JP2008197237A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately forming a gap for a separating plate and a gap for a non-contact sensor by a costless structure. <P>SOLUTION: The image forming apparatus includes: a gap adjustment member 46 disposed on a fixing roller 15 and having the separating plate 43 slidably disposed on the peripheral face of the developing roller 15 and providing a predetermined gap X between the leading end of the separating plate 43 and the peripheral face of the fixing roller 15; and a support plate 44 supporting the separating plate 43, following the thermal expansion of the fixing roller 15, and movable while maintaining the gap X. A non-contact temperature sensor 51 follows the movement of the support plate 44, and moves in the direction in which a distance between the peripheral face of the fixing roller 15 and sensor 51 is kept constant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus in which a non-contact temperature sensor arranged at a predetermined interval on a surface of a fixing roller can maintain a constant interval even when the fixing roller is thermally expanded.

In image forming apparatuses such as printers, copiers, and facsimile machines, a toner image formed on an image carrier such as a photoreceptor or an intermediate transfer medium is transferred to a recording medium, and then the toner image is fixed on the recording medium. A device is provided.
The fixing device includes a hollow cylindrical fixing roller that is rotatably held by a bearing mounted on the frame and rotates at a predetermined rotation speed. At the center of the fixing roller, a rod-shaped heater disposed in parallel with the axial direction of the fixing roller 3 is provided. The fixing roller is provided with a rubber pressure roller so as to face the fixing roller, and the pressure roller abuts on the fixing roller with a predetermined pressure by a pressure spring and rotates.

A temperature sensor is disposed around the fixing roller. The temperature sensor detects the surface temperature of the fixing roller heated by the heater, and the temperature control unit controls the heater based on the detected surface temperature to control the fixing roller. Temperature control is performed so as to be within a certain temperature range. Therefore, the temperature control unit plays a role in detecting and stopping heating when the surface of the fixing roller is abnormally heated above the normal use temperature.
JP-A-2005-173447 JP 2006-91342 A

Some fixing devices have a separation claw in contact with the fixing roller in order to prevent the paper from being wrapped around the fixing roller when unfixed toner such as an image is thermally welded to the paper.
However, when the separation claw is brought into contact with the fixing roller surface, scratches are generated on the surface of the fixing roller, so that the nail mark is generated. By using a separation plate managed with a gap of 1 mm, adhesion of nail marks is prevented. However, since the fixing roller is thermally expanded (a material having an elastic layer on the surface is more prominent), it is difficult to obtain a high-accuracy gap with normal mounting.
Therefore, as in Patent Document 1, contact members that define the gap between the front end of the separation plate and the outer peripheral surface of the fixing roller are provided at both left and right ends of the separation plate, and the corresponding contact member is other than the sheet passing through the outer peripheral surface of the fixing roller. (The both ends where the paper does not pass) are in contact. With this contact member, a method of making the separation plate follow a thermally expanded roller to create a state close to a certain gap has come to be used.

As with the separation plate, a temperature sensor that detects the temperature of the fixing roller generates sensor marks when the contact sensor is used in the paper. Therefore, a non-contact sensor may be used. Since the non-contact sensor is not as responsive as the contact sensor that contacts the surface of the fixing roller, the gap between the non-contact sensor and the fixing roller (in order to distinguish it from the gap between the separation plate and the fixing roller, It is necessary to manage with high accuracy. Therefore, a technique that requires positioning with a non-contact sensor using a portion other than the paper passing portion as disclosed in Patent Document 2 is also disclosed.
At present, it is possible to create a high-accuracy gap, but when using both a non-contact separation plate and a non-contact sensor, two types of positioning members are required, increasing the cost and both ends of the fixing roller. Has a complicated structure.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can accurately form a gap of a separation plate and a gap of a non-contact sensor with a structure that does not cost.

In order to achieve the above object, the image forming apparatus of the present invention records a fixing means for fixing the toner image transferred to the recording medium by a transfer means for transferring the toner image formed on the image carrier to the recording medium. A fixing roller provided on the medium conveyance path, in which the fixing unit thermally welds the toner image to the recording medium, a pressure roller for pressure-bonding to the fixing roller, and a pressure-bonding portion between the fixing roller and the pressure roller A separation member having a separation plate for preventing the recording medium from being wound and disposed on the downstream side in the rotation direction of the fixing roller with a gap from the outer peripheral surface of the fixing roller; and a heater for heating the fixing roller; An image forming apparatus including a non-contact temperature sensor that detects heat of the fixing roller and is spaced apart from an outer peripheral surface of the fixing roller, wherein the separation member is the fixing roller A gap adjusting member that is slidably disposed on the outer peripheral surface and provides a predetermined gap to the outer peripheral surface of the fixing roller at the tip of the separating plate, and supports the separation plate and follows the thermal expansion of the fixing roller. And a separation plate support member movable while maintaining the gap, the non-contact temperature sensor following the movement of the separation plate support member, It moved to the direction which maintains the space | interval with an outer peripheral surface constant.
The separation plate support member of the image forming apparatus is provided with a rotation shaft on one end side away from the fixing roller, and a hook portion that engages with the non-contact temperature sensor on the other end side. The sensor can be provided with a one end side away from the hook portion so as to be rotatable, and can form a placement portion for placing the other end side on the hook portion.
Further, the non-contact temperature sensor of the image forming apparatus forms a guide surface on a surface of the mounting portion that is placed on the hook portion, and follows the movement of the hook portion to move the guide surface to the non-contact temperature sensor. Preferably, the contact temperature sensor is formed so as to maintain a constant distance from the outer peripheral surface of the fixing roller.
Further, in the image forming apparatus, it is preferable that the hooking portion is disposed in a paper passing portion of the fixing roller.

In the image forming apparatus of the present invention, the separation plate for separating the sheet of the fixing roller is slidably disposed on the outer peripheral surface of the fixing roller, and the leading end of the separation plate is predetermined with respect to the outer peripheral surface of the fixing roller. A non-contact temperature sensor, comprising: a gap adjusting member that provides a gap; and a separation plate support member that supports the separation plate and follows the thermal expansion of the fixing roller and is movable while maintaining the gap. Following the movement of the separation plate support member, the separation plate is moved in a direction to maintain a constant distance from the outer peripheral surface of the fixing roller, so that the separation plate positioned so as to follow the thermal expansion is non-contact. By positioning the sensor, the separation plate and the non-contact sensor can be simultaneously created with a high-precision gap to save cost.
The separation plate support member of the image forming apparatus is provided with a rotation shaft on one end side away from the fixing roller, and a hook portion that engages with the non-contact temperature sensor on the other end side. Since the temperature sensor is provided with one end side away from the hook part so as to be rotatable and the other end side is placed on the hook part, the non-contact temperature sensor is located close to the separation plate. The correction of the displacement of the separation plate is accurately transmitted to the non-contact temperature sensor, and the adjustment can be performed accurately.
In the image forming apparatus, a guide surface is formed on a surface of the mounting portion that is placed on the hook portion, and the guide surface follows the movement of the hook portion, and the non-contact temperature sensor is Since the gap between the fixing roller and the outer peripheral surface is kept constant, the mechanical contact between the non-contact temperature sensor and the fixing roller can be made accurately with a simple mechanical structure without using a complicated structure such as an electronic circuit. The interval can be made constant.
Further, the image forming apparatus can be implemented without complicating the configuration of both end portions of the fixing roller since the hooking portion is disposed in the sheet passing portion of the fixing roller.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
An image forming apparatus 1 as a printing apparatus shown in FIG. 1 is provided with a paper feed cassette 2 that accommodates paper as a printing medium on the lower side, and paper is fed to the paper discharge port side of the paper feed cassette 2. A pick-up roller 3 pulled out from 2 and a paper feed roller 4 and a separation roller 5 disposed in a pair on the upstream side thereof are provided.
A paper transport path 7 is formed on the downstream side of the paper feed roller 4 along the paper flow. In the conveyance path 7, the first feed roller pair 10, the registration roller pair 11, the driving roller 12 and the secondary transfer roller 13, the fixing roller 15 of the fixing device assembly 14, and the addition roller are provided downstream from the paper feed roller 4. A pressure roller 16, a second feed roller pair 17, and a discharge roller pair 18 are disposed. By these roller groups 10 to 18, the sheet is discharged from the discharge port 19 through the conveyance path 7.

A drive roller 12 that is paired with the secondary transfer roller 13 is provided with a driven roller 21 that is spaced apart from the horizontal direction of the drive roller 12. A transfer belt is provided between the drive roller 12 and the driven roller 21. 22 is disposed. Primary transfer rollers 28 to 31 are arranged at intervals on the inner peripheral side of the transfer belt 22, and the printing unit 24 is positioned below the transfer belt 22 at positions corresponding to the primary transfer rollers 28 to 31. -27 are arranged.
These printing units 24 to 27 are substantially the same, and only the ink colors handled at the time of printing are different. That is, process units of yellow (Y), magenta (M), cyan (C), and black (K) are provided along the circumferential direction A of the transfer belt 22. Each process unit has the same basic configuration except that the toner color is different. Therefore, here, the yellow printing unit 24 positioned on the upstream side will be described in detail, and the description of the other toner color printing units 25 to 27 will be omitted.

  The printing unit 24 is provided with a photosensitive drum 32 that is rotatable in the clockwise direction. Around the photosensitive drum 32, a cleaning unit 33, a charger 34, and a developing unit 35 are disposed along the rotation direction. The charger 34 uniformly charges the outer peripheral surface of the photosensitive drum 32 to a predetermined surface potential, and has a function as a charging unit. A surface region between the charger 34 and the developing unit 35 is an irradiation region of the light beam from the exposure unit 36, and the photosensitive drum 32 is exposed by the light beam, and an image signal is transferred onto the photosensitive drum 32. An electrostatic latent image corresponding to is formed.

The electrostatic latent image formed in this manner is visualized by toner supplied from the developing unit 35 of the developing unit 35 via the toner cartridge 37 and transferred to the transfer belt 22 by the primary transfer roller 28. The same processing is performed in the downstream printing units 25 to 27, and the toner image transferred to the transfer belt 22 is transferred to the paper by the secondary transfer roller 13.
The unfixed toner image transferred to the paper is fixed on the paper by the heat of the heater provided in the fixing roller 15 and the pressure of the pressure roller 16 when passing through the fixing roller 15 shown in FIG. The sheet on which the toner is fixed is disposed from the discharge port 19. On the other hand, in the photosensitive drum 32, residual toner attached to the photosensitive drum 32 is removed by the cleaning unit 33.

  As shown in FIG. 2, the fixing unit is integrally formed by the fixing device assembly 14, and the fixing roller 15 and the pressure roller 16 are side plates (not shown) disposed on the left and right sides of the frame 41 of the fixing unit. Are supported by each. The fixing roller 15 and the pressure roller 16 are arranged parallel to each other with their axes oriented in the horizontal direction (see FIGS. 3 and 4), and the outer peripheral surface of the fixing roller 15 is pressed against the outer peripheral surface by the pressure roller 16. Is done. This press contact portion becomes a nip portion 42 for fixing the toner image while sandwiching the paper 20.

  With reference to FIGS. 2 and 5, a separation plate 43 is disposed facing the downstream conveyance path 7 a located above the nip portion 42 of the fixing roller 15 in the conveyance path 7. The separation plate 43 serves to separate the paper 20 to be wound around the fixing roller 15 at the time of fixing the paper 20 from the fixing roller 15 and return it to the downstream conveyance path 7a. The separation plate 43 is attached to a support plate 44, and the support plate 44 can rotate about a rotation shaft 44a on one end side. In addition, since it is not necessary to take the range of a rotation angle large about the separating plate 43, you may provide a stopper in order to suppress rotation more than necessary.

  The front end of the separation plate 43 extends in the axial direction of the outer peripheral surface of the fixing roller 15 and extends in parallel with the outer peripheral surface. It is a separation plate that requires accuracy managed with a gap X of 1 mm. For this reason, it is desirable to use a material that is as thin as possible for the separation plate 43 and has a high strength so that it can withstand the impact of the paper 20. For other parts, use thick materials with emphasis on strength, and it is preferable to align the linear expansion coefficients when heat is applied, and use the same material welded with different thickness plates. Is preferred. In this embodiment, stainless steel is used.

As shown in FIG. 6, gap adjusting members 46 are disposed at both ends of the separation plate 43. The gap adjusting member 46 slightly protrudes from the front end portion of the separation plate 43 toward the fixing roller 15 to form a gap X having a predetermined protruding width. The position at which the gap adjusting member 46 is disposed with respect to the fixing roller 15 needs to be disposed other than the sheet passing portion of the fixing roller 15, that is, at both ends.
A heater 45 extending from one end in the axial direction to the other end is disposed at the axial center of the fixing roller 15. The material of the gap adjusting member 46 needs to be a material that can withstand high heat, easily slide, and has no frictional force in order to contact the fixing roller 15 whose temperature rises to around 200 degrees and rotates.

Referring to FIGS. 5 and 7, the other end (tip) side of the support plate 44 of the separation plate 43 is on the downstream side in the rotation direction of the fixing roller 15, and is hook-like hooking portion 44 b at the intermediate position in the axial direction of the fixing roller 15. The hook 44b is bent toward the rotation direction of the fixing roller 15, and the tip is formed obliquely upward. And the front-end | tip of the non-contact temperature sensor 51 is supported by the hook part 44b.
The sensor support member 52 that supports the non-contact temperature sensor 51 rotatably supports the non-contact temperature sensor 51 with a shaft 52a that is pivotally supported by the opening 52b as a rotation center. Further, the sensor support member 52 arranges the non-contact temperature sensor 51 so as to be parallel to the tangent line of the fixing roller 15, and arranges the thermistor 51 a for detecting the temperature on the radial extension line of the fixing roller 15 intersecting the tangent line. is doing.
As described above, the non-contact temperature sensor 51 has a distal end placed on the hook portion 44b and a proximal end supported by the sensor support member 52 disposed on the frame 41 of the fixing portion.
The tip portion of the non-contact temperature sensor 51 forms a substantially inverted stepped portion at the lower portion, and a guide surface 51b is formed at this step portion that contacts the hook portion 44b.

As shown in FIG. 5, when the separation roller 43 rotates in the direction of the arrow b when the fixing roller 15 is thermally expanded, the guide surface 51b is displaced by ΔY. The contact position with the hook 44b is shifted. The guide surface 51b is shaped so that the distance between the thermistor 51a and the outer peripheral surface of the fixing roller 5 can be maintained at Y even at this shifted point. Therefore, the guide surface 51b may be a linear inclined surface or a curved surface as long as the distance Y between the thermistor 51a of the non-contact temperature sensor 51 and the outer peripheral surface of the fixing roller 15 is constant.
In this embodiment, the thermistor 51a opens an interval Y of 1 mm ± 0.1 to 0.2 mm with respect to the outer peripheral surface of the fixing roller 15 with the guide surface 51b placed on the hook portion 44b. It is formed as follows.

With this configuration, when a print command is issued from the user to the image forming apparatus 1, the paper 20 as a print medium is pulled out from the paper feed cassette 2 by the pickup roller 3, and the paper feed roller 4 and the separation roller 5 is transferred to the conveyance path 7. In the conveyance path 7, the toner is transferred to the secondary transfer roller 13 through the first feed roller pair 10 and the registration roller pair 11. On the sheet 20, the toner image is transferred between the transfer belt 22 and the secondary transfer roller 13 wound around the driving roller 12. At this time, since the toner image transferred to the paper 20 is unfixed toner that has not been fixed to the paper 20 yet, the nip portion between the fixing roller 15 and the pressure roller 16 is used for fixing the paper 20. It is conveyed to 42.
In the nip portion 42, the toner image is fixed on the sheet 20 by the heat of the fixing roller 15 by the heater 45 and the pressure force of the pressure roller 16. After the toner image is fixed, the toner image is discharged from the discharge port 19 through the second feed roller pair 17 and the discharge roller pair 18.

  As shown in FIG. 5, the non-contact temperature sensor 51 detects the surface temperature of the fixing roller 15 by a thermistor 51a, and controls the temperature of the fixing roller 15 by a control means (not shown). When the fixing roller 15 is heated by the heater 45, it thermally expands radially outward. At this time, the separation plate 43 rotates in the direction following the diameter variation of the fixing roller 15, that is, in the direction of the arrow b shown in FIG. 5, but the gap X between the separation plate 43 and the fixing roller 15 is relative to the separation plate 43. Since the protrusion width X of the gap adjusting member 46 is constant, the gap X is maintained as it is. Since the support plate 44 is supported so as to be rotatable with respect to the shaft 44 a, the support plate 44 rotates around the shaft 44 a and plays a role of allowing tracking of the diameter variation of the fixing roller 15.

On the other hand, the position of the non-contact temperature sensor 51 also fluctuates with the movement of the separation plate 43. However, when the separation plate 43 moves in the direction of the arrow b, the hooking portion that is a part that contacts the separation plate 43 is moved. The tip of 44b rotates in a direction away from the surface of the fixing roller 15. Normally, the non-contact temperature sensor 51 placed on the hook 44b moves away from the surface of the fixing roller 15, but the placement surface of the non-contact temperature sensor 51 approaches the fixing roller 15 side. Since the guide surface 51b is formed as described above, the non-contact temperature sensor 51 approaches the fixing roller 15 side, and the gap Y is maintained at a certain length. That is, the interval Y can be maintained constant by forming the inclination angle or the surface shape of the guide surface 51b arbitrarily. When the temperature decreases and the heat shrinks, the separation plate 43 moves to the opposite side to the arrow b direction, but the interval Y between the surface of the non-contact temperature sensor 51 and the fixing roller 15 is increased by the opposite operation. Can be constant.
As described above, the separation plate 43 and the non-contact sensor can simultaneously create a highly accurate gap and interval. Further, when assembling the position of the non-contact temperature sensor 51, the interval can be adjusted without using both end portions other than the sheet passing portion of the fixing roller. Moreover, in this embodiment, the gap Y of the separation plate 43 and the interval between the non-contact temperature sensors 51 can be formed with high accuracy by a structure that does not cost. Further, since the non-contact temperature sensor 51 is disposed in the sheet passing portion of the fixing roller, the present invention can be implemented without complicating the configuration of both ends of the fixing roller.

The embodiments of the present invention have been described above. However, of course, the present invention can be variously modified or changed based on the technical idea of the present invention.
For example, in the above embodiment, the image forming apparatus 1 has been described as a printing apparatus. However, the present invention can be applied to other image forming apparatuses such as a copying machine and a fax machine in addition to the printing apparatus.

1 is a cross-sectional view in an up-down direction of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view around a fixing device of the image forming apparatus of FIG. 1. FIG. 2 is an enlarged perspective view of the fixing device in FIG. 1. FIG. 4 is an enlarged perspective view seen from another direction of the fixing device of FIG. 1. FIG. 2 is an enlarged cross-sectional view of the fixing device in FIG. 1. FIG. 2 is an enlarged cross-sectional view of one end side of the fixing device in FIG. 1. FIG. 2 is an enlarged cross-sectional view of a non-contact temperature sensor disposed in the fixing device of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 14 Fixing roller assembly 15 Fixing roller 16 Pressure roller 43 Separation plate 44b Hook part 44 Support plate 45 Heater 46 Gap adjustment member 51 Non-contact temperature sensor 51a Thermistor 51b Guide surface 52 Sensor support member

Claims (4)

A fixing means for fixing the toner image transferred to the recording medium by a transfer means for transferring the toner image formed on the image bearing member to the recording medium is provided on the conveying path of the recording medium;
The fixing unit rotates the fixing roller more than a fixing roller that thermally welds the toner image to the recording medium, a pressure roller that presses against the fixing roller, and a pressure-bonding portion between the fixing roller and the pressure roller. A separation member having a separation plate for preventing the recording medium from being wound, which is arranged on the downstream side in the direction with a gap with respect to the outer peripheral surface of the fixing roller, a heater for heating the fixing roller, and detecting heat of the fixing roller And an image forming apparatus including a non-contact temperature sensor disposed at a distance from the outer peripheral surface of the fixing roller.
The separation member is slidably disposed on the outer peripheral surface of the fixing roller, and a gap adjusting member that gives a predetermined gap to the outer peripheral surface of the fixing roller at the tip of the separation plate, and supports the separation plate And a separation plate support member that follows the thermal expansion of the fixing roller and is movable while maintaining the gap.
The non-contact temperature sensor follows the movement of the separation plate support member, and moves in a direction to maintain a constant distance between the non-contact temperature sensor and the outer peripheral surface of the fixing roller. Image forming apparatus.   The separation plate support member is provided with a rotation shaft on one end side away from the fixing roller, and provided with a hook portion that engages with the non-contact temperature sensor on the other end side, and the non-contact temperature sensor includes the hook portion 2. The image forming apparatus according to claim 1, wherein one end side that is remote from the first end portion is rotatably provided, and a placement portion is provided on which the other end side is placed on the hook portion.   The non-contact temperature sensor forms a guide surface on a surface of the mounting portion that is placed on the hook portion, and the non-contact temperature sensor follows the movement of the hook portion so that the non-contact temperature sensor is fixed to the fixing portion. The image forming apparatus according to claim 2, wherein the image forming apparatus is formed so as to maintain a constant distance from the outer peripheral surface of the roller.   The image forming apparatus according to claim 2, wherein the hooking portion is disposed in an intermediate portion in the axial direction of the fixing roller.

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