Patent Application
20130251418
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-069243 filed Mar. 26, 2012.
The present invention relates to fixing devices and image forming apparatuses.
According to an aspect of the invention, there is provided a fixing device including a rotating member, a pressing member, a heat source, and a driving member. The rotating member has a shape of a cylinder and rotates in a circumferential direction of the cylinder. The rotating member has a slot at an end of the cylinder and a protruding section extending along an edge of the slot at a front side in a rotational direction of the rotating member. The rotating member receives a rotational driving force via the slot. The slot extends through the cylinder from an inside to an outside thereof and also extends from the end toward a center of the cylinder. The protruding section protrudes in a direction that intersects a peripheral wall of the cylinder. The pressing member presses a recording medium bearing an unfixed toner image on a surface thereof by nipping the recording medium together with the rotating member so as to fix the toner image onto the surface. The heat source heats the recording medium nipped between the rotating member and the pressing member. The driving member has an engagement section that is engaged with the slot in the rotating member and is in contact with the protruding section at a position separated from the peripheral wall of the cylinder by a certain distance. The driving member imparts the rotational driving force to the rotating member via the engagement section.
An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:
An exemplary embodiment of the present invention will be described below with reference to the drawings.
A printer 10 shown in
The printer 10 receives an image signal, which is generated outside the printer 10 and expresses an image, via a signal cable (not shown). The printer 10 includes a controller 11 that controls the operation of each component included in the printer 10, and the aforementioned image signal is input to this controller 11. Under the control of the controller 11, the image based on the image signal is formed in the printer 10.
Two sheet feed trays 21 are accommodated in a lower area of the printer 10. The sheet feed trays 21 each accommodate therein sheets P of paper in a stacked state. The accommodated sheets P have different sizes between the two sheet feed trays 21. The sheet feed trays 21 are ejectable so that new sheets P can be supplied thereto.
From one of the two sheet feed trays 21, a corresponding pickup roller 22 feeds sheets P with dimensions suitable for the dimensions of the image expressed by the image signal input to the controller 11. The fed sheets P are separated into individual sheets by a corresponding separation roller 23. Each of the separated sheets P is transported upward so that the leading edge of the sheet P reaches a standby roller 24. The standby roller 24 has a role of transporting the sheet P while adjusting a subsequent transport timing. The sheet P that has reached the standby roller 24 is transported further while the standby roller 24 adjusts the subsequent transport timing.
In the printer 10, a photoconductor 12 that rotates in a direction indicated by an arrow A is provided above the standby roller 24. A charging device 13, an exposure device 14, a developing device 15, a transfer device 16, and a photoconductor cleaner 17 are arranged around the photoconductor 12.
The photoconductor 12 is cylindrical and extends in the depth direction in
The charging device 13 includes a charging roller that rotates by being in contact with the surface of the photoconductor 12. The charging roller imparts an electric charge to the surface of the photoconductor 12 so as to electrostatically charge the surface. In the charging device 13, a corona discharger not in contact with the photoconductor 12 may be employed as an alternative to the charging roller.
The exposure device 14 includes a light-emitting unit that emits laser light (exposure light) modulated in accordance with the image signal supplied from the controller 11, and a rotating polygonal mirror for scanning the laser light across the photoconductor 12. The exposure light is output from the exposure device 14. The photoconductor 12 is exposed to this exposure light so that an electrostatic latent image is formed on the surface of the photoconductor 12. As an alternative to the laser-light emission type, a light-emitting diode (LED) array having multiple LEDs arranged in the scanning direction may be employed as the exposure device 14. Furthermore, as an alternative to the exposure type, the latent-image forming unit may be of a type that uses multiple electrodes arranged in the scanning direction so as to directly form a latent image on the surface of the photoconductor 12.
The electrostatic latent image formed on the surface of the photoconductor 12 due to the surface thereof being exposed to the exposure light is subsequently developed by the developing device 15. The developing device 15 includes a developing roller 15c. The developing device 15 is connected to a toner container 15a via a toner supply path 15b. The developing device 15 accommodates therein a developer containing a toner and a magnetic carrier. The toner contained in the toner container 15a is appropriately supplied to the developing device 15 via the toner supply path 15b. The magnetic carrier is, for example, iron powder coated with a resin coating. The toner particles are composed of, for example, binding resin, a colorant, and a releasing agent. The developing device 15 electrostatically charges the toner and the magnetic carrier by stirring the developer having a mixture of magnetic carrier particles and toner particles. The developer in the developing device 15 is supplied to the surface of the photoconductor 12 by the developing roller 15c so that the latent image on the surface of the photoconductor 12 is developed by the electrostatically-charged toner in the developer, whereby a toner image is formed.
The aforementioned standby roller 24 transports the sheet P such that the sheet P reaches a position facing the transfer device 16 at a timing at which the toner image on the photoconductor 12 reaches that position. Then, the transfer device 16 transfers the toner image on the photoconductor 12 onto the transported sheet P. The transfer device 16 used may alternatively be of a type that indirectly transfers the toner image onto the transported sheet P via an intermediate transfer body.
The toner remaining on the photoconductor 12 after the toner-image transfer process is removed from the photoconductor 12 by the photoconductor cleaner 17.
A combination of the photoconductor 12, the charging device 13, the exposure device 14, the developing device 15, and the transfer device 16 corresponds to an image forming unit according to an exemplary embodiment of the present invention.
The sheet P with the toner image transferred thereto travels in a direction indicated by an arrow B and is heated and pressed by a fixing device 100, whereby the toner image is fixed onto the sheet P. As a result, an image formed of the fixed toner image is formed on the sheet P. The fixing device 100 corresponds to a fixing device according to an exemplary embodiment of the present invention.
The sheet P passing through the fixing device 100 travels toward a sheet output device 200 in a direction indicated by an arrow C, and is transported further in a direction indicated by an arrow D by the sheet output device 200 so as to be output onto a sheet output tray 18.
The fixing device 100 includes a heating roller 101 and a pressing roller 102. The heating roller 101 is formed of a metallic cylinder whose outer peripheral surface is coated with a releasing material. Moreover, a heat source 103 is disposed within the heating roller 101. The pressing roller 102 is also cylindrical, and the peripheral surface of the pressing roller 102 is pressed against the peripheral surface of the heating roller 101. The sheet P that has reached the fixing device 100 by traveling in the direction of the arrow B enters a contact section between the pressing roller 102 and the heating roller 101. The sheet P is nipped between the heating roller 101 and the pressing roller 102 at the contact section. In this case, the sheet P is disposed such that the surface thereof with the toner image faces toward the heating roller 101.
The heating roller 101 and the pressing roller 102 rotate in a direction indicated by arrows F while being in contact with each other. Therefore, the sheet P entering the contact section travels through the contact section due to the rotation of the heating roller 101 and the pressing roller 102, thereby traveling toward the sheet output device 200 in the direction of the arrow C. While traveling through the contact section, the sheet P is heated by the heat source 103 disposed within the heating roller 101 and is also pressed by the pressing roller 102 so that the toner image is fixed onto the sheet P, whereby an image formed of the fixed toner image is formed on the sheet P.
The heating roller 101 corresponds to a rotating member according to an exemplary embodiment of the present invention. The pressing roller 102 corresponds to a pressing member according to an exemplary embodiment of the present invention. The heat source 103 corresponds to a heat source according to an exemplary embodiment of the present invention.
The sheet output device 200 is provided with a sheet output roller 203 that continuously transports the sheet P entering the sheet output device 200 in the direction of the arrow C and then further transports the sheet P in the direction of the arrow D. The sheet output roller 203 transports the sheet P in the direction of the arrow D from the sheet output device 200 so as to output the sheet P onto the sheet output tray 18.
The heating roller 101 will now be described in detail.
A drive gear 104 that rotationally drives the heating roller 101 is fitted around one end of the heating roller 101. The drive gear 104 has teeth (not shown) arranged therearound and receives a driving force from a motor via the teeth. Furthermore, the drive gear 104 is provided with inwardly-protruding keys 105. The keys 105 are engaged with keyways 106 provided at the end of the heating roller 101. The driving force received by the drive gear 104 from the motor is transmitted to the heating roller 101 via the keys 105, so that the heating roller 101 receives the driving force at the keyways 106. The heating roller 101 rotates in the direction of the arrow F due to the driving force.
The drive gear 104 corresponds to a driving member according to an exemplary embodiment of the present invention. The keys 105 correspond to engagement sections according to an exemplary embodiment of the present invention. The keyways 106 correspond to slots in the rotating member according to an exemplary embodiment of the present invention.
As demands for increasing the processing speed in image forming apparatuses are growing in recent years, it is desirable that the driving force imparted to the heating roller 101 by the drive gear 104 be maximized. Therefore, it is also desirable that the heating roller 101 have enough strength to withstand such a driving force. In order to increase the strength of the heating roller 101 to withstand the driving force, it is particularly desirable that the keyways 106 can withstand a large force.
In
The rotational direction of the drive gear 104 and the heating roller 101 is the direction of the arrow F shown in
Based on simulation performed on the heating roller 101 having the above structure, it is confirmed that the safety factor is improved by about 1.4 to 1.9 times that of a comparative example in which the protruding walls 107 are entirely in contact with the keys 105.
Although the above exemplary embodiment relates to a monochrome printer as an example of an image forming apparatus, the image forming apparatus according to the exemplary embodiment of the present invention may be a color printer, a facsimile apparatus, a copier, or a multifunction apparatus.
Furthermore, although the image forming unit in the above exemplary embodiment of the present invention is of a type that transfers a toner image formed on a photoconductor onto a recording medium, the image forming unit according to the exemplary embodiment of the present invention may alternatively be of a type that directly forms a toner image on a recording medium.
Furthermore, although the rotating member in the above exemplary embodiment of the present invention is provided with two keyways, the rotating member according to the exemplary embodiment of the present invention may alternatively have a single keyway, or three or more keyways.
The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-069243 | Mar 2012 | JP | national |
