JP4798165B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus employed in a copying machine, a printer, or a multifunction machine having a facsimile function thereof, and more specifically, an image forming apparatus including a fixing device in which a temperature sensor such as a thermistor is assembled. Relates to the device.

As the image forming apparatus as described above, a pair of conveyance rollers (registration roller pair) installed in the middle of the recording paper conveyance path is fed out one by one from a recording paper supply unit equipped with a recording paper cassette or the like. Then, an image is recorded by an electrophotographic image recording unit.
The toner image formed on the surface of the photosensitive drum is transferred to the recording paper conveyed and supplied to the nip portion between the photosensitive drum and the transfer roller constituting the image recording unit. The toner image transferred to the recording paper is fixed as a permanent image by a fixing device installed in the middle of the recording paper conveyance path, and then discharged to a discharge tray.
Examples of the fixing device include those provided with a heat roller and a press roller that rotate while pressed against each other. The heat roller has a built-in heater, and the toner image transferred onto the recording paper is fixed as a permanent image by heating and pressing at a nip portion with the press roller.

  In order to perform good fixing with the fixing device, it is important to fix the toner image on the recording paper at an appropriate fixing temperature. Therefore, the fixing device has a preset fixing temperature that is suitable for the characteristics of the image forming apparatus and the like, and in order to maintain the surface temperature of the heat roller at the set fixing temperature, in the vicinity of the heat roller, A temperature sensor for detecting the surface temperature of the heat roller is provided. As the temperature sensor, a contact type thermistor is frequently used as one having excellent high-speed response even in an environment where mechanical heat or vibration is repeated due to repeated cooling and heating. However, since the thermistor is incorporated in the housing of the housing together with the heat roller and the press roller, there is a problem that the assembled state of the thermistor cannot be seen from the outside of the housing once incorporated.

6 and 7 are cross-sectional views schematically showing the above-mentioned problems of the conventional fixing device. FIG. 6 is a diagram in which the thermistor is properly assembled. FIG. 7 is a diagram in which the thermistor is irregularly assembled. The figure is shown.
In the drawing, 6000 is a fixing device, 600 is a halogen lamp, 610 is a heat roller, 620 is a press roller, 630 is a thermistor, 630 is a heat sensitive part, 6310 is a bracket for fixing the thermistor 630, 6320 is for fixing the thermistor 630 to the bracket 6310. A screw 6400 is a part of a housing for housing the heat roller 610 and the press roller 620.
A thermistor element (not shown) is attached to the heat collecting plate of the heat sensitive part 6300 of the thermistor 630, and the thermistor 630 has a detection surface 6301 on which the thermistor element is attached so as to contact the outer surface 611 of the heat roller 610. The inner wall of the housing 6400 is assembled.

  As shown in FIG. 6, if the detection surface 6301 of the thermistor 630 is properly assembled so as to contact the outer surface 611 of the heat roller 610, the surface temperature of the heat roller 610 can be detected properly. On the other hand, when the non-detection surface (back surface side) of the heat-sensitive part 6300 is assembled so as to contact the outer surface 611 of the heat roller 610 as shown in FIG. 7, the surface temperature of the heat roller 610 is accurately detected. This is not possible, causing a detection error. Further, since the surface temperature of the heat roller 610 cannot be accurately detected, the energization of the halogen lamp 600 is not properly turned on / off, and the heat roller 610 becomes too hot and becomes uncontrollable. Nevertheless, the thermosensitive part 6300 of the thermistor 630 clears the temperature detection inspection at the time of manufacture because the thermistor element reacts to some extent even when the non-detection surface side is in contact with the surface of the heat roller 610. May end up.

JP 2001-133910 A JP 2005-62690 A JP 2007-168132 A

Therefore, it is desirable that the thermistor 630 can be visually recognized even after the thermistor 630 is assembled to the housing 6400.
Japanese Patent Application Laid-Open No. H10-260260 discloses a device that can confirm the movement state of the scanning device of the image forming apparatus from the outside.
Japanese Patent Application Laid-Open No. 2004-228688 discloses an image recording unit of an image forming apparatus in which a light transmission window for confirming a contact state between a developing roller and a supply roller is formed.
Japanese Patent Application Laid-Open No. H10-260260 discloses a cover that can be opened and closed at a portion where an ink or toner cartridge of an image forming apparatus is mounted, and the cover is made transparent so that the inside can be seen.

  As described above, some of the image forming apparatus is made of a transparent member so that the internal state can be visually recognized. However, if the thermistor assembled state can be visually recognized from outside the fixing device housing, There wasn't.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly reliable image forming apparatus by preventing an assembly error of a temperature sensor assembled in a housing.

  An image forming apparatus according to the present invention includes a fixing device that nips a recording medium by a heat roller and a press roller incorporated in a housing and fixes a toner image transferred to the recording medium. An image forming apparatus that detects a surface temperature of the heat roller and controls the surface temperature to be maintained at a predetermined fixing temperature. The housing is provided with a temperature sensor that detects the surface temperature of the heat roller. A part of the housing is made of a transparent member so that the assembled state of the temperature sensor can be visually recognized from outside the housing.

  In the present invention, the temperature sensor may be provided in contact with the outer surface of the heat roller. The transparent member may be attached to a window formed in the housing.

According to the image forming apparatus of the present invention, since a part of the housing is made of a transparent member so that the assembled state of the temperature sensor can be visually recognized from the outside of the housing, the temperature sensor is assembled after the temperature sensor is assembled to the housing. Can be easily confirmed.
Therefore, even when the assembly error is not clarified by the temperature detection inspection at the time of manufacture, it is possible to determine the assembly error only by visually recognizing through the transparent member.
As described above, since the temperature sensor assembly error can be recognized before the fixing device is attached to the image forming apparatus, there is no possibility of an error caused by the temperature sensor assembly error or the temperature control of the heat roller being disabled. High image forming apparatus can be configured.
In particular, when the temperature sensor is provided in contact with the outer surface of the heat roller, it is easy to cause an assembly error such as contacting the back side of the temperature sensor, but it is easy to check the assembled state of the temperature sensor. As a result, assembly errors can be prevented.
If the transparent member is to be attached to a window portion formed in the housing, it can be a housing having a transparent member with a simple structure.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an example of a multifunction machine in which the image forming apparatus of the present invention is adopted, FIG. 2 is a schematic perspective view of a fixing unit provided in the image forming apparatus, and FIG. FIG. 4 is a schematic plan view of a temperature sensor assembled to the identification wearer unit, and FIG. 5 is a view showing a modification of the identification wearer unit, similar to FIG. FIG.

    FIG. 1 shows a so-called multi-function machine having a facsimile function, a copying function, and a printer function. An image forming apparatus 1 according to the present invention is a facsimile machine, a copying machine, a printer, and an apparatus in which these are combined. It also applies to. The image forming apparatus 1 shown in the figure includes an automatic document feeder (ADF) 2, an image reading unit 3, an image recording unit 4, and a recording paper supply unit 5 in a stacked state from above. The ADF 2 feeds and separates the originals deposited on the original tray 21 one by one by the pickup roller 22 and the separation means (a pair of separation roller and retard roller) 23. While the curved conveying path 27 is conveyed by each of the conveying roller pairs 24, 25, 26, the image is read by a stationary reading scanning device (described later) 31 at the reading point 100 of the ADF document. Then, the paper is sequentially discharged onto the document discharge tray 29 by the discharge roller pair 28. In addition, as the separating means 23, many things which consist of a separation roller and a separation pad are also employ | adopted.

  The image reading unit 3 includes an ADF reading unit 32 and a flat plate scanning unit (FBS) 33. FIG. 1 shows a state in which the reading scanning device 31 is stationary on the ADF reading unit 32 immediately below the ADF reading point 100 and reads an image of a document that is automatically and sequentially conveyed by the ADF 2. When performing image reading in the FBS 33, the reading scanning device 31 moves to the FBS 33, and reads an image of a document placed downward on the platen glass 34 while reciprocating left and right under the platen glass 34. A series of mechanisms constituting the ADF 2 also serves as a platen cover (document pressing plate) and can be opened and closed up and down with the back side of the paper surface as a hinge portion.

An image recording unit 4 shown in the figure is an electrophotographic image recording unit employing a cleanerless system, and includes a photosensitive drum 41, a charger 42, an exposure unit 43, a developing unit 44, a transfer unit 46, and a memory removal brush. 45.
The photosensitive drum 41, the charger 42, and the memory removal brush 45 are incorporated in a resin drum unit housing and configured as a drum unit 410. The drum unit 410 is configured to be freely detachable from a predetermined portion in the apparatus main body 11 of the image forming apparatus 1.
Although the charger 42 is a brush charger in the illustrated example, it may be a roller charger or a scorotron charger. When the drum unit 410 is mounted in the apparatus main body 11, it is connected to a drive transmission system (not shown) for rotating the photosensitive drum 41 in the direction of the arrow. The charger 42 is connected to a high voltage power source for uniformly charging the surface of the photosensitive drum 41 and applying a predetermined bias potential. The charger 42 applies a predetermined photoreceptor potential to the surface of the photoreceptor drum 41.
The exposure device 43 includes an LED head array in which a large number of LEDs are arranged along the scanning direction (the axial direction of the photosensitive drum 41), and is installed in the apparatus main body 11. The transfer unit (transfer roller) 46 is rotatably provided in the recording paper conveyance path between the registration roller pair 12 and the fixing unit 6 in the apparatus main body 11, and the drum unit 410 is a predetermined part in the apparatus main body 11. When attached to the photoconductor drum 41, a predetermined bias potential is applied in contact with the photoconductive drum 41, and the photoconductive drum 41 rotates in cooperation with the photoconductive drum 41. Here, the irradiation body of the exposure device 43 is not limited to the LED, and may be a laser or the like.
The memory removal brush 45 is provided so as to be in contact with the surface of the photosensitive drum 41, and the residual toner after the transfer is disturbed and dispersed by the memory removal brush 45, the afterimage is erased, and the electrostatic latent image is transferred to the electrostatic latent image. It is collected in the developing device 44 in a state where the influence is avoided.

  The fixing unit 6 is provided on the downstream side of the photosensitive drum 41 and the transfer unit 46, and incorporates a heat roller 61 incorporating a halogen lamp 60 serving as a heating source, and a press roller 62. The fixing unit 6 also includes a discharge roller pair 7 for discharging the recording paper 9 to the discharge tray 8.

The developing device 44 includes a stirrer 442, a supply roller 443, and a developing roller 444, and is configured as a developing device unit 440.
In the coupled state of the drum unit 410 and the developing unit 440, the photosensitive drum 41 and the developing roller 444 are in contact with each other. When the developing device unit 440 is mounted in the apparatus main body 11, a rotation transmission system (not shown) for rotating the stirrer 442 is connected. Further, the supply roller 443 and the developing roller 444 are connected to a rotation transmission system (not shown) for rotating in the arrow direction in FIG. 1, and the supply roller and the developing roller 444 are not shown for applying a predetermined developing bias potential. Connected to a power connector or a high voltage power source.

  The supply unit 5 for the recording paper 9 includes a recording paper cassette (paper placing unit) 51 that can be taken in and out in the direction perpendicular to the paper surface, and a supply roller 16 is provided on the front end of the recording paper cassette 51. The supply roller 16 is provided so that the separation pad 17 is in contact therewith, and the recording paper 9 accommodated in the recording paper cassette 51 is fed out from the uppermost layer portion as the supply roller 16 rotates around the support shaft, and the separation pad 17 Under the action of 17, the sheets are separated and conveyed one by one. In the recording paper cassette 51, there are provided a push-up plate 54 configured to be able to swing up and down with the hinge pin 53 as a fulcrum and a position-adjustable restricting plate 52 that restricts the rear end of the recording paper 9. Yes. The push-up plate 54 is provided in a state where elasticity is applied upward by the compression spring 55. In addition, although illustration and description are omitted, it goes without saying that additional members necessary as the recording paper cassette 51 are also provided. An optional cassette (not shown) may be further provided below the recording paper cassette 51 to configure a multi-cassette system having two or more stages.

  The separation pad 17 is supported by a pad base 18, and the pad base 18 is a compression spring at a substantially central portion of a paper guide member 19 formed over the entire paper width at the recording paper discharge side end of the recording paper cassette 51. It is installed in a state where elasticity is applied upward (not shown). The separation pad 17 is brought into contact with the peripheral surface of the supply roller 16 by the upward action of the compression spring. A jam access cover (maintenance open / close cover) 14 is attached behind the paper guide member 19 with an interval through which the recording paper from the lower cassette can pass. The jam access cover 14 is attached to the image forming apparatus 1. Is attached to the right side wall portion of the box-shaped housing (device main body) 11 with the hinge pin 141 as a fulcrum. The upper part of the inner surface of the jam access cover 14 is curved toward the recording paper cassette 51 to form a part of the curved conveyance path 13 to be described later.

  A press roller 151 is mounted inside the jam access cover 14 so as to face the transport roller 15 installed in the apparatus main body 11. If the jam access cover 14 is opened with the hinge pin 141 as a fulcrum, the transport roller 15 and the press roller 151 are released, and the jammed recording paper can be taken out. The curved conveyance path 13 changes the direction of the recording paper fed from the recording paper cassette 51 by approximately 180 degrees, conveys it in a U-turn shape, and directs it toward the image recording unit 4. A registration roller pair 12 is provided near the upstream side of the image recording unit 4 in the curved conveyance path 13 so that the recording paper is registered and introduced into the image recording unit 4. The conveyance roller 15, the curved conveyance path 13, and the registration roller pair 12 constitute recording sheet conveyance means for conveying the recording sheet 9 fed from the recording sheet cassette 51 to the image recording unit 4.

Next, the configuration of the fixing unit 6 according to the present embodiment will be described with reference to FIGS. In FIG. 3, the two-dot chain line indicates the conveyance path of the recording paper 9.
The fixing unit 6 is provided on the downstream side of the above-described drum unit 410 (see FIG. 1), and a heat roller 61, a press roller 62, and a discharge roller pair 7 are accommodated in the housing 64.
The housing 64 is formed of a box having an opening on the lower side, and a part of the upper central portion is formed of a transparent member 65 so that the inside of the housing can be visually recognized. The configuration of the transparent member 65 will be described in detail later.
Fixing portions 641 made of a steel plate are provided at both longitudinal ends of the housing 64. A screw hole 642 is formed in the fixing portion 641. A housing 64 is attached to the apparatus main body 11 by inserting a screw (not shown) into the screw hole 642 and fixing it to a predetermined position of the apparatus main body 11. . An upstream opening 643 for receiving the recording paper 9 transported along the transport path is formed on the upstream side of the housing 64 in the transport direction of the recording paper 9 (on the right side in FIG. 3). Further, a downstream opening 644 for discharging the recording paper 9 on which the toner image is fixed toward the discharge tray 8 (see FIG. 1) is formed on the downstream side in the conveyance direction of the recording paper 9 (left side in FIG. 3). Has been.

The heat roller 61 and the press roller 62 are arranged such that the nip portion 67 is along the conveyance path of the recording paper 9.
The heat roller 61 is made of a hollow aluminum cylinder, and a halogen lamp 60 as a heat source is accommodated in the aluminum cylinder. A coating layer (not shown) of a fluororesin is formed on the outer peripheral surface of the heat roller 61 in the region where the recording paper 9 passes.
The press roller 62 is made of a rubber body such as silicone or urethane or a sponge body, and is fixed to a press roller shaft 68 formed of a metal material such as a steel material via an adhesive or the like. Both ends of the press roller shaft 68 are supported by a bearing body 644 so as to freely rotate. A press roller 62 is provided in contact with the heat roller 61 by a roller support portion 643 formed of a coil spring, and a nip portion 67 is provided. Is formed.
An end portion of the heat roller 61 is configured to freely rotate by a bearing (not shown) or the like, a gear (not shown) is attached, and driving is controlled by a drive motor. The press roller 62 is rotated following the rotation of the heat roller 61.

The downstream opening 644 is provided with a discharge roller pair including a discharge roller 70 and a press roller 71 that rotate while pressed against each other. The discharge roller 70 and the press roller 71 are arranged such that the nip portion 73 is along the conveyance path of the recording paper 9 discharged from the heat roller 61 and the press roller 62. Three discharge rollers 70 are provided at a predetermined interval on a discharge roller shaft 72 formed of a metal material such as a steel material. An end portion of the discharge roller shaft 72 is configured to be freely rotatable by a bearing (not shown) or the like, and a gear (not shown) is attached to the end portion of the heat roller 61 described above. Drive. The press roller 71 is configured to rotate following the rotation of the discharge roller 70, and three press rollers 71 are provided at similar intervals so as to contact the discharge roller 70.
As described above, in the fixing unit 6, the recording paper 9 on which the toner image is transferred is heated and pressed by the heat roller 61 and the press roller 62, and the toner image is fixed as a permanent image. Thereafter, the recording paper 9 recorded by the discharge roller pair 7 is discharged to the discharge tray 8.

Next, the configuration of the fixing unit 6 and the temperature sensor 63 will be described in more detail with reference to FIGS. In FIG. 2, the temperature sensor 63 is shown by a dotted line, and the bracket 66 is omitted. Further, in FIG. 4, a screw 75 and a bracket 66 for fixing the temperature sensor 63 to the housing 64 are not shown for the sake of explanation.
A temperature sensor 63 for detecting the surface temperature of the heat roller 61 is assembled to the housing 64, and a part of the housing 64 is transparent member 65 so that the assembled state of the temperature sensor 63 can be seen from outside the housing 64. It consists of The transparent member 65 is made of glass or a heat resistant resin material, and is fixed to the housing 64 with screws 74.
The temperature sensor 63 includes a heat sensitive part 631, a holder 632, an electric wire 633, and a connector 634, and a thermistor element 6310 is attached to the heat collecting plate of the heat sensitive part 631. The heat sensitive part 631 is configured by a spring plate such as SUS so as to contact the outer surface 69 of the heat roller 61 with a predetermined contact pressure. The heat sensitive part 631 is covered with a resin tape having heat resistance and wear resistance such as polyimide in order to prevent the heat roller 61 from being scratched or worn. The connector 634 of the temperature sensor 63 is led to the outside of the fixing unit 6 and is connected to a connector 635 connected to a power source, thereby enabling power supply to the temperature sensor 63 and transmission of a detection signal. A screw hole 6321 is formed in the holder 632.

The temperature sensor 63 is disposed so that the detection surface on which the thermistor element 6310 is attached contacts the outer surface 69 of the heat roller 61, and is fixed to the inner wall 645 of the housing 64 with a screw 75 via a bracket 66 made of sheet metal. Mounted like so.
Therefore, when it is visually confirmed from the outside of the housing 64 through the transparent member 65 after the assembly, it is found that the non-detection surface is assembled so as to contact the outer surface 69 of the heat roller 61 as shown in FIG. What is necessary is just to correct so that it may become a regular assembly | attachment state.
Here, if the screw 74 is removed and the transparent member 65 is removed, the temperature sensor 63 itself is not removed, and the detection surface of the heat-sensitive part 631 is corrected to a proper assembly state so as to contact the outer surface 69 of the heat roller 61. can do.

According to the above, it is possible to easily confirm the assembled state of the temperature sensor 63 from outside the housing 64 through the transparent member 65 after the temperature sensor 63 is assembled in the housing 64. Therefore, even when the assembly error is not clarified by the temperature detection inspection at the time of manufacture, the assembly error can be determined only by visually recognizing through the transparent member 65. As described above, since the assembly mistake of the temperature sensor 63 is known before the fixing unit 6 is attached to the apparatus main body 11, an error caused by the assembly mistake of the temperature sensor 63 or the temperature control of the heat roller 61 becomes impossible. Therefore, it is possible to configure the image forming apparatus 1 with high reliability.
As shown in FIG. 2, if the transparent member 65 is formed large in the upper center portion of the housing 64, not only the assembled state of the temperature sensor 63 but also the assembled state of the heat roller 61 and the press roller 62 can be visually confirmed. Therefore, after the fixing device unit 6 is assembled, not only the assembled state of the temperature sensor 63 can be easily confirmed from the outside of the housing 64, but also a jam condition of the recording paper 9 or a toner accumulation condition can be confirmed.

  Here, the configurations and shapes of the fixing unit 6, the housing 64, and the temperature sensor 63 are not limited to those illustrated. The heat source of the heat roller 61 is not limited to the halogen lamp 60, and may be a planar heater, for example. The number of discharge roller pairs is not limited to three.

The configuration of the transparent member 65 is not limited to the illustrated example.
FIG. 5 is a view showing a modified example of the housing 64, which is the same as FIG. In FIG. 5, the temperature sensor 63 is indicated by a dotted line, and the illustration of the bracket 66 is also omitted here.
Portions common to those in the above example are denoted by common reference numerals, and description thereof is omitted.
A rectangular window portion 76 is formed above the housing 64 and at a position where the assembled state of the temperature sensor 63 can be visually recognized, and is different from the above example in that a transparent member 65 is attached to the window portion 76. A stepped portion may be formed on the side portion of the window portion 76, the transparent member 65 may be placed there and fixed with an adhesive, or a knob portion may be provided on the transparent member 65 so that the structure can be opened and closed vertically. The temperature sensor 630 is assembled in the same manner as in the above example as indicated by the dotted line in the figure.
Also by this, the assembled state of the temperature sensor 63 can be visually recognized from the outside of the housing 64 through the transparent member 65, and the housing 64 including the transparent member 65 can be obtained with a simple structure.
As described above, the transparent member 65 configured in the housing 64 is not limited to the illustrated example, and may be any configuration as long as the assembled state of the temperature sensor 63 can be visually recognized from the outside of the housing 64.

  Although the image forming apparatus 1 of the one-component development system has been described above, the present invention is not limited to this and can be applied to a two-component development system. Further, it is needless to say that the configurations of the image forming apparatus 1, the fixing unit 6, the drum unit 410, and the developing unit 440 shown in FIG.

1 is a schematic longitudinal sectional view showing an example of a multi-function machine in which an image forming apparatus of the present invention is adopted. FIG. 2 is a schematic perspective view of a fixing device unit including a fixing device and a discharge roller pair provided in the image forming apparatus. It is XX arrow directional cross-sectional view of the identification dressing device unit in FIG. FIG. 2 is a schematic plan view of a temperature sensor assembled in the fixing unit. FIG. 6 is a view showing a modification of the fixing unit and is the same as FIG. 2. It is sectional drawing which showed typically the above-mentioned problem of the conventional fixing device, and is a figure which assembled | attached the thermistor normally. It is sectional drawing which showed the above-mentioned problem of the conventional fixing device typically, and is a figure in which the thermistor was assembled | attached irregularly.

Explanation of symbols

1 Image forming apparatus 6 Fixing unit (fixing unit)
61 Heat roller 62 Press roller 63 Temperature sensor 64 Housing 65 Transparent member 76 Window 9 Recording paper (recording medium)

Claims (3)

A heat roller and a press roller incorporated in the housing are provided with a fixing device for nip-conveying the recording medium and fixing the toner image transferred to the recording medium, and detecting the surface temperature of the heat roller. An image forming apparatus that controls a temperature to be maintained at a predetermined set fixing temperature,
A temperature sensor for detecting the surface temperature of the heat roller is assembled to the housing, and a part of the housing is made of a transparent member so that the assembled state of the temperature sensor can be seen from outside the housing. An image forming apparatus. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the temperature sensor is provided in contact with an outer surface of a heat roller. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the transparent member is attached to a window portion formed in the housing.

Images