JP2007031104A - Sheet transporting device and sheet transport condition sensing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet transporting device capable of sensing a failure in the transport of a sheet simply using an acceleration sensor. <P>SOLUTION: A sheet transport path is fitted with a pair of vibration transmitting flags 207a and 207b and the acceleration sensor 205 to sense the vibrations transmitted from the vibration transmitting flags 207a and 207b. In the case of normal sheet transport, the vibrations which the flags 207a and 207b give to the acceleration sensor are generated simultaneously, so that the output signals from the acceleration sensor 205 overlaps each other as the peaks in the same timing. In the case the sheet is being transported askew, the output signals of the acceleration sensor 205 form two peaks in the transport of one sheet. The degree of skewing is determined according to the time difference between the two peaks. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet and a sheet conveying state detection method.

  Conventionally, as a means for discriminating the type of sheet material in a sheet conveying apparatus, a contact portion that comes into contact with the surface of the sheet to be conveyed is provided, and vibration, sliding, and the like caused by the contact portion contacting the conveyed sheet It is known that the roughness of the sheet surface is detected from the physical phenomenon (see Patent Document 1).

  FIG. 16 is a diagram showing a configuration of a conventional sheet surface roughness detection device. The sheet surface roughness detection device 1024 includes a pre-transfer guide 1017, a vibration sensor 1020, and a sensor base 1021. The paper P is transported to the pre-transfer guide 1017 by a paper feed roller and a transport roller.

  The pre-transfer guide 1017 bears a guide member that smoothly guides the paper P at a transfer nip portion formed by the contact portion of the photosensitive drum 1001 and the transfer roller 1008. The pre-transfer guide 1017 is made of a metal such as aluminum, a gin-coated copper plate, or stainless steel, and is electrically grounded. As the pre-transfer guide 1017, there is a guide integrated with a mold frame and insulated. Note that the pre-transfer guide 1017 may be made of either a conductive material or an insulating material, but it is preferable that the pre-transfer guide 1017 has conductivity in order to remove electric charges from the paper P. Further, the pre-transfer guide 1017 also has a role of adjusting the posture of the sheet that enters the transfer nip portion. The image quality at the time of transfer changes depending on the paper entry angle. In general, when the paper P enters the transfer nip portion along the photosensitive drum 1001, the resolution tends to be improved.

  In the conventional sheet surface roughness detection device 1024, the pre-transfer guide 1017 is always disposed at a position where the pre-transfer guide 1017 rubs against the non-printing surface side of the sheet during conveyance of the sheet. The angle of the paper portion coming out of the paper is set to be about 175 degrees. That is, the pre-transfer guide 1017 is arranged at a position where the sheet angle is bent by about 5 degrees.

  As the piezoelectric vibration sensor 1020, for example, a commercially available piezoelectric element having a diameter of about 18 mm and a thickness of about 0.7 mm is used. Such a piezoelectric vibration sensor 1020 may be fixed to a rubbing member such as the pre-transfer guide 1017. However, in order to measure vibration with higher sensitivity, the sheet surface roughness detector 1024 has a structure in which a piezoelectric vibration sensor 1020 is sandwiched between a molded sensor base 1021 and a pre-transfer guide 1017 made of sheet metal. It has become.

  With such a structure, the sheet surface roughness detecting device 1024 can measure the vibration of the pre-transfer guide 1017 with high sensitivity by concentrating the vibration energy of the pre-transfer guide 1017 on the piezoelectric vibration sensor 1020 and contacting the moving paper. .

  The image forming apparatus changes the energy supplied to the fixing device based on the sheet type identified by the measurement result of the sheet surface roughness detection device, or changes the high voltage output such as the developing bias to change the image. Was forming. Nowadays, an inexpensive and simple sheet identification device is required in order to perform optimum image formation for individual sheets due to diversification of sheets. Furthermore, when used in an image forming apparatus, a sheet identifying apparatus that corrects a detection result according to individual differences between apparatuses and can accurately identify the type of sheet is desired.

  In recent years, image forming apparatuses have been required to have high image quality and high performance year by year. In order to prevent deterioration in image quality due to sheet skew, skew feeding, and the like, the sheet conveyance state is inclined. When a line detection sensor (CCD, CIS, etc.) detects and a deviation of a predetermined amount or more is detected, it is determined that the image is defective and the image forming apparatus is stopped.

  FIG. 17 is a diagram showing a print position adjusting mechanism in a conventional image forming apparatus. The figure (a) is the figure seen from the horizontal direction, and the figure (b) is the figure seen from the upper surface. Reference numeral 1201 denotes a photosensitive drum for performing image formation, and 1202 denotes a laser that irradiates the photosensitive drum 1201 with laser light to form a latent image. Reference numeral 1203 denotes a registration clutch (registration roller) that determines the sheet feeding timing, and 1204 denotes a sheet sensor 1204 that is provided on the opposite side of the registration clutch 1203 from the photosensitive drum 1201 and detects the sheet 1207 conveyed in the feeding direction 1206. Reference numeral 1205 denotes a misalignment detection sensor that detects the misalignment of the lateral edge in the direction perpendicular to the paper feeding direction. The print adjustment mechanism is composed of the above members. Each of these members is controlled by a control circuit (not shown).

The printing position adjustment operation in the image forming apparatus having the above configuration will be described. A control circuit (not shown) detects the amount of misalignment of the paper in the direction perpendicular to the paper feed direction based on the output of the misalignment detection sensor 1205, and the presence / absence of paper in the paper feed direction detected by the paper sensor 1204 To get. Based on the acquired information, the transfer timing of image data to a laser control circuit (not shown) that drives the laser 1202 and the paper feed timing of the registration clutch 1203 are adjusted. When the amount of misalignment greater than or equal to a predetermined value is acquired by the above detection, the position accuracy of the image recording with respect to the paper becomes very poor, and the image forming apparatus is stopped as a jam.
JP 2000-314618 A

  However, the conventional sheet conveying apparatus has the following problems. Sensors (CCD, CIS) for detecting skew feeding and skew feeding are expensive and are often mounted on devices with relatively high print output speeds such as high-speed machines. It was rarely mounted on devices with slow print output speeds. For this reason, in a device with a relatively slow print output speed such as a low or medium speed machine, no measures have been taken with respect to the sheet conveyance state such as skew feeding and skew feeding.

  Further, although the type of sheet is identified using an acceleration sensor (piezoelectric vibration sensor), skew detection is not performed.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet conveying apparatus and a sheet conveying state detecting method capable of easily detecting an abnormality in conveying a sheet using an acceleration sensor. Another object of the present invention is to provide a sheet conveying apparatus and a sheet conveying state detecting method capable of identifying the sheet type together with sheet skew detection.

  In order to achieve the above object, a sheet conveying apparatus of the present invention is a sheet conveying apparatus that conveys a sheet, and is arranged in a width direction of a sheet conveying path, and a vibration transmitting member that is vibrated by the conveyed sheet And an acceleration detection means for detecting vibration applied to the vibration transmission member, and a conveyance abnormality of the conveyed sheet based on the state of vibration applied to the vibration transmission member detected by the acceleration detection means And a conveyance abnormality detecting means for detecting the above.

  The sheet conveyance state detection method of the present invention is a sheet conveyance state detection method for detecting the state of a conveyed sheet, and is added to the vibration transmission member arranged in the width direction of the sheet conveyance path by the conveyed sheet. An abnormality detection step of detecting an abnormality in conveyance of the conveyed sheet based on an acceleration detection step of detecting the generated vibration by an acceleration sensor and a state of vibration applied to the vibration transmission member detected by the acceleration sensor And a step.

  According to the sheet conveying apparatus of the first aspect of the present invention, the vibration applied to the vibration transmitting member arranged in the width direction of the sheet conveying path is detected by the acceleration sensor, and this detection is performed. Since the conveyance abnormality of the conveyed sheet is detected based on the state of vibration applied to the vibration transmitting member, the sheet conveyance abnormality can be easily detected using an acceleration sensor (acceleration detection means).

  According to the sheet conveying apparatus of the second aspect, it is possible to easily detect the skew of the sheet. According to the sheet conveying apparatus of the third aspect, it is possible to detect the jam of the sheet. According to the sheet conveying apparatus of the fourth aspect, it is possible to identify the sheet type as well as the sheet skew detection. According to the sheet conveying apparatus of the fifth aspect, it is possible to easily determine conveyance failure. According to the sheet conveying apparatus of the seventh aspect, it is possible to clearly distinguish and detect sheet skew and skew feeding.

  Embodiments of a sheet conveying apparatus and a sheet conveying state detection method of the present invention will be described with reference to the drawings. The sheet conveying apparatus of this embodiment is mounted on an image forming apparatus.

[overall structure]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment. The image forming apparatus includes an image forming apparatus main body 10, a folding device 40, and a finisher 50. The image forming apparatus main body 10 includes an image reader 11 and a printer 13 that read a document image.

  A document feeder 12 is mounted on the image reader 11. The document feeder 12 feeds the documents set upward on the document tray 12a one by one from the top page in order to the left in the figure, and conveys them onto the platen glass through a curved path. The original is read by stopping at the position and scanning the scanner unit 21 from the left side to the right side in this state. After reading, the original is discharged toward the external paper discharge tray 12b.

  The original reading surface is irradiated with light from the lamp of the scanner unit 21, and reflected light from the original is guided to the lens 25 via the mirrors 22, 23 and 24. The light that has passed through the lens 25 forms an image on the imaging surface of the image sensor 26.

  Then, the entire original image is read by moving the scanner unit 21 in the sub-scanning direction while reading the original image by the image sensor 26 line by line in the main scanning direction. The optically read image is converted into image data by the image sensor 26 and output. Image data output from the image sensor 26 is subjected to predetermined processing in an image signal control unit (image processing circuit) (not shown) and then input as a video signal to an exposure control unit (laser control circuit) (not shown) of the printer 13. To do.

  The exposure control unit of the printer 13 modulates laser light output from a laser element (not shown) based on the input image data. The modulated laser light is irradiated onto the photosensitive drum 201 through the lenses 28 and 29 and the mirror 30 while being scanned by the polygon mirror 27.

  An electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 201. The electrostatic latent image on the photosensitive drum 201 is visualized as a developer image by the developer supplied from the developing device 33. In addition, at the timing synchronized with the start of laser light irradiation, paper is fed from each cassette 34, 35, 36, 37, manual paper feed unit 38 or double-sided conveyance path, and the timing is adjusted by registration rollers 203 to form an image. It is conveyed to the part.

  This sheet is conveyed between the photosensitive drum 201 and the transfer roller 39, and the developer image formed on the photosensitive drum 201 is transferred onto the sheet fed by the transfer roller 39. The sheet on which the developer image is transferred is conveyed to the fixing unit 32, and the fixing unit 32 fixes the developer image on the sheet by heat-pressing the sheet. The sheet that has passed through the fixing unit 32 is discharged from the printer 13 to the outside (the folding device 40) through a flapper and a discharge roller.

  Here, when the sheet is discharged with its image forming surface facing downward (face-down state), the sheet that has passed through the fixing unit 32 is once guided into the reversing path 42 by a flapper switching operation. After the trailing edge of the paper guided into the reverse path 42 passes through the flapper, the paper is switched back and discharged from the printer 13 by the discharge roller.

  In addition, when a hard sheet such as an OHP sheet is fed from the manual sheet feeding unit 38 and an image is formed on the sheet, the image forming surface is faced upward without introducing the sheet to the reverse path (face-up state). ) Is discharged by the discharge roller.

  Further, when double-sided recording for forming an image on both sides of a sheet is set, an unrecorded sheet is guided to a reverse path 42 by a flapper switching operation and then conveyed to a duplex conveyance path. The sheet guided to the duplex conveyance path is conveyed to the position nipped by the duplex conveyance roller 41 via the duplex conveyance roller 40a, and temporarily stops until the next sheet feeding timing. If there is already a sheet that stops at the position nipped by the duplex conveying roller 41 in the duplex conveying path, the sheet is stopped at the position nipped by the duplex conveying roller 40a located upstream of the duplex conveying roller 41.

  Here, if the cassette 35 is used even if there is no paper that stops at the position nipped by the double-sided conveyance roller 41 in the double-sided conveyance path, the paper is conveyed to the position nipped by the conveyance roller 40a and stops the paper. .

  Then, after being fed from the cassette and transported to the image forming unit, the single-side printed paper nipped by the duplex transport roller 41 is fed again. Thereafter, when the single-sided paper that has been printed is conveyed to the image forming unit, the paper is fed from the cassette. Double-sided recording is performed by alternating paper feeding that repeats the above operation. At this time, a maximum of two sheets remain in the duplex conveyance path.

  The paper discharged from the printer 13 is sent to the folding device 40. The folding device 40 performs a process of folding the paper into a Z shape. For example, when A3 size or B4 size paper is specified and folding processing is specified, folding processing is performed by the folding device 40. In other cases, the paper discharged from the printer 13 passes through the folding device 40. It is sent to the finisher 50. The finisher 50 is provided with an inserter 90 for feeding a special sheet such as a cover sheet or a slip sheet to be inserted into a sheet on which an image is formed. In the finisher 50, bookbinding processing, binding processing, punching, and the like are performed.

  The first discharge tray 51 is a tray from which sheets that are not subjected to stapling or bookbinding processing and error sheets to be described later are discharged. The second discharge tray 52 is a tray from which the sheets stapled by the staple processing tray 53 are discharged. In this embodiment, the photosensitive drum is used as the image carrier of the image forming apparatus, but a photosensitive belt may be used.

  The image forming apparatus is provided with an operation panel 60. FIG. 2 is a diagram illustrating the configuration of the operation panel 60. In the figure, reference numeral 400 denotes a copy start key for instructing the start of copying. Reference numeral 401 denotes a reset key for returning to the standard mode. Reference numeral 402 denotes a guidance key that is pressed when the guidance function is used. Reference numeral 403 denotes a numeric keypad for inputting a numerical value such as a set number of sheets. Reference numeral 404 denotes a clear key for clearing a numerical value. Reference numeral 405 denotes a stop key for stopping copying during continuous copying. Reference numeral 406 denotes a liquid crystal display unit and a touch panel for displaying various mode settings such as a staple mode, a bookbinding mode, and a double-sided print setting, and a printer status. Reference numeral 407 denotes an interrupt key for interrupting and taking an emergency copy during continuous copying or during use as a fax or printer. Reference numeral 408 denotes a personal identification key for inputting a personal identification number when it is necessary to input the personal identification number in order to manage the number of copies by individual or department. Reference numeral 409 denotes a soft power switch for turning on / off the power of the image forming apparatus main body. Reference numeral 410 denotes a function key used when changing the function of the image forming apparatus. Reference numeral 411 denotes a user mode key for entering a user mode in which a user sets each item of the apparatus in advance, such as ON / OFF of auto cassette change or a change of a setting time until entering an energy saving mode.

(Configuration of printer unit)
FIG. 3 is a diagram showing an electrical configuration of the printer unit 13. The printer unit 13 controls sheet feeding, conveyance, transfer, fixing, and the like, and includes a CPU 310, a ROM 311, a RAM 312, an EEPROM 313, a developing bias generation unit 314, a signal processing unit 315, a registration detection sensor 316, and the like. The CPU 310 is connected to a ROM 311, a RAM 312, an EEPROM 313, a developing bias generator 314, a signal processor 315, a registration sensor 204, and the like, as well as a PWM unit 320, a scanner unit 12, a finisher unit 50, and an operation unit 60. .

  The ROM 311 stores a control program executed by the CPU 310 and the like. The RAM 312 temporarily stores data for controlling the printer unit 13, calculation results by the CPU 310, and the like. The EEPROM 313 stores development bias, adjustment values of various sensors, and the like. The developing bias generator 314 generates a bias voltage for the developing device 317. Details of the signal processing unit 315, the acceleration sensor 205, and the registration sensor 204 will be described later.

(Print position adjustment mechanism)
FIG. 4 is a diagram showing a print position adjusting mechanism in the image forming apparatus. The figure (a) is the figure seen from the horizontal direction, and the figure (b) is the figure seen from the upper surface. Reference numeral 204 denotes a paper (registration) sensor that is provided on the side opposite to the photosensitive drum 201 with respect to the registration clutch (registration roller) 203 and detects the conveyed paper 206. 207a and 207b are a pair of vibration transmission flags arranged at equal distances around the sheet conveyance path. Reference numeral 205 denotes an acceleration sensor that detects vibration transmitted from the pair of vibration transmission flags 207a and 207b.

  When performing the image forming operation, when the paper 206 is conveyed to the registration clutch 203, the registration clutch 203 is stopped. Therefore, a paper loop is formed by the registration clutch 203, and correction processing such as skew is performed. A predetermined time after the registration sensor 204 detects the paper 206, the registration clutch 203 is turned on. At this time, using the vibration transmission flag 207 and the acceleration sensor 205, the paper conveyance state and the paper type are determined.

  The vibration transmission flag and the acceleration sensor will be described in detail. FIG. 5 is a perspective view showing the structure of the vibration transmission flag 207. Since the pair of vibration transmission flags 207a and 207b have the same structure, they are collectively referred to as the vibration transmission flag 207. The vibration transmission flag 207 includes a shaft 207c provided in the width direction perpendicular to the paper feeding direction 206, and a swing member 207d swingable about the shaft 207c. The swing member 207d has a bar member 207e through which the shaft 207c is inserted, a projection 207f formed conically at one end of the bar member 207e, and an arc formed at the other end of the bar member 207e. The structure has a hammer portion 207g. The swinging member 207d is normally stable with the protrusion 207f facing upward because the hammer 207g side is slightly heavier with respect to the protrusion 207f side around the shaft 207c. It slightly protrudes from the conveyance surface of the paper 206. In this state, when the sheet 206 passes, the sheet 206 collides with the protrusion 207f, and the swing member 207d swings so that the protrusion 207f sinks from the conveyance surface of the sheet 206. By this swinging, the end surface of the hammer portion 207g hits the bottom surface of the acceleration sensor 205, and gives vibration to the acceleration sensor 205.

(Acceleration sensor)
FIG. 6 is a diagram showing a basic structure of a sensor unit in the acceleration sensor 205. The acceleration sensor is a converter that converts vibration or the like into an electrical quantity. There are various types of acceleration sensors, and representative examples include capacitance type acceleration sensors and piezoelectric acceleration sensors. In this embodiment, the case where the acceleration sensor of an analog device company is used as an electrostatic capacitance type acceleration sensor is shown.

  The acceleration sensor 205 is a capacitive acceleration sensor having a sensor unit 205A. The sensor unit 205A has a polysilicon structure whose surface is micromachined, and is formed on a silicon wafer. On the wafer surface, this structure is supported by a polysilicon spring so as to resist the force generated by the acceleration. Reference symbols h, i, j, and k represent anchors (fixed portions). In this structure, a differential capacitor 205e is composed of independent fixed plates 205a and 205b and a central plate 205d attached to a movable mass portion (beam) 205c. A square wave signal having a phase difference of 180 degrees is applied to the fixed plates 205a and 205b, and the shake of the structure is detected from the change in the signal generated in the differential capacitor 205e. That is, in a state where there is no deflection of the beam 205c due to acceleration, the electrical signals between the fixed plates 205a and 205b cancel each other, and the output signal from the differential capacitor 205e becomes almost zero. On the other hand, when the beam 205c is swung due to acceleration, an unbalance occurs in the differential capacitor 205e, and a square wave output signal having an amplitude proportional to the acceleration is generated in the differential capacitor 205e.

  FIG. 7 is a diagram showing an electrical configuration of the acceleration sensor 205. The acceleration sensor 205 includes the above-described sensor unit 205A, gain amplifier 251, demodulator 252, buffer amplifier 253, and clock generation unit 254. The sensor unit 205A detects the shake of the structure as acceleration using the above-described differential capacitor 205e. The gain amplifier 251 amplifies the acceleration detected by the sensor unit 205A into a signal having an appropriate size. The demodulator 252 demodulates the amplified signal. The buffer amplifier 253 amplifies the demodulated signal again and outputs it as an output signal. The clock generation unit 254 outputs a square wave signal to the sensor unit 205A and the demodulator 252. The acceleration sensor 205 can output both an output signal VoutX in the X-axis direction corresponding to the paper feeding direction and an output signal VoutY in the Y-axis direction corresponding to the paper width direction. However, in this embodiment, since the vibration transmission flag for transmitting the vibration in the width direction of the paper is not provided, the output signal VoutY is almost 0, and the output signal VoutX in the X-axis direction corresponding to the paper feeding direction. Are output as acceleration signals only.

  FIG. 8 is a block diagram showing a configuration of the signal processing unit 315. The signal processing unit 315 includes a filter 341, an A / D converter 342, a timing control unit 343, and a feature amount calculation unit 345. In the signal processing unit 315, when the output signal VoutX from the acceleration sensor 205 is input, the filter 341 removes the DC component and the high frequency noise component of the input signal. The A / D converter 342 converts the filtered analog signal into digital data. The timing control unit 343 divides the continuous digital data into data for each sheet according to the detection start / end signal from the registration sensor 204.

  The detection start / end signal is output from the registration sensor 204 as described above, and remains on while the sheet being conveyed passes through the registration sensor 204 (see FIG. 9). Of the output signal of the timing control unit 343, only the signal component in the period in which the detection start / end signal is maintained at the on level is extracted and provided to the feature amount calculation unit 345. When the feature amount calculation unit 345 obtains detection data for one sheet, the feature amount calculation unit 345 calculates a feature amount necessary to determine the conveyance state of the sheet. Examples of the feature amount include a height of a vibration peak necessary for detecting paper quality, a time difference between two vibration peaks necessary for skew detection, and the like. Note that the timing control unit 343 and the feature amount calculation unit 345 represent functions realized by a processor (not shown) in the signal processing unit 315 executing a program. The registration sensor 204 is arranged downstream of the vibration transmission flags 207a and 207b, and is configured to mechanically apply vibration to the acceleration sensor 205 almost simultaneously with the ON of the registration sensor.

(Sheet type detection)
As described above, the acceleration sensor 205 detects the vibration energy applied by the swing of the vibration transmission flag 207. That is, when the sheet collides with the vibration transmission flag 207, the hammer portion 207g swings and applies an impact force to the bottom surface of the acceleration sensor 205. As a result, vibration energy is detected by the acceleration sensor 205. Then, it can be seen that the leading edge of the sheet has reached the vibration transmission flag 207. The force applied to the acceleration sensor 205, that is, the vibration energy, differs depending on the type of seat. In general, when the basis weight of a sheet is large, the thickness increases and the rigidity of the sheet increases. Therefore, when thick paper having a large basis weight collides with the vibration transmission flag 207, vibration energy larger than that of plain paper is detected.

  FIG. 9 is a timing chart showing changes in the output signal and the detection start / end signal from the timing control unit 343 when conveying plain paper. FIG. 10 is a timing chart showing changes in the output signal and the detection start / end signal from the timing control unit 343 when transporting thick paper. Here, vibration energy (output signal from the timing control unit 343) when three sheets are continuously fed is shown. When the seat collides with the vibration transmission flag, a signal proportional to the vibration energy from the timing control unit rises. Then, as shown in FIGS. 9 and 10, it was found that the peak value of the vibration energy is proportional to the basis weight of the paper. By setting the threshold value of the peak value around 0.6, it is possible to distinguish between plain paper and thick paper.

  Note that either output signal of the vibration transmission flags 207a and 207b may be used, or determination may be made from the average value of the two output signals.

(Slave feed and skew feed detection)
Conventionally, skew detection is performed using an optical sensor such as a CCD or CIS, and further, a process of correcting a skew by forming a loop on the sheet by temporarily stopping the sheet conveyance by a registration roller. It was done. However, the loop forming operation is limited in time, and it is difficult to say that all skews are corrected, and there has been a problem of image defects due to jamming or registration misalignment due to skewing.

  In contrast, in the present embodiment, two vibration transmission flags 207a and 207b are arranged in the width direction of the sheet conveyance path, and the vibration is detected by the acceleration sensor 205, thereby detecting the skew of the sheet.

  FIG. 11 is a graph showing changes in the output signal of the acceleration sensor. When the sheet is conveyed with almost no skew, vibrations given to the acceleration sensor by the two vibration transmission flags 207a and 207b are generated almost simultaneously, and the output signal from the actual acceleration sensor 205 is shown in FIG. As shown in (), they overlap as peaks at the same timing. On the other hand, when the sheet is conveyed while being skewed, vibrations given to the acceleration sensor by the two vibration transmission flags 207a and 207b occur at different timings. Therefore, as shown in FIG. 11B, the output signal of the acceleration sensor 205 forms two peaks in the conveyance of one sheet. Then, the degree of skew is detected according to the time difference between the two peaks. Further, according to this time difference, the time for stopping the sheet by the registration roller is changed, that is, the sheet feeding timing of the registration clutch 203 is adjusted. If the time difference is greater than or equal to a predetermined value, the position accuracy of the image recording on the paper is very poor, so it is determined that a jam has occurred and the operation of the image forming apparatus is stopped. Note that the skew detection of the sheet can be detected by the same method as the skew detection. Here, “skew feeding” means that the sheet is conveyed obliquely, and “skew” means that the sheet inclined obliquely is conveyed in parallel.

(Sheet edge detection and jam detection)
In FIG. 9, the ON timing of the registration sensor 204 coincides with the peak value of the signal obtained from the acceleration sensor 205. This peak value represents vibration energy when the leading edge of the sheet reaches the registration sensor. Therefore, the leading edge of the paper can be detected by detecting the timing when the signal from the acceleration sensor peaks.

  FIG. 12 is a diagram showing sheet jam detection. FIG. 5A shows an output signal of the acceleration sensor when one sheet is conveyed in a normal state. In normal conveyance, the signal output from the acceleration sensor has a peak first, and then settles to an average steady value (effective value level) while repeating some amplitude fluctuations. On the other hand, FIG. 5B shows an output signal of the acceleration sensor when a jam occurs. The output signal at the time of jam does not show a peak waveform in normal conveyance, and further, it does not settle down to a steady value level, and always repeats a large amplitude change. This is because the sheet is deformed due to the sheet jamming, and the unevenness of the sheet collides with the vibration transmission flag 207 many times in the deformed state, and the vibration is transmitted to the acceleration sensor 205. It is considered a thing.

(Sheet conveyance processing)
FIG. 13 is a flowchart showing a sheet conveyance processing procedure. This processing program is stored in the ROM 311 in the printer unit 13 and is executed by the CPU 310. First, the presence / absence of a job (JOB) is determined (step S1). If there is no job, the process waits until the job is generated. When the job is generated, the paper feeding operation is started (step S2). Then, it is determined whether or not the sheet is conveyed at a predetermined timing and the registration sensor 204 is turned on (step S3).

  If the registration sensor 204 is on, acceleration detection data is acquired from the signal processing unit 315 (step S4). Based on the acceleration detection data, the type (material) of the paper is determined (step S5). This discrimination of the paper type is reflected in the control of the high voltage output and the temperature control temperature of the fixing device in the image forming operation.

  Thereafter, skew / slope feed is determined (step S6). That is, it is determined whether or not the time difference between the peak timings of the acceleration signals is within a predetermined value. If the time difference is within the predetermined value, the ON timing of the registration clutch that drives the registration rollers is calculated (step S7). It is determined whether or not the sheet is normally conveyed without causing jamming according to whether the output of the acceleration signal is repeatedly increased or decreased (step S8). If it is determined that the sheet is being conveyed normally, an image forming operation is performed based on the calculation result of step S7 (step S9). After the image formation, the paper is discharged out of the machine (step S10), and this process ends.

  On the other hand, if the registration sensor 204 is not turned on within a predetermined time in step S3, it is determined that a jam (paper jam) has occurred due to a paper conveyance failure, and the conveyance operation is stopped (step S11). If the time difference exceeds the predetermined value in step S6, it is determined that the skew / skew feeding state is present, and the position accuracy of image recording on the sheet is very poor, and the conveying operation is stopped as a jam in step S11. Also, if it is determined in step S8 that the paper transport is not normal, the transport operation is stopped as a jam in step S11. Thereafter, the process waits for the jam processing to end, and when the jam processing ends, the paper feeding operation in step S2 is started.

  As described above, according to the sheet conveying apparatus of the present embodiment, the acceleration sensor is arranged on the sheet conveying path, and the signal is detected to thereby detect the sheet conveying state (skew / diagonal feeding detection, leading edge detection, jam detection). ) And the type of paper can be identified.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

  For example, in the above-described embodiment, the case where one acceleration sensor is arranged is shown, but a plurality of acceleration sensors may be arranged. FIG. 14 is a diagram showing a print position adjusting mechanism when two acceleration sensors are arranged. The figure (a) is the figure seen from the horizontal direction, and the figure (b) is the figure seen from the upper surface. The two acceleration sensors are arranged so as to detect vibrations from the two vibration transmission flags, respectively. Thus, by providing two acceleration sensors, the bar member (see FIG. 5, reference numeral 207e) can be omitted, and the structure of the vibration transmission flag can be simplified. In addition, the protrusion and hammer portion of the vibration transmission flag can be swung on the same plane.

  Further, since the leading edge of the paper can be detected by the acceleration sensor, it can be configured without providing a registration sensor. Moreover, in the said embodiment, although the acceleration sensor is arrange | positioned upstream from a registration sensor, you may arrange | position downstream. Further, in the present embodiment, the capacitance type acceleration sensor is used as the means for detecting the vibration. However, as described above, a piezoelectric vibration sensor, a displacement sensor, a strain sensor, or the like may be used.

  In the above embodiment, the skew of the sheet is detected by the detection mechanism including the pair of vibration transmission flags and the acceleration sensor. However, the skew of the sheet may be detected by using another detection mechanism. FIG. 15 is a diagram showing a mechanism for detecting skew and skew feeding of a sheet. In FIG. 2A, a pair of detection mechanisms are provided in the width direction of the sheet. In this detection mechanism, the balls 351 and 352 that also serve as sheet conveying rollers (such as track balls used in PCs) 351 and 352 are movable in conjunction with the rotation of the ball rotation axis from the sheet width direction. Acceleration sensors 353 and 354 are attached. The acceleration sensors 353 and 354 can detect biaxial acceleration composed of the X direction (sheet conveyance direction) and the Y direction (sheet width direction). When the sheet is conveyed to the balls 351 and 352, the rotation axis of the ball is tilted, and when the acceleration sensors 353 and 354 move, the acceleration components in the X and Y directions are detected as vibrations applied by the sheet. To do. As the acceleration sensor, for example, the capacitance type acceleration sensor described above can be used.

  When a skewed sheet is conveyed, the skew amount is detected from a time difference in which the leading edge of the sheet contacts the ball 351 and the ball 352. Further, when the sheet is conveyed obliquely, as described above, the balls 351 and 352 are inclined, and each acceleration sensor is determined by the acceleration vector component in the X direction and the acceleration in the Y direction according to the inclination of the ball. The vector component of is detected. Then, by synthesizing the vector components in the X direction and the Y direction, as shown in FIG. In addition, when the oblique feeding does not occur, only the acceleration component in the X direction is detected.

  In addition, an object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the embodiments to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus as a storage medium. This can also be achieved by reading and executing the stored program code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, and a DVD. -RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, etc. can be used. Alternatively, the program code may be downloaded via a network.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

 Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes the case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment. 3 is a diagram illustrating a configuration of an operation panel 60. FIG. 2 is a diagram illustrating an electrical configuration of a printer unit 13. FIG. FIG. 3 is a diagram illustrating a print position adjustment mechanism in the image forming apparatus. 7 is a perspective view showing a structure of a vibration transmission flag 207. FIG. It is a figure which shows the basic structure of the sensor part in the acceleration sensor. It is a figure which shows the electrical structure of the acceleration sensor. 3 is a block diagram illustrating a configuration of a signal processing unit 315. FIG. 6 is a timing chart showing changes in an output signal and a detection start / end signal from a timing control unit 343 when transporting plain paper. It is a timing chart which shows the change of the output signal from the timing control part 343 at the time of conveying a thick paper, and a detection start / end signal. It is a graph which shows the change of the output signal of an acceleration sensor. It is a figure which shows the jam detection of a sheet | seat. It is a flowchart which shows a sheet conveyance processing procedure. It is a figure which shows the printing position adjustment mechanism in case two acceleration sensors are arrange | positioned. It is a figure which shows the mechanism which detects skew feeding and skew feeding of a sheet | seat. It is a figure which shows the structure of the conventional sheet surface roughness detection apparatus. It is a figure which shows the printing position adjustment mechanism in the conventional image forming apparatus.

Explanation of symbols

203 Registration roller 204 Registration sensor 205, 205a, 205b Acceleration sensor 205A Sensor unit 207, 207a, 207b Vibration transmission flag 310 CPU
315 Signal processor

Claims (10)

A sheet conveying apparatus for conveying a sheet,
A vibration transmission member disposed in the width direction of the sheet conveyance path, to which vibration is applied by the conveyed sheet;
Acceleration detecting means for detecting vibration applied to the vibration transmitting member;
A sheet conveyance apparatus comprising: a conveyance abnormality detection unit that detects a conveyance abnormality of the conveyed sheet based on a state of vibration applied to the vibration transmission member detected by the acceleration detection unit. . A pair of the vibration transmitting members are arranged in the width direction of the sheet conveying path,
The acceleration detecting means detects vibration applied to the pair of vibration transmitting members,
The conveyance abnormality detection unit detects skew of the conveyed sheet based on a time difference of vibration applied to the pair of vibration transmission members detected by the acceleration detection unit. The sheet conveying apparatus according to 1.   2. The conveyance abnormality detection unit according to claim 1, wherein jam detection of the conveyed sheet is performed based on a state of vibration applied to the vibration transmission member detected by the acceleration detection unit. Sheet conveying device.   3. A sheet conveying apparatus according to claim 2, further comprising sheet type determining means for detecting skew of the sheet and determining the type of the sheet.   3. The sheet conveying apparatus according to claim 2, wherein the conveyance abnormality detecting unit detects a conveyance abnormality of the conveyed sheet when the time difference exceeds a predetermined value. The vibration transmitting member is disposed so as to protrude from the conveyance surface of the sheet conveyance path, and is a protrusion that is swingable about an axis in the sheet width direction, and is swingable about the axis. A hammer part provided on the opposite side of the part,
The sheet conveying apparatus according to claim 1, wherein the hammer portion applies vibration to the acceleration detecting unit in conjunction with the protrusion portion colliding with the sheet and swinging. The pair of vibration transmitting members are a pair of balls that also serve as a sheet conveying roller,
The acceleration detecting means is attached in the sheet width direction of each ball, and the sheet is conveyed to the ball, and the sheet moves when the rotation axis of the ball is tilted from the sheet width direction. A biaxial acceleration detecting means for detecting acceleration components in the sheet conveying direction and the sheet width direction as vibration applied by
3. The sheet according to claim 2, further comprising a skew feeding detecting unit that detects the skew feeding of the conveyed sheet by vector-combining the detected acceleration components in the sheet conveying direction and the sheet width direction. Conveying device.   An image forming apparatus comprising the sheet conveying device according to claim 1. A sheet conveyance state detection method for detecting a state of a sheet being conveyed,
An acceleration detecting step of detecting, by an acceleration sensor, vibration applied to the vibration transmitting member disposed in the width direction of the sheet conveying path by the conveyed sheet;
A sheet conveyance state detection method comprising: a conveyance abnormality detection step for detecting a conveyance abnormality of the conveyed sheet based on a state of vibration applied to the vibration transmission member detected by the acceleration sensor. .   A program having computer-readable program code for realizing the sheet conveying apparatus according to claim 1.

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