JPH0566693A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent defective fixation caused by the reduction of a fixation efficiency irrespective of the fluctuation of environmental conditions, and to improve the quality of an image. CONSTITUTION:The device is provided with a reference voltage adjusting device 48 which is controlled by a controller 38 in accordance with the fluctuation of a measured value from an environment sensor 34, and the surface temperature of a heating roller 27b is varied to upper and lower values with reference to the standard temperature by varying the reference voltage for controlling the on and off of the heater 27a. Thus, the reduction of the fixation efficiency caused by the deterioration of the environmental conditions is covered by increasing the temperature of the heating roller 27b, so that the defective fixation can be prevented and the quality of the image can be improved, meanwhile, in the case of having good environmental conditions, power consumption is saved and the rising of the ambient temperature is prevented by reducing the temperature of the heating roller 27b.

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 for fixing a toner image on a sheet of paper by a fixing roller to obtain an image in an electrophotographic apparatus or the like.

[0002]

2. Description of the Related Art In conventional image forming apparatuses such as copying machines,
In a device for inserting a sheet of paper into a fixing roller consisting of a heating roller and a pressure roller, which incorporates a heater, and fixing the toner image under heat and pressure, the heating roller is used. The surface temperature of the toner is set to a fixed specific temperature, and after the power is turned on, the heater is turned on / off by a switching element so that the surface of the fixing roller maintains the specific temperature.

[0003]

Conventionally, the surface temperature of the heating roller is fixedly set in the fixing roller, and the fixing is always performed at a constant temperature regardless of the fluctuation of the surrounding environment at the time of fixing. Was being done. Therefore, as the ambient temperature becomes lower or the humidity rises, the fixing efficiency is lowered, resulting in poor fixing and image quality being lowered.

Further, such a decrease in fixing efficiency is caused not only by the surrounding environment but also when the sheet paper is not properly stored and absorbs moisture.

In view of the above, the present invention eliminates the above problems and prevents the fixing efficiency from deteriorating irrespective of the surrounding environmental conditions at the time of fixing or the moisture absorption state of the sheet paper, and is good without causing defective fixing. An object is to provide an image forming apparatus capable of obtaining an image.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to a rotatable heating roller having heating means and a developer between a pressure roller rotating in contact with the heating roller. In an image forming apparatus having a fixing means for fixing the developer image through the image-receiving material to be transferred, there is provided a first measuring means for measuring a fixing environmental condition of the material to be transferred, and a heating roller. The second measuring means for measuring the surface temperature, the switching means for controlling ON / OFF of the heating means when the measurement result from the second measuring means reaches an arbitrary set value, and the arbitrary set value A control unit that changes according to the measurement result of the first measurement unit is provided.

[0007]

The present invention is constructed as described above, and a stable fixing efficiency can be obtained without causing a fixing failure regardless of the surrounding environmental conditions at the time of fixing or the fluctuation of the moisture absorption amount of the sheet paper. The image quality can be improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS.

FIG. 1 shows the entire image forming apparatus. A drum-shaped photosensitive member 10 as an image bearing member is provided at a substantially central portion of an apparatus main body 1 having an automatic double-sided device 4, a large-capacity feeder 5 and the like. Around the photoconductor 10, the charging device 11 and the exposure unit 12 of the exposure device 12 are sequentially arranged along the rotation direction of the photoconductor 10.
a, a developing device 13, a transfer peeling charger 14, a cleaning device 16, and a charge eliminating device 17 are provided. Further, on the right side of the apparatus main body 1, there are provided a paper feed cassette 18a for accommodating the sheet P, a manual paper feed tray 18b, and a large-capacity feeder 5. Further, in the main body 1 of the apparatus, a pickup cassette 20a, a manual feed tray 18b, an automatic double-sided device 4 or a large-capacity feeder 5 is connected to the pickup rollers 20,4.
A conveyance path 22 is formed for guiding the sheet P taken out by the sheets a and 5a to the sheet discharge tray 21 provided on the left side of the apparatus main body 1 via the photoconductor 10.

The first and second separation rollers 23a and 23b, and the first separation rollers 23a and 23b are provided on the upstream side of the photosensitive member 10 in the conveying path 22.
Of the temperature sensor 34a and the humidity sensor 34
An environment sensor 34 having a position b and a registration roller 24 are arranged, and on the downstream side, any one of a conveyance belt 26, a fixing roller 27 as a fixing means, a paper discharge roller 28 side, or an automatic double-sided device 4 side is provided. A gate 29 for guiding the sheet of paper P is arranged.

The fixing roller 27 is connected to an A.S.P. by a thyristor (hereinafter referred to as SSR) 36 which is a switching means. C. A heater 27a, which is a heating means whose conduction with the power source 52 is controlled to be turned on / off, is built in, and PTFE (polytetrafluoroethylene) is coated on the surface of the aluminum tube.
Heated heating roller 27b and metallic roller core 5
The outer circumference of 4a is covered with a heat-resistant silicone rubber 54b, and a pressure roller 27c coated with PTFE on the surface is formed. The pressure roller 27c is brought into pressure contact with the heating roller 27b by a pressure spring (not shown), and is rotated by the rotation of the heating roller 27b.

Further, on the rear side surface of the heating roller 27b,
A thermistor 37, which is the second measuring means and detects the temperature of the surface of the heating roller 27b, is in contact therewith. Further, 56 is a peeling claw, and 57 is a cleaning felt.

An original placing table 30 is provided above the apparatus main body 1.
A document cover 31 that covers the document placing table 30 is also provided.

Next, a detailed description will be given of the control device 38 which is a control means for varying and controlling an arbitrary set value that enables the SSR 36 to perform the switching operation according to the detection result from the sensor 34.

The control device 38 controls the switching of the SSR 36 so that the surface temperature of the heating roller 27b maintains the temperature characteristics shown in FIG. 4 in accordance with the environmental conditions at the time of fixing. That is, the surface temperature characteristic of the heating roller 27b increases as the fixing efficiency decreases as the temperature of the sheet paper P decreases or the moisture absorption amount of the sheet paper P increases. To be controlled.

However, the controller 38 controls the entire image forming apparatus including the apparatus main body 1, the automatic duplexer 4 and the large-capacity feeder 5, and has an operation panel (not shown) on its input side. ) The input switches 41, the sheet detecting means 42, and other switches / sensors 43 necessary for image forming operation are connected. On the other hand, on the output side of the control device 38, a display device 44 on an operation panel (not shown),
The image forming means 46 such as the photoconductor 10 and the developing device 13 are connected.

Further, the control device 38 has an SSR 36
While the data for controlling the fluctuation of the reference voltage (a) which is an arbitrary set value for switching the
A set temperature control circuit 47 is connected to the output side.

That is, the temperature sensor 34a and the humidity sensor 34b are connected to the input side of the control device 38, and the conveying path 22
The temperature or the humidity of the sheet of paper P passing through the sheet of paper P is measured, and the voltage corresponding to the measured temperature or the measured humidity is supplied from the temperature sensor 34a or the humidity sensor 34a to the first or second analog input section 38a ,. 38b is input.

On the other hand, the set temperature control circuit 47 connected to the output side of the control device 38 has a reference voltage adjusting device 48 and a reference which is set variably by a required output voltage (c) from the reference voltage adjusting device 48. Voltage (a) and thermistor 37
And a comparator 50 for comparing the measured voltage (b) corresponding to the measured temperature from the. And the control device 38
However, in order to set the surface temperature characteristic of the heating roller 27b as shown in FIG. 4 according to the measured values from the temperature sensor 34a and the humidity sensor 34b, the control signal is set to the reference voltage adjusting device 4.
8 is input, the reference voltage adjusting device 48 is controlled so as to change the resistance division ratio and output the required output voltage (c) in a variable manner.

Further, in the comparator 50, the reference voltage (a) input to the first terminal 50a and the measured voltage (b) from the thermistor 37 input to the second terminal 50b are provided. In comparison, when (b)> (a), no output is made. As a result, the SSR 36 maintains the off state and the heater 27a becomes non-conductive. on the other hand,
When (b) ≦ (a), the comparator 50 is output,
The SSR 36 is turned on and the A.S. C. Power supply 52
Is conducted to increase the temperature of the heating roller 27b.

Next, the operation will be described. At the start of copying, when a power source (not shown) is turned on, warm-up is started and the heater 27a is turned on. When the surface of the heating roller 27b reaches the standard temperature of 200 [° C.], the warm-up is completed, the apparatus main body 1 is in the ready state, and the fact is displayed on the display device 44 on the operation panel. Then, the operator inputs necessary conditions from an operation panel (not shown), sets the document D on the document table 30, and turns on a copy button on the operation panel (not shown) to make a copy. Start.

As a result, the copy operation is started, and in the apparatus main body 1, the photoconductor 10 rotates and the charging device 1
1 is uniformly charged, and an electrostatic latent image is formed on the exposed portion 12a. Next, the photoconductor 10 is developed and visualized in the developing device 13, and reaches the transfer peeling charger 14. On the other hand, in synchronization with this, the sheet paper P is fed from the paper feed cassette 18a, the manual paper feed tray 18b or the large-capacity feeder 5, and the sheet paper P is separated by the separation roller 23a,
23b and the photoconductor 10 via the registration roller 24.
Transfer peeling chart when the top edge of the electrostatic latent image is aligned
It is sent to Ja 14.

Here, the sheet P is the registration roller 24.
In front, while passing through the environment sensor 34, the temperature sensor 34a and the humidity sensor 34b measure the temperature and moisture absorption amount of the sheet P, and the measurement result is input to the control device 38. Then, the control device 38 outputs a control signal according to the measurement result to the reference voltage adjusting device 48 according to the surface temperature characteristic of FIG. By the control signal, for example, when the temperature measured by the environment sensor 34 is 20 [° C.] and the moisture absorption amount is 50 [%], the reference voltage adjusting device 48 sets the reference voltage (a) input to the comparator 50 to 203 []. The output voltage (c) is set to a voltage corresponding to [° C.].

The comparator 50 has a first terminal 50a.
The reference voltage (a) corresponding to 203 [° C.] is input to the second terminal 50b, while the thermistors 37 to 200 are input to the second terminal 50b.
When the measured voltage (b) corresponding to [° C] is input,
Since (b) .ltoreq. (A), the comparator 50 is output, whereby the SSR 36 is turned on and the A.A. The C power source 52 is turned on to heat the heating roller 27b. And the surface temperature of the heating roller 27b is 203
When the temperature exceeds [° C], the measured voltage (b) from the thermistor 37 is input to the comparator 50, and (b)> (a).
Then, the comparator 50 is not output and the SSR 36
Is turned off and the heater 27a is turned off. After that, in the fixing roller 27, the surface temperature of the heating roller 27a is set to 203 [° C] which is 3 [° C] higher than the standard temperature until the measured value from the environment sensor 34 fluctuates. The fixing operation will be performed in this state.

Therefore, the sheet of paper P having the toner image on the photoconductor 10 transferred after passing through the resist roller 24 and peeled off from the photoconductor 10 is heated to 203 [° C.] which is higher than the standard temperature and fixed. After being conveyed to the roller 27 and fixed at a high temperature, the sheet is discharged onto the sheet discharge tray 21 by the sheet discharge roller 28.

On the other hand, after the transfer is completed, the photoconductor 10 is cleared.
The residual toner is removed by the cleaning device 16, the charge is removed by the charge removing device 17, the next copy is made possible, and the above copy operation is repeated until the required number of sheets is reached.

During the copying operation, when the measured value from the environment sensor 34 is changed due to temperature rise or the like, the heating roller 27b is adjusted so that the temperature again becomes the temperature according to the surface temperature characteristic of FIG.
The surface temperature of will be reset.

With this configuration, the reference temperature (a) for switching the heater 27a is changed according to the measurement value input from the environment sensor 34, so that the surface temperature of the heating roller 27b is changed to the ambient temperature. Since the temperature can be changed according to the environment, even if the temperature is low or the humidity is high during copying, a sufficient fixing efficiency can be obtained by setting the surface temperature of the heating roller 27b higher than the standard temperature. Obtained,
It is possible to prevent deterioration of image quality due to poor fixing and obtain good images. Also, at high temperature or low humidity,
By setting the surface temperature of the heating roller 27b low, it is possible to save power consumption and prevent the temperature rise in the apparatus main body 1 due to extra heat generation.

The present invention is not limited to the above-mentioned embodiment, but can be changed within the scope of the present invention. For example, the surface temperature characteristic of the heating roller is the same as that of the toner. It is optional accordingly. Also, the first measuring means for measuring the fixing environmental condition may be attached to the side wall of the apparatus main body or the like to measure the surrounding environment instead of directly measuring the sheet.

[0030]

As described above, according to the present invention, the surface temperature of the heating roller can be increased at low temperature or high humidity, while the surface temperature of the heating roller can be decreased at high temperature or low humidity. Since such control can be performed, sufficient fixing efficiency can be obtained even at low temperature or high humidity, and a good image can be obtained without causing fixing failure. On the other hand, when the temperature is high or the humidity is low, the power consumption for heating can be saved, and the device around the fixing roller can be prevented from being excessively heated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an apparatus main body according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a fixing roller according to an exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing a control device and a temperature control circuit according to an embodiment of the present invention.

FIG. 4 is a graph showing surface temperature characteristics of a heating roller according to a change in temperature or humidity according to an embodiment of the present invention.

[Explanation of symbols]

 10 ... Photosensitive member 27 ... Fixing device 27a ... Heater 27b ... Heating roller 34 ... Environmental sensor 36 ... SSR 37 ... Thermistor 38 ... Control device 47 ... Set temperature control circuit

Claims (1)

[Claims] 1. A transfer roller having a developer image is inserted between a rotatable heating roller having heating means and a pressure roller rotating in contact with the heating roller, and the developer image is transferred. In an image forming apparatus having a fixing means for fixing, a first measuring means for measuring a fixing environmental condition of the transferred body, a second measuring means for measuring a surface temperature of the heating roller, and a second measuring means. Switching means for performing on / off control of the heating means when the measurement result from the measuring means reaches an arbitrary set value, and control for varying the arbitrary set value according to the measurement result by the first measuring means. An image forming apparatus comprising: