JP5182171B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device.

  2. Description of the Related Art Conventionally, a fixing device that thermally fixes a toner image printed on a sheet and a pair of conveying rollers that are arranged on the downstream side of the fixing device in the sheet conveying direction and convey the sheet that has come out of the fixing apparatus to the downstream side are provided. An image forming apparatus is known (see Patent Document 1). Specifically, in this technique, the pair of transport rollers is composed of a metal roller and a rubber roller.

JP-A-5-162916

  By the way, in the case where the metal roller is provided on the downstream side of the fixing device as in the prior art described above, the inventor of the present application absorbs the heat of the paper heated by the fixing device by the metal roller. It has been found that the amount of cylinder curl (curl centered on the axis along the paper conveyance direction) is small. That is, it has been discovered that even when the paper is curled due to heating in the fixing device, the amount (degree) of the curl is reduced by absorbing the heat of the paper by the metal roller.

  However, if the heated paper passes through the metal roller many times, the metal roller accumulates heat, making it difficult for the heat of the paper to be absorbed by the metal roller, making it impossible to reduce the amount of cylinder curl. That is expected.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing the amount of cylinder curl of a sheet (recording sheet).

The present invention that solves the above-described problems includes a fixing device that thermally fixes a recording sheet by a heating member, and a material that is in contact with the recording sheet after passing through the fixing device and has high thermal conductivity. An image forming apparatus comprising a high thermal conductivity member, a temperature estimation unit for estimating a temperature of the high thermal conductivity member, and a temperature estimated by the temperature estimation unit when the temperature estimated by the temperature estimation unit is equal to or higher than a predetermined value. Control means for lowering the temperature, and the high thermal conductivity member constitutes a part of one of the pair of transport rollers arranged immediately after the fixing device, and the one of the transport rollers Among them, the recording sheet is provided at portions corresponding to both ends in the width direction of the recording sheet .

  According to the present invention, until the temperature of the high thermal conductivity member reaches a predetermined value, the recording sheet heated by the heating member and curled in the cylinder is heated when passing through the high thermal conductivity member. By being robbed by the sex member, the amount of the cylindrical curl becomes small. And when the temperature of a highly heat conductive member becomes more than predetermined value, the temperature of a heating member is lowered | hung by a control means.

  This reduces the amount of cylinder curl of the recording sheet that is heated by the relatively low temperature heating member, so that even after the heat of the recording sheet is not taken away by the high thermal conductivity member, after passing through the high thermal conductivity member The amount of cylinder curl of the recording sheet can be reduced.

  On the other hand, when the temperature of the heating member is lowered, the heat fixing by the heating member becomes incomplete, but the second heat fixing can be performed by the high thermal conductive member stored to a temperature equal to or higher than a predetermined value. Also, heat fixing can be performed well. Furthermore, in order to lower the temperature of the heating member, it is only necessary to reduce the amount of electricity flowing to the heating member (heat source). Therefore, it is possible to save energy by suppressing power consumption.

  According to the present invention, when the temperature of the high thermal conductivity member reaches a predetermined value or more, the temperature of the heating member is lowered by the control means, so that the amount of cylinder curl of the recording sheet can be reduced.

1 is a cross-sectional view illustrating an overall configuration of a laser printer as an example of an image forming apparatus according to the present invention. It is explanatory drawing which shows a pair of conveyance roller. It is explanatory drawing which shows the map memorize | stored in the memory | storage device of the control apparatus. It is a flowchart which shows the content of the program which the control apparatus which concerns on other embodiment follows. (A)-(c) is explanatory drawing which shows the modification of arrangement | positioning of a highly heat conductive member.

<Overall configuration of laser printer>
Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, a laser printer 1 as an example of an image forming apparatus includes a feeder unit 4 for feeding a sheet 3 as an example of a recording sheet in an apparatus main body 2, and a fed sheet 3. An image forming unit 5 for forming an image is provided.

  The feeder unit 4 mainly includes a paper feed tray 6 that is detachably attached to the bottom of the apparatus main body 2 and a paper supply mechanism 7 that transports the paper 3 from the paper feed tray 6 to the image forming unit 5. In the feeder unit 4, the sheets 3 in the sheet feeding tray 6 are separated one by one by the sheet supply mechanism 7 and supplied to the image forming unit 5.

  The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a fixing device 18, and the like.

  The scanner unit 16 is provided in the upper part of the apparatus main body 2 and includes a laser light emitting unit (not shown), a polygon mirror 19 that is rotationally driven, lenses 20, 21 and reflecting mirrors 22, 23, 24, and the like. . In the scanner unit 16, the laser beam is irradiated on the surface of the photosensitive drum 27 of the process cartridge 17 by high-speed scanning through a path indicated by a chain line in the drawing.

  The process cartridge 17 is disposed below the scanner unit 16 and is configured to be detachably attached to the apparatus main body 2. The process cartridge 17 includes a known photosensitive drum 27, a charger 29, a transfer roller 30, a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, a toner hopper 34, and the like.

  In the process cartridge 17, the surface of the photosensitive drum 27 charged by the charger 29 is exposed with a laser beam from the scanner unit 16, whereby an electrostatic latent image is formed on the photosensitive drum 27. A toner image (developer image) is formed on the photosensitive drum 27 by supplying toner in the toner hopper 34 to the electrostatic latent image via the supply roller 33 and the developing roller 31. Thereafter, when the sheet 3 is conveyed between the photosensitive drum 27 and the transfer roller 30, the toner image on the photosensitive drum 27 is transferred to the sheet 3.

<Configuration of fixing device>
The fixing device 18 includes a halogen heater HH, a heating roller 41 as an example of a heating member, and a pressure roller 42.

  The halogen heater HH is disposed in the cylindrical heating roller 41 and heats the heating roller 41 from the inside. The halogen heater HH is appropriately controlled by a control device 100 as control means described in detail later.

  The heating roller 41 is a metal member formed in a substantially cylindrical shape, and is rotatably supported by the apparatus main body 2. The heating roller 41 is rotated by receiving a driving force from a driving device (not shown) driven by a control signal from the control device 100. As the heating roller 41, for example, a PTFE-coated surface of an aluminum cylindrical member can be used.

  The pressure roller 42 is pressed against the heating roller 41 by a spring (not shown), and comes into contact with the rotating heating roller 41 to rotate. As the pressure roller 42, for example, a silicon rubber provided around the core metal and the surface of the silicon rubber covered with a PTFE tube can be used.

  Then, behind the fixing device 18 (immediately after), a pair of conveying rollers 43 that are in contact with the sheet 3 after passing through the fixing device 18 are arranged so as to be arranged substantially vertically. Of the pair of transport rollers 43, the upper (one) transport roller 43 is configured as a metal roller 43A (illustrated by oblique hatching), and the lower (other) transport roller 43 is elastically deformed such as rubber or sponge. It is configured as an elastic roller 43B formed of a possible material.

  The metal roller 43A is formed of a metal as an example of a high thermal conductivity member that includes a material having high thermal conductivity as a whole, and is on the same side (upper side) as the heating roller 41 described above with respect to the paper 3. ). Here, the “high thermal conductivity member” means a member having a thermal conductivity of 10 W / mK or more, preferably 15 W / mK or more. Specifically, as the high thermal conductivity member, a carbon nanotube or the like can be employed in addition to a metal such as aluminum.

  As shown in FIG. 2, the metal roller 43 </ b> A is continuously formed with a width equal to or larger than the width of the maximum width paper 3 among the plurality of types of paper 3 that can be printed by the laser printer 1. Further, the metal roller 43A is formed in an inverted crown shape in which the diameter is smoothly reduced from both ends toward the center so that the center in the width direction (axial direction) is recessed.

  Similar to the metal roller 43A, the elastic roller 43B is continuously formed with a width equal to or greater than the width of the maximum width paper 3 among a plurality of types of paper 3 that can be printed by the laser printer 1.

  As shown in FIG. 1, a temperature sensor 50 as an example of a temperature estimation unit is provided around (above) the metal roller 43A. The temperature sensor 50 is a sensor that detects the temperature of the metal roller 43A, and is disposed to face the metal roller 43A. The temperature detected by the temperature sensor 50 is output to the control device 100.

  In the structure around the fixing device 18 configured as described above, the heating roller 41 is heated by the halogen heater HH, so that the sheet 3 passes between the heating roller 41 and the pressure roller 42. The toner image transferred to the paper 3 is thermally fixed. Thereafter, the sheet 3 is transported to the paper discharge path 44 by the transport roller 43. The paper 3 sent to the paper discharge path 44 is discharged onto a paper discharge tray 46 by a paper discharge roller 45.

<Control device>
Next, the control device 100 will be described.
The control device 100 has known hardware such as a CPU, ROM, RAM, and communication device, and mainly controls the temperature of the heating roller 41 by controlling the halogen heater HH based on the temperature detected by the temperature sensor 50. Is controlling.

  Specifically, a map as shown in FIG. 3 is stored in the storage device (ROM or the like) of the control device 100. Here, in the map of FIG. 3, “Te” indicates the temperature of the metal roller 43A detected by the temperature sensor 50, and “Th” indicates the target temperature of the heating roller 41 (or halogen heater HH). That is, when the temperature Te detected by the temperature sensor 50 is lower than a predetermined value (in this embodiment, “80 ° C.”), the control device 100 that executes control according to this map sets the target temperature Th of the heating roller 41 to the initial value. The value is “α ° C.”. In addition, when the temperature Te detected by the temperature sensor 50 becomes equal to or higher than a predetermined value, the control device 100 decreases the target temperature Th of the heating roller 41 from “α ° C.” to “α-5 ° C.”.

  Here, a predetermined value (“80 ° C.” in the present embodiment) to be compared with the temperature Te detected by the temperature sensor 50 and a temperature decrease range of the heating roller 41 (5 ° C. in the present embodiment) are experimental, simulation, etc. Can be set arbitrarily.

Next, the operation of the heating roller 41 and the metal roller 43A that are appropriately controlled by the control device 100 will be described.
As shown in FIG. 1, when printing on the paper 3, until the temperature of the metal roller 43A reaches a predetermined value (80 ° C.), the paper 3 heated by the heating roller 41 of “α ° C.” Curl a little larger. The sheet 3 having a large amount of cylinder curl is reduced in heat by the metal roller 43A when passing through the metal roller 43A, so that the amount of cylinder curl becomes small.

  When such printing is continuously performed for a relatively short time, the temperature of the metal roller 43A that has taken heat from the plurality of sheets 3 becomes equal to or higher than a predetermined value (80 ° C.). The controller 100 lowers the temperature of the heating roller 41 by 5 ° C.

  As a result, the amount of cylinder curl of the paper 3 heated by the “α-5 ° C.” heating roller 41 becomes smaller than when heated at “α ° C.”. Therefore, the amount of cylinder curl of the paper 3 after passing through the metal roller 43A can be reduced even if the heat of the paper 3 is not taken so much by the stored metal roller 43A.

  On the other hand, when the temperature of the heating roller 41 is lowered, the heat fixing by the heating roller 41 becomes incomplete, but the second heat fixing is performed by the metal roller 43A that has accumulated heat to a temperature equal to or higher than a predetermined value (80 ° C.). Therefore, heat fixing can be performed well. Further, in order to lower the temperature of the heating roller 41, the amount of electricity flowing to the heating roller 41 (halogen heater HH) may be reduced, so that it is possible to save energy by reducing power consumption.

According to the above, in addition to the effects described above, the following effects can be obtained in the present embodiment.
Since the temperature sensor 50 is employed as the temperature estimating means for estimating the temperature of the metal roller 43A, the temperature of the metal roller 43A can be estimated with high accuracy, and highly accurate control can be performed.

  Since the metal roller 43A is arranged immediately after the fixing device 18, a large amount of heat can be taken away from the high-temperature paper 3 immediately after coming out of the fixing device 18 by the metal roller 43A, and the temperature of the heating roller 41 is lowered more quickly. Power consumption can be further reduced.

  Since the metal roller 43A is disposed on the same side as the heating roller 41 with respect to the paper 3, the toner image printed on one surface of the paper 3 is heated and fixed satisfactorily by the two rollers 41 and 43A. Can do.

  Since the metal roller 43A is continuously formed with a width equal to or larger than the width of the paper 3, the metal roller 43A can easily receive heat from the paper 3, so that the temperature of the heating roller 41 can be lowered earlier to further reduce the power consumption. Can be suppressed.

  Since the metal roller 43 </ b> A has an inverted crown shape, it is possible to suppress wrinkles on the paper 3.

  Since the transport roller 43 facing the metal roller 43A is an elastic roller 43B configured to be elastically deformable with a width equal to or larger than the width of the paper 3, the paper 3 can be transported favorably with the metal roller 43A. . Further, since heat is difficult to be transmitted to the elastic roller 43B formed of, for example, rubber or sponge, the heat can be efficiently transmitted to the metal roller 43A.

  Since the entire metal roller 43A is made of metal, the entire metal roller 43A can take heat away from the paper 3, so that the temperature of the heating roller 41 can be lowered earlier to further reduce power consumption.

In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below.
In the above embodiment, the temperature sensor 50 is employed as the temperature estimating means. However, the present invention is not limited to this, and a program stored in a storage device such as a ROM of the control device may be employed. Specifically, as this program, for example, as shown in FIG. 4, a program for obtaining information on the number of printed sheets from a print job and estimating the temperature of the metal roller based on this information can be employed. In the following description, the initial value of the target temperature Th of the heating roller is described as “α ° C.” as in the above embodiment.

  When a control device that executes control according to the program shown in FIG. 4 receives a print job (START), it first obtains information on the number of prints from the print job, and the number of continuous prints is 10 or more based on this information. It is determined whether or not (S1). When a plurality of print jobs are received at the time of step S1, the control device sets the total number of print jobs of each print job as the continuous print number.

  If the number of continuously printed sheets is less than 10 in step S1 (No), the control device ends this control (END). If the number of continuous prints is 10 or more in step S1 (Yes), the control device determines whether printing for 10 of the continuous prints has been completed (S2).

  When printing for 10 sheets is completed in step S2 (Yes), the control device lowers the target temperature Th of the heating roller from the initial value “α ° C.” to “α-5 ° C.” (S3). After step S3, the control device determines whether or not the print job (JOB) is completed, that is, for example, if the continuous print number is 15, the remaining 5 prints are completed (S4). ).

  When the print job is completed in step S4 (Yes), the control device determines whether or not one minute or more has elapsed since the previous print stop, and the temperature of the metal roller has dropped below a predetermined value. It is determined whether or not (S5). Here, “previous printing” refers to the printing completed in step S4, and if the control device receives a new printing job before the completion of steps S1 to S5, the new printing job. The printing performed by is also included. Therefore, for example, if the control device receives a new print job while waiting for 1 minute in step 5, the control device resets the counted time, and after printing based on the new print job is completed. Redo the 1 minute count.

  If it is determined in step S5 that one minute or more has elapsed since the previous printing stop (Yes), the control device determines that the temperature of the metal roller has become less than a predetermined value, and sets the target temperature of the heating roller 41 to the initial value. The value is returned to “α ° C.” and this control is finished (END).

  As described above, when the temperature of the metal roller is estimated from the print job, it is not necessary to provide the temperature sensor as in the above-described embodiment, so that the cost can be reduced. Each numerical value (“10 sheets”, “α-5 ° C.”, “1 min (min)”, etc.) in the flowchart of FIG. 4 can be arbitrarily set by experiment, simulation, or the like.

  In the above embodiment, the entire transport roller 43 (metal roller 43A) is made of metal. However, the present invention is not limited to this, and for example, as shown in FIG. 5A, a part of one transport roller 43C. Only a high thermal conductivity member HT such as a metal may be used. Further, as shown in FIG. 5B, only two portions corresponding to both ends in the width direction of the sheet 3 (the maximum width sheet 3 among the plural types of printable sheets 3) of the one transport roller 43D. Two high thermal conductivity members HT may be provided so as to be spaced from each other. In this case, since the heat at both end portions of the paper 3 is positively absorbed by the high thermal conductivity member HT, the cylindrical curl of the paper 3 can be corrected satisfactorily.

  Further, as shown in FIG. 5C, a plurality of high thermal conductivity members are provided only at portions corresponding to both ends in the width direction of each of the plurality of types (two types in the drawing) of the papers 3 and 3A in the one transport roller 43E. HT may be provided so as to be spaced apart from each other. In this case, it is possible to satisfactorily correct the cylinder curl of each type of paper 3 and 3A.

In the above-described embodiment, the conveyance roller 43 is employed as the high thermal conductivity member. However, the present invention is not limited to this, and any member may be used as long as it is a member that contacts the recording sheet after passing through the fixing device. For example, a member that guides the paper may be a high thermal conductivity member.
In the above-described embodiment, the heating roller 41 is employed as the heating member. However, the present invention is not limited to this. For example, a cylindrical fixing film that is slidably supported by a guide may be used.

In the above embodiment, the present invention is applied to the laser printer 1. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.
In the embodiment, the paper 3 such as a thick paper, a postcard, and a thin paper is used as an example of the recording sheet. However, the present invention is not limited to this, and may be an OHP sheet, for example.

DESCRIPTION OF SYMBOLS 1 Laser printer 3 Paper 18 Fixing apparatus 41 Heating roller 43 Conveyance roller 43A Metal roller 43B Elastic roller 50 Temperature sensor 100 Control apparatus

Claims (8)

A fixing device for thermally fixing the recording sheet by a heating member;
An image forming apparatus comprising a high thermal conductivity member that is in contact with the recording sheet after passing through the fixing device and includes a material having high thermal conductivity,
Temperature estimation means for estimating the temperature of the high thermal conductivity member;
Control means for lowering the temperature of the heating member when the temperature estimated by the temperature estimation means becomes a predetermined value or more ,
The high thermal conductivity member is
Constituting a part of one of the pair of transport rollers disposed immediately after the fixing device;
An image forming apparatus, wherein the image forming apparatus is provided at portions corresponding to both ends of the recording sheet in the width direction of the one conveying roller . The temperature estimating means includes
The image forming apparatus according to claim 1, wherein the image forming apparatus is a temperature sensor provided to face the high thermal conductivity member. The temperature estimating means includes
2. The image forming apparatus according to claim 1, wherein information on the number of printed sheets of the print job is obtained, and the temperature of the high thermal conductivity member is estimated based on the information. The image forming apparatus according to claim 1, wherein the one conveying roller is disposed on the same side as the heating member with respect to the recording sheet. The image forming apparatus according to claim 1 , wherein the high thermal conductivity member is a metal. Wherein the one transport roller and the high heat conductivity member of the image according to any one of claims 1 to 5, characterized in that it is formed continuously in width than the width of the recording sheet Forming equipment. The image forming apparatus according to claim 6 , wherein the one conveyance roller has an inverted crown shape. The other transport roller opposed to the conveying roller of the one is, the image forming apparatus according to claim 6 or claim 7, characterized in that it is elastically deformable construction in width than the width of the recording sheet.

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