JP2007304566A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device in which faulty separation of recording material is reduced, and an image forming apparatus equipped with the fixing device. <P>SOLUTION: A gap sensor (reflection type photosensor or laser system sensor) 103 for detecting the length of a gap between a fixing belt 1 and a separation plate 12 is attached to the inside of the fixing device. Relation among the length of the gap, the kind of paper and the margin width of the leading edge of the paper is recorded in a look-up table (LUT) 106 according to both of the length of the gap and the kind of paper, and an image processing means 104 is controlled and adjusted to obtain a corresponding margin area at the leading edge of the recording material 10 based on the detected length of the gap and the kind of paper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device used in an electrophotographic image forming apparatus and an image forming apparatus provided with the same, and in particular, prevents a recording material that has passed through a fixing nip from being wound around a fixing member (fixing roller or fixing belt). The present invention relates to an image forming apparatus including a fixing device that is characteristic in technology.

In electrophotographic image forming apparatuses such as copying machines, printers, and facsimile machines, a recording material holding an unfixed toner image conveyed from a transfer apparatus is heated and pressed in a fixing nip of the fixing apparatus. When the image is fixed, but the melted toner has adhesive force and adheres to a fixing member such as a fixing belt or a fixing roller, the recording material is discharged from the leading edge while being wound around the fixing member. For this reason, the occurrence of winding jam and image defects due to overfixing are likely to occur. Such an accident is likely to occur particularly when an image is formed without a margin from the leading edge of the recording material.
For this reason, normally, a blank area of about 1 to 5 mm is set from the front end of the recording material, and an image is not formed in that area. By doing so, immediately after leaving the fixing nip, the recording material conveyed is discharged without being wrapped around the fixing member, so that a gap is generated between the fixing member and the recording material. . The recording material is forcibly separated from the fixing member by inserting a separation member installed in the vicinity of the downstream side of the fixing nip into the gap.

As described above, even if a blank area is formed at the leading end of the recording material and the recording material is forcibly separated from the fixing member by the separation member, the recording material may be wound around under various conditions. . Various conditions such as toner adhesion amount, output image, fixing temperature, recording material, separation member configuration, environment (temperature, humidity), etc. can be cited as conditions for the recording material to be wound around the fixing member. The conditions change, and it is impossible to control everything.
In order to prevent such a recording material from being wound around the fixing member, the recording material on the fixing member is controlled by controlling the operation of the separating member so that the separating member is brought into contact with or separated from the fixing member according to the margin width at the front end. There has been proposed a technique for suppressing the occurrence of wraparound jam (see, for example, Patent Document 1).
JP 2005-173486 A

However, in the case of the technique described in Patent Document 1, it is necessary to add a mechanism for controlling the operation, leading to an increase in the size of the device. It is also difficult to control a separation mechanism that requires high-precision positioning. By the way, the applicant of the present invention indicates that the number of occurrences of poor recording material separation (winding of the recording material around the fixing member) is largely caused by the material of the recording material, specifically, the thickness of the recording material. I found it.
SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus including the fixing device that can reduce recording material separation failure in the fixing device.

In order to achieve the above object, the invention described in claim 1 is directed to an image forming apparatus having a fixing device having a separating member for separating the recording material discharged from the fixing nip from the fixing member. Paper margin detecting means for detecting the margin, margin area adjusting means for adjusting the margin area at the leading edge of the recording material, and the margin area adjustment so as to adjust the margin area at the leading edge of the recording material according to the detection result of the paper type detecting means. And a control means for controlling the means.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the margin adjusting means widens a margin area at the leading end of the recording material in the thin paper passing mode.
According to a third aspect of the present invention, there is provided an image forming apparatus including a fixing device having a separation member that separates the recording material discharged from the fixing nip from the fixing member, and a gap sensor that detects a gap between the fixing member and the separation member; A margin area adjusting means for adjusting a margin area at the leading edge of the recording material; and a control means for controlling the margin area adjusting means to adjust the margin area at the leading edge of the recording material according to a detection result of the gap sensor. Features.
According to a fourth aspect of the present invention, in the image forming apparatus having a fixing device having a separating member for separating the recording material discharged from the fixing nip from the fixing member, a paper type detecting means for detecting the thickness of the recording material to be used. And a gap sensor for detecting a gap between the fixing member and the separating member, a margin area adjusting means for adjusting a margin area at the leading edge of the recording material, and a detection result of the paper type detection means and a detection result of the gap sensor. And a control means for controlling the margin area adjusting means to adjust the margin area.

According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, a plurality of the gap sensors are arranged along the rotation axis of the fixing member.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the image forming apparatus further includes a determination unit that determines a maximum value of the gap detected by the plurality of gap sensors as a gap between the fixing member and the separation member. It is characterized by that.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, a gap value detected by at least one gap sensor of the plurality of gap sensors is detected by the one gap sensor. An abnormality detection means is provided for detecting an abnormality when a measurement difference of a predetermined value or more has occurred from the previous gap value.
According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the operation of the image processing unit is stopped by an abnormality detection signal from the abnormality detecting means.

  According to the present invention, by adopting the above configuration, it is possible to provide a fixing device that can reduce recording material separation failure in the fixing device and an image forming apparatus including the same.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a paper type detection unit 102, a gap sensor 103, and an image processing unit 104 with a CPU 101 as a center. The paper type detection unit 102 detects the thickness of the recording material to be passed. The gap sensor 103 detects a gap value between a separation plate and a fixing belt, which will be described later. The image processing unit 104 includes a margin area adjusting unit 105 that adjusts a margin area at the leading end of the recording material.
FIG. 2 is a configuration diagram of a fixing device according to an embodiment of the present invention. An outline of the belt fixing device of the vertical conveyance machine will be described. The fixing belt 1 is wound around the fixing roller 2 and the heating roller 3, is given tension by the tension roller 4, and is in close contact with the fixing roller 2 and the heating roller 3. A fixing nip is formed by pressing the pressure roller 5 against a portion corresponding to the fixing roller 2 of the fixing belt loop configured as described above.

The fixing belt 1 is made of polyimide (PI) which is an endless film of a heat resistant resin as a belt base material. A thickness of about 50 to 90 μm is appropriate. On the belt substrate, there is an elastic layer such as silicone rubber or fluororubber in order to maintain the flexibility of the image, and the thickness is suitably 100 to 300 μm. Furthermore, a release layer such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE) is provided on the surface layer, and the thickness is about 20 to 50 μm. The release layer may be covered with a tube type or may be formed by coating or baking liquid or powder PFA or PTFE.
Inside the heating roller 3, a heat source 6 (halogen heater, infrared heater, or other thermal resistance is also possible) is provided, and its temperature is detected by a temperature detection element 7 such as a thermistor to control the blinking of the heat source 6 and heat. The surface temperature of the roller 3 or the fixing belt 1 is controlled.
The heating roller 3 is made of a metal such as aluminum or iron, and the thinner it is, the better. However, since it is subjected to bending stress by the tension of the belt 1, a thickness of 0.4 mm or more is required for aluminum and 0.2 mm or more for iron. It becomes. Inside the heating roller 3, a paint that promotes heat absorption such as black is applied so as to easily absorb heat from the heat source 6.

The fixing roller 2 is made of a highly rigid core material such as metal, with the surface layer covered with an elastic body such as silicone rubber. Iron and aluminum are suitable for the core material. High-strength resin may be used. As the elastic body of the surface layer, sponge rubber is most suitable and can be configured with low hardness (50 HS or less: Asker C). Therefore, not only the load on the fixing belt 1 is small, but also heat conduction is lower than that of ordinary rubber. Therefore, there is an advantage that heat of the fixing belt is not easily released.
The tension roller 4 is provided at a substantially intermediate position between the fixing roller 1 and the heating roller 3 and the fixing roller 2. In this figure, the tension roller 4 is pressed by a pressing member such as a spring 8 from the outside of the belt 1 loop. .
The tension roller 4 uses a highly rigid material such as metal for the core material, and covers the surface layer with a material having a certain degree of elasticity such as heat-resistant felt or silicone rubber. These surface materials do not damage the fixing belt 1 at the time of pressurization, can ensure a uniform pressing force even in a setting lacking a certain degree of accuracy, and heat conduction is not so fast. It also helps to prevent. The tension roller 4 may be applied from the inside of the fixing belt 1 or may be used in place of the tension roller 4 so that the heating roller 3 and the fixing roller 2 can be moved.

The pressure roller 5 has a configuration in which an elastic body such as silicone rubber is disposed on a rigid core material such as metal. It is effective to wind a member having good releasability such as a PFA tube on the surface layer. At this time, if the hardness of the pressure roller 5 is set higher than that of the fixing roller 2 (such as reducing the thickness of the rubber or increasing the hardness of the rubber), the fixing nip becomes concave on the fixing roller 2 side.
In a color image, since the toner amount is larger than that in a monochrome image, the adhesive force of the toner at the time of melting is high, and it is difficult to peel off from the fixing belt 1. Therefore, a nip that is concavely curved on the fixing roller 2 side makes it easy to peel off the image after fixing from the fixing belt by curvature separation. Also in this example, the heating roller 3 and the heat source 6 are arranged on the fixing roller 2 (fixing belt 1) side, and the fixing roller 2 side is used as an image surface. For this reason, the fixing roller 2 has a lower hardness than the pressure roller 5 so that the fixing nip is concave on the image side.

FIG. 3 is a diagram showing a recording material conveyance path before and after the fixing device. The recording material 10 on which the unfixed image 10-1 conveyed from the upstream transfer device 9 is placed enters the fixing nip N along the entrance guide plate 11. In the fixing nip N, a predetermined heat and pressure are applied so that the toner image is melted and fixed on the surface of the recording material 10.
A separation plate 12 is installed on the image side at the fixing device outlet. The separation plate 12 is preferably sized to cover the entire conveyance width and made of metal. The tip 12-1 is made as thin as possible (for example, within 0.2 mm). Since the tip is thin, it can be installed as close as possible to the fixing nip, and the heat capacity is low, so that the temperature rises to a level at which water vapor cannot easily adhere. The tip portion may be crushed thinner than the plate thickness, or another thin plate of 0.2 mm or less may be attached.

The separation plate 12 can reduce damage to the fixing belt 1 by making no contact with the fixing belt 1 within the image range. In general, the gap between the tip of the separation plate 12 and the fixing belt 1 is about 1 mm or less. If the gap is too large, the recording material 10 discharged from the fixing nip is caught on the separation plate 12 and causes paper jam. If the gap is too close, the recording material 10 comes into contact with the fixing belt 1 and damages the fixing belt 1. End up.
In order to maintain this gap accurately, a positioning member 13 having a separation plate 12 is attached to the fixing belt 1 against both ends of the separation plate 12 outside the image. Thereby, the separation plate 12 and the fixing belt 1 are always in a stable positional relationship, and the gap is stabilized.
When the recording material 10 that has exited the fixing nip is wound around the fixing belt 1 and is conveyed along the fixing belt 1 for a longer time than the target time, unevenness is likely to occur in the image. The closer to N, the better. The recording material 10 discharged from the fixing device is transported along the separation plate 12, sandwiched between the downstream transport roller pair 14, and further transported to the downstream (discharge port of the image forming apparatus).

In the present invention, in view of the fact that the occurrence of poor recording material separation (winding of the recording material around the fixing member) is largely caused by the material of the recording material 10, specifically, the thickness of the recording material. Control as follows.
[Example 1]
Embodiment 1 proposes a method of adjusting the leading edge margin width depending on the recording material. There are various types of recording materials that differ in size, thickness, fiber and fiber direction, etc., but there are usually thin papers depending on the paper thickness that greatly contributes to fixability and transportability. -It is classified into various types such as plain paper and cardboard, and is set by the user each time it is used.
These segmentation is thin (60 g / m ² or less) as a guide, plain paper (60~105g / m ^2), a division such as cardboard (105 g / m ² or higher).
The thicker the paper, the stronger the stiffness. Therefore, even if the toner melts and has adhesive strength at the time of fixing, the paper is thick to some extent with plain paper / thick paper, so the winding around the fixing belt 1 occurs. Hard to do. On the other hand, thin paper is extremely easy to wrap because the stiffness of the paper is extremely weak, and the probability of occurrence of wrapping becomes very high in the tip margin width under the same conditions as the other two types.

  Therefore, in the present invention, control is performed to widen the leading edge margin width when the thin paper passing mode is selected. Specifically, in FIG. 1, when the paper type detection unit 102 detects that thin paper is being passed, the CPU 101 controls the margin area adjustment unit 105 of the image processing unit 104 to increase the leading margin width. I do. An experiment of winding unfixed paper with the leading edge margin adjusted with the fixing device having the above-described configuration shown in FIG. 2 shows that, as shown in FIG. 5, plain paper and cardboard can be separated if the leading margin width is 2 mm or more. However, it can be seen that a margin width of 3.5 mm or more is required for thin paper. As described above, since the separation property of the thin paper is extremely deteriorated, it is possible to prevent the wrapping by widening the leading margin width when the thin paper passing mode is selected as a wrapping prevention measure.

In the first embodiment, a control method of adjusting the leading edge margin width according to the paper type has been proposed, but here, as another factor that greatly affects the separation performance, the separation plate 12 and the fixing belt 1 shown in FIG. The gap G will be described.
As described above, by setting the gap length between the separation plate 12 and the fixing belt 1 to 1 mm or less, the narrower the separation performance, the more the separation performance is improved. The fixing belt 1 is damaged. When used continuously without maintenance, paper dust, scattered toner, dust, and the like accumulate in the gap G, eventually filling the gap G and contacting the fixing belt 1. In order to damage it, a gap length of at least 0.1 mm must be secured.
As described above, the non-contact type separation plate mechanism requires a gap length accuracy of 0.1 mm unit, but includes a tolerance variation of about 0.2 mm due to the limit of processing accuracy and assembly accuracy. The median value should be around 0.3 to 0.4 mm. In that case, as shown in FIG. 6, when the separation performance result in each gap is seen, it can be seen that there is a large difference in the separation performance at the upper and lower tolerances of the gap length even in the same sheet passing mode.
However, since the gap length variation depends on the processing accuracy and assembly accuracy, it is difficult to further improve the accuracy, and it is not realistic to inspect each point of mass-produced products.

[Example 2]
Therefore, in the second embodiment, a configuration is proposed in which a gap sensor 103 that detects the gap length between the fixing belt 1 and the separation plate 12 is attached. FIG. 4 is a view showing a mounting position of the gap sensor 103 for detecting the gap length between the fixing belt and the separation plate. As shown in FIG. 4, a gap sensor (reflective photo sensor or laser sensor) 103 for detecting the gap length between the fixing belt 1 and the separation plate 12 is attached inside the fixing device.
When a print request is made, the gap length is detected by the gap sensor 103, and the gap length, the paper type, and the leading edge margin as shown in FIG. 6 are detected based on the gap length or both the gap length and the paper type. The width relationship is recorded in a look-up table (LUT) 106 or the like, and image processing is performed so that the leading margin area of the corresponding recording material 10 is based on the detected gap length and paper type as shown in FIG. The means 104 is controlled and adjusted. Here, by setting the heat resistance of the gap sensor 103 to 150 ° C. or higher, the gap sensor 103 can also be installed inside the fixing device.

[Example 3]
FIG. 7 is a diagram showing a schematic configuration of a fixing device according to another embodiment of the present invention. In this embodiment, the gap sensors 103 a, 103 b, and 103 c shown in FIG. 4 are attached at three locations in the center and both ends in parallel along the rotation axis 2 a of the fixing roller 2. As described above, by attaching a plurality of gap sensors 103 along the rotation axis 2a of the fixing roller 2, it is possible to detect the gap length between the surface of the fixing belt 1 and the tip of the separation plate 12 at a plurality of points. In most cases, sensor readings in the plurality of gap sensors 103 do not all match, and variations occur.
However, as shown in FIG. 6, the separation performance of the recording material 10 varies depending on the gap length of the separation plate 12. If the gap length between the fixing belt 1 and the separation plate 12 at the left and right ends of the fixing roller 2 is greatly different, the recording material 10 is separated on one side when it is conveyed, but on the other side. It is also conceivable that winding will occur. In order to cope with such a problem, the leading edge margin of the recording material is determined with reference to the maximum value of the gap measurement values at a plurality of points.
That is, as shown in FIG. 8, among the gap measurement values detected by the plurality of gap sensors 103a, 103b, and 103c, the maximum value of the gap measurement values obtained by the determination by the determination means 107 is used. The leading edge margin width is determined with reference to the LUT 106 that records the relationship between the gap length, the paper type, and the leading edge margin width shown in FIG.

As a method for adjusting the leading edge margin width, not only the relationship between the gap length, the paper type, and the leading edge margin length shown in FIG. 6 described above is directly used, but the leading edge margin width is set in advance in the image forming apparatus based on the relationship. For example, when the measured gap value between the fixing belt 1 and the separation plate 12 is 0.2 mm to 0.4 mm, the margin width at the tip is set to 2.5 mm, and the measured gap value is over 0, 4 mm. In such a case, a method of forming an image with reference to a setting value of 3.5 mm at the leading edge margin width can also be used.
As a result, even when gap values vary at multiple points, the maximum value of those readings is determined as the gap length, and the leading edge margin width corresponding to the determined gap length is determined, so that wrapping occurs appropriately Can be suppressed.
The plurality of gap sensors for detecting the gap between the fixing roller 2 and the separation plate 12 are provided for the following reason.
That is, although the separation plate 12 is a component that requires extremely high accuracy, it is difficult to obtain accuracy because the separation plate 12 is a single sheet metal processed (the tip is crushed). Therefore, the gap varies in the axial direction even within the same component. Therefore, in this embodiment, a plurality of gap sensors are provided in the axial direction, the gap at each location is detected, and the measured value at the location where the gap is maximized is used as the gap, so that the leading edge margin is adjusted accordingly. Like to do.

Further, in the fixing device according to the present embodiment, when a print request is made by the image forming apparatus, the gap length between the fixing belt and the separation plate is detected by the three gap sensors 103a, 103b, and 103c as described above. However, at that time, if at least one gap sensor has a measurement difference of ± 0.1 mm or more with the reading at the previous detection, it is detected as an abnormality, and printing is not performed until the abnormality clear process is performed. Alternatively, printing can be stopped.
That is, as shown in FIG. 8, the gap measurement values from the gap sensors 103a, 103b, and 103c are recorded and compared with the previous gap measurement values from the previous gap sensors 103a, 103b, and 103c. An abnormality detection means 108 is provided for determining an abnormality when the difference between the measured gap measurement value and the previous measurement value is ± 0.1 mm or more, and an output signal from the abnormality detection means is supplied to the CPU 101. Then, it is possible to display an alarm or to interrupt the printing process by stopping the operation of the image processing unit 104 as will be described later.
For example, even when a winding jam occurs for some reason at the time of the previous printing and the recording material 10 is completely wound around the fixing belt, the gap length corresponding to the amount of the recording material 10 wound at the next printing request is detected. Can be detected as an abnormality. Further, even when the recording material 10 is caught somewhere in the middle of conveyance and causes a bellows-like jam to lift the separation plate 12, it is determined that the gap length has increased and an abnormality is detected. Can do.
And when these gap lengths are detected abnormally, the printing request is stopped and printing is not resumed until the abnormality is cleared, thereby preventing early detection of abnormalities such as jams and damage to unit machines. It becomes possible to prevent.

[Example 4]
In this embodiment, an example in which the fixing device described in Embodiment 3 is used for an image forming apparatus will be described in detail.
FIG. 9 is a diagram illustrating a schematic configuration of a four-tandem full-color printer as an image forming apparatus according to an embodiment of the present invention.
This printer uses four color toner images of yellow (Y), magenta (M), cyan (C), and black (Bk) on the corresponding photosensitive drums 1Y, 1M, 1C, and 1Bk (image carrier). In order to form on the surface, four sets of image forming units 10Y, 10M, 10C, 10Bk (image forming means) of an electrophotographic system are provided.
Below these image forming units 10Y, 10M, 10C, and 10Bk, a conveyance belt 20 for conveying a sheet (recording medium) 11 through each image forming unit is stretched. The photosensitive drums 1Y, 1M, 1C, and 1Bk of the image forming units 10Y, 10M, 10C, and 10Bk are respectively arranged in contact with the conveyance belt 20, and the sheet 11 is electrostatically attracted to the surface of the conveyance belt 40. . The four sets of image forming units 10Y, 10M, 10C, and 10Bk have substantially the same structure. Therefore, here, the yellow image forming unit 10Y disposed on the most upstream side in the transport direction (arrow E direction) of the paper 11 will be described as a representative, and the image forming units 10M, 10C, and 10Bk for other colors will be described. Are denoted by the same reference numerals, and detailed description thereof is omitted.

The image forming unit 10Y has a photosensitive drum 1Y that is in rolling contact with the transport belt 40 at a substantially central position. Around the photosensitive drum 1Y, a charging device 2Y for charging the surface of the photosensitive drum 1Y to a predetermined potential, the charged drum surface is exposed based on the color-separated image signal, and the surface of the drum is electrostatically charged. An exposure device 3Y that forms a latent image, a developing device 4Y that supplies yellow toner to the electrostatic latent image formed on the surface of the drum 1Y and develops the paper, and a sheet on which the developed toner image is conveyed via the conveying belt 40 A transfer roller 5Y (transfer device) for transferring the toner, a cleaner 6Y for removing residual toner remaining on the drum surface without being transferred, and a charge eliminating lamp for removing electric charge remaining on the surface of the drum 1Y (not shown) are provided on the photosensitive drum 1Y. Are arranged in order along the rotation direction.
A paper feed mechanism 50 for feeding paper onto the transport belt 20 is disposed on the lower right side of the transport belt 40 in the drawing. On the left side of the conveying belt 40 in the figure, the fixing device 60 described in the first embodiment is disposed. The paper 11 transported by the transport belt 40 is transported through a transport path continuously extending from the transport belt 20 through the fixing device 60 and passes through the fixing device 60. The fixing device 60 heats and pressurizes the transported paper 11, that is, the paper on which the toner image T of each color is transferred on the surface thereof.
Then, the toner images of the respective colors are melted and permeated into the paper to be fixed. In addition, the paper is discharged to the downstream side of the conveyance path of the fixing device 40 via a paper discharge roller. In FIG. 9, reference numeral 102 denotes a paper type detection sensor, which is a paper type detection unit, which determines the paper type by detecting the paper thickness. The paper type detection sensor 102 may determine the paper type using characteristics such as the paper weight in addition to the paper thickness.

As described above, in the image forming apparatus according to the present embodiment, the fixing device shown in the above-described third embodiment is incorporated as the fixing device 60, and the fixing device 60 includes a separation not shown in FIG. A plurality of gap sensors 103 are attached along the rotation axis 2 a of the plate 12 and the fixing roller 2. Further, the image forming apparatus includes a paper type detection unit 102, a determination unit 107, and an abnormality detection unit 108 as shown in FIG. 8, and as described above, the gap measurement values from the plurality of gap sensors 103. The maximum gap measurement value is determined based on the determination, and the margin area adjustment unit 15 of the image processing unit 104 that controls the image forming units 10Y, 10M, 10C, and 10Bk is adjusted based on the gap measurement value obtained by the determination. Then, the margin width is adjusted.
Further, based on the gap measurement values from the plurality of gap sensors 103, when the difference from the previous measurement value exceeds a predetermined value, for example, ± 0.2 mm, an abnormality occurrence signal is output from the abnormality detection means 108. The abnormality is displayed by the CPU 101, and the operation of the image processing unit 104 is controlled and the operations of the image forming units 10Y, 10M, 10C, and 10Bk are stopped. By the abnormality display, the user or the like performs the above-described abnormality repair of the fixing device and starts it, so that the image processing unit 104 starts the image forming units 10Y, 10M, 10C, and 10Bk.
In this way, when a gap length abnormality is detected, the printing request is stopped and printing is not resumed until the abnormality is cleared, thereby preventing early detection of abnormalities such as jams and damage to the unit machine. It becomes possible to prevent.

In this embodiment, the four-tandem full-color printer is exemplified as the image forming apparatus. However, even a black-and-white type printer having the black and single-color image forming unit 10Bk can be used effectively. Can do.
In the embodiment according to the present invention, a belt-type fixing member using a fixing belt is exemplified as the fixing member, but a roller-type fixing member not using a fixing belt may be used.
In the above-described embodiment according to the present invention, the pressure roller 5 is exemplified as the pressure member that presses the recording material 10 against the fixing member. However, the pressure roller 5 is not a roller but a fixed pressure pad, a driving roller, and a pressure roller. A belt-type pressure member in which an endless belt is stretched may be used.
Further, the mechanism for adjusting the margin area shown in FIGS. 1 and 8 may be incorporated in the fixing device when the fixing device is used separately from the image forming apparatus.

1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a side view illustrating a schematic configuration of a fixing device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a recording material conveyance path before and after the fixing device. It is a figure which shows the attachment position of the gap sensor which detects the gap of a fixing belt and a separating plate. It is a figure which shows the separability by paper type. It is a figure which shows the separability by the gap of a fixing belt and a separating plate. FIG. 9 is a perspective view illustrating a schematic configuration of a fixing device according to a third embodiment of the present invention. FIG. 10 is a block diagram illustrating a margin area adjustment mechanism used in a fixing device according to Embodiment 3 of the present invention. FIG. 10 is a diagram illustrating a schematic configuration of an image forming apparatus according to Embodiment 4 of the present invention.

Explanation of symbols

  1 fixing belt, 2 fixing roller, 3 heating roller, 4 tension roller, 5 pressure roller, 10 recording material, 1Y, 1M, 1C, 1Bk photosensitive drum, 2Y, 2M, 2C, 2Bk charging device, 3Y, 3M, 3C, 3Bk exposure device, 4Y, 4M, 4C, 4Bk developing device, 5Y, 5M, 5C, 5Bk transfer roller, 6Y, 6M, 6C, 6Bk cleaner, 10Y, 10M, 10C, 10Bk image forming unit, 12 separator ( Separation member), 60 fixing device, 101 CPU (control means), 102 paper type detection means, 103, 103a, 103b, 103c gap sensor, 104 image processing means, 105 margin area adjustment means, 106 LUT, 107 determination means, 108 Abnormality detection means

Claims (8)

In an image forming apparatus including a fixing device having a separating member for separating a recording material discharged from a fixing nip from a fixing member,
Paper type detecting means for detecting the thickness of the recording material to be used, margin area adjusting means for adjusting the margin area at the leading end of the recording material, and adjusting the margin area at the leading end of the recording material according to the detection result of the paper type detecting means An image forming apparatus comprising: control means for controlling the margin area adjusting means. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the margin adjusting means widens a margin area at the leading end of the recording material in the thin paper passing mode. In an image forming apparatus including a fixing device having a separating member for separating a recording material discharged from a fixing nip from a fixing member,
A gap sensor for detecting a gap between the fixing member and the separation member; a margin area adjusting means for adjusting a margin area at the leading edge of the recording material; and the margin area to adjust the margin area at the leading edge of the recording material according to a detection result of the gap sensor. An image forming apparatus comprising: a control unit that controls the adjustment unit. In an image forming apparatus including a fixing device having a separating member for separating a recording material discharged from a fixing nip from a fixing member,
A paper type detecting means for detecting the thickness of the recording material to be used, a gap sensor for detecting a gap between the fixing member and the separating member, a margin area adjusting means for adjusting a margin area at the leading end of the recording material, and a paper type detecting means. An image forming apparatus comprising: a control unit that controls a margin area adjusting unit so as to adjust a margin area at the leading end of the recording material based on both the detection result and the detection result of the gap sensor. The image forming apparatus according to claim 3 or 4, wherein:
An image forming apparatus comprising a plurality of gap sensors arranged along a rotation axis of the fixing member. The image forming apparatus according to claim 5.
An image forming apparatus comprising: a determination unit that determines a maximum gap detected by the plurality of gap sensors as a gap between a fixing member and a separation member. The image forming apparatus according to claim 5 or 6,
An abnormality occurs when a gap value detected by at least one gap sensor of the plurality of gap sensors is more than a predetermined difference from the previous gap value detected by the one gap sensor. An image forming apparatus comprising an abnormality detecting means for detecting The image forming apparatus according to claim 7.
An image forming apparatus, wherein an operation of an image processing unit is stopped by an abnormality detection signal from the abnormality detecting means.

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