JP2001042699A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of restraining occurrence of uneveness in image quality. SOLUTION: Prescribed fixing test images TA and TC are formed periodically on a recording body S or according to selection by an operator (S1) or the like. Next, a unified control part obtains the glossiness LA and LC of the respective images TA and TC on the basis of the intensity of reflected light obtained by an image information detection part and calculates a difference (LA-LC) between them (S2 and S3). Then, the unified control part decides the rank of the distortion amount of a roller on the basis of the calculated result (S4), and a cam 210C is driven to correct the pressing force of a pressure roller 213 in accordance with the rank, so that the distortion is made smaller (S5). Thus, fixing pressure is uniformized in a direction orthogonal to the recording body carrying direction. Accordingly, occurrence of uneveness in the image quality is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile. More specifically, the present invention relates to an image forming apparatus capable of suppressing occurrence of image quality unevenness.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic copying machine, a permanent image is obtained by fixing a toner image transferred to a recording medium. Here, as a fixing method, there are methods such as heat fixing, pressure fixing, and solvent fixing. Among them, a heat roller type fixing device using heat fixing is widely and generally used. As this fixing device, for example, a fixing device including a heating roller and a pressure roller is known. The heating roller is a metal roller having good heat conduction and small heat capacity. The heating roller has a heater lamp inside, and the surface temperature is detected by a thermistor or the like, and the temperature is controlled so as to be within a predetermined fixing temperature range. On the other hand, the pressing roller has a core material whose surface is coated with elastic silicon rubber or the like. The heating roller and the pressure roller are rotatably supported in a state where they are pressed against each other. When the recording material on which the toner image is transferred passes between the heating roller and the pressure roller, the toner melts. At the same time, the toner image is pressed against the recording medium to fix the toner image, thereby obtaining a permanent image. In the fixing device provided in the color image forming apparatus, the surface of the heating roller is also covered with silicone rubber.

[0003]

However, in the conventional apparatus, the heating roller or the pressure roller may be distorted while using the apparatus.
This is because these rollers are pressed against each other and are repeatedly subjected to a thermal load, so that the core material of the roller itself is distorted, or the silicone rubber covering the core material is deformed due to wear or deterioration. When distortion occurs in the heating roller or the pressure roller, the distribution of the pressing force in the axial direction of the roller becomes uneven. For this reason, the fixing condition changes in a direction orthogonal to the recording medium conveyance direction, and thus, the image quality becomes uneven in the fixed image. This is because a poorly fused toner or an overmelted portion of the toner is formed in a fixed image formed on one recording medium, a uniform image state cannot be obtained, and the image state of the fixed image fluctuates. . However, the only way to suppress the occurrence of such image quality unevenness is to perform adjustment / repair or replacement of parts by a service person, and there is a problem that it takes much time and effort.

Accordingly, the present invention has been made to solve the above-described problem, and has as its object to provide an image forming apparatus capable of suppressing the occurrence of image quality unevenness.

[0005]

According to the image forming apparatus of the present invention, which has been made to solve the above-described problems, it is possible to obtain test image data for generating a predetermined fixing test image. Image forming means for forming an unfixed image on a recording medium based on image data, and a heater provided inside at least one of the rollers while pressing the two rollers, and heating the roller by the heater And a contact heating and fixing unit that heats and fixes the unfixed image by passing the recording medium carrying the unfixed image between the rollers in the image forming apparatus. A light emitting element for irradiating light to the fixing test image fixed on the body, and reflecting or transmitting the fixing test image irradiated from the light emitting element; A light receiving element for detecting light intensity information; and image information detecting means for detecting image information of the fixing test image at at least two or more positions of the recording medium different in a direction orthogonal to the recording medium conveyance direction. And calculating a difference between the image information of each of the fixing test images based on the detection result of the image information detecting unit, and based on the difference, one of the rollers in the contact heating and fixing unit is used as a reference for the other roller. There is provided a roller distortion amount estimating unit for estimating the distortion amount, and a fixing condition correcting unit for correcting a fixing condition in the contact heating fixing unit based on the distortion amount estimated by the roller distortion amount estimating unit.

In this image forming apparatus, the image forming means includes:
An unfixed image (toner image) is created on a recording medium. Here, the unfixed image created on the recording medium by the image creating means includes a copy image of a document to be copied, an image based on image data input to the image forming apparatus, and a predetermined test image based on test image data. included. Note that the test image is created based on test image data acquired by a test image data acquisition unit from a memory in which test image data is stored in advance or from outside. Next, the contact heating fixing unit fixes the unfixed image created by the image creating unit on the recording medium.

Here, when the image forming means creates a test image on the recording medium based on the test image data at least at two or more locations of the recording medium in different directions in the direction orthogonal to the recording medium transport direction, The test image (unfixed image) is fixed on the recording medium by the heat fixing means.
Then, when the fixing of the test image is completed, the image information detecting means detects the image information of the fixing test image fixed on the recording medium.

The image information is detected by irradiating the fixing test image on the recording medium with light by the light emitting element and receiving light reflected or transmitted from the fixing test image by the light receiving element.
Here, the image information refers to, for example, information related to the state of the image such as the surface state, translucency, and coloring,
Any information that allows the user to know the image state is included. Specifically, the intensity of the transmitted light (transmittance), the intensity of the reflected light (reflectance, glossiness), or the color shift (shift of lightness, hue, and saturation) of the fixing test image are exemplified.

Subsequently, the roller distortion amount estimating means calculates a difference in image information between the fixing test images from the detection result of the image information detecting means, and based on the difference, determines one roller in the contact heating fixing means as a reference. Then, the amount of distortion of the other roller is estimated. Then, the fixing condition correcting means,
The fixing condition in the contact heating fixing unit is corrected based on the distortion amount estimated by the roller distortion amount estimating unit. By this correction, the result of estimation by the roller distortion amount estimating means is reflected in the fixing condition so that the unfixed image is uniformly fixed on the recording medium in the direction orthogonal to the recording medium conveyance direction in one recording medium ( (Feedback), it is possible to control the image quality unevenness to be suppressed. Therefore, it is possible to obtain a fixed image in which the occurrence of image quality unevenness is suppressed.

[0010] As the recording medium, in addition to plain paper, any recording medium that can fix an image, such as a thick paper, an OHP sheet, or a special paper coated with a resin may be used. The light emitting element may be any element that emits light in the visible light region.
For example, a halogen lamp, a light emitting diode, a semiconductor laser, and the like can be given. Furthermore, the light receiving element only needs to have a sensitivity range that responds to light emitted from the light emitting element. For example, a CCD, a photodiode, and the like can be given.

Here, in order to obtain the reflectance and the transmittance, the intensity of the incident light is necessary in addition to the intensity of the reflected light or the transmitted light. Therefore, the intensity of the incident light may be separately detected in addition to the reflected light or the transmitted light. However, when the intensity of the incident light is known, such as when the intensity is constant, the evaluation can be performed only with the intensity of the reflected light or the transmitted light. In addition, in the measurement of the intensity of the incident light, a method of directly measuring the intensity using a half mirror or the like, and a method of indirectly measuring the applied voltage, the current consumption, the power consumption, and the like of the light emitting element can also be used. .

In the image forming apparatus according to the present invention, it is preferable that the fixing condition correcting means corrects one of a fixing temperature and a fixing speed in the contact heating fixing means.

As described above, the fixing condition correcting means corrects one of the fixing temperature and the fixing speed in the contact heating fixing means, so that the developer adhering to the recording medium can be appropriately melted. Here, by increasing the fixing temperature, the developer attached to the recording medium is easily melted, so that the image surface of the fixed image becomes smoother and glossiness and transmittance are increased. The value changes.
Further, when fixing is performed at the same fixing temperature, if the fixing pressure is different depending on the location due to the distortion of the roller, the image information such as the glossiness of the fixed image will be different. This difference in image information differs depending on the fixing temperature, and increases as the fixing temperature decreases, and decreases as the fixing temperature increases (see FIG. 11). Therefore, by increasing the fixing temperature, it is possible to reduce the difference in image information and to approach a uniform image state.

That is, it is possible to control so as to suppress the image quality unevenness by increasing (fixing) the fixing temperature by reflecting (feeding back) the result of estimation by the roller distortion estimating means on the fixing temperature. Therefore, it is possible to obtain a fixed image in which the occurrence of image quality unevenness is suppressed. A similar effect can be obtained by correcting the fixing speed instead of correcting the fixing temperature.

The correction target in the fixing condition correction means is:
Either the fixing temperature or the fixing speed in the contact heating fixing unit may be used, or the two conditions may be corrected simultaneously. By correcting two conditions at the same time, the range that can be corrected can be increased synergistically, so that it is particularly effective when, for example, correcting only one condition is not sufficient.

Alternatively, in the image forming apparatus according to the present invention, the contact heating fixing unit may include a fixing condition changing unit capable of changing at least one or more fixing conditions in a direction orthogonal to the recording medium conveying direction. preferable.

In this image forming apparatus as well, the image information detecting means detects the image information of the fixing test image at at least two or more places on the recording medium where the positions in the direction orthogonal to the recording medium conveyance direction are different. Subsequently, the roller distortion amount estimating means calculates a difference in image information between the fixing test images from the detection result by the image information detecting means, and based on one of the rollers in the contact heating fixing means based on the difference. Of the other roller is estimated.

Then, based on the distortion amount estimated by the roller distortion amount estimating unit, the fixing condition changing unit determines at least one or more fixing conditions (fixing temperature, fixing pressure, etc.) in the contact heating fixing unit and conveys the recording medium. The correction is made in the direction orthogonal to the direction. This makes it possible to change the fixing condition in the recording medium conveyance direction. Therefore, by controlling the feedback of the estimation result of the roller distortion amount estimating means in the fixing condition so as to uniformly fix the unfixed image on the recording medium, it is possible to control the image quality unevenness to be suppressed. it can. Therefore, it is possible to obtain a fixed image in which occurrence of image quality unevenness is suppressed.

In the image forming apparatus according to the present invention, the fixing condition changing means changes the axial distribution of the pressing force of the roller by changing the distance between the two pressed rollers. It is preferable that the fixing condition correcting unit is a roller pressing force correcting unit that corrects an axial distribution of the pressing force of the roller by the roller pressing force changing unit.

In this image forming apparatus as well, the image information detecting means detects the image information of the fixing test image at at least two or more places on the recording medium which are different in the direction perpendicular to the recording medium conveyance direction. Subsequently, the roller distortion amount estimating means calculates a difference in image information between the fixing test images from the detection result by the image information detecting means, and based on one of the rollers in the contact heating fixing means based on the difference. Of the other roller is estimated.

Then, the roller pressing force correcting means corrects the roller pressing force by the roller pressing force variable means based on the estimation result by the roller distortion amount estimating means. Thereby, the distribution of the fixing pressure in the axial direction of the contact heating fixing unit can be changed. Therefore, the result of comparison by the roller distortion amount estimating means is reflected on the pressing force of the roller so that the unfixed image on the recording medium is uniformly fixed in the direction orthogonal to the recording medium conveyance direction in one recording medium ( Feedback), it is possible to control so as to suppress the occurrence of image quality unevenness. Therefore, it is possible to obtain a fixed image in which occurrence of image quality unevenness is suppressed.

Further, in the image forming apparatus according to the present invention, the fixing condition changing means includes a plurality of the heaters in a direction orthogonal to the recording medium conveying direction and can change the control temperature of each of the plurality of heaters. It is also preferable that the fixing condition correcting means is a temperature correcting means for correcting a control temperature of each of the heaters.

In this image forming apparatus as well, the image information detecting means detects the image information of the fixing test image at at least two or more places in the recording medium where the positions in the direction orthogonal to the recording medium conveyance direction are different. Subsequently, the roller distortion amount estimating means calculates a difference in image information between the fixing test images from the detection result by the image information detecting means, and based on one of the rollers in the contact heating fixing means based on the difference. Of the other roller is estimated.

The temperature correcting means corrects the control temperature of each heater provided in the divided heating means based on the result of estimation by the roller distortion estimating means. This allows
The fixing temperature in the axial direction of the contact heating fixing means can be changed. Therefore, in order to uniformly fix the unfixed image on the recording medium in a direction orthogonal to the recording medium conveyance direction in one recording medium, the control result of each heater is compared with the control result of the roller distortion amount estimating means. Reflection (feedback)
By doing so, it is possible to control so as to suppress the occurrence of image quality unevenness. Therefore, it is possible to obtain a fixed image in which occurrence of image quality unevenness is suppressed.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the drawings. First, the first embodiment will be described. The first embodiment is an electrophotographic copying machine in which the image forming apparatus according to the present invention is mounted, creates a predetermined fixing test image, and obtains from the intensity information of reflected light of the fixing test image and the like. The amount of distortion of the fixing roller is estimated, and the pressing force of the fixing roller is corrected based on the estimation result.

As shown in FIG. 1, the copying machine 1 includes an image reader section IR and a page printer section PRT. Then, based on the image data transferred from the image reader section IR, the page printer section PRT prints the image of the document by an electrophotographic process.

The image reader section IR includes an original glass 10
An image reading unit 2 that detects reflected light from an image of a document set thereon, photoelectrically converts the reflected light, and reads image data corresponding to the image of the document, and an image that performs data processing according to various image forming modes. And a processing unit 3. Note that the image reading section 2 includes a data memory section 9 for temporarily storing the read image data. A document cover 11 for holding a document is mounted above the image reader IR.

On the other hand, the page printer section PRT has an optical scanning section 4, an image processing section 5, and a transport section 6.
The optical scanning section 4 includes a polygon mirror 21 and a reflection mirror 22 for scanning and irradiating the photosensitive drum 30 with laser light. The image processing unit 5 includes a photosensitive drum 30, a charging charger 31, and developing units 32Y and 3
2C, 32M, 32K, a transfer drum 34 having a transfer charger 33, and a cleaning device 35. The transport unit 6 includes a paper cassette 44 for stacking and storing the recording medium.
And various transport rollers for transporting the recording medium supplied from the paper cassette 44 or the manual feed tray 45; a fixing device 40; and an image information detecting unit 43 including halogen lamps 41A and 41C and CCD sensors 42A and 42C. And a paper discharge tray 46 for accommodating a recording medium that has been copied and discharged outside the apparatus.

Here, the fixing device 40 is composed of a heating roller 212 and a pressure roller 213 arranged vertically. The details will be described with reference to FIG. FIG. 2 shows a cross section of the fixing device 40 in the longitudinal direction. As shown in FIG. 2, the heating roller 212
Silicon rubber 212 is provided on the surface of a metal cylinder 212a made of a material such as aluminum which has good heat conduction and small heat capacity.
b. A heater lamp 221 is provided inside the heating roller 212, and is supplied with power and heated based on temperature control by a general control unit 54 (see FIG. 6) described later. The surface temperature of the heating roller 212 is detected by a temperature sensor 222 such as a thermistor provided in contact with the surface. The surface temperature signal detected here is
It is input to the overall control unit 54 described later. On the other hand, similarly to the heating roller 212, the pressure roller 213 also includes the silicon rubber 21 in the metal cylinder 213a having the heater lamp 221 therein.
3b.

When the pressure roller 213 is driven by a drive control unit 55 (see FIG. 6), which will be described later, the heating roller 212 also rotates following the pressure roller 213. Note that, instead of the pressing roller 213, the heating roller 212 may be driven by the drive control unit 55, and the pressing roller 213 may be rotated by following the heating roller 212.

Further, the fixing device 40 can change the axial distribution of the pressing force of the pressing roller 213 against the heating roller 212. The mechanism for varying the pressing force will be described with reference to FIG. FIG. 3 is a side view of the mechanism for varying the pressing force. The heating roller 212 and the pressure roller 213 are located near both ends (fixing test images TA and TC described later).
(See FIG. 4) corresponding to the area where the pressure support members 214 are formed, as shown in FIG.
A, 214C and 215A, 215C are mutually pressed and rotatably supported. The pressing support members 215A and 215C are formed by pressing support members 214A and 214A.
C are rotatably attached to C by support shafts 216, respectively. Further, elastic members 211A and 211C for pressing the pressing roller 213 against the heating roller 212 are provided below the pressing support members 215A and 215C that support the pressing roller 213. Further, cams 210A and 210C connected to the drive motors MA and MC are provided below the elastic members 211A and 211C, respectively.

The pressing force is changed by rotating the cam 210A or 210C by a predetermined angle by the drive motor MA or MC. That is, the cam 2
By rotating counterclockwise 10A, the elastic member 211A is compressed and contracted, so that the pressing force of the pressing roller 213 against the heating roller 212 changes the fixing test image TA (see FIG. 4) described later. And the fixing pressure increases. On the other hand, when the cam 210A is rotated clockwise, the elastic member 211A is extended, so that the pressing force of the heating roller 212 and the pressing roller 213 is reduced, and the fixing test image TA (see FIG. 4) described later is created. And the fixing pressure decreases.

Similarly, when the cam 210C is rotated counterclockwise, the elastic member 211C is pressed and contracted, so that the pressing force of the heating roller 212 and the pressing roller 213 causes the fixing test image TC (see FIG. Is higher in the area where the reference pressure is generated, and the fixing pressure becomes higher. On the other hand, when the cam 210C is rotated clockwise, the elastic member 211C is extended, so that the pressing force of the pressing roller 213 against the heating roller 212 causes the fixing test image TC to be described later.
(See FIG. 4) becomes lower in the region where the image is formed, and the fixing pressure becomes smaller. In this way, by rotating the cams 210A and 210C, the axial distribution of the pressing force of the pressing roller 213 against the heating roller 212 can be changed.

The image information detecting section 43 (see FIG. 1)
Is for detecting the image information of the fixing test image, and specifically, for detecting the glossiness ((direct reflection light amount / incident light amount) × 100 = direct reflectance) of the fixing test image. . For example, as shown in FIG. 4, the image information detection unit 43 includes two substantially rectangular fixing test images TA, TA, arranged in the vicinity of the upper side of the recording material S when the transport direction indicated by the arrow is directed upward. When the TC is formed on the recording medium S, it is arranged at a position where the intensity of the regular reflection light (direct reflection light) of the fixing test image TA or the like can be measured.
In other words, the image information detection unit 43 detects the two light-emitting element and light-receiving element pairs (light-emitting / light-receiving element pairs) arranged in a direction intersecting (in the present embodiment, orthogonal to) the conveying direction of the recording material S. It is configured.

Specifically, the halogen lamp 41A and the CC
D sensor 42A, halogen lamp 41C and CCD
The sensor 42C includes two light emitting / light receiving element pairs. Then, the halogen lamp 41A and the CCD sensor 4
2A is located at a position where the intensity of the reflected light of the fixing test image TA can be measured. That is, in the conveyance path of the recording material S, behind the fixing device 40, a halogen lamp, which is a light emitting element, is positioned obliquely upper right (diagonally upper in the anti-conveying direction) with respect to the recording material S discharged from the fixing device 40 in FIG. 41A
FIG. 4 in which the incident angle α and the reflection angle β with respect to the fixing test image TA (recording medium S) are equal so that the specular reflection light with respect to the incident light that enters the fixing test image TA from the halogen lamp 41A can be received. A CCD sensor 42A, which is a light receiving element, is provided on the upper left side in the middle (in the upper direction in the transport direction). In a similar positional relationship, a halogen lamp 41C and a CCD sensor 42C are also arranged. The specularly reflected light (directly reflected light) refers to the incident light of the incident light incident on the fixing test image on the incident surface formed by the incident light and the normal line of the fixing test image at the incident point. It refers to reflected light that travels while reflecting at the same reflection angle as the angle (in the following description, “specularly reflected light” is used in the same sense).

Also, a pair of halogen lamps 41A and 41A
The CD sensor 42A, the lamp 41C, and the sensor 42C may be arranged at opposite positions. Further, as shown in FIG. 5, the halogen lamp 41A and the like and the CCD sensor 42A and the like are arranged such that the directions of the incident light and the reflected light are orthogonal to the transport direction (the left direction behind the fixing device 40 in FIG. 1). Illuminate the fixing test image TA, etc.
Any arrangement may be used as long as the arrangement can receive the regular reflection light.

However, it is desirable that the incident angle α and the reflection angle β are not less than 25 degrees. If the angle is smaller than 25 degrees, the component of the diffused light circling from the periphery becomes large, so that the intensity information of the specularly reflected light cannot be measured accurately, and the arrangement of the halogen lamps 41A and 41C and the CCD sensors 42A and 42C becomes difficult. is there. Further, the incident angle α is more preferably 45 degrees or more. When the halogen lamps 41A and 41C and the CCD sensors 42A and 42C are arranged in this manner, the fixing test images TA and TC are less susceptible to the influence of the thickness of the fixing test images TA and the rising of the recording medium S during measurement,
This is because the intensity information of the specularly reflected light can be measured more accurately.

As described above, the halogen lamps 41A, 41
C and the CCD sensors 42A and 42C are arranged so that the image information detecting unit 43 performs the fixing test images TA and TC.
Glossiness can be detected. That is, the image information detection unit 43 determines the intensity IbA, IbC of the reflected light received by the CCD sensors 42A, 42C and the intensity of the halogen lamps 41A, 41B.
By detecting the incident light intensities (light emission intensities) IaA and IaC of 1C, the glossiness of the fixing test images TA and TC can be calculated. The light emission intensity IaA, IaC of the halogen lamps 41A, 41C can be detected by directly measuring the intensity using a half mirror or the like, or indirectly based on the applied voltage, current consumption, power consumption, etc. of the light emitting element. Measurement method.

Next, a brief description will be given of the operation of the copying machine 1 configured as described above when copying is performed. In the copying machine 1, the following processing is performed in the order of yellow (Y), cyan (C), magenta (M), and black (K) reproduction colors. First, the processing of yellow (Y) will be described. The image reading unit 2 detects yellow (Y) of the original image
Read the image data corresponding to. Further, the surface of the photosensitive drum 30 is uniformly charged by the charging charger 31.

Then, a laser control unit 59 (to be described later) (FIG. 6)
), The image data read by the image reading unit 2 is input. Next, the laser light is modulated and emitted from the laser light source, and the laser light is scanned by the polygon mirror 21 in the main scanning direction, and further reflected by the reflection mirror 22 to be incident on the photosensitive drum 30. As a result, an electrostatic latent image corresponding to the reproduced color of yellow (Y) is formed on the photosensitive drum 30. This electrostatic latent image is developed by the developing device 32Y.
To form a toner image. This toner image is transferred to the transfer charger 3 disposed opposite the photosensitive drum 30.
3, the image is transferred onto the recording medium S supplied from the paper cassette 44 or the manual feed tray 45.

Next, cyan (C), magenta (M),
The processing for black (K) is performed similarly. By these processes, the four color toner images are transferred onto the recording medium S in a superimposed manner. Thereafter, the recording material S to which these toner images have been transferred is heated and pressed in the fixing device 40. As a result, the toner is melted, and the toner image is fixed on the recording medium S to form a full-color image. After the image is fixed, the recording medium is discharged out of the apparatus and stored in the paper discharge tray 46. This completes the copying for one sheet.

Here, a control system of the copying machine 1 for controlling such a copying operation and the like will be described. As shown in the block diagram of FIG. 6, the control circuit of the copier 1
4 as the center. The general control unit 54 corresponds to a roller distortion amount estimating unit and a fixing condition correcting unit of the present invention.
It is a microcomputer configured by combining M and the like. Various programs and reference data necessary for executing the control of the copying machine 1 are prepared and stored in the ROM incorporated in the general control unit 54 in advance. In addition,
Test image data and the like for creating a test image to be described later are also stored in the ROM. Further, the RAM is provided with various buffers for temporarily storing numerical values and the like appearing during execution of the arithmetic processing and for reading out the data as needed.

An input / output port of the general control unit 54 includes an IR control unit 51 for controlling the operation of the image reading unit 2 and a fixing unit 4.
A drive control unit 55 for controlling the driving / stopping of the zero and the speed control of the pressure roller 213; a conveyance control unit 56 for controlling the supply of the recording medium; a scanner control unit 57 for controlling the laser beam scanning by the polygon mirror 21; A high-voltage control unit 58 for controlling high voltages such as charging of the photosensitive drum 30, application of a developing bias and a transfer bias, a laser control unit 59 for controlling laser light modulation, an image information detecting unit 43, and a fixing device 4
0 fixing temperature (exactly the surface temperature of the heating roller 212)
Temperature sensor 222 which detects
1 etc. are connected. In addition, the general control unit 54 includes:
A signal is input from the operation panel 53 via the controller 52.

The copying machine 1 is controlled by the general control unit 54 and operates as follows. First, control information such as the size and type of the recording medium is input from the operation panel 53 to the controller 52. Next, when the copy button on the operation panel 53 is pressed, a copy request signal is transmitted, and this signal is received by the controller 52. Subsequently, a print command is output from the controller 52 to the overall control unit 54. With this command, the general control unit 5
4 instructs the IR control unit 51 to start reading an image of a document, and instructs the transport control unit 56 to start supplying a recording medium.
Is instructed to scan. In addition, the high pressure control unit 58
, A charge to the photosensitive drum 30, a developing bias, and a transfer bias are set, and preparation for image formation is made. When the reading of the image of the original by the image reading unit 2 is completed, the read image data is input to the laser control unit 59.

Next, the overall control unit 54
2 to output a vertical synchronization request signal and wait for reception of a vertical synchronization signal. Then, when the controller 52 outputs the vertical synchronization signal, the laser light is modulated and emitted based on the image data input to the laser control unit 59. As a result, an electrostatic latent image is formed on the photosensitive drum 30 and the developing device 32Y
(32C, 32M, 32K) to form a toner image. This toner image is transferred to a recording medium, and is
The image is fixed by 0 to form a fixed image. At this time, the temperature sensor 222 detects the surface temperature (fixing temperature) of the heating roller 212 of the fixing device 40 and outputs the detection result to the overall control unit 5.
Send to 4.

Next, the correction control for suppressing the image quality unevenness of the fixed image will be described with reference to the flowchart shown in FIG. The subroutine shown in this flowchart is executed after a predetermined number of copies have been made, after a predetermined operating time has elapsed, or when the operator has selected a test mode from the operation panel 53.

First, test image data acquired from the internal ROM by the general control unit 54 is input to the laser control unit 59 shown in FIG. 6, and predetermined fixing test images TA and TC are created by the above-described procedure. Is performed (S1). Next, when the image information detection unit 43 detects the intensity IbA of the regular reflection light of the fixing test image TA and the light emission intensity IaA of the halogen lamp 41A, the general control unit 54 calculates the glossiness LA of the fixing test image TA using these. (S2). Further, when the image information detecting unit 43 detects the intensity IbC of the specular reflection light of the fixing test image TC and the light emission intensity IaC of the halogen lamp 41C, the general control unit 54 calculates the gloss LC of the fixing test image TC using them. (S3).

Then, the overall control unit 54 determines the roller distortion amount rank based on the gloss difference (LA-LC) between the fixing test images TA and TC (S4). The roller distortion amount rank is divided into seven stages (A to G ranks) as shown in Table 1. This rank is based on the fixing test images TA and T
When there is no difference in the glossiness of C, that is, the fixing test image TA
The case where there is no roller distortion in the area where the fixing test image TC is created with reference to the area where is created is defined as the standard (D rank). Also, the gloss LA is the gloss L
C, that is, when roller distortion occurs such that the pressing force increases in the area where the fixing test image TC is created with reference to the area where the fixing test image TA is created, Depending on three stages (A ~
(C rank). On the other hand, when the glossiness LA is smaller than the glossiness TC, that is, the fixing test image TA
When roller distortion occurs such that the pressing force is reduced in the area where the fixing test image TC is created based on the area where the image is created, there are three levels (E to G ranks) according to the magnitude of the roller distortion. Is ranked.

[0049]

[Table 1]

Since the roller distortion amount can be grasped by such ranking, the correction amount of the pressing force required to eliminate the uneven pressing force of the pressing roller 213 due to the roller distortion, that is, The rotation angle of the cam 210C can be specifically determined. Then, the cam 210C is rotated by a predetermined angle so that the pressing force of the pressing roller 213 against the heating roller 212 becomes uniform in the axial direction according to the roller distortion amount rank, and the pressing force of the pressing roller 213 is changed. Is changed (S5). Accordingly, even when the heating roller 212 or the pressure roller 213 is distorted, the fixing pressure can be made substantially uniform in the direction orthogonal to the recording medium conveyance direction. Therefore, it is possible to obtain a fixed image in which the occurrence of image quality unevenness is suppressed.

As described above in detail, according to the copying machine 1 of the first embodiment, predetermined fixing test images TA and TC are created on the recording medium S periodically or by an operator's selection. Is done. Next, the overall control unit 54
Based on the reflected light intensity and the like obtained by the image information detection unit 43, the glossiness of each of the fixing test images TA and TC is obtained, and the difference is calculated. Thereafter, the overall control unit 54 drives the cam 210C based on the calculation result to correct the pressing force of the pressing roller 213. As a result, the fixing pressure can be made uniform in a direction orthogonal to the recording medium conveyance direction.
Therefore, occurrence of image quality unevenness is suppressed.

In the first embodiment, the gloss LC is subtracted from the gloss LA based on the fixing test image TA in order to determine the roller distortion rank.
The glossiness LA may be subtracted from the glossiness LC based on the fixing test image TC. However, in this case, it is necessary to drive the cam 210A instead of the cam 210C.

Alternatively, the average value Lav of the glossiness LA and the glossiness LC is calculated, and the roller distortion rank is determined based on the difference between the average value Lav and the respective glossinesses LA and LC. Is also good. In addition, the fixing test image T
Required glossiness of A and TC (glossiness that should be obtained) Lr
May be calculated in advance, and the roller distortion rank may be determined based on the difference between the required gloss Lr and the respective gloss LA and LC. In these cases, both the cams 210A and 210C are driven. However, not only the image quality unevenness is suppressed, but also other image quality (image gloss, etc.) can be brought close to a required value. Having.

(Second Embodiment) Next, a second embodiment will be described. The copying machine according to the second embodiment has substantially the same basic configuration as the copying machine 1 according to the first embodiment, but instead of compensating for the pressing force of the pressure roller, a copier The difference is that the control temperature of the provided heater is corrected. Accordingly, the configuration of the fixing device is also different from that of the first embodiment. Also, the number of fixing test images created differs. Specifically, as shown in FIG. 8, three fixing test images TA and T are set in a direction orthogonal to the recording material conveyance direction.
B and TC are created. That is, a new fixing test TB is created as compared with the first embodiment. Accordingly, another difference is that a halogen lamp 41B and a CCD sensor 42B are newly added to the image information detecting unit 63 for detecting the reflected light intensity information of the fixing test image and three sets of sensors are provided. The description of the same components as those in the first embodiment, the copy operation, and the like is omitted, and the same components are denoted by the same reference numerals.

First, the configuration of the fixing device will be described with reference to FIG. As shown in FIG. 9, the fixing device 400 according to the present embodiment includes a heating roller 412 and a pressure roller 413.
Is provided with three heater lamps, that is, a first heater lamp 421A, a second heater lamp 421B, and a third heater lamp 421C. These heater lamps 421A to 421C are connected to the overall control unit 54, and the first heater lamp 421A and the second heater lamp 42
Different temperatures can be set for the 1B and third heater lamps 421C. Accordingly, when the toner image transferred onto the recording medium S is fixed on the recording medium S, the control temperatures of the heater lamps 421A to 421C can be set separately. Therefore, the fixing temperature in the fixing device 400 can be corrected in the axial direction of the heating roller 412.

The correction control for suppressing the image quality unevenness of the fixed image in the copying machine configured as described above will be described.
This will be described with reference to the flowchart shown in FIG. The subroutine shown in this flowchart is executed after a predetermined number of copies have been made, after a predetermined operating time has elapsed, or when the operator has selected a test mode from the operation panel 53.

First, test image data previously stored in the ROM in the overall control unit 54 is input to the laser control unit 59 shown in FIG. 6, and the predetermined fixing test images TA, TB, TC Is created (S1
1). Next, the image information detecting unit 63 sets the fixing test image T
A intensity IbA of specular reflected light of A and halogen lamp 41A
When the overall control unit 54 detects the light emission intensity IaA of the fixing test image TA, the overall control unit 54 calculates the glossiness LA of the fixing test image TA (S12). Further, the image information detection unit 63 determines whether the intensity IbB of the regular reflection light of the fixing test image TB and the halogen lamp 4
When detecting the light emission intensity IaB of 1B, the general control unit 54 calculates the glossiness LB of the fixing test image TB using the detected light intensity IaB (S13). Further, when the image information detection unit 63 detects the intensity IbC of the regular reflection light of the fixing test image TC and the emission intensity IaC of the halogen lamp 41C, the general control unit 5
4 calculates the gloss LC of the fixing test image TC by using this (S14).

Then, based on the glossiness difference (LB-LA) between the fixing test image TB and TA, the overall control unit 54 sets the fixing test image TA based on the area of the fixing test image TB.
(S1)
5). The roller distortion rank is 7 as shown in Table 2.
It is divided into stages (A to G ranks). Note that this ranking is based on the same criteria as in Table 1.

[0059]

[Table 2]

Next, the control temperature of the first heater lamp 421A is corrected in accordance with the roller distortion amount rank so that the glossiness in the area of the fixing test image TB and the area of TA are equal (S16). As a result, even if the heating roller 412 or the pressure roller 413 is distorted and the fixing pressure in the area of the fixing test image TB and the area of the fixing test image TA are not uniform, the glossiness can be made substantially equal.

Further, based on the glossiness difference (LB-LC) between the fixing test images TB and TC, the general control section 54 sets the fixing test image TC based on the area of the fixing test image TB.
The roller distortion amount rank (see Table 2) in the region (1) is determined (S17). Next, according to the roller distortion amount rank, the third heater lamp 421C is set so that the glossiness in the area of the fixing test image TB and the glossiness in the area of TC are equal.
Is corrected (S18). As a result, even when the heating roller 412 or the pressure roller 413 is distorted and the fixing pressure in the area of the fixing test image TB and the fixing pressure in the area of TC are not uniform, the glossiness can be made substantially equal.

Even if the heat roller 412 or the pressure roller 413 is distorted by these processes and the fixing pressure in the area of each of the fixing test images TA, TB and TC is not uniform, the glossiness should be substantially equal. Can be. That is, in the direction orthogonal to the recording medium transport direction,
The toner image on the recording medium can be uniformly melted.
This makes it possible to obtain a fixed image in which the occurrence of image quality unevenness is suppressed.

As described above in detail, according to the copying machine of the second embodiment, a predetermined fixing test image T
A, TB, and TC are created. Next, the general control unit 54
Is based on the reflected light intensity and the like obtained by the image information detection unit 63,
The glossiness of each of the fixing test images TA, TB, TC is obtained, and the difference is calculated. After that, the overall control unit 54
The first heater lamp 421A and the third
The control temperature of the heater lamp 421C is corrected. This makes it possible to equalize the fixing conditions in a direction orthogonal to the recording medium conveyance direction. Therefore, occurrence of image quality unevenness is suppressed.

In the second embodiment, the gloss LA and the gloss LC are subtracted from the gloss LB with reference to the fixing test image TB in order to determine the roller distortion rank. The glossiness LB and the glossiness LC may be subtracted from the glossiness LA based on the image TA. However, in this case, the second heater lamp 421
It is necessary to correct the control temperatures of B and the third heater lamp 421C. Further, the glossiness LA and the glossiness LB may be subtracted from the glossiness LC based on the fixing test image TC. However, in this case, the first heater lamp 4
It is necessary to correct the control temperatures of 21A and the second heater lamp 421B.

Further, an average value Lav of the glossiness LA, the glossiness LB, and the glossiness LC is calculated, and a roller distortion amount rank is calculated based on a difference between the average value Lav and the respective glossinesses LA, LB, LC. May be determined. Furthermore, the required glossiness (glossiness to be originally obtained) Lr of the fixing test images TA, TB, TC is calculated in advance, and based on the difference between the required glossiness Lr and each of the glossiness LA, LB, LC. Thus, the roller distortion amount rank may be determined. In these cases, the first heater lamp 42
1A, second heater lamp 421B, third heater lamp 4
Although the control temperature of all 21C is corrected, there is an advantage that not only the image quality unevenness is suppressed but also other image quality (image gloss and the like) can be brought close to a required value.

(Third Embodiment) Finally, a third embodiment will be described. The configuration of the copying machine according to the third embodiment is substantially the same as that of the copying machine 1 according to the first embodiment, but the configuration of the fixing device is slightly different. That is, the fixing device in this embodiment does not include a mechanism for varying the pressing force of the pressing roller 213 against the heating roller 212. The description of the same components as those in the first embodiment, the copy operation, and the like is omitted, and the same components are denoted by the same reference numerals.

A description will be given of the correction control for suppressing the image quality unevenness of the fixed image in the copying machine having the above configuration. This correction control is performed by increasing the fixing temperature, that is, by increasing the control temperature of the heater lamp 211. That is, the fixing temperature is raised to suppress the image quality unevenness. Such correction is possible because, as shown in FIG. 11, when the amount of toner adhering to a recording medium is constant, image quality unevenness, that is, a difference in image information is caused by a difference in fixing temperature even when fixing pressure is different. This is because the value becomes smaller as the value becomes higher.

For example, consider a case where two fixing test images are created in a direction orthogonal to the recording medium conveyance direction. Assume that when fixing is performed at a standard fixing temperature (160 ° C.), the glossiness of each fixing test image becomes 65 and 30, respectively. The reason why the glossiness differs in spite of the fact that the fixing is performed at the same fixing temperature is considered that the fixing pressure is different in each fixing test image area as can be seen from FIG. Here, the fixing temperature is set to 185 ° C.
If it is increased, the glossiness becomes 90 and 81, respectively, so that the glossiness difference becomes 35 to 9 and becomes small to an allowable range. As described above, even when the fixing pressure varies depending on the location, the glossiness can be made uniform to some extent by increasing the fixing temperature (actually, increasing the control temperature of the heater lamp).

Next, a specific correction control method will be described. First, fixing test images TA and TC are created in the same manner as in the first embodiment (see FIG. 4). Next, the image information detection unit 43 sets the intensity IbA of the regular reflection light of the fixing test image TA and the emission intensity IaA of the halogen lamp 41A.
Is detected, the general control unit 54 calculates the glossiness LA of the fixing test image TA using this. Similarly, the glossiness LC of the fixing test image TC is calculated.

Then, the overall control unit 54 determines the roller distortion rank based on the gloss difference (absolute value) between the fixing test images TA and TC. Table 3 shows the roller distortion rank.
Are divided into four stages (A to D ranks). The case where there is no roller distortion is defined as a standard (D rank) according to the magnitude of the roller distortion in three stages (A to C ranks).
Is ranked.

[0071]

[Table 3]

Next, the overall control unit 54 corrects the control temperature of the heater lamp 221 according to the roller distortion amount rank. As a result, distortion occurs in the heating roller 212 or the pressure roller 213, and the fixing test images TA and TC
Even if there is a difference in glossiness between the two, the difference in glossiness can be reduced. Therefore, it is possible to obtain a fixed image in which the occurrence of image quality unevenness is suppressed. Note that the control temperature of the heater lamp 221 is corrected only by increasing the temperature, not by the correction for lowering the temperature. This is because, as the fixing temperature decreases, the gloss difference between fixing test images having different fixing pressures increases (see FIG. 11).

As described above in detail, according to the copying machine according to the third embodiment, the predetermined fixing test image T on the recording medium S is periodically or selected by the operator.
A and TC are created. Next, based on the reflected light intensity and the like obtained by the image information detection unit 43, the overall control unit 54 calculates the glossiness of each of the fixing test images TA and TC, and calculates the difference. Thereafter, the overall control unit 54 corrects the control temperature of the heater lamp 221 based on the calculation result. Thereby, the difference in glossiness between the fixing test images TA and TB can be reduced. That is, the occurrence of image quality unevenness is suppressed.

The above-described embodiment is merely an example, and does not limit the present invention in any way. Needless to say, various improvements and modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, the intensity information (gloss) of the reflected light of the fixing test image is detected to determine the roller distortion rank, and the fixing condition is corrected according to this rank. It is also possible to determine the roller distortion rank and correct the fixing condition according to the rank by detecting information (transmittance), color shift (shift in brightness, hue, saturation) and the like.

In the third embodiment, the case where the fixing temperature (control temperature of the heater) is corrected has been described.
The same effect can be obtained by correcting the fixing speed (the peripheral speed of the pressure roller 213).

Further, in the above embodiment, an example in which the present invention is applied to a copying machine has been described. However, any apparatus having an image forming means and a fixing means such as a printer such as a page printer or a facsimile can be used. Can also be applied. Furthermore, the test image data for creating the fixing test image can be obtained from an external device through an input / output port instead of being obtained from a memory or the like stored in advance. Alternatively, it can be obtained from the image reading unit 2 using a test chart or the like on which a test pattern is printed in advance.

[0077]

As described above, according to the image forming apparatus of the present invention, at least two or more fixing positions of the recording medium differing in the direction orthogonal to the recording medium conveyance direction are determined by the roller distortion amount estimating means. From the difference in the image information of the test image, the amount of distortion of one roller in the contact heating and fixing means with respect to the other roller is estimated. Then, the fixing condition correcting means corrects the fixing condition based on the estimation result of the roller distortion amount estimating means so as to uniformly fuse the unfixed image on the recording medium. This allows
The occurrence of image quality unevenness is suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a copying machine according to a first embodiment.

FIG. 2 is a sectional view showing a configuration of a fixing device in the copying machine of FIG.

FIG. 3 is a side view showing a configuration of a fixing device in the copying machine shown in FIG. 1, particularly a variable mechanism of a pressing force.

FIG. 4 is a perspective view illustrating a configuration of an image information detection unit in the copying machine of FIG. 1;

FIG. 5 is a perspective view illustrating another configuration of the image information detection unit.

FIG. 6 is a block diagram showing a part of a control circuit of the copying machine shown in FIG. 1;

FIG. 7 is a flowchart illustrating control for correcting a pressing force to suppress image quality unevenness.

FIG. 8 is a perspective view illustrating a configuration of an image information detection unit in a copying machine according to a second embodiment.

FIG. 9 is a cross-sectional view illustrating a configuration of a fixing device in a copying machine according to a second embodiment.

FIG. 10 is a flowchart illustrating control for correcting a fixing temperature in order to suppress image quality unevenness.

FIG. 11 is a graph showing the relationship between the fixing temperature and the gloss when the fixing pressure is changed as a parameter.

[Explanation of symbols]

 5 Image Processing Unit 30 Photoconductor Drum 31 Charger 32Y, 32C, 32M, 32K Developing Device 33 Transfer Charger 34 Transfer Drum 40 Fixing Unit 41A, 41C Halogen Lamp 42A, 42C CCD Sensor 43 Image Information Detecting Unit 54 Overall Control Unit 212 Heating Roller 213 Pressing roller 214A, 214C Pressing support member (heating roller side) 215A, 215C Pressing supporting member (pressing roller side) 210A, 210C Cam 211A, 211C Drive motor 221 Heater lamp 222 Temperature sensor MA, MCS Recording medium TA , TC fixing test image

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA12 EA12 ED25 HA07 HB05 2H033 AA01 AA10 AA11 BA60 BB14 BB15 BB29 BB34 CA01 CA18 CA30 CA36

Claims (5)

[Claims] 1. An image forming means comprising: test image data obtaining means for obtaining test image data for generating a predetermined fixing test image; and image forming means for generating an unfixed image on a recording medium based on the image data. A heater is provided inside at least one of the rollers while the two rollers are pressed against each other, and the recording medium carrying the unfixed image is passed between the rollers in a state where the rollers are heated by the heater. An image forming apparatus comprising: a contact heating fixing unit that heats and fixes an image; a light emitting element that irradiates light to a fixing test image fixed on the recording medium by the contact heating fixing unit; A light-receiving element for detecting intensity information of light reflected or transmitted from the fixing test image, wherein the light-receiving element is orthogonal to a recording medium transport direction of the recording medium. Image information detecting means for detecting the image information of the fixing test image at at least two or more locations having different orientations; and calculating the difference between the image information of each fixing test image from the detection result of the image information detecting means. A roller distortion amount estimating unit for estimating a distortion amount of the other roller based on one of the rollers in the contact heating and fixing unit based on the difference; and a distortion amount estimated by the roller distortion amount estimating unit. And a fixing condition correcting means for correcting a fixing condition in the contact heating fixing means. 2. The image forming apparatus according to claim 1, wherein the fixing condition correcting unit corrects one of a fixing temperature and a fixing speed in the contact heating fixing unit. 3. The image forming apparatus according to claim 1, wherein the contact heating fixing unit includes a fixing condition changing unit that can change at least one or more fixing conditions in a direction orthogonal to a recording medium conveyance direction. An image forming apparatus comprising: 4. The image forming apparatus according to claim 3, wherein the fixing condition changing means changes the axial distribution of the pressing force of the rollers by changing a distance between the axes of the two pressed rollers. An image forming apparatus, wherein the fixing condition correcting unit is a roller pressing force correcting unit that corrects an axial distribution of the pressing force of the roller by the roller pressing force changing unit. apparatus. 5. The image forming apparatus according to claim 3, wherein the fixing condition changing unit includes a plurality of heaters in a direction orthogonal to a recording medium conveyance direction, and changes control temperatures of the plurality of heaters. An image forming apparatus, wherein the fixing condition correcting unit is a temperature correcting unit that corrects a control temperature of each of the heaters.