JP7380231B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device that fixes a toner image to a sheet, and an image forming apparatus that includes the fixing device.

In an image forming apparatus that forms images using an electrophotographic process, fixing members (fixing belt, fixing roller, etc.) are rotated by clock input to a motor. Whether the fixing member is rotating normally is determined by detecting the rotation of a pulse plate provided at the end of the fixing member in the axial direction.

A sheet is pressed against the fixing member by a pressure roller. Since the end portion of the sheet in the width direction intersecting the conveyance direction is repeatedly pressed against the same position on the fixing member, streak-like scratches are formed in the circumferential direction due to long-term use. Then, when a larger size sheet is used, these scratches come into contact with the toner image, resulting in poor fixing. Since these scratches are unavoidable in the fixing device, the time to replace the fixing belt is set in consideration of the number of fixing operations until the scratches are formed. However, if heavy paper is used, the period until scratches are formed is significantly shortened, resulting in defective fixing occurring before the fixing belt is replaced.

Therefore, it is conceivable to provide means for detecting flaws on the fixing belt. For example, Patent Document 1 proposes detecting scratches on an intermediate transfer belt using an optical sensor.

Japanese Patent Application Publication No. 2009-139591

However, adding more sensors is undesirable because it increases costs.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a fixing device and an image forming apparatus that can detect flaws on a fixing belt while suppressing increases in costs.

In order to solve the above problems, a fixing device according to the present invention includes a rotatable fixing member, a pressure roller that pinches and conveys a sheet between the fixing member, and the sheet of the fixing member contacts. a measuring section that irradiates an end of the area in a width direction intersecting the conveyance direction of the sheet and measures the rotational speed of the fixing member using reflected light of the light; controlling the drive of the fixing member based on the rotational speed, and outputting information indicating that a scratch has occurred on the fixing member when the occurrence of a measurement error due to insufficient reflected light meets a predetermined condition; The present invention is characterized by comprising a control unit that performs the following steps.

The fixing device according to the present invention includes a plurality of measuring units corresponding to the size of the sheet in the width direction, and the control unit is configured to select one of the plurality of measuring units according to the size of the sheet in the width direction. The rotational speed may be measured by the measuring section depending on the size.

The fixing device according to the present invention includes a moving mechanism that moves the measuring section in the width direction, and the control section moves the measuring section to a position corresponding to the size of the sheet being conveyed in the width direction. The measuring section may be moved.

In the fixing device according to the present invention, the control section may cause the movement mechanism to move the measuring section in the width direction within a predetermined range including a position according to the width direction size of the sheet being conveyed. Then, the location where the measurement error occurs may be detected.

Further, the image forming apparatus according to the present invention is characterized by comprising an image forming device that forms a toner image on the sheet, and any one of the fixing devices described above that fixes the formed toner image on the sheet. shall be.

According to the present invention, it is possible to detect flaws on the fixing belt while suppressing an increase in cost.

1 is a front view schematically showing the internal configuration of a printer according to an embodiment of the present invention. 1 is a sectional view of a fixing device according to an embodiment of the present invention. FIG. 3 is a perspective view showing a measurement unit facing a fixing belt according to an embodiment of the present invention. It is a flowchart showing the procedure of flaw detection processing according to one embodiment of the present invention. It is a perspective view showing a movement mechanism concerning a modification of one embodiment of the present invention.

Hereinafter, a printer 1 (an example of an image forming apparatus) and a fixing device 7 according to an embodiment of the present invention will be described with reference to the drawings.

First, the overall configuration of the printer 1 will be explained. FIG. 1 is a front view schematically showing the internal configuration of the printer 1. As shown in FIG. Hereinafter, the front side of the paper in FIG. 1 will be referred to as the front side (front side) of the printer 1, and the left and right directions will be explained based on the direction when the printer 1 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr indicate upper, lower, left, right, front, and rear, respectively.

The printer 1 includes a box-shaped main body housing 2. The main body housing 2 includes a paper feed roller 5 that feeds the sheet S from the paper feed cassette 3 to a conveyance path 8, an image forming device 6 that forms a toner image on the sheet S, and a fixing device 7 that fixes the toner image on the sheet S. and a discharge roller 16 that discharges the sheet S on which the toner image is fixed from the discharge port 15 to the discharge tray 4 are housed.

The image forming device 6 includes a drum unit 12, an exposure device 13, a developer container 10, an intermediate transfer belt 11, and a secondary transfer roller 14. The drum unit 12 includes a rotationally driven photoreceptor drum, a charging device that charges the photoreceptor drum, and a developing device that forms a toner image by developing the latent image formed on the photoreceptor drum by the exposure device 13 with toner. , a primary transfer roller that transfers the toner image onto the intermediate transfer belt 11 , and a cleaning device that cleans the surface of the photosensitive drum. The exposure device 13 forms a latent image by irradiating the photosensitive drum with laser light based on image data. The developer container 10 stores a developer containing toner and supplies the developer to a developing device. The intermediate transfer belt 11 is wound around a driving roller and a driven roller. The secondary transfer roller 14 transfers the toner image on the intermediate transfer belt 11 onto the sheet S. The printer 1 includes four drum units 12 and a developer container 10. The four developer containers 10 contain developers containing toners of different colors, and the four drum units 12 transfer toner images of different colors onto the intermediate transfer belt 11 in an overlapping manner. Note that the present invention may be applied to a printer 1 that includes one to three sets or five or more sets of drum units 12 and developer containers 10.

When the printer 1 receives an image forming job from an external computer or the like, the sheet S is sent from the paper feed cassette 3 to the conveyance path 8, and a latent image based on the image data is formed by the exposure device 13 on the surface of the charged photoreceptor drum. be done. A toner image is formed on the photoreceptor drum by developing the latent image by the developing device, and the toner image formed on the photoreceptor drum is transferred onto the intermediate transfer belt 11 in an overlapping manner by a primary transfer roller. The toner image on the intermediate transfer belt 11 is transferred onto the sheet S by the secondary transfer roller 14 and fixed onto the sheet S by the fixing device 7. The sheet S with the toner image fixed thereon is discharged onto the discharge tray 4 .

Next, the configuration of the fixing device 7 will be explained. FIG. 2 is a sectional view of the fixing device 7. The fixing device 7 includes a rotatable fixing belt 21 (an example of a fixing member), a planar heater 23 that contacts the inner peripheral surface of the fixing belt 21 and heats the fixing belt 21, and a heater that holds the planar heater 23. A pressure roller 27 that sandwiches and conveys the sheet S between the holding member 25, the support member 24 that supports the heater holding member 25, and the fixing belt 21, and a drive source such as a motor that drives the pressure roller 27. 28. The fixing device 7 is housed in a housing (not shown), and the housing is fixed to the main body housing 2. In this embodiment, an example is shown in which the fixing device 7 is arranged with the pressure roller 27 positioned below the fixing belt 21, but the fixing device 7 may be arranged in any attitude.

The fixing belt 21 is a cylindrical endless belt having a hollow portion penetrating in the front-rear direction, and its length in the front-rear direction is longer than the width of the sheet S. The fixing belt 21 includes a base material layer, an elastic layer provided on the outer peripheral surface of the base material layer, and a release layer provided on the outer peripheral surface of the elastic layer (not shown), and has flexibility. The base layer is made of metal such as stainless steel or nickel alloy. The elastic layer is made of silicone rubber or the like. The release layer is formed of a PFA (tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin) tube or the like. A sliding layer may be formed on the inner peripheral surface of the base layer. The sliding layer is made of polyimide amide, PTFE (polytetrafluoroethylene), or the like.

The planar heater 23 is formed into a generally rectangular plate shape whose longitudinal direction is the front-rear direction. The planar heater 23 includes a base material, a heat insulating layer, a heat generating layer, and a coating layer. The base material is made of an electrically insulating material such as ceramics, and is formed into a generally rectangular plate shape whose longitudinal direction is the front-rear direction. The heat insulating layer is made of a material having electrical insulation and low thermal conductivity, such as ceramics or glass, and is laminated on the lower surface of the base material. The heat insulating layer suppresses the heat generated by the heat generating layer from being transmitted to the base material side. The heat generating layer is formed on the lower surface of the heat insulating layer using a conductive material such as a metal with a high resistance value. The coat layer covers the heat generating layer, and the lower surface of the coat layer contacts the inner surface of the fixing belt 21 . The coating layer is made of a material such as ceramics, which has electrical insulation properties and has low sliding friction resistance with respect to the fixing belt 21 .

The heater holding member 25 holds the planar heater 23 so as to be in contact with the inner peripheral surface of the fixing belt 21 . The heater holding member 25 has a length equivalent to the width of the fixing belt 21 in the front-rear direction, and is made of, for example, a heat-resistant resin such as a liquid crystal polymer.

A support member 24 whose longitudinal direction is in the front-back direction passes through the hollow portion of the fixing belt 21, and both ends of the support member 24 are fixed to the housing. The support member 24 is made of metal such as stainless steel or aluminum alloy. The support member 24 supports the heater holding member 25. The fixing belt 21 is supported by an arcuate belt guide (not shown) supported by a support member 24, and is rotatable along the belt guide.

The pressure roller 27 includes a core metal, an elastic layer provided on the outer peripheral surface of the core metal, and a release layer provided on the outer peripheral surface of the elastic layer (not shown). The core metal is made of metal such as stainless steel. The elastic layer is made of silicone rubber or the like. The release layer is formed of a PFA tube or the like. The pressure roller 27 is biased to the right by a biasing member (not shown) such as a spring, thereby sandwiching the fixing belt 21 between the sheet heater 23 and the fixing belt 21 and the pressure roller 27 . A nip region N is formed in which the two surfaces are in contact with each other.

Next, the fixing operation of the fixing device 7 will be explained. When the pressure roller 27 is driven and rotates in a predetermined rotation direction, the fixing belt 21 rotates following the rotation of the pressure roller 27, and the inner peripheral surface of the fixing belt 21 slides against the planar heater 23. do. When power is supplied to the heat generating layer of the planar heater 23, the heat generating layer generates heat and the fixing belt 21 is heated. After the fixing belt 21 reaches a predetermined temperature, the sheet S onto which the toner has been transferred is conveyed to the nip area N. In the nip region N, the sheet S is conveyed while being sandwiched between the fixing belt 21 and the pressure roller 27. At this time, the toner is heated and pressurized by the fixing belt 21, and the toner is fixed on the sheet S. The sheet S with the toner fixed thereon is separated from the fixing belt 21 and conveyed along the conveyance path 8 .

Next, the electrical configuration of the fixing belt 21 will be explained. FIG. 3 is a perspective view showing the measuring section 41 facing the fixing belt 21. As shown in FIG.

[Measurement part]
The measurement unit 41 is a non-contact optical speedometer, and includes a light source 41L, an image sensor 41S, and a processor 41P (not shown). The light source 41L irradiates the surface of the fixing belt 21 with light, the image sensor 41S reads the reflected light, and the processor 41P calculates the moving speed of the image indicated by the reflected light, thereby determining the rotational speed of the fixing belt 21. Measure. The light source 41L is, for example, a semiconductor laser.

FIG. 3 shows how the fixing process is performed, for example, by vertically feeding an ISO (International Organization for Standardization) A4 size sheet (conveying the sheet S with its long side parallel to the conveying direction Y). Each time the sheet S is conveyed, the sheet S contacts the same area of the fixing belt 21. This area is called a contact area 21C. The measuring section 41 is arranged to face one of the ends 21E in the width direction intersecting the rotational direction of the fixing belt 21 in the contact area 21C. The light source 41L irradiates the widthwise end 21E of the contact area 21C with light.

[Operation section]
The operation unit 32 is provided on the upper part of the main body housing 2, and includes, for example, a display panel using liquid crystal or the like, a touch panel stacked on the display panel, and a keypad adjacent to the touch panel.

[Control unit]
The fixing device 7 is controlled by a control section 31. The control unit 31 may be realized by a processor and software, or may be realized by hardware such as an integrated circuit. A processor performs various processes by reading and executing programs stored in memory. As the processor, for example, a CPU (Central Processing Unit) is used. The memory includes storage media such as ROM (Read Only Memory), RAM (Random Access Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). A control program used to control the fixing device 7 is stored in the memory.

A measurement section 41 and an operation section 32 are connected to the control section 31 . The control unit 31 performs feedback control on the drive source 28 so that the difference between the rotation speed measured by the measurement unit 41 and the set rotation speed falls within a predetermined range. Further, the control unit 31 causes the operation unit 32 to display information such as an operation menu for operating the printer 1, and receives operations for the printer 1 via the operation unit 32.

Further, the control unit 31 is connected to a service center through a communication line, and transmits and receives data to and from the service center. When the control unit 31 detects a flaw in the fixing belt 21 based on the measurement result by the measuring unit 41, it transmits information to the service center that the flaw has occurred in the fixing belt 21.

Next, the function of detecting flaws on the fixing belt 21 will be explained. When the sheet S is pressed against the fixing belt 21 by the pressure roller 27, the contact area 21C of the fixing belt 21 is compressed. A stepped deformation along the edge of S occurs. As this deformation is repeated, cracks occur on the surface of the fixing belt 21, forming annular scratches.

For example, if a scratch occurs on the widthwise end 21E of the contact area 21C due to a large amount of fixing processing being performed during vertical feeding of A4 size (see Figure 3), If the fixing process is carried out by transporting the toner image with the sides parallel to the transport direction Y, it is conceivable that scratches on the fixing belt 21 may come into contact with the toner image. In this case, the heating and pressurizing of the portion that has come into contact with the scratches may be insufficient, leading to a risk of defective fixing.

Therefore, the fixing device 7 according to the present embodiment detects flaws in the fixing belt 21 using the following configuration. The fixing device 7 includes a rotatable fixing belt 21 (an example of a fixing member), a pressure roller 27 that conveys the sheet S while sandwiching it between the fixing belt 21, and an area where the sheet S of the fixing belt 21 contacts. (contact area 21C), a measurement unit 41 that irradiates light onto an end 21E in the width direction intersecting the conveyance direction Y of the sheet S and measures the rotational speed of the fixing belt 21 using reflected light of the light; , the drive of the fixing belt 21 is controlled based on the rotational speed measured by the measuring unit 41, and if the occurrence of a measurement error due to insufficient reflected light meets a predetermined condition, it is determined that a scratch has occurred on the fixing belt 21. and a control unit 31 that outputs information that indicates the information.

FIG. 4 is a flowchart showing the procedure of flaw detection processing. When an image forming job is input to the printer 1, the control unit 31 executes the following flaw detection process. First, the control unit 31 initializes a counter n that accumulates the number of measurement errors to 0 (step S01), and rotates the fixing belt 21 by rotating the pressure roller 27 using the drive source 28 (step S03). ).

Next, the control unit 31 causes the measurement unit 41 to measure the rotational speed of the fixing belt 21 (step S05), and determines whether a measurement error has occurred (step S07). If there is no scratch on the fixing belt 21, the amount of reflected light necessary for measurement will be obtained, and no measurement error will occur. Since light is scattered by the scratches, it becomes impossible to obtain the amount of reflected light necessary for measurement, resulting in measurement errors. If the control unit 31 determines that a measurement error has occurred (step S07: YES), the process proceeds to step S09, and if it determines that a measurement error has not occurred (step S07: NO). , the process moves to step S19.

In step S09, the control unit 31 causes the measuring unit 41 to measure the rotational speed again, and determines whether a measurement error has occurred (step S11). If the control unit 31 determines that a measurement error has occurred (step S11: YES), the process proceeds to step S13, and if it determines that a measurement error has not occurred (step S11: NO). , the process moves to step S19.

In step S13, the control unit 31 adds 1 to the counter n. Next, the control unit 31 determines whether the value of the counter n has reached 10 (step S15). If the control unit 31 determines that the value of the counter n has reached 10 (step S15: YES), the control unit 31 proceeds to the process of step S17, and if it determines that the value of the counter n has not reached 10, the control unit 31 proceeds to the process of step S17. (Step S15: NO), the process from step S09 onward is repeated.

In step S17, the control unit 31 causes the operation unit 32 to display information indicating that a flaw has occurred in the fixing belt 21. For example, a message such as "The fixing belt may be damaged. Please contact the service center as soon as possible." is displayed. Alternatively, the control unit 31 may transmit information indicating that a flaw has occurred on the fixing belt 21 to the service center via a communication line.

On the other hand, in step S19, the control unit 31 determines whether the image forming job has been completed. If the control unit 31 determines that the image forming job has ended (step S19: YES), the control unit 31 proceeds to the process of step S21, and if it determines that the image forming job has not ended (step S19: NO), repeat the process from step S01 onwards.

In step S21, the control unit 31 determines whether or not the sheet S has been completely discharged onto the discharge tray 4. If the control unit 31 determines that the discharge of the sheet S has been completed (step S21: YES), it ends the flaw detection process, and if it determines that the discharge of the sheet S has not been completed (step S21: :NO), the process of step S21 is repeated.

According to the fixing device 7 according to the present embodiment described above, it is possible to detect flaws in the fixing belt 21 by using the measurement unit 41 that measures the rotational speed of the fixing belt 21. Conventionally, to detect the rotational speed of the fixing belt 21, the rotation of a cap attached to the end of the fixing belt 21 is transmitted to a pulse plate via a gear, and the rotational speed of the pulse plate is measured using a photointerrupter. However, according to the fixing device 7 according to the present embodiment, by replacing the conventional configuration with the measuring section 41, the function of measuring the rotational speed of the fixing belt 21 and the function of measuring the rotational speed of the fixing belt 21 can be achieved. The measurement unit 41 can also have a flaw detection function. Therefore, according to the fixing device 7 according to the present embodiment, it is possible to detect flaws on the fixing belt 21 while suppressing an increase in cost.

The above embodiment may be modified as follows.

In the embodiment described above, an example was shown in which the measuring unit 41 was arranged to face the end 21E in the width direction of the contact area 21C when performing the fixing process by vertically feeding an A4 size sheet, but the width of the sheet S The control unit 31 includes a plurality of measuring units 41 according to the size in the direction, and the control unit 31 measures the rotational speed by the measuring unit 41 according to the size in the width direction of the sheet S to be conveyed among the plurality of measuring units 41. It may be configured as follows. For example, in addition to the position in the above embodiment, the contact area 21C is opposite to the widthwise end 21E of the contact area 21C corresponding to vertical feeding or horizontal feeding of A5 size, A6 size, JIS (Japanese Industrial Standards) B4 size, B5 size, etc. A plurality of measuring units 41 are provided, and the control unit 31 causes the measuring unit 41 corresponding to the widthwise size of the sheet S specified in the image forming job to measure the rotational speed. According to this configuration, even when two or more types of sheets S having different sizes in the width direction are used, scratches on the fixing belt 21 can be detected.

In the above embodiment, an example in which the measuring section 41 is fixed is shown, but the moving mechanism 51 that moves the measuring section 41 in the width direction is provided, and the control section 31 controls the sheet S conveyed by the moving mechanism 51. The measurement unit 41 may be configured to be moved to a position according to the size in the width direction. FIG. 5 is a perspective view showing a moving mechanism 51 according to this modification. The moving mechanism 51 includes a plurality of pulleys 52 and a belt 53 wound around the plurality of pulleys 52, and the measuring section 41 is fixed to the belt 53. The measuring section 41 is supported by a guide member such as a rail that guides the movement of the measuring section 41 in the front-back direction (not shown). The control unit 31 causes the moving mechanism 51 to move the measuring unit 41 to a position corresponding to the size in the width direction of the sheet S specified in the image forming job and measure the rotation speed. According to this configuration, even when two or more types of sheets S having different sizes in the width direction are used, one measurement unit 41 can detect flaws in the fixing belt 21.

In addition, if the pressure in the nip region N becomes uneven in the width direction due to wear or deformation of the member, at the end 21E with higher pressure among the ends 21E in the width direction of the contact region 21C, It is conceivable that scratches occur before the portion 21E. Therefore, it is desirable that the flaw detection process according to this modification is performed at both ends 21E in the width direction of the contact area 21C. According to this configuration, even if the pressure in the nip region N becomes uneven in the width direction, it is possible to detect flaws in the fixing belt 21 at an early stage.

Further, since the position of the contact area 21C changes in the width direction due to wear or deformation of the member, it is conceivable that scratches occur at a position different from the position assumed in advance. Therefore, the control unit 31 moves the measuring unit 41 in the width direction using the moving mechanism 51 within a predetermined range including a position according to the size in the width direction of the sheet S to be conveyed, so that a measurement error occurs at a location where a measurement error occurs. may be configured to detect. Specifically, the control unit 31 measures the measurement unit 41 by 0.5 mm at 1 second intervals within a 4 mm width range centered on a position corresponding to the widthwise size of the sheet S specified in the image forming job. The rotational speed of the fixing belt 21 is measured while moving the fixing belt 21, and when 10 measurement errors occur in succession, information indicating that a flaw has occurred in the fixing belt 21 is displayed on the operation unit 32.

This process may be executed every time an image forming job is input to the printer 1. Alternatively, the number of printed pages may be accumulated for each size of the sheet S, and the process may be executed only when the cumulative number of printed pages of the sheet S specified in the image forming job exceeds a threshold value. Alternatively, the process may be executed periodically for each size of the sheet S. According to this configuration, even if the position of the flaw that was assumed in advance and the position of the flaw that actually occurred are different from each other, it is possible to detect the flaw on the fixing belt 21.

In the above embodiment, an example was shown in which the rotational speed of the fixing belt 21 is measured by calculating the moving speed of the image indicated by the reflected light. The moving speed of the object may be calculated from the frequency shift when the unevenness on the surface of the object crosses.

In the above embodiment, an example is shown in which the present invention is applied to the fixing device 7 that includes the planar heater 23, but the present invention may also be applied to the fixing device 7 that includes an induction heating heater, a halogen heater, or the like. Further, in the above embodiment, an example is shown in which the present invention is applied to the fixing device 7 including the fixing belt 21 (an example of a fixing member), but instead of the fixing belt 21, a fixing roller (an example of a fixing member) is used. The present invention may be applied to a fixing device 7 including:

1 Printer (image forming device)
6 Image forming device 7 Fixing device 21 Fixing belt (fixing member)
21C Contact area (area where the sheet of the fixing member comes into contact)
21E End portion 27 Pressure roller 31 Control section 41 Measurement section 51 Movement mechanism

Claims (5)

a rotatable fixing member;
a pressure roller that pinches and conveys the sheet between the fixing member;
It has a single light source and a single image sensor, irradiates light to an end in the width direction intersecting the conveyance direction of the sheet among the areas of the fixing member that are in contact with the sheet, and reflects the light. a measuring unit that measures the rotational speed of the fixing member using light;
a moving mechanism that moves the measuring section in the width direction;
Drive of the fixing member is controlled based on the rotational speed measured by the measuring unit, and when a measurement error occurrence situation due to insufficient reflected light falls under a predetermined condition, a scratch occurs on the fixing member. A fixing device comprising: a control unit that outputs information indicating that a fixing device has been installed. 2. The fixing device according to claim 1, wherein the control section moves the measuring section by the moving mechanism to a position corresponding to the widthwise size of the sheet being conveyed. 3. The fixing device according to claim 2, wherein the control unit measures the rotational speed at both ends in the width direction of the region in contact with the sheet. The control unit causes the measurement error to occur by causing the movement mechanism to move the measurement unit in the width direction within a predetermined range that includes a position according to the width direction size of the sheet being conveyed. The fixing device according to claim 2 or 3, wherein the fixing device detects a location. an image forming device that forms a toner image on the sheet;
An image forming apparatus comprising: the fixing device according to claim 1 , which fixes the formed toner image on the sheet.

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