JP2000181277A - Image forming apparatus and heat fixing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diminish the temperature difference between a heating roller and a pressurizing roller and to prevent the curling of recording paper by a control means which controls an auxiliary heating means to a first temperature in the state that an image forming signal is not emitted and to a second temperature higher than the first temperature in the state that image formation is started. SOLUTION: The supply of electric power to a heat source H2 of the auxiliary heating roller 13 for heating the pressurizing roller 12 is controlled according to environment conditions. The setting of a control level is executed by the environmental conditions detected by a sensor S3 after the start of the operation of the image forming apparatus by on of a main switch. For example, under the prescribed environment conditions, i.e., at temp. >=25 deg.C and relative humidity >=70%, the temperature of the auxiliary heating roller 13 is set under such conditions A under which the temperatures during idling and during image formation are respectively 200 deg.C and 230 deg.C. Except under the prescribed environmental conditions, the temperature of the auxiliary heating roller 13 is set under such conditions B under which the temperatures during idling and during image formation are respectively 160 deg.C and 190 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an improvement of a fixing device in an image forming apparatus for forming an image by an electrophotographic method.

[0002] An image forming apparatus according to the present invention is used for a copying machine, a facsimile, a printer and the like.

[0003]

2. Description of the Related Art As the above-mentioned fixing device, a contact heating type heat fixing device for heating and fixing a toner image in contact with a toner image is widely used, and further, a heating roller and a pressure roller carry the toner image. A heat fixing device that heats and fixes a toner image while nipping and transporting the recording paper is most widely used.

[0004] As a problem in fixing the recording paper by heating the recording paper, there is a problem of deformation of the recording paper due to heat, particularly curling. The recording paper that has passed through the heating and fixing device is curled, and the recording paper such as a sorter or a finisher is curled. Inconveniences such as poor conveyance in the post-processing device and irregularities in the paper discharge tray occur.

As a countermeasure against such a problem of curling of the recording paper, a means for squeezing the recording paper that has passed through the heat fixing device has been adopted. There is also a proposal to heat the pressure roller in order to increase the temperature of the pressure roller facing the heating roller.

[0006]

The above-mentioned means for treating the recording paper to eliminate the curl is to apply a bending force to only one side of the recording paper. It is effective against curls, but has the disadvantage that the curl is further increased for curls in the other opposite direction of the recording paper and is not effective for all curls. There is also a problem that the curl preventing means does not work effectively depending on the degree of curl.

[0007] A proposal for curling prevention, in which the pressure roller is heated to remove the curl, is based on the fact that there is a difference in temperature between the heating roller and the pressure roller. This is a measure focusing on a curl generation mechanism that causes curl to occur, and reduces the temperature difference between the heating roller and the pressure roller.

Although the latter countermeasures against curling have been proposed in public publications and the like, research for implementation has not been advanced, and there are various problems in implementation.

The first problem is that when the pressure roller is heated, the pressure roller is deteriorated by heat.
That is, when fixing is performed by heating only the heating roller without heating the pressure roller, a difference of 100 ° C. or more occurs between the surface temperature of the heating roller and the surface temperature of the pressure roller. When the pressure roller is heated to a high temperature in order to reduce this temperature difference, the pressure roller, particularly silicon rubber which forms the surface layer of the pressure roller, is deteriorated by heat, and the heat fixing device is heated. Life is shortened.

Second, energy consumption increases due to the addition of auxiliary heating means for heating the pressure roller.

The third problem is that toner, paper powder and the like adhere to the auxiliary heating means for heating the pressure roller, thereby lowering the heating efficiency of the auxiliary heating roller and making it difficult to control the temperature of the auxiliary heating roller. It is a problem.

Accordingly, an object of the present invention is to solve the above-mentioned problem in the technology for preventing the curling of the recording paper by heating the pressure roller and reducing the temperature difference between the heating roller and the pressure roller. The purpose is to:

[0013]

SUMMARY OF THE INVENTION An object of the present invention to solve the first problem is to provide a heating roller, a pressure roller which presses against the heating roller, and a pressure roller which comes into contact with the surface of the pressure roller. An auxiliary heating unit for heating the roller, a control unit for controlling the temperature of the auxiliary heating unit, and a heating and fixing device for fixing the toner image while conveying the recording paper by driving the heating roller and the pressure roller. An image forming apparatus, wherein the control unit controls the auxiliary heating unit to a first temperature in a first control in a state where no image forming signal is output and a state in which the auxiliary heating unit is started due to an image forming start signal. The second control is achieved by an image forming apparatus which controls the second temperature to be higher than the first temperature.

An object of the present invention to solve the above second problem is to provide a heating roller having a heat source for heating and fixing a toner image in contact with a recording paper, a pressure roller for pressing against the heating roller,
A heat fixing device having a heat source, having an auxiliary heating means for heating the pressure roller in contact with the surface of the pressure roller, and a control means for controlling the temperature of the auxiliary heating means, and detecting environmental conditions An image forming apparatus including an environmental condition detecting unit, wherein the control unit controls the heat source of the auxiliary heating unit based on information from the environmental condition detecting unit. Achieved.

An object of the present invention to solve the third problem is to provide a heating roller having a heat source for heating and fixing, a pressing roller in pressure contact with the heating roller, and a heating roller in contact with the surface of the pressing roller. This is achieved by a heat fixing device having an auxiliary heating unit that heats a pressure roller, wherein a cleaning unit is provided in at least one of the pressure roller and the auxiliary heating unit. You.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below. FIG. 1 is a sectional view of a heat fixing device incorporated in an image forming apparatus according to an embodiment of the present invention.

1 is a frame that forms the outer shape of the heat fixing device, 2
Is an upper entry guide plate, 3 is a lower entry guide plate, 4 is an upper discharge guide plate, and 5 is a lower discharge guide plate. Reference numeral 6 denotes an upper separating claw for separating the recording paper from the heating roller 10, and reference numeral 7 denotes a lower separating claw for separating the recording paper from the pressing roller 12.

A heating roller 10 is provided with a heat source H1 composed of two halogen lamps at the center. The heating roller 10 includes a core metal 101 made of an aluminum alloy and a heat-resistant release layer 102 made of PFA (tetrafluoroethylene / perfluoroalkylvinyl ether copolymer) or tetrafluoroethylene resin forming a surface layer. 1
Reference numeral 2 denotes a pressure roller that is in pressure contact with the heating roller 10 and includes a core metal 121 made of an aluminum alloy and a heat-resistant elastic layer 122 made of silicon rubber formed outside the metal core 121. Reference numeral 13 denotes an auxiliary heating roller as an auxiliary heating unit that contacts the pressure roller 12 and heats the pressure roller 12, and is made of an aluminum alloy. At the center of the auxiliary heating roller 13, a heat source H2 composed of a halogen lamp is provided. As the auxiliary heating means in place of the auxiliary heating roller 13, any known heating means such as a heating roller having a sheet resistance heating element or a heating belt can be used.

Reference numeral 15 denotes a cleaning roller as cleaning means constituted by a cleaning web.
Reference numeral 6 denotes a take-up roller that takes up the cleaning web fed from the cleaning roller 15. S1 is a contact-type temperature sensor composed of a thermistor,
A surface temperature of 0 is detected. S2 is a contact-type temperature sensor composed of a thermistor, which detects the surface temperature of the auxiliary heating roller 13. It should be noted that a non-contact type sensor, that is, a sensor in which a heat-sensitive element is disposed in close contact with the roller surface in a non-contact manner can be used as the sensors S1 and S2, and a thermocouple can also be used as the heat-sensitive element. Reference numeral 14 denotes a cleaning pad for cleaning the surface of the auxiliary heating roller 13. A process in which the toner and paper dust on the heating roller 10 are cleaned by the cleaning roller 15, but the toner and paper dust attached to the pressure roller 12 are removed by the cleaning roller 15 after being transferred to the heating roller 10. Cleaning indirectly, but not enough. Then, the toner and paper powder adhering to the pressure roller 12 are removed by the auxiliary heating roller 1.
3 to cause problems such as lowering the sensitivity of the sensor S2 and lowering the conductivity of heat from the auxiliary heating roller 13 to the pressure roller 12. By cleaning the auxiliary heating roller with the cleaning pad 14, such a problem is solved. A heat-resistant felt is used for the cleaning pad 14.

As a cleaning means in place of the cleaning pad 14 as a cleaning means, any conventionally known cleaning means such as a cleaning roller and a cleaning web can be used.

In the heat fixing apparatus described above, an offset preventing agent applying means for applying an offset preventing agent such as silicone oil to the heating roller 10 may be provided.

In the heat fixing device shown in FIG. 1, the heating roller 10, the pressure roller 12, and the auxiliary heating roller 13 rotate in the directions indicated by the arrows, and enter from between the upper and lower entrance guide plates 2, 3. The heated recording paper is heated to fix the toner image. Cleaning roller 15 and take-up roller 16
Rotate at extremely low rotational speeds in the directions indicated by the arrows to remove paper dust adhering to the surface of the heating roller 10.

FIG. 2 is a block diagram showing functional units of the image forming apparatus according to the present embodiment.

The control unit CPU as control means includes information from the sensors S1, S2, and S3, information from the image forming unit PU for executing image forming steps such as charging, exposure, and development, and information from the operating unit OP. Information is entered.

The sensor S3 is a sensor for detecting environmental conditions. It is considered that the curling of the recording paper caused by the fixing process is mainly caused by the effect of the moisture contained in the recording paper and is caused by the following mechanism. With a heating roller having a heat source and a pressure roller without a heating source,
There is a difference in the surface temperature, and a temperature difference occurs between the front and back surfaces of the recording paper due to the temperature difference between these rollers. Due to such a temperature difference, the amount of moisture evaporating from the recording paper passing through the fixing device is different between the front surface and the back surface. The recording paper curls due to the difference in the amount of evaporated water. And
The water content of the recording paper depends on the environment where the recording paper is placed, that is, the temperature and humidity.

Therefore, in order to prevent curling, it is important to detect the environmental temperature and the humidity which influence the amount of water contained in the recording paper. The sensor S3 is a sensor for detecting the temperature and the relative humidity for this purpose, and is desirably installed at an appropriate position on the exterior part of the image forming apparatus. In the present embodiment, the environmental condition used for controlling the temperature of the auxiliary heating roller 13 is at least one of the temperature and the relative humidity.

In the present embodiment, the supply of electric power to the heat source H2 of the auxiliary heating roller 13 for heating the pressure roller 12 is controlled in accordance with environmental conditions, as described later. In a configuration in which a heat source is provided in the pressure roller 12, the core metal 1
21 and a thick heat-resistant elastic layer 122 to heat the pressure roller 12 having a large heat capacity, which consumes a large amount of power. However, as in the present embodiment, the surface of the pressure roller 12 is heated. The method saves a lot of power.
However, the heat source H2 of the auxiliary heating roller 13 is 2
A heater of about 00 W to 400 W is required, and it is desirable to further save power even when using the auxiliary heating roller 13 for heating the surface of the pressure roller 12. In the present embodiment, by detecting the environmental condition and supplying the necessary minimum power to the heat source H2 of the auxiliary heating roller 13,
Power consumption is being further reduced.

OP is an operation unit, and the control unit CPU receives an image formation start signal and the like by operating a copy button of the operation unit OP. CP is a computer as an external device, M
D is communication means for performing facsimile communication, and the control unit C
The PU also receives an image formation start signal from these functional units.

PU is an image forming section, which forms a toner image on a recording paper by charging, exposing, developing and transferring. A control unit CPU as a control means monitors and controls each of these functional units.

The control of the control unit CPU will be described with reference to the flowcharts shown in FIGS.

In FIG. 3, after the start, that is, the operation of the image forming apparatus is started by turning on the main switch, the sensor S
The control level is set based on the environmental condition detected by the control unit 3. For example, predetermined environmental conditions, that is, a temperature of 25 ° C.
When the relative humidity is 70% or more, the auxiliary heating roller 1
The temperature A during idling of the auxiliary heating roller 13 and the temperature during image formation are set to 160 during the idling of the auxiliary heating roller 13 and 160 ° C. under conditions other than the above-mentioned predetermined environmental conditions. ° C, 190 ° C
A control target value is set for each of the conditions B.

Next, a first control which is a control during idling, that is, a control after the main switch is turned on and in a standby state where image formation is not performed is performed. This control is shown in FIG.

In each of the heating roller 10 and the auxiliary heating roller 13, the heat sources H1 and H2 are controlled on / off based on the detected temperature information from the sensors S1 and S2. For the heat source H1, the upper limit is T _1MAX (20
5 ° C.) and the lower limit is set to T _1MIN (195 ° C.). Further, with respect to the heat source H2, under the condition A, the upper limit value is t _1MAX (205 ° C.), and the lower limit value is t _1MIN (195 ° C.).
In the condition B, the temperature control of the heat source H1 is the same as the condition A, the upper limit of the heat source H2 is t _1MAX (165 ° C.), and the lower limit is t
The first control of the target value of 160 ° C. to be _1MIN (155 ° C.) is performed. As is apparent from the figure, the condition setting may be changed due to a change in the environmental condition during idling.

The first control is a control during idling of the image forming apparatus. In the first control, the heating roller 10
The driving of the pressure roller 12 and the auxiliary heating roller 13 is not performed, and they are stopped.

An image forming signal is received, that is, the operation unit O
An image formation start signal by operating a copy button (not shown) of P, an image formation start signal from the computer CP, or an image formation start signal from the communication unit MD is transmitted to the control unit CPU.
Is accepted, the control is changed to the third control.

In the third control, the first control is continued for the heat source H1. That is, control is performed to set T _3MAX , T _3MIN and the control target value to 205 ° C., 195 ° C., and 200 ° C., respectively. The following control is performed on the heat source H2.

That is, under the condition A, the upper limit value is t
_3MAX (215 ° C.) and a lower limit of t _3MIN (205 ° C.), which is the second control with a target value of 210 ° C. Under condition B, t _1MAX and t _1MIN similar to those in the first control are _set as upper limits. This is the first control with the lower limit. In the third control, the heating roller 10, the pressure roller 12, and the auxiliary heating roller 13 are driven to rotate as indicated by arrows. However, in the third control, the recording paper is not conveyed to the heat fixing device. The third control is shown in FIG.

Next, when the image formation is started, the second control is performed. In the second control, as for the control of the heat source H1, the first and second controls are continued as they are. That is, T
_2MAX , _T2MIN and target values are 205 ° C and 195, respectively.
And 200 ° C. are controlled. For heat source H2, the upper limit is t _2MAX (235 ° C.) and the lower limit is t _2MIN
(225 ° C.) second control at a target value of 230 ° C. is performed.

In the second control, the heating roller 10, the pressure roller 12, and the auxiliary heating roller 13 are driven to rotate as indicated by arrows, and the recording paper is conveyed to the heat fixing device to perform fixing. The second control is shown in FIG.

The above upper and lower limit temperatures and the target temperature are merely examples, and optimal values are selected according to the configuration, material, purpose, etc. of the apparatus.

As described above, by controlling the temperature of the auxiliary heating roller 13 during idling, during the period from when the image formation start signal is received until the start of image formation, and during the image formation, the following effects can be obtained. Is obtained.

When the auxiliary heating roller 13 is heated to a high temperature during idling in which the pressure roller 12 and the auxiliary heating roller 13 do not rotate and come into contact with each other in a stationary state, the pressure roller 1
2 is locally degraded by heat, while the auxiliary heating roller 13 is kept at a relatively low temperature during idling, such thermal degradation is prevented, and the temperature of the auxiliary heating roller 13 during image formation is raised to a high temperature. By doing so, the difference between the surface temperature of the heating roller 10 and the surface temperature of the pressure roller 12 can be reduced, and curling of the recording paper can be effectively prevented. According to experiments, when the auxiliary heating roller 13 is not used, the surface temperature of the heating roller 10 and the pressure roller 12
The difference in surface temperature was 100 ° C. or more and the recording paper was curled. However, when the above control was performed using the auxiliary heating roller 13, the temperature difference was reduced to 50 ° C. or less, and Effectively prevented.

It should be noted that the above effect is the third effect in FIG.
The control target value of the heat source H2 of the auxiliary heating roller 13 in the control is made equal to the control target value in the second control, that is, the control during idling is set as the first control, and the control from the reception of the image formation start signal to the end of the image formation is performed. Is the second control 2
This can be sufficiently achieved by performing step control.

[0044]

Since the auxiliary heating means for heating the pressure roller is provided, the temperature difference between the heating roller and the pressure roller is reduced, and curling of the recording paper is effectively prevented. In addition, deterioration of the pressure roller due to heat generated by heating the pressure roller is prevented. In addition, since the heating of the surface of the pressure roller is controlled in accordance with each stage of the control of the image forming apparatus and the heating of the pressure roller is controlled in accordance with the environmental conditions, the power consumption is increased by adding the auxiliary heating roller. Is minimized and energy consumption is saved.

Further, by cleaning the toner and paper dust adhering to the auxiliary heating roller, the temperature of the auxiliary heating roller can be accurately controlled, and the recording paper can be prevented from being curled by heating the pressure roller. become.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heat fixing device incorporated in an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a functional unit of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 3 is a flowchart of control of the image forming apparatus shown in FIGS.

FIG. 4 is a flowchart of control of the image forming apparatus shown in FIGS.

FIG. 5 is a flowchart of control of the image forming apparatus shown in FIGS.

FIG. 6 is a flowchart of control of the image forming apparatus shown in FIGS.

[Explanation of symbols]

 Reference Signs List 10 heating roller 12 pressure roller 13 auxiliary heating roller 14 cleaning pad 15 cleaning roller 16 winding roller H1, H2 heat source S1, S2, S3 sensor CPU control unit CP computer OP operation unit PU image forming unit MD communication means

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 21/00370 G03G 21/00370

Claims (12)

[Claims] 1. A heating roller, a pressure roller in pressure contact with the heating roller, an auxiliary heating means for contacting the surface of the pressure roller and heating the pressure roller, and a control means for controlling the temperature of the auxiliary heating means An image forming apparatus comprising: a heat fixing device that fixes a toner image while conveying a recording sheet by driving the heating roller and the pressure roller, wherein the control unit controls the auxiliary heating unit to output an image. In the state where no formation signal is output, the first temperature is controlled to the first temperature, and in the state where the image formation start signal is started, the second control is controlled to the second temperature higher than the first temperature. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the driving of the heating roller and the pressing roller is not performed in the first control, and the driving is performed in the second control. 3. The control by the third control is performed in a state from the time of receiving the image formation signal to the start of the image formation, and the control by the second control is performed after the start of the image formation. 3. The image forming apparatus according to claim 1, wherein the temperature of the auxiliary heating unit is controlled to a third temperature between the first temperature and the second temperature. 4. 4. The image forming apparatus according to claim 1, wherein in the third control, the heating roller and the pressure roller are driven. 5. The image according to claim 4, wherein in the third control, a preliminary operation for driving the heating roller and the pressure roller is performed without conveying the recording paper to the heat fixing device. Forming equipment. 6. The image forming apparatus according to claim 1, wherein said auxiliary heating means comprises a roller. 7. A heating roller having a heat source for heating and fixing a toner image in contact with recording paper, a pressure roller for pressing against the heating roller, and a heat source for contacting the surface of the pressure roller. A heating fixing device having an auxiliary heating unit for heating the pressure roller and a control unit for controlling the temperature of the auxiliary heating unit;
And an image forming apparatus provided with an environmental condition detecting means for detecting an environmental condition, wherein the control means controls the heat source of the auxiliary heating means based on information from the environmental condition detecting means. Image forming apparatus. 8. The image forming apparatus according to claim 7, wherein the environmental condition is at least one of temperature and humidity. 9. A temperature detecting means for detecting a temperature of the auxiliary heating means, wherein the control means controls the heat source of the auxiliary heating means based on information from the temperature detecting means. An image forming apparatus according to claim 7 or 8, wherein 10. The image forming apparatus according to claim 7, wherein said auxiliary heating means comprises a roller. 11. A heat fixing device comprising a heat roller having a heat source for heating and fixing, a pressure roller in pressure contact with the heat roller, and an auxiliary heating means in contact with the surface of the pressure roller to heat the pressure roller. A heat fixing device, wherein a cleaning unit is provided in at least one of the pressure roller and the auxiliary heating unit. 12. The heat fixing device according to claim 11, wherein said auxiliary heating means comprises a roller.