JP5369793B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device including a branch guide member that favorably guides paper sheets in any direction irrespective of the types of the paper sheets without the rubbing of an image surface. <P>SOLUTION: Paper sheets on which images are formed by an image forming part 2 are fed by a branch guide member 70 having a suction belt 80 wound between a conveyance roller 75 and a tension roller 78. During a normal paper discharge mode, the branch guide member 70 is upwardly rotated around the shaft of the conveyance roller 75 to discharge the paper sheets into a paper discharge tray 7. During a horizontal paper discharge mode, the paper sheets are directly discharged. During a double-sided paper discharge mode, the branch guide member 70 is downwardly rotated to guide the paper sheets to a double-sided unit that is not shown. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, a printing machine, and a multifunction machine having at least one of them.

For example, in an image forming apparatus (ink jet printer) using ink, in recent years, it has been desired to discharge the printed paper in various directions.
In order to reduce the planar projection size of the device, the paper is discharged into the cylinder, or the paper is transported downward due to the layout that installs a mechanism for double-sided printing at the bottom of the device body. There is a need for means to change the transport direction of the paper.
As this type of route changing means, there has conventionally been known a branch guide method in which a branch claw is driven by a solenoid or the like and selectively guided to a plurality of conveyance paths.
In the case of the branch guide method that transports paper along the conventional branching claw (guide plate), the printing surface contacts the guide surface of the guide plate (if the paper after single-sided printing is guided downward, the paper after double-sided printing In the case of guiding the image upward), there is a concern that an abnormal image (rubbed image) may be generated due to the rubbing between the guide plate and the printing surface.
In order to avoid abnormal images, measures have been taken with restrictions such as waiting until the ink dries or limiting the amount of ink applied, but this leads to a decrease in work efficiency and a decrease in image quality due to a decrease in density.

Patent Document 1 discloses a configuration in which a switching belt is provided at a branch portion, and a course is changed while the belt is rotated.
Patent Document 2 discloses a configuration in which a paper discharge guide plate that discharges paper to the top of the apparatus body is rotated so that paper can also be discharged in the horizontal direction, as shown in FIG.
Patent Document 3 discloses a configuration in which a sheet is electrostatically adsorbed and held on an adsorbing belt and transferred to the next process (sheet discharge unit).

In the configuration described in Patent Document 1, since the switching belt as the guide member also moves with respect to the conveyed paper, it can be said that the degree of sliding on the image surface is lower than that of the fixed guide member. Since it is difficult to match the two, and the movable members are in contact with each other, the concern about the rubbed image cannot be eliminated.
In the configuration described in Patent Document 2, the paper discharge guide plate itself is rotated, but as a result, there is no difference from the method of rotating the conventional branching claw.
As described in Patent Document 3, if the sheet is conveyed while being adsorbed to the suction belt, there is a problem that the image surface is rubbed in any condition and combination of single-sided printing, double-sided printing, upward guidance, and downward guidance. Absent.
However, the configuration disclosed in Cited Document 3 is a delivery configuration that uses the curvature separation due to the coercive force of the paper on the linear conveyance path, and is applicable to applications as a branch guide member such as the types of paper are limited. Not suitable.

  An object of the present invention is to provide an image forming apparatus provided with a branch guide member that can satisfactorily guide in any direction regardless of the type of paper without causing image surface rubbing.

To achieve the above object, according to the first aspect of the present invention, a branch guide member for selectively guiding a recording medium on which an image is recorded by the image forming unit to a plurality of conveyance paths, and a downstream side of the image forming unit. possess a transport drive source responsible for transporting the recording medium in the branching guide member is provided with an endless suction belt for conveying adsorbs the recording medium,
An adsorption source for imparting an adsorption function to the adsorption belt, guide member driving means for driving the branch guide member to rotate the adsorption belt, and the branch guide member after the recording medium is adsorbed to the adsorption belt. A rotation unit that rotates to correspond to any one of the plurality of conveyance paths, and controls the guide member driving unit and the rotation unit based on a conveyance destination signal ,
The transport driving source also serves as the guide member driving means,
The conveyance speed of the suction belt is changed while the branch guide member is rotated .

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the branch guide member is rotated downward, a loop is formed on the recording medium between the branch guide member and the image forming unit. The conveyance speed is adjusted so that the recording medium is not conveyed when the branch guide member is rotated .
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the branch guide member has a separation claw for separating the recording medium adsorbed by the adsorption belt. And

According to the present invention, it is possible to satisfactorily guide in any direction regardless of the type of the recording medium without causing an abnormal image due to rubbing of the image surface, and sufficient multi-functionality can be achieved by having a plurality of discharge ports. You can make use of it.
Further, it is not necessary to rotate the branch guide member at a high speed, the impact sound can be suppressed (quiet), and the restriction on the increase in the conveyance speed by the branch guide member can be avoided.
Further, since the branch guide member has the separation claw, the recording medium can be favorably separated from the suction belt.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a schematic perspective view of a paper discharge unit including a branch guide member. It is a figure which shows the drive structure of the paper discharge unit containing a branch guide member. It is a perspective view of a branch guide member. It is a perspective view from another viewpoint, such as a branch guide member. It is a detailed perspective view of a branch guide member etc. It is a figure which shows the structure which controls the upper limit and lower limit in rotation of a branch guide member. It is a control block diagram. It is a figure which shows the fundamental operation | movement of a branch guide member. It is a figure which shows operation | movement of the branch guide member in horizontal paper discharge mode. 6 is a flowchart of a control operation in a horizontal paper discharge mode. It is a flowchart of discharge mode setting. It is a figure which shows operation | movement of the branch guide member in normal paper discharge mode. 6 is a flowchart of a control operation in a normal paper discharge mode. It is a figure which shows operation | movement of the branch guide member in double-sided paper discharge mode. It is a flowchart of the control operation in the duplex paper discharge mode. It is a figure which shows the malfunction accompanying rotation of the branch guide member in double-sided paper discharge mode. It is a figure which shows the malfunction accompanying rotation of the branch guide member in normal paper discharge mode. 10 is a flowchart of a control example for solving a problem in a normal paper discharge mode. It is a flowchart of the example of control which eliminates the malfunction in double-sided paper discharge mode. It is a flowchart of the other example of control which eliminates the malfunction in double-sided paper discharge mode. 12 is a flowchart of another control example for solving the problem in the normal paper discharge mode.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, an outline of a configuration of an ink jet printing apparatus as an image forming apparatus according to the present embodiment will be described with reference to FIG. An image forming unit 2 for forming an image, a sub-scanning conveying unit 3 and the like are provided inside the apparatus main body 1. A paper feeding unit 4 is provided on the bottom side of the apparatus main body 1 so that paper 5 as a recording medium is separated and fed one by one. A duplex unit 50 is provided further below the sheet feeding unit 4.
While the paper 5 is intermittently conveyed at a position facing the image forming unit 2 by the sub-scanning conveying unit 3, the image forming unit 2 discharges droplets onto the paper 5 to form a required image.
In the normal paper discharge mode, after the image formation, the paper 5 is discharged onto a paper discharge tray 7 formed on the upper surface of the apparatus main body 1 through the paper discharge conveyance unit 6. The image forming unit 2 and the sub-scanning conveyance unit 3 are unitized to form an engine unit 100 that is detachably attached to the apparatus main body 1.

  As an input system for image data (print data) formed by the image forming unit 2, an image reading unit (scanner unit) 11 for reading an image is provided above the apparatus main body 1 and above the paper discharge tray 7. In the image reading unit 11, the scanning optical system 15 including the illumination light source 13 and the mirror 14 and the scanning optical system 18 including the mirrors 16 and 17 are moved, and the image of the document placed on the contact glass 12 is scanned. The scanned original image is read as an image signal by an image reading element (CCD) 20 disposed behind the lens 19, and the read image signal is digitized and subjected to image processing. Can be printed. A pressure plate 10 is provided on the contact glass 12 for pressing the document.

The image forming unit 2 includes a carriage 23 and a recording head 24 including a droplet discharge head that discharges black (K), cyan (C), magenta (M), and yellow (Y) inks. A shuttle type is used in which the carriage 23 is moved in the main scanning direction and droplets are ejected from the recording head 24 while the paper 5 is fed in the paper conveyance direction (sub-scanning direction) by the sub-scanning conveyance unit 3.
A sub tank 25 is mounted on the carriage 23 in order to supply a recording liquid of a required color to each recording head 24. Reference numeral 26 denotes an ink cartridge containing the inks of the respective colors. The ink cartridge 26 is detachable from the apparatus main body 1 and replenishes and supplies ink (recording liquid) from each color ink cartridge 26 to each color sub-tank 25 via a tube (not shown).

  As the recording head 24, a piezoelectric plate is used as pressure generating means (actuator means) for pressurizing ink in the ink flow path (pressure generating chamber), and the vibration plate forming the wall surface of the ink flow path is deformed to change the ink flow path. A so-called piezo type that ejects ink droplets by changing the internal volume, or a so-called thermal that ejects ink droplets with pressure by heating the ink in the ink flow path using a heating resistor to generate bubbles The volume of the ink flow path is changed by deforming the vibration plate by the electrostatic force generated between the vibration plate and the electrode. For example, an electrostatic type that discharges ink droplets can be used.

The sub-scanning conveyance unit 3 includes a conveyance roller 32 that is a driving roller and a tension roller for conveying the paper 5 fed from below by facing the image forming unit 2 while changing the conveyance direction by approximately 90 degrees. An endless conveyance belt 31 that is bridged between the driven rollers 33, a charging roller 34 that is a charging means to which an AC bias voltage that is an alternating voltage is applied to charge the surface of the conveyance belt 31, and a conveyance belt A platen guide member 35 that guides the sheet 31 in a region facing the image forming unit 2, a first pressure roller (inlet pressure roller) 36 that presses the sheet 5 toward the conveyance belt 31 at a position facing the conveyance roller 32, and A second pressure roller (front end) that presses the sheet 5 toward the conveying belt 31 at a position facing the platen guide member 35 between the conveying roller 32 and the recording head 34 as image forming means. A pressure roller) 37, and a separation claw 39 for separating the sheet 5 on which an image is formed by the image forming section 2 from the conveying belt 31.
The conveyance belt 31 is configured to circulate in the paper conveyance direction (sub-scanning direction) when the conveyance roller 32 is rotated from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133.

The paper feeding unit 4 is detachable from the apparatus main body 1 and separates the paper 5 in the paper feeding cassette 41 one by one from the paper feeding cassette 41 which is a storing means for stacking and storing a large number of papers 5. A sheet feeding roller 42 and a friction pad 43 for feeding out and a registration roller pair 44 for registering the sheet 5 to be fed are provided.
The paper feed unit 4 includes a manual tray 46 for stacking and storing a large number of sheets 5 and a manual feed roller 47 for feeding the sheets 5 one by one from the manual tray 46. Members for feeding the paper 5 to the sub-scanning conveyance unit 3 such as the paper feed roller 42, the registration roller pair 44, and the manual feed roller 47 are rotationally driven by a driving means (not shown) via an electromagnetic clutch (not shown).

The paper discharge conveyance unit 6 includes a pair of conveyance rollers 61 and 62 for conveying the paper 5 on which image formation has been performed, and a pair of conveyance rollers 63 and a pair of paper discharge rollers 65 for sending the paper 5 to the paper discharge tray 7. In addition, a reverse discharge path 66 is provided for transporting the transported paper 5 by reversing (here, making a U-turn). As described above, the paper discharge tray 7 faces the space formed between the image forming portion and the image reading device 11 and performs in-cylinder paper discharge.
A paper discharge sensor (hereinafter also referred to as “paper discharge SW”) 74 is provided in the vicinity of the upstream side of the paper discharge roller pair 65. The paper discharge sensor 74 is omitted as appropriate in other drawings.

As will be described later, a branch guide member 70 having a suction belt is integrally provided in the paper discharge conveyance unit 6. In the normal paper discharge mode in which paper is discharged to the paper discharge tray 7, the branch guide member 70 is rotated upward with the upstream side in the paper transport direction as a fulcrum.
In the horizontal paper discharge mode in which paper is discharged to a paper discharge tray 72 provided on the left side of the apparatus main body 1 in the drawing, the branch guide member 70 is set to a substantially horizontal position as shown in FIG.
In the duplex mode, the branch guide member 70 is rotated downward. The paper is guided to the duplex unit 50 and an image is formed on the back surface (second surface), and then discharged to the discharge tray 7 or the discharge tray 72.
In the duplex unit 50, duplex transport roller pairs 53a, 53b, 53c, 53d, and 53e are arranged along the sheet transport direction on the downstream side of the duplex entrance roller pair 51, and these rollers are driven by a duplex motor (not shown). The
The sheet 5 on which an image is formed on one side is guided downward by the branch guide member 70, and is conveyed from the pair of duplex entrance rollers 51 to the first duplex standby unit 53 via the duplex conveyance path 52.
A pair of reversing rollers 55a and 55b are arranged in the second double-sided standby unit 55, and the paper 5 conveyed from the first double-sided standby unit 53 side is switched back. Thereafter, the branch plate 54 is switched and conveyed to at least the duplex exit roller pair 56 by the reverse drive of the duplex motor.

The paper discharge conveyance unit 6 will be described in detail with reference to FIGS. FIG. 2 is a perspective view of the paper discharge conveyance unit 6 as viewed from the back side of the apparatus, and FIG. 3 is a schematic explanatory view of FIG.
A conveyance roller shaft 164 is rotatably supported between the side plates 161 and 162 of the paper discharge conveyance unit 6. In FIG. 2, reference numeral 163 denotes a paper discharge guide member.
The side plate 161 is provided with a paper discharge motor 165. The rotation of the paper discharge motor 165 is transferred to the conveying roller pair 61 via the pulley 166, the timing belt 167 and the integral pulleys 168A and 168B, and further from the roller 168B to the timing belt. 169 and the pulley 170 to the conveying roller pair 62, and further from the pulley 170 to the conveying roller pair 63 via the timing belt 171 and the pulley 172, and further from the pulley 172 to the pulleys 173, 174, 175 and 176, the conveying roller shaft. A driving force transmission mechanism is provided that transmits to the driving roller 65 </ b> A of the paper discharge roller pair 65 via a pulley 177 and a timing belt 178 fixed to 164.
In FIG. 3, reference numeral 182 denotes a branch sensor (hereinafter also referred to as “branch SW”) provided in the vicinity of the upstream side of the branch guide member 70 in the sheet conveyance direction, and reference numeral 181 denotes a sensor that detects opening and closing of the paper discharge guide member 163. Is shown. The paper discharge guide member 163 can be opened and closed for jam processing in the normal paper discharge mode.

The branch guide member 70 and the like will be described in detail with reference to FIGS.
The branch guide member 70 includes a conveyance roller shaft 164, a roller 75 fixed to the conveyance roller shaft 164, a pair of brackets 76 and 77 that are rotatably provided on the conveyance roller shaft 164, and the brackets 76 and 77. The tension roller 78 rotatably supported on the end side, the suction belt 80 wound around the roller 75 and the tension roller 78, and the shaft roller insertion holes of the tension rollers 78 of the brackets 76 and 77 are arranged. And a pressurizing member (spring) 81 that urges toward the downstream side in the sheet conveying direction.
A charging roller 82 is provided as a suction source for charging the suction belt 80 and imparting a suction function (electrostatic suction force) below the upstream side of the branch guide member 70 in the sheet conveyance direction. The charging roller 82 is supported between the side plates 161 and 162. The suction belt 80 is charged by pressing the charging roller 82 against the suction belt 80 and applying an AC bias voltage which is an alternating voltage.
On the downstream side of the branch guide member 70 in the sheet conveyance direction, a separation claw 83 for separating the sheet adsorbed by the adsorption belt 80 is pressed against the adsorption belt 80 and provided. The separation claw 83 is supported between the side plates 161 and 162.

A platen gear 84 with a torque limiter is integrally fixed (press-fitted) to the bracket 76, and the platen gear 84 is fixed to a motor gear 86 fixed to a rotating shaft of a DC motor 85 as a rotational drive source fixed to the side plate 162. Meshing.
The platen gear 84, the DC motor 85, and the motor gear 86 constitute a rotating means for rotating the branch guide member 70.
The brackets 76 and 77 are rotatable with respect to the conveying roller shaft 164. However, when the DC motor 85 is not rotated, the branch guide member 70 is prevented from rotating due to its own weight due to the engagement of the platen gear 84 and the motor gear 86. The
The rotation of the discharge motor 165 rotates the timing belt 178 and the pulley 177, and the rotation of the transport roller shaft 164 rotates the suction belt 80 in the sheet transport direction. That is, in the present embodiment, the guide member driving means for rotating the suction belt 80 is configured to serve also as the paper discharge motor 165 that is the drive source of the paper discharge conveyance unit 6.
With the above configuration, the branch guide member 70 can be rotated in the vertical direction by the rotation of the DC motor 85 independently of the rotation of the suction belt 80.

As shown in FIG. 6, a paper presence / absence detection sensor (hereinafter also referred to as “paper presence / absence SW”) 92 is installed in a recess 83 a formed by cutting out the central portion of the separation claw 83.
A photo sensor 90 is provided at a position facing the free end side of the bracket 76 so as to detect the horizontal paper discharge mode (standby position or home position) of the branch guide member 70.
As shown in FIG. 7, a detection convex portion 76 a for detection by the photosensor 90 is formed at the free end of the bracket 76. The position where the detection convex portion 76a is detected by the photosensor 90 is the standby position.
The upward rotation of the branch guide member 70 is restricted by the stopper A, and the downward rotation is restricted by the stopper B. When the bracket of the branch guide member 70 comes into contact with the stoppers A and B, the platen gear 84 with a torque limiter idles.
The photo sensor 90 and the stoppers A and B are supported via one or both of the side plates 161 and 162.

As shown in FIG. 8, control such as rotation of the branch guide member 70 is performed by a control unit 88 serving as a conveyance control unit. The control means 88 is a microcomputer having a CPU, ROM, RAM, I / O interface and the like.
The basic operation of the branch guide member 70 will be described with reference to FIG. The paper discharge motor 165 is rotated in accordance with the timing at which the image forming unit 2 forms an image, and the suction belt 80 is also rotated at the same time. The paper is transported so that the leading end thereof reaches the center of the suction belt 80 in the paper transport direction.
When the sheet is on the suction belt 80, the branch SW 182 is turned on, the control unit 88 recognizes that there is a sheet, and controls so that the next sheet is not conveyed.
The subsequent operation differs depending on the paper discharge mode. The operation in each paper discharge mode will be described below.

[Horizontal output mode]
As shown in FIG. 10, the sheet on which the image has been formed is transported substantially horizontally while being sucked by the suction belt 80 of the branch guide member 70 that is held substantially horizontally, and is discharged on the discharge guide member 163. The paper is discharged to the paper discharge tray 72 through the opening 163a (not shown in other drawings).
The control operation is shown in FIG. The control unit 88 determines whether or not the duplex mode is selected, and sets the paper discharge mode if the duplex mode is not set. In the discharge mode setting, it is determined whether the horizontal discharge mode or the normal discharge mode.
In the present embodiment, in the horizontal paper discharge mode, after the paper is conveyed by the suction belt 80 and the branch SW 182 is turned off, the rotation of the paper discharge motor 165 is turned off one second later, and the paper discharge is completed.
As shown in FIG. 12, in the paper discharge mode setting, when the horizontal paper discharge mode is not set, the normal paper discharge mode is set.

[Normal output mode]
As shown in FIG. 13, the control means 88 rotates the DC motor 85 to rotate the branch guide member 70 upward. The sheet is guided by the sheet discharge guide member 163 while being conveyed by the suction belt 80 and is discharged to the sheet discharge tray 7 (in-cylinder sheet discharge).
When the paper discharge sensor 74 is turned off, the paper discharge motor 165 is stopped and the discharge is completed.
The control operation is shown in FIG. Explaining the main part, the DC motor 85 is rotated counterclockwise 25 ms (milliseconds) after the branch SW 182 is turned on, the branch guide member 70 is rotated upward, and the bracket comes into contact with the stopper A and stops. To do. The DC motor 85 is turned off 25 ms after starting rotation.
Thereafter, when the paper discharge sensor (paper discharge SW) 74 is turned off, the DC motor 85 is rotated clockwise to rotate the branch guide member 70 downward. When the bracket detection convex portion 76a is detected by a photo sensor (also referred to as a photo sensor) 90, the DC motor 85 is stopped and set to a standby position (horizontal paper discharge mode position).
Two seconds after the stop of the DC motor 85, the paper discharge motor 165 is turned off to complete the discharge.

[Double-sided output mode]
As shown in FIG. 15, the control means 88 rotates the DC motor 85 to rotate the branch guide member 70 downward.
After the sheet is conveyed by the suction belt 80 and the branch SW 182 is turned off, the discharge motor 165 is stopped after a predetermined time, and the rotation of the suction belt 80 is stopped.
The control operation is shown in FIG. Explaining the main part, 25 ms after the branch SW 182 is turned on, the DC motor 85 is rotated in the clockwise direction, and the branch guide member 70 stops with its bracket abutting against the stopper B. The DC motor 85 is stopped 25 ms after starting to rotate.
When it is confirmed that the sheet presence / absence SW 92 is turned off and the sheet is completely removed from the branch guide member 70, the DC motor 85 is rotated counterclockwise. When the photo sensor 90 detects the sheet, the DC motor 85 is stopped and the standby position ( (Horizontal paper delivery mode position). After double-sided printing, the normal paper discharge mode is entered.

As described above, the branch guide member 70 rotates in a state where the leading end portion of the sheet is adsorbed by the adsorption belt 80. However, in this case, there is a concern that a malfunction may occur due to the displacement of the adsorption point accompanying the rotation. . This will be described with reference to FIGS.
FIG. 17 shows a case where the branch guide member 70 is rotated downward in the duplex paper discharge mode. As the branch guide member 70 rotates downward, the suction point P1 of the paper 5 moves to P2. Therefore, the sheet 5 is pulled out by the distance L1 as the branch guide member 70 rotates.
FIG. 18 shows a case where the branch guide member 70 is rotated upward in the normal paper discharge mode. As the branch guide member 70 rotates upward, the suction point P1 of the paper 5 moves to P2. Therefore, the sheet 5 is pushed back by the distance L2 as the branch guide member 70 rotates.
A control example (embodiment) for preventing such a problem will be described below.

FIG. 19 shows an example of control for suppressing the push-back phenomenon in the normal paper discharge mode. The present embodiment is characterized in that the conveyance speed of the suction belt 80 is changed while the branch guide member 70 is rotating.
The main part will be described. 25 ms after the branch SW 182 is turned on (that is, after the front end of the sheet 5 is sucked for a predetermined length), the DC motor 85 is rotated counterclockwise to rotate the branch guide member 70 upward. Move. At the same timing, the rotational speed of the paper discharge motor 165 is switched to high speed.
The DC motor 85 is stopped 25 ms after the rotation is started, and the rotational speed of the paper discharge motor 165 is returned to the steady drive at the same timing.
By controlling in this way, the suction point of the paper 5 is conveyed by the suction belt 80 without causing a shift (push back) due to the rotation of the branch guide member 70.

FIG. 20 shows an example of control that suppresses the pulling out phenomenon in the duplex paper discharge mode. The present embodiment is characterized in that the conveyance speed of the suction belt 80 is changed during the rotation of the branch guide member 70 as described above.
Explaining the main part, 25 ms after the branch SW 182 is turned on (that is, after the front end of the paper 5 is sucked for a predetermined length), the DC motor 85 is rotated clockwise to turn the branch guide member 70 downward. Let At the same timing, the rotation speed of the paper discharge motor 165 is switched to a low speed.
The DC motor 85 is stopped 25 ms after the rotation is started, and the rotational speed of the paper discharge motor 165 is returned to the steady drive at the same timing. When it is confirmed that the paper presence / absence SW 92 is turned off and the paper has completely removed from the branch guide member 70, the DC motor 85 is rotated counterclockwise.
By controlling in this way, the suction point of the paper 5 is conveyed by the suction belt 80 without causing a deviation (drawing) due to the rotation of the branch guide member 70.

FIG. 21 shows another example of control that suppresses the pulling out phenomenon in the duplex paper discharge mode.
In the present embodiment, the conveyance speed is adjusted so that a loop is formed on the sheet between the branch guide member 70 and the image forming unit 2, and the conveyance of the sheet is not performed when the branch guide member 70 is rotated. Features.
The main part of FIG. 21 is demonstrated. In this embodiment, there is a display “image forming motor ON” after “paper feeding”, but this display is omitted in the above embodiment, not the control specific to this embodiment.
The paper discharge motor 165 is stopped 25 ms after the branch SW 182 is turned on. At this time, the leading edge of the paper enters the suction belt 80 and is sucked, but the rotation of the suction belt 80 is also stopped.
The image forming motor (= sub-scanning motor 131) is stopped 10 ms after the discharge motor 165 is stopped. As a result, the sheet is fed in a state where the leading end is sucked and stopped by the suction belt 80, and a loop (sag) is formed between the branch guide member 70 and the image forming unit 2.

After the image forming motor is stopped, the DC motor 85 is rotated clockwise, and the branch guide member 70 is rotated downward. In this case, since a loop is formed in advance so as to cancel the “drawing phenomenon”, the drawing phenomenon due to the downward rotation of the branch guide member 70 does not occur.
The DC motor 85 is rotated at a lower rotational speed and is turned off 500 ms after the rotation starts. Thereafter, the paper discharge motor 165 and the image forming motor are turned on, and conveyance is resumed.
When it is confirmed that the paper presence / absence SW 92 is turned off and the paper has completely removed from the branch guide member 70, the DC motor 85 is rotated counterclockwise.
Since the sheet is not conveyed while the branch guide member 70 is rotating, the rotation speed of the DC motor 85 (the rotation speed of the branch guide member 70) can be reduced. Thereby, the impact sound by the bracket of the branch guide member 70 coming into contact with the stopper B vigorously can be reduced. Of course, a shock absorber function may be provided on the stopper B side without slowing the rotational speed of the DC motor 85. For example, a surface layer made of an elastic material such as rubber can be provided on the surface of the stopper B which is a shaft or the lower surface of the bracket of the branch guide member 70.

FIG. 22 shows another example of control for suppressing the push-back phenomenon in the normal paper discharge mode.
In the present embodiment, when the branch guide member 70 is rotated upward, the sheet is conveyed after the branch guide member 70 is previously rotated.
The main part of FIG. 22 is demonstrated. After the paper discharge motor 165 is turned on, the DC motor 85 is rotated counterclockwise at a low speed to rotate the branch guide member 70 upward, and the rotation is stopped after 500 ms from the start of the rotation. At this time, the leading edge of the paper does not reach the suction belt 80.
Due to the low-speed rotation of the DC motor 85, it is possible to mitigate the impact sound caused by the bracket of the branch guide member 70 coming into contact with the stopper A vigorously. Of course, a shock absorber function may be added to the stopper A side without slowing the rotational speed of the DC motor 85. For example, a surface layer made of an elastic material such as rubber can be provided on the surface of the stopper A that is a shaft or the upper surface of the bracket of the branch guide member 70.

  After the upward rotation of the branch guide member 70 is completed in a state where the suction belt 80 is not sucking paper, the paper is conveyed by the suction belt 80 of the branch guide member 70, the paper presence / absence SW 92 is turned off, and the paper is branched. When it is confirmed that the guide member 70 has been completely removed, the branch guide member 70 is rotated downward by rotating the DC motor 85 clockwise.

In the above embodiment, specific numerical values are shown for the rotation start timing of the DC motor 85, but these are merely examples, and the optimum values can be set experimentally.
In the above-described embodiment, the configuration in which the sheet is adsorbed to the adsorption belt 80 by the electrostatic adsorption force is illustrated, but the configuration may be adopted in which the sheet is adsorbed by negative air pressure.
In the above embodiment, an ink jet printer is exemplified as the image forming apparatus. However, the image forming apparatus can be similarly applied to an electrophotographic image forming apparatus.

2 Image forming unit 5 Paper as recording medium 70 Branch guide member 80 Adsorption belt 82 Charging roller as adsorption source 83 Separation claw 85 DC motor as rotation means 88 Control means as conveyance control means 165 Guide member drive means Paper discharge motor

Japanese Patent No. 3257712 JP 2008-120529 A JP 2006-232500 A JP 2005-263341 A

Claims (3)

The recording medium on which an image is recorded by the image forming section, possess a branching guide member for selectively guiding the plurality of the transport path, and a conveying drive source responsible for transporting the recording medium in the downstream of the image forming unit, wherein The branch guide member includes an endless suction belt that sucks and conveys the recording medium,
An adsorption source for imparting an adsorption function to the adsorption belt, guide member driving means for driving the branch guide member to rotate the adsorption belt, and the branch guide member after the recording medium is adsorbed to the adsorption belt. A rotation unit that rotates to correspond to any one of the plurality of conveyance paths, and controls the guide member driving unit and the rotation unit based on a conveyance destination signal ,
The transport driving source also serves as the guide member driving means,
An image forming apparatus , wherein the conveyance speed of the suction belt is changed while the branch guide member is rotated . The image forming apparatus according to claim 1.
When the branch guide member is rotated downward, the conveyance speed is adjusted so that a loop is formed on the recording medium between the branch guide member and the image forming unit. An image forming apparatus, wherein the recording medium is not conveyed . The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the branch guide member has a separation claw for separating the recording medium adsorbed by the adsorption belt.

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