JP2006208509A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of obtaining stable fixability in which the fixability is satisfactory without causing curl of paper after the fixation, by performing the control for correcting the fixing temperature by environmental detection with the lapse of time, in addition to that during the standby time. <P>SOLUTION: A plurality of temperature detection means are provided in a fixing device 1, and a plurality of detection means for detecting the temperature and the humidity are provided in the image forming apparatus 20. The temperature correction for changing the target control temperature of the fixing device 1 to a prescribed value is performed, according to the temperature or the humidity detected by the plurality of detection means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and the like. By performing temperature correction control of the fixing device, the fixing property is stabilized and curling of transfer paper after fixing does not occur. It is about.

In recent years, full-color image forming apparatuses have become widespread, and high image quality, energy saving, and convenience have been demanded. In particular, since the heat fixing unit of the fixing device consumes 50% or more of the energy consumed by the image forming apparatus, improvement for energy saving is being promoted. For this reason, the rise time and the return time are shortened by reducing the thickness of the fixing member and reducing the heat amount of the fixing device. For example, as compared with the fixing roller method, a fixing belt method in which the heat capacity of the fixing portion is significantly smaller and the warm-up time is shortened is widely used as an effect for energy saving.
However, a specific part of the fixing member can be rapidly heated by reducing the heat capacity of the fixing member, and rapid start-up is possible. "Time"), the amount of heat applied to the toner and transfer paper when the entire fixing device or the entire image forming device is warmed up, abnormal images, poor transfer due to curling of transfer paper, poor stack quality, etc. Invite. On the other hand, if the target heat control temperature of the fixing device is set low from the beginning by predicting an increase in the amount of heat over time, an abnormal image is generated due to a shortage of heat at the start-up of the fixing device or early after the return operation.
In addition to the above problems, the temperature of the pre-transfer paper is not constant due to the storage environment. For this reason,
Depending on the storage environment temperature of the paper before transfer, the amount of heat required when the paper after transfer enters the fixing device may change. Therefore, in addition to controlling the temperature inside the fixing device, the fixing temperature is controlled based on the temperature and humidity of the outside air held by the image forming device and a plurality of detection means for detecting the temperature and humidity inside the image forming device. There is a need to.

As a conventional technique related to the control of the fixing temperature, there is a temperature detecting means for detecting the temperature of the fixing belt and a control unit for controlling the image forming process based on the detected temperature, and the temperature inside the image forming apparatus becomes high. There is an image forming apparatus that suppresses this (see, for example, Patent Document 1). In addition, by correcting the fixing control temperature during standby according to the environmental temperature, even if there is a change in the environmental temperature during standby, the difference between the standby control temperature and the operating control temperature does not increase, which is favorable. There is an image forming apparatus that provides fixing properties (for example, see Patent Document 2).

JP 2004-221968 A Japanese Patent No. 3425040

The above prior art does not correct the fixing temperature by detecting the environment over time. For this reason,
Even if the temperature of the paper after transfer is not affected by the storage environment, the temperature around the fixing device and the transport path rises over time, so when entering the fixing device, the amount of heat applied to the paper after transfer is excessive. Thus, there arises a problem that the paper after fixing is curled. When the paper is curled, the paper discharge becomes inconsistent, and stitching or misalignment occurs at the finisher.

The present invention has been made in view of the above problems. By performing control for correcting the fixing temperature by detecting the environment over time in addition to during standby, the fixing property is good and paper curling occurs after fixing. It is an object of the present invention to provide a fixing device and an image forming apparatus that can obtain stable fixing properties.

In order to solve the above problems, the present invention has the following features.
The present invention provides a fixing means for fixing toner on a recording medium, a temperature detecting means having a first temperature detecting means at a position where the heat influence of fixing is large, and a second temperature detecting means at a position where the heat influence of fixing is small. The image forming apparatus includes a control unit that performs temperature correction that changes the target control temperature of the fixing unit to a predetermined value based on the first and second temperature detecting units. In the image forming apparatus, the fixing device includes a detecting unit configured to detect a temperature and / or humidity of outside air in which the image forming apparatus is held and a temperature and / or humidity at a predetermined position in the image forming apparatus. The target control temperature of the fixing device is corrected in accordance with the temperature detected by the temperature detection unit included in the image forming apparatus and the temperature and humidity detected by the detection unit included in the image forming apparatus.
By detecting the temperature of multiple parts and controlling based on the comparison of those temperatures, it is possible to correct in real time the temperature rise of the part that affects fixing, and in addition to waiting time, In addition, by performing control for correcting the fixing temperature by detecting the environment, it is possible to provide an image forming apparatus that has good fixing properties and does not cause paper curling after fixing.

The present invention has humidity detection means for detecting the humidity of outside air held by the image forming apparatus or humidity at a predetermined position in the image forming apparatus, and the temperature detected by the plurality of temperature detection means of the fixing device. In addition, the target control temperature of the fixing device is corrected in accordance with the temperature detected by a detection unit included in the image forming apparatus.
By detecting the temperature of multiple parts and performing control based on the comparison of those temperatures, it is possible to detect a temperature rise at a predetermined position in the image forming apparatus that is not affected by environmental changes. A stable image can be provided by setting and adjusting the unfixed image and the amount of heat applied to the transfer paper to an optimum value.

The present invention has humidity detection means for detecting the humidity of outside air held by the image forming apparatus or humidity at a predetermined position in the image forming apparatus, and the temperature detected by the plurality of temperature detection means of the fixing device. In addition, the target control temperature of the fixing device is corrected in accordance with the humidity detected by the detecting means included in the image forming apparatus.
Considering the outside air or humidity in the image forming apparatus, temperature correction can be performed according to the toner or the moisture content of the transfer paper, which affects the fixability and curling of the transfer paper. A stable image can be provided by adjusting the amount of heat generated to an optimum value.

  The present invention is characterized in that the fixing device has a fixing belt at least as a fixing means. Energy saving can be achieved by using a fixing belt having a small heat capacity as the fixing means.

The present invention is characterized in that the image forming apparatus performs temperature correction for changing a target control temperature of the fixing device to a predetermined value in accordance with a difference between temperatures detected by the plurality of temperature detecting units.
By detecting the temperature of a plurality of parts and taking the difference between them, a temperature rise at a predetermined position in the image forming apparatus that is not affected by environmental changes can be detected, and the temperature rise of the part that affects fixing is corrected in real time. Can provide stable image quality.

The present invention provides a target of the fixing device based on a difference between a temperature detected by the plurality of temperature detection units when the power is turned on and a temperature detected by the plurality of temperature detection units when a print job is started. The temperature correction is performed to change the control temperature to a predetermined value.
By taking the difference between the temperature detected when the power is turned on and the temperature detected at the start of the printing operation, the outside air temperature before being affected by the temperature rise of the image forming apparatus can be compared with the temperature inside the image forming apparatus. A stable image can be provided by correcting the amount of heat given to the received image and the transfer paper more accurately to the optimum value.

According to the present invention, the target control temperature of the fixing device is predetermined according to a value obtained by dividing the difference between the temperatures detected by the plurality of temperature detection units by the elapsed time from the power-on to the start of the printing operation. It is characterized in that temperature correction is performed to change the value to.
The elapsed time from the power-on to the start of the printing operation is the time obtained by repeating the printing operation several times including the standby time since the power-on. Since the temperature correction is performed based on the value obtained by dividing the differential temperature by the elapsed time from power-on to the start of the printing operation, the temperature correction can be performed based on the rate of temperature increase over time. The temperature can be corrected considering the usage frequency.

According to the present invention, the image forming apparatus responds to both the temperature of the outside air in which the image forming apparatus is held or the temperature detected by at least one temperature detecting means in the image forming apparatus and the temperature difference between them. The temperature correction is performed to change the target control temperature of the fixing device to a predetermined value.
Since the amount of heat stored in the transfer paper or toner differs depending on the temperature of the outside air itself, more accurate temperature correction can be performed by changing the temperature correction amount using both the absolute value of the detected temperature and the difference temperature.

The present invention is characterized in that the image forming apparatus performs temperature correction for changing a target control temperature of the fixing device to a predetermined value in accordance with a speed at which an unfixed image is fixed.
Since the nip time varies depending on the speed at which the recording medium is fixed, the required heat amount is different, and the temperature correction amount is also different. Therefore, the correction can be performed more accurately by correcting each speed.

By means for solving the above-mentioned problems, in the present invention, by performing control to correct the fixing temperature by detecting the environment over time in addition to during standby, the fixing property is good and paper curling does not occur after fixing. It was possible to provide an image forming apparatus capable of obtaining stable fixing properties.

The best mode for carrying out the present invention will be described below with reference to FIGS. However, these are merely embodiments, and do not limit the scope of the claims of the present invention.

FIG. 1 is a schematic configuration diagram of an image forming apparatus.
In FIG. 1, an image forming apparatus 20 includes the following apparatuses. Image forming devices 21C, 21Y, 21M, and 21Bk that form images of respective colors according to the original image, transfer devices 22 that are arranged to face the image forming devices 21C, 21Y, 21M, and 21Bk, and the respective image forming devices The devices 21C, 21Y, 21M, and 21Bk and the transfer device 22 are conveyed from the manual feed tray 23, the paper feed cassette 24, and the paper feed cassette 24 as sheet-like medium supply means for supplying various sheet-like media to the transfer area where the transfer device 22 faces. And a fixing roller 1 for fixing the sheet-like medium after transfer in the transfer region. The registration roller 30 supplies the sheet-like medium in accordance with the timing of image formation by the image forming apparatuses 21C, 21Y, 21M, and 21Bk. ing.
Each of the image forming devices 21C, 21Y, 21M, and 21Bk performs development of each color of cyan, yellow, magenta, and black. The configuration of the image forming device 21C will be described as a representative of the image forming devices 21C, 21Y, 21M, and 21Bk. The image forming device 21C includes a photosensitive drum 25C as an electrostatic latent image carrier, a charging device 27C arranged in order in the clockwise direction in the drawing, which is the rotational direction of the photosensitive drum 25C, and a developing device. 26C and a cleaning device 28C, and a well-known configuration is used that receives exposure light from the writing device 29 between the charging device 27C and the developing device 26C. In addition to the drum shape, the electrostatic latent image carrier may have a belt shape.
The image forming apparatus 20 includes temperature sensors 31 and 32 and a humidity sensor 33. The temperature sensor 31 is installed for the purpose of observing the temperature rise inside the image forming apparatus. In the present embodiment, the temperature sensor 31 is installed on the side surface of the writing device 29 on the fixing side. You may install in the appropriate position near. The temperature sensor 32 is installed around the outer wall of the image forming apparatus 20 that is not easily affected by the temperature rise inside the image forming apparatus.

FIG. 2 is a side view of the belt fixing device.
In FIG. 2, a fixing device 1 includes an endless fixing belt 2 for conveying a sheet-like medium on which toner is fixed, a heating roller 3 and a fixing roller 4 around which the fixing belt 2 is stretched, and a fixing belt 2. Pressure roller 5 disposed opposite to fixing roller 4, heater 6 for heating roller, heater 7 for pressure roller 5, fixing belt 2, and pressure roller 5. As a temperature detecting means for detecting the above, a fixing belt side temperature sensor 13 and a pressure roller side temperature sensor 14 are provided.
The fixing belt 2 applies an appropriate predetermined tension to the fixing belt 2 by urging the tension roller 120 from the inside of the fixing belt 2 by an elastic body (not shown) such as a spring.
The fixing roller 4 includes a cored bar 9 and a heat-resistant porous layer heat insulating layer 10 that covers the cored bar 9. The fixing roller 4 is urged in a direction to come into pressure contact with the pressure roller 5 by an elastic body (not shown) such as a spring. The guide 12 guides the sheet-like medium P to be fixed toward the first fixing unit.
The minute amount oil application roller 121 is brought into contact with the pressure roller 5 by an elastic body (not shown) such as a spring, and for the purpose of improving the releasability between the fixing belt 2 and the toner, a small amount of silicon oil is applied to the fixing belt 2 and the pressure roller 5. It is applied to the surface. Further, the cleaning roller 122 is in contact with the surface of the minute amount oil application roller 121 for the purpose of preventing toner sticking on the surface of the minute amount oil application roller 121.
The belt and the pressure roller in the fixing device 1 are heated by the heating roller heater 6 and the pressure roller heater 7, respectively, and the fixing belt side temperature sensor 13 and the pressure roller side temperature sensor 14 applied to the belt and the pressure roller, respectively. It is controlled and heated so as to be maintained at the target control temperature. The image forming apparatus has two modes of 600 dpi and 1200 dpi as the resolution of the print image, and each has a black single color mode and a full color mode, and thus has a total of four modes. When a print request is sent to the control unit, the fixing device can arbitrarily set a target control temperature so as to obtain an optimum image for the mode to which the print request belongs. For example, the target control temperature on the belt side is controlled to 170 ° C. for a black monochrome 600 dpi print request, and to 155 ° C. for a full color 600 dpi print request. Further, the target control temperature on the pressurization side is set 15 ° C. to 30 ° C. lower than the target control temperature on the belt side.

FIG. 3 is a diagram illustrating the operation of the control unit.
This control can be performed by returning the output value of the humidity sensor 33 to the control unit in addition to the temperature sensors 31 and 32 at the time when the print request is made, and flowing the target control temperature determined by these output values to the drive unit. it can.

FIG. 4 is a flowchart showing a flow from when a print request is sent to the control unit to when fixing is started.
Hereinafter, temperature correction control will be described by taking as an example a case where a black monochrome 600 dpi print request is received. In the other modes as well, whether or not temperature correction is performed is similarly determined, and control is performed with a temperature correction amount corresponding to each.
When a print request is sent to the control unit, the output values T1 and T2 of the temperature sensors 31 and 32 at that time are acquired (step 1). Next, the difference ΔT between the previously acquired temperatures T1 and T2 is acquired by ΔT = T1−T2 (step 2).
The magnitude relationship between the temperature of ΔT and an arbitrarily set threshold temperature (5 ° C. in this embodiment) is compared (step 3). When ΔT <5 ° C., the inside of the image forming apparatus is not warmed. It is determined that temperature correction is not necessary, and fixing is started with the target control temperature T = 170 ° C. (step 4).
When ΔT ≧ 5 ° C., the threshold Th that can be set to an arbitrary value is first compared with T2 (step 5). The correction amount for the target control temperature is changed based on the comparison determination result. T2 is installed on the outside air side of the image forming apparatus, and can be considered to be almost the outside air temperature. Therefore, when T2 is higher than Th (34 ° C. in this embodiment), it is considered that the transfer paper is sufficiently warmed, and it is necessary to greatly reduce the fixing temperature, and when T2 is lower than Th, the target is set. It is determined that it is not necessary to correct the control temperature too much.
Subsequently, the magnitude relationship between the temperature of ΔT and a threshold temperature that can be arbitrarily set (in this embodiment, 10 ° C.) is compared (step 6a or step 6b), and when T2 <Th and ΔT <10 ° C. When the correction amount Ta (step 7), T2 <Th and ΔT> 10 ° C., the correction amount Tb (step 8), when T2> Th and ΔT <10 ° C., the correction amount Tc (step 9), T2> Th and When ΔT> 10 ° C., temperature correction is performed with the correction amount Td (step 10). For example, when T2 <Thh and ΔT <10 ° C., fixing is started by changing the target temperature control to 170 ° C.−Ta. This determination is made again when the print request is completed and the next print request is received. As a result, it is possible to set the optimum fixing heat amount in consideration of the temperature rise in the image forming apparatus at the time when a print request is made.
As described above, since the target control temperature of the fixing device is different for each print request mode (for example, monochrome, full color, 600 dpi, 1200 dpi), the above-described temperature correction amounts can be individually set.
In this embodiment, the difference temperature ΔT is obtained in step 2 of FIG. 4 and used as a threshold value for whether or not temperature correction is performed. The difference temperature ΔT is obtained by dividing the difference temperature ΔT by the time from when the power is turned on until a print request is received. It can also be used as a threshold. It is also possible to use a value obtained by subtracting T2 from the output value T1 of the temperature sensor 31 at the time of a print request, by storing the value T2 of the temperature sensor 32 when the power is turned on in the control unit. Although the temperature sensor 32 is attached to the periphery of the outer wall of the image forming apparatus, the temperature may increase due to heat transfer or heat conduction such as convection, and the outside air temperature and the output value of the temperature sensor 32 are Since there is a possibility of divergence, the value at the time of power-on that is not easily affected is used for control.

Although not mentioned in the present embodiment, the humidity sensor 33 is used to change the temperature correction amount according to the outside air that greatly affects the moisture content of the transfer paper or the humidity in the image forming apparatus. You can also. In this case, as shown in FIG. 3, the output value of the humidity sensor 33 is returned to the control unit in addition to the temperature sensors 31 and 32 at the time of the print request, and the target control temperature determined by these output values is driven. This control can be performed by flowing it through the section.

FIG. 5 is a diagram showing a graph of the temperature transition in the apparatus from power ON.
FIG. 5 shows an example of a graph of the temperature transition in the apparatus with respect to the time from power ON. The temperature of the temperature sensor 31 on the side close to the fixing device 1 increases with the time since the power is turned on, and conversely, the temperature of the temperature sensor 32 near the outer wall does not increase so much, so the difference ΔT increases. In this embodiment, the threshold values for whether or not temperature correction is performed are set to ΔT = 5 ° C. and ΔT = 10 ° C., but the desired threshold values are set according to the configuration of the image forming apparatus 20 and the position of the temperature sensor. be able to.

1 is a schematic configuration diagram of an image forming apparatus. It is a side view of a belt fixing device. It is the figure which showed the function of the control part. 6 is a flowchart showing a flow from when a print request is sent to a control unit to when fixing starts. It is the figure which showed the graph of the temperature transition in an apparatus after power ON.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing belt 3 Heating roller 4 Fixing roller 5 Pressure roller 6 Heating roller heater 7 Pressure roller heater 9 Core metal 10 Heat insulator layer 12 Guide 13 Fixing belt side temperature sensor 14 Pressure roller side temperature sensor 20 Image forming devices 21C to 21Bk Image forming device 22 Transfer device 23 Manual feed tray 24 Paper feed cassettes 25C to 25Bk Photosensitive drums 26C to 26Bk Developing device 27C Charging device 28C Cleaning device 29 Writing device 30 Registration roller 31 Temperature sensor 32 Temperature sensor 33 Humidity Sensor 120 Tension roller 121 Trace oil application roller 122 Cleaning roller

Claims (9)

Fixing means for fixing toner on the recording medium;
A fixing device having a first temperature detecting unit at a position where the thermal influence of fixing is large and a temperature detecting unit having a second temperature detecting unit at a position where the thermal influence of fixing is small;
In the image forming apparatus, the image forming apparatus includes a control unit that performs temperature correction based on the first and second temperature detecting units to change the target control temperature of the fixing unit to a predetermined value.
The image forming apparatus has detection means for detecting the temperature and / or humidity of the outside air held by the image forming apparatus and the temperature and / or humidity at a predetermined position in the image forming apparatus,
In accordance with the temperature detected by the temperature detecting means of the fixing device and the temperature and humidity detected by the detecting means of the image forming apparatus,
An image forming apparatus, wherein a target control temperature of the fixing device is corrected. The image forming apparatus has humidity detecting means for detecting the humidity of outside air held by the image forming apparatus or humidity at a predetermined position in the image forming apparatus,
In addition to the temperatures detected by the plurality of temperature detection means of the fixing device, according to the temperatures detected by the detection means of the image forming apparatus,
The image forming apparatus according to claim 1, wherein a target control temperature of the fixing device is corrected. The image forming apparatus has humidity detecting means for detecting the humidity of outside air held by the image forming apparatus or humidity at a predetermined position in the image forming apparatus,
In addition to the temperatures detected by the plurality of temperature detection means of the fixing device, according to the humidity detected by the detection means of the image forming apparatus,
The image forming apparatus according to claim 1, wherein a target control temperature of the fixing device is corrected. The image forming apparatus according to claim 1, wherein the fixing unit included in the fixing device includes a fixing belt. 5. The image forming apparatus according to claim 1, wherein the target control temperature of the fixing device is corrected to a predetermined value in accordance with a difference between temperatures detected by the plurality of temperature detecting units. The image forming apparatus described. The image forming apparatus determines a target control temperature of the fixing device based on a difference between a temperature detected by the plurality of temperature detection units at power-on and a temperature detected by the plurality of temperature detection units at the start of a printing operation. The image forming apparatus according to claim 1, wherein the image forming apparatus corrects the value to a value of. The image forming apparatus, according to a value obtained by dividing a difference in temperature detected by the plurality of temperature detection means by an elapsed time from power-on to the start of a printing operation,
The image forming apparatus according to claim 1, wherein a target control temperature of the fixing device is corrected to a predetermined value. The image forming apparatus is responsive to the temperature and / or humidity of the outside air held by the image forming apparatus, the temperature and / or humidity detected by the detection means in the image forming apparatus, and the difference between the temperature and / or humidity. The image forming apparatus according to claim 1, wherein the target control temperature of the fixing device is corrected to a predetermined value. The image forming apparatus according to claim 1, wherein the image forming apparatus corrects a target control temperature of the fixing device to a predetermined value in accordance with a speed at which an unfixed image is fixed. .

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