Image forming apparatus and image forming method

Abstract

To provide an image forming apparatus that can obtain a stable image density regardless of a transfer pressure.SOLUTION: An image forming apparatus comprises control means comprising: a calculation unit that, based on a target value of the attachment amount of a toner image to be transferred onto a second moving body and an attachment amount detection value from attachment amount detection means, calculates a variation in the attachment amount of the toner image on the second moving body varying in association with a change in transfer pressure; a correction unit that reflects the variation in the attachment amount calculated by the calculation unit on the attachment amount detection value to correct the attachment amount detection value; and an image forming condition adjustment unit that adjusts an image forming condition for the toner image based on the attachment amount detection value after the correction made by the correction unit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an image forming method. [Background Art]

[0002] Patent Document 1 discloses an image forming apparatus comprising: an image forming unit including a photoreceptor, a developing unit and the like; and a control section that performs target value correction processing to correct a control target value of a control parameter affecting the developing capability of the image forming unit with a correction amount obtained by a predetermined algorithm, wherein the image forming apparatus is provided with an image density sensor that detects the image density of an image formed by the image forming unit, and the control section is configured to perform correction processing to correct the algorithm based on a detection result of the image density obtained by the image density sensor. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2014-056124 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] When conveying a recording medium at high speed, it is necessary to change the transfer pressure of the secondary transfer nip between a preceding recording medium and a succeeding recording medium (inter-sheet gap) so as not to reduce the productivity of the image forming apparatus. However, with the configuration as disclosed in Patent Document 1, switching of the transfer pressure in the inter-sheet gap cannot be completed in time, and there is a risk that the transfer pressure for the preceding recording medium is still applied to the succeeding recording medium. As described above, when the transfer pressure is changed according to the type of the recording medium to be used (particularly when the change is made under high-speed conveyance), it is difficult to optimize image forming conditions during image formation in accordance with the change of the transfer pressure, which causes a problem that the image density cannot be stabilized. [Means for Solving the Problem]

[0005] The present invention provides an imaging means for forming a toner image on an image carrier; a first transfer means having a first moving body onto which the toner image on the image carrier is transferred; a second transfer means having a second moving body onto which the toner image on the first moving body is transferred; a transfer pressure changing means for changing the transfer pressure of the second moving body to the first moving body; an adhesion amount detection means for detecting the toner image transferred onto the second moving body and outputting an adhesion amount detection value; and a control for setting the imaging conditions of the toner image in the imaging means based on the adhesion amount detection value. An image forming apparatus comprising means, wherein the control means comprises: a calculation unit that calculates a toner image adhesion amount fluctuation value on the second moving body that fluctuates with changes in the transfer pressure, based on a target value for the amount of toner image to be transferred onto the second moving body and the adhesion amount detection value; a correction unit that reflects the adhesion amount fluctuation value calculated by the calculation unit into the adhesion amount detection value and corrects the adhesion amount detection value; and an image forming condition adjustment unit that adjusts the image forming conditions based on the adhesion amount detection value corrected by the correction unit. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide an image forming apparatus that can obtain a stable image density regardless of the transfer pressure. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] An explanatory diagram showing an example of the peripheral configuration of the secondary transfer unit. [Figure 3] An explanatory diagram showing an example of a concentration sensor. [Figure 4] An explanatory diagram showing the relationship between transfer pressure and detected adhesion amount. [Figure 5] Block diagram of the parts involved in adjusting the image creation conditions. [Figure 6] A block diagram showing an example of the hardware configuration of the control unit. [Figure 7] A flowchart showing an example of correcting the detected amount of adhesion. [Modes for carrying out the invention]

[0008] The embodiments for carrying out the invention will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numeral, and redundant explanations will be omitted.

[0009] <Overall configuration of the image forming apparatus> First, the overall configuration of the image forming apparatus will be explained using Figure 1. Figure 1 is a schematic diagram showing an example of an image forming apparatus according to an embodiment of the present invention. The illustrated image forming apparatus is a printing apparatus that uses an electrophotographic method to form a toner image, which is then transferred and fixed onto a recording medium such as paper, and output as a printed material.

[0010] The printing apparatus 500 comprises a toner image forming unit 1, a primary transfer unit 2, a sheet supply unit 3, a secondary transfer unit 4, a transport belt unit 5, a fixing unit 6, a double-sided transport unit 7, a sheet discharge unit 8, an exposure unit 9, and a toner bottle mounting unit 10. Of these, the toner image forming unit 1, which is an example of an image-forming means, comprises a plurality of photosensitive developing units 10a, 10b, 10c, and 10d.

[0011] The photosensitive developing units 10a to 10d are arranged along the direction of movement of the primary transfer belt 20, which will be described later. For example, photosensitive developing unit 10a forms a yellow (Y) toner image, photosensitive developing unit 10b forms a magenta (M) toner image, photosensitive developing unit 10c forms a cyan (C) toner image, and photosensitive developing unit 10d forms a black (K) toner image.

[0012] Each photosensitive developing unit 10a to 10d includes a drum-shaped photoreceptor 11a, 11b, 11c, 11d, which is an example of an image carrier; charging devices 12a, 12b, 12c, 12d for charging the surface of the photoreceptors 11a to 11d; developing devices 13a, 13b, 13c, 13d for developing the electrostatic latent image formed on the photoreceptors 11a to 11d; and cleaning devices 14a, 14b, 14c, 14d for cleaning the surface of the photoreceptors 11a to 11d.

[0013] The primary transfer unit 2, which is an example of a first transfer means, is disposed below the toner image forming section 1. The primary transfer unit 2 includes a primary transfer belt 20 which is an example of a first moving body, primary transfer rollers 21a, 21b, 21c, 21d, a secondary transfer counter roller 22, a primary transfer belt cleaning device 23, and the like.

[0014] The primary transfer belt 20 is an endless belt formed of a single layer or multiple layers of PVDF (polyvinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), or the like. Further, the primary transfer belt 20 is stretched across the primary transfer rollers 21a to 21d, the secondary transfer counter roller 22, and a plurality of support rollers, and moves in the clockwise direction (direction of arrow A) in the drawing.

[0015] The primary transfer rollers 21a to 21d sandwich the primary transfer belt 20 between the corresponding opposing photoreceptors 11a to 11d. Thereby, the primary transfer belt 20 abuts against the photoreceptors 11a to 11d to form a primary transfer portion (primary transfer nip portion). The primary transfer portion forms a primary transfer electric field between the primary transfer rollers 21a to 21d and the photoreceptors 11a to 11d such that the toner images formed on the surfaces of the photoreceptors 11a to 11d are electrostatically transferred to the primary transfer belt 20. When the primary transfer belt 20 receives the toner images from the photoreceptors 11a to 11d at positions in contact with the photoreceptors 11a to 11d, the movement of the primary transfer belt 20 in the direction of arrow A conveys the toner images toward the secondary transfer counter roller 22 side.

[0016] The secondary transfer counter roller 22 forms a secondary transfer portion (secondary transfer nip portion) together with a secondary transfer roller 41 described later.

[0017] The primary transfer belt cleaning device 23 is disposed on the downstream side in the moving direction of the primary transfer belt 20 with respect to the secondary transfer counter roller 22, and cleans the surface of the primary transfer belt 20 that has passed through the secondary transfer counter roller 22.

[0018] The sheet supply unit 3 is disposed below the primary transfer unit 2, and includes conveyance rollers 30, 31 and the like for conveying, to the secondary transfer unit 4, a recording medium separated and fed one sheet at a time from a sheet storage portion. Note that the sheet storage portion is connected to the main body of the printing apparatus 500 so as to communicate with sheet conveyance paths 3a, 3b, 3c of the sheet supply unit 3, but illustration thereof is omitted here.

[0019] The secondary transfer unit 4, which is an example of a second transfer means, is disposed below the primary transfer unit 2, and the secondary transfer unit 4 includes a secondary transfer belt 40, which is an example of a second moving body, a secondary transfer roller 41, and the like.

[0020] The secondary transfer belt 40 is an endless belt formed of a single layer or a plurality of layers using PVDF (polyvinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate) or the like. The secondary transfer belt 40 moves counterclockwise in the drawing in a state of being stretched across the secondary transfer roller 41 and a plurality of support rollers. The secondary transfer belt 40 conveys the recording medium sent from the conveyance roller 30, and causes the toner image on the primary transfer belt 20 to be transferred onto the recording medium at a position facing the secondary transfer roller 41 and the secondary transfer counter roller 22 (secondary transfer portion). Note that details of the secondary transfer unit 4 will be described later.

[0021] The conveyance belt unit 5 is disposed below the primary transfer unit 2, and guides the recording medium that has passed through the secondary transfer unit 4 to the fixing unit 6.

[0022] The fixing unit 6 is disposed below the primary transfer unit 2, and fixes the toner image onto the recording medium by, for example, applying heat and pressure to the toner image transferred onto the recording medium by the secondary transfer unit 4.

[0023] The double-sided conveyance unit 7 is disposed below the secondary transfer unit 4, the conveyance belt unit 5, the fixing unit 6, and the like, and when performing double-sided printing, the recording medium after fixing passes through the inside of the double-sided conveyance unit 7 and is returned to the conveyance roller 31 side.

[0024] The sheet discharge unit 8 is located downstream of the fuser unit 6 (downstream in the direction of transport of the recording medium) and transports the recording medium discharged from the fuser unit 6 to the outside of the printing device 500 or toward the duplex transport unit 7.

[0025] The exposure unit 9 is positioned above the toner image forming unit 1. The laser light emitted from the light source is guided to the photoreceptors 11a to 11d via optical components such as lenses and mirrors, and the laser light forms an electrostatic latent image on the surface of the photoreceptors 11a to 11d.

[0026] The toner bottle mounting section 10 is located above the exposure unit 9, and toner bottles 100a, 100b, 100c, and 100d, which contain toner for supplying to the developing devices 13a to 13d, are detachably provided on the toner bottle mounting section 10.

[0027] In the above configuration, when the printing device 500 receives image data from an external computer or the like, it starts a print job and begins driving the toner image forming unit 1, the primary transfer unit 2, and the exposure unit 9. In the toner image forming unit 1, the charging devices 12a to 12d uniformly charge the surfaces of the rotating photoreceptors 11a to 11d to a predetermined charging potential. After charging, an electrostatic latent image is formed on the surface of the photoreceptors 11a to 11d by the exposure unit 9 based on the image data. The electrostatic latent image formed on the photoreceptors 11a to 11d is developed as a toner image by the developing devices 13a to 13d and then sequentially transferred onto the primary transfer belt 20. After the toner image transfer, the surfaces of the photoreceptors 11a to 11d are cleaned by the cleaning devices 14a to 14d.

[0028] In parallel with the toner image formation described above, the sheet supply unit 3 transports the recording medium toward the transport roller 30. The transport roller 30 also functions as a resist roller, and when the recording medium hits the transport roller 30, the transport of the recording medium stops temporarily. The transport roller 30 then resumes transporting the recording medium in accordance with the timing when the toner image transferred to the primary transfer belt 20 reaches the secondary transfer nip. Once the transport of the recording medium has resumed, the toner image is transferred to the surface of the recording medium in synchronization with the toner image on the primary transfer belt 20 within the secondary transfer nip. After the toner image has been transferred, the recording medium is transported to the fuser unit 6 by the transport belt unit 5. In the fuser unit 6, heat and pressure are applied to the recording medium with the toner image on it, and the toner image is fixed to the recording medium.

[0029] After fixing, the recording medium is moved to the sheet discharge unit 8, where, for example, the movement of a direction switching claw switches the path of the recording medium to either outside the printing device 500 or to the duplex transport unit 7. If the recording medium is sent from the sheet discharge unit 8 to the duplex transport unit 7, it is sent again to the secondary transfer nip section, where a toner image is formed on the back surface of the recording medium, and then discharged from the sheet discharge unit 8. The surface of the primary transfer belt 20 after passing through the secondary transfer nip section is cleaned by the primary transfer belt cleaning device 23 to remove any toner remaining on the surface of the primary transfer belt 20. The printing device 500 is equipped with a temperature and humidity sensor 200 that detects the temperature and humidity inside the main body, and the temperature and humidity information detected by the temperature and humidity sensor 200 is used when adjusting the image formation conditions described later.

[0030] The number of photosensitive developing units 10a to 10d and toner bottles 100a to 100d installed in the printing device 500 may be increased or decreased as appropriate depending on the types and quantities of toner colors used in the printing device 500.

[0031] Furthermore, the recording medium used for printing is not limited to paper. It can be applied to a variety of materials other than paper, such as textiles, fabrics, leather, metals, plastics, glass, wood, and ceramics.

[0032] <Configuration of the secondary transfer unit> Next, we will explain the configuration around the secondary transfer unit using Figure 2. Figure 2 is an explanatory diagram showing an example of the configuration around the secondary transfer unit.

[0033] In addition to the secondary transfer belt 40 and secondary transfer roller 41 shown in Figure 1, the secondary transfer unit 4 includes a plurality of support rollers 42a, 42b, 42c, and 42d, a concentration sensor 43 which is an example of an adhesion amount detection means, a secondary transfer belt cleaning device 44, and a frame 45 that holds the secondary transfer belt 40, secondary transfer roller 41, support rollers 42a to 42d, concentration sensor 43, and secondary transfer belt cleaning device 44. The secondary transfer unit 4 also includes a pressurizing device 46 which is an example of a transfer pressure changing means.

[0034] The secondary transfer belt 40 moves counterclockwise in the figure (direction of arrow B) while being stretched over the secondary transfer roller 41 and a plurality of support rollers 42a to 42d. The secondary transfer roller 41 sandwiches the secondary transfer belt 40 between itself and the opposing primary transfer belt 20, forming a secondary transfer section (secondary transfer nip section) P at the point where the primary transfer belt 20 and the secondary transfer belt 40 meet. The secondary transfer nip section P forms a secondary transfer field for electrostatically transferring the toner image T transferred to the surface of the primary transfer belt 20 to the conveyed recording medium S. The secondary transfer section P also forms a secondary transfer field for electrostatically transferring the toner image T' transferred to the surface of the primary transfer belt 20 to the secondary transfer belt 40.

[0035] The density sensor 43 is positioned opposite the surface of the secondary transfer belt 40 and detects the amount of toner (toner adhesion amount) that adheres to the secondary transfer belt 40 when the toner image T' is transferred from the primary transfer belt 20 to the secondary transfer belt 40. The density sensor 43 comprises a light-emitting element consisting of an infrared LED (Light Emitting Diode) or the like, and a light-receiving element consisting of a phototransistor or the like that receives reflected light and outputs an electrical signal according to the intensity of the received light. Note that the density sensor 43 does not need to be any other type of sensor that can detect the amount of toner adhesion.

[0036] The secondary transfer belt cleaning device 44 is positioned downstream of the concentration sensor 43 in the direction of movement of the secondary transfer belt 40, and cleans the surface of the secondary transfer belt 40 after it has passed the concentration sensor 43.

[0037] The pressurizing device 46 comprises a cam member 47 and an arm member 48 that is supported so as to be able to swing in the direction of arrow C as the cam member 47 rotates. The pressurizing device 46 is positioned so that the arm member 48 can come into contact with a part of the frame 45, and the frame 45 is also positioned so as to be able to be displaced in the direction of arrow C according to the position of the arm member 48. In other words, the pressure (transfer pressure) generated in the secondary transfer nip section P can be changed by the pressurizing device 46.

[0038] In the secondary transfer nip section P, the recording medium S onto which the toner image T has been transferred from the primary transfer belt 20 is then transported in the direction of arrow D, where the toner image fixing and other processes described above are performed. On the other hand, the toner image T' is not transferred to the recording medium S in the secondary transfer nip section P, but is transferred to the secondary transfer belt 40 in a recording medium-free section (between sheets of paper) set between the preceding recording medium and the succeeding recording medium. Here, the toner image T' is, for example, a predetermined test pattern image, and the toner image T' is formed on the secondary transfer belt 40 each time the transfer of the toner image T to the recording medium S is performed a predetermined number of times, and is detected by the density sensor 43.

[0039] Here, the reason why the concentration sensor 43 is provided in the secondary transfer unit 4 will be explained using Figure 3. Figure 3 is an explanatory diagram showing an example of a concentration sensor.

[0040] The concentration sensor 43 comprises a light-emitting element 43a consisting of an infrared LED or the like, a specular reflection light-receiving element 43b that receives so-called specular reflected light reflected at a reflection angle equal to the incident angle of light to the reflective surface Rs, and a diffuse reflection light-receiving element 43c that receives light diffusely reflected by the reflective surface Rs. This concentration sensor 43 is used in a specular reflection detection method in which specular reflected light is detected by the specular reflection light-receiving element 43b, and we consider the case where the reflective surface Rs is an elastic material.

[0041] In that case, in the state shown in Figure 3(a), there is no toner image on the reflective surface Rs, so the light from the light-emitting element 43a is reflected in proportion to the specular gloss of the elastic surface, and the reflected light is detected by the specular reflection light-receiving element 43b.

[0042] However, as shown in Figure 3(b), when a toner image t is attached to the reflective surface Rs, light is scattered by the toner image t, so the specular reflected light decreases as the amount of toner attached increases. In particular, when the toner image t is black toner, the light from the light-emitting element 43a is scattered or absorbed at the toner surface, and the decrease in specular reflected light becomes significant.

[0043] Furthermore, when determining the amount of toner deposited based on the specularly reflected light detected by the specularly reflected light receiving element 43b, it can be determined using the ratio of the smoothness of the reflective surface Rs to the roughness of the toner image t, i.e., the ratio of specular glossiness. However, if the reflective surface Rs is an elastic material, its surface is relatively rough, making it difficult for the density sensor 43 to obtain specularly reflected light from the reflective surface Rs, thus posing a problem in correctly detecting the amount of toner deposited.

[0044] In the printing apparatus 500 of this embodiment, the primary transfer belt 20 is made of an elastic belt having at least an elastic layer on its surface. Therefore, when attempting to detect the amount of toner deposited on the primary transfer belt 20, a problem arises in that the amount of toner deposited cannot be detected correctly. In contrast, the secondary transfer belt 40 is made of a resin film with high gloss, such as PI (polyimide). Therefore, the density sensor 43 can easily obtain specular reflected light from the reflective surface Rs, and it is also easier to determine the ratio of the specular gloss between the reflective surface Rs and the toner image t. For these reasons, in this embodiment, the density sensor 43 is provided in the secondary transfer unit 4.

[0045] Incidentally, the secondary transfer unit 4 is equipped with a pressurizing device 46 as shown in Figure 2 to enable printing on various types of recording media (for example, paper of various thicknesses and surface roughness). The secondary transfer unit 4 sets the pressure of the secondary transfer nip section P (transfer pressure) to an appropriate value using the pressurizing device 46 according to the type of recording media, and transfers the toner image T to the recording media S.

[0046] On the other hand, the toner image T' (test pattern image) formed between the sheets of paper is transferred to the secondary transfer belt 40, and therefore should be transferred to the secondary transfer belt 40 under a constant transfer pressure regardless of the type of recording medium S used for printing.

[0047] However, in previous printing devices 500, the transfer of the test pattern image T' to the secondary transfer belt 40 was performed at the same transfer pressure as when transferring the toner image T to the recording medium S. In other words, if an attempt were made to switch the transfer pressure between sheets of paper, the pressure switching operation would not keep up with the printing speed, reducing the productivity of printed materials. Therefore, the transfer of the toner image T to the recording medium S and the transfer of the test pattern image T' to the secondary transfer belt 40 were performed using the same transfer pressure.

[0048] As a result, the transfer rate of the test pattern image T' to the secondary transfer belt 40 decreases, and the amount of toner deposited, calculated based on the detection value of the density sensor 43, also becomes lower than the actual amount of toner deposited. Consequently, a new problem arises: the image formation conditions cannot be optimized. In other words, the inability to optimize the image formation conditions leads to unstable toner image density during continuous printing, resulting in a decrease in image quality.

[0049] Therefore, in this invention, the amount of toner deposited in the test pattern image T', which fluctuates due to a change in the transfer pressure of the secondary transfer nip section P, is predicted to change, and the detected value of the density sensor 43 is corrected according to this change. Then, the image formation conditions are adjusted based on the corrected detected value. As a result, the detection of the amount of toner deposited in the secondary transfer belt 40 is no longer affected by fluctuations in the transfer pressure of the secondary transfer nip section P, and the printing device 500 can stabilize the density of the toner image during continuous printing.

[0050] <Regarding transfer pressure and detected adhesion amount> The relationship between transfer pressure and detected adhesion amount will be explained below using Figure 4. Figure 4 illustrates the relationship between transfer pressure and detected adhesion amount, with Figure 4(a) being an explanatory diagram for a comparative example and Figure 4(b) being an explanatory diagram for this embodiment. In Figure 4, it is assumed that the transfer pressure at the secondary transfer nip P can be set in four stages from 1 to 4, with higher numbers indicating higher transfer pressure. It is also assumed that the optimal transfer pressure setting for the secondary transfer belt 40 is 1.

[0051] In Figure 4(a), when the transfer pressure is anything other than 1, the transfer rate of the toner image T' (test pattern image) from the primary transfer belt 20 to the secondary transfer belt 40 decreases. As a result, the detected amount of toner, calculated based on the detection value of the density sensor 43, also decreases as shown by the dashed line. In other words, the relationship becomes "target amount of toner > detected amount of toner".

[0052] In the comparative example, the value shown by this dashed line is considered the correct value, and toner images T and T' are formed on the primary transfer belt 20. As a result, variations in image density occur even in toner images formed at, for example, a transfer pressure of 4.

[0053] In contrast, this embodiment is shown in Figure 4(b). The adhesion amount fluctuation values ​​(Δ2, Δ3, Δ4) for each transfer pressure 1 to 4 can be expressed as "adhesion amount fluctuation value (Δn) = adhesion amount target value - adhesion amount detection value (where n = 1 to 4)". Since the adhesion amount fluctuation value at each transfer pressure 1 to 4 can be considered a correction value (correction amount), the corrected adhesion amount detection value can be expressed as "corrected adhesion amount detection value = adhesion amount target value = adhesion amount detection value + adhesion amount fluctuation value".

[0054] Let M be the target value of the amount of adhesion in the test pattern image T'. The detected amount of adhesion Mn based on the test pattern image T' differs for each transfer pressure. Therefore, when the pressure values ​​for transfer pressures 1 to 4 are T1, T2, T3, and T4, the detected amounts of adhesion on the secondary transfer belt 40 for the actual test pattern image T' are M1, M2, M3, and M4 (≠M). Furthermore, the difference from the target amount of adhesion M, i.e., the adhesion variation values ​​(Δ1, Δ2, Δ3, Δ4), can be expressed as Δ1=M-M1, Δ2=M-M2, Δ3=M-M3, and Δ4=M-M4 for each transfer pressure.

[0055] In the comparative example, the density sensor 43 detects the amount of adhesion detected values ​​M1 to M4 (≠M) which fluctuate according to the pressure values ​​T1 to T4 of transfer pressures 1 to 4, and the image formation conditions are adjusted to bring these detected adhesion values ​​closer to the target adhesion value M. In this embodiment, the amount of adhesion fluctuation values ​​Δ1 to Δ4 are predicted based on the detected adhesion values ​​M1 to M4, and the target adhesion values ​​M1+Δ1, M2+Δ2, M3+Δ3, M4+Δ4 corrected according to the amount of adhesion fluctuation values ​​Δ1 to Δ4 are used as the detected adhesion values ​​for each transfer pressure 1 to 4. The image formation conditions are then adjusted to bring these values ​​closer to the corrected detected adhesion values ​​that reflect the amount of adhesion fluctuations. As a result, the amount of the test pattern image T' that adheres to the secondary transfer belt 40 during continuous printing can be kept constant regardless of the transfer pressure.

[0056] Although this embodiment has been described based on a configuration in which the detected amount of adhesion decreases as the transfer pressure increases, the opposite configuration is also possible, in which the detected amount of adhesion increases as the transfer pressure increases. The relationship between the transfer pressure and the detected amount of adhesion may differ depending on the combination of materials of the primary transfer belt 20 and the secondary transfer belt 40. In this embodiment, the primary transfer belt 20 is an elastic belt and the secondary transfer belt 40 is a PI film. In this case, the effect of minute gap discharge occurring between the elastic belt and the toner image, and between the PI film and the toner image, tends to increase as the transfer pressure increases, and it is considered that the detected amount of adhesion decreases as the transfer pressure increases.

[0057] <About operation and processing> The following describes an example of the operation and processing in the embodiment using Figures 5 to 7. Figure 5 is a block diagram of the parts related to adjusting the image formation conditions, Figure 6 is a block diagram showing an example of the hardware configuration of the control unit, and Figure 7 is a flowchart showing an example of correction of the adhesion amount detection value.

[0058] In Figure 5, the control unit 400, which is an example of a control means, includes a calculation unit 401, a correction unit 402, and an image formation condition adjustment unit 403.

[0059] The calculation unit 401 is connected to a density sensor 43 and a storage unit 404. Based on the target adhesion amount value stored in the storage unit 404 and the adhesion amount detected from the density sensor 43, the calculation unit 401 calculates the adhesion amount fluctuation value of the toner image T' on the secondary transfer belt 40, which fluctuates with changes in transfer pressure. In addition to the density sensor 43, the calculation unit 401 may also be connected to a temperature and humidity sensor 200 that detects the temperature and humidity inside the main body of the printing device 500. By acquiring temperature and humidity information inside the main body of the printing device 500, it becomes possible to calculate the adhesion amount fluctuation value more appropriately.

[0060] The correction unit 402 reflects (for example, adds) the adhesion amount fluctuation value calculated by the calculation unit 401 to the adhesion amount detection value and performs a correction on the adhesion amount detection value.

[0061] The image formation condition adjustment unit 403 adjusts the image formation conditions for the toner image forming unit 1 based on the corrected adhesion amount detection value corrected by the correction unit 402.

[0062] The storage unit 404 stores information used by the calculation unit 401 to calculate the adhesion amount fluctuation value. For example, it stores a correction value table that contains information about the type of recording medium S (thickness, surface roughness, etc.) in addition to the adhesion amount target value. When a temperature and humidity sensor 200 is connected to the calculation unit 401, the correction value table may be configured to take temperature and humidity information into account, for example, by making the correction amount of the adhesion amount correction value larger in a high temperature and high humidity environment than in a normal temperature and humidity environment. The storage unit 404 may be provided inside the control unit 400.

[0063] The hardware configuration of the control unit 400 will now be described with reference to Figure 6. The hardware configuration shown in Figure 6 may have components added or removed as needed.

[0064] The control unit 400 includes a CPU (Central Processing Unit) 4001, a ROM (Read Only Memory) 4002, a RAM (Random Access Memory) 4003, an HDD (Hard Disk Drive) / SSD (Solid State Drive) 4004, an I / O (Input / Output) interface 4005, a communication interface 4006, and a bus line 4007.

[0065] The CPU 4001 controls the entire image forming apparatus 500. The CPU 4001 is a processing unit that realizes each function of the image forming apparatus 500 by reading programs or data stored in the ROM 4002 onto the RAM 4003 and executing processing.

[0066] ROM4002 is a non-volatile memory that can retain programs or data even when the power is turned off. RAM4003 is a volatile memory used as a work area for CPU4001, etc. HDD / SSD4004 controls the reading and writing of various data according to the control of CPU4001. The functions of the storage unit 404 described above are realized by HDD / SSD4004.

[0067] The I / O interface 4005 is an interface for input and output between the image forming apparatus 500 and various motors, various sensors (density sensor 43, temperature and humidity sensor 200, etc.), heaters of the fixing unit 6, and other equipment mounted on the image forming apparatus 500.

[0068] The communication interface 4006 is an interface that communicates (connects) with equipment that processes data for input to the image forming apparatus 500, such as a DFE (Digital Front End), via a communication network.

[0069] Bus line 4007 is an address bus, data bus, etc., for electrically connecting the above components, and transmits address signals, data signals, and various control signals. The CPU 4001, ROM 4002, RAM 4003, HDD / SSD 4004, I / O interface 4005, and communication interface 4006 are interconnected via bus line 4007.

[0070] In the above configuration, when adjusting the image formation conditions of the printing device 500 based on the toner image T' (test pattern image), the printing device 500 forms the toner image T' using the toner image forming unit 1, etc., as shown in Figure 7 (step S1).

[0071] The toner image T' formed in step S1 is transferred to the secondary transfer belt 40 via primary and secondary transfer, and passes directly beneath the density sensor 43. At this time, the density sensor 43 detects the passing toner image T' (step S2) and outputs the detected amount value to the calculation unit 401.

[0072] Next, the calculation unit 401 calculates the adhesion amount variation value based on the adhesion amount detected from the concentration sensor 43 and the transfer pressure at that time (step S3). For example, if secondary transfer is not performed on the secondary transfer belt 40 at an appropriate transfer pressure, the difference between the adhesion amount target value and the adhesion amount detected value is calculated as the adhesion amount variation value at that transfer pressure.

[0073] Next, the adhesion amount variation value calculated in step S3 is reflected in the adhesion amount detection value (added in this embodiment), and the adhesion amount detection value is corrected (step S4). The corrected adhesion amount detection value obtained in step S4 is notified to the toner image forming unit 1, etc., via the image formation condition adjustment unit 403. The toner image forming unit 1, etc., considers the notified adhesion amount detection value to be the correct value, and the image formation conditions are adjusted by the image formation condition adjustment unit 403 so that the image density becomes constant.

[0074] As described above, this embodiment includes a toner image forming unit 1 that forms a toner image T' on photoreceptors 11a to 11d, a primary transfer unit 2 having a primary transfer belt 20 onto which the toner image T' on the photoreceptors 11a to 11d is transferred, a secondary transfer unit 4 having a secondary transfer belt 40 onto which the toner image T' on the primary transfer belt 20 is transferred, a pressurizing device 46 that changes the transfer pressure of the secondary transfer belt 40 relative to the primary transfer belt 20, a density sensor 43 that detects the toner image T' transferred onto the secondary transfer belt 40 and outputs a deposition amount detection value, and a toner image forming unit 1 that uses the deposition amount detection value to perform A printing apparatus 500 comprising a control unit 400 for setting the image formation conditions for a toner image T', wherein the control unit 400 includes a calculation unit 401 that calculates a value of the amount of toner image T' on the secondary transfer belt 40 that fluctuates with changes in transfer pressure, based on a target value of the amount of toner image T' to be transferred onto the secondary transfer belt 40 and the detected amount of toner image T', a correction unit 402 that reflects the value of the amount of toner image T' calculated by the calculation unit 401 into the detected amount of toner image T' and corrects the detected amount of toner image T', and an image formation condition adjustment unit 403 that adjusts the image formation conditions based on the detected amount of toner image T' after correction by the correction unit 402.

[0075] This allows for adjustment of imaging conditions based on a corrected deposition amount detection value, which is always corrected to a constant value regardless of the transfer pressure, thereby stabilizing the image density.

[0076] The embodiments of the present invention described above can be modified, added to, or deleted as appropriate without departing from the spirit of the invention. The present invention is not limited to the embodiments described above, and many modifications are possible within the technical concept of the present invention by those with ordinary skill in the art. [Explanation of Symbols]

[0077] 1. Toner image forming unit 2 Primary Transfer Unit 20 Primary Transfer Belt 21a, 21b, 21c, 21d Primary transfer rollers 22 Secondary transfer opposing roller 4. Secondary Transfer Unit 40 Secondary transfer belt 41 Secondary transfer roller 43. Concentration Sensor 46 Pressurizing device 200 Temperature and Humidity Sensors 400 Control Unit 401 Calculation Unit 402 Correction Unit 403 Imaging condition adjustment section 404 Storage section 500 printing equipment

Claims

1. An imaging means for forming a toner image on an image carrier, A first transfer means having a first movable body onto which the toner image on the image carrier is transferred, A second transfer means having a second moving body onto which the toner image on the first moving body is transferred, A transfer pressure changing means for changing the transfer pressure of the second moving body to the first moving body, A means for detecting the toner image transferred onto the second moving body and outputting an adhesion amount detection value, A control means for setting the toner image formation conditions in the image formation means based on the detected amount of adhesion, An image forming apparatus comprising, The control means is A calculation unit calculates a value of the toner image adhesion amount on the second moving body that fluctuates with changes in the transfer pressure, based on a target value of the toner image adhesion amount to be transferred onto the second moving body and the detected adhesion amount. A correction unit that reflects the adhesion amount fluctuation value calculated by the calculation unit into the adhesion amount detection value and corrects the adhesion amount detection value, A picture creation condition adjustment unit adjusts the picture creation conditions based on the corrected adhesion amount detected by the correction unit, An image forming apparatus characterized by comprising:

2. The image forming apparatus according to claim 1, characterized in that the toner image transferred onto the second moving body is a toner image transferred onto the second moving body between recording media transported within the image forming apparatus.

3. The image forming apparatus according to claim 1 or 2, characterized in that the toner image transferred onto the second moving body is a test pattern image.

4. The image forming apparatus according to claim 1, characterized in that the adhesion amount fluctuation value is corrected according to the temperature and humidity inside the image forming apparatus.

5. An imaging means for forming a toner image on an image carrier, A first transfer means having a first movable body onto which the toner image on the image carrier is transferred, A second transfer means having a second moving body onto which the toner image on the first moving body is transferred, A transfer pressure changing means for changing the transfer pressure of the second moving body to the first moving body, A means for detecting the toner image transferred onto the second moving body and outputting an adhesion amount detection value, A control means for setting the toner image formation conditions in the image formation means based on the detected amount of adhesion, An image forming method for an image forming apparatus comprising, A calculation step to calculate a value of the toner image adhesion amount variation on the second moving body that fluctuates with changes in the transfer pressure, based on a target value of the toner image adhesion amount to be transferred onto the second moving body and the adhesion amount detection value, A correction step in which the adhesion amount variation value calculated by the calculation step is reflected in the adhesion amount detection value and the adhesion amount detection value is corrected, A picture-forming condition adjustment step, which adjusts the picture-forming conditions based on the detected adhesion amount after correction by the correction step, An image forming method characterized by comprising the following:

Images