JP3755275B2 - Image forming target sheet conveying apparatus in image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming target sheet conveying apparatus in an image forming apparatus that reverses an image forming target sheet and then conveys it again.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, an apparatus capable of forming an image on both sides of a sheet has been developed. In such an image forming apparatus, after an image is formed on one side of a sheet, the sheet is reversed and conveyed again to the image forming unit. An image is formed on the other surface by the image forming unit.
[0003]
Japanese Patent Application Laid-Open Nos. Hei 2-291372 and Hei 9-12197 disclose an apparatus that performs reversal of paper during double-sided image formation as described above and paper refeeding to an image forming unit. These devices include a reversing device that reverses the paper on which an image is formed on one side by switching back, and a re-conveying device that supplies the paper reversed by the reversing device to the image forming device again. A drive source for driving the reversing device and a drive source for driving the re-conveying device are provided separately.
[0004]
Japanese Patent Application Laid-Open No. 63-112326 discloses an apparatus for driving a conveyance roller provided in each of a reversing device and a re-conveyance device with one drive source.
[0005]
[Problems to be solved by the invention]
However, the apparatus disclosed in Japanese Patent Laid-Open Nos. 2-291372 and 9-12197 requires a reversing drive source and a refeeding drive source. There is a problem of increased quantity. In addition, a control device that performs speed matching of the two drive sources during the conveyance of the paper and stops driving when a paper jam occurs is required, and the control configuration becomes complicated.
[0006]
Further, in the apparatus disclosed in Japanese Patent Laid-Open No. 63-112326, even when the sheet is conveyed only by the reversing apparatus, the conveyance roller of the re-conveyance apparatus rotates, and an extra load is applied to the drive source. Will be added. For this reason, useless power consumption at the time of paper conveyance increases.
[0007]
The present invention has been made in consideration of the above circumstances, and is excellent in cost while having a simple control configuration when performing reversal of an image forming target sheet and re-conveying to an image forming apparatus. An object of the present invention is to provide an image forming target sheet conveying apparatus in an image forming apparatus capable of reducing power consumption.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, an image forming target sheet conveying device in an image forming apparatus according to the present invention includes:
A reverse conveyance path through which an image forming target sheet on which an image is formed on one side by an image forming apparatus can enter;
A double-sided conveyance path for guiding the image forming target sheet to the image forming apparatus in order to form an image on the other side of the image forming target sheet;
Provided in the reverse conveyance path, the image formation target sheet fed from the image forming apparatus is conveyed by rotating forward, and reversely rotated after the image formation target sheet has entered the reverse conveyance path. A reversing roller that feeds the image forming target sheet toward the double-sided conveyance path,
A double-sided conveyance roller that conveys the image forming target sheet sent to the double-sided conveyance path by the reverse roller toward the image forming apparatus;
A drive source capable of switching the direction of rotation in the forward and reverse directions and capable of rotating the reverse roller and the double-sided transport roller forward or backward; and
Drive force transmission restricting means for restricting transmission of the drive force generated by the drive source to the duplex conveying roller when the drive source is rotating forward is provided.
[0009]
According to this configuration, the image forming target sheet on which the image is formed on one surface by the image forming apparatus is temporarily stored in the reverse conveyance path. Thereafter, when the reversing roller rotates in the reverse direction, the image forming target sheet in the reversing conveyance path is fed out from the reversing conveyance path with the front and rear ends reversed from when it is stored, and the image forming target sheet is reversed. The image forming target sheet reversed in this way is conveyed toward the image forming apparatus by the double-sided conveyance roller in the double-sided conveyance path, and an image is formed on the other side. In this apparatus, the reversing roller that reverses the image forming target sheet and the double-sided transport roller that transports the image forming target sheet toward the image forming target sheet are driven by the same drive source. Manufacturing cost and power consumption can be reduced as compared with the case of driving with a drive source. Further, a complicated control device such as speed matching of the reversing roller and the duplex conveying roller is not required.
[0010]
Further, when the reversing roller is rotating forward, that is, when the sheet to be image-formed is sent toward the double-sided conveyance path, the transmission of the driving force to the double-sided conveyance roller is restricted by the driving force transmission restricting means. That is, when the image forming target sheet is not fed into the double-sided conveyance path, the double-sided conveyance roller is stopped, so that the load on the driving source can be reduced and the power consumption can be reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
A. Image Forming Unit First, FIG. 1 shows an example of an image forming apparatus including an image forming target sheet conveying apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a photosensitive drum as an image carrier. Around the photosensitive drum 1, a charging corotron 2, a developing device 3, a transfer roll 4, a cleaner 5, and a charge eliminating roll 6 are disposed. The photosensitive drum 1 is rotated in the direction indicated by the arrow in the figure, and accordingly, the surface of the photosensitive drum 1 is uniformly charged by the charging corotron 2.
[0012]
Thereafter, light from a mirror of the image reading device (not shown), a latent image writing device or the like is irradiated onto the photosensitive drum 1. As a result, a latent image corresponding to an image to be formed on a sheet S such as paper or an OHP sheet conveyed by a conveyance mechanism described later is written on the surface of the photosensitive drum 1. Then, a toner image which is a visible image is formed by electrostatically attaching the toner supplied from the developing device 3 to the latent image.
[0013]
A sheet S is conveyed between the photosensitive drum 1 and the transfer roll 4 by a conveyance mechanism described later. Then, the toner image on the photosensitive drum 1 is electrostatically transferred to the sheet S by the electric field generated by the transfer roll 4. Note that a broken line in FIG. 1 indicates a path along which the sheet S is conveyed.
[0014]
Thereafter, the sheet S is conveyed to the heat fixing device 22. The heat fixing device 22 includes a heat roll 22a and a pressure roll 22b arranged substantially in parallel with each other, and the toner image is heated and pressed by allowing the sheet S to pass through the nip therebetween. And fixing on the sheet S. On the other hand, the toner remaining on the photosensitive drum 1 without being transferred to the sheet S is removed by a cleaner 5 such as a blade, and thereafter, the surface of the photosensitive drum 1 is removed from the static eliminating roll 6 for the image forming process again. To remove static electricity.
[0015]
Reference numerals 30, 31, 32, and 33 denote sheet storage trays that initially store the sheets S. From any one of the sheet storage trays 30, 31, 32, 33, the sheet S is pulled out toward the main conveyance path 34. A plurality of pairs of conveyance rollers 35 and a pair of registration rolls 37 are arranged in the main conveyance path 34, so that the sheet S is directed toward the nip between the photosensitive drum 1 and the transfer roll 4. Are transported.
[0016]
Reference numeral 38 denotes a manual feed tray extending outside the cabinet of the image forming apparatus. Also from the manual feed tray 38, the sheet S is introduced into the main conveyance path 34 by the roll 38 a and conveyed toward the registration roll 37.
[0017]
A conveyance roller 46 that conveys the sheet S to the discharge tray 45 or the reverse conveyance unit 50 that extends outside the cabinet of the image forming apparatus is disposed downstream of the heat fixing device 22.
[0018]
On the downstream side of the transport roller 46, a switching gate 51 is provided for switching the transport path so that the sheet S on which an image is formed as described above is sent to either the discharge tray 45 or the reverse transport unit 50. ing. When the sheet S is discharged to the discharge tray 45, the sheet S is advanced along the conveyance path 56 by the switching gate 51 and discharged to the discharge tray 45 by the discharge roller 47. On the other hand, when images are formed on both sides of the sheet S, the sheet S is advanced along the conveyance path 57 by the switching gate 51 and conveyed into the reverse conveyance unit 50.
[0019]
B. The reverse conveyance unit and the double-sided conveyance unit and the reverse conveyance unit 50 have a reverse conveyance path 52 that can accommodate the length in the conveyance direction of the maximum size sheet S handled by the image forming apparatus. A plurality of pairs of reverse rollers 53 are disposed in the reverse conveyance path 52. The reverse roller 53 conveys the sheet S conveyed to the reverse conveyance path 52 by the conveyance roller 46 downward. At this time, the sheet S advances by pushing the elastic member 51a. When the sheet S reaches a predetermined position, the reverse roller 53 is temporarily stopped.
[0020]
Thereafter, the reverse roller 53 rotates in the reverse direction and pulls up the sheet S toward the upper side of the reverse conveyance path 52. At this time, the front end portion of the sheet S abuts against the elastic member 51a, the traveling direction is restricted, and the sheet S is sent out toward the double-sided conveyance unit 60 side. When the sheet S is reversed and then discharged to the discharge tray 45, the sheet S is sent out along the conveyance path 58 and discharged to the discharge tray 45 by the discharge roller 47.
[0021]
The sheet S sent out from the reverse conveyance unit 50 toward the double-sided conveyance unit 60 proceeds in the double-sided conveyance path 61. A plurality of pairs of conveyance rollers 62 are arranged in the double-sided conveyance path 61, and by these, the sheet S is conveyed to the left side in the drawing and sent out toward the main conveyance path 34.
[0022]
Next, the driving mechanism for the reversing roller 53 and the conveying roller 62 will be described with reference to FIG. In the figure, reference numeral 70 denotes a stepping motor as a drive source. The stepping motor 70 is a motor whose rotation direction and rotation speed are variable. A gear 71 is attached to the rotation shaft of the stepping motor 70, and the gear 71 is engaged with the idler gear 73. On the other hand, gears 72 are respectively attached to the rotation shafts of the reversing rollers 53, and these gears 72 are engaged with idler gears 74 and 75 engaged with an idler gear 73. With this configuration, the driving force of the stepping motor 70 is transmitted to the reverse roller 53 so that the reverse roller 53 rotates.
[0023]
An idler gear 80 is meshed with the gear 71 attached to the rotating shaft of the stepping motor 70, and an idler gear 81 having a smaller pitch circle than the idler gear 80 is attached coaxially with the idler gear 80. The idler gear 81 is meshed with the gear 82. With this configuration, the gear 82 rotates as the stepping motor 70 rotates.
[0024]
Here, FIG. 3 is a view taken along line III-III in FIG. As shown in the drawing, a rotation shaft 65 of a conveyance roller (double-side conveyance roller) 62 a disposed on the upstream side of the double-side conveyance path 61 is connected to a gear 82 via a one-way clutch (driving force transmission regulating means) 83. The gear 82 and the rotary shaft 65 are connected when the stepping motor 70 rotates clockwise in FIG. As a result, the transport roller 62a rotates as the gear 82 rotates. That is, the driving force of the stepping motor 70 is transmitted to the transport roller 62a, and the transport roller 62a rotates. When the stepping motor 70 rotates counterclockwise in FIG. 2, the gear 82 and the rotating shaft 65 are not connected, and the gear 82 rotates freely with respect to the rotating shaft 65. Note that the shaft to which the gear 82 is attached and the rotary shaft 65 may be connected by a one-way clutch joint.
[0025]
Further, the above-described transport roller 62a and the left transport roller 62b in FIG. As described above, the reverse roller 53 and the transport rollers 62 a and 62 b are driven by the single stepping motor 70.
[0026]
C. Control System Next, a control system for the reverse conveyance unit 50 and the double-side conveyance unit 60 will be described with reference to FIG. As shown in the figure, the control system includes an inversion sensor 54, a control unit 90, and an excitation distribution circuit 91.
[0027]
The reverse sensor 54 is disposed on the side of the upper portion of the reverse conveyance path 52 shown in FIG. The inversion sensor 54 detects the presence or absence of the sheet S on the side, and outputs the detection result to the control unit 90 shown in FIG.
[0028]
The control unit 90 includes a CPU 92 connected to a CPU (not shown) of the image forming apparatus main body, a ROM 93 in which basic programs necessary for sheet conveyance control of the reverse conveyance unit 50 and the double-side conveyance unit 60 are stored, and the above-described control unit 90. A RAM 94 that captures a detection result from the reversing sensor 54 and the like, and generates a pulse signal based on the information input by the user and the detection result of the reversing sensor 54. This pulse signal is input to the excitation distribution circuit 91, and an excitation current based on the pulse signal is supplied to the stepping motor 70. In this way, the rotation direction, rotation angle, and rotation speed of the stepping motor 70 are controlled.
[0029]
D. Next, the operations of the reversing conveyance unit 50 and the double-sided conveyance unit 60 will be described. In the present embodiment, the user can select a double-sided image forming mode in which images are formed on both sides of the sheet S and a reverse discharge mode in which the sheet S is reversed and then discharged. The mode will be described.
[0030]
D-1. Double-sided image forming mode First, when the user selects the double-sided image forming mode, the selection information is input to the control unit 90 from the CPU of the main body of the image forming apparatus. Then, the stepping motor 70 is rotated in the arrow direction (counterclockwise) in FIG. As a result, the reverse roller 53 is also rotated in the direction of the arrow via the gear 71 and idler gears 73, 74, and 75, and the sheet S on which an image is formed is conveyed toward the lower side of the reverse conveyance path 52.
[0031]
At this time, the driving force of the stepping motor 70 is transmitted to the gear 82 via the idler gears 80 and 81. In this case, the one-way clutch 83 and the rotating shaft 65 are not connected, so the transport roller 62a rotates. do not do.
[0032]
When the sheet S is no longer detected by the reversing sensor 54 after the front end in the conveying direction of the sheet S traveling downward in the reverse conveying path 52 is detected, that is, the rear end of the sheet S is reversed. The stepping motor 70 temporarily stops after a predetermined time has elapsed from when it has passed the side of the sensor 54. Here, the predetermined time is stored in the control unit 90 in advance, so that the rear end of the sheet S stops at the position indicated by the arrow A in FIG.
[0033]
Thereafter, the stepping motor 70 is rotated in the direction of the arrow in FIG. 6 (clockwise) by the control of the control unit 90, whereby the reversing roller 53 is also rotated in the direction of the arrow via the gear 71 and idler gears 73, 74, 75. . In addition, the driving force of the stepping motor 70 is transmitted to the gear 82 via the idler gears 80 and 81. In this case, since the gear 82 and the rotating shaft 65 are connected by the one-way clutch 83, the transport roller 62a rotates in the direction of the arrow, and the transport roller 62b also rotates accordingly.
[0034]
In this way, when the stepping motor 70 rotates clockwise, the transport rollers 62 a and 62 b are driven in addition to the reverse roller 53. For this reason, the load on the stepping motor 70 increases, but in this embodiment, as shown in FIG. 7, the stepping motor 70 is made slower by rotating the rotational speed of the stepping motor 70 counterclockwise. The output torque of 70 is increased.
[0035]
Then, the sheet S is conveyed upward by the reverse roller 53 with the front and rear ends reversed. Then, when the front end portion of the sheet S abuts against the elastic member 51 a, the traveling direction is restricted, and the sheet S is conveyed toward the double-sided conveyance unit 60.
[0036]
Thereafter, the sheet S is sent to the main transport path 34 by a plurality of pairs of transport rollers 62, and is transported toward the nip between the photosensitive drum and the transfer roll 4 by the transport rollers 35 and the registration roll 37. Then, an image is formed on the other surface of the sheet S.
[0037]
D-2. On the other hand, when the user selects the reverse discharge mode, the selection information is input to the control unit 90 from the CPU of the image forming apparatus main body. Then, as in the image forming mode, the sheet S is transported downward of the reverse transport path 52.
[0038]
Then, the stepping motor 70 is temporarily stopped after a predetermined time has elapsed since the rear end of the sheet S has passed the side of the reversing sensor 54. In the reverse discharge mode, the control unit 90 stops the stepping motor 70 so that the rear end portion of the sheet S stops at the position indicated by the arrow B in FIG.
[0039]
Thereafter, the stepping motor 70 rotates clockwise under the control of the control unit 90, and the reversing roller 53 rotates clockwise accordingly. As a result, the sheet S is conveyed upward with its front and rear ends reversed. At this time, since the rear end portion of the sheet S is located above the elastic member 51a (position indicated by the arrow B), the traveling direction is not restricted by the elastic member 51a, and along the conveyance path 58. It advances and is discharged to the discharge tray 45.
[0040]
E. Effect In this embodiment, since one stepping motor 70 is structured to drive the reversing roller 53 and the conveying rollers 62a and 62b, it is manufactured in comparison with a conventional apparatus in which the reversing roller and the conveying roller are driven by different motors. Costs can be suppressed and power consumption during use can be reduced. In addition, the conventional device requires a control device that performs speed matching between two motors, stops driving when a paper jam occurs, and the like, but does not require such a control device in the present embodiment.
[0041]
Further, when the stepping motor 70 is rotating counterclockwise, that is, when the sheet S is being conveyed downward in the reverse conveyance unit 50, the conveyance rollers 62a and 62b are not interlocked with the stepping motor 70. Further, an extra load is not applied to the stepping motor 70, and the power consumption during sheet conveyance can be reduced.
[0042]
On the other hand, when the stepping motor 70 is rotating in the clockwise direction, the number of rollers to be rotated increases. However, by reducing the rotation speed as described above, each roller can be conveyed without using a large motor. The force drop can be suppressed.
[0043]
In the above-described embodiment, the stepping motor 70 is configured to drive only the conveyance rollers 62a and 62b of the double-side conveyance unit 60. However, the stepping motor 70 is configured to drive the other conveyance rollers 62 shown in FIG. Also good.
[0044]
【The invention's effect】
As described above, according to the present invention, a complicated control system is not required when the image forming target sheet is reversed and re-conveyed to the image forming apparatus. In addition, the cost is excellent and the power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an image forming apparatus including an image forming target sheet conveying apparatus according to an embodiment of the invention.
FIG. 2 is a diagram illustrating the vicinity of a reverse conveyance unit and a double-side conveyance unit of the image forming apparatus.
3 is a view taken along line III-III in FIG. 2;
FIG. 4 is a block diagram illustrating a configuration of a control system for a reverse conveyance unit and a double-side conveyance unit in the image forming apparatus.
FIG. 5 is a diagram illustrating a state when a sheet is conveyed into a reverse conveyance path of the reverse conveyance unit.
FIG. 6 is a diagram illustrating a state when a sheet is conveyed from the reverse conveyance path of the reverse conveyance unit toward the double-sided conveyance unit.
FIG. 7 is a diagram illustrating a relationship between a motor rotation speed and an output torque of the image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 45 ... Discharge tray, 50 ... Reverse conveyance part, 51 ... Switching gate, 52 ... Reverse conveyance path, 53 ... Reverse roller, 60 ... Double-sided conveyance part, 61 ... Double-sided conveyance path, 62 ... Conveyance roller, 62a ... conveying roller (double-sided conveying roller), 70 ... stepping motor (drive source), 71, 72, 82 ... gear, 74, 73, 75, 80, 81 ... idler gear, 83 ... one-way clutch (driving force transmission restricting means) )

Claims (1)

A reverse conveyance path through which an image forming target sheet on which an image is formed on one side by an image forming apparatus can enter;
A double-sided conveyance path for guiding the image forming target sheet to the image forming apparatus in order to form an image on the other side of the image forming target sheet;
Provided in the reverse conveyance path, the image formation target sheet fed from the image forming apparatus is conveyed by rotating forward, and reversely rotated after the image formation target sheet has entered the reverse conveyance path. A reversing roller that feeds the image forming target sheet toward the double-sided conveyance path,
A double-sided conveyance roller that conveys the image forming target sheet sent to the double-sided conveyance path by the reverse roller toward the image forming apparatus;
A drive source capable of switching the direction of rotation in the forward and reverse directions and capable of rotating the reverse roller and the double-sided transport roller forward or backward; and
Driving force transmission regulating means for regulating transmission of the driving force generated by the driving source to the double-sided conveying roller when the driving source is rotating forward,
The drive source is a drive source having a variable rotation speed, and the rotation speed of the drive source during reverse rotation of the reversing roller is made slower than the rotation speed of the drive source during normal rotation of the reversing roller. An image forming target sheet supply device in an image forming apparatus.

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