JPH04238380A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention involves passing a transfer sheet onto which a toner image has been transferred, which is conveyed along a conveying path, through a pressure contact portion between a fixing roller and a pressure roller that is in pressure contact with the fixing roller, so that the toner image thereon is removed. The present invention relates to an image forming apparatus that forms images by fixing them.

0002

2. Description of the Related Art In an image forming apparatus such as a copying machine equipped with a fixing device having a pair of rollers, the quality of the entry of the transfer paper into the fixing nip has a significant effect on the occurrence of wrinkles in the fixing process. affect This is often due to a difference in the time it takes for the leading edge of the transfer paper to reach the nip on the left and right sides, or between the edge and the center.

[0003] In response to this problem, conventional copying machines etc.
This problem is solved by providing auxiliary mechanisms such as a vacuum fan and a conveyor belt on the upstream side of the fixing device (between the photoreceptor and the fixing device) to ensure conveyance stability.

However, even with this method, fixing wrinkles may occur because the transfer paper does not enter the nip accurately. Further, the above-mentioned auxiliary mechanism may be abolished due to cost reduction or the like.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the prior art and to provide an image forming apparatus that can reliably prevent the occurrence of fixation wrinkles.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a first aspect of the invention, in which a transfer paper having a toner image transferred thereon and conveyed on a conveyance path is connected to a fixing roller and a pressure applied thereto. In an image forming apparatus that forms an image by passing a toner image through a pressure contact portion with a pressure roller and fixing the toner image thereon,
The invention according to claim 2 is characterized in that a stopping means is provided for once stopping the leading edge of the transfer paper in a state parallel to the pressing part and then releasing the stop before the leading edge of the transfer paper passes the pressing part, In addition to the above, the fixing roller may be rotated by a driving means, and the stopping means may be configured to stop the fixing roller before the leading edge of the transfer paper reaches the pressure contact portion and rotate the fixing roller after the leading edge of the transfer paper reaches the pressure contact portion. The invention of claim 3 is characterized in that it is a drive control means for actuating the means, and the invention of claim 3 is characterized in that
In addition to the above invention, the stop means is switchable in the conveyance path between a position protruding onto the conveyance path on the upstream side of the pressure contact portion and a position retracted from the conveyance path, and when protruding, the stop means stops the transfer paper. a stop member whose contact surface is parallel to the pressure contact portion; switching means for switching the stop member between the protruding position and the retracted position; and a switching control means for controlling the switching means so that the stop member is placed in the protruding position and the stopping member is placed in the retracted position after reaching the protruding position.

[0007]

[Operation] According to the invention of claim 1, with the above structure, before the transfer paper passes the pressure contact part, the transfer paper is once stopped so as to be parallel to the pressure contact part by the stopping means, and then the transfer paper is stopped. is released, so the leading edge of the transfer paper enters the press-contact part in a parallel state. As a result, there is no difference in time between the left and right edges of the transfer paper, or between the center and the left and right sides of the transfer paper, when they enter the pressure contact portion, and wrinkles are prevented from occurring.

According to the second aspect of the invention, the stopping means is a drive control means for controlling the drive timing of the drive means for driving the fixing roller, and this drive control means causes the leading edge of the transfer paper to arrive at the pressure contact portion. The driving means is not activated before the transfer sheet is moved, and the driving means is activated to rotate the fixing roller after the leading edge of the transfer paper reaches the pressure contact area, so that the leading edge of the transfer paper can accurately enter the pressure contact area. Wrinkles do not occur when passing through the pressure welding part.

According to the third aspect of the invention, the stop member, the switching means, and the switching control means are provided, and the stop member moves the leading edge of the transfer paper once on the conveyance path upstream of the pressure contact part so that it becomes parallel to the pressure contact part. Since the stop is released after the stop, the leading edge of the transfer paper can enter the pressure contact portion in a parallel state, and wrinkles are prevented from occurring.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of a copying machine which is an example of an image forming apparatus to which the present invention can be applied. Around the photoreceptor drum 1, in the order of the rotational direction indicated by the arrow, there is a charger 2 that uniformly charges the photoreceptor, an exposure section 4 where the reflected light of the original image is formed by an optical system 3, and an exposure section 4 that A developing device 5 develops the electrostatic latent image formed on the photoreceptor drum 1 with toner, and the toner image is transferred onto a transfer paper fed at the same timing from the registration roller 10, and the transferred transfer paper is transferred to the photoreceptor. A transfer/separation charger 6 that separates from the drum 1, a separation claw 7, a cleaning device 8 that removes toner remaining on the photosensitive drum 1 after transfer, and the like are provided.

The transfer paper on which the toner image has been transferred is further transported along the transport path 9 by the registration rollers 10 and reaches the fixing device 11. After the toner image is fixed thereon by the fixing device 11, The image is completed after being discharged to the outside. In this embodiment, a conveyance belt 9a and a vacuum fan (not shown) are provided in the conveyance path 9 as conveyance auxiliary mechanisms.

FIGS. 2A and 2B show the state before the transfer paper P reaches the nip 11c, which is the pressure contact area between the fixing roller 11a of the fixing device 11 and the pressure roller 11b that is pressed against it. show. As shown in the figure, the leading edge P1 of the transfer paper P may reach the nip 11c in a state where the left and right sides are not aligned. In addition, as shown in FIGS. 3(a) and 3(b), the tip P-
1 may be wavy or curled at both ends. Therefore, in this embodiment, as shown in FIG. 4, the fixing roller 11a is stopped until the leading edge P-1 of the transfer paper P reaches the nip 11c. As a result, the leading edge P-1 of the transferred transfer paper P hits the nip 11c and is evenly aligned, and even in the states shown in FIGS. It becomes a uniform plane along the line.

FIG. 5 shows an example of the configuration of the driving means for the fixing roller 11a. The fixing roller 11a receives a driving force from a fixing roller drive input section 16 via a fixing gear 13, an intermediate gear 14, and a fixing clutch 15 connected to the shaft end thereof, and these constitute a driving means. The operation of the fixing clutch 15 is controlled by, for example, a CPU 100, which serves as a drive control means and controls the entire copying machine.

FIG. 6 is a diagram showing the timing of operation control for rotating the fixing roller 11a by the drive means and drive control means. The paper feed clutch is turned on by the start key of the copying machine, and the registration clutch is turned on after T1 hours after the registration of the fed transfer paper is detected.
The transfer paper is sent out by the registration rollers 10 (FIG. 1), and after a time T2 has passed, its leading edge reaches the nip 11.
reach c. The transfer paper is further fed and bent with its leading edge abutted against the nip 11c, and its leading edge is uniformly adjusted as described above. After the time T3 has elapsed, the fixing clutch 15 (FIG. 5) is turned on, the fixing roller 11a is rotated, and the transfer paper passes through the nip 11c between the fixing roller 11a and the pressure roller 11b pressed against it. ,
As mentioned above, it is ejected from the aircraft. Here, the time T3 during which the leading edge of the transfer paper is stopped is set to a time during which the deflection of the transfer paper does not become too large. Then, when the transfer paper is discharged outside the machine, the fixing clutch 15 is also turned off.

By performing such an operation, the leading edge of the transfer paper is aligned and passes through the nip 11c, so that wrinkles do not occur on the transfer paper. In this way, if the leading edge of the transfer paper is aligned using the fixing roller 11a and its driving device and then passed through the nip 11c, there is no need to additionally equip a special stopping member or its driving device, and for example, the main body There is an advantage in that the purpose can be achieved by making slight changes to the CPU.

FIG. 7 shows another embodiment. In this example,
There is a nip 11c on the upstream side of the nip 11c in the conveyance path 9.
A pair of stoppers 17, which are an example of stop members, are provided parallel to the nip (parallel to the length direction of the nip). However, the stopper 17 may be a single wide plate. The stopper 17 is rotatably supported by a fulcrum 18 and is connected to a stopper solenoid 20 as a switching means via a link 19, and when turned off or on, the stopper 17 moves to a position projecting onto the conveyance path 9 shown by a solid line. It is designed to be able to switch between a position on the transport path 9 indicated by a broken line and a retracted position. As in the case of the first embodiment, the timing of this switching is controlled by, for example, the CPU 100, which serves as a switching control means and controls the entire copying machine.

FIG. 8 is a diagram corresponding to FIG. 6, and shows the timing of controlling the operation of the stopper plate. After T2 hours after the registration clutch is turned on, the leading edge of the transfer paper reaches the position of the stopper 17, which is in the protruding position when the stopper solenoid 20 is off, and the leading edge of the transfer paper becomes inclined as shown in FIG. Even if the
It creates sag and aligns its tips. And T
After 3 hours, the stopper solenoid 20 is turned on.
The stopper 17 is retracted from the conveyance path 9, and the transfer paper is conveyed until it reaches the nip 11c, where it passes through the nip 11c and is fixed by the rotating fixing roller 11a. In this case, since the leading edges of the transfer paper are aligned, wrinkles do not occur in the transfer paper when it passes through the nip. When the transfer paper is ejected, the stopper solenoid 20 is turned off again, and the stopper 17 is again in the protruding position.

[0018]

As described above, according to the present invention, before the leading edge of the transfer paper passes through the pressure contact part, the stop means once stops the transfer paper so that it is parallel to the pressure contact part, and then releases the stop and moves the transfer paper to the pressure contact part. , so that the leading edge of the transfer paper enters the pressure contact portion in a uniform state parallel to the pressure contact portion, and it is possible to prevent the occurrence of fixation wrinkles.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a copying machine which is an example of an image forming apparatus according to an embodiment.

FIG. 2 is an explanatory diagram showing a state in which a transfer sheet enters a fixing nip, in which (a) is a plan view and (b) is a side view.

FIGS. 3A and 3B are side views showing a state in which the leading edge of the transfer paper is not normal.

FIG. 4 is a side view showing a state in which the leading edge of the transfer paper is aligned by the fixing nip.

FIG. 5 is an explanatory diagram of a drive system for a fixing roller.

FIG. 6 is an operation timing diagram.

FIG. 7 is an explanatory diagram of another embodiment, (a) is a plan view, (b)
) is a side view.

FIG. 8 is an operation timing diagram.

FIG. 9 shows the state before the transfer paper hits the stopper, (
A) is a plan view, and (b) is a side view.

FIG. 10 shows the state in which the transfer paper hits the stopper;
A) is a plan view, and (b) is a side view.

[Explanation of symbols]

9 Conveyance path 11a Fixing roller 11b Pressure roller 11c Nip (pressure contact part) 15 Fixing clutch (driving means) 17 Stopper (stopping member) 20 Stopper solenoid (switching means) 100 C
PU (drive control means, switching control means) P-1 Leading edge of transfer paper

Claims (3)

[Claims] [Claim 1] A transfer sheet having a toner image transferred thereto and conveyed along a conveyance path is passed through a pressure contact portion between a fixing roller and a pressure roller that is pressed against the fixing roller, and the toner image thereon is fixed to form an image. The image forming apparatus is characterized in that a stopping means is provided for once stopping the leading edge of the transfer paper in a state parallel to the pressing part and then releasing the stop before the leading edge of the transfer paper passes the pressing part. Forming device. 2. A drive means for rotating the fixing roller, wherein the stopping means is configured to stop the fixing roller before the leading edge of the transfer paper reaches the pressure contact portion and rotate the fixing roller after the leading edge of the transfer paper reaches the pressure contact portion. The image forming apparatus according to claim 1, characterized in that the image forming apparatus is a drive control means for activating the means. 3. The stopping means is switchable in the transport path between a position protruding onto the transport path on the upstream side of the pressure contact portion and a position retracted from the transport path, and when protruding, stops the transfer paper. a stop member whose abutting surface is parallel to the pressure contact portion; switching means for switching the stop member between the protruding position and the retracted position; and switching the stop member before the leading edge of the transfer paper reaches the protruding position. The image forming apparatus according to claim 1, further comprising a switching control means for controlling the switching means to bring the stop member to the retracted position after reaching the protruding position.