JPH04306688A - Image formation device - Google Patents

Abstract

PURPOSE:To reduce generation of contraction or curling of a recording sheet that is copy processed in a double-surface mode or in a synthetic mode. CONSTITUTION:A copying condition such as double-surface mode or synthetic mode is selected by an operational part 202, and when a fixing process is carried out for one recording sheet twice, the fixation temperature in the double-surface mode or in the synthetic mode is kept lower than that in a single surface mode, while the second fixation temperature is kept higher than the first fixation temperature by a control part 201. Turning ON/OFF of the voltage applied to a heater 122 through a heater driving circuit 203 is controlled based on the detection result of a thermistor 124 so that the fixation temperature is kept at determined level.

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 that controls fixing temperature based on copying conditions such as double-sided mode, single-sided mode, and composite mode.

0002

[Prior Art] Image forming apparatuses such as copying machines that use electrophotography generally form an electrostatic latent image by exposing a photoreceptor to light, and then apply toner to the electrostatic latent image by developing it. is applied to form a toner image, then the toner image is transferred onto recording paper in a transfer process, and then copied onto the recording paper by applying heat to the toner image transferred to the recording paper and fixing it in a fixing process. It executes image formation.

[0003] Further, for example, as one of the multi-functionality of image forming apparatuses, there is an automatic duplex function, an image compositing function, etc. The automatic duplex function is a mode that forms a copy image on only one side (
In addition to the single-sided mode (hereinafter referred to as single-sided mode), there is also a mode (hereinafter referred to as single-sided mode) in which the recording paper is automatically reversed and conveyed to form copy images on both sides of the recording paper.
This function has a double-sided mode (hereinafter referred to as double-sided mode). Also,
The image compositing function is a function that has a mode (hereinafter referred to as a compositing mode) in which a plurality of copied images are superimposed on the same surface. Therefore, in an image forming apparatus that has an automatic duplex function or an image composition function, in addition to the conveyance path (discharge conveyance path) that discharges the recording paper after the fixing process to a paper output tray outside the apparatus, A conveyance path (paper refeed conveyance path) is provided to convey the recording paper to the paper feed section. Note that the refeeding conveyance path is generally more complicated than the discharge conveyance path, and the curvature of the conveyance path is configured to be small in order to downsize the apparatus. Further, a stock tray or the like is disposed on the paper refeed transport path to temporarily store the transported recording paper.

0004

[Problems to be Solved by the Invention] However, according to conventional image forming apparatuses, when copying is performed in duplex mode or composite mode, residual heat from the first fixing process still remains on the recording paper. Then, since the second fixing process is performed, an excessive amount of heat is applied to the recording paper compared to the one-sided mode, which causes the recording paper to easily expand, contract, or curl. .

[0005]Furthermore, since residual heat from the first fixing process still remains on the recording paper, the recording paper is conveyed through a complicated conveyance path with a small curvature for the second fixing process. There was also the problem that it was easy to stretch or curl.

The present invention has been made in view of the above, and an object of the present invention is to reduce the occurrence of expansion/contraction or curling of recording paper subjected to copy processing in duplex mode or composite mode.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a method for controlling a fixing device based on copying conditions such as single-sided mode, double-sided mode, composite mode, etc. input through a predetermined input means. The present invention provides an image forming apparatus that controls fixing temperature, and includes a control unit that sets the fixing temperature in duplex mode and composite mode to a temperature lower than the fixing temperature in single-sided mode.

Further, in the above-described configuration, it is preferable that the control means sets the first fixing temperature of each recording paper to a temperature lower than the second fixing temperature in the duplex mode or composite mode.

[0009]

[Function] In the image forming apparatus according to the present invention, when the fixing process is performed twice on one sheet of recording paper by selecting duplex mode, composite mode, etc., the control means controls the fixing process in duplex mode or composite mode. By setting the temperature lower than the fixing temperature set in single-sided mode,
Keeps the temperature of the recording paper low as it passes through the refeed paper transport path,
Also, avoid applying excessive heat to the recording paper. Also, at this time, the second fixing temperature is set higher than the first fixing temperature.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of a copying machine 100 to which an image forming apparatus of the present invention is applied, and includes a contact glass 101 on which an original (not shown) is placed, and a pressure plate for pressing the original against the contact glass 101. 102, an optical system 103 that is disposed below the contact glass 101 and optically reads the original image, and a photoreceptor 104 that receives reflected light (exposure) from the optical system 103 to form an electrostatic latent image.
, a charger 105 that performs a charging process on the surface of the photoreceptor 104 prior to exposure processing, an eraser 106 that removes the charged potential of a non-image area on the photoreceptor 104, and a
A developing unit 107 that attaches toner to the electrostatic latent image formed on the electrostatic latent image formed on the image forming apparatus 4, a paper feed cassette 108 that stores recording paper of different sizes, and a paper feed roller 109 that takes out the recording paper from the paper feed cassette 108. A registration roller 110 that conveys the recording paper at a predetermined timing so as to match the leading edge of the toner image formed on the photoconductor 104, and a transfer charger that transfers the toner image on the photoconductor 104 to the conveyed recording paper. 1
11, a separation charger 112 for separating the recording paper after the transfer process from the photoreceptor 104, and a photoreceptor 104.
a separation claw 113 that reliably separates the recording paper from the photoreceptor 104; a cleaning section 114 that removes residual toner on the photoreceptor 104 after the transfer process; a conveyor belt 115 that transports the recording paper separated from the photoreceptor 104; A fixing device 116 that performs fixing processing on the toner image on the paper, a switching claw 117 that controls the conveyance of the recording paper after the fixing processing, a paper discharge roller 118 that discharges the recording paper outside the machine, and a duplex mode, It is comprised of a paper refeed conveyance system 119 for conveying the recording paper to the image forming section again in the composition mode.

The fixing device 116 is of a heat roller fixing type, and as shown in the figure, includes a fixing roller 123 having an internal heater 122 serving as a heat source, and a thermistor 124 for detecting the surface temperature of the fixing roller 123. It has

The paper refeed conveyance system 119 also includes a recording paper surface reversing system 120 for reversing the recording paper surface in the duplex mode, a stack tray 121 for temporarily storing the conveyed recording paper, and a stack tray 121 for temporarily storing the conveyed recording paper, and A switching claw 125 for changing the conveyance path of the recording paper depending on the time and composition mode.
Consists of etc.

With the above configuration, the general operation of the copying machine 100 will be explained. First, the charger 105 charges the photoreceptor 104 by performing corona discharge. When the charging process by the charger 105 is completed, the eraser 106 removes the charged potential outside the image forming area on the photoconductor 104, and then the photoconductor 10 is removed via the optical system 103.
4 is exposed to light, and the charge is erased depending on the strength of the light, forming an electrostatic latent image. Next, in the developing section 107, the electrostatic latent image on the photoreceptor 104 is visualized as a toner image. When the development process is completed, the toner image is transferred by the transfer charger 111 onto the recording paper conveyed via the registration rollers 110 at a predetermined timing. Subsequently, the recording paper on which the transfer process has been completed is separated from the photoreceptor 104 by a separation charger 112. The recording paper separated from the photoreceptor 104 is heated by a fixing device 116 to fix the toner image thereon. After the fixing process has been completed, the recording paper is transferred to the paper ejection roller 118 by the switching claw 117.
Alternatively, the paper is sent to the paper refeed conveyance system 119. At this time, the recording paper sent to the paper ejection roller 118 is ejected to the outside of the machine, and the series of processing ends.

On the other hand, the recording paper sent to the paper refeed conveyance system 119 is temporarily stocked in the stock tray 121, and then
It is transported to the image forming area again and the above-described process is repeated. In addition, the recording paper stocked in this stock tray 121 is stored in the switching claw 12 in the duplex mode.
5 (solid line: position in double-sided mode, broken line: position in composite mode) is sent to the recording paper reversing system 120 for reversing. Switching claw 1 indicated by a solid line in the diagram
Reference numeral 17 indicates a state in which the recording paper is conveyed to the paper refeed conveyance system 119, and a switching claw 117 indicated by a broken line indicates a state in which the recording paper is conveyed outside the machine. Furthermore, the switching claw 125 drawn in solid lines shows the state in which the recording paper is conveyed to the recording paper reversing system 120, and the switching claw 125 drawn in broken lines shows the state in which the recording paper is transported as it is to the stock tray 121. It shows.

FIG. 2 shows a control block diagram for controlling the fixing temperature of the image forming apparatus according to the present invention, including a control section 201 that controls the entire apparatus, and a control section 201 that controls the entire apparatus, and a control section that detects the temperature on the fixing roller 123 (fixing temperature). an operation section 202 for inputting copying conditions such as single-sided mode, double-sided mode, composite mode, etc., and a heater drive circuit 203 for applying voltage to the heater 122.

With the above configuration, fixing temperature control according to the present invention will be explained. The control unit 201 receives a signal according to copying conditions from the operation unit 202, and controls the heater drive circuit 20.
3, a control signal is sent out so that a predetermined fixing temperature is reached according to the copying conditions, and a heater drive circuit 203 applies a voltage to the heater. At this time, the thermistor 124 is connected to the fixing roller 12.
The surface temperature (fixing temperature) of No. 3 is detected and output to the control unit 201. The control unit 201 controls the heater 12 via the heater drive circuit 203 based on the detection result of the thermistor 124.
The voltage applied to the fixing roller 123 is controlled on/off so that the surface temperature of the fixing roller 123 is maintained at a predetermined fixing temperature.

Here, fixing temperature control in the duplex mode will be explained with reference to FIG. 3 as an example. As shown,
In the case of double-sided mode, the fixing temperature on the second side (i.e., second time) is higher than the fixing temperature on the first side (i.e., first time);
Further, the fixing temperature on the second side is controlled to be lower than that in the single-sided mode.

In this way, in the first time, the fixing process is performed at a low fixing temperature, so the temperature of the recording paper is kept relatively low when passing through the paper refeed conveyance system 119, and the recording paper Since curling and the like are less likely to occur, it is possible to suppress the occurrence of jams and stock defects due to curling of the recording paper. The reason why the fixing temperature in duplex mode (first and second fixing temperatures) is lower than the fixing temperature in single-sided mode is because the fixing process is performed twice on the recording paper. In other words, if the fixing process is performed at the fixing temperature in the single-sided mode, the amount of heat applied to the recording paper increases, making it easier for the recording paper to expand, contract, curl, etc.

Furthermore, the reason why the first fixing temperature is lower than the second fixing temperature is that after the first fixing process,
In order to carry out the second fixing process while residual heat remains on the recording paper, it is necessary to transport it through a complicated transport path with a small curvature, so the temperature must be lowered to prevent jams and stock defects. It is meant to be.

In the embodiments described above, the first fixing temperature was set lower than the second fixing temperature, but the second fixing temperature may be set as low as the first fixing temperature. It goes without saying that the above-mentioned fixing temperatures are all within a range appropriate for the fixing process.

[0021]

As is clear from the above, according to the present invention, the fixing temperature of the fixing device can be controlled based on the copying conditions such as single-sided mode, double-sided mode, composite mode, etc. input through a predetermined input means. Image forming apparatuses equipped with a control means for setting the fixing temperature in duplex mode and composite mode to a temperature lower than the fixing temperature in single-sided mode prevent the expansion and contraction of recording paper that has been copied in duplex mode or composite mode. Alternatively, the occurrence of curls and the like can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a copying machine to which an image forming apparatus according to the present invention is applied.

FIG. 2 is a block diagram of a control system of an image forming apparatus according to the present invention.

FIG. 3 is an explanatory diagram of fixing temperature control of the image forming apparatus according to the present invention.

[Explanation of symbols]

116 Fixing device
122 Heater 124 Thermistor
201 Control unit 20
2 Operation section
203 Heater drive circuit

Claims (2)

[Claims] 1. An image forming apparatus that controls the fixing temperature of a fixing device based on copying conditions such as simplex mode, duplex mode, and composite mode input through a predetermined input means, wherein the duplex mode and composite mode are controlled. The fixing temperature of
An image forming apparatus comprising: a control means for setting a temperature lower than the fixing temperature in the single-sided mode. 2. The control means sets the first fixing temperature of each recording sheet to a temperature lower than the second fixing temperature in the duplex mode or the composite mode. The image forming apparatus described above.