JP2005338111A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of forming high quality images in which displacement is restrained by easily detecting an amount of variation in an intermediate transfer belt from outside and by adjusting the timing of writing. <P>SOLUTION: A variation amount detecting part 22 is disposed near part of the edge of the intermediate transfer belt 18 (belt edge), receives light emitted from a light emitting element 27 with a light receiving element 28, and outputs a variation amount measurement signal vm (=kI). A reference value setting part 51 sets the variation amount measurement signal vm of a variation amount dx=0 as a reference variation amount measurement signal v0. A variation voltage differential amplifying unit 52 outputs a variation voltage vd=B×(v0-vm), and a variation voltage addition part 53 outputs a shift signal sh=A×v0+vd. A scanning light detection part 38 outputs a detection signal s1. A delay part 54 outputs a delay signal s2. A differential part 55 generates a differential signal d1. A first comparison part 57 outputs a periodic signal dg. An LPF 581 outputs an inclination signal fd. A second comparison part 582 outputs a synchronous signal ds that rises at a point in time that the inclination signal fd has the value of a shift signal sh. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus for transferring an image on an intermediate transfer belt in an overlapping manner.

  In an image forming apparatus that temporarily transfers a toner image formed on an image carrier to an intermediate transfer belt, superimposes a plurality of toner color toner images at the same position, and collectively transfers a color toner image onto a sheet, When the transfer belt is displaced and the toner images are superimposed at different positions, the image formed on the sheet is displaced and the image quality is deteriorated. The deviation of the intermediate transfer belt is partly caused by the fluctuation (also referred to as a shift) of the intermediate transfer belt in the direction orthogonal to the running direction.

  In Patent Document 1, a detection member is provided on the entire circumference of one end of the intermediate transfer belt, and an optical detection unit is provided to face a part of the rotation locus of the detection member, so that fluctuations in the width direction of the intermediate transfer belt are achieved. There has been proposed an image forming apparatus having a control unit that detects an amount via a member to be detected and controls to change an image writing start position with respect to the image carrier in accordance with the variation amount detection information.

In Patent Document 1, it is necessary to provide a member to be detected on the entire circumference of one end of the intermediate transfer belt, so that the process of processing the intermediate transfer belt is complicated, and the thickness of the intermediate transfer belt is increased by the amount of the member to be detected. There is also a possibility that the apparatus becomes large and causes poor running. In addition, since a method is described in which the amount of fluctuation is detected by irradiating light toward the cross section of the intermediate transfer belt, the detection accuracy decreases when the intermediate transfer belt is wavy.
JP 2002-268499 A

  An image forming apparatus capable of forming a high-quality image with reduced deviation by simply detecting the amount of fluctuation from the outside and adjusting the write timing without providing an unnecessary member for detecting the amount of fluctuation on the intermediate transfer belt side The purpose is to provide.

  The first image forming apparatus of the present invention is synchronously controlled based on the timing at which the belt mark provided on the intermediate transfer belt is detected by the belt mark detecting means, and forms a toner image on the image carrier for each toner color, An image forming apparatus for transferring toner images of a plurality of colors onto a sheet in a lump after superimposing toner images of a plurality of colors on the same position of an intermediate transfer belt, comprising: Synchronization signal generating means and a light source are provided. The fluctuation amount detection means detects the edge of the running intermediate transfer belt and outputs a fluctuation amount measurement signal having a magnitude uniquely corresponding to the fluctuation amount in the direction orthogonal to the running direction of the intermediate transfer belt. The shift signal generating means outputs a shift signal having a magnitude uniquely corresponding to the magnitude of the fluctuation amount measurement signal of the fluctuation amount measurement signal. The scanning light receiving means receives scanning light from a light source that exposes and scans the image carrier at a constant cycle, and outputs a detection signal. The synchronization signal generating means includes a delay means, a difference means, a first comparison means, and a delay time control means, the delay means outputs a delay signal obtained by delaying the detection signal, and the difference means includes the detection signal, the delay signal, The first comparison means outputs a binary signal that rises at a time position where the sign of the difference signal is switched, and the delay time control means delays the binary signal uniquely corresponding to the shift signal. A synchronization signal that rises at a time position delayed by an amount of time is generated. The light source exposes in the main scanning direction from a position determined by the timing of the synchronization signal.

  The second image forming apparatus of the present invention is synchronously controlled based on the timing at which the belt mark provided on the intermediate transfer belt is detected by the belt mark detecting means, and forms a toner image on the image carrier for each toner color. An image forming apparatus for transferring toner images of a plurality of colors onto a sheet in a lump after superimposing toner images of a plurality of colors on the same position of an intermediate transfer belt, comprising: a variation amount detecting means, a shift signal generating means, a scanning light receiving means, Synchronization signal generating means and a light source are provided. The intermediate transfer belt has a plurality of belt marks arranged at equal intervals in the running direction. The fluctuation amount detecting means is a fluctuation in a direction orthogonal to the traveling direction of the other one belt mark every time the belt mark detecting means detects the belt mark at a position separated from the belt mark detecting means by the same distance as the belt mark interval. A variation measurement signal having a magnitude uniquely corresponding to the quantity is output. The shift signal generating means outputs a shift signal having a magnitude uniquely corresponding to the magnitude of the fluctuation amount measurement signal of the fluctuation amount measurement signal. The scanning light receiving means receives scanning light from a light source that exposes and scans the image carrier at a constant cycle, and outputs a detection signal. The synchronization signal generating means includes a delay means, a difference means, a first comparison means, and a delay time control means, the delay means outputs a delay signal obtained by delaying the detection signal, and the difference means includes the detection signal, the delay signal, The first comparison means outputs a binary signal that rises at a time position where the sign of the difference signal is switched, and the delay time control means delays the binary signal uniquely corresponding to the shift signal. A synchronization signal that rises at a time position delayed by an amount of time is generated. The light source exposes in the main scanning direction from a position determined by the timing of the synchronization signal.

  Further, in any of the above image forming apparatuses, each image carrier may transfer a toner image developed in a different color to the intermediate transfer belt each time the intermediate transfer belt rotates. Each of the image forming apparatuses includes two image carriers, and each image carrier includes a variation amount detector, a shift signal generator, a scanning light receiver, a synchronization signal generator, and a light source. The body may be transferred to the intermediate transfer belt with toner images developed in different colors in the first and second rotations of the intermediate transfer belt. Each of the image forming apparatuses includes a plurality of image carriers, a variation amount detecting unit, a shift signal generating unit, a scanning light receiving unit, a synchronization signal generating unit, and a light source for each image carrier. The body may transfer toner images of different colors onto the intermediate transfer belt.

  In any of the above image forming apparatuses, the capture holding unit is provided, and the fluctuation amount detecting unit has a distance from a transfer position at which the toner image is transferred from the image carrier to the intermediate transfer belt, upstream from the image carrier. The exposure position of the image carrier is arranged at the same distance as the rotational movement to the transfer position, and the capture holding means captures and holds the fluctuation amount measurement signal from the fluctuation amount detection means for each non-image forming period. And output to the synchronization signal generating means. Further, the capture holding unit captures the variation measurement signal from the variation detection unit a plurality of times within the same non-image forming period, adds and averages the captured variation measurement signal, and synchronizes the variation signal as a variation measurement signal. It is good to output to a production | generation means.

  According to the first aspect of the present invention, when the intermediate transfer belt changes in a method orthogonal to the running direction, the toner image of each color is accurately superimposed in order to change the timing of exposing the image carrier following the amount of change. Can be matched. According to the second aspect of the present invention, the belt mark detection and the fluctuation amount detection are configured by the same belt mark, thereby detecting the fluctuation amount at low cost and detecting the timing at which the belt mark passes through the fluctuation amount detection means. The amount of change can be detected at low cost as unnecessary. According to the third aspect of the present invention, in the image forming apparatus that transfers a plurality of toner color toner images with one image carrier, the toner images of the respective colors can be accurately superimposed. According to the fourth aspect of the present invention, since the timing for exposing each image carrier is changed following the amount of variation for each image carrier, the toner images of each color are accurately superimposed even if the image carrier is separated. Can do. According to the fifth aspect of the present invention, the toner images of the respective colors can be accurately superimposed even when the intermediate transfer belt rotates a plurality of times. According to the invention of claim 6, the position where the fluctuation amount of the intermediate transfer belt is detected can coincide with the position of the image carrier that forms the toner image transferred to the position where the fluctuation amount is detected. By detecting the fluctuation amount for each image forming period, the fluctuation amount can be detected in more detail. According to the invention of claim 7, it is possible to detect a fluctuation amount with less noise.

  As shown in the configuration diagram of FIG. 1, the image forming apparatus 1 according to the first embodiment includes a transfer device 10, an optical writing unit 11, a paper feed unit 12, a fixing device 13, a paper discharge unit 14, and a control unit 15. A printing apparatus. The image forming apparatus 1 is not limited to a printing apparatus, and may be a facsimile transmission / reception apparatus, a copying apparatus, a copying apparatus, a composite image forming apparatus, or the like.

  The transfer device 10 includes a transfer unit 16 and a station 17. The transfer unit 16 includes an intermediate transfer belt 18, a driven roller 19, a drive roller 20, a belt mark detection unit 21, a fluctuation amount detection unit 22, a transfer brush 23, a cleaning blade 24, and a transfer roller 25. The intermediate transfer belt 18 that is stretched around the driven roller 19 and the driving roller 20 and is rotationally driven by the driving roller 20 has a width about the paper, and has one belt mark 26 on the surface. The belt mark detection unit 21 is disposed in a path through which the belt mark 26 passes in the vicinity of the intermediate transfer belt 18, detects the belt mark 26 while the intermediate transfer belt 18 is rotating, and outputs a belt mark detection signal.

  As shown in the plan view of FIG. 2A and the side view of FIG. 2B, the transmissive variation amount detection unit 22 includes a light emitting element 27, a light receiving element 28, and a variation measurement signal output unit 29. The light emitting element 27 and the light receiving element 28 are disposed so as to sandwich the outer peripheral surface and the inner peripheral surface in the vicinity of a part of the end portion (belt edge) of the intermediate transfer belt 18. The received light is received and a current I corresponding to the amount of received light is output, and the fluctuation amount measurement signal output unit 29 converts the current I into a fluctuation amount measurement signal vm (= kI) and outputs it. That is, the fluctuation amount detection unit 22 outputs a fluctuation amount measurement signal vm having a magnitude uniquely corresponding to the fluctuation amount. In the width direction (X direction) orthogonal to the running direction (Y direction) of the intermediate transfer belt 18, the direction in which the belt edge approaches the fluctuation amount detection unit 22 from the center of the light receiving element 28 (positive), Assuming that the moving direction is a negative direction (-), the amount of light received by the light receiving element 28 decreases as the intermediate transfer belt 18 moves in the positive direction, and the current I decreases. Increasing the current I increases.

As shown in the characteristic diagram of FIG. 3, when the fluctuation amount dx is between -A and + A, the current I changes in proportion to the fluctuation amount dx. Therefore, if the current I is measured, the fluctuation amount dx can be obtained. When the variation dx is 0, I _1/2 , and when the variation dx is −A or less, the current I is the maximum value I ₁ , and when the variation dx is + A or more, the current I is the minimum value 0. For example, when the belt mark detection unit 21 detects the belt mark 26, the position passing through the fluctuation amount detection unit 22 is set as a reference position, and the fluctuation amount detection unit 22 is set at a position where the current I at the reference position becomes I1 _{/ 2.} Install. Similarly, as long as the relationship between the fluctuation amount dx and the output value is obtained, the fluctuation amount detection unit 22 may have another configuration.

  By measuring the amount of fluctuation by sandwiching the intermediate transfer belt 18 between the light emitting element 27 and the light receiving element 28, it is not necessary to provide the intermediate transfer belt 18 with means for measuring the amount of fluctuation, and the intermediate transfer belt 18 can be easily measured. Since the thickness does not change, the size can be reduced. Even if the intermediate transfer belt 18 is slack, it is sandwiched between the light emitting element 27 and the light receiving element 28, and the amount of variation can be measured accurately. When the linear light receiving element 28 that is long in the direction orthogonal to the traveling direction of the intermediate transfer belt 18 is used, the fluctuation amount can be detected with higher accuracy.

  The transfer brush 23 applies a transfer bias to the intermediate transfer belt 18 at a position facing the station 17 across the intermediate transfer belt 18. The transfer roller 25 facing the driven roller 19 is pressed against and retracted from the intermediate transfer belt 18. The cleaning blade 24 facing the driving roller 20 contacts the intermediate transfer belt 18 after the image formation is completed, removes residual toner, and retracts from the intermediate transfer belt 18 before image formation.

  The station 17 includes an image carrier 30, a charging roller 31 disposed around the image carrier 30, an exposure slit 32, a developing unit 33, and a cleaning unit 34. The image carrier 30 formed of the photosensitive drum rotates in contact with the intermediate transfer belt 18 while facing the transfer brush 23 with the intermediate transfer belt 18 interposed therebetween. The surface of the image carrier 30 is charged by a charging roller 31 during rotation, and is exposed to light incident from an exposure slit 32 to form a latent image. The developing unit 33 has four color toners of cyan (C), yellow (Y), magenta (M), and black (B) and a developing roller for developing with each toner color, and selects one of the toner colors. The toner image is visualized from the latent image on the image carrier, and the toner image on the image carrier 30 is transferred to the intermediate transfer belt 18 by the bias applied to the transfer brush 23. After the transfer, the transfer residual toner remaining on the image carrier 30 is removed by the cleaning unit 34.

  The optical writing unit 11 includes an LD 35, a polygon mirror 36, an optical system 37, and a scanning light detection unit 38. The optical writing unit 11 scans the light emitted from the modulation-controlled LD 35 with the rotating polygon mirror 36, such as a mirror or a lens. The optical system 37 guides to the exposure slit 32 of the station 17 to expose the image carrier 30. The scanning light detector 38 provided outside the scanning area on the scanning start side detects the light emitted from the LD 35 and outputs a detection signal S1.

  The paper supply unit 12 stores a recording medium such as paper. The fixing device 13 presses the second-transferred paper while being heated while being sandwiched between a heating roller and a pressure roller, fixes the toner image on the paper, and discharges it to the paper discharge unit 14.

  As shown in the configuration diagram of FIG. 4, the control unit 15 includes a shift signal generation unit 39, a synchronization signal generation unit 40, a writing processing unit 41, a transfer device control unit 42, an optical writing unit control unit 43, and a fixing device control unit. 44, a paper feed unit control unit 45, a paper discharge unit control unit 46, an image memory 47, a CPU 48, a ROM 49, and a RAM 50, which are connected to each other and transmit / receive data to / from each other.

  The writing processing unit 41 reads image data from the image memory 47 and creates a writing signal for creating a toner image. The image data may be input from the outside via a communication line or a recording medium, or may be read by providing a document reading device. The transfer device control unit 42, the optical writing unit control unit 43, the fixing device control unit 44, the paper feeding unit control unit 45, and the paper discharge unit control unit 46 are respectively fed to the transfer device 10, the optical writing unit 11, and the paper feeding. The unit 12, the fixing device 13, and the paper discharge unit 14 are operated. The CPU 48 reads the control program stored in the ROM 49 into the RAM 50 and performs arithmetic processing to control the overall operation of the image forming apparatus 1.

  The shift signal generation unit 39 includes a reference value setting unit 51, a variable voltage differential amplifier 52, and a variable voltage adder 53.

  When the reference value setting unit 51 receives the belt mark detection signal output by detecting the belt mark from the belt mark detection unit 21, the reference value setting unit 51 uses the fluctuation amount measurement signal vm output from the fluctuation amount detection unit 22 as the fluctuation amount dx = It is set as the reference fluctuation amount measurement signal v0 at the zero reference position. The fluctuation voltage differential amplification section 52 having a differential amplifier circuit is the difference between the reference fluctuation amount measurement signal v0 set in the reference value setting section 51 and the fluctuation amount measurement signal vm output from the fluctuation amount detection section 22. And a fluctuation voltage vd = B × (v0−vm) obtained by multiplying a predetermined function B depending on the fluctuation amount measurement signal vm is output. The fluctuation voltage adding section 53 multiplies the constant A by the reference fluctuation amount measurement signal v0 set by the reference value setting section 51, and adds the fluctuation voltage vd output from the fluctuation voltage differential amplification section 52 to a shift signal sh. = A × v0 + vd is output.

  The synchronization signal generation unit 40 includes a delay unit 54, a difference unit 55, a set value storage unit 56, a first comparison unit 57, and a delay time control unit 58. The delay time control unit 58 includes an LPF 581 (low-pass filter) and a first delay time control unit 58. 2 comparison unit 582.

  When the scanning light from the LD 35 is incident, the scanning light detection unit 38 outputs a detection signal s1 as shown by a solid line in FIG. The delay unit 54 delays the detection signal s1 output from the scanning light detection unit 38 for a predetermined time, and outputs a delay signal s2 as shown by the solid line in FIG. The difference unit 55 takes the difference between the detection signal s1 and the delay signal s2 as shown by the solid line in FIG. 5C to generate the difference signal d1 as shown by the solid line in FIG. The first comparison unit 57 compares the value r1 preset in the set value storage unit 56 with the difference signal d1, rises when the difference signal d1 becomes the value r1, and when the difference signal d1 becomes the value r1 again. The binary signal dg falling at is output. For example, if r1 = 0, a binary signal dg as shown in FIG. 5 (e) is output. The LPF 581 outputs a slope signal fd as shown in FIG. 5 (f) with the rise and fall of the binary signal dg moderated.

  When the power of the scanning light from the LD 35 changes and the detection signal s1 and the delay signal s2 change as shown by the broken lines in FIG. 5A and FIG. 5B, respectively, they are substantially line symmetric with respect to the peak value. Since the signal level sc at the intersection of the detection signal s1 and the delay signal s2 is substantially the same, the position on the time axis of the intersection of the detection signal s1 and the delay signal s2 does not change as shown in FIG. As shown in FIG. 5D, the position on the time axis at which the difference signal d1 first becomes 0 does not change. Therefore, by setting the value r1 to 0, the rising edge position of the binary signal dg can always be made constant without depending on the power change of the scanning light from the LD 35.

  The second comparison unit 582 compares the shift signal sh output from the fluctuation voltage addition unit 53 of the shift signal generation unit 39 with the gradient signal fd output from the LPF 581, and as illustrated in FIG. A synchronization signal ds that rises at a time position where fd takes the value of the shift signal sh is output.

  For example, when the fluctuation amount dx of the intermediate transfer belt 18 is Xb, the current I = Ib is output from the light receiving element 28 as shown in FIG. 3, and the shift signal generator 39 shifts as shown in FIG. The signal sh = sh1 is generated, and the synchronization signal generator 40 generates the synchronization signal ds (FIG. 5 (h)) delayed by the time dt = dt1 from the synchronization signal ds at the reference position (FIG. 5 (g)). The When the fluctuation amount dx of the intermediate transfer belt 18 is Xa, the current I = Ia is output from the light receiving element 28 as shown in FIG. 3, and the shift signal sh as shown in FIG. = sh2 is generated, and the synchronization signal generator 40 generates the synchronization signal ds (FIG. 5 (i)) earlier than the synchronization signal ds at the reference position (FIG. 5 (g)) by time dt = dt2.

  Here, the delay time dt is determined by the time required for the scanning light to move by the fluctuation amount dx of the intermediate transfer belt 18. In order to delay the toner image formation timing by the delay time dt with respect to the fluctuation amount dx of the intermediate transfer belt 18, the synchronization signal ds is delayed by the delay time dt. The time constant of the LPF 581 is set to a size that can secure the delay time dt that covers the entire range or the necessary range of the fluctuation amount dx within the time from the start to the end of the ramp signal fd. The value of the shift signal sh required to obtain the delay time dt is determined depending on the time constant of the LPF 581, and the constant A and the function are output so that the shift signal sh is output from the shift signal generation unit 39 according to the variation dx. Set B. Specifically, at the reference position, the constant A for determining the shift signal sh is set so that the synchronization signal ds rises at a substantially central time position between the time position where the gradient signal fd rises and the time position where the maximum value is obtained. Further, the function B is set so that the value of the shift signal sh corresponding to the fluctuation amount dx determined by the LPF 581 matches the value of the shift signal sh obtained from the fluctuation voltage vm. That is, the shift signal sh is a synchronization signal compared to the case where there is no fluctuation amount dx at the reference position for the time required for the scanning light to move the distance of the fluctuation amount dx uniquely corresponding to the magnitude of the fluctuation amount measurement signal vm. Has a magnitude that delays the rise of ds

  The LD 35 synchronizes with the timing of the synchronization signal ds output from the synchronization signal generation unit 40, delays the timing to start lighting by the delay time dt when the synchronization signal ds is delayed, and writes the write signal of the write processing unit 41 Illuminates while modulating with a lighting pattern according to the above. As a result, even if the position where the image carrier 30 is exposed fluctuates by a distance corresponding to the delay time dt, and the intermediate transfer belt 28 fluctuates, the toner images can be accurately superimposed at the same position.

  An outline of the operation of the image forming apparatus 1 will be described. The intermediate transfer belt 18 rotates with the transfer roller 25 and the cleaning blade 24 separated from the intermediate transfer belt 18. The LD 35 is turned on in synchronization with the detection signal output from the belt mark detection unit 21 by detecting the belt mark 26 of the intermediate transfer belt 18, and a toner image is formed at the station 17, and each rotation of the intermediate transfer belt 18. The toner color developed by the developing unit 33 changes, and toner images of different colors are superimposed on the intermediate transfer belt 18 and transferred. When the transfer of the four colors is completed, the transfer roller 25 is pressed against the intermediate transfer belt 18, and the four color toner images on the intermediate transfer belt 18 are transferred to the sheet conveyed from the paper feeding unit 12. When the transfer to the paper is completed, the transfer roller 25 is separated from the intermediate transfer belt 18. The sheet on which the toner image is transferred is fixed by the fixing device 13 and discharged to the paper discharge unit 14. The cleaning blade 24 comes into contact with the image-formed region of the intermediate transfer belt 18 to clean the transfer residual toner. When the cleaning is completed, the cleaning blade 24 is separated from the intermediate transfer belt 18.

  If the intermediate transfer belt 18 changes in a meandering or offset direction due to contact / separation of the transfer roller 25 or the cleaning blade 24 or a change in belt tension in a method orthogonal to the traveling direction of the intermediate transfer belt 18, the intermediate transfer belt 18 The timing at which the image carrier 30 is exposed is changed so as to follow the fluctuation amount of 18, so that the toner images of the respective colors can be accurately superimposed on the intermediate transfer belt 18.

  According to this image forming apparatus 1, the toner image can be accurately superimposed on the intermediate transfer belt 18 from the image carrier 30 by measuring the fluctuation amount in the direction orthogonal to the traveling direction of the intermediate transfer belt 18. A high-quality image without color misregistration can be formed on paper.

  As shown in the configuration diagram of FIG. 6, the image forming apparatus 2 according to the second embodiment includes a delay time control unit 58 having an LPF 581 and a second comparison unit 582 of the image forming apparatus 1 according to the first embodiment. The difference is that the delay time control unit 60 having the delay element group 601 and the selector 602 is replaced, and other configurations and operations are the same as those of the image forming apparatus 1 according to the first embodiment. The delay element group 601 delays the binary signal dg output from the first comparison unit 57 by Δt and generates n binary delay signals de1 to den as shown in FIG. Based on the input of the shift signal sh, the selector 602 uses, as the synchronization signal ds, one binary delay signal that is selected from the n binary delay signals de1 to den corresponding to the value of the shift signal sh. Output.

  Here, in order to delay the toner image formation timing by the delay time dt with respect to the fluctuation amount dx of the intermediate transfer belt 18, the synchronization signal ds is delayed by the delay time dt. The range of the binary delay signals de1 to den is set to a size that can secure the delay time dt that covers the entire range or the necessary range of the fluctuation amount dx. The value of the shift signal sh is uniquely determined for the delay time dt, and the constant A and the function B are set so that the shift signal sh corresponding to the variation dx is output from the shift signal generation unit 39. Specifically, at the reference position, a binary delay signal dem having a delay amount that is about half of the binary delay signal de1 and the binary delay signal den among the binary delay signals de1 to den is selected as the synchronization signal ds. The constant A for obtaining the shift signal sh is set so that Further, the function B is set so that the value of the shift signal sh for obtaining the delay time dt corresponding to the fluctuation amount dx matches the value of the shift signal sh obtained from the fluctuation voltage vm.

  According to this image forming apparatus 2, the toner image can be accurately superimposed on the intermediate transfer belt 18 from the image carrier 30 by measuring the amount of fluctuation in the direction orthogonal to the traveling direction of the intermediate transfer belt 18. A high-quality image without color misregistration can be formed on paper.

  The image forming apparatus 3 according to the third embodiment includes a station 63 instead of the station 17 in the image forming apparatus 1 according to the first embodiment, and an optical writing unit 65 instead of the optical writing unit 11. An intermediate transfer unit 66 is provided instead of the intermediate transfer unit 16, and a control unit 67 is provided instead of the control unit 15. As shown in the block diagram of FIG. 8, the station 63 includes four image carriers 30 arranged around each other, and a charging roller similar to that of the image forming apparatus 1 according to the first embodiment is provided around each image carrier 30. 31, an exposure slit 32, and a cleaning unit 34 are provided, and a developing unit 64 is provided instead of the developing unit 33, and one toner color is developed and transferred for each image carrier 30. The optical writing unit 65 has the LD 35 and the scanning light detection unit 38 for each image carrier 30, the intermediate transfer unit 66 has the fluctuation amount detection unit 22 for each image carrier 30, and the control unit 67 has the configuration shown in FIG. As shown in the figure, each image carrier 30 has a synchronization signal generator 40 and a shift signal generator 39. Each of the fluctuation amount detection units 22 is disposed upstream of the transfer position of the image carrier 30 with respect to the traveling direction of the intermediate transfer belt 18. The set of the image carrier 30, the LD 35, the scanning light detection unit 38, the fluctuation amount detection unit 22, the synchronization signal generation unit 40, and the shift signal generation unit 39 is the same as that of the image forming apparatus 1 according to the first embodiment. The other configurations and operations are the same as those of the image forming apparatus 1 according to the first embodiment. Note that the synchronization signal generation unit 62 according to the second embodiment may be used instead of the synchronization signal generation unit 40.

  By measuring the amount of fluctuation in the direction orthogonal to the running direction of the intermediate transfer belt 18, the toner image can be accurately superimposed on the intermediate transfer belt 18 from the image carrier 30, and a high-quality image without color misregistration can be obtained. Can be formed on paper. In the image forming apparatus 3 in which the range D in which the image carrier 30 is arranged is long and different for each image carrier 30, the fluctuation amount is accurately obtained by providing the fluctuation amount detection unit 22 for each image carrier 30 and obtaining the fluctuation amount. An image can be formed by measurement.

  As shown in the configuration diagram of FIG. 10, the image forming apparatus 4 of the fourth exemplary embodiment includes a transfer unit 69, a first station 70, and a second station 71. The optical writing unit 72 includes an LD 35 and a scanning light detection unit 38 corresponding to each of the first station 70 and the second station 71. The transfer unit 69 has a fluctuation amount detection unit 22 corresponding to each of the first station 70 and the second station 71. As shown in the configuration diagram of FIG. 11, the control unit 73 includes a synchronization signal generation unit 40 and a shift signal generation unit 39 corresponding to each of the first station 70 and the second station 71.

  The first station 70 is different from the first station 17 according to the first embodiment in that the developing unit 33 is provided with any one of two colors of cyan (C), yellow (Y), magenta (M), and black (B). The toner is stored, and the toner image is visualized from the latent image of the image carrier 30 with the toner selected from two colors, and the toner image of the image carrier 30 is changed by the bias applied to the transfer brush 23. Transfer to the intermediate transfer belt 18. The second station 71 is located downstream of the first station 70 in the traveling direction of the intermediate transfer belt 18 and has the same structure as the first station 70 except that the color to be developed is different.

  The optical writing unit 72 scans the light emitted from the two LDs 35 that are separately modulated and controlled corresponding to the first station 70 and the second station 71 with the rotating polygon mirror 36, and scans the first with a mirror or the like. The image carrier 30 is exposed by being guided to the exposure slits 32 of the station 70 and the second station 71, respectively. The lights emitted from the two LDs 35 are separately detected by two scanning light detectors 38 provided outside the scanning region on the scanning start side, and a detection signal S1 is output.

  Each set of the first station 70 or the second station 71, the LD 35, the scanning light detection unit 38, the fluctuation amount detection unit 22, the synchronization signal generation unit 40, and the shift signal generation unit 39 is an image according to the first embodiment. The same operation as that of the forming apparatus 1 is performed, and other configurations and operations are the same as those of the image forming apparatus 1 according to the first embodiment.

  An outline of the operation of the image forming apparatus 4 will be described. The intermediate transfer belt 18 rotates with the transfer roller 25 and the cleaning blade 24 separated from the intermediate transfer belt 18. Each LD 35 is lit in synchronization with a detection signal output from the belt mark detection unit 21 by detecting the belt mark 26 of the intermediate transfer belt 18. The first color is transferred, the second color is transferred at the second station 71, the third color is transferred at the first station 70 on the second round, and the fourth color is transferred at the second station 71. The four color toner images are formed by being aligned and superimposed. When the transfer of the four colors is completed, the transfer roller 25 is pressed against the intermediate transfer belt 18, and the four color toner images on the intermediate transfer belt 18 are transferred to the sheet conveyed from the paper feeding unit 12. When the transfer to the paper is completed, the transfer roller 25 is separated from the intermediate transfer belt 18. The sheet on which the toner image is transferred is fixed by the fixing device 13 and discharged to the paper discharge unit 14. The cleaning blade 24 comes into contact with the image-formed region of the intermediate transfer belt 18 to clean the transfer residual toner. When the cleaning is completed, the cleaning blade 24 is separated from the intermediate transfer belt 18.

  The image forming apparatus for transferring two colors at two stations has been described. However, four colors may be transferred at one station, or each color may be transferred at another station. An image forming apparatus using color types may be used. Further, the present invention may be applied to the image forming apparatus according to the second or third embodiment.

  By measuring the amount of fluctuation in the direction orthogonal to the running direction of the intermediate transfer belt 18, the toner image can be accurately superimposed on the intermediate transfer belt 18 from the image carrier 30, and a high-quality image without color misregistration can be obtained. Can be formed on paper.

  The image forming apparatus 5 according to the fifth embodiment has the same configuration as the image forming apparatus 1 according to the first embodiment as shown in the configuration diagram of FIG. 12, and the image carrier 30 is attached to the intermediate transfer belt 18. The distance L2 from the position at which the image is transferred to the position at which the fluctuation amount detection unit 22 detects the fluctuation amount is such that the position exposed by the LD 35 on the surface of the image carrier 30 rotates to transfer the image to the intermediate transfer belt 18. The fluctuation amount detection unit 22 is disposed upstream of the image carrier 30 in the traveling direction of the intermediate transfer belt 18 and is equal to the distance L1 until the position is reached.

  As shown in the configuration diagram of FIG. 13, the control unit 74 further includes an acquisition instruction signal generation unit 75 and an acquisition holding unit 76 in the image forming apparatus 1 according to the first embodiment. FIG. 14A shows the timing of the binary signal dg generated from the detection signal s1 detected by the light receiving element. FIG. 14B shows a signal indicating an effective image area in main scanning, and a part of the period outside the effective image area is a non-image forming period. The capture instruction signal generator 75 outputs a capture instruction signal each time a non-image forming period occurs as shown in FIG. When the capture holding unit 76 receives the capture instruction signal, the capture holding unit 76 captures the variation measurement signal vm from the variation detection unit 22 and holds it as a retained variation measurement signal vs until the next non-image forming period, while maintaining the effective image region. The held variation measurement signal vs is continuously output as the variation measurement signal vm at the time of exposure.

  Other configurations and operations are the same as those of the image forming apparatus 1 according to the first embodiment. In addition to correcting the timing at which writing is started by delaying the synchronization signal ds and capturing the variation measurement signal vm for each non-image formation period, the number of captures and timing are set to match the actual belt fluctuation behavior. May be. The number of captures (samples) during the non-image forming period is arbitrary. Further, the present invention may be applied to the image forming apparatuses according to the second to fourth embodiments.

  The capture holding unit 76 includes a capture unit, an addition unit, an averaging unit, and a storage unit. The capture unit captures a plurality of variation measurement signals vm during a non-image forming period, and the addition unit performs a plurality of variations. The amount measurement signal vm is added, the average value is taken by the averaging unit to obtain the holding variation amount measurement signal vs, and the holding variation amount measurement signal vs is held in the holding unit until the next non-image forming period, while the effective variation area The retained fluctuation amount measurement signal vs may be continuously output as the fluctuation amount measurement signal vm at the time of exposure.

  Since the amount of fluctuation is detected during each non-image formation period, the toner images of each color can be superimposed more accurately, and the fluctuation amount measurement signal vm with reduced noise is detected by averaging the fluctuation amount measurement signal vm. can do. By measuring the amount of fluctuation in the direction orthogonal to the running direction of the intermediate transfer belt 18, the toner image can be accurately superimposed on the intermediate transfer belt 18 from the image carrier 30, and a high-quality image without color misregistration can be obtained. Can be formed on paper.

  The image forming apparatus 6 according to the sixth embodiment has the same configuration as the image forming apparatus 1 according to the first embodiment except for the difference between the intermediate transfer unit 16 and the intermediate transfer unit 77. A plurality of belt marks 26 are provided at equal intervals along the belt running direction as shown in FIG. 15 on the outer peripheral surface on which the image of the intermediate transfer belt 78 included in the intermediate transfer unit 77 is formed. The reflection type fluctuation amount detection unit 79 includes a light emitting element 80, a light receiving element 81, and a fluctuation amount measurement signal output unit 82, as shown in the plan view of FIG. 16A and the side view of FIG. The intermediate transfer belt 78 is disposed so as to be opposed to a part near the end (belt edge).

Light emitted from the light emitting element 80 and reflected by the surface of the intermediate transfer belt 78 is received by the light receiving element 81, the light receiving element 81 outputs a current I corresponding to the amount of received light, and the fluctuation amount measurement signal output unit 82 The current I is converted into a fluctuation amount measurement signal vm (= kI) and output. Since the reflectance differs between the intermediate transfer belt 78 and the belt mark 26, the belt edge is away from the center of the intermediate transfer belt 78 in the width direction (X direction) orthogonal to the traveling direction (Y direction) of the intermediate transfer belt 78. Is the positive direction (+), and the approaching direction is the negative direction (−), the amount of light received by the light receiving element 81 decreases as the intermediate transfer belt 78 moves in the positive direction, the current I decreases, and the more it moves in the negative direction. The amount of light received by the light receiving element 28 increases and the current I increases. As shown in the characteristic diagram of FIG. 17, the current I becomes the maximum value I ₁ when the fluctuation amount dx is 0 or less, and the current I becomes the minimum value I _1/5 when the fluctuation amount dx is + A or more.

  When the belt mark detection unit 21 detects any one of the belt marks 26, the fluctuation amount detection unit 79 is arranged at a position where any other belt mark 26 can be detected. Only when the belt mark detection unit 21 detects the belt mark 26, the fluctuation amount detection unit 79 outputs the fluctuation amount measurement signal vm. By maintaining the positional relationship between the belt mark detection unit 21 and the fluctuation amount detection unit 79, a fluctuation amount measurement signal vm is output from the fluctuation amount detection unit 79 in accordance with the detection of the belt mark 26 by the belt mark detection unit 21. There is no need to provide a timing circuit or the like, and the configuration can be simplified. Further, the belt mark 26 can be detected by the belt mark detector 21 and the fluctuation amount can be measured by the fluctuation amount detector 79 without depending on the change in the rotational speed of the intermediate transfer belt 78. Even when the rotational speed of the intermediate transfer belt 78 changes, the amount of change can be sampled without changing or adding a circuit.

  The arrangement position of the fluctuation amount detection unit 79 in the belt width direction is set so that the current I output from the light receiving element 81 at the reference position is approximately the center value of the output range.

  According to this image forming apparatus 6, by measuring the amount of fluctuation in the direction orthogonal to the running direction of the intermediate transfer belt 78, the toner image can be accurately superimposed on the intermediate transfer belt 78, and there is no color misregistration. High quality images can be formed on paper.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. It is the top view and side view of the variation | change_quantity detection part of 1st Embodiment. It is a characteristic figure of the electric current-fluctuation amount of the fluctuation amount detection part of 1st Embodiment. 1 is a configuration diagram of a signal system of an image forming apparatus according to a first embodiment. FIG. 4 is a signal waveform diagram transmitted by the image forming apparatus according to the first embodiment. FIG. 6 is a configuration diagram of a signal system of an image forming apparatus according to a second embodiment. It is a signal waveform diagram transmitted by the image forming apparatus of the second embodiment. It is a block diagram of the image forming apparatus of 3rd Embodiment. It is a block diagram of the signal system | strain of the image forming apparatus of 3rd Embodiment. It is a block diagram of the image forming apparatus of 4th Embodiment. It is a block diagram of the signal system | strain of the image forming apparatus of 4th Embodiment. FIG. 10 is an enlarged view near a transfer unit according to a fifth embodiment. It is a block diagram of the signal system | strain of the image forming apparatus of 5th Embodiment. It is a signal waveform diagram of a 5th embodiment. It is a block diagram of the transfer unit of 6th Embodiment. It is the top view and side view of the variation | change_quantity detection part of 6th Embodiment. It is a characteristic figure of the electric current-variation amount of the variation detection part of a 6th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Image forming apparatus, 2; Image forming apparatus, 3; Image forming apparatus, 4; Image forming apparatus,
5; Image forming apparatus, 6; Image forming apparatus, 10; Transfer apparatus, 11; Optical writing unit,
12; paper feeding unit, 13; fixing device, 14; paper discharge unit, 15; control unit, 16; transfer unit,
17; station; 18; intermediate transfer belt; 19; driven roller; 20; drive roller;
21; belt mark detection unit; 22; fluctuation amount detection unit; 23; transfer brush;
24; cleaning blade; 25; transfer roller; 26; belt mark;
27; light emitting element, 28; light receiving element, 29; fluctuation amount measurement signal output unit, 30; image carrier,
31; Charging roller, 32; Exposure slit, 33; Developing section, 34; Cleaning section,
35; LD, 36; Polygon mirror, 37; Optical system, 38; Scanning light detection unit,
39; shift signal generation unit; 40; synchronization signal generation unit; 41; write processing unit;
42; transfer device control unit; 43; optical writing unit control unit; 44; fixing device control unit;
45; paper feed control unit, 46; paper discharge control unit, 47; image memory, 48; CPU,
49; ROM, 50; RAM, 51; reference value setting unit, 52; variable voltage differential amplification unit,
53; Fluctuating voltage addition unit, 54; Delay unit, 55; Difference unit, 56; Set value storage unit,
57; first comparison unit, 58; delay time control unit, 60; delay time control unit,
62; synchronization signal generating unit, 63; station, 64; developing unit,
65; optical writing unit, 66; intermediate transfer unit, 67; control unit, 68; transfer device,
69; transfer unit, 70; first station, 71; second station,
72; optical writing unit; 73; controller; 74; controller; 75; capture instruction signal generator;
76; capture holding section, 77; intermediate transfer unit, 78; intermediate transfer belt,
79; fluctuation amount detection unit, 581; LPF, 582; second comparison unit, 601; delay element group,
602; selector.

Claims (7)

The toner marks are formed on the image carrier for each toner color by synchronous control based on the timing when the belt mark provided on the intermediate transfer belt is detected by the belt mark detection means, and the toner images of a plurality of colors are the same on the intermediate transfer belt. An image forming apparatus that collectively transfers toner images onto a sheet after being superimposed on a position,
A fluctuation amount detecting means, a shift signal generating means, a scanning light receiving means, a synchronization signal generating means, and a light source;
The fluctuation amount detecting means detects an edge of the intermediate transfer belt that is running, and outputs a fluctuation amount measurement signal having a magnitude that uniquely corresponds to a fluctuation amount in a direction orthogonal to the running direction of the intermediate transfer belt,
The shift signal generating means outputs a shift signal having a magnitude uniquely corresponding to the magnitude of the fluctuation amount measurement signal of the fluctuation amount measurement signal;
The scanning light receiving means receives scanning light from a light source that performs exposure scanning of the image carrier at a constant cycle, and outputs a detection signal;
The synchronization signal generating means includes a delay means, a difference means, a first comparison means, and a delay time control means, the delay means outputs a delay signal obtained by delaying the detection signal, and the difference means detects the detection A differential signal obtained by taking a difference between the signal and the delayed signal, the first comparing means outputs a binary signal that rises at a time position where the positive and negative of the differential signal are switched, and the delay time controlling means is the binary signal Generating a synchronization signal that rises at a time position delayed by a delay time uniquely corresponding to the shift signal,
The image forming apparatus, wherein the light source exposes in a main scanning direction from a position determined by the timing of the synchronization signal. The toner marks are formed on the image carrier for each toner color by synchronous control based on the timing when the belt mark provided on the intermediate transfer belt is detected by the belt mark detection means, and the toner images of a plurality of colors are the same on the intermediate transfer belt. An image forming apparatus that collectively transfers toner images onto a sheet after being superimposed on a position,
A fluctuation amount detecting means, a shift signal generating means, a scanning light receiving means, a synchronization signal generating means, and a light source;
The intermediate transfer belt has a plurality of belt marks arranged at equal intervals in the running direction,
The fluctuation amount detecting means is located at the same distance as the belt mark interval from the belt mark detecting means, and each time the belt mark is detected by the belt mark detecting means, the direction of travel of the other belt mark is detected. Output a fluctuation measurement signal with a magnitude uniquely corresponding to the fluctuation quantity in the direction orthogonal to
The shift signal generating means outputs a shift signal having a magnitude uniquely corresponding to the magnitude of the fluctuation amount measurement signal of the fluctuation amount measurement signal;
The scanning light receiving means receives scanning light from a light source that performs exposure scanning of the image carrier at a constant cycle, and outputs a detection signal;
The synchronization signal generating means includes a delay means, a difference means, a first comparison means, and a delay time control means, the delay means outputs a delay signal obtained by delaying the detection signal, and the difference means detects the detection A differential signal obtained by taking a difference between the signal and the delayed signal, the first comparing means outputs a binary signal that rises at a time position where the positive and negative of the differential signal are switched, and the delay time controlling means is the binary signal Generating a synchronization signal that rises at a time position delayed by a delay time uniquely corresponding to the shift signal,
The image forming apparatus, wherein the light source exposes in a main scanning direction from a position determined by the timing of the synchronization signal.   3. The image forming apparatus according to claim 1, wherein each of the image carriers transfers a toner image developed in a different color to the intermediate transfer belt each time the intermediate transfer belt rotates.   The image carrier includes two image carriers, and the variation amount detector, the shift signal generator, the scanning light receiver, the synchronization signal generator, and the light source for each of the image carriers. 3. The image forming apparatus according to claim 1, wherein toner images developed in different colors at the first rotation and the second rotation of the intermediate transfer belt are transferred to the intermediate transfer belt.   A plurality of image carriers, and a variation amount detector, a shift signal generator, a scanning light receiver, a synchronization signal generator, and a light source for each of the image carriers. The image forming apparatus according to claim 1, wherein toner images of different colors are transferred to the intermediate transfer belt. Including a holding means;
The fluctuation amount detecting means is located upstream of the image carrier, the distance from the transfer position where the toner image is transferred from the image carrier to the intermediate transfer belt, and the position where the image carrier is exposed is the transfer position. Placed at the same distance as the rotational movement to the position,
6. The capture holding unit captures and holds a variation measurement signal from the variation detection unit for each non-image forming period, and outputs the variation measurement signal to the synchronization signal generation unit. Image forming apparatus. The capture holding unit captures a variation amount measurement signal from the variation amount detection unit a plurality of times within the same non-image forming period, adds and averages the captured variation amount measurement signal, and performs the synchronization as the variation amount measurement signal. The image forming apparatus according to claim 6, wherein the image forming apparatus outputs the signal to a signal generation unit.

Images