JPH1124461A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an external heating type fixing device capable of obtaining excellent fixation by controlling the press-contact and separation periods of an external heating body capable of contact/uncontact. SOLUTION: A contact/uncontact means 6 bringing/separating the external heating body 3 which heats a heating roll 1 from the outside into contact with/ from the heating roll 1 is provided and a contact/uncontact control means 7 controls the contact/uncontact means 6, so that the external heating body 3 is arranged in press-contact with the heating roll 1 under the condition that the heating body 3 has a reference temp. at a toner softening point or more. At this time, it is preferable that a rotary driving means 8 is provided in the heating roll 1 and the contact/uncontact control means 7 executes control for idling the roll 1 by the time when at least the heating body 3 comes into press- contact with the roll 1. In such a case, the rotary driving means 8 can be shared by use for the driving device of the heating roll. l used for making a normal copy. The press-contact is attained in the state where toner fixed on the surface of the external heating body is softened, so that stable fixation can be executed without damaging the roll 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 pressure fixing an unfixed image in an image information recording apparatus such as a copying machine, a printer, a facsimile, etc. The present invention relates to an improvement of a so-called external heating type fixing device in which an external heating element is provided.

[0002]

2. Description of the Related Art Generally, in an image information recording apparatus such as a copying machine adopting an electrophotographic system, a heating / pressing type fixing device is usually provided in order to fix a toner image transferred onto a recording sheet. . Conventionally, as this type of fixing device,
A heating roll, which has an elastic layer on its surface, and a pressure roll, which rotate while being pressed against each other, and a recording sheet on which the unfixed toner image is formed is inserted between these rolls to fix the unfixed toner image. What is done is known. Further, in this type of fixing device, the heating roll has an elastic layer having poor heat conductivity on its surface, and the temperature is raised to a set temperature only by supplying heat from a heating source inside the heating roll. Need a lot of time to do. Therefore, a technology is disclosed in which an external heating element is provided on the surface of the heating roll to shorten the time required for temperature rise.

[0003] For example, as shown in FIG. 8, a rotatable heating roll 102 having a heating source 104 at the center and an elastic layer 103 on the surface thereof, and a pressurizing contact with the heating roll 102 to form a contact nip area. An external heating roll 1 having a pressure roll 101 and a heating source 106 and constantly pressing the heating roll 102 to heat the heating roll 102 from the outside
05 (see, for example, Japanese Patent Laid-Open No.
No. 85).

[0004]

However, in the above prior art, since the heating roll 102 and the external heating roll 105 are always in pressure contact with each other, the heating roll 102
When the rotation is stopped, the external heating roll 105 is stopped while being pressed. For this reason, the heating roll 1
There is a technical problem that the imprint of the external heating roll 105 remains on the surface of No. 02, and the fixed image is likely to be disturbed. In order to solve such a technical problem, it is conceivable to dispose the heating roll and the external heating roll so as to be able to contact and separate from each other, and to make pressure contact only during heating.

[0005] However, when the heating roll and the external heating roll are arranged so as to be able to be separated from each other and are brought into pressure contact only at the time of heating, the heating of the external heating roll is started at a low temperature such as at the time of warm-up or return from the standby mode. When carrying out the above, a technical problem was found that the toner transferred from the heating roll and fixed and deposited on the external heating roll rubs and damages the heating roll.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and it is possible to obtain good fixing by controlling the timing of pressing and separating an externally heatable body that can be contacted and separated. It is an object of the present invention to provide an external heating type fixing device that can be used.

[0007]

That is, as shown in FIG. 1, the present invention relates to a heating roll 1 having at least an elastic layer 2, an external heating body 3 for heating the heating roll 1 from outside, The external heating unit 3 is pressed against the heating roll 1 under the condition that the external heating unit 3 has a reference temperature equal to or higher than the toner softening point, and a contact / separation unit 6 for bringing the heating unit 3 into and out of the heating roll 1. And a contact / separation control means 7 for controlling the contact / separation means 6 as described above.

In such technical means, a heating roll 1 having a built-in heating source and having an elastic layer 2 on the surface is used as the heating roll 1. The external heating member 3 may be appropriately selected as long as it can externally heat the heating roll 1, but from the viewpoint of simplification of the configuration, a rotating member such as a roll or a belt is used. Preferably, it is used. Further, the external heating element 3 is used not only for heating the heating roll 1 but also for heating the heating roll 1 during continuous copying.
May be shared with an external heating element for compensating for the temperature drop. Further, the configuration and number of the heating source 4 may be arbitrarily selected as long as the external heating element 3 can be heated, but from the viewpoint of simplification of the configuration and efficiency, It is preferable that a heating source 4 is provided inside the heating element 3.

The contacting / separating means 6 may be any mechanical, electrical, or magnetic means as long as the external heating element 3 is brought into or out of contact with the control signal obtained from the contacting / separating control means 7. It can be arbitrarily selected.

Further, the contact / separation control means 7 starts pressure contact with the contact / separation means 6 when the external heating element 3 reaches a reference temperature equal to or higher than the toner softening point temperature based on temperature information of the external heating element 3. Any signal may be selected as long as it sends a signal to perform the operation. Here, the reference temperature of the external heating element 3 may be a temperature equal to or higher than the softening point of the toner, and from the viewpoint of improving the durability of the external heating element 3,
It is preferable that the temperature be equal to or lower than the set temperature of the external heating body 3. The means for detecting the temperature information of the external heating element 3 may be appropriately selected from various methods. However, from the viewpoint of simplification of the configuration, the temperature sensor 5 may be provided on the external heating element 3. preferable.

By the way, in a mode in which the external heating body 3 is pressed against the heating roll 1 when the reference temperature is equal to or higher than the toner softening point temperature, the pressing is performed when the heating roll 1 is stopped. Since the pressure contact position between the heating roll 1 and the external heating body 3 is fixed, there is a concern that only a part of the heating roll 1 is heated and uneven fixing and a trace of pressure contact are likely to occur. From the viewpoint of effectively preventing such a concern, the heating roll 1 is provided with the rotation driving means 8, and the heating / rolling means 8 is controlled by the contact / separation control means 7 at least until the external heating body 3 is pressed against the heating roll 1. It is preferable to perform control so as to perform idle rotation. In this case, the rotation drive means 8 may be shared with the drive device of the heating roll 1 used at the time of normal copying.

Further, in a mode in which pressing of the heating roller 1 is started when the temperature of the external heating body 3 reaches a reference temperature equal to or higher than the toner softening point temperature,
May be lower than the toner softening point temperature. At this time, even if the residual toner on the external heating member 3 is in a softened state, the residual toner which has been in a softened state while being pressed against the heating roll 1 is solidified again, which may cause damage to the heating roll 1. There is. From the viewpoint of effectively preventing such a concern, the contact / separation control means 7 presses the external heating body 3 and the heating roll 1 into pressure contact with each other when the respective reference temperatures are equal to or higher than the toner softening point. Preferably, control is performed. Here, the reference temperature of the heating roll 1 may be a temperature equal to or higher than the toner softening point as in the case of the reference temperature of the external heating body 3, but may be different from the reference temperature of the external heating body 3. From the viewpoint of improving the durability of the heating roll 1, the temperature is preferably equal to or lower than the set temperature of the external heating body 3.

Further, in a mode in which the pressurization of the heating roll 1 is started when the external heating body 3 reaches a reference temperature equal to or higher than the softening point of the toner, for example, when returning from the standby mode,
When heating is performed from a state in which the heating roll 1 has a certain amount of heat, the temperature of the heating roll 1 may be higher than that of the external heating body 3 at the start of pressing. At this time, if the external heating body 3 is pressed against the heating roll 1, the heat of the heating roll 1 is taken away by the external heating body 3, and the original heating action of the external heating body 3 is impaired. There is a concern that the heating time will be long. From the viewpoint of effectively preventing such a concern, the contact / separation control means 7 determines that the external heating element 3 has a reference temperature equal to or higher than the toner softening point and that the temperature of the external heating element 3
It is preferable to perform control so as to perform pressure contact under conditions that are equal to or higher than the temperature.

In the external heating type fixing device, there is a prior art in which an external heating body and a heating roll can be brought into contact with and separated from each other. However, this is irrelevant to that of the present invention. Keep it. Japanese Patent Application Laid-Open No. 52-40143 proposes a heating roll provided with an external heating element that can be brought into contact with and separated from the heating roll. However, in the prior art, when the amount of heat taken by the recording sheet during continuous copying increases and the temperature of the heating roll becomes lower than the fixing temperature, an external heating body is pressed against the heating roll to compensate for the temperature drop. This is not a technique of quickly raising the temperature of the heating roll 1 during warm-up or in a standby mode as in the present invention. Further, the purpose of this prior art is to save energy, and since the external heating body is heated at a time other than during copying and the external heating body is not heated during copying, the heating roll 1 and the external heating body 3 are simultaneously heated. This is a completely different idea from the present invention.

Next, the operation of the above technical means will be described. In FIG. 1, the contact / separation control means 7 controls the contact / separation means 6 for bringing the external heating element 3 into and out of contact based on the temperature information of the external heating element 3. Specifically, in the initial state,
The contact / separation control unit 7 controls the contact / separation unit 6 to separate the external heating body 3. Next, when the external heating body 3 reaches a reference temperature equal to or higher than the toner softening point, the contact / separation control means 7 controls the contact / separation means 6 so as to press the external heating body 3 against the heating roll 1. At this time, the external heating element 3 is pressed against the surface of the heating roll 1 with the toner fixed on the surface of the external heating element 3 softened.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. 2 and 3
1 shows an embodiment of a fixing device to which the present invention is applied. In the figure, the fixing device according to the present embodiment includes a heating roll 40 driven to rotate by a motor 46, an endless belt 80 disposed in pressure contact with the heating roll 40, a bar 75 and a cam 76. An external heating roll 71 is provided so as to be capable of coming and going with respect to 40.

In the present embodiment, the heating roll 40
A hollow core 42 made of aluminum having a thickness of 1.5 mm and covering a heating source 41 composed of a 650 W halogen lamp;
A heat-resistant elastic layer 43 made of silicon rubber is provided on the outer peripheral surface of the hollow core 42, and a top coat layer 44 made of fluoro rubber is further provided on the outer peripheral surface of the heat-resistant elastic body 43. Temperature sensor 45 provided on the surface of roll 40
Is controlled by a temperature control circuit (not shown) to turn on and off the heating source 41 to adjust the temperature to a certain constant temperature.

In order to prevent the unfixed toner 31 on the recording paper 30 from being offset during fixing, an oil supply device 90 for supplying a fixed amount of silicone oil to the heating roll 40 is provided. Further, a cleaning device 91 is provided to clean the offset residual toner.

On the other hand, the endless belt 80 is stretched around support rolls 81, 82, 83 made of stainless steel and
It is press-fitted at 0 with a predetermined nip width. The endless belt 80 was provided with an elastic layer of silicon rubber having a thickness of 170 μm on a base material of a polyimide film having a thickness of about 75 μm, and further provided with a release layer of fluoro rubber having a thickness of 30 μm thereon. Things.

In this embodiment, the support roll 81
Is also used as a pressure roll disposed at the exit of the contact nip region between the heating roll 40 and the endless belt 80, and is urged toward the center of the heating roll 40 by the compression coil spring 62. Further, a 250 W halogen lamp 84 is provided inside the support roll 81,
In response to a signal from a temperature sensor 63 provided on the surface of the support roll 81, a temperature control circuit (not shown) controls on / off of the halogen lamp 84 to adjust the temperature to a certain constant temperature.

Further, inside the endless belt 80, a pressure pad 5 which is pressed and arranged by a compression coil spring 53 is provided.
0 is provided. In the present embodiment, the pressure pad 5
Numeral 0 denotes an elastic layer 52 made of silicon rubber provided on a metal base 51 made of stainless steel.

In this embodiment, the external heating roll 71 shown in FIG. 3 is a stainless steel hollow core that covers a heating source 72 composed of a halogen lamp. In response to a signal from the sensor 77, the heating source 72 is turned on / off by a temperature control circuit (not shown) to adjust the temperature to a certain constant temperature. Further, a rotation shaft 73 of the external heating roll 71 is rotatably attached to a tip of a bar 75 that can rotate around a fulcrum 74. Further, a rotatable eccentric cam 76 is in contact with the opposite side of the fulcrum of the bar 75,
A coil spring 78 for urging the end of the bar 75 toward the eccentric cam 76 is disposed at the end of the bar 75. Now, when the eccentric cam 76 rotates 180 degrees as indicated by the dotted line, the bar 75 rotates around the fulcrum 74 as indicated by the dotted line due to the shape of the eccentric cam 76, and separates the external heating roll 71 from the heating roll 40. It has become.

FIG. 4 shows a drive control system of the fixing device used in this embodiment. In the figure, the temperature signals of the temperature sensor 45 of the heating roll 40 and the temperature sensor 77 of the external heating roll 71 are taken into the CPU 96 via the input interface 95. Then, the CPU 96
After executing a drive control processing program (see FIG. 5) stored in the ROM 97 in advance and performing appropriate data processing with the RAM 98, the heating source 41 of the heating roll 40 and the external Heating roll 71
A predetermined control signal is transmitted to the heating source 72, the motor 46, and the contact / separation device 70.

Next, drive control of the fixing device according to the present embodiment will be described. In FIG. 5, when the start switch of the copying machine is turned on, the control driving device (CPU 9
6, the ROM 97 and the RAM 98), the temperature of the heating roll 40 and the external heating roll 71 are detected by the temperature sensors 45 and 77, respectively, and the temperature of the heating roll 40 and the external heating roll 71 are raised by the respective heating. Started by sources 41,72. Next, the temperature of the external heating roll 71 was compared with a reference temperature (in the present embodiment, set at the toner softening point temperature), and it was confirmed that the temperature of the external heating roll 71 was equal to or higher than the toner softening point. rear,
Next, the temperature of the heating roll 40 is compared with a reference temperature (in the present embodiment, the toner softening point is set). Then, when it is confirmed that the temperature of the heating roll 40 has become equal to or higher than the toner softening point, that is, when both the heating roll 40 and the external heating roll 71 have reached the temperature equal to or higher than the toner softening point, the drive control device When the motor 46 for driving the heating roll 40 is idled, the external heating roll 7
1 is pressed against the heating roll 40. On the other hand, the external heating roll 71 already at a temperature equal to or higher than the toner softening point continues to be further heated, and when the temperature reaches the set temperature, the drive control device controls the external heating roll heating source 72 to turn on / off, thereby controlling external heating. Roll 71 continues to be controlled at the set temperature. In the present embodiment, the set temperature of the external heating roll 71 is set higher than the set temperature of the heating roll 40 from the viewpoint of improving the external heating efficiency. Next, the temperature of the heating roll 40 is compared with the set temperature, and when the temperature of the heating roll 40 reaches the set temperature, the drive control device stops the idling of the motor 46 for driving the heating roll 40 and simultaneously Then, the external heating roll 71 is separated from the heating roll 40, and the heating roll heating source 41 is turned on / off to keep the heating roll 40 at the set temperature. Then, the heating operation ends.

In the present embodiment, when the above-mentioned temperature raising operation is required, it is roughly classified into two types of states. One is a case such as at the time of warm-up in which the temperature needs to be raised from room temperature, and the other is a case where the heating roll returns from a state in which the heating roll has some heat, such as a standby mode. Hereinafter, the operation in each case will be described based on a timing chart.

FIG. 6 shows a timing chart and a graph of temperature change when heating is performed from room temperature. In this example, the room temperature was set at 20.
° C. Now, at time t1, when the heating of the heating roll 40 and the external heating roll 71, which are substantially the same temperature, is started, the external heating roll 71 has a smaller heat capacity than the heating roll 40. At t2, the toner is first heated to the toner softening point temperature T1 or higher. Further, the external heating roll 71 is further heated as in this example,
When the temperature of the external heating roll 71 reaches the set temperature T3 earlier, the process waits until the temperature of the heating roll 40 reaches the toner softening point temperature T1 while being controlled at the external heating roll set temperature T3. When the heating roll 40 reaches the toner softening point temperature T1, the heating roll 4 is driven by the motor 46.
The external heating roll 71 is pressed against the heating roll 40 at the same time when the idle rotation of 0 is started. Further, when the temperature of the heating roll 40 reaches the heating roll set temperature T2, the external heating roll 71 is separated from the heating roll 40, and the idle rotation of the heating roll 40 is stopped. In the graph of FIG. 6, the heating time t5 of the present embodiment is 1
In the comparative example without the external heating roll, the required heating time t6 was 260 seconds.

FIG. 7 shows a timing chart and a graph of temperature change when heating is performed from a state in which heat is applied to some extent. still,
In this example, the heating roll 40 at the heating start time t1 '
The temperature of the external heating roll 71 is set to 80 ° C. and 30 ° C., respectively. Now, at time t1 ', the heating roll 4
When the heating of 0 and the external heating roll 71 is started, the temperature difference at time t1 'is large, so that the temperature of the heating roll 40 is first heated to the toner softening point T1 or higher at time t2'. Then, at time t2 ″, the external heating roll 7
1 is also heated to the toner softening point T1, but at this point, since the heating roll 40 has been heated to a higher temperature,
External heating by pressure welding is not performed. When the temperature of the external heating roll 71 reaches the time t4 at which the temperature of the external heating roll 71 exceeds the temperature of the heating roll, the motor 46 starts the idle rotation of the heating roll 40, and at the same time, the external heating roll 71 is heated.
Press to 0. Further, when the external heating roll 71 reaches the set temperature T3 during the pressure contact as in this example, the external heating roll 71 is pressed against the heating roll 40 while being controlled at the set temperature. Further, after that, when the heating roll 40 reaches the set temperature T2, the external heating roll 71 is separated from the heating roll 40, and the idle rotation of the heating roll 40 is stopped.

[0028]

As described above, according to the present invention,
During warm-up or in standby mode, the external heating element is pressed against the heating roll in a state where the toner that has adhered to the external heating element surface has softened, so that the toner that has adhered to the external heating element surface may damage the heating roller. And stable fixing can be performed. Further, in the present invention, by performing idle rotation of the heating roll before pressing the external heating body against the heating roll, stable fixing can be performed without causing uneven heating of the heating roll.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a fixing device according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment to which the present invention is applied.

FIG. 3 is an enlarged view of a contact / separation unit according to FIG. 2;

FIG. 4 is a block diagram illustrating an overall control system of the fixing device according to the exemplary embodiment;

FIG. 5 is a flowchart illustrating processing performed by a drive control device of the fixing device according to the exemplary embodiment;

FIG. 6 is a timing chart and a graph showing a heating state when the temperature is raised from room temperature in the fixing device according to the embodiment.

FIGS. 7A and 7B are a timing chart and a graph showing a temperature rising state when the temperature is raised from a heated state in the fixing device according to the embodiment;

FIG. 8 is an explanatory diagram illustrating an example of a conventional fixing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roll, 2 ... Elastic layer, 3 ... External heating body, 4 ... Heating source, 5 ... Temperature sensor, 6 ... Contact / separation means, 7 ... Contact / separation control means, 8 ... Rotation drive means

Claims (7)

[Claims] 1. A fixing device for fixing an unfixed image on a recording sheet by heat and pressure, comprising: a heating roll having at least an elastic layer; an external heating body for heating the heating roll from outside; A contacting / separating means for contacting / separating from the heating roll; and a contacting / controlling means for controlling the contacting / separating means such that the external heating body is pressed against the heating roll under the condition that the temperature of the external heating body is equal to or higher than the toner softening point. A fixing device comprising: a separation control unit. 2. The fixing device according to claim 1, wherein the contact / separation control unit controls the contact / separation unit by taking in information from a temperature sensor that detects the temperature of the external heating element. apparatus. 3. The fixing device according to claim 1, wherein the contact / separation control means causes the heating roll to idle and rotate by the rotation driving means at least until the external heating body is pressed against the heating roll. apparatus. 4. The fixing device according to claim 1, wherein the contact / separation control means is configured such that when the heating roll and the external heating body reach respective reference temperatures equal to or higher than the toner softening point, the external heating body is heated. A fixing device that controls the contact / separation means so as to be in pressure contact with the fixing device. 5. The fixing device according to claim 1, wherein the contact / separation control means has a reference temperature of the external heating body equal to or higher than a toner softening point, and the temperature of the external heating body is equal to or higher than a temperature of a heating roll. A fixing device wherein the contacting / separating means is controlled such that the external heating member is pressed against the heating roll under the conditions. 6. The fixing device according to claim 1, wherein the external heating body is a rotating body. 7. The fixing device according to claim 1, wherein the external heating element has a heating source inside.