JP2002366010A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dew condensation in a machine under low-temperature environment. SOLUTION: When the temperature in the machine is lower than specified temperature, a fixing heater is turned on and an exhausting fan is turned off.

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 using an electrophotographic method, and more particularly, to a transferable image (toner image) formed on a photoreceptor serving as a first image carrier. Copiers, printers, faxes, etc., in which an image (copies / prints) is primarily transferred onto an intermediate transfer body, and is secondarily transferred from the intermediate transfer body to a transfer material as a third image carrier by a transfer member to obtain an image (copy / print) Related to an image forming apparatus.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus will be described by taking a full-color printer using an intermediate transfer member as an example.
A photosensitive member as a first image bearing member and an intermediate transfer member as a second image bearing member; a primary charging member, an exposing member, a developing device, and an intermediate transfer member around the photosensitive member along a rotation direction of the photosensitive member; Body and cleaner are arranged. The intermediate transfer member forms a primary transfer nip with the photoreceptor. A secondary transfer portion is provided downstream of the intermediate transfer member in the rotation direction, and a secondary transfer nip is formed by the secondary transfer member. A fixing device is arranged downstream from the secondary transfer section in the paper transport direction.

The surface of the photoreceptor is made uniform by a primary charging member such as a corona charger or a roller charger, for example, at -55.
It is charged to 0V. When an image pattern is exposed on the surface of the photoreceptor charged by an exposure means such as a laser, the surface potential of the exposed portion of the photoreceptor surface attenuates to about -150 V, and a potential difference is generated between the exposed portion and the unexposed portion, resulting in static An electrostatic latent image is formed. By developing the electrostatic latent image with a negatively chargeable toner, the charged developer adheres to the exposed portion, and a visible image is formed.

Then, in the primary transfer section, a voltage (primary transfer bias: T1) having a polarity opposite to that of the toner is applied to the intermediate transfer member by, for example, +3.
By applying a constant value of 00V, the toner image developed on the photoconductor is transferred to the intermediate transfer body.

In the full-color image formation, this process is repeated while adjusting the positions of the toners of a plurality of colors, thereby forming an overlapped image of a plurality of colors on the surface of the intermediate transfer member.

Next, in the secondary transfer section, a current (secondary transfer bias: T2) having a polarity opposite to that of the toner is applied to the transfer belt by, for example, +2.
By applying a constant value of 0 μA, an image of a single color or a plurality of colors formed on the intermediate transfer member is transferred to a recording medium such as paper. Further, the secondary transfer belt sucks and conveys the recording medium and sends it to the fixing device. The fixing unit has a pair of rollers and has a built-in heater or an external heating unit in one or both, and is pressed against each other at a constant pressure. When the recording paper passes through the fixing device, the toner image is fixed on the paper at the same time as the color mixture by heat and pressure, and a full-color image is obtained. When the heating means of the fixing device is in operation, the inside heat of the apparatus is discharged to the outside of the apparatus by using an exhaust means such as a fan in order to prevent an excessive temperature rise in the apparatus.

[0007]

However, the above configuration has the following problems. In a full-color printer, the number of process parts, such as a developing unit, a photoreceptor, and an intermediate transfer body, increases, and at the same time, the entire apparatus increases in size. It is difficult to follow changes.

Further, since color misregistration at the time of color printing deteriorates the quality of a printing result, a printing position accuracy of each color on an intermediate transfer member is required. In order to suppress the deviation of the printing position accuracy due to the deformation of the intermediate transfer member, a drum-shaped intermediate transfer member having an intermediate transfer member formed on a rigid metal core such as metal is effective. However, the heat capacity of the entire intermediate transfer drum increases as the thickness of the core increases as the core increases, so that it becomes difficult to follow changes in the surrounding temperature.

For example, when the installation environment of the apparatus rises in a short time due to heating in the morning of winter, the temperature of the intermediate transfer member cannot follow the change in room temperature, and a temperature difference between room temperature and the intermediate transfer member occurs. The toner image was not transferred satisfactorily due to the formation of dew on the surface of the toner, and as a result, there was a possibility that an image defect occurred. Further, when dew condensation occurs in the recording material transport path in the apparatus, the recording material sticks to the transport path due to water droplets, and there is a possibility that transport failure may occur. Therefore, a method of providing a dedicated heater for warming the inside of the apparatus and a method of operating the fixing device to warm the inside of the apparatus have been considered. For example, Japanese Patent Application Laid-Open No. H11-038861 adopts a method of reducing the temperature difference between the inside and the outside of the machine by operating the exhaust means and taking in air outside the machine. Further, a method is employed in which the inside of the apparatus is heated by using heat of the fixing device.

However, in the above method, when the power of the apparatus is turned on in the winter morning, while the ambient atmosphere temperature is low, cold air outside the apparatus is taken into the apparatus by the operation of the exhaust means. In some cases, it can interfere. For the same reason, the heat of the fixing device may not efficiently contribute to the temperature rise in the apparatus. Further, since the fixing device is operated based on the temperature difference between the inside and the outside of the machine, there is a concern that the inside of the machine may overheat in summer.

In the above-described image forming apparatus, in the case of an image forming apparatus using a plurality of developing units, one photosensitive member and an intermediate transfer member, a fixing unit is disposed below the developing units as shown in FIG. In many cases, in the above configuration, there is a fear that an excessive temperature rise in the apparatus may cause a rise in the temperature of the developing device, which may lead to the fixation of the toner in the developing device.

[0012]

In order to solve the above-mentioned problems, the present invention provides one or more image carriers and one or more image forming means for forming a toner image on the image carriers. Transfer means for transferring the toner image formed on the image carrier directly or via an intermediate transfer member to a recording medium, fixing means for fixing the toner image to the recording medium by heat, and heating means for heating the fixing means; An image forming apparatus comprising: a temperature detecting unit for detecting a temperature of a fixing unit; and an exhaust unit for discharging air inside the apparatus to the outside of the apparatus. The apparatus has a standby mode and a second standby mode in which the heating unit is operated to stop the exhaust unit, and the two standby modes are selectively used based on the temperature inside the apparatus. When the temperature inside the apparatus is lower than the predetermined temperature, the exhaust means is stopped by using the second standby mode, and the temperature rise inside the apparatus is promoted by the heating means with little heat exchange with the outside. .

Further, according to the present invention, control corresponding to various use environments can be performed by switching between the first standby mode and the second standby mode based on the difference between the temperature and humidity outside the apparatus and the temperature and humidity inside the apparatus. It is to be.

With the above configuration, the temperature inside the device can be secured in a short time without providing any special means for heating the inside of the device. The temperature difference can be reduced, and dew condensation in a high humidity environment can be reduced.

[0015]

Embodiments of the present invention will be described below. In this embodiment, a full-color laser beam printer using a negative process will be described. FIG. 1 is a schematic sectional view of a full-color laser beam printer (or a copying machine or the like) using an intermediate transfer member. First, an image forming process will be described. The apparatus includes a photoconductor 1 as a first image carrier. The photoreceptor 1 rotates in the direction of the arrow, and a primary charger 2 for uniformly charging the surface of the photoreceptor 1 to a negative polarity from the upstream. The photoreceptor 1 is exposed based on an image signal to form an electrostatic latent image. A laser exposure device 3 and developing devices 4 and 5 for attaching toner to an electrostatic latent image and developing the toner are arranged.

An intermediate transfer member 6 is disposed downstream of the photosensitive member 1 at a developing position as a second image carrier. Intermediate transfer member 6
A secondary transfer belt 7 is disposed downstream of the image forming apparatus, and a fixing device 8 is disposed downstream of the secondary transfer belt 7 in the paper transport direction.
For example, the surface of the photoreceptor is uniformly charged to -550 V by the primary charger 2 and then the image pattern is exposed by the laser exposure device 3 to form an electrostatic latent image. The exposed photoconductor surface has an unexposed partial potential (V _D ) of -550 V,
The exposed portion potential ( _VL ) becomes -150V. Developing unit 4,
When a developing bias of -350 V is applied to the developing sleeve No. 5, the _VL portion having a low photoconductor surface potential is developed with negatively charged negative toner, and the electrostatic latent image is visualized. The intermediate transfer member 6 is a cylindrical roller having a metal core serving as a conductive support and an elastic layer made of at least rubber, elastomer, and resin, and a drum having one or more coating layers on the elastic layer. Of shape. Intermediate transfer member 6
Also serves as a first transfer member and rotates at substantially the same speed as the photoconductor. When a primary transfer bias (T1) of +300 V is applied to the metal core of the intermediate transfer member 6, the toner image on the photoconductor 1 is changed by a potential difference of 450 V between the _VL portion of the photoconductor 1 and the intermediate transfer member 6 in the primary transfer nip portion. The image is transferred to the intermediate transfer member 6. The above process is repeated for the four color toners of yellow (Y), magenta (M), cyan (C), and black (K) at the same timing, so that the image in which the four color plates are superimposed on the intermediate transfer member 6 is obtained. It is formed. Then 2
The secondary transfer nip is formed by pressing the next transfer belt 7 against the intermediate transfer body 6, and a recording medium such as paper is fed into the secondary transfer nip in synchronization with the leading edge of the image on the intermediate transfer body 6. When a secondary transfer bias of +20 μA is applied to the secondary transfer belt 7, the toner image is transferred to paper.

The paper on which the toner image has been transferred is sent to a fixing device 8. The fixing unit 8 has a heater 82 built in one or both of a pair of rollers and is pressed against each other at a constant pressure. A fixing temperature sensor 9 for detecting the temperature of the surface of the fixing roller 81 is provided.
The heater 82 is turned on / off based on the output value of the fixing roller 81 to control the temperature of the fixing roller 81. When the printer is in a standby state, the fixing roller 81 is set to a standby temperature of 1
At the time of printing, the fixing roller 81 is controlled to have a printing temperature of 180 ° C. so as to be 70 ° C. When the recording paper passes through the fixing unit 8, the toner image is fixed on the paper at the same time as the color mixture by heat and pressure, and a full-color image is obtained. An exhaust fan 11 serving as an exhaust unit discharges air inside the apparatus to the outside of the apparatus, whereby air outside the apparatus is introduced into the inside of the apparatus from an intake port or a clearance on the exterior of the apparatus. When the temperature of the fixing device 8 is equal to or higher than a predetermined value, the cooling fan 11 operates to prevent an excessive temperature rise in the apparatus. In the first standby mode of the present invention, at the time of non-printing operation, ON / OFF of the heater 82 is controlled based on the output of the fixing temperature sensor 9 to keep the fixing roller temperature at 170 ° C. and at the same time, operate the exhaust fan 11. Then, the heat inside the machine is discharged outside the machine to prevent the inside of the machine from overheating. In the second standby mode, control of the heater 82 is performed based on the output of the fixing temperature sensor 9 as in the first standby mode, but by stopping the exhaust fan 11, heat exchange with the outside of the apparatus is reduced.

In this embodiment, an in-machine temperature sensor 12 is provided near the intermediate transfer member, and the first and second standby modes are switched based on the output of the in-machine temperature sensor 12.

FIG. 4 shows the results of the following experiment conducted using the printer having the above-described configuration. First, an experiment was performed using only the first standby mode, which is a conventional method. The printer with the power turned off was left for 10 hours or more in an environment at room temperature of 5 ° C. The temperature inside the apparatus after standing was 5 ° C., which was almost the same as room temperature. Next, when the power of the apparatus was turned on to set it in the first standby mode and the installation environment was gradually heated and humidified to 25 ° C. and 50%, and the image was output, dew condensation occurred on the surface of the intermediate transfer member. Transfer failure occurred, and toner adhered to the surface of the intermediate transfer body due to water droplets, resulting in image failure due to poor cleaning of the intermediate transfer body. In addition, paper adhered due to dew condensation on the paper transport path in the machine, resulting in a transport failure. It took about 60 minutes for the condensation to disappear, and the internal temperature at this time was about 12 ° C.

Next, an experiment was conducted using the second standby mode according to the present invention. The printer with the power supply turned off was left for 10 hours or more in an environment at room temperature of 5 ° C. to lower the internal temperature to the same level as the room temperature. Thereafter, the power supply of the apparatus was turned on, and the apparatus was set in the second standby mode until the internal temperature of the apparatus reached 12 ° C. At the same time, the installation environment was gradually heated and humidified to 25 ° C. and 50%. As a result, after about 20 minutes, the temperature inside the apparatus became 12 ° C., and even if the temperature and humidity of the installation environment increased, no dew condensation occurred and no image defects occurred. After the temperature inside the machine exceeded 12 ° C., the apparatus was placed in a first standby mode in order to prevent an excessive temperature rise inside the machine.
Also, as shown in the flowchart of FIG. 5, when the temperature inside the device exceeds 12 ° C., the first standby mode is set, so that the temperature inside the device does not become excessively high except in a low-temperature environment.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. In this embodiment, an internal temperature and humidity detection sensor 13 and an external temperature and humidity detection sensor 14 are provided in addition to the conventional image forming apparatus. For example, the outside temperature and humidity detection sensor 14
The temperature (dew point) at which dew condensation occurs when the temperature and humidity outside the apparatus detected at 23 ° C. are 23 ° C. and 60% is about 15 ° C. 1
When the temperature rises to the above temperature and humidity by heating in a room cooled to about 0 ° C., the first standby mode is operated in a state where the temperature inside the machine detected by the temperature / humidity detecting sensor 13 is still 15 ° C. or less. The fan caused warm air outside the machine to enter the cabin, touching the inside of the cabin at a temperature of 15 ° C or lower, causing dew condensation. On the other hand, when the first standby mode was operated after the temperature in the device became 15 ° C. or higher, no dew condensation occurred in the device.

Under the same conditions, based on the flow chart of FIG. 7, the exhaust fan is stopped in the second standby mode until the temperature inside the apparatus becomes 15 ° C. or more. As a result, no dew condensation occurred in the apparatus, and no image defect occurred even when an image was formed. Then, when the inside of the machine was warmed to 15 ° C. or higher, the first standby mode was set to prevent the inside of the machine from overheating.

In the present embodiment, several methods can be considered as a method of actually switching between the first standby mode and the second standby mode. The determined dew point temperature may be used as a criterion by a method of storing the information in the ROM or a method of calculating the amount of water in the air from the temperature and humidity and calculating the dew point temperature from the amount of water.

[0024]

As described above, according to the present invention, it is possible to effectively promote a rise in the temperature in a low-temperature environment at low cost without providing a new heat source in the image forming apparatus. It is possible to improve image defects and recording material conveyance defects due to dew condensation inside the apparatus. In addition, by automatically switching the standby mode according to the comparison result of the temperature and humidity outside the machine and the temperature inside the machine, it is possible to prevent the inside of the machine from overheating under conditions where dew condensation is not required. Control became possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus according to a first embodiment.

[Fig. 2] Apparatus external view

FIG. 3 shows a conventional image forming apparatus.

FIG. 4 is a graph of a temperature change in the machine.

FIG. 5 is a flowchart of the first embodiment.

FIG. 6 is an explanatory view of a second embodiment.

FIG. 7 is a flowchart of a second embodiment.

[Explanation of symbols]

 Reference Signs List 1 photoconductor 2 primary charging roller 3 laser exposure device 4 black developing device 5 color developing device 6 intermediate transfer member 7 transfer belt 8 fixing device 81 fixing roller 82 fixing heater 9 fixing roller temperature detection sensor 10 CPU 11 exhaust fan 12 internal temperature detection Sensor 13 Temperature and humidity detection sensor inside the machine 14 Temperature and humidity detection sensor outside the machine

Continued on the front page F-term (reference) 2H027 DA11 DA12 DA13 DA14 EA11 EA12 ED25 EF16 JA11 JA12 JB17 JB23 2H033 AA32 AA35 AA39 BA29 BA30 BB01 CA05 CA07 CA08 CA11 CA32 CA45 CA53

Claims (3)

[Claims] 1. An image forming apparatus comprising: one or a plurality of image carriers; one or a plurality of image forming means for forming a toner image on the image carrier; A fixing unit, a heating unit for heating the fixing roller, and a roller temperature detecting unit for detecting the temperature of the fixing roller. A first standby mode for operating the heating unit and the exhaust unit, and a second standby mode for operating the heating unit and stopping the exhaust unit. An image forming apparatus having two standby modes. 2. The apparatus according to claim 1, further comprising at least one or more internal temperature detecting means for detecting a temperature of a predetermined portion other than the fixing device in the image forming apparatus main body, in addition to the roller temperature detecting means. The first standby mode and the second standby mode are switched based on the result, and if the internal temperature detected by the internal temperature detection unit is equal to or lower than a predetermined value, the second standby mode is switched to the second standby mode.
An image forming apparatus that operates in a standby mode. 3. One or more image carriers, one or more image forming means for forming a toner image on the image carrier, and a toner image formed on the image carrier directly or through an intermediate transfer member. A fixing unit, a heating unit for heating the fixing roller, and a roller temperature detecting unit for detecting the temperature of the fixing roller. The fixing unit includes a controlled fixing unit, and an exhaust unit that discharges air inside the apparatus to the outside.The unit includes a unit that detects temperature and humidity outside the unit and a unit that detects temperature and humidity inside the unit. A first standby mode for operating, and a second standby mode for operating the heating unit to stop the exhaust unit. The first standby mode is based on the detected difference in greenhouse temperature between the outside and inside the apparatus. Second
An image forming apparatus that switches between a standby mode and a standby mode.