JP3984709B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device.
[0002]
[Prior art]
In the conventional fixing device, since the image forming apparatus has been reduced in size, when the transfer material as a recording medium enters the fixing device, the transfer material vibrates due to the impact. Since the rear end of the transfer material does not pass through the transfer charger, transfer deviation may occur. In order to prevent this, as described in Japanese Patent Application Laid-Open No. 08-241008, a fixing device uses a flywheel as a hand throw to improve the image quality by keeping the rotation speed of a fixing roller as a fixing member constant. Those using a control member having a large inertial force such as the above are known and put into practical use.
[0003]
In this fixing device (fixing device 118), as shown in FIG. 10, a flywheel 133 and a gear G106 are fixed on a rotation shaft 132, and rotation of the fixing roller 118a is transmitted via gears G105, G106 and a shaft 132. It is transmitted to the flywheel 133.
[0004]
The flywheel 133 has an appropriate size according to conditions such as the size of the fixing roller 118a and the pressure roller 118b in order to give sufficient inertial force to the fixing roller 118a and the pressure roller 118b.
[0005]
The fixing roller 118a is electrically driven by turning off a fixing clutch (not shown) at the time of completion of copying or a jam at the fixing portion (pressure contact portion between the fixing roller 118a and the pressure roller 118b). The drive transmission of a motor (not shown) is released, and the motor is stopped while being naturally decelerated by the rotational resistance of the fixing roller 118a itself.
[0006]
[Problems to be solved by the invention]
However, since the fixing device 118 is configured to stop while naturally decelerating due to the rotational resistance of the fixing roller 118a itself, the stop distance increases correspondingly if the inertial force of the flywheel 133 is large. .
[0007]
As a result, for example, when the transfer material P is jammed at the leading end 144b of the separation claw 144, the fixing roller 118a continues to rotate due to inertial force even when the driving to the fixing roller 118a is released. There is a possibility that problems such as breakage of the pressure roller 118b may occur due to the claw 144 being pressed by the transfer material P in the rotation direction of the pressure roller 118b.
[0008]
Further, the transfer material P that has jammed in the fixing device 118 is wound inside by the rotation of the fixing roller 118a and enters the inside of the machine due to tearing of the transfer material, etc., and jam processing (removing the accumulated transfer material) is performed. There was a risk of becoming impossible.
[0009]
In recent years, as the image forming apparatus is downsized and more stable image quality is required, the use of a large control member such as a flywheel is inevitable in order to keep the fixing roller rotating speed constant. When the transfer material stays, the above-described problem may be further increased.
[0010]
Accordingly, an object of the present invention is to provide a fixing device that can stop the rotation of the fixing body quickly with an inexpensive and simple structure.
[0011]
[Means for Solving the Problems]
According to the present invention, the above object can be achieved. The present invention relates to a rotatable fixing body, a driving means for rotationally driving the fixing body, an inertia applying means for increasing the inertial force of the fixing body, and a jam of a recording medium in the fixing device to stop the rotation of the fixing body. And a disengagement means for releasing the engagement between the inertia applying means and the fixing body when a jam of the recording medium is detected by the sensor,
In order to shift to the standby state in accordance with the jam processing, the fixing body is rotated, and when the presence or absence of the jam processing is confirmed by the sensor, the engagement between the inertia applying means and the fixing body is released. It is.
[0019]
That is, in the first invention according to the present application, the disengagement unit releases the engagement between the inertia applying unit and the fixing body.
[0020]
In the second invention according to the present application, the electromagnetic clutch releases the engagement between the inertia applying means and the fixing body.
[0021]
Further, in the third invention according to the present application, when the recording medium stays in the fixing device, the engagement releasing means releases the engagement between the inertia applying means and the fixing body.
[0022]
In the fourth invention according to the present application, when the recording medium stays in the fixing device, the driving means releases the rotational drive to the fixing body.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5 of the accompanying drawings.
[0028]
(First embodiment)
First, an electrophotographic copying machine 10 as an example of an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
[0029]
1 is a cross-sectional view showing a schematic configuration of the copier 10, FIG. 2 is a cross-sectional view showing a schematic configuration of a main part of the copier 10 in FIG. 1, and FIG. 2 is a top view illustrating a schematic configuration of a fixing device 18 provided. FIG.
[0030]
As shown in FIG. 1, the copying machine 10 includes a drum-shaped photosensitive drum 1 on which an electrostatic latent image is formed on the outer peripheral surface, and a roller-shaped primary for charging the outer peripheral surface of the photosensitive drum 1 to a specified potential. The charger 2, the optical system 20, 21, 22, 23, 24, 25, 26, 50 that forms an electrostatic latent image on the outer peripheral surface charged to a specified potential by exposure, and the electrostatic latent image A developing device 3 that forms a visible image with a developer, a roller-shaped transfer charger 4 that transfers a visible image (visible image) formed on the outer peripheral surface to a transfer material P that is a sheet-shaped recording medium, and a fixing device 18. And.
[0031]
In the copying machine 10, a photosensitive drum 1 as a latent image carrier is rotatably supported in the copying machine 10, and a primary charger 2, a developing device 3, and a transfer charger around the photosensitive drum 1. 4, process equipment such as a separation charger 5 and a cleaner 6 are arranged.
[0032]
A toner hopper 7 for replenishing toner as a developer is installed above the developing device 3, and a plurality of transfer materials P are stacked and accommodated on one side (right side in FIG. 3) of the copying machine 10 main body. The sheet cassettes 11, 12, 13, and 14 are provided in four upper and lower stages.
[0033]
The transfer material P supplied from each of the paper feed cassettes 11, 12, 13, and 14 is conveyed in the copying machine 10 main body in the direction of the arrow shown in FIG. 16, a pre-fixing guide 17, a fixing roller 18a as a fixing body, and a pressure roller 18b. The pressure roller 18b has a surface layer portion formed of an elastic body.
[0034]
On the other hand, a lamp 20, a reflecting mirror 21, 22, 23, 24, 25, and 26, an optical lens 50, and the like constituting an optical system are arranged in the upper part of the copying machine 10 main body. Thus, when the original 51 set on the original placing table 301 provided on the upper surface of the copying machine 10 is read by the optical system and an optical image corresponding to the original is exposed on the photosensitive drum 1, primary charging is performed. An electrostatic latent image is formed on the photosensitive drum 1 whose surface is charged by the device 2, and the electrostatic latent image is developed by the developing device 3 and visualized as a toner image.
[0035]
On the other hand, the transfer material P is supplied from, for example, the paper feed cassette 11, and the transfer material P is fed to the transfer portion between the photosensitive drum 1 and the transfer charger 4 by the registration roller 15, and is transferred onto the photosensitive drum 1. The toner images formed on the toner image are transferred, and thereafter separated from the photosensitive drum 1 by the action of the separation charger 5.
[0036]
Then, the transfer material P separated from the photosensitive drum 1 is sent to the fixing device 18 by the belt conveying device 16, and is sandwiched between the fixing roller 18 a and the pressure roller 18 b of the fixing device 18 and passes through them, thereby being heated. Then, after the toner image is fixed by the pressure, it is discharged out of the apparatus main body 10 by the discharge roller 19.
[0037]
Next, a schematic configuration of the fixing device 18 will be described with reference to FIGS.
[0038]
The fixing device 18 includes a rotatable fixing roller 18a, a pressure roller 18b that is in pressure contact with the fixing roller 18a, an electric motor 27 that is a driving unit that rotationally drives the fixing roller 18a, and an inertia that increases the inertial force of the fixing roller 18a. It has a flywheel 33 as an applying means, and an electromagnetic clutch 61 (hereinafter referred to as a clutch 61) as an engagement releasing means for releasably engaging the flywheel 33 with the fixing roller 18a.
[0039]
The fixing roller 18 a provided in the fixing device 18 includes a fixing clutch 35 that transmits or cuts off (ON / OFF) the rotational force from the electric motor 27 to the fixing roller 18 a.
[0040]
The clutch 61 can switch the inertia force from the flywheel 33 to the fixing roller 18a to transmission (ON) or cutoff (OFF).
[0041]
As shown in FIG. 3, the fixing roller 18 a is rotationally driven by an electric motor 27 and is connected between a pulley 28 bonded to the output shaft end of the electric motor 27 and a pulley 30 bonded to one end of the rotating shaft 29. An endless drive belt 31 is wound, a gear G1 is bound to the other end of the rotating shaft 29, and a gear G4 is bound to one end of the rotating shaft 18a-1 of the fixing roller 18a. Has been.
[0042]
The gear G1 meshes with a gear G2 provided on the fixing clutch 35, and when the fixing clutch 35 is turned ON, the driving of the gear G2 is transmitted to the gear G3, and the gear G4 meshed with the gear G3 rotates. Let
[0043]
A large-diameter gear G5 is attached to the other end of the rotation shaft 18a-1 of the fixing roller 18a. The gear G5 is connected to a small-diameter gear G6 provided on the clutch 61 at one end of the rotation shaft 32. Meshed.
[0044]
The gear G6 engages with the rotary shaft 32 when the clutch 61 is ON, and a flywheel 33 is attached to the other end of the rotary shaft 32.
[0045]
In the copying machine 10, when the image forming operation is started, the electric motor 27 is driven, and the rotation of the electric motor 27 is transmitted to the rotating shaft 29 through the pulley 28, the driving belt 31, and the pulley 30.
[0046]
The rotation of the rotary shaft 29 is transmitted to the gear G1, the gear G2, and the gear G3 when the fixing clutch 35 is ON, and further transmitted to the fixing roller 18a via the gear G4, and the fixing roller 18a is rotationally driven at a predetermined speed. Then, it is used for fixing an unfixed toner image.
[0047]
The clutch 61 is turned on at the same time as the fixing clutch 35 is turned on. The rotational speed of the fixing roller 18a is accelerated by the gears G5 and G6 and transmitted to the rotary shaft 32.
[0048]
The flywheel 33 settled on the rotating shaft 32 is driven to rotate at a speed higher than that of the fixing roller 18a, so that the inertial force of the fixing roller 18a is increased, so that the rotational speed of the fixing roller 18a is not affected by disturbance. The image can be kept constant, the occurrence of image disturbance due to transfer deviation is suppressed, and a high-quality image can always be obtained.
[0049]
The transfer material P that has been subjected to the fixing process is normally separated from the fixing roller 18a by a separation claw 43 and a separation claw 44 that are rotatable about shafts 43a and 44a, and is discharged after passing through a jam detection sensor flag 40. When the fixing clutch 35 is turned off, the fixing roller 18a and the flywheel 33 are decelerated while rotating by inertia, and the clutch 61 is turned off.
[0050]
On the other hand, when the sensor 41 for detecting the transfer material P staying in the fixing device 18 (hereinafter referred to as jammed paper) detects the transfer material P staying in the fixing device 18, the fixing clutch 35 and the clutch 61 are simultaneously turned on. By turning OFF, the drive of the rotating shaft 32 and the gear G6 is cut off, and only the flywheel 33 and the rotating shaft 32 rotate with inertial force, so that the inertial force of the flywheel 33 is given to the rotation of the fixing roller 18a. Thus, the rotation of the fixing roller 18a can be stopped in a short time.
[0051]
Thus, as shown in FIG. 4, in the copying machine 10, when the transfer material P stays (claw jam) at the tip 43b of the separation claw 43, the separation claw 43 is fixed to the fixing roller by the transfer material P. It is possible to prevent the fixing roller 18a from being damaged or damaged by being pressed in the rotational direction of the 18a.
[0052]
Further, the copying machine 10 drives the fixing roller 18a immediately after the jam processing, first drives the electric motor 27 and then drives only the fixing clutch 35 for a certain period of time to check the presence or absence of jammed paper. After confirming that there is no paper, the fixing clutch 35 is turned off and the fixing roller 18a is stopped, and the clutch 61 is turned on to enter a standby state.
[0053]
As a result, the copying machine 10 rotates the fixing roller 18a while the flywheel 33 does not rotate, so that when the user forgets to remove the jammed paper, the sensor detects the jammed paper, and the fixing roller 18a The rotation can be stopped and the fixing roller 18a can be prevented from being damaged.
[0054]
Therefore, according to the present embodiment, since the clutch 61 releases the engagement between the flywheel 33 and the fixing roller 18a, the inertial force of the fixing roller 18a is reduced with an inexpensive and simple structure. The rotation of the fixing roller 18a can be quickly stopped without imposing a burden on the motor 27. When the transfer material P stays in the fixing device 18, the transfer material P is caught in the fixing roller 18a or the fixing roller 18a. Can be prevented.
[0055]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a top view showing a schematic configuration of the fixing device provided in the image forming apparatus according to the present embodiment. The same configurations as those in the first embodiment are denoted by the same reference numerals. The description is omitted.
[0056]
In the present embodiment, the configuration provided at both ends of the rotating shaft 18a-1 of the fixing roller 18a in the first embodiment is configured at one end of the rotating shaft 18a-1 by meshing the gear G6 with the gear G4. Therefore, when the installation space of the fixing device is limited, or when a very thin fixing roller is used in the future, it can be attached to the driving side of the fixing roller.
[0057]
The fixing roller currently used is a thick fixing roller with sufficient rigidity, so it can withstand twisting even if a flywheel is used on the side without a drive train, but it is thin and can withstand twisting. In the case of an incapable fixing roller, the twisting can be prevented by attaching it to the driving side.
[0058]
Also in this embodiment, when the sensor 41 detects jammed paper, the electromagnetic clutch 61 is turned off simultaneously with the fixing clutch 35, and the inertial force of the flywheel 33 is cut off, so that the fixing roller 18a is intentionally rotated. It can be stopped in a short time.
[0059]
In normal paper feeding, the fixing clutch 35 is turned off after the clutch 61 is turned off immediately after the final transfer material is discharged.
[0060]
In the present embodiment, when the sensor 41 detects jammed paper, the fixing clutch 35 and the clutch 61 are simultaneously turned off. However, an abnormality caused by jammed paper does not damage the fixing roller 18a. In the range, the fixing clutch 35 and the clutch 61 may not be turned off simultaneously.
[0061]
Therefore, according to the present embodiment, since the clutch 61 releases the engagement between the flywheel 33 and the fixing roller 18a, the inertial force of the fixing roller 18a is reduced with an inexpensive and simple structure. The rotation of the fixing roller 18a can be quickly stopped without imposing a burden on the motor 27. When the transfer material P stays in the fixing device 18, the transfer material P is caught in the fixing roller 18a or the fixing roller 18a. Can be prevented.
[0062]
【The invention's effect】
As described above, according to the present invention, when the recording medium is jammed in the fixing device, not only the rotation of the fixing member is quickly stopped but also the device is shifted to the standby state. The fixing member can be quickly stopped even when unprocessed jam (forgetting to remove the recording medium by the operator) is confirmed. Therefore, it is possible to effectively prevent the recording medium from being caught in the fixing member and the fixing member from being damaged.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.
2 is a schematic cross-sectional view illustrating a schematic configuration of a main part of the image forming apparatus in FIG. 1;
FIG. 3 is a schematic top view showing a schematic configuration of a fixing device provided in the image forming apparatus of FIG. 1;
FIG. 4 is a schematic diagram illustrating a state when a jam occurs in the main part of the image forming apparatus according to the first embodiment.
FIG. 5 is a schematic top view illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view illustrating a schematic configuration of a main part of a conventional image forming apparatus.
[Explanation of symbols]
10 Copying machine (image forming device)
18a Fixing roller (fixing body)
18 Fixing device 27 Motor (drive means)
33 Flywheel (Inertia imparting means)
61 Electromagnetic clutch (disengagement means)
P transfer material (recording medium)

Claims (1)

A rotatable fixing body, a driving means for rotationally driving the fixing body, an inertia applying means for increasing the inertial force of the fixing body, and a sensor for detecting a jam of the recording medium in the fixing device to stop the rotation of the fixing body And a disengaging unit that disengages the inertia applying unit and the fixing member when a jam of the recording medium is detected by the sensor,
The fixing device is characterized in that the engagement between the inertia applying means and the fixing member is released when the presence or absence of the jam processing is confirmed by a sensor by rotating the fixing member to shift to a standby state in accordance with the jam processing. apparatus.

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