JP6160279B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus example Bei fixing device for fixing a toner on a recording paper by heating.

  An electrophotographic image forming apparatus uses a toner image (unfixed image) transferred and carried on a sheet-like recording medium such as paper (hereinafter referred to as recording paper) to heat and fix it on the recording paper. Or output recorded material. As such an image forming apparatus, a copying machine, a facsimile machine, a printer, and a digital multifunction machine having these functions are known.

  Some fixing devices include a fixing roller having a heating source. In the image forming apparatus including the fixing device, in order to control the temperature of the fixing roller, the temperature of the fixing roller is made constant by controlling the heating source based on the temperature detection value of the thermistor that detects the temperature of the fixing roller. I am doing so.

  However, in the control for keeping the temperature of the fixing roller constant, the influence of the type of recording paper is not taken into consideration, so that an error may occur in the fixing strength of the toner at the time of fixing, and the image quality of the fixed image may vary. As a means to deal with the variety of recording paper types, a technology has been proposed in which the user selects the recording paper type from the paper type selection unit and controls the temperature and pressure of the fixing device optimal for each recording paper type. ing.

  Japanese Patent Application Laid-Open No. 2004-228561 includes a fixing device that includes a paper type selection unit, and a user selects a recording paper type using the paper type selection unit, and controls the temperature and pressure of the fixing device optimal for each recording paper type. Have been described. That is, the fixing device described in Patent Document 1 includes a fixing roller having a heating unit therein, a pressure roller that rotates while being pressed against the fixing roller, and a pressure for changing the pressure applied to the pressure roller. And a recording paper thickness detection means provided upstream of the pair of rollers of the fixing roller and the pressure roller in the recording paper conveyance direction, and a control means. The temperature of the fixing roller and the pressing force of the pressure unit that are optimal for fixing are set according to the type of toner of the different color tone and the thickness of the recording sheet detected by the thickness detection unit.

  However, the conventional fixing device described in Japanese Patent Laid-Open No. 2004-133260 has a problem that the user needs to set the recording paper type and the operation is complicated. At the same time, since it is necessary to set the recording paper type to be selected in advance in the paper type selection unit, there is a problem that it is not possible to deal with newly released recording paper and the like, and the versatility is poor.

  It is an object of the present invention to eliminate the need for a user to select and set a recording paper type in advance, and can easily control a fixing device suitable for each recording paper, and can be used for a new recording paper. Is to provide.

An image forming apparatus according to the present invention includes a fixing member that is heated by a heating source, and a pressure member that forms a fixing nip portion between the fixing member and a recording sheet on which a toner image is transferred by a transfer device. In the image forming apparatus having a fixing device that passes through the fixing nip portion and fixes the toner carried on the recording paper, upstream of the fixing nip portion in the passing direction of the recording paper and upstream of the transfer device. are arranged on the side provided with the roller member of polyester which rotates while in contact with the recording paper, and a force measuring unit for measuring a frictional force or peel force between the recording sheet and the roller member, the measurement of the force measuring unit results based have the temperature control, the conveying speed control, and a fixing control unit for controlling the fixing conditions including at least one surface pressure control, characterized and this with a.

  According to the present invention, since an optimum fixing condition according to the type of recording paper is set in the fixing device without setting the type of recording paper in advance, a good fixed image can be obtained without performing a special operation. be able to.

1 is a cross-sectional view illustrating an image forming apparatus according to an embodiment of an image forming apparatus according to the present invention. 1 is a schematic diagram illustrating a fixing device according to an embodiment of a fixing device according to the present invention. 6 is a graph illustrating an example of torque fluctuation measured by a force measurement unit of the fixing device. 6 is a graph showing a relationship between a predicted value of fixing strength and a setting temperature of a fixing roller in the fixing device. 6 is a graph showing the relationship between the fixing strength and the conveyance speed in the fixing device. 6 is a graph showing the relationship between the fixing strength and the set pressure at the nip portion in the fixing device.

  A fixing device and an image forming apparatus according to an embodiment for carrying out the present invention will be described. First, an image forming apparatus using a fixing device according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus in which a recording paper guide apparatus according to the present invention is used. Hereinafter, a monochrome copying machine will be described as an example of the image forming apparatus. The image forming apparatus includes an image reading unit 11 that reads a document D, an image forming unit 12 that is an image forming unit that forms a toner image, and an automatic document feeder 13. The image forming apparatus also includes a document discharge tray 14 for stacking documents D sent from the automatic document feeder 13, a sheet feed unit 19 including sheet cassettes 15 to 18, and a sheet discharge tray 20 for stacking recording sheets.

  When the document D is set on the document table 21 of the automatic document feeder 13 and an operation on an operation unit (not shown), for example, a press operation of a print key is performed, the uppermost document D is rotated in the direction of the arrow B1 by the rotation of the pickup roller 22. Sent out. The document D is transported onto the contact glass 24 fixed to the image reading unit 11 by the rotation of the document transport belt 23 and stops there. The image of the document D placed on the contact glass 24 is read by a reading device 25 located between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light source 26 that illuminates the document D on the contact glass 24, an optical system 27 that forms an image of the document, a photoelectric conversion element 28 that includes a charge coupled device (CCD) that forms an image of the document, and the like. doing. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is conveyed one by one onto the contact glass 24 and the document image is read by the image reading unit 11.

  On the other hand, the photoreceptor 30 of the image forming unit 60 is disposed inside the image forming unit 12. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the reading device 25, and the surface of the charged photoreceptor 30 is exposed with the laser beam L, whereby the photoreceptor is exposed. An electrostatic latent image is formed on the surface 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred onto a recording sheet P that is a recording medium conveyed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  Recording paper P such as paper is accommodated in a plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12. The recording paper P is sent out from any of the paper feed cassettes 15 to 18 in the direction of arrow B3, and the toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording paper P. Next, the recording paper P is passed through the fixing device 100 in the image forming unit 12 as indicated by an arrow B4, and the toner image carried on the recording paper P is fixed by the action of heat and pressure. Then, the recording paper P that has passed through the fixing device 100 is conveyed by the discharge roller pair 36 and discharged to the paper discharge tray 20 as indicated by an arrow B5.

  The image forming apparatus can be a color copier having a plurality of image forming units corresponding to a plurality of colors, or a multi-function machine having functions such as a printer, a copier, and a facsimile.

<Embodiment 1>
The fixing device according to Embodiment 1 of the fixing device according to the present invention will be described below. The fixing device according to the first exemplary embodiment has the following characteristics in control. That is, the fixing device controls the temperature of the heating source based on the fixing strength predicted according to the type of recording paper by the fixing strength prediction unit. Thereby, an optimal image can be provided according to the type of recording paper. Here, the fixing strength prediction is performed by the fixing strength prediction unit. The fixing strength prediction unit predicts the fixing strength based on the frictional force and the peeling force that are applied when the force measuring member measured by the force measuring member comes into contact with the recording paper.

  Next, a fixing device according to Embodiment 1 will be described with reference to the drawings. FIG. 2 is a schematic view showing a fixing device according to an embodiment of the fixing device according to the present invention. The fixing device 100 includes a fixing roller 110 that is a fixing unit that forms the fixing nip portion N1, and a pressure roller 120 that is a pressing unit. Further, the fixing device 100 includes a conveyance motor (not shown), a force measuring unit 130 disposed on the upstream side of the fixing nip N1, and a fixing strength predicting unit that predicts the fixing strength between the recording paper P and the toner from the measured value by the force measuring unit 130. 140. The fixing device 100 further includes a fixing control unit 150 that controls the fixing conditions of the fixing device 100 based on the fixing strength predicted by the fixing strength prediction unit 140.

  The recording paper P passes through the nip N2 formed by the force measuring unit 130, the fixing nip N1 formed by the fixing roller 110, and the pressure roller 120 in this order. Although not shown in FIG. 2, an image forming means 60 (see FIG. 1) for transferring toner onto the recording paper P is provided downstream of the force measuring unit 130 and upstream of the fixing roller 110 and the pressure roller 120. Yes. The recording paper P passes through the nip portion N2 before the toner is transferred, and passes through the fixing nip portion N1 after the toner is transferred.

  Next, the fixing roller 110 and the pressure roller 120 will be described. The fixing roller 110 and the pressure roller 120 rotate in the direction of the arrow in FIG. 2, and the recording paper P passes from the left to the right as shown in the drawing through the fixing nip portion N1, and the transferred toner is heated and heated. The recording paper P is fixed by pressing.

  The fixing roller 110 is a roller member in which a fixing member surface layer 111 is provided on the surface of a fixing member core metal 112. The fixing member core metal 112 is made of aluminum, and the fixing member surface layer 111 is made of a fluororesin (for example, Teflon (registered trademark)). The heater 113 heats the fixing member in a changeable manner by generating heat inside the hollow core. The pressure roller 120 is a roller in which a pressure member surface layer 121 is provided on the surface of a pressure member cored bar 122 arranged to face the fixing member. The pressure member core 122 is made of aluminum, and the pressure member surface layer 121 is made of a fluororesin (for example, Teflon (registered trademark)). The conveyance motor is composed of a motor capable of changing the speed, such as a stepping motor, an AC motor, or a DC motor, and rotates the pressure roller 120 around the central axis of the pressure member core 122.

  Next, the force measuring unit 130 will be described. The force measuring unit 130 is formed of a resin roller 131 that is a roller member and a holding member 132, and forms a nip portion N2. As shown in FIG. 2, the recording paper P passes through the nip portion N2 from the left to the right in the drawing. The resin roller 131 is driven by a transport motor in the same manner as the pressure roller 120. The resin roller 131 is rotated at a predetermined rotational speed and conveys the recording paper P.

  The resin roller 131 is made of a polyester resin. In the force measuring unit 130, the resin roller 131 imitates toner, and the force measured between the resin roller 131 and the recording paper P is used to predict the fixing strength between the toner and the recording paper P later. Is done. For this reason, as the material of the resin roller 131, polyester is used as a material similar to toner. As a material of the resin roller 131, a resin such as polyethylene or PET can be used in accordance with the toner material. Further, the resin roller 131 can be heated in order to reproduce the properties of the melted toner.

  The holding member 132 is made by processing the surface of a metal such as stainless steel (SUS) with a fluororesin (for example, Teflon (registered trademark)). In order for the resin roller 131 to detect the frictional force between the resin roller 131 and the recording paper P later, it is desirable that the coefficient of friction with the recording paper P is as small as possible on the surface of the holding member 132. It can be.

  As shown in FIG. 2, the force measuring unit 130 detects torque when the resin roller 131 rotates. The force applied to the resin roller 131 changes before and after the recording paper P passes through the nip portion N2. The force acting between the recording paper P and the resin roller 131 is measured by obtaining the difference in torque at this time.

  As described above, since the resin roller 131 is a material simulating toner, the fixing strength between the toner and the recording paper P can be estimated. At this time, the force F1 (see FIG. 3) is a difference in torque between when the recording paper P passes through the nip portion N2 and when it does not pass. This can be detected as a frictional force between the resin roller 131 and the recording paper P. Further, the force F2 (see FIG. 3) is a difference in torque between the moment when the recording paper P peels from the nip portion N2 and when the recording paper P does not pass. This can be detected as a peeling force between the resin roller 131 and the recording paper P. The obtained frictional force F1 and peeling force F2 are used when the fixing strength prediction unit 140 predicts the fixing strength.

  Next, the fixing strength prediction unit 140 will be described. The fixing strength prediction unit 140 predicts the fixing strength using the measurement results of the frictional force and peeling force between the resin roller 131 and the recording paper P measured by the force measuring unit 130. In addition, the fixing control unit 150 controls the heater 113 of the fixing roller 110 according to the fixing strength predicted by the fixing strength prediction unit 140 and changes the set temperature of the fixing roller 110.

FIG. 3 is a graph showing an example of a variation in torque measured by the force measuring unit of the identification fixing device, and FIG. 4 is a graph showing a relationship between a predicted value of fixing strength and a set temperature of the fixing roller in the identification fixing device. The horizontal axis of the graph of FIG. 4 is obtained by calculating a relative value with 1 as the reference plain paper for the sum of the frictional force and the peeling force measured by the force measuring unit 130 as a predicted value of the fixing strength. The vertical axis represents the optimum fixing roller temperature determined from the experiment on the strength of the fixed image and the offset amount to the fixing roller. When the respective values were plotted with respect to 10 types of recording paper, it was found that both showed a good correlation. The recording temperature with a fixing strength of 1.0 is optimal at a setting temperature of 130 ° C., whereas the recording temperature of 2.0 recording paper with a high fixing strength is optimal at a setting temperature of 120 ° C. The optimum recording paper is 140 ° C.

  From the above, it can be seen that the force measuring unit 130 measures the frictional force and the peeling force of the conveyed recording paper P, and using the results, the fixing roller 110 can be controlled to an optimum temperature for each recording paper. In the first embodiment, the fixing strength is the sum of the frictional force and the peeling force obtained in the force measuring unit 130, but only the frictional force or only the peeling force is weighted and added to the frictional force and the peeling force. Can do. It is desirable that the parameter has a good correlation with the optimum fixing roller temperature in the fixing device.

  Next, the operation of the fixing device 100 according to the first embodiment will be described. First, the recording paper P passes through the force measuring unit 130, that is, the nip N2 formed by the resin roller 131 and the holding member 132. At this time, as shown in FIG. 3, the force measurement unit 130 measures the frictional force and the peeling force with the resin roller 131. Next, the fixing strength prediction unit 140 calculates a predicted value of the fixing strength from the measured frictional force and peeling force. Then, the fixing control unit 150 receives the predicted value and controls the heater 113 of the fixing roller 110 so that the temperature of the fixing roller 110 becomes an optimum temperature for each recording paper P using the relational expression of FIG. .

  Then, after the toner image is transferred, the recording paper P that has passed through the force measuring unit 130 passes through a fixing nip portion N1 formed by the fixing roller 110 and the pressure roller 120 that are controlled to an optimum temperature. As a result, the conveyed recording paper P and the heat generating fixing roller 110 come into contact with each other at the fixing nip portion N1, and the toner image on the recording paper P is heated and melted in an optimum state.

  The fixing device 100 according to the first embodiment includes a force measurement unit 130 and a fixing strength prediction unit 140 to predict the fixing strength of toner and recording paper. The fixing control unit 150 controls the temperature of the fixing device 100 by controlling the heater 113 based on the predicted fixing strength. For this reason, it is not necessary to set the type of recording paper in advance, and the fixing device can be controlled automatically and simply under conditions suitable for each recording paper. Therefore, it is possible to provide a fixing device that supports a wide variety of recording paper types. In addition, it is possible to flexibly cope with recording paper that is newly released in the future.

<Embodiment 2>
In the fixing device 100 according to the first exemplary embodiment, the fixing control unit 150 controls the recording paper P so that the temperature of the fixing roller 110 is optimized based on the fixing strength, but the target to be controlled by the fixing control unit 150 is the fixing roller. The temperature may be other than 110. For example, the conveyance speed control of the recording paper in which the recording paper P passes through the fixing nip portion N1 can be performed. FIG. 5 is a graph showing the relationship between the fixing strength and the conveyance speed in the identification apparatus. In the fixing device according to the second exemplary embodiment, a relational expression between the fixing strength and the conveyance speed is obtained by experiments. Then, the fixing control unit 150 controls the number of rotations of the transport motor that drives the pressure roller 120 according to the fixing strength predicted by the fixing strength prediction unit 140 for each recording paper P.

<Embodiment 3>
Further, the surface pressure of the fixing nip portion N1 formed by the fixing roller 110 and the pressure roller 120 can be controlled. FIG. 6 is a graph showing the relationship between the fixing strength and the set pressure at the nip portion in the identification apparatus. In the fixing device according to the third embodiment, the fixing control unit 150 controls the surface pressure of the fixing nip portion N1 formed by the fixing roller 110 and the pressure roller 120 based on the fixing strength from the relational expression shown in FIG. At this time, the pressure roller 120 is provided with a mechanism capable of adjusting the amount of pressing with respect to the fixing roller 110, and the pressing force of the pressure roller 120 to the fixing roller 110 is controlled to control the surface pressure of the fixing nip portion N1. To control.

  Further, a plurality of parameters can be selected and controlled from the temperature of the fixing roller 110, the conveyance speed, and the surface pressure of the fixing nip portion N1. In this case, an optimum fixed image corresponding to the recording paper P can be obtained more precisely by controlling each of them by the fixing control unit 150 according to the fixing strength predicted by the fixing strength prediction unit 140.

  As described above, according to the fixing device according to each embodiment, recording is performed in the fixing device by providing a mechanism for controlling the heating source based on the fixing strength predicted according to the type of recording paper by the fixing strength prediction unit. An optimal image can be provided according to the type of paper.

100: fixing device 110: fixing roller (fixing member)
113: Heater (heating means)
120: Pressure roller 122: Pressure member mandrel 130: Force measuring unit 131: Resin roller (roller member)
132: Holding member 140: Fixing strength prediction unit 150: Fixing control unit

JP 2003-15461 A

Claims (3)

Fixing member heated by the heating source, and the comprises a pressure member forming a fixing nip portion between the fixing member, said recording paper having the toner image is passed through the fixing nip portion by the transfer device In an image forming apparatus having a fixing device for fixing toner carried on a recording sheet,
A polyester roller member disposed upstream of the fixing nip portion in the recording paper passage direction and upstream of the transfer device and rotating in contact with the recording paper; and the roller member and the recording A force measuring unit for measuring friction force or peeling force with the paper,
A fixing control unit that controls fixing conditions including at least one of temperature control, conveyance speed control, and surface pressure control based on the measurement result of the force measuring unit;
An image forming apparatus comprising: A fixing strength prediction unit that predicts a fixing strength between the recording paper and the toner based on a measurement value of the force measuring unit, and the fixing control unit controls the fixing condition based on the predicted fixing strength. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein a frictional force or a peeling force acting between the roller member and the recording sheet is measured from a torque by which the roller member rotates .