JP5489888B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multifunction machine that integrates these functions. More specifically, the present invention relates to an image forming apparatus such as an electrophotographic system provided with a transfer conveying member for carrying and transferring a transfer material to an image transfer unit.

  Patent Documents 1 and 2 are typical examples of conventional image forming apparatuses in which a density detection toner pattern directly transferred to a transfer conveyance member is read by a density detection sensor and image correction control is performed.

  Patent Document 1 discloses a technique in which a density detection pattern is secondarily transferred to a transfer roller instead of a sheet, and the density of the density detection pattern is detected by a density detection sensor. The transfer roller uses white whiskers as the conductivity-imparting agent, and the color of the transfer roller itself is white, so that it is possible to simply detect the image density. Further, by measuring the image density after the secondary transfer, it is possible to detect a density closer to the actual image (image on the paper).

  Further, Patent Document 2 discloses an example of a color image forming apparatus including an intermediate transfer member that can perform image density control in a state similar to that performed on a transfer material. In this technique, a density pattern is formed on a secondary transfer conveyance belt of a color image forming apparatus, and the density can be controlled by reading the pattern with a density detection sensor.

Japanese Patent Laid-Open No. 08-044122 Japanese Patent Laid-Open No. 11-194578

  The following techniques are known as image control techniques for suppressing density fluctuations in a short time in recent image forming apparatuses. That is, a toner pattern for image adjustment in parallel with the image pattern outside of the transfer material in the image forming main scanning direction of the transfer material belt in the image forming main scanning direction of the transfer material in the image forming main scanning direction of the transfer material. (Toner patch) is formed. In this technique, the toner patch is read by a patch detection sensor, and image correction and alignment image control are performed.

  However, in the examples of Patent Documents 1 and 2, a toner patch is formed in parallel with the image pattern outside the transfer material conveyance area in the image forming main scanning direction of the transfer conveyance member that carries and conveys the transfer material. The following points were pointed out when the image control technology was implemented. In other words, the transfer efficiency of the toner patch onto the transfer / conveying member may change due to the effect that the transfer voltage setting value differs depending on the paper type (transfer material type). As a result, it is difficult to perform accurate image correction and aligned image control.

  The present invention has been made in view of the above-described circumstances, and performs image correction and alignment image control with high accuracy even if the transfer efficiency of the toner patch onto the transfer / conveying member changes for each paper type. It is to provide an image forming apparatus capable of performing the above.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image carrier on which a toner image is formed, a transfer material, and the image carrier to the transfer material. An image forming apparatus having a transfer conveying member that conveys the toner image to a transfer unit, wherein an image adjustment toner pattern is formed in the main scanning direction of the image carrier in parallel with the formation of the toner image. The image is formed outside the transfer material conveyance area at the transfer portion, transferred at the transfer portion outside the transfer material conveyance area in the image forming main scanning direction of the transfer conveyance member, and the density of the transferred toner pattern is read by the density detection means and detected. In the image forming apparatus having a control unit that performs image adjustment control based on a signal, an environment detection sensor that detects a temperature and a relative humidity inside the image forming apparatus, and a transfer material to be passed through Transfer material information recognizing means for recognizing information, and the control unit is configured to input information from the environment detection sensor, input information from the transfer material information recognizing means, and the image stored in advance in a storage means. Based on the transfer efficiency table in which the transfer efficiency characteristics of the toner image from the carrier to the transfer conveying member are arranged, image control is performed by correcting the detection signal of the toner pattern read by the density detector. It is characterized by.

  According to the present invention, it is possible to provide an image forming apparatus that can perform image correction and alignment image control with high accuracy even if the transfer efficiency of the toner patch to the transfer conveyance member changes for each paper type.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1. FIG. (A) is a control block circuit diagram for image processing and image correction, and (b) is a quadrant chart in which the gradation of the output image shows the reproduction characteristics. FIG. 5 is a schematic view of a drum and a transfer / conveyance belt unit, omitting a central portion. (A) is a block circuit diagram relating to density detection of the patch detection sensor, and (b) is a flowchart of image correction. (A) is a flowchart which determines a paper sharing voltage, (b) is the schematic of a paper sharing voltage table. (A) is a flowchart for determining an appropriate transfer voltage, and (b) is a schematic diagram of a transfer efficiency table. It is a flowchart which determines transfer efficiency. It is an operation | movement flowchart of a patch detection sensor. FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment. (A) is a flowchart for determining an appropriate transfer voltage, and (b) is a schematic diagram of the toner charge amount detection means. FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a third embodiment. (A) is a schematic cross-sectional view of the main configuration of the transfer unit, and (b) is an equivalent circuit of the transfer unit. It is a flowchart which determines transfer efficiency. FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a fourth embodiment. (A) is a schematic diagram of the configuration of the paper thickness detection means, (b) is a schematic diagram of the stiffness characteristics representing the detection results of the paper thickness detection means. FIG. 10 is a schematic configuration diagram of an image forming apparatus according to a fifth embodiment.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[Example 1]
(1) Outline of Image Forming Apparatus FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 500 in this embodiment. An apparatus 500 according to this embodiment is an electrophotographic image forming apparatus using a transfer conveyance belt 10 as a transfer conveyance member that carries and conveys a transfer material to an image transfer unit, and includes a reader unit 200 and a printer unit 300. Based on the electrical image information input from the reader unit 200 to the control unit (control circuit unit: CPU (central processing unit)) 60, a monochrome image (black ( Bk) single color) can be formed and output. The transfer material P is an image on which the apparatus 500 forms an image, and includes, for example, paper, an OHT sheet, a postcard, an envelope, a label, and the like.

  The control unit 60 controls the operation of the apparatus 500 in an integrated manner, and performs a printer according to a predetermined image forming sequence in accordance with signals from the reader unit 200 and the operation panel 501 and signals from various sensors in the printer unit 300. The image forming operation of the unit 300 is controlled. The panel 501 is a user interface unit of the apparatus 500, and a user can input various user setting information from the panel 501 to the control unit 60. The panel 501 is provided with paper information input means 70 as transfer material information recognition means, and the user can manually input basis weight information of the transfer material (paper) P by this means 70. The apparatus 500 is provided with an environment detection sensor 120 that can detect the temperature and relative humidity inside the apparatus. Environment detection information is input from the sensor 120 to the control unit 60, and the input information is stored in a storage device (storage unit: memory) 20 built in the control unit 60 in a state that can be always read.

  The reader unit 200 is a mechanism unit that photoelectrically reads an image of a document as electrical image information by a CCD sensor (solid-state imaging device) 201 (FIG. 2A), and the photoelectric read image information is input to the control unit 60. To do. An external host device (not shown) such as a personal computer or a facsimile can be connected to the control unit 60 via an interface, and image information can be input to cause the printer unit 300 to execute image formation.

  The printer unit 200 is an electrophotographic image forming mechanism unit, and includes a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) 1 as a rotatable image carrier. The control unit 60 activates a drive source (main motor) M based on the print start signal to rotationally drive the drum 1 in the clockwise direction indicated by an arrow at a predetermined speed (process speed). A primary charger 2, an exposure device 3, a developing device 4, a transfer charger 31, and a cleaner 5 are disposed on the outer periphery of the drum 1 as process means that act on the drum 1 along the rotation direction of the drum 1. ing.

  The charger 2 is a charging unit that uniformly charges the surface of the drum 1 to a predetermined polarity / potential. It is possible to use the charging means.

  The exposure device 3 is a latent image forming unit that forms an electrostatic latent image corresponding to an exposure pattern by exposing the charging surface of the drum 1 to image exposure. In this embodiment, the exposure apparatus 3 is a laser scanner. Laser light emitted from a light source device (laser light modulated in accordance with image information) is scanned by rotating a polygon mirror, the light beam of the scanning light is changed by a reflection mirror, and the drum 1 is rotated by an fθ lens. The light is condensed on the bus bar and exposed (main scanning exposure) L. As a result, the potential of the exposed portion of the drum surface is attenuated, and an electrostatic latent image is formed on the drum surface by the electrostatic contrast between the bright portion potential Vl and the dark portion potential Vd of the non-exposed portion.

  The developing device 4 is a developing unit that visualizes the electrostatic latent image on the drum surface as a toner image T1 using a developer (chromatic toner). In this embodiment, the developing device 4 is filled with a predetermined amount of a developer in which a non-magnetic toner having a negative charging polarity and a magnetic carrier having a positive charging polarity are mixed at a predetermined mixing ratio. A visible toner image is formed by electrostatically transferring toner to the electrostatic latent image on the drum 1 by the developing device 4. As the image forming system, there are a system using a background exposure system and a regular development system, and a system using an image exposure system and a reverse development system. The former is a method in which the charged drum surface is exposed corresponding to the background portion of the image information, and a portion other than the background portion is developed. The latter is a method in which exposure is performed corresponding to the image information portion and non-exposed portions are developed. It is used taking advantage of each feature.

  A transfer / conveying belt unit 30 is disposed below the drum 1. The configuration of the unit 30 will be described later. The transfer material P is stacked and accommodated in a feeding cassette (paper feeding unit) 80 disposed below the unit 30. When the paper feed roller 81 is driven at a predetermined control timing, the transfer material P in the cassette 80 is separated and fed one by one, conveyed in the conveyance path 82, and conveyed to the registration roller pair 6. The roller pair 6 is controlled to a rotation stop state and a drive state by a registration drive unit (registration drive unit: not shown) controlled by the control unit 60. The transfer material P conveyed on the conveyance path 82 is received at the front end at the nip portion of the roller pair 6 in a rotation stopped state at that time, and the skew is corrected. The roller pair 6 is driven at a predetermined control timing in synchronization with image formation on the drum 1. As a result, the recording material P is conveyed to the unit 30, is carried on the belt 10 that is a transfer conveyance member, and is conveyed to the transfer unit 7. While the transfer material P is passing through the transfer unit 7, a predetermined voltage or constant current is transferred from the transfer control unit (transfer bias power supply unit) 13 controlled by the control unit 60 to the transfer charger 31. A bias is applied at a predetermined control timing. As a result, in the transfer unit 7, the toner image T <b> 1 on the drum 1 side is sequentially electrostatically transferred onto the surface of the transfer material P conveyed by the belt 10. Reference numeral 50 denotes transfer voltage control means (ATVC; Auto Transfer Voltage Control) built in the control unit 60. The means 50 detects a resistance value of the transfer unit 7 that transfers the toner image T1 formed on the drum 1 to the transfer material P, and an appropriate transfer voltage is applied from the transfer control unit 13 to the transfer unit 7 (transfer charger 31). Apply.

  The transfer material P that has passed through the transfer unit 7 is continuously conveyed on the belt 10, separated from the upper surface of the belt 10 at the separation roller 33, passed through the upper side of the separation claw 29, and guided to the fixing inlet guide 93. It is conveyed to a fixing device (fixing unit) 9. The apparatus 9 includes a fixing roller 92 and a pressure roller 91. Although not shown in the figure, a heat resistant cleaning member for cleaning the rollers 92 and 91 and a heater installed in each roller are provided. Further, the roller 92 has an application roller for applying a release agent oil such as dimethyl silicone oil, an oil reservoir, and a thermistor for detecting the surface temperature of the roller 92 and controlling the fixing temperature. The transfer material P is heated and pressed in the process of being nipped and conveyed at a fixing nip portion that is a pressure contact portion between the roller 92 and the roller 91. As a result, the unfixed toner image on the transfer material P is fixed as a fixed image, and is discharged and stacked on the discharge tray 12 outside the apparatus by the discharge roller 11 as an image formed product. The drum 1 after the toner image is transferred to the transfer material P by the transfer unit 7 is cleaned by removing the toner remaining on the surface by the cleaner 5 and used for the next image formation.

(2) Unit 30
The unit 30 has a flexible endless belt (endless belt) 10 as a transfer conveyance member. The belt 10 is suspended and stretched between three parallel driving rollers 32, a separation roller 33, and a tension roller 34 as a plurality of suspension members. The roller 32 and the roller 33 are positioned on the upstream side and the downstream side, respectively, with respect to the transfer material conveyance direction from the drum 1. In the following description, the upstream side and the downstream side are the upstream side and the downstream side in the transfer material conveying direction or the belt moving direction. The roller 34 is in contact with the lower belt portion of the belt 10 between the roller 32 and the roller 33. The upper surface of the ascending belt portion of the belt 10 and the lower surface of the drum 1 are in contact with each other. The contact portion is the transfer portion 7. The charger 31 is disposed in the transfer portion 7 so as to face the drum 1 through the belt 10.

As the material of the belt 10, rubber materials having elastic properties such as CR and urethane, and resin materials such as PET, PVdF, PC (polycarbonate), and PI (polyimide) can be used. Alternatively, a composite material containing an appropriate amount of carbon black as an antistatic agent can be used as necessary. In this embodiment, the belt 10 is made of a CR rubber material having a circumferential length of 440 mm and a thickness of 500 μmt. Use an elastic material whose Young's modulus E measured by the tensile test method (JIS-K6301) is E ≦ 10 MPa and rubber hardness Hs (conforms to JIS-K6253) is Hs ≦ 75 °. Is desirable. As for the Young's modulus E, since the elastic characteristics disappear in the region exceeding 10 MPa, an expensive deviation control mechanism similar to that of a belt made of a resin material is used to regulate the deviation of the belt 10 in the main scanning direction of image formation. It becomes necessary. Here, the image forming main scanning direction is a direction parallel to the direction perpendicular to the transfer material conveyance direction on the conveyance path surface of the transfer material P. As for the rubber hardness Hs, when the rubber hardness is 75 ° or more, the surface crack of the belt occurs and the durability of the belt tends to be lowered. However, the rubber material characteristics of the belt 10 that can be used in the image forming apparatus of the present embodiment are not limited to the above-described ranges of the Young's modulus E and the rubber hardness Hs. The resistance value of the belt 10 is a volume resistivity of 5.0 × 10 ^{9 to} 1.0 × 10 ¹² Ω · cm (using a probe conforming to the JIS-K6911 method, applied voltage 100 V, applied time 60 sec, 23 ° C., 50% RH). The resistance level was varied within the range of. When the volume resistivity is less than 5.0 × 10 ⁹ Ω · cm, a leak phenomenon through the belt 10 is likely to occur particularly in a high humidity environment. On the other hand, if the volume resistivity exceeds 1.0 × 10 ¹² Ω · cm, charge accumulation becomes remarkable particularly in a low humidity environment, and it is difficult to eliminate static electricity. The belt 10 is an endless belt made of a seamless belt (seamless), and is suspended by a driving roller 32, a driven rotating separation roller 33, and a tension roller 34.

The roller 32 used was formed by molding a conductive rubber (volume resistance value <10 ⁵ Ωcm or less) having a thickness of 1.5 mm around a SUS core having an outer diameter of φ20 mm. The roller 33 is supported by a spring pressure mechanism (not shown), and also functions to apply tension to the belt 10 by pressing the belt 10 from the inner peripheral surface side. A roller made of SUS having an outer diameter of 19 mm was used. The roller 33 is disposed on the downstream side in the belt movement direction from the transfer portion 7 of the plurality of belt suspension members 32, 33, 34, and also has a function of separating the transfer material P from the belt 10 with a function of curvature separation. It is a member. A roller 34 made of SUS having an outer diameter of 20 mm was used, and the cleaning fur brush 35 was disposed opposite to the belt 10. The brush 35 cleans and removes the toner remaining on the belt.

  Further, in order to monitor the state of the image at a position opposite to the roller 33 with the belt 10 interposed therebetween, as shown in FIG. 3, a patch detection for reading an image adjustment toner pattern T2 formed on the belt 10 is performed. A sensor (patch detection sensor) S is arranged. The sensor S is a density detecting means for detecting the density of the toner pattern T2, and an optical sensor (photo sensor) generally used in an electrophotographic image forming apparatus is used. The toner pattern T2 and the latent S will be described later.

The belt 10 circulates at a speed corresponding to the rotational speed of the drum 1 in the counterclockwise direction indicated by the arrow B when the roller 32 is rotationally driven at a predetermined control timing. As the process speed of the image forming apparatus shown in the present embodiment, the belt 10 rotates in the direction of arrow B at a speed of 300 mm / sec. When the belt 10 rotates and reaches a certain speed, the transfer material P is sent from the roller pair 6 onto the ascending belt portion of the belt 10, and the transfer material P is conveyed toward the transfer unit 7 by the belt 10. The transfer material conveying speed of the roller pair 6 and the moving speed of the belt 10 substantially correspond to each other. At the same time, the image writing signal is turned on, and image formation is performed on the drum 1 at a predetermined control timing based on the signal. Thereafter, the transfer unit 7 applies a predetermined transfer bias from the control unit 13 to the transfer charger 31, whereby the toner image T <b> 1 formed on the drum 1 is electrostatically transferred to the transfer material P. . The charger 31 may be a non-contact charger such as corona discharge, or a contact charger using a charging member such as a charging roller, charging brush, or charging blade. In this embodiment, a charging roller ( Hereinafter, it is referred to as a transfer roller). The transfer roller 31 is composed of a conductive core metal having a diameter of 7.0 mm and an EPDM foamed elastic layer having a medium resistance value of 3.5 mm thickness. The roller hardness (Asker-C) is 30 °. The resistance value is measured by rotating the roller 31 at a peripheral speed of 50 mm / sec with respect to the ground (earth surface) under a load of 4.9 N (500 g weight) and applying a voltage of 1000 V to the cored bar. The value was found to be about 10 ⁶ Ω (23 ° C./50% RH).

  The transfer material P onto which the toner image T1 has been transferred is separated and separated (curvature separation) from the belt 10 by a roller 33 located downstream in the conveyance direction of the belt 10, and is guided to the separation claw 29 and the guide 93 to be a fixing device. It is conveyed to 9. Further, the belt 10 after separating the transfer material P is cleaned by the brush 35. The brush 35 is a conductive fur brush, and is a rotating body arranged to face the roller 34 with the belt 10 interposed therebetween, and rubs the surface of the belt 10. As a result, toner and other foreign matters remaining on the belt 10 are cleaned, and accumulated charges are removed (static elimination). The shaft cores of the brush 35 and the alignment roller 34 are grounded. As the brush 35, a conductive web (nonwoven fabric) can also be used.

(3) Outline of Image Processing FIG. 2A is a block diagram illustrating a configuration example of an image processing unit for obtaining a gradation image. The luminance signal of the image obtained by the CCD sensor 201 is converted into a frame sequential density signal in the image processing unit 202. The converted density signal is a signal corresponding to the gamma characteristic of the printer at the initial setting, that is, a lookup table LUT (gamma lookup table) so that the density of the original image matches the density of the output image. The characteristic is corrected by (γLUT) 25.

  FIG. 2B is a quadrant chart showing how the gradation of the output image is reproduced in the apparatus 500 of this embodiment. The first quadrant indicates the reading characteristic of the reader unit 200 that converts the density of the original image into a density signal. The second quadrant shows the conversion characteristics of the LUT 25 for converting the density signal into the laser output signal. The third quadrant indicates recording characteristics of the printer unit 300 that converts the laser output signal into the density of the output image. The fourth quadrant indicates the relationship between the density of the original image and the density of the output image. That is, it shows the total tone reproduction characteristics of the apparatus. In order to make the total tone characteristic of the apparatus, that is, the tone characteristic of the fourth quadrant linear, the non-linear printer characteristic of the third quadrant is corrected by the LUT 25 of the second quadrant. The image signal whose tone characteristics are converted by the LUT 25 is converted into a pulse signal corresponding to the dot width by the pulse width modulation (PWM) circuit 26 of the laser driver. The pulse signal is sent to an LD driver 27 that controls on / off of a laser light source (not shown: light emission source of laser light L in FIG. 2A). In this embodiment, only Bk single color (monochrome image) is used, but in the case of a four-color full-color image forming apparatus, all the colors Y (yellow), M (magenta), C (cyan) and Bk (black) are pulsed. A gradation reproduction method using width modulation is used. Then, an electrostatic latent image having a predetermined gradation characteristic in which the gradation is controlled by the change in the dot area is formed on the drum 1 by scanning with the laser light L output from the laser light source. Then, the gradation image is reproduced through the process of transfer and fixing.

(4) Formation of toner pattern T2 and sensor S
FIG. 3 is a schematic diagram in which the central portion of the drum 1 and the unit 30 is omitted. Regarding the dimensions of the main constituent means of the transfer unit 7 in the image forming main scanning direction, the belt 10 has W10 (belt width) = 360 mm, the drum 1 has W1 (drum length) = 350 mm, and the transfer roller 31 has W31 (transfer roller length). And the like) = 340 mm. WP is the maximum sheet passing width (transfer material conveyance area) of the transfer material P. In the present embodiment, the transfer material P is fed at the center reference conveyance center of the transfer material width. W10>W1>W31> WP.

  T2 is an image adjustment toner pattern (system control developer image, system control toner image: hereinafter referred to as toner patch or patch) formed on the belt 10 to monitor the state of the image. The patch T2 is, for example, an image density correction patch image for determining the amount of toner to be replenished to the developing device 4, or an intermediate for ensuring the gradation of image data for determining the correction amount of charging / exposure. Tone image patch image for tone correction. The patch T2 is formed in the non-image forming portion (drum end region: drum surface region outside the maximum sheet passing width WP) of the drum 1, and in the transfer unit 7, it is outside the maximum sheet passing width WP (transfer) in the belt 10. It is transferred to the belt surface area W10A outside the material conveying area. A toner image T1 corresponding to the image information is formed on the image forming portion of the drum 1, and the toner image T1 is transferred by the transfer portion 7 to the transfer material P carried on the belt 10 and conveyed. Then, the patch T2 formed in the region W10A of the belt 10 is photoelectrically read by the sensor S, and the read information is input to the control unit 60. The sensor S is disposed at a position corresponding to the belt surface area W10A and facing the roller 33 (a transfer material separating suspension member). The control unit 60 executes necessary system control based on the patch reading information input from the sensor S. That is, the control unit 60 performs image control based on the photoelectric reading information of the sensor S.

  More specifically, an image adjustment patch T2 is formed outside the transfer material conveyance area in the image forming main scanning direction of the drum 1 in parallel with the formation of the toner image T1, and the image forming main of the belt 10 is formed in the transfer unit 7. Transfer is performed outside the transfer material conveyance area W10A in the scanning direction. The control unit 60 reads the density of the transferred patch T2 by the sensor S which is a density detection unit, and performs image adjustment control based on the detection signal. The patch T2 on the belt 10 whose information has been read by the sensor S reaches the position of the brush 35 by the subsequent movement of the belt 10 and is removed from the belt 10.

  FIG. 4A is a block circuit diagram showing a circuit configuration example for processing the output signal of the sensor S. The reflected light (near infrared light) from the patch T2 formed on the belt 10 that is input to the sensor S is converted into an electrical signal. The electric signal is converted into a digital signal by the A / D conversion circuit 51, converted into density information by the density conversion circuit 52, and sent to a circuit unit (CPU) 60. FIG. 4B is a flowchart showing a process for creating a γLUT correction table, which starts with the start of normal image formation. First, the table data of the LUT 25 is corrected by the γLUT correction table obtained by the image correction flow performed during the previous image forming operation (S21), the correction result table data is set in the LUT 25 (S22), and the LUT 25 is used. Then, an image is output (S23). At this time, the patch T2 is formed on the belt 10 and the density of the patch T2 is read (S24). Then, ΔDn is calculated (S25), an integrated value ΔD = ΔD + ΔDn is obtained (S26), and a γLUT correction table is created (S27). Thereafter, it is determined whether or not to continue the print job (S28). If the job continues, the process returns to step S21, and if the job ends, the process ends.

(5) Outline of Transfer Efficiency Determination Method A method of determining the transfer efficiency of the patch T2 and correcting the density of the patch T2 based on the transfer efficiency and correcting the γLUT in the image forming apparatus described above will be described below.

  FIG. 5A is a flowchart showing a process for determining the paper sharing voltage. The temperature and relative humidity of the device 500 are always detected by the environment detection sensor 120 built in the device 500. Based on the detected temperature and relative humidity, the absolute water content is derived, and the information on the absolute water content is stored in the storage device 20 in the control unit 60 in a state where it can always be read (S21). By referring to the absolute water content and the paper basis weight information (S22) input from the paper information input means 70 and the paper sharing voltage table stored in advance in the storage device of the control unit 60 (S23), the paper sharing is performed. The voltage (a) is determined (S24).

A typical example of the paper sharing voltage table is shown in FIG. Low-humidity environment, a normal environment, a humid environment, the image forming apparatus inside the environmental conditions, in absolute water content, respectively ^{1.0g / m 3, 10.3g / m} 3, shows the case of a 24.3 g / ^{m 3} ing. 5B shows the paper sharing voltage when the sheet passing surface of the transfer material P is the first surface. For example, the absolute water amount derived based on the detection result of the sensor 120 is 10.3 g / m ³ . Further, it is assumed that the basis weight of the transfer material P (paper) input from the paper information input unit 70 on the panel 501 by the user is 100 g / m ² . In this case, the paper sharing voltage is determined to be 750 V from the paper sharing voltage table of FIG.

  FIG. 6A is a flowchart showing a process for determining an appropriate transfer voltage. In a recent electrophotographic image forming apparatus, developer replenishment control is generally performed so that the charge amount Q of developer toner developed on a photoconductor from a developing unit becomes constant. Under the assumption, the representative value of the toner Q / S can be predicted empirically from the absolute water content inside the apparatus obtained by the sensor 120 described above. Table 1 shows a representative example of the predicted toner Q / S.

By referring to the predicted toner Q / S value and the transfer efficiency table previously stored in the storage device of the control unit 60 (S41), the transfer charge density required for transfer is determined (S42). A representative example of the transfer efficiency table is shown in FIG. The transfer efficiency table is the following information. That is, from the toner charge amount Q / S and the transfer charge density applied to the transfer portion 7 by the transfer bias applied to the transfer roller 31 when the toner image on the drum 1 is transferred to the transfer material P, the drum 1 of the toner image. This is information in which characteristics that can lead to transfer efficiency from the toner to the belt 10 are arranged. Here, the transfer bias is a constant voltage in this embodiment.

Graph (1) of FIG. 6 (b), in (2), (3), each toner ^{Q / S = 0.012μC / cm 2} , 0.018μC / cm 2, the 0.024μC / cm ² Conditions 3 shows the relationship between the transfer charge density [μC / cm ² ] and the transfer efficiency [%]. For example, when the absolute water content in the image forming apparatus is 10.3 g / m ³ , the toner charge amount Q / S estimated from Table 1 is 0.018 μC / cm ² . The transfer charge density σ under the condition that the transfer efficiency is the best when the toner Q / S = 0.018 μC / cm ² is σ = 0.015 μC / cm ² (S42). A transfer target current value is determined from the transfer charge density σ, the process speed of the image forming apparatus of this embodiment, and the dimension (longitudinal dimension) W31 of the image forming main scanning direction of the transfer roller 31 (S43). Next, the resistance value of the transfer unit 7 that transfers the toner image from the drum 1 in a state where no toner image is interposed is detected by applying a predetermined transfer voltage (S44). An appropriate transfer voltage (b) is determined from the transfer target current (S43) and the resistance value (S44) of the transfer portion 7 obtained above (S45).

FIG. 7 is a flowchart showing a process for determining the transfer efficiency of the toner patch portion. The paper sharing voltage (a) and the proper transfer voltage (b) are determined by the paper sharing voltage determination flow (S51) in FIG. 5A and the appropriate transfer voltage determination flow (S52) in FIG. Is done. In order to transfer the toner image T1 corresponding to the image information formed on the image forming unit of the drum 1 to the transfer material P, the transfer application voltage applied to the transfer unit 7 is “(c) transfer application voltage = (a)”. Paper sharing voltage + (b) proper transfer voltage ”is determined (S53). The transfer unit 7 transfers the toner image T1 corresponding to the image information formed on the image forming unit of the drum 1 to the transfer material P, and at the same time, applies the patch T2 formed on the non-image forming unit of the drum 1 to the transfer material P. Are transferred onto the belt 10 in the outer region in the main scanning direction. The transfer current flowing in the toner patch portion is obtained by dividing the “transfer applied voltage (c)” by the “transfer portion resistance value” shown in S44 in the appropriate transfer voltage determination flowchart of FIG. (S54). The transfer charge density applied to the transfer unit 7 when the patch unit transfer current (S54) is energized to the transfer unit 7 depends on the process speed of the apparatus 500 and the transfer roller 31 to which the transfer bias is applied. It is calculated | required from the information of the longitudinal dimension W31 (S55). For example, when the patch portion transfer current value I [μA] is 20 μA, if the unit time t [sec] and the amount of charge passing through the transfer portion 7 per unit time t [sec] is Q [μC], I = Q / t. Therefore, the charge amount Q is Q = 20 μC from Q = I / t. If the transfer charge density is σ and the transfer area is S [cm ² ], σ = Q / S. Here, the transfer area S [cm ² ] is obtained by multiplying the longitudinal dimension W31 of the transfer roller 31 to which the transfer voltage is applied by the movement distance in the sub-scanning direction per unit time t [sec]. In this embodiment, W31 is 340 mm = 34.0 cm, and the moving distance in the sub-scanning direction is 30.0 cm (the moving speed of the belt 10 is 300 mm / sec = 30.0 cm / sec). Therefore, σ = 20 μC / (34.0 cm × 30.0 cm) = 0.020 μC / cm ² . The transfer efficiency of the patch T2 is determined by referring to the obtained transfer charge density and the “transfer efficiency table” shown in FIG. 6B (S56) (S57). For example, if the determined transfer charge density is 0.020 μC / cm ² , the transfer efficiency of the patch T2 is 83%.

  FIG. 8 is a flowchart showing a process for reading the density of the patch T2 by the sensor S and correcting the transfer efficiency of the patch density. When a plurality of continuous image forming jobs are input to the apparatus 500, the transfer material P is fed from the cassette 80 and conveyed to the roller pair 6 (S31). The transfer efficiency determination flow (S32) shown in FIG. 7 is performed, and image formation of the toner image T1 and the patch T2 corresponding to the image information is started on the image portion and the non-image portion of the drum 1, respectively. (S33). The transfer material P is fed to the belt 10 by the roller pair 6 by turning on a registration drive motor (not shown) in synchronization with image formation. Then, the transfer material is carried on the belt 10 and sequentially sent to the transfer section 7 where the drum 1 and the belt 10 are in contact with each other (S34). Subsequently, the transfer of the toner image T1 onto the transfer material P and the transfer of the patch T2 formed on the outer side in the main scanning direction of the transfer material conveyance area onto the belt 10 are performed (S35). The density of the patch T2 formed on the belt 10 is detected by the sensor S (S36) and sent to the control unit 60 through necessary signal conversion ((a) of FIG. 4). Further, the patch density information sent to the control unit 60 is subjected to density correction (S37) in accordance with the transfer efficiency determined in the flow S32 of FIG. Used for. The γLUT correction is as described in the outline of the image processing in the item (3).

  Therefore, in the image forming apparatus shown in the first embodiment, the transfer efficiency attenuation can be corrected with respect to the density of the image adjustment patch T2 on the belt 10 detected by the sensor S. Image correction and alignment image control can be performed.

  In summary, the control unit 60 performs image control by correcting the detection signal of the patch T2 read by the sensor S as follows. That is, the input information from the sensor 120, the input information from the means 70, and the transfer efficiency table in which the transfer efficiency characteristics of the toner image from the drum 1 to the belt 10 stored in advance in the storage device 20 are arranged. Based on this, the detection signal is corrected and image control is performed. Thereby, the attenuation of the transfer efficiency can be corrected for the density of the patch T2 on the belt 10 detected by the sensor S. For this reason, it is possible to perform image correction and alignment image control with high accuracy, and to provide an image forming apparatus with little color variation.

[Example 2]
In an environmental condition where the image forming apparatus 500 is installed, particularly in a high humidity environment, the toner charge amount may change in a short period of time immediately after the apparatus 500 is started up. When the toner charge amount changes, the transfer efficiency also changes. Therefore, more preferably, a process for detecting the toner charge amount Q / S is added to the flow chart for determining the appropriate transfer voltage in FIG. 6A described in the first embodiment. Thereby, more accurate transfer efficiency of the patch T2 is required, and more accurate image correction and aligned image control can be performed.

(1) Overview of Image Forming Apparatus FIG. 9 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 500 according to the second embodiment. FIG. 10A is a flowchart for determining an appropriate transfer voltage with the toner Q / S detection process added, and FIG. 10B is an explanatory diagram of a toner charge amount detection method. The apparatus 500 according to the second embodiment includes the toner Q / S detection means (toner charge amount detection means) 40 in addition to the apparatus 500 (FIG. 1) according to the first embodiment. Since the apparatus configuration other than the means 40 is the same as that of the apparatus 500 of the first embodiment, the description thereof will be omitted.

(2) Outline of toner charge amount detection method An outline of a toner charge amount detection method by the toner Q / S detection means 40 will be described below. As shown schematically in FIG. 10B, the developing device 4 is provided with a developing ammeter AM for detecting a developing current when the toner T is developed on the drum 1. From the detected development current, the charge amount of the developed toner can be known. For example, in the development in which the electrostatic latent image on the drum 1 is developed to form a toner image on the drum 1, a developing bias voltage is applied to the developing sleeve GS by the power source E. In the developing process, the toner T carrying a charge (negative charge in the figure) moves from the developing sleeve GS to the drum 1, whereby a developing current flows through the bias voltage applying circuit. Since the current flows only from the developing sleeve GS to the drum 1 by the movement of the toner T, the amount of moving charge can be measured by measuring the developing current with the ammeter AM. If the size of the electrostatic latent image formed on the drum 1 for developing the toner T is set to a known area S, the toner charge amount Q / S can be calculated from the measured moving charge amount Q. I understand. Table 2 shows the relationship between the developing current (μA) and the toner charge amount Q / S in the apparatus 500 of this example. The obtained toner Q / S is stored in a storage unit (not shown) built in the control unit 60 of the apparatus 500 of this embodiment in a state where it can be read out at all times.

(3) Appropriate Transfer Voltage Determination Flow with Addition of Toner Q / S Detection Process A description will be given along the flowchart of FIG. Refer to the toner Q / S value (S71) detected by the toner Q / S detection means 40, and the transfer efficiency table shown in FIG. 6B previously stored in the storage device of the control unit 60. (S72) determines the transfer charge density necessary for transfer (S73). For example, if a toner Q / S of the toner detected by the detection means 40 a charge amount Q / S = 0.018μC / cm ^2, the transfer efficiency becomes the best when the toner Q / S = 0.018μC / cm ² The condition transfer charge density σ is σ = 0.015 μC / cm ² (S73). A transfer target current value is determined from the transfer charge density σ, the process speed of the apparatus 500, and the longitudinal dimension W31 of the transfer roller 31 (S74). Next, the resistance value of the transfer unit 7 that transfers the toner image from the drum 1 in a state where no toner image is interposed is detected by applying a predetermined transfer voltage (S75). An appropriate transfer voltage (b) is determined from the transfer target current (S74) and the resistance value (S75) of the transfer portion 7 obtained above (S76).

  The paper sharing voltage determination process in the image forming apparatus 500 of the present embodiment is the same as the flowchart of FIG. The transfer efficiency determination process and the process of reading the density of the patch T2 portion by the patch detection sensor S and correcting the transfer efficiency of the patch density are the flowcharts shown in FIGS. 7 and 8 in the apparatus 500 of the first embodiment, respectively. Since it is the same as that of FIG. Further, the γLUT correction is the same as that described in the section of the image processing overview of the first embodiment, and thus the description thereof is omitted.

    In summary, the control unit 60 performs image control by correcting the detection signal of the patch T2 read by the sensor S as follows. That is, the input information from the sensor 120, the input information from the means 70, the input information from the means 40, and the transfer efficiency characteristics of the toner image from the drum 1 to the belt 10 stored in advance in the storage device 20 are organized. The detection signal is corrected based on the transferred transfer efficiency table. Image control is performed using the corrected signal. The transfer efficiency table is transferred from the drum 1 to the belt 10) from the toner charge amount and the transfer charge density applied to the transfer unit 7 when the toner image T1 formed on the drum 1 is transferred to the transfer material P. This is a table for guiding the transfer efficiency of the patch T2.

  The image forming apparatus according to the second embodiment can also correct the attenuation of the transfer efficiency with respect to the density of the patch T2 on the belt 10 detected by the sensor S. Control can be performed.

[Example 3]
(1) Outline of Image Forming Apparatus FIG. 11 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 500 according to the third embodiment. In the apparatus 500 of the present embodiment, the constant current power source 15 is used as a transfer bias applying unit when the toner image is transferred from the drum 1 to the transfer material P in the apparatus 500 (FIG. 9) of the second embodiment. Further, a transfer portion resistance detecting means 51 for detecting the resistance value of the transfer portion 7 is provided. Since the apparatus configuration other than the power supply 15 and the means 51 is the same as that of the apparatus 500 of the second embodiment, the description thereof is omitted.

(2) Outline of Transfer Efficiency Determination Method The transfer efficiency determination method when the constant current power supply 15 is used as the transfer bias application means will be described in detail. FIG. 12A shows a cross-sectional model view of the apparatus 500 in the image forming main scanning direction, and FIG. 12B shows an equivalent circuit thereof. In (a), 1 is a drum, 10 is a belt, 31 is a transfer roller, P is a paper as a transfer material, T1 is a toner image transferred to the transfer material P, and T2 is outside the paper conveyance area in the image forming main scanning direction. A patch 15 formed on W10A is a constant current power source as a transfer bias applying means. WP is a dimension (paper width) of the transfer material P in the image forming main scanning direction, W31 is a dimension (length dimension) of the transfer roller 31 in the image forming main scanning direction, and Rd is a detection for detecting the resistance value of the transfer unit 7. A resistor V1 represents a detection voltage applied to both ends of the detection resistor. In this embodiment, the dimensions of the main constituent means of the transfer unit 7 in the image forming main scanning direction are such that the belt 10 has W10 = 360 mm, the drum 1 has W1 = 350 mm, and the transfer roller 31 has W31 = 340 mm.

  In the equivalent circuit (b), A indicates the constant current power source 15, Rtr indicates the resistance value of the transfer portion 7 under the condition that there is no toner image with the transfer material P, and Rp indicates the resistance value of the transfer material P. . In addition, It (Itotal) represents a total current value flowing through the transfer portion 7, I1 represents a transfer current value flowing through the region of the transfer material P, and I2 represents a transfer current value flowing through the region of the toner patch portion. The resistance value Rtr of the transfer unit 7 is equal to both ends of the detection resistor Rd shown in FIG. It is calculated | required by detecting the voltage V1 concerning. The resistance value Rp of the transfer material P includes the paper basis weight information input from the paper information input unit 70, the paper basis weight, the paper thickness, the absolute moisture amount, and the aligned paper resistance value stored in the storage unit of the control unit 60. It is obtained by referring to a paper sharing voltage table ((b) of FIG. 5) in which the correlation of the paper sharing voltage is arranged.

  From the equivalent circuit of (b), the transfer current I1 flowing through the transfer material P and the transfer current value I2 flowing through the aligned patch T2 are derived by the following equations 1) and 2).

I1 = It · Rtr / (2Rtr + Rp) × WP / W31 (1)
I2 = It · (Rtr + Rp) / (2Rtr + Rp) × (W31−WP) / W31
... 2)
Further, the following formula 3) is derived from the formula 1).

It = I1 · (2Rtr + Rp) / Rtr × W31 / WP (3)
FIG. 13 is a flowchart showing a process for determining the transfer efficiency of the patch T2 formed in the outer area W10A of the transfer material conveyance area in the image forming main scanning direction of the belt 10. When the flow for determining the transfer efficiency is started, the toner Q / S is detected by the toner Q / S detection means 40 (S61). The transfer charge density is determined by referring to the toner Q / S and the transfer efficiency table shown in FIG. 6B (S62) (S63). A transfer target current value Itgt is obtained from the transfer charge density, the process speed of the apparatus 500 of this embodiment, and the longitudinal dimension W31 of the transfer roller 31 to which the transfer bias is applied (S64). By substituting the transfer target current value Itgt into I1 in the above equation 3), the total current value It flowing through the transfer unit 7 (= the current value energizing the transfer roller) is determined (S65). Next, by substituting the total current value It flowing through the transfer section 7 into It of Formula 2), the patch section transfer current value I2 flowing through the patch T2 section is derived (S66). The patch portion transfer charge density is determined from the transfer current value I2 flowing through the derived patch T2 portion and the process speed of the apparatus 500 of this embodiment and the longitudinal dimension W31 of the transfer roller 31 to which the transfer bias is applied. (S67). The transfer efficiency of the patch T2 is determined (S69) by referring to the patch portion transfer charge density, the already detected toner Q / S value, and the arrangement transfer efficiency table (S68).

  In the image forming apparatus of the third embodiment, the process of reading the density of the patch T2 portion by the sensor S and correcting the transfer efficiency of the patch density is the same as the flowchart shown in FIG. To do. Further, the γLUT correction is the same as that described in the section of the image processing overview of the first embodiment, and thus the description thereof is omitted.

  Also in the image forming apparatus shown in the third embodiment, the attenuation of the transfer efficiency can be corrected for the density of the patch T2 on the belt 10 detected by the sensor S. Arrangement image control can be performed.

[Example 4]
(1) Outline of Image Forming Apparatus FIG. 14 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 500 according to the fourth embodiment. In the apparatus 500 (FIG. 9) according to the second embodiment, instead of the paper information input unit 70 that is a manual transfer material information recognition unit, the thickness of the transfer material P to be passed is automatically detected and the control unit 60 is detected. A paper thickness detecting means 100 as a transfer material information recognizing means for feeding back is provided. Since the rest of the apparatus configuration excluding the paper thickness detecting means 100 is the same as that of the apparatus 500 of the second embodiment, the description thereof will be omitted.

(2) Outline Description of Paper Thickness Detection Method In the apparatus 500 of this embodiment, the transfer material information recognition means 100 for the fed transfer material P is provided in the middle of the conveyance path 82 from the cassette 80 to the roller pair 6. It is arranged. Means 100 is means for recognizing information relating to the transfer material P conveyed by the belt 10. The means 100 of the present embodiment is a transfer material rigidity detection means that detects the rigidity of the transfer material P using ultrasonic waves. FIG. 15A is a schematic diagram of the means 100. The transfer material P separated and fed from the cassette 80 is sandwiched in the transport path 82 by the upstream transport roller pair 104/105 and the downstream transport roller pair 106/107, and is directed toward the roller pair 6. It is conveyed in the direction C. In the middle of the conveyance path, the ultrasonic transmission element 101 and the reception element 102 are arranged on the upstream side and the downstream side so as to contact the transfer material P being conveyed. When the transfer material P is conveyed to a position in contact with both the element 101 and the element 102 during an image forming operation or the like, an ultrasonic signal 103 is transmitted from the element 101. As the signal 103, a signal having a certain frequency / output is transmitted, and the transmitted signal 103 changes in accordance with the rigidity characteristic of the transfer material P. The changed signal is received by the element 102. The control unit 60 calculates a change amount (attenuation rate) of the transmission signal from the element 101 and the reception signal by the element 102. The attenuation rate correlates with the rigidity characteristic value of the transfer material P as shown in FIG. The control unit 60 stores the correlation characteristic data as a reference table. Based on the correlation characteristic data, the control unit 60 derives a stiffness characteristic value X1 corresponding to the attenuation rate Y1 calculated for the transferred transfer material P. The rigidity characteristic value is correlated with the basis weight (thickness) of the paper that is the transfer material P. As the transfer material P, paper having a basis weight of 50 g / m ² (thickness 50 μm), 64 g / m ² (thickness 65 μm), and 80 g / m ² (thickness 80 μm) is passed through the apparatus 500 of this embodiment. Then, when the stiffness characteristic value was obtained by means 100, the results shown in Table 3 were obtained.

The process for determining the transfer efficiency of the image adjustment patch T2 and the process of correcting the transfer efficiency of the patch density by reading the density of the patch T2 portion by the patch detection sensor S in the image forming apparatus of the present embodiment are the same as in the second embodiment. Because of this, the description is omitted. Further, the γLUT correction is the same as that described in the section of the image processing overview of the first embodiment, and thus the description thereof is omitted.

  Also in the image forming apparatus shown in the fourth embodiment, the attenuation of the transfer efficiency can be corrected with respect to the density of the patch T2 on the belt 10 detected by the sensor S. Arrangement image control can be performed.

[Example 5]
(1) Outline of Example of Image Forming Apparatus FIG. 16 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus 500 in this embodiment. Components and parts common to the apparatus 500 of the fourth embodiment are denoted by the same reference numerals and description thereof is omitted. The apparatus 500 of this embodiment is a full-color electrophotographic image forming apparatus, and includes first to fourth electrophotographic image forming units U (UY, UM, UC, UK) arranged in parallel. Each image forming unit U includes a drum (first image carrier) 1, a primary charger 2, an exposure device 3, a developing device 4, and a cleaner 5, similarly to the image forming unit of the apparatus 500 of the fourth embodiment. The drum 1 is rotationally driven in a counterclockwise direction indicated by an arrow R at a predetermined speed, in this embodiment, 300 mm / sec. The first image forming unit UY forms a yellow (Y color) toner image on the drum 1. The second image forming unit UM forms a magenta (M color) toner image on the drum 1. The third image forming unit UC forms a cyan (C color) toner image on the drum 1. The fourth image forming unit UK forms a black (Bk) toner image on the drum 1. A reversal development method is used in which toner is attached to the exposed portion of the electrostatic latent image for development.

  An intermediate transfer belt unit 70 is disposed below the first to fourth image forming units UY, UM, UC, and UK. The unit 70 includes an endless intermediate transfer belt (second image carrier) 74 having flexibility, and a tension roller 71, a drive roller 72, two rollers serving as a plurality of stretching rollers that stretch the belt 74. The next transfer counter roller 73 has three rollers. The belt 74 is circulated and moved in the clockwise direction indicated by the arrow Z at a predetermined speed, 300 mm / sec in this embodiment, by driving the roller 72. A primary transfer roller 75 is disposed on the inner side of the ascending belt portion between the rollers 71 and 72 at positions corresponding to the lower surfaces of the drums of the image forming units UY, UM, UC, and UK. Each roller 75 is in pressure contact with the lower surface of the drum 1 via a belt 74. A pressure contact portion between the belt 74 and the lower surface of the drum is a primary transfer portion. As the belt 74, an appropriate amount of carbon black as an antistatic agent is contained in a resin such as polyimide and polycarbonate, or various rubbers, the volume resistivity is 1E + 9 to 1E + 14 [Ω · cm], and the thickness is 0.07 to 0.1. [Mm] is used.

  A transfer conveyance belt unit 30 having the same configuration as that of the apparatus 500 according to the fourth embodiment is disposed below the unit 70. The charger (secondary transfer roller) 31 faces the secondary transfer counter roller 73 via the belt (secondary transfer belt) 10 and the belt 74. A pressure contact portion between the belt 74 and the belt 10 is a transfer portion (secondary transfer portion) 77 that transfers the toner image formed on the belt 74 to the transfer material P that is carried by the belt 10 and conveyed. The belt 10 is made of an elastic material having a Young's modulus measured by a tensile test method (JIS-K-6301) of 10 MPa or less. The belt 10 is circulated by the roller 32 in the counterclockwise direction indicated by the arrow B at a predetermined speed, in this embodiment, 300 mm / sec. The belt 10 is made of an elastic material having a Young's modulus measured by a tensile test method (JIS-K-6301) of 10 MPa or less. By using a member capable of sufficiently elastic deformation with a Young's modulus of the belt 10 of about 10 MPa or less, the belt shift control means in the image forming main scanning direction of the belt 10 is simple and low-cost. Is possible. In addition, since a member that can be sufficiently elastically deformed easily undergoes a stress relaxation phenomenon, it is possible to prevent a reduction in the life of the belt 10.

  The Y-color toner image, M-color toner image, C-color toner image, and Bk-color toner image formed on the drum 1 of each of the first to fourth image forming units UY, UM, UC, and UK are circulated in the primary transfer. The image is superimposed on the surface of the belt 74 to be primarily transferred. As a result, a four-color full-color toner image is formed on the belt surface that has passed through the primary transfer portion of the fourth image forming portion UK. The toner image is conveyed to the secondary transfer unit 77 by the subsequent movement of the belt 74. On the other hand, the transfer material P is conveyed to the secondary transfer unit 77 by the belt 10 at a predetermined control timing, and the toner image on the belt 74 is secondarily transferred onto the transfer material P. That is, the toner image on the belt 74 is collectively transferred onto the transfer material P by applying a secondary transfer current having a reverse polarity to the toner by the roller 31. The roller 31 is made of an elastic layer of an ion conductive foamed rubber (NBR rubber) and a metal core, has an outer diameter of 24 mm, a roller surface roughness Rz = 6.0 to 12.0 (μm), and a resistance value of N / N (23 ° C., 50% RH) measurement A transfer roller of 1E + 5 to 1E + 7Ω with 2 kV applied is used. A secondary transfer high-voltage power supply 13 with a variable supply bias is attached to the roller 31. The transfer material P on which the unfixed toner image is placed in the secondary transfer unit 77 is continuously conveyed by the belt 10 and separated from the belt 10 at the position of the roller 33. Thereafter, the toner image is conveyed to the fixing device 9 to fix the toner image, and is then discharged out of the machine.

  Further, an image adjustment toner pattern (toner patch) T2 is formed on the belt surface area W10A outside the transfer material conveyance area of the belt 10 and is read by the sensor S.

  The rotation speed of the belt 74 and the belt 12 is an example, and is not limited to the above conditions. In the present embodiment, the tension roller 33 is a separation tension roller corresponding to a separation portion of the transfer material P from the belt 10.

(2) Overview of Toner Charge Amount Detection Method The toner charge amount detection method by the toner Q / S detection means 40 in this embodiment is the same as the method described in the second embodiment. That is, in each of the image forming units UY, UM, UC, and UK, in the developing device 4, in order to detect a developing current when developing the toner onto the drum 1, FIG. The development ammeter AM shown is provided. Then, the charge amount of the developed toner can be found from the development current detected by the development ammeter AM. Since the other toner Q / S detection methods are the same as those in the second embodiment, description thereof will be omitted. The relationship between the development current (μA) and the toner charge amount Q / S in the image forming apparatus of this example is as shown in Table 2. The obtained toner Q / S is stored in a storage unit (not shown) built in the control unit 60 of the image forming apparatus of this embodiment in a state where it can be read out at all times.

  Since the paper thickness detection process and the transfer efficiency determination process of the image adjustment patch T2 in the image forming apparatus of the present embodiment are the same as those in the fourth embodiment, description thereof is omitted. Further, the process of reading the density of the patch T2 portion by the sensor S and correcting the transfer efficiency of the patch density is the same as that of the fourth embodiment, and thus the description thereof is omitted. Further, the γLUT correction is the same as that described in the section of the image processing overview of the first embodiment, and thus the description thereof is omitted.

  In the image forming apparatus shown in the fifth embodiment, similarly to the image forming apparatus in the third embodiment, the attenuation of the transfer efficiency is corrected for the density of the patch T2 on the belt 10 detected by the sensor S. Therefore, accurate image correction and alignment image control can be performed.

[Others]
1) The toner image forming method of the image forming apparatus is not limited to the electrophotographic image forming process of the embodiment. Other image forming processes such as an electrostatic recording image forming process using an electrostatic recording dielectric as an image carrier and a magnetic recording image forming process using a magnetic recording magnetic material as an image carrier may be used.

  2) The transfer material information recognition unit 100 is not limited to the transfer material rigidity detection unit of the embodiment. It may be a transfer material thickness detecting means for detecting the thickness of the transfer material from the distance corresponding to the thickness of the transfer material of the pair of rollers that sandwich and convey the transfer material.

  T1 ... toner image 1, 74 ... image carrier, P ... transfer material 7, 77 ... transfer unit, 10 ... transfer conveying member, 500 ... image forming apparatus, T2 / ... for image adjustment Toner pattern, W10A ·· Outside transfer material conveyance area, S ·· Density detection means, 60 ·· Control unit, 120 ·· Environment detection sensor, 70, 100 ·· Transfer material information recognition means, 20 ·· Storage means

Claims (4)

An image forming apparatus comprising: an image carrier on which a toner image is formed; and a transfer conveyance member that carries a transfer material and conveys the toner image from the image carrier to the transfer material. In parallel with the formation of the toner image, a toner pattern for image adjustment is formed outside the transfer material conveyance area in the image formation main scanning direction of the image carrier, and the image forming main scan of the transfer conveyance member is performed in the transfer section. In the image forming apparatus having a control unit that transfers the density of the transferred toner pattern by the density detection unit and performs image adjustment control based on the detection signal.
An environment detection sensor for detecting an internal temperature and relative humidity of the image forming apparatus; and a transfer material information recognition unit for recognizing information of a transfer material to be passed, wherein the control unit receives from the environment detection sensor. A transfer efficiency table in which transfer efficiency characteristics of the toner image from the image carrier to the transfer conveying member are arranged in advance, which is stored in advance in the storage unit, and input information from the transfer material information recognition unit; The image forming apparatus according to claim 1, wherein the image control is performed by correcting the detection signal of the toner pattern read by the density detection means.   Toner charge amount detection means for detecting the charge amount of toner; and the control unit receives input information from the environment detection sensor, input information from the transfer material information recognition means, and toner charge amount detection means. Based on the input information and a transfer efficiency table in which transfer efficiency characteristics of the toner image from the image carrier to the transfer conveying member, which are stored in advance in the storage means, are read by the density detection means. 2. The image forming apparatus according to claim 1, wherein image control is performed by correcting the detection signal of the toner pattern.   The transfer efficiency table includes a toner charge amount and a transfer charge density applied to the transfer portion when the toner image formed on the image carrier is transferred to the transfer material. The image forming apparatus according to claim 2, wherein the image forming apparatus is a table that guides transfer efficiency of the toner pattern transferred to the transfer conveyance member.   4. The image according to claim 1, wherein the transfer material information recognition unit is a thickness detection unit that detects a thickness of the transfer material provided in a transfer path of the transfer material. 5. Forming equipment.