JP2005283769A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of optimum control of a conveyance belt depending on a print mode in forming an image. <P>SOLUTION: The image forming apparatus is equipped with a belt speed detection means for detecting the speed of a belt type intermediate transfer body or the conveyance belt and a judgement means for judging that the speed of the belt becomes stable according to output from the belt speed detection means, and generates image forming start timing according to output from the belt speed judgement means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus, and in particular, a plurality of developing devices are juxtaposed to form a toner image of each color on each image carrier in the developing device, and the toner image is transferred to an endless belt-shaped intermediate transfer member. In addition, the present invention relates to an image forming apparatus that re-transfers to a print medium or directly transfers onto a print medium conveyed by an endless belt-like conveyance belt.

  Conventionally, as an image forming apparatus that outputs a color image, for example, toner images of each color such as yellow, cyan, magenta, and black are formed on a photosensitive drum in a developing device of each color, and thereafter, are formed on an intermediate transfer belt or a conveyance belt. The image data is directly transferred to the conveyed printing medium and output through a fixing process. At this time, each belt starts driving at the same time as the image forming process is started, and after a predetermined time has elapsed from the start of driving, image formation is performed on a portion related to belt conveyance (transfer process from the photosensitive drum).

  However, in the image forming apparatus as described above, when the belt speed is not stable, for example, when the image forming apparatus is left without image formation for a long time, or when the life of the image forming apparatus is approaching, The belt speed changes during image formation, which adversely affects image quality. As an adverse effect on image quality, for example, color misregistration may occur when multiple colors are superimposed.

Therefore, a technique for preventing color misregistration is known by previously detecting and storing the thickness of the belt with a sensor and correcting the exposure timing to a plurality of photosensitive drums in accordance with the stored belt thickness. (For example, refer to Patent Document 1).
JP 2000-356875 A

  However, the method of detecting the thickness of the belt with a sensor in advance has a problem that it takes time to measure the thickness of the belt in addition to the cost of using the sensor.

  Therefore, a method of estimating the time during which the belt speed stabilizes in advance and preventing the adverse effect on the image by performing image formation after a certain time can be considered, but the belt speed is stable before the certain time elapses. In some cases, excessive time is spent on image formation.

  The present invention has been made in view of the above problems, and a first invention for solving the above-described problems is that a plurality of developing devices are juxtaposed, and toners of respective colors are arranged on the image carriers in the developing device. In an image forming apparatus that forms an image and transfers the toner image to an endless belt-shaped intermediate transfer member and retransfers it to a printing medium or directly onto a printing medium conveyed by an endless belt-shaped conveying belt A belt speed detecting means for detecting the speed of the belt-shaped intermediate transfer member or the conveying belt, and a judging means for judging that the belt speed is stabilized by the output of the belt speed detecting means. An image forming apparatus that generates image formation start timing.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus includes an image determining unit that determines a color image and a monochrome image from image data for image formation. The image determining unit outputs the output of the belt speed determining unit. An image forming apparatus that determines priority and generates image formation start timing.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect of the present invention, the image forming apparatus includes image quality selecting means capable of selecting an image quality at the time of image formation, and the priority of the output of the belt speed determining means according to the selected image quality mode. And an image formation start timing is generated.

  According to a fourth aspect of the present invention, in the image forming apparatus of the second aspect, when it is confirmed that the image data formed by the image determination unit is a full-color image, the speed is stabilized by the output of the belt speed determination unit. An image forming apparatus, wherein image formation is not performed until it is determined that it has been performed.

  According to a fifth invention, in the image forming apparatus according to the second invention, when it is confirmed that the image data formed by the image judging means is a monochrome image, the speed is stabilized by the output of the belt speed judging means. An image forming apparatus, wherein image formation is performed when a predetermined time has elapsed even if it is not determined.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the third aspect of the invention, when the high image quality mode is selected by the image quality selecting means, the image is formed until it is determined that the speed is stabilized by the output of the belt speed determining means. An image forming apparatus which is not performed.

  According to a seventh aspect of the present invention, in the image forming apparatus of the third aspect, when the low image quality mode is selected by the image quality selecting means, the output of the belt speed determining means does not determine that the speed is stable even if the speed is not stable. An image forming apparatus that forms an image when it has elapsed.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the third aspect of the present invention, the user can arbitrarily select the print image quality by the image quality selection means.

  According to a ninth aspect of the present invention, in the image forming apparatus of the first aspect, the belt speed detecting means for detecting the speed of the conveying belt detects the speed by an encoder attached to a driven roller by driving the belt. An image forming apparatus.

  According to a tenth aspect of the present invention, in the image forming apparatus of the first aspect, the belt speed detecting means for detecting the speed of the conveying belt detects the speed by reading at least one detection mark formed on the belt. An image forming apparatus.

  According to the present invention, it is possible to optimally control the conveyance belt according to the print mode during image formation. Therefore, the selectivity of high image quality priority and print speed priority is expanded, and a user desired mode can be selected.

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

(First embodiment)
FIG. 1 is a diagram showing the features of the present invention. In FIG. 1, reference numeral 1 denotes a scanner unit, which is composed of a semiconductor laser (not shown) and two rotating polygon mirrors. 3 is a cartridge for storing waste toner generated when the developer is stored and excess toner on the photosensitive member 4 is cleaned. A developing sleeve 5 develops the electrostatic latent image on the surface of the photosensitive member into a toner image. 6, 3, 4, and 5 are collectively referred to as a developing device (hereinafter referred to as a developing cartridge), and 6, 7, 8, 9 and 9 are yellow Y, magenta M, cyan C, and black BK developing cartridges, respectively, in particular the order. It does not matter. Reference numeral 10 denotes a transfer roller disposed to face the photoconductor for transferring the toner image on the photoconductor 4 developed by each color developing cartridge to a printing medium. Reference numeral 11 denotes a conveying belt constituted by an endless belt for conveying a printing medium. In this embodiment, eleven transport belts are used as the means for transporting the print medium, but a configuration using a belt-shaped image carrier is also used. Reference numeral 12 denotes a paper feed unit, and 13 denotes a print medium mounted in the paper feed unit. 14 is a fixing device for fixing the toner image on the printing medium to the printing medium, 15 is a fixing roller, and 16 is a heater roller for heating the fixing device for fixing.

  FIG. 2 mainly shows the belt conveyance unit of FIG.

  In FIG. 2, 17 is a tension roller for keeping the belt tension uniform, 18 is a driven roller that is rotated by a driving force applied by a conveyor belt, and 19 is an encoder attached to the shaft of the 18 driven rollers. And a photointerrupter (light transmission sensor) 21 having slits at equal intervals along the line. As for the encoder, a reflection optical system, a disk-shaped magnetic pattern, and the like are used.

  The photo interrupter 21 is arranged so as to sandwich the disk 20 of the encoder. When the light of the photo interrupter passes through the slit of the disk, the rotation speed detection signal becomes LOW level.

  Therefore, when the driven roller 18 rotates, the disk 20 provided on the shaft rotates, and slits at equal intervals along the circumference are sequentially sent between the light emitting and light receiving elements of the photo interrupter 21.

  For this reason, the speed detection signal has a pulse-like waveform, and it is possible to detect the speed of the conveyor belt based on how many times it is detected at regular intervals. Therefore, the rotational speed can be detected more accurately as the encoder has higher definition. For detecting the rotational speed, an optical sensor that outputs 1 PULSE for one rotation of the driven roller may be used. In this case, the speed of the conveyor belt can be detected by measuring the time between PULSEs.

  As another means for detecting the speed of the conveyor belt, there is a method of forming marks and slits on the belt at equal intervals and reading them with an optical sensor.

  FIG. 3 is a block diagram showing the configuration of this embodiment.

  In FIG. 3, 22 is a speed detector for monitoring the output of the encoder, 23 is a speed determining means for determining whether the current belt speed is a level at which printing can be performed with respect to a predetermined belt speed, and 24 is a speed of 23. An image formation signal generating means for forming an image formation start signal based on the result of the determination means, 25 a motor as a drive source for driving the conveyor belt, 26 a CPU for controlling the image forming apparatus, and 27 a transmission from the 28 host computer The image data discriminating means discriminates the color data of the image data.

  In this embodiment, the operation of the image forming apparatus having the above configuration will be described.

  When image data is received from the 28 host computers, the 26 CPUs first transmit drive start signals to the 25 motors. The 25 motors are controlled to rotate at a predetermined speed. Simultaneously with the 25 motor driving, the output monitoring of 19 encoders is started. The speed detection means 22 sequentially checks the pulse output period of 19 encoders. The encoder pulse output period is compared with a predetermined conveyance belt period that is optimal for image formation, and the speed is determined by 23 speed determination means. For speed determination, there are a method in which the number of coincidence pulse periods within a certain period is used, and a method in which an average value of pulse periods within a certain period is calculated.

  Here, the speed judgment method will be described.

1. Method for discriminating the number of coincidence of pulse periods in a certain period FIG. 4 shows the pulse output of the encoder. T is a sampling time and sampling is repeated in T cycles. In this example, 5 pulses are output within the T period, but the number of pulses is not particularly limited.

  The period of each pulse is measured for 5 pulses within the T period. If each cycle is t1, t2, t3, t4, t5, it is determined for each cycle whether or not it is the same cycle as Ts, which is the stable cycle of the conveyor belt. If the number of coincidence between the pulse period and Ts within the T period is 4 or more, for example, the conveying belt is defined as being stably driven, and the speed coincidence is determined.

  However, it is assumed that the number of matches that is a criterion can be arbitrarily set.

2. Method of comparing and discriminating the average value of pulse periods over a certain period Measure the period of each of the 5 pulses within the sampling time T When the periods are t1, t2, t3, t4, and t5, the average period Ta is Ta = (t1 + t2 + t3 + t4 + t5) / 5. When Ta calculated here and Ts, which is the stable period of the conveying belt, coincide with each other, it is defined that the conveying belt is driven stably, and the speed coincidence is determined.

  In the above two discrimination methods, any of the rising edge, falling edge, and both edges may be detected as the period of the pulse output from the encoder. In addition, the encoder pulse output sampling may be performed using either a method of updating every fixed period or a method of updating every pulse.

  Next, a description will be given with reference to FIG.

  The image data color discrimination means 27 confirms whether the image data transmitted from the host computer 28 is a color image or a monochrome image.

  If the image data is a color image, the 19 CPUs do not start image formation until the output of the speed OK is confirmed by the 23 speed determining means. When the output of the speed OK is confirmed by the speed determination means 23, an image formation start signal is generated.

  If the image data is a monochrome image, the output of the speed determination means 23 is ignored, and an image formation start signal is generated after a predetermined time has elapsed from the start of driving the motor 25, and the image formation process is started.

  After the image formation start signal is generated, 13 print media stored in 12 paper feed units are conveyed to the image forming unit. The transported print medium is adsorbed by 11 transport belts and transported to the front edge of the 9 BK developing cartridge. Here, the toner image formed on the photoconductor of 9 BK developing cartridge is transferred onto 13 printing media. From here, the toner images on the photoconductors 8, 7 and 6 are sequentially transferred onto the print medium 13 in accordance with the transport of the transport belt 11 to form a full-color image.

  If the image data is a monochrome image, 13 print media stored in 12 paper feed units are conveyed to the image forming unit before the image formation start signal is generated. The transported print medium is adsorbed by 11 transport belts and transported to the front edge of the 9 BK developing cartridge. Here, the toner image formed on the photoconductor of 9 BK developing cartridge is transferred onto 13 print media. Since it is a monochrome image, it is then transported to 14 fixing devices according to 11 transport belts. The toner image is fixed on the print medium and discharged.

  The said control is demonstrated using the flowchart of FIG.

  When image data is received from the host computer (S501), the CPU determines whether the image data is monochrome image data or color image data (S502).

  If the image data is a monochrome image, an image formation start signal is generated without waiting for the conveyance belt to stabilize (S507), and image formation is started (S508). If the image data is a color image, speed detection of the conveyor belt is started (S503). The period of the conveyor belt is measured (S504), and if the measured period coincides with the defined period (S505), the speed determination OK is determined (S506). Based on the determination of speed determination OK, an image formation start signal is generated (S507), and image formation is started (S508).

(Second embodiment)
FIG. 6 is a diagram that clearly represents the features of the present embodiment. The same functions and components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 6, reference numeral 29 denotes image quality mode selection means, which can select at least two modes, for example, a high image quality mode and a low image quality mode.

  Reference numeral 30 denotes a panel operation unit mounted on the image forming apparatus, and the user can make various settings. Here, the user can select the image quality mode from the panel operation unit.

  The image forming apparatus having the above configuration will be described.

  When image data is received from the 27 host computers, the 26 CPU first transmits a drive start signal to the 25 motors. The 25 motors are controlled to rotate at a predetermined speed. Simultaneously with the 25 motor driving, the output monitoring of 19 encoders is started. The speed detection means 22 sequentially checks the pulse output period of 19 encoders. The encoder pulse period is compared with a predetermined conveying belt period that is optimal for image formation, and the speed is determined by 23 speed determination means. For speed determination, there are a method in which the number of coincidence pulse periods within a certain period is used, and a method in which an average value of pulse periods within a certain period is calculated. In addition, a predetermined conveyance belt cycle is stored in the memory 31 and conveyance corresponding to various speeds (for example, when forming an image on a printing medium such as OHT, a lower speed than that of plain paper is set). Stores the belt cycle.

  Here, 29 image quality mode selection means confirms the image quality mode designated by 27 host computers. On the host computer, an image quality mode is selected on the screen by a so-called printer driver.

  As another means, it is also possible to directly select the image quality mode from a panel operation unit mounted on the image forming apparatus.

  When the selected image quality mode is the image quality mode, the 26 CPUs do not start image formation until the output of the speed OK is confirmed by the 23 speed determination means. When the output of the speed OK is confirmed by the speed determination means 23, an image formation start signal is generated, and the above-described series of image formation processes is started.

  When the image quality mode is the low image quality mode, the output of the speed determination means 23 is ignored, and an image formation start signal is generated after a predetermined time has elapsed from the start of the 25 motor drive, and the image formation process is started.

  After the image formation start signal is generated, 13 print media stored in 12 paper feed units are conveyed to the image forming unit. The transported print medium is adsorbed by 11 transport belts and transported to the front edge of the 9 BK developing cartridge. Here, the toner image formed on the photoconductor of 9 BK developing cartridge is transferred onto 13 print media. From here, the toner images on the photoconductors 8, 7 and 6 are sequentially transferred onto the print medium 13 in accordance with the transport of the transport belt 11 to form a full-color image.

  When the image data is in the low image quality mode, 13 print media stored in 12 paper feed units are conveyed to the image forming unit before the image formation start signal is generated. The transported print medium is adsorbed by 11 transport belts and transported to the front edge of the 9 BK developing cartridge. Thereafter, the toner images of the respective colors are superposed on the print medium according to 11 transport belts and transported to 14 fixing devices. The toner image is fixed on the print medium and discharged.

  The said control is demonstrated using the flowchart of FIG.

  When image data is received from the host computer (S701), the CPU determines whether the image quality mode information received from the host computer is the high image quality mode or the low image quality mode (S702). Similarly, it is determined whether the mode selected by the operation panel is the high image quality mode or the low image quality mode (S703).

  If the selected mode is the low image quality mode, an image formation start signal is generated without waiting for the stability of the conveyor belt (S708), and image formation is started (S709). If the selected mode is the high image quality mode, the conveyor belt speed detection is started (S704). The period of the conveyor belt is measured (S705), and if the measured period coincides with the specified period (S706), the speed determination OK is determined (S707). Based on the determination of speed determination OK, an image formation start signal is generated (S708), and image formation is started (S709).

1 is a diagram illustrating a schematic configuration of a printer that is an image forming apparatus according to a first embodiment. FIG. FIG. 2 is a diagram illustrating a conveyance belt and a drive system of the image forming apparatus according to the first exemplary embodiment. FIG. 3 is a control block diagram of the image forming apparatus in the first embodiment. It is a block diagram for demonstrating the speed detection of the conveyance belt in a 1st Example. 3 is a flowchart illustrating an operation of the image forming apparatus in the first embodiment. It is a block diagram for demonstrating the speed detection of the conveyance belt in a 2nd Example. 6 is a flowchart illustrating an operation of the image forming apparatus according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scanner unit 2 Rotating polygon mirror 3 Cartridge 4 Photoconductor 5 Developing sleeve 6 Y developing cartridge 7 M developing cartridge 8 C developing cartridge 9 BK developing cartridge 10 Transfer roller 11 Conveying belt 12 Paper feeding unit 13 Printing medium 14 Fixing device 15 Fixing roller 16 Heater roller 17 Tension roller 18 Driven roller 19 Encoder 20 Code wheel 21 Photo interrupter 22 Speed detection means 23 Speed determination means 24 Image formation signal generation means 25 Motor 26 CPU
27 Image data discrimination means 28 Host computer 29 Image quality mode selection means 30 Operation panel 31 Memory

Claims (10)

  A plurality of developing devices are juxtaposed, a toner image of each color is formed on each image carrier in the developing device, and the toner image is transferred to an endless belt-like intermediate transfer member and re-transferred to a printing medium, or In an image forming apparatus that directly transfers onto a print medium conveyed by an endless belt-shaped conveyance belt, a belt speed detection unit that detects the speed of the belt-shaped intermediate transfer member or the conveyance belt, and a belt that is output from the belt speed detection unit An image forming apparatus comprising: a determination unit that determines that the speed of the belt is stable; and generating an image formation start timing based on an output of the belt speed determination unit.   The image forming apparatus according to claim 1, further comprising an image determination unit that determines a color image and a monochrome image from image data for image formation, and determines the output priority of the belt speed determination unit by the image determination unit, An image forming apparatus that generates image formation start timing.   3. The image forming apparatus according to claim 1, further comprising an image quality selection unit capable of selecting an image quality at the time of image formation, and determining the priority of the output of the belt speed determination unit according to the selected image quality mode. An image forming apparatus that generates start timing.   3. The image forming apparatus according to claim 2, wherein when the image data formed by the image determination unit is confirmed to be a full-color image, it is determined that the speed has been stabilized by the output of the belt speed determination unit. An image forming apparatus that does not perform image formation until.   3. The image forming apparatus according to claim 2, wherein when it is confirmed that the image data formed by the image determination unit is a monochrome image, it is not determined that the speed is stabilized by the output of the belt speed determination unit. However, an image forming apparatus that performs image formation when a predetermined time has elapsed.   4. The image forming apparatus according to claim 3, wherein when the high image quality mode is selected by the image quality selecting means, image formation is not performed until it is determined by the output of the belt speed determining means that the speed is stable. Image forming apparatus.   4. The image forming apparatus according to claim 3, wherein when the low image quality mode is selected by the image quality selecting means, the image is formed when a predetermined time elapses even if the output of the belt speed determining means does not determine that the speed is stable. An image forming apparatus.   4. The image forming apparatus according to claim 3, wherein the user can arbitrarily select the print image quality by the image quality selection means.   2. The image forming apparatus according to claim 1, wherein the belt speed detecting means for detecting the speed of the conveying belt detects the speed by an encoder attached to a roller driven by driving the belt. .   2. The image forming apparatus according to claim 1, wherein the belt speed detecting means for detecting the speed of the conveying belt detects the speed by reading at least one detection mark formed on the belt. Image forming apparatus.