JPH08248815A - Fixing device - Google Patents

Abstract

PURPOSE: To reduce power consumption between pages space without lowering a recording processing speed by stopping the rotation of a heating roll in a paper non-passing state between the pages and keeping the heating roll at a temp. capable of reaching a fixed required temp. during a time from the start of the rotation to the reaching of the leading edge of a recording paper. CONSTITUTION: A stopping means 31 stops the rotation of the heating roll when a page memory for output 29 is not filled with data for a page (the paper nonpassing state between the pages). A starting means 33 starts to carry the recording paper and rotate the heating roll when the data for a page is stored in the page memory for the output 29. A temperature setting means 35 in the case of stopping the rotation of the heating roll sets the temp. of the heating roll 17 so that it reaches a fixable temp. during a period of time from the start of the carrying of the recording paper to the arrival of the leading edge to a fixing device 15. A control means 37 controls the temp. of the heating roll during stop to be the fixable temp.

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 fixing a toner image on a recording sheet by heat in an image forming apparatus such as a copying machine, and more particularly to a temperature maintaining power between pages without slowing machine processing speed. It relates to a fixing device capable of achieving a reduction.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a non-fixed surface on the recording paper is fixed by a pressure roll provided in pressure contact with a heat roll heated by a heating means. A fixing device that heats and fixes a toner image on a recording sheet is known. In low-end laser printers and plain paper laser facsimiles, this fixing device occupies 90% or more of the power consumption of the entire device, and is therefore a target for energy saving from the standpoint of environmental protection. Here, what is particularly emphasized is the power consumption during operation standby. In electrophotographic equipment,
For the purpose of being able to immediately raise the temperature of the fixing portion to a fixable value, an operation has been performed in which the temperature of the fixing portion is maintained at or near the fixing temperature even during operation standby. In these devices, the ratio of the standby time to the total operating time is 95% or more on average, and therefore, companies are studying to eliminate the temperature maintenance during the standby.

In these devices, a data communication time is required for data transfer, and the required communication time between pages is longer than the paper passing recording time even in the actual operation time, and the temperature maintenance power in that case is required. It has a large share. Therefore,
Even in this case, it is desirable from the standpoint of environmental protection to abolish temperature maintenance as in the case of standby. When the temperature of the fixing roll is not maintained during the above standby time or required time between pages,
There is a problem that a warm-up time is required after the preparation for passing recording is completed, and the processing speed of the machine is reduced to hinder the user's productivity.

Further, as a conventional technique, Japanese Patent Laid-Open No. 64-4
Japanese Patent Application Laid-Open No. 4-6412 discloses a technique for setting the heat capacity of a fixing roll so that the fixing roll can reach a fixable temperature in the time from the start of recording paper conveyance to the arrival of the leading end of the fixing unit in Japanese Patent Publication No. 78412. In the publication, there is a technique for switching the heater power control method by a predetermined calculation formula according to the rising time, and in JP-A-1-161511, the heater warm-up time is calculated from the temperature rising speed between the first and second set temperatures. However, none of the conventional examples is sufficient for solving the above problems.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to achieve reduction in temperature maintenance power between pages without reducing machine processing speed. It is to provide a fixing device that can perform.

[0006]

In order to achieve the above object, the invention according to claim 1 is to perform the above recording by passing a recording paper having a toner image in an image forming apparatus between a heated heat roll and a pressure roll. In a fixing device that fixes a toner image on paper, if the output page memory is not full of data for one page, a means for stopping the heat roll rotation and one page of data is stored in the output page memory. At the same time, the means for starting the conveyance of the recording paper and the rotation of the heat roll, and the rotation of the heat roll for enabling the heat roll to reach the fixable temperature in the time from the start of the conveyance of the recording paper to the arrival of the leading edge of the fixing device It is characterized in that it is provided with a temperature setting means at the time of stop and a means for controlling the fixing roll temperature while the rotation of the heat roll is stopped at the set temperature. According to a second aspect of the present invention, the fixing device according to the first aspect further includes means for changing a set value for heating power control according to whether or not the heat roll is rotated. . According to a third aspect of the present invention, in the fixing device according to the first aspect, the temperature is higher than at least the first predetermined temperature only when the temperature at the start of warm-up is equal to or lower than the first predetermined temperature. It is characterized by further comprising means for changing an appropriate constant value of the heating power control from the measured value of the time required to reach the third predetermined temperature which is higher than the second predetermined temperature.

[0007]

According to the above construction, since the heat roll is not rotating in the paper-free state between pages, heat diffusion via the pressure roll is reduced, and the temperature maintenance power can be reduced. Furthermore, since the set temperature of the heat roll is maintained at a temperature that can reach the required fixing temperature between the start of rotation and the arrival of the leading edge of the recording paper at the fixing device, the power consumption between pages can be reduced without impairing the recording processing speed. Is. Further, it is possible to switch the power supply to the heat roll depending on whether the heat roll is rotated or not, and it is possible to prevent the temperature ripple of the heat roll by suppressing the control delay.
Further, since the control of the heating control power can be corrected from the temperature rising rate during warm-up, it is possible to cancel the variations in the power supply voltage and the heater power. Further, by performing the correction only when the initial temperature is lower than the predetermined value, it is possible to exclude the correction operation when there is a change in the temperature rising rate due to the residual heat of the previous printing operation. It can be prevented.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a recording paper path from a paper feed unit including a fixing device embodying the present invention to a paper discharge unit. In FIG. 1, the recording paper 5 sent out from the recording paper feeding section 1 by the pickup roller 3 is a registration sensor 7
Further, after the toner image is transferred from the photoconductor 13 at the transfer portion 11 via the resist roller 9, the fixing heat roller 17 and the pressure roller 19 constituting the fixing device 15 heat the nipping pressure at the same time. The sheet is conveyed at a linear velocity of 60 mm / SEC until it is ejected.

FIG. 2 is a diagram showing the structure of the fixing device 15, and the heat roll 17 has a halogen lamp heater 21 built therein as a heating means. The heat roll 17 is mainly made of a metal material such as aluminum, iron or SUS, and the surface of the pressure roll 19 is covered with a silicone rubber 23. In the embodiment, the heat roll 17 is 20φ × 0.7t × 270L, and the pressure roll 19 is 10φ core 25 and 6t silicon rubber 23 (JIS.
A hardness 16) is coated. Pressurization on one side 2.
The lamp is rated at 7 with a power of 0 kgf.
I am using the one of 00W. Further, a thermistor 27 as a heat roll temperature detecting element is attached to a part of the heat roll 17.

In this embodiment, the power supply to the heat roll 17 is limited when the recording operation is necessary. When the recording operation is required, the laser writing polygon motor is started and the power supply to the heater 21 is started. Done.
The triggering conditions include the input of ringing detect or copy start signal or print data at the time of facsimile reception.

FIG. 3 shows the state of the warm-up and the printing operation immediately after that, together with the heat roll temperature and the thermistor output temperature. When the heat roll temperature reaches the set value, the paper is passed. As described above, the recording operation is started in advance (this refers to the pickup operation of the paper feeding unit 1, but in this example, the activation of the main motor that drives the photoconductor 13 and the fixing device 15) at a predetermined heat roll temperature lower than the set value. It is set to be allowed.

That is, the time (time B in FIG. 3) from the start of the recording operation until the leading edge of the recording paper reaches the fixing device 15 from the paper feeding section 1 is determined by the recording paper path and the conveying speed as shown in FIG. Which is about 4.5 seconds in this example. During this period, the rate of temperature rise of the heat roll 17 is substantially constant, and therefore the minimum temperature at which the start of the recording operation can be permitted with respect to the fixing set temperature is substantially uniform. Here, there is a difference between the actual heat roll temperature and the temperature detected by the thermistor 27 except at the warm-up start time point C because of the thermistor heat capacity and the thermistor response delay determined by the heat roll 17 and the thermal resistance to the outside. is there. This detection error is remarkable when the temperature change is abrupt such as warm-up, but is small when the temperature change is slow such as during standby or during fixing.

In this embodiment, means for predicting the time required for the heat roll temperature to reach the predetermined temperature from the warm-up start temperature (time A in FIG. 3) is provided.
Moreover, it has means for measuring the elapsed time after warm-up, and the recording operation start permission is transmitted at an appropriate time. As the means for measuring the time, for example, a software timer or a hardware timer provided in the device controller can be used. As a means for predicting the time required for the fixing heat roll 17 to reach the proper temperature for starting the recording operation, the warm-up required time corresponding to the thermistor detection temperature at the start of the warm-up is set, so that the recording operation can be performed very accurately. It is possible to predict when the fixing heat roll 17 reaches the appropriate starting temperature.

Here, in the output of a laser printer, a facsimile, etc., the recording output interval between pages is relatively long, and it is desirable to reduce the temperature maintenance power during this period. On the other hand, it is preferable from the viewpoint of speed that the recording operation is executed promptly after the page output data is completed.

Therefore, in the first embodiment, as shown in FIG.
As shown in, when the output page memory 29 is not full of data for one page (no paper passing between pages), the stop means 31 for stopping the rotation of the heat roll and the output page memory 29 are stored. The heat roller 17 can be fixed in the time from the start of recording paper conveyance to the end of the fixing device 15 when the recording paper conveyance and the heat roll rotation are started at the same time when one page of data is accumulated. By having the temperature setting means 35 at the time of stopping the heat roll rotation capable of reaching the temperature and the control means 37 for controlling the temperature of the heat roll at the time of stopping the heat roll rotation, the recording output speed is not impaired. Power consumption between pages is reduced as much as possible. The heat roll rotation stop means 31, the heat roll rotation start means 33, the heat roll stop temperature setting means 35, and the temperature control means 37.
Is actually achieved by the CPU, RAM, ROM, etc. provided in the image forming apparatus having the fixing device 15.

The operation mechanism of the first embodiment will be described below with reference to FIGS. 5 and 6. When the heat roll 17 is rotating, heat is transferred from the heat roll 17 to the entire circumference of the rotating pressure roll 19 as shown in FIG.
The heat transfer to the core 5 is similarly performed from the entire circumference of the pressure roll to the core 25. On the other hand, while the rotation of the heat roll 17 is stopped, heat is transferred from the heat roll 17 only to the nip portion D of the pressure roll 19 as shown in FIG. Heat transfer to the core rod 25 is also performed from the nip portion D to the core rod 25. Comparing the two, the latter has a smaller thermal resistance, so that the latter requires much smaller electric power to maintain the temperature of the heat roll 17.

Further, since the maintenance set temperature is set to a temperature that can be raised from the start of the recording operation to the arrival of the recording paper at the fixing device 15, the power consumption can be reduced as compared with the maintenance power at the fixing temperature. is there. This is (temperature maintenance power) = (heat resistance between heat roll and outside)
This is due to the relationship of x (the temperature difference between the heat roll and the outside).

In the first embodiment, since the rotation of the heat roll 17 is stopped in the paper non-passage state between pages, the inter-page maintaining temperature of 150 ° C. can be set against the fixing temperature of 180 ° C. In addition, the temperature maintenance power is 20
% Could be reduced. That is, since the heat roll 17 does not rotate in the non-sheet passing state between pages, the heat diffusion via the pressure roll 19 is reduced and the temperature maintenance power can be reduced. Further, in order to maintain the set temperature of the heat roll 17 at a temperature at which the required fixing temperature can be reached from the start of rotation to the arrival of the leading edge of the recording paper at the fixing device 15, the interpage power consumption is reduced without impairing the recording processing speed. It can be reduced.

Next, a second embodiment of the fixing device according to the present invention will be described. FIG. 7 shows the state of the heat roll temperature when the rotation of the heat roll is stopped between pages together with the line showing the presence or absence of the heat roll rotation. As shown in FIG. 7, normally, in order to reduce the temperature variation above and below the set temperature, the ON power and the OFF power in the ON / OFF control are not the maximum and zero which are the usual values, but the temperature changes gradually. 400W each
And about 50 W, and power is supplied by each phase control. That is, when the thermistor detected temperature is higher than the set temperature (ON), 400 W, and when it is lower than the set temperature (OFF), the power supply is set to 50 W, respectively, and the temperature fluctuation is slowed to slow the temperature control response delay. The ripple width due to is reduced. However, the maximum rated power is supplied to the heater during the warm-up at the start of the recording operation and the warm-up time B of about 4.5 seconds until the fixing set temperature after the inter-page as shown in FIG.

Further, in FIG. 7, overshoot between pages and undershoot during rotation of the heat roll are large, and the ripple width is not sufficiently small. This is because the supply power setting value during ON / OFF is set to the optimum value during heat roll rotation when the heater is ON, and to the optimum value between pages when the heater is OFF. Here, if the power supply at the time of OFF is set in accordance with the optimum value during the rotation of the heat roll, the temperature always rises while the heat roll is stopped between pages. Further, if the power supply at the time of ON is set in accordance with the optimum value while the heat roll is stopped, there is a problem that the temperature always drops during the rotation of the heat roll. In either case, it will be out of control. In addition to the control as described above, PID control that determines the supply power by a table or a calculation formula from the difference value between the set temperature and the detected temperature and the differential value and the rate of change of the detected temperature may be performed. Since the optimum value or coefficient of the table or the calculation formula differs depending on whether or not the roll is rotated, the same problem as described above occurs.

Therefore, in the second embodiment, as shown in FIG.
In order to solve the above problems and sufficiently reduce the temperature ripple width, the temperature setting means 39 is provided with means 43 for changing the set value for heating power control according to the presence / absence of rotation of the fixing roll. It is provided. In the second embodiment,
400 W when ON and 150 when OFF while the heat roll is rotating
W, 180 W when ON and 5 when OFF when heat roll is stopped
In order to set the supply power of 0 W, the optimum power supply control is performed in each state, and as shown in FIG. 9, the temperature ripple as shown in FIG. 7 can be reduced.

When the second embodiment is combined with the first embodiment, the effect of reducing the power as shown in FIG. 10 is produced. Note that these effects are the same in general PID control, and in that case, the power control set value is changed by switching each constant of PID or changing the reference table. Thus, according to this second embodiment,
The heat roll 17 depends on whether the heat roll 17 is rotated or not.
It is possible to switch the power supply to the heat roll 17 and suppress the delay of the control, so that the temperature ripple of the heat roll 17 can be prevented.

Next, a third embodiment of the fixing device according to the present invention will be described. First, the inter-page set temperature in the first embodiment is affected by the maximum power supply to the heater 21 because it depends on the time required to raise the temperature to the fixable temperature within a fixed time. In addition, the control power in the second embodiment is set based on the maximum power supply to the heater 21 unless a power supply monitor that is practically difficult to mount because it is expensive is used. Here, the maximum electric power supplied to the heater 21 greatly changes due to fluctuations in the power supply voltage and variations in the heater resistance, so some correction is actually required.

Therefore, in the third embodiment, in order to solve the above problem, as shown in FIG. 11, the temperature setting means 45 is used.
In addition, only when the detected heat roll temperature value at the start of warm-up is equal to or lower than the first predetermined temperature, at least the second predetermined temperature higher than the first predetermined temperature to the third predetermined temperature higher than the second predetermined temperature. Means 47 is provided for performing correction by changing the appropriate constant value of the heating power control from the measured value of the time required to reach the temperature.

In the third embodiment, the maximum supply power is supplied to the heater 21 in order to reduce the required time as much as possible during warm-up. Factors of this heating rate are
In addition to the supplied power, the heat capacity of the heater 21 and the thermal resistance to the outside exist. The heat capacity of the heater is stable with almost no change over time, and the accuracy is equivalent to the processing accuracy, so the variation can be ignored. Most of the heat resistance to the outside goes through the pressure roll 19, but since the rotation is stopped during warm-up, the contribution of this heat resistance to the heat roll temperature rising rate is extremely small. For this reason, the maximum supply power fluctuation can be monitored at the rate of temperature rise during warm-up. The actually detected heat roll temperature is a measured value by the thermistor 27 and is different from the actual heat roll temperature as shown in FIG. 3, but relative correction can be made by appropriately selecting the temperature range.

In the third embodiment, the correction is performed based on the time required for the thermistor detection value to rise from 50 ° C. to 80 ° C., and only when the warm-up start temperature is 40 ° C. or less. There is. The value of the maximum supply power corresponding to the temperature rise time has the following relationship. 3 seconds 790W 3.5 seconds 680W 4 seconds 600W The maximum supply power was calculated by interpolating these results. From this result, the inter-page maintaining temperature in the first embodiment is calculated from the following correspondence. Maximum supply power Inter-page maintenance temperature 790W 145 ° C 680W 150 ° C 600W 154 ° C The power control in the second embodiment can be performed by correcting from the ratio of the maximum supply power value and the standard rating of 700W.

When the warm-up start temperature is around 50 ° C. due to the influence of the previous printing operation, the temperature detected by the thermistor immediately after the start of warm-up has a non-linear rise as shown in FIG. This is considered to be due to the delay due to the thermal response of the thermistor, but this is not preferable because the estimation error of the maximum power consumption becomes large. On the contrary,
In the third embodiment, the correction is performed only when the detected heat roll temperature value at the start of warm-up is equal to or lower than the first predetermined temperature. That is, in the third embodiment, this problem is solved by performing the correction only when the warm-up start temperature is 40 ° C. or lower.

According to the third embodiment, the control of the heating control power can be corrected from the rate of temperature rise during warm-up, so that variations in power supply voltage and heater power can be offset. Further, by performing the above correction only when the initial temperature is lower than the predetermined value, it is possible to exclude the correction operation when there is a change in the temperature rising rate due to the residual heat of the previous printing operation. Can be prevented.

[0029]

According to the present invention, since the heat roll is not rotating in the paper-free state between pages, the heat diffusion via the pressure roll is reduced and the temperature maintenance power can be reduced. Furthermore, since the set temperature of the heat roll is maintained at a temperature that can reach the required fixing temperature between the start of rotation and the arrival of the leading edge of the recording paper at the fixing device, the power consumption between pages can be reduced without impairing the recording processing speed. Is.

Further, the power supply to the heat roll can be switched depending on whether the heat roll is rotated or not, and the temperature ripple of the heat roll can be prevented by suppressing the control delay. Further, since the control of the heating control power can be corrected from the temperature rising rate during warm-up, it is possible to cancel the variations in the power supply voltage and the heater power. Further, by performing the correction only when the initial temperature is lower than the predetermined value, it is possible to exclude the correction operation when there is a change in the temperature rising rate due to the residual heat of the previous printing operation. It can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a recording paper path from a paper feed unit including a fixing device embodying the present invention to a paper discharge unit.

FIG. 2 is a schematic configuration diagram of the fixing device shown in FIG.

FIG. 3 is an explanatory diagram of heat roll temperature control in the first embodiment of the fixing device according to the present invention.

FIG. 4 is a functional configuration diagram of a control unit in the first embodiment of the fixing device according to the present invention.

FIG. 5 is an operation explanatory diagram of the fixing device according to the first embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of the fixing device according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of heat roll temperature control in the second embodiment of the fixing device according to the present invention.

FIG. 8 is a functional configuration diagram of a controller in a second embodiment of the fixing device according to the present invention.

FIG. 9 is an explanatory diagram of heat roll temperature control in the second embodiment of the fixing device according to the present invention.

FIG. 10 is an explanatory diagram of heat roll temperature control in the second embodiment of the fixing device according to the present invention.

FIG. 11 is a functional configuration diagram of a control unit in a third embodiment of the fixing device according to the present invention.

[Brief description of reference numerals]

1 ... Recording paper feeding section, 3 ... Pickup roller, 5 ... Recording paper,
7 ... Registration sensor, 9 ... Registration roller,
11 ... transfer part, 13 ... photoconductor,
15 ... Fixing device, 17 ... Heat roll, 19 ... Pressure roll, 21 ...
Heater, 23 ... Silicon rubber, 25 ... Core, 27 ...
Thermistor, 29 ... Output page memory,
31 ... Heat roll rotation stop means, 33 ... Heat roll rotation start means, 35 ... Heat roll stop temperature setting means, 37, 41 ... Temperature control means, 39, 45 ... Temperature setting means, 43 ... Set value changing means, 47 …
Constant value changing means,

Claims (3)

[Claims] 1. A fixing device for fixing a toner image on a recording paper having a toner image on the recording paper by passing the recording paper having the toner image between a heated heat roll and a pressure roll in the image forming apparatus. A means for stopping the rotation of the heat roll when the memory is not full of data for one page, and a means for starting the conveyance of the recording paper and the rotation of the heat roll at the same time when the data for one page is accumulated in the output page memory. And a means for setting the temperature when the heat roll is stopped so that the heat roll can reach the fixing possible temperature during the time from the start of the recording paper conveyance to the arrival of the leading edge of the fixing device, and the heat roll is heated to the set temperature. And a means for controlling the temperature of the fixing roll while the rotation of the roll is stopped. 2. The fixing device according to claim 1, wherein the fixing device further comprises means for changing a set value for heating power control according to the presence or absence of rotation of a heat roll. 3. The fixing device further increases the temperature from a second predetermined temperature higher than at least the first predetermined temperature to a higher temperature only when the temperature at the start of warm-up is equal to or lower than the first predetermined temperature. The fixing device according to claim 1, further comprising means for changing an appropriate constant value of heating power control from a measured value of a time required to reach a certain third predetermined temperature.