JP2006343726A - Recording paper conveyance mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording paper conveyance mechanism that increases flexibility of layout and enables designing of an image forming apparatus with a small footprint. <P>SOLUTION: The conveyance speed of a recording paper is controlled by a control means which can control a conveyance means, such that the recording paper is conveyed at a first conveyance speed; a second conveyance speed which is slower than the first conveyance speed; and a third conveyance speed which is faster than the first conveyance speed, thereby making a predetermined position of the recording paper pass a paper feed sensor at the second conveyance speed. Then, the recording paper is conveyed at the third conveyance speed temporarily, and further the recording paper is conveyed at the first conveyance speed. Consequently, the time from when the predetermined position of the recording paper is detected by the paper feed sensor until when arriving at a print is equalized with the time from when the predetermined position of the recording paper is detected by the paper feed sensor until when arriving at a target position, if it is considered that the predetermined position of the recording paper is conveyed by the first conveyance speed uniformly from the time detected by the paper feed sensor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on recording paper using electrophotography, and more particularly to a recording paper transport mechanism that is used in the image forming apparatus and controls the transport speed of the recording paper.

  Conventionally, image forming apparatuses using electrophotography have been widely used. This type of image forming apparatus forms an electrostatic latent image by exposing a uniformly charged photosensitive drum surface with a laser modulated in accordance with image information, and attaches toner to the latent image. Development (toner image formation). The toner image is transferred to a recording sheet introduced into the apparatus by a conveying roller disposed in the sheet feeding unit at a transfer position of a printing unit (image forming unit), and the toner image is fixed on the recording sheet by a fixing device. . As examples of such an image forming apparatus, a copying machine, a laser beam printer, and the like are known. An image forming apparatus using such an electrophotographic method is provided with a recording paper transport mechanism having a transport roller and a paper detection sensor so that printing can be performed at a desired position on the recording paper.

  The recording paper transport mechanism transports the recording paper in the order of the transport roller (recording paper insertion slot) -paper detection sensor-printing unit (transfer position). The transport roller is rotated by a pulse motor, and transports the recording paper while being sandwiched between a pair of rollers. The paper detection sensor detects a predetermined position of the recording paper being conveyed, and controls the timing at which the image forming apparatus irradiates the laser based on the detection timing.

  For example, Patent Document 1 discloses a mechanism for conveying recording paper (original). That is, a document reading device that reads image information of a document while conveying the document to a document reading unit in a facsimile machine or a copying machine is described. When the leading edge of the original is conveyed to a predetermined position upstream from the reading position, the original reading apparatus temporarily stops the conveyance of the original and puts it in a standby state, and changes the pulse according to the original reading timing required by the original reading unit. By inputting an acceleration pulse signal whose frequency is increased at a rate of change that does not cause a step-out from the self-starting region to the motor, and rotating the pulse motor at a speed exceeding the self-starting region, the desired reading speed can be obtained. The original is conveyed to the reading position at a corresponding conveyance speed. With this configuration, the original is read at a conveyance speed corresponding to a desired reading speed (corresponding to a printing unit in the image forming apparatus) without being limited to a self-starting area of a pulse motor as a document conveyance drive source. The document reading speed can be increased.

JP-A-11-265096

  Also in the image forming apparatus described above, like the document reading apparatus disclosed in Patent Document 1, it is desired to increase the conveyance speed of the recording paper. For example, if the conveyance mechanism of the document reading apparatus described in Patent Document 1 is adopted in the image forming apparatus, the recording sheet conveyance speed in the printing unit in the image forming apparatus is set to a desired speed exceeding the self-activation area of the pulse motor. It becomes possible to do. However, in the above-described image forming apparatus, for the purpose of synchronizing the detection timing of the predetermined position of the recording paper by the paper detection sensor and the timing of laser irradiation, the recording paper conveyance speed at the paper detection sensor position and the printing unit It is necessary to control so that the conveyance speed of the recording paper becomes equal. Since the pulse motor normally has to be controlled to accelerate at a rate of change that does not cause a step-out from within the self-starting area, the rotation of the pulse motor after the recording paper reaches the desired conveyance speed A predetermined transport distance was required. Therefore, a space corresponding to at least the predetermined transport distance must be provided between the transport roller and the paper detection sensor.

  The present invention has been made in view of the above-described problems of the prior art, and can increase the degree of freedom in layout and increase the layout of the image forming apparatus while increasing the recording paper conveyance speed. An object of the present invention is to provide a recording paper transport mechanism.

  In order to solve the above problems, the present invention provides a conveying means for conveying a recording sheet to a target position on a conveying path, and a control means for controlling the conveying speed by the conveying means, wherein the recording sheet is A control means capable of controlling the transport means to transport at a second transport speed that is slower than the first transport speed, and a third transport speed that is faster than the first transport speed. A detection means for detecting a predetermined position of the recording paper provided between the target position on the conveyance path and the conveyance means, and the control means controls the conveyance means, The recording paper is conveyed at the second conveying speed, and after the detection unit detects the predetermined position of the recording paper, the recording paper is temporarily conveyed at the third conveying speed, and then the recording The paper is transported at the first transport speed, and the third transport A time period from when the predetermined position of the recording paper conveyed at the first conveying speed through the speed reaches the target position after the detection unit detects the predetermined position; When it is assumed that the recording paper has been transported uniformly at the first transport speed from the detection of the predetermined position of the recording paper by the detection means, the predetermined position of the recording paper is the position of the predetermined position by the detection means. Provided is a recording paper transport mechanism characterized in that it is equal to the time from the detection to the arrival of the target position.

  With the above configuration, the present invention can shorten the transporting distance of the recording paper from the transporting means to the detecting means, so that the recording paper transporting mechanism can be designed to save space.

  Further, the conveying means conveys the recording paper by a driving motor.

  Further, the drive motor is a pulse motor.

  Further, the second transport speed is a speed at which the recording paper can be transported by a torque within a self-starting region of the pulse motor.

  Further, the predetermined position includes a leading end portion of the recording paper.

  Further, the predetermined position is characterized in that the reflectance of the surface of the recording paper is different from other portions.

  Further, the recording paper transport speed at the target position on the transport path is the first transport speed.

  In the present invention, a paper feeding unit that transports the recording paper and introduces the recording paper to a target position on the transport path in the image forming apparatus; an image forming unit that forms an image on the recording paper at the target position on the transport path; An image forming apparatus including: a sheet feeding unit configured to convey a recording sheet to a target position on the conveyance path; and a control unit configured to control a conveyance speed of the conveyance unit. The transport means can be controlled to transport paper at a first transport speed, a second transport speed that is slower than the first transport speed, and a third transport speed that is faster than the first transport speed. And a control means provided between the target position on the transport path and the transport means for detecting a predetermined position of the recording paper, and the control means controls the transport means. And control the recording paper at the second transport speed. After the predetermined position of the recording paper is detected by the detection means, the recording paper is temporarily transported at the third transport speed, and then the recording paper is transported at the first transport speed. And a time from when the predetermined position of the recording paper conveyed at the first conveyance speed through the third conveyance speed reaches the target position after the detection unit detects the predetermined position. When the recording paper is considered to have been transported uniformly at the first transport speed since the detection means detects the predetermined position of the recording paper, the predetermined position of the recording paper is detected as There is provided an image forming apparatus provided with a recording paper transport mechanism, characterized in that the time is equal to the time from when the predetermined position is detected by the means until the target position is reached.

  The present invention also provides a transport roller for transporting the recording paper to a predetermined position on the transport path, a pulse motor that rotationally drives the transport roller, and a control unit that controls the transport speed of the recording paper by the transport roller; A detection means for detecting the recording paper provided between a predetermined position on the conveyance path and the conveyance roller; and a holding means for holding the recording paper upstream of the conveyance roller in the conveyance path. A conveyance load adjusting unit provided between the conveyance roller and the holding unit and capable of adjusting a load necessary for conveyance of the recording paper in the conveyance roller, and the control unit includes the control unit, Before the detection of the recording paper by the detection means, the first conveyance speed corresponding to the rotation speed in the self-starting area of the pulse motor corresponds to the rotation speed outside the self-starting area of the pulse motor. When the recording paper changes from the first transport speed to the second transport speed, the transport load control means changes the transport speed to a second transport speed that is faster than the first transport speed. Provided is a recording paper transport mechanism which functions to reduce a load necessary for transporting the recording paper in a roller.

  In this recording paper transport mechanism, the transport load control unit reduces a load necessary for transporting the recording paper by the transport roller by shortening a transport distance between the transport roller and the holding unit. It can be done. The transport load adjusting means includes a guide roller for guiding the recording paper, and the guide roller is configured to change the transport speed from the first transport speed to the second transport speed. The transfer roller and the holding means are arranged so as to be movable so that the transfer distance is shortened. Further, the transport load adjusting means includes a guide roller support member that pivotally supports the guide roller and swings the guide roller so as to be movable, and the guide roller support member includes the transport roller and the holding means. It is biased in the direction in which the transport distance between the two becomes longer.

  Further, the recording paper is a continuous paper, and the holding means winds and holds the recording paper.

  According to another aspect of the present invention, there is provided a paper feeding unit that conveys a recording paper and introduces the recording paper to a predetermined position on a conveyance path in the image forming apparatus, an image forming unit that forms an image on the recording paper at a predetermined position on the conveyance path, The sheet feeding unit includes a conveyance roller for conveying the recording paper to a predetermined position on the conveyance path, a pulse motor that rotationally drives the conveyance roller, and the recording by the conveyance roller. A control means for controlling the paper conveyance speed, a detection means for detecting the recording paper, provided between a predetermined position on the conveyance path and the conveyance roller, and on the upstream side of the conveyance path from the conveyance roller , A holding unit that holds the recording paper, and a conveyance load adjustment that is provided between the conveyance roller and the holding unit and that can adjust a load necessary for conveyance of the recording paper in the conveyance roller. And the control means detects the pulse motor from the first conveyance speed corresponding to the rotation speed in the self-activation area of the pulse motor before the detection means detects the recording paper. The conveyance load control means is configured to change the second conveyance speed from the first conveyance speed to the second conveyance speed, which is faster than the first conveyance speed corresponding to the rotation speed outside the activation area. Provided is an image forming apparatus that functions to reduce a load necessary for transporting the recording paper in the transport roller when the speed is changed.

  According to the present invention, the path length from the conveyance roller to the paper detection sensor can be shortened. As a result, the degree of freedom in layout increases, and the image forming apparatus can be designed in a smaller space.

  Hereinafter, a specific embodiment of an image forming apparatus including a recording paper transport mechanism according to the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing a schematic configuration of an image forming apparatus 100 including a recording paper transport mechanism according to an embodiment of the present invention. The image forming apparatus 100 exposes the photosensitive member on the surface of the rotating photosensitive drum 4 with a laser 9 modulated based on input image information, and forms an image on the recording paper 10 using electrophotography. And is used as an output device such as a computer.

  The image forming apparatus 100 includes a roll shaft 1, a roll-shaped recording paper 10, paper feed rollers 2a and 2b, a paper feed sensor 3, and the like (including the paper feed rollers 2a and 2b and the paper feed sensor 3). A sheet conveying mechanism), a photosensitive drum 4, an intermediate transfer roller 5, a secondary transfer roller 6, a developing roller 11, a printing unit (image forming unit) including an optical unit for outputting a laser 9, and a fixing roller. 7a and 7b, and a paper discharge unit including a paper discharge sensor 8 and the like. In this embodiment, a roll-shaped recording paper is used. However, the recording paper transport mechanism according to the present invention is not limited to a roll-shaped recording paper.

  The image forming apparatus 100 sequentially conveys the recording paper 10 to the paper feeding unit, the printing unit, and the paper discharging unit during image formation. At the end of image formation, the printed portion of the recording paper 10 is discharged to the outside of the image forming apparatus 100, and the recording paper 10 is cut automatically or manually with a cutter or the like. Thereafter, at the time of standby for image formation, the leading end portion of the recording paper 10 is positioned at the discharge portion. In this case, the next image formation is started from the state where the leading end portion of the recording paper 10 is positioned at the discharge portion (normal printing). However, in this state, no image formation is performed on the recording paper 10 from the printing unit to the discharge unit at the next image formation, and therefore, if printing is continued, paper is wasted. Therefore, the image forming apparatus 100 may have a function of rewinding the leading end portion of the recording paper 10 in the paper discharge unit to the paper supply unit at the start of image formation when waiting for image formation (rewind printing).

  The recording paper 10 is wound in a roll shape on a roll shaft 1 rotatably supported on a predetermined support portion fixed to the apparatus main body. The recording paper 10 wound around the roll shaft 1 is guided toward the paper feed rollers 2 a and 2 b through a guide 1 a extending in the axial direction of the roll shaft 1. The roll shaft 1 rotates clockwise in the drawing by the paper feeding operation by the rotational force of the paper feed roller 2a (forward feed direction). At the time of rewind printing, the paper feed roller 2a performs a paper rewinding operation at the end of image formation or at the start of image formation. During the paper return operation, the roll shaft 1 is rotated counterclockwise in the drawing by a predetermined biasing means (reverse feed direction), so that the recording paper 10 can be taken up without sagging.

  The sheet feeding roller 2a is rotated by a driving force from a driving motor (pulse motor) M. The paper feed roller 2a rotates counterclockwise in the figure during the paper feed operation (forward feed direction). The paper feed roller 2a rotates clockwise in the drawing (reverse feed direction) during the paper return operation. At the time of rewind printing, the paper feed roller 2a performs a paper return operation in which the paper feed roller 2a rotates in the reverse direction, and the leading end of the recording paper 10 near the paper discharge unit is positioned between the paper feed roller 2a and the paper feed sensor 3. set. When the leading end of the recording paper 10 is rewound to the position between the paper feed roller 2a and the paper feed sensor 3, for example, the number of pulses at the time of rewind is determined in advance for the pulse motor M, and the rewind distance is determined. Is fixed. The paper feed roller 2b holds the recording paper 10 together with the paper feed roller 2a, and rotates following the paper feed roller 2a. That is, the recording paper 10 is conveyed by a pair of rollers of the paper feed rollers 2a and 2b.

  The paper feed sensor 3 is configured to detect a predetermined position of the recording paper 10. The predetermined position of the recording paper 10 is, for example, a front end portion (paper front end portion) of the recording paper 10, a predetermined marked position on the paper, or the like. Further, when the recording paper 10 is a label paper, the recording paper 10 is composed of a base paper which is a continuous paper and a label paper which is a printing area, and therefore the predetermined position is the leading edge of the label paper (label leading edge) or For example, a predetermined marked position on the mount.

  The paper feed sensor 3 includes, for example, a light emitting element and a light receiving element. As one form of the paper feed sensor 3, a light emitting element and a light receiving element are arranged to face each other, and the recording paper 10 passes between both elements. In this case, it is possible to detect the leading end portion of the recording paper 10 by utilizing the fact that the light receiving element cannot detect light when the leading end portion of the sheet passes the paper feed sensor 3. Further, when the recording paper 10 is a label paper, the leading end of the label can be detected by the difference in the detected light amount of the light receiving element if the mount and the label paper are configured to have different light transmittances. Similarly, if the light transmittance differs between the mark position on the recording paper 10 (including the mount) and other areas, the paper feed sensor 3 can detect the mark position. As another form of the paper feed sensor 3, the light emitting element and the light receiving element are disposed adjacent to each other without facing each other. In this case, when the leading edge of the sheet passes through the paper feed sensor 3, the leading edge of the sheet can be detected by reflecting light on the recording paper 10 and entering the light receiving element. When the recording paper 10 is a label paper, the paper feed sensor 3 can detect the leading edge of the label if the reflectance of light differs only between the portion of the mount and the portion where the label paper is attached. Further, if the mark position printed on the surface of the recording paper 10 on the light emitting element side of the paper feed sensor 3 on the recording paper 10 (including the mount) and the other areas are configured to have different light reflectivities. The mark position can be detected by the difference in the amount of light detected by the light receiving element. The image forming apparatus 100 controls the timing of emitting the laser 9 with reference to the time when the paper feed sensor 3 detects a predetermined position of the recording paper 10 conveyed by the paper feed rollers 2a and 2b.

  The photosensitive drum 4 rotates counterclockwise, and is charged to about +700 V by a charger (not shown), and then scanned in the rotational axis direction (main scanning direction) of the photosensitive drum 4 based on image formation information. The laser beam 9 is exposed. The position (point) irradiated with the laser beam 9 drops to about +100 V, and as a result, an electrostatic latent image having a contrast of +700 V and +100 V is formed on the photosensitive drum 4.

  The photosensitive drum 4 on which the electrostatic latent image is formed further rotates, and then the toner is attracted and moved only from the developing roller 11 to which about +500 V is applied to the position where the potential on the photosensitive drum 4 is lowered. . That is, when the potential is +500 V near the surface of the developing roller 11 and the exposed portion of the photosensitive drum 4 is +100 V, the toner is developed by applying approximately +500 V to the developing roller 11. It moves to the electrostatic latent image by the electric field. On the other hand, since no toner adheres to the portion where the potential is +700 V, a toner image corresponding to the electrostatic latent image is formed on the photosensitive drum 4.

  Since about −100 V is applied to the intermediate transfer roller 5 that rotates clockwise, the toner having a positive charge moves from the photosensitive drum 4 to the intermediate transfer roller 5. As a result, the toner image is transferred onto the intermediate transfer roller 5.

  The secondary transfer roller 6 that rotates counterclockwise is applied with about −1 kV. On the recording paper 10 that is sandwiched between the intermediate transfer roller 5 and the secondary transfer roller 6, the toner on the intermediate transfer roller 5 is transferred. It is drawn toward the secondary transfer roller 6 side. As a result, the toner image is transferred to the upper side of the recording paper 10. In this printing unit, the recording paper 10 is conveyed by a pair of rollers, an intermediate transfer roller 5 and a secondary transfer roller 6. Note that the conveyance speed of the recording paper 10 by the printing unit is set to be slightly higher than the conveyance speed supplied by the paper feeding rollers 2a and 2b of the paper feeding unit.

  Further, the secondary transfer roller 6 can be moved (retracted) to a position indicated by a downward broken line in the drawing. When the secondary transfer roller 6 is retracted, the contact between the recording paper 10 and the intermediate transfer roller 5 can be released. Accordingly, when the recording paper 10 is wound up (when printing after rewinding), if the secondary transfer roller 6 is retracted, the recording paper 10 is released from the state of being sandwiched between the intermediate transfer roller 5 and the secondary transfer roller 6. The Thus, the recording paper 10 can be rewound by rotating the paper supply roller 2a clockwise in the drawing. Further, since the recording paper 10 is not in contact with the intermediate transfer roller 5, the surface of the intermediate transfer roller 5 is not damaged by friction with the recording paper 10.

  The recording paper 10 that has passed through the printing unit advances in the direction of the fixing rollers 7a and 7b. The fixing roller 7 a has a function of heating the recording paper 10. The fixing roller 7b has a function of pressing the recording paper 10 in the direction of the fixing roller 7a. By the fixing rollers 7a and 7b, the toner image on the recording paper 10 is fixed to the recording paper 10 by heating and pressing. The fixing roller 7b can be retracted to a position indicated by a broken line in the downward direction in the drawing.

  The paper discharge sensor 8 senses the passage of a predetermined position of the recording paper 10 after the toner image is heated and pressurized and fixed. For example, when the predetermined position of the recording paper 10 does not pass the paper discharge sensor 8 within a predetermined time after passing through the paper feed sensor 3, the image forming apparatus 100 can determine whether the paper is jammed.

  Next, a recording paper transport mechanism according to an embodiment of the present invention will be described with reference to FIG.

  The recording paper transport mechanism transports the recording paper 10 by the paper feed rollers 2a and 2b. The paper feed roller 2a is driven by a pulse motor M (FIG. 1). The recording paper transport mechanism controls the transport speed of the recording paper 10 by controlling the rotational speed of the pulse motor M.

  The arrangement relationship between the recording paper transport mechanism and the printing unit will be described. A position A (hereinafter referred to as a recording paper transport position A) for sandwiching the recording paper 10 between the paper feed rollers 2a and 2b and a position P (hereinafter referred to as a paper detection position C) where the paper feed sensor 3 detects the recording paper 10. ) Is L. Let M be the distance from the paper detection position C to the transfer position (D in the figure, hereinafter referred to as transfer position D). The distance from the irradiation position of the laser 9 on the photosensitive drum 4 (E in the figure, hereinafter referred to as irradiation position E) travels around the photosensitive drum 4 counterclockwise and reaches the contact position with the intermediate transfer drum 5. From there, the distance around the intermediate transfer drum 5 is clockwise, and the total distance to the transfer position D is N (the path length N of the bold line portion in the figure). Further, at the time of printing standby or at the start of printing, a predetermined position of the recording paper 10 is arranged at a position of point B in the drawing (hereinafter referred to as recording paper standby position B).

  In the embodiment of the present invention, the paper feed sensor 3 is arranged so that the distance M is equal to the path length N, and the irradiation position E is irradiated with the laser 9 simultaneously with the detection of the paper feed sensor 3. . In this case, an image formed at the irradiation position E simultaneously with the detection is formed as an image on the recording paper 10 at a predetermined position on the recording paper 10 detected at the detection position C. On the other hand, the paper feed sensor 3 may be arranged such that the distance M is longer than the path length N. In this case, if irradiation of the laser 9 is started after a predetermined time has passed after the predetermined position of the recording paper 10 passes the paper detection position C, an image is transferred from the predetermined position of the recording paper 10 at the transfer position D. Can be formed.

FIG. 3 is a flowchart showing control of the conveyance speed of the recording paper 10 by the recording paper conveyance mechanism according to the embodiment of the present invention. When the recording paper 10 is conveyed in the feeding direction by the paper feed rollers 2a and 2b, the predetermined position of the recording paper 10 moves from the recording paper standby position B to the paper detection position C. In step S10, it is determined whether or not a predetermined position of the recording paper 10 is detected at the paper detection position C. The predetermined position of the recording paper 10 reaches the paper detection position C at a speed V ₁ as described later. When a predetermined position of the recording paper 10 is detected at the paper detection position C (step S10: YES), the process proceeds to step S20. In step S20, the recording paper 10 is accelerated at a constant acceleration until reaching a speed V ₂ (> V ₁ ) as will be described later. After reaching the speed V ₂ , the recording paper 10 is conveyed at a constant speed V ₂ .

In step S30, the constant-speed transfer at the speed V ₂ to determine whether or not performed for a predetermined time. Constant velocity transport time at a speed V ₂ is calculated to meet the conditions as described below (i.e., is calculated as the area of the hatched portion a and the hatched portion b in FIG. 4 become equal). After a predetermined time has elapsed (step S30: YES), the conveyance speed of the recording paper 10 is decelerated at a constant acceleration to a speed V ₀ (V ₁ <V ₀ <V ₂ ) as described later, and is constant at a speed V ₀ . It is conveyed (step S40). By control of the recording sheet conveying mechanism, a predetermined position of the recording paper 10 reaches the transfer position D at the speed V _0.

FIG. 4 is a diagram showing the conveyance speed of the recording paper 10 by the control (FIG. 3) of the recording paper conveyance mechanism according to the embodiment of the present invention. In the graph, t = 0 indicates when a predetermined position of the recording paper 10 is detected at the paper detection position C (FIG. 2). Further, the speed V ₀ (for example, about 200 mm / sec) is the same speed as the conveyance speed of the recording paper 10 in the printing unit (that is, equal to the circulation speed when the image travels the path length N). During standby for image formation, the recording paper 10 is stationary with its predetermined position aligned with the recording paper standby position B (FIG. 2). At the start of image formation, the pulse motor M (FIG. 1) is activated to rotate the paper feed roller 2a. The transport speed of the recording paper 10 by the paper feed roller 2a is a transport speed V ₁ (<V ₀ , for example, about 100 mm) that can be reached immediately after the start of the pulse motor M, which is determined by the number of revolutions in the self-starting region of the pulse motor M. / sec), and the rotated at a constant speed at a speed V ₁ to a paper detection position C. Distance between the recording sheet standby position B and the paper detection position C, the recording paper 10 may be equal to or greater than the distance that can be reached with the conveyance speed V _1.

At time t = 0, the paper detection position C, the recording paper 10 which is conveyed at the speed V ₁ is detected with the predetermined location. Simultaneously with the detection at the paper detection position C, the recording paper transport mechanism accelerates the pulse motor M. At this time, the conveyance speed is increased from V ₁ to V ₂ (> V ₀ ) with a constant acceleration. During this time, the transport speed is V ₀ at t = t1, and V ₂ at t = t2. Thereafter, from t = t ₂ to t = t ₃ , the sheet is conveyed at a constant speed at the conveyance speed V ₂ . From t = t ₃ to t = t ₄ , the conveyance speed is decreased from V ₂ to V ₀ at a constant acceleration. Then, t = _{t 4} later conveyed at a constant speed at a speed _{V 0.} Predetermined position of the recording paper 10 reaches the transfer position D to the time t = t ₄ later.

From t = 0 (paper detection position C), the distance the recording paper 10 until t = _{t 4} is conveyed, the integral value of the conveying speed from the time t = 0 to t = _{t 4.} In the embodiment of the present invention, the conveyance speed is controlled so that the area indicated by the hatched portion a in FIG. 4 is equal to the area indicated by the hatched portion b. Are equal the area of the shaded portion a and the shaded portion b, the transport distance from t = 0 to t = t _4, the transport when it is transported from t = 0 to t = t ₄ at a constant speed of the speed V ₀ Equal to the distance. Therefore, even if the conveyance speed of the recording paper 10 is the speed V ₁ slower than the speed V _{0 at the} paper detection position C (t = 0), the recording paper 10 has a constant speed V ₀ after t = t _4. It is possible to advance by a distance equal to the transport distance when transported. That is, even when the conveyance speed is a speed V ₁ slower than V _{0 at} t = 0, the detection timing of the predetermined position of the recording paper by the paper detection sensor 3 and the timing of irradiating the laser are from the paper detection sensor 3. it may be controlled as if evenly conveying speed to the print section is V _0.

With the above-described configuration, the recording paper standby position B and the paper detection position C are more likely to pass through the paper detection position C at the transport speed V ₁ than through the paper detection position C at the transport speed V ₀ . The distance can be shortened. As shown in FIG. 4, it takes time t ₁ for the recording paper 10 to reach the conveyance speed V ₁ to V ₀ . In that case, it is necessary to secure a path length between the paper detection position C and the recording paper standby position B at least by a distance corresponding to the time. Therefore, according to the embodiment of the present invention, since the distance between the recording paper standby position B and the paper detection position C can be shortened, the distance L can be shortened, and the paper feed rollers 2a and 2b can be further connected to the paper feed sensor 3. It can be arranged close to the side.

In FIG. 4, from the conveyance speed V ₁ to the conveying speed V ₂ or from the conveying speed V ₂ to the transport velocity V ₀ are transported at a constant acceleration, the acceleration may not be constant. That may be curved in t = t ₄ the line indicating the speed from t = 0, consequently, it becomes equal area corresponding to the hatched portion a and the hatched portion b.

  According to the present invention, paper detection is performed by the paper detection sensor before the pulse motor M reaches a desired conveyance speed, and therefore the distance from the conveyance roller to the paper detection sensor can be shortened. As a result, the degree of freedom of the layout of the recording paper transport mechanism is increased, and the image forming apparatus can be designed to be more space-saving.

  Next, another embodiment of the present invention will be described.

  FIG. 5 is a schematic configuration diagram of an image forming apparatus 200 including a recording paper transport mechanism according to another embodiment of the present invention. Note that the same members as those of the image forming apparatus 100 are denoted by the same reference numerals, and redundant description is omitted.

  The recording paper 10 is wound around the roll shaft 1 in a roll shape. The recording paper 10 is conveyed to the paper feed rollers 2a and 2b, and a buffer guide mechanism 300 is provided on the conveyance path. The buffer guide mechanism 300 includes a guide roller 310 that is a roller member for guiding the recording paper 10, a guide support member 320 that pivotally supports the guide roller 310 and that can swing around the other end side, and a guide support member. And a spring member 340 for biasing 320. The guide support member 320 is a plate-like member that extends from the swing shaft to the shaft of the guide roller 310, and one end of a spring member 340 is connected to the vicinity of the center portion thereof. The other end of the spring member 340 is fixed at a predetermined hounding position of the image forming apparatus 200. Further, the spring member 340 biases the guide support member 320 from the bottom surface side (lower side in FIG. 5) of the image forming apparatus 200 so as to rotate clockwise in the figure. The set of the guide support member 320 and the spring member 340 is disposed on both sides of the guide roller 310, that is, on the front side and the back side in FIG. The width of the peripheral surface of the guide roller 310 is equal to or greater than the width of the recording paper 10.

  When waiting for image formation, that is, when the pulse motor M is stopped, the buffer guide mechanism 300 is in the initial state A. The recording sheet 10 in the initial state A is fixed on the downstream side in the transport direction by paper feed rollers 2a and 2b, and the upstream side in the transport direction is fixed to the roll shaft by a predetermined urging means provided on the roll shaft 1. 1 is pulled upstream by a force that attempts to rotate counterclockwise in the figure. Accordingly, in the initial state A, the recording paper 10 has the feed rollers 2a and 2b as fixed ends and the other end is pulled by the roll shaft 1, and as a result, acts to push up the guide roller 310 substantially upward in the drawing. . That is, the recording paper 10 acts to rotate the guide support member 320 counterclockwise in the drawing. In the initial state A, the recording paper 10 tries to rotate the guide support member 320 counterclockwise in the figure, and the spring member 340 tries to rotate the guide support member 320 clockwise in the figure. The power to do is balanced. In this initial state A, the spring member 340 is selected so as to have an arrangement, a length, a spring coefficient, and the like that do not become the most extended state.

  When rotation of the pulse motor M starts at the start of image formation, the paper feed roller 2a pulls the recording paper 10 in the transport direction. In order for the paper feed roller 2a to rotate the roll shaft 1, a torque that opposes a load (hereinafter referred to as an impact load) caused by the inertia of the roll shaft 1 or the recording paper is required. In the embodiment of the present invention, until just before the roll shaft 1 starts to rotate, the guide roller 310 acts like a pulley, and the guide support member 320 rotates counterclockwise in the drawing. At this time, the guide support member 320 rotates against the tension of the spring member 340. The impact load is reduced by the rotation of the guide support member 320. When the guide support member 320 is rotated by a predetermined amount, the roll shaft 1 starts to rotate. When the roll shaft 1 starts to rotate, the spring member 340 is not fully extended, and its arrangement, length, spring coefficient, etc. are selected so that there is still room for extension.

  Even when the paper feed roller 2a suddenly tries to transport the recording paper 10 at a higher transport speed from the state where the roll shaft 1 is rotating at a constant rotational speed, the paper feed roller 2a resists the impact load. Torque is required. The guide support member 320 also rotates counterclockwise in the drawing when the paper feed roller 2a suddenly transports the recording paper 10 at a higher transport speed. That is, the impact load at this time is also reduced by the action of the buffer guide mechanism 300. In other words, the buffer guide mechanism 300 can change the transport path length of the recording paper 10 to the paper feed roller 2a by the rotation of the guide support part 320, and can buffer the impact load. Further, the buffer guide mechanism 300 changes the transport path length of the recording paper 10 to the paper feed roller 2a by the rotation of the guide support 320, and prevents the recording paper 10 from sagging to the paper feed roller 2a and is optimal. It functions to maintain a proper tension. Therefore, even if the rotation speed of the paper feed roller 2a is rapidly increased to rapidly increase the conveyance speed of the recording paper 10, the pulse motor M is difficult to step out (in other words, the pulse motor M is not stepped out). The upper limit of the speed range that can be increased rapidly can be increased).

FIG. 6 is a flowchart illustrating control of the conveyance speed of the recording paper 10 by the recording paper conveyance mechanism in the image forming apparatus 200. The conveyance speeds V ₀ and V ₁ have the same meaning as the conveyance speeds V ₀ and V ₁ described in the image forming apparatus 100. At step S110, control such conveying speed of the recording paper 10 is V ₁ is a conveyance speed corresponding to the speed of self-activation in the region of the pulse motor M. In step S120, the conveying speed of the recording paper 10 is controlled to be set to V ₀ is the conveyance velocity of the printing unit. This process is a process performed before a predetermined position of the recording paper 10 is detected by the paper feed sensor 3.

  FIG. 7 is a diagram illustrating the conveyance speed of the recording paper 10 by the control of the recording paper conveyance mechanism in the image forming apparatus 200 (FIG. 6). In the graph, t = 0 assumes that the predetermined position of the recording paper 10 is at the paper detection position B (FIG. 2).

When starting the pulse motor M at the time of image formation start (t = 0), the conveying speed of the recording paper 10 by the paper feed roller 2a becomes V _1. Thereafter, at t ₁ (> 0), the conveyance speed instantaneously changes (switches) from V ₁ to V ₀ . At t ₂ (> t ₁ ), the predetermined position of the recording paper 10 passes the paper detection position C (FIG. 2). Incidentally, _{t 2} is set to after _{t 1,} may be _t 1 = t _2. That is, the conveyance speed at the paper detection position C may be changed from V ₁ to V ₀ .

In the image forming apparatus 200, the shock load when the recording paper 10 is conveyed is reduced by the action of the buffer guide mechanism 300, and the recording paper 10 is automatically detected from the conveyance speed V ₁ of the recording paper 10 within the self-activation area of the pulse motor M. It is possible to instantaneously reach V ₀ that is the transport speed outside the activation area. In the image forming apparatus 200, if rapidly changing the recording paper 10 from the conveyance speed V ₁ to V _0, the shock load caused by the roll shaft 1 or the like, is mitigated by the elongation of the spring member 340 of the buffer guide mechanism 300 Therefore, the step-out of the pulse motor M can be prevented because the spring normally extends at a rate similar to that at the time of high load even at low load. Therefore, in the image forming apparatus 200, the distance of the conveying speed of the recording paper 10, since after the activation of the pulse motor M capable of reaching into the V ₀ in a short time, and the recording sheet standby position B and the paper detection position C The paper feed rollers 2a and 2b can be arranged closer to the paper feed sensor 3 side.

  Note that the recording paper conveyed in the image forming apparatus 200 is not limited to roll paper. For example, cut paper may be used. That is, a pair of rollers for holding the cut sheet may be provided on the upstream side of the conveying roller 2a for the purpose of conveying the cut sheet or preventing sagging. In such a case, when the paper feed roller 2a conveys the cut paper, an impact load is generated by the roller pair. Therefore, the present invention can also be implemented for an image forming apparatus using cut paper.

  Further, according to the present invention, the distance from the transport roller 2a to the paper detection sensor 3 can be shortened. In the image forming apparatuses 100 and 200, a recording sheet press (not shown) is disposed on the upstream side in the transport direction from the transport roller 2a. The recording paper presser is a member that presses both ends of the recording paper 10 and positions the recording paper 10 in the width direction. The recording paper presser extends linearly along the recording paper conveyance direction (substantially left-right direction in FIGS. 1 and 5). Therefore, when the position of the conveying roller 2a is brought closer to the paper detection sensor 3, that is, the conveying roller 2a is moved to the substantially left side in FIGS. 1 and 5, the recording paper presser can be moved to the substantially left side in FIGS. Therefore, it is more effective for space saving of the image forming apparatus.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is the schematic for demonstrating the recording paper conveyance mechanism in embodiment of this invention. 6 is a flowchart illustrating control of a recording paper conveyance speed according to an embodiment of the present invention. It is a figure which shows the conveyance speed of the recording paper in embodiment of this invention. It is sectional drawing which shows schematic structure of the image forming apparatus in other embodiment of this invention. 6 is a flowchart showing control of a recording paper conveyance speed in another embodiment of the present invention. It is a figure which shows the conveyance speed of the recording paper in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roll shaft 2a, 2b Paper feed roller 3 Paper feed sensor 4 Photosensitive drum 5 Intermediate transfer roller 6 Secondary transfer roller 7a, 7b Fixing roller 8 Paper discharge sensor 9 Laser 10 Recording paper 11 Developing roller M Pulse motor 100, 200 Image Forming device 300 Buffer guide mechanism

Claims (14)

Transport means for transporting the recording paper to a target position on the transport path;
Control means for controlling the transport speed by the transport means, wherein the recording paper is transported at a first transport speed, a second transport speed slower than the first transport speed, and the first transport speed. Control means capable of controlling the conveying means to convey at a fast third conveying speed;
A detection unit provided between a target position on the conveyance path and the conveyance unit, and detecting a predetermined position of the recording paper;
The control means controls the conveying means to convey the recording paper at the second conveying speed, and after the detection means detects a predetermined position of the recording paper, the recording paper is temporarily transferred to the first recording paper. The recording paper is conveyed at the first conveyance speed, and then the recording paper is conveyed at the first conveyance speed via the third conveyance speed. The time until the position reaches the target position from the time when the detection means detects the predetermined position is uniformly set from the time when the recording paper detects the predetermined position of the recording paper. When a predetermined position of the recording paper is regarded as being conveyed at a conveyance speed of the recording paper, the predetermined position of the recording paper is made equal to the time from the detection of the predetermined position to the arrival of the target position. Recording paper transport mechanism.   The recording paper transport mechanism according to claim 1, wherein the transport means transports the recording paper by a drive motor.   The recording paper transport mechanism according to claim 2, wherein the drive motor is a pulse motor.   The recording paper transport mechanism according to claim 3, wherein the second transport speed is a speed at which the recording paper can be transported by a torque within a self-starting region of the pulse motor.   5. The recording paper transport mechanism according to claim 1, wherein the predetermined position includes a leading end portion of the recording paper.   6. The recording paper transport mechanism according to claim 1, wherein the predetermined position has a reflectance of the surface of the recording paper different from other portions.   The recording paper transport mechanism according to claim 1, wherein a transport speed of the recording paper at a target position on the transport path is the first transport speed. A paper feeding unit that conveys the recording paper and introduces the recording paper to a target position on the conveyance path in the image forming apparatus;
An image forming apparatus that forms an image on the recording paper at a target position on the conveyance path,
The paper feeder is
Conveying means for conveying the recording paper to a target position on the conveying path;
Control means for controlling the transport speed by the transport means, wherein the recording paper is transported at a first transport speed, a second transport speed slower than the first transport speed, and the first transport speed. Control means capable of controlling the conveying means to convey at a fast third conveying speed;
A detection unit provided between a target position on the conveyance path and the conveyance unit, and detecting a predetermined position of the recording paper;
The control means controls the conveying means to convey the recording paper at the second conveying speed, and after the detection means detects a predetermined position of the recording paper, the recording paper is temporarily transferred to the first recording paper. The recording paper is conveyed at the first conveyance speed, and then the recording paper is conveyed at the first conveyance speed via the third conveyance speed. The time until the position reaches the target position from the time when the detection means detects the predetermined position is uniformly set from the time when the recording paper detects the predetermined position of the recording paper. When a predetermined position of the recording paper is regarded as being conveyed at a conveyance speed of the recording paper, the predetermined position of the recording paper is made equal to the time from the detection of the predetermined position to the arrival of the target position. Image type with recording paper transport mechanism Apparatus. A transport roller for transporting the recording paper to a predetermined position on the transport path;
A pulse motor for rotationally driving the transport roller;
Control means for controlling the conveyance speed of the recording paper by the conveyance roller;
A detecting means provided between a predetermined position on the conveying path and the conveying roller, for detecting the recording paper;
Holding means for holding the recording paper on the upstream side of the conveyance path from the conveyance roller;
A conveyance load adjusting unit provided between the conveyance roller and the holding unit, and capable of adjusting a load necessary for conveyance of the recording paper in the conveyance roller;
Before the detection of the recording paper by the detection means, the control means changes from the first transport speed corresponding to the rotation speed in the self-starting area of the pulse motor to the rotation speed outside the self-starting area of the pulse motor. Change the second transport speed faster than the corresponding first transport speed,
The transport load control means acts to reduce a load necessary for transporting the recording paper in the transport roller when the recording paper changes from the first transport speed to the second transport speed. A recording paper transport mechanism.   The conveyance load control unit can reduce a load necessary for conveyance of the recording paper in the conveyance roller by shortening a conveyance distance between the conveyance roller and the holding unit. Item 10. The recording paper transport mechanism according to Item 9. The transport load adjusting means includes a guide roller for guiding the recording paper,
The guide roller is arranged to be movable so that a conveyance distance between the conveyance roller and the holding unit is shortened when the conveyance speed changes from the first conveyance speed to the second conveyance speed. The recording paper transport mechanism according to claim 9 or 10, wherein the recording paper transport mechanism is provided. The transport load adjusting means includes a guide roller support member that pivotally supports the guide roller and swings the guide roller so as to be movable.
The recording paper transport mechanism according to claim 11, wherein the guide roller support member is biased in a direction in which a transport distance between the transport roller and the holding unit becomes longer.   The recording paper transport mechanism according to claim 9, wherein the recording paper is a continuous paper, and the holding unit winds and holds the recording paper. A paper feeding unit that conveys the recording paper and introduces the recording paper to a predetermined position on the conveyance path in the image forming apparatus;
An image forming apparatus having an image forming unit that forms an image on the recording paper at a predetermined position on the conveyance path,
The paper feeder is
A conveyance roller for conveying the recording paper to a predetermined position on the conveyance path;
A pulse motor that rotationally drives the transport roller;
Control means for controlling the conveyance speed of the recording paper by the conveyance roller;
A detecting means provided between a predetermined position on the conveying path and the conveying roller, for detecting the recording paper;
Holding means for holding the recording paper on the upstream side of the conveyance path from the conveyance roller;
A conveyance load adjusting unit provided between the conveyance roller and the holding unit, and capable of adjusting a load necessary for conveyance of the recording paper in the conveyance roller;
Before the detection of the recording paper by the detection means, the control means changes from the first conveyance speed corresponding to the rotation speed in the self-starting area of the pulse motor to the rotation speed outside the self-starting area of the pulse motor. Change the second transport speed faster than the corresponding first transport speed,
The transport load control means functions to reduce a load necessary for transport of the recording paper in the transport roller when the recording paper changes from the first transport speed to the second transport speed. An image forming apparatus.

Images