JP2011180312A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which suppresses thermal deformation of transfer paper and damage of a sensor or the like by absorbing heat of the transfer paper heated by a fixing device, preliminarily heats the transfer paper not subjected to fixing yet to improve fixing ability by radiating the absorbed heat to the transfer paper not subjected to fixing yet on a upstream side from the fixing device, and also, can contribute to energy saving by lowering fixing temperature, and besides, can contribute to uniformization and stabilization of image quality such as the fixing ability on the transfer paper and glossiness. <P>SOLUTION: The image forming apparatus includes: a preliminary heating part 71 which absorbs the heat of the transfer paper having subjected to fixing on a downstream side in a conveying direction from a fixing part 24 that fixes the toner image on the transfer paper by heating and pressing the transfer paper not subjected to fixing yet on which a toner image has been formed, and preliminarily heats the transfer paper not subjected to fixing yet on the upstream side from the fixing part 24; and a temperature control part which lowers heating temperature of the fixing part 24 in accordance with rise of heat absorption temperature of the preliminary heating part 71. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine equipped with these functions, and in particular, transfers a toner image by heating and pressurizing a transfer sheet before fixing on which a toner image is formed. The present invention relates to an image forming apparatus including a fixing device for fixing to paper.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine equipped with these functionally, a transfer to which a toner image is transferred in order to fix the toner image transferred to a transfer sheet. The transfer paper is fixed by heating and pressurizing the paper with a fixing device.

  Also, during this fixing process, the transfer paper onto which the toner image has been transferred is heated at a high temperature. This heating causes the transfer paper after the fixing process to be thermally deformed, and various sensors arranged in the transfer paper transport path. May cause problems such as thermal damage or toner fusion between transfer sheets on the discharge tray.

  Therefore, a heat exchanging device including a cooling unit that absorbs heat from the transfer paper heated by the fixing device, a transmission unit that transmits the heat, and a heat dissipation unit that dissipates the transmitted heat to the transfer paper before fixing processing. The transfer paper heated by the fixing device is cooled, the thermal deformation of the transfer paper after the fixing process, the thermal damage of various sensors arranged in the transfer paper transport path, the transfer on the discharge tray A technique for preventing toner fusion between papers is known (see, for example, Patent Document 1).

JP 2000-122467 A

  However, as described above, when such a heat exchanging means is arranged, the temperature of the preheating unit rises according to the number of fixed sheets of transfer paper that has been heat-fixed by the fixing device, and as a result, the transfer before the fixing process is performed. Since the amount of heat supplied to the paper increases gradually, if fixing is continued at the same fixing temperature in the fixing device, the glossiness of the image increases with the number of sheets passing through due to the difference in the toner fixing state. In this case, there is a possibility that a problem such as hot offset occurs if the amount of heat is excessively supplied.

  Therefore, the present invention suppresses thermal deformation of the transfer paper and damage to the sensors by absorbing the heat of the transfer paper heated by the fixing device, and the heat absorbed before the fixing on the upstream side of the fixing device. By heat dissipation to the transfer paper, the pre-fixing transfer paper can be preheated to improve the fixability, and at the same time, the fixing temperature can be lowered to contribute to energy savings. An object of the present invention is to provide an image forming apparatus that can contribute to uniform and stable image quality.

  An image forming apparatus according to the present invention includes an image forming apparatus including a fixing device that fixes a toner image onto a transfer sheet by heating and pressurizing the transfer sheet before fixing on which the toner image is formed. A preheating unit that absorbs heat of the transfer paper after fixing on the downstream side in the direction and preheats the transfer paper before fixing on the upstream side of the fixing device, and the fixing according to an increase in the endothermic temperature of the preheating unit. And a temperature controller that lowers the heating temperature of the apparatus.

  According to such a configuration, the heat of the transfer paper heated by the fixing device is used to preheat the transfer paper before fixing, and the heating temperature of the transfer device is lowered according to the preheating temperature of the transfer paper. Therefore, by absorbing the heat of the transfer paper heated by the fixing device, thermal deformation of the transfer paper and damage prevention of the sensors are suppressed, and the absorbed heat is upstream of the fixing device before fixing. By preliminarily heating the transfer paper prior to fixing by radiating heat to the transfer paper, it is possible to contribute to energy saving by lowering the fixing temperature, and also image such as fixability to the transfer paper and glossiness. Contributes to uniform and stable quality.

  The image forming apparatus according to claim 2, wherein the preheating unit absorbs the heat of the transfer paper after fixing, and transfers the heat absorbed by the heat absorption unit to the downstream side of the fixing device. A heat transfer section, and a heat dissipation section that dissipates the heat transferred by the heat transfer section to the transfer paper before fixing, and the temperature control section includes the heat absorption section, the heat transfer section, and the heat dissipation section. A temperature sensor for monitoring the current temperature at least at one location is provided.

  According to the configuration of the second aspect, the amount of heat radiation for each transfer paper in real time can be determined by monitoring the temperature sensor at a fixed location, and the fixing property and glossiness can be easily uniformized and stabilized. Can be secured.

  The image forming apparatus according to claim 3, wherein the heat dissipating unit uses at least one of a registration roller pair, a pre-fixing guide, and a metal conveyance chute disposed upstream of the fixing device. Features.

  The image forming apparatus according to a fourth aspect is characterized in that the heat absorbing portion uses a pair of conveying rollers disposed downstream of the fixing device.

  According to the structure of Claim 3 and Claim 4, the existing component can be utilized as a heat absorption part or a heat radiation part as it is, and it can contribute to reduction of a number of parts, but also a narrow in-machine space. Can contribute to the effective use of.

  The image forming apparatus according to claim 5 is characterized in that a heat pipe is disposed in at least one of the heat absorbing portion and the heat radiating portion.

  According to the structure of Claim 5, the effective use of the temperature at the time of heat absorption or heat dissipation can be aimed at by using a heat pipe.

  The image forming apparatus according to claim 6, wherein a transfer device that transfers a toner image onto transfer paper is disposed upstream of the fixing device, and the heat radiating portions are disposed on the upstream side and the downstream side of the transfer device, respectively. It is characterized by.

  According to the configuration of the sixth aspect, since an unfixed toner image is not carried on the transfer paper on the upstream side of the transfer device, it is possible to dissipate heat within a range in which the toner after transfer does not aggregate. The preheating can be efficiently performed without being restricted by the configuration of the heat radiating unit, and an unfixed toner image is carried on the transfer paper downstream of the transfer device and upstream of the fixing device. It is possible to preheat the transfer paper before fixing and before and after the transfer step by step so as to constitute a supplementary heat radiating part that compensates for the temperature of the transfer paper absorbed by the heat, thereby improving versatility. it can.

  The image forming apparatus according to claim 7, wherein the temperature control unit includes a switching unit that blocks heat transfer from the heat transfer unit to the heat radiating unit when a monitored temperature of the temperature sensor becomes equal to or higher than a predetermined temperature. It is characterized by having.

  According to the seventh aspect of the present invention, excessive preheating can be prevented by the print switching unit during a large amount of continuous printing or the like, and toner aggregation after transfer can be prevented.

  The image forming apparatus of the present invention absorbs heat of the transfer paper heated by the fixing device to suppress thermal deformation of the transfer paper and damage to the sensors, and the absorbed heat is more upstream than the fixing device. Dissipating heat to the transfer paper before fixing improves the fixability by preheating the transfer paper before fixing, and at the same time can contribute to energy savings by lowering the fixing temperature. This can contribute to uniform and stable image quality.

1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing of the other image forming apparatus which concerns on one Embodiment of this invention. 1 illustrates an image forming apparatus according to Embodiment 1 of the present invention, in which (A) is a side view of an essential part, and (B) is a plan view of the essential part. It is a chart of the example of fixing temperature control correction value in Example 1 of the present invention. FIG. 2 illustrates an image forming apparatus according to Embodiment 2 of the present invention, in which (A) is a side view of the main part and (B) is a plan view of the main part. It is a chart of the example of fixing temperature control correction value in Example 2 of the present invention. FIG. 3 shows an image forming apparatus according to Embodiment 3 of the present invention, in which (A) is a side view of the main part, and (B) is a plan view of the main part. It is a chart of the example of fixing temperature control correction value in Example 3 of the present invention. FIG. 4 shows an image forming apparatus according to Embodiment 4 of the present invention, in which (A) is a side view of the main part and (B) is a plan view of the main part. It is a chart of the example of fixing temperature control correction value in Example 4 of the present invention.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. The following embodiments are preferred specific examples of the image forming apparatus of the present invention, and may have various technically preferred limitations. However, the technical scope of the present invention is particularly limited to the present invention. As long as there is no description which limits, it is not limited to these aspects.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention.

(Overall configuration of MFP)
In FIG. 1, a multifunction machine 11 as an image forming apparatus according to an embodiment of the present invention includes a multifunction machine main body 12 and a plurality of stages of paper feed cassettes 13, 14, 15 that can be pulled out from the front surface of the multifunction machine main body 12. In order to enable the use of transfer paper different from the paper feed cassettes 13, 14, and 15, a manual feed tray 16 provided on one side surface of the multifunction machine main body 12 so as to be openable and closable, and a copying machine, a facsimile machine, and a scanner. As the various functions, an automatic document feeder (ADF) 17 used for reading a document and a display unit 18 and an operation unit 19 for setting and selecting various functions and the like are provided. Note that the shape, configuration, function, and the like of the multifunction machine 11 are not limited to those illustrated.

(Internal configuration of MFP main body 12)
Further, inside the multifunction machine main body 12, transfer paper (not shown) stored in a paper feed cassette 13, 14, 15 or manual feed tray 16 serving as storage means is taken out and conveyed toward a paper discharge tray 20. A conveying path 21, a registration roller pair 22 disposed on the upstream side in the sheet conveying direction of the conveying path 21, an image forming unit 23 disposed on the downstream side in the sheet conveying direction of the conveying path 21 relative to the registration roller pair 22, A fixing unit (fixing device) 14 for fixing the toner image transferred to the surface of the transfer paper by the image forming unit 23 and the most downstream portion in the MFP main body 12 of the transport path 21 is disposed. And a discharge unit 25.

Further, a plurality of paths are branched and merged in the conveyance path 21. In the present embodiment, a branch path 26 disposed on the downstream side of the conveyance path 21 in the sheet conveyance direction from the fixing unit 24, and a branch path A switchback path 27 that reverses the transfer paper led to 26, and a reversal path 28 that returns the transfer paper reversed by the switchback path 27 to the transport path 21 upstream of the registration roller pair 22 in the sheet transport direction. And a reverse discharge path 29 that guides the discharge surface of the transfer paper after the single-sided printing process to the discharge unit 25 in a state in which the originals are set in order when there are a plurality of originals set on the ADF 17.
(Configuration of registration roller pair 22)

  The registration roller pair 22 detects the leading edge of the transfer paper taken out from the paper feed cassettes 13, 14, 15 or the manual feed tray 16 with the registration sensor 30, thereby detecting the leading edge position of the transfer paper and the photosensitive drum 31. It synchronizes with the position of the toner image formed on the surface.

Specifically, after a predetermined time has elapsed since the registration sensor 30 detected the leading edge of the transfer paper, the rotational driving of the registration roller pair 22 and the photosensitive drum 31 is started, and the registration sensor 30 detects the trailing edge of the transfer paper. After a predetermined time has elapsed, the rotation of the registration roller pair 22 and the photosensitive drum 31 is stopped. The registration sensor 30 detects the sheet length along the sheet conveyance direction of the transfer paper fed from the paper feed cassettes 13, 14, 15 to the conveyance path 21, and after detecting the leading edge of the transfer paper, The length of the transfer paper (direction along the sheet conveyance direction) is detected based on the time until the end is detected.
The registration roller pair 22 is connected to a drive source (not shown) such as a motor. Then, in a stationary state, the registration roller pair 22 corrects the oblique feeding of the transfer paper by instantaneously stopping the transfer paper when the leading edge of the transfer paper is nipped.

(Configuration of image forming unit 23)
The image forming unit 23 includes a photosensitive drum 31, and a charging device 32, an exposure device 33, a developing device 34, a transfer roller 35, a cleaning device 36, a static eliminating device 37, and the like disposed around the photosensitive drum 31. .

  Thus, in the image forming unit 23, the photosensitive drum 31 is rotationally driven by a driving unit (not shown) at a predetermined process speed (circumferential speed), and the surface thereof is uniformly charged to a predetermined polarity and potential by the charging device 32. .

An electrostatic latent image is formed on the surface of the charged photosensitive drum 31 by the exposure device 33. Here, for example, the exposure device 33 is connected via a communication line such as a print data read by the scanner unit using the ADF 17 by a copying machine function, a print data received through a telephone line by a facsimile function, or a network by a printer function. Based on the print data output from a personal computer or the like, the surface of the photosensitive drum 31 is irradiated with laser light, and the charge on the laser light irradiated portion of the surface of the photosensitive drum 31 is removed, and electrostatic in accordance with image information. A latent image is formed.
The electrostatic latent image formed on the surface of the photosensitive drum 31 is developed as an untransferred toner image by electrostatically attaching a charged toner to the developing device 34. Further, the untransferred toner image is transferred as an unfixed toner image onto the surface of the transfer paper by the cooperation of the photosensitive drum 31 and the transfer roller 35.

  At this time, the photosensitive drum 31 on which the untransferred toner image is transferred onto the surface of the transfer paper is removed by the cleaning device 36 and the charge is removed by the charge removal device 37 for charging at the next image formation. .

(Configuration of the fixing unit 24)
The fixing unit 24 heats as a heating member disposed on the surface side of the transfer paper, that is, on the unfixed toner image side, in order to fix the unfixed toner image transferred to the surface of the transfer paper by the image forming unit 23. A roller (or heating belt) 28 and a pressure roller 39 as a pressure member facing the heating roller 38 across the conveyance path 21 are provided, and the pressure roller 39 is brought into pressure contact with the heating roller 38 to transfer paper. Is conveyed in a nip (nip portion).

  The unfixed toner image formed on the surface of the transfer paper is melted by directly contacting the heating roller 38, and is melted on the surface of the transfer paper as it is by being pressed by the pressure roller 39 from the back surface side of the transfer paper. The toner is transported to the next transport roller pair 40 while being fixed as a fixed image.

(Other image forming devices)
Incidentally, the image forming apparatus of the present invention can be applied to, for example, a color printer 41 as a full-color image forming apparatus as shown in FIG.

(Overall configuration of the color printer 41)
In FIG. 2, a color printer 41 as an image forming apparatus according to an embodiment of the present invention has a paper feed cassette 43 that can be pulled out from one surface (for example, the front surface) of the printer main body 42, and an upside down on one surface of the printer main body 42. A manual feed tray 44 that can be provided, a transport path 45 that transports transfer paper (not shown) set in the paper feed cassette 43 or the manual feed tray 44, and a paper feed that forms the upstream end of the transport path 45 The unit unit 46, the registration roller pair 22 disposed downstream of the sheet feeding unit unit 46 in the conveyance path 45, and the second disposed in the sheet conveyance direction downstream side of the conveyance path 45 from the registration roller pair 22. An endless belt-like intermediate transfer belt 47 that forms a toner transfer image on the surface of the transfer paper in cooperation with the secondary transfer roller 35 and the secondary transfer roller 35, and the intermediate transfer belt 47 A plurality of image forming units 48 (each color symbol shown in FIG. 2) that transfers toners of various colors (for example, yellow (Y), magenta (M), cyan (C), and black (K)) as necessary on the surface. ), A fixing unit 24 that is disposed near the end of the transport path 45 and fixes the toner transfer image formed on the surface of the transfer paper, and the fixed transfer paper from the downstream end of the transport path 45 to the printer. A discharge unit 50 that discharges to a discharge tray 49 of the main body 42 is provided.

  The intermediate transfer belt 47 has a function as an image carrier, an elastic intermediate transfer belt using at least one elastic layer in the layer structure is employed, and a driven roller 51 and a driven roller having functions as a tension roller. It rotates between the roller 52 and the pressure roller 53 (see the arrow in the figure).

  The pressure roller 53 is disposed opposite to the secondary transfer roller 35 with the intermediate transfer belt 47 interposed therebetween. By applying a transfer bias to the secondary transfer roller 35, toner is applied to the surface of the transfer paper conveyed to the conveyance path 45. The image is transferred to form a toner transfer image.

(Configuration of the image forming unit 48)
In the present embodiment, the image forming units 48 are arranged at four locations in a tandem manner along the rotational movement direction of the intermediate transfer belt 47, and those having substantially the same configuration are arranged. The image forming unit 48 includes a toner container 54 that stores toner of each color, a supply unit 55 that supplies toner stored in the toner container 54, and a drum-like electrostatic that is supplied with toner from the supply unit 55 on the surface. A photosensitive drum 56 as a latent image carrier, a transfer roller 57 disposed opposite to the photosensitive drum 56 with the intermediate transfer belt 47 interposed therebetween, and a cleaning device that removes residual toner and the like attached to the surface of the photosensitive drum 56 58, a charge eliminating device 59 for removing the charge of the photosensitive drum 56, a charging device 60 for charging the surface of the photosensitive drum 56, and an exposure device 61 for forming a predetermined electrostatic latent image on the surface of the photosensitive drum 56. And.

  In the present exemplary embodiment, each image forming unit 48 includes a magenta image forming unit 48 (M), a cyan image forming unit 48 (C), and a yellow image along the rotational movement direction of the intermediate transfer belt 47. The image forming unit 48 (Y) for black is disposed in this order, and the black image forming unit 48 (K) is disposed at the right end in the figure.

(Image formation processing)
In the color printer 41 having such a configuration, when print data is output from a personal computer (not shown) or the like, the surface of the photosensitive drum 56 is charged by the charging device 60 (charging process), and then is exposed by the exposure device 61. The surface of the photosensitive drum 56 is exposed to form an electrostatic latent image (exposure process).

  On the other hand, in the supply unit 55, only the toner of the two-component developer is allowed to fly, the toner is attached to the electrostatic latent image on the photosensitive drum 56, and the electrostatic latent image is developed as a toner image (development process). The toner image is primarily transferred from the photosensitive drum 56 to the intermediate transfer belt 47 by the transfer roller 57 (primary transfer process).

  Next, the toner image primarily transferred to the intermediate transfer belt 47 is conveyed to the secondary transfer roller 35 by the rotational movement of the intermediate transfer belt 47, and the transfer paper is applied by the transfer bias applied to the secondary transfer roller 35. (Secondary transfer process).

  The toner remaining on the surface of the intermediate transfer belt 47 after the toner image is secondarily transferred by the secondary transfer roller 35 is the cleaning device 62 disposed on the downstream side of the secondary transfer roller 35 in the rotational movement direction. Removed by.

(Configuration of the fixing unit 24)
The fixing unit 24 includes a heating roller 38 disposed on the surface side of the transfer paper, that is, the unfixed toner image side, in order to fix the unfixed toner image transferred to the surface of the transfer paper by the image forming unit 48. A pressure roller 39 that opposes the heating roller 38 across the conveyance path 45 is provided. The pressure roller 39 is pressed against the heating roller 38 to convey the transfer sheet in the nip.

  The unfixed toner image formed on the surface of the transfer paper is melted by directly contacting the heating roller 38, and is melted on the surface of the transfer paper as it is by being pressed by the pressure roller 39 from the back surface side of the transfer paper. The toner is transported to the next transport roller pair 40 while being fixed as a fixed image.

  By the way, in the above-described embodiment, the conveyance direction of the transfer paper from the resist to the fixing is disclosed as being substantially horizontal. However, at least a part of the transfer paper conveyance direction from the registration to the fixing is an upward conveyance. Etc. are also possible.

(Example)
Next, specific examples of the present invention will be described. In the following description, the secondary transfer roller 35 shown in FIG. 2 is disposed so as to face the pressure roller 53 with the intermediate transfer belt 47 interposed therebetween. Since the image transfer is performed, the toner drum has substantially the same function as the toner image transfer by the photosensitive drum 31 and the transfer roller 35 shown in FIG.

  Therefore, in the following description, for the sake of convenience, the presence of the intermediate transfer belt 47 is ignored in the drawing, and the pressure roller 53 is replaced with the photosensitive drum 31, and the secondary transfer roller 35 is replaced with the transfer roller 35. To do.

Example 1
Next, Example 1 in the image forming apparatus according to the embodiment of the present invention will be described.

  3A and 3B illustrate the image forming apparatus according to the first exemplary embodiment. FIG. 3A is a side view of the main part, and FIG. 3B is a plan view of the main part.

  The heating roller 38 has a halogen heater 38a disposed therein as a heating source. The halogen heater 38a is constantly monitored by a control circuit (not shown) by monitoring the surface temperature, ambient temperature (humidity), and the like of the heating roller 38. The heating temperature by is controlled.

  A pair of conveyance rollers 40 arranged downstream of the fixing unit 24 in the conveyance direction and nip-conveying the transfer sheet after fixing includes a metal conveyance roller 40a disposed on the image forming surface side (front side) of the transfer sheet, and a metal And an elastic conveying roller 40b that pressurizes the conveying roller 40a. In the present embodiment, the metal transport roller 40a has a fluorine layer formed as a release layer on the surface of a metal pipe such as SUS by a coating process, and also serves as a heat absorbing portion. Further, a pipe or roller made of Si rubber is used for the elastic conveyance roller 40b.

  The registration roller pair 22 disposed upstream of the transfer roller 35 in the transport direction includes a metal registration roller 22a disposed on the image forming surface side (front surface side) of the transfer paper and an elastic registration roller that pressurizes the metal registration roller 22a. 22b. In the present embodiment, the metal registration roller 22a has a fluorine layer as a release layer formed on the surface of a metal pipe such as SUS by a coating process, and also serves as a heat radiating portion. Further, a pipe or roller made of Si rubber is used for the elastic registration roller 22b.

  Between both ends of the metal conveying roller 40a also serving as the heat absorbing portion and the metal resist roller 22a also serving as the heat radiating portion, both side surfaces of the heat transfer portion 75 made of a metal pipe such as SUS are in surface contact with each other. It is connected. In addition, a heat absorption heat pipe 76, a heat transfer heat pipe 77, and a heat dissipation heat pipe 78 in which water is contained in a copper pipe are disposed in each of the metal transport roller 40a, the heat transfer unit 75, and the metal registration roller 22a. Therefore, heat absorption, heat transfer, and heat radiation efficiency are improved.

  Therefore, in the present embodiment, the preliminary heating unit 71 is configured by the metal transport roller 40a, the heat transfer unit 75, the metal registration roller 22a, and the heat pipes 76, 77, and 78.

  According to such a configuration, the heat accumulation of the transfer sheet after fixing heated by the heating roller 38 is absorbed by the metal conveying roller 40a as the heat absorbing portion and transferred to the metal registration roller 22a via the heat transfer portion 75. Be heated.

  As a result, the transfer paper conveyed next is preheated by heat radiation of the metal registration roller 22a before fixing.

  On the other hand, the surface temperature of the metal registration roller 22a is monitored by a registration temperature detection thermistor 79, and the heating temperature (fixing temperature) of the heating roller 38 is controlled by a control circuit based on the detection temperature of the registration temperature detection thermistor 79. The

  As a heating temperature control method by this control circuit, for example, in addition to the known fixing temperature control set based on the thickness (type) information of the transfer paper, the ambient environment temperature, etc., the detection is performed by the resist temperature detection thermistor 79. Correction is performed based on the difference between the detected temperature and the ambient temperature.

  Specifically, as shown in FIG. 4, a known temperature detection sensor (not shown) that detects the ambient temperature (environment temperature) in the vicinity of the fixing unit 24 with respect to the detection temperature of the resist temperature detection thermistor 79. The heating temperature (surface temperature) of the heating roller 38 is controlled according to the difference.

  As a result, the heating temperature of the heating roller 38 can be lowered as the amount of heat radiation rising due to continuous fixing processing increases, and the power consumption can be suppressed by the amount of heating of the halogen heater 38a. .

(Example 2)
5A and 5B show an image forming apparatus according to the second embodiment, where FIG. 5A is a side view of the main part, and FIG. 5B is a plan view of the main part.

  In FIG. 5, components substantially the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Between the fixing unit 24 and the transfer roller 35, a pre-fixing guide 80 that supports the non-image forming surface side (bottom surface side / back surface side) of the transfer paper is disposed. In this embodiment, the pre-fixing guide 80 also functions as a heat radiating portion, and is an existing component having a known transfer paper guide function (see FIG. 2). Further, a heat transfer portion 81 having a substantially L shape in plan view is provided between the metal conveying roller 40a as the heat absorbing portion and the pre-fixing guide 80 as the heat radiating portion.

  A metal member such as SUS is used for the heat transfer portion 81 and is configured to be in surface contact with the entire longitudinal direction of the pre-fixing guide 80 that also serves as a heat dissipation portion. In addition, a heat pipe 82 for heat transfer / heat radiation is disposed inside.

  Therefore, in this embodiment, the preheating unit 72 is configured by the metal transport roller 40a, the heat transfer unit 81, the pre-fixing guide 80, and the heat pipes 76 and 82.

  According to such a configuration, the heat accumulated in the transfer paper after fixing heated by the heating roller 38 is absorbed by the metal conveying roller 40a as the heat absorbing portion, and is transferred to the pre-transfer guide 80 via the heat transfer portion 81. Be heated.

  As a result, the transfer paper conveyed next is preheated by the heat radiation of the pre-transfer guide 80 before fixing.

  On the other hand, the surface temperature of the pre-transfer guide 80 is monitored by a guide temperature detection thermistor 83, and the heating temperature (fixing temperature) of the heating roller 38 is controlled by a control circuit based on the detection temperature of the guide temperature detection thermistor 83. The

  As a heating temperature control method by this control circuit, for example, in addition to the known fixing temperature control set based on the thickness (type) information of the transfer paper, the ambient environment temperature, etc., it is detected by the guide temperature detection thermistor 83. Correction is performed based on the difference between the detected temperature and the ambient temperature.

  Specifically, as shown in FIG. 6, a known temperature detection sensor (not shown) that detects the ambient temperature (environment temperature) in the vicinity of the fixing unit 24 with respect to the detection temperature of the guide temperature detection thermistor 83. The heating temperature (surface temperature) of the heating roller 38 is controlled according to the difference from the detected temperature.

  As a result, the heating temperature of the heating roller 38 can be lowered as the amount of heat radiation rising due to continuous fixing processing increases, and the power consumption can be suppressed by the amount of heating of the halogen heater 38a. .

(Example 3)
7A and 7B illustrate an image forming apparatus according to the third exemplary embodiment. FIG. 7A is a side view of the main part, and FIG. 7B is a plan view of the main part.

  In FIG. 7, the same reference numerals are given to the substantially same components as those in the first and second embodiments, and the description thereof is omitted.

  Between the metal conveying roller 40a, the pre-transfer guide 80, and the metal registration roller 22a, a heat transfer portion 84 having a substantially T-shape in plan view (sideways in FIG. 7B) is disposed.

  The heat transfer portion 84 is configured to be in surface contact with the entire longitudinal direction of the pre-fixing guide 80 that also serves as a heat radiating portion. In addition, a heat transfer heat pipe 85 is disposed so as to match the shape of the heat transfer section 84.

  Further, a pipe-shaped resist temperature adjusting member 86 is disposed between the heat transfer section 84 and the metal registration roller 22a.

  The resist temperature adjusting member 86 has a function of transferring heat from the heat transfer section 84 to the metal resist roller 22 a, and a resist temperature adjusting drive arm provided on the output shaft 87 a of the resist temperature adjusting drive motor 87. 88 is configured to be switched between a heat transfer position located between the heat transfer section 84 and the metal registration roller 22a and a blocking position retracted from between the heat transfer section 84 and the metal registration roller 22a. Yes. The output shaft 87 a is provided with a resist temperature adjustment actuator 89 that protrudes in the opposite direction to the resist temperature adjustment drive arm 88, and its position is detected by the resist temperature adjustment PI sensor 90.

  Accordingly, whether or not the resist temperature adjusting member 86 is located at the heat transfer position between the heat transfer portion 84 and the metal registration roller 22a is detected by the resist temperature adjusting PI sensor 90 by detecting the resist temperature adjusting actuator 89. It can be confirmed by whether or not.

  Therefore, in this embodiment, the preheating unit 73 is configured by the metal transport roller 40a, the heat transfer unit 84, the pre-fixing guide 80, the metal registration roller 22a, the heat pipes 76, 85, 78, and the resist temperature adjusting member 86. Has been.

  According to such a configuration, the heat accumulation of the transfer paper after fixing heated by the heating roller 38 is absorbed by the metal conveying roller 40a as the heat absorbing portion, and the pre-transfer guide 80 and the metal are transferred via the heat transfer portion 84. Heat is transferred to the registration roller 22a.

  As a result, the transfer paper conveyed next is preheated by heat radiation of the metal registration roller 40a before transfer and by heat radiation of the pre-transfer guide 80 before fixing.

  On the other hand, the surface temperature of the metal registration roller 22a and the surface temperature of the pre-transfer guide 80 are monitored by a resist temperature detection thermistor 79 and a guide temperature detection thermistor 83, respectively, and the resist temperature detection thermistor 79 and the guide temperature detection thermistor. The heating temperature (fixing temperature) of the heating roller 38 is controlled by the control circuit based on the detected temperatures 83.

  The driving of the resist temperature adjustment drive motor 87 is controlled by the control circuit based on the detected temperature of the resist temperature detecting thermistor 79.

  As a heating temperature control method by this control circuit, for example, in addition to the known fixing temperature control set based on the thickness (type) information of the transfer paper, the ambient environment temperature, etc., it is detected by the guide temperature detection thermistor 83. Correction is performed based on the difference between the detected temperature and the ambient temperature.

  Specifically, as shown in FIG. 8, the detection temperature of the resist temperature detection thermistor 79 is associated with each detection temperature of the temperature guide temperature detection thermistor 83, and the ambient temperature in the vicinity of the fixing unit 24 is associated with each temperature. The heating temperature (surface temperature) of the heating roller 38 is controlled in accordance with the difference from the temperature detected by a known temperature detection sensor (not shown) that detects (environment temperature).

  As a result, the heating temperature of the heating roller 38 can be lowered as the amount of heat radiation rising due to continuous fixing processing increases, and the power consumption can be suppressed by the amount of heating of the halogen heater 38a. .

  When the detection temperature of the resist temperature detection thermistor 79 exceeds a preset threshold (for example, an actual temperature of 45 ° C.), the resist temperature adjustment driving motor 87 rotates, and the resist temperature adjustment member 86 becomes the heat transfer portion 84 and the metal. The heat transfer from the heat transfer portion 84 to the metal registration roller 22a is blocked away from the registration roller 22a.

  When the transfer paper takes away the heat stored in the metal registration roller 22a and the detection temperature of the registration temperature detection thermistor 79 falls below a preset threshold value, the registration temperature adjustment drive motor 87 rotates in the reverse direction, and the registration temperature adjustment member 86 is positioned between the heat transfer section 84 and the metal registration roller 22a.

  As a result, the temperature rise of the photosensitive drum 31 and the developing unit (not shown) is suppressed to a certain temperature or less, and waste toner existing in the photosensitive drum 31 and toner in the developing unit (not shown) are aggregated by heat to cause an image. It is possible to suppress problems such as adversely affecting the performance and damage due to increased torque.

Example 4
9A and 9B show an image forming apparatus according to the fourth embodiment. FIG. 9A is a side view of the main part, and FIG. 9B is a plan view of the main part.

  In FIG. 9, the same reference numerals are given to substantially the same configurations as those in the first, second, and third embodiments, and the description thereof is omitted.

  Between the metal conveyance roller 40a, the pre-transfer guide 80, and the metal registration roller 22a, a heat transfer portion 91 having a substantially T-shape in plan view (sideways in FIG. 9B) is disposed.

  The heat transfer section 91 is disposed on the upstream side in the transport direction with respect to the pre-fixing guide 80 and is in surface contact with the entire longitudinal direction of the metal transport chute 92 that can be rotated so that the downstream side in the transport direction is a free end. It is configured. Further, the heat transfer section 91 is divided near one end of the metal conveyance chute 92, and a pipe-shaped conveyance chute temperature adjusting member 93 is disposed therebetween. As a result, the heat transfer unit 91 includes a first heat transfer unit 91a that extends in a straight line between the metal transfer roller 40a and the metal registration roller 22a, and a transfer chute temperature from the middle part of the first heat transfer unit 91a. It is substantially divided into a second heat transfer portion 91b extending in the direction orthogonal to the plan view via the adjustment member 93. Further, a first heat transfer heat pipe 94 and a second heat transfer heat pipe 95 are arranged in the first heat transfer section 91a and the second heat transfer section 91b, respectively.

  The conveyance chute temperature adjusting member 93 has a function of transferring heat from the first heat transfer unit 91a to the metal conveyance chute 92 via the second heat transfer unit 91b. The heat transfer position located between the heat transfer portion 91 and the metal transfer chute 92 and the heat transfer portion 91 and the metal transfer chute 92 are It is configured to be switched to a blocking position retracted from between. The output shaft 96 a is provided with a conveyance chute temperature adjusting actuator 98 that protrudes in the opposite direction to the conveyance chute temperature adjustment drive arm 97, and the position thereof is detected by the conveyance chute temperature adjustment PI sensor 99.

  Accordingly, whether or not the conveyance chute temperature adjusting member 93 is located at the heat transfer position between the heat transfer portion 91 and the metal conveyance chute 92 is determined by the conveyance chute temperature adjustment PI sensor 99 by the conveyance chute temperature adjustment actuator 98. It can be confirmed by detecting whether or not.

  An elliptical cam 100 is provided on the bottom surface of the metal conveyance chute 92 near both ends in the transfer paper width direction.

  The pair of cams 100 are fixed to the output shaft 101a of the conveyance chute rotation motor 101, and a heat radiation position where the conveyance chute rotation motor 101 comes into contact with the bottom surface of the transfer paper and at least a free end near the bottom surface of the transfer paper. It is configured to be switched to a non-heat dissipating position that is separated from the head. The output shaft 101 a is provided with a conveyance chute actuator 102, and its position is detected by a conveyance chute PI sensor 103.

  Thereby, whether or not the metal conveyance chute 92 is located at the heat radiation position can be confirmed by whether or not the conveyance chute PI sensor 103 detects the conveyance chute actuator 102.

  Therefore, in this embodiment, the metal transport roller 40a, the heat transfer section 91, the metal transport chute 92, the metal registration roller 22a, the heat pipes 76, 94, 95, 78, the resist temperature adjusting member 86, and the transport chute temperature adjustment. The preheating unit 74 is configured by the member 93.

  According to such a configuration, the heat accumulation of the transfer sheet after fixing heated by the heating roller 38 is absorbed by the metal conveyance roller 40a as the heat absorption unit, and the metal conveyance chute 92 via the heat transfer unit 91 is absorbed. Heat is transferred to the metal registration roller 22a.

  As a result, the transfer sheet conveyed next is preheated by heat radiation of the metal registration roller 40a before transfer and by heat radiation of the metal conveyance chute 92 before fixing.

  On the other hand, the surface temperature of the metal registration roller 22a and the surface temperature of the metal conveyance chute 92 are monitored by a resist temperature detection thermistor 79 and a conveyance chute temperature detection thermistor 104, respectively. Based on each detection temperature with the temperature detection thermistor 104, the heating temperature (fixing temperature) of the heating roller 38 is controlled by the control circuit.

  The driving of the conveyance chute temperature adjustment driving motor 96 is controlled by the control circuit based on the detection temperature of the resist temperature detection thermistor 79, and the conveyance chute temperature adjustment driving motor 96 and the conveyance are controlled based on the detection temperature of the conveyance chute temperature detection thermistor 104. The drive of the chute rotation motor 101 is controlled by the control circuit.

  As a heating temperature control method by this control circuit, for example, in addition to the known fixing temperature control set based on the thickness (type) information of the transfer paper, the ambient environment temperature, etc., the detection is performed by the resist temperature detection thermistor 79. Correction is performed based on the difference between the detected temperature detected by the detected thermistor 104 and the detected temperature detected by the thermistor 104 and the ambient temperature.

  Specifically, as shown in FIG. 10, the detection temperature of the resist temperature detection thermistor 79 is associated with each detection temperature of the temperature conveyance chute temperature detection thermistor 104, and the vicinity of the fixing unit 24 is associated with each temperature. The heating temperature (surface temperature) of the heating roller 38 is controlled in accordance with the difference from the temperature detected by a known temperature detection sensor (not shown) that detects the temperature (environment temperature).

  As a result, the heating temperature of the heating roller 38 can be lowered as the amount of heat radiation rising due to continuous fixing processing increases, and the power consumption can be suppressed by the amount of heating of the halogen heater 38a. .

  Further, when the detection temperature of the resist temperature detection thermistor 79 exceeds a preset threshold value (for example, actual temperature 45 ° C.), the conveyance chute temperature adjustment drive motor 96 rotates and the conveyance chute temperature adjustment member 93 becomes the heat transfer portion 91. Further, the heat transfer from the heat transfer portion 91 to the metal transfer chute 92 is cut off from the metal transfer chute 92.

  When the transfer paper takes away the heat stored in the metal conveyance chute 92 and the detection temperature of the resist temperature detection thermistor 79 falls below a preset threshold value, the conveyance chute temperature control drive motor 96 rotates in reverse and the conveyance chute The temperature adjustment member 93 is positioned between the heat transfer unit 91 and the metal conveyance chute 92.

  Similarly, when the detection temperature of the conveyance chute temperature detection thermistor 104 exceeds a preset threshold value (for example, actual temperature 40 ° C.), the conveyance chute temperature adjustment driving motor 96 rotates and the conveyance chute temperature adjustment member 93 performs heat transfer. The heat transfer from the heat transfer portion 91 to the metal conveyance chute 92 is cut off from the portion 91 and the metal conveyance chute 92.

  When the detection temperature of the conveyance chute temperature detection thermistor 104 exceeds a preset threshold value (for example, actual temperature 40 ° C.), the conveyance chute rotating motor 101 rotates and the metal conveyance chute 92 is moved closer to the free end. Rotates to the transfer paper non-contact position to block heat dissipation to the transfer paper.

  When the transfer paper takes heat storage of the metal conveyance chute 92 and the detection temperature of the conveyance chute temperature detection thermistor 104 falls below a preset threshold, the conveyance chute temperature adjustment drive motor 96 and the conveyance chute rotation motor 101 reversely rotates, and the conveyance chute temperature adjusting member 93 is positioned between the heat transfer portion 91 and the metal conveyance chute 92, and the metal conveyance chute 92 is returned to the original contact position.

  Therefore, when the temperature of the metal conveyance chute 92 is lower than the temperature of the transfer paper preheated by the heat radiation of the metal registration roller 22a, the metal conveyance chute 92 is not brought into contact with the transfer paper (no heat absorption), Only when the temperature of the metal conveyance chute 92 is higher than the transfer paper temperature, the transfer paper can be preheated.

  As a result, the temperature rise of the photosensitive drum 31 and the developing unit (not shown) is suppressed to a certain temperature or less, and waste toner existing in the photosensitive drum 31 and toner in the developing unit (not shown) are aggregated by heat to cause an image. It is possible to suppress problems such as adversely affecting the performance and damage due to increased torque.

  Further, until the temperature detected by the resist temperature detection thermistor 79 exceeds the threshold value, the resist temperature adjusting member 86 is positioned between the heat transfer section 84 and the metal registration roller 22a, and the conveyance chute temperature adjusting member 93 is the heat transfer section 91. Further, the temperature of the resist can be intensively increased until the threshold value is exceeded by being controlled by the control circuit so as to be separated from the metal conveyance chute 92 and to be in the opposite positions when the threshold value is exceeded.

  Further, when the control circuit determines that the detection temperature of the conveyance chute temperature detection thermistor 104 exceeds the threshold value, the metal conveyance chute 92 is lifted to a position where it contacts the transfer paper, and the detection temperature of the conveyance chute temperature detection thermistor 104 falls below the threshold value. When the control circuit determines, the metal conveyance chute 92 is lowered to a position where it does not contact the transfer paper.

  As described above, according to the image forming apparatus of the present invention, the fixing property is improved by preheating the transfer paper before fixing (before transfer) using the heat of the transfer paper heated by the fixing unit 24, By reducing the fixing temperature in accordance with the temperatures of the metal transport roller 40a, the pre-fixing guide 80, and the metal transport chute 92 as a heat radiating section, energy can be saved in the fixing section 24, and the fixing performance for each transfer sheet can be improved. It is possible to contribute to uniform glossiness and to output a stable image without offset.

  Further, the pre-fixing guide 80 and the metal conveyance chute 92 as the heat radiating unit transmit heat to the transfer paper immediately before the fixing nip, so that re-preheating from the transfer paper whose temperature has been increased by heat transfer is minimized. Since the existing components can be used as the heat radiating portion, it is not necessary to arrange an extra dedicated member for the heat radiating portion.

  Further, since the metal transport roller 40a, the pre-fixing guide 80, and the metal transport chute 92, which are heat radiating parts, extend over substantially the entire width in the transfer paper width direction, the transfer paper can be preheated uniformly in the width direction. In addition, by arranging the heat dissipation heat pipe 78, the heat transfer / heat dissipation heat pipe 82, the heat transfer heat pipe 85, and the second heat transfer heat pipe 95, the preheating temperature in the width direction of the transfer paper can be made uniform. In addition, the fixing property, glossiness, and the like within one transfer sheet can be made uniform, and a stable image can be obtained.

  Further, if the metal registration roller 22a positioned on the transfer surface side of the registration roller pair 22 is used as the heat radiating portion, the front and back sides of the transfer paper on which the toner image before transfer is not formed are conveyed in a pressure nip, while the transfer paper The transfer surface side can be efficiently preheated.

  Further, by disposing the heat radiating portion on the upstream side and the downstream side of the photosensitive drum 31, an unfixed toner image is not carried on the transfer paper on the upstream side of the photosensitive drum 31. By using the pair 22 and applying pressure while sandwiching the transfer paper, it is possible to efficiently transfer heat to the transfer paper. However, if the temperature of the transfer paper is too high on the upstream side of the transfer device. When the transfer paper passes through the transfer device, the temperature of the transfer device becomes high, and unfixed toner may be agglomerated, so that fixing is performed as a second heat radiating unit between the photosensitive drum 31 and the fixing unit 24. By arranging the front guide 80 and the metal conveyance chute 92, a well-balanced preheating can be ensured.

DESCRIPTION OF SYMBOLS 22 ... Registration roller pair 22a ... Metal registration roller 22b ... Elastic registration roller 31 ... Photoconductor drum 35 ... Transfer roller 38 ... Heating roller 38a ... Halogen heater 39 ... Pressure roller 40 ... Conveyance roller pair 40a ... Metal conveyance roller 40b ... Elasticity Conveying roller 71 ... Preheating section 72 ... Preheating section 73 ... Preheating section 74 ... Preheating section 75 ... Heat transfer section 76 ... Heat absorption heat pipe 77 ... Heat transfer heat pipe 78 ... Heat dissipation heat pipe 79 ... Resist temperature Detection thermistor 80: Pre-fixing guide 81 ... Heat transfer section 82 ... Heat transfer / heat dissipation heat pipe 83 ... Guide temperature detection thermistor 84 ... Heat transfer section 85 ... Heat transfer heat pipe 86 ... Resist temperature adjustment member 91 ... Heat transfer section 92 ... Metal conveyance chute 93 ... Conveyance chute temperature adjusting member 94 ... First heat transfer heat pad Flop 95 ... second heat transfer heat pipe 104 ... conveying chute temperature sensing thermistor

Claims (7)

In an image forming apparatus including a fixing device that fixes a toner image to a transfer paper by heating and pressurizing the transfer paper before fixing on which the toner image is formed.
A preheating unit that absorbs heat of the transfer paper after fixing on the downstream side in the transport direction from the fixing device and preheats the transfer paper before fixing on the upstream side of the fixing device; and an endothermic temperature of the preheating unit An image forming apparatus comprising: a temperature control unit that lowers the heating temperature of the fixing device as the temperature rises.   The preheating unit includes a heat absorption unit that absorbs heat of the transfer paper after fixing, a heat transfer unit that transfers heat absorbed by the heat absorption unit to a downstream side of the fixing device, and a heat transfer unit. A temperature sensor that radiates the heated heat to the transfer paper before fixing, and the temperature control unit monitors a current temperature of at least one of the heat absorbing unit, the heat transfer unit, and the heat radiating unit. The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 2, wherein the heat dissipating unit uses at least one of a registration roller pair, a pre-fixing guide, and a metal conveyance chute disposed upstream of the fixing device. apparatus.   4. The image forming apparatus according to claim 2, wherein the heat absorption unit uses a pair of conveyance rollers disposed downstream of the fixing device. 5.   The image forming apparatus according to claim 2, wherein a heat pipe is disposed in at least one of the heat absorbing portion and the heat radiating portion.   3. A transfer device for transferring a toner image onto a transfer sheet is disposed upstream of the fixing device, and the heat radiating portion is disposed on an upstream side and a downstream side of the transfer device, respectively. The image forming apparatus according to claim 5.   The said temperature control part is provided with the switching part which interrupts | blocks the heat transfer to the said thermal radiation part by the said heat-transfer part, when the monitoring temperature of the said temperature sensor becomes more than predetermined temperature. The image forming apparatus according to claim 6.

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