JP2017107143A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for enabling printing on thin paper even when the thin paper slips at a high linear velocity over the lapse of time.SOLUTION: An image forming apparatus has a plurality of process linear velocities and comprises a fixing device inside an image forming apparatus body. The fixing device includes: a rotatable fixing belt 1; a halogen heater 2 that heats the fixing belt 1; a pressure roller 3 that forms a nip with the fixing belt 1; a nip forming member 6 that faces the pressure roller 3 inside the fixing belt 1 to form the nip; and slip detection means that detects the occurrence of slip between a recording material and the pressure roller 3. When the occurrence of slip is detected by the slip detection means, the image forming apparatus limits the process linear velocities.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a multi-function machine equipped with a fixing device.

  A fixing device used in an electrostatic recording image forming apparatus such as a copying machine, a facsimile machine, or a printer, more specifically, a nip is formed between an endless pressure member and a fixing member, and passes through the nip. A fixing device that performs a fixing process on a material to be fixed and an image forming apparatus equipped with the fixing device are well known.

  In recent years, market demands for energy saving and high speed have been increasing for such image forming apparatuses. In an image forming apparatus, an unfixed toner image is transferred to a recording material sheet, printing paper, photosensitive paper, electrostatic recording paper, etc. by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, and magnetic recording. Formed on recording material. As a fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely used.

  As an example of such a fixing device, a belt-type fixing device (for example, see Patent Document 1) and a surf fixing (film fixing) fixing device (for example, see Patent Document 2) using a ceramic heater are known.

  In recent years, with belt type fixing devices, further warm-up time (time required from room temperature to a predetermined printable temperature (reload temperature) such as when the power is turned on) and first print time (after receiving a print request, It is desired to shorten the time required for the printing operation after the printing preparation and the paper discharge to be completed (hereinafter referred to as problem 1). Further, as the speed of the image forming apparatus increases, the number of sheets to be passed per unit time increases and the required heat amount increases, so that there is a problem that the heat amount is insufficient (so-called temperature drop) particularly at the beginning of continuous printing. (Hereinafter referred to as “Problem 2”).

  As a method for solving the problem of the problem 1, surf fixing using a ceramic heater has been proposed. With this method, it is possible to reduce the heat capacity and reduce the size as compared with a belt-type fixing device. However, since only the nip portion is locally heated, the other portions are not heated, and the belt is the most at the entrance of a recording material such as printing paper in the nip (hereinafter referred to as printing paper unless otherwise specified). There is a problem that it is in a cold state, and fixing defects are likely to occur. In particular, in a high-speed machine (because the belt rotates fast and the heat radiation of the belt outside the nip portion increases), there is a problem that fixing failure is more likely to occur (hereinafter referred to as problem 3).

  In order to solve the above problems 1 to 3, in the configuration using an endless belt, the entire belt can be heated, the first print time from the heating standby time can be shortened, and at the time of high-speed rotation There has been proposed a fixing device that can solve the above shortage of heat and obtain good fixability even when mounted in a high-production image forming apparatus (see Patent Document 3).

  FIG. 1 is a schematic view of a fixing device described in Patent Document 3. A pipe-shaped metal heat conductor 2 is fixed inside the endless belt 1 so as to be able to guide the movement of the endless belt 1, and endlessly passed through the metal heat conductor 2 by a heat source 3 in the metal heat conductor 2. The belt 1 is heated. Further, a pressure roller 4 that forms a nip portion N in contact with the metal heat conductor 2 via the endless belt 1 is provided, and the endless belt 1 is moved in the circumferential direction so as to rotate as the pressure roller 4 rotates. Let With this configuration, it is possible to warm the entire endless belt constituting the fixing device, to shorten the first print time from the heating standby time, and to solve the shortage of heat during high-speed rotation. Yes.

  However, it is necessary to further improve the thermal efficiency in order to further improve the energy saving and the first print time. From the configuration in which the endless belt is indirectly heated via the metal heat conductor, the endless belt (metal heat conductor) A direct heating arrangement has been proposed. In this configuration, it is possible to reduce the power consumption by greatly improving the heat transfer efficiency and to further shorten the first print time from the heating standby time. In addition, the cost can be reduced without using a metal heat conductor. That is, by adopting a configuration in which the endless belt is directly heated, energy saving is high, and it is possible to further shorten the first print time from the heating standby time.

  However, in the above configuration, a sliding problem between the fixing member or the pressure member and the nip forming member is remarkably generated. Specifically, the torque is increased at the contact sliding portion. To solve this problem, the torque increase is conventionally suppressed by winding a torque reduction sheet called a sliding sheet around the nip forming member, or by adding a lubricant such as silicone oil to the sliding sheet. Has been reduced. However, even with these means, torque is a very big problem.

  The pressure member or the fixing member is rotated, and the fixing member or the pressure member is rotated through the printing paper, but the fixing member or the pressure member is rotated by the torque increase between the fixing member or the pressure member and the nip forming member. The printing paper is transported at the same linear velocity as the fixing member or the pressure member due to the influence of the melted toner, and slippage (slip) occurs between the printing paper and the pressure member or the fixing member. The conveyance speed of printing paper decreases, and the heating time in fixing increases. Even if a jam (paper jam) occurs as a result of the decrease in the conveyance speed or the jam does not occur, a hot offset or a decrease in gloss occurs due to a long heating time.

  Slip occurs due to an increase in friction coefficient and torque increase between the fixing member or pressure member and the nip forming member. Slip is more likely to occur at higher linear speeds because of the higher original torque. Also, the thinner the printing paper, the easier it is to slip. Thin paper is weak and easily follows the curve of the fixing member or pressure member, and since the toner tends to be hotter in thin paper, the pressure member or fixing member tends to be in close contact with the fixing member or pressure member. It is estimated that slip is likely to occur between the member and the printing paper. Therefore, when the pressure member or the fixing member decreases in hardness over time and the surface pressure decreases, the torque also increases over time. Therefore, when paper is passed at high linear speed, slip is particularly likely to occur. . That is, thin paper cannot be passed at high linear speeds over time.

  As the frictional resistance between the fixing member or the pressure member and the nip forming member increases with time, the rotation speed of the fixing member or the pressure member decreases, and slip occurs between the printing paper and the pressure member or the fixing member. As a result, the printing paper cannot be transported and jammed. This slip occurs remarkably at high line speeds and is difficult to occur at low line speeds. Further, it occurs remarkably on thin paper, and does not occur when the paper thickness is thick. Even when jamming does not occur, the heating time becomes longer than usual, so that hot offset and gloss reduction occur remarkably.

  An object of the present invention is to provide means for enabling printing with thin paper even when the thin paper slips over time at a high linear velocity.

  An image forming apparatus according to the present invention is an image forming apparatus in which an image forming process has a plurality of process linear velocities. The image forming apparatus includes a fixing device in a main body of the image forming apparatus, and the fixing device includes a rotatable fixing member; A heating source that heats the fixing member; a pressure member that forms a nip with the fixing member; a nip forming member that forms the nip opposite to the pressure member inside the fixing member; a recording material; Slip detecting means for detecting the occurrence of slip between the pressure members, and limiting the process line speed when the slip detecting means detects that slip has occurred. It is characterized by.

  According to the present invention, by performing the fixing operation at a low linear velocity, even when the paper is thin, slip (jam) itself can be prevented and a target heating time can be secured, so that hot offset can be prevented.

It is explanatory drawing which shows one Embodiment of the fixing device of a conventional structure. FIG. 2 is a cross-sectional explanatory view showing an embodiment of a fixing device of the present invention. FIG. 5 is a cross-sectional view of an example when a fixing member rotation speed detection unit is used. It is explanatory drawing which shows an example of the image forming apparatus at the time of using a torque detection means. Approach detection means. FIG. 4 is an explanatory diagram illustrating an example of an image forming apparatus when a discharge detection unit is used. It is explanatory drawing which shows an example of the mode which restrict | limits paper thickness and slip detection. It is sectional drawing of an example at the time of using the rotational speed detection means of a pressurization member. It is explanatory drawing which shows an example of the image forming apparatus at the time of using a torque detection means. Approach detection means. FIG. 4 is an explanatory diagram illustrating an example of an image forming apparatus when a discharge detection unit is used. It is explanatory drawing which shows an example of the image forming apparatus to which this invention is applied. 1 is an explanatory diagram illustrating a configuration of an image forming apparatus using a fixing device according to the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
In the following embodiments of the present invention, a nip is formed between an endless fixing member and a pressure member, and a fixing device that performs a fixing process on a material to be fixed passing through the nip, and the fixing device are mounted. The present invention relates to an image forming apparatus.

<Embodiment 1>
FIG. 2 is a configuration diagram illustrating the fixing device according to the first exemplary embodiment of the present invention. The fixing device has a pressure rotator (pressure roller 3 in the case of FIG. 2) and the fixing belt 1, and the fixing belt 1 is directly heated from the inner peripheral side by a heat source (halogen heater 2 in the example of FIG. 2). The At this time, in the fixing belt 1 of FIG. 2, there is a nip forming member 6 that forms a nip with the pressure roller 3 opposed via the fixing belt 1, and directly on the inner surface of the fixing belt (or a sliding sheet (not shown)). (Indirectly through).

  Although the shape of the nip portion is flat in FIG. 2, it may be a concave shape or other shapes (the concave shape of the nip means that the discharge direction of the recording paper tip is closer to the pressure roller, The separation is improved, so the occurrence of jam is suppressed). The fixing belt 1 is preferably a substantially cylindrical endless belt (or film) using a metal belt such as nickel or SUS or a resin material such as polyimide. The surface layer of the belt has a release layer formed of PFA, PTFE, FEP or the like, and has a release property so that toner does not adhere. There may be an elastic layer formed of a silicone rubber layer or the like between the base material of the belt formed of a polymer such as polyimide, polyamide, polyimide amide, or a metal such as SUS, nickel, or copper and the release layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and the image has a crusty skin shape. There arises a problem that the gloss unevenness (zudder skin image) remains. In order to improve this, it is necessary to provide a silicone rubber layer of 100 [μm] or more. Due to the deformation of the silicone rubber layer, fine irregularities are absorbed and the skin image is improved.

  A support member 7 (stay) for supporting the nip portion is provided inside the fixing belt 1 to prevent the nip forming member 6 that receives pressure from the pressure roller from being bent and to obtain a uniform nip width in the axial direction. I am doing so. This support member 7 is held and fixed to a holding member 7a (flange) at both ends and positioned. Further, a reflection member 9 is provided between the heat source 2 and the support member 7, and wasteful energy consumption due to the support member 7 being heated by radiant heat from the heat source 2 or the like is suppressed. Here, the same effect can be obtained even if the surface of the support member 7 is heat-insulated or mirror-finished instead of having the reflecting member 9. The heat source 2 may be the illustrated halogen heater, but may be IH, a resistance heating element, a carbon heater, or the like.

  The pressure roller 3 has an elastic rubber layer 4 on a cored bar 5 and a release layer (PFA or PTFE layer) on the surface in order to obtain releasability. The pressure roller 3 is rotated by a driving force transmitted through a gear from a driving source such as a motor provided in the image forming apparatus. The pressure roller 3 is pressed against the fixing belt 1 side by a spring or the like, and has a predetermined nip width when the elastic rubber layer 4 is crushed and deformed. The pressure roller 3 may be a hollow roller, and the pressure roller 3 may have a heating source such as a halogen heater. The elastic rubber layer 4 may be solid rubber, but if there is no heater inside the pressure roller 3, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt to lose heat.

The fixing belt 1 is rotated by the pressure roller 3. In the case of FIG. 2, the pressure roller 3 is rotated by a driving source (not shown), and the driving force is transmitted to the belt at the nip portion N, whereby the fixing belt 1 is rotated. The fixing belt 1 is sandwiched and rotated at the nip portion N, and travels while being guided by the holding member 7a at both ends except the nip portion.
With the above configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up.

  As the slip detection means, the rotation speed detection means of the fixing member may be installed in the image forming apparatus or the fixing apparatus, and the rotation speed of the fixing member may be directly measured to detect the slip (see FIG. 3). When the rotation linear velocity of the fixing member decreases with respect to the rotation linear velocity of the pressure member, the linear velocity difference is generated between the printing paper and the pressure member. At this time, if the rotational linear velocity falls below a predetermined value, it can be determined that slip has occurred.

  As the slip detection means, the torque applied to the fixing motor (drive is on the pressure side) may be measured, and the slip may be detected according to the output result (see FIG. 4). In this case, if the detected torque value is higher than the predetermined torque value, it is determined that the possibility of slipping is very high, and the slip detecting means can be used. The timing to measure the torque here is important, but it can be any time as long as there is a timing to reliably grasp the torque fluctuation, such as the torque immediately before starting up, or the torque immediately before the printing paper being fed enters the nip. . In this case, it is possible to detect the slip in advance before the actual slip occurs by using a means for appropriately monitoring the temporal variation of the torque at a predetermined timing from the start of use of the image forming apparatus. I can do it.

  Further, when this means is used, it is possible to detect slip more reliably by measuring the torque while the printing paper is actually passing through the nip. When slip actually occurs between the printing paper and the pressure roller, the pressure motor loses the force to forcefully convey the fixing member and the printing paper, so the torque drops extremely steeply compared to the torque immediately before passing the paper. . By detecting this decrease in torque, it becomes possible to detect slip.

  Further, the slip may be detected from the timing at which the printing paper starts to enter the fixing device or the timing at which the printing paper is completed and the timing at which the printing paper starts to discharge the fixed device or the timing at which the printing paper is completed (see FIG. 5). ). When slip starts to occur, the interval between the fixing approach timing and the fixing discharge timing becomes longer. It can be determined that a slip has occurred when the interval is longer than a certain interval. The entry timing / discharge timing can be determined by the output of a paper sensor installed before and after the fixing unit. The start management / entry completion and the discharge start / discharge completion may be timing management starting from either. In addition, as a sensor having the same function, a registration sensor, a paper discharge sensor, or the like can be used as a paper transport timing detection sensor, and any sensor can be used as long as it can determine the paper transport timing. As a paper sensor, various other means such as a paper presence / absence sensor using a filler, which has been conventionally used, can be used.

  As the slip detection means, the number of printed sheets, travel distance, paper passing distance, etc. are counted from the start of use of the fixing device, and when the count value reaches the specified value, there is a possibility of slipping in further use. Also good. For example, when the number of printed sheets is accumulated every print or periodically, and the number of printed sheets exceeds 100,000, it is assumed that there is a possibility of occurrence of slip thereafter. In addition, it is possible to judge whether the sliding distance between the actual fixing member and the nip forming member exceeds 100 km or whether the distance that the printing paper actually passes through the nip exceeds 50 km. . When this method is used, even a customer who uses the fixing device beyond the life of the fixing device can use the fixing device until the end.

  Here, each integrated value is counted, but an area where slip is likely to occur with only one item may be determined, but slip may be comprehensively determined using a plurality of items. For example, depending on how the customer is used, there are few cases where the paper is actually passed, and in most cases, the fixing means is only rotating. For example, when the operation panel operation is carried out for a long time, the preparation is made to pass the paper for paper passing, but the time is long, and only one sheet is actually passed. Even if the same number of printed sheets is passed, the rotation time at other times is long, so that the slipping is likely to occur. In such a case, it is necessary to provide slip detection means using a plurality of conditions.

  In addition, when counting the sheet passing distance and the number of printed sheets, the integrated value is counted while weighting the process conditions each time in consideration of the color mode and paper type paper thickness at the time of sheet passing. Also good. Further, instead of weighting and integrating, a slip determination threshold value may be provided for each condition, and slip may be determined for each condition threshold value for each process condition to be printed. However, since the result of integrating all the conditions affects slip and torque increase, the method of integrating the results weighted for each condition is more preferable because it is easier to detect the slip.

The precautions for the slip criterion will be described. Although the slip detection means and conditions are defined as described above, it is desirable that the slip determination criteria be defined as follows.
In the slip determination by the slip detection means described above, slip must be determined before an abnormal image (hot offset), gloss reduction, or jam occurs. On the other hand, the slip / torque up does not occur suddenly from a certain moment, but occurs when the torque gradually increases from the beginning of use of the image forming apparatus and increases excessively.

  Therefore, it is necessary to determine the slip at the stage where the decrease in the conveyance speed of the printing paper that seems to be slipped is detected before the slip actually occurs. This is just before the torque reaches the limit, or when the rotation speed of the fixing member starts to decrease, or when the conveyance speed of the printing paper starts to decrease. However, if slip detection is performed too early (too much margin for slipping), the customer's use will be limited wastefully, so it is necessary to set it appropriately according to the characteristics of the fixing device.

A description will be given of when the limited operation is performed when the slip is detected. The recommended operation when a slip is detected is to maintain the linear velocity until the job is completed. After the job is finished, once the image forming apparatus is stopped, the process linear velocity is limited from the start of the next job.
If slip is detected here, it is desirable to change the process linear velocity immediately. However, it is necessary to change not only the operation of the fixing device but also all process linear speeds such as other image forming processes and paper conveyance. Therefore, it is desirable that the process line speed continues until the job is completed, and that the process line speed is limited from the start of the next job. However, even when a slip is detected in a high-speed machine, an operation such as passing about 5000 sheets is often performed until the job is completed. In this case, slip may actually occur during printing after slip detection. As a means for avoiding this, when a slip is detected, the machine operation may be temporarily interrupted, and the process linear velocity may be changed and restarted.

  When slip is detected, the process linear velocity is limited. Specifically, since slip is likely to occur at a high linear speed, when a slip is detected, the machine operation is limited so that only an operation at a low linear speed is permitted. When slip is not detected, even in a printing mode that normally operates at a process line speed of 250 mm / second, if slip is detected, the process line speed is prohibited and the process line speed is less than 250 mm / second. Only the operation of is allowed.

  Since a normal image forming apparatus often has a lower line speed process for passing paper at 1200 dpi or when passing paper such as thick paper, it is possible to limit to only those operations. Easy to take as a means. For example, when a slip is detected under a process condition of 250 mm / second, the operation is limited so that it can be operated only at a lower 200 mm / second or 100 mm / second. Alternatively, the process line speed is limited so as to operate only at a process line speed of 100 mm / sec.

  Here, for example, when a slip is detected on a paper having a paper thickness (paper thickness category B) of 250 mm / second, the operation at 250 mm / second is prohibited for all paper thicknesses, and the linear velocity is less than that. It is also possible to limit to only the operation (FIG. 6, pattern 1).

  Since slip is likely to occur in thin paper, restricting all operations in the following and subsequent steps significantly impairs usability. Therefore, when slip is detected in the paper thickness section B, it is necessary to narrow the influence range as much as possible, such as limiting the process linear velocity of the paper thickness section A and the paper thickness section B (FIG. 6, pattern 2). .

  Even if a slip is detected in the paper thickness section B, depending on the paper type, a slip may not easily occur in the thinner paper thickness section A. In that case, the process linear velocity need not be limited until the slip is actually detected in the paper thickness section A. Only the process linear velocity at which slip is actually detected may be limited (FIG. 6, pattern 3).

  For example, when slip is detected in the paper thickness section E, there is a possibility of slipping in the thinner paper thickness section A to the paper thickness section D. Especially in the paper thickness section A, the slip becomes almost deterministic. In this case, if slip is detected in the paper thickness section F, the process line speed is limited in the paper thickness F, and the process line speed is set in the paper thickness section A and the paper thickness section B without waiting for the next sheet to pass. It is necessary to decide how to limit the speed, such as limiting the linear speed if slip is detected appropriately when the paper is passed at that linear speed next time, without limiting the speed, the paper thickness B to the paper thickness E, and the paper thickness G. Yes (Fig. 6, Pattern 4).

  Although the case of the paper thickness has been described here, the slip margin varies depending on the paper type, and the slip margin varies depending on the color mode and the image to be formed. Regulations and conditions may be changed according to these conditions.

How long the limited operation when the slip is detected will be described.
When the slip is detected, it is preferable that the process line speed is limited until the fixing device is replaced with a new one. The determination as to whether or not the product is new may be provided with a new product detection means in the machine, or a new product may be detected by setting a flag when the service person or the user replaces the product with a new product. Alternatively, the process linear velocity may be limited until a replacement is made with a fixing device having no slip history by using means for storing the slip history in the fixing device. Even if it is replaced with a fixing device used halfway in another image forming apparatus, the fixing device can be automatically used without any trouble. By memorizing which process conditions caused the slip here, even when a new image forming device is replaced, the method of limiting the process linear speed is more limited so that the customer's usability is not impaired. Is possible.

<Embodiment 2>
FIG. 7 is a block diagram showing a fixing device according to Embodiment 2 of the present invention. In this embodiment, it has a slip detection means which can detect a slip. Hereinafter, the slip detection means and the slip determination method will be described.
As the slip detection means, the rotation speed detection means of the pressure member may be installed in the image forming apparatus or the fixing device, and the rotation speed of the pressure member may be directly measured to detect the slip (see FIG. 8). ). When the rotation linear velocity of the pressure member decreases with respect to the rotation linear velocity of the fixing member, the linear velocity difference is generated between the printing paper and the fixing member. At this time, if the rotational linear velocity falls below a predetermined value, it can be determined that slip has occurred. The fixing member preferably has a structure in which a metal pipe having a heat source inside is coated with a rubber coating (see, for example, FIG. 6 of Patent Document 4).

  As the slip detection means, the torque applied to the fixing motor (drive is on the pressure side) may be measured, and the slip may be detected according to the output result (see FIG. 9: described as torque detection means 14 in the figure). ) In this case, if the detected torque value is higher than the predetermined torque value, it is determined that the possibility of slipping is very high, and the slip detecting means can be used. The timing to measure the torque here is important, but it can be any time as long as there is a timing to reliably grasp the torque fluctuation, such as the torque immediately before starting up, or the torque immediately before the printing paper being fed enters the nip. . In this case, it is possible to detect the slip in advance before the actual slip occurs by using a means for appropriately monitoring the temporal variation of the torque at a predetermined timing from the start of use of the image forming apparatus. I can do it.

  Further, when this means is used, it is possible to detect slip more reliably by measuring the torque while the printing paper is actually passing through the nip. When slip actually occurs between the printing paper and the pressure roller, the pressure motor loses the force to forcefully convey the pressure member and the printing paper, so the torque drops extremely steeply compared to the torque immediately before passing the paper. To do. By detecting this decrease in torque, it becomes possible to detect slip.

  Further, the slip may be detected from the timing at which the printing paper starts to enter the fixing device or the timing at which the printing paper is completed and the timing at which the printing paper starts to discharge the fixed device or the timing at which the printing paper is completed (see FIG. 8). ). When slip starts to occur, the interval between the fixing approach timing and the fixing discharge timing becomes longer. It can be determined that a slip has occurred when the interval is longer than a certain interval. The entry timing / discharge timing can be determined by the output of a paper sensor installed before and after the fixing unit. The start management / entry completion and the discharge start / discharge completion may be timing management starting from either. In addition, as a sensor having the same function, a registration sensor, a paper discharge sensor, or the like can be used as a paper transport timing detection sensor, and any sensor can be used as long as it can determine the paper transport timing. As a paper sensor, various other means such as a paper presence / absence sensor using a filler, which has been conventionally used, can be used.

  As the slip detection means, the number of printed sheets, travel distance, paper passing distance, etc. are counted from the start of use of the fixing device, and when the count value reaches the specified value, there is a possibility of slipping in further use. Also good. For example, when the number of printed sheets is accumulated every print or periodically, and the number of printed sheets exceeds 100,000, it is assumed that there is a possibility of occurrence of slip thereafter. In addition, it is possible to judge whether the sliding distance between the actual pressure member and the nip forming member exceeds 100 km, or whether the distance that the printing paper has actually passed through the nip exceeds 50 km. is there. When this method is used, even a customer who uses the fixing device beyond the life of the fixing device can use the fixing device until the end.

  Here, each integrated value is counted, but an area where slip is likely to occur with only one item may be determined, but slip may be comprehensively determined using a plurality of items. For example, depending on how the customer is used, there are few cases where the paper is actually passed, and in most cases, the fixing means is only rotating. For example, when the operation panel operation is carried out for a long time, the preparation is made to pass the paper for paper passing, but the time is long, and only one sheet is actually passed. Even if the same number of printed sheets is passed, the rotation time at other times is long, so that the slipping is likely to occur. In such a case, it is necessary to provide slip detection means using a plurality of conditions.

  In addition, when counting the sheet passing distance and the number of printed sheets, the integrated value is counted while weighting the process conditions each time in consideration of the color mode and paper type paper thickness at the time of sheet passing. Also good. Further, instead of weighting and integrating, a slip determination threshold value may be provided for each condition, and slip may be determined for each condition threshold value for each process condition to be printed. However, since the result of integrating all the conditions affects slip and torque increase, the method of integrating the results weighted for each condition is more preferable because it is easier to detect the slip.

The precautions for the slip criterion will be described. Although the slip detection means and conditions are defined as described above, it is desirable that the slip determination criteria be defined as follows.
In the slip determination by the slip detection means described above, slip must be determined before an abnormal image (hot offset), gloss reduction, or jam occurs. On the other hand, the slip / torque up does not occur suddenly from a certain moment, but occurs when the torque gradually increases from the beginning of use of the image forming apparatus and increases excessively.

  Therefore, it is necessary to determine the slip at the stage where the decrease in the conveyance speed of the printing paper that seems to be slipped is detected before the slip actually occurs. This is just before the torque reaches the limit, or when the rotation speed of the pressure member starts to decrease, or when the conveyance speed of the printing paper starts to decrease. However, if slip detection is performed too early (too much margin for slipping), the customer's use will be limited wastefully, so it is necessary to set it appropriately according to the characteristics of the fixing device.

A description will be given of when the limited operation is performed when the slip is detected. The recommended operation when a slip is detected is to maintain the linear velocity until the job is completed. After the job is finished, once the image forming apparatus is stopped, the process linear velocity is limited from the start of the next job.
If slip is detected here, it is desirable to change the process linear velocity immediately. However, it is necessary to change not only the operation of the fixing device but also all process linear speeds such as other image forming processes and paper conveyance. Therefore, it is desirable that the process line speed continues until the job is completed, and that the process line speed is limited from the start of the next job. However, even when a slip is detected in a high-speed machine, an operation such as passing about 5000 sheets is often performed until the job is completed. In this case, slip may actually occur during printing after slip detection. As a means for avoiding this, when a slip is detected, the machine operation may be temporarily interrupted, and the process linear velocity may be changed and restarted.

  When slip is detected, the process linear velocity is limited. Specifically, since slip is likely to occur at a high linear speed, when a slip is detected, the machine operation is limited so that only an operation at a low linear speed is permitted. When slip is not detected, even in a printing mode that normally operates at a process line speed of 250 mm / second, if slip is detected, the process line speed is prohibited and the process line speed is less than 250 mm / second. Only the operation of is allowed.

  Since a normal image forming apparatus often has a lower line speed process for passing paper at 1200 dpi or when passing paper such as thick paper, it is possible to limit to only those operations. Easy to take as a means. For example, when a slip is detected under a process condition of 250 mm / second, the operation is limited so that it can be operated only at a lower 200 mm / second or 100 mm / second. Alternatively, the process line speed is limited so as to operate only at a process line speed of 100 mm / sec.

  Note that the paper thickness and slip detection mode are the same as those in the first embodiment described with reference to FIG.

<Embodiment 3>
The configuration of an image forming apparatus using the fixing device having the above-described configuration will be described with reference to FIG.
The image forming apparatus shown in FIG. 11 is a color printer that uses a tandem system in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction. However, the present invention is not limited to this method, and can be applied not only to a printer but also to a copying machine, a facsimile machine, and the like.

  An image forming apparatus 1000 shown in FIG. 11 includes photosensitive drums 20Y, 20C, and 20M as image carriers that can form images as images corresponding to colors separated into yellow, cyan, magenta, and black, respectively. , 20Bk (hereinafter referred to as photosensitive drum 20 if not particularly required) is employed in parallel. Further, the image forming apparatus 1000 uses an intermediate transfer body (hereinafter referred to as a transfer belt) in which an endless belt that can move a visible image formed on each photoconductive drum 20 in the direction of arrow A1 while facing the photoconductive drum 20 is used. The primary transfer process is performed on 11 and the respective images are superimposed and transferred, and then the secondary transfer process is performed on the recording paper S on which the recording sheet or the like is used, and the images are collectively transferred.

  Around each photosensitive drum 20, an apparatus for performing image forming processing according to the rotation of the photosensitive drum 20 is disposed. To describe the photosensitive drum 20Bk that performs black image formation, a charging device 30Bk, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk that perform image forming processing along the rotational direction of the photosensitive drum 20Bk are arranged. ing. For the writing performed after charging, the optical writing device 8 is used.

  In the superimposing transfer with respect to the transfer belt 11, the visible image formed on each photoconductive drum 20 is transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the direction of arrow A 1. As described above, the primary transfer rollers 12Y, 12C, 12M, and 12Bk disposed opposite to the respective photosensitive drums 20 with the transfer belt 11 interposed therebetween (hereinafter referred to as the primary transfer roller 12 unless otherwise required). The voltage is applied according to (described below). Accordingly, the timing is shifted from the upstream side in the arrow A1 direction toward the downstream side.

  The photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the arrow A1 direction. Each photosensitive drum 20 is provided in an image station for forming yellow, cyan, magenta, and black images.

  In addition, the image forming apparatus 1000 is provided with four image stations that perform image forming processing for each color, and above each photosensitive drum 20, and is provided with a transfer belt 11 and a primary transfer roller 12. The unit 10 is disposed opposite to the transfer belt 11, and is driven by the transfer belt 11. The secondary transfer roller 5 is a transfer roller as a transfer member that rotates with the unit 10, and the transfer belt 11 is disposed opposite to the transfer belt 11. It has an intermediate transfer belt cleaning device 13 for cleaning the belt 11 and an optical writing device 8 as an optical writing device disposed facing these four image stations below.

  The optical writing device 8 is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror as a deflecting means, and the like. Writing light Lb corresponding to each color is emitted to each photosensitive drum 20 to form an electrostatic latent image on the photosensitive drums 20Y, 20C, 20M, and 20Bk. In FIG. 7, for the sake of convenience, reference numerals are given only to black image stations, but the same applies to other image stations.

  The image forming apparatus 1000 is conveyed from a sheet feeding device 61 as a paper feeding cassette loaded with recording paper S conveyed between the photosensitive drum 20 and the transfer belt 11, and the sheet feeding device 61. The registration roller pair 4 that feeds the recording sheet S to the transfer portion between the photosensitive drums 20 and the transfer belt 11 at a predetermined timing in accordance with the toner image formation timing by the image station, and the recording sheet. A sensor (not shown) that detects that the tip of S has reached the registration roller pair 4 is provided.

  The image forming apparatus 1000 includes a fixing device 100 as a roller fixing type fixing unit for fixing the toner image to the recording paper S on which the toner image is transferred, and the main body of the image forming apparatus 1000 with the fixed recording paper S A paper discharge roller 75 that discharges to the outside, a paper discharge tray 17 that is disposed on the top of the main body of the image forming apparatus 1000 and that stacks the recording paper S discharged to the outside of the main body of the image forming apparatus 1000 by the paper discharge roller 75; Located below the paper discharge tray 17 are provided toner bottles 9Y, 9C, 9M and 9Bk filled with toners of yellow, cyan, magenta and black.

  In addition to the transfer belt 11 and the primary transfer roller 12, the transfer belt unit 10 includes a driving roller 72 and a driven roller 73 around which the transfer belt 11 is wound. The driven roller 73 also has a function as a tension urging unit for the transfer belt 11. For this reason, the driven roller 73 is provided with an urging unit using a spring or the like. The transfer belt unit 10, the primary transfer roller 12, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

  The sheet feeding device 61 is disposed at the lower part of the main body of the image forming apparatus 1000. A feeding roller 3 is provided as a paper feeding roller in contact with the upper surface of the uppermost recording paper S. Then, the uppermost recording paper S is fed toward the registration roller pair 4 by the rotational feeding of the feeding roller 3 in the counterclockwise direction.

  Although not shown in detail, the cleaning device 13 provided in the transfer device 71 has a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11. Then, the transfer belt 11 is cleaned by scraping and removing foreign matters such as residual toner on the transfer belt 11 with a cleaning brush and a cleaning blade. The cleaning device 13 also has a discharge means (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

  The present invention is not limited to the embodiments described above, and many variations are possible by those having ordinary knowledge in the art within the technical idea of the present invention.

1: fixing belt 2: heat source 2-1: central heater 2-2: end heater 3: pressure roller 4: elastic body 5: core metal 6: nip forming member 7: support member 8: holding member 9: reflecting member 11: Central temperature sensor 12: End temperature control sensor N: Nip part

JP 2004-286922 A Japanese Patent No. 2861280 JP 2007-334205 A JP 2005-331574 A

Claims (13)

An image forming apparatus having an image forming process having a plurality of process linear velocities,
A fixing device is provided in the image forming apparatus main body,
The fixing device includes:
A rotatable fixing member;
A heating source for heating the fixing member;
A pressure member that forms a nip with the fixing member;
A nip forming member that forms the nip opposite to the pressure member inside the fixing member;
Slip detecting means for detecting the occurrence of slip between the recording material and the pressure member;
Have
If it is detected that slip has occurred by the slip detection means, the process linear velocity is limited,
An image forming apparatus. An image forming apparatus having an image forming process having a plurality of process linear velocities,
A fixing device is provided in the image forming apparatus main body,
The fixing device includes:
A rotatable fixing member;
A heating source for heating the fixing member;
A pressure member that forms a nip with the fixing member;
A nip forming member that forms the nip opposite to the fixing member inside the pressure member;
Slip detecting means for detecting that slip has occurred between the recording material and the fixing member;
Have
If it is detected that slip has occurred by the slip detection means, the process linear velocity is limited,
An image forming apparatus. The image forming apparatus according to claim 1.
The slip detection means is a rotation speed detection means that is installed in the fixing device or the image forming apparatus main body and measures the rotation speed of the fixing member,
Detecting the slip from the rotational speed detected by the rotational speed detecting means;
An image forming apparatus. The image forming apparatus according to claim 2.
The slip detection means is a rotation speed detection means that is installed in the fixing device or the image forming apparatus main body and measures the rotation speed of the pressure member,
Detecting the slip from the rotational speed detected by the rotational speed detecting means;
An image forming apparatus. The image forming apparatus according to claim 1, wherein
The slip detection means is a torque measurement means for measuring a torque applied to a fixing motor installed in the fixing device or the image forming apparatus main body and driving the fixing member or the pressure member;
Detecting the slip from the torque measured by the torque measuring means;
An image forming apparatus. The image forming apparatus according to claim 1.
The fixing device includes a fixing motor for driving the pressure member;
The slip detection means is a torque measuring means that is installed in the fixing device or the image forming apparatus main body and measures the torque applied to the fixing member or the fixing motor;
Measure the torque at a predetermined timing from the beginning of the image forming operation,
Detecting the slip from the transition of the measurement result of the torque measured by the torque measuring means;
An image forming apparatus. The image forming apparatus according to claim 2.
The fixing device includes a fixing motor for driving the pressure member;
The slip detection means is a torque measurement means for measuring a torque applied to a fixing motor installed in the fixing device or the image forming apparatus main body and driving the pressure member or the fixing member;
Measure the torque at a predetermined timing from the beginning of the image forming operation,
Detecting the slip from the transition of the measurement result of the torque measured by the torque measuring means;
An image forming apparatus. The image forming apparatus according to claim 1, wherein
The slip detection means detects the slip from the timing at which the recording material starts to enter the fixing device or the timing at which the recording material has been completed and the slip from the timing at which the fixing device starts to discharge or the discharge device completes discharging. Detect
An image forming apparatus. The image forming apparatus according to claim 1, wherein
The slip detection means detects the slip based on the number of prints on the recording material, the travel distance of the fixing member or the pressure member, the paper passing distance of the recording material, the image forming mode, or any combination of the above. Change the rules
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 9,
When the slip is detected, it is limited to an operation at a process line speed equal to or lower than a predetermined process line speed, or the image forming process is executed only at a predetermined process line speed.
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 9,
When the slip is detected, the process linear speed is limited only for jobs with a predetermined process condition.
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 9,
When the slip is detected, only the process condition in which the slip is detected limits the process line speed.
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 9,
When the slip is detected, the process linear speed is limited from the next job and the process is performed until the fixing device is replaced with a new one or until the fixing device is replaced with a fixing device in which the slip is not detected. Limit the line speed,
An image forming apparatus.