JP2008083390A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has simple constitution and can surely suppress thermal deformation of a brush roller abutting against a rotary body having a heating source. <P>SOLUTION: The image forming apparatus includes a control unit 96 which controls a driving motor 97 of a fixing device 9, namely, controls the start and stop of rotation of a fixing roller 91, and slightly rotates the fixing roller 91 each time a rotation stop state of the fixing roller 91 lasts for a predetermined time so as to prevent the thermal deformation of the brush roller 93 abutting against the fixing roller 91. The brush roller 93 is driven by the slight rotation of the fixing roller 91 to rotate. Then two slight rotation times R1 and R2 which are different from each other are set in the image forming apparatus. The control unit 96 selects one of them when performing slight rotation control. Further, the control unit 96 selects the slight rotation time different from a slight rotation time selected in the preceding rotation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing device that heat-fixes a toner image on a recording medium. More specifically, the present invention relates to an image forming apparatus in which the fixing device includes a rotating body having a heating source and a brush roller in contact with the rotating body, and controls the rotation of the brush roller.

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image onto a recording sheet. As a fixing device, a roller system that includes a roller pair including a fixing roller and a pressure roller, and that fixes a toner image by passing a recording sheet through a nip portion of the roller pair is widely used. In this roller-type fixing device, a heating source such as a halogen heater is provided inside the fixing roller, and the toner image is fixed on the recording paper by heat and pressure with the pressure roller.

  Further, a cleaning member for cleaning the surface of the roller having a heating source such as a fixing roller (hereinafter referred to as “heating roller”) is in contact with the roller. As the cleaning member, a roller having a heat-resistant paper wound around the surface or a brush roller having a heat-resistant fiber planted on the surface is used.

  Among the types of cleaning members, a roller around which heat-resistant paper is wound has a lifetime when toner accumulates on the heat-resistant paper. In this respect, the brush roller has a merit that it has a long life compared to the one wrapped with heat-resistant paper because the brush roller has a large surface area and dirt hardly accumulates on the brush. However, since the contact portion is a brush, the brush may be thermally deformed if the heating roller is stopped for a long time. If the brush is thermally deformed, the cleaning performance will be degraded, or abnormal noise will occur due to uneven rotation.

As described above, when a rotating body that is likely to be thermally deformed is brought into contact with the heating roller for a long time, control is performed to rotate the rotating body at regular intervals and periodically change the contact position. Usually, since the cleaning member such as a brush roller is driven and rotated by the heating roller, the heating roller is periodically rotated minutely. As a technique for controlling the rotation of the rotating body by paying attention to such a problem of thermal deformation, for example, there are fixing devices disclosed in Patent Document 1 and Patent Document 2.
JP-A-6-51668 JP 2006-30777 A

  However, the conventional fixing device described above has the following problems. That is, the amount of rotation of the heating roller during a predetermined rotation time may vary due to endurance variation of the DC motor that is the drive source of the heating roller or torque variation of the drive system. For example, the amount of rotation from the start of rotation of the motor until it reaches steady rotation, and the amount of rotation by which the motor rotates due to inertia after a stop instruction varies depending on torque fluctuations. Therefore, even if the motor driving time is constant, the rotation amount of the roller is not necessarily constant. Along with this, the rotation amount of the brush roller also fluctuates, and depending on the conditions, when the heating roller is slightly rotated, the rotation amount of the brush roller is just one rotation of the brush roller, and the same portion may be the contact position. . For this reason, the deformation of the brush has not been reliably suppressed.

  Further, as in Patent Document 1 or Patent Document 2, it is conceivable to detect the actual rotation amount of the roller and control the rotation time of the roller. However, when such control is performed, a detection means for detecting the rotation amount is required. As a result, the equipment becomes larger, more complex, and more expensive.

  The present invention has been made to solve the problems of the conventional fixing device described above. That is, an object of the present invention is to provide an image forming apparatus that has a simple configuration and can reliably suppress thermal deformation of a brush roller that is in contact with a rotating body having a heating source.

  An image forming apparatus designed to solve this problem includes a fixing device including a rotating body having a heating source, a brush roller in contact with the rotating body, and a control unit that controls the rotation of the brush roller. The control unit is an image forming apparatus that performs minute rotation control for rotating the brush roller every time the rotation stop state of the brush roller elapses with the rotating body heated, and the rotation time of the brush roller is reached At least two minute rotation times are set, and during the minute rotation control, the control unit selects a minute rotation time different from the minute rotation time selected at the previous rotation, and rotates the brush roller according to the minute rotation time. It is characterized by.

  That is, in the image forming apparatus of the present invention, in order to prevent thermal deformation of the brush roller in contact with a rotating body (for example, a fixing roller) having a heating source, the rotation stop state of the brush roller is maintained while the rotating body is heated. When a predetermined time elapses, it has a function of rotating the brush roller slightly. The rotation start and stop of the brush roller are controlled by the control unit. Then, when the rotating body continues to stop with preheating in the energy saving mode or the like, the control unit performs the minute rotation control as described above. When rotating the brush roller, the brush roller may be directly rotated, or may be driven and rotated by a rotating body. In the case of driven rotation, the rotation of the brush roller is indirectly controlled by controlling the rotation of the rotating body.

  Further, at least two minute rotation times are set in the image forming apparatus. The minute rotation time is a time for rotating the brush roller in the minute rotation control, and the set minute rotation times are different from each other. The control unit selects one of these minute rotation times when performing minute rotation control. Further, in selecting the minute rotation time, the control unit selects a minute rotation time different from the minute rotation time selected in the previous rotation. As a result, the rotation amount at the previous rotation and the current rotation amount are different. Therefore, the situation where the same position is repeated as the contact position with the rotating body is extremely small, and the life of the brush roller can be extended.

  In the image forming apparatus of the present invention, it is not necessary to detect the actual amount of rotation of the brush roller (or rotating body). Therefore, there is no need to provide a sensor or the like that detects the amount of rotation. Therefore, the apparatus configuration is simple and the apparatus can be made compact.

  Further, it is better that at least one of the set minute rotation times is shorter than the time for which the brush roller makes one rotation. That is, by avoiding one rotation of the brush roller, it is possible to reliably avoid the situation where the contact position is the same position.

  The image forming apparatus of the present invention has a motor for driving the fixing device, and the motor transmits a signal indicating that the rotation is stable to the control unit, and the control unit instructs the motor to start rotation. It is better to measure the response time from receiving the signal until receiving the signal and correcting the rotation time of the brush roller based on the response time. That is, a change in the rotational speed of the motor occurs due to the torque fluctuation of the motor. For this reason, the desired rotation amount may not be achieved even with the same rotation time. Therefore, the response time until the motor rotation is stabilized is measured, and the amount of torque fluctuation is estimated from the response time. That is, the rotation time is corrected so as to obtain a desired rotation amount based on the response time. Thereby, the situation where the contact position becomes the same position can be avoided more reliably.

  According to the present invention, an image forming apparatus that has a simple configuration and can reliably suppress thermal deformation of a brush roller that is in contact with a rotating body having a heating source is realized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a fixing device provided in an electrophotographic laser printer.

[First embodiment]
The image forming apparatus 100 according to the first embodiment is an electrophotographic laser printer, and as shown in FIG. 1, a laser oscillator 2, a polygon mirror 3 and a reflection mirror 4 are arranged in an optical system. In addition, the image forming apparatus 100 is a rotating drum type electrophotographic photosensitive member in an image process unit, and includes a photosensitive drum 1 that is a negatively chargeable organic photoconductor (OPC). It rotates at a constant speed in the direction of the arrow in FIG. Around the photosensitive drum 1, a charger 5, a developing device 6, a transfer device 7, and a cleaning blade 8 are arranged along the rotation direction. In addition, in the image forming apparatus 100, a paper feed roller 11, a paper discharge roller 15, a paper feed sensor 10, a paper discharge sensor 14, a fixing device 9 and the like are arranged in the transport unit. .

  Next, the operation of the image forming apparatus 100 configured as described above will be briefly described. The photosensitive drum 1 rotates in the direction of the arrow in FIG. 1, and the charger 5 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential. Next, laser light is modulated and emitted from the laser oscillator 2 based on the image signal. This laser beam is scanned in the main scanning direction by the polygon mirror 3, is reflected by the reflecting mirror 4, and enters the photosensitive drum 1. Thereby, an electrostatic latent image is formed on the photosensitive drum 1. This electrostatic latent image is developed by the developing device 6 to become a toner image. The toner image is transferred onto the recording sheet S fed by the sheet feeding roller 11 by the transfer unit 7 disposed opposite to the photosensitive drum 1. Thereafter, the recording paper S to which the toner image has been transferred is heated in the fixing device 9, and the toner image is melted and fixed on the recording paper S by the heat. After the image is fixed, the recording paper S is discharged out of the apparatus by a paper discharge roller 15. With the above operation, printing for one sheet is performed.

  Next, the configuration of the fixing device 9 provided in the laser printer of this embodiment will be described. As shown in FIG. 2, the fixing device 9 includes a fixing roller 91, a pressure roller 92, and a brush roller 93. Further, the fixing roller 91 (material: stainless steel, roller diameter: 30 mm, wall thickness: 0.6 mm) has a hollow structure, and a heater 94 (for example, a halogen lamp) is provided therein. The entire fixing roller 91 is heated by the radiant heat from the heater 94. The pressure roller 92 is in pressure contact with the fixing roller 91 to form a nip portion. The pressure roller 92 is a known one in which an elastic layer (material: silicon rubber, layer thickness: 7 mm) is formed on a metal core (material: stainless steel, core diameter: 16 mm). The brush roller 93 is a well-known one in which a brush core (material: PPS (polyphenylene sulfide), fine diameter: 15 denier, pile length: 4 mm) is implanted in a metal core (material: stainless steel, core diameter: 9 mm). Yes, the pressing pressure is set to 6N, and the fixing roller 91 is brought into contact with the roller. In addition, the material and size of each roller are examples, and are not limited thereto.

  Further, the image forming apparatus 100 according to the present embodiment includes a drive motor 97 (for example, a DC brushless motor) that drives the fixing roller 91, a control unit 96 that controls the drive motor 97, and a counter 98. A signal for instructing rotation start (hereinafter referred to as “rotation start signal”) or a signal for instructing stop (hereinafter referred to as “rotation stop signal”) is transmitted from the control unit 96 to the drive motor 97. On the other hand, a signal (hereinafter referred to as “rotation lock signal”) notifying that the rotation has been stabilized after the start of rotation is transmitted from the drive motor 97 to the control unit 96. In addition, the control unit 96 can use the counter 98 to measure various times.

  In the fixing device 9 configured as described above, when the recording paper S to which the toner image has been transferred is conveyed to the fixing device 9, the nip portion formed by the fixing roller 91 and the pressure roller 92 is recorded on the recording sheet S. The paper S passes. At this time, the recording sheet S is passed through the nip portion with the printing surface facing the fixing roller 91. Then, the toner is heated and melted by the fixing roller 91 and fixed to the recording paper S. That is, fixing is performed.

  Next, the rotation control of the control unit 96 when the operation of the fixing device 9 is stopped by shifting to the standby mode or the power saving mode will be described with reference to the flowchart of FIG. During this control, the stop time T1 means an interval for slightly rotating the drive motor 97, and the rotation time T2 means a time for rotating the drive motor 97. In the control unit 96, two minute rotation times R1 and R2 are set. Furthermore, the minute rotation time R1 and the minute rotation time R2 are different times. In addition, the value of the minute rotation time R1 is set as the initial value in the rotation time T2.

  First, when the image forming apparatus 100 shifts to the standby mode or the power saving mode, the rotation of the fixing roller 91 is stopped. That is, the control unit 96 transmits a rotation stop signal to the drive motor 97 and stops the drive motor 97 (S1). At this time, even when the fixing roller 91 is stopped, the heater 94 remains on, and the fixing roller 91 is kept at a constant temperature. Then, from the time when the rotation stop signal is transmitted to the drive motor 97, the stop time during which the drive motor 97 is stopped is started. That is, the counter 98 starts counting the stop time timer t1 (S2).

  Next, it is determined whether or not the stop time timer t1 is within the stop time T1 (S3). If it is within the stop time T1 (S3: YES), it is determined whether or not the standby mode or the power saving mode is cancelled, that is, whether or not a cancel signal is received (S4). When the release signal is received (S4: YES), the normal rotation of the fixing roller 91 is resumed. That is, a rotation start signal is transmitted to the drive motor 97, and normal rotation of the drive motor 97 is resumed (S5). After the process of S5, this process is terminated. On the other hand, if the release signal has not been received (S4: NO), the process returns to S3 to determine whether or not the stop time timer t1 is within the stop time T1.

  On the other hand, when the stop time timer t1 exceeds the stop time T1 (S3: NO), it is determined whether or not the rotation time T2 is equal to the minute rotation time R1 (S6). If it is the same value (S6; YES), the value of the minute rotation time R2 is set to the rotation time T2 (S7). If it is not the same value (S6: NO), the value of the minute rotation time R1 is set to the rotation time T2 (S8). That is, the rotation time T2 is set so as to be alternately repeated between the value of the minute rotation time R1 and the value of the minute rotation time R2 by the processing of S6 to S8.

  Thereafter, rotation of the fixing roller 91 is started. That is, a rotation start signal is transmitted to the drive motor 97, and the drive motor 97 is rotated (S9). From this point of time, timing of the rotation time during which the drive motor 97 is rotating is started. That is, the counter 98 starts counting the rotation time timer t2 (S10).

  Next, it is determined whether or not the rotation time timer t2 is within the rotation time T2 (S11). When the rotation time timer t2 exceeds the rotation time T2 (S11: NO), the stop time timer t1 and the rotation time timer t2 are reset (S12). Then, returning to the processing of S1, the drive motor 97 is stopped, and the stop time timer t1 is restarted.

  By the above processing, the brush roller 93 periodically rotates slightly, so that thermal deformation of the brush roller 93 can be avoided. Further, the rotation time T2 is alternately set between the value of the minute rotation time R1 and the value of the minute rotation time R2. Therefore, the rotation amount of the fixing roller 91, that is, the rotation amount of the brush roller 93 is different from the previous rotation amount, and the contact position after the rotation is different from the previous contact position. Thereby, the situation where the contact position of the brush roller 93 is the same every time is extremely small, and the thermal deformation of the brush roller 93 can be avoided reliably.

  Further, at least one of the set minute rotation times R1 and R2 is shorter than the time required for the brush roller 93 to make one rotation. That is, when the minute rotation time is selected, the brush roller 93 does not rotate once. Therefore, the situation where the contact position is the same can be avoided more reliably.

[Second form]
The image forming apparatus according to the second embodiment performs control to adjust the rotation time in consideration of torque fluctuation of the drive motor 97. That is, even if two minute rotation times are provided, a desired rotation amount may not be obtained due to torque fluctuation of the drive motor 97. Therefore, the rotation time is corrected from the rotation state of the drive motor 97, and the rotation amount of the drive motor 97 is brought close to the desired rotation amount. Hereinafter, the control will be described based on the flowchart of FIG. Note that the configuration of the apparatus is the same as that of the first embodiment, and a description thereof will be omitted.

  In the control of the second form, the operations from the process of S21 to the process of S27 are the same as those of the first form. That is, the drive motor 97 is stopped at the time of transition to the standby mode or the power saving mode (S21), and the timing for slightly rotating the drive motor 97 is detected (S22 to S24). If it is the timing for minute rotation (S23: NO), one of the two minute rotation times R1, R2 is selected and set as the rotation time T2 (S26 to S28).

  Next, a rotation start signal is transmitted to the drive motor 97, and the drive motor 97 is rotated (S29). From this point of time, timing of the rotation time during which the drive motor 97 is rotating is started. That is, the counter 98 starts counting the rotation time timer t2 (S30).

  Next, when the drive motor 97 reaches a steady rotation state, a rotation lock signal is transmitted to the control unit 96. Then, the control unit 96 receives the rotation lock signal (S31). A response coefficient α is obtained based on the rotation time timer t2 when the lock signal is received (S32). Then, an actual minute rotation time T3 (= α × T2) is obtained based on the response coefficient α (S33).

  That is, the response time and the rotation speed vary depending on the torque of the drive motor 97. When the torque is small, as shown in FIG. 5, it stabilizes early and the rotation speed is fast. On the other hand, when the torque is large, it takes time to stabilize as shown in FIG. Therefore, the amount of rotation is different even at the same rotation time. Therefore, in order to correct the fluctuation amount due to the torque, the torque is estimated based on the response time, and the rotation time is reset so that the desired rotation amount is obtained.

  Thereafter, it is determined whether or not the rotation time timer t2 is within the minute rotation time T3 corrected by the process of S33 (S34). When the rotation time timer t2 exceeds the minute rotation time T3 (S34: NO), the stop time timer 1 and the rotation time timer t2 are reset (S35). Then, the process returns to S21 to stop the drive motor 97 and restart the count of the stop time timer t1.

  By the above processing, the rotation time T2 is alternately set between the value of the minute rotation time R1 and the value of the minute rotation time R2. Further, the rotation time T2 is corrected based on the response time until the rotation is steady. Therefore, the rotation amount of the fixing roller 91 can be brought close to a desired value, and the contact position of the brush roller 93 becomes a desired position. Therefore, the rotation amount of the fixing roller 91 is surely different from the previous rotation amount, and the contact position of the brush roller 93 is more reliably changed. Therefore, the thermal deformation of the brush roller 93 can be avoided reliably.

  In the embodiment, since the brush roller 93 is in contact with the fixing roller 91 and the brush roller 93 is driven to rotate by the fixing roller 91, the rotation time of the fixing roller 91 is controlled. If a source is provided, the rotation time of the brush roller 93 may be directly controlled.

  In the embodiment, the brush roller 93 is in contact with the fixing roller 91. However, the present invention is not limited to this. That is, the present invention can be applied to any brush roller that is in contact with a rotating body having a heating source. For example, as shown in FIG. 7, the present invention can also be applied to a fixing device in which the pressure roller 92 has a built-in heater 94 and the brush roller 93 contacts the pressure roller 92. Further, as shown in FIG. 8, the present invention can be applied to a fixing device in which the pressure roller 92 is in contact with the auxiliary heating roller 95 including the heater 94 and the brush roller 93 is in contact with the auxiliary heating roller 95.

  In the embodiment, two types of minute rotation times R1 and R2 are provided. However, the present invention is not limited to this, and three or more types of minute rotation times may be provided. That is, it is only necessary to select a minute rotation time different from the previous time.

  As described above in detail, the image forming apparatus 100 according to the embodiment includes the control unit 96 that controls the drive motor 97 of the fixing device 9, that is, controls the start and stop of rotation of the fixing roller 91. Then, the control unit 97 slightly rotates the fixing roller 91 every time the rotation stop state of the fixing roller 91 elapses for a predetermined time in order to prevent thermal deformation of the brush roller 93 that contacts the fixing roller 91. The brush roller 93 is driven to rotate by the slight rotation of the fixing roller 91. In the image forming apparatus 100, two different micro-rotation times R1 and R2 are set. The control unit 96 selects one of the minute rotation controls. Specifically, the control unit 96 alternately selects the minute rotation times R1 and R2. That is, a minute rotation time different from the minute rotation time selected at the previous rotation is selected. As a result, the rotation amount at the previous rotation and the current rotation amount are different. Therefore, the same position as the contact position with the fixing roller 91 is prevented from being repeated, and the life of the brush roller 93 can be increased.

  In the image forming apparatus 100, it is not necessary to detect the actual rotation amount of the brush roller 93 (or the fixing roller 91). Therefore, there is no need to provide a sensor or the like that detects the amount of rotation. Therefore, the device configuration is simple and the device can be made compact. Accordingly, an image forming apparatus that has a simple configuration and can reliably suppress thermal deformation of the brush roller that contacts the fixing roller is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, in the embodiment, the present invention is applied to a laser printer, but the present invention is not limited to this. That is, even a copying machine, scanner, FAX, word processor, or the like can be applied as long as it has a fixing device. In addition to a color printer, a monochrome printer may be used. Further, as long as it is a color image forming apparatus, a tandem system or a 4-cycle system may be used.

  In the fixing device of this embodiment, the fixing nip portion is formed by two rollers, but the present invention is not limited to this. For example, a fixing belt having a heating source may be used instead of the fixing roller having a heating source. In addition to the halogen heater, the heating source may be, for example, a metal layer that generates electromagnetic induction heat.

It is sectional drawing which shows schematic structure of the image forming apparatus concerning a 1st form. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a first embodiment. 6 is a flowchart showing fixing roller rotation control of the fixing device according to the first embodiment. 6 is a flowchart showing fixing roller rotation control of a fixing device according to a second embodiment. It is a figure which shows the timing of the lock signal in a small torque state. It is a figure which shows the timing of the lock signal in a large torque state. FIG. 6 is a cross-sectional view (part 1) illustrating a schematic configuration of a fixing device according to an application example. FIG. 6 is a cross-sectional view (part 2) illustrating a schematic configuration of a fixing device according to an application example.

Explanation of symbols

9 Fixing Device 91 Fixing Roller 92 Pressure Roller 93 Brush Roller 94 Heating Heater 95 Auxiliary Heating Roller 96 Control Unit 97 Motor 98 Counter 100 Image Forming Apparatus

Claims (3)

A fixing device including a rotating body provided with a heating source, a brush roller in contact with the rotating body, and a control unit that controls rotation of the brush roller, wherein the control unit is configured to heat the rotating body. In an image forming apparatus that performs fine rotation control for rotating the brush roller every time a predetermined time elapses when the rotation of the brush roller is stopped,
At least two minute rotation times that are the rotation time of the brush roller are set,
The image forming apparatus, wherein the control unit selects a minute rotation time different from the minute rotation time selected during the previous rotation during the minute rotation control, and rotates the brush roller according to the minute rotation time. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein at least one of the minute rotation times is shorter than a time during which the brush roller makes one rotation. The image forming apparatus according to claim 1, wherein:
A motor for driving the fixing device;
The motor transmits a signal indicating that the rotation is stable to the control unit,
The control unit measures a response time from when the motor is instructed to start rotation to when the signal is received, and corrects the rotation time of the brush roller based on the response time. apparatus.

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