeling claw 88 is pressed against the surface of the heating roll 72, and is wound around the heating roll 72. The paper to be removed is peeled off.
[0023]
Next, the heating roll 72 and its peripheral configuration will be described in detail.
Bearings 90 and 90 are attached to the heating roll 72 at both ends slightly forward, and are supported by the first casing 68 by the bearings 90 and 90 so as to be rotatable. The heating roll 72 has a cylindrical core 92 and a release layer coated on the surface side of the core 92. The core 92 has an outer diameter of, for example, 25 mm and a thickness of, for example, 1 mm. The material forming the core 92 is, for example, iron or aluminum. The release layer is made of, for example, perfluoroalkoxy (PFA), and has a thickness of, for example, 30 to 100 μm.
[0024]
A gear 96 described later is fitted into one end of the core 92 of the heating roll 72 by being inserted from the direction of arrow A. A notch 94 is formed at one end of the core 92 in parallel with the axial direction. A connecting portion 104 of a gear 96 described later is fitted in the notch 94, and the gear 96 is connected to the heating roll 72. The gear 96 is engaged with another gear (not shown), the driving force from the other gear is transmitted to the heating roll 72 via the gear 96, the heating roll 72 is rotated in the direction of arrow B, and the pressure roll 74 is moved in the direction of arrow C.
[0025]
Next, the gear 96 will be described in detail.
In FIG. 6, a perspective view of the gear 96 is shown. The gear 96 is made of a heat-resistant resin such as glass fiber-containing polyphenylene sulfide (PPS), for example, a gear main body 98, a shaft hole 100 that is formed inside the gear main body 98 and into which the heating roll 72 is inserted, and a gear. And a tooth 102 which is formed outside the main body 98 and receives a driving force from another gear. The gear body 98 includes a connecting portion 104 connected to the heating roll 72 and a weld 106 formed at the time of molding. The connecting portion 104 is formed in a protruding shape having a width of 4 mm, for example, on the radially inner side of the gear body 98. The weld 106 is formed in the vicinity of the connection portion 104 and on the upstream side in the rotation direction by providing, for example, the gate 108 in the vicinity of the position facing the connection portion 104 and on the upstream side in the rotation direction. The shaft hole 100 is formed, for example, so that the inner diameter of the gear body 98 is substantially equal to the outer diameter of the core 92, and has a stopper portion 110 at one end.
The gear 96 has, for example, 38 teeth 102, is formed in a ring shape so that the module is, for example, 0.9, and the outer diameter is, for example, 36 mm. The gear 96 has an axial thickness of 8 mm, for example, and a radial thickness of 3.5 mm, for example.
[0026]
In FIG. 7, a schematic diagram of a method of forming the gear 96 is shown. The gear 96 is formed by, for example, injecting molten resin into the mold 112 from the position of the gate 108. The mold 112 has a ring-shaped flow path that matches the shape of the gear 96 so that the weld 106 can be formed at a position facing the gate 108, for example.
If the gear 96 is formed by the one-point gate method, the weld 106 can be formed in one place, and the position of the weld 106 can be set by the arrangement of the gates. For example, the molten resin injected from the gate 108 flows separately in the directions of arrows D and E according to the shape of the mold 112, and merges in the vicinity of the position facing the gate 108. A weld 106 is formed in the portion where the molten resin has joined. The weld 106 is a portion where the bonding force of the resin is weak and the strength of the gear 96 is low.
The peak value of the rotational load of the heating roll 72 is, for example, 0.35 N · m, and the stress value is about 3.04 MPa. Further, the ambient temperature near the heating roll 72 rises to about 180 ° C. Therefore, stress is applied to the gear 96 in a state where heat is applied.
[0027]
In FIG. 8, the schematic diagram showing the experimental result which the inventor implemented regarding the stress concerning the gearwheel 96 is shown. 8A to 8F, slits 114 are provided at different positions with respect to the connecting portion 104, and the positional relationship between the connecting portion 104 and the slit 114 is shown on the left side of each drawing. A change in the width of the slit 114 is shown on the right side. In addition, the position of the slit 114 with respect to the connection part 104 and the connection part 104 is shown as an example of the position of the short hand of the analog timepiece. For example, when the connecting portion 104 is used as a reference (the position of the short hand at noon) and the slit 114 is provided at a position 120 ° clockwise (clockwise in FIG. 8), a 4:00 break (4 o'clock) Is broken). In FIG. 8, the drive gear 116 rotates counterclockwise (counterclockwise in FIG. 8), and the gear 96 rotates clockwise.
[0028]
As shown in FIGS. 8A and 8B, the gear 96 having the 11:30 crack and the 10:00 crack transmitted the driving force of the gear 116 without opening the slit 114.
As shown in FIG. 8 (C), in the gear 96 that was split at 8:00, the slit 114 started to open when the connecting portion 104 was rotated to the position of about 3:30.
As shown in FIGS. 8D and 8E, in the gear 96 having the 6:00 split and the 4:00 split, the slit 114 started to open when the connecting portion 104 was rotated to the position of about 4:30.
As shown in FIG. 8F, in the 12:30 split gear 96, the slit 114 started to open when the connecting portion 104 was rotated to the position of about 4:00.
[0029]
Hereinafter, a summary of the stress applied to the gear 96 will be described.
FIG. 9 is a schematic diagram showing a consideration regarding the stress applied to the gear 96 from the result shown in FIG. FIG. 9A shows a case where the weld 106 exists in the selection range 118 from the approximate center of the connecting portion 104 of the gear 96 to the upstream side in the rotational direction and a position shifted by 90 ° from the approximate center of the connecting portion 104. 9B shows a case where the weld 106 exists in the non-selection range 120 excluding the range shown in FIG.
As shown in FIG. 9A, when the gear 116 rotates the gear 96 in a state where the weld 106 is located within the selection range 118, the gear 96 receives a reaction force from the core 92 at the connecting portion 104. In this case, it is considered that a force that compresses the weld 106 acts on the weld 106 due to a tangential component of the reaction force received by the gear 96 in the tangential direction. As shown in FIG. 9B, when the gear 116 rotates the gear 96 in a state where the weld 106 is located in the non-selection range 120, similarly, the gear 96 is counteracted from the core 92 by the connecting portion 104. Receive power. In this case, it is considered that a pulling force acts on the weld 106 due to a tangential component of the reaction force received by the gear 96 in the tangential direction.
[0030]
As described above, it is considered that when the gear 96 is rotated, a compressive stress is applied to the weld 106 when the weld 106 is within the selection range 118, and a tensile stress is applied to the weld 106 when the gear 96 is within the non-selection range 120. Therefore, by disposing the weld 106 in a range where the weld 106 is subjected to the compressive stress, the weld 106 is less likely to be damaged than the gear having the weld 106 at the position where the tensile stress is received. For example, the gear 96 provided on the heating roll 72 or the like. Even gears that are difficult to obtain a sufficient thickness in the radial direction, are subject to a large rotational load, and are further affected by heat, prevent damage to the gears and stably transmit the driving force to the rotating body. can do.
From the experimental results shown in FIG. 8, the selection range 118 is a range from the approximate center of the coupling portion 104 of the gear 96 to the upstream side in the rotational direction and a position shifted by 60 ° from the approximate center of the coupling portion 104. Is more preferable.
[0031]
【The invention's effect】
As described above, according to the present invention, since the weld of the resin gear is formed in the vicinity of the connecting portion and on the upstream side in the rotation direction, the resin gear is prevented from being broken by the weld, The driving force can be transmitted stably.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating a fixing device of the image forming apparatus according to the embodiment of the invention.
3 is a cross-sectional view of the fixing device shown in FIG.
FIG. 4 is a perspective view showing a state in which a heating roll is disposed together with a pressure roll.
FIG. 5 is a diagram illustrating a configuration of a roll unit and a rotating direction.
FIG. 6 is a perspective view showing a gear used in the image forming apparatus according to the embodiment of the invention.
7 is a schematic view showing a method for forming the gear shown in FIG. 6. FIG.
FIG. 8 is a schematic diagram showing a result of an experiment conducted by the inventor regarding stress applied to a gear.
FIG. 9 is a schematic diagram showing a consideration on the stress applied to the gear from the result shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 14 Image carrier forming means 36 Fixing apparatus 66 Unit main body 68 First housing 70 Second housing 72 Heating roll 74 Pressurizing roll 80 Heater 92 Core 94 Notch 96 Gear 98 Gear body 100 Shaft hole 102 Teeth 104 Connecting portion 106 Weld 108 Gate 112 Form 114 Slit 118 Selection range 120 Non-selection range

Claims (6)

A gear body;
A shaft hole formed inside the gear body and into which the rotating body is inserted;
A tooth formed outside the gear body and receiving a driving force from another gear;
The gear body is
A connecting portion connected to the rotating body;
One weld formed during molding of the gear body, and
The weld is,
A resin gear, wherein the resin gear is formed on the upstream side in the rotation direction from the connecting portion and within a range of 90 degrees or less from the connecting portion . The weld is
The resin gear according to claim 1, wherein the resin gear is formed on the upstream side in the rotation direction from the connecting portion and within a range of 60 degrees or less from the connecting portion. Claim 1 or 2 resin gear, wherein the gate mark is formed at a position of approximately 180 degrees in the rotational direction from the weld. A fixing device for fixing the developer on the sheet, the fixing device characterized by having a resin gear according to any one of claims 1 to 3. An image forming apparatus comprising the fixing device according to claim 4 . A method of molding a gear by injecting molten resin from one place ,
Injecting the molten resin from the flow path into the mold,
A rotating direction upstream side from the connection portion that is connected to the rotating body, and the molding method of the resin gear, which comprises forming the gear so that said one weld from the connecting portion within a range of 90 degrees is formed .

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