Patent Application
20170075278
This application is based on Japanese Patent Application No. 2015-183436 filed with the Japan Patent Office on Sep. 16, 2015, the entire content of which is hereby incorporated by reference.
Field of the Invention
This invention relates to a sheet conveying apparatus, an image forming apparatus, a control method of a sheet conveying apparatus, and a control program of a sheet conveying apparatus. In particular, this invention relates to a sheet conveying apparatus, an image forming apparatus, a control method of a sheet conveying apparatus, and a control program of a sheet conveying apparatus, which can detect thickness of sheets.
Description of the Related Art
When paper sheets are manually set to feed them into an image forming apparatus, a user may not comprehend the thickness of the sheets to be used. In case that image forming behavior is performed based on an incorrect configuration of the thickness of the sheets, there is the potential for the occurrence of a sheet jam, or the occurrence of the problem in transferring images to the sheets or image fixing performance. To cope with these problems, a thickness of the sheet to be conveyed by a sheet conveying apparatus is detected (sheet thickness detection), for preventing the printing failure and for improving users' convenience.
To detect sheet thickness, a sheet thickness detection method using the amount of displacement of a detection roller, when a sheet is pinched between a reference roller and the detection roller is typically used. Such a method has a problem in which the detection result varies, since the amount of displacement of the detection roller includes an amount of displacement caused by an eccentricity of the roller, in response to a rotation cycle. Because of the problem, the desired degree of detection accuracy can not be obtained.
In
More specifically, where the diameter of detection roller 810 is represented by D, and the conveying velocity of sheet P is represented by S, rotation cycle C of detection roller 810 is calculated by D*π/S. When sheet P is not pinched, the amount of displacement of detection roller 810 periodically fluctuates for each rotation cycle C. The periodical fluctuation is caused by the eccentricity or the like of detection roller 810 and reference roller 805. When sheet P is pinched, the periodical fluctuation is still included in the entire amount of displacement, though the level of the amount of displacement of detection roller 810 rises by the thickness of the sheet. Hence, the detection result varies based on the detection timing.
As for such the problem, there are conventional techniques which adopt the following structures.
In the Document 1 below, the detection of the correct sheet thickness is attempted, by performing memorizing, calculating and compensating behavior for the eccentricity amount of the reference roller. More specifically, displacement signals of the detection roller within a certain period of time are recorded, after a sheet is entered between the reference roller and the detection roller. A calculation is executed between the displacement signal of the detection roller when a certain period of time which is the integral multiple of a rotation cycle of the reference roller has elapsed from when the sheet was entered, and the recorded displacement signal. Herewith, the eccentricity amount of the reference roller is corrected, for the recorded displacement signal.
According to the Document 2 below, thickness of a sheet is calculated, by using variation data during more than or equal to a rotation cycle of a roller for sheet thickness detection when the sheet is pinched and when the sheet is not pinched.
According to the Document 3 below, thickness of a sheet is calculated upon synchronizing an amount of displacement of a detection roller when a sheet is not pinched, with an amount of displacement of the detection roller when the sheet is pinched, after detection of a rotation cycle of the roller.
[Document 1] Japan Patent Publication No. (HEI) 5-294512
[Document 2] Japan Patent Publication No. 2011-079665
[Document 3] Japan Patent Publication No. 2012-030937
However, the methods disclosed in the above-mentioned Documents 1 to 3 have the following problem. According to the methods, variation data during more than or equal to one rotation cycle when a sheet is pinched by a roller for sheet thickness detection, and variation data during more than or equal to one revolution when a sheet is not pinched, are used. To calculate sheet thickness by using the variation data, the variation data should be acquired until the roller rotates one revolution. In addition, the dedicated calculation algorithm for calculating sheet thickness should be prepared, to execute the calculation. Further, the variation data should be recorded in a storage device. Hence, a structure of the sheet conveying apparatus may become complex. The manufacturing cost of the sheet conveying apparatus may become higher.
This invention is to solve the above problems. The object of this invention is to provide a sheet conveying apparatus, an image forming apparatus, a control method of a sheet conveying apparatus, and a control program of a sheet conveying apparatus, which can detect thickness of a sheet with a high degree of accuracy, by employing simple structure.
To solve the above problems, a sheet conveying apparatus according to the invention comprises: a pair of rollers including a reference roller and a detection roller, wherein the detection roller can move and faces and makes contact with the reference roller, a detection sensor for outputting a signal corresponding to displacement of the detection roller, a conveying unit for conveying a sheet to a nip portion of the pair of rollers, a timing detection unit for detecting timing when an edge portion of the sheet which is conveyed by the conveying unit passes through the nip portion, and a thickness detection unit for detecting a thickness of the sheet, in response to the timing detected by the timing detection unit, based on the signal output from the detection sensor.
An image forming apparatus according to the embodiment of this invention will be explained in the followings.
The image forming apparatus is an MFP (Multi Function Peripheral) which has a scanner function, a copying function, a function of a printer, a facsimile function, a data transmitting function, and a server function. The scanner function is to read images of documents being set, and accumulate them in a HDD (Hard Disk Drive) or the like. The copying function is to print (printing) them on sheets or the like. The function of a printer is to execute printing on sheets, based on instructions, when receiving the instructions from an external terminal, for example, a PC or the like. The facsimile function is to receive facsimile data from an external facsimile device or the like, and accumulate it in the HDD or the like. The data transmitting function is to transmit data to connected external devices and receive data from connected external devices. The server function is to make data being stored in a HDD or the like sharable among a plurality of users.
The image forming apparatus is equipped with a sheet conveying apparatus. The sheet conveying apparatus conveys a sheet, and can detect the thickness of the sheet.
As shown in
In
As shown in
Control unit 11 reads out control program 12a stored in storage unit 12. Control unit 11 controls main body 10 and scanner unit 31 by executing control program 12a read out. Control unit 11 can be formed with a CPU (Central Processing Unit), a RAM (Random Access Memory), and so on.
For example, control unit 11 processes images generated by image generation unit 16, using image processing unit 17. Control unit 11 forms images on a sheet by using image forming unit 20, based on gradation values of image pixels after image processing.
Storage unit 12 stores control program 12a and data, for example, sheet setting information 12b which is used when control program 12a is executed. The control program 12a and the information can be read out by control unit 11. Sheet setting information 12b is data used for image forming behavior of the image forming unit 20, for example.
As storage unit 12, a large capacity memory, for example, a hard disk drive can be employed.
As shown in
Operation unit 13 generates operation signals corresponding to operations of the user. Operation unit 13 outputs the generated operation signals to control unit 11. Operation unit 13 is configured with keys or a touch panel, for example. The touch panel is configured, integrated with display unit 14.
Display unit 14 displays an operation screen or the like, in accordance with instructions from control unit 11. As display unit 14, an LCD (Liquid Crystal Display), an OELD (Organic Electro Luminescence Display), or the like can be employed.
As shown in
Communication unit 15 receives data via network from external device 50 as a user terminal, for example. Communication unit 15 receives PDL data described in a page-description language (PDL: Page Description Language).
Image generation unit 16 rasterizes the PDL data received via communication unit 15, to generate images. The images are bit map formatted images, which have gradation values for pixels. Image generation unit 16 generates images for colors of C (cyan), M (magenta), Y (yellow) and K (black). The gradation values are data values which represent grayscales of images. For example, an 8-bit data value represents a grayscale of a gradation of 0 to 255.
Image generation unit 16 acquires colored images of R (red), G (green) and B (blue), by reading documents by using scanner unit 31. Image generation unit 16 can generate colored images of C, M, Y and K, by converting colors of each colored image.
Image processing unit 17 processes images which were generated by image generation unit 16. The image processing is, for example, a gradation process, or a halftone process.
In the gradation process, gradation values of pixels in images are converted to corrected gradation values. The correction is to adjust the density characteristic of images formed on a sheet to a target density characteristic.
The halftone process is, for example, an error diffusion process, a screen process using a systematic dither method.
Image forming unit 20 forms an image which consists of a plurality of colors on a sheet, based on gradation values of pixels of the image processed by image processing unit 17.
As shown in
In addition to conveying unit 26 which conveys sheets from paper feeding tray 25, the image forming unit 20 has reverse mechanism 27. Conveying unit 26 has conveying rollers 26a installed at a plurality of locations on the sheet conveying path. Paper feeding tray 25 stores sheets. Conveying unit 26 conveys sheets from paper feeding tray 25, by using the plurality of conveying rollers 26a. On the sheet conveying path, secondary transfer roller 23b, fixing device 24, and so on are placed.
Four writing units 21C, 21M, 21Y and 21K form colored images of C, M, Y and K respectively. The structures of writing units 21 are the same. More specifically, one of writing units 21 is equipped with expose unit 22a, photo conductor 22b, developping unit 22c, electrostatic charging unit 22d and cleaning unit 22e.
Each of writing units 21 forms each colored image, as follows. More specifically, electrostatic charging unit 22d applies electrical voltage onto photo conductor 22b, so that photo conductor 22b gets electrostatic charged. Expose unit 22a irradiates photo conductor 22b with laser beams in response to gradation values of pixels of each colored image of C, M, Y or K, to expose photo conductor 22b. Developping unit 22c supplies color material, as exemplified by toner, to photo conductor 22b, so that an electrostatic latent image formed on photo conductor 22b is developed. Then, each colored image is formed on photo conductor 22b in each of writing units 21.
The images on photo conductors 22b are transferred onto secondary transfer belt 23a to overlap the images in series, so that an image which consists of a plurality of colors is formed on secondary transfer belt 23a. After the transferring of the images onto secondary transfer belt 23a, each of writing units 21 removes residual color materials on photo conductor 22b, by using cleaning unit 22e.
Sheets are fed by paper feeding trays 25. Sheets are conveyed along with a sheet conveying path by conveying unit 26. Secondary transfer roller 23b transfers an image, which consists of a plurality of colors on secondary transfer belt 23a, onto a sheet. The sheet is conveyed to fixing device 24. Fixing device 24 heats and applies pressure on the sheet. Herewith, the image is fixed to the sheet. After that, the sheet is discharged from main body 10, by discharge roller 26c.
When forming images on both side of a sheet, after an image was fixed, the sheet is conveyed to reverse mechanism 27. Reverse mechanism 27 has conveying roller 27a and so on. Reverse mechanism 27 reverses the side of the sheet by using conveying roller 27a, and conveys the sheet to secondary transfer roller 23b again. Herewith, an image is formed on the reverse side of the sheet.
As shown in
Scanner unit 31 reads document M which is being conveyed, as an image, while making document M and contact glass 32 close to each other. Scanner unit 31 can read sheets on which images were formed by image forming unit 20. In that case, a user places sheets output from image forming apparatus 1, on document mounting table 35a, to execute reading.
In the inner part of the scanner main body, light source 33a, image sensor 33b, mirrors 34a, 34b and 34c, and lens 34d are placed. Image sensor 33b is a CCD, for example. When light is emitted from light source 33a, the light reflects at the surface of document M (the surface facing downward in
In scanner unit 31, document mounting table 35a and document receiving tray 35b are provided. On document mounting table 35a, documents M to be conveyed into the inner part of scanner unit 31 and be read are stacked. Document M which was read is discharged from the inner part of scanner unit 31 onto document receiving tray 35b.
In the inner part of scanner unit 31, sheet conveying path 41 which connects document mounting table 35a and document receiving tray 35b is provided. Sheet conveying apparatus 40 has a plurality of conveying rollers 37a to 37g and 38 installed along with conveying path 41 (hereinafter, they may not be distinguished and may be referred to as conveying rollers 37) (an example of a conveying unit).
Conveying rollers 37 are driven by a plurality of paper feeding conveying motors (which are not shown in the figures). For example, a paper feeding motor (which is not shown in the figures) drives pick roller 37a and paper feeding roller 37b via a clutch (which is not shown in the figures). Pick roller 37a and paper feeding roller 37b feed documents M on document mounting table 35a one by one, by a function of the clutch. A paper feeding motor drives conveying roller 37c, detection roller 38, upstream side conveying roller 37d which is located just before the reading location. A reading motor (which is not shown in the figures) drives downstream side roller 37e which is located just after the reading location, conveying roller 37f which is located a further downstream side, and so on. A paper ejection motor (which is not shown in the figures) drives paper ejection roller 37g.
The paper feeding conveying motors are stepping motors, for example. Control unit 11 can control the rotation of conveying rollers 37, as needed.
Scanner unit 31 pulls document M stacked on document mounting table 35a into the direction of arrow S in
As shown in
Timing sensor 36 is placed at an upstream side of a pair of detection rollers 39 in the conveying direction of a sheet. Timing sensor 36 is placed on conveying path 41 between conveying roller 37c and the pair of detection rollers 39. Timing sensor 36 detects an edge portion of a sheet being conveyed, for example document M. The sheet is conveyed at the proper timing, based on the detection result of timing sensor 36, and document M is read.
According to the embodiment, timing sensor 36 which detects displacement of a lever making contact with a sheet being conveyed, is used. When the leading end (an example of an edge portion) of the sheet makes contact with the lever, and the lever is displaced, timing sensor 36 detects the displacement. When the posterior end (an example of an edge portion) of the sheet passed timing sensor 36, and the lever is put back into the original location, timing sensor 36 detects the displacement.
As substitute for the above mentioned timing sensor 36, a sensor for detecting an edge portion of a sheet by using ultrasonic waves, or a sensor for detecting an edge portion of a sheet optically may be employed, for example.
Sheet conveying apparatus 40 has detection sensor 42. Detection sensor 42 is configured to output signals corresponding to displacement of detection roller 38. More specifically, according to the embodiment, an optical encoder with an actuator is used as detection sensor 42. Detection sensor 42 has lever 42a, and base 42b which supports lever 42a making lever 42a rotatable. Prism disk 42c which consists of transparent resin is provided with lever 42a. By reading prism disk 42c optically at the side of base 42b, pulse signals are output from detection sensor 42, in response to displacement of lever 42a.
Detection sensor 42 is attached, so that lever 42a is slightly pushed in from the natural state by making contact with a bearing of detection roller 38 in a state in which there is not a sheet at nip portion 39a (a state in which a pair of detection rollers 39 does not pinch a sheet). More specifically, when detection roller 38 is displaced, lever 42a is less likely to jounce, and lever 42a is kept making contact with the bearing of detection roller 38 at all times.
As shown in
Control unit 11 counts pulse signals of phase A and phase B which were output. Herewith, the information of the amount of displacement and the displacement direction of detection roller 38 is acquired.
In the embodiment, detection sensor 42 which has the following specifications is used, for example. The detection range is 30-600 micrometers. The resolution is 5 micrometers per count (one pulse is output for each 5 micrometers displacement). The response frequency is 60 kilohertz.
As shown in
According to the embodiment, image forming apparatus 1 can detect the thickness of a sheet by using sheet conveying apparatus 40 (thickness detection behavior). The thickness detection behavior is performed, when a behavior mode of image forming apparatus 1 is the thickness detection mode. For example, when an operation is performed from a user via operation unit 13, control unit 11 sets the thickness detection mode as a behavior mode of image forming apparatus 1. When a user performs an operation to start detecting in a state in which the user placed sheet P to be detected onto document mounting table 35a, thickness detection behavior is executed, based on control of control unit 11.
The thickness detection behavior is performed by the pair of detection rollers 39, detection sensor 42, timing sensor 36, and so on.
In
At step S11, it is assumed that sheet P is being conveyed toward nip portion 39a, in conveying direction F. At this situation, when the anterior end of sheet P arrives at timing sensor 36, timing sensor 36 detects the timing. Then, control unit 11 detects the timing (hereinafter, it may be referred to as passing timing) when the anterior end of sheet P passes through nip portion 39a (the anterior end of sheet P arrives at nip portion 39a), based on the timing detected by timing sensor 36, a conveying velocity of sheet P being conveyed, and length L1 of conveying path 41 from timing sensor 36 to nip portion 39a. The passing timing is detected before sheet P actually arrives at the pair of detection rollers 39.
When control unit 11 detects the passing timing, control unit 11 detects displacement of detection roller 38 in a predetermined period, with reference to timing immediately before the passing timing. Here, the predetermined period is from the time the detection is started to the time immediately after the anterior end of sheet P is assumed to pass nip portion 39a. The predetermined period is set beforehand. Control unit 11 may appropriately set the predetermined period, by using the conveying velocity of sheet P, predetermined parameters, and so on.
At step S12, when sheet P arrives at nip portion 39a, sheet P is pinched between detection roller 38 and reference roller 38b. At this time, the location of reference roller 38b is unchanged and detection roller 38 is displaced to move away from reference roller 38b through a distance of the thickness of sheet P. The displacement of detection roller 38, during a period between the time immediately before the passing timing and the time when the anterior end of sheet P was assumed to pass nip portion 39a is detected, to detect the thickness of sheet P.
The upper part of
When sheet P does not arrive at nip portion 39, detection roller 38 is periodically displaced. After control unit 11 detects passing timing, with sheet P being conveyed, control unit 11 begins to detect displacement of detection roller 38 at clock time t1 that is immediately before the passing timing (paper thickness detection start). Here, clock time t1 should be a time earlier than the detected passing timing by a predetermined time. More specifically, control unit 11 sets detection starting timing (clock time t1) of the displacement of detection roller 38, based on the timing detected by timing sensor 36 or the like.
For example, clock time t1 should be set, in consideration of possibility of deviations of timing for detecting the leading end of sheet P by timing sensor 36 (for example, there is the potential for deviations caused by skew of sheet P), and possibility of deviations of the conveying velocity of sheet P. More specifically, clock time t1 is set, so that the detection of the displacement of detection roller 38 is certainly started before the sheet actually arrives at nip portion 39a.
When clock time t1 has come, the displacement of detection roller 38 is detected from clock time t1 to clock time t2 that is after predetermined period D1. In other words, the displacement is detected from clock time t1 to clock time t2, which are set by control unit 11 beforehand. Under normal conditions, the leading end of sheet P passes through nip portion 39 during this period. Period D1 in which the displacement is detected is set to a period quite shorter than the cycle of the periodical displacement of detection roller 38. Hence, even though detection roller 38 is displaced periodically, the amount of displacement detected during the detection period is near to the thickness of sheet P. Control unit 11 calculates the amount of displacement of detection roller 38 detected during this period, as thickness information of sheet P.
The process shown in
As shown in
At step S502, whether the thickness detection can be started or not is confirmed. When the thickness detection is to be started, the process of step S503 is performed. For example, when a predetermined operation is performed by a user, the thickness detection is started.
At step S503, sheet P is conveyed.
At step S504, the thickness detection process is performed. The detailed thickness detection process will be explained later.
At step S505, the thickness of sheet P is calculated, based on the result of the thickness detection process. Herewith, paper thickness information of sheet P is acquired.
According to the embodiment, the acquired paper thickness information is registered automatically in image forming apparatus 1. More specifically, at step S506, control unit 11 informs the paper thickness information to main body 10 of image forming apparatus 1. Control unit 11 stores the paper thickness information in storage unit 12, as the control of the side of main body 10.
At step S507, control unit 11 registers the paper thickness information so as to be associated with various sorts of information, so that the paper thickness information can be used on the control of main body 10. For example, the paper thickness information and the sheet name or the like specified by a user or automatically generated are registered as sheet setting information 12b, so as to be associated with each other.
The detected and acquired paper thickness information is registered as sheet setting information 12b. Hence, when image forming apparatus I performs image forming on sheet P to be detected, the sheet setting information 12b can be utilized. In this instance, displaying on display unit 14 or the like, control parameter configurations for fixing and transferring or the like related to image forming can be performed, based on sheet setting information 12b.
As shown in
At step S112, the timing when the sheet edge pass through nip portion 39a is calculated, based on the timing when the sheet edge was detected.
At step S113, control unit 11 waits till the timing to start detecting, that is immediately before the passing timing, based on the calculated passing timing. At the timing, the process of step S114 is executed.
At step S114, the displacement of detection roller 38 from when the detection was started to when the predetermined time elapsed is detected. Herewith, the thickness of the sheet edge is measured.
After the completion of the measurement, the processing is returned to
The thickness detection process will be explained more concretely, as follows.
In
As shown in
At step S132, in response to the detection timing of the leading end of sheet P, the passing timing when the leading end of sheet P arrives at nip portion 39a is calculated. Then, the period from now to immediately before the passing timing is counted.
At step S133, whether the counting was completed or not, more specifically, whether it is the time immediately before the passing timing or not is determined. When the counting was completed, the thickness measurement at step S134 and the following steps is performed.
At step S134, control unit 11 begins to count signal pulses output from detection sensor 42. More specifically, the location of detection roller 38 when starting of the counting for the thickness measurement is the reference for detecting the thickness of sheet P.
At step S135, control unit 11 confirms whether the predetermined period from starting of the pulse counting has elapsed or not. Until the predetermined time elapses, the counting is kept. When the predetermined time elapsed, the process of step S136 is performed. The predetermined time is from starting of the counting to an estimated time when the leading end of the sheet passed through nip portion 39a. Therefore, at this time, control unit 11 confirms whether the leading end of sheet P passed through nip portion 39a or not.
At step S136, control unit 11 stops the pulse counting. Herewith, the output pulses of detection sensor 42 in response to the displacement of detection roller 38 was counted, from the time immediately before the leading end of sheet P passes through nip portion 39a to immediately after the leading end of sheet P passes through nip portion 39a. The number of counted pulses corresponds to the difference between the location of detection roller 38 as the reference when starting of the detection, and the location of detection roller 38 when finishing of the detection after the predetermined time.
After the completion of the process of step S136, the processing is returned to
According to the embodiment, the thickness of the leading end of sheet P is detected as the thickness of sheet P. The thickness of the posterior end of sheet P may be detected as the thickness of sheet P.
In
When the leading end of sheet P is detected by timing sensor 36 at step S141, the apparatus waits till the detection timing of the posterior end of sheet P, at step S142.
When the posterior end of sheet P was detected, the passing timing when the posterior end of sheet P arrives at nip portion 39a is calculated, in response to the detecting timing of the posterior end of sheet P, at step S143. Then, the period from now to immediately before the passing timing is counted.
At step S144, whether the counting was completed or not is determined. When the counting was completed, the thickness measurement at step S145 and the following steps is performed.
At step S145, control unit 11 begins to count signal pulses output from detection sensor 42. At this time, nip portion 39a is pinching sheet P. The location of detection roller 38 at this time is the reference for detecting the thickness of sheet P.
At step S146, control unit 11 conforms whether the predetermined period from starting of the pulse counting has elapsed or not. Until the predetermined time elapses, the counting is kept. When the predetermined time elapsed, the process of step S147 is performed. The predetermined time is from starting of the counting to an estimated time when the posterior end of the sheet passed through nip portion 39a.
At step S147, control unit 11 stops the pulse counting. Herewith, the output pulses of detection sensor 42 in response to the displacement of detection roller 38 was counted, from the time immediately before the posterior end of sheet P passes through nip portion 39a to immediately after the posterior end of sheet P passes through nip portion 39a. After the completion of the process of step S147, the processing is returned to
In this manner, when the thickness of the posterior end of sheet P is to be detected, detection roller 38 is displaced to the direction for approaching reference roller 38b, around the time when the posterior end of sheet P passes through nip portion 39a. Hence, the thickness of sheet P can be detected.
As explained above, according to the embodiment, an amount of displacement of detection roller 38, from the time immediately before the edge portion of sheet P passes through nip portion 39a to the time immediately after the edge portion of sheet P passes through nip portion 39a, can be detected as thickness of sheet P. Therefore, even though the amount of displacement of detection roller 38 includes the periodical fluctuation, the fluctuation has minimal impact on the detection result of the thickness of sheet P. Therefore, the thickness of sheet P can be detected with high precision.
For the thickness detection, there is no necessity to use data related to the periodical fluctuation of the amount of displacement of detection roller 38. Then, there is no necessity to acquire or store such data separately from thickness detection behavior. In addition, there is no necessity to perform calculation by using the data with complex algorithm, separately from thickness detection behavior. Therefore, the structure of image forming apparatus 1 can be simplified, and the manufacturing cost of image forming apparatus 1 can be reduced.
According to the first embodiment, an optical encoder with an actuator to output pulse signals is used, as detection sensor 42. Then, it has an effect of the followings, compared to using a variety of sensors. More specifically, since detection sensor 42 outputs pulse signals, the output signals are less affected by noise, individual variability of the circuit, fluctuation of electric power supply voltage, or the like, and the displacement of detection roller 38 can securely be detected. As compared with outputting analog micro signals which demand comparatively complex signal process and calculation process, the detection result can be acquired only by detecting count up/countdown. Since detection sensor 42 is small, detection sensor 42 can be installed close to detection roller 38, as compared with using a triangulation type sensor that measures distance optically or the like. Hence, image forming apparatus 1 can be downsized. In addition, the displacement of detection roller 38 can be detected, regardless of the surface state of detection roller 38.
Since basic structure of the image forming apparatus according to the second embodiment is the same as shown in the first embodiment, the explanation will not be repeated. According to the second embodiment, a skew correction of sheet P is performed, before the thickness detection behavior. This point is different from the first embodiment.
In
When the skew correction is not performed, and sheet P is conveyed being skewed with respect to conveying direction F, for example, there is the potential for problems for the thickness detection behavior. More specifically, when sheet P is skewed, edge portions of the anterior end and the posterior end of sheet P are inclined with respect to a direction perpendicular to conveying direction F of sheet P. Therefore, when timing sensor 36 detects a portion of the edge, there is the potential for difference between the distance from the portion of the edge to nip portion 39a, and distance from another portion of the edge to nip portion 39a. In this instance, when the passing timing calculated based on the detection result of timing sensor 36 actually comes, there is the potential for cases in which another edge portion was already pinched by nip portion 39a, or another edge portion is far from nip portion 39a. In such the cases, the passing timing differs from the timing when the sheet actually passes through nip portion 39a. Therefore, there is the potential for lowering degree of thickness detection accuracy of the edge portion of sheet P.
On the other hand, as shown in the upper part of
According to the example shown in
Since basic structure of the image forming apparatus according to the third embodiment is the same as shown in the first embodiment, the explanation will not be repeated. According to the third embodiment, one detection roller which plays both two roles of a register roller and a roller for sheet thickness detection behavior is used. This point is different from the first embodiment.
According to the third embodiment, as substitute for detection roller 38, detection roller 138 is provided. This is different from the above mentioned the first embodiment. More specifically, detection roller 138 performs a skew correction of sheet P, and detection roller 138 is a register roller which adjusts paper re-feeding timing. A skew correction for sheet P is performed by detection roller 138 and reference roller 38b (which is not shown in
More specifically, it is assumed that skewed sheet P is being conveyed at step S31. At this time, timing sensor 36 detects the anterior end of sheet P. Paper re-feeding timing is set, in response to detection timing of timing sensor 36.
At step S32, the leading end of sheet P arrives at detection roller 138.
At step S33, the detection roller 138 prevents sheet P from entering nip portion 39a, so that the skew correction of sheet P is performed.
At step S34, paper re-feeding is performed by detection roller 138. Herewith, sheet P enters nip portion 39a the leading end first, and passes through nip portion 39a.
When thickness detection behavior is performed, the displacement of detection roller 138 is detected during a predetermined period which starts immediately before the paper re-feeding timing, wherein the paper re-feeding timing is determined by the detection result of timing sensor 36, for example. Herewith, as same as mentioned above, the thickness of the leading end of sheet P which passes through nip portion 39a is detected, when starting the paper re-feeding.
As shown by
At step S232, skew correction behavior for sheet P is performed till the paper re-feeding timing, in response to the detecting timing of the leading end of sheet P.
At step S233, whether it is immediately before paper re-feeding timing of detection roller 138 or not is determined.
At step S234, control unit 11 begins to count signal pluses output from detection sensor 42, immediately before paper re-feeding timing. More specifically, the location of detection roller 138 at the start of the counting for thickness measurement is the reference for detecting the thickness of sheet P.
At step S235, control unit 11 confirms whether the predetermined period has elapsed or not from the starting of the pulse counting. Until the predetermined time elapses, the counting is kept. When the predetermined time elapsed, the process of step S236 is performed.
At step S236, control unit 11 stops the pulse counting. Herewith, the output pulses of detection sensor 42 in response to the displacement of detection roller 138 was counted, from the time immediately before the anterior end of sheet P passes through nip portion 39a to immediately after the anterior end of sheet P passes through nip portion 39a. The number of counted pulses corresponds to the difference between the location of detection roller 38 as the reference immediately before the paper re-feeding timing, and the location of detection roller 38 when finishing of the detection after the predetermined time.
After the completion of the process of step S236, the processing is returned to
According to the third embodiment, the one detection roller 138 is configured to play two roles of a register roller and a roller for sheet thickness detection behavior. Hence, the mechanical structure of image forming apparatus 1 can be simplified. Further, after performing a skew correction, the thickness of sheet P can be detected with high precision.
In such a situation in which detection roller 138 plays two roles of a register roller and a roller for thickness detection behavior, control unit 11 may control the thickness detection behavior as follows. More specifically, when a skew correction for sheet P was performed and detection sensor 42 detected detection roller 138 vibrating, control unit 11 may wait and prevent sheet P passing through nip portion 39a, till the vibration of detection roller 138 is damped.
In
According to this modification, when a skew correction was performed, control unit 11 determines whether detection roller 138 is vibrating or not at step S333. When detection roller 138 is vibrating, the process of step S334 is performed. When detection roller 138 is not vibrating, the process of step S335 is performed.
At step S334, control unit 11 changes the paper re-feeding timing. More specifically, control unit 11 changes the paper re-feeding timing, so that the paper re-feeding timing is set to be later. Herewith, before the changed paper re-feeding timing, the waiting state in which the paper re-feeding is not performed is maintained.
At step S335, whether it is immediately before the paper re-feeding timing or not is detected. When it is not immediately before the paper re-feeding timing, the vibration detection (step S333) and the change of the paper re-feeding timing corresponding to the vibration detection (step S334) are performed again.
When the paper re-feeding timing comes, the process of step S336 and the following steps is performed.
When the thickness detection behavior is performed by using detection roller 138 which is used as a register roller, and sheet P butts detection roller 138 for the skew correction, the detection roller 138 may vibrate. Then, as shown in
Whether the vibration of detection roller 138 is damped or not can be determined as follows. For example, when a signal pulse output from detection sensor 42 was previously counted and a predetermined time elapsed, it can be determined that detection sensor 42 stabilized and the vibration of detection roller 138 is damped.
[Others]
The characterizing portions in the above mentioned embodiments can be appropriately exchanged. Parts of the characterizing portions may be omitted. In such a way, a sheet conveying apparatus and an image forming apparatus with the same can be configured.
When the detection behavior of the thickness of the sheet was performed, the information may not be registered in the main body of an image forming apparatus, as sheet setting information. For example, the acquired paper thickness information may be informed to users by displaying it on a display unit. When the paper thickness information was acquired, the paper thickness information can be used for the control related to the image forming, which is performed in the next image forming job.
The detection sensor is not limited to the above mentioned an optical encoder with an actuator. For example, an angle sensor in which an angle of a detection probe is changed in accordance with the displacement of the detection roller, can be used. A triangulation type optical sensor for detecting the displacement by receiving reflected light from the object, may be used.
The locations of the detection roller and the timing sensor on the sheet conveying path are not limited to the above mentioned. The timing sensor can be installed at an upstream side of the detection roller and the reference roller, in a conveying direction.
An image forming apparatus can be a copying machine, a printer, a facsimile device, multifunction machine (MFP) of these apparatuses, or the like of black-and-white/colors. The apparatus is not limited to an apparatus which forms images by electrophotographic technology. For example, the apparatus may form images by so-called ink jet method.
The hardware configuration of an image forming apparatus is not limited the above mentioned. The use of the sheet conveying apparatus which performs thickness detection behavior is not limited to a scanner unit. For example, in a sheet conveying apparatus which conveys sheets in a main body of an image forming apparatus, thickness detection behavior may be performed by using a pair of detection rollers, a timing sensor, and so on, placed on the conveying path. In this instance, a conveying path for thickness detection to make a detour to avoid a path on which sheets pass during the image forming behavior, when thickness detection behavior is performed, may be installed. To make a detour to avoid a transfer roller and a fixing roller in the image forming unit during thickness detection behavior, the lifetime of parts installed in the image forming unit can be extended.
The processes in the above mentioned embodiments can be performed by software and a hardware circuit.
A computer program which executes the processes in the above embodiments can be provided. The program may be provided recorded in recording media of CD-ROMs, flexible disks, hard disks, ROMs, RAMs, memory cards, or the like to users. The program is executed by a computer of a CPU or the like. The program may be downloaded to a device via communication lines like the internet. The processes explained in the above flowcharts and the description are executed by a CPU in line with the program.
According to the embodiments, the timing when an edge portion of a sheet being conveyed passes through a nip portion is detected. In response to the detected timing, the thickness of the sheet is detected, based on the output signals of the detection sensor. Therefore, a sheet conveying apparatus, an image forming apparatus, a control method for a sheet conveying apparatus, and a control program for a sheet conveying apparatus, which can detect the thickness of the sheet with the simple structure and high degree of accuracy, can be provided.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-183436 | Sep 2015 | JP | national |
