JP2005298168A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device, in which paper is carried in such a way that time of feeding paper till it reaches a resistration roller is stable. <P>SOLUTION: This image forming device 1 is provided with a supply paper tray 16 to contain paper 3, a paper feeding means 17 to feed the paper 3, an image forming part 22 to form an image, the resistration roller 38 to feed the paper 3 to the image forming part 22, a carrying passage to carry the paper 3, and a carrying control means 45 to control carrying of the paper. A first paper detecting sensor 40 is provided downstream of the paper feeding means 17 in the paper carrying direction. The carrying control means 45 measures time after start of feeding of the paper 3 by the paper feeding means 17 till it is detected by the first paper detecting sensor 40, and controls to change the carrying speed for the paper 3 from downstream of the first paper detecting sensor 40 to the resistration roller 38 based on the detected time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that stabilizes the time from when a sheet loaded on a sheet feeding tray starts to be fed by a sheet feeding unit until it reaches a registration roller.

  In an image forming apparatus such as a copying machine, a sheet feeding unit feeds sheets stacked on a sheet feeding tray to a conveying path, and a conveying roller provided in the conveying path conveys the fed sheet to a registration roller. It has a configuration. The time from when the paper feeding unit is driven until the paper reaches the registration roller is a predetermined value for each model, and when the paper does not reach the registration roller within that time, the image forming apparatus is jammed. It is determined that the image formation is interrupted.

  The paper feeding means prevents a pickup roller that picks up the top sheet from the stack of sheets stacked on the paper feeding tray and the second and subsequent sheets that are dragged out of the sheet from being fed into the transport path. There are separation rollers to make. In such a sheet feeding means, the sheet feeding timing differs for each sheet because the pickup roller slides on the sheet or the sheet has already protruded to the vicinity of the separation roller. Due to the difference in sheet feeding timing, the time required to reach the registration roller also varies from sheet to sheet.

In order to perform stable image formation, there is an image forming apparatus that keeps the paper interval constant (see, for example, Patent Document 1). The image forming apparatus includes first to third transport rollers, a first motor that drives the second transport rollers, a second motor that drives the first and third transport rollers, and a first transport roller. A sheet passing sensor or the like provided between the second conveying roller and the like, and from the time from when the sheet passing sensor detects the trailing edge of the preceding sheet to when detecting the leading edge of the next sheet, Is calculated, and the rotation speed of the first motor is controlled so that the paper interval is constant.
Japanese Patent Laid-Open No. 11-59965 (paragraph 0007, FIG. 1)

  In Patent Document 1, the second motor that drives the first and third transport rollers always rotates at a constant rotation, even if the distance between the preceding paper and the next transported paper is always kept constant. Rotating at speed. However, in reality, the sheet conveyance speed is not always constant due to variations in the diameter of the conveyance roller or the like, and wear of the conveyance roller due to use. Also, since variations in paper feed timing are not taken into account, if the paper feed timing of a certain paper is delayed, the next paper is conveyed so that the paper interval from the preceding paper is constant, so the timing is It is transported in a delayed state.

  Due to these causes, even in Patent Document 1, the time for the paper to reach the registration roller is delayed and paper jam may occur, and stable image formation cannot be achieved.

  Accordingly, the present invention provides an image forming apparatus capable of transporting sheets stacked on a sheet feeding tray so that the time from when the sheet is fed by the sheet feeding unit to when the sheet reaches the registration roller is stabilized. It is aimed.

  In order to achieve the above object, an image forming apparatus according to claim 1, a paper feed tray for stacking and storing paper to be fed, and a paper feed unit for feeding paper from the paper feed tray; An image forming unit for forming an image, a registration roller for feeding paper to the image forming unit, a transport path for transporting paper from the paper feed tray to the registration roller, and control of paper transport In the image forming apparatus having the conveyance control unit, a first sheet detection sensor is provided downstream of the sheet feeding unit in the sheet conveyance direction, and the conveyance control unit is fed from the sheet feeding tray by the sheet feeding unit. The arrival time from the start of paper feeding until it is detected by the first paper detection sensor is measured, and based on the measured arrival time, the arrival time from the first paper detection sensor to the registration roller is measured. It is characterized by controlling so as to change the conveying speed of the sheet.

  The image forming apparatus according to claim 2, wherein a second paper detection sensor is provided on the downstream side of the first paper detection sensor and on the upstream side of the registration roller, and the conveyance control unit is configured to transfer the conveyed paper to the first paper detection sensor. Measuring an elapsed time from detection by the first paper detection sensor to detection by the second paper detection sensor, and controlling to further change the speed at which the paper is conveyed based on the measured elapsed time. It is a feature.

  According to a third aspect of the present invention, the second sheet detection sensor is provided on the upstream side and in the vicinity of the registration roller.

  The image forming apparatus according to a fourth aspect is characterized in that the feeding roller provided in the feeding unit and in the feeding path and that feeds the paper to the registration roller is driven by the same driving source.

  The image forming apparatus includes a paper feed tray, a paper feed unit, an image forming unit, a registration roller, a conveyance path, and a conveyance control unit. The first paper detection sensor is provided on the downstream side in the paper conveyance direction from the paper supply means, and the conveyance control means is detected by the first paper detection sensor after the paper supply by the paper supply means is started. The arrival time is measured, and control is performed so as to change the sheet conveyance speed from the downstream from the first sheet detection sensor to the registration roller based on the measured arrival time. As a result, the arrival time of the sheet on the registration roller is kept constant.

  According to a second aspect of the present invention, a second paper detection sensor is provided between the first paper detection sensor and the registration roller. The conveyance control unit measures an elapsed time from detection of the conveyed paper by the first paper detection sensor to detection by the second paper detection sensor, and the paper is controlled based on the measured elapsed time. Control is performed to further change the conveyance speed. As a result, it is possible to eliminate a decrease in the conveyance speed due to wear of the conveyance roller, and the conveyance time of the sheet from the paper feeding to the registration roller is constant.

  According to another aspect of the image forming apparatus of the present invention, the second paper detection sensor is provided on the upstream side and in the vicinity of the registration roller. As a result, it is possible to accurately measure the time until the paper reaches the registration roller, and the conveyance speed can be controlled more accurately.

  According to another aspect of the image forming apparatus of the present invention, the conveyance roller that is provided in the sheet feeding unit and the conveyance path and conveys the sheet to the registration roller is driven by the same drive source. As a result, the conveyance speed until reaching the registration roller is constant.

Next, the image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an image forming apparatus of the present invention. An image forming apparatus 1 in FIG. 1 shows an example of an embodiment of the present invention. An image reading device 4 that reads an image to be formed on the sheet 3 from a document is provided on the image forming apparatus main body 2, and an automatic document feeder 5 that automatically sends the document to the image reading device 4 is provided above the image reading device 4. Is provided.

  The automatic document feeder 5 includes a document placing table 6 on which a document is placed. A document feeding roller 7 that feeds the documents one by one is provided at one end of the document placing table 6. A document discharge table 8 for discharging a document read by the image reading device 4 is provided below the document table 6. The document placed on the document placing table 6 is sent to the transport path in the automatic document feeder 5 by the document feed roller 7, and the document is read by the image reading device 4 while being transported by the plurality of transport rollers 9. It is discharged to the document discharge table 8.

  The image reading apparatus 4 further includes a first mirror unit 12 in which a light source 10 that irradiates light on a document and a mirror 11 that reflects reflected light from the document are integrally configured, and light from the first mirror unit 12. And a second mirror unit 13 for reflection. These mirror units 12 and 13 are movable in the left-right direction in FIG. Further, the image reading device 4 has an image sensor 14 that photoelectrically converts light, such as a CCD, and the reflected light from the second mirror unit 13 by a lens 15 disposed in front of the image sensor 14. Is imaged on the surface of the image sensor 14.

  A slit for irradiating the original with light is provided on the upper part of the image reading device 4. The image reading device 4 reads the image by positioning the first mirror unit 12 below the slit. The automatic document feeder 5 is provided so as to be openable and closable with respect to the image reading device 4. A document is placed on a platen glass on the upper surface of the image reading device 4, and the document is mirrored by the mirror units 12 and 13. It is also possible to read an image by scanning.

  Below the inside of the image forming apparatus main body 2, a plurality of paper feed trays 16 for stacking and storing a plurality of paper sheets 3 are arranged vertically, and an image is to be formed on one upper end side of the paper feed tray 16. A sheet feeding means 17 is provided for feeding sheets 3 to be fed one by one.

  An image forming unit 22 for forming an image is disposed above the paper feed tray 16. The image forming unit 22 has a photosensitive drum 23 around which a charging device 24, an exposure device 25, a developing device 26, a transfer device 27, and a cleaning device 28 are arranged. The image forming unit 22 has a fixing device 29 provided above the cleaning device 28.

  The photosensitive drum 23 has a cylindrical shape and is driven to rotate counterclockwise in FIG. 1 by a drum driving mechanism (not shown). The charging device 24 uniformly charges the surface of the photosensitive drum 23 by corona discharge.

  The exposure device 25 is disposed around the photosensitive drum 23 and downstream of the charging device 24, and image exposure based on an image signal is performed on the surface of the photosensitive drum 23 uniformly charged by the charging device 24. Is to do. As a result, the charge on the surface of the exposed photosensitive drum 23 is attenuated and extinguished to form an electrostatic latent image.

  A developing device 26 is disposed around the photosensitive drum 23 on the downstream side of the exposure device 25. The developing device 26 develops the electrostatic latent image on the surface of the photosensitive drum 23 with toner charged to the same polarity as the photosensitive drum 23 by a reversal developing method.

  The transfer device 27 is disposed on the downstream side of the developing device 26. In a state where the sheet 3 is pressed against the photosensitive drum 23, the transfer device 27 causes corona discharge from the back surface of the sheet 3 to transfer a toner image to the sheet 3 and discharge the charged sheet 3 to remove the sheet 3. Is separated from the photosensitive drum 23.

  A fixing device 29 is disposed downstream of the transfer device 27. When the sheet 3 to which the toner image has been transferred passes through the fixing device 29, the toner is melted by the heat from the fixing device 29 and is fixed to the sheet 3.

  The photosensitive drum 23 having the toner image transferred onto the sheet 3 is pressed against the surface and the remaining toner is removed by the cleaning device 28, and when there is an image to be formed next, the charging device 24 uniformly again. Charged.

  The paper 3 on which the toner is fixed by the fixing device 29 is discharged to the paper discharge tray 31 by the paper discharge roller 30. Further, when images are formed on both sides, the sheet is conveyed again to the image forming unit 22 through the reversing path 33 by the conveying path switching plate 32 with the front and back sides reversed.

  On the upper surface of the image forming apparatus main body 2, an input operation unit for inputting an instruction from a user is provided. The image forming apparatus main body 2 is also provided with a manual feed tray 34 in addition to the paper feed tray 16.

  FIG. 2 is a diagram illustrating a conveyance path from the sheet feeding unit to the photosensitive drum. The sheet feeding unit 17 includes a pickup roller 35, a sheet feeding roller 36, and a separation roller 37. The pickup roller 35 is a roller for taking out the uppermost sheet from the sheets 3 stacked on the sheet feeding tray 16 and swings up and down by a solenoid (not shown). When the paper 3 is fed from the paper feed tray 16, the pickup roller 35 is brought into contact with the paper 3 by the solenoid and the uppermost sheet can be taken out.

  The paper feed roller 36 contacts the upper surface of the paper 3 taken out by the pickup roller 35 and rotates so as to feed the paper 3 in the transport direction. Further, the separation roller 37 is driven to contact with the lower surface of the paper 3 and exceeds a predetermined torque, and rotates in the conveyance direction of the paper 3. When the pick-up roller 35 picks up a plurality of sheets 3, the separation roller 37 does not reach a predetermined torque or more so that it stops, and the second and subsequent sheets 3 are stopped so as not to be conveyed. Only the uppermost sheet 3 is sent in the transport direction.

  Each of the upper sheet feed tray 16 and the lower sheet feed tray 16 has a dedicated conveyance path, and merges together just before the registration rollers 38. One or a plurality of transport rollers 39 are arranged in each transport path, and transport the paper 3 toward the registration rollers 38 respectively.

  The registration roller 38 corrects the bending of the conveyed sheet 3 and then conveys the sheet 3 to the image forming unit 22. The conveyance roller 39 is driven for a while after the leading edge of the sheet 3 hits the registration roller 38, and the sheet 3 forms a deflection called a loop on the upstream side of the registration roller 38. This loop corrects the bending of the paper 3. The registration roller 38 starts rotating at a predetermined time after the paper feeding operation of the paper 3 by the pickup roller 35 starts, and conveys the paper 3 to the image forming unit 22.

  A first paper detection sensor 40 is disposed on the downstream side of the paper feeding unit 17 in each of the paper feeding units 17 arranged above and below. A second paper detection sensor 41 is disposed on the upstream side of the registration roller 38. The first and second paper detection sensors 40 and 41 are constituted by, for example, a photosensor in which a light emitting element and a light receiving element are arranged on the same surface, and detect the paper 3 by the intensity of reflected light. Yes.

  In the present invention, each roller of the paper feeding means 17 and the transport roller 39 on the transport path are driven by the same drive motor (not shown), and the rotation start / stop is controlled by a clutch (not shown) provided on each roller. ing. Further, the registration roller 38 is driven independently of the transport roller 39 by another drive motor.

  FIG. 3 is a block diagram of the present invention. The overall control unit 42 includes a CPU, a ROM, a RAM, and the like (not shown). A processing program stored in the ROM is expanded in the RAM, and the CPU executes the expanded program. The input operation unit 43 is used by the user to input the size of the paper 3 and the number of images to be formed.

  The image processing unit 44 is one of the processing programs described above, receives an image read by the image reading device 4 as an analog signal, performs analog processing, A / D conversion, shading correction, image compression processing, and the like. The image forming unit 22 is controlled to form an image.

  The transport control means 45 calculates the transport speed of the paper 3 using the first and second paper detection sensors 40 and 41 and controls the rotational speed of the transport roller 39 so as to reach the registration roller 38 in a predetermined transport time. This is one of the processing programs stored in the ROM (not shown) of the overall control unit 42.

  The conveyance control means 45 measures the time from when the first sheet detection sensor 40 detects the leading edge of the sheet 3 to when the second sheet detection sensor 41 detects the leading edge of the sheet 3 to measure the first conveyance speed. The first motor rotation speed is calculated, and the time from when the paper feeding unit 17 starts to drive until the first paper detection sensor 40 detects the leading edge of the paper 3 is measured. There is a process for calculating and setting the second transport speed and the second motor rotation speed, which is a transport speed of 3.

  The first transport speed is for eliminating a change in the transport speed caused by variations in the roller diameter of the transport roller 39 or wear of the transport roller 39 due to use. After calculating at the time of manufacturing or installing the image forming apparatus 1, this may be calculated once for every predetermined number of image forming sheets such as every 5000 image forming processes.

  The second transport speed is a speed until the paper 3 reaches the first paper detection sensor 40 from the pickup roller 35. This can be obtained from the time taken from when the paper 3 is fed by the paper feeding means 17 until it is detected by the first paper detection sensor 40. The second transport speed changes for each sheet depending on the cause such as when the pickup roller 35 slides on the surface of the sheet 3 or the sheet 3 has already protruded to the vicinity of the separation roller 37. Accordingly, the second transport speed and the second motor rotation number are calculated every time one sheet of paper 3 is fed.

  When the second transport speed is slow, the sheet 3 can reach the registration roller 38 within a predetermined time by increasing the transport speed of the transport roller 39, that is, the rotation speed of the motor that drives the transport roller 39. . Conversely, when the second paper transport speed is fast, the paper 3 reaches the registration roller 38 at a predetermined time by slowing the transport speed of the transport roller 39.

  FIG. 4 is a timing chart showing the timing of the sheet feeding operation of the image forming apparatus of the present invention. The paper feed solenoid is for abutting the pickup roller 35 against the paper 3. The time from when the feed solenoid starts driving until the first paper detection sensor 40 detects the leading edge of the paper 3 is T1, and after the first paper detection sensor 40 detects the leading edge of the paper 3, the first The time until the two-sheet detection sensor 41 detects the leading edge of the sheet 3 is represented as T2. Further, when the distance from the pickup roller 35 to the first paper detection sensor 40 is L1, and the distance from the first paper detection sensor 40 to the second paper detection sensor 41 is L2, the first conveyance speed and the first conveyance speed. The first motor rotational speed obtained from the above can be obtained by the following equation.

First transport speed = L2 / T2
First motor speed = design speed * (design speed / first transport speed)

  Here, the design rotation speed and the design speed are the motor rotation speed and the conveyance speed determined when the image forming apparatus 1 is designed. These numerical values, L1 and L2, are stored in advance in a ROM (not shown) of the overall control unit 42. Since the value of L2 differs depending on the upper and lower sheet feeding means 17, the value for each sheet feeding means 17 is stored in the ROM, and at the time of calculation, an appropriate value depends on which sheet feeding tray 16 is used for sheet feeding. Is used.

  Further, the second transport speed and the second motor rotation speed can be obtained by the following equations. L3 in the equation is the distance from the first paper detection sensor 40 to the registration roller 38.

Second transport speed = (L3) / (arrival time set value−T1)
Second motor speed = first motor speed × (first transport speed / second transport speed)

  Here, the arrival time setting value is the time from the start of the paper feeding operation until the paper 3 reaches the registration roller 38. The arrival time setting and L3 are stored in the ROM of the overall control unit 42 in advance. Similarly to L2, L3 stores a value for each sheet feeding means 17 in the ROM and uses an appropriate value at the time of calculation.

Next, a control procedure performed by the transport control unit 45 will be described based on the flowchart of FIG.
The conveyance control unit 45 is executed when the user gives an instruction to start image formation from the input operation unit 43. When execution is started, the paper feed solenoid is driven to take out the paper 3 from the paper feed tray 16 designated by the user, and the pickup roller 35 is brought into contact with the surface of the paper 3 (S01). At the same time, time measurement is started to calculate the conveyance speed (S02), and the paper feed count is incremented by 1 (S03). The conveyance control unit 45 waits until the first sheet detection sensor 40 detects the leading edge of the sheet 3 (S04N), and when it is detected (S04Y), the time measurement is terminated and the elapsed time from S02 is stored in T1. (S05). The second conveyance speed and the second motor rotation speed are calculated using T1 obtained by the time measurement, and the rotation speed is set in the drive motor (S06). The rotation speed of the drive motor can be changed by changing the operation clock of the drive motor. The first transport speed necessary for the calculation of S06 is calculated when the image forming apparatus 1 is installed or at the previous image forming process, and is stored in the RAM of the overall control unit 42.

  Thereafter, the conveyance control unit 45 starts driving the conveyance roller 39 (S07), and at the same time, determines whether there is an image to be formed next (S08). The process returns to S01 after waiting (S08Y). If there is no image to be formed next, the paper feed operation is not performed, and the program ends when the currently formed image formation ends (S08N).

  On the other hand, the conveyance control means 45 that has driven the conveyance roller 39 in S07 determines whether or not the remainder obtained by dividing the paper feed counter by 5000 has become zero (S09). Here, “mod” is an operator representing a remainder. If the remainder is 0 (S09Y), time measurement is started (S10). When the second paper detection sensor 41 detects the leading edge of the paper 3 (S11Y), the time measurement is finished and the elapsed time is stored in T2. (S12). Then, the first transport speed and the first motor rotation speed are calculated and stored in the RAM (S13). If the result is not 0 in S09 (S09N), the process proceeds to the next process without performing a series of processes up to S13. As described above, the processing from S09 to S13 corrects a change in the conveyance speed caused by wear of the conveyance roller 39 or the like every time the number of fed sheets exceeds 5000 sheets.

  If NO is determined in S09 or the calculation of S13 is performed, the conveyance control unit 45 waits for a time until the sheet 3 forms a loop, and then stops driving the conveyance roller 39 (S14). Thereafter, it waits until it receives a drive start signal for the registration roller 38 (S15N), and when it receives a drive start signal (S15Y), it starts driving the transport roller 39 and the registration roller 38 (S16). As a result, the sheet 3 is conveyed to the image forming unit 22.

  The conveyance roller 39 stops after a predetermined time from the start of driving of the registration roller 38 (S17). When a predetermined time has elapsed since the second paper detection sensor 41 detected the passage of the rear end of the paper 3 (S18Y), the driving of the registration roller 38 is stopped (S19). If there is a next image forming process (S20Y), the process returns to S07.

  In the above-described embodiment, two paper detection sensors are arranged. However, the present invention can be implemented using only the first paper detection sensor. In this case, the speed change due to wear of the transport roller 39 is not taken into consideration, and the second transport speed and the second motor speed are set using the design value speed and the design speed as the first transport speed and the first motor speed. Will be calculated.

  Further, the sheet feeding unit 17 and the conveyance roller 39 are described as being driven by the same drive motor, but the present invention is not limited to such an embodiment, and each may be driven by a separate drive motor.

1 is a configuration diagram of an image forming apparatus of the present invention. FIG. 6 is a diagram illustrating a conveyance path from a sheet feeding unit to a photosensitive drum. It is a block diagram of the present invention. 6 is a timing chart showing the timing of sheet feeding operation of the image forming apparatus of the present invention. It is a flowchart which shows the procedure of the conveyance control of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Paper 16 Paper feed tray 17 Paper feed means 22 Image forming part 38 Registration roller 39 Conveyance roller 40 1st paper detection sensor 41 2nd paper detection sensor 45 Conveyance control means

Claims (4)

A paper feed tray for stacking and storing paper to be fed;
A paper feed means for feeding paper from the paper feed tray;
An image forming unit for forming an image;
A registration roller for feeding paper to the image forming unit;
A transport path for transporting paper from the paper feed tray to the registration rollers;
In an image forming apparatus having a conveyance control unit that controls conveyance of a sheet,
A first paper detection sensor is provided downstream of the paper feeding means in the paper transport direction;
The transport control unit measures an arrival time from the start of feeding of the paper fed from the paper feed tray by the paper feeding unit to detection by the first paper detection sensor, and the measured arrival time And controlling to change the sheet conveyance speed from the downstream to the registration roller from the first sheet detection sensor.   A second paper detection sensor is provided on the downstream side of the first paper detection sensor and on the upstream side of the registration roller, and the conveyance control means detects the conveyed paper by the first paper detection sensor and then 2. The image according to claim 1, wherein an elapsed time until detection by the second paper detection sensor is measured, and control is performed so as to further change the speed at which the paper is conveyed based on the measured elapsed time. Forming equipment.   The image forming apparatus according to claim 2, wherein the second sheet detection sensor is provided on the upstream side and in the vicinity of the registration roller.   4. The image forming apparatus according to claim 1, wherein the sheet feeding unit and a conveyance roller that is provided in the conveyance path and conveys a sheet to the registration roller are driven by the same drive source. 5. .

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