JPH0883015A - Fixing device - Google Patents

Abstract

(57) [Abstract] [Purpose] Regardless of the difference in the layer thickness of the toner image, at the time of fixing, a proper amount of heat is applied to the toner image to obtain good fixing, thereby increasing thermal efficiency and saving power consumption. With
Prevents high-temperature offset, prevents deterioration of the heating roller due to the release agent, and extends the service life of the fixing roller. [Configuration] A scanner unit 43 for reading image data,
An image processing unit 44 that extracts density information with the nip portion 28d as one cycle from the image data, and an arithmetic processing unit 44a that sets an appropriate fixing temperature based on the image information are provided. The power supply to the infrared heater 28a is controlled in each cycle so that a predetermined area on the heating roller 28b that reaches the nip portion in synchronism reaches the set fixing temperature.

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 obtaining a fixed image by heating and melting a toner image on a sheet of paper in an electrophotographic apparatus, a printer or the like.

[0002]

2. Description of the Related Art In an image forming apparatus such as a conventional printer, a sheet of paper is inserted between a fixing roller composed of a heating roller and a pressure roller, which contains a heater, to form a toner image. In the apparatus for heating, pressing and fixing, the set temperature of the heating roller heated by the heater is controlled to be constant regardless of the layer thickness of the toner image.

That is, in order to surely fix all the toner images formed on the sheet of paper, the heating roller is set in temperature so as to give a heat quantity capable of surely fixing the image of the maximum expected layer thickness. Was there.

Therefore, the fixing property becomes uneven due to the difference in the layer thickness of the toner image.
An excessive amount of heat is applied to the toner, the viscosity of the toner is reduced more than necessary, and a so-called high temperature offset phenomenon occurs in which the toner adheres to the heating roller.

In order to prevent such an offset phenomenon,
For example, an apparatus for applying a release agent to a heating roller on the side in contact with a toner image has been used, such as a heat fixing apparatus described in "Japan Hardcopy '92" (Fuji Xerox Co., Ltd.).

[0006]

In a conventional fixing device using a heating roller, regardless of the toner image layer thickness,
Since the surface temperature is set to a constant temperature at which a heat amount capable of fixing an image of the maximum expected layer thickness can be provided, an offset is often caused due to an excessive heat amount in a thin toner layer, and a heating roller is used. However, there is a problem that the image is stained due to the stain.

Particularly, in a color image, there is a considerable variation in the layer thickness, such as a multi-layer solid image in which toners of a plurality of colors are all overlaid and a single-layer image of one color toner. Depending on the amount of heat required for fixing,
With the conventional heating roller 7 that is constantly heated to 150 ° C,
As shown in FIG. 9, when the toner image composed of the three layers of the first to third toners t1 to t3 is fixed, the toner temperature at the boundary surface with the sheet P is 107 ° C. and good fixing property is obtained. Although obtained, under the same conditions, when a toner image composed of only one layer of the first toner t1 is fixed as shown in FIG. 10, the toner temperature at the boundary surface with the sheet P is as high as 131 ° C. Therefore, the adhesiveness of the toner t1 is lowered, and an offset occurs.

Therefore, in order to prevent such offset, a releasing agent such as silicone oil is applied to the surface of the heating roller. However, the heating roller has a releasing layer on its surface due to the influence of a large amount of the releasing agent and heat. Was deteriorated and the durability was remarkably lowered. Moreover, compared to the solid image part where all the toners of multiple colors are overlaid, the actual image is
Since there are many image parts with a small amount of toner, the heating temperature actually required may be lower than the set constant temperature in many cases, and heat loss due to excessive heating is large, which is an obstacle to saving power consumption. It was

In view of the above, the present invention eliminates the above-mentioned problems, and does not cause an offset phenomenon due to an excessive amount of heat regardless of the layer thickness of the toner image, reduces the amount of release agent used, and lengthens the heating roller. An object of the present invention is to provide a fixing device capable of achieving a longer life, reducing heat loss due to an excessive amount of heat, and saving power consumption.

[0010]

As a first means for solving the above-mentioned problems, the present invention transfers the developer image formed on the image support by the image forming means to heat the developer image. Heating means, identification means for identifying the layer thickness of the developer image, and control means for sequentially controlling the amount of heat generated by the heating means in accordance with the layer thickness identified by the identification means are provided. Further, the present invention provides, as a second means for solving the above-mentioned problems, a heating roller having a heating element for rollingly contacting the developer image formed on the image support by the image forming means to heat the developer image. An identifying means for identifying the layer thickness of the developer image and a controlling means for sequentially controlling the heat generation amount of the heating element according to the layer thickness identified by the identifying means are provided.

As a third means for solving the above-mentioned problems, the image forming means forms an image based on the image information from the information reading means as a developer image on the image support, and the identifying means is provided. Is for identifying the layer thickness from the image information from the information reading means.

As a fourth means for solving the above-mentioned problems, the present invention is such that the identifying means identifies the layer thickness from the developer image formed on the image support.

[0013]

The present invention is configured as described above and prevents the occurrence of offset due to the application of an excessive amount of heat by controlling the temperature of the heating roller according to the layer thickness of the toner image on the sheet paper.
Furthermore, by reducing heat loss, power consumption is saved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the first embodiment shown in FIGS. FIG. 1 is a schematic configuration diagram showing an image forming unit 10 of a copying machine having a scanner unit 43. In the apparatus main body 1, photosensitive drums 11Y, 11M, and 1 are provided, respectively.
1C, 11BK and its surroundings are irradiated with exposures from an optical unit 13 for converting an image signal from the chargers 12Y, 12M, 12C, 12BK and the scanner 43a which is an information reading means into an optical signal along the rotation direction. Exposure positions 13Y, 13M, 13C, 13BK, developing device 14
Y, 14M, 14C, 14BK, transfer rollers 15Y, 1
5M, 15C, 15BK, cleaning device 16Y, 1
6M, 16C, 16BK, static elimination lamps 19Y, 19M,
19C and 19BK are sequentially arranged, and toners TY, TM, and T each made of a non-magnetic powder one-component developer of yellow (Y), magenta (M), cyan (C), and black (BK)
Four sets of recording devices 1 for forming images using C and TBK
0Y, 10M, 10C, and 10BK are arranged in parallel along the conveyor belt 17.

Further, in the apparatus main body 1, a paper feed cassette device 18 for accommodating the sheet paper P, a pickup roller 20 for taking out the sheet paper P from the paper feed cassette device 18 and carrying it to a carrying belt 17, and a registration roller. 23 are provided.

A fixing device 24, a pair of paper discharge rollers 26, and a paper discharge tray 27 are arranged downstream of the conveyor belt 17.

Next, the fixing device 24 will be described in detail. Reference numeral 28 denotes a pair of fixing rollers, which are infrared heaters 2 which are heating elements.
8mm built-in heating means 30mmφ, wall thickness 0.5
mm of the heating roller 28b and a pressure spring (not shown) pressed against the heating roller 30m
It has a pressure roller 28c of mφ. As a result, the length of the nip portion 28d of the fixing roller 28 is set to 3.5 mm.

The heating roller 28b is provided around the heating roller 28b.
The thermistor 30 for detecting the temperature of the surface b, the coating roller 32 for coating the release agent, and the cleaning device 33 are in contact with each other.

FIG. 3 is a block diagram showing the temperature control system of the fixing device 24. The main CPU 41 has an image processing section 44 as an identification means and an arithmetic processing section 44a having a temperature / density table 44b. A scanner 43a and a sensor 43 are provided on the input side through the input interface 42.
b, a scanner unit 43 which is an information reading unit having a line memory 43c is connected, and a fixing unit controller 47 having a heater driver 47a is connected to an output side via an output interface 46. The infrared heater 28a is connected to the heater driver 47a, and the temperature detection result from the thermistor 30 is input.

Further, FIG. 4 is a wiring diagram of the fixing device controller 47 for controlling the temperature of the fixing device 24. The fixing device controller 47 is connected to the thermistor 30 and the thyristor 48, while the infrared heater 48a is a thermo switch. 50 and an AC power source 51, and is connected to the thyristor 48.

Next, the operation will be described. When a color image signal is sent to the device body 1 by the start of printing,
The recording devices 10Y, 10M, 10C and 10BK are driven, and the image forming process is sequentially performed according to the rotation of the photoconductor drums 11Y to 11BK.

That is, each of the photosensitive drums 11Y to 11BK
Is first uniformly charged by each of the chargers 12Y to 12BK, then read by the scanner unit 43, and based on the image signal processed by the information processing unit 44, at each of the exposure positions 13Y to 13BK. Image lights for yellow, magenta, cyan, and black are emitted by the optical unit 13, respectively, and electrostatic latent images corresponding to the image signals are formed.
Further, the photoconductor drums 11Y to 11BK are connected to the developing devices 14
After being developed by Y to 14BK to form toner images of respective colors, the toner images are sequentially transferred to the sheet P.

That is, while the toner image is formed on the photosensitive drums 11Y to 11BK, the pickup roller 20 is driven, the sheet paper P is taken out from the paper feeding cassette device 18, and is temporarily stopped at the position of the registration roller 23. ing. Next, the sheet P is the photosensitive drums 11Y to 11B.
The toner images are transferred to the transfer position of the conveyor belt 17 in synchronization with the toner image on K, and the toner images are sequentially transferred from the photoconductor drums 11Y to 11BK in a multiple-transfer manner. After this, the sheet paper P is separated from the conveyor belt 17, conveyed to the fixing device 24, the toner image is heat-fixed, and the image is completed, and then the sheet is ejected onto the sheet ejection tray 27 by the sheet ejection roller pair 26.

On the other hand, in each of the recording devices 10Y to 10BK, the cleaning devices 16Y to 16Y are performed after the toner image is transferred.
After passing through the BK and the static elimination lamps 19Y to 19BK, the next image formation is awaited.

Next, referring to the flow chart shown in FIG.
The temperature control of the heating roller 28b in the fixing device 24 will be described in detail.

When the copying machine starts, step 100
Then, the scanning is started at, the print image is copied by the scanner 43a, and then at step 101, the scanner 43
The printed image copied by a is a CCD (Charge)
The reading is performed by the Coupling Device) sensor 43b, and the process proceeds to step 102.

In step 102, the image data read by the CCD sensor is stored in the line memory 43c,
This image data is input to the main CPU 41 via the input interface 42.

Next, in step 103, the main CP
In the image processing unit 44 of U41, the toner amount is identified as the density information for each cycle from the image data input from the scanner unit 43, with the area area of the nip portion 28d as one cycle of the control block, and step 104 At this time, the calculation processing unit 44a predicts the toner layer thickness based on the density information, and an appropriate value is calculated from the temperature / density table 44b having the related data of the fixing temperature of the toner and the toner layer thickness which are determined by the measurement in advance. Set the fixing temperature.

The set fixing temperature information is input to the fixing device controller 47 via the output interface 46.

Next, at step 106, the thermistor 3
According to the detection result of the heating roller 28b temperature from 0 and the fixing temperature information from the main CPU 41, the area on the heating roller 28b that reaches the nip portion 28d in synchronization with the measured toner image has an appropriate fixing temperature. As described above, the amount of electric power applied to the infrared heater 28a by the heater driver 47a is sequentially controlled for each cycle.

That is, during normal printing standby, the surface temperature of the heating roller 28b is about 130.degree. C., which can supply the amount of heat required to fix one layer of toner having a thickness of about 15 .mu.m.
When the toner layer thickness is two or more layers based on the image data from the scanner unit 43, the infrared heater 2 supplies the necessary amount of heat corresponding to the increased thickness.
The supply of electric power to 8a is increased to control the surface temperature of the heating roller 28b. The thermistor 30
The power supply to the infrared heater 28a is feedforward controlled in consideration of the delay in the thermal response of the above.

At the time of printing, when the main CPU 41 predicts that the layer thickness is one layer from the image data read by the scanner unit 43, the proper fixing temperature should be 130 ° C. From the heater driver 47a
Controls the thyristor 48 so that the amount of electric power supplied to the infrared heater 28a becomes the same as in the print standby, and heats when the area of the one-layer toner image read by the scanner unit 43 reaches the nip portion 28d. 13 rollers 28b
Set to 0 ° C.

As a result, the toner temperature of the toner image having a single layer thickness is 110 ° C. at the boundary with the sheet P as shown by the solid line (a) in FIG. 6, and a good fixing result is obtained. . Next, when the layer thickness is predicted to be three layers from the image data read by the scanner unit 43, the appropriate fixing temperature is set to 180 ° C., and therefore the heater driver 4
7a controls the thyristor 48 so as to increase the amount of electric power supplied to the infrared heater 28a, and when the area of the three-layer toner image read by the scanner unit 43 reaches the nip portion 28d, the heating roller 28b moves 180 degrees. Set it to be ° C.

As a result, the toner temperature of the three-layer toner image was 107 ° C. at the boundary surface with the sheet P as shown by the solid line (b) in FIG. 6, and good fixing results were obtained.

When the layer thickness is two layers, the heating roller 28b is set to 165 ° C., so that the solid line in FIG.
As shown in FIG. 6, the toner temperature at the boundary surface with the sheet P is 109 ° C., and when the layer thickness is four layers, the heating roller 28b is set to 200 ° C., and the solid line (d) in FIG. As shown, the toner temperature at the boundary surface with the sheet P was 102 ° C., and good fixing results were obtained in all cases.

According to this structure, the layer thickness of the toner image is calculated for each cycle from the image data read by the scanning unit 43 even for color images in which the layer thickness of the toner image is remarkably different. In response to this, the amount of electric power supplied to the infrared heater 28a is controlled, and the fixing temperature can be sequentially set for each cycle. Therefore, the toner temperature during fixing can be made substantially constant regardless of the layer thickness. As described above, in a toner layer having a thin layer thickness, an excessive amount of heat is applied, and there is no fear that offset will occur due to a decrease in toner adhesiveness. The release agent can be minimized, deterioration of the heating roller 28b due to the release agent can be prevented, and the life of the fixing roller 28 can be extended.

Further, since the heat loss can be reduced without giving an excessive amount of heat to the toner image, the power consumption thereof can be remarkably reduced as compared with the conventional apparatus.

Next, a second embodiment of the present invention shown in the block diagram of FIG.
Will be described with reference to the embodiment. In the second embodiment, the density information is obtained not by using the image data input from the scanner unit 43 to the main CPU, but by using the image data sent to the optical unit 13 at the time of writing an image. Since the other parts are the same as those in the first embodiment, the same parts are designated by the same reference numerals and the description thereof will be omitted.

That is, in the second embodiment, the image processing unit 44 of the main CPU 41 does not have an arithmetic processing unit for setting the fixing temperature based on the image density, and the image processing unit 44 includes An image writing control unit 56 for controlling the optical unit 13 is connected via the output interface 46. Reference numeral 57 is an arithmetic processing unit that sets an appropriate fixing temperature based on the density information transmitted from the image writing control unit 56 to the optical unit 13.
The fixing device controller 47 is connected to the output side of the.

When printing is started, the scanner unit 4
3 is transmitted to the main CPU 41, and the density information is input to the arithmetic processing unit 57 from the image writing control unit 56 via the output interface 46, the arithmetic processing unit 57 causes the main CPU 41 to perform the same processing as in the first embodiment. The toner layer thickness is predicted on the basis of the density information from, and an appropriate fixing temperature is set from a table having the related data of the toner fixing temperature and the toner layer thickness, which are determined in advance by measurement.

The set fixing temperature information is input to the fixing device controller 47, the detection result of the temperature of the heating roller 28b from the thermistor 30 and the arithmetic processing unit 5 are detected.
According to the fixing temperature from 7, the amount of electric power applied to the infrared heater 28a by the heater driver 47a is controlled for each cycle.

According to this structure, by controlling the amount of electric power of the infrared heater 28a according to the fixing temperature information set by the arithmetic processing unit 57, the toner image can be reproduced in the same manner as in the first embodiment. Since an appropriate amount of heat is always applied regardless of the layer thickness, there is no risk of offset due to the application of an excessive amount of heat, and the heating roller 2 using a release agent is used.
The deterioration of 8b can be prevented, and the life of the fixing roller 28 can be extended and the stain of the image can be prevented. Further, like the first embodiment, the heat loss due to the application of an excessive amount of heat can be reduced, and the power consumption can be remarkably saved as compared with the conventional device.

Next, a third embodiment of the present invention shown in the block diagram of FIG.
Will be described with reference to the embodiment. In the third embodiment, the toner density of the toner image transferred and formed on the sheet P is directly detected and the density information is obtained. Since the other is the same as the first embodiment, it is the same. The same reference numerals are given to the parts, and the description thereof will be omitted.

That is, in the third embodiment, each of the photosensitive drums 11Y to 11B is connected to the main CPU 41.
K and the chargers 12Y to 12BK around it, and the developing device 14
The printer control unit 60 that controls each image forming unit such as Y to 14BK includes a line sensor 61 and a detection data processing unit 6.
3 and the arithmetic processing unit 62 are connected, and the fixing device controller 47 is connected to the output side of the arithmetic processing unit.

When printing is started, the image forming process is carried out in the same manner as in the first embodiment, and the toner images are sequentially transferred onto the sheet P on the conveyor belt 17, and when all the transfer is completed, The line sensor 61 causes the sheet paper P
The upper image density is detected, and the arithmetic processing unit 62 predicts the toner layer thickness based on the density information as in the first embodiment.
An appropriate fixing temperature is set from a table having data relating to the toner fixing temperature and the toner layer thickness, which are calculated in advance.

Then, the set fixing temperature information is input to the fixing device controller 47, and the detection result of the temperature of the heating roller 28b from the thermistor 30 and the arithmetic processing section 62 are inputted.
The amount of electric power applied to the infrared heater 28a by the heater driver 47a is controlled for each cycle in accordance with the fixing temperature from the above.

With this structure, as in the first embodiment, the heating temperature of the heating roller 28b can be sequentially set according to the layer thickness of the toner image, and there is no risk of offsetting due to application of an excessive amount of heat. Also, the release agent for offset prevention can be minimized, deterioration of the heating roller 28b due to the release agent can also be prevented, and the fixing roller 28 can have a long life and contamination can be prevented. Further, there is no extra heat loss due to application of an excessive amount of heat, and the power consumption can be remarkably saved.

In addition, since the image information is directly obtained from the toner image transferred and formed on the sheet P, the image density of the image density caused by the difference in the characteristics of the optical unit 13 and the individual devices such as the developing devices 14Y to 14BK. It is possible to set more appropriate temperature without causing the influence of fluctuation.

The present invention is not limited to the above-described embodiment, and modifications can be made without departing from the spirit of the invention. For example, the apparatus main body may be a laser beam color printer or the like. The heating means is not limited to the roller, and may be in the shape of a belt as long as it can be brought into contact with the toner image, and the position of the heat source thereof is arbitrary and may be provided around the roller or the belt.

The size of one cycle for temperature control is also arbitrary.

[0051]

As described above, according to the present invention, by controlling the temperature of the heating means in accordance with the layer thickness of the developer image on the image support, good fixing property can be obtained on the developer image. Since the optimum amount of heat that can be obtained can be given, extra heat loss is eliminated and power consumption can be saved. Particularly in the case of an image in which the thickness of the toner layer changes remarkably, such as a color image, offset due to an excessive amount of heat can be prevented, stains on the heating means and the image can be prevented, and the heating means is deteriorated by the release agent. Can be prevented and the life of the device can be extended.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a device body of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a fixing device according to a first exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing a temperature control system according to the first embodiment of the present invention.

FIG. 4 is a wiring diagram for controlling the temperature of the fixing device according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing a temperature control operation of the fixing device according to the first embodiment of the present invention.

FIG. 6 is a graph showing the heating characteristics of the toner according to the layer thickness of the first embodiment of the present invention.

FIG. 7 is a block diagram showing a temperature control system of a second embodiment of the present invention.

FIG. 8 is a block diagram showing a temperature control system of a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a state in which a toner image including three layers of toner is fixed by a conventional device.

FIG. 10 is an explanatory view showing a state in which a toner image including one layer of toner is fixed by a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Device main body 24 ... Fixing device 28a ... Infrared heater 28b ... Heating roller 30 ... Thermostat 43 ... Scanner part 44 ... Image processing part 44a ... Arithmetic processing part 47 ... Fixing device controller

Claims (4)

[Claims] 1. A heating unit for transferring the developer image formed on the image support by the image forming unit to heat the developer image, an identifying unit for identifying the layer thickness of the developer image, and an identifying unit for identifying the layer thickness of the developer image. And a control unit that sequentially controls the heat generation amount of the heating unit according to the layer thickness identified by the fixing unit. 2. A heating roller which has a heating element and heats the developer image by being in contact with the developer image formed on the image support by the image forming means, and an identification for identifying the layer thickness of the developer image. A fixing device comprising: a unit and a control unit that sequentially controls the heat generation amount of the heating element according to the layer thickness identified by the identification unit. 3. The image forming means forms an image based on the image information from the information reading means on the image support as a developer image, and the identifying means identifies the layer thickness from the image information from the information reading means. The fixing device according to claim 1, wherein the fixing device is a fixing device. 4. The fixing device according to claim 1, wherein the identifying means identifies the layer thickness from the developer image formed on the image support.