JPH1097150A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the temperature overrising of a paper nonpassing area by a constitution efficiently smoothing the uneven distribution of the surface temperature of a fixing rotary body by making the heat capacity of a thermal conductive rotary body provided in press-contact with the outer peripheral surface of the fixing rotary body larger than the thermal conductivity of the fixing rotary body. SOLUTION: This device is provided with a fixing roller 1 as the fixing rotary body, a pressure roller 2 as a pressure rotary body, a heat roller 3 as a heat rotary body incorporating a heater 4 and a thermal conductive roller 6 as the thermal conductive rotary body provided in press-contact with the outer peripheral surface of the fixing roller 1. Then, the thermal conductive roller 6 having a larger thermal conductivity than the fixing roller 1 and the heat roller 3 is disposed so as to be always brought into contact with the surface of the fixing roller 1. Thus, the heat of the paper nonpassing area whose temperature is high of the fixing roller 1 is transferred to the paper passing area whose temperature is low of the fixing roller 1 through the thermal conductive roller 6. Therefore, the temparature of the paper nonpassing area of the fixing roller 1 is prevented from abnormally rising.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided as one of the subsystems of an image forming apparatus for fixing toner on a recording medium by heating and pressing. In particular, the present invention relates to a mechanism for reducing excessive temperature rise in a non-sheet passing area of a fixing rotator.

[0002]

2. Description of the Related Art Generally, an image forming apparatus using an electrophotographic method such as the Carlson process has a fixing device as one of subsystems. When a recorded image is output, the image formed by the colored toner (charged particles) is printed on paper or OH by operating the fixing device.
A process for fixing on a recording medium (recording sheet) such as a transparent sheet for P is executed. Usually, in a fixing process, in a fixing device having a fixing roller and a pressure roller which rotate while being pressed against each other, a recording sheet carrying an unfixed toner image is nipped and conveyed by a pressure contact portion (nip portion) of both rollers. This is performed by applying heat or pressure to the toner image together with the recording sheet.

[0003] The configuration of such a fixing device is roughly divided into two types: a type in which the fixing roller is heated from the inside by a heater disposed in the fixing roller, and a type in which the fixing roller is heated from the outside by a heater disposed outside the fixing roller. There are things to do. In any of the configurations, the fixing roller is heated by the heat supply from the heater to control the temperature. Generally, this temperature control detects the surface temperature of the fixing roller using a temperature sensor, compares the detected signal with a reference signal corresponding to a predetermined target temperature, and inputs the detected signal to a heater based on the comparison result. This is done in a feedback manner that controls the current flow.

[0004] An external heating arrangement for heating the fixing roller from the outside is employed with one main purpose of improving the control response of the temperature of the surface of the fixing roller. That is, the external heating configuration can reduce the time required to raise the temperature of the surface of the fixing roller to a temperature suitable for fixing when the fixing device is started, or when the fixing device is to output a large amount of recorded images continuously. There is a practical feature that it is possible to quickly increase the temperature of the surface of the fixing roller, which decreases due to the loss of heat by the recording medium passing through the fixing roller.

[0005] This feature leads to an effect of improving the fixing degree of the toner image. That is, when a toner image is fixed on a recording medium having a rough surface, irregularities in the degree of fixation of the toner image tend to occur in accordance with the pattern of the roughness of the recording medium surface. By using the elastic fixing roller using the elastic material, the unevenness of the fixing degree can be reduced. This is because the heated elastic fixing roller is deformed according to the roughness pattern of the recording medium surface at the pressure contact portion with the pressure roller, and adheres well to the toner image carried in the recess on the recording medium surface. This is considered to be because the heating and pressurization are performed more reliably. However, heat-resistant rubbers generally employed here are silicone rubber and fluorine rubber, and these materials have high specific heat or low thermal conductivity. For this reason, in the fixing device using the elastic fixing roller, in the case of the internal heating configuration, the temperature of the fixing roller surface becomes difficult to respond to the heat generation control of the heater, but in the case of the external heating configuration, the fixing device described above is used. The feature that the time required to raise the temperature of the fixing roller surface at startup is shortened, or that the temperature of the fixing roller surface, which decreases due to heat being taken by the recording medium passing through it, becomes faster, is particularly effective. It is easier to control the temperature of the fixing roller surface than in the case of (1).

[0006]

However, as in the prior art described above, while the recording medium is nipped and conveyed at the pressure contact portion between the fixing roller heated by the heater controlled by the feedback system and the pressure roller, the recording is performed. In a fixing device that fuses and fixes a toner image carried on a medium, there is a problem that an excessive temperature rise occurs in a non-sheet passing area.

When the recording medium is supplied to and conveyed to the fixing device, in the sheet passing area where the fixing roller contacts the recording medium, the heat of the fixing roller is taken away and the surface temperature falls below a predetermined control target temperature. The operation of the heater is controlled so as to compensate, and heat is supplied from the heater to the fixing roller. on the other hand,
In the non-sheet passing area where the fixing roller does not come into contact with the recording medium, heat is supplied from the heater despite the fact that heat is not taken away, so that the surface temperature of the fixing roller rises above a predetermined target temperature.

In the dimension measured in the axial direction of the roller, the length of the heated area of the fixing roller is the width L of the recording medium.
It is designed to be slightly larger than the assumed maximum width L (S.max) of (S). Width L (S) is assumed maximum width L
If a large number of recording media smaller than (S.max) are continuously supplied and conveyed to the fixing device, the surface temperature of the non-sheet passing area of the fixing roller abnormally rises. If the fixing roller becomes extremely hot, not only the material of the fixing roller itself deteriorates, but also the damage or deformation of the pressure roller, peeling claw, cleaning member, support frame, etc., which is placed in contact with or close to the fixing roller. Will be caused.

Particularly, in the fixing device using the above-described elastic fixing roller, the distribution of the surface temperature of the fixing roller is non-sheet passing due to the large heat capacity of the fixing roller and the low thermal conductivity. If the area becomes non-uniform due to excessive temperature rise, it becomes more difficult to make the area uniform by heat radiation or heat diffusion during the interval between conveyance of the recording medium. as a result,
When the supply and conveyance of the recording medium having a small width L (S) are continuously performed,
There is a problem that the excessive temperature rise in the non-sheet passing area is significantly deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce an excessive temperature rise in a non-sheet passing area in a fixing device having an external heating structure by efficiently smoothing an uneven distribution of a surface temperature of a fixing rotating body. .

[0011]

According to a first aspect of the present invention, an object of the present invention is to provide a fixing rotator and a recording medium held between the fixing rotator by pressing the outer peripheral surface of the fixing rotator. A pressurizing rotator so that the unfixed toner image conveyed and carried on the recording medium is in contact with the outer peripheral surface of the fixing rotator; and a heat rotator provided with a heater provided in pressure contact with the outer peripheral surface of the fixing rotator. And a fixing device for fixing the toner on the recording medium by heating and pressurizing the recording medium. The fixing device is provided in pressure contact with the outer peripheral surface of the fixing rotator, and has a heat capacity larger than the thermal conductivity of the fixing rotator. This is achieved by providing a rotating body.

Further, according to the second invention of the present application,
The above object is achieved in the first aspect of the present invention in that the heat-conduction rotator includes a metal cylinder and a liquid heat medium sealed in the cylinder.

Further, according to the third invention of the present application,
The above object is achieved in the first invention or the second invention by the pressure rotator, the heat conduction rotator, and the heat rotator being sequentially arranged along the rotation direction of the fixing rotator. You.

According to a fourth aspect of the present invention,
The above object is achieved in any one of the first to third inventions by incorporating a heater in the heat-conducting rotating body.

According to a fifth aspect of the present invention,
According to a fourth aspect of the present invention, in the fourth aspect, a temperature detecting means for detecting a temperature of an outer peripheral surface of the fixing rotating body, and a heat rotating body and a heat conducting rotating body in accordance with a detection signal of the fixing rotating body temperature detecting means. The heating value of the heater built in the rotating body closer to the pressure contact portion between the fixing rotating body and the pressing rotating body along the rotation direction of the fixing rotating body is the same as the heating value of the heater built in the farther rotating body. Heat operation control means for controlling the operation of the heater of the heat rotator and the heater of the heat transfer rotator so that the outer peripheral surface temperature of the fixing rotator becomes a predetermined temperature. Is achieved by

According to a sixth aspect of the present invention,
According to a fourth aspect of the present invention, in the fourth aspect, a second temperature detecting means for detecting an outer peripheral surface temperature of the heat rotator, a third temperature detecting means for detecting an outer peripheral surface temperature of the heat conductive rotator, The operation of the heater incorporated in the heat rotator is controlled so that the outer peripheral surface temperature of the heat rotator becomes the second predetermined temperature according to the detection signal of the temperature detector, and the detection signal of the third temperature detector is provided. And controlling the operation of the heater built in the heat conduction rotator so that the outer peripheral surface temperature of the heat conduction rotator becomes the third predetermined temperature in accordance with the temperature, and fixing the temperature between the second predetermined temperature and the third predetermined temperature. Heat operation for controlling the predetermined temperature of the rotating body closer to the pressure contact portion between the fixing rotating body and the pressing rotating body along the rotating direction of the rotating body to be equal to or lower than the predetermined temperature of the farther rotating body. This is achieved by providing control means.

That is, the first invention according to the present application includes a heat conducting rotator provided in pressure contact with the outer peripheral surface of the fixing rotator and having a thermal conductivity larger than that of the fixing rotator. The heat of the high temperature non-sheet passing area of the fixing rotator moves to the low temperature sheet passing area of the fixing rotator via the heat conduction rotator.

In the second invention according to the present application,
The heat conduction rotator of the first invention has a metal cylinder and a liquid heat medium sealed in the cylinder, and performs heat convection and rotation of the heat medium sealed in the heat conduction rotator. The resulting agitation causes heat transfer.

In the third invention according to the present application, the pressing rotator, the heat conduction rotator and the heat rotator according to the first or second invention are arranged along the rotation direction of the fixing rotator. The heat transfer rotator is brought into contact with the fixing rotator when the temperature difference between the sheet passing area and the non-sheet passing area of the fixing rotator is large.

Further, in the fourth invention according to the present application, since the heater is built in the heat conduction rotator according to any one of the first to third inventions, the fixing rotator is used together with the heat rotator. Heat.

According to a fifth aspect of the present invention, in the fourth aspect, the surface temperature of the fixing rotating body is detected based on the temperature detecting means, and the heat rotating body and the heat transfer rotating body are detected in accordance with the detection signal. The heater included in the rotating body closer to the pressure contact portion of the fixing rotating body and the pressing rotating body along the rotating direction of the fixing rotating body has a heater built in the rotating body farther away. The operation of the heater of the heat rotator and the heater of the heat conduction rotator is controlled so as to be equal to or smaller than the heat generation amount so that the outer peripheral surface temperature of the fixing rotator is controlled to a predetermined temperature. The efficiency of smoothing the surface temperature can be increased.

According to a sixth aspect of the present invention, in the fourth aspect, the temperature of the heat rotator and the temperature of the heat conduction rotator are determined based on the second temperature detecting means and the third temperature detecting means, respectively. Temperature, and the predetermined temperature of the rotating body closer to the press contact portion between the fixing rotating body and the pressing rotating body along the rotating direction of the fixing rotating body in the heat rotating body and the heat conducting rotating body is farther. Since the temperature is controlled to be equal to or lower than the predetermined temperature of the rotating body, the efficiency of smoothing the surface temperature of the fixing rotating body can be increased.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The fixing device according to the embodiment described below is used as a subsystem of an image forming apparatus such as an electrophotographic copying machine or a printer. The process up to the formation of the unfixed toner image on the recording medium can be appropriately selected from various known techniques, and is not illustrated for the sake of simplicity. It is assumed that the Carlson process generally used for the apparatus is adopted. That is, after uniformly charging a photoconductive photoconductor, the photoconductor is exposed to light in a pattern corresponding to information of an image to be recorded, thereby forming an electrostatic latent image. An unfixed toner image is formed on the recording medium by developing the image to form a toner image and transferring the toner image onto the recording medium.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of a main part of the fixing device according to the first embodiment. The arrows in the figure indicate the direction of rotation of the rollers or the transport direction of the recording medium by a mechanism (not shown). This rotation or transport mechanism is not particularly limited and may be appropriately selected from known techniques as long as it does not affect the gist of the present invention, and a description thereof will be omitted.

The fixing device generally includes, for example, a fixing roller 1 as a fixing rotator, and a pressing roller 2 as a pressing rotator provided in pressure contact with the outer peripheral surface of the fixing roller 1. For example, the heat roller 3 is provided as a heat rotator provided in pressure contact with the outer peripheral surface of the fixing roller 1 and incorporates the heater 4, and the heat conductive roller 6 is provided as a heat conductive rotator provided in pressure contact with the outer peripheral surface of the fixing roller 1. And

Here, the fixing roller 1 is, for example, a roller made of silicone rubber or a roller in which a core metal is coated with a heat-resistant elastic material such as silicone rubber or fluorine rubber, and has a surface releasability. A fluorine resin film may be provided to increase the thickness. In the present embodiment, the thickness 5
mm JIS-A altitude 40-60 degrees H
The TV silicone rubber layer is coated with a thickness of 15 mm, and the surface thereof is further coated with a PFA tube having a thickness of 50 μm to 150 μm, and a roller having an outer diameter of 60 mm is used.

The pressure roller 2 is, for example, a cylinder made of aluminum or iron provided with a fluororesin coating on the surface thereof. In the present embodiment, a 4 mm-thick iron cored cylinder is coated with a fluororesin such as PFA or PTFE having a thickness of 20 μm to 100 μm or a hybrid thereof, and a roller having an outer diameter of 60 mm is used.

The heat roller 3 is a metal cylinder made of, for example, aluminum, iron, stainless steel, or the like. The surface of the heat roller 3 is provided with corrosion resistance, hardening or high releasability as required. It has been subjected to a coating process. In this embodiment, a surface of an aluminum cylinder having a thickness of 3 mm is subjected to oxidized alumite treatment, and a roller having an outer diameter of 30 mm is used.

The heater 4 of the heat roller 3 is an infrared lamp such as a halogen heater extending in the direction of the rotation axis at the center of the heat roller 3, and is supplied with power from a power supply 5. ing. The axial distribution of the calorific value of the heater 4 is designed so that the temperature of the surface of the heat roller 3 becomes substantially uniform. Actually, since the amount of heat radiation at both ends in the axial direction of the heat roller 3 is larger than that of the other portions, the amount of heat generated by the heater 4 at both ends is increased in order to compensate for this. As a result, the heat roller 3 supplies heat to the fixing roller 1 substantially uniformly in the rotation axis direction.

The maximum power supplied from the power source 5 to the heater 4 is preferably in the range of 800 W to 2000 W,
Output is automatically controlled. The power supply control method is the power supply 5
In addition to the on / off switching of the operation, a known method such as voltage level switching control, temporal control of output voltage phase oscillation or frequency control can be appropriately selected and used.

The temperature sensor 14 is disposed substantially at the center of the fixing roller 1 in the axial direction and in contact with or close to the outer peripheral surface of the fixing roller 1, and detects the temperature of the outer peripheral surface of the fixing roller 1. It is provided as follows. On the basis of the detection signal, the surface temperature of the outer peripheral surface of the fixing roller 1 is controlled so as to be maintained at a predetermined target temperature. As the temperature sensor 14, an element such as a thermistor or a thermocouple can be used.

The cut-off sensor 15 is disposed substantially at the center of the heat roller 3 in the axial direction and in contact with or close to the outer peripheral surface of the heat roller 3.
When the heater is heated above a predetermined allowable limit temperature, the heater is melted or deformed to cut off the power supply from the power supply 5 to the heater 4. As the cutoff sensor 15, an element such as a thermal fuse or a thermostat can be used.

Further, the logic control circuit 16
A detection signal from the temperature sensor 14 is input, the signal level is averaged, converted into a temperature, compared with a reference temperature, and the like, and a signal for controlling the output level of the power supply 5 is output. Is provided.

The heat conduction roller 6 is the most characteristic feature of the present invention. The heat conductive roller 6 is made of a material whose heat conductivity is higher than the material of the surface of the fixing roller 1 and the material of the elastic layer, and is arranged so as to always contact the surface of the fixing roller 1. 1 prevents an abnormal rise in the temperature of the non-sheet passing area. Heat conduction roller 6 of the present embodiment
Is a solid roller made of, for example, aluminum or iron, and has a higher thermal conductivity than the fixing roller 1 and the heat roller 3 and a heat capacity of the heat roller 3.
Larger than. In the illustrated embodiment, the outer diameter is 30 m.
m aluminum roller is used.

The oil application roller 7 is provided in pressure contact with the outer peripheral surface of the fixing roller 1, and is, for example, a heat-resistant fiber or resin roller impregnated with silicone oil. The oil is applied little by little to the surface while being driven to rotate.

The conveyance guide 8 is arranged at a position for guiding the recording medium 9 conveyed while carrying the unfixed toner image 10 to a pressure contact portion between the fixing roller 1 and the pressure roller 2.

The separation claws 11 and 12 are disposed in contact with or close to the outer peripheral surfaces of the fixing roller 1 and the pressure roller 2, respectively. Reference numeral 13 denotes a discharge guide roller pair for the recording medium 9.

Next, the positional relationship between the four rollers of the fixing roller 1, the pressing roller 2, the heat roller 3, and the heat conducting roller 6 and the method of supporting, pressing and rotating will be described.

These rollers 1, 2, 3, and 6 are all rotatably supported, and the pressure roller 2, the heat roller 3, and the heat conduction roller 6 are pressed against the outer peripheral surface of the fixing roller 1. , And are arranged to be rotated by the frictional force at the pressure contact portion.

An example of the positional relationship between these four rollers 1, 2, 3, and 6 will be described with reference to FIG.

Here, the fixing roller 1, the pressure roller 2,
The rotation centers of the heat roller 3 and the heat conduction roller 6 are denoted by C (F), C (P), C (H), and C (L), respectively. Furthermore, three angles around C (F), ΔC (H) −
C (F) -C (P), ΔC (L) -C (F) -C
(P) and ΔC (H) −C (F) −C (L) are denoted as θ (1), θ (2), and θ (3), respectively.

The positional relationship is θ (1) ≦ θ (2) and θ
(3) ≦ 120 deg.

Further, referring to FIGS. 1 and 2,
The configuration for supporting and pressing the four rollers 1, 2, 3, and 6 will be described.

In the first configuration example, the support positions of the heat roller 3 and the heat conduction roller 6 are fixed to the entire frame (not shown) of the fixing device, respectively.
The fixing roller 1 is disposed between the pressure roller 2 and the pressure roller 2. The contact positions of the fixing roller 1 and the heat roller 3 or the heat conduction roller 6 are denoted by N1 and N2, respectively. The pressure roller 2 is urged in a direction connecting the center position N3 between N1 and N2 and the rotation center C (F) of the fixing roller 1. In this configuration, the fixing roller 1
Has its outer peripheral surface held in contact with the other three rollers 2, 3, 6.

In the second configuration example, the fixing roller 1 is rotatably supported at a position fixed to the entire frame of the fixing device, and the other three rollers 2, 3, and 6 are rotated by the rotation of the fixing roller 1, respectively. Bias toward center C (F).

The pressure contact between the fixing roller 1 and the pressure roller 2 is
By a mechanism not shown, preferably from 100 kg to 2 kg
Applying a load of 50 kg, the width (nip width) of the pressed part is 5
mm to 15 mm. In addition, the second
In the case of the configuration example, further, a mechanism (not shown) is added for the press-contact between the fixing roller 1 and the heat roller 3 or the press-contact between the fixing roller 1 and the heat conductive roller 6.
Preferably, a load of 80 kg to 150 kg is applied so that the width of the press contact portion is 4 mm to 8 mm.

In the above configuration, it can be said that it is preferable in terms of the design of the drive mechanism to rotate these rollers to rotate the rollers supported at the fixed position (the drive mechanism is not shown). That is, in the first configuration example, one of the heat roller 3 and the heat conduction roller 6 may be rotationally driven. When it is required to keep the peripheral speed of the fixing roller 1 constant, it is preferable to rotationally drive a roller disposed downstream of the fixing roller 1 in the rotation direction. In the embodiment shown in FIG. 1, the heat conduction roller 6 is disposed on the downstream side, and since the component configuration is simple, the component processing of the connection portion with the drive mechanism becomes easy, so that the heat conduction roller 6 is heated. The roller 6 is driven to rotate. In the second configuration example, the fixing roller 1 is driven to rotate.

According to the fixing device of the present embodiment configured as described above, the heat conductive roller 6 having a higher thermal conductivity than the fixing roller 1 and the heat roller 3 is connected to the fixing roller 1.
Is arranged so as to be always in contact with the surface of the fixing roller 1, heat of the high-temperature non-sheet passing area of the fixing roller 1 moves to the low-temperature sheet passing area of the fixing roller 1 via the heat transfer roller 6.
The temperature of the non-sheet passing area of the fixing roller 1 is prevented from abnormally rising.

(Second Embodiment) FIG. 3 is a schematic sectional view of a main part of a fixing device according to a second embodiment of the present invention. In FIG. 3, components and arrows indicated by the same reference numerals as those in FIG. 1 are the same as those in the first embodiment. Also,
For simplicity, some components in FIG. 1 are not shown.

The heat transfer roller 17 of this embodiment is of a heat pipe type in which a heat medium 18 is sealed in a metal cylinder. The material of the cylinder is stainless steel,
Aluminum, iron, or the like, and if necessary, an outer surface or an inner surface is subjected to a coating treatment for the purpose of corrosion resistance, hardening or high releasability, and an inner surface is roughened.
As the heat medium 18, a substance having a large specific heat, such as glycerin, water, or wax, is used to increase the heat capacity. In the present embodiment, a stainless steel cylinder having an outer diameter of 30 mm and a thickness of 3 mm in which a glycerin solution is sealed is used.

The heat transfer roller 17 of the present embodiment includes a heat transfer medium 18 in addition to the heat transfer of stainless steel as a cylinder material.
The heat transfer is performed by the heat convection of the glycerin solution enclosed as a mixture and the agitation generated during rotation, and the temperature distribution of the entire roller is smoothed. Further, since the heat transfer roller 17 of the present embodiment has a larger heat capacity than the heat transfer roller 6 of the first embodiment, the function of smoothing the surface temperature distribution of the fixing roller 1 is maintained for a longer time.

The positional relationship among the fixing roller 1, the pressure roller 2, the heat roller 3, and the heat transfer roller 17 and the method of supporting, pressing, and rotating are substantially the same as those described in the first embodiment. . The difference from the first embodiment is that the pressure roller 2, the heat conduction roller 17, and the heat roller 3 are arranged so as to sequentially contact each other along the rotation direction of the fixing roller 1. Arranging in this order works as follows.

When a recording medium having a small width L (S) is nipped and conveyed by the pressure contact portion between the fixing roller 1 and the pressure roller 2, the temperature of the paper passing area and the non-paper passing area on the surface of the fixing roller 1 is increased. The difference is greatest at the outlet of the crimp and then decreases over time.

On the other hand, regardless of the temperature difference, the heat roller 3 supplies heat to the fixing roller 1 substantially uniformly in the rotation direction. However, in accordance with the thermodynamic principle that the larger the temperature difference between the two positions, the larger the temperature difference between the two positions, the larger the temperature difference between the two positions, the more the heat transfer amount at the contact portion between the fixing roller 1 and the heat roller 3. Then, the amount of heat transfer to the sheet passing area becomes larger than the amount of heat transfer to the non-sheet passing area. As a result, after heating at the contact portion between the fixing roller 1 and the heat roller 3, the temperature difference on the surface of the fixing roller 1 becomes small.

Further, according to the same thermodynamic principle as above, the effect of smoothing the temperature difference of the fixing roller 1 by the heat transfer roller 17 is higher as the temperature difference is larger.

Therefore, as in the present embodiment, the heat conduction roller 17 is moved upstream of the heat roller 3 along the rotation direction of the fixing roller 1, that is, between the paper passing area and the non-paper passing area of the fixing roller 1. When the temperature difference is large, the order of contact with the fixing roller 1 increases the efficiency of the action of smoothing the temperature difference of the fixing roller 1 by the heat transfer roller 17.

(Third Embodiment) FIG. 4 is a schematic sectional view of a main part of a fixing device according to a third embodiment of the present invention. In FIG. 4, components and arrows indicated by the same reference numerals as those in FIG. 1 are the same as those in the first embodiment.
In addition, for simplification, some components in FIG. 1 are not shown.

The heat conduction roller 19 is made of aluminum, iron,
It is a metal cylinder such as stainless steel. If necessary, the surface is subjected to a coating treatment for the purpose of corrosion resistance, hardening or high mold release. In this embodiment,
It has a configuration in which the surface of an aluminum cylinder having a thickness of 8 mm is treated with oxidized alumite, and a roller having an outer diameter of 30 mm is used.

The heat transfer roller 19 of the present embodiment uses a hollow cylinder, and a second heater 20 is provided in the hollow portion.
Is arranged. The heat conduction roller 19 is a metal thick cylinder having a high thermal conductivity, and has a function of smoothing the surface temperature distribution of the fixing roller 1 similarly to the heat conduction roller 6 of the first embodiment. In the present embodiment, furthermore, power is supplied from the second power supply 21 to the built-in second heater 20 to perform the function of heating the fixing roller 1 as a second heat roller. As a result, the area of the heat source in contact with the outer peripheral surface of the fixing roller 1 is increased, so that the efficiency of heat supply to the fixing roller 1 is further improved.

The second heater 20, the second power supply 21, and the second cutoff sensor 22 use parts or elements having the same functions as those of the heater 4, the power supply 5, and the cutoff sensor 15 of the first embodiment. And make the same arrangement.

The positional relationship among the fixing roller 1, the pressure roller 2, the heat conduction roller 19, and the heat roller 3 and the method of supporting, pressing, and rotating are substantially the same as those described in the first embodiment. . The contact order of the other three rollers 2, 19, 3 which contact the outer peripheral surface of the fixing roller 1 is the second order.
This is the same as the embodiment.

The temperature sensor 14 is a temperature detecting means for detecting the surface temperature of the fixing roller 1. The detection signal is transmitted to the logic control circuit 1 as a heater operation control means.
6 is input. The logic control circuit 16 compares the input detection signal with a reference signal corresponding to a predetermined target temperature, and outputs a signal for individually controlling operating conditions of the power supply 5 and the second power supply 21 based on the comparison result. It is supposed to. In this way, the power supplied from the power supply 5 and the second power supply 21 to the heater 4 and the second heater 20 is feedback-controlled, and the surface temperature of the fixing roller 1 is controlled to a predetermined temperature.

By the way, when the surface temperature of the fixing roller 1 is unevenly distributed, a comparison is made between the amount of heat supplied to the region having a lower surface temperature and the amount of heat supplied to the region having a relatively high surface temperature. Since the lower the temperature of the heat source for further heating the fixing roller 1 becomes, the distribution of the surface temperature of the fixing roller 1 is easily smoothed. Therefore, in order to increase the efficiency of the function of smoothing the surface temperature distribution of the fixing roller 1 by the heat conductive roller 19, a heat conductive roller disposed upstream of the heat roller 3 along the rotation direction of the fixing roller 1. It is preferable that the surface temperature of the heat roller 19 is equal to or lower than the surface temperature of the heat roller 3 (same or lower).

Therefore, the second power source 21 supplies the second heater 20
The power supplied to the heater 4 is designed to be equal to or less than the power supplied from the power supply 5 to the heater 4. For example, when the same voltage is applied to the two heaters 20 and 4, the heaters are selected such that the rated power consumption of the second heater 20 is equal to or less than the rated power consumption of the heater 4. Alternatively, when the second heater 20 and the heater 4 have the same rated power consumption, the second power output from the logic control circuit 16 is set so that the ON time of the second power supply 21 is shorter than the ON time of the power supply 5.
Control signals for operating conditions of the power supply 21 and the power supply 5 are programmed.

According to the present embodiment, by disposing the second heater 20 inside the heat conductive roller 19, the heat conductive roller 19 can not only function to smooth the surface temperature distribution of the fixing roller 1, but also It also serves to heat 1.

In particular, according to the present embodiment, the heat conduction roller 19 is disposed upstream of the heat roller 3 in the rotation direction of the fixing roller 1 and one heat sensor 14 is provided.
By controlling the two heaters 20 and 4 so that the surface temperature of the heat transfer roller 19 is equal to or lower than the surface temperature of the heat roller 3, the heat transfer roller 19 smoothes the surface temperature distribution of the fixing roller 1. Increase efficiency.

In this embodiment, the heat conductive roller 19 is disposed upstream of the heat roller 3 along the rotation direction of the fixing roller 1, and the temperature of the heat conductive roller 19 is lower than the temperature of the heat roller 3. However, the present invention is not limited to this. The heat roller 3 is disposed upstream of the heat transfer roller 19, and the temperature of the heat roller 3 is controlled by the heat transfer roller 1.
The temperature may be controlled so as to be equal to or lower than the temperature of No. 9.

(Fourth Embodiment) FIG. 5 is a schematic view of a cross section of a main part of a fixing device according to a fourth embodiment of the present invention. In FIG. 5, components and arrows indicated by the same reference numerals as those in FIG. 1 are the same as those in the first embodiment. Also,
For simplicity, some components in FIG. 1 are not shown.

Instead of the temperature sensor 14 used in the first and third embodiments, for example, the second temperature sensor 23 is used as the second temperature detecting means, and the third temperature detecting means is used, for example, the third temperature detecting means. Temperature sensors 24 are provided so as to contact the outer peripheral surfaces of the heat roller 3 and the heat conduction roller 19, respectively, so as to detect the surface temperatures of the heat roller 3 and the heat conduction roller 19 that contact.

The control of the surface temperature of these rollers 3 and 19 is exactly the same as in the third embodiment, and is individually controlled by feedback. That is, the second temperature sensor 23
And the detection signal of the third temperature sensor 24 is input to, for example, the logic control circuit 16 as a heater operation control means, and based on the processing result of the detection signal in the logic control circuit 16, the heaters 4 and 21 are supplied from the power sources 5 and 21, respectively. The power supplied to the second heater 20 is individually feedback-controlled, and the surface temperature of the heat roller 3 and the surface temperature of the heat conduction roller 19 are controlled so as to become the predetermined second predetermined temperature and the third predetermined target temperature, respectively. It has become so.

At this time, similarly to the third embodiment, in order to increase the efficiency of the function of smoothing the surface temperature distribution of the fixing roller 1 by the heat conduction roller 19, heat is applied along the rotation direction of the fixing roller 1. It is desirable that the surface temperature of the heat conduction roller 19 disposed upstream of the roller 3 be equal to or lower than the surface temperature of the heat roller 3. In the present embodiment, since the surface temperatures of the heat roller 3 and the heat transfer roller 19 are individually controlled by the two temperature heaters 4 and 20, this can be achieved more easily.

That is, the design is made so that the third predetermined temperature is equal to or lower than the second predetermined temperature. For this purpose, for example, the circuit design or the program of the logic control circuit 16 may be changed.

When the third target temperature on the heat conduction roller 19 side is designed to be lower than the second target temperature on the heat roller 3 side, the bearing of the heat conduction roller 19 is accordingly adjusted. It is possible to lower the heat-resistant guaranteed temperature of the material of the component and other components arranged in the vicinity.
As a result, a more general spread material can be adopted, and the cost of parts is reduced. In addition, the heat conduction roller 19
The rated operating temperature of the second cutoff sensor 22 on the side of the heat roller 3 may be lower than the rated operating temperature of the cutoff sensor 15 on the side of the heat roller 3. Thus, if an accident occurs in which the control of the second heater 20 goes out of control due to some abnormality and the temperature of the second heater 20 becomes high, the second power supply 21 is switched to a safer stage.
, The power supply to the second heater 20 can be cut off.

In particular, according to the fixing device of this embodiment, the two heaters 4 and 20 are individually controlled based on the detection signals of the two temperature sensors 23 and 24. The surface temperature is controlled precisely. Heat roller 3 and heat conduction roller 19
It is easy to increase the efficiency of smoothing the surface temperature distribution of the fixing roller 1 by the heat conduction roller 19 by individually setting the respective predetermined temperatures.

In this embodiment, the fixing roller 1
Heat transfer roller 19 along the rotation direction of heat roller 3
And the temperature of the heat transfer roller 19 is controlled to be equal to or lower than the temperature of the heat roller 3. However, the present invention is not limited to this, and the heat roller 3 is provided upstream of the heat transfer roller 19. Alternatively, the temperature of the heat roller 3 may be controlled to be equal to or lower than the temperature of the heat transfer roller 19.

The present invention is not limited to the above-described embodiment, and various modifications can be made.

For example, in the above-described embodiment, a roller using a roller as a rotating member such as a heat-conducting rotating member, a fixing rotating member, a pressing rotating member, and a heating rotating member has been described. A belt or the like may be used.

[0079]

As described above, the first embodiment according to the present application is described.
According to the invention, the heat conductive rotator having heat conductivity larger than that of the fixing rotator is disposed in pressure contact with the outer peripheral surface of the fixing rotator. Since the heat moves to the low-temperature paper passing area via the heat-conducting rotating body, the uneven distribution of the surface temperature of the fixing rotating body can be smoothed, and the excessive temperature rise in the non-paper passing area can be efficiently reduced. .

According to the second aspect of the present invention,
Since the heat conduction rotator of the first invention comprises a metal cylinder and a liquid heat medium sealed in the cylinder, heat transfer is performed by heat convection of the heat medium and agitation generated during rotation. In addition, the temperature distribution of the entire fixing rotating body can be further smoothed. Further, since the heat conduction rotator has a heat medium having a large heat capacity, the function of smoothing the surface temperature distribution of the fixing rotator can be maintained for a longer time.

According to the third aspect of the present invention,
In the first invention or the second invention, the pressurizing rotator, the heat-conducting rotator, and the heat rotator are sequentially arranged along the rotation direction of the fixing rotator, so that the paper passing area of the fixing rotator can be reduced. Since the heat-conduction rotator is brought into contact with the fixing rotator at a stage where the temperature difference from the non-sheet passing area is large, the efficiency of the heat-conduction rotator to smooth the temperature difference of the fixing rotator can be increased.

According to the fourth aspect of the present invention,
Since the heater is built in one of the heat conducting rotators of the first invention to the third invention, heat is supplied to the fixing rotator as compared with the case where the fixing rotator is heated only by the heat rotator. Efficiency can be improved.

According to the fifth invention of the present application,
In the fourth invention, the surface temperature of the fixing rotator is detected by the temperature detecting means, and the fixing rotator is selected from the heat rotator and the heat conduction rotator along the rotation direction of the fixing rotator according to the detection signal. The heater and heat of the heat rotator so that the heat value of the heater built in the rotator closer to the pressure contact portion of the pressure rotator is equal to or smaller than the heat value of the heater built in the distant rotor. By controlling the operation of the heater of the conduction rotating body, the temperature of the outer peripheral surface of the fixing rotating body is controlled to be a predetermined temperature.

Therefore, the efficiency of smoothing the surface temperature distribution of the fixing rotating body by the heat conducting rotating body can be improved.

According to the sixth aspect of the present invention,
In the fourth invention, the temperature of the heat rotator and the temperature of the heat transfer rotator are detected by the second temperature detector and the third temperature detector, and the temperature of the fixing rotator is determined along the rotation direction of the fixing rotator. Control is performed such that the predetermined temperature of the rotating body closer to the pressure contact portion with the pressurizing rotating body is equal to or lower than the predetermined temperature of the farther rotating body.

Therefore, it is possible to easily control the surface temperature of the heat rotator and the surface temperature of the heat conduction rotator with high accuracy, and to increase the efficiency of smoothing the surface temperature distribution of the fixing rotator by the heat conduction rotator.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a fixing device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a positional relationship of rollers of the fixing device of FIG.

FIG. 3 is a schematic cross-sectional view of a main part of a fixing device according to a second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a main part of a fixing device according to a third embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a main part of a fixing device according to a fourth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 fixing roller (fixing rotating body) 2 pressure roller (pressing rotating body) 3 heat roller (heat rotating body) 4 heater 5 power supply 6, 17, 19 heat conduction roller (heat conduction rotating body) 14 temperature sensor (temperature detection) Means) 15 Cutoff sensor 16 Logic control circuit (heater operation control means) 18 Heat medium 20 Second heater 21 Second power supply 22 Second cutoff sensor 23 Second temperature sensor (Second temperature detection means) 24 Third temperature sensor (third temperature detecting means)

Claims (6)

[Claims] An image forming apparatus comprising: a fixing rotator; and a non-fixed toner image held on the recording medium, the recording medium being nipped and conveyed by the pressure contact portion. A pressurizing rotator disposed in contact with the outer peripheral surface, and a heat rotator provided with a heater built therein in pressure contact with the outer peripheral surface of the fixing rotator to heat and press toner on the recording medium. A fixing device which is provided in pressure contact with the outer peripheral surface of the fixing rotator and has a heat conductivity higher than that of the fixing rotator. 2. A heat conduction rotating body comprising: a metal cylinder;
The fixing device according to claim 1, further comprising a liquid heat medium sealed in a cylinder. 3. The fixing device according to claim 1, wherein the pressure rotator, the heat conduction rotator, and the heat rotator are sequentially arranged along the rotation direction of the fixing rotator. apparatus. 4. The fixing device according to claim 1, wherein a heater is built in the heat conduction rotating body. 5. A temperature detecting means for detecting a temperature of an outer peripheral surface of a fixing rotator, and a heat rotator and a heat conduction rotator along a rotation direction of the fixing rotator according to a detection signal of the temperature detecting means. The heating rotator so that the heating value of the heater incorporated in the rotator closer to the pressure contact portion between the fixing rotator and the pressing rotator is equal to or smaller than the heating value of the heater incorporated in the distant rotator. 5. A fixing device according to claim 4, further comprising a heat operation control means for controlling the operation of the heater and the heater of the heat conduction rotary member so as to control the outer peripheral surface temperature of the fixing rotary member to a predetermined temperature. apparatus. 6. A second temperature detecting means for detecting an outer peripheral surface temperature of the heat rotating body, a third temperature detecting means for detecting an outer peripheral surface temperature of the heat conducting rotating body, and a detection of the second temperature detecting means. The operation of the heater incorporated in the heat rotator is controlled so that the outer peripheral surface temperature of the heat rotator becomes the second predetermined temperature according to the signal, and the heat conduction is performed according to the detection signal of the third temperature detecting means. The operation of the heater incorporated in the heat-conducting rotator is controlled so that the outer peripheral surface temperature of the rotator becomes the third predetermined temperature, and the rotation direction of the fixing rotator is determined between the second predetermined temperature and the third predetermined temperature. Heat operation control means for controlling the predetermined temperature of the rotating body closer to the pressure contact portion between the fixing rotator and the pressing rotator to be equal to or lower than the predetermined temperature of the distant rotating body along The fixing device according to claim 4, wherein: