Patent Grant
7546049
1. Field of the Invention
The present invention relates to an image forming device of the electrophotographic type such as a copier, facsimile machine, printer or printing machine, and a control method therefor, and particularly relates to a fixing device and a control method therefor in which fixing properties are stable and curl is not produced in the transfer paper after fixing, by performing temperature correction control of fixing of the toner image on the transfer paper constituting a sheet-like recording medium, using pressure or heat.
2. Description of the Related Art
Image forming device of this type have become very common in recent years. In particular, improvements in for example image quality, energy saving, and convenience are continually being demanded. Of these, since the energy consumption of the fixing device that is mounted in the image forming device represents 50% or more, efforts are being made to improve energy saving of the fixing device. Efforts are therefore being made to shorten the starting up time or recovery time by reducing the thickness and decreasing the amount of heat used by the fixing members constituting the fixing device.
As a fixing device, a construction of the fixing roller type is known, in which a pair of rollers are arranged facing each other, one of the rollers being used as a heating roller while the other roller is used as a pressurizing roller for applying pressure to the sheet-like recording medium, such as transfer paper. In this construction, fixing is effected by melt bonding of the unfixed image by heat from the heating roller, while the recording medium is fed while being gripped in the nip between the heating roller and pressurizing roller.
Apart from this fixing roller type construction, a fixing belt type construction is also known, comprising an assembly of rollers and a belt. In this construction, instead of the heating roller, a belt is employed that is passed over a pair of rollers, with a pressurizing roller being arranged facing one of these rollers. Of this pair of rollers, a heat source is provided for heating from the inside face of the belt at the roller that drives the belt in co-operation with the roller on the side facing the pressurizing roller, and a heat source is also provided at the pressurizing roller for heating the outside face of the belt. The belt is of smaller volume than the rollers and its heat capacity is small, so it can be raised in temperature in a short time, so the advantage is obtained that initial elevation of temperature at start-up can be achieved more rapidly than in the case of a construction using only a heating roller and pressurizing roller as described above. Furthermore, elevation of temperature at both the outside and inside of the belt is speeded up by providing a heat source at the pressurizing roller. It should also be noted that a double layer construction is known, in which, when aluminum, which is of high thermal conductivity, is used to construct the rollers in the case of a belt construction, in the case where stainless-steel is employed as the substrate that effects contact at the outer surface of the rollers, a belt body comprising a releasing layer made of silicone rubber or fluorine-based resin is arranged at the outer surface thereof.
However, as described above, although, with the conventional fixing device, rapid start-up can be achieved, since it is possible to rapidly heat specified portions of the fixing member by reducing the or heat capacity of the fixing member, when the entire fixing device or the entire image forming device becomes warmed up, in the case of several printing cycles or where the time for which the printing action is repeated is prolonged (hereinbelow this will simply referred to as “over time”), the amount of heat that is applied to the toner or transfer paper becomes excessive, so problems arise in that abnormal images, poor feeding or poor stacking due to curling of the transfer paper tend to occur. For this reason, consideration has been given to predicting the temperature increase over time and setting the target control temperature of the fixing device lower from the initial period. However this leads to problems of generation of abnormal images due to insufficient heating in the initial period on starting up or after recovery of operation of the fixing device.
Furthermore, in addition to the above problems, the transfer paper constituting the recording medium prior to transfer is not at a fixed temperature but is affected by the storage environment. Consequently, the amount of heat that is required when introducing the transfer paper to the fixing device after transfer may change, depending on the storage environment temperature of the transfer paper prior to transfer. In addition to temperature control within the fixing device, the fixing temperature must therefore be controlled using a plurality of detection means that detect the temperature and humidity of the external air wherein the image forming device is held and the temperature and humidity within the image forming device.
As prior art relating to control of fixing temperature, an image forming device as disclosed in Laid-open Japanese Patent Application No. H. 10-39672 is known. In this image forming device, a temperature sensor is arranged in a position where it is unlikely to be affected by the heat generated by the fixing device in the device interior, but the internal temperature of the image forming device changes depending on the job, so the environmental temperature cannot be precisely detected. Consequently, the value of this sensor is not used after job commencement; rather, the fixing temperature is corrected in accordance with environmental temperature detection during standby. It should be noted that this publication does not disclose the specific location of the sensor.
Furthermore, Laid-open Japanese Patent Application No. 2004-212968 discloses an image forming device wherein elevation of the temperature within the image forming device is suppressed by the provision of temperature detection means that detects the temperature of the fixing belt and a control unit that performs control of the image forming processing in accordance with the detected temperature. In addition, Japanese Patent No. 3425040 discloses an image forming device that provides excellent fixing properties by preventing the existence of a large difference between the standby control temperature and operating control temperature, even where fluctuation of the environmental temperature during standby has taken place, by correcting the fixing control temperature during standby, in accordance with the environmental temperature.
However, in these items of prior art, fixing temperature correction in accordance with environment detection is not performed over time. Consequently, even in cases where the temperature of the transfer paper after transfer is not affected by the storage environment, since the periphery of the fixing device and the feed path rise in temperature over time, when the transfer paper enters the fixing device, the amount of heat applied to the transfer paper after transfer becomes excessive, leading to problems of curling of the transfer paper after fixing. When the paper curls, alignment of the paper on discharging is lost, giving rise to problems of the transfer paper escaping from the binding by the finisher or being displaced in this binding.
An object of the present invention is to provide an image forming device and control method therefor comprising a fixing device of excellent toner fixing properties and that does not generate transfer paper curling after printing.
A further object of the present invention is to provide an image forming device and control method therefor comprising a fixing device of excellent fixing properties and that does not generate curling of the paper after fixing and wherein stable fixing properties are obtained, by exercising control that effects correction of fixing temperature by environmental sensing over time, in addition to during standby.
In accordance with an aspect of the present invention, an image forming device comprises a fixing device that fixes a transfer member that carries a toner image that is not yet fixed; a temperature detection device that detects the temperature within the image forming device in which this fixing device is provided; and a control device that corrects the control temperature of the fixing device in accordance with the detection result of this temperature detection device. The temperature detection device is arranged in the vicinity of the fixing device.
In accordance with another aspect of the present invention, an image forming device comprises a fixing device that performs fixing by heating a transfer member that carries a toner image that is not yet fixed; a temperature detection device that detects the temperature within the image forming device in which this fixing device is provided; and a control device that corrects the control temperature of the fixing device in accordance with the detection result of this temperature detection device. The temperature detection device detects the temperature of a cover of the fixing device.
In accordance with another aspect of the present invention, an image forming device comprises a fixing device that performs fixing by heating a transfer member that carries a toner image that is not yet fixed; a temperature detection device that detects the temperature within the image forming device in which this fixing device is provided; and a control device that corrects the control temperature of the fixing device in accordance with the detection result of this temperature detection device. The temperature detection device detects the temperature of a feed guide plate arranged between a transfer nip and a fixing nip.
In accordance with another aspect of the present invention, an image forming device comprises a fixing device that performs fixing by heating a transfer member that carries a toner image that is not yet fixed; a temperature detection device that detects the temperature within the image forming device in which this fixing device is provided; and a control device that corrects the control temperature of the fixing device in accordance with the detection result of this temperature detection device. The temperature detection device detects the temperature of a transfer belt.
In accordance with another aspect of the present invention, in an image forming device, an image that is not yet fixed formed on a recording medium is fixed by application of heat and pressure by passing the image through a fixing nip formed by at least two or more fixing members, and-at least one of the fixing members can be controlled to a target temperature. A first temperature detection device is provided in a position that is greatly affected by heat when fixing is performed, and a second temperature detection device is provided in a position that is less affected by heat when fixing is performed, on the paper feed path upstream of the fixing nip. The fixing target temperature is changed in accordance with the result of comparison of these first and second devices. The amount of the temperature change is altered in accordance with the size of the recording medium that carries this image that has not yet been fixed.
In accordance with another aspect of the present invention, a method of control for an image forming device fixes an image that is not yet fixed formed on a recording medium by application of heat and pressure by passing the image through a fixing nip formed by at least two or more fixing members. At least one of the fixing members is controlled to a target temperature. A first temperature detection device is provided in a position that is greatly affected by heat when fixing is performed. A second temperature detection device is provided in a position that is less affected by heat when fixing is performed, on the paper feed path upstream of the fixing nip. The fixing target temperature is changed in accordance with the result of comparison of these first and second devices. The amount of the temperature change is altered in accordance with the size of the recording medium that carries this image that has not yet been fixed.
In accordance with another aspect of the present invention, an image forming device comprises a fixing device that fixes toner on a recording medium; a temperature detection device comprising first temperature detection device provided at a position that is greatly affected by heat when fixing is performed, and second temperature detection device provided at a position that is less affected by heat when fixing is performed; a control device that performs temperature correction wherein the target control temperature of the fixing device is changed to a prescribed value in accordance with the first and second temperature detection device; and a detection device that detects temperature and/or humidity of an outside air in which the image forming device is held, and temperature and/or humidity of a prescribed position within the image forming device. The target control temperature of a fixing device is corrected in accordance with the temperature and humidity detected by the detection device of the image forming device and the temperature detected by temperature detection device of the fixing device.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:
Embodiments of the present invention are described in detail below.
It should be noted that, although the image forming device comprising a fixing device according to the various embodiments of the present invention is applied as a copier, printer, or facsimile machine wherein a full-color image is formed by a tandem arrangement of four linked devices, it could of course also be applied to a device in which a monochromatic image is formed.
As can be seen from this Figure, this image forming device 20 comprises: image creation devices 21Y, 21M, 21C, 21BK, that form images of each respective color in accordance with the original image; a transfer device 22 arranged facing these image creation devices 21Y, 21M, 21C, 21BK; a hand-feed tray 23 constituting sheet supply means that supplies sheet-like recording media to the transfer zone facing the image creation devices 21Y, 21M, 21C, 21BK and the transfer device 22; a first paper feed cassette 24A and a second paper feed cassette 24B installed in a paper feed device 24; a register roller 30 that feeds the sheet-like recording media that are fed in from this hand-feed tray 23 and paper supply cassettes 24A, 24B, with a timing matching the image creation timing of the image creation devices 21Y, 21M, 21C, 21BK; and a fixing device 1 that performs fixing of the image on the sheet-like recording medium after transfer in the transfer zone.
This image forming device 20 can employ as sheet-like recording medium any of ordinary paper that is generally employed in copiers, for example, or so-called special sheets (hereinbelow simply referred to as special sheets) of larger thermal capacity than printing paper such as OHP sheets, 90 K paper i.e. postcards, thick paper corresponding to an average weight of about 100 g/m2 or more, or envelopes.
The image creation devices 21C, 21Y, 21M, 21BK perform development of the respective colors: cyan, yellow, magenta and black and employ toner of different colors; however, their construction is the same, so the construction of the image creation device 21C will be described as a typical example of these image creation devices 21C, 21Y, 21M, 21BK. For the image creation device 21C, a device of a known construction is employed, comprising an electrostatic latent image carrier constituted by a photosensitive body drum 25C, a charging device 27C, developing device 26C and cleaning device 28C that are arranged in order along the direction of rotation in the clockwise direction in the drawing i.e. the direction of rotation of the photosensitive body drum 25C; in this device exposure light is received from a writing device 29 arranged between the charging device 27C and developing device 26C. The electrostatic latent image carrier may be in the form of a drum or may be in the form of a belt.
The fixing roller 4 comprises a metal core 9 and an elastic body layer 10 of a heat-resistant porous layer that covers this metal core 9. The fixing roller 4 is biased into pressure contact with the pressurizing roller 5 by an elastic body, not shown, such as spring. The reference symbol 12 indicates a guide whereby the transfer paper P that is to be fixed is guided towards the first fixing unit.
A roller 121 for applying a minute amount of oil is brought into contact with the pressurizing roller 5 by means of an elastic body, not shown, such as a spring, so that a minute amount of silicone oil is applied to the surface of the fixing belt 2 and pressurizing roller 5, with the object of improving release of the fixing belt 2 and toner. Also, a cleaning roller 122 is brought into contact with the surface of the roller 121 for applying a minute amount of oil, with the object of preventing sticking of toner to the surface of the roller 121 for applying a minute amount of oil.
As shown in
As shown in
It should be noted that, as practical example 6, it would also be possible to combine any two of the practical examples 1 to 5 described above. In this way, temperature correction can be performed with high accuracy over time from the initial period.
Furthermore, while it is known that a characteristic feature of a fixing device 1 using an endless belt is that it provides effective means for example for shortening the warm-up
time or decreasing the energy consumption, the present embodiment provides temperature correction for eliminating the problem caused by excessive amount of heat, such as curling,
and, at the same time, as shown in
the temperature when the amount of heat is tending to be excessive (for example when the temperature is 35° C. or more): thus its effect is exhibited in the case of fixing means such as a belt whose heat capacity is small compared with a roller, in other words fixing means which easily tend to heat up or cool down.
As described above, according to this first embodiment, there can be provided an image forming device and a method of control therefor, comprising a fixing device providing excellent toner fixing and in which curling of the transfer paper after printing does not occur.
The construction of an image forming device according to this embodiment is shown in
As shown in
An example of temperature correction control according to this embodiment is described below in a case in which there is an incoming request for printing of monochromatic black. However, apart from this, in the case for example of full-color mode also, a decision is made in the same way as to whether or not to execute temperature correction, and control is performed with respectively corresponding temperature amounts. A description of the flow from delivery of a print request to the control unit up to the start of fixing is given with reference to the flowchart of
When a print request is sent to the control unit, the output values T1, T2 of the temperature sensors SS, S6 at that point are acquired. Next, the difference ΔT of the temperatures T1, T2 that were previously acquired is acquired by ΔT=T1−T2. Next, the magnitude relationship of the temperature ΔT and a threshold value temperature, that may be arbitrarily set, (assumed in the case of this embodiment to be 5° C.) is compared. If ΔT<5° C., it is concluded that temperature correction is unnecessary, since the interior of the image forming device is not heating up, and fixing is commenced with the target control temperature Tcont left at Tcont=170° C. If ΔT≧5° C., next, T2 is first compared with the threshold value Th that is capable of being set to an arbitrary value. The correction amount in respect of the target control temperature is altered in accordance with the result of this comparison. If T2 is arranged on the outside air side of the image forming device, T2 can be considered as substantially equal to the outside air temperature. Consequently, if T2 is higher than Th (34° C. in the case of this embodiment), it is considered that the transfer paper must have been thoroughly warmed up, so the fixing temperature needs to be considerably lowered; but if T2 is lower than Th, it is concluded that there is no need to make much correction to the target control temperature.
Next, the magnitude relationship of the temperature of ΔT and the arbitrarily settable threshold temperature (assumed to be 10° C. in the case of this embodiment) is compared; if T2<Th and ΔT<10° C., temperature correction is performed with a correction amount Ta; if T2<Th and ΔT>10° C., temperature correction is performed with a correction amount Tb; if T2>Th and ΔT<10° C., temperature correction is performed with a correction amount Tc; and if T2>Th and ΔT>10° C., temperature correction is performed with a correction amount Td. For example, if T2<Th and ΔT<10° C., fixing is commenced after altering the target temperature control to (170° C.−Ta) ° C. This evaluation is repeated when a printing request is terminated or when the next printing request arrives. In this way, it is possible to set the optimum amount of heat for fixing taking into account the rise in temperature within the image forming device at the time point where the printing request arrives.
In practical example 1 of this embodiment, as shown in
In practical example 2 of this embodiment, the correction amount is altered in accordance with the type of paper or paper thickness. In the case of paper thickness as great as 100 g/m2, if fixing is performed with the same speed as in the case of ordinary paper in order to achieve the same productivity, the quantity of heat already tends to be insufficient; if this correction were to be performed, the margin in this respect would disappear. Thick paper does not easily curl, so it is beneficial not to apply this correction. More stable images can be provided by performing temperature correction in accordance with the type of paper and paper thickness of the recording medium.
In practical example 3 of this embodiment, the correction amount is altered in accordance with the paper source. For example, paper from the hand-feed tray conforms more closely to the environment than paper from the main tray and requires a different correction than in the case of the main tray: thus, at low temperature, no correction is made for paper from the hand-feed tray whereas a correction such as to effect a lowering in temperature of 5° C. may be applied in the case of paper from the main tray. More stable images can be provided by performing temperature correction in accordance with the paper source of the recording medium.
In practical example 4 of this embodiment, as shown in
Exceptions in respect of the temperature correction of this embodiment will now be described.
In view of design concepts regarding energy saving in recent years, when the device is not used (left to stand), after a certain time, the device shifts from low power mode (=in the case of the device of this embodiment, the temperature of the pressurizing roller, which is of large heat capacity, is lowered by about 40° C. from the normal standby temperature), and on being left to stand even further, to sleep mode (mode in which the fixing heater is OFF, but the CPU is live). In this case, as shown in the
In practical example 6 of this embodiment, in addition to practical example 5 described above, warm-up control is performed during turning ON of the power source, in the case of running out of toner or error recovery such as jam recovery, or in the case of recovery from low power mode; in this case, the pressurizing roller temperature is detected, and the fixing condition is evaluated in terms of a threshold value, as a result of which a decision is made to shift, or not to shift, to correction decision control (item “pressurization at 60° C.” in the flowchart of
In practical example 7 of this embodiment, the threshold value of correction and the exclusion time are changed in accordance with the temperature on switching on of the power source, so more accurate correction can be performed, making possible the provision of more stable images.
In practical example 8 of this embodiment, a belt fixing system is adopted, so the start-up time can be shortened. As described above, with this second embodiment, by comparing the temperatures detected by a plurality of sensors in the image forming device, the target control temperature is corrected in accordance with the result thereof. By correcting the target control temperature using the difference temperature of a plurality of sensors, rise in temperature within the image forming device can thereby be detected and the increase in amount of heat when the target fixing device as a whole or the image forming device as a whole has warmed up can be estimated, making possible optimal temperature correction.
Also, by taking into account the humidity of the outside air, temperature correction can be achieved taking into account the influence of the moisture content, which affects fixing. By combining the present invention with fixing using a belt of low thermal capacity, stable fixing can be achieved together with energy saving.
The construction of an image forming device according to this embodiment is shown in
In the case of the image forming device of this embodiment, just as in the case of the image forming device of the second embodiment illustrated in
In this embodiment, the belt and pressurizing roller within the fixing device 1 are respectively heated by a heating roller heater 6 and pressurizing roller heater 7, heating being conducted under control exercised by a fixing belt temperature sensor 13 and pressurizing roller temperature sensor 14 with which these are respectively provided so that the desired target control temperature is maintained. This image forming device has two modes, namely 600 dpi and 1200 dpi in regard to resolution of the printed image and also has, respectively for each of these, a monochromatic black mode and full-color mode, making a total of four modes. The target control temperature of the fixing device can be set at will when a printing request arrives at the control unit such that optimum images are obtained for the mode specified by the printing request. For example, the target control temperature of the belt is controlled to 170° C. in the case of a printing request for monochromatic black of 600 dpi and is controlled to 155° C. in the case of a printing request for full-color of 600 dpi. Also, the target control temperature in the case of the pressurizing roller is set lower by 15° C. to 30° C. than the target control temperature in the case of the belt.
When a printing request arrives at the control unit, the output values T1, T2 of the temperature sensors 31, 32 at this point are acquired (step ST1). Next, the difference ΔT of the previously acquired temperatures T1, T2 i.e. ΔT=T1-T2 is acquired (step ST2). Next, the magnitude relationship of the temperature ΔT and a threshold value temperature (taken as 5° C. in this embodiment) that can be arbitrarily set is compared (step ST3). If ΔT<5° C., it is concluded that temperature correction is not required since the interior of the image forming device has not heated up, and fixing is commenced with the target control temperature left at T=170° C. (step ST4). If ΔT≧5° C., T2 is compared with a threshold value Th that can be pre-set to an arbitrary value (step ST5) . The correction amount to be applied to the target control temperature is altered in accordance with the results of this comparative evaluation.
T2 is arranged on the outside air side of the image forming device so that a temperature which is substantially that of the outside air can be take into account. Thus, if T2 is higher than Th (34° C. in the case of this embodiment), it is considered that the transfer paper must be sufficiently warm, so a considerable reduction in the fixing temperature is necessary; and if T2 is lower than Th, it is considered that there is no need to apply much correction to the target control temperature.
Next, the magnitude relationship of the temperature of ΔT (assumed to be 10° C. in the case of this embodiment) and a threshold temperature that can be arbitrarily set is compared (step ST6A or ST6B). If T2<Th and ΔT<10° C., temperature correction is performed with a correction amount Ta (step ST7); if T2<Th and ΔT>10° C., correction is performed with a correction amount Tb (step ST8); if T2>Th and ΔT<10° C., temperature correction is performed with a correction amount Tc (step ST9); and if T2>Th and ΔT>10° C., correction is performed with a correction amount Td (step ST10). For example if T2<Th and ΔT<10° C., fixing is commenced after altering the target temperature control to 170° C.−Ta. This evaluation is repeated when a printing request is terminated or when the next printing request arrives. In this way, it is possible to set the optimum amount of heat for fixing taking into account the rise in temperature within the image forming device at the time point where the printing request arrives.
As mentioned above, the target control temperature of the fixing device is different for each of the various print request modes (for example, monochromatic, full-color, 600 dpi, 1200 dpi), so the temperature correction amounts referred to above may also be individually set.
In step ST2 of
It should be noted that, although not discussed in the embodiments, by using the humidity sensor S7, a temperature correction value can be employed which is altered in accordance with the humidity of the outside air or in the image forming device, which considerably affects the water content of the transfer paper. In this case, as shown in
As described above, in this embodiment, an image forming device can be provided whereby stable fixing performance is obtained and wherein excellent fixing properties are achieved and curling of the paper after fixing does not occur, by performing control in which fixing temperature correction is performed by environmental sensing over time, in addition to during standby.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-013777 | Jan 2005 | JP | national |
| 2005-016338 | Jan 2005 | JP | national |
| 2005-017546 | Jan 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5581341 | Tanaka | Dec 1996 | A |
| 5832354 | Kouno et al. | Nov 1998 | A |
| 5895152 | Ide et al. | Apr 1999 | A |
| 5915147 | Kouno et al. | Jun 1999 | A |
| 6219520 | Ehara et al. | Apr 2001 | B1 |
| 6389247 | Chung | May 2002 | B1 |
| 6628916 | Yasui et al. | Sep 2003 | B2 |
| 6636709 | Furukawa et al. | Oct 2003 | B2 |
| 6778790 | Yoshinaga et al. | Aug 2004 | B2 |
| 6778804 | Yoshinaga et al. | Aug 2004 | B2 |
| 6785505 | Yasui et al. | Aug 2004 | B2 |
| 6807386 | Yasui et al. | Oct 2004 | B2 |
| 6881927 | Yoshinaga et al. | Apr 2005 | B2 |
| 6892044 | Yasui et al. | May 2005 | B2 |
| 20030002881 | Hirose et al. | Jan 2003 | A1 |
| 20040258425 | Phillips | Dec 2004 | A1 |
| 20050025539 | Yoshinaga | Feb 2005 | A1 |
| 20050095043 | Yoshinaga et al. | May 2005 | A1 |
| 20050163524 | Shiobara et al. | Jul 2005 | A1 |
| 20060051113 | Kishi et al. | Mar 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 02-217876 | Aug 1990 | JP |
| 10-039672 | Feb 1998 | JP |
| 2000-315034 | Nov 2000 | JP |
| 2003-014558 | Jan 2003 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20060177232 A1 | Aug 2006 | US |
