JP7714979B2 - Fixing device and image forming apparatus - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus.

Conventionally, a known fixing device for an image forming apparatus is one that passes a recording medium (paper) carrying a toner image through a fixing nip formed by a fixing member having a heating means and a pressure member, and fixes the toner image to the recording medium by applying heat and pressure.
Also known is a configuration in which a means is provided for cleaning the surface of the fixing member by pressing a cleaning web configured to be retractable against the surface of the fixing member.

A known cleaning means configuration includes, for example, a web holding member to which the end of the cleaning web is fixed, a winding member to which the leading end of the cleaning web is fixed and which rotates to wind up the cleaning web, and a pressing member that presses the cleaning web against the fixing member. By winding up the cleaning web with the winding member, a new web unwound from the web holding member can be used to wipe the surface of the fixing member. This ensures that the cleaning function for the fixing member remains good over time and does not deteriorate.

Among such cleaning devices, there is one known that has a mechanism that detects the remaining or used amount of cleaning web wound around the web holding member, and issues a warning to replace the cleaning web with a new one if the remaining amount is low (see, for example, Patent Document 1).

Continuing to operate the device with insufficient cleaning web remaining can result in problems such as a decline in image quality and damage to the drive motor and gears. Furthermore, if printing is continued after a warning to replace the cleaning web is displayed, the cleaning web may run out completely, causing an error and causing the device to emergency stop.
Regarding the remaining amount of the cleaning web, it is required to be able to detect both a web near-end state, in which the cleaning web is about to run out, and a web end state, in which the cleaning web has run out.

To address this issue, the device in Patent Document 1 discloses a configuration in which a web remaining amount detection sensor detects a notch in the cleaning web (fixing web) that indicates the remaining amount. It is described as being able to display a predetermined number of remaining copies corresponding to the notch, allowing the operator to replace the web at the appropriate time.

The device in Patent Document 1 requires the use of a cleaning web with notches formed in it that correspond to the remaining number of copies that can be made. This poses a problem in terms of the cost of consumables. Furthermore, a sensor must be precisely positioned so that the notches can be detected, and there is the issue that it is not easy to achieve sufficient detection efficiency or effectiveness with a single detection means.

The present invention therefore aims to provide a fixing device that can efficiently and effectively detect the remaining amount of cleaning web using a single detection means, without using a special cleaning web.

In order to solve the above problems, the fixing device of the present invention is a fixing device that includes a fixing member that is a rotating body heated by a heating means, and a pressure member that forms a fixing nip portion between the fixing member and the fixing member, and that conveys a recording medium carrying an unfixed toner image to the fixing nip portion and fixes the toner image to the recording medium, and that includes cleaning means that removes residual toner adhering to the surface of the fixing member, and the cleaning means includes a cleaning web that wipes the surface of the fixing member, a web holding member that holds the cleaning web so that it can be fed out, a winding member that can wind up the cleaning web, and a pressure member that applies pressure to the fixing member. and a single detection means for detecting the remaining amount of the cleaning web held by the web holding member, wherein the detection means has a filler that displaces according to the remaining amount of the cleaning web and a sensor that detects the filler, and is characterized in that the detection means detects a web near-end state in which the cleaning web is about to run out, and a web end state in which the cleaning web has run out, and the sensor of the detection means is off when there is a sufficient remaining amount of the cleaning web held by the web holding member, is on in the web near-end state, and is off again in the web end state .

The present invention provides a fixing device that can efficiently and effectively detect the remaining amount of cleaning web using a single detection means, without using a special cleaning web.

1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention. 1 is a schematic perspective view of an external appearance of a fixing device according to the present invention; 1 is a schematic perspective view of an external appearance of a fixing device according to the present invention; FIG. 2 is a schematic diagram illustrating an example of a configuration of a fixing device according to the present invention. FIG. 10 is an explanatory diagram showing the positional relationship between the remaining amount of cleaning web and a detecting means. FIG. 10 is an explanatory diagram showing the positional relationship between the remaining amount of cleaning web and a detecting means. FIG. 10 is an explanatory diagram showing the positional relationship between the remaining amount of cleaning web and a detecting means. FIG. 10 is an explanatory diagram showing the positional relationship between the remaining amount of cleaning web and a detecting means.

The fixing device and image forming apparatus of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and other modifications, additions, corrections, deletions, and other changes may be made within the scope of what one skilled in the art can conceive. Any aspect that achieves the functions and effects of the present invention is within the scope of the present invention.

[Image forming apparatus]
An embodiment of an image forming apparatus according to the present invention will be described with reference to FIG.
1 is a schematic diagram showing the configuration of an image forming apparatus, specifically a copying machine capable of forming monochrome images, which can also function as a printer when connected to a PC.

Note that, because the image forming apparatus of this embodiment is a copier, it has a document reading unit that functions as a scanner, but if it is a machine dedicated to PC online output, such as a so-called printer version, and has a built-in controller, the document reading unit may be omitted.

The general configuration and operation of the image forming apparatus of this embodiment will be described below.
The image forming apparatus has a scanner that houses an illumination device, an optical system, a CCD image sensor, and the like.
Above the scanner is provided an automatic document reader (hereinafter referred to as an "ADF unit" (ADF: Auto Document Feeder)) 100. The ADF unit 100 automatically transports documents and sends them to the reading surface of the contact glass.

The operator places the document on the ADF unit 100, which has an integrated pressure plate, selects the mode using the function selection keys on the operation panel, and while checking the contents displayed on the LCD screen, operates the numeric keypad and function keys to set the desired image formation conditions.

The image signal read by the document reading unit 102 is A/D (Analog/Digital) converted by the SBU (Sensor Board Unit) and then emitted as laser light from the laser writing unit 107. The laser light is focused by a cylindrical lens in the laser writing unit 107 and line-scanned in the main scanning direction by a polygon mirror, forming an electrostatic latent image on the photosensitive drum 108.

The developing unit 110 includes a drum cleaning unit 105 and a charger 106 around the photosensitive drum 108. The charger 106 is used to charge the surface of the photosensitive drum 108.
A high voltage is applied to the charger 106 from a power supply unit (PSU) via a receptacle, electrode terminals, conductive bearings, and the like.

Toner supplied from the toner supply unit 109 at any time and developer previously filled in the development unit 110 are stirred and mixed by an internal conveying screw and transported to the development roller. The toner is electrostatically attracted by magnetic force and is negatively charged.

The two-component developer carried by the developing roller is regulated to an appropriate amount by a developer brush regulation member such as a doctor blade or casing located below the developing roller. Then, the frictionally charged toner in the two-component developer moves to the photosensitive drum 108 due to the bias voltage, and selectively adheres to the electrostatic latent image.

The toner concentration inside the developing unit 110 is detected from the charge amount by a toner concentration sensor located at the bottom.
Any untransferred toner remaining on the photosensitive drum 108 after transfer is scraped off by a cleaning blade provided in the drum cleaning unit 105 and transported to a waste toner bottle 119 for collection.

In addition, an entrance seal made of Mylar or a sponge-like material is appropriately installed around the development unit 110 to prevent toner from scattering.

The visible image formed by the toner on the photosensitive drum 108 is temporarily transferred onto an intermediate transfer belt unit 113 .
When the recording medium is transported by the paper transport unit 114 and passes through the registration roller unit, the toner on the intermediate transfer belt unit 113 is transferred to the recording medium by the positive charge from the transfer unit as it passes through the nip between the photosensitive drum 108 and the intermediate transfer belt unit 113.

The recording medium (paper) onto which the toner has been transferred is transported to a fixing device (fixing unit) 121, where a certain temperature and pressure are applied to heat-fuse the toner image.
The fixing roller in the fixing device 121 is provided with a thermistor to detect the surface temperature and control the ON/OFF of the heater. The thermistor may be of a contact type or a non-contact type. A thermal fuse is also provided to prevent excessive temperature rise.

The fixing device 121 of this embodiment includes at least a fixing member (fixing roller), a heating unit, and a pressure member. The pressure member (pressure roller) is, for example, a hollow member that rotates in contact with the fixing member, forming a fixing nip portion. Pressure application and depressurization of the fixing nip portion are controlled by a cam. A heating member may be provided inside the pressure member.
Other configurations of the fixing device 121 will be described later.

The recording medium with the heat-fused toner image is separated from the heating member and the fixing member by a fixing separation plate, and then passes through a reversing and discharging unit 120, or is printed on both sides according to the set conditions, and is then discharged onto a paper discharge tray 125. If a post-processing device or the like is connected, the recording medium is transported to the recording medium inlet of the connected device.
The image forming apparatus is also provided with casters 124 for moving the main body.

The image forming apparatus of this embodiment forms images using the electrophotographic method using the configuration and operation described above.

[Fixing device]
Next, the configuration of the fixing device 121 according to the present invention will be described with reference to FIGS.
The fixing device 121 of this embodiment is mounted so as to be removable from the image forming apparatus shown in FIG.
The fixing device 121 of this embodiment includes a fixing member (fixing roller) 30, a pressure member (pressure roller) 31 that contacts the fixing member 30 to form a fixing nip portion, and a separation unit 13 having a separation member that separates the recording medium (paper) P after the toner image is fixed.

2 and 3 are schematic perspective views of the exterior of the fixing device 121. FIG.
FIG. 2 shows the separation unit 13 in a state where it is fixed in a closed position, and FIG. 3 shows the separation unit 13 in a state where it is completely opened.

The fixing device 121 of this embodiment is equipped with a fixing member 22. In conventional fixing devices, a coil spring or the like is provided as an opening/closing assist member 25 to prevent the separation unit 13 from falling under its own weight, and its tension maintains weight balance when opening and closing. However, if the tension of the coil spring is insufficient, the holding force is also insufficient, and the separation unit 13 may fall under its own weight. In contrast, the fixing device 121 of this embodiment can fix the separation unit 13 at a desired position between the open position and the closed position using the fixing member 22, preventing the separation unit 13 from accidentally falling or moving.

In the fixing device 121 of this embodiment, the separation unit 13 is pivotally rotated and opened/closed by manually moving the fixed member 22 and the operation knob 23 .
First, while pressing the biasing member 26, slide the fixing member 22 with your left hand, and then raise the operating knob 23 to the position 23a (see Figure 2) with your right hand, thereby releasing the lock and allowing the separation unit 13 to be opened and closed.

FIG. 4 is a schematic diagram showing an example of the configuration of the fixing device 121 according to the present invention.
The fixing device 121 of this embodiment comprises a fixing member 30, which is a rotating body heated by a heating means, and a pressure member 31 that forms a fixing nip portion N between the fixing member 30, and transports a recording medium P carrying an unfixed toner image to the fixing nip portion N, and fixes the toner image to the recording medium P.
Also provided is a cleaning means 122 for removing residual toner adhering to the surface of the fixing member 30 .
The cleaning means 122 includes a cleaning web 41 that wipes the surface of the fixing member 30, a web holding member 44 that holds the cleaning web 41 so that it can be fed out, a winding member 46 that can wind up the cleaning web 41, a pressing member 45 that presses the cleaning web 41 against the fixing member 30, and a single detection means that detects the remaining amount of cleaning web 41 held by the web holding member 44.
The single detection means has a filler 40 that displaces depending on the remaining amount of cleaning web 41 and a sensor 42 that detects the filler 40, and detects a web near-end state in which the cleaning web is about to break, and a web end state in which the cleaning web has broken.

Not all of the toner melted in the fixing nip N is fixed to the recording medium P after passing through the fixing nip N, but some adheres to the surface of the fixing member 30 and moves with the rotation of the fixing member 30. The toner that has moved to the fixing member 30 adheres to the pressure member 31 that comes into contact with the fixing member 30, the recording medium P that is next passed through, and the like, causing problems such as soiling them.
To prevent this problem from occurring, the fixing device 121 of this embodiment is provided with a cleaning unit 122 that cleans the toner adhering to the surface of the fixing member 30 .

The cleaning means 122 includes a cleaning web 41 that wipes the surface of the fixing member 30 , a web holding member 44 , a take-up member 46 , and a pressing member 45 .
Any known long-length cleaning web 41 can be used as long as it is capable of wiping off residual toner from the surface of the fixing member 30, and examples thereof include nonwoven fabric. Specific examples include fiber sheets, webs, etc., in which fibers are oriented in one direction or randomly and are bonded together by alternating current, fusion, and/or adhesion. Examples of natural fibers include cotton, wool, hemp, pulp, and silk, while examples of chemical fibers include rayon, nylon, polyester, polypropylene, acrylic fiber, vinylon, and aramid fiber.
When the winding member 46 is driven by the drive motor 43 and rotates in the winding direction, the unused portion of the cleaning web 41 (the portion not in contact with the fixing member 30) is sent out from the web holding member 44 side and moves.
As the cleaning operation continues, the diameter of the roll-shaped cleaning web 41 wound around the web holding member 44 decreases, and the diameter of the roll-shaped cleaning web 41 wound around the winding member 46 increases.

One end of the filler 40, which displaces depending on the remaining amount of cleaning web 41, abuts against the outer surface of the cleaning web 41 wound around the web holding member 44, and displaces according to the change in the remaining amount of unused cleaning web 41, i.e., the change in the roll diameter.
The displacement of the filler 40 is, for example, a rotation about a fulcrum.

The relationship between the remaining amount of cleaning web 41 and the position of the detection means will be described with reference to FIGS.
5 to 8 are explanatory diagrams that schematically show the cleaning means 122, with (a) in each diagram being a cross-sectional view (configuration side view) on the cleaning web 41 side, and (b) in each diagram being a configuration side view from the rear side when (a) is the front side of the side plate 50. Note that in (b) in each diagram, the outer periphery of the cleaning web 41 wound around the web holding member 44 and the invisible portion of the filler 40 are shown by dashed lines.

As shown in Figures 5 to 8, the detection means filler 40 is a member having a contact portion 40a that contacts the outer surface of the cleaning web 41 wound around the web holding member 44 and a detection target portion 40b that is detected by the sensor 42, and rotates and displaces around a fulcrum 40c.

The sensor 42 can be any known sensor that can detect the displacing filler 40, such as an optical sensor that uses light to detect the presence or position of an object (filler 40).
As the optical sensor, a transmissive photointerrupter or a reflective photoreflector is preferable. A photointerrupter is a sensor in which a light-emitting element and a light-receiving element are arranged opposite each other, and the light-receiving element detects when the light from the light-emitting element is blocked by the detected portion 40b of the filler as the light passes through. A photoreflector is a sensor in which the light from the light-emitting element is reflected by the detected portion 40b of the filler, and the reflected light is detected by the light-receiving element.

5A and 5B show the positional relationship between the filler 40 and the sensor 42 when the cleaning web 41 is brand new (the proportion of unused cleaning web is 100%).
When there is a sufficient amount of cleaning web 41 remaining wound around the web holding member 44, the contact portion 40a of the filler abuts against the outer periphery 41a, and the detected portion 40b of the filler is located away from the sensor 42, so the sensor 42 is in the "detection off" state.

6A and 6B show the positional relationship between the filler 40 and the sensor 42 when the cleaning web 41 is in a web near-end state (the proportion of unused cleaning web is about 20%).
In a web near-end state where the remaining amount of cleaning web 41 wound around the web holding member 44 is small and the cleaning web is about to break, the contact portion 40a of the filler comes into contact with the outer periphery 41b. By rotating around the fulcrum 40c from the position where it was in contact with the outer periphery 41a in Figure 5, the detected portion 40b of the filler is displaced to a position where it can be detected by the sensor 42, and the sensor 42 turns "detection on."

7(a) and 7(b) show the positional relationship between the filler 40 and the sensor 42 when the cleaning web 41 is in a web end state (the proportion of unused cleaning web is about 2 to 3%).
In the web end state, where almost no cleaning web 41 remains wound around the web holding member 44 and the cleaning web is broken, the contact portion 40a of the filler comes into contact with the outer periphery 41c. By further rotating about the fulcrum 40c from the position where it was in contact with the outer periphery 41b in Figure 6, the detected portion 40b of the filler is displaced to a position where it cannot be detected by the sensor 42, and the sensor 42 again becomes "detection off."

8A and 8B show the positional relationship between the filler 40 and the sensor 42 when the ratio of unused cleaning webs 41 is 0%.
There is no remaining amount of cleaning web 41 wound around the web holding member 44, and the contact portion 40a of the filler comes into contact with the core metal 41d of the web holding member 44. The filler further rotates about the fulcrum 40c from the position where it was in contact with the outer periphery 41c in Figure 7, but the detected portion 40b of the filler is in a position where it cannot be detected by the sensor 42, and the sensor 42 remains in the "detection off" state.

As shown in Figures 5 to 8, in the cleaning means provided in the fixing device of this embodiment, the sensor 42 of the detection means is off when there is a sufficient amount of cleaning web 41 remaining held by the web holding member 44, is on when the web is near end, and is off again when the web is at end.

The filler 40 is not detected by the sensor 42 when there is a sufficient amount of cleaning web 41 remaining, displaces to a position where it is detected by the sensor 42 when the web is near end, and displaces to a position where it is not detected by the sensor 42 when the web is at end.

In other words, by determining the signals received when the detected portion 40b of a single filler 40 passes a single sensor 42 before, during, and after the passage of the single sensor 42 as indicating that there is a sufficient amount of cleaning web 41 remaining, that the web is near-end, and that the web is at end, respectively, the remaining amount of cleaning web can be detected efficiently and effectively using a single detection means without using a special cleaning web.

As shown in FIG. 4, the fixing device of this embodiment includes a drive motor 43 for a take-up member 46 and a control means 11.
In addition, the device may further include a means for detecting a change in the current value due to torque fluctuations of the drive motor 43, and the amount of cleaning web 41 wound around the winding member 46 may be calculated from the change in the current value, and the amount may be compared with the remaining amount of cleaning web 41 detected by the detection means (sensor 42).

By comparing the torque fluctuations of the drive motor 43 with the detection results from the sensor 42, the accuracy of detecting the remaining amount of cleaning web 41 can be further improved.

It is preferable to correct the current value associated with torque fluctuations of the drive motor 43 based on at least one of the temperature conditions, the power supply voltage value, and the horizontal position of the device.

Alternatively, initialization may be performed when the cleaning web 41 is replaced with a new one, and the current value immediately after use (initial period) may be detected, and this value may be used to correct fluctuations in the current value.

The fixing device of this embodiment, which has the above-described configuration, can easily, efficiently, and effectively detect the remaining amount of cleaning web using a single detection means, without using a special cleaning web, while preventing increased costs and malfunctions.

30 Fixing member 31 Pressurizing member 40 Filler 40a Contact portion 40b Detected portion 40c Fulcrum 41 Cleaning web 42 Sensor 43 Drive motor 44 Web holding member 45 Pressing member 46 Winding member 50 Side plate 121 Fixing device 122 Cleaning means

Japanese Utility Model Application Laid-Open Publication No. 5-90505

Claims (8)

A fixing device comprising: a fixing member which is a rotating body heated by a heating means; and a pressure member which forms a fixing nip portion between the fixing member and the pressure member; the fixing device conveys a recording medium carrying an unfixed toner image to the fixing nip portion, and fixes the toner image on the recording medium,
a cleaning unit for removing residual toner adhering to the surface of the fixing member;
the cleaning means comprises a cleaning web that wipes the surface of the fixing member, a web holding member that holds the cleaning web so that it can be fed out, a winding member that can wind up the cleaning web, a pressing member that presses the cleaning web against the fixing member, and a single detection means that detects the remaining amount of the cleaning web held by the web holding member;
the detection means has a filler that is displaced depending on the remaining amount of the cleaning web and a sensor that detects the filler, and detects a web near-end state in which the cleaning web is about to break, and a web end state in which the cleaning web has broken , respectively;
a fixing device characterized in that the sensor of the detection means is turned off when there is a sufficient amount of the cleaning web held by the web holding member, turned on when the web is near end, and turned off again when the web is at end . A fixing device comprising: a fixing member which is a rotating body heated by a heating means; and a pressure member which forms a fixing nip portion between the fixing member and the pressure member; the fixing device conveys a recording medium carrying an unfixed toner image to the fixing nip portion, and fixes the toner image on the recording medium,
a cleaning unit for removing residual toner adhering to the surface of the fixing member;
the cleaning means comprises a cleaning web that wipes the surface of the fixing member, a web holding member that holds the cleaning web so that it can be fed out, a winding member that can wind up the cleaning web, a pressing member that presses the cleaning web against the fixing member, and a single detection means that detects the remaining amount of the cleaning web held by the web holding member;
the detection means has a filler that is displaced depending on the remaining amount of the cleaning web and a sensor that detects the filler, and detects a web near-end state in which the cleaning web is about to break, and a web end state in which the cleaning web has broken, respectively;
The fixing device is characterized in that the filler is not detected by the sensor when there is a sufficient amount of cleaning web remaining, displaces to a position where it is detected by the sensor when the web is near-end, and displaces to a position where it is not detected by the sensor when the web is at its end. A fixing device comprising: a fixing member which is a rotating body heated by a heating means; and a pressure member which forms a fixing nip portion between the fixing member and the pressure member; the fixing device conveys a recording medium carrying an unfixed toner image to the fixing nip portion, and fixes the toner image on the recording medium,
a cleaning unit for removing residual toner adhering to the surface of the fixing member;
the cleaning means comprises a cleaning web that wipes the surface of the fixing member, a web holding member that holds the cleaning web so that it can be fed out, a winding member that can wind up the cleaning web, a pressing member that presses the cleaning web against the fixing member, and a single detection means that detects the remaining amount of the cleaning web held by the web holding member;
the detection means has a filler that is displaced depending on the remaining amount of the cleaning web and a sensor that detects the filler, and detects a web near-end state in which the cleaning web is about to break, and a web end state in which the cleaning web has broken, respectively;
a drive motor for the winding member, and a means for detecting a change in a current value due to a torque fluctuation of the drive motor; calculating the amount of the cleaning web wound onto the winding member from the change in the current value, and comparing the amount with the remaining amount of the cleaning web detected by the detection means. 2. The fixing device according to claim 1, wherein the filler is not detected by the sensor when there is a sufficient amount of cleaning web remaining, displaces to a position where it is detected by the sensor when the web is near-end, and displaces to a position where it is not detected by the sensor when the web is at its end. A fixing device as described in any one of claims 1, 2, and 4, further comprising a drive motor for the winding member and a means for detecting changes in current value due to torque fluctuations of the drive motor, and calculating the amount of the cleaning web wound onto the winding member from the change in current value and comparing it with the remaining amount of the cleaning web detected by the detection means. 6. The fixing device according to claim 1, wherein the sensor is a photosensor. 6. The fixing device according to claim 3 , wherein a current value caused by torque fluctuations of the drive motor is corrected based on at least one of temperature conditions, a power supply voltage value, and a horizontal state of the device. An image forming apparatus comprising the fixing device according to any one of claims 1 to 7 .