JP2018054792A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus for performing transfer processing with an optimum transfer voltage even about a medium in which the thickness of the medium changes in a medium conveyance direction.SOLUTION: The invention relates to an image forming apparatus. The image forming apparatus includes developer image formation means for forming a developer image on an image carrier, transfer means for transferring the developer image formed on the image carrier to a medium, voltage application means for applying voltage to the transfer means, distribution information acquisition means for acquiring distribution information corresponding to a distribution of medium thicknesses, and voltage control means for controlling voltage applied by the voltage application means on the basis of the distribution information of the medium acquired by the distribution information acquisition means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus, and can be applied to, for example, a printer that forms an image on a folded recording medium such as an envelope by an electrophotographic method.

  Conventionally, some color image forming apparatuses such as electrophotographic color printers adopt a tandem system (a system in which a plurality of process units each including a photoconductor, a charging unit, an exposure unit, a development unit, and the like are arranged). In a color image forming apparatus employing a conventional tandem method, black (hereinafter also referred to as “K”), yellow (hereinafter also referred to as “Y”), magenta (hereinafter also referred to as “M”), and cyan (hereinafter also referred to as “M”). The four process units corresponding to the respective colors (toner colors) (hereinafter also referred to as “C”) are arranged, and the toner images are sequentially primary transferred onto the intermediate transfer belt. Further, a color image forming apparatus employing a conventional tandem method performs secondary transfer onto a sheet (medium) that has been fed in accordance with the position of a toner image that has been primarily transferred onto an intermediate transfer belt. It was.

  Some color image forming apparatuses adopting a conventional tandem method stably perform secondary transfer by changing the secondary transfer voltage for secondary transfer according to the width of the paper (Patent Document). 1).

JP 2014-106413 A

  However, in the case of using an envelope medium in which the thickness of the medium changes in the medium conveyance direction in a conventional intermediate transfer type image forming apparatus, it is possible to control the secondary transfer voltage to an optimum value in accordance with the changing envelope thickness. could not.

  Therefore, there is a demand for an image forming apparatus that can perform transfer processing with an optimal transfer voltage even on a medium whose thickness changes in the medium conveyance direction.

  The image forming apparatus of the present invention includes (1) developer image forming means for forming a developer image on an image carrier, and (2) transfer for transferring the developer image formed on the image carrier to a medium. Means, (3) voltage application means for applying a voltage to the transfer means, (4) distribution information acquisition means for acquiring distribution information in accordance with the thickness distribution of the medium, and (5) distribution information acquisition means. And voltage control means for controlling the voltage applied by the voltage application means based on the distribution information of the medium acquired by the above.

  According to the present invention, it is possible to provide an image forming apparatus that performs transfer processing with an optimal transfer voltage even on a medium whose thickness changes in the medium conveyance direction.

3 is a flowchart illustrating the operation of the printer according to the first embodiment. 1 is a schematic cross-sectional view of a printer according to a first embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the printer according to the first embodiment. It is explanatory drawing shown about the structural example (the 1) of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing shown about the structural example (the 2) of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing shown about the example of distribution of the thickness of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing (the 1) shown about the example of the thickness distribution information of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing (the 2) shown about the example of the thickness distribution information of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing shown about the structural example of the thickness distribution information of the envelope medium used with the printer which concerns on 1st Embodiment. It is explanatory drawing shown about the structural example of the secondary transfer voltage table which concerns on 1st Embodiment. It is explanatory drawing shown about the example of distribution of the correction value which concerns on 1st Embodiment. It is explanatory drawing shown about the structural example of the last secondary transfer voltage table which concerns on 1st Embodiment. It is explanatory drawing (the 1) shown about the structural example of the medium information setting screen displayed with the printer which concerns on 1st Embodiment. It is explanatory drawing (the 2) shown about the structural example of the medium information setting screen displayed with the printer which concerns on 1st Embodiment. It is the flowchart shown about operation | movement of the thickness distribution calculation part which concerns on 1st Embodiment. It is the block diagram shown about the structure of the control system of the printer which concerns on 2nd Embodiment. It is explanatory drawing shown about the example of a data structure of distribution information of the resistance value of the envelope medium hold | maintained with the printer which concerns on 2nd Embodiment.

(A) First Embodiment Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Hereinafter, an example in which the image forming apparatus of the present invention is applied to a printer will be described.

(A-1) Configuration of First Embodiment First, the main configuration of the printer 1 as an image forming apparatus according to the first embodiment will be described with reference to FIGS. 2 and 3. The printer 1 is an electrophotographic image forming apparatus capable of printing a toner image based on input print data on a medium.

  FIG. 2 is a schematic sectional view of the printer 1 of this embodiment. FIG. 3 is an explanatory diagram showing the configuration of the control system of the printer 1 of this embodiment.

  The printer 1 includes intermediate printing mechanisms 2K, 2Y, 2M, and 2C, which are four independent process units (developer image forming units) corresponding to four colors (black K, yellow Y, magenta M, and cyan C). The belt 12 is disposed along the conveyance direction. The printing mechanism 2K forms a toner image corresponding to each color of black, the printing mechanism 2Y is yellow, the printing mechanism 2M is magenta, and the printing mechanism 2C is cyan. Any of the printing mechanisms 2K, 2Y, 2M, and 2C has charging rollers 3K, 3Y, 3M, and 3C, and photosensitive drums 4K, 4Y, 4M, and the like that are uniformly charged by the charging rollers 3K, 3Y, 3M, and 3C. 4C, developing rollers 5K, 5Y, 5M, and 5C constituting a developing unit for forming a toner image, developing blades 6K, 6Y, 6M, and 6C, supply rollers 7K, 7Y, 7M, and 7C, and a photosensitive drum Discharging light sources 8K, 8Y, 8M, 8C for discharging the surface of 4Y, 4M, 4C, 4K, and toner cartridges 9K, 9Y, 9M, 9C for supplying toner as a developer to the developing unit. Yes.

  In the printer 1, LED heads 11 (11K, 11Y, 11M, 11C) corresponding to the printing mechanisms 2 (2K, 2Y, 2M, 2C) are arranged. The LED heads 11K, 11Y, 11M, and 11C cause the LED array to emit light corresponding to the image data signal. Among the color image signals, a black image signal is input to the LED head 11K. Similarly, a yellow image signal, a magenta image signal, and a cyan image signal are input to the LED heads 11Y, 11M, and 11C, respectively. . The LED heads 11K, 11Y, 11M, and 11C irradiate the surfaces of the respective photosensitive drums 4K, 4Y, 4M, and 4C with light based on the input image signals to form electrostatic latent images.

  The intermediate transfer belt 12 as an image carrier is an endless belt (for example, a high resistance semiconductive plastic film formed in a seamless endless shape), and includes a driving roller 13, a driven roller 14, and a secondary roller. The transfer counter roller 24 is stretched with a predetermined tension. The driving roller 13 is rotated by a belt motor 46 and conveys the intermediate transfer belt 12 in the direction of arrow e. The driven roller 14 and the secondary transfer counter roller 24 are rotated around the intermediate transfer belt 12.

  The intermediate transfer belt 12 is pressed against the photosensitive drums 4K, 4Y, 4M, and 4C by the primary transfer rollers 10K, 10Y, 10M, and 10C. The primary transfer rollers 10K, 10Y, 10M, and 10C are the intermediate transfer belt 12. Is in contact with the photosensitive drums 4K, 4Y, 4M, and 4C to form a primary transfer nip. A predetermined DC voltage is applied to the primary transfer rollers 10K, 10Y, 10M, and 10C by the primary transfer voltage generator 54, and the toner images on the photosensitive drums 4K, 4Y, 4M, and 4C are transferred onto the intermediate transfer belt 12. To do.

  A paper feeding mechanism 16 for supplying a medium (paper) to a conveyance path 15 (dotted line portion shown in FIG. 2) is provided at the lower part of the printer 1. This paper feed mechanism is configured to have a paper storage cassette 17, a hopping roller 18 that sends out a medium (paper) stored in the paper storage cassette 17, and when the medium is skewed (a state where the medium is obliquely fed is referred to as skew). A pinch roller 19 that corrects the skew of the medium, a registration roller 20 that sends the medium to the secondary transfer roller 23, a guide 21 that guides the medium to the secondary transfer roller 23, and a medium between the pinch roller 19 and the registration roller 20 A paper feed sensor 22 is provided for detecting the arrival.

  The secondary transfer roller 23 serving as a transfer unit can be made of, for example, a metal shaft and urethane foam having a volume resistivity of about 107 Ω · cm to 109 Ω · cm. Further, the secondary transfer counter roller 24 can be constituted by, for example, a metal shaft and a metal roller. The secondary transfer roller 23 is disposed to face the secondary transfer counter roller 24 with the intermediate transfer belt 12 therebetween. The metal shaft of the secondary transfer roller 23 is connected to the secondary transfer voltage generator 55 via a fixed resistor 56 for suppressing the occurrence of transfer failure due to the fluctuation of the resistance value in the circumferential direction of the secondary transfer roller 23. The metal shaft of the next transfer counter roller 24 is connected to the ground. The secondary transfer roller 23 rotates around the intermediate transfer belt 12.

  The intermediate transfer belt 12 is pressed against the secondary transfer counter roller 24 by the secondary transfer roller 23, and the secondary transfer roller 23 comes into contact with the secondary transfer counter roller 24 with the intermediate transfer belt 12 interposed therebetween, and the secondary transfer roller 23. A transfer nip portion 23a is formed. A predetermined DC voltage is applied to the secondary transfer roller 23 by the secondary transfer voltage generator 55 to transfer the toner image on the intermediate transfer belt 12 onto the medium.

  The medium that has passed through the secondary transfer roller 23 is separated from the intermediate transfer belt 12 and conveyed to a guide 27 that guides the medium to the fixing mechanism 29. A secondary transfer discharge sensor 28 is provided downstream of the secondary transfer roller 23 in the medium conveyance direction, and monitors the winding of the medium around the secondary transfer roller 23 and the failure of separation of the medium from the intermediate transfer belt 12. ing.

  The fixing mechanism 29 includes a heat roller 30 and a pressure roller 31 that presses the heat roller 30. The heat roller 30 is driven by a heater motor 49, and the pressure roller 31 rotates around the heat roller 30. The heat roller 30 incorporates a heater 32 composed of a halogen lamp that functions as a heat source. The fixing mechanism 29 is for heating and melting the toner on the medium and fixing the toner image on the medium. A thermistor 33 is disposed near the surface of the heat roller 30 to monitor the temperature of the heat roller 30.

  A fixing discharge sensor 34 is provided on the downstream side of the fixing mechanism 29 to monitor jamming of the fixing mechanism 29 and winding of the medium around the heat roller 30. A guide 36 for transporting the medium to the stacker 35 at the top of the housing of the printer 1 is provided on the downstream side of the fixing discharge sensor 34 in the medium transport direction, and the printed medium is discharged to the stacker 35. Further, in the guide 36, a transport roller 37, a transport roller 38, and a transport roller 39 for transporting the medium to the stacker 35 are provided. The conveyance roller 37, the conveyance roller 38, and the conveyance roller 39 are driven by a conveyance motor 48.

  On the downstream side of the intermediate transfer belt 12 with respect to the secondary transfer roller 23 in the conveyance direction, a cleaning blade 25 that removes residual secondary transfer toner that has not been transferred to the medium in the secondary transfer and remains on the intermediate transfer belt 12 is driven. It is arranged so as to face the roller 14. The cleaning blade 25 is made of a flexible rubber material or plastic material, and scrapes off the secondary transfer residual toner remaining on the intermediate transfer belt 12 to the waste toner tank 26.

  Next, the configuration of the control system of the printer 1 of this embodiment will be described with reference to FIG.

  The printer 1 includes a host interface unit 40, a command / image processing unit 41, an LED head interface unit 42, a mechanism control unit 43, a hopping motor 44, a registration motor 45 as a configuration related to the control system in addition to the configuration of FIG. , Belt motor 46, drum motor 47, transport motor 48, heater motor 49, high voltage controller 50, charging voltage generator 51, supply voltage generator 52, development voltage generator 53, primary transfer voltage generator 54, secondary A transfer voltage generator 55, a fixed resistor 56, a thickness distribution calculator 58, a memory 59, an operation panel 60, and a recording medium setting information detector 61 are provided.

  The host interface unit 40 is a part responsible for a physical hierarchy interface with a host computer (not shown) (for example, a PC used by a user). As the host interface unit 40, for example, various interfaces such as a LAN interface and a USB interface can be applied.

  The command / image processing unit 41 is a part that interprets commands and image data from the host side or develops them into a bitmap, and controls the entire printer 1.

  The LED head interface unit 42 processes the image data developed in the bitmap from the command / image processing unit 41 according to the interfaces of the LED heads 11K, 11Y, 11M, and 11C of the respective colors.

  The mechanism control unit 43 controls each part of the engine unit of the printer 1. Further, the mechanism control unit 43 refers to signals from the paper feed sensor 22, the secondary transfer discharge sensor 28, and the fixing discharge sensor 34 according to a command from the command / image processing unit 41, and a hopping motor 44, registration motor 45, drive control of the belt motor 46, drum motor 47, transport motor 48, and heater motor 49 is performed. Further, the mechanism control unit 43 refers to a signal from the thermistor 33 and performs temperature control of the heater 32 and high voltage output control to the high voltage control unit 50.

  The operation panel 60 serving as an input unit is a device that performs a user interface function. The operation panel 60 can receive information output to the user and input from the user. In the example of this embodiment, it is assumed that the operation panel 60 is configured using a touch panel display 64 that displays an operation screen and performs information output and information input (operation reception) to the user. The touch panel display 64 displays an operation screen and receives an input (operation) according to the control of the mechanism control unit 43.

  The memory 59 stores (stores) data and the like used when each component (for example, the mechanism control unit 43, the high-pressure control unit 50, etc.) that performs control processing operates. The memory 59 of this embodiment stores a secondary transfer voltage table 62, a final secondary transfer voltage table 63, and a recording medium thickness distribution table 66.

  The mechanism control unit 43 sets (inputs) information (hereinafter simply referred to as “medium information”) of the medium to be printed (image formation) in accordance with a user operation (for example, menu selection) (hereinafter referred to as “media information”). , Called “medium information setting screen”) on the touch panel display 64. In the medium information setting screen, the setting of medium information can be received from the user. The mechanism control unit 43 uses the medium information setting screen to acquire information for determining the shape of the medium (medium thickness distribution) as medium information.

  Hereinafter, the dimension of the medium in the direction along the transport direction on the transport path 15 is referred to as “length”, and the dimension in the direction orthogonal to the transport direction is also referred to as “width”.

  For example, the mechanism control unit 43 acquires information such as the type and size of the medium (the length and width of the medium) as medium information. In addition, the mechanism control unit 43 acquires information on specific items as medium information according to the type of medium. For example, if the medium is a normal medium (rectangular medium), the mechanism control unit 43 may acquire information on items of size and basis weight (or continuous weight) as medium information.

  Here, the structure of a general envelope medium will be described.

  Envelope media made in Japan have a fixed shape such as a long shape and a square shape, for example, a long shape 4 and a square shape 1. Specifically, Japanese envelope media can be broadly divided into regular envelopes and non-standard envelopes. The standard envelope includes long size 3, western shape length 3, long shape 4, western shape 2, western shape 3, western shape 4 and the like. In addition, the standard outer envelope includes square No. 1, square No. 2, square No. 1, and the like. In general, the dimensions of the fixed envelope and the fixed envelope are both set to predetermined dimensions.

  In addition, for Japanese-made envelope media, “Fold Center”, “Diamond Paste”, “Inner Comb Paste”, which are laminated in the center of the envelope media, are folded in the direction of conveyance. On the other hand, there is a folding method (folding type) such as “side bonding” in which bonding is performed on the edge side in the width direction.

  Below, it illustrates using a drawing about one part from the above-mentioned envelope media made in Japan.

  FIG. 4 is an explanatory diagram (schematic diagram) showing a configuration outline of an envelope medium made in Japan.

  FIG. 4 shows the configuration of the center-attached envelope medium M1. 4A shows the printing surface of the center-attached envelope medium M1, and FIG. 4B shows the back surface (the surface opposite to the printing surface) of the center-attached envelope medium M1.

  Usually, Japanese envelope media are printed such that the open flap portion is on the rear end side with respect to the envelope medium conveyance direction, as shown in FIG. FIG. 4 shows a state in which the flap portion M11 of the envelope medium M1 is arranged so as to be on the rear end side in the medium transport direction X.

  In addition, there is usually a Japanese envelope medium in which the back surface of the flap portion is processed to be glued. In other words, there are various types of envelope media, such as those in which glue is attached to the back surface of the flap, those in which a double-sided tape is applied, and those in which nothing is processed. A flap M12 of the envelope medium M1 shown in FIG.

  As described above, the general shape of Japanese-made envelope media is fixed. Next, the envelope medium made in Europe and America will be described.

  As an envelope medium made in Europe and America, there are various standards such as an announcement type and a baronial type in addition to the commercial flap type.

  Such envelope media made in Europe and America include sizes used in North America such as COM-10 size and A-6 size, and sizes used in Europe such as DL size and C-5 size. In the case of envelope media made in Europe and the United States, diamonds can be folded (a form in which bonding is performed by folding the four sides of the envelope medium at the center of the envelope medium) or side seams (both ends on the width direction in the conveying direction). Fold the flap and close the back end side).

  FIG. 5 is an explanatory diagram (schematic diagram) showing an outline of the configuration of an envelope medium made in the United States and Europe.

  FIG. 5 shows the configuration of an envelope medium M2 with a folding type of diamond. 5A shows the printing surface of the diamond-coated envelope medium M2, and FIG. 5B shows the back surface (the surface opposite to the printing surface) of the diamond-coated envelope medium M2.

  In general, as shown in FIG. 5, the envelope medium made in the US and Europe is printed such that the flap portion is folded and the flap portion side is the leading end side with respect to the conveyance direction of the envelope medium. FIG. 5B shows a state in which the flap portion M21 of the envelope medium M2 is folded and arranged so as to be on the leading end side in the medium transport direction X.

  As described above, the general shape of the envelope medium made in the United States and Europe is also determined.

  In addition, among the envelope media made in Japan and Europe and America, the materials that are generally used for the base paper material (basis weight or continuous amount of raw materials) are limited.

As a base paper for envelope media, general basis weights such as 75 [g / m ² ] and 85 [g / m ² ], thin 50 [g / m ² ], 60 [g / m ² ], thick 100 [g / m ² ] and 120 [g / m ² ] are used. In North America, paper having a basis weight (US continuous weight) such as 24 [1b], 28 [1b], or 32 [1b] is used as the envelope medium base paper.

  As described above, since the configuration of the envelope medium is generally limited to a de facto standard, the configuration of the envelope medium to be printed includes the type of envelope medium, how to fold, whether or not to paste, base paper It can be easily specified based on information on several items such as basis weight (medium information on items specific to envelope media).

  Therefore, when the medium is an envelope medium, the mechanism control unit 43 according to this embodiment uses the envelope medium type (envelope medium type 4 or type such as COM-10), envelope flap shape (envelope medium type 4 or COM-10) as medium information specific to the envelope medium. Information indicating the open / closed state of the flap being open or closed, and the state of the shape of whether it is V-shaped or straight), envelope flap size (dimension of the flap part of the envelope medium; the flap part extends from the envelope medium body) Existing dimensions: the difference between the dimensions when the flap part is opened and closed with the envelope medium), the envelope folding type (types of folding the envelope medium such as center bonding and diamond bonding), and envelope glue processing Presence / absence (information on the presence or absence of glue to close the flap of the envelope medium, presence or absence of tape, etc.), envelope medium base paper basis weight (basis weight of the base paper used for the envelope medium) It shall acquire the information items containing a ream weight). If the mechanism control unit 43 can recognize the thickness distribution of the medium (envelope medium) (at least the thickness distribution of the portion having the maximum thickness in the transport direction), the number of items of medium information to be acquired Is not limited. For example, when the configuration for each size of the envelope medium set in the printer 1 is limited, the mechanism control unit 43 may accept only the size information of the envelope medium as the medium information of the envelope medium.

  In other words, when the mechanism control unit 43 receives the setting of the medium information of the envelope medium, the information of some items is set as a fixed value, and only the information of the items that are not fixed (for example, only the envelope medium type). May be received and the medium information of all items may be held.

  As described above, the mechanism control unit 43 accepts input of medium information of a medium (a normal medium or an envelope medium).

  The recording medium setting information detection unit 61 detects and holds the medium information set on the medium information setting screen under the control of the mechanism control unit 43.

  The high voltage control unit 50 as a voltage control unit controls the charging voltage generation unit 51, the supply voltage generation unit 52, the development voltage generation unit 53, and the primary transfer voltage generation unit 54 in accordance with instructions from the mechanism control unit 43. Further, the high voltage control unit 50 controls the secondary transfer voltage generation unit 55 based on the calculation result of the thickness distribution calculation unit 58.

  The charging voltage generator 51 generates and stops charging voltages to the charging rollers 3K, 3Y, 3M, and 3C in accordance with instructions from the high-voltage controller 50.

  The supply voltage generation unit 52 generates and stops supply voltages to the supply rollers 7K, 7Y, 7M, and 7C in accordance with instructions from the high voltage control unit 50.

  The development voltage generation unit 53 generates and stops the development voltage to the development rollers 5K, 5Y, 5M, and 5C in accordance with instructions from the high voltage control unit 50.

  The primary transfer voltage generator 54 generates and stops primary transfer voltages to the primary transfer rollers 10K, 10Y, 10M, and 10C in accordance with instructions from the high voltage controller 50.

  The secondary transfer voltage generation unit 55 as a voltage application unit generates and stops the secondary transfer voltage to the secondary transfer roller 23 via the fixed resistor 56 in accordance with an instruction from the high voltage control unit 50.

  The secondary transfer voltage generation unit 55 performs control processing using data in the secondary transfer voltage table 62 and the final secondary transfer voltage table 63.

  The thickness distribution calculation unit 58 is based on the medium information held by the recording medium setting information detection unit 61 (medium information input using the operation panel 60), and the thickness distribution in the medium conveyance direction of the medium to be printed. A process for obtaining (the thickness distribution of the thickest portion in the width direction) is performed.

  The thickness distribution calculation unit 58 records data indicating the acquired thickness distribution in the medium transport direction of the medium to be printed in the recording medium thickness distribution table 66.

  FIG. 6 shows the distribution of thickness for each region of the envelope medium M2 made in the US and Europe shown in FIG.

  The medium information of the envelope medium M2 shown in FIG. 6 is “envelope medium size: # 10 (4.125 [inch] × 9.5 [inch]), envelope medium type: commercial COM-10, envelope flap shape: V-shaped Mold flap / closed state, envelope flap size: flap length 2 [inch], envelope fold type: diamond pasting, envelope glue processing presence / absence: pasting, envelope medium base paper basis weight: 24 [1b] (US ream) It has become. As shown in FIG. 6, the flap M21 of the envelope medium M2 is provided with a paste M22 in a band shape along the triangular shape at the tip of the flap M21.

  As shown in FIG. 6, the envelope medium M2 has a difference in thickness due to the overlap of the base paper and the glue. The thickness distribution calculation unit 58 clarifies the position and number of edges of the base paper by reading detailed envelope medium shape information. As shown in FIG. 6, in the envelope medium, the portion where the base paper is folded is in a state where two base papers are overlapped, but the portion that is folded and pasted is also the portion that overlaps three or four sheets, and the portion where the flap is glued In the position where the two overlap with each other, a difference in thickness such as three sheets of base paper overlap + glue, four sheets overlap + glue occurs.

  7 and 8 are explanatory views showing examples of the thickness distribution information of the envelope medium calculated (acquired) by the thickness distribution calculation unit 58. FIG.

  FIG. 7 shows the thickness distribution of the envelope medium M3 in which the folding type is center pasting, the flap shape is a straight flap, and the closed flap (straight flap) is glued. FIG. 8 shows the thickness distribution of an envelope medium M4 in which the folding type is diamond bonding, the flap shape is a V flap, and a closed flap portion (V flap) is provided with a seal (a glued seal).

  FIGS. 7A and 8A are explanatory diagrams (schematic diagrams) showing the configurations of the envelope media M3 and M4, respectively. FIGS. 7B and 8B are graphs showing the thickness distribution information of the envelope media M3 and M4, respectively. In the graphs of FIGS. 7B and 8B, the horizontal axis represents the position in the medium conveyance direction, and the vertical axis represents the thickness of the envelope medium (the thickness of the thickest portion in the width direction).

  As shown in FIG. 7, in the thickness distribution of the center medium and straight flap envelope medium M3, the thickness is the thickest at the flap portion M31 and the portion where the glue M32 overlaps at the flap portion. Further, as shown in FIG. 7, in the thickness distribution of the envelope medium M3, the folded portion M34 at the rear end is also thicker than the central portion M33. Further, as shown in FIG. 7, in the thickness distribution of the envelope medium M3, even in the central portion M33, the portion (center portion in the width direction) that is folded by center pasting is thick.

  As shown in FIG. 8, in the thickness distribution of the envelope medium M4 with diamond bonding and V flap, the overall thickness varies along the shape of the flap portion M41 (V flap). Further, as shown in FIG. 8, the thickness distribution of the envelope medium M4 is the thickest because the flap portion M41 (V flap) and the seal (including glue) M42 are folded at the central portion M43.

  The thickness distribution calculation unit 58, for example, includes medium information (information including the above-described envelope medium type, envelope medium size, envelope flap shape, envelope flap size, envelope folding type, presence / absence of envelope glue processing, and envelope medium base paper basis weight). As shown in FIGS. 7 and 8, if information on the shape and structure of the envelope medium specified based on the distribution (including the distribution of the portion where the base paper and glue are folded and the basis weight of the base paper) is held in advance, The thickness distribution of the envelope medium can be obtained. In other words, the thickness distribution calculation unit 58 calculates the thickness of the thickest portion in the width direction along the medium transport direction if the information on the shape of the medium to be printed and the thickness distribution information for each region can be specified based on the medium information. By doing so, thickness distribution information (for example, each numerical value of the graph shown in FIG. 7B or FIG. 8B) can be obtained.

  In addition, the thickness distribution calculation unit 58 does not necessarily need to obtain the thickness distribution by calculation, but stores the thickness distribution information for each combination of medium information, and acquires the thickness distribution information corresponding to the set medium information. Alternatively, a part of the thickness distribution information held in advance according to the medium information may be edited and acquired. For example, the thickness distribution calculation unit 58 holds the thickness distribution information of the envelope medium having an arbitrary shape and the presence / absence of the envelope glue processing being “no glue”, and if necessary, the area of the region to be glued to the thickness distribution information. The thickness may be added and acquired as thickness distribution information of the envelope medium with “gluing”. That is, in the thickness distribution calculation unit 58, thickness distribution information corresponding to a certain amount of medium information combination is held in advance, and when the held thickness distribution information cannot be used as it is, according to the difference medium information. By changing the distribution of the thickness distribution information (for example, changing the distribution according to the difference such as the presence / absence of envelope glue processing or the envelope flap shape), the thickness distribution information corresponding to the set medium information may be acquired. Good. This eliminates the need for the thickness distribution calculation unit 58 to hold the thickness distribution information corresponding to all combinations of medium information.

  When the medium type to be printed is a normal medium, the thickness is uniform, so that the thickness distribution calculation unit 58 can easily recognize the thickness distribution.

  FIG. 9 shows a configuration example of the thickness distribution information acquired by the thickness distribution calculation unit 58 and recorded in the recording medium thickness distribution table 66.

  As shown in FIG. 9, in the recording medium thickness distribution table 66, as thickness distribution information, each position (hereinafter referred to as “application position”) at a predetermined interval (m [mm] in the example of FIG. 9) in the medium transport direction. The data of the thickness of the medium is also recorded.

  In FIG. 9, the thickness of the applied position is 0 [mm] (tip position of the medium) is D0 [mm], and the applied position is m [mm] (position of m [mm] from the tip of the medium) is D1. The thickness of the application position is 2 m [mm] (position of 2 * m [mm] from the front end of the medium) is D2,..., The application position is n * m [mm] (n * m [mm] from the front end of the medium) The thickness of (position) is illustrated as Dn. In the following, it is assumed that n * m is a dimension not longer than the length Mw of the medium.

  As described above, in the first embodiment, a distribution information acquisition unit is realized by the mechanism control unit 43, the thickness distribution calculation unit 58, and the like.

  The mechanism control unit 43 also performs a calculation process (acquisition process) of the width (medium width) of the medium to be printed. For example, the mechanism control unit 43 may acquire the medium width by recognizing the shape of the medium to be printed based on the medium information, or actually feeds the medium onto the conveyance path 15 and recognizes it (conveyance). Recognition by each sensor on the path 15).

  The high voltage controller 50 applies the thickness distribution information (thickness distribution information recorded in the recording medium thickness distribution table 66) acquired by the mechanism controller 43 and the medium width to the secondary transfer voltage generator 55. The secondary transfer voltage is obtained.

  The high voltage controller 50 corrects the reference secondary transfer voltage Vm [V] according to the correction value α based on the thickness distribution information, and finally applies the secondary transfer to the secondary transfer voltage generator 55. Assume that the voltage Vtr [V] is obtained.

  In this embodiment, the reference secondary transfer voltage Vm is set by the secondary transfer voltage generation unit 55 in a setting state when a normal medium is printed and when there is no medium in the secondary transfer nip portion 23a. It is assumed that the secondary transfer voltage is applied to the secondary transfer roller 23.

  In the printer 1, the secondary transfer voltage Vm [V] is registered in the secondary transfer voltage table 62 of the memory 59.

  FIG. 10 shows a configuration example of the secondary transfer voltage table 62.

  In the secondary transfer voltage table 62 shown in FIG. 10, two secondary transfer voltages Vm1 and Vm2 are registered. The high voltage control unit 50 acquires the secondary transfer voltage Vm (Vm1 or Vm2 in this embodiment) from the secondary transfer voltage table 62 according to the setting (for example, printing speed or printing mode). The number of secondary transfer voltages Vm set in the secondary transfer voltage table 62 is not limited. Here, the secondary transfer voltage VM (VM1, VM2) registered in the secondary transfer voltage table 62 is adjusted to a voltage corresponding to the medium width of the medium to be printed before printing.

  The high voltage controller 50 determines a correction value α [V] for the secondary transfer voltage Vm according to the thickness distribution information.

  The high voltage control unit 50 sets a large correction value α for the thick application position. For example, the high-pressure control unit 50 is configured such that, at the application position where the flap part is opened and the thickness of only one base paper is reached, the correction value α is smaller than the application position of the thickness where the two base papers are stacked. A correction value α is calculated.

  For example, when the distribution of the correction value α is obtained based on the thickness distribution information shown in FIG. 9, the content is as shown in FIG.

  In FIG. 11, the correction value for the application position of 0 [mm] is α0 [V], the correction value for the application position is m [mm] is α1 [V], and the correction value for the application position is 2 m [mm] is α2 [V]. ],..., Αn [V] is a correction value of the application position n * m [mm].

  For example, for each application position, the high voltage control unit 50 may set a correction value α (that is, α = k * D) to a value obtained by multiplying the thickness D of the medium by a predetermined conversion coefficient k. For example, α0 = k * D0, α1 = k * D1, α2 = k * D2,..., Αn = k * Dn. Note that the conversion coefficient k needs to be set in advance by obtaining an appropriate value through experiments or the like.

  Then, the high voltage controller 50 obtains the final distribution of the secondary transfer voltage Vtr based on the distribution of the acquired correction value α (α0 to αn) and registers it in the final secondary transfer voltage table 63.

For example, the high voltage control unit 50 may obtain the distribution of the secondary transfer voltage Vtr (secondary transfer voltage Vtr for each application position) using the following formula (1) or (2). The following formula (1) is a calculation formula when Vm1 is applied as the secondary transfer voltage Vm that is the reference before correction, and the following formula (2) is the secondary transfer that is the reference before correction. This is a calculation formula when Vm2 is applied as the voltage Vm.
Vtr = Vm1 + α (1)
Vtr = Vm2 + α (2)

  FIG. 11 is an explanatory diagram showing a configuration example of data registered in the final secondary transfer voltage table 63.

  For example, when the distribution of the correction value α is obtained based on the distribution (α0 to αn) of the correction value α shown in FIG. 11, the content is as shown in FIG.

  In FIG. 12, the final secondary transfer voltage with an application position of 0 [mm] is Vtr — 0 [V], the final secondary transfer voltage with an application position of m [mm] is Vtr — 1 [V], and the application position is 2 m. The final secondary transfer voltage for [mm] is Vtr_2 [V],..., and the final secondary transfer voltage for the application position n * m [mm] is Vtr_n [V].

  Then, the high voltage controller 50 controls the secondary transfer voltage Vtr [V] for each applied position (controls the secondary transfer voltage generator 55) according to the content of the final secondary transfer voltage table 63.

(A-2) Operation of the First Embodiment Next, the operation of the printer 1 of the first embodiment having the above configuration will be described.

  First, a specific example of processing in which the mechanism control unit 43 accepts setting (input) of medium information from the user before printing is started by the printer 1 will be described.

  The mechanism control unit 43 displays a medium information input screen on the touch panel display 64 of the operation panel 60 according to the user's operation, and accepts the setting of the medium information from the user. The menu configuration until the mechanism control unit 43 displays the medium information setting screen on the touch panel display 64 is not limited, and a description thereof is omitted here.

  FIG. 13 and FIG. 14 are explanatory diagrams showing configuration examples of the medium information setting screen.

  In the medium information setting screen shown in FIGS. 13 and 14, a field F10 in which a medium type (“normal medium” or “envelope medium”) can be selected by radio buttons and medium information items specific to the medium type are input. A field F20 capable of (selective input) is arranged.

  FIG. 13 shows a state where the envelope medium is selected as the medium type of the field F20, and FIG. 14 shows a state where the normal medium is selected as the medium type of the field F20.

  As shown in FIG. 13, in the medium information setting screen, as the medium information items specific to the envelope medium, the envelope medium type, the envelope medium size, the envelope flap shape, the envelope flap size, the envelope folding type, the presence or absence of the envelope glue processing, and the envelope The basis weight of the medium base paper can be set.

  As shown in FIG. 14, on the medium information setting screen, the medium size (for example, A3, A4, A5, etc.) and the medium basis weight can be set as items of medium information of the normal medium.

  Furthermore, each item that can be set in the field F20 may be input by a soft keyboard (not shown) or the like, and a user can present a value that can be set by an object such as a combo box (list box). You may make it accept selection from.

  As described above, the mechanism control unit 43 receives a medium information setting from the user using the medium information setting screen (touch panel display 64). The recording medium setting information detection unit 61 holds the received medium information.

  Next, an operation when the printer 1 performs print processing on a medium will be described.

  When the printer 1 receives image data (print data) sent from an external device (not shown) (for example, a host computer not shown), the command / image processing unit 41 causes the mechanism control unit 43 to start warming up the fixing mechanism 29. In addition, the image data is developed and bitmap data for each page is generated corresponding to each color.

  Upon receiving the warm-up start instruction from the command / image processing unit 41, the mechanism control unit 43 controls the heater motor 49, drives the heat roller 30, and turns on / off the heater 32 while watching the signal from the thermistor 33. Control and adjust the fixing temperature. The mechanism control unit 43 starts the printing operation when the fixing temperature reaches a temperature at which the toner image on the medium set in advance can be fixed.

  The mechanism control unit 43 controls the belt motor 46 and the drum motor 47 to drive the driving roller 13 and the rollers of the printing mechanisms 2K, 2Y, 2M, and 2C.

  Upon receiving the high voltage output instruction from the mechanism control unit 43, the high voltage control unit 50 reads the set values of the charging voltage, the supply voltage, and the developing voltage stored in the memory 59, and the charging voltage generation unit 51 and the supply voltage generation unit 52 are read out. Then, a high voltage bias is supplied from the development voltage generator 53 to each roller of the printing mechanisms 2K, 2Y, 2M, and 2C.

  Here, a toner image forming operation in the printing mechanisms 2K, 2Y, 2M, and 2C will be described. Here, the black printing mechanism 2K will be described as a representative. Since yellow, magenta, and cyan are the same as black, redundant description is omitted.

  When each high-voltage bias is supplied by the high-voltage controller 50, a charging voltage of -1100V is supplied to the charging roller 3K, and the surface of the photosensitive drum 4K is charged to about -600V. Further, a developing voltage of −200 V is supplied to the developing roller 5K, and a supply voltage of −250V is supplied to the supply roller 7K. Is formed.

  The toner cartridge 9K of the printing mechanism 2K contains black toner, and the toner supplied from the toner cartridge 9K is rubbed strongly against the developing roller 5K and the supply roller 7K and is frictionally charged. In this embodiment, it is assumed that the toner is frictionally charged to a negative polarity due to the characteristics of the developing rollers 5K, 5Y, 5M, and 5C and the supply rollers 7K, 7Y, 7M, and 7C.

  The toner that is frictionally charged to the negative polarity adheres on the developing roller 5K by the Coulomb force received from the electric field directed from the developing roller 5K to the supplying roller 7K in the vicinity of the contact area between the developing roller 5K and the supplying roller 7K. The adhering toner is carried to the contact portion between the developing roller 5K and the developing blade 6K as the developing roller 5K rotates, and is made uniform by the developing blade 6K to form a toner layer. The developing roller 5K continues to rotate and conveys the toner layer to the nip portion with the photosensitive drum 4K.

  On the other hand, the command / image processing unit 41 transmits bitmap data for each page to the LED head interface unit 42. The LED head interface unit 42 blinks the LED of the LED head 11K corresponding to the transmitted bitmap data, exposes the photosensitive drum 4K charged to −600 V, discharges it to −50 V, and generates an electrostatic latent image. Write.

  As the photosensitive drum 4K rotates, the electrostatic latent image written on the surface of the photosensitive drum 4K reaches a contact area with the developing roller 5K. Between the developing roller 5K and the photosensitive drum 4K, the electric field in the direction from the photosensitive drum 4K to the developing roller 5K is negative in the exposed portion where the charge is discharged to -50V, and the reverse electric field is in the non-exposed portion where the charge is not removed. Therefore, the toner selectively adheres only to the exposed portion from the negatively charged toner layer on the developing roller 5K, and the electrostatic latent image is developed as a toner image.

  The mechanism controller 43 instructs the high-voltage controller 50 to generate a primary transfer voltage in accordance with the timing at which the toner images developed on the photosensitive drums 4K, 4Y, 4M, and 4C sequentially reach the primary transfer nips. put out. The high voltage controller 50 reads the set value of the primary transfer voltage stored in the memory 59 and supplies the primary transfer voltage from the primary transfer voltage generator 54 to the primary transfer rollers 10K, 10Y, 10M, and 10C. . In this embodiment, the primary transfer voltage is + 1500V. At this time, an electric field in the direction from the primary transfer rollers 10K, 10Y, 10M, and 10C toward the photosensitive drums 4K, 4Y, 4M, and 4C is formed in the primary transfer nip portion, and the photosensitive drums 4K, 4Y, 4M, and 4C are formed. The negatively developed toner image is primarily transferred onto the intermediate transfer belt 12.

  The mechanism control unit 43 drives the hopping motor 44 and rotates the hopping roller 18 before the toner image primarily transferred onto the intermediate transfer belt 12 reaches the secondary transfer nip portion 23a, and the sheet storage cassette 17 Is fed between the pinch roller 19 and the registration roller 20. The mechanism control unit 43 monitors the output of the paper feed sensor 22 and stops the hopping motor 44 when detecting that the leading edge of the medium has reached between the pinch roller 19 and the registration roller 20.

  Further, the mechanism control unit 43 drives the registration motor 45 in accordance with the timing at which the toner image primarily transferred onto the intermediate transfer belt 12 reaches the secondary transfer nip portion 23a, and the pinch roller 19 and the registration roller 20 are driven. The medium in between is conveyed to the guide 21. The medium is guided by the guide 21 and reaches the secondary transfer nip portion 23a.

  At the same time, the mechanism control unit 43 instructs the high voltage control unit 50 to generate a secondary transfer voltage in accordance with the timing at which the toner image primarily transferred onto the intermediate transfer belt 12 reaches the secondary transfer nip portion 23a. The secondary transfer voltage is supplied from the secondary transfer voltage generator 55 to the secondary transfer roller 23. At this time, an electric field in the direction from the secondary transfer roller 23 to the secondary transfer counter roller 24 is formed in the secondary transfer nip portion 23a, and the negative polarity toner image primarily transferred onto the intermediate transfer belt 12 is a medium. Secondary transferred on top.

  In this embodiment, the time from when the printer 1 receives image data sent from the host computer until the toner image primarily transferred onto the intermediate transfer belt 12 reaches the secondary transfer nip portion 23a. However, the calculation timing of the secondary transfer voltage Vtr is not limited to this, and at least the intermediate transfer belt 12 and the secondary transfer roller 23 are driven and It is sufficient if there is no medium in the secondary transfer nip portion 23a.

  The mechanism control unit 43 monitors the winding of the medium around the secondary transfer roller 23 and the failure of separation of the medium from the intermediate transfer belt 12 by the secondary transfer discharge sensor 28, and transfers the medium after the transfer process to the fixing mechanism 29. And transport. When the medium reaches the fixing mechanism 29, the toner is nipped and conveyed by the heat roller 30 that has already reached the fixing temperature and the pressure roller 31 that is in pressure contact with the heat roller 30, and the toner on the medium is heated and melted. Is fixed to the medium.

  The mechanism control unit 43 drives the conveyance motor 48 to rotate the conveyance roller 37, the conveyance roller 38, and the conveyance roller 39 before the medium after the fixing process reaches the guide 36.

  The mechanism control unit 43 monitors the jam of the fixing mechanism 29 and the wrapping of the medium around the heat roller 30 by the fixing discharge sensor 34, and the medium after the fixing process is transferred to the conveying roller 37, the conveying roller 38, and the conveying roller 39. To the stacker 35.

  Simultaneously with the fixing step, the secondary transfer residual toner remaining on the intermediate transfer belt 12 is scraped off to the waste toner tank 26 by the cleaning blade 25.

  When all the steps are completed, the mechanism control unit 43 stops the belt motor 46, the drum motor 47, and the conveyance motor 48, and simultaneously issues an instruction to the high voltage control unit 50, and the charging voltage generation unit 51, the supply voltage generation unit 52, the supply of the high-voltage bias from the developing voltage generator 53 to the rollers of the printing mechanisms 2K, 2Y, 2M, 2C, and 2W is stopped. In addition, the mechanism control unit 43 stops the heater motor 49 and the heater 32 and completes the printing operation.

  Next, a process in which the high voltage controller 50 calculates the secondary transfer voltage Vtr will be described with reference to the flowchart of FIG.

  When the printer 1 receives print data (image data) sent from a host computer (not shown), the high voltage control unit 50 starts calculating the secondary transfer voltage Vtr (S101).

  Next, the high voltage controller 50 reads the secondary transfer voltage Vm (here, Vm1 or Vm2) stored in the memory 59 (S102).

  Next, the thickness distribution calculation unit 58 calculates (acquires) the thickness distribution information of the medium to be printed based on the medium information held by the recording medium setting information detection unit 61. Then, the thickness distribution calculation unit 58 records the acquired thickness distribution information in the recording medium thickness distribution table 66 (S103).

  Next, the high voltage controller 50 obtains the final secondary transfer voltage Vtr (distribution of the secondary transfer voltage Vtr for each applied position) from the calculation results of Steps S102 and S103, and performs the final secondary transfer. It records in the voltage table 63 (S104).

  In this embodiment, the medium width is calculated in advance before the printing operation, and the predetermined secondary transfer voltage setting based on the medium width is included in the secondary transfer voltage Vm [V] in step S102. To do. This is performed before the user transmits image data from the host computer after the user finishes storing the medium in the paper storage cassette 17. The medium width calculation operation is the same as the printing operation except that a toner image is not formed (same as blank paper printing where nothing is printed) and the fixing temperature is not adjusted (heater 32 remains off).

  As described above, the high-voltage controller 50 determines the correction value α (α0 to αn) based on the calculated thickness distribution information, and calculates the final secondary transfer voltage Vtr (Vtr_0 to Vtr_n). The high voltage controller 50 supplies the medium from the secondary transfer voltage generator 55 to the secondary transfer roller 23 in accordance with the timing at which the medium reaches the secondary transfer nip 23a. Using the secondary transfer voltage Vtr calculated so as to be suitable for the medium as described above, the high voltage control unit 50 applies a voltage to the medium in the secondary transfer to perform the transfer.

  As described above, the mechanism control unit 43 performs the secondary transfer to the high-pressure control unit 50 in accordance with the timing at which the medium and the toner image primarily transferred onto the intermediate transfer belt 12 reach the secondary transfer nip portion 23a. A voltage generation instruction is issued, and a secondary transfer voltage Vtr (Vtr_1 to Vtr_n) is supplied from the secondary transfer voltage generator 55 to the secondary transfer roller 23. In this embodiment, the high voltage control unit 50 performs control to sequentially switch the secondary transfer voltage Vtr (Vtr_1 to Vtr_n) calculated in step S104 at every interval m in accordance with the conveyance of the medium.

  FIG. 15 is a flowchart showing details of the medium (envelope medium) thickness distribution calculation process performed by the thickness distribution calculation unit 58 in step S103 described above.

  The thickness distribution calculation unit 58 starts calculation (acquisition) of thickness distribution information based on the medium information input by the operation panel 60 and held by the recording medium setting information detection unit 61 (S201).

  First, the thickness distribution calculation unit 58 reads the envelope medium size from the medium information (S202).

  Next, the thickness distribution calculation unit 58 reads the envelope medium type (envelope medium type No. 4 or COM-10) from the medium information (S203).

  Next, the thickness distribution calculation unit 58 reads an envelope flap shape (information indicating an open / close state such as the flap being opened or closed, or a shape state such as a V shape or a straight shape) from the medium information. (S204).

  Next, the thickness distribution calculator 58 reads the envelope flap size (the length of the flap) from the medium information (S205).

  Next, the thickness distribution calculation unit 58 reads the envelope folding type (the type of envelope medium folding method such as center pasting or diamond pasting) from the medium information (S206).

  Next, the thickness distribution calculation unit 58 reads the presence / absence of envelope glue processing (information such as the presence / absence of glue for closing the flap of the envelope medium and the presence / absence of tape) from the medium information (S207).

  Next, the thickness distribution calculation unit 58 reads the envelope medium base paper basis weight (basis weight or continuous amount of the base paper used for the envelope medium) from the medium information (S208).

  The thickness distribution calculation unit 58 calculates (acquires) the distribution information of the thickness of the envelope medium to be printed based on the medium information as described above and registers it in the recording medium thickness distribution table 66 (S209). The information calculation process is terminated.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  In the printer 1 of the first embodiment, even when an envelope medium whose thickness changes in the medium conveyance direction is used, it can be controlled with an optimal secondary transfer voltage in accordance with the changing thickness of the medium. . That is, in the printer 1 of the first embodiment, the print quality can be maintained regardless of the change in the thickness of the medium.

(B) Second Embodiment Hereinafter, a second embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Hereinafter, an example in which the image forming apparatus of the present invention is applied to a printer will be described.

(B-1) Configuration and Operation of Second Embodiment FIG. 16 is a block diagram showing the configuration of the control system of the printer 1A according to the second embodiment, and is the same as or corresponding to FIG. Are given the same or corresponding symbols.

  Hereinafter, differences of the second embodiment from the first embodiment will be described.

  In the printer 1A of the second embodiment, configurations for processing medium information and thickness distribution information (thickness distribution calculation unit 58, recording medium setting information detection unit 61, etc.) are excluded. In the printer 1A of the second embodiment, the mechanism control unit 43 and the high-pressure control unit 50 are replaced with a mechanism control unit 43A and a high-pressure control unit 50A.

  In the printer 1 of the first embodiment, the thickness distribution information of the medium (envelope medium) is acquired based on the medium information, and the correction value α of the secondary transfer voltage is held based on the thickness distribution information.

  On the other hand, in the printer 1A (mechanism control unit 43A, high-pressure control unit 50A) of the second embodiment, a medium (envelope medium) is once passed through the secondary transfer nip portion 23a to obtain a secondary transfer voltage (for example, A secondary transfer voltage Vm) is applied. In the printer 1A (mechanism control unit 43A, high voltage control unit 50A) of the second embodiment, the resistance value R for each application position is measured (for example, the current value when a constant voltage is applied is measured to determine the resistance value). The correction value α for each application position may be acquired based on the acquired resistance value R for each application position.

  The resistance value R increases at an application position where the medium mass is large (application position where the medium is thick), and the resistance value R decreases at an application position where the medium mass is low (application position where the medium is thick). Therefore, the distribution of the resistance value R has a correlation with the thickness distribution of the medium according to the first embodiment. That is, it can be said that the distribution of the resistance value R is a kind of information corresponding to the distribution of the thickness of the medium (hereinafter also referred to as “distribution information”). Note that the “thickness distribution information” in the first embodiment is also a kind of the above-described distribution information.

  As described above, in the second embodiment, the mechanism control unit 43A, the high voltage control unit 50A, and the resistance value means for measuring the resistance value R of the envelope medium (secondary transfer voltage generation unit 55, secondary transfer roller 23, etc. ) And the like to realize distribution information acquisition means.

  The mechanism control unit 43A and the high-pressure control unit 50A, for example, after the user finishes storing the medium in the paper storage cassette 17, before the user transmits print data (image data) from a host computer (not shown), The distribution of the resistance value R of the medium (envelope medium) is inspected. The mechanism control unit 43A and the high-pressure control unit 50A, for example, feed the medium (envelope medium) of the sheet storage cassette 17 onto the conveyance path 15, pass the secondary transfer nip 23a, and pass a predetermined secondary transfer voltage ( For example, the distribution of the resistance value R for each applied position in the medium conveyance direction may be inspected by applying Vm) set in the secondary transfer voltage table 62 and measuring the current value at that time.

  FIG. 17 is an explanatory diagram showing a configuration example of information indicating the distribution of the resistance value R in the medium (envelope medium).

  As illustrated in FIG. 17, the mechanism control unit 43A and the high-voltage control unit 50A acquire data on the resistance value R of the medium for each application position (for each interval m [mm]).

  In FIG. 17, the resistance value when the application position is 0 [mm] is R0 [mm], the resistance value when the application position is m [mm] is R1, the resistance value when the application position is 2 m [mm] is R2,. Represents the resistance value of n * m [mm] as Rn.

  Then, the high voltage controller 50A determines the correction value α [V] for the secondary transfer voltage Vm according to the distribution of the resistance value R for each application position.

  The high voltage control unit 50 sets a large correction value α for the application position where the resistance value R is large.

  For example, the high voltage control unit 50A may set a correction value α (that is, α = q * R) by multiplying the resistance value R of the medium by a predetermined conversion coefficient q for each application position. For example, α0 = q * D0, α1 = q * D1, α2 = q * D2,..., Αn = q * Dn. Note that the conversion coefficient q needs to be set in advance by obtaining an appropriate value through experiments or the like.

  Then, the high voltage controller 50A obtains the final distribution of the secondary transfer voltage Vtr based on the acquired distribution of the correction value α (α0 to αn) and registers it in the final secondary transfer voltage table 63.

  Since the configuration and operation of the other printer 1A (mechanism control unit 43A and high-pressure control unit 50A) are the same as those in the first embodiment, detailed description thereof is omitted.

(B-2) Effects of Second Embodiment According to the second embodiment, the following effects can be achieved.

  In the printer 1A of the second embodiment, similarly to the first embodiment, even when an envelope medium whose thickness changes in the medium conveyance direction is used, the thickness of the medium (resistance corresponding to the thickness changes). Value) and an optimal secondary transfer voltage can be controlled. That is, in the printer 1A of the second embodiment, the print quality can be maintained regardless of the change in the thickness of the medium, as in the first embodiment.

  In the first embodiment, the thickness distribution information is generated by extracting the thickest portion in the width direction of the medium. However, the resistance value R acquired by the printer 1A of the second embodiment is the medium R Since it becomes a value that takes into account all thicknesses in the width direction for each application position in the transport direction, it is possible to generate a secondary transfer voltage Vtr that is more suitable (higher accuracy) than in the first embodiment. For example, in the method of acquiring the thickness distribution of the first embodiment, even when the portion is folded in the width direction only (for example, the central portion M33 of the medium M3 shown in FIG. 7), the thickness is folded in the whole width direction. However, although the acquired thickness is the same (thickness of the thickest portion), in the second embodiment, since the entire resistance value R in the width direction of the medium is acquired in an integrated manner, the overlapping width is obtained. Accordingly, the secondary transfer voltage varies.

(C) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

  (C-1) In each of the above embodiments, it is assumed that plain paper is used as the base paper used for the envelope medium. However, the base paper of the envelope medium is not limited to plain paper, and is cardboard, fine paper, recycled paper, glossy Options such as paper may be increased as necessary. That is, an item of the envelope medium base paper type (envelope medium base paper type) as well as the envelope medium base paper basis weight may be added as the medium information of the envelope medium.

  (C-2) In the printers of the above embodiments, the example in which the input of medium information is received using the operation panel 60 has been described. However, the present invention is not limited to this, and image data that the user wants to print is transmitted to the printer 1. It may be settable when That is, in the printer of each of the above embodiments, the medium information may be acquired as part of image data (print data) received by the host interface unit 40, or an external device (for example, for example, The medium information may be acquired from a control signal supplied from a driver of a host computer (not shown) used by the user.

  (C-3) In each of the above embodiments, an example in which the image forming apparatus of the present invention is applied to a printer has been described. However, the image forming apparatus of the present invention is not limited to a printer, and is a multifunction peripheral (MFP that can handle envelope media). : Multifunction Printer), and other image forming apparatuses such as a copying machine.

  (C-4) In the printer of each of the above embodiments, the intermediate transfer belt 12 is used. However, a method of directly transferring a toner image (developer image) onto a medium using a photosensitive drum as an image carrier. It is good. In this case, the transfer voltage adjusted based on the distribution information (thickness distribution information, distribution information of the resistance value R) is a transfer voltage applied to the transfer member (transfer roller) facing the photosensitive drum.

  In the printers of the above-described embodiments, the example of the color printer including a plurality of process units has been described. However, the printer may be configured as a monochrome printer including only one process unit.

  DESCRIPTION OF SYMBOLS 1 ... Printer 2, 2C, 2K, 2M, 2Y ... Printing mechanism 3, 3C, 3K, 3M, 3Y ... Charging roller 4, 4C, 4K, 4M, 4Y ... Photosensitive drum 5, 5C, 5K, 5M 5Y: Developing roller, 6, 6C, 6K, 6M, 6Y ... Developing blade, 7, 7C, 7K, 7M, 7Y ... Supply roller, 8, 8C, 8K, 8M, 8Y ... Static elimination light source, 9, 9C, 9K , 9M, 9Y ... toner cartridge, 10, 10C, 10K, 10M, 10Y ... primary transfer roller, 11, 11C, 11K, 11M, 11Y ... LED head, 12 ... intermediate transfer belt, 13 ... drive roller, 14 ... driven Roller, 15 ... Conveying path, 16 ... Feeding mechanism, 17 ... Paper storage cassette, 18 ... Hopping roller, 19 ... Pinch roller, 20 ... Registration roller, 21 ... Guide, 22 ... Feed sensor, 23 ... Secondary Copy roller, 23a ... secondary transfer nip, 24 ... secondary transfer counter roller, 25 ... cleaning blade, 26 ... waste toner tank, 27 ... guide, 28 ... secondary transfer discharge sensor, 29 ... fixing mechanism, 30 ... heat Roller, 31 ... Pressure roller, 32 ... Heater, 33 ... Thermistor, 34 ... Fixing discharge sensor, 35 ... Stacker, 36 ... Guide, 37, 38, 39 ... Conveying roller, 40 ... Host interface unit, 41 ... Image processing unit 42 ... LED head interface unit, 43 ... mechanism control unit, 43A ... mechanism control unit, 44 ... hopping motor, 45 ... registration motor, 46 ... belt motor, 47 ... drum motor, 48 ... transport motor, 49 ... heater motor, DESCRIPTION OF SYMBOLS 50 ... High voltage control part, 50A ... High voltage control part, 51 ... Charging voltage generation part, 52 ... Supply voltage generation part, 53 ... Development voltage generation 54, primary transfer voltage generation unit, 55 ... secondary transfer voltage generation unit, 56 ... fixed resistance, 58 ... thickness distribution calculation unit, 59 ... memory, 60 ... operation panel, 61 ... recording medium setting information detection unit, 62 ... Secondary transfer voltage table, 63 ... Final secondary transfer voltage table, 64 ... Touch panel display, 66 ... Recording medium thickness distribution table.

Claims (8)

Developer image forming means for forming a developer image on the image carrier;
Transfer means for transferring the developer image formed on the image carrier to a medium;
Voltage application means for applying a voltage to the transfer means;
Distribution information acquisition means for acquiring distribution information according to the distribution of thickness of the medium;
An image forming apparatus comprising: a voltage control unit that controls a voltage applied by the voltage application unit based on the distribution information of the medium acquired by the distribution information acquisition unit. Medium information holding means for holding medium information of the medium;
2. The image formation according to claim 1, wherein the distribution information acquisition unit acquires information indicating a thickness distribution of the medium as distribution information based on the medium information held by the medium information holding unit. apparatus. An input means for receiving information input;
The image forming apparatus according to claim 2, wherein the medium information holding unit receives and holds information input of each item constituting the medium information using the input unit.   The image forming apparatus according to claim 3, wherein the medium information holding unit holds unique information corresponding to a type of the medium with respect to the medium information.   When the medium is an envelope medium, the distribution information acquisition means includes, as information specific to the envelope medium, an envelope medium type, an envelope medium size, an envelope flap shape, an envelope flap size, an envelope folding type, an envelope glue processing presence / absence, and an envelope The image forming apparatus according to claim 4, wherein information including a basis weight of the medium base paper is held.   The image forming apparatus according to claim 1, wherein the distribution information acquisition unit acquires a distribution of resistance values of the medium as distribution information. A resistance value measuring means for measuring a distribution of resistance values of the medium;
The image forming apparatus according to claim 6, wherein the distribution information acquisition unit acquires a distribution of resistance values of the medium based on a measurement result of the resistance value measurement unit.   The image forming apparatus according to claim 1, wherein the distribution information acquisition unit acquires the distribution information of the medium before an image forming process operation of the image forming apparatus.

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