JP4615320B2 - Image forming apparatus and control method - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus used for a copying machine, a facsimile, a printer, a printing machine, and the like, and a control method thereof. Regarding the method.

In an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a printing machine, an unfixed image that is transferred and carried on a recording medium such as paper may be fixed to obtain a copy or a printed output.
An apparatus used for fixing has a configuration in which a pair of rollers are arranged to face each other, one roller is used as a heating roller, and the other roller is used as a pressure roller for a recording medium. In this configuration, the unfixed image is fused and fixed by the heat from the heating roller while the recording medium is nipped and conveyed in the nip portion between the heating roller and the pressure roller.

As a device used for fixing, there is a configuration in which a roller and a belt are combined in addition to the configuration described above. In this configuration, instead of the heating roller, a belt wound around a pair of rollers is used, and a pressure roller is opposed to one of the rollers.
Of the pair of rollers, the roller that drives the belt in cooperation with the roller on the side facing the pressure roller is provided with a heat source for heating from the back side of the belt. A heat source is provided for heating. The belt has a smaller volume and a smaller heat capacity than the roller, so that the temperature can be increased for a short time, and the temperature rise at the start-up is faster than the configuration using only the heating roller and the pressure roller described above. There is. In addition, by applying a heat source with a pressure roller, the temperature rise is accelerated on both the front and back sides of the belt.

When aluminum having a high thermal conductivity is used for each roller as a constitution of the belt, stainless steel is used as a base in contact with the roller surface, and a belt body made of a release layer made of silicon rubber or fluorine resin is arranged on the surface 2. There is a layer structure.
It is well known that the temperature of the fixing member is achieved by controlling the heating of the heater so as to be detected by the temperature detecting means and maintain the target temperature.

However, the recording medium to be fixed is affected by the storage environment and the temperature is not constant. Since the required amount of heat changes depending on the temperature at which the recording medium is fixed, it is often proposed to detect the external environment and control the fixing temperature, and Patent Document 1 is an example.
According to Patent Document 1, the temperature sensor provided in the image forming apparatus room is disposed at a position that is not easily affected by the heat generated by the fixing unit. Since the temperature cannot be detected, the value of this sensor is not used after starting Job. During standby, the fixing temperature is corrected based on environmental temperature detection. Moreover, the specific position is not disclosed by the sensor.

If the fixing temperature is not corrected by detecting the environment at the initial power-on or job initial temperature, even if the temperature of the transfer paper before feeding does not change, the temperature rises around the fixing unit and the conveyance path. The amount of heat applied to the transfer paper at the time of fixing entered became excessive, causing a problem of curling after fixing. The curl leads to stitching and misalignment at the finisher.

Japanese Patent Laid-Open No. 10-39672

In view of the above problems, an object of the present invention is to provide an image forming apparatus that has good fixability and no transfer paper curl.

As means for solving the above problems, the present invention has the following features.
The image forming apparatus of the present invention is an image forming apparatus in which an unfixed image formed on a recording medium is fixed by passing through a fixing nip formed by at least two fixing members and heating and pressing. The first temperature detecting means and the sheet feeding conveyance upstream of the fixing nip have a configuration capable of controlling at least one of the fixing members to a target temperature and having a large heat influence of the fixing. A second temperature detection unit is provided at a position where the thermal influence of the path is small, and the fixing target temperature is determined based on the difference ΔT between the temperature acquired by the first temperature detection unit and the temperature acquired by the second temperature detection unit. an image forming apparatus for changing, when said inside the image forming apparatus ΔT is less than the temperature that is determined not to warm, the fixing target temperature is controlled to be higher, the image forming apparatus When the [Delta] T the temperature rises and becomes large, the fixing temperature was controlled to lower according to the value of [Delta] T, the temperature variation of the fixing target temperature, depending on the size of the recording medium carrying an unfixed image characterized in that it change Te.
In the image forming apparatus of the present invention, the image forming apparatus further changes the temperature change amount according to a paper type or a paper thickness of a recording medium carrying an unfixed image.
In the image forming apparatus according to the aspect of the invention, the image forming apparatus may further change the temperature change amount according to a paper supply source that supplies the recording medium.
In the image forming apparatus of the present invention, the image forming apparatus further changes the temperature correction in accordance with a paper discharge destination to which the recording medium is discharged.
In the image forming apparatus of the present invention, the temperature correction is not performed for a predetermined time when the image forming apparatus is powered on or returned, and the temperature correction is performed after a predetermined time has elapsed. .
In the image forming apparatus of the present invention, the temperature correction is not performed for a predetermined time when the temperature detected by the fixing member is equal to or lower than a predetermined temperature when the image forming apparatus is powered on or returned. after a predetermined time has elapsed you and performs the temperature correction.
In the image forming apparatus of the present invention, the image forming apparatus further includes an endless fixing belt for conveying a recording medium, a heating roller and a fixing roller around which the fixing belt is wound, and the fixing belt. A pressure roller disposed opposite to the fixing roller, and the recording medium conveying member is the fixing belt and / or the pressure roller.

The control method of the present invention is an image forming method in which an unfixed image formed on a recording medium is fixed by passing through a fixing nip formed by at least two fixing members and heating and pressing. The first temperature detecting means and the sheet feeding conveyance path upstream of the fixing nip have a configuration capable of controlling at least one of the fixing members to a target temperature and having a large heat influence of fixing. The second temperature detecting means is provided at a position where the heat influence of the temperature is small, and the fixing target temperature is changed based on the difference ΔT between the temperature acquired by the first temperature detecting means and the temperature acquired by the second temperature detecting means. a control method for, when the ΔT than the temperature inside the image forming apparatus is determined not to warm is small, the fixing target temperature controlled to be higher, the temperature inside the image forming apparatus When [Delta] T becomes large by raising the controls to lower the fixing temperature depending on the value of [Delta] T, the temperature variation of the fixing target temperature, varying according to the size of the recording medium carrying an unfixed image It is characterized by changing.
In the control method of the present invention, the control method is characterized in that the temperature change amount is changed according to a paper type or a paper thickness of a recording medium carrying an unfixed image.
In the control method of the present invention, the control method further changes the amount of temperature change in accordance with a paper supply source that supplies the recording medium.
In the control method of the present invention, the control method is characterized in that the temperature correction is changed in accordance with a paper discharge destination for discharging the recording medium.
In the control method of the present invention, the control method may further include performing the temperature correction after a predetermined time has elapsed without performing the temperature correction for a predetermined time when the image forming apparatus is turned on or restored. Features.
In the control method of the present invention, the control method may further include performing the temperature correction for a predetermined time when the temperature detected by the fixing member is equal to or lower than a predetermined temperature when the image forming apparatus is turned on or restored. without, you and performs the temperature correction after the lapse of a predetermined time.
In the control method of the present invention, the control method further includes an endless fixing belt for conveying a recording medium, a heating roller and a fixing roller around which the fixing belt is wound, and the fixing via the fixing belt. A pressure roller disposed opposite to the roller, and the recording medium conveying member is the fixing belt and / or the pressure roller.

The present invention compares the temperatures detected by a plurality of sensors in the image forming apparatus and corrects the target control temperature based on the result. The target control temperature is corrected by using the differential temperature of a plurality of sensors, so that the temperature rise in the image forming apparatus can be detected, and the entire fixing device or the entire image forming apparatus is heated It is possible to predict an increase in the amount of heat at the time, and it is possible to perform optimum temperature correction.
Further, by considering the humidity of the outside air, it is possible to perform temperature correction in consideration of the influence of moisture content that affects fixing. By combining this invention and fixing with a belt having a low heat capacity, energy saving and stable fixing are realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing one of image forming apparatuses to which a fixing device according to an embodiment of the present invention is applied. The image forming apparatus shown in FIG. 1 is used as a copying machine or a printer capable of forming a full-color image. In addition to this, there is a facsimile apparatus capable of performing the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image. The image forming apparatus 20 shown in FIG. 1 sequentially transfers images for each color separation to the same intermediate transfer member, and collectively transfers the images superimposed on the intermediate transfer member onto a sheet-like recording medium such as paper. The method is used.

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 disposed to face the image forming devices 21C, 21Y, 21M, and 21BK, and the respective image forming devices Manual feed tray 23, sheet feeding cassettes 24, 24, manual feed tray 23, paper feed as a sheet-like medium feeding means for feeding various sheet-like media to the transfer area where the devices 21C, 21Y, 21M, 21BK and the transfer device 22 face each other. A registration roller 30 that supplies the sheet medium conveyed from the paper cassettes 24 and 24 in accordance with the timing of image formation by the image forming apparatuses 21C, 21Y, 21M, and 21BK, and fixing of the sheet medium after transfer in the transfer region. And a fixing device 1 for performing the above.

The image forming apparatus 20 is a plain paper (hereinafter simply referred to as plain paper) generally used for copying and the like, an OHP sheet, a card, a postcard, 90 K paper, a thick paper having a basis weight of about 100 g / m ² or more, an envelope, and the like. Any of the so-called special sheets (hereinafter simply referred to as “special sheets”) having a larger heat capacity than the paper can be used as the sheet-like medium.

Each of the image forming devices 21C, 21Y, 21M, and 21BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors, but the configuration is the same. The configuration of 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.

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. Via the pressure roller 5 disposed opposite to the fixing roller 4, the heating roller 3, the heaters 6 and 7 provided inside the pressure roller 5, the fixing belt 2, and the pressure roller 5. The belt side thermistor 13 and the pressure side thermistor 14 are provided as temperature detecting means for detecting the respective temperatures.
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 elastic body 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. Reference numeral 12 denotes a guide for guiding the sheet-like medium P to be fixed toward the first fixing unit.
The minute application roller 121 is brought into contact with the pressure roller by an elastic body (not shown) such as a spring, and a small amount of silicon oil is applied to the surfaces of the fixing belt 2 and the pressure roller 5 for the purpose of improving the releasability between the fixing belt 2 and the toner. It is applied to. A cleaning roller 122 is brought into contact with the surface of the minute amount oil application roller 121 for the purpose of preventing toner adhesion on the surface of the minute amount application roller 21.

Hereinafter, the temperature correction control will be described by taking as an example a case where a black monochrome print request is received. Similarly, in the case of other full color modes, the presence / absence of temperature correction is similarly determined, and control is performed with a temperature correction amount corresponding to each.
The flow from when a print request is sent to the control unit until the start of fixing will be described with reference to the flowchart of FIG. 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. Subsequently, the difference ΔT between the previously acquired temperatures T1 and T2 is acquired by ΔT = T1−T2.
The magnitude relationship between the temperature of ΔT and the threshold temperature that can be arbitrarily set (5 ° C. in this embodiment) is compared. When ΔT <5 ° C., the image forming apparatus is not warmed and temperature correction is required. Therefore, fixing is started with the target control temperature Tcont = 170 ° C.
When ΔT ≧ 5 ° C., the threshold value Th that can be set to an arbitrary value is first compared with T2. 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. When T2 <Th and ΔT <10 ° C., the correction amount Ta, T2 <Th When ΔT> 10 ° C., the temperature is corrected with the correction amount Tb. When T2> Th and ΔT <10 ° C., the correction amount Tc. When T2> Th and ΔT> 10 ° C., the temperature correction is performed with the correction amount Td. For example, when T2 <Th and ΔT <10 ° C., fixing is started by changing the target temperature control to (170 ° C.−Ta) ° C. 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.

In the present invention , the correction amount Tx (x is a, b, c, d) is changed for each paper size. The smaller size fixing device without an end heater is more likely to curl due to an increase in the temperature at the end in the axial direction . The paper size may be calculated as an area, or may be a length in the transport direction or a length in the direction perpendicular to the transport direction. A more stable image can be provided by performing temperature correction in accordance with the size of the recording medium.

In the present invention , the correction amount is changed according to the paper type and paper thickness. A paper thickness of up to 100 g / m ² is set to the same productivity as plain paper, and fixing is performed at the same speed, so that the amount of heat is likely to be insufficient. Since thick paper is difficult to curl, it is effective not to perform correction. A more stable image can be provided by performing temperature correction according to the paper type and paper thickness of the recording medium.

In the present invention , the correction amount is changed depending on the paper supply source. For example, the paper in the manual feed tray is more adapted to the environment than the main body, and correction different from that of the main body tray is necessary. A more stable image can be provided by performing temperature correction in accordance with the paper supply source of the recording medium.

In the present invention , the correction amount is changed depending on the paper discharge destination. Since there is room for curling in the main body, the correction can be turned off with emphasis on fixability, and the correction amount can be increased because there is no curl margin when the finisher discharges paper (Table 3). Since the recording medium transport path and distance differ depending on the discharge destination, the amount of heat received from the image forming apparatus and other influences (stresses) change, and a more stable image is provided by performing temperature correction accordingly. can do.

Next, the invention regarding the exclusion of this correction will be described.
Due to the recent energy-saving design concept, when not in use (leaved), in a certain time, the low power mode (= in the apparatus of this embodiment, the pressure roller temperature with a large heat capacity is about 40 degrees from the normal standby temperature. After that, the mode shifts to the sleep mode (the fixing heater is turned off but the CPU is alive). In this case, the temperature detection unit 1 is in a state where the temperature is high and the temperature detection unit 2 is low, that is, a state where correction is executed (FIGS. 4 and 5). However, correction is not preferable for fixing because it is cold. That is, it has been found that if the correction unit is turned on before the fixing unit warms up not only the surface of the member but also the metal such as the core, the fixing is defective. This is because even when the temperature of the temperature detection means 1 is left unattended, it becomes higher due to overshoot for a certain period of time. In the present invention, due to this problem, an exclusion time is provided.

In the present invention, the warm-up control is further performed at the time of power-on, toner end or jam recovery error recovery, and low power mode recovery.At that time, the pressure roller temperature is detected and the fixing state is determined by a threshold value. Judgment is made to decide whether or not to shift to control of correction judgment (in the flow of FIG. 3, “term of pressure 60 ° C.”).
In a state where the entire fixing unit is at a low temperature, the fixing property is not sufficient, and it is necessary to recover from the cold state until the entire fixing unit is warmed and sufficient fixing property can be obtained. According to the present invention, by providing an exclusion time during which the above-described temperature correction is not performed for a predetermined time, accurate correction is possible, and a stable image can be provided.

In the present invention , the correction threshold value and the exclusion time are changed according to the temperature when the power is turned on, so that more accurate correction can be performed, and a stable image that can be corrected with high accuracy can be provided. Can do.
According to the present invention , since the belt fixing system is used, the rise time can be shortened.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating an embodiment of a fixing unit according to the present invention. FIG. 3 is a control flow diagram from power ON to fixing start in the image forming apparatus of the present invention. FIG. 6 is a diagram illustrating changes in temperature and pressure conditions of the fixing device when the image forming apparatus of the present invention is left for 2.5 H from early morning. It is a figure which shows transition of the output value of a temperature sensor at the time of leaving the image forming apparatus of this invention for 2.5H from early morning.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing belt 3 Heating roller 4 Fixing roller 5 Pressure roller 6, 7 Heater 9 Core 10 Thermal insulator layer 12 Guide 13 Belt side thermistor 14 Pressure side thermistor 20 Image forming device 21 Image forming device 22 Transfer device 23 Manual feed Tray 24 Paper feed cassette 25 Photosensitive drum 26 Developing device 27 Charging device 28 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 P Sheet-like medium

Claims (14)

An image forming apparatus for fixing an unfixed image formed on a recording medium by passing through a fixing nip formed by at least two fixing members and heating and pressurizing, wherein at least one of the fixing members The first temperature detecting means and the position where the thermal effect of the paper feed path upstream of the fixing nip is small where the thermal effect of the fixing is large and the one is controlled to the target temperature. In the image forming apparatus, the second temperature detection unit is provided, and the fixing target temperature is changed based on a difference ΔT between the temperature acquired by the first temperature detection unit and the temperature acquired by the second temperature detection unit .
When ΔT is smaller than the temperature at which it is determined that the inside of the image forming apparatus is not warmed, the fixing target temperature is controlled to be higher,
When the temperature in the image forming apparatus rises and ΔT increases, control is performed to lower the fixing temperature according to the value of ΔT,
The temperature variation of the fixing target temperature, the image forming apparatus, characterized in that the change in accordance with the size of the recording medium carrying an unfixed image. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the temperature change amount is changed according to a paper type or a paper thickness of a recording medium carrying an unfixed image. The image forming apparatus according to claim 1, wherein
The image forming apparatus changes the temperature change amount according to a paper supply source that supplies a recording medium. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the temperature correction is changed in accordance with a paper discharge destination for discharging the recording medium. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the temperature correction is not performed for a predetermined time when the image forming apparatus is turned on or returned, and the temperature correction is performed after a predetermined time has elapsed. The image forming apparatus according to claim 1,
When the image forming apparatus is powered on or returned, when the temperature detected by the fixing member is equal to or lower than a predetermined temperature, the temperature correction is not performed for a predetermined time, and the temperature correction is performed after a predetermined time has elapsed. An image forming apparatus. The image forming apparatus according to claim 1,
The image forming apparatus is arranged to face an endless fixing belt for conveying a recording medium, a heating roller and a fixing roller around which the fixing belt is wound, and the fixing roller via the fixing belt. An image forming apparatus comprising: a pressure roller, wherein the recording medium conveying member is the fixing belt and / or the pressure roller . An image forming method for fixing an unfixed image formed on a recording medium by passing through a fixing nip formed by at least two fixing members and heating and pressurizing, wherein at least one of the fixing members The first temperature detecting means and the position where the thermal effect of the paper feed path upstream of the fixing nip is small where the thermal effect of the fixing is large and the one is controlled to the target temperature. A control method of providing a second temperature detection means and changing the fixing target temperature based on a difference ΔT between the temperature acquired by the first temperature detection means and the temperature acquired by the second temperature detection means;
When ΔT is smaller than the temperature at which it is determined that the inside of the image forming apparatus is not warmed, the fixing target temperature is controlled to be higher,
When the temperature in the image forming apparatus rises and ΔT increases, control is performed to lower the fixing temperature according to the value of ΔT,
The temperature change amount of the fixing target temperature is changed according to the size of the recording medium carrying the unfixed image.
A control method characterized by that. The control method according to claim 8, wherein
The control method changes the temperature change amount according to a paper type or a paper thickness of a recording medium carrying an unfixed image.
A control method characterized by that. The control method according to claim 8 or 9,
The control method changes the temperature change amount according to a paper supply source that supplies a recording medium.
A control method characterized by that. The control method according to any one of claims 8 to 10 ,
The control method is characterized in that the temperature correction is changed according to a paper discharge destination for discharging the recording medium . The control method according to any one of claims 8 to 11 ,
The control method is characterized in that, when the image forming apparatus is powered on or restored, the temperature correction is not performed for a predetermined time, and the temperature correction is performed after a predetermined time has elapsed . The control method according to any one of claims 8 to 12,
The control method does not perform the temperature correction for a predetermined time when the temperature detected by the fixing member is equal to or lower than a predetermined temperature when the image forming apparatus is turned on or restored, and after a predetermined time has elapsed. A control method comprising performing the temperature correction . The control method according to any one of claims 8 to 13,
The control method includes an endless fixing belt for conveying a recording medium, a heating roller and a fixing roller around which the fixing belt is wound, and an additive disposed so as to face the fixing roller via the fixing belt. A control method comprising: a pressure roller, wherein the conveyance member for the recording medium is the fixing belt and / or the pressure roller .

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