Patent Grant
8588632
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2011-058118 filed Mar. 16, 2011.
(i) Technical Field
The present invention relates to an information processor, an image forming apparatus, an information processing method, and a non-transitory computer-readable medium.
(ii) Related Art
A sheet of paper used in an image forming apparatus varies in condition with a variation in water content. When the condition of the sheet of paper varies, it has various influences on the formation of an image. A technique of suppressing the influence and forming an appropriate image is known.
According to an aspect of the invention, there is provided an information processor including: a storage unit that stores a first coefficient, which is preset on the basis of the relationship between a water content of a sheet of paper and a signal output from a signal output unit on the basis of the water content when a sheet of paper having each characteristic has the water content, in correspondence with the characteristics; a first acquisition unit that acquires a first signal output from the signal output unit on the basis of the water content of a first sheet of paper not having a first image formed thereon; a second acquisition unit that acquires a second signal output from the signal output unit on the basis of the water content of the first sheet of paper which has the first image formed on a first surface thereof and which is heated to fix the first image; a determination unit that determines the characteristic of the first sheet of paper; a first calculation unit that calculates a variation in water content of the first sheet of paper using the difference between the acquired first signal and the acquired second signal and the first coefficient stored in correspondence with the determined characteristic in the storage unit; and a second calculation unit that calculates an expansion and contraction ratio of the first sheet of paper using the variation in water content calculated by the first calculation unit.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
The image forming unit 3 includes image forming sections 12Y, 12M, 12C, and 12K, an intermediate transfer belt 13, a secondary transfer roller 14, a fixing unit 15, a cooling unit 16, a sheet feeding unit 17, a register roller 18, and a turnover unit 19. The image forming sections 12Y, 12M, 12C, and 12K form toner images of yellow, magenta, cyan, and black, respectively, and transfer the formed toner images to the intermediate transfer belt 13. More specifically, each of the image forming sections 12Y, 12M, 12C, and 12K includes a photosensitive drum, a charging device, an exposing device, a developing device, and a primary transfer roller. The photosensitive drum has a photosensitive layer and rotates about an axis. The charging device uniformly charges the surface of the photosensitive drum. The exposing device exposes the charged photosensitive drum to light to form an electrostatic latent image. The developing device develops the electrostatic latent image formed on the photosensitive drum with toner to form a toner image. The primary transfer roller transfers the toner image formed on the photosensitive drum to the intermediate transfer belt 13.
The intermediate transfer belt 13 rotates in the direction of arrow A in the drawing and carries the toner images transferred by the image forming sections 12Y, 12M, 12C, and 12K to the secondary transfer roller 14. The secondary transfer roller 14 transfers the toner images carried by the intermediate transfer belt 13 to a sheet of paper P. Accordingly, an image is formed on the sheet of paper P. The fixing unit 15 fixes the toner image to the sheet of paper P by applying heat and pressure. The cooling unit 16 cools the sheet of paper P passing through the fixing unit 15. The sheet feeding unit 17 receives plural sheets of paper P and feeds the sheets of paper P sheet by sheet. The register roller 18 positions the sheet of paper P sent from the sheet feeding unit 17 or the turnover unit 19 and sends out the sheet of paper P to the secondary transfer roller 14. The turnover unit 19 turns over the sheet of paper P after an image is formed on the first surface of the sheet P when images are formed on both surfaces of the sheet of paper P.
Referring to
The principle of the water content sensor 6 will be described below with reference to
The light-receiving portion 23 receives the light reflected by the sheet of paper P, converts the received light into an electrical signal, and outputs the electrical signals. The pre-amplifier 24 amplifies and outputs the electrical signal output from the light-receiving portion 23. The A/D converter 25 converts the analog electrical signal output from the pre-amplifier 24 into a digital electrical signal and outputs the digital electrical signal. The CPU 26 calculates a difference between the reflectance of the light of a wavelength λ1 and the reflectance of the light of a wavelength λ2 on the basis of the electrical signal output from the A/D converter 25. Then, the CPU 26 outputs a signal corresponding to the calculated difference in reflectance.
The temperature correction coefficient α is a coefficient which is preset on the basis of the relationship between the temperature and the signal output from the water content sensor 6. The voltage of the signal output from the water content sensor 6 may have an error depending on the temperature around the water content sensor 6. The temperature correction coefficient α is used to correct the error.
When the water content of a sheet of paper P varies, the sheet of paper P expands or contracts. For example, when the sheet of paper P passes through the fixing unit 15, it is heated by the fixing unit 15 and the amount of water contained in the sheet of paper P decreases. At this time, the sheet of paper P contracts by the decreasing amount of water. When images are formed on both surfaces of the sheet of paper P, an image is formed on the second surface after the sheet of paper P contracts. In this case, when the images are formed on the first and second surfaces of the sheet of paper P under the same conditions, the images vary in size or position.
After the image I1 is formed on the first surface, the sheet of paper P is heated by the fixing unit 15. Accordingly, as shown in
An image I2 is formed on the second surface of the sheet of paper P as shown in
The image I2 is formed on the second surface of the sheet of paper P with the same magnification as the image I1. As described above, the image I1 formed on the first surface of the sheet of paper P is reduced with the contraction of the sheet of paper P. Accordingly, the image I1 formed on the first surface of the sheet of paper P and the image I2 formed on the second surface are different in size. The formation of the image I2 is started from the position separated apart by the distance G1 from the top edge of the sheet of paper P and apart from the distance F1 from the left edge of the sheet of paper P. In this case, the position at which an image is formed is different between the first surface and the second surface of the sheet of paper P.
The image forming apparatus 100 performs the following process to correct such a difference.
In step S102, the water content sensor 6a determines whether the sheet sensor 5a senses a sheet of paper P. This determination is repeatedly performed until the sheet sensor 5a senses a sheet of paper P (NO in step S102). When a sheet of paper P is carried to the sensing position D1 from the sheet feeding unit 17, the sheet sensor 5a senses the sheet of paper P. When the sheet sensor 5a senses the sheet of paper P (YES in step S102), the water content sensor 6a applies light to the sheet of paper P and outputs a signal corresponding to the water content of the sheet of paper P. In step S103, the computing unit 7 acquires the signal output from the water content sensor 6a and reads the voltage V1 of the signal. Then, the computing unit 7 stores data representing the read voltage V1 in the memory 32. In step S104, the computing unit 7 reads the temperature T measured by the temperature sensor 4 on the basis of the signal output from the temperature sensor 4. Then, the computing unit 7 stores data representing the read temperature T in the memory 32.
In step S105, the image forming unit 3 forms a first image on the first surface of the sheet of paper P on the basis of the first image data. Then, the image forming unit 3 heats the sheet of paper P by the use of the fixing unit 15 to fix the first image. The sheet of paper P passing through the fixing unit 15 is cooled by the cooling unit 16. The sheet of paper P passing through the cooling unit 16 is carried to the sensing position D2.
In step S106, the water content sensor 6b determines whether the sheet sensor 5b senses the sheet of paper P. This determination is repeatedly performed until the sheet sensor 5b senses the sheet of paper P (NO in step S106). When the sheet of paper P is carried to the sensing position D2, the sheet sensor 5b senses the sheet of paper P. When the sheet sensor 5b senses the sheet of paper P (YES in step S106), the water content sensor 6b applies light to the sheet of paper P and outputs a signal corresponding to the water content of the sheet of paper P. In step S107, the computing unit 7 acquires the signal output from the water content sensor 6b and reads the voltage V2 of the signal. Then, the computing unit 7 stores data representing the read voltage V2 in the memory 32. As described above, the water content of the sheet of paper P is reduced by passing through the fixing unit 15. Accordingly, the voltage V2 is smaller than the voltage V1.
In step S108, the computing unit 7 calculates the expansion and contraction ratios δ1 and δ2 of the sheet of paper P. The expansion and contraction ratio is a ratio of the size after expansion and contraction to the original size in terms of percentage. For example, when the original size is 10 and the size after the expansion and contraction is 9, the expansion and contraction ratio is (9−10)÷10×100=−10%.
In step S13, the computing unit 7 specifies coefficients β1 and β2 described in correspondence with the type and the basis weight of the sheet of paper P determined in step s11 in the second correction table 35 stored in the memory 32. For example, when the type of the sheet of paper P determined in step S11 is “high-quality paper” and the basis weight is “150 to 200 g/m2”, the coefficients β1=0.057 and β2=0.154 described in the second correction table 35 shown in
In step S14, the computing unit 7 calculates a variation in water content Δσ by the use of Expression 1 using the voltage V1, the voltage V2, and the temperature T represented by the data stored in the memory 32, the temperature correction coefficient α stored in the memory 32, and the coefficient γ specified in step S12.
Variation in water content Δσ=(V1−V2)×γ×T×α Expression 1
In step S15, the computing unit 7 calculates the expansion and contraction ratios δ1 and δ2 of the sheet of paper P by the use of Expressions 2 and 3 using the variation in water content Δσ calculated in step S15 and the coefficients β1 and β2 specified in step S13. The expansion and contraction ratio of the sheet of paper P represents an expansion and contraction ratio in the first direction of the sheet of paper P. The expansion and contraction ratio δ2 of the sheet of paper P represents an expansion and contraction ratio in the second direction of the sheet of paper P.
Expansion and contraction ratio δ1=Δσ×β1 Expression 2
Expansion and contraction ratio δ2=Δσ×β2 Expression 3
Subsequently, the computing unit 7 stores the calculated expansion and contraction ratios δ1 and δ2 in the memory 32.
Referring to
The control unit 1 changes the distance between the edge of the sheet of paper P and the position at which the formation of an image is started using the expansion and contraction ratios δ1 and δ2. For example, when the expansion and contraction ratio δ1 is −1% and the first direction corresponds to the sub scanning direction of the second image, the control unit 1 changes the distance between the top edge of the sheet of paper P and the position at which the formation of an image is started to be smaller by 1% than the original distance. Similarly, when the expansion and contraction ratio δ2 is −2% and the second direction corresponds to the main scanning direction of the second image, the control unit 1 changes the distance between the left edge of the sheet of paper P and the position at which the formation of an image is started to be smaller by 2% than the original distance. Accordingly, the difference in the image forming position between the first surface and the second surface of the sheet of paper P is corrected.
The sheet of paper P passing through the water content sensor 6b is carried to the turnover unit 19. The sheet of paper P is turned over by the turnover unit 19. The sheet of paper P passing through the turnover unit 19 is carried to the secondary transfer roller 14 again. In step S110, the image forming unit 3 forms the second image on the second surface of the sheet of paper P on the basis of the second image data corrected in step S109. The image forming unit 3 heats the sheet of paper P by the use of the fixing unit 15 so as to fix the second image. The sheet of paper P passing through the fixing unit 15 is cooled by the cooling unit 16. The sheet of paper P passing through the cooling unit 16 is carried to the outside of the image forming apparatus 100.
In step S111, the control unit 1 determines whether the formation of all images is ended. When it is determined that an image to be formed remains (NO in step S111), the control unit 1 performs again the process of step S102. On the other hand, when it is determined that the formation of all images is ended (YES in step S111), the control unit 1 performs the process of step S112. In step S112, the control unit 1 ends the image forming process.
In the first exemplary embodiment, the coefficient γ described in the first correction table 34 is used to calculate the variation in water content Δσ. Accordingly, the error of the signal output from the water content sensor 6, which is based on the difference in characteristic of the sheet of paper P, is corrected. Accordingly, it is possible to improve the calculation precision of the expansion and contraction ratio of the sheet of paper P. In the first exemplary embodiment, the coefficients β1 and β2 described in the second correction table 35 are used to calculate the expansion and contraction ratios δ1 and δ2 of a sheet of paper. Accordingly, even when the expansion and contraction ratio in the first direction of the sheet of paper P and the expansion and contraction ratio in the second direction are different from each other, it is possible to calculate the expansion and contraction ratio of the sheet of paper P with high precision.
The water content sensor 6a (an example of the signal output unit) in the second exemplary embodiment outputs a signal (an example of the first signal) corresponding to the water content of a sheet of paper P not having an image formed thereon and a signal (an example of the second signal) corresponding to the water content of the sheet of paper P having an image formed on the first surface thereof and being heated to fix the image. Specifically, when the leading edge of the sheet of paper P not having an image formed thereon reaches the sensing position D1 and the sheet of paper P is sensed by the sheet sensor 5a, the water content sensor 6a outputs a signal corresponding to the water content of the sheet of paper P. The sheet of paper P has a first image formed on the first surface thereof, is heated by the fixing unit 15, is turned over by the turnover unit 19, and is carried again to the sensing position D1. When the sheet of paper P reaches the sensing position D1 again and the sheet of paper P is sensed by the sheet sensor 5a, the water content sensor 6a outputs a signal corresponding to the water content of the sheet of paper P.
The operating timing of the image forming apparatus 100 will be described below for the purpose of comparison with the operating timing of the image forming apparatus 200.
In step S207, the water content sensor 6a determines whether the sheet sensor 5a senses the sheet of paper P. This determination is repeatedly performed until the sheet sensor 5a senses the sheet of paper P (NO in step S207). When the sheet of paper P is carried to the sensing position D1 from the turnover unit 19, the sheet sensor 5a senses the sheet of paper P. When the sheet sensor 5a senses the sheet of paper P (YES in step S207), the water content sensor 6a applies light to the sheet of paper P and outputs a signal corresponding to the water content of the sheet of paper P. In step S208, the computing unit 7 acquires the signal output from the water content sensor 6a and reads the voltage V2 of the signal. Then, the computing unit 7 stores data representing the read voltage V2 in the memory 32.
In step S209, the computing unit 7 calculates the expansion and contraction ratios δ11 and δ12 of the sheet of paper P. The process of calculating the expansion and contraction ratios δ11 and δ12 is the same as the process of calculating the expansion and contraction ratios 81 and 62. The computing unit 7 stores the calculated expansion and contraction ratios δ11 and δ12 in the memory 32. In step S210, the image forming unit 3 forms a second test image on the second surface of the sheet of paper P. Then, the image forming unit 3 heats the sheet of paper P by the use of the fixing unit 15 so as to fix the second test image. The sheet of paper P passing through the fixing unit 15 is cooled by the cooling unit 16. The sheet of paper P passing through the cooling unit 16 is carried to the outside of the image forming apparatus 200. In step S211, the control unit 1 ends the formation of a test image.
The image forming apparatus 200 forms an actual image.
In step S306, the computing unit 7 determines whether the expansion and contraction ratios δ1 and δ2 are stored in the memory 32. For example, when an image is formed on a first sheet of paper P, the process of calculating the expansion and contraction ratios δ1 and δ2 of the sheet of paper P is not performed yet. Accordingly, the expansion and contraction ratios δ1 and δ2 are not stored in the memory 32 (NO in step S306). In this case, the computing unit 7 performs the process of step S307. In step S307, the computing unit 7 corrects the second image represented by the second image data on the basis of the expansion and contraction ratios δ11 and δ12 stored in the memory 32. The expansion and contraction ratios δ11 and δ12 are calculated in the process of forming the test image. This correction is performed in the same way as the process of step S109. Then, the computing unit 7 performs the process of step S309.
The processes of steps S309 to S311 are the same as the processes of steps S106 to S108. Accordingly, the expansion and contraction ratios δ1 and δ2 of the sheet of paper P calculated in step S311 are stored in the memory 32. The processes of steps S312 and S313 are the same as the processes of steps S110 and S111.
In this way, when the process of forming an image on the first sheet of paper P is ended, a process of forming an image on the second sheet of paper P is started. The processes of steps S302 to S305 are the same as forming the image on the first sheet of paper P. However, when an image is formed on the second sheet of paper P or the sheets of paper subsequent thereto, the expansion and contraction ratios δ1 and δ2 calculated in step S311 are stored in the memory 32 in step S306 (YES in step S306). In this case, the computing unit 7 performs the process of step S308.
In step S308, the control unit 1 corrects the second image represented by the second image data on the basis of the expansion and contraction ratios δ1 and δ2 of the sheet of paper P stored in the memory 32. As described above, the expansion and contraction ratios δ1 and δ2 are calculated in step S311. This correction is performed in the same way as the process of step S109.
In this way, the processes of steps S302 to S313 are repeatedly performed until the formation of all images is ended. When the formation of all images is ended (YES in step S313), the control unit 1 performs the process of step S314. In step S314, the control unit 1 ends the formation of an image.
In the second exemplary embodiment, the image forming apparatus 200 does not have to be provided with plural water content sensors 6. Accordingly, it is easy to design the image forming apparatus 200, thereby reducing the manufacturing cost.
The invention not limited to the above-mentioned exemplary embodiments, but may be modified in various forms. Several modifications will be described below. The following modifications may be combined to put the invention into practice.
When the expansion and contraction ratio of a sheet of paper P is calculated, an average of the variations in water content may be used.
In step S27, the computing unit 7 determines whether the number of prints i counted in step S21 is smaller than a variable N. The variable N is an integer equal to or greater than 2. When it is determined that the number of prints i counted in step S21 is smaller than the variable N (YES in step S27), the computing unit 7 ends the process. On the other hand, when the number of prints i counted in step S21 is equal to or greater than the variable N (NO in step S27), the computing unit 7 performs the process of step S28.
When the number of prints i is equal to or greater than the variable N, plural variations in water content Δσ are stored in the memory 32. In step S28, the computing unit 7 calculates the average variation in water content Δσ_Avg by the use of Expression 4 using the plural variations in water content Δσ stored in the memory 32.
Average variation in water content Δσ_Avg=Avg(Δσ[i−N+1]˜Δσ[i]) Expression 4
In step S29, the computing unit 7 calculates the expansion and contraction ratios δ1 and δ2 by the use of Expressions 5 and 6 using the average variation in water content Δσ_Avg calculated in step S28 and the coefficients β1 and β2 specified in step S24.
Expansion and contraction ratio δ1=Δσ_Avg×β1 Expression 5
Expansion and contraction ratio δ2=Δσ_Avg×β2 Expression 6
As described above, the water content sensor 6 employs 1.3 μm as the wavelength λ1 and employs 1.43 μm as the wavelength λ2. In this way, when 1.43 μm is employed as the wavelength λ2, the manufacturing cost is suppressed low but the precision of the signal output from the water content sensor 6 is lowered, compared with the case where 1.94 μm or 3.0 μm is employed as the wavelength λ2. However, in this modification, since the average variation in water content Δσ_Avg is used to calculate the expansion and contraction ratios δ1 and δ2 of the sheet of paper P, it is possible to calculate the expansion and contraction ratios δ1 and δ2 of the sheet of paper P with high precision even when the signal output from the water content sensor 6 is not uniform.
The characteristics of a sheet of paper are not limited to the type or the basis weight. The characteristics of a sheet of paper may be, for example, a material of the sheet of paper or a processing method thereof. The characteristics of a sheet of paper are features of the sheet of paper and preferably have an influence on the signal output from the water content sensor 6.
The type or the basis weight of a sheet of paper P may be determined by the control unit 1 on the basis of a feature amount of the sheet of paper P. For example, a sensor detecting a feature amount of a sheet of paper P may be disposed in the sheet feeding unit 17 and the control unit 1 may determine the type or the basis weight of the sheet of paper P on the basis of the feature amount detected by the sensor.
In the first exemplary embodiment, two temperature sensors 4 may be disposed. In this case, the second temperature sensor 4 is disposed around the water content sensor 6b and the temperature around the water content sensor 6b. The computing unit 7 also uses the temperature measured by the second temperature sensor 4 to calculate the variation in water content Δσ. The temperature sensor 4 is not necessarily disposed. In this case, the variation in water content Δσ is calculated using only the voltages V1 and V2 and the coefficient γ specified in step S12.
Only one of the coefficients β1 and β2 may be described in the second correction table 35. In this case, since the expansion and contraction ratios δ1 and δ2 of a sheet of paper P are equal to each other, the computing unit 7 can calculate only one of the expansion and contraction ratios δ1 and δ2. The second correction table 35 may not be necessarily disposed. Instead of the second correction table 35, only one coefficient of the coefficients β1 and β2 described in the second correction table 35 may be stored in the memory 32. In this case, the expansion and contraction ratio of the sheet of paper P is calculated using the variation in water content Δσ and the coefficient.
In the above-mentioned exemplary embodiments, both the size and position of an image to be formed on the second surface are corrected. However, one of the size and position of the image to be formed on the second surface may be corrected.
The control unit 1 instead of the computing unit 7 may implement a partial function of the computing unit 7 shown in
The image forming apparatus 100 or 200 may form a black and white image. In this case, the image forming apparatus 100 or 200 includes only the image forming section 12K among the image forming sections 12Y, 12M, 12C, and 12K. The image forming apparatus 100 or 200 does not include the intermediate transfer belt 13.
The control unit 1 may include an application specific integrated circuit (ASIC). In this case, the function of the control unit 1 may be implemented by the ASIC or may be implemented by both the CPU and the ASIC. Similarly, the computing unit 7 may include an ASIC. In this case, the function of the computing unit 7 may be implemented by the ASIC or may be implemented by both the CPU and the ASIC.
A program implementing the function of the control unit 1 or the computing unit 7 may be provided in a state where it is stored in a computer-readable medium such as a magnetic medium (a magnetic tape, a magnetic disk (such as an HDD (Hard Disk Drive) and an FD (Flexible Disk)) an optical medium (such as an optical disk (a CD (Compact Disc), a DVD (Digital Versatile Disk), and the like), a magneto-optical medium, and a semiconductor memory and may be installed in the image forming apparatus 100 or 200. The program may be downloaded via a communication network and may be installed.
The foregoing description of the exemplary embodiments of the invention has been provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention is defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
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