JPH043760A - Image forming device - Google Patents

Abstract

PURPOSE:To surely and quickly detect any jam generated at any position of a rotor by providing multiple detecting sensors within the width of a recording material with the minimum size. CONSTITUTION:A rotor 2 pinching and conveying a recording material supporting a manifest image and fixing the manifest image is provided. The recording material after passing the rotor 2 is detected by detecting sensors 7a-7c, and the jam of the recording material is judged by a judging means 10 based on signals of the detecting sensors 7a-7c. Multiple detecting sensors 7a-7c are provided within the width of the recording material with the minimum size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine or a printer having a fixing rotating body for fixing a visible image.

[Prior Art] Conventionally, in image forming apparatuses such as copying machines, a roller fixing method has been widely used in which a toner image formed on a recording material is fixed by being conveyed between a pair of rollers.

An example of this roller fixing device 1 is shown in FIG.

The toner image is fixed by conveying the recording material sheet supporting the toner image between the fixing roller 2 and a pressure roller (not shown).

Also, in contact with the fixing roller 2, a plurality of separation claws 3a
, 3b, 3c, and 3d are arranged at predetermined intervals.

The sheet S with the toner image fixed thereon is separated by separation claws 3a, 3b, 3.
c and 3d, it is separated from the fixing roller 2 and conveyed to the downstream side.

By the way, when the sheet s is separated from the fixing roller 2, a separation failure of the sheet s occurs due to each or some or all of the separation claws 3a, 3b, 3c, and 3d, and the separation claws 3a, 3b, 3c, and 3d are pressed against the fixing roller 2 from below and may damage the fixing roller, thereby causing the fixing roller to reach the end of its lifespan.

Therefore, as shown in FIG. 7(b), two sheet presence/absence detection sensors 7a and 7c, which are composed of an optical sensor 5, a lever 6, etc., are arranged downstream of the fixing roller 2 in the sheet conveying direction. When a separation failure occurs in the sheet S, the separation failure of the sheet s' is detected based on the signals of the sheet presence/absence detection sensors 7a and 7c, and the main motor is stopped, causing the drive system to rotate by a certain amount of inertia. Sheet S'
The conveyance of the sheet s is stopped to prevent the fixing roller 2 from being damaged by the poorly separated sheet s.

That is, when the sheet s is not conveyed downstream of the fixing roller 2, the optical path of the sheet presence detection sensors 7a and 7c is blocked by the lever 6 of the optical sensor 5, and a sheet absence signal is sent to the control unit. When the sheet S is conveyed, the lever 6 rotates around the rotation center 6a to open the optical path of the optical sensor 5 and send a sheet presence signal to the control section. The time required for conveying the sheet S from the paper feed section to the sheet presence/absence detection sensors 7a and 7C is input in advance to the control section, and the control section is based on the sheet feeding signal from the paper feed section. , the actual sheet presence/absence detection sensor 7 for the wide size sheet SL and the narrow size sheet S5
a, the conveyance time up to 7C is compared with a predetermined conveyance time to determine whether or not the sheet has jammed. For example, in FIG. 11, the sheet SL is separated by separation claws 3a, 3b, 3C13d.
If the leading edge of the sheet SL gets caught in one or more of the nails, causing a nail jam, and the leading edge of the sheet SL reaches only the sheet presence/absence detection sensor 7a and does not reach 7C within a predetermined time, a jam is determined and the roller drive is started. Stop. Furthermore, as shown in Fig. 12, if the actual conveyance speed is within the predetermined conveyance time but the detection timing Δt of the two sensors 7a and 7c exceeds the predetermined time, the actual conveyance speed exceeds the predetermined conveyance time. In this case, it is determined that the sheet S has been separated or is being conveyed incorrectly, and a signal is issued to stop the conveyance of the sheet S. Note that the sheet presence/absence detection sensors 7a and 7c are arranged at positions slightly closer to the reference member 8 when the sheet conveyance method is based on one side, as shown in FIG. 10, and near the center when the sheet conveyance method is based on the center. It is preferable to do so.

Problems solved by the invention The sheet conveyed based on the standard is not detected by the sheet presence/absence detection sensor 7c because the sheet is small, and the sheet is detected only by the sheet presence/absence detection sensor 7a.

At this time, if the sheet is caught by the claw 3a, the sheet will be bent and the sheet presence/absence detection sensor 7a will not detect the sheet.

In addition, if the separation claw 3b jams as shown in FIG. A jam occurs when the conveyance direction is completely fed. In this case, although a jam actually occurs in the claw 3b, the occurrence of the jam is not detected due to the detection delay of the sensor 7a.

For this reason, the roller is driven until the next recording material is detected to be stuck, so more jammed paper than necessary is stacked in an accordion shape, and the adjacent claws of 3b are pushed up from the lower part of the stack to the roller, so more jams are detected. Since the inertia of the main motor 15 is large and it takes a long time until the fixing roller stops, the pressure of the tip of the claw on the roller further increases, causing damage to the roller and shortening the life of the fixing roller.

Means for Solving Problem E] The present invention that solves the above problems includes a rotating body that nip and conveys a recording material supporting a visible image and fixing the visible image, and a detection sensor for the recording material after this rotating body. , and a determining means for determining whether a recording material is jammed based on a signal from the detection sensor, wherein a plurality of the detection sensors are provided within the width of the recording material of a minimum size. be.

[Example] The present invention will be explained in detail below.

FIG. 4 is a sectional view of an image forming apparatus according to an embodiment of the present invention. 21 is the main body of the electrophotographic copying machine, and 21 is a sorter 2 that layers and stacks transfer sheets as recording materials.
3 is a large capacity paper feed stacker, 24 is a document feeder, 25
26 is a cleaner that scrapes off unnecessary toner on the photosensitive drum 25; 27 is a primary charger that uniformly charges the drum; 26 is a cleaner that scrapes off unnecessary toner on the photosensitive drum 25; A developing device 28 places toner on the latent image formed on the drum 25 corresponding to the document. On the other hand, the transfer sheet P is fed from the large-capacity paper feed stacker 23 by a pair of separation rollers 38, passes through a pair of paper feed second registration rollers 31, passes through a pair of conveyance rollers 30, and then is transferred to the original roller from a 32nd rugi roller. A sheet of paper is fed in accordance with the toner image, and the toner image is transferred onto a transfer sheet P on a transfer separation/charging device 29, and then guided to a fixing device 1 via a conveyance section 33. In the fixing device 1, the toner image is fixed on the transfer sheet between a pair of fixing rollers 2 and a pair of pressure rollers 41;
After peeling off the transfer paper from the fixing roller with the separating claw, selectively
The paper is sent to the sorter 22 from the pair of paper discharge rollers 5 and stacked, and then guided to the paper refeed conveyance path 39, and once
After being stored on the intermediate tray of No. 0, the paper is re-fed and then fed again to the No. 2 intermediate tray of No. 32.
After being guided by the registration rollers, the paper is fed again in accordance with the toner image of the document, and the toner image is transferred onto the transfer sheet P on the transfer separation charger 29, and then transferred to the fixing device 1 after passing on the conveyance section 33. be led to. In the fixing device 1, the toner image is fixed on the transfer sheet by heat and pressure between a pair of fixing rollers 2 and a pair of pressure rollers 41, and after separating the transfer paper from the fixing roller with a separating claw 3, the sheet 35 is discharged. The sheets are sent to 22 sorters by a pair of rollers and stacked.

Next, the jam detection mechanism of this embodiment will be explained using FIG. 1.

The roller fixing device 1 includes a fixing roller 2 and four separation claws 3a, 3b, 3c, and 3d facing the fixing roller 2. Further, downstream of the fixing roller 2 in the sheet conveyance direction, there is a sheet jam detection device including three sheet presence/absence detection sensors 7a, 7b, and 7C, which are composed of an optical sensor 5, a lever 6, etc., similar to the sheet presence/absence detection sensor 7 described above. 9
These three sheet presence/absence detection sensors 7a, 7b, and 7c are arranged at predetermined intervals in the axial direction of the fixing roller 2 so that 7a and 7b detect both ends of the predetermined minimum size paper. 7C is similarly arranged along with other detection sensors so as to detect both ends of paper near the maximum size, and is conveyed to the downstream side of each fixing roller 2. The presence or absence of the sheet S is detected at at least two locations facing each part of the various sheets S.

Therefore, even if the sheet is bent or jammed, it can be detected by at least one sensor, and the jam can be detected reliably.

FIGS. 5(a) and 5(b) show a mechanism for transmitting driving force to the fixing roller.

The power from the main motor pulley 15 is transmitted to the clutch pulley 13b by the power transmission means (timing belt) 14, and is transmitted from the boss 13d to the fixing drive shaft 13a via the clutch spring 13c, and then the power is transmitted to the fixing drive shaft 13a 13e, 13f,
The drive is transmitted to the gear directly connected to the fixing roller 2 through a 13g gear train to rotate the fixing roller and perform a fixing operation.

Further, as shown in the timing chart of FIG. 5(C), when the sheet jam detection sensor determines that there is a jam based on the signals from the discharged paper jam detection sensors 7a, 7b, and 7C, the sheet conveyance stop command means 12 operates the solenoid 13h.

As shown in FIG. 5(b), the solenoid 13h operates and the claws provided at the tip of the solenoid move from 13i to 131'.
, and engages with the claw portion of the control tube 13j, and 13b
The power of rotation in one direction is not transmitted to the clutch spring portion 130, and the power transmission is turned off. Therefore, the rotational force due to the inertia after the image motor 15 is powered off is not transmitted to the fixing roller, and the fixing roller is stopped immediately after the sheet conveyance stop command 12 is transmitted, thereby improving the jam recovery response.

Compared to the conventional timing chart in FIG. 5(d),
As shown in Figure (C), the roller stop response after jam detection is improved.

FIG. 6 shows a block diagram of the present invention. A control unit 10 consisting of a CPU (Central Processing Unit) 61 and the like is provided, and a paper feed clutch 62, a drum conveyance motor 63, and a fixing drive solenoid 13h are connected to an output boat of the CPU 61, and an input boat is connected to a Sheet presence detection sensor 7a
, 7b, 7c, a paper feed signal transmitter 15, and a drum encoder 16 are connected.

On the other hand, in FIG. 1, the sheet jam detection device 9 includes:
The signals from the three sheet presence/absence detection sensors 7a, 7b, and 7C are compared (compared), and the signals from these three sensors 7 are
A sheet jam detection means 11 is provided which is programmed to detect a jam of the sheet S when the difference γ between the maximum sheet detection times of a, 7b, and 7c is greater than a predetermined value, and the sheet jam detection means 11 is controlled. It is stored in section 10.

The sheet jam detection device 9 also commands the fixing drive solenoid 13h, drum conveyance motor 63, and paper feed clutch 62 to stop conveyance of the sheet S based on the sheet jam signal from the sheet jam detection means 11. A sheet conveyance stop command means 12 is provided, and conveyance of the sheet S is stopped by a command from the sheet conveyance stop command means 12.

FIG. 9(a) shows the flow from jam occurrence to jam display.

When the sheet S is caught in the separation claw 3d and jammed, it passes the sheet presence/absence detection sensor 7a corresponding to one leading edge Sa of the sheet S at approximately the scheduled time and is detected by the sensor 7a, but the other end of the sheet S The leading end sb of the sheet passes through the corresponding sheet presence detection sensor 7b, 7C with a delay and is detected by the sensor 7b, 7C. The sheet jam detection means 17 detects these sheet presence/absence detection sensors 7a and 7b.

It is compared whether the difference γ in the maximum slow speed of the sheet detection time in step 7c is greater than or equal to a predetermined value. If the difference γ between the maximum slow speeds of the sheet detection times is greater than or equal to a predetermined value, it is determined that the sheet is jammed due to a claw jam, and a sheet jam signal is transmitted. Furthermore, when the sheet jam signal is transmitted, a signal to stop the conveyance of the sheet S is sent by the sheet conveyance stop command means 19, and the drive transmitted from the drum conveyance motor 15 of the copying machine main body via the timing belt 14 is activated. The force is not transmitted due to the power transmission OFF operation of the fixing drive clutch 13, and the fixing roller 2 is stopped instantaneously due to the large frictional torque with the pressure roller that is in pressure contact with the fixing roller 2, and the conveyance of the sheet S is stopped. The same applies when the sheet S gets caught in the separation claw 3a and jams. Further, if the other leading end sb of the sheet S' remains caught in the separating claw 3d and is not detected by the corresponding sheet presence detection sensor 7b, 7C, it is determined that the sheet is jammed due to a claw jam. As a result, the sheet S
However, even if the sheet jams at any position on the fixing roller 2, the sheet jam can be detected accurately and quickly, and the conveyance of the sheet (S) is stopped based on the sheet jam signal to prevent damage to the fixing roller 2. Prevented.

The improvement in jam detection accuracy in this embodiment is shown in FIGS. 13 and 14.

The third sensor is indicated by the dashed line.

As shown in Figures 7 and 8, by using the third or higher sensor of 7b in addition to the two sensors of 78.7C as in the past, depending on the paper size, sensors 7a and 7C can be used to detect the tip of the sheet. Now, by detecting the delay from both ends of the leading edge of the sheet using the sensors 7a and 7b, even if the leading edge of the jam reaches the sensor with a large skew, even if the signal 7b in FIG. Since the signal 7a indicates no paper, it is determined to be JAN, and the fixing roller 2 is immediately stopped as described above.

Also, as shown in Figure 8, there is a jam at a part other than the separation claw at the edge of the paper, and 3b
However, the paper was separated by the claw of roller 2, but the paper was wrapped around the roller and was torn by the claw of 3b or its vicinity, and the sheet was broken as shown at P', and as for sensor 7a detection, Even if the feeding timing of a sheet of this size is allowed, the sheet is not detected by the sensor 7b (because it is broken and jammed), so the jam is detected and the fixing roller 2 is immediately stopped as described above. To surely prevent damage to a fixing roller.

In this embodiment, a jam is detected based on the difference γ between the sheet detection times of the sheet presence/absence detection sensors 7a, 7b, and 7c.Next, this embodiment also includes a jam detection mechanism that detects a jam based on a delay in sheet detection and accumulation of sheets. I will explain about it.

The sheet jam detection means of this embodiment detects a sheet jam when any one of the three sheet presence/absence detection sensors 7a, 7b, and 7c does not detect the sheet S' even after a preset sheet conveyance time period has elapsed. It is programmed to detect and compare to send a sheet jam signal.
A sheet jam is detected according to the flow shown in FIG. 9(b) in addition to the flow shown in FIG. 9(a).

That is, the sheet jam detection means detects the sheet S from the sheet presence/absence detection sensors 7a and 7b after the sheet feed signal is transmitted.
, 7c, one of the sheet presence/absence detection sensors 7a, 7b, and 7c detects the sheet S depending on the sheet size within a predetermined sheet conveyance time (jam detection timing X) until the sheet passes through the sheet S
Detects a sheet jam if not detected. As a result, sheet jams can be detected reliably and quickly even if a jam occurs in any of the separation claws 3a, 3b, 3c, and 3d.

In the above embodiments, the presence or absence of the sheet may be detected by delaying the leading edge of the sheet or detecting the presence or absence of the sheet at least once within a certain period of time within the sheet conveyance time after the skew amount is detected, especially when the sheet is long in longitudinal size. As a result, jammed paper can be detected reliably and quickly regardless of the shape of the sheet that is broken at the leading edge or in the middle, as shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, regardless of the size of the recording material, it is detected by multiple detection sensors, so no matter where a jam occurs on the rotating body, it can be detected reliably and quickly. can do.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Figs. 2 and 3 are partial sectional views of an embodiment of the present invention, Fig. 2 shows when paper is being passed, and Fig. 3 shows when illegal paper is being passed. . FIG. 4 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention, FIG. 5(a) is a cross-sectional view of a drive transmission mechanism according to an embodiment of the present invention, and FIG. A front view of the drive transmission mechanism, FIG. 5(C) is a timing chart showing the operation of the embodiment of the present invention, FIG. 5(d) is a timing chart showing the operation of the conventional example, and FIG. 6 is the implementation of the present invention. 7(a), (b) and FIG. 8(a), (b) are diagrams for explaining the differences between the conventional example and the embodiment of the present invention. Same figure (
a) is a plan view, FIG. 9(b) is a sectional view, FIGS. 9(a) and 9(b) are flowcharts showing an embodiment of the present invention, and FIGS. 10 to 12 are conventional jam detection It is a schematic diagram showing a mechanism. 1 is a fixing device, 2 is a fixing roller, 38 to 3d are fixing separation claws, 7a to 7c are paper discharge sensors, 10 is a sheet jam detection system, 13 is a fixing drive clutch, 14 is a drive belt,
15 is a main motor. G9 Song diagram ((1) Flute diagram (b) 小■ Flute // Figure

Claims (3)

[Claims] (1) A rotating body that clamps and conveys a recording material that supports a visible image and fixes the visible image, a sensor that detects the recording material after this rotating body, and a jam of the recording material is determined based on the signal of this detection sensor. An image forming apparatus comprising a determining means, wherein a plurality of the detection sensors are provided within a width of a recording material of a minimum size. (2) The image forming apparatus according to claim 1, wherein the apparatus further includes a plurality of separating members that come into contact with the rotating body for separating the recording material from the rotating body. (3) The image forming apparatus according to claim 1 or 2, wherein the driving of the rotating body is stopped when the determining means determines that there is a jam.