JP2009202955A - Sheet-like member thickness detection device, image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet-like member thickness detection device capable of detecting thickness of a sheet-like member with high accuracy, while reducing the cost, and an image forming device with the sheet-like member detection device. <P>SOLUTION: This sheet-like member thickness detection device 120 comprises: a pair of rollers 71 comprising a first roller member 124 and a second roller member 123 for nipping and delivering a sheet-like member 118 and so constituted so that the first roller member 124 rotates, in accordance with the movement of the sheet-like member 118; a direct-current motor 127 for rotary driving the second roller member 123; a power source 140 for applying a voltage to the direct-current motor 127; current value detection means 125 for detecting the current value of the current flowing in the direct-current motor 127; a storage means 139 for storing the correlation information of the current value and the thickness of the sheet-like member 118, in advance; and calculation means 129 for calculating the thickness of the sheet-like member 118 from detection results of the current value detection means 125 and the correlation information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet-like member thickness detection device that detects the thickness of a sheet-like member, and an image forming apparatus such as a printer, a facsimile machine, and a copier equipped with the sheet-like member thickness detection device.

  In this type of image forming apparatus, it is necessary to optimize the image forming conditions in accordance with the thickness of the recording paper in order to obtain a high-quality image.

  For example, in the transfer process in which toner is transferred to a recording paper, the volume resistance value is different if the thickness of the recording paper is different. Therefore, the transfer current for driving the transfer charger needs to be changed according to the thickness of the recording paper. . Also, in the fixing process in which the toner transferred onto the recording paper is heated and pressurized and fixed on the recording paper, the amount of heat required varies depending on the thickness of the recording paper. It is necessary to change the temperature.

  As a method for detecting the thickness of the recording paper, a method using a reflective optical sensor is known (Patent Document 1, etc.).

  An example of a recording paper thickness detection method by the recording paper thickness detection device 220 having a reflective optical sensor will be described with reference to FIG. The laser light emitted from the laser emission unit 221 of the recording paper thickness detection device 220 to the surface of the recording paper 218 is point A (an example of a thin recording paper) or point B (thick recording paper) on the surface of the recording paper 218. Reflected in paper example). The laser light reflected at point A enters the point C of the laser light receiving unit 222, and the laser light reflected at the point B enters the point D of the laser light receiving unit 222. As described above, the position at which the laser light irradiated from the laser light emitting unit 221 onto the surface of the recording paper is incident on the laser light receiving unit 222 varies depending on the thickness of the recording paper 218. Therefore, the thickness of the recording paper 218 can be measured from the incident position of the laser light incident on the laser light receiving unit 222.

  However, even if the recording paper has the same thickness, if the recording paper is curved or the route through which the recording paper passes is different, the distance between the laser light emitting unit or the laser light receiving unit and the recording paper changes, and the laser light receiving unit The incident position is shifted from the original position corresponding to the paper thickness. Therefore, there arises a problem that accurate thickness measurement cannot be performed.

  In the recording paper thickness detection device described in Patent Document 2, a roller pair for holding and conveying the recording paper is provided, and one roller member of the roller pair is configured to be displaced according to the thickness of the recording paper. Has been. Then, the thickness of the recording paper is detected by detecting the displacement amount of the distance between the axes of the roller pair in a state where the recording paper is nipped and conveyed by the roller pair. In this way, by detecting the thickness of the recording paper with the recording paper sandwiched between the roller pair, the thickness of the recording paper is curved or the route through which the recording paper passes can be accurately measured. There will be no malfunctions.

Japanese Patent Laid-Open No. 2003-112840 JP 2007-290844 A

  Since the thickness of the recording paper that is normally used is about 0.05 [mm] to 0.5 [mm], the displacement amount of the inter-axis distance of the roller pair when the recording paper is sandwiched is very small. Therefore, when the displacement amount of the distance between the axes of the roller pair is detected by an optical sensor as described in Patent Document 2, the detection accuracy of the displacement amount is lowered unless the optical sensor is attached to the apparatus main body with high accuracy. . If the optical sensor is attached to the apparatus main body with high accuracy so that the detection accuracy is not lowered, there arises a problem that the cost is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet-like member thickness detection device capable of detecting the thickness of a sheet-like member with high accuracy while achieving cost reduction, and An object of the present invention is to provide an image forming apparatus including the sheet-like member detection device.

In order to achieve the above object, the invention of claim 1 comprises a first roller member and a second roller member for holding and conveying the sheet-like member, and the first roller member moves the sheet-like member. A roller pair configured to rotate in accordance with the motor, a direct current motor that rotationally drives the second roller member, a power source that applies a voltage to the direct current motor, and a current value that detects a current value of a current flowing through the direct current motor The thickness of the sheet-like member is calculated from the detection means, the storage means storing the correlation information between the current value and the thickness of the sheet-like member in advance, and the detection result of the current value detection means and the correlation information. And an arithmetic means for performing the processing.
According to a second aspect of the present invention, in the sheet-like member thickness detecting device according to the first aspect, at least the second roller member is made of an elastic body.
According to a third aspect of the present invention, in the sheet-like member thickness detecting device according to the second aspect, the first roller is provided so that the distance between the axes of the first roller member and the second roller member does not fluctuate. A member and the second roller member are provided in the apparatus main body.
According to a fourth aspect of the present invention, in the sheet-like member thickness detecting device according to the first, second, or third aspect, a sheet-like member having a known thickness is divided between the first roller member and the second roller member. It has a correction means which carries and corrects the correlation information using the detection result of the current value detection means at that time.
Further, the invention of claim 5 is the sheet-like member thickness detection device of claim 4, further comprising an input means for a user to input information relating to the thickness of the sheet-like member, and the correction means comprises: Information regarding the thickness of the sheet-like member input to the input means, and the current value detection means when the sheet-like member having a thickness corresponding to the information input to the input means is conveyed by the roller pair. The correlation information is corrected using the detection result of the above.
According to a sixth aspect of the present invention, in the sheet-like member thickness detecting device according to the first, second, third, fourth or fifth aspect, the current value detecting means uses current value data for an integral multiple of one rotation of the roller. Then, the current value is detected.
The invention according to claim 7 is the sheet-like member thickness detection device according to claim 1, 2, 3, 4, 5 or 6, wherein at least one of the first roller member and the second roller member is provided. The width in the roller axis direction is narrower than the minimum width of the sheet-like member that can be conveyed by the apparatus main body.
According to an eighth aspect of the present invention, there is provided an image carrier that carries an image, a transfer unit that transfers an image on the image carrier to a sheet-like member, and a transfer unit that includes the image carrier and the transfer unit. 8. An image forming apparatus comprising a conveying means for conveying the sheet-like member, wherein the sheet-like member according to claim 1, 2, 3, 4, 5, 6 or 7 is disposed upstream of the transfer portion in the sheet-like member conveying direction. A member thickness detection device is provided.

  In the present invention, the sheet-like member is considered as a part of the first roller member when the sheet-like member is held by the roller pair. As a result, the radius of the first roller member from the center of the rotation axis of the first roller member toward the contact portion between the sheet-like member and the first roller member apparently increases according to the thickness of the sheet-like member. . When the radius increases in this way, the driving force required to rotationally drive the first roller member by the second roller member becomes smaller than when the sheet-like member is not pinched by the roller pair. When the driving force is thus reduced, the load torque applied to the direct current motor for rotationally driving the second roller member is smaller than when the sheet-like member is not held, and the generated torque of the direct current motor is accordingly increased. Get smaller. In a DC motor, there is a correlation between the generated torque and the current flowing through the DC motor, and the current flowing through the DC motor decreases as the generated torque decreases. Since the load torque changes with the amount of change according to the distance from the contact point to the center of the rotation axis, in other words, the amount of change according to the thickness of the sheet-like member, the generated torque also varies with the thickness of the sheet-like member. It changes with the corresponding change amount. There is such a correlation between the generated torque and the thickness of the sheet-like member. As described above, since the current flowing through the DC motor changes according to the generated torque, there is a correlation between the current flowing through the drive motor and the thickness of the sheet-like member. Accordingly, the calculation means uses the current value detected by the current value detection means to flow through the DC motor and the correlation information between the current value stored in advance in the storage means and the thickness of the sheet-like member. The thickness of the member can be obtained. Therefore, it is not necessary to measure the amount of displacement of the roller pair's inter-axis distance with an optical sensor and detect the thickness of the sheet-like member from the amount of displacement. Can be planned.

  As mentioned above, according to this invention, there exists the outstanding effect that the thickness of a sheet-like member can be detected with high precision, aiming at cost reduction.

Hereinafter, an electrophotographic copying machine as an image forming apparatus to which the present invention is applied will be described.
FIG. 2 is a schematic configuration diagram showing the copying machine according to the present embodiment. The copying machine includes a printer unit 1 that forms an image on recording paper, a paper feeding device 200 that supplies the recording paper 118 to the printer unit 1, a scanner 300 that reads a document image, and a document that is automatically fed to the scanner 300. An automatic document feeder (hereinafter referred to as ADF) 400 is provided.

  The scanner 300 is placed on the contact glass 301 as the first traveling body 303 equipped with a document illumination light source or mirror and the second traveling body 304 equipped with a plurality of reflecting mirrors reciprocate. Scanning of a document (not shown) is performed. The scanning light sent out from the second traveling body 304 is condensed on the imaging surface of the reading sensor 306 installed behind the imaging lens 305 and then read as an image signal by the reading sensor 306.

  On the side surface of the housing of the printer unit 1, a manual feed tray 2 for manually placing the recording paper 118 to be fed into the housing, and a paper discharge tray 3 for stacking the recording paper 118 having undergone image formation discharged from the housing. Is provided.

  FIG. 4 is a partially enlarged configuration diagram illustrating a part of the internal configuration of the printer unit 1 in an enlarged manner. In the housing of the printer unit 1, a transfer unit 50 is disposed as transfer means for stretching an endless intermediate transfer belt 51 as a transfer body by a plurality of stretching rollers. The intermediate transfer belt 51 is made of a material in which carbon powder for adjusting electric resistance is dispersed in a polyimide resin with little elongation. Then, while being stretched by a driving roller 52, a secondary transfer backup roller 53, a driven roller 54, and four primary transfer rollers 55Y, 55Y, 55C, 55K, which are driven to rotate in the clockwise direction in the drawing by a driving means (not shown) By the rotation of the driving roller 52, it is moved endlessly in the clockwise direction in the figure. Note that the suffixes Y, C, M, and K attached to the ends of the symbols of the primary transfer roller indicate the members for yellow, cyan, magenta, and black. Hereinafter, the subscripts Y, C, M, and K attached to the ends of the symbols are the same.

  The intermediate transfer belt 51 is greatly curved at the portions where the intermediate transfer belt 51 is wound around the driving roller 52, the secondary transfer backup roller 53, and the driven roller 54, so that the intermediate transfer belt 51 is stretched in an inverted triangular posture with the bottom side directed vertically upward. ing. The belt upper stretch surface corresponding to the base of the inverted triangle extends in the horizontal direction. Above the belt upper stretch surface, four process units 10Y, 10C, 10M, and 10K are provided on the upper stretch surface. It arrange | positions so that it may align with a horizontal direction along the extending direction.

  In FIG. 2 shown above, an optical writing unit 60 is disposed above the four process units 10Y, 10C, 10M, and 10K. Based on the image information of the original read by the scanner 300, the optical writing unit 60 drives four semiconductor lasers (not shown) by a laser control unit (not shown) to emit four writing lights L. Then, the drum-shaped photoconductors 11Y, 11C, 11M, and 11K serving as latent image carriers of the process units 10Y, 10C, 10M, and 10K are scanned in the dark by the writing light L, respectively. , K, electrostatic latent images for Y, C, M, and K are written.

  In this embodiment, the optical writing unit 60 performs optical scanning by deflecting laser light emitted from a semiconductor laser by a polygon mirror (not shown) and reflecting it with a reflection mirror (not shown) or passing it through an optical lens. Is used. Instead of such a configuration, an LED array that performs optical scanning may be used.

  FIG. 3 is an enlarged configuration diagram showing the process units 10Y and 10 for Y and C together with the intermediate transfer belt 51. As shown in FIG. The Y process unit 10Y includes a charging member 12Y, a charge eliminating device 13Y, a drum cleaning device 14Y, a developing device 20Y as developing means, a potential sensor 49Y, and the like around a drum-shaped photoconductor 11Y. And while these are hold | maintained with the casing which is a common holding body, it is attached and detached integrally as one unit with respect to a printer part.

  The charging member 12Y is a roller-like member that is rotatably supported by a bearing (not shown) while being in contact with the photoreceptor 11Y. The surface of the photoconductor 11Y is uniformly charged with, for example, the same polarity as that of Y toner by rotating in contact with the photoconductor 11Y while a charging bias is applied by a bias supply means (not shown). Instead of the charging member 12Y having such a configuration, a scorotron charger or the like that performs a uniform charging process in a non-contact manner on the photoconductor 11Y may be employed.

  A developing device 20Y in which a Y developer containing a magnetic carrier (not shown) and non-magnetic Y toner is contained in a casing 21Y has a developer conveying device 22Y and a developing unit 23Y. In the developing unit 23Y, a developing sleeve 24Y as a developer carrying member that is endlessly moved by being rotated by a driving unit (not shown) exposes a part of its peripheral surface to the outside through an opening provided in the casing 21Y. ing. As a result, a developing region is formed in which the photoconductor 11Y and the developing sleeve 24Y face each other with a predetermined gap.

  Inside the developing sleeve 24Y made of a non-magnetic hollow pipe-like member, a magnet roller (not shown) having a plurality of magnetic poles arranged in the circumferential direction is fixed so as not to rotate with the developing sleeve 24Y. The developing sleeve 24Y is driven to rotate while adsorbing the Y developer in the developer conveying device 22Y, which will be described later, to the surface by the magnetic force generated by the magnet roller, thereby pumping the Y developer from the developer conveying device 22Y. Then, the Y developer conveyed toward the developing area as the developing sleeve 24Y rotates, the doctor blade 25Y having the tip opposed to the surface of the developing sleeve 24Y with a predetermined gap, and the sleeve A doctor gap of 0.9 [mm] formed with the surface is entered. At this time, the layer thickness on the sleeve is regulated to 0.9 [mm] or less. When the developing sleeve 24Y is rotated and conveyed to the vicinity of the developing area facing the photoconductor 11Y, it receives a magnetic force of a developing magnetic pole (not shown) of the magnet roller and rises on the sleeve to become a magnetic brush. .

  For example, a developing bias having the same polarity as the charging polarity of the toner is applied to the developing sleeve 24Y by a bias supply unit (not shown). As a result, in the development region, non-development in which Y toner is electrostatically moved from the non-image portion side to the sleeve side between the surface of the development sleeve 24Y and the non-image portion (uniformly charged portion = background portion) of the photoreceptor 11Y. Potential acts. Further, a developing potential for electrostatically moving Y toner from the sleeve side toward the electrostatic latent image acts between the surface of the developing sleeve 24Y and the electrostatic latent image on the photoreceptor 11Y. The Y toner in the Y developer is transferred to the electrostatic latent image by the action of the developing potential, so that the electrostatic latent image on the photoreceptor 11Y is developed into the Y toner image.

  The Y developer that has passed through the developing area as the developing sleeve 24Y rotates is separated from the developing sleeve 24Y due to the influence of the repulsive magnetic field formed between the repelling magnetic poles provided in the magnet roller (not shown). The developer returns to the developer conveying device 22Y.

  The developer conveying device 22Y includes two first screw members 26Y, a second screw member 32Y, a partition wall interposed between the two screw members, a toner concentration detection sensor 45Y including a magnetic permeability sensor, and the like. The partition wall divides the first transport chamber, which is a developer transport section, in which the first screw member 26Y is accommodated, and the second transport chamber, which is a developer transport section in which the second screw member 32Y is accommodated. In the region facing both ends of the screw member in the axial direction, both transfer chambers are communicated with each other through an opening (not shown).

  The first screw member 26Y and the second screw member 32Y as the agitating / conveying members are respectively provided with a rod-like rotary shaft member whose both ends are rotatably supported by a bearing (not shown), and a spiral projection on the peripheral surface thereof. And a spiral blade. Then, as it is driven to rotate by a driving means (not shown), the Y developer is conveyed in the rotation axis direction by the spiral blade.

  In the first transport chamber in which the first screw member 26Y is accommodated, the Y developer is transported from the near side to the far side in the direction orthogonal to the drawing surface as the first screw member 26Y is driven to rotate. . And if it conveys to the edge part vicinity of the back | inner side of casing 21Y, it will approach into a 2nd conveyance chamber via the opening which is not provided in the partition wall.

  The above-described developing unit 23Y is formed above the second transfer chamber in which the second screw member 32Y is accommodated, and the second transfer chamber and the developing unit 23Y communicate with each other in the entire area of the opposing part. ing. As a result, the second screw member 32Y and the developing sleeve 24Y disposed obliquely above the second screw member 32Y face each other while maintaining a parallel relationship. In the second transport chamber, the Y developer is transported from the back side to the near side in the direction orthogonal to the drawing sheet as the second screw member 32Y is driven to rotate. In this transport process, the Y developer around the rotation direction of the second screw member 32Y is appropriately pumped up to the developing sleeve 24Y, and the developed Y developer is appropriately collected from the developing sleeve 24Y. Then, the Y developer transported to the vicinity of the near end of the second transport chamber in the drawing returns to the first transport chamber through an opening (not shown) provided in the partition wall.

  A toner concentration detection sensor 45Y as a toner concentration detection means including a magnetic permeability sensor is fixed to the lower wall of the first transfer chamber, and the toner concentration of the Y developer conveyed by the first screw member 26Y is lowered. And outputs a voltage according to the detection result. A control unit (not shown) replenishes an appropriate amount of Y toner into the first transfer chamber by driving a Y toner supply device (not shown) as necessary based on the output voltage value from the toner concentration detection sensor 45Y. As a result, the toner concentration of the Y developer, which has been lowered with the development, is recovered.

  The Y toner image formed on the photoreceptor 11Y is primarily transferred onto the intermediate transfer belt 51 at a Y primary transfer nip described later. The transfer residual toner that has not been primarily transferred onto the intermediate transfer belt 51 adheres to the surface of the photoreceptor 11Y after passing through the primary transfer process.

  The drum cleaning device 14Y cantilever-supports a cleaning blade 15Y made of, for example, polyurethane rubber, and the free end thereof is brought into contact with the surface of the photoreceptor 11Y. In addition, the brush tip side of the brush roller 16Y, which includes a rotating shaft member that is driven to rotate by a driving means (not shown) and an infinite number of conductive brushes erected on the peripheral surface thereof, is brought into contact with the photoreceptor 11Y. Yes. The transfer residual toner is scraped off from the surface of the photoreceptor 11Y by the cleaning blade 15Y and the brush roller 16Y. A cleaning bias is applied to the brush roller 16Y via a metal electric field roller 17Y that is in contact with the brush roller 16Y, and the tip of the scraper 18Y is pressed against the electric field roller 17Y. The transfer residual toner scraped off from the photoconductor 11Y by the cleaning blade 15Y and the brush roller 16Y passes through the brush roller 16Y and the electric field roller 17Y, and is then scraped off from the electric field roller 17Y by the scraper 18Y and onto the recovery screw 18Y. Fall. Then, after the recovery screw 18Y is driven to rotate, the recovery screw 18Y is discharged out of the casing, and then returned to the developer transport device 22Y via a toner recycling transport means (not shown).

  The surface of the photoreceptor 11Y from which the transfer residual toner has been cleaned by the drum cleaning device 14Y is neutralized by the neutralizing device 13Y including a neutralizing lamp and then uniformly charged again by the charging member 14Y.

  The potential of the non-image portion of the photoreceptor 11Y that has passed the optical writing position by the writing light L is detected by the potential sensor 49Y, and the detection result is sent to a control unit (not shown).

  The photoreceptor 11Y having a diameter of 60 [mm] is rotationally driven at a linear speed of 282 [mm / s]. The developing sleeve 24Y having a diameter of 25 [mm] is driven to rotate at a linear speed of 564 [mm / s]. Further, the charge amount of the toner in the developer supplied to the development area is in the range of about −10 to −30 [μC / g]. The development gap, which is the gap between the photoconductor 11Y and the development sleeve 24Y, is set in the range of 0.5 to 0.3 [mm]. The thickness of the photosensitive layer of the photoreceptor 11Y is 30 [μm]. Further, the beam spot diameter of the writing light L on the photoconductor 11Y is 50 × 60 [μm], and the amount of light is about 0.47 [mW]. Further, the uniform charging potential of the photoconductor 11Y is, for example, −700 [V], and the potential of the electrostatic latent image is −120 [V]. Further, the developing bias voltage is, for example, −470 [V], and a developing potential of 350 [V] is secured.

  Although the Y process unit 10Y has been described in detail, the process units (10C, M, K) of other colors have the same configuration as that of Y except that the color of the toner to be used is different. .

  In FIG. 4 shown above, the photoconductors 11Y, C, M, and K of the process units 10Y, 10C, 10M, and 10K are in contact with the upper stretched surface of the intermediate transfer belt 51 that is endlessly moved in the clockwise direction. Rotating to form primary transfer nips for Y, C, M, and K. On the back side of the primary transfer nips for these Y, C, M, and K, the above-described primary transfer rollers 55Y, 55C, 55M, and 55K are in contact with the back surface of the intermediate transfer belt 51. A primary transfer bias having a polarity opposite to the charging polarity of the toner is applied to each of the primary transfer rollers 55Y, 55C, 55M, 55K by a bias supply unit (not shown). Due to this primary transfer bias, a primary transfer electric field is formed in the primary transfer nips for Y, C, M, and K to electrostatically move the toner from the photoreceptor side to the belt side. The Y, C, M, and K toner images formed on the photoreceptors 11Y, 11C, 11M, and 11K are primary for Y, C, M, and K as the photoreceptors 11Y, 11C, 11M, and 11K rotate. When entering the transfer nip, primary transfer is performed by sequentially superimposing on the intermediate transfer belt 51 by the action of the primary transfer electric field and nip pressure. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface (loop outer peripheral surface) of the intermediate transfer belt 51. Instead of the primary transfer rollers 55Y, 55C, 55M, 55K, a conductive brush to which a primary transfer bias is applied, a non-contact type corona charger, or the like may be employed.

  An optical sensor unit 61 is disposed on the right side of the K process unit 10K in the drawing so as to face the front surface of the intermediate transfer belt 51 with a predetermined gap. As shown in FIG. 5, the optical sensor unit 61 includes a rear position detection sensor 62R, a Y image density detection sensor 63Y, a C image density sensor 63C, and a center position detection sensor 62C, M arranged in the width direction of the intermediate transfer belt 51. An image density detection sensor 63M, a K image density detection sensor 63K, and a front position detection sensor 62F are provided. Each of these sensors is a reflection type photosensor, and reflects light emitted from a light emitting element (not shown) by a toner image on the front surface of the intermediate transfer belt 51 or the belt, and the amount of reflected light is detected by a light receiving element (not shown). To do. A control unit (not shown) can detect a toner image on the intermediate transfer belt 51 based on output voltage values from these sensors, and can detect the image density (toner adhesion amount per unit area). .

  As shown in FIG. 4, a secondary transfer roller 56 is disposed below the intermediate transfer belt 51. The secondary transfer roller 56 is driven to rotate counterclockwise in the drawing by a driving means (not shown). A secondary transfer nip is formed in contact with the front surface of 51. Then, on the back side of the secondary transfer nip, a secondary transfer backup roller 53 that is electrically grounded is wound around the intermediate transfer belt 51.

  A secondary transfer bias having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 56 by a bias supply unit (not shown), whereby 2 is placed between the secondary transfer roller 56 and the grounded secondary transfer backup roller 53. A next transfer electric field is formed. The four-color toner image formed on the front surface of the intermediate transfer belt 51 enters the secondary transfer nip as the intermediate transfer belt 51 moves endlessly.

  In FIG. 2 described above, the paper feeding device 200 is fed with a paper feeding cassette 201 for storing the recording paper 118, and a paper feeding roller 202 for feeding the recording paper 118 stored in the paper feeding cassette 201 out of the cassette. A plurality of separation roller pairs 203 for separating the recording paper 118 one by one, a plurality of conveyance roller pairs 205 for conveying the separated recording paper 118 along the delivery path 204, and the like are provided. The sheet feeding device 200 is disposed directly below the printer unit 1 as shown in the figure. The feeding path 204 of the paper feeding device 200 is connected to the paper feeding path 70 of the printer unit 1. As a result, the recording paper 118 sent out from the paper feed cassette 201 of the paper feed device 200 is sent into the paper feed path 70 of the printer unit 1 via the feed path 204.

  A registration roller pair 71 is disposed near the end of the paper feed path 70 of the printer unit 1, and the recording paper 118 sandwiched between the rollers can be synchronized with the four-color toner image on the intermediate transfer belt 51. Send to the secondary transfer nip. In the secondary transfer nip, the four-color toner image on the intermediate transfer belt 51 is collectively transferred to the recording paper 118 due to the influence of the secondary transfer electric field and the nip pressure, and combined with the white color of the recording paper 118, Become. The recording paper 118 on which the full-color image is formed in this way is separated from the intermediate transfer belt 51 when discharged from the secondary transfer nip.

  On the left side of the secondary transfer nip in the figure, a conveyor belt unit 75 is provided that moves the endless paper conveyor belt 76 endlessly in the counterclockwise direction in the figure while being stretched by a plurality of stretching rollers. . The recording paper 118 separated from the intermediate transfer belt 51 is transferred to the upper stretched surface of the paper conveying belt 76 and conveyed toward the fixing device 80.

  The recording paper 118 sent into the fixing device 80 is sandwiched in a fixing nip formed by a heating roller 81 containing a heat source such as a halogen lamp (not shown) and a pressure roller 82 pressed toward the heating roller 81. The full color image is fixed on the surface by being heated while being pressurized, and is sent to the outside of the fixing device 80.

  A small amount of secondary transfer residual toner that has not been transferred to the recording paper 118 adheres to the surface of the intermediate transfer belt 51 after passing through the secondary transfer nip. The secondary transfer residual toner is removed from the belt by a belt cleaning device 57 that is in contact with the front surface of the intermediate transfer belt 51.

  In FIG. 2 described above, a switchback device 85 is disposed below the fixing device 80. When the recording paper 118 discharged from the fixing device 80 reaches the conveyance path switching position by the swingable switching claw 86, the paper discharge roller pair 87 or the switchback device according to the swing stop position of the switching claw 86. Sent to 85. When the paper is sent toward the paper discharge roller pair 87, the paper is discharged out of the apparatus and then stacked on the paper discharge tray 3.

  On the other hand, when it is sent toward the switchback device 85, it is turned upside down by the switchback conveyance by the switchback device 85 and then conveyed toward the registration roller pair 71 again. Then, it again enters the secondary transfer nip, and a full-color image is formed on the other side.

  The recording paper 118 manually fed onto the manual feed tray 2 provided on the side surface of the housing of the printer unit 1 passes through the manual feed roller 72 and the manual separation roller pair 73 and then toward the registration roller pair 71. Sent. The registration roller pair 71 may be grounded, or a bias may be applied to remove paper dust from the recording paper 118.

  As shown in FIG. 6, the intermediate transfer belt 51 is suspended from a drive roller 52, a driven roller 54 and a secondary transfer backup roller 53, and is driven at a constant speed by a drive motor 112 via a reduction gear 111.

  As described above, the image transferred from the photosensitive member of each color onto the intermediate transfer belt 51 is transferred again on the recording paper 118, that is, secondarily transferred. The leading end of the recording paper 118 is aligned by the registration roller pair 16 through the recording paper insertion detection sensor 17.

  In the copying machine of this embodiment, the registration roller pair 71 also has a function as the recording paper thickness detection device 120 that detects the thickness of the recording paper 118, and the registration paper pair 71 holds and conveys the recording paper 118. By doing so, the thickness of the recording paper 118 can be detected. That is, in the copying machine of the present embodiment, the thickness of the recording paper 118 can be measured while the recording paper 118 is being conveyed. The recording paper 118 conveyed by the registration roller pair 71 passes through the recording paper detection sensor 119 and is conveyed to the position of the secondary transfer roller 56.

  The recording paper detection sensor 119 is configured by a transmission sensor, a reflection type sensor, a micro switch, or the like as is generally known. The leading end of the recording paper 118 conveyed from the registration roller pair 71 is first detected by the recording paper detection sensor 119. When the leading edge of the recording paper 118 is detected by the recording paper detection sensor 119, the recording paper 118 reaches the secondary transfer roller pair composed of the secondary transfer roller 56 and the secondary transfer backup roller 53 by an arithmetic unit 129 described later. The time is measured, and the optimum secondary transfer voltage value corresponding to the thickness of the conveyed recording paper 118 and its generation timing are determined. When the leading edge of the recording paper 118 reaches the vicinity of the secondary transfer roller pair, correction control of the secondary transfer voltage value is performed.

  Further, the recording paper 118 on which the image is formed is conveyed to the fixing device 80 shown in FIG. 2, and the toner image on the recording paper 118 is thermally welded to the recording paper 118 and fixed. Also at this time, temperature correction control is performed so that the fixing temperature becomes the optimum temperature condition of the recording paper 118.

  As shown in FIG. 6, by arranging the recording paper thickness detection device 120 on the upstream side in the recording paper conveyance direction of the secondary transfer roller pair, the secondary transfer voltage, the fixing temperature condition, and the like are set to the thickness of the recording paper 118. It is possible to set optimum conditions according to the conditions, and it is possible to form a high-quality image.

  As described above, an image forming condition corresponding to the actual thickness of the recording paper 118 used for image formation is set by providing the image forming apparatus such as a copying machine with the function of the recording paper thickness detecting device 120. Therefore, it is possible to provide a highly reliable and high quality image.

  Further, the registration roller pair 71 conventionally provided in the copying machine as the copying machine of the present embodiment also functions as the recording paper thickness detecting device 120, so that cost and space can be reduced. .

  FIG. 7 shows a schematic configuration of the recording paper thickness detection device 120 of the present embodiment. An elastic roller 123 and a rigid roller 124 are arranged to face each other. The elastic roller 123 is made of a soft elastic material whose roller diameter changes depending on the thickness of the recording paper 18 when the recording paper is conveyed between the elastic roller 123 and the rigid roller 124. . The rigid roller 124 is made of a rigid material with little deformation such as metal.

  A DC motor 127 is connected to the shaft of the elastic roller 123 via a reduction gear 126 and is driven at a constant angular velocity. The direct current motor 127 is driven and controlled by the arithmetic unit 129 shown in FIG. 8 via the drive driver 130, and the drive current detector 125 detects the current value of the drive current flowing through the direct current motor 127 and determines the current value. This is input to the arithmetic unit 129.

  FIG. 9 shows an example of the current detector 125. This is a final stage current amplifier of a general DC motor driving circuit, and can rotate the motor shaft forward and backward. In this circuit, a voltage is applied to the DC motor 127 by the power source 140, and when the A signal becomes active, the transistors Q1 and Q4 are turned on (ON), and the DC motor 127 follows the path indicated by the dotted line in the figure. The drive current i flows through. The detection voltage V is generated by the drive current i flowing through the current detection fixed resistor r. Then, the drive current i is calculated from the detected voltage V.

  Here, the drive current i flowing through the DC motor 127 periodically changes as shown in FIG. 10 due to the eccentricity of the shaft of the elastic roller 123. Therefore, when measuring the current supplied to the DC motor 127 by the drive current detector 125, it is possible to detect an accurate current value without variation by taking an average of integer multiples of the data for one round. .

  In FIG. 1, an elastic roller 123 is in contact with a rigid roller 124 at a point P. In this state, there is no recording paper 118 between the elastic roller 123 and the rigid roller 124, and the thickness of the recording paper 118 is naturally zero. The elastic roller 123 at this time is represented by an elastic roller 123a drawn by a solid line in FIG. 1, and the elastic roller 123 has a distance between XP that is a distance between the point X which is the center of the rotation axis and the point P. The distance is R0.

  When the recording paper 118 having a thickness Tm is conveyed to a roller pair composed of the elastic roller 123 and the rigid roller 124, the elastic roller 123 is moved from the elastic roller 123a to the elastic roller 123b drawn by a dotted line in FIG. Thus, the surface of the recording paper 118 and the elastic roller 123b are in contact with each other at the Q point.

  At this time, since the rigid body roller 124 is made of a material with a small deformation amount, only the elastic body roller 123 is deformed by the thickness of the recording paper 118 and becomes the shape of the elastic body roller 123b shown in FIG. Therefore, the apparent roller diameter of the elastic body roller 123 can be regarded as the pseudo elastic body roller 128 having a radius Rm shown by a one-dot chain line in FIG.

Accordingly, since the deformation amount of the elastic roller 123 at this time is a value obtained by subtracting the XQ distance Rm from the XP distance R0, the recording paper thickness Tm can be obtained by the following equation (1).

  Here, when the recording paper 118 is being conveyed between the elastic roller 123 and the rigid roller 124, the point X that is the center of the rotation axis of the elastic roller 123 and the point Y that is the center of the rotation axis of the rigid roller 124. , The distance Rm between XQ does not deform as much as the thickness of the recording paper 118.

Therefore, the elastic roller 123 and the rigid roller 124 are provided in the apparatus main body so that the roller axial distance L between the elastic roller 123 and the rigid roller 124 does not vary, and the roller axial distance L (XY distance) is known. To a fixed distance. As a result, the distance L between the roller shafts and the roller radius S0 of the rigid roller 124 do not change. Therefore, when the thickness of the recording paper 118 is 0 [mm], the XP distance R0 is constant as shown in Equation 2.

Further, the distance Rm between XQ when the thickness of the recording paper 118 is Tm is expressed by Equation 3, and the deformation of the elastic roller 123 is proportional to the thickness Tm of the recording paper 118.

  As described above, by fixing the roller shaft distance L, the deformation amount of the elastic roller 123 can be accurately measured from R0 and the thickness Tm of the recording paper 118, and the thickness of the recording paper 118 can be accurately measured. Tm can be measured.

Next, an example of a calculation method for calculating the thickness of the recording paper 118 will be described.
First, in FIG. 11, when the recording paper 118 is not held and conveyed by the elastic roller 123 and the rigid roller 124, in other words, when the thickness of the recording paper 118 is 0 [mm], the rotation shaft of the elastic roller 123 is rotated. Td1 is obtained for the load torque applied to (X point). It is assumed that the load torque applied to the rotation axis (Y point) of the rigid roller 124 is Ts, the radius of the elastic roller 123 at this time is R0, and the radius of the rigid roller 124 is S0.

When the thickness of the recording paper 118 is 0 [mm], the driving force necessary to rotationally drive the rigid roller 124 by the elastic roller 123, that is, the point P where the elastic roller 123 and the rigid roller 124 are in contact with each other. The force F1 to be applied can be expressed by Equation 4.

Therefore, the load torque Td1 can be expressed by Equation 5.

Next, in FIG. 11, the load torque Td2 applied to the rotation shaft (point X) of the elastic roller 123 when the elastic sheet 123 and the rigid roller 124 are holding and transporting the recording paper 118 having a thickness Tm is obtained. As described above, the load torque applied to the rotation shaft (point Y) of the rigid roller 124 is Ts. As described above, the elastic roller 123 is elastically deformed by a deformation amount corresponding to the thickness Tm of the recording paper 118 when the elastic paper 123 and the rigid roller 124 sandwich and convey the recording paper 118 having the thickness Tm. Therefore, when the radius of the elastic body roller 123 at this time is Rm, it can be expressed by Equation 6. Although the elastic roller 123 is deformed depending on the thickness of the recording paper 118, the rigid roller 124 is made of a rigid material and hardly deforms. Therefore, the radius of the rigid roller 124 at this time is S0.

When the thickness of the recording paper 118 is Tm, the driving force required to rotationally drive the rigid roller 124 by the elastic roller 123 via the recording paper 118, that is, the elastic roller 123 and the recording paper 118 are in contact with each other. The force F2 to be applied to the point Q can be expressed by Equation 7 from FIG.

Therefore, the load torque Td2 can be expressed by Equation 8.

  Comparing Equation 5 and Equation 8, the load torque Td2 becomes smaller than the load torque Td1 as the thickness Tm of the recording paper 118 increases, and there is a correlation between the load torque Td2 and the thickness Tm of the recording paper 118. There is a relationship.

  Further, when the load torque Td applied to the rotation shaft of the elastic roller 123 is reduced, the motor load torque applied to the DC motor 127 that rotationally drives the elastic roller 123 is reduced accordingly, so that the generated torque τ of the DC motor 127 is reduced. Becomes smaller. As is generally known, a DC motor has a correlation as shown in FIG. 12 between the generated torque τ and the drive current i flowing through the DC motor, and the drive current i decreases as the generated torque τ decreases. Become. Since the load torque Td changes with the change amount according to the thickness of the recording paper 118 from Equation 8, the generated torque τ also changes with the change amount according to the thickness Tm of the recording paper 118 as shown in FIG. There is such a correlation between the generated torque τ and the thickness Tm of the recording paper 118. As described above, since the drive current i flowing through the DC motor 127 changes according to the generated torque τ, there is also a correlation between the drive current i and the thickness Tm of the recording paper 118. FIG. 14 shows the relationship between the thickness Tm of the recording paper 118 and the drive current i.

  It should be noted that at the timing when the recording paper 118 enters the roller pair composed of the elastic roller 123 and the rigid roller 124, the load torque applied to the rotating shaft of the elastic roller 123 instantaneously increases as the thickness of the recording paper 118 increases. growing. The load torque, which has increased instantaneously, decreases as the recording paper 118 is conveyed by the roller pair, and becomes constant at the value of the load torque Tb. Therefore, in the recording paper thickness detection device 118 of the present embodiment, the drive current i is detected at a stable timing with the load torque Tb without detecting the drive current i at the inrush timing. Such timing may be obtained by an experimental machine or the like as an elapsed time after the recording paper 118 is detected by the recording paper insertion detection sensor 117, for example.

  As described above, in the recording paper thickness detection device 120 of this embodiment, the relationship between the drive current i and the generated torque τ is a necessary and important characteristic, and this embodiment is used as a drive motor for driving the elastic roller 123. The function can be achieved by using the DC motor 127 as described above.

  Further, as shown in FIG. 15, the DC motor 127 has a characteristic that when the generated torque τ increases, the drive current i increases and the rotational speed N decreases. Thus, the rotational speed N can be controlled by changing the drive current i, and the rotational speed of the elastic roller 123 can be freely changed by changing the drive current i.

  FIG. 8 is a control block diagram of the present invention. The arithmetic device 129 calculates the thickness of the recording paper 118 from the drive current i supplied to the DC motor 127 detected by the drive current detector 125 using the method described above. For example, the correlation between the drive current i and the thickness Tm of the recording paper 118 as shown in FIG. 14 is obtained by an experimental machine having the same configuration as the recording paper thickness detection device 120 of this embodiment, and the correlation is obtained. Can be stored in advance in the storage unit 139 as an approximate expression or table, and the thickness Tm of the recording paper 118 corresponding to the measured drive current i can be obtained from the approximate expression or the table by the arithmetic unit 129.

  Then, the secondary transfer voltage correction amount, the fixing temperature correction, the setting of the timing of each correction start / end time, and the like corresponding to the obtained thickness of the recording paper 118 are calculated, and the transfer unit 50, the fixing temperature control, Control the fixing heater. The DC motor 127, the transport roller drive motor 136, and a secondary transfer roller pressure motor, although not described in detail, are controlled as necessary. The arithmetic device 129 has a file that stores data necessary for each correction described above as a table.

  Here, in this embodiment, the distance between XP and the distance between XQ are represented by R0 and Rm. This is because the point P of the contact point between the elastic roller 123 and the rigid roller 124 and the point Q of the contact point between the recording paper 118 and the elastic roller 123 are in contact with each other. In general, since the elastic roller 123 is pressed against the rigid roller 124, a nip width is formed. Therefore, the point P and the point Q are not in point contact but in line contact. As a result, the relational expressions using R0 and Rm cannot be expressed simply and become complicated. Therefore, in this embodiment, in order to simplify the description, it is assumed that the elastic roller 23 and the rigid roller 124 are joined at a point.

  In the configuration in which the elastic roller 127 is rotationally driven to convey the recording paper 118 as in the present embodiment, a change in load torque applied to the rotation shaft of the elastic roller 123 is caused between the elastic roller 127 and the recording paper 118. The frictional force that occurs in is affected. That is, the magnitude of the frictional force itself does not change regardless of the thickness of the recording paper 118, but the elastic roller 123, the recording paper 118, and the like from the rotational axis center of the elastic roller 123 according to the thickness of the recording paper 118. Therefore, the load torque due to the frictional force is reduced. Therefore, strictly speaking, it is necessary to add the load torque due to the frictional force to the load torque Td2 obtained by Equation 8. However, when the distance is reduced, that is, when the thickness of the recording paper 118 is increased, the load torque due to the frictional force is reduced. Therefore, when the thickness of the recording paper 118 is substantially increased, the torque generated by the DC motor 127 is increased. The thickness of the recording paper 118 can be detected based on the idea that the driving current i decreases accordingly, and the drive current i decreases accordingly.

  Further, in the recording paper thickness detection device 120 of the present embodiment, there may be a problem that the detection accuracy varies from device to device due to variations in accuracy of parts used in the recording paper thickness detection portion. Because of such problems, before shipment from the manufacturing plant, a plurality of types of recording paper 118 having different thicknesses are actually conveyed on the production line, and the current supplied to the DC motor 127 at that time is actually conveyed. Each value is measured by the drive current detector 125, the arithmetic unit 129, etc., and the above approximate expression or the table indicating the correlation between the drive current i and the thickness Tm of the recording paper 118 is corrected.

  For example, a table correction mode is executed from an operation panel (not shown) of the copying machine, and a value of the thickness of the recording paper 118 to be conveyed is input to the operation panel, and a memory (not shown) provided in the arithmetic unit 129 is provided. Remember me. Thereafter, the recording paper 118 having the input thickness is passed through the copying machine, and the current flowing through the DC motor 127 when the recording paper 118 is conveyed by the roller pair of the recording paper thickness detection device 120 is detected as a driving current. Measure with the instrument 125. By performing such measurement, the thickness Tm of the recording paper 118 as shown in the graph of FIG. 14 is calculated from the thickness value of the recording paper 118 stored in the memory and the detection result of the drive current detector 125. And the drive current i can be obtained. A linear approximation line or a polynomial approximation curve is calculated from the data represented by this graph, and the calculated drive current i is corrected by the arithmetic unit 129 shown in FIG. 8 as correction data for calculating the thickness of the recording paper 118. Store in the data storage table. As a result, individual variations among apparatuses can be eliminated, and the thickness of the recording paper 118 can be obtained with high accuracy.

  Further, by driving the elastic roller 123 by the DC motor 127 as in the present embodiment, when the thickness of the recording paper 118 is 0 [mm], the driving current i supplied to the DC motor 127 is changed to the recording paper 118. Can be detected without being conveyed. Therefore, when the thickness of the recording paper 118 is 0 [mm], the drive current i supplied to the DC motor 127 is determined by the current value obtained by conveying the recording paper 118 having a known thickness and the thickness of the recording paper 118. An accurate value actually detected can be used without using a value obtained from an approximate line or the like indicating the correlation.

  Furthermore, when the DC motor 127 is driven without conveying the recording paper 118 and the driving current i supplied to the DC motor 127 when the thickness of the recording paper 118 is 0 [mm] is detected, the thickness is determined. Is supplied to the DC motor 127 detected by driving the rigid roller 124 without conveying the recording paper 118, and the drive current i supplied to the DC motor 127 detected by conveying one type of known recording paper 118. The linear approximation line, the polynomial approximation curve, and the like can be calculated using only the driving current i. Thereby, it is possible to save the trouble of preparing a plurality of types of recording paper 118 having a known thickness and transporting a plurality of types of recording paper 118. Needless to say, even when the drive current i supplied to the DC motor 127 when the thickness of the recording paper 118 is 0 [mm] without detecting the recording paper 118 is detected, the recording with a known thickness is performed. By conveying a plurality of types of paper 118 and detecting the drive current i supplied to each DC motor 127, the linear approximation line, the polynomial approximation curve, and the like can be calculated with higher accuracy.

  In addition, by making it possible to make the above corrections as needed by service personnel and users after shipment from the factory as needed, even if a deviation occurs due to aging in the field, etc., the recording paper has a known thickness. 118 can be inserted into the apparatus and corrected again, and the accurate thickness of the recording paper 118 can be continuously detected.

  When detecting the thickness of the recording paper 118 by the method of the present embodiment, it is necessary to convert the thickness Tm of the recording paper 118 into deformation of the elastic roller 123. Here, if the length of the elastic roller 123 and the rigid roller 124 in the axial direction of the roller is longer than the width of the recording paper 118 to be used, the recording paper 118 is conveyed to a roller pair composed of the elastic roller 123 and the rigid roller 124. The elastic roller 123 and the rigid roller 124 come into contact with each other outside the both ends of the recording paper 118 in the width direction. If the elastic roller 123 and the rigid roller 124 are in contact with each other outside both ends of the recording paper 118 in the width direction, the elastic roller 123 may not be deformed with an appropriate deformation amount even if the recording paper 118 is conveyed to the roller pair. is there.

  For this reason, it is possible to prevent the above-described problem by making the width in the axial direction of at least one of the elastic roller 123 and the rigid roller 124 smaller than the minimum width of the recording paper 118 used in the apparatus. Become.

  In this embodiment, a roller pair including the elastic roller 123 and the rigid roller 124 is used as the roller pair provided in the recording paper thickness detection device 120. However, the elastic roller 123 and other elastic rollers are used. Even if a pair of rollers is used, the thickness of the recording paper 118 can be obtained in the same manner as described above. However, when the recording paper 118 is sandwiched between a pair of rollers composed of two elastic rollers, both elastic rollers are deformed depending on the thickness of the recording paper 118, and the respective radii change. Therefore, it is necessary to measure the amount of deformation of the radius of each elastic roller according to the thickness of the recording paper 118 in advance and use an arithmetic expression or a table corresponding to the amount of deformation.

  Further, even if a pair of rollers consisting of two rigid rollers is used as the roller pair provided in the recording paper thickness detection device 120, the rigid body roller that is rotationally driven by the DC motor 127 when the recording paper 118 is nipped and conveyed by the roller pair. The load torque applied to changes. Therefore, in consideration of the fact that the radius of the rigid roller that is rotationally driven by the DC motor 127 does not change, the thickness of the recording paper 118 can be obtained in the same way as the method described above.

As described above, according to the present embodiment, the recording paper thickness detection device 120 sandwiches and conveys the recording paper 118 that is a sheet-like member, and the rigid roller 124 that is the first roller member and the elastic that is the second roller member. A pair of rollers composed of a body roller 123 and configured so that the rigid body roller 124 rotates according to the movement of the recording paper 118, a DC motor 127 that rotationally drives the elastic body roller 123, a power source that applies a voltage to the DC motor 127, A drive current detector 125 that is a current value detection unit that detects a current value of a current flowing through the DC motor 127, and a storage unit 139 that is a storage unit that previously stores correlation information between the current value and the thickness of the recording paper 118. And a calculation device 129 that is a calculation means for calculating the thickness of the recording paper 118 from the detection result of the drive current detector 125 and the correlation information. Considering the recording paper 118 as a part of the rigid roller 124 when the recording paper 118 is held by the pair of rollers, the rigid roller 124 that goes from the center of the rotation axis of the rigid roller 124 to the contact point between the recording paper 118 and the rigid roller 124. Apparently becomes longer depending on the thickness of the recording paper 118. When the radius increases in this way, the driving force required to rotate the rigid roller 124 by the elastic roller 123 becomes smaller than when the recording paper 118 is not pinched by the roller pair. When the driving force is thus reduced, the load torque applied to the DC motor 127 that rotationally drives the elastic roller 123 becomes smaller than when the recording paper 118 is not held, and the generated torque of the DC motor 127 is accordingly corresponding. Becomes smaller. The DC motor 127 has a correlation between the current flowing through the DC motor 127 and the generated torque, and the current flowing through the DC motor decreases as the generated torque decreases. Since the load torque changes with the amount of change according to the distance from the contact point to the center of the rotation axis, in other words, the amount of change according to the thickness of the recording paper 118, the generated torque also varies with the thickness of the recording paper 118. It changes with the corresponding change amount. There is such a correlation between the generated torque and the thickness of the recording paper 118. As described above, since the current flowing through the DC motor 127 changes according to the generated torque, there is a correlation between the current flowing through the DC motor 127 and the thickness of the recording paper 118. Therefore, the current value flowing through the DC motor 127 detected by the drive current detector 125 and the correlation information between the current value stored in advance in the storage unit 139 and the thickness of the recording paper 118 are used for calculation. The apparatus 129 can determine the thickness of the recording paper 118. Therefore, it is not necessary to measure the amount of displacement of the distance between the axes of the roller pair with an optical sensor and detect the thickness of the recording paper 118 based on the amount of displacement, so that it is not necessary to make the mounting accuracy higher than in the case of cost reduction. Can be planned. Therefore, the thickness of the recording paper 118 can be detected with high accuracy while reducing the cost.
Further, according to the present embodiment, the roller member that is rotationally driven by the DC motor 127 is the elastic roller 123, and as can be seen from the above equation 8, the DC motor when the recording paper 118 is held by the roller pair. The amount of change in load torque applied to 127, in other words, the amount of change in torque generated by DC motor 127 increases. Therefore, the change in the driving current i becomes more remarkable, and the detection accuracy of the thickness of the recording paper 118 can be improved.
Further, according to the present embodiment, the elastic roller 123 and the rigid roller 124 are provided in the apparatus main body so that the inter-roller distance L that is the distance between the elastic roller 123 and the rigid roller 124 does not vary. As a result, the entire thickness of the recording paper 118 can be contributed to the deformation of the elastic roller 123, so that the thickness of the recording paper 118 can be detected with high accuracy.
Further, according to the present embodiment, the recording paper 118 having a known thickness is conveyed by the elastic roller 123 and the rigid roller 124, and the correlation information is obtained using the detection result of the drive current detector 125 at that time. And an arithmetic unit 129 functioning as a correction means for correcting the above. As a result, it is possible to eliminate variations in the detection results of individual devices as described above without increasing the accuracy of the components, thereby reducing costs.
In addition, according to the present embodiment, the operation device 129 that functions as the correction unit includes the operation panel that is an input unit for the user to input information regarding the thickness of the recording paper 118, and the operation unit 129 functions as the operation unit. Information regarding the thickness of the recording paper 118 input to the panel, and a detection result of the drive current detector 125 when the recording paper 118 having a thickness corresponding to the information input to the operation panel is conveyed by a roller pair, and Is used to correct the correlation information. As a result, the correlation information can be easily corrected by a service person or a user not only before shipment but also after shipment. Therefore, the thickness of the recording paper 118 can be detected with high accuracy over time.
Further, according to the present embodiment, the drive current detector 125 detects the current value using current value data for an integral multiple of one rotation of the roller. The roller member has an eccentric error due to processing accuracy. To reduce the amount of eccentricity, it is necessary to increase the processing accuracy, but increasing the processing accuracy increases the cost. For this reason, by calculating the data for one rotation of the roller for measuring the current supplied to the DC motor 127 from data that is an integral multiple of one rotation of the roller, it is possible to increase the accuracy without increasing the component accuracy as described above. Measurement can be performed with accuracy.
Further, according to the present embodiment, the width in the axial direction of at least one of the elastic roller 123 and the rigid roller 124 is made narrower than the minimum width of the recording paper 118 that can be conveyed by the apparatus main body. Thus, as described above, the elastic roller 123 can be deformed with an appropriate deformation amount when the recording paper 118 is held by a pair of rollers, so that the thickness of the recording paper 118 can be detected with high accuracy. .
Further, according to the present embodiment, the intermediate transfer belt 51 that is an image carrier that carries an image, and the secondary transfer roller that is a transfer unit that transfers the image on the intermediate transfer belt 51 to the recording paper 118 that is a sheet-like member. 56 and a registration roller pair 71 which is a conveying means for conveying the recording paper 118 to a secondary transfer portion composed of the intermediate transfer belt 51 and the secondary transfer roller 56. By disposing the recording paper thickness detection device 120 of the present invention upstream of the transfer unit in the recording paper conveyance direction, a secondary transfer voltage according to the thickness of the recording paper 118 detected with high accuracy, It is possible to optimize the pressure applied to the secondary transfer roller, the fixing temperature, the conveyance speed, and the like, and a high-quality image can be obtained.

  In this embodiment, the case where the recording paper thickness detection device is provided in the electrophotographic image forming apparatus has been described. However, other image forming apparatuses, for example, ink jet image forming, are used regardless of the electrophotographic system. By using the recording paper thickness detection apparatus of the present invention in the apparatus, it is possible to determine optimum image forming conditions and conveying conditions, and high quality images can be obtained.

FIG. 3 is an enlarged configuration diagram of a roller pair of the recording paper thickness detection apparatus according to the present embodiment. 1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is an enlarged configuration diagram showing process units for Y and C together with an intermediate transfer belt. FIG. 3 is a partially enlarged configuration diagram illustrating an enlarged part of an internal configuration of a printer unit. FIG. 3 is a plan view showing an optical sensor unit and an intermediate transfer belt in a printer unit. FIG. 3 is an enlarged configuration diagram in the vicinity of an intermediate transfer belt. 1 is a schematic configuration diagram of a recording paper thickness detection device. Control block diagram. The schematic diagram which showed an example of the drive current detector. DC motor drive current distribution. The conceptual diagram at the time of calculating the thickness of a recording paper. The graph which showed correlation with generated torque (tau) and drive current i. The graph which showed correlation with thickness Tm of recording paper, and generated torque (tau). 6 is a graph showing the correlation between recording paper thickness Tm and drive current i. The graph which showed the correlation of generated torque, drive current, and rotation speed. Explanatory drawing of the recording paper thickness detection method using an optical reflection type displacement sensor.

Explanation of symbols

51 Intermediate transfer belt 56 Secondary transfer roller 71 Registration roller pair 80 Fixing device 117 Recording paper insertion detection sensor 118 Recording paper 119 Recording paper detection sensor 120 Recording paper thickness detection device 123 Elastic roller 124 Rigid roller 125 Driving current detector 126 Reduction gear 127 Drive motor 128 Pseudo elastic body roller 129 Arithmetic unit 139 Storage unit

Claims (8)

A pair of rollers composed of a first roller member and a second roller member that sandwich and convey the sheet-like member, and configured so that the first roller member rotates according to the movement of the sheet-like member;
A direct current motor that rotationally drives the second roller member;
A power supply for applying a voltage to the DC motor;
Current value detection means for detecting a current value of a current flowing through the DC motor;
Storage means for storing correlation information between the current value and the thickness of the sheet-like member in advance;
A sheet-like member thickness detecting device comprising: a calculating means for calculating the thickness of the sheet-like member from the detection result of the current value detecting means and the correlation information. In the sheet-like member thickness detection device according to claim 1,
A sheet-like member thickness detecting device, wherein at least the second roller member is made of an elastic body. In the sheet-like member thickness detection device according to claim 2,
The first roller member and the second roller member are provided in the main body of the apparatus so that the distance between the axes of the first roller member and the second roller member does not fluctuate. Member thickness detector. In the sheet-like member thickness detection device according to claim 1, 2, or 3,
A sheet-like member having a known thickness is conveyed by the first roller member and the second roller member, and the correlation information is corrected using the detection result of the current value detection means at that time. A sheet-like member thickness detection apparatus comprising a correction unit. In the sheet-like member thickness detection device according to claim 4,
It has an input means for the user to input information regarding the thickness of the sheet-like member,
The correction means includes information regarding the thickness of the sheet-like member input to the input means and a sheet-like member having a thickness corresponding to the information input to the input means when the roller pair conveys the sheet-like member. The sheet-like member thickness detection apparatus, wherein the correlation information is corrected using the detection result of the current value detection means. In the sheet-like member thickness detection device according to claim 1, 2, 3, 4 or 5,
The sheet-like member thickness detecting device, wherein the current value detecting means detects the current value using current value data for an integral multiple of one rotation of the roller. In the sheet-like member thickness detection device according to claim 1, 2, 3, 4, 5 or 6,
The sheet-like member thickness detection, wherein a width of at least one of the first roller member and the second roller member in the axial direction of the roller is narrower than a minimum width of the sheet-like member that can be conveyed by the apparatus main body. apparatus. An image carrier for carrying an image;
Transfer means for transferring an image on the image carrier to a sheet-like member;
In an image forming apparatus provided with a conveying unit that conveys the sheet-like member to a transfer unit including the image carrier and the transfer unit.
An image forming apparatus comprising the sheet-like member thickness detection device according to claim 1, disposed upstream of the transfer portion in the sheet-like member conveyance direction.

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