JP3915399B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to an apparatus having a double-sided conveyance mechanism.
[0002]
[Prior art]
The image forming apparatus can mount a double-sided conveyance mechanism (double-sided unit) on the main body in order to provide a double-sided copy function.
[0003]
Japanese Patent Application Laid-Open No. 9-136772 discloses a technique in which when a duplex unit is mounted on a main body, the driving source of the reversing roll is switched to the duplex unit side. In such a conventional technique, when normal one-side printing is performed by an apparatus equipped with a duplex unit, the reversing roll is driven by the second drive source on the duplex unit side even though it rotates only in the normal rotation direction. Therefore, the two driving sources always operate simultaneously. Therefore, there is a problem that noise is large, power consumption is large, and the second driving source has a large number of times of driving, so that heat generation is large. Further, since the arrangement of the gear train is switched in accordance with the double-sided unit, it is difficult to maintain the gear meshing accuracy, which causes a problem of image quality such as banding.
[0004]
A technique is also known in which a plurality of electromagnetic clutches are used to constitute a drive source with a single device. In this case, the reversing speed cannot be set freely and the electromagnetic clutch that consumes a large amount of power is always energized, resulting in a problem of increased power consumption.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to operate an inversion drive source (second drive source) only when paper is reversed in an image forming apparatus capable of performing copying on both sides of the paper, thereby reducing noise and saving power consumption. At the same time, it is to provide a technique capable of suppressing the heat generation amount of the second drive source, maintaining the safety of the peripheral portion, and reducing the cost of the mechanical parts on the apparatus main body side.
[0006]
Another object of the present invention is to keep the gear train on the main body side and the reverse gear train in a meshed state without being separated, maintain the gear meshing accuracy, and suppress the occurrence of banding.
[0007]
[Means for Solving the Problems]
The present invention includes an image forming unit that forms an image on a sheet ;
A paper transport mechanism you send transportable said sheet on which an image is formed,
And an image forming apparatus main body having a first driving source for driving the paper transport mechanism,
A double-sided conveyance unit having a second drive source and detachable from the image forming apparatus body ;
In an image forming apparatus having
The paper transport mechanism includes a discharge roll for discharging the paper to the outside of the image forming apparatus,
The discharge roller, when carrying the sheet in the discharging direction is driven in the forward direction by the first drive source, when transporting the paper reversing direction, as driven by the second drive source configured to,
The first gear train from the discharge roll to the first drive source and the second gear train from the discharge roll are always meshed,
While providing a clutch in the second gear train in the duplex conveying unit,
When the driving force is transmitted from the second driving source, the merging portion of the first gear train and the second gear train releases the driving force transmitted from the first driving source. An image forming apparatus characterized by the above.
[0008]
The first gear train preferably includes a series that rotates the discharge roller in a forward direction at least via a heating roll gear, and the merging is performed in the gear train from the merging portion to the second drive source. Provided is an image forming apparatus provided with a rotation delay device for operating transmission and release of driving force in a section .
[0009]
The discharge roll may be configured by the same unit as a fixing unit housing including a fixing roll and a pressure roll. The merging portion is a spring clutch gear, and the first gear train from the discharge roll to the first drive source and the second gear train from the discharge roll to the second drive source are always in mesh. An image forming apparatus is preferable. This can be realized, for example, by interposing a rotation delay device for operating on / off of the spring clutch in the gear train from the spring clutch gear to the second drive source.
[0010]
If the discharge roll is configured in the same unit as the fixing unit casing including the fixing roll and the pressure roll, a compact design can be achieved.
[0011]
Wherein a spring clutch gear and the input gear shaft and the output gear shaft, said input gear and said output gear and two axes coaxial, tightening of the coil spring via the coil spring, the clutch of the spring clutch by loosening and freely off, a control gear for operating the spring clutch to turn-off directions to provide an image forming apparatus having a rotation delaying device equipped control gear for operating the control gear.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 6 is an explanatory diagram showing the entire image forming apparatus 100 to which the present invention is applied. The image forming apparatus 100 applies static electricity from the electrostatic roll 104 to the photosensitive drum 102 to charge it, and irradiates light such as laser from the exposure apparatus 106 to form a latent image on the photosensitive drum 102, and develops the developing device. The powder is supplied by the developing roll 110 and an image appears on the photosensitive drum 102. The paper supplied through the paper supply path 126 is passed between the photosensitive drum 102 and the transfer roll 112 to transfer the image onto the paper, and then the fixing roll 114 fixes the image on the paper. In the paper supply path, the paper is pulled out from the paper feed cassette 120, advanced by the feed rolls 122 and 124, positioned by the registration roll 126, and passed between the photosensitive roll 102 and the transfer roll 112 via the paper supply path 128 at the paper feed timing. To supply. The paper onto which the image has been transferred is fixed by the fixing roll 114 and discharged by the discharge roll 140. Reference numerals 130 and 132 denote paper feed levers. The present invention provides an invention characterized by the thermal fixing device 150 of the image forming apparatus 100.
[0014]
FIG. 5 shows an example of the prior art in which a duplex unit for duplex copying is mounted on the main body. The paper transport mechanism is driven by the first drive source 10 of the main body together with the drive of the image forming means. The gear 80 in the gear train that rotates the paper discharge roll gear 26 is in mesh with the first drive source by the swing arm 82. In order to switch this to the reversing drive source (second drive source 50), the swing arm 82 is swung to switch to the position shown by the gear 80a and the swing arm 82a. At this time, the first driving source 10 drives the image forming means, and the second driving source 50 performs reverse rotation driving of the paper discharge device. For this reason, it is necessary to operate the second drive source 50 even in the case of single-sided printing, and there are problems such as an increase in noise and electric power, and a reduction in gear meshing accuracy due to gear switching.
[0015]
1 to 4 show an embodiment of the present invention, and FIG. 1 is a schematic side view of a gear train showing a developed gear train. In FIG. 1, a main motor 10 that is a first drive source rotates a spring clutch input gear 18 via an idler 12, a heating roll gear 14, and a decurler roll gear 16. The spring clutch input gear 18 rotates a discharge roll gear 26 through a coaxial output gear 20 and an idler 22. The paper 40 is discharged through the nip between the discharge roll 27 and the idler 28. At this time, the gears 14, 16, and 18 always rotate forward in the same direction.
[0016]
On the other hand, a detachable duplex conveying unit 60 is attached. In the double-sided conveyance unit 60, a second drive source 50 that is a reverse drive source is connected to the other gear 24 of the spring clutch via idlers 52 and 54, an electromagnetic clutch 56, and an operation gear 58. The electromagnetic clutch 56 is engaged only when the discharge roll gear 26 is driven in reverse. In FIG. 1, an arrow indicated by a solid line indicates the rotation direction of each gear during normal rotation, and an arrow indicated by a chain line indicates the rotation direction of each gear during reverse rotation.
[0017]
FIG. 2 is a front view of the gear train shown in FIG. As shown in FIG. 2, the spring clutch input gear 18 is rotated through the heating roll gear 14 and the decurler roll gear 16, and rotates the discharge roll gear 26 through the idler 22. This is as indicated by the arrow of the normal rotation transmission path 62. On the other hand, the rotation from the second drive source rotates the output gear 22 of the spring clutch via the operation gears 58 and 58a via the electromagnetic clutch 56. This is indicated by the arrow in the reverse transmission path 64.
[0018]
As shown in FIGS. 1 and 2, the double-sided conveyance unit 60 is detachable. However, in the present invention, it is not necessary to disengage the main body side gear train. It is preferable that the fixing unit housing unit 90 is constituted by the same unit as the fixing unit housing including the roll, and the gear train is integrally incorporated therein. As a result, the gear train mounting accuracy and mounting portion rigidity can be further improved.
[0019]
FIG. 3 is a sectional view of the gear device of the spring clutch. When the boss of the spring clutch input gear 18 and the boss of the spring clutch output gear 20 are formed of coaxial cylinders and are fitted to each other, they are integrated by coupling via the coil spring 19 and the coupling of the coil spring 19 is released. It has become a separate body. The coil spring 19 is interposed between the boss of the spring clutch input gear 18 and the spring retainer 21 screwed into the boss of the spring clutch output gear. The control gear 24 of the spring clutch is fitted coaxially with the input gear 18 and the output gear 20 on the outer diameter of the coil spring 19. The control gear 24 meshes with the operation gear device 58. When the operation gear device 58 is stationary, the control gear 24 biases the coil spring 19 in the tightening direction, and the input gear 18 and the output gear 20 are It is coupled via a spring 19. That is, the spring clutch is clutch-on. Accordingly, the forward rotation of the input gear 18 is transmitted to the output gear 20 as it is, and the output gear 20 is also rotating forward. The operation gear device 58 is provided with a rotation transmission gear 59 coaxially, and this rotation transmission gear 59 is always meshed with the spring clutch output gear 20. When the output gear 20 rotates in the forward direction, the electromagnetic clutch 56 is disengaged and the rotation transmission gear 59 is idle.
[0020]
When the electromagnetic clutch 56 is turned on to rotate the operation gear device 58 in the reverse rotation direction, the operation gear device 58 rotates the control gear 24 in the reverse direction, and the control gear 24 acts in the direction of loosening the spring 19 to output the input gear 18 and the output gear 18. The edge of the gear 20 is cut. That is, the spring clutch is turned off. In this state, the reverse rotation transmission gear 59 applies reverse rotation to the output gear 20.
[0021]
FIG. 4 shows a mechanism for tightening the spring 19 when the operation gear device 58 imparts rotation in the reverse direction to the control gear 24 of the spring clutch. The operation gear device 58 is provided with a protrusion 70 on the outer periphery of the rotation drive shaft, and a play 72 is provided on the inner diameter of the gear so that the protrusion 70 can move by a certain central angle in the rotation direction. This play 72 forms a rotation delay device that acts to delay the transmission of rotation at the time of starting to rotate the shaft in the forward or reverse direction. For example, in the state shown in FIG. 4, when the shaft is rotated in the direction indicated by the arrow 74, the gear starts to rotate with a delay of the play 72. Both the rotational delays are determined by the size of the play 72, and the size of the play varies depending on the design of the clutching operation by tightening and loosening the coil spring of the spring clutch, but is usually designed to be about 30 degrees at the center angle. It is possible.
[0022]
As is clear from the above description, in the gear train of the present invention, all the forward and reverse gears are always meshed, and it is not necessary to release the meshing of the gears. Therefore, there is no factor that impairs the meshing accuracy of the gear, and no gear play or abnormal wear occurs.
[0023]
【The invention's effect】
The present invention has the following effects.
(A) Since the second drive source operates only when the paper is reversed, noise can be reduced and power consumption can be reduced. In addition, the safety of the peripheral portion can be maintained by suppressing the amount of heat generated by the second drive source.
(B) Since the gear train is always meshed, meshing accuracy can be maintained and occurrence of banding can be suppressed.
(C) Since no electromagnetic clutch or the like is used on the apparatus main body side, the mechanical parts are inexpensive, and since the electromagnetic clutch is not always used, the amount of power used can be reduced.
[Brief description of the drawings]
FIG. 1 is a development view of a gear train of an embodiment.
FIG. 2 is a front view of the gear train of the embodiment.
FIG. 3 is a diagram illustrating the principle of a spring clutch gear.
FIG. 4 is an explanatory view showing a rotation delay mechanism.
FIG. 5 is a development view of a gear train showing an example of a conventional gear train.
FIG. 6 is an overall explanatory diagram of an image forming apparatus.
[Explanation of symbols]
10 First drive source (main motor)
12 idler 14 heating roll gear 16 decurler roll gear 18 spring clutch input gear 19 spring 20 spring clutch output gear 21 spring restraint 22 idler 24 spring clutch control gear 26 discharge roll gear 27 discharge roll 28 idler 40 paper 50 second drive Sources 52, 54 Idler 56 Electromagnetic clutch 58 Operation gear 59 Transmission gear 60 Double-sided conveyance unit 62 Forward rotation transmission path 64 Reverse rotation transmission path 70 Protrusion 72 Play 74 Arrow 80 Gear 82 Swing arm 90 Fixing unit housing unit 100 Image forming apparatus 102 Photosensitive drum 104 Electrostatic roll 106 Exposure device 108 Developing device 110 Developing roll 112 Transfer roll 114 Fixing roll 120 Paper feed cassette 122, 124 Feed roll 126 Registration roll 128 Paper supply path 30,132 sheet delivery lever 140 discharge roller 150 thermal fixing device

Claims (6)

Image forming means for forming an image on paper ;
A paper transport mechanism you send transportable said sheet on which an image is formed,
And an image forming apparatus main body having a first driving source for driving the paper transport mechanism,
A double-sided conveyance unit having a second drive source and detachable from the image forming apparatus body ;
In an image forming apparatus having
The paper transport mechanism includes a discharge roll for discharging the paper to the outside of the image forming apparatus,
The discharge roller, when carrying the sheet in the discharging direction is driven in the forward direction by the first drive source, when transporting the paper reversing direction, as driven by the second drive source configured to,
The first gear train from the discharge roll to the first drive source and the second gear train from the discharge roll are always meshed,
While providing a clutch in the second gear train in the duplex conveying unit,
When the driving force is transmitted from the second driving source, the merging portion of the first gear train and the second gear train releases the driving force transmitted from the first driving source. An image forming apparatus. The image forming apparatus according to claim 1, wherein the first gear train includes a series in which the discharge roller is rotated forward through at least a heating roll gear . 3. The image according to claim 1 , wherein a rotation delay device for operating transmission and release of driving force in the merging portion is interposed in a gear train from the merging portion to the second driving source. Forming equipment. The image forming apparatus according to claim 1 , wherein the discharge roll is configured by the same unit as a fixing unit housing including a fixing roll and a pressure roll . The image forming apparatus according to claim 1 , wherein the merging portion is a spring clutch gear . Wherein a spring clutch gear and the input gear shaft and the output gear shaft, said input gear and said output gear and two axes coaxial, tightening of the coil spring via the coil spring, the clutch of the spring clutch by loosening and freely off, a control gear for operating the spring clutch to turn-off both directions, the image forming apparatus according to claim 5, wherein further comprising a rotation delaying device equipped control gear for operating the control gear.

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