JP2005031570A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus carrying out optimum color deviation correction and forming a color image of good quality with an easy method without the increase in cost. <P>SOLUTION: The temperature of a scanner is estimated by a temperature sensor provided in a fixing means 71. Control is carried out so that the correction result when the temperature of the scanner is high is not used when the temperature of the scanner is low, or correction of the color shift is not carried out when the temperature of the scanner is high. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus using an electrophotographic process.

  Conventionally, as a color image forming apparatus for forming a color image at high speed, a photosensitive drum and a scanning optical device are provided for each color of yellow (Y), magenta (M), cyan (C), and black (Bk) along a conveying belt. The transfer paper is sequentially conveyed by a conveyor belt and images of each color are sequentially transferred, or the toner images of each color are sequentially transferred onto the intermediate transfer belt so as to overlap each other, and finally the toner images are collectively transferred onto the transfer paper. There is an in-line method in which the image is transferred and fixed by a fixing device.

  In a scanning optical device, light is modulated from a light source means according to an image signal and emitted, and is spot-shaped on the surface of a recording medium (or photosensitive drum) having photosensitivity by a scanning optical element (imaging element) having fθ characteristics. The image is recorded by optically scanning the surface of the recording medium.

FIG. 9 is a schematic view of the main part of this type of conventional scanning optical apparatus. In the scanning optical device shown in FIG.
The divergent light beam emitted from the light source means 101 is made into a substantially parallel light beam by the collimator lens 102, and the light beam (light amount) is limited by the diaphragm 103 to be a cylinder lens (cylindrical lens) 104 having a predetermined refractive power only in the sub-scanning direction. Incident. The substantially parallel light beam incident on the cylinder lens 104 is emitted in the state of a substantially parallel light beam as it is in the main scanning section, and is converged in the sub-scanning section to be an optical deflector 105 composed of a rotating polygon mirror (polygon mirror). Is formed as a substantially linear image on the deflection surface (reflection surface) 105a.

  Thus, the light beam deflected and reflected by the deflecting surface 105a of the optical deflector 105 is guided to the photosensitive drum surface 108 as the scanned surface through the scanning optical element (fθ lens) 106 having the fθ characteristic, By rotating the optical deflector 105 in the direction of arrow A, the photosensitive drum surface 108 is optically scanned in the direction of arrow B. As a result, an image is recorded on the photosensitive drum surface 108 as a recording medium.

  One of the main problems in an in-line type color image forming apparatus is a color shift between colors of a color image. Components of color misregistration include a laser scanning direction (main scanning direction) displacement, a belt conveyance direction (sub-scanning direction) displacement, an image expansion / contraction in the main scanning direction, and an angle displacement in the main scanning direction. Each color shift is adjusted so as to be equal to or less than an allowable value at the time of shipment of the apparatus. However, due to changes in environmental temperature and apparatus temperature during adjustment and use, distortion of the apparatus due to a difference in floor surface, and displacement of the photosensitive drum due to cartridge replacement, etc., color misregistration exceeding an allowable value occurs. Therefore, as a means for correcting the color misregistration amount in a timely manner, a color misregistration amount measurement pattern is formed at a predetermined interval on the conveyance belt or the intermediate transfer belt, and this measurement pattern is detected by the toner image detector, and the detection result Therefore, it is necessary to calculate the color misregistration amount based on the above and correct the image forming position based on the calculation result.

  At this time, the color misregistration measurement pattern has four color lines formed at equal intervals L in the direction perpendicular to the conveying direction as shown in FIG. 3, for example. As shown in FIG. The color misregistration amount is corrected based on a value obtained by averaging the respective measurement values.

As a result, the amount of color misregistration can be suppressed within an allowable value, and an image with an optimum image quality can always be held.
Japanese Patent Laid-Open No. 04-149477

  However, in a scanning optical device in a conventional color image forming apparatus, when an optical deflector disposed inside a housing is driven, a rotating unit (coil) and a driving circuit (driving IC) generate heat, and the housing or light Heat is transferred to the element. Similarly, when a semiconductor laser is driven, the heat generated by the laser or the heat generated by the drive circuit is transferred to the housing, the laser holder, the optical element, or the like. As a result, thermal expansion of the housing and the optical element occurs, and the irradiation position shift of the laser beam is caused.

  Due to the phenomenon described above, the correction value is different between the case where the color misregistration correction is performed when the scanning optical device is at a high temperature and the case where the color misregistration correction is performed when the scanning optical device is at a low temperature. When color misregistration correction is performed, there is a problem that an optimal correction value cannot be obtained.

  In order to solve this problem, it is effective to optimize the color misregistration correction timing based on the temperature of the scanner.

  Therefore, the present invention predicts the temperature of the scanner by a temperature sensor provided in the fixing means, and the correction result when the scanner temperature is high performs control not to be used when the temperature is low, or the temperature of the scanner It is an object of the present invention to provide a color image forming apparatus that is inexpensive and can obtain an optimum image quality by not performing color misregistration correction when the color shift is high.

  In order to achieve the above-mentioned object, as a means for obtaining the temperature of the scanning optical device, there is provided a temperature detecting means provided in the fixing device.

  Accordingly, it is possible to provide a color image forming apparatus that can perform an optimal color misregistration correction and forms a color image with a good image quality by an easy method without increasing costs.

  As described above, according to the present invention, the color misregistration detection error can be reduced, the optimum color misregistration correction can be performed, and a color image that forms a good-quality color image by an easy method without increasing the cost. An image forming apparatus can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  A first embodiment of the present invention will be described with reference to FIGS. 1, 2, 5, 6, 7, and 8. FIG.

  FIG. 1 is a schematic cross-sectional view of an example of a color laser printer targeted by the present invention. In FIG. 1, 11, 12, 13, and 14 are scanning optical devices for yellow, magenta, cyan, and black, respectively, 21, 22, 23, and 24 are photosensitive drums for each color, and 31, 32, 33, and 34 are respectively. Each color charging roller 41, 42, 43, 44 is a sleeve roller for each color, 51, 52, 53, 54 is a transfer roller for each color, 61 is a conveyor belt, 62 and 63 are conveyor belt support rollers, 64a is a cassette feeding pickup roller, 64b is a manual feeding pickup roller, 65 is a registration roller, 66 is a suction roller, 71 is a fixing device, 81 is a plain paper cassette, 82 is a manual feeding tray, and 90 and 91 are A toner image detection sensor.

  Further, FIG. 5 shows a schematic diagram of the scanning optical device therein. In the color image forming apparatus, four-color scanning optical devices 11, 12, 13, and 14 are fixed. In the scanning optical devices 11, 12, 13, and 14, as shown in FIG. 5, a laser unit 10 including a semiconductor laser that emits laser light L and a collimator lens (not shown) that makes the laser light L substantially parallel light, a cylindrical lens 15, A polygon mirror 17 that is rotated in a certain direction by a motor 16, two imaging lenses 18 and 19, and a mirror 20 that deflects the laser light L downward are provided.

  Photoconductors 31, 32, 33. 34 including four-color rotary drums are disposed below the laser emission port, a fixing unit 71 is disposed behind the photoreceptors, and a power supply unit (not shown) and a control circuit for controlling the whole are disposed below the fixing unit 71. It is arranged.

  During operation, the laser light L emitted from the semiconductor laser of the laser unit 10 becomes parallel light by the collimator lens, is focused in the sub-scanning direction by the cylindrical lens 15, and is condensed on the reflection surface of the polygon mirror 17. This laser beam L is reflected and deflected and scanned by the polygon mirror 17 rotated by the motor 16, reflected downward by the mirror 20 through the two imaging lenses 18 and 19, and the photosensitive drums 31, 32 and 33 of the rotating drum. .34 is imaged. The laser light L formed on the photosensitive members 31, 32, 33.34 forms an electrostatic latent image by main scanning by the rotation of the polygon mirror 17 and sub-scanning by the rotation of the rotating drum. In addition, the recording medium is conveyed by the conveyance belt 61, toner associated with the electrostatic latent image on the photoconductors 31, 32, 33.34 is transferred and fixed in the fixing unit 71.

  FIG. 8 shows a partial schematic configuration of the fixing device 71 of the present embodiment. In FIG. 8, reference numeral 201 denotes a fixing film having a small heat capacity. In order to enable quick start, it is made of polyimide having heat resistance and thermoplasticity with a thickness of 20 to 100 μm or less. Further, in order to prevent offset and ensure separation of the recording material, the surface layer is coated with a heat-resistant resin having a good releasability such as a silicone resin.

  Reference numeral 202 denotes a heater for heating provided inside the fixing film 201. Along the longitudinal direction on the surface of a highly insulating ceramic substrate, for example, an energization heating resistance layer such as Ag / Pd (silver palladium) is applied in a linear shape having a thickness of about 10 μm and a width of about 1 to 5 mm by screen printing or the like. Further, the heating resistance layer forming surface is covered with a thin glass protective layer. The temperature rise of the heater 202 is detected by the temperature detecting means 205 installed on the back surface of the heater and fed back to an energization control unit (not shown). The energization control unit controls power supply to the heater 202 so that the heater temperature detected by the temperature detecting unit 205 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 202 is heated and adjusted to a predetermined fixing temperature.

  Reference numeral 203 denotes an insulating stay holder for holding the heater 202, which is formed of liquid crystal polymer, phenol resin, or the like. The fixing film 201 is loosely fitted with a margin and is arranged to be rotatable in the direction of the arrow. ing. Further, since the fixing film 201 rotates while rubbing against the internal heating heater 202 and the heat insulating stay holder 203, it is necessary to reduce the frictional resistance between the heating heater 202 and the heat insulating stay holder 203 and the fixing film 201. . For this reason, a small amount of lubricant such as heat-resistant grease is interposed on the surfaces of the heater 202 and the heat insulating stay holder 203. As a result, the fixing film 201 can rotate smoothly.

  Reference numeral 204 denotes a pressure roller as a pressure member that presses against the heater 202 via the fixing film 201 to form a pressure nip N. The structure is composed of an elastic layer 207 formed by foaming heat-resistant rubber such as silicon rubber or fluoro rubber on the outside of the core metal 206, and a release layer 208 such as fluoro resin such as PFA or PTFE is formed thereon. Yes. The pressure roller 204 is sufficiently pressed from both ends in the longitudinal direction so as to form a nip portion necessary for heat fixing, and is driven to rotate counterclockwise as indicated by an arrow in FIG. Along with the rotation of the pressure roller 204, the cylindrical fixing film 201 is guided by the stay holder 203 and rotated in the clockwise direction of the arrow.

  When a recording material on which an unfixed image is formed is introduced between the fixing film 201 and the pressure roller 204 in the fixing nip N, the recording material is brought into close contact with the fixing film 201 together with the film. The nip portion N is nipped and conveyed, and the unfixed image is heated and fixed on the recording material by the heat from the heater 202 adjusted to a predetermined fixing temperature and the pressure contact force of the nip portion N.

  The internal structure of the fixing device 71 has been described above.

  Next, a color misregistration correction method will be described. This color laser printer is provided with a color misregistration amount measurement pattern generating means for transferring a predetermined color misregistration amount measurement pattern onto the surface of the transport belt 61 prior to the start of image transfer onto a sheet. . Further, the color laser printer detects an image position of the color misregistration amount measurement pattern formed on the surface of the conveyance belt 61 on the most fixing device 71 side in the conveyance direction of the recording material by the conveyance belt 61. A toner image detection sensor 90 is provided. The color misregistration amount measurement pattern generating means forms a color misregistration amount measurement pattern on the conveyance belt 61 at desired intervals for each of yellow, magenta, cyan, and black. When the color misregistration amount measurement pattern reaches the position of the toner image detection sensor 90, the toner image detection sensor 90 detects each color misregistration amount measurement pattern as a light intensity distribution waveform by an optical sensor or the like and outputs it as a voltage. Each output voltage is input to the control circuit board, and the position of the toner image is detected from the voltage waveform input by the image position detection circuit and input to the control circuit. The control circuit obtains the image interval between the colors by measuring the position interval between the detected colors. This measurement is performed a plurality of times, and the difference between the average value for the interval of each color and the desired interval is obtained to obtain the color misregistration amount. Based on this value, the control circuit changes the image writing timing.

  FIG. 6 shows data obtained by measuring a deviation amount from an image while printing the image in an actual image forming apparatus. The horizontal axis represents the continuous drive (printing) time (minutes), and the vertical axis represents the deviation from the initial position of the sub-scanning position.

  As described above, the color misregistration in the sub-scanning direction varies in accordance with the driving time To while drawing a profile like a curve that rises to the right as shown in FIG. This data is read from an image actually printed on a recording medium.

  As a result, when continuous printing is performed, a deviation of 20 μm occurs in 10 minutes and 40 μm in 20 minutes, and the registration a at the tip becomes a-40 μm in 20 minutes as shown in FIG.

  At this time, if the output of the temperature detection means 205 of the fixing device is high, it is assumed that the temperature of the scanning optical devices 11, 12, 13, and 14 is also high, and the color misregistration correction performed at this time is the case where the internal temperature of the image forming apparatus is high. Use only when the temperature inside the machine is low. As a result, it is possible to mitigate a decrease in color misregistration detection error and improve detection accuracy.

  As described above, a color misregistration amount detection error can be reduced by an easy method without an extra cost increase, and a color image forming apparatus that forms a color image with a small color misregistration amount by optimal color misregistration correction can be realized.

  A second embodiment of the present invention will be described. Since the basic configuration is the same as that of the first embodiment, the same reference numerals are used for the same parts as in the first embodiment and the description is omitted by using the same reference numerals, and the first embodiment is different from the first embodiment. Only explained.

  In the conventional color misregistration correction method, correction values are obtained when the color misregistration correction operation is performed when the temperature of the scanning optical device is high and when the color misregistration correction operation is performed when the temperature of the scanning optical device is low. There was a variation in color misregistration due to the difference.

  Therefore, when the output value of the temperature detecting means 205 provided in the fixing device is high, the temperature of the scanning optical device is also high and the correction operation is not performed. As a result, variations in color misregistration correction values can be reduced.

  As described above, it is possible to equalize the color misregistration amount detection error for each color by an easy method without an extra cost increase, and it is possible to realize a color image forming apparatus that forms a color image with a small amount of color misregistration by optimal color misregistration correction. .

The figure showing the image forming apparatus concerning the form of the 1st, 2nd Example of this invention Diagram showing outline of sensor for measuring color misregistration The figure which shows the example of the pattern for color misregistration amount measurement A diagram showing a conventional series of color misregistration measurement patterns Schematic sectional view showing a scanning optical device provided in the image forming apparatus of the present invention in the first embodiment. The graph which shows the scanning position shift | offset | difference of the subscanning direction at the time of the drive in a 1st Example The schematic diagram which shows the scanning position shift of the subscanning direction in a 1st Example. Sectional view showing the structure of the fixing device in the first embodiment Schematic diagram showing a scanning optical device in a conventional example

Explanation of symbols

11, 12, 13, 14..., Yellow, magenta, cyan, black scanning optical devices 21, 22, 23, 24..., Respectively, photosensitive drums 31, 32, 33.34. Each color charging roller 41, 42, 43, 44..., Each color sleeve roller 51, 52, 53, 54..., Each color transfer roller 61. Belt support roller 64a ... cassette feed pickup roller 64b ... manual feed pickup roller 65 ... registration roller 66 ... suction roller 67 ... transfer roller 68 from the intermediate transfer belt to the recording material, 69, 70 ... intermediate transfer belt support roller 71 ... fixing device 81 ... plain paper cassette 82 ... manual feed trays 90, 91, ... Toner image detection sensor 100 ... control circuit board 103 ... control circuit 104 ... image position detection circuit 16, ... motor L ... laser beam 10, 101 ... semiconductor laser 17, 105 ... Rotating polygon mirror 15 ... cylindrical lens 18 ... first scanning lens 20 ... folding mirror 19 ... second scanning lens 201 ... film 202 ... heater 203 ... Heater stay 204 ... Pressure roller 205 ... Thermistor 206 ... Core metal 207 ... Elastic layer 208 ... Releasable layer

Claims (2)

A scanning optical device including a laser light source, a rotary polygon mirror, and a scanning lens in a casing, and an image carrier along the driving direction of the conveyor belt or the intermediate transfer member that moves around, and the image carrier by the scanning optical device. A latent image is formed on the body, and toner images of a plurality of colors obtained by developing the latent image are sequentially superimposed and transferred onto the intermediate transfer member or a recording medium conveyed by the conveying belt, and then fixed. A color image forming apparatus for obtaining a color image composed of the plurality of colors on the recording medium by fixing the plurality of color toner images on the recording medium in a unit;
Detection means for controlling the scanning optical device to form a color misregistration amount measurement pattern by toner on the conveying belt or the intermediate transfer member, detecting the color misregistration amount measurement pattern, and outputting a pattern detection signal And calculating means for calculating a color misregistration amount for each color based on the pattern detection signal from the detecting means, and correcting a latent image forming position of each color based on the color misregistration amount calculated by the calculating means. A color image forming apparatus having correction means for performing an operation,
Determining a correction operation timing of a latent image forming position of each color based on an output value of a temperature detection unit provided in the fixing unit;
A color image forming apparatus.   2. The color image forming apparatus according to claim 1, wherein when the output value of the temperature detecting unit provided in the fixing unit is high, the operation of correcting the latent image forming position of each color is not performed. .

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