JP2003036000A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent failure occurring due to heat taken away from a sheet member suddenly when recording paper advances to a nip part in a fixing device consisting of a heat transmitting member and the sheet member. SOLUTION: This fixing device is provided with a fixing roller and the sheet member and fixes a toner image on the recording paper by making the recording paper, to which the toner image is transferred, pass through the nip part between the fixing roller and the sheet member and pressed and heated. While the recording paper passes through the nip part between the fixing roller and the sheet member, turn-on of a heating source is controlled by a turn-on signal being generated intermittently with a specified on-duty cycle, and the fixing roller is heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus applied to an electrophotographic apparatus such as a facsimile machine, a printer, a copying machine, or a multifunction machine having these functions.

[0002]

2. Description of the Related Art FIG. 6 is a side view showing an internal structure of a conventional fixing device. Reference numeral 100 is a fixing roller, 101 is a pressure roller which is in pressure contact with the fixing roller 100, and 102 is a fixing roller 1.
00 is a fixing heater arranged to heat the fixing roller 100, 103 is a temperature detecting means for detecting the temperature of the fixing roller 100, 104 is a separation claw for separating the recording paper wound around the fixing roller 100 from the fixing roller 100, 10
Reference numeral 5 is a cleaning pad that contacts the fixing roller 100 to clean the fixing roller 100, 106 is a cleaning pad holder that supports the cleaning pad 105, and 107 is provided downstream of the cleaning pad 105 in the rotation direction of the fixing roller 100. A cleaning pad entry restriction member, 108 is an entrance guide plate attached to the recording paper entrance of the fixing device main body, and 109 is a paper discharge roller provided on the recording paper exit side of the fixing device.

The recording paper on which the toner image is transferred is fixed to a fixing roller 100 and a pressure roller 101 via an entrance guide plate 108.
Enter the nip part with. Then, after the toner image is fixed on the recording paper by being pressed / heated in the nip portion, it is discharged to the outside via the paper discharge roller 109. The toner attached to the fixing roller 100 when the recording paper passes through the nip portion is removed by the cleaning pad 105.

The surface temperature of the fixing roller 100 is detected by the temperature detecting means 103, and based on the detection result of the temperature detecting means 103, heating control by the fixing heater 102 is performed by a control means (not shown).

By the way, conventionally, in the fixing device, an infrared heater or a halogen heater is adopted as a fixing heater, and it is most general that it is constituted by a pair of a fixing roller and a pressure roller. However, since the pressure roller has a structure in which a silicon rubber layer is formed on a core metal and a release layer such as a Teflon (registered trademark) tube is formed on the core rubber, the heat capacity is large, and even if heating is started. The pressure roller does not warm up easily, which is a cause of poor fixing. Furthermore, there was the disadvantage that the cost of parts was high. Further, in order to secure an appropriate nip width in the nip portion between the fixing roller and the pressure roller, a large pressure is required, and the pressure causes a stress on the recording paper, which causes fixing wrinkles.

Therefore, instead of the pressure roller, a sheet-shaped member is pressed against the fixing roller to form a nip, and the recording paper is passed through the nip portion to fix an unfixed image on the recording paper. Are being studied. With such a configuration, since it is a sheet-shaped member, it is easy to warm, it is possible to secure the nip width, and it is possible to improve the thermal efficiency as compared with the conventional machine.

[0007]

However, in the fixing device using the sheet-shaped member, the heat capacity of the nip portion is small, and when the recording paper enters the nip, heat is rapidly taken away. At this time, the temperature detected by the so-called thermistor may be located outside the nip, and the temperature of the nip may decrease due to a delay in the response speed of the detection, which may cause improper fixing of the trailing edge of the recording paper. There is.

According to the present invention, in a fixing device comprising a heat transfer member and a sheet member, when the recording paper enters the nip,
An object of the present invention is to provide a fixing device and an image forming apparatus that are capable of preventing a problem caused by abrupt heat removal from a sheet member.

[0009]

In order to achieve the above object, the invention according to claim 1 has a heat transfer member having a heat source inside and a sheet member for contacting and pressing the heat transfer member. , One end of the sheet member is fixed to a mounting portion provided upstream of the heat transfer member in the recording paper conveyance direction, and the other end of the sheet member is brought into contact with the heat transfer member under pressure. A fixing device for fixing a toner image on a recording sheet by pressurizing / heating the recording sheet on which the toner image is transferred when passing through the nip portion between the heat transfer member and the sheet member, Is provided with a control means for controlling the heat source so as to heat the heat transfer member while entering the nip portion. With this configuration, it is possible to prevent the temperature of the nip portion from rapidly decreasing when the recording paper passes through the nip portion between the heat transfer member and the sheet member.

According to a second aspect of the invention, in the invention according to the first aspect, the control means controls the heating source while the recording paper is entering the nip portion between the heat transfer member and the sheet member. It is characterized by intermittently switching on / off. With this configuration, the temperature change in the nip portion can be made smooth.

According to a third aspect of the present invention, there is provided a photoconductor, a transfer device for transferring the toner image formed on the photoconductor onto a recording sheet, and the fixing device according to the first or second aspect. And With this configuration, it is possible to prevent the temperature of the nip portion from rapidly decreasing when the recording paper passes through the nip portion between the heat transfer member and the sheet member.

According to a fourth aspect of the present invention, in the third aspect of the present invention, detection means for detecting the leading edge of the recording paper is provided upstream of the fixing device in the recording paper conveyance direction, and a detection signal of the detection means is provided. Based on the above, the control means starts the heating control by the heating source. With this configuration, based on the detection signal from the detection means,
It becomes possible to obtain the timing when the leading edge of the recording paper passes through the fixing nip portion, and it becomes possible to start the heating control for the heating source when the leading edge of the recording paper reaches the fixing nip portion.

According to a fifth aspect of the invention, in the invention according to the fourth aspect, a sheet feeding unit for feeding the recording sheet and a timing for the recording sheet fed from the sheet feeding unit are provided to the transfer device. A registration roller that conveys while picking up is provided, and a registration sensor is provided as the detection unit in the vicinity of the registration roller, and the control unit stores the moving time until the leading edge of the recording paper reaches the nip portion from the registration sensor. Storage means is provided, and the control means starts heating control for the heating source when the moving time has elapsed after the registration sensor detects the leading edge of the recording paper. With this configuration, it is not necessary to separately provide a member for detecting that the recording paper passes through the nip portion.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view showing an internal configuration of a facsimile apparatus having a fixing device and an image forming apparatus according to an embodiment of the present invention, in which 1 is a main body of the facsimile apparatus and 2 is a main body of the facsimile apparatus.
Is a process cartridge that is detachably attached to the main body 1 and that houses various process devices for performing image formation by an electrophotographic process. 3 is a photoconductor provided in the process cartridge 2. 4 is image data. An optical writing device for scanning the photoconductor 3 with a laser beam modulated based on 5 is a paper feed cassette for storing recording paper, 6 is a paper feed roller for feeding the recording paper from the paper feed cassette 5, and 7 is a photoconductor. 3 is a transfer roller that contacts the toner image formed on the photoconductor 3 on the recording paper, 8 is a fixing device that fixes the toner image on the recording paper, 9 is a paper discharge roller, 10 is a contact sensor, and 11 is 1 shows a document table formed on the upper surface of the main body 1.

The original set on the original placing table 11 is discharged to the outside through the contact sensor 10 by the conveying system. When the document passes through the contact sensor 10, the image of the document is optically read by the contact sensor 10. The image data read by the contact sensor 10 or the image data input from the outside is sent to the optical writing device 4, and the photoconductor 3 is uniformly charged with the laser light modulated by the optical writing device 4 based on the image data. By irradiating the surface of the photosensitive member 3, an electrostatic latent image is formed on the surface of the photoconductor 3. Toner is attached to this electrostatic latent image to form a toner image, and this toner image is transferred to the recording paper by the transfer roller 7. And
The toner image is fixed on the recording paper by applying pressure / heating by the fixing device 8, and is discharged to the outside by the discharge roller 9.

FIG. 2 is an explanatory view showing the structure of the fixing device and its surroundings. 20 is a fixing roller, 21 is a sheet member that abuts the fixing roller 20 while applying pressure, and 22 is one end of the sheet member 21 fixed. Seat member pasting stand, 23
Is a thermistor that contacts the fixing roller 20 to detect the temperature, 24 is a registration roller installed downstream of the paper feed roller 6 in the recording paper conveyance direction, and 25 is a registration roller 2.
A pressure roller that is in pressure contact with 4 is a registration sensor that is installed near the downstream side of the registration roller 24 in the recording paper conveyance direction,
27 is a guide plate that guides the recording paper from the paper feed roller 6 to the registration roller 24, 28 is a guide plate that guides the upper surface of the recording paper from the registration roller 24 to the transfer roller 7, and 29 is opposed to the guide plate 28. Registration roller 2
4 is a guide plate for guiding the lower surface of the recording paper from the transfer roller 7, and 30 is installed near the downstream side of the transfer roller 7 in the recording paper conveyance direction. A brush, 31 is a pre-fixing guide plate that guides the recording paper from the transfer roller 7 to the fixing roller 20, 32 is a post-fixing guide plate that guides the upper surface of the recording paper from the fixing roller 20 to the paper discharge roller 9, and 33 is a fixing roller. Below the post-fixing guide plate that guides the lower surface of the recording paper from 20 to the paper discharge roller 9, 34 is a pressure roller that comes into pressure contact with the paper discharge roller 9.

The recording paper conveyed by the paper feed roller 6 is registered by the registration roller 24 by the guide of the guide plate 27.
When the registration sensor 26 detects the leading edge of the recording sheet, the rotation of the registration roller 24 is stopped and the conveyance is interrupted. Then, when the toner image formed on the photoconductor 3 reaches the nip portion with the transfer roller 7, the registration roller 2 is reached at such a timing that the recording paper reaches the nip portion.
Resume rotation of 4. The recording paper conveyed by the registration rollers 24 is above the guide plate 28 and below the guide plate 2.
It is guided to the nip portion between the photoconductor 3 and the transfer roller 7 by the guide 9. The recording paper on which the toner image is transferred after passing through the nip portion is guided to the nip portion between the fixing roller 20 and the sheet member 21 by the guide of the pre-fixing guide plate 31.
The recording paper on which the toner image is fixed after passing through the nip portion is guided to the paper ejection roller 9 by the guides on the post-fixing guide plate 32 and the post-fixing guide plate lower 33, and the paper ejection roller 9 and the pressure roller 34 are connected. It passes through the nip part of and is discharged to the outside.

FIG. 3 is a block diagram showing a control system of the apparatus shown in FIG. 1. Reference numeral 35 is a central processing unit (hereinafter referred to as CPU) for controlling the entire apparatus, 36 is a heating source for heating the fixing roller 20, 37 is a heater driver that drives and controls the heating source 36 based on a command from the CPU 35; 38 is a main motor that serves as a drive source for the recording paper conveyance system; 39 is a motor driver that drives and controls the main motor 38 based on a command from the CPU 35; Reference numeral 40 denotes a transmission mechanism that transmits or cancels rotation of the registration roller 24.

By the way, in the case of a conventional fixing device having a fixing roller and a pressure roller, the pressure roller is hard to warm but hard to cool. Therefore, when the fixing roller falls below a predetermined temperature, the fixing roller is heated. As a result, the temperature of the nip portion is maintained. When such control is applied to a fixing device including the fixing roller 20 and the sheet member 21, the sheet member 21 is likely to be warmed but is likely to be cooled. Therefore, as shown in FIG. 4, before the recording paper passes through the nip portion. (<A> in the figure
However, when the recording paper passes through the nip portion (see <B> in the figure), the temperature of the nip portion may decrease due to the recording paper and fall below the fixable temperature. There is. When the temperature becomes lower than the fixable temperature, the heating source is turned on to start heating, but by the time the fixable temperature is reached, the recording paper has finished passing through the nip portion (<C in the figure).
>)).

FIG. 5 is a time chart showing the heating control in this embodiment. Before the image recording, if the fixing roller 20 is below the fixable temperature, the heating source 36
Is turned on to raise the fixing temperature, and then the heating source 36 is turned off. The image recording operation and the paper feeding operation are started, and the registration roller 24 is temporarily stopped when the registration sensor 26 detects the leading edge of the recording paper. Further, the time t1 required for the leading edge of the recording paper to reach the nip portion between the registration sensor 26 and the fixing roller 20 and the sheet member 21 in advance, and the recording paper is fixed to the fixing roller 20 and the sheet member 2.
The time t2 required to pass through the nip portion with 1 is stored in the memory. At time t1, the registration sensor 26
It is set by the distance L between the fixing nip and the recording paper conveyance speed, and the time t2 is set by the width of the recording paper in the conveyance direction and the recording paper conveyance speed.

Then, the transmission mechanism 40 (see FIG. 3) is operated to restart the rotation of the registration roller 24, and then the time t is reached.
Until the time t2 elapses from the time when 1 has passed, that is, the time when the leading edge of the recording paper reaches the nip portion between the fixing roller 20 and the sheet member 21, the CPU 35 causes the lighting signal which is an intermittent signal of a predetermined ON duty cycle. Is generated to control the lighting of the heating source 36. After the time t2 has passed,
When the temperature of the fixing roller 20 is lower than the fixable temperature, the lighting signal of the heating source 36 is turned on, and when it is higher than the fixable temperature, the lighting signal is turned off. The ON duty is set in advance according to the recording paper type, recording paper size, and the like.

With this configuration, the heating source 36 is turned on while the recording paper passes through the nip portion between the fixing roller 20 and the sheet member 21, so that the temperature drop in the nip portion can be prevented. A good image with no fixing defects can be obtained over the entire recording paper. In particular, since the lighting signal is an intermittent signal with a predetermined ON duty cycle, heating control can be performed without raising the temperature of the nip portion more than necessary.

Further, in the present invention, the fixing roller 20
Although a sensor may be provided in the vicinity of and the heating control may be performed by a lighting signal of a predetermined ON duty while the sensor is detecting the recording paper, the detection signal of the registration sensor 26 is used as described above. Therefore, the fixing roller 2
It is not necessary to provide a sensor near 0.

In the present embodiment, control for changing the ON duty according to the temperature gradient, that is, so-called difference control may be performed. That is, qualitatively, the temperature gradient of the fixing roller 20 may be made gentle by lowering the ON duty when the temperature is rapidly increasing and increasing the ON duty when the temperature is rapidly decreasing. . Further, in addition to the control of intermittently turning on / off the heating source 36, for example, the voltage applied to the heating source may be lowered to perform heating.

In the above-described embodiment, the fixing device in which the sheet-like pressure member is brought into pressure contact with the fixing roller has been described, but the fixing device may be applied to another type.

For example, a fixing belt is stretched between a fixing roller having a heat source and a tension roller, a sheet member is brought into contact with the fixing belt, and the fixing belt is rotated to nip a portion between the fixing belt and the sheet member. A fixing device that fixes the toner image onto the recording paper by passing the recording paper onto which the toner image has been transferred, or a heating source is fixed inside a cylindrical fixing film, and the sheet is attached to the heating source through the fixing film. It is applied to a fixing device of a type in which a member is brought into contact with the fixing film, the fixing film is rotated, and the recording paper on which the toner image is transferred is passed through the nip portion between the heat source and the sheet member to fix the toner image on the recording paper. Is also good.

[0028]

According to the present invention configured as described above, the temperature of the nip portion is controlled by turning on the heating source while the recording paper passes through the nip portion between the fixing roller and the sheet member. It is possible to prevent the deterioration, and it is possible to obtain a good image with no fixing failure over the entire recording paper.

[Brief description of drawings]

FIG. 1 is a side view showing an internal configuration of a facsimile apparatus having a fixing device and an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a fixing device and its periphery.

3 is a block diagram showing a control system of the apparatus shown in FIG.

FIG. 4 is a time chart showing conventional heating control.

FIG. 5 is a time chart showing heating control in the embodiment of the present invention.

FIG. 6 is a side view showing an internal structure of a conventional fixing device.

[Explanation of symbols]

1 body 2 process cartridge 3 photoconductor 4 Optical writing device 5 paper cassettes 6 paper feed rollers 7 Transfer roller 8 fixing device 9 Paper ejection roller 10 Contact sensor 11 Document holder 20 fixing roller 21 sheet member 22 Sheet member attached cradle 23 Thermistor 24 Registration roller 26 Registration sensor 35 Central Processing Unit (CPU) 36 heating source 37 heater driver 38 Main motor 40 transmission mechanism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kota Takenaka             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H033 AA02 BA08 BA30 BB01 BB39                       CA04 CA07 CA22 CA30 CA37                       CA45 CA48                 3K058 AA43 AA71 BA18 CA12 CB19                       DA01

Claims (5)

[Claims] 1. A heat transfer member having a heat source inside, and a sheet member for contacting and pressing the heat transfer member,
One end of the sheet member is fixed to a mounting portion provided upstream of the heat transfer member in the recording paper conveyance direction, and the other end of the sheet member is brought into contact with the heat transfer member under pressure.
A fixing device for fixing a toner image on a recording sheet by pressurizing / heating the recording sheet on which the toner image is transferred when the recording sheet passes through a nip portion between the heat transfer member and the sheet member. The fixing device is provided with a control means for controlling the heating source so as to heat the heat transfer member while entering the nip portion. 2. The control means intermittently switches ON / OFF of the heating source while the recording paper is entering the nip portion between the heat transfer member and the sheet member. The fixing device according to item 1. 3. An image forming apparatus comprising a photoconductor, a transfer device for transferring a toner image formed on the photoconductor onto a recording sheet, and the fixing device according to claim 1. 4. A detection means for detecting the leading edge of the recording paper is provided upstream of the fixing device in the recording paper conveyance direction, and the control means starts heating control by the heating source based on a detection signal of the detection means. The image forming apparatus according to claim 3, wherein the image forming apparatus comprises: 5. A paper feed means for feeding the recording paper, and a registration roller for feeding the recording paper fed from the paper feeding means to the transfer device at a timing.
As the detection means, a registration sensor is provided in the vicinity of the registration roller, and the control means is provided with a storage means for storing a moving time until the leading edge of the recording paper reaches from the registration sensor to the nip portion, and the registration sensor records. 5. The image forming apparatus according to claim 4, wherein the control unit starts heating control for the heating source when the moving time has elapsed after detecting the leading edge of the paper.