JP2019117319A - Image forming device - Google Patents

Abstract

To solve the problem that when a change occurs to a label roll paper conveyance speed due to a cut operation, there occurs a positional deviation between the label of roll paper and the developer image that is transferred, causing print quality to degrade.SOLUTION: The present invention comprises: an image formation unit 20 for forming a toner image on the basis of image data; an intermediate transfer belt 12; a control unit 70; secondary transfer means (16a, 16b) for transferring the toner image of the intermediate transfer belt 12 to a label 46; nonvolatile memory 78 for storing a plurality of timing information; and a cutter 38 for cutting label roll paper 31; and further including a command/image processing unit 72 for sequentially generating image data. Thus, determination is made as to a conveyance load condition for the label 46 to which the toner image of the image data is transferred when the label roll paper 31 is cut, and on the basis of this, intervals between the sequentially generated image data are set on the basis of the timing information selected from the nonvolatile memory 78.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of label printing by an intermediate transfer method.

  Conventionally, in an image forming apparatus of this type, for example, an image forming apparatus such as an electrophotographic printer, an image forming unit for forming toner images of respective colors such as black, yellow, magenta and cyan is a toner image on an intermediate transfer belt. Is first transferred, and the toner image primarily transferred onto the intermediate transfer belt is secondarily transferred to a recording medium such as printing paper at the secondary transfer portion to form a full-color toner image on the recording medium. An intermediate transfer type image forming apparatus is known.

  However, in the above-described image forming apparatus, when the recording medium is a so-called label roll paper in which a plurality of labels are pasted at a predetermined pitch on continuous band roll paper, the pitch of the toner image formed on the intermediate transfer belt Since there is generally a slight error between the label and the pitch of the label on the label roll, when the image is continuously formed on the label roll, the position of the toner image formed on each label gradually The problem of shifting will occur.

  In order to cope with such a problem, it is conceivable to use label roll paper in which a black mark is printed at a position corresponding to the top of each label on the back surface of the roll paper which is a backing sheet. Then, by performing image formation while detecting the pitch of the black mark with a detection unit such as a sensor, the pitch of the image and the pitch of the label are made to coincide, and the position of the toner image formed on each label shifts Can be prevented.

  Moreover, even if it is label roll paper to which a black mark is not given, when using label roll paper whose roll paper is thin compared with each label, and label roll paper whose roll paper is a transparent film, labels and labels Since the difference in transmittance from the label gap to which the label is not attached is detected by a transmission type optical sensor or the like to measure the pitch of the label, each of them is similar to the case of detecting the pitch of the black mark. It is possible to prevent the position of the toner image formed on the label from shifting.

  By the way, if a sensor for detecting the pitch of black marks or label gap is provided in the image forming apparatus and a toner image is continuously formed on label roll paper while feeding back the pitch of labels, the following problems occur. Occurs.

  That is, in the image forming apparatus, after the LED head as the exposure unit writes the latent image on the photosensitive body, the distance from the secondary transfer portion to the secondary transfer of the toner image on the label roll paper as the recording medium is very long. Long, on the order of hundreds of mm. On the other hand, the length of each label in general label roll paper is around 100 [mm]. Therefore, when the label pitch is measured in the vicinity of the secondary transfer portion, the toner image to be transferred onto the label and the subsequent several labels has already been transferred onto the intermediate transfer belt, and the label Alignment based on the pitch measurement results is applied to the label after several sheets. That is, based on the measurement result of the label pitch, the label pitch of several sheets ahead is predicted to adjust the pitch of the toner image.

  Therefore, as a method to make label pitch measurement timing earlier and feed back the label pitch measurement result to the toner image as quickly as possible, the second position detection sensor closest to the secondary transfer unit, and more upstream in the transport direction A method has been proposed in which label pitch measurement is performed by two of the position detection sensors 1 and faster feedback is performed using the measurement results of the first position detection sensor until measurement can be performed by the second position detection sensor (for example, , Patent Document 1).

JP, 2017-15921, A (page 17, FIG. 1)

  However, if roll paper conveyance load changes such as the roll paper cutting operation after passing the position detection sensor further upstream, the speed of label roll paper changes, so this method may not solve the misregistration. . As an example in which the change in the conveyance load becomes large, in the paper conveyance method in which back tension is applied in the direction opposite to the conveyance direction to apply tension to the roll paper in order to suppress the meandering of the label roll paper It can be easily imagined that the transfer speed changes with the release. Further, even in the case of the conveyance configuration in which the back tension is not positively applied, if any load change occurs before and after the roll paper is cut, a slight speed change occurs to cause positional deviation of the print image.

The present invention is an image forming apparatus for forming an image on the plurality of labels of a medium having a plurality of labels arranged at intervals on a backing sheet,
Image forming means for forming a developer image based on image data, an intermediate transfer member to which the developer image is primarily transferred, control means for controlling the formation timing of the developer image, and the label Medium transfer direction from the secondary transfer means for transferring the developer image of the transfer body, the medium transfer means for transferring the medium to the secondary transfer means along the transfer path, and the first detection means of the transfer path A cutter, disposed upstream, for cutting the intervals of the plurality of labels of the medium, and a storage unit for storing transport load information to be given to the medium upstream of the secondary transfer portion of the medium by the medium cutting by the cutter. Equipped with
The control means includes image processing means for sequentially generating the image data in order to form the developer image corresponding to the plurality of labels, and the image processing means is configured to sequentially generate the image data. An interval of the image data to be sequentially generated is set based on the conveyance load information of the medium stored in the storage unit.

  According to the present invention, even when there is a speed change in the label roll paper conveyed by the roll paper cutting operation, the positional deviation between the roll paper label and the developer image transferred to the label is suppressed. be able to.

FIG. 1 is a main part configuration diagram showing a main part configuration of a roll paper printer of a first embodiment as an image forming apparatus according to the present invention. FIG. 6 is a main part configuration diagram showing a main part configuration of a black (K) image forming unit. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure where it uses for description of the 1st type label roll paper, (a) is the top view, (b) is the side view, (c) is the dotted line of the figure (b). It is the elements on larger scale of the enclosed part. It is a figure which is provided for explanation of the second type label roll paper, (a) is the top view, (b) is the side view, (c) is the dotted line in the same figure (b) It is the elements on larger scale of the enclosed part. It is a figure where it is used for explanation of label gap detection of the 1st type label roll paper by the 1st label gap detection sensor, (a) is a top view of the 1st type label roll paper, (b) is a The positional relationship of the side surface and a 1st label gap detection sensor is shown, (c) shows the output voltage signal waveform of a 1st label gap detection sensor. It is a figure where it is used for explanation of detection of the black mark of the 2nd type label roll paper with the 1st black mark detection sensor, (a) is the top view of the 2nd type label roll paper, (b) These show the positional relationship of the side surface and a 1st black mark detection sensor, (c) shows the output voltage signal waveform of a 1st black mark detection sensor. FIG. 6A is a diagram showing a state in which light is transmitted through the label gap of the first type of label roll paper, and FIG. 7B is a diagram showing the structure of the first label gap detection sensor. It is a figure which shows the state which permeate | transmits a label. FIG. 6A is a perspective view showing the appearance of a first black mark detection sensor and a second type of label roll paper passing above the first black mark detection sensor; FIG. (B) is a side view of these. FIG. 2 is a block diagram showing the configuration of a control unit of the roll paper printer. 5 is a timing chart provided to explain the relationship between cut timing, image length, cut status information, and blank length of an image. In a comparative example, it is a timing chart which is provided for explanation of the image formation timing of an image formation unit, and the detection timing of the black mark of label roll paper. In the control method in a comparative example, it is a figure where it uses for explanation in case a position gap does not arise. FIG. 17 is a diagram for describing the case where positional deviation occurs due to transport speed fluctuation due to cutting or the like in the control method in the comparative example.

Embodiment 1
FIG. 1 is a main part configuration view showing a main part configuration of a roll paper printer 10 of a first embodiment as an image forming apparatus according to the present invention. The roll paper printer 10 is an electrophotographic color printer compatible with label roll paper.

  In the figure, the roll paper printer 10 may be of any type, but here, the roll paper printer 10 will be described as an electrophotographic printer that forms an image by an electrophotographic method. The roll paper printer 10 may form a monochrome image or a color image. Here, printing is performed on the label roll paper 31 as a medium by an intermediate transfer method. The case of a color printing apparatus to be performed will be described.

  The roll paper printer 10 has four independent image forming units 20Y and 20M as image forming means for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C) and black (K). , 20C, 20K along the direction of the arrow B indicating the moving direction in which the intermediate transfer belt 12 as an intermediate transfer member of the intermediate transfer belt unit 90 described later moves at the upper portion of the intermediate transfer belt unit 90. , Are arranged in order from the upstream side.

  The four image forming units 20Y, 20M, 20C, and 20K basically have the same configuration, and only the color of the toner used differs. Therefore, for the sake of explanation, the four image forming units 20Y, 20M, 20C, and 20K are simply described as the image forming unit 20 when it is not necessary to distinguish them. Furthermore, each member and other members included in the image forming unit 20 also need to be distinguished as corresponding to each color of yellow (Y), magenta (M), cyan (C) and black (K). The symbols Y, M, C, and K are assigned and described, and the symbols Y, M, C, and K are not assigned, unless otherwise specified.

  The intermediate transfer belt unit 90 applies tension to the intermediate transfer belt 12 by urging means such as a drive roller 13 driven by a drive unit (not shown), an idle roller 14 for determining a movement path of the intermediate transfer belt 12, and a coil spring. The secondary transfer backup roller 16b disposed opposite to the tension roller 18, the secondary transfer roller 16a and constituting the secondary transfer nip portion 16, and the intermediate transfer belt 12 stretched around those rollers are provided. The intermediate transfer belt 12 is rotationally moved in the arrow B direction as the drive roller 13 is rotationally driven. The secondary transfer roller 16a and the secondary transfer backup roller 16b correspond to a secondary transfer unit.

  The intermediate transfer belt unit 90 is further disposed to face the photosensitive drums 11 of the respective image forming units 20 via the intermediate transfer belt 12, and sequentially superimposes toner images of respective colors formed on the respective photosensitive drums 11. And four primary transfer rollers 15 and the like for applying a predetermined voltage for primary transfer onto the intermediate transfer belt 12. Each primary transfer roller 15 is pressed against the corresponding photosensitive drum 11 by a spring (not shown) to form a primary transfer nip portion as a primary transfer portion.

  FIG. 2 is a main part configuration diagram showing the main part configuration of the four image forming units 20. As shown in FIG. Here, the configuration will be described with reference to the black (K) image forming unit 20K.

  As shown in the figure, the image forming unit 20 selectively exposes the photosensitive drum 11 as an image carrier, the charge roller 21 for charging the surface of the photosensitive drum 11, and the surface of the charged photosensitive drum 11. LED head 22 for writing an electrostatic latent image, developing roller 23 for developing the electrostatic latent image on the surface of photosensitive drum 11 with toner as a developer, developing roller 23 while supplying toner to the surface of developing roller 23 The toner is rubbed between the sponge roller 24 to frictionally charge to the negative polarity, the developing blade 25 to form a uniform thin layer of toner supplied to the surface of the developing roller 23, the predetermined color (here, black (here K) toner reservoir for supplying toner, and cleaning blur for cleaning toner remaining on the surface of the photosensitive drum 11 With a de 27.

  The photosensitive drum 11, the developing roller 23, the sponge roller 24, and the charge roller 21 rotate in the direction of the arrow shown in FIG. The photosensitive drum 11 is rotationally driven by a driving unit (not shown), the driving is transmitted from the photosensitive drum 11 to the developing roller 23 by a gear (not shown), and the driving is transmitted from the developing roller 23 to the sponge roller 24 by an idle gear (not shown). . The charge roller 21 rotates by being in contact with the photosensitive drum 11.

  At a primary nip where the photosensitive drum 11 and the primary transfer roller 15 are in pressure contact with each other via the intermediate transfer belt 12, an intermediate transfer belt 12 of a toner image as a developer image formed on the photosensitive drum 11. The transfer to the upper side is performed, and the intermediate transfer belt 12 carries the toner image transferred to the surface and conveys it to the secondary transfer nip portion 16.

  As shown in FIG. 1, the label roll paper 31 is prepared in the state of a roll 31 'previously wound around a core (not shown), and the roll paper printer is designed to be rotatable about this core by the user. It is attached to ten. Then, as the roll 31 ′ rotates, the label roll paper 31 is drawn out and conveyed. The image-formed label roll paper 31 is discharged from the roll paper printer 10, and is cut off from the roll 31 'by the cutter 38 at that time.

  Here, the label roll paper 31 will be described. Here, two types of label roll paper 31 will be described. FIG. 3 is a diagram for explaining the label roll paper 31a of the type (hereinafter referred to as the first type) in which the label gap between labels does not have a label residue, and FIG. 4 shows the label residue in the label gap between labels It is a figure where it uses for description of label roll paper 31b of a type (henceforth a 2nd type).

  3 (a) is a plan view of the first type of label roll paper 31a, FIG. 3 (b) is a side view thereof, and FIG. 3 (c) is FIG. 3 (b). It is the elements on larger scale of the part enclosed with the dotted line of.

  As shown in the figure, the first type of label roll paper 31 a is a long base paper 47 on which a plurality of labels 46 are arranged at equal intervals along the longitudinal direction. The toner image is transferred for printing. The backing sheet 47 is a long strip-like or tape-like paper, a resin film or the like, and wound to form a roll 31 '. Further, the label 46 is a paper, a resin film or the like which is releasably adhered to the surface of the mount 47 by an adhesive or the like, and a plurality of labels 46 are adhered in a longitudinal direction or a traveling direction of the mount 47 at predetermined intervals. Ru. Then, the label 46 is used by peeling it off the backing sheet 47 after printing is completed.

  4 (a) is a plan view of the second type of label roll paper 31b, FIG. 4 (b) is a side view thereof, and FIG. 4 (c) is FIG. 4 (b). It is the elements on larger scale of the part enclosed with the dotted line of.

  As shown in the figure, in the second type of label roll paper 31b, a paper, resin film or the like having a size equal to that of the mount 47 is releasably attached to the surface of the long mount 47, and then the longitudinal direction is obtained. Are formed by die cutting or cutting out a part to a predetermined size and shape at equal intervals, and the die cut part is a label 46, and the margin remaining around it is a label waste 48 and It is called. Then, the label 46 is used by peeling it off the backing sheet 47 after printing is completed.

  Furthermore, in this second type of label roll paper 31b, as shown in FIG. 4C, on the back surface of the mount 47, as a mark indicating the position of the leading end of each label 46 in the direction of arrow A indicating the transport direction. Black marks 43 are formed by printing.

  The first type of label roll paper 31a is the second type of label roll paper 31b from which the label residue 48 as a margin portion has been removed, and therefore between adjacent labels 46 (label gap) and each No label residue 48 as a margin remains around the label 46. In this case, the black mark 43 may or may not be printed on the back of the mount 47, but as described later, in the case of the roll paper printer 10 of the present embodiment, it can be used in either case. is there. When the first type of label roll paper 31a and the second type of label roll paper 31b are described integrally without distinction, the label roll paper 31 will be described.

  As shown in FIG. 1, the label roll paper 31 delivered from the roll 31 'is detected by a paper feed sensor 59 including a mechanical lever and a transmission sensor as a paper feed detection means for the label roll paper 31, and a paper feed roller The sheet 33 is conveyed while being sandwiched between the sheet 33 and the pinch roller 34. It is guided by the guide 35 and passes the positions of the first label gap detection sensor 36 and the first black mark detection sensor 37.

  The first label gap detection sensor 36 is a transmissive optical sensor, and includes a light emitting unit 41 and a light receiving unit 42, and the label roll paper 31 passes between the light emitting unit 41 and the light receiving unit 42. The first black mark detection sensor 37 is a reflective optical sensor and detects the black mark 43 (FIG. 4) on the back surface of the mount 47.

  Here, the first label gap detection sensor 36 and the first black mark detection sensor 37 will be further described.

  FIG. 5 is a view for explaining the detection of the label gap of the first type of label roll paper 31a by the first label gap detection sensor 36, and FIG. 5 (a) shows the first type of label roll paper 31a. It is a top view, the figure (b) shows the position relation of the side and the 1st label gap detection sensor 36, and the figure (c) shows the output voltage signal waveform of the 1st label gap detection sensor 36. As shown in FIG.

  As shown in FIG. 6B, the light emitting unit 41 and the light receiving unit 42 of the first label gap detection sensor 36 are disposed to face each other across the conveyance path of the label roll paper 31. Then, when the label gap consisting only of the backing sheet 47 passes between adjacent labels 46 of the first type of label roll paper 31a conveyed in the conveyance direction (arrow A direction) in the conveyance path, as shown in FIG. Since the output voltage level of the first label gap detection sensor 36 changes as shown in (c), the positions of the individual labels 46 can be detected based on the output voltage signal of the first label gap detection sensor 36 It becomes.

  Here, the configuration of the first label gap detection sensor 36 will be further described. FIG. 7 is a diagram for describing the configuration of the first label gap detection sensor 36, and FIG. 7A is a diagram showing a state in which light passes through the label gap of the first type of label roll paper 31a. FIG. 7B shows a state in which light passes through the label 46.

  As shown in FIG. 7, the first label gap detection sensor 36 has a configuration in which the light emitting unit 41 is from the top, and the light receiving unit 42 is from the bottom, sandwiching the first type of label roll paper 31a. An LED 67 as light emitting means driven by a circuit (not shown) is fixed inside the light emitting portion 41, and emits light with a predetermined amount of light emission. A phototransistor 68 as light receiving means driven by a circuit (not shown) is fixed inside the light receiving portion 42, and the light from the LED 67 transmitted through the first type label roll paper 31a is received, and the light receiving amount is received. Output a voltage corresponding to

  The light emitting means is not limited to the LED, and the light receiving means is not limited to the phototransistor, and may be another kind of element that exhibits the same function. Further, the positions of the light emitting unit 41 and the light receiving unit 42 may be any position as long as light can be transmitted through and received by the first type label roll paper 31 a. For example, it may be upside down with respect to the position of FIG.

  Furthermore, the circuit is configured such that the output voltage of the first label gap detection sensor 36 is low here at the position of the label gap where the transmittance is higher than that of the surroundings, as shown in FIG. 5C. The present invention is not necessarily limited to this, and the output voltage may be increased at the position of the label gap.

  FIG. 6 is a diagram for explaining the detection of the black marks 43 of the second type label roll paper 31b by the first black mark detection sensor 37, and FIG. 6A shows the second type of label roll paper. FIG. 31B is a plan view of 31b, and FIG. 31B shows the positional relationship between the side surface and the first black mark detection sensor 37, and FIG. 31C shows the output voltage signal waveform of the first black mark detection sensor 37. .

  As shown in FIG. 6B, the first black mark detection sensor 37 is disposed only on one side (here, the lower side) of the conveyance path of the label roll paper 31. Then, when the black mark 43 formed on the back surface of the backing sheet 47 of the second type of label roll paper 31b transported in the transport direction (arrow A direction) along the transport path passes as shown in FIG. Since the output voltage level of the first black mark detection sensor 37 changes, the position of each label 46 can be detected based on the output voltage signal of the first black mark detection sensor 37.

  Here, the configuration of the first black mark detection sensor 37 will be further described. FIG. 8 is a diagram for describing the configuration of the first black mark detection sensor 37, and FIG. 8A is a diagram of the first black mark detection sensor 37 and the second type of label roll paper 31b passing above it. It is an appearance perspective view, and the figure (b) is a side view of these. In FIG. 6A, the label 46 and the label residue 48 (FIG. 6) of the second type of label roll paper 31b are omitted, and the mount 47 is seen through.

  As shown in FIG. 8, the first black mark detection sensor 37, which is a reflective optical sensor, is a black mark 43 formed on the back surface of the mount 47 from the lower side (back side) of the second type label roll paper 31 b. To detect The first black mark detection sensor 37 includes an LED 65 as light emitting means and a phototransistor 66 as light receiving means. The light emitting means is not limited to the LED, and the light receiving means is not limited to the phototransistor, and may be another kind of element that exhibits the same function.

  The LED 65 is driven by a circuit (not shown) to irradiate light to the back surface of the label roll paper 31 with a predetermined light emission intensity, and the light reflected by the back surface is received by the phototransistor 66. The phototransistor 66 is connected to a reading circuit (not shown), and the reading circuit outputs a voltage corresponding to the reflection intensity of the back surface of the label roll paper 31 as an output voltage of the first black mark detection sensor 37.

  In the output voltage of the first black mark detection sensor 37, as shown in FIG. 6C, the circuit is configured such that the output voltage is low at the position of the black mark 43 whose reflectance is lower than that of the surroundings here. However, the present invention is not necessarily limited to this, and the output voltage may be increased at the position of the black mark 43.

  Here, the first label gap detection sensor 36 and the first black mark detection sensor 37 are mainly used for detecting the standby position of the label roll paper 31.

  The label roll paper 31 having passed the positions of the first label gap detection sensor 36 and the first black mark detection sensor 37 is further guided by the guide 35 and conveyed in the conveyance direction (arrow A direction) to reach the position of the cutter 38 Do. The cutter 38 can cut the label roll paper 31 at a predetermined timing described later. Subsequently, the label roll paper 31 is guided to the guide 35, and is engaged with the nip portion between the first intermediate conveyance roller 51 and the first pinch roller 53 opposed to the first intermediate conveyance roller 51, and the first intermediate conveyance roller It is driven by 51 and transported.

  Subsequently, the label roll paper 31 is further bitten by the nip portion between the second intermediate conveyance roller 52 and the second pinch roller 54 and conveyed, and is guided by the guide 35 to be guided by the second label gap detection sensor 55 and the second The position of the black mark detection sensor 56 is passed.

  The second label gap detection sensor 55 includes the light emitting unit 57 and the light receiving unit 58, and the configuration is the same as the configuration of the first label gap detection sensor 36 described above, and the detailed description thereof is omitted here. Similarly to the first label gap detection sensor 36, the output voltage shown in FIG. 5C at which the voltage is lowered at the position of the label gap of the passing first type label roll paper 31a is output. The second black mark detection sensor 56 as a label position detection means has the same configuration as that of the first black mark detection sensor 37 described above, and thus the detailed description thereof is omitted here. Similar to the sensor 37, an output voltage shown in FIG. 6C at which the voltage is lowered at the position of the black mark 43 of the passing second type label roll paper 31b is output.

  Subsequently, the label roll paper 31 is further guided to the guide 35, and is formed by the secondary transfer roller 16a and the secondary transfer backup roller 16b, and the secondary transfer nip portion 16 as a secondary transfer portion functioning as a transfer unit. Bite into. When printing on the label roll paper 31, as described later, it is necessary to control so that each label 46 and the toner image on the intermediate transfer belt 12 reach the secondary transfer nip 16 at the same timing. There is. As a result, the toner image can be secondarily transferred to each label 46 in a properly positioned state.

  Subsequently, the label roll paper 31 reaches the fixing device 61. The fixing device 61 includes an upper roller 62 and a lower roller 63 which are in pressure contact with each other to form a fixing nip. A halogen lamp 64 is disposed inside the upper roller 62 and supplies heat for melting and fixing the toner image. Here, while the label roll paper 31 is conveyed while being caught in the fixing nip, the toner image secondarily transferred to each label 46 is pressurized and heated to be fixed, and then conveyed to the outside of the apparatus.

  The roll paper printer 10 has a configuration capable of printing continuously on the label roll paper 31 as described above.

  Next, the configuration of the main control system of the roll paper printer 10 will be described. FIG. 9 is a block diagram showing the configuration of the control unit 70 as control means of the roll paper printer 10. As shown in FIG.

  As shown in the figure, the control unit 70 includes an engine control unit 71, a command / image processing unit 72 as an image processing unit, an interface unit 73, a RAM 75Y, 75M, 75C and 75K, a high voltage supply unit 77, and a storage unit. Non-volatile memory 78 of In the components provided corresponding to each color of yellow (Y), magenta (M), cyan (C) and black (K), the symbols of Y, M, C and K are necessary if they need to be distinguished. In the case where it is not necessary to distinguish, it will be described without the signs of Y, M, C and K.

  The command / image processing unit 72 communicates with the host PC 74, which is a high-order device of the roll paper printer 10, via the interface unit 73, and processes commands and image data received from the host PC 74. Then, the command / image processing unit 72 outputs an instruction to the engine control unit 71 according to the command received from the host PC 74, interprets the image data received from the host PC 74, and develops it into a bit map. Write a bitmap to the RAM 75. Each RAM 75 is connected to the corresponding LED head 22 via the engine control unit 71, and the engine control unit 71 reads the bit map data of the RAM 75 and transfers it to the LED head 22.

  Then, the engine control unit 71 controls the printing operation according to the instruction from the command / image processing unit 72. Therefore, the engine control unit 71 includes the LED head 22, the high-pressure supply unit 77, the halogen lamp 64, the RAM 76, the first label gap detection sensor 36, the first black mark detection sensor 37, the second label gap detection sensor 55, and the second It is connected to the black mark detection sensor 56 and is further connected to a rotary blade rotation motor (not shown) for cutting the label roll paper 31 by the cutter 38.

  A high voltage supply unit 77 controlled by the engine control unit 71 supplies necessary high voltages to the image forming unit 20, the primary transfer roller 15, and the secondary transfer roller 16a. Similarly, the halogen lamp 64 has the upper roller 62 inside. Heat from

  The engine control unit 71 detects the position of the label gap or the black mark based on the output change of the second label gap detection sensor 55 and the second black mark detection sensor 56, and calculates the period of the label, that is, the label pitch. Further, as described later, the engine control unit 71 determines which label pitch has been cut during measurement based on the timing at which the label roll paper 31 is cut by the cutter 38, as described later.

  Specifically, for the label pitch measurement result, a label pitch measurement value before cutting, a label pitch measurement value during cutting, a label pitch measurement value after cutting, and a cut for identifying three conveyance load conditions The status information is added, and the label pitch measurement value to which the cut status information is added is notified to the command / image processing unit 72. The command / image processing unit 72 stores label pitch measurement values separately for each cut status information in three storage areas 79a, 79b, 79c of the label pitch measurement value storage area 79, which is a partial area of the nonvolatile memory 78. Do. These label pitch measurement values correspond to timing information.

  In addition to the control described above, the engine control unit 71 controls the overall hardware operation of the roll paper printer 10, such as the intermediate transfer belt unit 90, the paper feed roller 33, and the intermediate conveyance rollers 51 and 52.

  Next, the operation of the roll paper printer 10 configured as described above will be described.

  First, when the command / image processing unit 72 receives image data for printing on the label roll paper 31 from the host PC 74, that is, print data, the roll paper printer 10 starts an image forming operation, and the command / image processing unit 72 interprets the received print data and develops it into bitmap data of each toner color. The expanded bitmap data is stored in the RAM 75. Further, the command / image processing unit 72 instructs the engine control unit 71 to start the printing operation simultaneously with the development of the print data into bit map data.

  As a result, the engine control unit 71 controls the halogen lamp 64 to heat the fixing device 61 so that the temperature of the fixing device 61 falls within the temperature range in which the toner image can be fixed to the label roll paper 31. Then, when the temperature of the fixing device 61 sufficiently rises, the engine control unit 71 starts driving of the driving roller 13 and each image forming unit 20. Further, at the same time, the engine control unit 71 controls the high pressure supply unit 77 to supply the image forming unit 20 and the primary transfer roller 15 with a predetermined high voltage bias.

  Here, an operation of forming a toner image on the photosensitive drum 11 will be described with reference to FIGS. 1 and 2.

  First, the charge roller 21 to which the charge bias of -1000 [V] is supplied from the high voltage supply section 77 as the high voltage bias charges the surface of the photosensitive drum 11 to -600 [V]. Further, from the high voltage supply unit 77, a developing bias of -200 V is supplied to the developing roller 23 as a high voltage bias, and a sponge bias of -250 V is supplied to the sponge roller 24.

  On the other hand, the toner supplied from the toner tank 26 is strongly rubbed by the sponge roller 24 and the developing roller 23 and is frictionally charged to the negative polarity. The toner frictionally charged to the negative polarity is caused to adhere to the developing roller 23 by the potential difference between the sponge bias and the developing bias. The toner attached to the developing roller 23 is flattened by the developing blade 25 to form a toner layer on the developing roller 23. The toner layer thus formed on the developing roller 23 is conveyed to the nip with the photosensitive drum 11 by the rotation of the developing roller 23.

  The engine control unit 71 also causes the LED head 22 to start writing of the latent image on the photosensitive drum 11. In this case, the engine control unit 71 sequentially reads bit map data of the print data written in the RAM 75 from the leading end of the image, and transfers the bit map data to the LED head 22 one by one. The LED head 22 blinks the LED according to the transferred bit map data, and exposes the surface of the photosensitive drum 11 charged to -600 [V]. The exposed portion on the surface of the photosensitive drum 11 is discharged to -50 V to form an electrostatic latent image. The portion of the surface of the photosensitive drum 11 on which the electrostatic latent image is formed is conveyed to the nip with the developing roller 23 as the photosensitive drum 11 rotates.

  At this time, the toner layer negatively charged as described above is formed on the developing roller 23, and the developing bias of -200 [V] is supplied to the developing roller 23. Due to the potential difference between the surface of the photosensitive drum 11 and the electrostatic latent image, the toner is selectively adhered only to the electrostatic latent image, and the electrostatic latent image is developed as a toner image.

  A toner image of the corresponding color is formed on the photosensitive drum 11 in each of the image forming units 20, and these toner images are the contact portion between the intermediate transfer belt 12 and the photosensitive drum 11, that is, the primary transfer When reaching the nip portion, the primary transfer bias as a high voltage bias is supplied from the high voltage supply portion 77 to the primary transfer roller 15, so the toner images of the respective colors are sequentially transferred from the respective photosensitive drums 11 to the intermediate transfer. It is superimposed and transferred onto the belt 12.

  At this time, the formation of each color toner image on each photosensitive drum 11Y, 11M, 11C, and 11K is performed by shifting the timing by the arrangement interval of each photosensitive drum 11Y, 11M, 11C, and 11K. The color toner images transferred onto the intermediate transfer belt 12 are stacked one on another without shifting.

(Comparative example)
Here, as a comparative example of the present invention, the control unit 70 generates a developer image, that is, a toner image based on the detection result of the second label gap detection sensor 55 or the second black mark detection sensor 56 as a label position detection unit. A method of controlling the timing of forming the toner image on the intermediate transfer belt 12 will be described.

  FIG. 11 is a timing chart for explaining the image formation timing of the image forming unit 20 and the detection timing of the black mark 43 of the label roll paper 31 in the comparative example.

  First, the conveyance start method of the label roll paper 31 will be described. Here, for convenience of explanation, the label roll paper 31 is the second type of label roll paper 31 b having the black mark 43 (FIG. 4) attached on the back side, which is referred to as the first black mark detection sensor 37 and the It is assumed that the black mark detection sensor 56 detects the black mark.

  Before the command / image processing unit 72 receives image data from the host PC 74, the leading edge of the label roll paper 31 is drawn into the roll paper printer 10 by a predetermined amount, and stands by.

Specifically, the user of the roll paper printer 10 first inserts the label roll paper 31 into the nip portion between the feed roller 33 and the pinch roller 34 before the start of image formation. Thereafter, the engine control unit 71 detects the insertion of the roll sheet by the sheet feed sensor 59 and starts the leading edge pull-in operation of the label roll sheet 31. Then, the engine control unit 71 drives the paper feed roller 33 while monitoring the output voltage of the first black mark detection sensor 37, and after the leading edge of the first black mark 43 is detected, the distance L _IN [Line When the label roll paper 31 is conveyed by only the above, the paper feed roller 33 is stopped.

By operating the paper feed roller 33 in this manner, the label at the position where the leading end of the first black mark 43 of the label roll paper 31 has passed the first black mark detection sensor 37 by the distance L _IN [Line]. The roll paper 31 is in a stopped state.

In order to print on the first label 46 of the label roll paper 31 in the image forming unit 20 Y which is the image forming unit 20 with the longest distance from the primary transfer nip along the intermediate transfer belt 12 to the secondary transfer nip 16 A value obtained by converting the time until the drive of the label roll paper 31 is started after the image formation of the above is started into the distance by the circumferential speed of the photosensitive drum 11 (hereinafter may be referred to as a predicted distance) L _R [Line] is obtained as follows.

From the position where the LED head 22Y exposes the surface of the photosensitive drum 11Y, along the circumferential surface of the photosensitive drum 11Y via the primary transfer nip portion of the image forming unit 20Y, the intermediate transfer in the rotational direction of the intermediate transfer belt 12 The distance to reach the secondary transfer nip 16 along the surface of the belt 12 is L _ID [Line], and the distance from the first black mark detection sensor 37 to the secondary transfer nip 16 along the guide 35 is L _{Assuming that SR1} [Line], the leading end of the label roll paper 31 passes the first black mark detection sensor 37 by the distance L _IN [Line] and stands by, and therefore, it is expressed by the following equation (1).
L _R = L _ID − (L _SR1 −L _IN ) (1)

In the roll paper printer 10, since the distance L _SR1 [Line] is shorter than the distance L _ID [Line], the predicted distance L _R [Line] takes a positive value. When the predicted distance L _R [Line] is a positive value, after the LED head 22 Y starts the exposure of the photosensitive drum 11 Y, the photosensitive drum 11 Y moves circumferentially by the predicted distance L _R [Line] and then the label roll paper is used. 31 Start transportation. In the case of the roll paper printer 10 in _{which the} distance L _SR1 [Line] is longer than the distance L _ID [Line], that is, when the predicted distance L _R [Line] is a negative value, conveyance of the label roll paper 31 is started. After that, at the stage of transporting the same by the predicted distance L _R [Line], the exposure of the LED head 22 Y to the photosensitive body 11 Y may be started.

  Further, in the image forming units 20M, 20C and 20K, which are the image forming units 20 in which the distance to the secondary transfer nip portion 16 is shorter than that of the image forming unit 20Y, the LED heads 22M, 22C and 22K correspond to the photosensitive drums 11M and 11C. And the timing of starting the exposure of 11K by the time corresponding to the interval between the photosensitive drum 11Y and the photosensitive drums 11M, 11C, and 11K from the timing when the LED head 22Y starts the exposure of the photosensitive drum 11Y. The toner images of the respective colors of yellow (Y), magenta (M), cyan (C) and black (K) can be transferred onto the intermediate transfer belt 12 in an overlapping manner without misalignment.

  Next, an operation of secondarily transferring toner images of respective colors on the second and subsequent labels 46 (FIG. 4) will be described.

  If the printing operation is continued without using any special control, that is, the detection result of the second black mark detection sensor 56 after the alignment operation to the leading label 46, the following problems occur.

The engine control unit 71 forms a toner image of each label 46 at a label image pitch P _L0 [Line] obtained by adding an initial value G ₀ [Line] of a fixed blank length to the image of the image length P _IM [Line]. Keep doing. On the other hand, the mark cycle (label pitch) length P _BM [Line] at which each label 46 on the label roll paper 31 reaches the secondary transfer nip 16 does not match the label image pitch P _L0 [Line]. It is common to include a deviation of only the error ΔP _L [Line]. Such a deviation is a dimensional error of the label 46 itself or a dimensional error of the transport member.

Then, an error ΔP _L [between the formation pitch of the toner image, ie, the label image pitch P _L0 [Line], and the arrival pitch of the label 46 to the secondary transfer nip portion 16, ie the mark cycle length P _BM [Line]. When printing is continued in the presence of Line], when the toner image is transferred to the Nth label 46, a positional error of (N-1) × ΔP _L [Line] occurs.

Even if the error ΔP _L [Line] is about 1/1200 [inch 1 Line], that is, 21 [μm], if N = 100, the positional deviation of the toner image to be secondarily transferred is about 2 [mm] It becomes. This is an error that can not be tolerated in printing on the label roll paper 31, which may also be the case where hundreds or more labels 46 are continuously printed. Therefore, it is necessary to reduce the amount of accumulated deviation until the mark cycle length P _BM [Line] is measured by the position detection sensor by making the error ΔP _L [Line] smaller.

Here, the mark cycle length P _{L (N)} [Line] of the past is stored in a fixed number in the non-volatile memory 78 <FIG. 9>, and in the case of the same roll paper setting, the image of the past cycle results stored A fixed blank initial value G ₀ [Line] to be added to the image of the long P _IM [Line] is optimized. If the print roll cycle history is not stored in the non-volatile memory 78, a fixed margin length calculated from the set roll paper information is used. Further, by performing control as follows, positional deviation of the toner image to be secondarily transferred is suppressed.

As described above, after the exposure of the photosensitive drum 11Y by the LED head 22Y and the conveyance of the label roll paper 31 are started, the LED head 22Y sets the initial value G ₀ of the blank length in the image of the image length P _IM [Line]. At the label image pitch P _L0 [Line] to which [Line] is added, the photosensitive drum 11 Y is exposed to repeat image formation.

On the other hand, the engine control unit 71 starts monitoring the output of the second black mark detection sensor 56 and detects the leading edge position of the black mark 43 (FIG. 4) printed on the back surface of the label roll paper 31. The black mark 43 is printed so that its leading edge coincides with the leading edge of the label 46 as described above. The label roll paper 31 is subsequently conveyed, and the second black mark detection sensor 56 detects the black mark 43 corresponding to the second label 46. Then, the engine control unit 71 sets the difference between the position of the first label 46 and the position of the second label 46, that is, the interval P _BM2 (1) [Line] between the first and second labels 46. ] Is detected.

Similarly, the engine control unit 71 sets an interval P _BM2 between the second and third labels 46 (2) [Line], and an interval P _BM2 (3) between the third and fourth labels 46. [Line] ... ... The interval P _{BM2 (k)} of the label 46 between the k-th and (k + 1) -th sheets is continuously detected.

As shown in FIG. 11, when the second black mark detection sensor 56 detects the interval P _BM2 (1) [Line], the LED head 22Y is exposing the (M + 1) -th image. Since the label pitch measurement information can not be obtained by the second black mark detection sensor 56 until the (M + 1) th image is formed, the engine control unit 71 determines the blank length G of the first and second images. 1) The blank length G (M) of the image of [Line] to the Mth and (M + 1) th sheets [Line] is the initial value G ₀ [Line] of the blank length of the fixed image and the photosensitive drum The image is formed by exposing to 11Y.

Then, when the second black mark detection sensor 56 detects the interval P _BM2 (1) [Line], the engine control unit 71 determines the blank length G of the image between the (M + 1) -th and (M + 2) -th sheets. The value of M + 1) [Line] is corrected as follows, and the (M + 2) th sheet is corrected to be printed at the correct position.

The image formation pitch by the LED head 22Y up to the M-th sheet, that is, the label image pitch P _L0 [Line] is expressed by the following equation (2).
P _L0 = P _IM + G ₀ (2)
The toner image is formed at the label image pitch P _L0 [Line] up to the (M + 1) th sheet. On the other hand, since the pitch of the labels 46 of the first and second sheets detected by the second black mark detection sensor 56 is the interval P _BM2 (1) [Line], the error of the label pitch per sheet of labels 46 Δ P _L (1) [Line] is expressed by the following equation (3).
ΔP _L (1) = P _{BM 2} (1) -P _{L 0} (3)

Therefore, the position error ΔD (M + 1) [Line] integrated at the position of the (M + 1) th image is expressed by the following equation (4).
ΔD (M + 1) = M × ΔP _L (1) (4)
The correct value of the blank length G (M + 1) [Line] of the image between the (M + 1) th and (M + 2) th sheets is the initial value of the blank length of the image as expressed by the following equation (5) It can be obtained by adding the position error ΔD (M + 1) [Line] accumulated at the position of the (M + 1) -th image to the value G ₀ [Line].
G (M + 1) = G ₀ + ΔD (M + 1) ... (5)

Then, when the label roll paper 31 is further conveyed, the second black mark detection sensor 56 detects an interval P _BM2 (2) [Line] of the labels 46 between the second and third sheets. The blank length G (M + 2) [Line] of the image between the (M + 2) -th and (M + 3) -th sheets is an initial value G ₀ of the blank length of the image as expressed by the following equation (6). It can be obtained as a value obtained by adding the position error accumulated at the position of the (M + 2) -th image to [Line] and subtracting the correction applied to G (M + 1) [Line] from there.
G (M + 2) = G ₀ + ΔD (M + 2)-ΔD (M + 1) (6)

However, the position error ΔD (M + 2) [Line] is calculated based on the average value of the interval 46 of the label 46 with the interval P _BM2 (1) [Line] and the interval P _BM2 (2) [Line]. The error in the pitch of the label 46 expressed by the following equation (7) ΔP _L (2) [Line] is used to improve the reliability of the detected value of the pitch of the label 46.
ΔP _L (2) = Average (P _{BM 2} (1), P B _{M 2} (2)) − P _LO (7)
Thus, the position error ΔD (M + 2) [Line] is expressed by the following equation (8).
Δ D (M + 2) = (M + 1) × Δ P _L (2)
= (M + 1) x (Average (P B M ₂ (1), P B M ₂ (2))-P _{L 0} )
... (8)
In addition, the meaning of Average (x1, x2, x3, ...) used here represents an average value of x1, x2, x3, ....
Therefore, the blank length G (M + 2) [Line] to be added to the image between the (M + 2) th and (M + 3) th sheets is obtained by substituting the above formulas (4) and (8) into the formula (6) It can be asked.

Thereafter, assuming that the value of the pitch of the label 46 detected by the second black mark detection sensor 56 is an average value of the measured values of the pitches of the three labels 46 in the past, the error of the label pitch per one label 46 ΔP _{L (k)} and position error ΔD (M k k) can generally be determined as in the following equations (9) and (10).
P P _L (k)
= Average (P _BM2 (k-2), P _BM2 (k-1), P _BM2 (k))-P _L0
... (9)
ΔD (M + k−1) = (M + k−2) × ΔP _L (k)
= (M + k-2) x
(Average (P _BM2 (k-2), P _BM2 (k-1), P _BM2 (k))-P _L0 )
(10)

Therefore, in general, the blank length G (M + k-1) [Line] of the image between the (M + k-1) th and (M + k) th sheets is expressed by the following equation (11).
G (M + k-1) = G 0 + △ D (M + k-1) - △ D (M + k-2) ··· (11)
By controlling the inter-image gap, that is, the blank length G of the image based on the above equation (11), it is possible to match the image position to each label 46 on an average.

  According to the above-described control of the blank length G of the image, when the transport speed of the labels 46 does not change significantly, the labels 46 and the positions of the toner images transferred to the corresponding labels 46 are merged on an average. Thus, the position of the toner image can be matched with the position of the label 46 with high accuracy.

  However, in the method of controlling the blank length G of the image according to the above-described comparative example, when the label conveyance speed fluctuates due to the cutting of the label roll paper 31, etc., the toner image length already formed on the transfer belt is transferred. A difference occurs in the apparent length of the label 46, resulting in positional deviation after transfer.

  FIG. 12 and FIG. 13 are diagrams for describing the case where positional deviation does not occur and the case where positional deviation occurs due to transport speed fluctuation due to cutting or the like in the control method according to the comparative example.

  FIG. 12A shows an example of secondary transfer when the transport speed of the label roll paper 31 does not change. In this case, as shown in FIG. 12B, the length of the toner image 101 on the transfer belt and the apparent length of the label paper to be transferred are equal. Therefore, no positional deviation of the printed toner image with respect to the label paper occurs.

  On the other hand, FIG. 13 (a) shows an example of secondary transfer when the transport speed of the label roll paper 31 is changed by roll cutting. Incidentally, it is assumed that the toner image at this time is primarily transferred by feedback control based on the label pitch of the label roll paper 31 detected by the position detection sensor as in the above-described control method of the blank length G. .

  In this case, when the transport load is reduced by the cutting operation of the label roll paper 31 and the speed of the label passing through the secondary transfer nip portion 16 is increased, the apparent label length is short as shown in FIG. Become. In FIG. 13, 146a indicates the apparent label of the label in which the cutting operation has been performed during the secondary transfer, and 146b indicates the apparent label of the label to be secondarily transferred after the cutting operation. These labels have a reduced apparent length compared to the labels before cutting. Further, the position P1 indicates the cut timing of the label roll paper.

  This is equivalent to the label length being shorter than the toner image if the conveyance speed of the label roll paper 31 becomes faster on the basis of the speed of the intermediate transfer belt 12 to which the toner image is transferred. If the transport speed of the paper 31 changes slower than the transfer belt speed, it is equal to the label pitch becoming longer than the toner image.

  Therefore, when the label roll paper 31 is cut during secondary transfer, as shown in FIG. 13B, a difference is generated between the pitch of the toner image predicted and the pitch of the label to be transferred. It occurs.

  Next, a method of controlling the label image pitch of the present embodiment, which solves these problems, will be described below.

  Here, when the label 46 for transferring the toner image on the intermediate transfer belt 12 enters the secondary transfer nip portion 16, it is printed what conveyance load conditions (before cutting, during cutting, after cutting). The blank length G of the image is adjusted with reference to the label cycle information measured under the corresponding transport load condition, which is determined from the data length and the roll cut page. The details will be described below.

FIG. 10 is a timing chart for explaining the relationship among the cut timing, the image length P _IM , the cut status (before cutting, during cutting, after cutting) information, and the blank length G of the image.

  In order to perform control corresponding to load fluctuation at the time of cutting of the label roll paper 31, the following processes (1) to (4) are performed.

(1) Command / image processing unit 72, the print data received from the upper host PC 74, calculates the total image length .SIGMA.P _L of the connecting number N of pages to cut equation (12). In FIG. 10, a model in which the number of connected pages N is N = 7 is described as an example.
ΣP _L = N × P _{L 0} (12)
P _LO is a label image pitch obtained by adding a fixed initial value G ₀ [Line] of the blank length to the image of the image length P _IM [Line] as determined by the above equation (2).

(2) The distance L _CR2 from the total image length 2 PLo to the cutter 38 and the secondary transfer nip 16 is subtracted from the total image length PL PLo, and the distance L _C to the cut timing position is calculated by the following equation (12).
L _C = (ΣP _L ) − (L _CR2 ) (13)
The reason why the distance L _C to the cut timing position is set by the above equation is as follows.
The cut position of the label roll paper 31 is determined by the number N of connected pages, and here, the label is cut between the Nth sheet and the (N + 1) th sheet from the label of the leading end of the label roll paper 31 The page data is set to correspond to the last label of the cut label roll paper 31.

(3) The command / image processing unit 72 calculates the blank length G before developing the first print data into a bitmap. The blank length Go initially set is selectively used from the past label pitch measurement values stored in the non-volatile memory 78.

  Here, the label pitch measurement value stored in the non-volatile memory 78 will be described. During the printing operation, the engine control unit 71 constantly measures the label pitch based on the detection data from the second black mark detection sensor 56, and notifies the command / image processing unit 72 of the measurement result. At that time, it is a transport load condition at the time of measurement, that is, a measured value measured before the cutting by the cutter 38 is performed, or a measured value measured while the cutting by the cutter 38 is performed, further, the cutter The cut status information indicating whether it is a measured value measured after the cut by 38 is attached is attached.

  The command / image processing unit 72 measures the label pitch measurement value notified to the three storage areas of the non-volatile memory 78 based on the attached cut status information, ie, the label pitch before cut as the first storage area. The value storage area 79a, the in-cut label pitch measurement storage area 79b as a second storage area, and the post-cut label pitch measurement value storage area 79c as a third storage area are sequentially sorted and stored for each status.

  In each storage area, a plurality of past label pitch measurement values corresponding to each are stored. Here, it is assumed that the latest N label pitch measurement values are always stored by sequentially updating.

The command / image processing unit 72 takes out N label pitch measurement values from each of the label pitch measurement value storage areas 79a, 79b, 79c of the non-volatile memory 78 as necessary, and displays the following blanks from their average values. Calculate the length G. Here, the blank length G calculated from the label pitch measured value storage area 79a before cutting is
Let G = G _(NC) ,
The blank length G calculated from the label pitch measured value storage area 79b during cutting is
Let G = G _(TC) ,
The blank length G calculated from the label pitch measured value storage area 79c after cutting is
Let G = G _(AC) .

(4) First, the command / image processing unit 72 determines which cut status the label 46 to which the toner image of the first print page to be developed is transferred is at the time of secondary transfer.
If ΣP _L > L _C
Although the total image length PP _L of the print data is equal to or more than the distance L _C to the cut timing position, it is determined that the toner image of the first page is transferred to the first label 46 at the timing before cutting. In this case, the blank length G = G _(NC) is selected to generate image data.
That is, G (1) = G _(Nc) corresponding to the image length P _IM is added to the first label image pitch P _L1 .
P _L1 = P _IM + G _(Nc)
Expand the image with.

When there is image data of the next page, the command / image processing unit 72 calculates the blank length of the next page. Specifically, it is determined whether the cumulative image length up to the page to be developed next reaches the distance L _C to the cut timing position.
However, the label image pitch of the image data at the rear end to be determined is a length obtained by adding the initial value G ₀ of the blank length to the image length P _IM .
Therefore,
In the case of (P _L1 + P _L2 ) = (P _L1 + (P _IM + G ₀ ))> (L _C + P _IM (image length)), the image is transferred to the label leading to the secondary transfer nip 16 after cut timing,
If (L _C + P _IM )> (P _L1 + (P _IM + G ₀ ))> Lc, it is transferred to the label in the secondary transfer nip 16 during cutting,
If L _C > (P _L1 + P _L2 ) = (P _L1 + (P _IM + G ₀ )), it is determined that the image is transferred to the label reaching the secondary transfer nip 16 before cutting.

As described above, each time the image of one page is expanded, the accumulated image length up to that point is calculated, and it is determined whether or not the distance L _C to the cut timing position is reached. And based on that judgment,
When it is determined that the print data of the page to be transferred to the label before cutting is selected, the blank length G = G _(NC) is selected to generate the image data,
When it is determined that the print data of the page to be transferred to the label being cut, the blank length G = G _(TC) is selected to generate image data,
When it is determined that the print data of the page to be transferred to the label after cutting, that is, the print data after the image of the page being cut, the blank length G = G _(AC) is selected to generate image data.

In the example of the timing chart of FIG. 10, the accumulated image length up to four pages is shorter than the cut timing position. That is, P _L1 + P _L2 + P _L3 + P _L4 <L _C
Therefore, these image data are adjusted by the blank length G = G _(NC) .
However, here, P _L4 = P _IM + G ₀ .

When the image of the fifth page is accumulated, (L _C + P _IM )> P _L1 + P _L2 + P _L3 + P _L4 + P _L5 > L _C.
However, here, P _L5 = P _IM + G ₀ .
Therefore, the image data of the fifth page is adjusted with the blank length G = G _(TC) .
Further, since the sixth and seventh pages correspond to labels after cutting, these image data are adjusted by G = G _(AC) .

  As described above, the command / image processing unit 72 calculates the cumulative image length up to the cut timing for each one-page expansion, and adjusts the blank length G of the image that matches the transport condition, to obtain the before and after the cut. Thus, even if a speed change occurs in the sheet conveyance speed, the image position can be aligned on an average basis with respect to each label 46.

  Here, the label roll paper 31 is the second type of label roll paper 31 b having the black mark 43 (FIG. 4) attached on the back side, which is referred to as the first black mark detection sensor 37 and the second black mark Although an example of detection by the detection sensor 56 is shown, the label roll paper 31 is the first type of label roll paper 31 a of a type in which there is no label residue in the label gap between labels, and this is used as the first label gap detection sensor 36. The second label gap detection sensor 55 operates in exactly the same manner.

  As described above, according to the roll paper printer 10 of the present embodiment, the cumulative image length up to the distance Lc to the cut timing position is calculated for each one-page expansion, and the transfer load condition for the label to be transferred is Since the blank length G of the image is controlled with reference to the calculated transport load condition and the matched label pitch measurement value to calculate in advance whether it is transported to the secondary transfer nip portion, as before and after cutting Even if the transport speed of the label roll paper 31 changes, the image position can be aligned on each label 46 on average, so higher-level alignment can be realized.

  In the present embodiment, a roll paper printer has been described as an example of an image forming apparatus, but in addition to a printer, an image forming apparatus such as a copier, a fax machine or an MFP (Multi Function Peripheral) combining functions of these apparatuses Is also useful.

  10 Roll Paper Printer, 11 Photosensitive Drum, 12 Intermediate Transfer Belt, 13 Drive Roller, 14 Idle Roller, 15 Primary Transfer Roller, 16 Secondary Transfer Nip, 16a Secondary Transfer Roller, 16b Secondary Transfer Backup Roller, 18 Tension roller, 20 image forming unit, 21 charge roller, 22 LED head, 23 developer roller, 24 sponge roller, 25 developer blade, 26 toner tank, 27 cleaning blade, 31 label roll paper, 31a first type label roll paper , 31b second type label roll paper, 31 ′ roll, 33 paper feed roller, 34 pinch roller, 35 guide, 36 first label gap detection sensor, 37 first black mark detection sensor, 8 cutter, 41 light emitting unit, 42 light receiving unit, 43 black mark, 46 labels, 47 mounts, 48 labels, 51 first intermediate conveying roller, 52 second intermediate conveying roller, 53 first pinch roller, 54 second pinch roller, 55 second label gap detection sensor, 56 second black mark detection sensor, 57 light emitting unit, 58 light receiving unit, 59 paper feed sensor, 61 fixing device, 62 upper roller, 63 lower roller, 64 halogen lamp, 65 LED, 66 phototransistor , 67 LED, 68 phototransistor, 70 control unit, 71 engine control unit, 72 command / image processing unit, 73 interface unit, 74 host PC, 75 RAM, 76 RAM, 77 high voltage supply unit, 78 Volatile memory 79 label pitch measured value storage area 90 intermediate transfer belt unit.

Claims (5)

In an image forming apparatus for forming an image on a plurality of labels of a medium having a plurality of labels arranged at intervals on a backing sheet,
An image forming unit that forms a developer image based on image data;
An intermediate transfer member to which the developer image is primarily transferred;
Control means for controlling the formation timing of the developer image;
A secondary transfer unit that transfers the developer image of the intermediate transfer member to the label;
A medium transport means for transporting the medium along the transport path to the secondary transfer means, and an upstream side in the medium transport direction from the first detection means of the transport path, and the spacing of the plurality of labels of the medium is With a cutter to cut
A storage unit storing transfer load information to be provided to a medium upstream of the secondary transfer unit of the medium by cutting the medium by the cutter;
The control means has an image processing means for sequentially generating the image data in order to form the developer image corresponding to the plurality of labels.
The image forming apparatus, wherein the image processing unit sets an interval of the image data sequentially generated to the image data sequentially generated based on conveyance load information of the medium stored in the storage unit.   The transport load condition is that the label to which the developer image is secondarily transferred passes the secondary transfer position when the interval between the plurality of labels of the medium is cut by the cutter. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises three conditions: a second condition which is passing through the secondary transfer position, and a third condition which is not reached to the secondary transfer position. . Label position detection means, located upstream of the secondary transfer means in the medium transfer direction and upstream of the cutter in the medium transfer direction, for detecting the end of each of the plurality of labels of the medium being transferred;
The storage means has a first storage area, a second storage area, and a third storage area.
The control means measures a label pitch based on detection information of the label position detection means.
It is determined whether the measurement is performed at a first timing before cutting the medium, at a second timing during cutting, or at a third timing after cutting.
The label pitch measured at the first timing is stored in the first storage area, and the label pitch measured at the second timing is stored in the second storage area, and measured at the third timing. Storing the label pitch in the third storage area;
The image processing means sets an interval of the image data based on stored data of the first storage area when the generated image data is secondarily transferred to a label of the first condition, When the secondary transfer is performed to the label of the second condition, the interval of the image data is set based on the storage data of the second storage area, and when the secondary transfer is performed to the label of the third condition, 3. The image forming apparatus according to claim 2, wherein an interval of the image data is set based on stored data of the third storage area. The storage means sequentially updates stored data in the first storage area, the second storage area, and the third storage area, and stores label pitches for the latest predetermined number,
4. The image forming apparatus according to claim 3, wherein the image processing unit sets an interval of the image data based on average information of a predetermined number of label pitch stored in each storage area.   The control means determines the number N of connected pages corresponding to the number of labels to be transferred based on the print data input from the upper apparatus, and between the Nth label and the (N + 1) th label from the leading edge of the medium. The image forming apparatus according to any one of claims 1 to 4, wherein the medium is cut with

Images