JP2001066943A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device constituted so that waiting time after a power source is turned on can be shortened and fixing temperature can be stabilized by enhancing temperature detecting accuracy. SOLUTION: A backup roller 2 is obtained by forming silicone rubber at the outside circumferential surface thereof and arranged side by side so as to be pressed to the lower surface of a heat roller 1. Then, a halogen lamp 3 is fixedly installed at the central position of the roller 1. A fixing film whose width is approximate to the longitudinal-direction width of the roller 1 is shown by No.8 in a figure. Then, the film 8 is laid between the roller 1 and an idle roller 9 in a belt state and a recording material 6 is heated by the roller 1 through the film 8. When the roller 1 is rotated, the material 6 to which a toner image 5 is stuck is carried in a right direction on a condition that it is pressed to the roller 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for heating and fixing a toner image formed on a recording material by an electrophotographic printer or the like.

[0002]

2. Description of the Related Art An electrophotographic printer is used as an output device of an image processing apparatus such as a copying machine or a computer, and heat-fixes a toner image formed on a recording material such as paper used as a recording medium. Equipment. In a conventional fixing device, a heat roller type in which an aluminum pipe maintained at a predetermined temperature is used as a heat roller is generally used.

FIG. 10 is a schematic diagram showing the structure of a conventional fixing device. In the figure, 1 is a tubular heat roller, 2
Is a backup roller, 3 is a halogen lamp, 4 is a spring for pressing the backup roller 2 in the direction of the heat roller 1, 5 is a toner image formed on the recording material 6, and 7 is a thermistor.

FIG. 11 is a diagram showing a front shape of an aluminum pipe constituting the heat roller 1 and a partially enlarged cross section thereof. On the outer peripheral surface of the aluminum base 11, a PFA (perfluoroalkoxyethylene) or PT
A surface coat 12 made of a fluororesin such as FE (polytetrafluoroethylene) is formed to prevent toner from adhering.

[0005] Such a tubular heat roller 1 is rotatably driven by a motor (not shown) via gears and the like, and a halogen lamp 3 fixed at its center position.
Is connected to a power supply (not shown) and is turned on to heat the heat roller 1. When the heat roller 1 rotates, the backup roller 2 pressed against it rotates around and the recording material 6 is conveyed between them, so that the toner image 5 on the recording material 6 is heated and fixed. Is done.

Here, the backup roller 2 is generally formed as a rubber roller, and the rotation speed of the motor and the power supply voltage are controlled by the control unit of the electrophotographic printer. Further, the temperature of the heat roller 1 is detected by the thermistor 7 and based on the temperature signal,
The ON / OFF of the power is controlled by the control unit, and the halogen lamp 3 is appropriately turned on and off, so that the fixing temperature is kept constant.

[0007]

In the conventional fixing device described above, the wait time until the heat roller 1 is heated to a temperature required for fixing is increased, and the aluminum pipe is maintained at a predetermined temperature. When used as a heat roller, there is a problem that the power consumption of the halogen lamp 3 increases.

In order to shorten the wait time,
It is also conceivable to reduce the thickness of the aluminum base 11 constituting the heat roller 1 to reduce the heat capacity. But,
When the heat capacity becomes small, the recording material 6 provided with the thermistor 7
Of the recording material 6 of the heat roller 1
When the temperature of the contact portion becomes low, and particularly when a recording material having a narrow width is continuously fixed, defective fixing occurs.

There is also a proposal to shorten the wait time by using a fixing device having a heat-resistant endless film and a fixed heating element. However, since the heating member is fixed, the recording material is conveyed only by the backup roller, so that there is a problem that a thick recording material cannot be stably conveyed.

Further, in order to prevent toner from adhering,
When the surface coat 12 is formed on the heat roller 1,
The recording material is not completely adhered to the recording material, and the heating and the pressurization do not work uniformly. Therefore, in an image in which the entire surface of the recording material is painted out, there is a problem that density unevenness occurs in a printing result.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and provides a fixing device capable of shortening a wait time after turning on a power supply, improving temperature detection accuracy, and stabilizing a fixing temperature. With the goal.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a cylindrical heat roller having a metal substrate, a fixing film including the heat roller, and a backup pressurized by the heat roller via the fixing film. A roller, a temperature sensor that is disposed at a position in contact with the heat roller and detects a surface temperature thereof, and a temperature control unit that controls the temperature of the heat roller based on a temperature signal detected by the temperature sensor. It is provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The fixing device of the present invention can be used in an electrophotographic printer or a plain paper facsimile device to shorten the rise time (wait time) of a fixing operation.

An embodiment of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a diagram showing a configuration of a fixing device according to Embodiment 1 of the present invention.

The heat roller 1 is formed of a thin aluminum pipe having a thickness of about 0.3 mm to 1.0 mm. The backup rollers 2 are arranged in parallel so that silicone rubber is formed on the outer peripheral surface and pressed against the lower surface of the heat roller 1. At the center of the heat roller 1, a halogen lamp 3 is fixedly installed.
If the heat roller 1 is made of a metal having high hardness, such as a titanium alloy, instead of an aluminum pipe, the thickness can be further reduced.

The heat roller 1 is driven to rotate in the direction of arrow a by a drive unit (not shown). A pressure is applied to the backup roller 2 in the direction of the heat roller 1 by a spring 4 at a linear pressure of about 300 g / cm. Therefore, when the heat roller 1 rotates, the recording material 6 to which the toner image 5 has adhered is conveyed in the right-hand direction in the figure while being pressed against the heat roller 1. The thermistor 7 is arranged so as to be in contact with the surface of the heat roller 1 at a central portion in the longitudinal direction of the heat roller 1, and controls the fixing temperature of the heat roller 1.

Reference numeral 8 denotes a fixing film having a width approximating the width of the heat roller 1 in the longitudinal direction. This fixing film 8
The heat roller 1 heats the recording material 6 via the fixing film 8 because the heat roller 1 and the idle roller 9 are stretched in a belt shape. The fixing film 8 is made of a heat-resistant resin such as polyimide and has a surface coated with a fluorine resin, and has a thickness of about 0.05 mm.

The idle roller 9 extends the fixing film 8 in the conveying direction of the recording material 6, and preferably has a diameter as small as possible. Even when the recording material 6 is pressed by the backup roller 2 and adheres to the fixing film 8, the recording material 6
Can be easily peeled off. However, if the diameter of the idle roller 9 is too small, the fixing film 8 is subjected to fatigue damage. So, in practice,
The diameter of the idle roller 9 is designed in the range of 8 mm to 15 mm, preferably about 10 mm. Reference numeral 10 denotes a printer control unit, which receives a temperature signal detected by the thermistor 7 and inputs the temperature signal to the printer control unit 10.
Is controlled to blink.

Next, the operation of the fixing device having the above configuration will be described.

FIG. 2 is an explanatory diagram showing the overall configuration of the electrophotographic printer.

The recording material 6 is conveyed to a conveyance path 22 by a paper feed roller 21, and is first inserted between a photosensitive drum unit 23 and a transfer roller 24. In the photosensitive drum unit 23, image data is written on the rotating photosensitive drum 23a by an optical head 25 built therein, and the image data is developed with a toner agent, so that the toner image 5 as shown in FIG. Obtained on drum 23a.

When the recording material 6 passes over the transfer roller 24, the toner image on the photosensitive drum 23a is transferred to the recording material 6. The recording material 6 is heat-fixed with the toner image 5 by a fixing device 20 disposed further downstream, and is discharged. Here, the fixing device shown in FIG. 1 is used for the fixing device 20, and the surface temperature of the heat roller 1 is maintained at a predetermined value.

That is, as shown in FIG. 1, when the heat roller 1 and the backup roller 2 rotate in the directions of arrows a and b, respectively, the fixing film 8 rotates in the direction of arrow a. The recording material 6 guided to the fixing device 20 is heated via the fixing film 8, and the toner image 5 is fixed. The halogen lamp 3 is turned on simultaneously with the start of the printing operation,
The heat roller 1 is started up to a predetermined fixing temperature. Here, when the heat roller 1 is constituted by a thin aluminum pipe having a thickness of about 0.3 mm to 1.0 mm, the wait time is about 5 to 15 seconds.

By reducing the thickness of the heat roller 1, the wait time can be reduced. But,
When the thickness is reduced, the temperature when the heat is taken away by the recording material 6 becomes remarkably low, and a temperature difference easily occurs between the heat roller 1 portion through which the recording material 6 passes and other portions. . In such a case, the thermistor 7 for temperature detection is arranged at the central portion in the longitudinal direction of the heat roller 1, and
It is necessary to improve the temperature detection accuracy. By doing so, even when the recording material 6 having a small width is continuously fixed, the fixing device can be operated so that the fixing failure does not occur.

The recording material 6 is heated via a fixing film 8, and the temperature of the heat roller 1 is detected by a thermistor 7 disposed inside the fixing film 8. Therefore, even if the fixing film 8 does not contact the thermistor 7 and the thermistor 7 is disposed at the central portion in the longitudinal direction of the heat roller 1, the temperature detection portion of the thermistor 7 due to the toner or paper powder adhering to the recording material 6. There is no risk of becoming dirty. Moreover, since the thermistor 7 is not in contact with the fixing film 8, there is no possibility that the film surface is damaged. Even if the drum surface of the heat roller 1 is damaged due to contact with the thermistor 7, the recording material 6 is heated via the fixing film 8, so that the printing state is not affected.

Further, in the process of fixing the recording material 6 having a small width, only the temperature of both ends of the heat roller 1 through which the recording material 6 does not pass may increase. Therefore, a plurality of thermistors 7 are arranged apart from each other in the longitudinal direction of the heat roller 1 so that, when temperature unevenness is detected on the heat roller 1, the subsequent printing operation on a wide recording material is temporarily stopped. , Unevenness in fixing and unevenness in print density can be eliminated. In this case, for example, if the temperature difference between any two thermistors exceeds a predetermined value, printing is stopped when the recording of the recording material 6 during printing is completed, and the system waits until the temperature difference becomes equal to or less than the predetermined value. .

After the detected temperature of the thermistor 7 reaches the fixing temperature, the printer controller 10 turns on / off the halogen lamp 3 during the printing operation to maintain the fixing temperature. After the toner image 5 is melted by heat and fixed, the recording material 6 is separated from the fixing film 8 and discharged to the stacker of the printer. At this time, if the surface curvature of the idle roller 9 is large, the recording material 6 can be easily separated from the fixing film 8 without using a special separation claw or the like.

In the fixing device of the first embodiment described above, the rising time of the fixing operation can be shortened, and the recording material having a width smaller than the width of the heat roller 1 can be continuously fixed. .

Incidentally, a thermocouple or the like can be used as a temperature sensor instead of the thermistor 7. The material of the heat roller 1 does not have to be aluminum. Further, a heating element other than the halogen lamp 3 can be used.

Embodiment 2 FIG. FIG. 3 is a timing chart showing a lamp flicker cycle in the second embodiment of the present invention. FIG. 2A is a timing chart showing a conventional lamp blinking cycle, and FIG. 2B is a timing chart showing a lamp blinking at a fixed cycle (T seconds).

In a conventional heat roller type fixing device, a heat roller is constituted by a thick aluminum pipe, and a halogen lamp is turned on when the temperature of the thermistor 7 is lower than a preset fixing temperature by detecting the temperature. It was off when it was high. However, when the aluminum pipe is thin and the lighting control is performed aperiodically, the temperature unevenness of the heat roller 1 becomes larger than when the thickness is large. Therefore, in the fixing device according to the second embodiment, in order to prevent temperature unevenness, control is performed so that the halogen lamp blinks at a fixed T-second cycle.

That is, as shown in FIG. 3B, the duty of the lighting control signal for blinking the halogen lamp 3 is changed according to the temperature of the heat roller 1 to control the energizing time of the halogen lamp 3. Have been. Here, when the lighting time of the halogen lamp is lengthened or shortened in accordance with the temperature detected by the thermistor 7, the blinking cycle is, for example, one cycle with respect to the rotation cycle of the heat roller 1.
The cycle is shorter than about / 5.

FIG. 4 is a block diagram showing a configuration of a control circuit of the electrophotographic printer according to the second embodiment.

The fixing device 20 has the same configuration as that of the first embodiment shown in FIG. 1, and is connected to the printer control unit 10 having a CPU and the like. The printer control unit 10 is provided with a print start command 31 and a temperature signal 32, and based on them, outputs a lighting control signal 34 from the power supply unit 33 to the fixing device 20 of the electrophotographic printer, and also outputs a voltage signal 35. The signals are output to the driving unit 36, the developing unit 37, and the transfer unit 38. The thermistor 7 is arranged so as to contact the surface of a heat roller (not shown).

FIG. 5 is a flowchart showing temperature control according to the second embodiment of the present invention.

When a print start command 31 is given to the printer controller 10, the temperature of the surface of the heat roller is detected from the thermistor 7 (step S1). The temperature signal 32 indicating the temperature detected by the thermistor 7 is transmitted to the printer control unit 10.
Is converted into a digital signal by an A / D converter (step S2). The printer control unit 10 has its CPU
Is detected from the temperature signal taken into the fixing device 20 to determine whether the fixing device 20 is heated to a usable temperature range, and controls the power supply unit 33 to output a lighting control signal 34 for lighting the halogen lamp 3. (Step S
3).

If the detected temperature is lower than the predetermined temperature range, the lighting control signal 34 is output as a signal having a large duty cycle and a constant period (step S4). The lighting time of the halogen lamp 3 of the fixing device 20 is lengthened by such a lighting control signal 34 (step S5).

By controlling the lighting time of the halogen lamp 3 in this manner, the fixing film is heated via the heat roller. At that time, the temperature of the fixing film is
It is almost equal to the temperature of the heat roller. When the temperature detected by the thermistor 7 falls within the predetermined temperature range, the printer control unit 10 outputs a lighting control signal 34 having a small duty cycle and a constant cycle based on the temperature signal 32 (step S6). The lighting control signal 34 shortens the lighting time, issues a recording material conveyance command, and supplies a voltage signal from the power supply unit 33 to the drive unit 36. In addition, a print command is issued from the printer control unit 10, a toner image is formed on the photosensitive drum of the developing unit 37, and is transferred to a recording material by the transfer unit 38 (Step S7). Thereafter, the recording material is conveyed to the fixing device 20, and the toner image transferred to the recording material is fixed (Step S).
8).

In the above description, when controlling the duty of the lighting control signal, switching is made in two ways, large and small. However, lighting is performed in multiple stages according to the magnitude of the difference up to the target temperature range. The duty of the control signal may be controlled.

As described above, in the fixing device of the second embodiment, the lighting period is changed by controlling the duty of the lighting control signal while keeping the lighting cycle of the halogen lamp constant. Unevenness can be prevented, and printing can be performed at a uniform density.

Embodiment 3 A surface coat 12 of PFA or PTFE is formed on the outer peripheral surface of the conventional heat roller to prevent toner from adhering. Embodiment 3
In this example, silicone rubber is applied to the surface of the heat roller to form an elastic layer. Further, a belt-like fixing film made of a heat-resistant material is covered so as to surround the heat roller, thereby preventing toner from adhering to the surface of the heat roller. In order for the elastic layer to be in close contact with the surface of the recording material via the fixing film, the thickness of the elastic layer is preferably, for example, about 0.5 mm to 2 mm.

FIG. 6A is a diagram showing a contact state of the heat roller with the recording material according to the third embodiment, and FIG.
FIG. 4 is a view showing a state of contact with a conventional heat roller on which an elastic layer is not formed.

In FIG. 6, 1a is an elastic layer, 8 is a fixing film, 6 is a recording material, and 2 is a backup roller.
Heat roller 1, recording material 6, and backup roller 2
Each of the surfaces has minute irregularities that cannot be recognized by the naked eye.

The conventional heat roller 1 shown in FIG.
The surface of the aluminum substrate 11 is covered with a hard surface coat 12, and the surface coat 12 does not deform so as to fill a concave portion on the surface of the recording material 6. On the other hand, since the backup roller 2 is a rubber roller, it comes into close contact with the back surface of the recording material 6 and presses the recording material 6 against the heat roller 1. As a result, a gap G is generated on the contact surface between the heat roller 1 and the recording material 6, causing unevenness in heat from the heat roller 1 and pressure from the backup roller 2. Becomes uneven. As a result, when forming an image in which the entire surface of the recording material 6 is painted out, density unevenness has occurred in the printing result.

The heat roller 1 according to the third embodiment is different from the heat roller 1 shown in FIG.
As shown in (A), the surface of the aluminum container 11 is covered with the elastic layer 1a made of a soft material, so that the aluminum container 11 adheres tightly to the surface of the recording material 6 via the fixing film 8. Accordingly, the recording material 6 comes into contact with the heated fixing film 8 by the pressure from the backup roller 2, and the toner image on the surface thereof is uniformly fixed. Further, since the surface of the heat roller is covered with the fixing film 8, and the elastic layer 1a does not directly contact the backup roller 2, wear of the elastic layer can be prevented.

In the third embodiment, the elastic layer 1a made of silicon rubber or the like is applied to the surface of the heat roller to prevent density unevenness in printing. The surface of the heat roller is covered with a fixing film 8 in order to prevent toner from adhering. Therefore, there arises a problem that the efficiency of heat transmitted from the inside of the heat roller to the surface is reduced by such an elastic layer and the fixing film. Therefore, it is also possible to improve the thermal conductivity inside the heat roller by mixing a minute metal filler inside the elastic layer or the fixing film.

Embodiment 4 FIG. 7 is a diagram illustrating a configuration of a fixing device according to a fourth embodiment of the present invention.

The fourth embodiment differs from the conventional apparatus of FIG. 9 in that a fixing film 8 is used and a plurality of thermistors 7a and 7b are provided as temperature sensors.

In the first to third embodiments, the thermistor 7
Is only one at the center in the longitudinal direction of the heat roller 1,
It was arranged so as to be in contact with the surface of the heat roller 1. However, the printing width of the recording material 6 is variously different,
The fixing device also needs to support printing from a postcard size (105 mm) to an A4 size (210 mm), for example.
Therefore, in the fixing device according to the fourth embodiment, the thermistor 7a is provided at the central portion in the longitudinal direction of the heat roller, and in addition, the thermistor 7b is provided to detect the temperature outside the printing range. .

A plurality of heat rollers are arranged in the longitudinal direction of the heat roller.
Alternatively, the heat roller may be arranged outside the printing range of the heat roller to control the heating of the heat roller by the halogen lamp. In this case, if a temperature unevenness exceeding a predetermined temperature range is detected from a plurality of temperature detection results, the printing operation is temporarily stopped so that appropriate printing can be performed on recording materials of all sizes. State can be maintained.

Embodiment 5 FIG. In Embodiments 1 to 4,
In each case, the heat roller had a halogen lamp disposed inside. However, since radiant heat from a halogen lamp is used as a heat source, there is a limit in heat transfer efficiency, and there is a possibility that power consumption will increase. Therefore, as shown in FIG. 8, in the fifth embodiment, power consumption is reduced by using the cylindrical resistance heating element 40 as a heat roller.

Embodiment 6 FIG. In Embodiments 1 to 5,
Each of the fixing films 8 including the heat roller 1 includes:
The belt was stretched between the idle roller 9 (see FIGS. 1 and 8). However, even if such an idle roller is not used, the heat roller 1 can be used as the fixing film 8.
Can be configured to heat the recording material 6.

FIG. 9 is a schematic diagram showing the structure of the fixing device according to the sixth embodiment. Here, a heat roller 1 having a halogen lamp 3 is rotatably supported inside the fixing device cover 20a, and is rotatably driven by a motor (not shown) via a gear or the like. The thermistor 7 is also disposed inside the fixing device cover 20a on the non-contact surface side (upper side in the drawing) of the heat roller 1 with the backup roller 2 and in contact with the central portion in the longitudinal direction. The fixing film 8 formed in a cylindrical shape slightly longer than the circumferential length of the heat roller 1 covers the heat roller 1 and the thermistor 7 so as to wrap the fixing film 8 therein.

Here, the recording material 6 is heated via the fixing film 8, and the temperature of the heat roller 1 is detected by the thermistor 7 disposed inside the fixing film 8. Therefore, the contact surface of the fixing film 8 with the recording material 6 does not come into contact with the thermistor 7, and even if the thermistor 7 is arranged at the longitudinal center portion of the heat roller 1, the recording material 6
There is no possibility that the temperature detection portion of the thermistor 7 is contaminated by toner or paper powder adhering to the surface.

[0055]

As described above, according to the present invention, it is possible to provide a fixing device in which the wait time after turning on the power is shortened, the temperature detection accuracy thereof is increased, and the fixing temperature is stabilized.

Even if the surface of the heat roller is damaged by the temperature sensor, the print quality does not deteriorate because the heat roller is in contact with the recording material via the fixing film.

Further, the power consumption can be reduced by using a heat roller in which a resistance heating element is disposed near the surface thereof.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a fixing device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an overall configuration of an electrophotographic printer.

FIG. 3 is a timing chart showing a lamp blinking cycle according to Embodiment 2 of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a control circuit of the electrophotographic printer.

FIG. 5 is a flowchart showing temperature control.

FIG. 6 is a diagram illustrating a contact state of a heat roller with a recording material.

FIG. 7 is a diagram illustrating a configuration of a fixing device according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a fixing device according to a fifth embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating a configuration of a fixing device according to a sixth embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a configuration of a conventional fixing device.

FIG. 11 is a diagram showing a front shape of an aluminum pipe and a partially enlarged cross section thereof.

[Explanation of symbols]

Reference Signs List 1 heat roller, 1a elastic layer, 2 backup roller, 3 halogen lamp, 4 spring, 5
Toner image, 6 recording material, 7, 7a, 7b thermistor, 8 fixing film, 9 idle roller, 1
0 Printer control unit, 20 fixing unit, 40 resistance heating element.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masamitsu Nagamine 4-11-11, Shibaura, Minato-ku, Tokyo Inside the company's offshore data (72) Kuniharu Hayashi 4-11-22, Shibaura, Minato-ku, Tokyo Shares Company offshore data F-term (reference) 2H033 BA11 BA31 BB01 BB17 BB28 3K058 AA71 BA18 CA28 CA92 DA02 DA04 GA06

Claims (12)

[Claims] 1. A cylindrical heat roller having a metal base, a fixing film including the heat roller, a backup roller pressed by the heat roller via the fixing film, and a contact with the heat roller. A temperature sensor disposed at a position where the temperature of the heat roller is detected, and a temperature controller for controlling the temperature of the heat roller based on a temperature signal detected by the temperature sensor. apparatus. 2. The fixing device according to claim 1, wherein the heat roller includes a heating element and a heating section that rotates while including the heating element. 3. The fixing device according to claim 2, wherein the heating element is a halogen lamp, and the heating section is an aluminum pipe. 4. The heat roller according to claim 1, wherein said temperature sensor is provided at a central portion in a longitudinal direction of said heat roller.
The fixing device according to any one of the above. 5. The temperature control device according to claim 1, wherein the temperature of the heat roller is controlled by changing a duty of the heat roller at a constant cycle to control an energization time. The fixing device according to any one of the above. 6. The fixing device according to claim 1, wherein the fixing film is covered with a fluororesin. 7. The fixing device according to claim 1, wherein the fixing film is wound around an idle roller and rotated together with a heat roller. 8. The fixing device according to claim 1, wherein the heat roller has a resistance heating element disposed near a surface thereof. 9. The fixing device according to claim 1, wherein an elastic layer is formed on a surface of the heat roller. 10. The fixing device according to claim 9, wherein the elastic layer on the surface of the heat roller contains a metal filler. 11. The fixing device according to claim 1, wherein the fixing film contains a metal filler. 12. The fixing device according to claim 1, further comprising two or more temperature sensors.