JP2009223276A - Image forming device and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming technique capable of minimizing deterioration of quality of a formed image while maximizing the number of image-formable sheets. <P>SOLUTION: A sensor 131 detects an image concentration of an image pattern formed on a photoreceptor drum 40 of each color by an imaging device and a light beam scanning apparatus. In a printer control part 117, the image concentration detected by the sensor 131 is compared with a predetermined value, and on a basis of its result, imaging conditions are changed. At this time, in the printer control part 117, when changing imaging conditions in regard to one color, imaging conditions of other colors are changed irrespective of a comparison result of the image concentration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for performing image density control at the time of toner near-end.

  Conventionally, in a color image forming apparatus that forms an image of a plurality of colors, different from a black and white image, the images of each color are overlapped. (Color unevenness) will occur, leading to a decrease in image quality. Therefore, it is necessary to match the image positions of the respective colors as much as possible. For this reason, in an image forming apparatus that forms a color image using a plurality of photoconductors, in order to correct misregistration between colors caused by various factors such as a change in environmental temperature and a change in internal temperature. In addition, a color misregistration detection pattern is formed on the transfer belt, which is detected by a sensor, and based on a signal from the sensor, a misregistration amount, for example, magnification in the main scanning direction, main scanning, and sub-scanning resist is detected, The shift between each color is corrected. As a result, not only the environmental change but also the position shift due to the change with time can be corrected, and a high-quality image without color shift can be obtained.

  By the way, in an electrophotographic image forming apparatus using toner, toner in the developing device is consumed by image formation, and the developed image density decreases accordingly. For this reason, the toner density in the developing device is detected, or the image density of the image formed on the photosensitive member and the transfer belt is detected, and if it falls below a specified value, the toner is supplied from the toner bottle to the developing device. , Always getting a stable image density. However, if toner supply is repeated, the toner in the toner bottle decreases, the toner cannot be replenished by a specified amount, the image density is lowered, and if the toner in the developing device eventually runs out, image formation cannot be performed. The bottle needs to be replaced with a new one.

  For this reason, in recent years, in an electrophotographic image forming apparatus using toner, image correction is performed on a sheet conveying belt at the time of power-on, at the time of toner near-end, at the time of toner empty, every predetermined number of printings, etc. For this reason, a method has been proposed in which a correction pattern for printing is printed and the image is corrected by reading the correction pattern (see, for example, Patent Document 1). With this method, stable image quality can be ensured at all times even if the toner is reduced. In addition, there has been proposed a method for simultaneously confirming toner end when detecting an overlay error (color shift) (see, for example, Patent Document 2). In this method, since the toner consumed for toner end confirmation is not necessary, the running cost can be reduced.

  In addition, in an electrophotographic image forming apparatus that uses toner, a decrease in image density due to a decrease in the remaining amount of toner in the toner bottle is detected, and if it is determined that the toner is near end, the image density is decreased. There has been proposed a method of changing the image forming condition so as to suppress it (for example, see Patent Document 3). In this method, it is possible to keep the image density good by suppressing the decrease in the image density from the determination of the toner near end to the end of the toner.

Japanese Patent Laid-Open No. 9-152796 JP 2007-193189 A JP-A-4-242766

  However, by suppressing the decrease in the image density after determining the toner near end, naturally, the number of prints on which an image can be formed before the toner end is reached is reduced. If a toner bottle filled with toner is at hand, there is no problem, but if it is necessary to arrange a toner bottle, image formation may not be possible until the toner bottle arrives. Also, some users may want to print as many sheets as possible even if the image density is lowered.

  Further, in a color image forming apparatus capable of color printing, when only one color toner is in the toner near end and the image density is reduced only for that color, a difference from the image density of other colors occurs. There is a risk that the color may change or color unevenness may occur. For black, it is mainly used for text and line drawings, so the effect of lowering the image density is small, but for yellow, magenta, and cyan, there is a risk that it will not be possible to simply reduce the image density, and the image quality will change significantly. There is a risk that.

  The present invention has been made in view of the above, and provides an image forming apparatus and an image forming method capable of suppressing deterioration in quality of an image to be formed as much as possible while increasing the number of images that can be formed as much as possible. The purpose is to do.

  In order to solve the above-described problems and achieve the object, the present invention provides a latent image forming unit that forms a latent image by irradiating a rotating or moving image carrier with a light beam according to image data. A developing unit that supplies a plurality of color toners to visualize the latent image, a transfer unit that transfers the developed image visualized by the developing unit onto a recording paper, and a toner obtained by the visualization A toner replenishing means for replenishing the developing means with respect to consumption, a remaining amount detecting means for detecting whether or not the remaining amount of toner for each of the plurality of colors is less than a predetermined value, and at least When the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for one color, the latent image formed on the image carrier is visualized for all colors. Change the image creation conditions to reduce the image density Characterized in that it comprises a changing means.

  The present invention also provides a latent image forming means for forming a latent image by irradiating a rotating or moving image carrier with a light beam according to image data, and supplying a plurality of colors of toner to the latent image. Developing means for visualizing the image, transfer means for transferring the visible image visualized by the developing means onto the recording paper, and supplying toner to the developing means for consumption of the toner due to the visualization An image forming method implemented in an image forming apparatus comprising a toner replenishing unit, a remaining amount detecting unit, and a changing unit, wherein the remaining amount detecting unit is configured to store the remaining toner for each of the plurality of colors. A remaining amount detecting step for detecting whether or not the amount is less than a predetermined value; and the changing means detects that the remaining amount of toner for the at least one color is less than a predetermined value. The above for all colors Characterized in that it comprises a changing step of changing the image forming condition so as to lower the image density at the time of visualizing the latent image formed on the carrier.

  According to the present invention, even in the toner near-end state, it is possible to suppress the deterioration of the quality of the formed image as much as possible while increasing the number of images that can be formed as much as possible.

  Exemplary embodiments of an image forming apparatus and an image forming method according to the present invention are explained in detail below with reference to the accompanying drawings.

[First embodiment]
(1) Configuration FIG. 1 is a diagram showing an outline of a mechanism portion of an image forming apparatus according to the present embodiment. The printer 100 of the image forming apparatus includes an intermediate transfer unit (not shown) in the center, and the intermediate transfer unit includes an intermediate transfer belt 10 that is an endless belt. The intermediate transfer belt 10 is wound around three support rollers 14 to 16 and is driven to rotate clockwise. To the right of the second support roller 15 is an intermediate transfer member cleaning unit 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer. The intermediate transfer belt 10 between the first support roller 14 and the second support roller 15 has yellow (Y), magenta (M), cyan (C), and black (BK) along the moving direction. ), The image forming apparatus 20 having the photosensitive drum 40, the charging unit 18, the transfer unit 62, the developing unit, the cleaning unit, and the charge eliminator (not shown). The image forming device 20 is detachably attached to the printer main body. Above the image forming device 20, there is a light beam scanning device 21 that irradiates each photoconductor drum 40 of each color with laser light for image formation. Below the intermediate transfer belt 10 is a secondary transfer unit 22. The secondary transfer unit 22 is arranged so that a secondary transfer belt 24 that is an endless belt is stretched between two rollers 23, the intermediate transfer belt 10 is pushed up and pressed against the third support roller 16. is there. The secondary transfer belt 24 transfers the image on the intermediate transfer belt 10 onto the recording paper. Next to the secondary transfer unit 22, there is a fixing unit 25 for fixing the transfer image on the recording paper, and the recording paper on which the toner image has been transferred is supplied thereto. The fixing unit 25 is obtained by pressing a heating and pressure roller 27 against a fixing belt 26 that is an endless belt. Below the secondary transfer unit 22 and the fixing unit 25, there is a sheet reversing unit 28 that feeds the recording paper immediately after the image is formed on the front surface with the front and back reversed to record the image on the back surface.

  The image forming apparatus includes an operation unit (not shown), an image reading unit 300 having a scanner, an automatic document feeder (ADF) 400, a first carriage 33, a second carriage 34, an imaging lens 35, and a CCD 36. . When the start switch of the operation unit is pressed, if there is a document on the document feeder table 30 of the automatic document feeder (ADF) 400, the ADF 400 transports the document onto the contact glass 32. When there is no document on the ADF 400, the scanner of the image reading unit 300 is driven to read and scan the first carriage 33 and the second carriage 34 in order to read a manually placed document on the contact glass 32. Then, light is emitted from the light source on the first carriage 33 to the contact glass 32, and reflected light from the document surface is reflected by a mirror (not shown) on the first carriage 33 toward the second carriage 34. 2 The image is reflected by a mirror (not shown) on the carriage 34 and imaged on a CCD 36 as a reading sensor through an imaging lens 35. Based on the image signal (image data) obtained by the CCD 36, recording data of each color of Y, M, C, and BK is generated.

  Further, when the start switch is pressed, the rotational driving of the intermediate transfer belt 10 is started, the image forming preparation of each unit of the image forming apparatus 20 is started, and the image forming sequence of each color image is started. Then, an exposure laser modulated based on the recording data of each color is projected onto the photosensitive drum 40 for each color, and each color toner image is transferred onto the intermediate transfer belt 10 as a single image by the color image forming process. Is done. That is, the latent image of each color is visualized. When the leading edge of the toner image enters the secondary transfer unit 22, the recording paper is supplied to the secondary transfer unit 22 at a timing so that the leading edge enters the secondary transfer unit 22 at the same time. The toner image on the transfer belt 10 is transferred to the recording paper. The recording paper onto which the toner image has been transferred is supplied to the fixing unit 25 where the toner image is fixed on the recording paper.

  Note that the recording paper described above is selectively rotated by one of the paper feed rollers 42 of the paper feed table 200 and is fed out from one of the paper feed trays 44 provided in multiple stages in the paper feed unit 43. Then, the recording sheet is separated by one sheet by the separation roller 45, put in the conveyance roller unit 46, conveyed by the conveyance roller 47, and guided to the conveyance roller unit 48 in the printer 100. After being abutted against the registration roller 49 and stopped, it is supplied to the secondary transfer unit 22 at the timing described above. Note that the user can also insert and feed a recording sheet onto the manual feed tray 51. When the user inserts the recording paper on the manual feed tray 51, the printer 100 drives the paper feed roller 50 and the paper feed roller 52 to separate one of the recording paper on the manual feed tray 51, thereby manually feeding the paper. 53, and abuts against the registration roller 49 to stop.

  The recording paper discharged after receiving the fixing process in the fixing unit 25 is guided to the discharge roller 56 by the switching claw 55 and stacked on the paper discharge tray 57. Alternatively, the recording paper is guided to the sheet reversing unit 28 by the switching claw 55, reversed there and guided again to the transfer position, and after the image is recorded on the back surface, the paper discharge tray 57 is discharged by the discharge roller 56. Discharged to the top.

  The image forming apparatus also includes an intermediate transfer member cleaning unit 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer. In addition, the image forming apparatus detects, for each color, a toner bottle receiver that detachably supports a toner bottle containing toner to be replenished to the developing unit, and a density of a toner image formed on the photosensitive drum 40. Sensors (both not shown). Further, the image forming apparatus includes a control unit (not shown) that controls the entire apparatus. The control unit stores a control device such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory) that stores various data and various programs, and stores various data and various programs. An external storage device such as an HDD (Hard Disk Drive) and a bus for connecting them.

  FIG. 2 is a diagram showing a detailed configuration of the image forming device 20 and the light beam scanning device 21. As described above, the image forming apparatus 20 includes the photosensitive drums 40 of yellow (Y), magenta (M), cyan (C), and black (BK). The light beam scanning device 21 includes a polygon mirror 70 and a polygon motor 71 that drives the polygon mirror 70. The polygon mirror 70 is used to deflect and scan light beams of different colors above and below the surface of the polygon mirror 70. By scanning the polygon mirror 70 so as to be opposed to each other, the light beams for four colors are scanned on the respective photosensitive drums 40. Further, the light beam scanning device 21 includes LD (Laser Diode) units (not shown) for selectively emitting light beams by being driven and modulated in accordance with image data for each color. The light beam emitted from the LD unit is deflected by the polygon mirror 70 rotated by the polygon motor 71, passes through the fθ lens 72, is reflected by the first mirror 73, is reflected by the second mirror 74, passes through the BTL 76, and is passed through the third. Reflected by the mirror 75 and scanned on the photosensitive drum 40. BTL76 is an abbreviation of Barrel Toroidal Lens, and performs focusing in the sub-scanning direction (condensing function and position correction in the sub-scanning direction (surface tilt, etc.)). Although not shown here, by receiving the light beam deflected by the polygon mirror 70 ahead of the image writing position in the non-image writing area in the main scanning direction, the writing start timing in the main scanning direction is set. A synchronization detection sensor is provided that outputs a synchronization detection signal for taking.

  Around the photosensitive drum 40 of each color, the above-described charging unit 18, the developing unit 80, the transfer device 62, the cleaning unit 82, and the static eliminator 83 are provided. The image forming apparatus 20 forms a first color image on the intermediate transfer belt 10 by charging, exposure, development (visualization), and transfer, which are normal electrophotographic processes, and then the second, third, and fourth colors. By transferring the images in this order, a color image in which the four color images are superimposed is formed. Then, the secondary transfer unit 22 shown in FIG. 1 transfers the image formed on the intermediate transfer belt 10 onto the conveyed recording paper, so that a color image in which the four color images are superimposed is formed. It is formed on recording paper. Then, a color image is fixed on the recording paper by the fixing unit 25 shown in FIG.

  FIG. 3 is a top view of the light beam scanning device 21 shown in FIG. The light beam scanning device 21 includes an LD unit 77 corresponding to each color of Y, BK, M, and C. Light beams from the LD unit 77 corresponding to Y and the LD unit 77 corresponding to BK pass through the CYL (cylinder lens) 78 and are incident on the lower surface of the polygon mirror 70 by the reflection mirror 79. Then, the light beam is deflected by the rotation of the polygon mirror 70, passes through the fθ lens 72, and is folded back by the first mirror 73. Light beams from the LD unit 77 corresponding to M and the LD unit 77 corresponding to C pass through the CYL 78 and enter the upper surface of the polygon mirror 70. Then, the light beam is deflected by the rotation of the polygon mirror 70, passes through the fθ lens 72, and is folded back by the first mirror 73. In the present embodiment, a synchronization mirror BKC90a, a synchronization mirror MY90b, a synchronization lens BKC91a, a synchronization lens MY91b, a synchronization sensor BKC92a, and a synchronization sensor MY92b are provided at the writing side end in the main scanning direction. Each color light beam transmitted through the fθ lens 72 is reflected by the synchronous mirror BKC90a and the synchronous mirror MY90b, collected by the synchronous lens BKC91a and the synchronous lens MY91b, and incident on the synchronous sensor BKC92a and the synchronous sensor MY92b. Yes. Each of the synchronization sensors BKC92a and the synchronization sensor MY92b serves as a synchronization detection sensor for detecting the synchronization detection signal XDETP. As can be seen from the figure, Y and M are scanned in the opposite direction with respect to C and BK.

  An image formation control function in which the image forming apparatus controls image formation will be described. This function is realized, for example, by executing various programs stored in the storage device or the external storage device by the control device of the control unit described above. FIG. 4 is a block diagram showing the image formation control function in more detail. The image formation control function includes a polygon motor control unit 110, an LD control unit 111, a sync detection lighting control unit 112, a pixel clock generation unit 113, a printer control unit 117, a charging potential control unit 118, a development bias control unit 119, an image. A data control unit 120 and a toner supply control unit 121 are included. Although detailed illustration is omitted here, the LD control unit 111, the sync detection lighting control unit 112, the pixel clock generation unit 113, the charging potential control unit 118, the development bias control unit 119, and the image data control unit 120. The toner replenishment control unit 121 is included in the image formation control function for each of Y, BK, M, and C colors. The polygon motor control unit 110 and the printer control unit 117 are common to each color.

  The synchronization detection signal separation unit 109 separates the synchronization detection signal XDETP output from the synchronization sensor 92a (92b) into the synchronization detection signal XDETP for each color. Note that the synchronization detection signal XDETP is output from the synchronization sensor 92a (92b) when the light beam passes over the synchronization sensor 92a (92b) of the light beam scanning device 21, but in this embodiment, the synchronization sensor 92a (92b) is shared by two colors. Therefore, the synchronization detection signal separation unit 109 separates the synchronization detection signals XDETP for two colors whose timings are shifted into the synchronization detection signals XDETP for the respective colors. Then, the synchronization detection signal separation unit 109 supplies the separated synchronization detection signal XDETP to the pixel clock generation unit 113 and the synchronization detection lighting control unit 112 corresponding to each color.

  The pixel clock generation unit 113 generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP, and supplies this to the LD control unit 111 and the synchronization detection lighting control unit 112. The detailed functions of the pixel clock generation unit 113 are divided into a reference clock generation unit 114, a VCO (Voltage Controlled Oscillator) clock generation unit 115, and a phase synchronization clock generation unit 116.

  FIG. 5 is a diagram showing the VCO clock generator 115 (PLL circuit: Phase Locked Loop). The VCO clock generation unit 115 includes a phase comparator 140, an LPF (low-pass filter) 141, a VCO 142, and a 1 / N frequency divider 143. The 1 / N frequency divider 143 divides the oscillation frequency (VCLK) output from the VCO 142 by N. Then, the reference clock signal FREF from the reference clock generator 114 and the signal obtained by dividing VCLK by N by the 1 / N divider 143 are input to the phase comparator 140. The phase comparator 140 compares the phases of the falling edges of both signals and outputs an error component with a constant current. The LPF 141 removes unnecessary high-frequency components and noise and supplies them to the VCO 142. The VCO 142 outputs VCLK depending on the output of the LPF 141. Therefore, the frequency of VCLK can be varied by varying the frequency of FREF and the frequency division ratio: N from the printer control unit 117.

  The phase synchronization clock generator 116 generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP from VCLK generated by the VCO clock generator 115.

  The synchronization detection lighting control unit 112 first turns on the synchronization detection lighting signal BD to forcibly light the LD in order to detect the synchronization detection signal XDETP. At this time, after the light beam is detected by the synchronization sensor 92a (92b) and the synchronization detection signal XDETP is output, the synchronization detection lighting control unit 112 reliably detects the synchronization sensor 92a (92b) without causing flare light. A lighting signal BD that is turned ON / OFF at a timing at which a light beam can be detected is generated from the synchronization detection signal XDETP and the pixel clock PCLK and supplied to the LD control unit 111 to light the LD. The lighting signal BD is turned on immediately before the light beam is incident on the synchronization sensor 92a (92b) and turned off after being incident (after the synchronization detection signal XDETP is output).

  The LD control unit 111 controls the lighting of the laser according to image data synchronized with the lighting signal BD for synchronization detection and the pixel clock PCLK. Then, a laser beam is emitted from the LD unit 77, deflected to the polygon mirror 70, passes through the fθ lens 72, and scans on the photosensitive drum 40. The polygon motor control unit 110 controls the rotation of the polygon motor 71 shown in FIG. 2 at a specified number of rotations based on a control signal from the printer control unit 117.

  Here, the sensor 131 and the operation unit 130 shown in FIG. 4 will be described. These have been outlined above. The sensor 131 is provided in the image forming apparatus for each of Y, BK, M, and C colors. Each of the sensors 131 detects the density (image density) of the image pattern formed on the photosensitive drum 40 of each color, and supplies the value of the image density to the printer control unit 117.

  FIG. 6 shows an image pattern. Here, the image pattern G1 is formed by forming a patch image sufficiently larger than the spot size of the sensor 131 on the photosensitive drum 40 of each color. Here, such an image pattern G1 is formed every time an image is formed on a predetermined number of recording sheets, for example. Then, the sensor 131 provided for each color detects the image density of each color of the image pattern G1 formed in this way.

  The operation unit 130 has an operation panel including operation keys such as the start key and operation buttons described above. The operation unit 130 receives an input of an operation instruction corresponding to the operation content from the user on the operation panel, and supplies this to the printer control unit 117. The operation instruction includes, for example, an image formation instruction for instructing image formation. Further, the operation unit 130 displays information from the printer control unit 117 on the operation panel.

  Returning to the description of the image formation control function. The printer control unit 117 appropriately supplies various control signals to each unit in order to control the LD control unit 111, the charging potential control unit 118, the development bias control unit 119, the image data control unit 120, and the toner replenishment control unit 121. Further, the printer control unit 117 changes the control state related to image formation so as to suppress toner consumption. Specifically, the printer control unit 117 compares the image density value supplied from the sensor 131 with a predetermined value, and changes the imaging condition based on the result. As a result, the control state relating to image formation is changed. The predetermined value may be stored in advance in a storage device or an external storage device, or may be set variably. Here, the printer control unit 117 changes the light amount of the light beam emitted from the LD as the image forming condition. In addition, the printer control unit 117 performs control according to an operation instruction supplied from the operation unit unit 130.

  The LD control unit 111 controls the LD according to a control signal from the printer control unit 117. FIG. 7 is a diagram illustrating a configuration of the LD control unit 111. The LD control unit 111 is divided into a PWM signal generation unit 150 and an LD drive unit 151. The PWM signal generator 150 controls the lighting time of the LD. The LD driving unit 151 controls lighting of the LD. Specifically, the PWM signal generation unit 150 outputs a PWM signal to the LD drive unit 151 based on the image data and the control signal 1 from the printer control unit 117, and the LD drive unit 151 lights the LD for that time. Let Further, by supplying the LD driving unit 151 with the synchronization detection lighting signal BD from the synchronization detection lighting control unit 112, the LD is lit for that time. The amount of light for turning on the LD is set by a control signal 2 from the printer control unit 117.

  The image data may be 1 bit width or plural bits (2 bit width or more). For example, in the case of 1 bit width, it may be configured to generate a predetermined pulse width. Alternatively, image data may be output by selecting a pulse width based on a control signal 1 (selection signal) from the printer control unit 117. When the image data is a plurality of bits (2 bits width or more), a pulse width corresponding to each image data may be generated. Alternatively, the pulse width corresponding to the image data may be variable by the control signal 1 (selection signal) from the printer control unit 117.

  FIG. 8 is a diagram showing the configuration of the LD. As is well known, the LD is composed of an LD and a PD (Photo diode). The LD driving unit 151 controls the LD current Id so as to keep the PD monitor voltage Vm constant in order to light the LD with the light amount instructed from the printer control unit 117 (APC operation: auto power control). When the amount of light is varied, Vm is varied by an instruction from the printer control unit 117, and the LD current Id is controlled so as to keep the set Vm constant.

  Returning to the description of the image formation control function. The charging potential control unit 118 controls the charging potential of the charging unit 18 shown in FIG. 2 according to a control signal from the printer control unit 117. The development bias control unit 119 controls the development bias voltage of the development unit 80 shown in FIG. 2 according to a control signal from the printer control unit 117. The image data control unit 120 controls the supply of image data to the LD control unit 111. The toner replenishment control unit 121 controls the amount of toner replenished from the toner bottle to the developing unit 80 in accordance with a control signal from the printer control unit 117.

(2) Operation Next, a procedure of image density control processing performed by the image forming apparatus according to the present embodiment will be described with reference to FIG. Here, it is assumed that the image density is controlled every time a predetermined number (for example, 10) of images are formed on the recording paper. In this case, the image forming apparatus performs the following image density control process every time ten images are formed on the recording paper. Further, the image forming apparatus performs the following image density control process for each color.

  The image forming apparatus counts the number of sheets each time an image is formed on one recording sheet. When the number of sheets reaches 10, the image density control process described below is started. To clear. The image forming apparatus first forms an image pattern on the photosensitive drum 40 of each color by the image forming device 20 and the light beam scanning device 21 (step S1), and the image density of the image pattern is measured by the sensor 131. Detect (step S2). Then, the image forming apparatus checks whether the toner near-end state is detected by the printer control unit 117 (step S3). If it is not the toner near end, then, if the value of the image density is greater than or equal to the first predetermined value, the image forming apparatus determines that it is not the toner near end, and then whether or not the image density value is less than the predetermined value A. Is determined (step S4). The predetermined value A is determined from the lower limit value of the allowable image density. If it is determined that the image density value is not less than the predetermined value A (step S4: NO), the image forming apparatus ends the image processing. When it is determined that the value of the image density is less than the predetermined value A (step S4: YES), the image forming apparatus determines whether or not the image density is continued N times (here, “N = 2” or more) (step S4). S5). The reason why “N = 2” or more is not determined only once is as follows. This is because there may be a detection error when the determination is made only once. In addition, it is for confirming whether the image density actually increases, does not change, or decreases by performing control to increase the image density in a state where the image density is continuous twice or more. The image forming apparatus counts the number of times that the image density value is less than the predetermined value A continuously occurs, and uses this number in step S5.

  If it is determined in step S5 that the image has not continued N times (step S5: NO), the image forming apparatus replenishes the developing unit 80 with toner and ends the process. If it is determined that the toner has continued N times (step S5: YES), the image forming apparatus determines that the toner remaining amount is low, that is, the toner near-end state, and indicates the toner near-end state. Information is displayed on the operation panel of the operation unit 130 (step S6). Further, the image forming apparatus changes the light amount of the light beam emitted from the LD (step S7). The image forming apparatus performs the next image formation with the changed light amount.

  The amount of light is changed in the direction of decreasing the image density. That is, here, the image forming apparatus reduces the light amount of the light beam emitted from the LD. The amount to be lowered is determined from an acceptable image density and image quality. In addition, when the determination result in step S5 is positive for one color and the light amount of the light beam emitted from the LD is changed in step S7, the image forming apparatus detects other colors as well. Regardless of the value of the image density, the amount of light beam emitted from the LD is changed. For example, when the light amount of the light beam emitted from the LD is ½ of the current value, the light amount of the light beam emitted from the LD is also reduced to ½ of the current value for each of the other colors. become. The timing for changing the light quantity of the light beam emitted from the LD is controlled by the image forming apparatus so as to be the timing for forming the same image (the same page) for each color. This is because in the configuration of the image forming apparatus according to the present embodiment, when an image is formed for a certain color, another image may be formed for another color.

  After step S7, the image forming apparatus supplies toner to the developing unit 80, and the process ends (step S8).

  On the other hand, if the toner near-end is reached in step S3, the image forming apparatus determines whether the image density value is less than a predetermined value B (step S10). The predetermined value B is determined from the lower limit value of the image density that is allowable in the toner near-end state. When it is determined that the image density value is not less than the predetermined value B (step S10: NO), the image forming apparatus supplies toner to the developing unit 80 and ends the process. When it is determined that the value of the image density is less than the predetermined value B (step S10: YES), the image forming apparatus determines whether or not it continues for N times (here, “N = 2” or more) (step S10). S11). The reason why “N = 2” or more is the same as the reason why “N = 2” or more in step S5 described above. The image forming apparatus counts the number of times that the image density value is less than the predetermined value B continuously, and uses this number in step S11.

  If it is determined that the image has not continued N times (step S11: NO), the image forming apparatus supplies toner to the developing unit 80 and ends the process. When it is determined that the image has continued N times (step S11: YES), the image forming apparatus determines that there is no toner, that is, the toner end state, and operates information indicating the toner end state. It is displayed on the operation panel of the copy unit 130 (step S12). Then, the image forming apparatus stops its own mechanical part (step S13).

  According to the above configuration, even in the toner near-end state, it is possible to suppress the deterioration of the quality of the formed image as much as possible while increasing the number of images that can be formed as much as possible.

[Second Embodiment]
Next, a second embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the first embodiment described above, the image forming apparatus changes the light amount of the light beam emitted from the LD as the image forming condition in the image density control process. However, in the present embodiment, The light emission time (PWM value) of the light beam emitted from the LD is changed.

  FIG. 10 is a flowchart showing a procedure of image density control processing according to the present embodiment. Steps S1-6 and 8-13 are the same as those in the first embodiment described above. In the present embodiment, the image forming apparatus performs step S20 after step S6. In step S20, the image forming apparatus changes the light emission time (PWM value) of the light beam emitted from the LD. Here, for example, the PWM value is set to 32 division PWM. In addition, when the image data has four values (0 to 3), it is assumed that the PWM value is set in advance as shown in FIG. 11 corresponding to each value. On the other hand, if the determination result in step S5 is positive for cyan (C), the image forming apparatus shows the PWM value in the second column in FIG. 12 corresponding to each value of the image data. Change as follows. At this time, for the other colors (M, Y, BK), the image forming apparatus changes the PWM value corresponding to each value of the image data as shown in the third column of FIG. That is, for the other colors (M, Y, BK), the image forming apparatus has a large influence on the halftone image with respect to the image data having values of “0” to “2”. The PWM value is changed to the same value as cyan (C). Since image data with a value of “3” is often used in the solid image portion, the PWM value is not changed from a preset value.

  For yellow (Y), the density drop is not noticeable visually in the solid color solid image portion. Therefore, if the PWM value is to be changed for yellow (Y), the image forming apparatus has a value of “3” only for yellow as shown in the second column of FIG. The PWM value of the image data is greatly changed.

  As described above, in the toner near-end state, the PWM value of each color is changed, and the change amount of the PWM value is appropriately changed according to the color. Thereby, even in the toner near-end state, it is possible to suppress the change in color and the occurrence of color unevenness as much as possible, and to increase the number of images that can be formed as much as possible.

[Third embodiment]
Next, a third embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment or 2nd Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the first or second embodiment described above, when the image forming condition is changed for a certain color in the image density control process, the image forming apparatus also adjusts the change for the other colors. The image forming conditions were changed. In the present embodiment, when the image forming condition is changed only for black (BK) in the image density control process, the image forming condition is not adjusted for the other colors. Do not change. This is because black (BK) is rarely used for a halftone image of a color image. For this reason, only for black (BK), changing the light quantity of the light beam emitted from the LD does not significantly affect the image quality.

  As the image forming condition, the light amount of the light beam emitted from the LD may be changed as in the first embodiment, or the PWM value is changed as in the second embodiment. You may do it. When the PWM value is used, for example, the PWM value for black (BK) is changed with respect to all the image data having the value “1” to “3” when the image data is four values (0 to 3). To.

  When it is not desired to affect the halftone image, the PWM value is not changed for the image data having the value “1” to “2”, and the value is “3”. You may make it change only with respect to image data.

[Fourth embodiment]
Next, a fourth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 3rd Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, the image forming apparatus changes image forming conditions in stages in the image density control process. Specifically, in step S7 after step S5 described in the first embodiment, the image forming apparatus changes the light quantity of the light beam emitted from the LD every predetermined number (n). The amount of light is gradually reduced. When changing the light amount of the light beam emitted from the LD for one color, the image forming apparatus changes the light amount of the light beam emitted from the LD for the other colors as well in the first embodiment described above. It is the same as the form.

  FIG. 14 is a flowchart showing a procedure of image density control processing according to the present embodiment. Steps S1 to S13 are the same as those in the first embodiment. If the determination result in step S3 is affirmative, in step S30, the image forming apparatus determines whether n or more images have been formed. If the determination result is affirmative, in step S31, the image forming apparatus changes the light amount of the light beam emitted from the LD to a value smaller than the value changed in step S7.

  For example, it is assumed that the image forming apparatus reduces the light amount of the light beam emitted from the LD by 80% from a preset value in step S7. After that, it is assumed that the image forming apparatus forms an image on n (for example, 20) recording sheets. At this time, the determination result in step S30 is affirmative, and in step S31, the image forming apparatus reduces the light amount of the light beam emitted from the LD by 60% from a preset value. Then, after forming an image on another 20 recording sheets, when performing the process of step S31 again, the image forming apparatus reduces the light amount of the light beam emitted from the LD by 40% from a preset value. .

  According to the above configuration, the number of images that can be formed can be increased as much as possible without degrading the image quality as much as possible even in the toner near-end state.

[Fifth embodiment]
Next, a fifth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 4th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In this embodiment, when the image immediately before the image density is detected and the image to be formed by changing the amount of light after detection are the same job (the same image formation instruction), the image forming condition is set. It does not change. When changing the light amount of the light beam emitted from the LD for one color, the image forming apparatus changes the light amount of the light beam emitted from the LD for the other colors as well in the first embodiment described above. It is the same as the form.

  Specifically, in the present embodiment, the image forming apparatus changes the light amount of the light beam emitted from the LD in step S7 after step S5 described in the first embodiment. First, it is determined whether the image immediately before the image density is detected and the image to be formed by changing the amount of light after the detection are formed by the same job. For example, the printer control unit 117 can determine whether the jobs are the same job based on an image formation instruction supplied from the operation unit unit 130. If it is determined that the jobs are not the same job, the image forming apparatus changes the light amount of the light beam emitted from the LD in the same manner as in the first embodiment. On the other hand, when it is determined that the jobs are the same, the image forming apparatus does not change the light amount of the light beam emitted from the LD until the image formation according to the same image formation instruction is completed.

  According to such a configuration, for example, when the same image is repeatedly formed, the image quality can be prevented from changing suddenly. That is, according to such a configuration, the number of images that can be formed can be increased as much as possible while eliminating the difference in image quality.

[Sixth embodiment]
Next, a sixth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 5th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, the image forming apparatus forms an image misregistration correction pattern on the intermediate transfer belt 10 and detects the image misregistration correction pattern (correction pattern) to correct image misregistration. When the image misregistration correction process is executed, if a toner near end is detected for at least one color, the control state related to image formation is changed so as to suppress toner consumption. In this case, specifically, the image forming apparatus performs control so as not to execute the image misregistration correction process thereafter.

(1) Configuration FIG. 15 is a block diagram showing the image formation control function according to the present embodiment in more detail. The image formation control function according to the present embodiment includes the polygon motor control unit 110, the LD control unit 111, the synchronization detection lighting control unit 112, the pixel clock generation unit 113, and the printer described in the first embodiment. In addition to the control unit 117, a writing start position control unit 160, toner detection sensors 161 to 162, and a correction data storage unit 163 are provided. In addition to the sensor 131, a sensor 132 is also provided. Here, each of the two sensors 131 to 132 detects an image misregistration correction pattern formed on the intermediate transfer belt 10 and supplies it to the printer controller 117 as image pattern detection information. The printer control unit 117 calculates correction amounts for each color using the image pattern detection information supplied from the sensors 131 to 132, generates correction data for correcting the shifts, and stores the correction data in the correction data storage unit 163. This correction data is for correcting image position deviation and magnification deviation, that is, data for determining the timing of the XLGATE and XFGATE signals and for determining the frequency of the pixel clock PCLK. The correction data storage unit 163 stores such correction data, and in response to an instruction from the printer control unit 117, the correction data is stored in the polygon motor control unit 110, the LD control unit 111, the synchronization detection lighting control unit 112, and the start of writing. Set in the position controller 160. The toner detection sensors 161 to 162 detect the presence or absence of toner in the replenishment path for sending toner from the toner bottle to the developing unit 80, and supply the detection result to the printer control unit 117. The printer control unit 117 determines whether the toner near-end state is reached or not using the detection result supplied from the toner detection sensor 161.

  FIG. 16 is a diagram illustrating the configuration of the toner detection sensors 161 to 162. The toner detection sensors 161 to 162 are optical sensors each including a light emitting unit and a light receiving unit. The toner detection sensor 161 is installed on the toner bottle side of the replenishment path for replenishing toner from the toner bottle to the development unit 80, and the toner detection sensor 162 is installed on the development unit 80 side, and each color toner in the replenishment path is received. To detect. That is, toner in the supply path is detected at two locations. However, the toner detection sensor 161 detects a toner near end, and the toner detection sensor 162 detects a toner end.

  FIG. 17 is a diagram illustrating a configuration of the writing start position control unit 160 according to the present embodiment. The writing start position control unit 160 includes a main scanning line synchronization signal generation unit 170, a main scanning gate signal generation unit 171, and a sub scanning gate signal generation unit 172. The main scanning gate signal generation unit 171 includes a main scanning counter 173, a comparator 174, and a gate signal generation unit 175. The sub scanning gate signal generation unit 172 includes a sub scanning counter 176, a comparator 177, and a gate signal generation unit 178.

  The main scanning line synchronization signal generation unit 170 generates a signal XLSYNC for operating the main scanning counter 173 and the sub scanning counter 176.

  The main scanning counter 173 operates with the signals XLSYNC and PCLK and outputs a counter value. The comparator 174 compares the counter value with the set value 1 (correction data) from the printer control unit 117 and outputs the result. From the comparison result from the comparator 174, the gate signal generation unit 175 generates a signal XLGATE that determines the image signal capture timing (image writing timing in the main scanning direction).

  The sub-scanning counter 176 operates in response to the control signal from the printer control unit 117 and the signals XLSYNC and PCLK, and outputs a counter value. The comparator 177 compares the counter value with the set value 2 (correction data) from the printer control unit 117 and outputs the comparison result. From the comparison result from the comparator 177, the gate signal generation unit 178 generates XFGATE that determines the image signal capture timing (image writing timing in the sub-scanning direction).

  The writing start position control unit 160 corrects the writing position in units of one cycle of the clock PCLK in the main scanning direction, that is, in units of one dot, and in the sub scanning direction in units of one cycle of XLSYNC, that is, in units of one line. it can. The correction data is stored in the correction data storage unit 163 in both the main scanning direction and the sub-scanning direction.

  FIG. 18 is a timing chart of signals input / output by the writing start position control unit 160 in the main scanning direction. The main scanning counter 173 is reset by XLSYNC and counted up by PCLK. When the counter value reaches the set value 1 (in this case, “X”) set by the printer control unit 117, the comparison result is output from the comparator 174. The gate signal generator 175 outputs XLGATE to “L” (valid). XLGATE is a signal that becomes ‘L’ by the image width in the main scanning direction.

  FIG. 19 is a diagram illustrating a timing chart of signals input / output in the writing start position control unit 160 in the sub-scanning direction. The control signal (image writing start trigger signal) sub-scanning counter 176 from the printer control unit 117 is reset and counted up by XLSYNC, and the counter value is the set value 2 set by the printer control unit 117 (in this case, 'Y The result of comparison is output from the comparator 177 when X becomes “L” (valid) by the gate signal generator. XFGATE is a signal that becomes 'L' by the image length in the sub-scanning direction.

  FIG. 20 is a diagram illustrating the configuration of the previous stage of the image formation control function shown in FIG. A line memory 180 is provided in the preceding stage of this image formation control function. The line memory 180 stores image data captured at the timing of XFGATE from the printer control unit 117, a storage device functioning as a frame memory provided in the control unit, a scanner (not shown), or the like. An image signal corresponding to the image data is output from the line memory 180 in synchronization with PCLK only during a period in which XLGATE is ‘L’. The output image signal is supplied to the LD control unit 111, and the LD is turned on at that timing.

  FIG. 21 is a diagram showing an image misregistration correction pattern formed on the intermediate transfer belt 10. The image misregistration correction pattern shown in the figure is for correcting image misalignment in the main scanning direction and the sub-scanning direction. The image forming device 20 forms images of horizontal lines and diagonal lines on the intermediate transfer belt 10 as image misregistration correction patterns at a preset timing for each color. Further, the image forming apparatus 20 forms a plurality of image misregistration correction patterns in the main scanning direction so that the sensors 131 to 132 can detect each of them. As the intermediate transfer belt 10 moves in the direction of the arrow, the horizontal lines and the diagonal lines of the respective colors are detected by the sensors 131 to 132 and supplied to the printer control unit 117 as image pattern detection information. The printer control unit 117 calculates the shift amount (time) of each color with respect to BK using this image pattern detection information. Then, the printer control unit 117 controls the image position deviation correction process (correction process) using the calculated deviation amount. For oblique lines, the detection timing is changed by shifting the image position or image magnification in the main scanning direction. As for the horizontal line, the detection timing is changed by shifting the image position in the sub-scanning direction. Details of the image misalignment correction processing will be described in the operation column.

  FIG. 22 is a diagram for explaining the calculation of the shift amount in the main scanning direction. For the main scanning direction, the time from the pattern BK1 to the pattern BK2 is used as a reference, and the time from the pattern C1 to the pattern C2 is compared to obtain the deviation TBKC12. Further, the time from the pattern BK3 to the pattern BK4 is used as the reference. Compared with the time from the pattern C3 to the pattern C4, the deviation TBKC34 is obtained. 'TBKC34-TBKC12' is a magnification error of the cyan image with respect to the black image. Therefore, the frequency of the pixel clock is varied by an amount corresponding to this amount. Further, the subtraction of the time change (correction) due to the magnification error correction at the position of the sensor 131 from the TBKC 12 obtained above is the main scanning deviation with respect to the black image of the cyan image, and the writing corresponding to the deviation amount is written. The timing of the XLGATE signal that determines the start timing is changed. The same applies to magenta and yellow.

  FIG. 23 is a diagram for explaining the calculation of the shift amount in the sub-scanning direction. In the sub-scanning direction, assuming that the ideal time is Tc, the time from the pattern BK1 to the pattern C1 is TBKC1, and the time from the pattern BK3 to the pattern C3 is TBKC3, '((TBKC3 + TBKC1) / 2) -Tc' This is a sub-scanning deviation of the cyan image with respect to the black image. The timing of the XFGATE signal that determines the writing start timing is changed by an amount corresponding to this amount. The same applies to magenta and yellow.

(2) Operation <Image displacement correction processing>
Next, the procedure of image misalignment correction processing executed by the image forming apparatus according to the present embodiment will be described with reference to FIG. The execution of the image misalignment correction process is controlled by the printer control unit 117. The implementation timing is, for example, every time an image is formed on a specified number of recording sheets, before the start of image formation, or when the power is turned on. When the image forming apparatus determines that the printer control unit 117 performs the image misregistration correction process, first, the correction data stored in the correction data storage unit 163 is used as the polygon motor control unit 110, the LD control unit 111, The synchronization detection lighting control unit 112 and the writing start position control unit 160 are set (step S30). This correction data is set values of the main scanning image position, sub-scanning image position, and main scanning image magnification determined by the previous image position deviation correction processing. Specifically, the pixel clock frequency setting value for determining the image magnification in the main scanning direction, the XLGATE signal setting value for determining the image position in the main scanning direction, and the XFGATE signal for determining the image position in the sub scanning direction. It is a set value. If the correction has not been performed, the correction data has a preset initial value. After the setting, the image forming apparatus forms the image misregistration correction pattern shown in FIG. 10 on the intermediate transfer belt 10 (step S31), detects the image misregistration correction pattern by the sensors 131 to 132, and uses this as an image. The pattern detection information is supplied to the printer control unit 117 (step S32).

  The printer control unit 117 calculates the shift amount of each color with respect to black (step S33), and determines whether to perform correction based on the shift amount (step S34). Specifically, the printer control unit 117 determines whether or not to perform correction by determining whether or not the deviation amount is ½ or more of the correction resolution. Then, the printer control unit 117 determines that the correction is performed when the deviation amount is ½ or more of the correction resolution. In this case (step S34: YES), the printer control unit 117 calculates correction data (step S35) and stores it in the correction data storage unit 163 (step S36). Then, the printer control unit 117 sets the correction data stored in the correction data storage unit 163 in the polygon motor control unit 110, the LD control unit 111, the synchronization detection lighting control unit 112, and the writing start position control unit 160. (Step S37). The correction data here includes a set value of a pixel clock frequency that determines an image magnification in the main scanning direction, a set value of an XLGATE signal that determines an image position in the main scanning direction, and an XFGATE that determines an image position in the sub scanning direction. This is the signal setting value. If it is determined in step S34 that correction is not performed, the printer control unit 117 does not update correction data. Thereafter, when the image forming apparatus performs image formation, the image forming apparatus performs image formation using the correction data stored in the correction data storage unit 163.

  Note that the image forming apparatus may form a plurality of image misregistration correction patterns shown in FIG. 21 in step S31. In this case, the image forming apparatus averages the detected deviation amounts in step S33, and determines in step S34 whether correction is performed using the deviation amounts. According to such a configuration, the correction accuracy is improved.

<Correction control processing>
Next, the procedure of correction control processing performed by the image forming apparatus according to the present embodiment will be described with reference to FIG. During the operation of the image forming apparatus, the toner detection sensors 161 to 162 constantly monitor the toner of each color in the supply path. In the image forming apparatus, the toner detection sensor 161 detects the toner of each color (step S50), and based on the detection result, the printer control unit 117 determines whether there is toner (step S51). Whether or not there is toner may be determined, for example, by determining whether or not the detected toner amount is equal to or greater than a preset value (referred to as a third predetermined value). The third predetermined value may be stored in advance in a storage device or an external storage device, or may be set variably. Note that when it is determined whether or not toner is simply present, the third predetermined value is set in advance as “0”, for example. When it is determined that there is no toner of a certain color, that is, a toner near end is detected for the color. In this case (step S51: NO), the image forming apparatus next detects toner by the toner detection sensor 162 (step S52), and determines whether or not there is toner by the printer control unit 117 based on the detection result. (Step S53). Again, whether there is toner may be determined, for example, by determining whether the detected toner amount is greater than or equal to a predetermined value (fourth predetermined value). The fourth predetermined value may be stored in advance in a storage device or an external storage device, or may be set variably. When it is determined whether or not there is simply toner, the fourth predetermined value is set in advance as “0”, for example. When the printer control unit 117 determines that there is toner, the image forming apparatus determines that there is little toner remaining, and displays information indicating the toner near end on the operation panel of the operation unit unit 130 (step S54). Then, the image forming apparatus prohibits execution of the above-described image misregistration correction process (step S55). Regarding the prohibition of the execution of the image misregistration correction process, when the toner near end is detected for one color, the image forming apparatus prohibits the subsequent image misregistration correction process regardless of the detection result for the other color. .

  On the other hand, if it is determined in step S53 that there is no toner of a certain color, that is, a toner end is detected for that color. In this case (step S53: NO), the image forming apparatus determines that there is no toner, and displays information indicating the toner end on the operation panel of the operation unit 130 (step S56). Then, the image forming apparatus stops its own mechanical part (step S57). When it is determined in step S51 that there is toner, the image forming apparatus ends the correction control process.

  According to the above configuration, the number of images that can be formed can be increased as much as possible even in the toner near-end state.

  In the above-described example, the toner near-end and the toner end are confirmed by installing toner detection sensors 161 to 162 at two locations in the toner supply path and detecting the presence or absence of toner at these two locations. did. However, only one toner detection sensor 161 may be installed so as to detect that the remaining amount of toner in the toner bottle is low.

  Further, instead of the toner detection sensor 162, a sensor for detecting the toner density in the developing unit 80 may be installed, and the sensor may detect the toner end.

  Further, as described in the first to fourth embodiments, the sensor 131 or the sensor 132 may detect the image density, and the image forming apparatus determines from the detection result. The toner near end or the toner end may be determined.

[Seventh embodiment]
Next, a seventh embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 6th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, when the image forming apparatus detects the toner near end for at least one color when performing the image misregistration correction process described in the sixth embodiment, Control is performed to change the frequency of executing the image misalignment correction processing.

  Since the hardware configuration of the image forming apparatus is the same as that of the above-described sixth embodiment, description thereof is omitted. The procedure of correction control processing performed by the image forming apparatus is different from that of the sixth embodiment. FIG. 26 is a flowchart illustrating a procedure of correction control processing executed by the image forming apparatus according to the present embodiment. Steps S50 to S54 and S56 to S57 are the same as those in the sixth embodiment. In the present embodiment, after step S54, in step S55 ′, the image forming apparatus changes the frequency of executing the image misregistration correction process. For example, assuming that the image misalignment correction processing is set in advance so as to be performed every time an image is formed on 100 sheets of recording paper, for example, the image forming apparatus is configured to perform it every time an image is formed on 200 sheets of recording paper. Change. It is assumed that information (referred to as processing information) such as the frequency and timing of executing the image misalignment correction processing is stored in advance in the correction data storage unit 163, for example. The image forming apparatus counts the number of sheets each time an image is formed on a recording sheet, stores the value in, for example, the correction data storage unit 163, and stores the value of the number of sheets and processing information stored in the correction data storage unit 163. The frequency of the image misregistration correction process is changed with reference.

  According to the above configuration, it is possible to suppress image deterioration as much as possible while increasing the number of images that can be formed as much as possible.

[Eighth embodiment]
Next, an eighth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 7th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, when the image forming apparatus detects the toner near end for at least one color when performing the image misregistration correction process described in the sixth embodiment, Control is performed to change the image misalignment correction pattern. Then, the image forming apparatus executes an image misalignment correction process using the changed image misalignment correction pattern.

  FIG. 27 is a diagram illustrating an image misregistration correction pattern to be changed. The image misregistration correction pattern shown in the figure is for correcting image misalignment only in the sub-scanning direction. The image misregistration correction pattern does not have an oblique pattern for detecting misalignment or magnification misalignment in the main scanning direction, as compared with the image misregistration correction pattern shown in FIG. The point that the image forming apparatus detects a horizontal line and calculates the amount of deviation in the sub-scanning direction is the same as in the sixth embodiment.

  The reason for using such an image misregistration correction pattern is as follows. In order to detect a positional deviation or a magnification deviation in the main scanning direction, both a horizontal line pattern and an oblique line pattern are required. On the other hand, the sub-scanning direction can be detected only by the horizontal line pattern. Therefore, as shown in FIG. 27, by using the image misregistration correction pattern of only the horizontal line pattern, the image misregistration correction cannot be performed in the main scanning direction, but the image misregistration correction can be performed in the sub scanning direction. This is because toner consumption can be suppressed.

  Since the hardware configuration of the image forming apparatus is the same as that of the above-described sixth embodiment, description thereof is omitted. Here, the procedure of correction control processing performed by the image forming apparatus is different from that of the above-described sixth embodiment. FIG. 28 is a flowchart illustrating a correction control process performed by the image forming apparatus according to the present embodiment. Steps S50 to S54 and S56 to S57 are the same as those in the sixth embodiment. In the present embodiment, after step S54, in step S55 ″, the image forming apparatus changes the image misregistration correction pattern from that shown in FIG. 21 to that shown in FIG.

  According to the above configuration, toner consumption can be suppressed, and image deterioration can be suppressed as much as possible while increasing the number of images that can be formed.

[Ninth embodiment]
Next, a ninth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 8th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, when the image forming apparatus executes the image misregistration correction process described in the sixth embodiment, an image misregistration correction pattern is placed on the intermediate transfer belt 10 in the sub-scanning direction. Assume that a plurality of sets are formed, and this image misalignment correction pattern is detected to execute image misalignment correction processing. In this case, when the toner forming end is detected for at least one color, the image forming apparatus then controls to change the number of sets of image misregistration correction patterns formed in the sub-scanning direction. For example, the number of sets is changed to one, and the image forming apparatus executes image position deviation correction processing using the changed image position deviation correction pattern.

  Since the hardware configuration of the image forming apparatus is the same as that of the above-described sixth embodiment, description thereof is omitted. The correction control processing procedure performed by the image forming apparatus is also the same as that in the eighth embodiment, and a description thereof will be omitted.

  According to the above configuration, toner consumption can be suppressed, and image deterioration can be suppressed as much as possible while increasing the number of images that can be formed.

[Tenth embodiment]
Next, a tenth embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 9th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  Also in the present embodiment, as in the above-described eighth embodiment, when the image near displacement end is detected for at least one color when the image displacement displacement correction processing is performed, the image displacement displacement correction is performed thereafter. Control to change the pattern. In the present embodiment, the image misregistration correction pattern to be changed is different from that of the above-described eighth embodiment.

  FIG. 29 is a diagram showing an image misregistration correction pattern that is changed in the present embodiment. The image misregistration correction pattern shown in the figure is for correcting image misalignment only in the sub-scanning direction, and is formed only at one location in the main scanning direction. In the image position deviation correction pattern, an image position deviation correction pattern is formed only at a position that can be detected by the sensor 131, as compared with the image position deviation correction pattern shown in FIGS. In this case, the shift amount is calculated using only the image pattern detection information detected by the sensor 131. Note that the image misalignment correction pattern may be formed only at a position detectable by the sensor 132 instead of the sensor 131.

  When the image displacement correction pattern shown in the figure is used, the image magnification in the main scanning direction cannot be corrected, but the image displacement in the sub-scanning direction can be corrected, and the image position can be corrected.

  Since the hardware configuration of the image forming apparatus is the same as that of the above-described sixth embodiment, description thereof is omitted. The correction control processing procedure performed by the image forming apparatus is also the same as that in the eighth embodiment, and a description thereof will be omitted.

  According to the above configuration, toner consumption can be further suppressed, and image deterioration can be suppressed as much as possible while increasing the number of images that can be formed.

[Eleventh embodiment]
Next, an eleventh embodiment of the image forming apparatus will be described. In addition, about the part which is common in the above-mentioned 1st Embodiment thru | or 10th Embodiment, it demonstrates using the same code | symbol or abbreviate | omits description.

  In the present embodiment, the image forming apparatus, when executing the image misregistration correction process described in the sixth embodiment, immediately after detecting the toner near end for at least one color. After that, the misregistration correction process is executed, and thereafter, the image misregistration correction process is controlled not to be executed as in the sixth embodiment. If the toner near end is detected during continuous image formation, the image forming apparatus interrupts the image formation, executes the image misregistration correction process, and then restarts the image formation.

  FIG. 30 is a flowchart illustrating a correction control process performed by the image forming apparatus according to the present embodiment. Steps S50 to S57 are the same as those in the sixth embodiment. In the present embodiment, after step S54, in step S60, the image forming apparatus determines whether or not an image misregistration correction process has been executed. If the determination result is negative, FIG. 24 is used. The image displacement correction process described above is executed (step S61). Next, the process proceeds to step S55. If the determination result of step S60 is negative, the process proceeds to step S55. In step S55, the image forming apparatus prohibits execution of the image misregistration correction process in the same manner as in the sixth embodiment described above.

  According to the above configuration, it is possible to suppress image deterioration as much as possible while increasing the number of images that can be formed as much as possible.

  Note that this embodiment can also be applied to the seventh to tenth embodiments described above. In this case, when the toner near end is detected, the image forming apparatus executes a normal image misregistration correction process, and thereafter, the frequency of executing the image misregistration correction process is changed, or the image misregistration correction is performed. The pattern for use will be changed.

[Modification]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined. Further, various modifications as exemplified below are possible.

  In each of the above-described embodiments, various programs executed by the image forming apparatus may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, the various programs are recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, and a DVD (Digital Versatile Disk) in an installable or executable file. And may be configured to be provided.

  In the above-described embodiment, the light amount and the light emission time of the light beam emitted from the LD are used as the image forming conditions to be changed in the image density control process. However, the present invention is not limited to this. At least one of the charging potential in the body drum 40 and the amount of toner replenished from the toner bottle to the photosensitive drum 40 may be used. Also, two or more of these may be used in combination.

  In the above-described embodiment, the image forming apparatus includes the printer 100 and the image reading unit 300. However, the present invention is not limited to this, and the image forming apparatus may further include a facsimile function, may include only a facsimile function, or may include only a printer function.

  In each of the embodiments described above, a personal computer may be connected to the image forming apparatus, and information to be displayed on the operation panel may be transmitted to the personal computer instead of the operation panel.

  Further, the image forming apparatus may accept an input of an image forming instruction via a personal computer.

  Further, when the image forming apparatus has a facsimile function, when an input instruction for facsimile is received from an external device, the rotational transfer of the intermediate transfer belt 10 is started and the image forming of each unit of the image forming device 20 is started. Preparation may be started.

  In the above-described embodiment, whether or not the toner near end has been detected is formed by forming an image pattern on the photosensitive drum 40 and detecting the image density of the image pattern. This may be performed by directly detecting the toner amount in the toner.

1 is a diagram illustrating an outline of a mechanism portion of an image forming apparatus according to a first embodiment. 2 is a diagram showing a detailed configuration of an image forming device 20 and a light beam scanning device 21 according to the embodiment. FIG. It is the figure which looked at the light beam scanning apparatus 21 shown in FIG. 2 from the top. It is a figure which shows what formed in detail the image formation control function concerning the embodiment. It is a figure which shows the VCO clock generation part 115 concerning the embodiment. It is a figure which shows the image pattern concerning the embodiment. It is a figure which shows the structure of the LD control part 111 concerning the embodiment. It is a figure which shows the structure of LD concerning the embodiment. 4 is a flowchart illustrating a procedure of image density control processing performed by the image forming apparatus according to the embodiment. 6 is a flowchart illustrating a procedure of image density control processing performed by an image forming apparatus according to a second embodiment. When image data is 4 values (0-3), it is a figure which shows the PWM value set corresponding to each value. It is a figure which shows the PWM value changed corresponding to each value, when image data is 4 values (0-3). It is a figure which shows the PWM value changed corresponding to each value, when image data is 4 values (0-3). 14 is a flowchart illustrating a procedure of image density control processing performed by an image forming apparatus according to a fourth embodiment. It is a figure which shows what formed in detail the image formation control function concerning 6th Embodiment. It is a figure which shows the structure of the toner detection sensors 161-162 concerning the embodiment. It is a figure which shows the structure of the writing start position control part 160 concerning the embodiment. It is a figure which shows the timing chart of the signal input / output in the writing start position control part 160 with respect to the main scanning direction. It is a figure which shows the timing chart of the signal input / output in the writing start position control part 160 with respect to a subscanning direction. FIG. 16 is a diagram illustrating a configuration of a previous stage of the image formation control function shown in FIG. 3 is a diagram showing an image misregistration correction pattern formed on the intermediate transfer belt 10 according to the same embodiment. FIG. It is a figure for demonstrating calculation of the deviation | shift amount of a main scanning direction. It is a figure for demonstrating calculation of the deviation | shift amount of a subscanning direction. 6 is a flowchart illustrating a procedure of image misregistration correction processing executed by the image forming apparatus according to the embodiment. 6 is a flowchart showing a procedure of correction control processing performed by the image forming apparatus according to the embodiment. 15 is a flowchart illustrating a procedure of correction control processing performed by an image forming apparatus according to a seventh embodiment. It is a figure which shows the image misalignment correction pattern changed in 8th Embodiment. 6 is a flowchart showing a procedure of correction control processing performed by the image forming apparatus according to the embodiment. It is a figure which shows the image misalignment correction pattern changed in 10th Embodiment. It is a flowchart which shows the procedure of the correction | amendment control processing which the image forming apparatus concerning 11th Embodiment performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 14 Support roller 15 Support roller 16 Support roller 17 Intermediate transfer body cleaning unit 18 Charging unit 20 Image forming device 21 Light beam scanning device 22 Secondary transfer unit 23 Roller 24 Secondary transfer belt 25 Fixing unit 26 Fixing belt 27 Pressure roller 28 Sheet reversing unit 30 Document feeding table 32 Contact glass 33 First carriage 34 Second carriage 35 Imaging lens 36 CCD
40 Photosensitive drum 42 Paper feed roller 43 Paper feed unit 44 Paper feed tray 45 Separating roller 46 Transport roller unit 47 Transport roller 48 Transport roller unit 49 Registration roller 50 Paper feed roller 51 Manual feed tray 52 Paper feed roller 53 Manual paper feed path 55 Switching claw 56 Discharge roller 57 Discharge tray 62 Transfer device 70 Polygon mirror 71 Polygon motor 72 fθ lens 73 First mirror 74 Second mirror 75 Third mirror 77 LD unit 78 CYL
79 Reflecting mirror 80 Developing unit 82 Cleaning unit 83 Static eliminator 90a Synchronous mirror BKC
90b Synchronous mirror MY
91a Synchronous lens BKC
91b Synchronous lens MY
92a Synchronous sensor BKC
92b Sync sensor MY
100 Printer 109 Synchronization Detection Signal Separation Unit 110 Polygon Motor Control Unit 111 LD Control Unit 112 Synchronization Detection Lighting Control Unit 113 Pixel Clock Generation Unit 114 Reference Clock Generation Unit 115 VCO Clock Generation Unit 116 Phase Synchronization Clock Generation Unit 117 Printer Control Unit 118 Charge potential control unit 119 Development bias control unit 120 Image data control unit 121 Toner supply control unit 130 Operation unit units 131 and 132 Sensor 140 Phase comparator 143 1 / N frequency divider 150 PWM signal generation unit 151 LD drive unit 160 Start position control units 161 and 162 Toner detection sensor 163 Correction data storage unit 170 Main scanning line synchronization signal generation unit 171 Main scanning gate signal generation unit 172 Sub scanning gate signal generation unit 173 Main scanning counter 174 Comparator 175 Gate signal Generating unit 176 sub-scanning counter 177 the comparator 178 gate signal generator 180 a line memory 200 feeder table 300 image reading unit

Claims (18)

Latent image forming means for forming a latent image by irradiating a rotating or moving image carrier with a light beam according to image data;
Developing means for supplying a plurality of color toners to visualize the latent image;
Transfer means for transferring the visible image visualized by the developing means onto a recording paper;
Toner replenishing means for replenishing toner to the developing means for consumption of toner due to visualization;
A remaining amount detecting means for detecting whether or not the remaining amount of the toner is less than a predetermined value for each of the plurality of colors;
And a changing unit that changes a control state related to image formation so as to suppress toner consumption when the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color. An image forming apparatus. The changing means is a latent image formed on the image carrier for all colors when the remaining amount detecting means detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 1, wherein the image forming condition is changed so as to reduce an image density when the image is visualized. The changing means reveals a latent image formed on the image carrier only for black when the remaining amount detecting means detects that the remaining amount of toner is less than a predetermined value only for black. The image forming apparatus according to claim 2, wherein the image forming condition is changed so as to reduce an image density at the time of imaging. An input receiving means for receiving an input of an image formation instruction for instructing image formation;
The changing unit is formed by the same image forming instruction received by the input receiving unit when the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color. 4. The image forming apparatus according to claim 2, wherein the change of the image forming condition is controlled so that the plurality of latent image images have the same image forming condition. 5. A density detecting means for detecting an image density of the latent image made visible on the image carrier by the developing means;
5. The remaining amount detecting means for detecting whether or not the remaining amount of toner for each color is less than a predetermined value by using the image density detected by the density detecting means. The image forming apparatus according to claim 1. 6. The density detecting unit detects an image density of the latent image visualized on the image carrier every time a predetermined number of transfers onto the recording paper are performed. The image forming apparatus described. When the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color, the changing unit performs the image carrier every time a predetermined number of transfers are performed on the recording paper. The image forming apparatus according to claim 6, wherein the image forming condition is changed step by step so as to gradually reduce the image density when the latent image formed on the body is visualized. The changing means is a latent image formed on the image carrier for all colors when the remaining amount detecting means detects that the remaining amount of toner is less than a predetermined value for at least one color. 8. The image formation according to claim 2, wherein the image forming condition is changed by a change amount corresponding to each color so as to reduce an image density when the image is visualized. apparatus. When the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color, the changing unit includes the light amount and irradiation time of the light beam, and the development as the image forming conditions. The apparatus changes at least one of a developing bias potential and a charging potential when the latent image is visualized and a toner replenishment amount from the toner replenishing means to the developing means. Item 9. The image forming apparatus according to any one of Items 2 to 8. Pattern forming means for forming a correction pattern for correcting image shift in each of the plurality of colors in the transfer means in at least one place in the main scanning direction;
At least one detecting means for detecting the correction pattern formed by the pattern forming means;
Correction means for executing correction processing for correcting image shift based on the result detected by the detection means;
The changing unit controls the correction unit to suppress toner consumption when the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 1. The changing unit controls the correction unit not to execute the correction process when the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 10. When the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color, the changing unit changes the frequency of the correction processing executed by the correcting unit to all colors. The image forming apparatus according to claim 10, wherein the image forming apparatus is controlled so as to be less than a frequency of the correction process executed when the remaining amount of toner is equal to or greater than a predetermined value. Pattern forming means for forming a correction pattern for correcting image shift in each of the plurality of colors in the transfer means in at least one place in the main scanning direction;
At least one detecting means for detecting the correction pattern formed by the pattern forming means;
Correction means for executing correction processing for correcting image shift based on the result detected by the detection means;
The changing unit controls the pattern forming unit to change the correction pattern when the remaining amount detecting unit detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 1, wherein: The pattern forming unit forms a correction pattern for correcting an image shift in the main scanning direction and the sub-scanning direction in each of the plurality of colors on the transfer unit in at least one position in the main scanning direction.
The changing means generates a correction pattern for correcting image shift only in the sub-scanning direction when the remaining amount detecting means detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 13, wherein the pattern forming unit is controlled to form. A plurality of the detection means are provided in the main scanning direction,
The pattern forming unit forms the correction pattern on the transfer unit at a plurality of positions in the main scanning direction so that each of the plurality of detection units can detect the correction pattern,
When the remaining amount detecting unit detects that the remaining amount of toner for at least one color is less than a predetermined value, the number of portions where the correction pattern is formed in the main scanning direction is all The pattern forming unit is controlled to be smaller than the number of portions formed in the sub-scanning direction when the remaining amount detecting unit detects that the remaining amount of toner is not less than a predetermined value for the color of The image forming apparatus according to claim 13 or 14. The pattern forming unit forms the correction pattern on the transfer unit at a plurality of locations in the sub-scanning direction for each of a plurality of colors.
When the remaining amount detecting unit detects that the remaining amount of toner for the at least one color is less than a predetermined value, the number of locations where the image misregistration correction pattern is formed in the sub-scanning direction is determined. The pattern forming unit is controlled to be smaller than the number of portions formed in the sub-scanning direction when the remaining amount detecting unit detects that the remaining amount of toner is not less than a predetermined value for all colors. The image forming apparatus according to claim 15. The change unit controls the correction unit to execute the correction process immediately after the remaining amount detection unit detects that the remaining amount of toner is less than a predetermined value for at least one color. The image forming apparatus according to claim 10, wherein the image forming apparatus is an image forming apparatus. A latent image forming unit that forms a latent image by irradiating a rotating or moving image carrier with a light beam according to image data, and supplying a plurality of colors of toner to visualize the latent image. Developing means for transferring, a transfer means for transferring the developed image visualized by the developing means onto a recording paper, a toner replenishing means for replenishing the developing means with respect to toner consumption due to the visualization, An image forming method realized in an image forming apparatus including a remaining amount detecting unit and a changing unit,
A remaining amount detecting step for detecting whether the remaining amount of the toner is less than a predetermined value for each of the plurality of colors;
When the change unit detects that the remaining amount of toner is less than a predetermined value for at least one color, the change unit changes a control state related to image formation so as to suppress toner consumption. An image forming method comprising: a changing step.

Images