JP2002268292A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an image forming part under an optimum control condition in accordance with temperature change inside a device without using a temperature sensor. SOLUTION: This image forming device is constituted of the image forming part consisting of a photoreceptor, an electrification part for uniformly electrifying the surface of the photoreceptor, an exposure part for exposing an electrostatic image on the photoreceptor, a developing part for forming a toner image by developing the electrostatic image, a transfer part having a transfer belt to transfer the toner image to a transfer material, and a fixing part for fixing the transferred toner image, a tension part for exerting fixed tensile force on the transfer belt, a displacement measuring part for measuring the displacement of the transfer belt on which the fixed tensile force is exerted, a calculation part for calculating temperature inside the device from the measured displacement by using a conversion expression table in which a conversion expression for converting the displacement of the transfer belt into the temperature inside the device is stored, a decision part for deciding the control conditions of the respective parts of the image forming part corresponding to the calculated temperature inside the device by using a control condition table in which the control condition of the respective parts of the image forming part is stored corresponding to the temperature inside the device, and a control part for controlling the respective parts based on the decided control conditions of the respective parts.

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 used for a copying machine, a facsimile, an electrostatic printer, and the like. More specifically, the present invention relates to a toner image formed on a photoreceptor on transfer paper conveyed by a transfer belt. The present invention relates to an image forming apparatus that forms an image by transferring.

[0002]

2. Description of the Related Art In recent years, as image forming apparatuses have become multifunctional, for example, a toner agent of each color formed on a photoreceptor using a transfer belt (conveyor belt) made of a resin called an "intermediate transfer member". Has been developed in which a color image is obtained by transferring an image onto a transfer paper and superimposing a plurality of colors.

In particular, in such a color image forming apparatus, it is necessary to control each part of the apparatus with high accuracy in order to maintain image quality. For example, the image forming position shift, that is, the color shift phenomenon is mainly caused by the speed fluctuation of the device components, but the printing condition (process condition) changes due to the change of the temperature inside the device due to the change of the ambient temperature, and the image quality is reduced. Deteriorate. For example, considering the charging of a photoconductor (electrostatic latent image carrier), the sensitivity of the photoconductor increases in a high temperature region compared to normal temperature (20 to 25 ° C), and becomes overcharged at a constant charging, and the image has a density There is a problem that the printed matter is dark and the background stain is conspicuous.

As a conventional technique for solving such a problem, for example, according to Japanese Patent Application Laid-Open No. Hei 9-171275, the temperature of an intermediate transfer member, or the temperature of an intermediate transfer member and the temperature of a portion correlated therewith are disclosed. Temperature measuring means for measuring the
There has been proposed an image forming apparatus having timing control means for controlling the timing of a latent image writing means so as to write a latent image on a latent image carrier (photoconductor) in accordance with the temperature measured by the temperature measuring means. ing.

According to Japanese Patent Application Laid-Open No. 10-123855, the transfer current value from the transfer means flowing into the electrophotographic photosensitive member during transfer is controlled to be constant according to the output of the temperature sensor. Accordingly, an electrophotographic apparatus capable of obtaining a high-quality image while suppressing the occurrence of a negative ghost, a positive ghost, or the like in an early stage of an image forming process has been proposed.

[0006]

However, in the image forming apparatus described in Japanese Patent Application Laid-Open Nos. 9-171275 and 10-123855, a temperature sensor is disposed at a necessary portion inside the apparatus, and the temperature sensor is used. Since an image forming method of changing a process condition according to a change in temperature is used, there is a problem that the detection temperature differs depending on the arrangement position of the temperature sensor, so that control cannot be performed under the optimum process condition.

The present invention has been made in view of the above circumstances. For example, a displacement of a transfer belt due to a temperature change is measured, and an optimum control condition is determined according to a temperature change in the apparatus. Provided is an image forming apparatus that can obtain a high-quality image that is hardly affected by a temperature change in the apparatus by controlling each unit of the image forming unit based on a control condition.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a photosensitive member, a charging portion for uniformly charging the surface of the photosensitive member, an exposure portion for exposing the charged photosensitive member to an electrostatic image, and a toner for developing the electrostatic image. An image forming section including a developing section for forming an image, a transfer section having a transfer belt for transferring the toner image to a transfer material, and a fixing section for fixing the transferred toner image, and a tension section for applying a constant tension to the transfer belt; A displacement measuring unit that measures the displacement of the transfer belt to which a constant tension is applied, a conversion formula table that stores a conversion formula for converting the displacement of the transfer belt into a temperature in the apparatus, and measurement using the conversion formula table. A calculating unit that calculates the temperature in the apparatus from the displacement of the transferred transfer belt,
A control condition table storing the control conditions of each unit of the image forming unit corresponding to the internal temperature of the device, and a determining unit that determines the control condition of each unit corresponding to the calculated internal temperature of the device using the control condition table. And a control unit that controls each unit of the image forming unit based on the determined control conditions of each unit.

According to the present invention, the displacement of the transfer belt due to the temperature change is measured, the optimum control condition is determined in accordance with the temperature change in the apparatus, and each part of the image forming section is controlled based on the optimum control condition. By doing so, it is possible to obtain a high-quality image which is hardly affected by a temperature change in the apparatus.

[0010] The displacement measuring section may be arranged near the tension section. According to this configuration, since the measurement is performed at a position where the displacement of the transfer belt greatly changes due to a temperature change, the displacement measuring unit can be configured with a displacement measuring sensor with low accuracy.

The displacement measuring unit uses a non-contact displacement detection method by reflected light detection, transmitted light detection, eddy current detection, capacitance detection, magnetic detection or a contact type displacement detection method by strain gauge detection and electric resistance detection. You may. According to this configuration, as the displacement measuring unit that measures the displacement of the transfer belt,
From the non-contact detection method or the contact detection method, a mechanism of a highly reliable displacement detection method with a simple structure can be incorporated.

The control condition table stores, as control conditions, control values for controlling a photosensitive member charge position, a developing bias voltage, a transfer voltage, and a fixing temperature corresponding to the temperature in the apparatus. Alternatively, the charging unit, the developing unit, the transfer unit, and the fixing unit of the image forming unit may be controlled based on each control value. According to this configuration, the charging unit, the developing unit, the transfer unit, and the fixing unit can be controlled based on each control value corresponding to the internal temperature of the apparatus.

The control condition table stores, as control conditions, control values for controlling a photosensitive member charge position, a developing bias voltage, a transfer voltage, and a fixing temperature corresponding to the temperature in the apparatus. When the transfer belt is thermally expanded more than the reference displacement, the transfer belt may be set lower than the reference value, and when the transfer belt is thermally contracted more than the reference displacement, the transfer belt may be set higher than the reference value. . According to this configuration, it is possible to increase the sensitivity of the photoconductor due to an increase in the temperature inside the apparatus and prevent overfixing of the fixing unit.

In the control condition table, each control value may be stored in a stepless or stepwise manner in accordance with the temperature in the apparatus. According to this configuration, a control value for controlling each unit with respect to the internal temperature of the apparatus calculated from the detected displacement of the transfer belt is determined steplessly or stepwise as necessary, and based on the determined control value. Each part of the image forming unit can be controlled.

When the displacement of the transfer belt is calculated from the control conditions changed so as to obtain the optimum image quality, and the calculated displacement of the transfer belt is compared with the displacement of the transfer belt measured by the displacement measuring unit, and the difference is different. A configuration may also be provided that further includes a correction unit that corrects the conversion formula so that the displacement measured by the displacement measurement unit matches the calculated displacement and updates and stores the conversion formula in the conversion formula table. According to this configuration, at the time of the initial operation of the image forming apparatus or at the time of exchanging the transfer belt, only the control conditions are changed so as to obtain an image having the optimum image quality, and the displacement measured by the displacement measuring unit is reduced to the internal temperature of the apparatus. Since the conversion formula for conversion is automatically corrected, it is possible to accurately convert the displacement of the transfer belt to the temperature in the apparatus at the time of initial operation or replacement of the transfer belt.

According to another aspect of the present invention, a photoreceptor, a charging section for uniformly charging the surface of the photoreceptor, an exposure section for exposing the charged photoreceptor to an electrostatic image, and a toner for developing the electrostatic image to form a toner An image forming section including a developing section for forming an image, a transfer section having a transfer belt for transferring the toner image to a transfer material, and a fixing section for fixing the transferred toner image, and a tension section for applying a constant tension to the transfer belt; A displacement measuring unit that measures the displacement of the transfer belt to which a constant tension is applied, a conversion formula table that stores a conversion formula for converting the displacement of the transfer belt into a temperature in the apparatus, and measurement using the conversion formula table. A calculating unit that calculates the temperature in the apparatus from the displacement of the transferred transfer belt,
A control condition table storing the control conditions of each unit of the image forming unit corresponding to the internal temperature of the device, and a determining unit that determines the control condition of each unit corresponding to the calculated internal temperature of the device using the control condition table. An image forming method for forming an image using an image forming apparatus including a control unit that controls each unit of the image forming unit based on the determined control conditions of each unit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. The present invention is not limited by this.

FIG. 1 is a front sectional view showing the structure of a tandem type color copying machine according to an embodiment of the present invention. Figure 1
In the color copier, the automatic duplex document feeder (RA
DF; Recircuating Automatic Document Feeder (I) 1, image reading unit 2, paper feeding unit 3, four image forming units 4a for forming B (black), C (cyan), M (magenta), and Y (yellow) images 4d, a transfer section 5 including a transfer belt 51 and a tension section 56, a displacement measuring section 57, four sets of transfer sections 6a to 6d, a fixing section 7, a paper discharge section 8, a control section 9,
It comprises a document table 10 and the like.

The control unit 9 is, for example, a computer CP.
U, a first memory, a second memory, an I / O (input / output interface), a clock oscillator for starting the CPU, and the like. The first memory is, for example, ROM, EE
It is composed of a PROM or the like, and stores a control program, control data, and a table for controlling each unit of the image forming apparatus. The second memory is, for example, a RAM, an EEPROM,
And the like, and stores color-converted document image information, control results, and various measured data.

The CPU controls the entire color copier according to various control programs stored in the first memory, and controls a document feed control unit, an image reading control unit, an image processing unit, a paper feed control unit, an image formation control unit, It functions as a transport control unit, a transfer control unit, a fixing control unit, and a paper discharge control unit.

Next, the automatic duplex document feeder 1 and the image reading section 2 will be described. The automatic duplex document feeder 1
The image reading unit 2 is supported on the upper surface of the document table 10 so as to be openable and closable, and one side of the document is positioned at a predetermined position on the document table 10.
The document is conveyed so as to face the document table, and after the image reading on one side is completed, the document is turned over so that the other side faces the image reading unit 2 at a predetermined position on the document table 10 and is placed on the document table 10. It is designed to be transported toward. The automatic double-sided document feeder 1 includes an image reading unit 2
Thus, after the reading of both sides of one document is completed, this document is ejected, and a double-sided document feeding operation for the next document is executed.

The image reading unit 2 includes an automatic double-sided document feeder 1
In order to read an image of a document conveyed onto the document table 10 by the scanner, the document is arranged below the document table 10. The image reading section 2 has document scanning bodies 21 and 22 which reciprocate in parallel along the lower surface of the document table 10, an optical lens 23, and a CCD line sensor 24 which is a photoelectric conversion element.

The original scanning body is composed of a first scanning unit 2
1 and a second scanning unit 22. The first scanning unit 21 has an irradiation lamp for irradiating the surface of the original image, and a first mirror for deflecting a reflected light image from the original in a predetermined direction. Are reciprocated in parallel at a predetermined scanning speed while maintaining the above distance.

The second scanning unit 22 has second and third mirrors for further deflecting the reflected light image from the document deflected by the first mirror of the first scanning unit 21 in a predetermined direction. In addition, it reciprocates in parallel with the first scanning unit 21 while maintaining a constant speed relationship. The optical lens 23 reduces the light image reflected from the document deflected by the third mirror of the second scanning unit, and forms the reduced light image at a predetermined position on the CCD line sensor 24. .

The CCD line sensor 24 sequentially photoelectrically converts the formed light image, reads it as a black and white image or a color image, and separates it into R (red), G (green), and B (blue) color components. Line data can be output. The read image is stored in the memory of the control unit.

Next, image formation of a color copying machine will be described. The paper feed unit 3 includes, for example, a pickup roller, a registration roller 31, a roller motor, a motor driver, a paper feed tray, and the like. As the transfer paper P, cut sheet-shaped paper is used. The transfer paper P is lifted one by one from a paper cassette by a pickup roller, and is sent to the transfer belt 51 by a feed roller.

The paper feed unit 3 includes image forming units 4a to 4d.
The transfer papers P provided below the paper feed tray and stacked in the paper feed tray are separated one by one and supplied toward the image forming units 4a to 4d. The transfer paper P separated and supplied one by one is fed to the image forming units 4a to 4d at a controlled timing by a pair of registration rollers 31 disposed in front of the image forming units 4a to 4d.

The first image forming unit 4a, the second image forming unit 4b, the third image forming unit 4c, and the fourth image forming unit 4
“d” is arranged adjacent to the transfer belt 51 of the transport unit 5 at predetermined intervals in order from the upstream side of the transport path of the transfer paper P.
Each of the image forming units 4a to 4d includes a photoconductor 41a to 41d, a charging unit 42a to 42b, an exposing unit 43a to 43c, and a developing unit 4.
4 to 44d, photoconductor cleaning units 45a to 45d, photoconductor discharging units 46a to 46d, and the like.

The photoconductors 41a to 41d are made of, for example, a drum-shaped aluminum material. Under the control of the control unit 9, a peripheral speed set in advance through a photoconductor drive unit including a photoconductor motor, a motor driver, and the like. To rotate in the direction of arrow F.

The charging units 42a to 42d are composed of, for example, a high voltage generating circuit, and are configured to uniformly charge the surfaces of the photoconductors 41a to 41d under the control of the control unit 9.

The exposure units 43a to 43d include, for example, a laser beam scanner unit including a laser light emitting element, a polygon mirror, an fθ lens, a mirror driver, and a mirror, and a writing optical system (LED head) including a light emitting diode array and an imaging lens array. ).

The LED head is smaller in size than the laser beam scanner unit, and has no moving parts and is silent. Therefore, it can be suitably used in an image forming apparatus such as a tandem type digital color copying machine which requires a plurality of optical writing units.

The exposure unit 43a receives a pixel signal corresponding to a black component image of a color original image, the exposure unit 43b receives a pixel signal corresponding to a cyan color component image of a color original image, and the exposure unit 43c. A pixel signal corresponding to the magenta color component image of the color document image is input to the exposure unit 43d, and a pixel signal corresponding to the yellow color component image of the color document image is input to the exposure unit 43d.

Under the control of the control unit 9, the charged photosensitive member 4
Forming an electrostatic image corresponding to the color-converted document image information on the photosensitive members 41a to 41d by scanning and exposing the surfaces of 1a to 41d with a laser beam modulated according to the color-converted document image information I do.

The developing units 44a to 44d include, for example, a developing roller, a developing roller motor, a toner box for filling color toner, and a toner supply device for supplying a set amount of toner. And cyan in the developing section 44b.
4c stores magenta toner, and the developing unit 44d stores yellow toner. Under the control of the controller 9, the electrostatic images exposed on the photoconductors 41a to 41d are developed to form toner images of respective colors.

The photosensitive member cleaning units 45a to 45d are:
For example, the cleaning unit includes a blade, a blade driver, and the like, and cleans residual toner, dust, and paper powder attached to the photoconductor.

The transport unit 5 includes, for example, the image forming units 4a to 4
transfer belt 5 having a loop structure arranged so as to be able to contact d.
1, a drive roller 52, a driven roller 53, a transport motor, a motor driver, a transfer belt static elimination unit 54, a transfer belt cleaning unit 55, a tension unit 56, and a displacement measurement unit 57, which are arranged below the image forming units 4a to 4d. A configuration is adopted in which a constant tension is applied to the transfer belt by the tension unit 56 so that the gap between the drive roller 52 and the driven roller 53 extends horizontally, and the transfer paper P is electrostatically attracted to the transfer belt 51 and transported by the control of the control unit 9. Have been.

The transfer belt static eliminator 54 includes, for example, an AC voltage generating circuit or the like, and removes static electricity by applying an AC voltage to the transfer paper P. Transfer belt cleaning unit 55
Has a cleaning blade 55a for cleaning the transfer belt 51.

The transfer paper P is transferred to each of the image forming sections 4a to 4a.
At a timing d, it is fed onto the transfer belt 51 rotating in the Z direction shown in FIG. The transfer belt 51 is
When the transfer roller P is frictionally driven in the Z direction shown in FIG. 1 by the drive roller 52 and is supplied from the paper supply unit 3, and the transfer image P is transferred to the toner image by the first image forming unit 4 a. At the same time, the transfer paper P is electrostatically attracted to the transfer belt 51, and the transfer paper P is transported to the fourth image forming unit 4d without being shifted.

The transfer belt 51 is made of a thin resin material such as PI (polyimide), PC (polycarbonate), PVDF (polyvinylidene fluoride), and ETFE (ethylene tetrafluoroethylene copolymer). It has a coefficient of thermal expansion.

The displacement measuring section 57 is arranged near a tension section 56 for applying a constant tension to the transfer belt 51, and is configured to measure a displacement of the transfer belt 51 due to a temperature change. As the displacement measuring unit 57, a mechanism using a non-contact displacement detection method using reflected light detection, transmitted light detection, eddy current detection, capacitance detection, magnetic detection or a contact type displacement detection method using strain gauge detection and resistance value detection. It consists of.

The ROM of the control unit 9 also stores a conversion formula table for storing a conversion formula for converting the displacement of the transfer belt into an internal temperature of the apparatus, and controls the control conditions of each unit of the image forming unit in accordance with the internal temperature of the apparatus. A storage area that functions as a stored control condition table is provided.

The CPU of the control unit 9 executes each control program, and uses the conversion formula table storing the conversion formula for converting the displacement of the transfer belt into the internal temperature of the apparatus. Control section for calculating the internal temperature of the apparatus from the displacement of the transfer belt 51 measured by the control section, the control conditions of the image forming sections 4a to 4d, the transfer sections 6a to 6d, and the fixing section 7, which are stored corresponding to the internal temperature of the apparatus. Using the table, it functions as a determining unit that determines the control condition of each unit corresponding to the calculated internal temperature of the apparatus, and based on the determined control condition of each unit, the image forming units 4a to 4d and the transfer units 6a to 6a.
d, controlling the fixing unit 7;

The transfer units 6a to 6d include, for example, a transfer roller, a transfer power source, a transfer roller motor, a motor driver, and the like.
The toner images of the respective colors formed by .about.4d are electrostatically attracted and sequentially transferred onto the transfer paper P conveyed by the transfer belt 51. When the transfer of the toner image by the fourth image forming unit 4 d is completed, an alternating current for separating the transfer paper P from the transport belt 51 is applied by the charge eliminator 54, and is guided to the fixing unit 7.

The fixing unit 7 includes, for example, a fixing roller incorporating a heater, a fixing roller motor, a motor driver, and the like. The transfer paper P is disposed downstream of the transport unit 5. The fixing unit 7 is configured to fix the toner image transferred onto the transfer paper P by superimposing the color while sequentially heating the toner image under the control of the control unit 9.

The paper discharge unit 8 includes, for example, a conveyance direction switching gate 81, a discharge roller 82, a roller motor, a motor driver, a paper discharge tray 83, and the like. Is discharged to a paper discharge tray 83 attached to the outer wall of the color copier main body via the transport direction switching gate 81.

The transport direction switching gate 82 reverses the front and back via the path for discharging the fixed transfer paper P to the paper discharge tray 83 and the switchback transport path 84 depending on whether or not to perform double-sided copying. It selectively switches between a path for resupplying the transfer paper P toward the forming units 4a to 4d.

FIG. 2 is a view showing a cross-sectional structure of the tension portion of this embodiment. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. The tension unit 56 includes a frame 56a,
Tension roller 56b, guide hole 56c, shaft 5
6d, a spring 56e and the like. The tension portion 57 is always weighted downward by its own weight and spring force by an auto tension system.

The transfer belt 51 is made of a resin material such as PI (polyimide), PC (polycarbonate), PVDF (polyvinylidene fluoride), and ETFE (ethylene tetrafluoroethylene copolymer).
It has a coefficient of thermal expansion of E10-5 / ° C.

Since the transfer belt 51 expands and contracts due to a temperature change in the apparatus, if the displacement sensor of the displacement measuring section 57 is fixed near the tension section 56, the distance between the lower portion of the tension section 56 and the displacement sensor fluctuates. I do.

As a method for detecting the displacement of the transfer belt 51, for example, a non-contact type displacement detection method using reflected light detection, transmitted light detection, eddy current detection, capacitance detection, and magnetic detection,
There is a contact type displacement detection method using strain gauge detection and resistance value detection. As a method of converting the expansion and contraction of the transfer belt into a temperature, the relationship between the temperature in the apparatus and the displacement of the transfer belt is recorded in advance by experiments, and when an actual machine is used, the environmental temperature is calculated back from the displacement measured by the displacement sensor (see FIG. 4).

FIG. 3 is a diagram showing a method for measuring the displacement of the transfer belt of this embodiment. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals. In this embodiment, the expansion coefficient of the resin belt: 8E10-5 / ° C., the belt length: 860 mm
Is operated at a temperature in the apparatus of 5 to 35 ° C. (temperature change width: 30 ° C.).

When calculating the circumferential length displacement of the transfer belt when the temperature change width is 30 ° C., 8E10−5 / ° C. × 860 × 3
0 = 2.064 mm (0.688 mm / ° C.)
On the lower surface (tension position) of the tension portion 56, when the belt length changes by 2 mm, the tension portion 56 becomes 10 mm.
Since it fluctuates to the extent, it can be measured even by a displacement sensor that is not high precision.

In the displacement measurement method shown in FIG. 3A, for example, a reflection type laser displacement meter comprising a semiconductor laser and a CCD line sensor is used to attach a reflection plate to the lower surface of the tension portion 56, It is CCD that the reflection position of the light beam emitted by the semiconductor laser changes due to the displacement in the direction.
This is a method of measuring the displacement of the transfer belt by measuring with a line sensor. A magnet may be attached to the lower surface of the tension portion 56, and the vertical displacement of the magnet may be measured with a magnetoresistive element.

In the displacement measuring method shown in FIG. 3B, a constant alternating magnetic field is applied to a metal tension roller 56b using, for example, an eddy current displacement meter to displace the surface of the tension portion 56 in the vertical direction. Is a method for measuring the displacement of the transfer belt by electrically measuring the change in the eddy current generated in the tension roller 56b.

In the displacement measuring method shown in FIG. 3C, for example, a strain gauge type displacement meter is used to mechanically transmit the vertical displacement of the tension portion to the strain gauge, and the displacement of the strain gauge is electrically transmitted. This is a method of measuring the displacement of the transfer belt 51 by performing the measurement. A change in resistance value may be converted into a voltage by using a slide resistance instead of the strain gauge and measured.

In the displacement measuring method shown in FIG. 3D, the position of the hole through which the light emitted from the light emitting diode passes through the transmission hole plate is determined by using a transmission type optical sensor including a transmission hole plate and a light emitting and receiving diode. This is a method of measuring the displacement of the transfer belt by detecting. In addition, the displacement of the transfer belt can be measured using a differential transformer.

FIG. 4 is a diagram showing the relationship between the displacement of the transfer belt and the temperature in the apparatus according to this embodiment. FIG. 4A is a diagram showing the measurement results of the displacement of the transfer belt and the temperature in the apparatus. FIG.
(B) is the displacement-graph and displacement for the temperature measurement result-
It is a figure which shows a temperature conversion formula.

From the displacement-temperature measurement result, the following approximate expression for converting the displacement-temperature is obtained. Here, S indicates the displacement (mm) of the transfer belt, and T indicates the temperature in the apparatus (° C.). Approximate expression of temperature-displacement conversion: S ≒ (10/29) · (T-8) Approximate expression of displacement-temperature conversion: T ≒ (29/10) · S + 8 Approximate expression of displacement-temperature conversion and displacement-temperature conversion Is stored in the conversion formula table area of the first memory of the control unit 9 in an updatable manner.

FIG. 4C is a diagram showing a displacement conversion formula with respect to the temperature in the apparatus and a numerical example. As shown in FIG.
By substituting the numerical value of the temperature in the apparatus for the approximate expression S 温度 (10/29) · (T−8) of the temperature-displacement conversion, the displacement S of the transfer belt at the temperature T in the apparatus can be obtained.

FIG. 5 is a diagram showing the configuration of the control condition table of this embodiment. The control condition table shown in FIG. 5 is stored in the first memory in advance. FIG. 5A shows a control condition table 1 for determining a control condition from the displacement of the transfer belt.
FIG. 5B shows a configuration of a control condition table 2 for setting a control value belonging to the control condition. Here, the control condition table is divided into two for the sake of explanation, but is stored in the first memory of the control unit 9 as one table.

When the displacement of the transfer belt is measured, an approximate expression of a preset belt displacement-temperature conversion (for example, T ≒
(29/10) · S + 8), the apparatus temperature T (° C.) is calculated, and a corresponding control condition can be selected from the control conditions 1-5 based on the calculated apparatus temperature T (° C.). Have been.

The control condition table includes a preset transfer voltage (kV), fixing temperature (° C.),
A control value including a photoconductor surface potential (V) and a developing bias voltage (V) is stored. When any one of the control conditions 1 to 5 is selected, the transfer voltage (kV), the fixing temperature (° C.), the photoconductor surface potential (V), and the developing bias voltage (V) corresponding to the selected control condition are included. Each control value is determined, and the charging unit, the transfer unit, and the fixing unit are respectively controlled based on the determined control values.

The control condition table includes, as control conditions, control values including at least a photosensitive member charge position, a transfer voltage, a developing bias voltage, and a fixing temperature for controlling the charging unit, the transfer unit, and the fixing unit, respectively. Correspondingly stored, the photoconductor charge potential, transfer voltage, developing bias voltage and fixing temperature are lower than the reference value when the transfer belt is thermally expanded from the reference displacement, and the transfer belt thermally contracts from the reference displacement. Is set higher than the reference value. In this control condition table, control conditions for controlling the image forming unit and their control values are stored in a stepwise manner corresponding to the temperature in the apparatus, but may be stored in a stepless manner.

When the control section 9 changes the control conditions so as to obtain an image having the optimum image quality during the initial operation of the image forming apparatus or when the transfer belt is replaced, the control section 9 determines the displacement of the transfer belt from the changed control conditions. When the calculated and calculated displacement of the transfer belt is different from the displacement of the transfer belt measured by the displacement measuring unit 57, the displacement measured by the displacement measuring unit 57 coincides with the calculated displacement. Function as a correction unit that corrects the conversion formula and updates and stores it in the conversion formula table, so that during the initial operation of the image forming apparatus or when the transfer belt is replaced, it is possible to accurately convert the displacement of the transfer belt to the temperature inside the apparatus. Can be.

[0066]

According to the present invention, the displacement of the transfer belt due to the temperature change is measured, the optimum control condition is determined according to the temperature change in the apparatus, and each part of the image forming section is determined based on the optimum control condition. , It is possible to obtain a high-quality image which is hardly affected by a temperature change in the apparatus.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a configuration of a tandem type color copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a cross-sectional structure of a tension portion according to the present embodiment.

FIG. 3 is a diagram illustrating a transfer belt displacement measuring method according to the present embodiment.

FIG. 4 is a diagram illustrating a relationship between the displacement of the transfer belt and the temperature in the apparatus according to the present embodiment.

FIG. 5 is a diagram illustrating a configuration of a control condition table according to the present embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Automatic double-sided document feeding unit 2 Image reading unit 3 Feeding unit 4 a to 4 d Image forming unit 41 a to 41 d Photoconductor 42 a to 42 d Charging unit 43 a to 43 d Exposure unit 44 a to 44 d Developing unit 45 a to 45 d Photoconductor cleaning unit 5 Transport unit REFERENCE SIGNS LIST 51 transfer belt 52 drive roller 53 driven roller 54 transfer belt static elimination unit 55 transfer belt cleaning unit 56 tension unit 57 displacement measurement unit 6a to 6b transfer unit 7 fixing unit 8 paper discharge unit 9 control unit 10 platen

Continued on the front page F-term (reference) 2H027 DA02 DA04 DA06 DA07 DA11 DE02 DE03 DE04 DE07 DE10 EA01 EA03 EA05 EA12 EA20 EC06 EC07 EC09 JC02 JC03 JC06 JC08 2H200 FA01 GA23 GA31 GA41 GB30 GB50 HA28 JB06 JB50 PB25 PB25

Claims (8)

[Claims] 1. A photoconductor, a charging unit for uniformly charging the surface of the photoconductor, an exposure unit for exposing the charged photoconductor to an electrostatic image, a developing unit for developing the electrostatic image to form a toner image, and a toner An image forming unit including a transfer unit having a transfer belt for transferring an image to a transfer material and a fixing unit for fixing the transferred toner image; a tension unit for applying a constant tension to the transfer belt; and a transfer belt to which a constant tension is applied A displacement measuring unit that measures the displacement of the transfer belt, a conversion formula table that stores a conversion formula for converting the displacement of the transfer belt into a temperature in the apparatus, and an apparatus that converts the measured displacement of the transfer belt using the conversion formula table. A calculating unit for calculating the internal temperature, a control condition table storing control conditions of each unit of the image forming unit corresponding to the internal temperature, and each unit corresponding to the calculated internal temperature using the control condition table. of A determination unit for determining a control condition;
A control unit for controlling each unit of the image forming unit based on the determined control condition of each unit. 2. The image forming apparatus according to claim 1, wherein the displacement measuring unit is disposed near the tension unit. 3. The non-contact displacement detection method using a reflected light detection, a transmitted light detection, an eddy current detection, an electrostatic capacitance detection, and a magnetic detection or a contact type displacement detection method using a strain gauge detection and an electric resistance detection. The image forming apparatus according to claim 1, wherein: 4. The control condition table stores, as control conditions, respective control values for controlling a photosensitive member charge position, a developing bias voltage, a transfer voltage, and a fixing temperature, respectively, in correspondence with the temperature in the apparatus. The image forming apparatus according to claim 1, wherein the control unit controls the charging unit, the developing unit, the transfer unit, and the fixing unit based on each control value. 5. The control condition table stores, as control conditions, control values for controlling a photoconductor charge position, a developing bias, a voltage transfer voltage, and a fixing temperature corresponding to an internal temperature of the apparatus. The control value is set lower than the reference value when the transfer belt is thermally expanded from the reference displacement,
When the transfer belt is thermally contracted from the reference displacement,
2. The image forming apparatus according to claim 1, wherein the setting is higher than the reference value. 6. The image forming apparatus according to claim 5, wherein the control condition table stores the control values in a stepless or stepwise manner in accordance with the temperature in the apparatus. 7. A transfer belt displacement is calculated from control conditions changed so as to obtain an optimum image quality, and the calculated transfer belt displacement is compared with the transfer belt displacement measured by a displacement measuring unit. When there is a difference, the correction unit further includes a correction unit that corrects the conversion formula so that the displacement measured by the displacement measurement unit matches the calculated displacement, and updates and stores the conversion formula in the conversion formula table. Item 2. The image forming apparatus according to Item 1. 8. An image forming method for forming an image using the image forming apparatus according to claim 1.