Image forming apparatus, program product, and image forming method

Abstract

An image forming apparatus, a program product, and an image forming method are provided with: a first image forming unit having an image forming section and an intermediate transfer body to which a toner image formed by the image forming section is primarily transferred; a second image forming unit having an image forming section and an intermediate transfer body to which the toner image formed by the image forming section is primarily transferred; a conveyor belt that conveys the sheet to a secondary transfer position at which the toner image formed on the intermediate transfer body is secondarily transferred; the detection device is arranged on the downstream side of the secondary transfer position in the conveying direction of the paper and is used for detecting the pattern image; a first temperature sensor for detecting temperature; a second temperature sensor for detecting temperature; and a processor that performs a process in which a pattern image is formed by the image forming unit when a difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is equal to or greater than a threshold value. And adjusting the position offset of the toner image.

Description

Technical Field

[0001] This invention relates to an image forming apparatus, a program article, and an image forming method. The invention can also be applied to programs and program articles. Background Technology

[0002] Patent Document 1 discloses an image forming apparatus in which temperature sensors are arranged at various positions on the front and rear frames to detect temperature rise, predict the amount of offset, and perform correction.

[0003] Patent Document 2 discloses an image forming apparatus in which a temperature sensor measures the temperature inside the apparatus. When the absolute value of the change in temperature inside the apparatus is less than a threshold, the registration control is adjusted according to a prediction table. When the absolute value of the change in temperature inside the apparatus is greater than the threshold, a registration adjustment patch is formed and the position offset is measured. If the measured position offset differs significantly from the value in the prediction table, the value in the prediction table is corrected to the measured value.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2005-010345

[0005] Patent Document 2: Japanese Patent Application Publication No. 2010-217544

[0006] In recent years, in order to expand the color gamut of images formed by image forming apparatuses, not only are toners based on the basic colors known as CMYK colors used, but also toners of special colors other than CMYK colors are used to form images. In such image forming apparatuses, a structure is sometimes used where multiple image forming units, each equipped with multiple image forming sections for forming toner images, form toner images on paper. In each image forming unit, the toner images formed by the multiple image forming sections are transferred once to an intermediate transfer body, and the toner images on the intermediate transfer body are then transferred a second time to the paper being transported along the paper transport path.

[0007] Then, the components of each image forming unit expand due to a rise in temperature within the apparatus or contract due to a drop in temperature. Therefore, with the temperature change within the apparatus, a positional shift sometimes occurs at the image forming position. Thus, a temperature sensor detects the temperature change within the image forming apparatus; if the detected temperature change is large, each image forming unit forms a pattern image to adjust the positional shift, and a detection device reads the pattern image that has been transferred onto the conveyor belt, thereby adjusting the positional shift of the toning agent image.

[0008] In this configuration where two image forming units are arranged within the image forming apparatus, the image forming unit that is closer to the fixing unit is more susceptible to the heat generated in the fixing unit and thus experiences a higher temperature compared to the single image forming unit. Conversely, the image forming unit that is farther from the fixing unit is less susceptible to the heat generated in the fixing unit and thus does not experience excessively high temperatures compared to the other image forming unit. Furthermore, if the temperature difference between the two image forming units increases, the difference in positional offset between the tonal images formed by the two image forming units also increases.

[0009] Therefore, when only one temperature sensor is installed in the image forming apparatus and the positional offset is adjusted only based on the temperature change at one point in the apparatus, the positional offset caused by the temperature difference between the two image forming units can sometimes be large. Summary of the Invention

[0010] The purpose of this invention is to provide an image forming apparatus, process article, and image forming method that can suppress positional offset of the image forming position of the tonal image formed by two image forming units, compared to the case where positional offset adjustment is made based on the temperature of a point within the apparatus.

[0011] In an image forming apparatus according to a first aspect of the present invention, it comprises: a first image forming unit having a plurality of image forming sections and an intermediate transfer body for primary transfer of toner images formed by the plurality of image forming sections; a second image forming unit disposed adjacent to the first image forming unit and having a plurality of image forming sections and an intermediate transfer body for primary transfer of toner images formed by the plurality of image forming sections; a conveyor belt for conveying paper to a secondary transfer position for secondary transfer of toner images formed on the intermediate transfer bodies of the first and second image forming units respectively; and a detection device disposed downstream of two of the secondary transfer positions in the conveying direction of the paper conveyed by the conveyor belt, and for detecting based on the secondary transfer position. A patterned image of a toner image transferred onto the conveyor belt; a first temperature sensor configured to detect the temperature around the first image forming unit; a second temperature sensor configured to detect the temperature around the second image forming unit; and a processor that performs the following processing: when the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is greater than or equal to a preset first threshold, a patterned image is formed on the conveyor belt by all the image forming parts of the first image forming unit and the second image forming unit; and the positional offset of the toner image formed by the first image forming unit and the second image forming unit is adjusted using the detection result of the detection device.

[0012] The image forming apparatus of the second aspect of the present invention, in the image forming apparatus of the first aspect, includes a memory storing temperatures detected by the first temperature sensor and the second temperature sensor respectively when the position offset was last adjusted. The processor performs the following processing: even when the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is less than a first threshold, and when the temperature difference between the temperature detected by the first temperature sensor when the position offset was last adjusted and the temperature detected by the first temperature sensor this time is greater than or equal to a preset second threshold, a pattern image is formed on the conveyor belt by a plurality of image forming units of the first image forming unit; and the position offset of the tonal image formed by the first image forming unit is adjusted using the detection result of the detection device.

[0013] In the image forming apparatus of the third aspect of the present invention, in the image forming apparatus of the second aspect, the processor performs the following processing: when the temperature difference between the temperature detected by the second temperature sensor when the position offset was last adjusted and the temperature detected by the second temperature sensor this time is a preset third threshold or higher, a pattern image is formed on the conveyor belt by a plurality of image forming units of the second image forming unit; and the position offset of the tonal image formed by the second image forming unit is adjusted using the detection result of the detection device.

[0014] In the image forming apparatus of the fourth aspect of the present invention, in the image forming apparatus of the first aspect, the processor performs the following processing: when all the image forming parts of the first image forming unit and the second image forming unit form a pattern image on the conveyor belt, a pattern image of another color is formed between the pattern images of a preset reference color in the second image forming unit.

[0015] In the fifth aspect of the image forming apparatus of the present invention, in the fourth aspect of the image forming apparatus, the image forming unit used as the reference color is the image forming unit closest to the secondary transfer position.

[0016] In the image forming apparatus of the sixth aspect of the present invention, the reference color is black, as in the image forming apparatus of the fourth aspect.

[0017] In the seventh aspect of the present invention, a program is recorded that causes a computer to perform the following steps: when the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is greater than or equal to a preset first threshold, a pattern image is formed on a conveyor belt by all image forming units of the first image forming unit and the second image forming unit, wherein the first temperature sensor is configured to detect the temperature around the first image forming unit, and the second temperature sensor is configured to detect the temperature around the second image forming unit, which is arranged adjacent to the first image forming unit; and the positional offset of the tonal image formed by the first image forming unit and the second image forming unit is adjusted using the detection result of the detection device.

[0018] In the image forming method of the eighth aspect of the present invention, the method includes the following steps: when the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is greater than or equal to a predetermined first threshold, a pattern image is formed on a conveyor belt by all image forming units of the first image forming unit and the second image forming unit, wherein the first temperature sensor is configured to detect the temperature around the first image forming unit, and the second temperature sensor is configured to detect the temperature around the second image forming unit which is arranged adjacent to the first image forming unit; and the positional offset of the tonal image formed by the first image forming unit and the second image forming unit is adjusted using the detection result of the detection device.

[0019] Invention Effects

[0020] According to the first aspect of the image forming apparatus of the present invention, compared with the case where position offset adjustment is performed based on the temperature of a location within the apparatus, position offset of the image forming position of the tonal image formed by the two image forming units can be suppressed.

[0021] According to the second aspect of the image forming apparatus of the present invention, compared with the case where a pattern image is formed by all image forming parts of two image forming units, the adjustment time for position offset can be shortened.

[0022] According to the third aspect of the image forming apparatus of the present invention, compared with the case where a pattern image is formed by all image forming parts of two image forming units, the adjustment time for position offset can be shortened.

[0023] According to the fourth aspect of the image forming apparatus of the present invention, the accuracy of position offset adjustment can be improved compared with the case where no reference color is used.

[0024] According to the fifth aspect of the image forming apparatus of the present invention, compared with the case where the image forming part closest to the secondary transfer position is not used as the reference color, the position offset adjustment accuracy can be improved.

[0025] According to the sixth aspect of the image forming apparatus of the present invention, the accuracy of position offset adjustment can be improved compared with the case of using an image forming unit with a color that has high reflectivity.

[0026] According to the seventh aspect of the present invention, the program article is able to suppress the positional shift of the image forming position of the tonal image formed by the two image forming units, compared with the case where the positional shift is adjusted according to the temperature of a point within the device.

[0027] According to the image forming method of the eighth aspect of the present invention, compared with the case where the position offset adjustment is made based on the temperature of a location within the apparatus, the position offset of the image forming position of the tonal image formed by the two image forming units can be suppressed. Attached Figure Description

[0028] The embodiments of the present invention will be described in detail with reference to the following figures.

[0029] Figure 1 This is a schematic diagram showing the structure of an image forming apparatus according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram showing the structure of the image forming unit according to one embodiment of the present invention;

[0031] Figure 3 This is a diagram used to illustrate a pattern image for position offset adjustment processing in an image forming apparatus according to an embodiment of the present invention;

[0032] Figure 4 This is a block diagram illustrating the control structure of an image forming apparatus according to an embodiment of the present invention;

[0033] Figure 5 This is a diagram illustrating an example of the temperature of an image forming apparatus according to an embodiment of the present invention, stored in a storage device and detected by a first temperature sensor and a second temperature sensor;

[0034] Figure 6 This is a flowchart illustrating an example of position offset adjustment processing in an image forming apparatus according to an embodiment of the present invention;

[0035] Figure 7 This is a diagram illustrating an example of a pattern image used for position offset adjustment processing in an image forming apparatus according to an embodiment of the present invention.

[0036] Symbol Explanation

[0037] 10-Image forming apparatus, 21-Conveyor belt, 30-Image forming unit, 50-Image forming unit, 80-Control device, 100-First temperature sensor, 150-Detection device, 200-Second temperature sensor. Detailed Implementation

[0038] Next, with reference to the accompanying drawings, embodiments of the present invention will be described in detail.

[0039] [Image forming apparatus]

[0040] Figure 1 This is a diagram showing the structure of an image forming apparatus 10 as an embodiment of the present invention.

[0041] like Figure 1 As shown, the image forming apparatus 10 includes: a receiving section 12 for receiving paper PP; a conveying section 11 for conveying paper PP along a conveying path 19; and image forming units 30 and 50 for forming a tonal image transferred onto paper PP. Image forming unit 30 serves as a first image forming unit. Image forming unit 50 serves as a second image forming unit.

[0042] The receiving part 12 can be pulled out from the image forming apparatus body 10A, which is the main body of the image forming apparatus 10, and contains paper PP.

[0043] The conveying unit 11 includes, in sequence from the upstream side of the conveying direction, a feed roller 13, a conveyor roller 14, a positioning roller pair 15, a conveyor belt device 20, a fixing device 18, and an exhaust roller 17.

[0044] The feed roller 13 feeds the paper PP contained in the receiving section 12 to the conveying path 19 that constitutes the conveying section 11. The conveying roller 14 conveys the paper PP along the conveying path 19.

[0045] The positioning roller pair 15 conveys the paper PP, which is conveyed by the transfer roller 14, to the secondary transfer position TJ2 on the downstream side, as described later. The positioning roller pair 15 clamps the paper PP with positioning roller 15A and pinch roller 15B and conveys the paper PP to the downstream side in the conveying direction.

[0046] The conveyor belt device 20 transfers the toner image formed by the image forming units 30 and 50 onto the paper PP, and conveys the paper PP downstream along the conveyor path 19. Further details about the conveyor belt device 20 will be described later.

[0047] The fixing device 18 has a fixing roller pair 16, and the toner image is fixed onto the paper PP by heating and pressurizing the paper PP with the toner image transferred between the fixing roller pair 16.

[0048] The discharge roller 17 discharges the paper PP, which has been fixed by the fixing device 18 with toner, to the discharge section 9.

[0049] Image forming unit 30 and image forming unit 50 are arranged adjacent to each other. Furthermore, in this embodiment, image forming unit 50 is positioned above image forming unit 30. Alternatively, image forming unit 50 is positioned downstream of image forming unit 30 in the paper transport direction.

[0050] In the image forming unit 30, for example, tonal images of special colors other than the basic colors of yellow, magenta, cyan, and black are formed. The image forming unit 30 includes four image forming sections 32 and an intermediate transfer belt 40, which serves as an intermediate transfer body for transferring the tonal images formed by the four image forming sections 32 in a single pass. The intermediate transfer belt 40 is annular, and the tonal images formed by the four image forming sections 32 are transferred thereon, and in the main view... Figure 1 It can be installed by rotating counterclockwise.

[0051] The image forming unit 32 includes: an image forming unit 32P, which forms a pink toner image; an image forming unit 32S, which forms a silver toner image; an image forming unit 32G, which forms a gold toner image; and an image forming unit 32Gr, which forms a green toner image. These four image forming units 32 are arranged sequentially in the order of image forming unit 32P, image forming unit 32S, image forming unit 32G, and image forming unit 32Gr, from the upstream side (the side closest to the support roller 44 described later) in the rotation direction of the intermediate transfer belt 40. Hereinafter, the upstream side in the rotation direction of the intermediate transfer belt 40 will be referred to as the "upstream side in the rotation direction," and the downstream side in the rotation direction will be referred to as the "downstream side in the rotation direction." That is, in the image forming unit 32, the image forming unit 32Gr is located at the position closest to the downstream side in the rotation direction. Furthermore, in the image forming unit 32, the image forming unit 32Gr is located at the position closest to the secondary transfer position TJ2.

[0052] In addition, P, S, G, and Gr are omitted from the description unless it is necessary to distinguish between them.

[0053] like Figure 2 As shown, the image forming unit 32 includes: a photoreceptor 33; a charging member 34 that charges the surface of the photoreceptor 33; an exposure device 35 that exposes the charged photoreceptor 33 by irradiation; and a developing device 36 that develops the electrostatic latent image formed by the exposure to visualize it as a toner image. The developing device 36 has a developing roller 39 and is subjected to a developing bias voltage.

[0054] Furthermore, primary transfer rollers 37P, 37S, 37G, and 37Gr are positioned opposite each photoreceptor 33 across the intermediate transfer belt 40 to transfer the tonal image formed by the image forming unit 32 onto the intermediate transfer belt 40. The intermediate transfer belt 40 is wound around a support roller 44 and a back-up roll 42, with the support roller 44 supporting the intermediate transfer belt 40 and the support roller 42 positioned in the upstream secondary transfer section 74 (described later). The primary transfer section 70 is configured to include the photoreceptor 33, the primary transfer roller 37, and the intermediate transfer belt 40. Primary transfer positions TP1, TS1, TG1, and TGr1 are respectively designated between the photoreceptors 33P, 33S, 33G, and 33Gr and the intermediate transfer belt 40.

[0055] Except for the different colors formed in the image, the image forming unit 50 has the same structure as the aforementioned image forming unit 30. In the image forming unit 50, for example, tonal images of basic colors such as yellow, magenta, blue-green, and black are formed.

[0056] The image forming unit 50 includes four image forming sections 52 and an intermediate transfer belt 60. The intermediate transfer belt 60 transfers tonal images formed by the four image forming sections 52 onto the image, and in the main view... Figure 1 It can be installed by rotating counterclockwise.

[0057] In addition, such as Figure 2 As shown, except for the different colors formed in the image, the image forming unit 52 has the same structure as the image forming unit 32 of the image forming unit 30. Furthermore, the intermediate transfer belt 60 and the primary transfer roller 57 (described later) also have the same structure as the intermediate transfer belt 40 and primary transfer roller 37 of the image forming unit 30. Moreover, the other components constituting the image forming unit 50 are also the same as those of the image forming unit 30.

[0058] The image forming unit 52 includes: an image forming unit 52Y, which forms a yellow tonal image; an image forming unit 52M, which forms a magenta tonal image; an image forming unit 52C, which forms a blue-green tonal image; and an image forming unit 52K, which forms a black tonal image. The four image forming units 52 are arranged sequentially from the upstream side of the rotational direction (the side closest to the support roller 64 described later) in the order of image forming unit 52Y, image forming unit 52M, image forming unit 52C, and image forming unit 52K. That is, in the image forming units 52, image forming unit 52K is located at the position furthest downstream in the rotational direction. Furthermore, in the image forming units 52, image forming unit 52K is located at the position closest to the secondary transfer position TK2.

[0059] In addition, when there is no need to distinguish between Y, M, C, and K, they are omitted from the description.

[0060] The image forming unit 52 includes a photosensitive element 53, a charged component 54, an exposure device 55, and a developing device 56. The developing device 56 has a developing roller 59 and is subjected to a developing bias voltage.

[0061] Furthermore, primary transfer rollers 57Y, 57M, 57C, and 57K are positioned opposite each photoreceptor 53, separated by the intermediate transfer belt 60. The intermediate transfer belt 60 is wound around a support roller 64 and a support roller 62, which is located in the downstream secondary transfer section 76 described later. The primary transfer section 72 is configured to include the photoreceptor 53, the primary transfer roller 57, and the intermediate transfer belt 60. The primary transfer positions TY1, TM1, TC1, and TK1 are respectively designated between the photoreceptors 53Y, 53M, 53C, and 53K and the intermediate transfer belt 60.

[0062] In image forming unit 30, a first temperature sensor 100 is disposed between the image forming unit 32Gr, which is closer to the secondary transfer position TJ2 than the other image forming units 32P, 32S, and 32G, and the conveyor belt 21. The first temperature sensor 100 is configured to detect the temperature around image forming unit 30. Furthermore, in image forming unit 50, a second temperature sensor 200 is disposed between the image forming unit 52K, which is closer to the secondary transfer position TK2 than the other image forming units 52Y, 52M, and 52C, and the conveyor belt 21. The second temperature sensor 200 is configured to detect the temperature around image forming unit 50.

[0063] Next, the details of the conveyor belt device 20 will be explained.

[0064] like Figure 1 As shown, the conveyor belt device 20 includes: an annular conveyor belt 21; support rollers 22 and 23 supporting the conveyor belt 21; and secondary transfer rollers 24 and 25, which are positioned opposite the support rollers 42 and 62 across the intermediate transfer belts 40 and 60.

[0065] The conveyor belt 21 is configured to transport paper to the secondary transfer positions TJ2 and TK2 of the toner images that are formed on the intermediate transfer belts 40 and 60 of the image forming units 30 and 50, respectively. Furthermore, the conveyor belt 21 is configured to transfer the toner images formed on the intermediate transfer belts 40 and 60 of the image forming units 30 and 50, respectively, during position offset adjustment processing.

[0066] The secondary transfer roller 24 holds the paper PP and the conveyor belt 21 between itself and the support roller 42, and transfers the toner image formed on the intermediate transfer belt 40 of the image forming unit 30 onto the paper PP. Similarly, the secondary transfer roller 25 holds the paper PP and the conveyor belt 21 between itself and the support roller 62, and transfers the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 onto the paper PP.

[0067] Furthermore, the secondary transfer section 74 is configured to include a support roller 42, a secondary transfer roller 24, and an intermediate transfer belt 40. Also, the secondary transfer section 76 is configured to include a support roller 62, a secondary transfer roller 25, and an intermediate transfer belt 60.

[0068] Apply transfer bias pressure to the secondary transfer rollers 24 and 25 respectively.

[0069] Furthermore, the intermediate transfer belt 40 of the image forming unit 30 and the conveyor belt 21 are designated as the secondary transfer position TJ2, and the intermediate transfer belt 60 of the image forming unit 50 and the conveyor belt 21 are designated as the secondary transfer position TK2. Additionally, the secondary transfer position TK2 is the downstream secondary transfer position.

[0070] Furthermore, the conveyor belt device 20 includes a belt cleaning device 78 for cleaning the conveyor belt 21. The belt cleaning device 78 cleans the conveyor belt 21 downstream of the paper transport direction at the downstream secondary transfer position TK2 and downstream of the detection device 150 described later. Additionally, the position cleaned by the belt cleaning device 78 in the conveyor belt 21 is designated as the cleaning position CL.

[0071] Here, as Figure 3 As shown in (C), each image forming unit 32 of the image forming unit 30 and each image forming unit 52 of the image forming unit 50 use a color tone to form a pattern image BC for position offset adjustment processing.

[0072] The pattern image BC includes toner images of eight colors: yellow (Y), magenta (M), cyan (C), black (K), special color pink (P), silver (S), gold (G), and special color green (Gr). Additionally, the symbols Y, M, C, K, P, S, G, and Gr listed after the pattern image BC indicate the colors of the toners; these are omitted when no distinction is needed. Each color's pattern image BC has the same shape and includes horizontal and diagonal lines extending along the main scanning direction (vertical in the figure) of the image forming units 30 and 50.

[0073] The pattern image BC is configured with three columns of patterns extending in a columnar manner along the sub-scanning direction (left-right direction in the figure) in the image forming units 30 and 50. The patterns in each column are identical, and the black pattern image BCK, which serves as the reference color, is alternated with the pattern images BC other than black. Furthermore, the pattern images are arranged at equal intervals.

[0074] In this embodiment, the pattern images BCP, BCS, BCG, and BCGr used for position offset adjustment processing are formed on the intermediate transfer belt 40. Furthermore, the pattern images BCY, BCM, BCC, and BCK used for position offset adjustment processing are formed on the intermediate transfer belt 60. Then, each is finally transferred a second time onto the conveyor belt 21.

[0075] like Figure 1 As shown, the detection device 150 is located near the upper end of the conveyor belt 21. Furthermore, the detection device 150 is located downstream of the secondary transfer positions TJ2 and TK2 in the conveying direction of the paper PP conveyed by the conveyor belt 21. Additionally, the detection device 150 is located upstream of the paper conveying direction, further downstream than the most downstream secondary transfer position TK2, and also upstream of the paper conveying direction where the cleaning device 78 is located.

[0076] The detection device 150 is configured to detect the pattern image BC based on the tonal image transferred to the conveyor belt 21 on the downstream side of the paper transport direction of the secondary transfer position TK2 and the upstream side of the paper transport direction of the cleaning position CL.

[0077] In other words, the detection device 150 is positioned to detect the pattern image BC further downstream in the paper transport direction than the downstream secondary transfer unit 76. Furthermore, the detection device 150 is positioned to detect the positions of all pattern images BC formed by all image forming units 32P, 32S, 32G, 32Gr, 52Y, 52M, 52C, and 52K.

[0078] The detection device 150 of this embodiment includes three detection units 150A, 150B, and 150C (see reference) arranged at intervals along the axial direction, or in other words, the width direction of the conveyor belt 21 (the paper width direction, also known as the main scanning direction). Figure 3 (C)). The pattern image BC forms three columns corresponding to the positions of the detection units 150A, 150B, and 150C.

[0079] Thus, by using three columns of patterned images BC extending along the sub-scanning direction, the positional offsets at three points (e.g., the two ends and the center) in the main scanning direction can be adjusted independently.

[0080] The pattern image BC used for position offset adjustment processing is formed as follows. First, as... Figure 3 As shown in (A), the image forming unit 30 transfers the pattern images BCP, BCS, BCG, and BCGr onto the intermediate transfer belt 40 in one step.

[0081] And, as Figure 3As shown in (B), multiple pattern images BCK, which will become the reference color, are transferred once to the intermediate transfer belt 60 by the image forming unit 50. Furthermore, pattern images BCY, BCM, and BCC are arranged between the multiple pattern images BCK and transferred once to the intermediate transfer belt 60. Thus, when transferred a second time to the conveyor belt 21, pattern images BCP, BCS, BCG, and BCGr are arranged between the multiple pattern images BCK.

[0082] Finally, as Figure 3 As shown in (C), the pattern image BC, which was first transferred onto the intermediate transfer belts 40 and 60, is transferred a second time onto the conveyor belt 21 to become the pattern image BC used for position offset adjustment processing. That is, pattern images of other colors BC are formed among multiple pattern images BCK, which serve as a preset reference color, such as black. In this way, by using the black pattern image BCK, which is closest to the downstream secondary transfer position TK2 and has low reflectivity, as the reference color, the accuracy of position offset adjustment can be improved.

[0083] [Control Device]

[0084] Next, use Figure 4 The control device 80 that controls the operation of the image forming apparatus 10 will be described.

[0085] like Figure 4 As shown, the image forming unit 30, image forming unit 50, detection device 150, transmission unit 11, communication unit 90, first temperature sensor 100 and second temperature sensor 200 are electrically connected to the control device 80.

[0086] like Figure 4 As shown, the control device 80 includes a CPU (Central Processing Unit) 81, ROM (Read Only Memory) 82, RAM (Random Access Memory) 83, a storage device 85 such as a hard disk drive, and an input / output interface (I / O) 84 for inputting and outputting data to and from various devices via a network. These components are interconnected via a control bus.

[0087] Here, an image forming control program (not shown) that is executed by the CPU 81 is stored in ROM 82. Then, the CPU 81 reads the image forming control program (not shown) from ROM 82 and loads it into RAM 83, thereby executing the printing process based on the image forming control program (not shown).

[0088] Furthermore, the image forming unit 30, image forming unit 50, detection device 150, transmission unit 11, communication unit 90, first temperature sensor 100, and second temperature sensor 200 are connected to I / O 84. The communication unit 90 is an interface for enabling data communication between a terminal device such as a personal computer and the image forming apparatus 10.

[0089] The storage device 85 stores the setting positions of the image forming units 32 and 52 of each color in the image forming units 30 and 50. Furthermore, if position offset adjustment processing is performed, the offset amount and correction amount during the adjustment processing are stored in the storage device 85. Figure 5 As shown, if position offset adjustment processing is performed, the temperature detected by the first temperature sensor 100 and the second temperature sensor 200 when the position offset adjustment processing was performed (set as the previous temperature), and the temperature detected by the first temperature sensor 100 and the second temperature sensor 200 when the power is turned on or when printing starts (set as the current temperature) are stored in the storage device 85. The storage device 85 is used as a memory.

[0090] The control device 80 performs various controls for forming tonal images on the intermediate transfer belts 40 and 60 by the image forming units 30 and 50 of each color.

[0091] Furthermore, the control device 80 controls the developing bias applied to the developing rollers 39 and 59 of the developing devices 36 and 56, respectively. Also, the control device 80 controls the transfer bias applied to the secondary transfer rollers 24 and 25, respectively.

[0092] Furthermore, the control device 80 controls the timing, duration, and amount of toner supply from each color toner cartridge to the developing devices 36 and 56.

[0093] Furthermore, the control device 80 calculates the temperature difference between the temperature detected by the first temperature sensor 100 and the temperature detected by the second temperature sensor 200. Then, based on the calculated temperature difference, the control device 80 forms a pattern image on the conveyor belt 21 using the image forming units of each color of the image forming unit 30 and / or the image forming unit 50.

[0094] Here, "A and / or B" has the same meaning as "at least one of A and B". That is, "A and / or B" means that it can be only A, only B, or a combination of A and B.

[0095] Furthermore, the control device 80 calculates the temperature difference between the temperature detected by the first temperature sensor 100 when the position offset was last adjusted (stored in the storage device 85) and the temperature detected by the first temperature sensor 100 when the power is turned on or printing begins. The control device 80 also calculates the temperature difference between the temperature detected by the second temperature sensor 200 when the position offset was last adjusted (stored in the storage device 85) and the temperature detected by the second temperature sensor 200 when the power is turned on or printing begins. Then, based on these calculated temperature differences, the control device 80 forms a pattern image on the conveyor belt 21 using the image forming units of each color in the image forming unit 30 and / or the image forming unit 50.

[0096] Then, the control device 80 detects the pattern image BC using the detection device 150. Based on the detection results, the control device 80 controls the timing of the formation of toner images on the intermediate transfer belts 40 and 60 (specifically, the exposure timing of each exposure device 35 and 55, etc.), the development bias applied to each developing roller 39 and 59, and the transfer bias applied to the secondary transfer rollers 24 and 25. That is, the positional offset adjustment of the toner images formed by the image forming unit 30 and image forming unit 50 is performed using the detection results of the detection device 150.

[0097] Then, the control device 80 stores the temperatures detected by the first temperature sensor 100 and the second temperature sensor 200 during the position offset adjustment process in the storage device 85.

[0098] [Image forming process]

[0099] Next, a general description of the image forming process in the image forming apparatus 10 will be given.

[0100] First, the control device 80 controls each image forming unit 32 to form a toner image on the intermediate transfer belt 40 of the image forming unit 30. Similarly, the control device 80 controls each image forming unit 52 to form a toner image on the intermediate transfer belt 60 of the image forming unit 50.

[0101] Specifically, the control device 80 applies voltage to the charged components 34 and 54, causing the surfaces of the photoreceptors 33 and 53 to become charged by the charged components 34 and 54, reaching a preset potential. Then, based on image data acquired via the communication unit 90, the control device 80 uses the exposure devices 35 and 55 to expose the charged surfaces of the photoreceptors 33 and 53 to form an electrostatic latent image. Thus, an electrostatic latent image corresponding to the image data is formed on the surface of the photoreceptors 33 and 53.

[0102] Next, the control device 80 develops the electrostatic latent image formed by the exposure devices 35 and 55 using the developing devices 36 and 56 to visualize it as a toner image. Furthermore, the control device 80 uses the primary transfer rollers 37 and 57 to overlap and transfer the toner images formed on the surfaces of the photoreceptors 33 and 53 of each color onto the intermediate transfer belts 40 and 60.

[0103] Thus, a toner image formed by the image forming unit 30, for example, by overlaying toners of special colors such as pink (P), silver (S), gold (G), and green (Gr), is formed on the intermediate transfer belt 40. Similarly, a toner image formed by the image forming unit 50, for example, by overlaying toners of yellow (Y), magenta (M), cyan (C), and black (K), is formed on the intermediate transfer belt 60.

[0104] Here, the paper PP, fed from the receiving section 12 to the conveying path 19 by the feed roller 13, is conveyed to the secondary transfer position TJ2 after the timing of the conveying is adjusted by the positioning roller 15 under the control of the control device 80. At this secondary transfer position TJ2, the paper PP is conveyed between the support roller 42 and the secondary transfer roller 24, so that the toner image on the outer peripheral surface of the intermediate transfer belt 40 is transferred onto the paper PP. Then, the paper PP with the toner image transferred is conveyed to the downstream side of the conveying direction and arrives at the secondary transfer position TK2 on the downstream side of the conveying direction.

[0105] At this time, the control device 80 adjusts the timing of the start of image formation so that the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 overlaps and is transferred onto the toner image on the paper PP conveyed from the upstream side of the conveying direction.

[0106] Paper PP, which has been superimposed and transferred with tonal images of various colors formed by image forming units 30 and 50, is fixed by the fixing roller of fixing device 18 to 16, and then discharged by discharge roller 17 to discharge section 9 provided on the upper part of the main body 10A of image forming device.

[0107] [Position Offset Adjustment Processing]

[0108] Next, use Figure 6 An example of position offset adjustment processing in the image forming apparatus 10 will be described.

[0109] First, in step S11, the control device 80 determines whether the temperature difference between the temperature detected by the first temperature sensor 100 and the temperature detected by the second temperature sensor 200 when the image forming apparatus 10 is powered on or when printing begins is greater than or equal to a preset first threshold (e.g., 5°C or more). If the temperature difference between the temperature detected by the first temperature sensor 100 and the temperature detected by the second temperature sensor 200 is greater than or equal to the first threshold, the process proceeds to step S14; if it is less than the first threshold, the process proceeds to step S12.

[0110] Then, in step S12, the control device 80 determines whether, if the temperature difference between the temperature detected by the first temperature sensor 100 and the temperature detected by the second temperature sensor 200 is less than a first threshold, the temperature difference stored in the storage device 85 based on the temperature detected by the first temperature sensor 100 during the last position offset adjustment process and the temperature detected by the first temperature sensor 100 at the current power-on or printing start time is greater than or equal to a preset second threshold (e.g., greater than 5°C). If the temperature difference between the temperature detected by the first temperature sensor 100 during the last position offset adjustment process and the temperature detected by the first temperature sensor 100 at the current power-on or printing start time is greater than or equal to the preset second threshold, the process proceeds to step S13; otherwise, it proceeds to step S16.

[0111] Then, in step S13, the control device 80 determines whether the temperature difference between the temperature detected by the first temperature sensor 100 during the last position offset adjustment process stored in the storage device 85 and the temperature detected by the first temperature sensor 100 at the current power-on or printing start time is greater than or equal to a second threshold. If the temperature difference between the temperature detected by the second temperature sensor 200 during the last position offset adjustment process stored in the storage device 85 and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is greater than or equal to a preset third threshold (e.g., greater than 5°C). If the temperature difference between the temperature detected by the second temperature sensor 200 during the last position offset adjustment process and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is greater than or equal to the preset third threshold, the process proceeds to step S14; otherwise, it proceeds to step S15.

[0112] Then, in step S14, the control device 80 forms a pattern image BC on the conveyor belt 21 using all the image forming units 32 and 52 of the image forming unit 30 and the image forming unit 50. That is, the toner image is transferred once onto the intermediate transfer belt 40 using the image forming units 32P, 32S, 32G, and 32Gr of the image forming unit 30. Furthermore, the toner image is transferred once onto the intermediate transfer belt 60 using the image forming units 52Y, 52M, 52C, and 52K of the image forming unit 50. Then, the toner image transferred once onto the intermediate transfer belts 40 and 60 is transferred a second time onto the conveyor belt 21 to form the pattern image BC. At this time, as... Figure 3 As shown in (C), a black pattern image BCK is formed between each of the pattern images BCP, BCS, BCG, BCGr, BCY, BCM, and BCC, with black as the base color.

[0113] Then, in step S15, if the temperature difference between the temperature detected by the second temperature sensor 200 during the previous position offset adjustment process stored in the storage device 85 and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is less than a third threshold, the image forming units 32P, 32S, 32G, and 32Gr of the image forming unit 30 transfer the toner image onto the intermediate transfer belt 40 once, and the image forming unit 52K of the image forming unit 50 (which serves as the reference color) transfers the toner image onto the intermediate transfer belt 60 once. Then, the toner image transferred once onto the intermediate transfer belts 40 and 60 is transferred a second time onto the conveyor belt 21 to form the pattern image BC. At this time, as... Figure 7 As shown in (A), a black pattern image BCK, serving as the base color, is formed between each of the pattern images BCP, BCS, BCG, and BCGr. Alternatively, any one of the image forming units 32 of the image forming unit 30 can be used as the base color. For example, when using a special color green as the base color, only the image forming unit 30 is used to form a pattern image BCGr, using the special color green as the base color, between each of the pattern images BCP, BCS, and BCG.

[0114] Then, in step S16, the control device 80 determines whether the temperature difference between the temperature detected by the first temperature sensor 100 during the last position offset adjustment process stored in the storage device 85 and the temperature detected by the first temperature sensor 100 at the current power-on or printing start time is less than a preset second threshold, and whether the temperature difference between the temperature detected by the second temperature sensor 200 during the last position offset adjustment process stored in the storage device 85 and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is greater than or equal to a preset third threshold. If the temperature difference between the temperature detected by the second temperature sensor 200 during the last position offset adjustment process and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is greater than or equal to the preset third threshold, the process proceeds to step S17; if the temperature difference is less than the third threshold, no position offset adjustment process is performed and the process ends.

[0115] Then, in step S17, if the temperature difference between the temperature detected by the second temperature sensor 200 during the previous position offset adjustment process stored in the storage device 85 and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is a third threshold or higher, the control device 80 uses the image forming units 52Y, 52M, 52C, and 52K of the image forming unit 50 to transfer the toner image onto the intermediate transfer belt 60 once, and then transfers the toner image transferred once onto the intermediate transfer belt 60 a second time onto the conveyor belt 21 to form the pattern image BC. At this time, as Figure 7 As shown in (B), a black pattern image BCK is formed between each of the pattern images BCY, BCM, and BCC, serving as the base color.

[0116] Specifically, for example, if the temperature detected by the first temperature sensor 100 is 21°C and the temperature detected by the second temperature sensor 200 is 22°C when the power is turned on or printing begins, the control device 80 makes these temperature differences 1°C. That is, when the first threshold is set to 5°C, the temperature difference between the temperature detected by the first temperature sensor 100 and the temperature detected by the second temperature sensor 200 becomes less than the first threshold.

[0117] Then, if the temperature detected by the first temperature sensor 100 during the last position offset adjustment process (stored in storage device 85) was 25°C, and the temperature detected by the first temperature sensor 100 during the current power-on or printing start is 21°C, the control device 80 sets these temperature differences to 4°C. That is, when the second threshold is set to 5°C, the temperature difference between the previous and current temperatures detected by the first temperature sensor 100 becomes less than the second threshold.

[0118] Furthermore, if the temperature detected by the second temperature sensor 200 during the last position offset adjustment process stored in the storage device 85 was 28°C, and the temperature detected by the second temperature sensor 200 at the current power-on or printing start time is 22°C, the control device 80 sets these temperature differences to 6°C. That is, when the third threshold is set to 5°C, the temperature difference between the previous and current temperatures detected by the second temperature sensor 200 becomes greater than or equal to the third threshold.

[0119] Then, at this time, the control device 80 uses the image forming units 52Y, 52M, 52C, and 52K in the image forming unit 50, where the temperature difference is greater than or equal to the third threshold, to transfer the toner image onto the intermediate transfer belt 60 once, and then transfers the toner image transferred once onto the intermediate transfer belt 60 onto the conveyor belt 21 a second time to form a pattern image BC.

[0120] Then, in step S18, the control device 80 performs position offset adjustment processing based on the formed pattern image BC. Specifically, the control device 80 uses the detection device 150 to detect the formed pattern image BC respectively, and performs position offset adjustment processing based on the detection results of the detection device 150.

[0121] Here, when performing positional offset adjustment processing between colors, the positional offset of the pattern image BC other than black is obtained based on the black pattern image BCK as the reference color. Then, a correction value is calculated based on the positional offset of the pattern image BCK, and the exposure timing of the exposure devices 35P, 35S, 35G, 35Gr, 55Y, 55M, 55C, and 55K is adjusted.

[0122] That is, the control device 80 adjusts the position offset relative to the pattern image BCK so that the pattern images BCP, BCS, BCG, and BCGr of the image forming unit 30 are in a preset position and positional relationship. Similarly, the control device 80 adjusts the position offset relative to the pattern image BCK so that the pattern images BCY, BCM, and BCC of other colors of the image forming unit 50 are in a preset position and positional relationship.

[0123] Thus, temperature sensors are arranged around adjacent image forming units 30 and 50. Based on the temperature difference between image forming units 30 and 50, or the temperature difference compared to the temperature during the previous position offset adjustment process, each image forming unit 32 and / or image forming unit 52 forms a pattern image BC and performs position offset adjustment processing. This reduces the position offset caused by the temperature difference between the two image forming units 30 and 50.

[0124] Furthermore, compared to the case where all image forming units 32 and 52 always form a pattern image BC of all colors and perform position offset adjustment processing, the reading time can be shortened. As a result, the position offset adjustment time can be shortened, thereby improving adjustment efficiency. Also, compared to the case where a pattern image BC of all colors is formed, the amount of toner consumed in the position offset adjustment process can be reduced.

[0125] Furthermore, position offset adjustment is not limited to the methods described above and can be performed using any other method.

[0126] Furthermore, in this embodiment, the detection device 150 detects the pattern image BC that has been transferred to the conveyor belt 21, thus improving the detection accuracy compared to the case of detecting the pattern image BC that has been transferred to paper PP with different surface conditions depending on the material, etc.

[0127] <Other methods>

[0128] Furthermore, the present invention is not limited to the embodiments described above.

[0129] For example, in the above embodiment, an image forming unit 50 was described with its structure positioned above the image forming unit 30, but this is not a limitation. The image forming unit 30 and the image forming unit 50 may be arranged adjacent to each other in the lateral direction.

[0130] Furthermore, in the above embodiment, the first temperature sensor 100 and the second temperature sensor 200 are disposed around the image forming sections 32Gr and 52K of their respective image forming units near the secondary transfer positions TJ2 and TK2, but are not limited thereto. They can be disposed at positions that can detect the temperature around the image forming units 30 and 50, respectively.

[0131] Furthermore, in the above embodiment, the detection device 150 for detecting the pattern image BC transferred to the conveyor belt 21 is located downstream of the multiple secondary transfer positions TJ2, TK2, but it is not limited to this. The detection device 150 may also be located in other positions.

[0132] Furthermore, a detection device for detecting the pattern image BC can be further installed between the downstream primary transfer positions TGr1, TK1 and the secondary transfer positions TJ2, TK2 in the intermediate transfer belts 40, 60.

[0133] Furthermore, in the above embodiment, the case where a black pattern image BCK is used as the reference color during position offset adjustment processing has been described, but it is not limited to this. Other colors may also be used as the reference color.

[0134] Furthermore, the cheapest color among the image forming units 30 and 50 can be used as the reference color. This reduces the consumption of expensive color toners.

[0135] Furthermore, in the above embodiments, a pattern image BC can be formed for each image forming unit 30, 50 without using a reference color, and the offset can be detected.

[0136] Furthermore, while the above embodiment describes the case where position offset adjustment is performed using a pattern image BC, it is not limited to this. Color adjustments, such as density adjustments, can also be performed in addition to position offset adjustment.

[0137] Furthermore, in the above embodiment, the detection device 150 detects the structure of the pattern image BC that has been transferred to the conveyor belt 21, but it is not limited to this. The detection device 150 can also detect the structure of the pattern image BC that has been transferred to the paper PP.

[0138] Furthermore, the structure of the image forming apparatus is not limited to the structure described in the above embodiment, and various structures are possible. Moreover, it can be implemented in various ways without departing from the spirit of the present invention.

[0139] Furthermore, in the above embodiments, processor refers to processor in a broad sense, and includes general-purpose processors (e.g., CPU, etc.) and special-purpose processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0140] Furthermore, the processor in the above embodiments can be operated not only by a single processor, but also collaboratively by multiple processors located in physically separate positions. Moreover, the order in which the processors operate is not limited to the order described in the above embodiments and can be appropriately modified.

[0141] The technology of this invention can also be applied to programs and program artifacts.

[0142] [Postscript]

[0143] The following are descriptions of the methods of the present invention. (1)

[0145] An image forming apparatus comprising:

[0146] The first image forming unit has a plurality of image forming sections and an intermediate transfer body for transferring a tonal image formed by the plurality of image forming sections in one step;

[0147] The second image forming unit is arranged adjacent to the first image forming unit and has a plurality of image forming sections and an intermediate transfer body for transferring a tonal image formed by the plurality of image forming sections in one step.

[0148] A conveyor belt transports the paper to the secondary transfer position where the toner image, which is formed on the intermediate transfer body of the first image forming unit and the second image forming unit, is transferred twice.

[0149] The detection device is located downstream of the two secondary transfer positions in the conveying direction of the paper being conveyed by the conveyor belt, and detects the pattern image based on the toner image transferred to the conveyor belt in the secondary transfer.

[0150] A first temperature sensor is configured to detect the temperature around the first image forming unit;

[0151] A second temperature sensor is configured to detect the temperature surrounding the second image forming unit; and

[0152] processor,

[0153] The processor performs the following processing:

[0154] When the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is greater than or equal to a preset first threshold, a pattern image is formed on the conveyor belt by all the image forming units of the first image forming unit and the second image forming unit; and

[0155] The detection results from the detection device are used to adjust the positional offset of the tonal image formed by the first image forming unit and the second image forming unit. (2)

[0157] The image forming apparatus according to (1) includes a memory,

[0158] The memory stores the temperatures detected by the first temperature sensor and the second temperature sensor respectively when the position offset was last adjusted.

[0159] The processor performs the following processing:

[0160] Even when the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is less than the first threshold, if the temperature difference between the temperature detected by the first temperature sensor at the time of the last position offset adjustment and the temperature detected by the first temperature sensor this time is greater than or equal to a preset second threshold, a pattern image is formed on the conveyor belt by the plurality of image forming units of the first image forming unit; and

[0161] The positional offset of the tonal image formed by the first image forming unit is adjusted using the detection results from the detection device. (3)

[0163] According to the image forming apparatus described in (2), wherein,

[0164] The processor performs the following processing:

[0165] If the temperature difference between the temperature detected by the second temperature sensor at the time of the last position offset adjustment (stored in the memory) and the temperature detected by the second temperature sensor this time is greater than or equal to a preset third threshold, a pattern image is formed on the conveyor belt by the plurality of image forming units of the second image forming unit; and

[0166] The positional offset of the tonal image formed by the second image forming unit is adjusted using the detection results from the detection device. (4)

[0168] According to the image forming apparatus described in (1), wherein,

[0169] The processor performs the following processing: when all the image forming parts of the first image forming unit and the second image forming unit form pattern images on the conveyor belt, pattern images of other colors are formed between pattern images of a preset reference color in the second image forming unit. (5)

[0171] According to the image forming apparatus described in (4), wherein,

[0172] The image forming unit used as the reference color is the image forming unit closest to the secondary transfer position. (6)

[0174] According to the image forming apparatus described in (4), wherein,

[0175] The base color is black. (7)

[0177] A program that causes a computer to perform the following steps:

[0178] When the temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is greater than or equal to a preset first threshold, a pattern image is formed on the conveyor belt by all image forming units of the first image forming unit and the second image forming unit. The first temperature sensor is configured to detect the temperature around the first image forming unit, and the second temperature sensor is configured to detect the temperature around the second image forming unit, which is arranged adjacent to the first image forming unit.

[0179] The positional offset of the tonal image formed by the first image forming unit and the second image forming unit is adjusted using the detection results of the detection device.

[0180] The effects of the appendix-based structure are described below.

[0181] According to the image forming apparatus of (1), compared with the case where the position offset is adjusted based on the temperature of a point within the apparatus, the position offset of the image forming position of the tonal image formed by the two image forming units can be suppressed.

[0182] According to the image forming apparatus of (2), compared with the case where a pattern image is formed by all image forming parts of two image forming units, the adjustment time for position offset can be shortened.

[0183] According to the image forming apparatus of (3), compared with the case where a pattern image is formed by all image forming parts of two image forming units, the adjustment time for position offset can be shortened.

[0184] According to the image forming apparatus of (4), the accuracy of position offset adjustment can be improved compared with the case where no reference color is used.

[0185] According to the image forming apparatus of (5), compared with the case where the image forming unit closest to the secondary transfer position is not used as the reference color, the adjustment accuracy of position offset can be improved.

[0186] According to the image forming apparatus of (6), compared with the case of using an image forming unit with a color that has high reflectivity, the adjustment accuracy of position offset can be improved.

[0187] According to the procedure in (7), compared with the case where the position offset is adjusted based on the temperature at a point within the device, the position offset of the image forming position of the tonal image formed by the two image forming units can be suppressed.

[0188] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. An image forming apparatus comprising: a first image forming unit having a plurality of image forming portions and an intermediate transfer body onto which toner images formed by the plurality of image forming portions are once transferred; a second image forming unit disposed adjacent to the first image forming unit and having a plurality of image forming portions and an intermediate transfer body onto which toner images formed by the plurality of image forming portions are once transferred; a conveyance belt that conveys a sheet to a secondary transfer position at which toner images formed on the intermediate transfer bodies of the first image forming unit and the second image forming unit are respectively secondary transferred; a detection device disposed on a downstream side of both of the secondary transfer positions in a conveyance direction in which a sheet is conveyed by the conveyance belt, and that detects a pattern image based on toner images secondary transferred onto the conveyance belt; a first temperature sensor configured to detect a temperature around the first image forming unit; a second temperature sensor configured to detect a temperature around the second image forming unit; and a processor, the processor performs processing of: forming a pattern image on the conveyance belt by all of the image forming portions of the first image forming unit and the second image forming unit, in a case where a temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is equal to or greater than a first threshold value that is set in advance; and adjusting a positional displacement of toner images formed by the first image forming unit and the second image forming unit using a detection result of the detection device.

2. The image forming apparatus according to claim 1, comprising a memory, the memory stores temperatures detected by the first temperature sensor and the second temperature sensor at a time when a positional displacement was last adjusted, the processor performs processing of: forming a pattern image on the conveyance belt by the plurality of image forming portions of the first image forming unit, in a case where a temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is less than the first threshold value, and a temperature difference between the temperature detected by the first temperature sensor at the time when the positional displacement was last adjusted and stored in the memory and the temperature detected by the first temperature sensor this time is equal to or greater than a second threshold value that is set in advance; and adjusting a positional displacement of toner images formed by the first image forming unit using a detection result of the detection device.

3. The image forming apparatus according to claim 2, wherein the processor performs processing of: forming a pattern image on the conveyance belt by the plurality of image forming portions of the second image forming unit, in a case where a temperature difference between the temperature detected by the second temperature sensor at the time when the positional displacement was last adjusted and stored in the memory and the temperature detected by the second temperature sensor this time is equal to or greater than a third threshold value that is set in advance; and adjusting a positional displacement of toner images formed by the second image forming unit using a detection result of the detection device.

4. The image forming apparatus according to claim 1, wherein ​ ​ The processor performs processing of forming a pattern image of another color between pattern images of a preset reference color in the second image forming unit when pattern images are formed on the conveyance belt by all of the image forming sections of the first image forming unit and the second image forming unit.

5. The image forming apparatus according to claim 4, wherein The image forming section serving as the reference color is the image forming section closest to the secondary transfer position.

6. The image forming apparatus according to claim 4, wherein The reference color is black.

7. A program product recording a program for causing a computer to execute the steps of: In a case where a temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is equal to or greater than a first threshold value that is set in advance, all of the image forming portions of the first image forming unit and the second image forming unit form a pattern image on the conveyance belt, wherein The first temperature sensor is configured to detect a temperature around the first image forming unit, and the second temperature sensor is configured to detect a temperature around the second image forming unit disposed adjacent to the first image forming unit; and A positional shift of toner images formed by the first image forming unit and the second image forming unit is adjusted using a detection result of the detection means.

8. An image forming method comprising the steps of: In a case where a temperature difference between the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor is equal to or greater than a first threshold value that is set in advance, all of the image forming portions of the first image forming unit and the second image forming unit form a pattern image on the conveyance belt, wherein The first temperature sensor is configured to detect a temperature around the first image forming unit, and the second temperature sensor is configured to detect a temperature around the second image forming unit disposed adjacent to the first image forming unit; and A positional shift of toner images formed by the first image forming unit and the second image forming unit is adjusted using a detection result of the detection means.

Images