JP2002296965A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents a thermo- protector from being operated in case recording paper of a narrow width is placed and passed ignoring a paper passage reference position. SOLUTION: In the longitudinal positional relationship of recording paper presence/absence sensor 21, a temperature detection means 73 of a heating body 71 of a fixing device, and a thermo-protector 77, when the thermo-protector 77 is disposed between the paper sensor 21 and the temperature detection means 73 and recording paper A having the minimum width in paper passage is passed opposite the paper sensor 21 while ignoring a central paper passage reference position, the paper sensor 21 cannot detect the passage of the paper, and paper feed is stopped. When the paper is passed the paper sensor 21, the recording paper A passes through an area of the thermo-protector 77 and, therefore, an abnormal temperature increase does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer (LBP), and a facsimile for forming an image by an image forming means such as an electrostatic recording system and an electrophotographic system. In particular, the present invention relates to an image forming apparatus in which a recording material on which an unfixed toner image is formed is guided to a pressure-contact portion of two rotating members that are pressed against each other, and heated and pressed to obtain a fixed image.

[0002]

2. Description of the Related Art Conventionally, in an electrostatic recording apparatus or an electrophotographic apparatus, the fixing of a toner image formed on a recording material is performed by using a halogen lamp or the like as a heating element and controlling the temperature within a predetermined temperature range. The recording material is nipped and conveyed by a heating roller and a pressure roller having an elastic layer (heat roller method).

Alternatively, as described in JP-A-63-313182 and JP-A-2-1577878, a fixedly supported heating element (ceramic heater) is conveyed while being pressed against the heating element. A heating unit comprising a heat-resistant film (fixing film), and a pressure member for bringing the recording material into close contact with the heater unit, and applying the heat of the heating element to the recording material via the fixing film. A heat fixing device (film heat fixing device) for fixing a toner image formed on a recording material has been proposed and put into practical use.

In the above-mentioned two typical fixing systems, at least one temperature detecting means for the heating element is arranged close to or in contact with the heating element in order to control the temperature of the heating member, and its output is controlled. Based on this, the control of the image forming apparatus controls the energization of the heating element, that is, the temperature control.

In the case of a page-type copying machine or LBP, a temperature sensor for a recording material presence / absence sensor (hereinafter, referred to as a paper sensor) including a photosensor and a flapper is appropriately provided in the conveyance path of the image forming apparatus in the case of a page type copying machine or LBP. By arranging, the leading and trailing edge positions of the recording material are detected, and the control temperature is changed depending on whether or not the recording material such as paper is in the fixing nip,
Depending on the timing at which the recording material enters the fixing nip, the control temperature may be changed for a certain period of time, or a paper jam warning may be issued by detecting that the recording material has remained in the fixing nip in the conveyance path. General.

Further, in the fixing device, due to a failure of a triac, a thermistor, a relay, or the like, which is a component of the power supply control circuit, or a runaway of the CPU, the state of excessive power supply to the heating element continues, and the heating element abnormally rises. As one of the safety measures for forcibly shutting off the power supply in the event of a heating accident, a thermoprotector such as a thermoswitch or a thermal fuse is usually connected in series to the AC line and is close to the heating element, or They are arranged in contact.

Here, a page-type image forming apparatus represented by a copying machine or an LBP is not limited to the A3 size, but may be B4, A4 horizontal,
Generally, recording materials of various sizes such as vertical, A5 horizontal, vertical, B5 horizontal, vertical, Western envelope, postcard, etc. can be passed.
Therefore, the paper sensor for detecting the leading and trailing edges of the recording material described above is provided in the longitudinal position of the image forming apparatus at a position where the paper having the minimum longitudinal width that guarantees the paper passing is reliably passed along the paper transport direction. It is common to arrange a plurality. The temperature detecting means of the heating element is generally disposed in an area through which a sheet having a minimum longitudinal width surely passes in order to detect the temperature of the paper passing portion of the heating element. Also, the thermoprotector is generally disposed in a region where the paper passes in the longitudinal position so that the thermoprotector operates only when the temperature control circuit runs out of control and the control cannot be performed normally.

That is, the three elements of the front and rear edge detection sensor of the paper, the temperature sensor of the heating element, and the thermoprotector are arranged at a longitudinal position where a recording material having a minimum longitudinal width which is guaranteed to pass by each image forming apparatus. It is commonplace to be located in the area through which it passes.

[0009]

Here, in the image forming apparatus in which the three elements are arranged in the above-described longitudinal positional relationship, when a paper cassette is selected as a paper feed port, an appropriate paper cassette is provided in the cassette. Unless a recording material having a size smaller than the size is erroneously set, the recording material passes through the longitudinal area where the three elements are arranged when being conveyed in the image forming apparatus.

[0010] If paper of a size different from the size to be originally set in the paper cassette is erroneously set, the length of the front and rear ends, etc., detected by the paper sensor disposed in the transport path is detected. In general, a discrepancy between paper sizes is identified, and a malfunction warning is issued after the ejection of the recording material.

However, in the case of an apparatus having a so-called multi-tray paper feed port, in which the image forming apparatus can arbitrarily change the regulation of the width in accordance with the size of the recording material, even if the paper size to be passed is within the guaranteed range. For example, if the user does not notice that the paper edge regulating plate of the tray is wider than the appropriate width of the envelope or postcard than the paper width, and the paper is passed to one side of the regulating plate, the paper originally passes Since the vehicle passes through a position deviating from the longitudinal position to be performed, the following inconvenience may occur.

1) Since the recording material does not pass through the position of the sensor for detecting the leading and trailing edges of the paper, a paper jam such as a delay jam occurs.

2) Since the recording material does not pass through the thermistor position, the temperature control of the recording material passing portion cannot be performed, resulting in defective fixing.

3) Since the recording material does not pass through the thermo-protector position, the temperature of the thermo-protector rises,
It works.

The above three points are all phenomena that occur when the recording material should not be originally placed on the multi-tray, but are placed at an inappropriate position. In 2), a desired output sheet can be obtained by performing jam processing of the recording material or the like, arranging the regulating plate at an appropriate position, and performing printing again.

However, in the case of 3), the fixing device becomes unusable due to the operation of the thermoprotector, and the image forming apparatus cannot be operated again unless at least the fixing device is replaced with a new one. Would.

An object of the invention according to the present application is to solve the above-mentioned problem 3), that is, when a recording material having a narrow width relative to a passable width is passed, the recording material in the image forming apparatus is not used. Regardless of the area of the transported longitudinal position, the recording material is allowed to continuously pass through the area where the thermoprotector is not located, and image formation that can prevent the thermoprotector from operating It is intended to provide a device.

Next, another object of the present invention will be described.

Image forming apparatuses such as copiers and LBPs can generally form and output images on recording materials of various dimensions as described above, but technically limit the guarantee of passing small-size media. One of the factors is an increase in the temperature of the non-sheet passing portion of the heating element of the fixing device.

The non-sheet-passing portion temperature raising means that when a recording material having a longitudinal width narrower than a paper-passable width of the apparatus is passed, a recording material to be heated is continuously connected to a heating element of the fixing device. A longitudinal region (paper passing portion) that passes through the recording medium and a longitudinal region (non-paper passing portion) through which the recording material that is the heated member does not pass despite the heat generating portion occur.
This is a phenomenon in which the temperature of the non-sheet passing portion where the heat load is smaller than that of the sheet passing portion is increased while the sheet passing region is maintained at the fixing temperature.

Accordingly, the rise of the temperature of the non-sheet passing portion causes the fluororesin layer formed on the surface of the heating roller, the polyimide resin and the fluororesin used for the fixing film in the case of the film type fixing, and the rubber or fluorine of the pressure roller. Resin, etc.
In order not to be exposed to a temperature exceeding their heat-resistant temperature, the feeding interval of the small-sized media is determined according to the paper size.
Generally, they are set to different values.

However, when the recording material is narrow and a thick recording material is passed through, the temperature of the non-sheet passing portion of the heating member exceeds the heat-resistant temperature of the resin or the rubber agent, and the fixing member is supplied to the fixing device. The likelihood of damage is increased. In addition, narrow recording materials often take a thick form such as envelopes and postcards. In spite of the fact that the recording material feeding interval can be shortened technically, there is a disadvantage that the recording material is opened.

Therefore, there has been proposed an image forming apparatus in which a temperature detecting means is arranged in a non-sheet passing portion when a small size medium is passed through to measure the temperature, and the feeding interval of the recording material is changed according to the temperature. Provided.

However, also in this case, as described above, when the recording material is passed through a position different from the original position where the longitudinal position should pass, with the side surface regulating plate of the recording material installed on the multi-tray opened. Particularly, in a device in which the temperature detecting means of the non-sheet passing portion is disposed only on one side, when the recording material is moved toward the side where the temperature detecting portion is present and the sheet is passed, the temperature detected by the temperature detecting portion becomes The temperature of the non-sheet passing area, which should be detected, cannot be detected.The member made of fluororesin or silicone rubber near the non-sheet passing area of the heating element may be thermally damaged, or the thermo protector may operate. Thereafter, there is a possibility that the fixing device may become unusable.

A second object of the invention according to the present invention is to provide an image forming apparatus having a plurality of temperature detecting means in the longitudinal direction of a heating element, when a recording material having a width narrower than a passable width is passed. Regardless of the length of the image forming apparatus where the recording material is conveyed, the recording material is allowed to continuously pass through the area where the thermoprotector is not located, and the thermoprotector operates. It is an object of the present invention to provide an image forming apparatus which can prevent the image forming operation.

[0026]

According to the present invention, the first object is to provide an image having at least one paper detecting sensor, a temperature detecting means for a heating element of a fixing device, and a thermoprotector for the heating element. In the forming apparatus, this is achieved by setting the longitudinal positional relationship of the three elements as follows. In the longitudinal position relationship, a thermoprotector is disposed between the paper detection sensor and the temperature detection means of the heating element. In particular, the paper detection sensor is arranged in an area through which a recording material having a minimum longitudinal width that guarantees paper passing by the image forming apparatus passes.

As described above, if the three elements are arranged, even if the recording material is placed at an inappropriate position on the multi-tray and the paper is passed, 1) the recording material operates the paper detection sensor. When the recording medium passes through an area where the temperature detecting means is not located, the temperature of the heating element corresponding to the area through which the recording material passes becomes lower than the temperature of the heating element where the temperature detecting means is located, and the fixing temperature is insufficient. Occurs, but the temperature of the thermoprotector part is
The temperature becomes substantially equal to or lower than the temperature of the temperature detecting means, and the thermoprotector does not operate.

2) The recording material operates the paper detection sensor,
In addition, when passing through the area where the temperature detecting means is located, at this time, although the inconvenience that the toner image formed on the recording material is displaced in the longitudinal direction occurs, the recording material is located in the longitudinal area where the three elements are located. Because of the passage, the temperature of the thermoprotector section is equal to the temperature of the temperature detecting section, and the thermoprotector does not operate.

3) When the recording material passes through an area where the paper detection sensor is not operated, a malfunction warning such as a paper feeding failure or a paper jam is issued, and the continuous operation of the apparatus is stopped.

As described above, if the three elements are arranged in the longitudinal positional relationship as shown in the present invention, the recording material is arranged at an inappropriate position on the multi-tray and the sheet feeding operation is performed. In addition, even if inconveniences such as misalignment of the printing position and deterioration of the fixing property occur, it is possible to prevent the thermoprotector of the heating element from operating and causing the fixing device and the image forming apparatus to become inoperable. Become.

A second object of the present invention is to provide an image forming apparatus having a plurality of temperature detecting means in the longitudinal direction of a heating element, wherein two temperature detecting means and a thermoprotector are disposed in a longitudinal positional relationship between two temperature detecting means. This is achieved by placing a thermoprotector between the means.

As described above, by arranging the thermoprotector and the temperature detecting means in the longitudinal direction, if the narrow recording material passes through an arbitrary paper possible area which does not follow the paper passing position standard, Even if the temperature control of the heating element is not abnormal, the thermoprotector of the heating element operates to bring the fixing device and the image forming apparatus into an inoperable state, or appropriately measure the temperature of the non-sheet passing portion It is possible to avoid causing thermal damage to the members constituting the fixing device without being able to do so.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS.
An embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows an electrophotographic laser printer (LBP) as an image forming apparatus to which the present invention is applied.
FIG. FIG. 2 shows the LBP shown in FIG.
FIG. 3 is a cross-sectional view of a main part of the fixing device of FIG. FIG. 3 is a front view of a heating body of the fixing device and a diagram for explaining temperature control of the heating body. FIG. 4 is a diagram for explaining the relationship between the longitudinal positions of the above-described three components, the paper detection unit, the temperature detection unit, and the thermoprotector, and the recording material conveyance region. FIG.
FIG. 4 is a diagram illustrating a relationship between the three components and a conveyance area when a recording material is conveyed while being shifted from a recommended paper passing area in the apparatus to which the exemplary embodiment is applied. FIG. 6 is a diagram illustrating a case where the paper passing area of the recording material is set to be opposite to the area illustrated in FIG. 5 in the longitudinal direction. FIG. 7 is a diagram illustrating, as a comparative example for explaining the effect of the present invention, a case where the three components are arranged in a positional relationship where the present invention is not performed.

First, the image forming process will be briefly described with reference to FIG. The paper which is the recording material is in the cassette 11
Alternatively, a multi-tray 19 corresponding to a general-purpose paper size
From the paper feed roller 12 or 13,
The sheet is fed in the direction of the arrow by the registration roller 20 in synchronization with the registration and the image writing timing. Immediately after passing through the registration roller 20, the leading and trailing edges of the paper are detected by a paper sensor 21 (top sensor) composed of a photosensor and a flapper. Whether the transport direction length is true or false is determined. Reference numeral 27 denotes a paper presence / absence sensor for determining whether or not a recording material is placed on the tray when feeding from the multi-tray 19.

In FIG. 1, reference numeral 1 denotes a photosensitive drum in which an organic photosensitive layer is formed on a grounded aluminum drum, which is uniformly charged by a bias power source and a charging roller 2 (not shown), and is driven by an arrow by a driving system (not shown). It is driven to rotate in the direction. In this embodiment, the conveying speed of the recording material and the peripheral speed of the photosensitive drum 1 are 90 mm / sec. The laser scanner 3 includes a semiconductor laser, a lens, a polygon mirror, a motor, and the like. The rotation of the polygon and the modulation of the laser according to the image signal are performed by a DC controller which is a control unit (not shown). Is subjected to laser exposure to form an electrostatic latent image.

The developing unit 4 is composed of a negative one-component magnetic toner, a developing magnet, a developing sleeve, and the like. A developing bias is applied from a bias power supply (not shown) to develop the electrostatic latent image. A toner image is transferred onto the recording material 10 by applying a positive bias from a bias power supply (not shown) to the transfer roller 6. The cleaning blade 5 cleans the transfer residual toner remaining on the photosensitive drum 1.
The recording material to which the toner image has been transferred is sent to a fixing device.

The fixing device according to the present embodiment includes a heating element in which an electric heating element made of a silver alloy is formed on an insulating substrate such as alumina or aluminum nitride, and a fixing film formed of a heat-resistant resin and holding the heating element. A guide and a PTF coated on a cylindrical polyimide resin,
E, a heater unit 7 composed of a fixing film or the like on which a fluororesin layer such as PFA is formed, and a pressing roller 8 having a metal core covered with silicone rubber or the like are pressed against each other to form a fixing nip. It is configured to rotate each other.

A paper sensor 23 is also provided downstream of the fixing nip.
(Paper discharge sensor) is arranged, and the paper transport state is monitored by the CPU in the DC controller. Even if the paper is sent to the toner image transfer unit by the top sensor 21, if the leading and trailing edges of the paper are not detected by the paper ejection sensor 23 within an appropriate time, a paper jam is generated as a paper jam. Power supply to the transformer, the heating element of the fixing device, and the like is cut off. After the recording material has passed through the fixing device,
The paper is sent by a paper discharge roller and output on a paper discharge tray.

Next, the fixing device according to the present embodiment will be described in more detail with reference to FIG.

In the figure, reference numeral 71 denotes a substrate made of alumina, on which a heating element 72 and a conduction electrode made of a silver alloy are screen-printed, and a thermistor 7 serving as a temperature detecting element is provided.
3 is a heater which is a heating element to which the bonding member 3 is bonded. The heating element 72 is connected to an AC power control circuit, and the thermistor 73 is a control circuit having a CPU.
Connected to C controller.

In the present embodiment, the control temperature (fixing temperature) of the heater 71 during paper passing is 185 ° C.
Reference numeral 74 denotes a fixing film in which a 50 μm-thick cylindrical polyimide film surface is provided with a primer layer made of fluororesin and carbon, and a fluororesin layer made of PTFE, PFA or the like as a silicon release layer. 75 is PP
S, a film guide made of a heat-resistant resin such as a liquid crystal polymer. Reference numeral 76 denotes a reinforcing sheet metal for suppressing bending deformation that occurs when the film guide 75 is pressed against the pressing roller 8. The heater unit 7 is formed from the above members.

Reference numeral 8 denotes a pressure roller in which an elastic layer made of silicone rubber, fluorine rubber, or the like is formed on a core metal made of aluminum, iron, or the like, and is driven to rotate by driving means (not shown). The heater unit 7 and the pressure roller 8 are pressurized by a pressure unit (not shown) to form a fixing nip portion. When the recording material 10 passes through the fixing nip portion, an unfixed toner image on the recording material is formed. Is established.

The relationship between the heater 71, the thermistor 73, and the temperature fuse 77 which is a thermoprotector in the present embodiment will be described with reference to FIG.

In the figure, the heater 71 shown in FIG. 7A shows the heating element printing surface of the heater, and the heater 71 shown in FIG.

Reference numeral 72 denotes an energizing heating element, and 73 denotes a thermistor. The thermistor 73 is connected to a DC controller 90 as a control circuit via a conductive electrode, and the temperature of the heater 71 is detected by detecting the resistance value. 30 is an AC power supply, 77 is an operating temperature of 230
It is a temperature fuse of ° C., and is arranged in contact with a region indicated by a broken line on the back surface of the heater 71. That is, in the present embodiment, the temperature of the contact region of the temperature fuse 77 becomes 230 ° C. is determined to be a case where the temperature control circuit runs away and normal temperature control becomes impossible, and the power supply is cut off. . Reference numerals 81 and 82 denote triacs, which are turned on / off, that is, energized by the DC controller 90 based on the output of the thermistor 73.

Referring to FIG. 4, the positional relationship between the paper sensor 21, the thermistor 73, the thermoprotector 77 and the paper passage area when the present invention is implemented will be described.

FIG. 4 is a view of the image forming apparatus according to the present embodiment as viewed from above the apparatus. In the figure, 100 is the apparatus main body, 19 is a multi-tray, and 191 and 192 are paper feeds from the multi-tray 19. And a sheet feeding guide (side regulating plate) for defining the sheet feeding position of the recording material from the left and right.

Reference numeral 71 denotes a heating element of the fixing device, and 73 denotes a thermistor. The same members as those described with reference to FIGS. The paper passing of this image forming apparatus is based on the central paper passing based on the paper passing position indicated by a thick broken line, and the thin broken line represents the recording material having the minimum width dimension indicated by A in FIG. This indicates the position where both ends pass.

The thermistor 73 is located on the left side of the paper passing reference position and inside the minimum width position, and the paper ejection sensor 23 is located between the thermistor 73 and the paper passing reference position. The top sensor 21 is disposed on the right side of the paper passing reference position and near the inside of the minimum width position.
Is disposed on the right side in the vicinity of the paper passing reference position, and the thermal fuse 77 is also disposed between the paper passing reference position and the minimum width position.

That is, in the image forming apparatus based on the center sheet passing of this embodiment, if the recording material having the size within the guaranteed sheet passing range is properly arranged in the sheet feeding port, the recording material indicated by the thin broken line It will pass through the small width area. in this case,
The leading and trailing ends of the recording material are detected by the top sensor 21, the temperature of the heating element 71 in the sheet passing area of the recording material is detected by the thermistor 73, and the temperature fuse 77
Is in contact with the heating element 71 in the paper passing area of the recording material.

FIG. 5 shows the side regulating plates 191 and 19 on the multi-tray 19 in the image forming apparatus of this embodiment.
2, the recording material passing area and each sensor when the operator feeds the recording material A with the recording material A being shifted to the left side in the transport direction in a state where the recording material is wider than the width of the recording material to be passed. It is a figure showing the longitudinal positional relationship. The side regulating plates 191 and 192 are moved to an equidistant position from the center sheet passing reference by a synchronous moving mechanism (not shown).

In this case, the recording material A is fed at the position for operating the paper sensor 27 on the multi-tray 19, but the top sensor 21 cannot be operated. After the paper is fed, the leading edge of the paper cannot be detected by the top sensor 21. Therefore, it is determined that the operation is abnormal in the DC controller that controls the apparatus, and the power supply to the motor, the heater, and the like is cut off. Is performed on the display unit of the image forming apparatus or the display unit of the host computer.

In this case, since an abnormal state is determined in the paper feeding operation, if the recording material remaining in the paper feeding unit is removed and the side regulating plates 191 and 192 are set at appropriate positions, image formation can be performed again. Can be.

FIG. 6 is a diagram showing the positional relationship between the recording material passing area and each sensor when the recording material A is moved to the longitudinal position opposite to the direction illustrated in FIG. .

In this case, the paper presence sensor 2 on the tray
7. Since all of the top sensor 21 and the paper discharge sensor 23 are included in the recording material passage area, it is not possible to perform abnormality detection depending on the operation status of each sensor. The inconvenience that occurs in this case is that the recording material A passes through a position deviated from the paper passing reference position of the image forming apparatus, so that the image writing position is deviated and the temperature based on the temperature of the heating element in an area where the recording material does not pass. In order to perform the control, the fixing property becomes worse than usual. In this case, when the recording material is arranged at an inappropriate position in the paper feeding unit, the writing position may be deviated, the fixing property may be reduced, and the like.
Does not cause damage such as replacement of parts.

FIG. 7 shows an image forming apparatus 101 as a comparative example in which the longitudinal positions of the temperature detecting element 73 and the thermoprotector 77 are replaced with the image forming apparatus 100 of the first embodiment, as viewed from above the apparatus. It is. Image forming apparatus 1
In No. 01, there is no thermo-protector (thermal fuse) between one of the paper presence / absence sensors (top sensor) and the temperature detecting means (thermistor) in the longitudinal positional relationship, that is, a thermo-protector is located on either longitudinal outside of the two. The state where the protector is arranged is shown.

In this case, for the recording material A, the three paper sensors are all operated and the thermistor is provided in the paper passing area, so that the fixing property is also good. It may be performed until you notice the deviation.

That is, when the recording material A is arranged at the position shown in FIG. 7, no abnormality in the arrangement position of the paper is detected by the paper sensor, and the thermistor is located within the paper passage area of the heating element. Although the fixing property is ensured by the contact, the thermal fuse 77 as the thermoprotector contacts the non-sheet passing area of the heating element. The temperature control of the heating element is performed to maintain the temperature of the contact portion of the thermistor 73 at the fixing temperature.

Therefore, as the number of passed sheets overlaps, the temperature of the contact portion of the thermal fuse 77 in the non-sheet passing portion of the heating element rises, and there is a risk that the thermal fuse 77 operates. When the thermal fuse 77 operates, the fixing device becomes unusable, and the image forming apparatus 100 cannot be used again unless at least the fixing device is replaced.

As described above, by arranging the recording material presence / absence detecting means, the temperature detecting means, and the thermoprotector in the longitudinal positional relationship as shown in the present embodiment, the size of the paper passing size can be reduced. Even if the recording material within the guaranteed range is fed at an arbitrary longitudinal position from the sheet feeding position, it is possible to eliminate the risk of causing a failure that causes replacement of parts to the image forming apparatus.

In the present embodiment, the top sensor 21 disposed in front of the registration roller is selected and described as one of the paper presence / absence detection sensors. This is because, regardless of the position, the position where the recording material passes, and the detection of a defect such as the sheet feeding position can be detected at a position upstream of the sheet discharge sensor position.

In the present invention, the means for detecting the presence or absence of the recording material is not limited to the top sensor 21. May be any of the sensors 27 or the paper ejection sensor 23, and the selected sensor is disposed in an area where a recording material having a minimum width dimension to pass the longitudinal position where the paper is to be assured is to pass. do it. Also, the case where the multi-tray 19 is selected as the paper feed port has been described as an example. However, in the case where the recording material having a narrow longitudinal width is arranged in the paper cassette 11 at a position different from the originally recommended regular position. However, by applying the present invention, it is possible to prevent the thermoprotector close to the heating element from operating by being exposed to the temperature of the non-sheet passing portion.

Although the description has been made by taking a thermal fuse as an example of a thermoprotector, the effects and effects of the present invention can be exerted even when a thermoswitch is used as a thermoprotector.

(Second Embodiment) FIGS. 8, 9, 10, and 1
Reference numeral 1 denotes a second embodiment of the present invention.

In the present embodiment, a fixing roller in which a halogen roller is included in a metal roller having a release layer formed on the surface is used as a heating member of the fixing device, and the reference position for passing the recording material is one side of the longitudinal direction. This is a case where the present invention is applied to an image forming apparatus disposed in the image forming apparatus.

FIG. 8 shows the present invention applied to a copying machine using a well-known heating roller type fixing device. In this copying machine, a recording material passing area, a paper presence / absence detection sensor, and a heating element are described. It is a figure showing the positional relationship of a temperature detector and a thermoprotector. In the figure, 190 is a multi-tray,
193 and 194 are guide plates for regulating the lateral position of the recording material. The paper passing reference position of the image forming apparatus according to the present embodiment is a left-side reference when viewed from the downstream side in the transport direction.

Reference numeral B denotes a recording material having a minimum width that the image forming apparatus 102 guarantees paper passing. Reference numeral 270 denotes a paper presence / absence detecting means arranged on the multi-tray, which is arranged at a substantially central position of the minimum width dimension. In the minimum width area, the top sensor 210 and the thermal fuse 770 are arranged near the left side, the sheet ejection sensor 230 is arranged on the right side of the presence / absence detecting means 270, and the thermistor 730 is arranged on the right side.

Reference numeral 710 denotes a fixing roller serving as a heating element. In the present embodiment, a 30 μm thick PT is formed on an aluminum cylinder having a diameter of 30 mm and an inner thickness of 1 mm.
An FE coating is performed, and a halogen lamp is included inside the cylinder as a heat source. A pressure roller (not shown) is pressed against the fixing roller 710 to form a fixing nip. The image formation on the recording material is performed by the well-known electrophotographic process as described above, and after the image is fixed by the fixing device, the image is output onto a discharge tray (not shown).

Also in the present embodiment, the top sensor 210 and the thermistor 73 are different in the longitudinal positional relationship.
The thermoswitch 70, which is a thermoprotector during 0, is disposed in contact with the fixing roller 710.
The operating temperature of the thermoswitch in the present embodiment is 250 ° C. Paper sensor 270 on multi-tray
The paper ejection sensor 230 is arranged in an area where a paper having a minimum width among the paper sizes for which the paper passing is to be guaranteed passes.

Here, if it is attempted to pass a recording material having a width smaller than the paper size for which the paper passage is guaranteed, an image forming apparatus embodying the present invention and an image forming apparatus not embodying the present invention In FIG. 9 and FIG.
This will be described with reference to FIG.

FIG. 9 shows an image forming apparatus 102 according to the present invention.
In contrast, C is a recording material that is narrower than the guaranteed paper passing size.
FIG. 10 is a diagram showing the positional relationship between the paper passing area of the recording material and each sensor when the paper is passed while being shifted to the thermistor 730 side in the longitudinal position. FIG. FIG. 9 is a diagram showing a positional relationship when a sheet is passed while being shifted to the thermoswitch 770 side.

FIG. 11 shows a recording material C in an image forming apparatus 103 which is a comparative example in which a thermo protector 770 is arranged outside the longitudinal direction of the paper detecting means 210 and the temperature detecting means 730.
Is outside the longitudinal arrangement area of the thermo protector 770,
FIG. 9 is a diagram illustrating a positional relationship between a sheet passing area and each sensor when the sheet passes through a longitudinally arranged area of the sheet detecting unit 210 and the temperature detecting unit 730.

First, an inconvenience when a recording material C having a width smaller than the guaranteed paper passing size is passed away from the paper detecting means 210 at the longitudinal position will be described with reference to FIG.

FIG. 9 shows an image forming apparatus 10 according to this embodiment.
2 is a diagram illustrating the positional relationship between the sheet passing position of the recording material C and each sensor when the recording material C having a width smaller than the guaranteed sheet passing size is shifted toward the thermistor 730 in the longitudinal position. It is.

In this case, since the leading end of the recording material is located at the position for operating the paper sensor 270 on the multi-tray, the sheet is fed. However, since the top sensor 210 cannot be operated, it is determined by the DC controller that the feeding is defective. And
Before the recording material enters the fixing device, the operation of the image forming apparatus 102 is stopped, and a paper jam warning is issued on the display unit of the image forming apparatus.

This is a disadvantage that occurs when the recording material is not arranged at the position where the top sensor 210 is operated.

Therefore, in the image forming apparatus 103 of the comparative example shown in FIG. 11, the same phenomenon occurs when the recording material is fed at a position where the top sensor 210 is not operated, and the recording material stays in the apparatus. The image forming apparatus is returned through the operation of removing the material. That is, the degree of inconvenience that occurs when a recording material whose size is outside the guaranteed range is passed through an area where the paper detection unit cannot operate is different between the image forming apparatus according to the present embodiment and the image forming apparatus according to the comparative example. Absent.

Next, the recording material C having a width smaller than the guaranteed paper passing size is set in the range where the top sensor 210 operates in the longitudinal position, and the paper feeding unit sensor 270 and the paper discharging sensor 2
The inconvenience of passing through the range in which both 30s operate will be described with reference to FIGS.

FIG. 10 shows a recording material passing area when the recording material C having a width smaller than the guaranteed paper passing size is moved toward the thermoswitch 770 side in the image forming apparatus 102 according to the present embodiment. And the positional relationship of each sensor. The inconvenience that occurs in this case is that the temperature is controlled based on the temperature of the heating element in a region where the image cannot be printed on the recording material and the recording material does not pass by passing the recording material C whose size is out of the guaranteed range. In addition, the fixing property becomes worse than usual. In this case, although the image writing position is deviated and the fixing property is reduced, the image forming apparatus 102
Does not cause damage such as replacement of parts.

FIG. 11 shows a comparative example of an image forming apparatus in which a thermoswitch 770 is arranged outside the paper detecting means 210 and the temperature detecting means 730 in a longitudinal direction. FIG. 9 illustrates a positional relationship between a recording material passing area and each sensor when the sheet is passed to the detection unit 730 side. In this case, since each paper sensor detects the leading and trailing edges of the recording material, and the temperature is controlled based on the temperature of the heating element in the area where the recording material passes, the fixing property is also good.

However, since the portion of the heating element which is in contact with the thermoswitch 770 is the non-sheet passing area of the recording material, the temperature gradually rises above the temperature regulation temperature when continuous sheet feeding is performed. There is a risk of working. Thermo switch 7
When the image forming apparatus 70 operates, the image forming apparatus 1 is operated as described above.
In the case of No. 03, the state becomes unusable unless at least the fixing device is replaced.

As described above, in the present embodiment,
Even if a recording material whose size is out of the guaranteed range is erroneously passed, it is possible to operate the thermoprotector of the fixing device and eliminate the danger of causing the image forming apparatus to become unusable. .

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIGS.

The present embodiment is directed to an image forming apparatus in which a plurality of temperature detecting means are arranged in the longitudinal direction of the heating element and the recording material feed interval is switched according to the output of the temperature detecting means. This is an example in which is applied.

FIG. 12 is a view showing the arrangement position of each sensor in the image forming apparatus to which the present invention is applied, the paper passing area of the minimum width paper for guaranteeing the paper passing, and the recording material D from the multi-tray to one longitudinal side. FIG. 9 is a diagram illustrating a sheet passing area when the printing is performed.

FIG. 13 shows an image forming apparatus of a comparative example,
FIG. 3 is a diagram illustrating a sheet passing area when the recording material D illustrated in FIG.

FIG. 12 shows a fixing device using a heating element 720 having an electric heating element formed on an aluminum nitride substrate as a heating element, and operating at a temperature of 260 ° C. as a thermoprotector between two temperature detecting means 735 and 737. FIG. 10 is a diagram illustrating the image forming apparatus 104 according to the present embodiment in which the thermoswitch 775 is disposed, and illustrates a positional relationship between the sensors and a paper passing area when the recording material D is moved toward one longitudinal side to pass the paper.

In the figure, a multi-tray 199 is a center reference, and side regulating plates 195 and 196 for recording material are provided.
The paper detection sensor 275 on the multi-tray 199 is arranged near the right side of the center reference. The top sensor 215 is disposed between the center reference and the leftmost minimum regulation width position and near the minimum regulation width position. Paper ejection sensor 2
35 is between the paper passing reference position and the rightmost minimum regulation width position,
It is arranged near the central reference position. That is, these paper sensors are arranged in an area through which a recording material having a minimum width for guaranteeing paper passing passes. Note that the paper passing reference position of the image forming apparatus according to the present embodiment is the longitudinal center.

In this embodiment, the right temperature detecting means 737 is disposed at the longitudinal end of the heating element 720.
The paper feed interval is switched according to the detected temperature. this is,
The feeding interval of B4 portrait, A5 portrait, B5 portrait, postcard, envelope, etc., is set so that the temperature of the non-sheet passing portion of the heating body does not exceed the heat resistant temperature of the member that contacts the heating body, and The aim is to reduce the interval as much as possible. In the present embodiment, the shortest sheet feeding interval is set so that the temperature detected by the temperature detecting means 737 is 260 ° C. or less.

In an image forming apparatus in which the temperature detecting means is not arranged at the end of the heating member, for example, the feeding interval of the B5 vertical size is determined when the feedable B5 size thick paper is continuously passed vertically. Is determined so that the maximum temperature of the non-sheet passing portion is equal to or lower than the heat-resistant temperature of the member in contact with the heating element.
That is, although it is B5 size, it is not an envelope etc.
In general, a recording material having a basis weight of 64 g / m @ 2 can be fed at a shorter interval than the set interval, but is fed at a constant interval. is there.

However, the image forming apparatus 10 of the present embodiment
Reference numeral 4 designates a temperature detecting means disposed at the end of the heating element, and changes the sheet feeding interval according to the output. In other words, if the B5 longitudinal paper is to be fed, the basis weight of 64 g / m 2 paper is sent 14 sheets in 60 seconds, and the envelope is fed at intervals of 10 sheets. 260
It is possible to minimize the paper feeding interval within the range of not more than ° C.

Here, in the image forming apparatus 104 of the present embodiment shown in FIG.
When the recording material D is moved to a position where the recording material D is moved to one side and the three paper sensors are operated in a state where the recording materials D and 95 are opened larger than the recording material size, the detection temperature of the thermistor 737 is 260 ° C. Paper is supplied at the shortest paper supply interval within the range below. At this time, the temperature of the contact portion of the thermoswitch 775 on the heating element is set to the thermistor 73.
Since the position is lower than the temperature of the contact portion 7, the thermoswitch 775 does not operate.

However, in the image forming apparatus 105 of the comparative example in which the thermoswitch 775 is disposed outside the longitudinal direction of the two temperature detecting elements 735 and 737 shown in FIG. When the sheet is passed to the left, the recording material D is fed regardless of the actually occurring temperature of the non-sheet passing portion Z because the edge temperature detection sensor 737 is in the sheet passing area. As a result, there is a danger that the thermoswitch 775 will be operated and the fixing device will be in a state where power cannot be supplied. When the thermoprotector 775 is operated, the image forming apparatus cannot be operated again unless at least the fixing device is replaced as described above.

[0095]

As described above, according to the present invention,
By arranging a thermoprotector between the recording material presence detecting means and the temperature detecting means of the fixing means, even if a recording material of a size that guarantees paper passing passes through any area on the conveyance path, Even when a recording material of a size other than the size that guarantees paper passing is passed, the thermoprotector operates, and as a result, it is possible to prevent the fixing device from becoming unusable.

Further, in an image forming apparatus having a fixing device in which a plurality of temperature detecting means are arranged in the longitudinal direction of the heating element,
Even if a narrow recording material is passed, the thermo protector operates, and as a result, the fixing device can be prevented from falling into an unusable state.

Therefore, according to the present invention, a more reliable image forming apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main configuration of a laser beam printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a main configuration of a fixing device of the image forming apparatus to which the present invention is applied.

FIG. 3 is a diagram illustrating a relationship between a heating element used in the fixing device according to the first embodiment of the present invention and members necessary for controlling the temperature of the heating element.

FIG. 4 is a diagram illustrating a positional relationship among a paper sensor, a temperature detecting element of a heating body, and a thermoprotector according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a case in which a recording material having a minimum width dimension for guaranteeing paper passing is fed in a longitudinal direction away from the thermoprotector in the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a case in which a recording material having a minimum width dimension for guaranteeing paper passing is fed while being shifted in the longitudinal direction on the thermoprotector side in the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a case where a recording material having a minimum width dimension for guaranteeing paper passing is fed while being shifted in a longitudinal direction away from a thermoprotector in an image forming apparatus that is not implemented in the present invention.

FIG. 8 is a diagram illustrating a positional relationship among a paper sensor, a temperature detecting element of a heating body, and a thermoprotector according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating a case in which a recording material having a width smaller than a minimum width dimension for guaranteeing paper feeding is shifted in a longitudinal direction away from the thermoprotector in the second embodiment of the present invention and fed.

FIG. 10 is a diagram illustrating a case in which a recording material having a width smaller than a minimum width dimension for guaranteeing paper passing is fed while being shifted in a longitudinal direction on the thermoprotector side in the second embodiment of the present invention.

FIG. 11 shows a comparative example of the second embodiment. In the image forming apparatus, a recording material having a width smaller than a minimum width dimension for guaranteeing paper feeding is fed while being shifted in a longitudinal direction away from the thermoprotector. FIG.

FIG. 12 is a diagram showing a positional relationship among a paper sensor, a temperature detecting element of a heating body, and a thermoprotector according to a third embodiment of the present invention.

FIG. 13 is a view showing a comparative example for explaining the effect of the third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic photosensitive drum 2 Charging member 4 Developing device 7 Heater unit 8 Pressure roller 11 Paper cassette 19, 190 Multi tray 21, 210, 215 Top sensor 23, 230, 235 Discharge sensor 27 Paper sensor 71, 710, 720 Heating element 73, 730, 735 Thermistor 77 Thermal fuse (thermo protector) 770, 775 Thermoswitch 90 DC controller 100 Image forming apparatus 101 applied to the first embodiment 101 Image forming apparatus serving as a comparative example of the first embodiment 102 Second Image forming apparatus according to the embodiment 103 Image forming apparatus as a comparative example of the second embodiment 104 Image forming apparatus according to the third embodiment 105 Image forming apparatus as a comparative example of the third embodiment

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[Procedure amendment]

[Submission date] April 2, 2001 (2001.4.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

2) Since the recording material does not pass through the thermistor position, the temperature of the recording material passage cannot be properly controlled.
Fixing failure occurs.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05B 3/00 335 H05B 3/00 335 F term (Reference) 2H033 AA42 BA31 BA32 BA38 BE03 CA04 CA22 CA45 3K058 AA62 BA18 CA23 CA92 CE13 CE19 CE23 CE29 DA05 GA06

Claims (5)

[Claims] A means for forming a toner image on an image carrier and transferring the toner image onto a recording material at a transfer position; a fixing means for fixing the toner image on the recording material onto the recording material; At least one recording material presence / absence detection unit for detecting the presence / absence of a recording material disposed in a paper feed path to the fixing unit;
At least one or more temperature detecting means for detecting a temperature of a heating element provided in the fixing means; and at least one or more temperature detecting means provided in the fixing means for interrupting energization to the fixing means at a predetermined or higher detected temperature. An image forming apparatus having a thermoprotector, wherein the thermoprotector is disposed between the at least one recording material presence / absence detecting means and the temperature detecting means in a longitudinal direction orthogonal to a recording material conveyance direction. Characteristic image forming apparatus. 2. The recording material presence / absence detecting means is disposed in an area through which a recording material having a minimum longitudinal width that guarantees paper passing passes in a longitudinal direction orthogonal to a conveyance direction of the paper feeding conveyance path. The image forming apparatus according to claim 1, wherein: 3. The fixing means includes a heater having an electric heating element formed on an insulating substrate as a heating element, the heater being fixedly supported;
A cylindrical film having flexibility is arranged in a form including the heat generating portion of the heating element, and a fixing nip is formed by pressing a heater and a pressing member through the cylindrical film.
The image forming apparatus according to claim 1, wherein the toner image is fixed on the recording material by passing the recording material through the fixing nip portion. 4. A temperature sensor is disposed in a longitudinal direction of the heating element, and a thermostat is provided between the two temperature detecting means in a longitudinal positional relationship between the two temperature detecting means and the thermoprotector. The image forming apparatus according to claim 1, wherein a protector is located. 5. A central reference system for forming an image on a recording material conveyed with a paper passing position as a central reference, wherein said at least one recording material presence / absence detecting means and said protector also employ a protector based on said paper passing position reference. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged on one side, and the one temperature detecting unit is arranged on the other side of the sheet passing position reference.