JP2744852B2 - Control device for heat fixing unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a heat fixing device for thermally fixing a transfer sheet on which a toner image has been transferred from a photosensitive member in, for example, an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, after uniformly charging the surface of a photoconductor made of a photoconductive material, the photoconductor is exposed to light such as a laser beam to record image information as an electrostatic latent image.
After the electrostatic latent image is developed with toner, the toner image is transferred to a transfer paper that is conveyed. Then, the transfer paper to which the toner image has been transferred is heated and fixed by, for example, a heat fixing device and discharged outside.

The heat fixing device used in such an apparatus comprises a heat roller containing a heater lamp and a backup roller provided in contact with the heat roller, and the transfer paper passes between the rollers to form the heat roller. The toner image transferred to the transfer paper is welded and heat-fixed.

In such a heat fixing device, when the power switch is turned off, and when the housing cover of the electrophotographic apparatus is opened, the power supply to the heater is stopped. The temperature of each roller decreases. Therefore, when the power is turned on such as when the power switch is turned on or when the cover is opened, the power supply to the heater is started with the temperature of each roller being low.

Since the heat roller includes a heater lamp, the entire surface of the roller is uniformly heated. However, the backup roller is heated by heat transfer from the heat roller. When the surface temperature of the heat roller reaches the toner welding temperature in this state and the warm-up period ends and the operation of the apparatus is started, the temperature of the heat roller and the backup roller is increased. Causes a large temperature difference, and as a result, a problem such as curling of the transfer paper during heating and fixing occurs.

In order to solve this problem, conventionally, for example, the heat roller and the backup roller are rotated for a predetermined time while the temperature of the heat roller is still low during the warm-up period, or the temperature of the heat roller is reduced during the warm-up period. It is known that a heat roller and a backup roller are rotated after reaching a toner softening temperature until reaching a toner fusing temperature.

[0007]

However, if the heat roller and the backup roller are rotated while the surface temperature of the heat roller is low, there is a problem that the roller is damaged by residual toner on the cleaning pad. When the heat roller and the backup roller are rotated until the temperature of the heat roller reaches the toner softening temperature and then reaches the toner fusing temperature, the temperature difference between the toner softening temperature and the toner fusing temperature is small. There is a problem that the heat of the heat roller cannot be sufficiently transmitted to the backup roller due to a short rotation time of the heat roller.

Accordingly, the present invention starts the rotation of the heat roller and the backup roller when the surface temperature of the heat roller reaches a temperature close to the toner fusing temperature, and thereafter passes an overshoot period in which the surface temperature of the heat roller exceeds the toner fusing temperature. By stopping the rotation of the heat roller and the backup roller when the surface temperature of the heat roller returns to the toner welding temperature, the heat of the heat roller during the overshoot period can be efficiently transmitted to the backup roller, and the temperature of the heat roller overshoots It is an object of the present invention to provide a control device for a heat fixing device that can reduce the size.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a heating and fixing device comprising a heat roller containing a heater and a backup roller which is in contact with the heat roller and is positioned so that a transfer sheet passes through the contact area. A temperature-sensing element for detecting the surface temperature of the roller; and energizing the heater in a state where the temperature detected by the temperature-sensing element falls below a first set temperature at which the toner is fused, and reaches the first set temperature. Then, heater control means for stopping energization of the heater,
If the surface temperature of the heat roller becomes equal to or higher than a second set temperature lower than the first set temperature when the power is turned on, the heat roller and the backup roller are driven to rotate, and the surface temperature of the heat roller reaches the first set temperature. After that, when the heater returns to the first set temperature by de-energization, the roller driving means for stopping the rotation drive of the heat roller and the backup roller is provided.

Further, according to the present invention, the second set temperature is set relatively low when the surface temperature of the heat roller at power-on is low, and the second set temperature is set relatively high when the surface temperature of the heat roller is high. It was done.

The present invention further comprises a set temperature changing means for changing the second set temperature so as to approach the first set temperature with the passage of time.

[0012]

In the present invention having such a structure, when the power is turned on such as when the power switch is turned on or when the housing cover is opened, the heater energization is started and the surface temperature of the heat roller reaches the second set temperature. Then, the rotation of the heat roller and the backup roller is started. Thereafter, when the surface temperature of the heat roller reaches the first set temperature, the power supply to the heater is stopped. However, the surface temperature of the heat roller continues to rise to some extent and then falls. When the temperature of the heat roller returns to the first set temperature, the rotation of the heat roller and the backup roller is stopped.

By such an operation, the second heat roller
Even if a delay occurs due to a mechanical or electrical delay between the set temperature detection timing and the start of rotation of the heat roller and the backup roller, the heat of the heat roller is reliably transmitted to the backup roller from the beginning of the overshoot period. After the surface temperature of the heat roller overshoots, the first
When the temperature returns to the set temperature, the rotation of the heat roller and the backup roller is stopped.

If the surface temperature of the heat roller is low when the power is turned on, the second set temperature is set low.
When the surface temperature of the heat roller is high, the second set temperature is set high.

Further, the second set temperature is changed so as to approach the first set temperature with the passage of time.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, an embodiment in which the present invention is applied to a fixing device of a laser printer will be described.

FIG. 2 shows the overall configuration of the laser printer. A housing 1 is pivotally supported at one end and the other end is vertically separable.
A photosensitive drum 2 is disposed at a substantially central portion of the photosensitive drum. The photosensitive drum 2 is driven to rotate in one direction by a drive motor 3, that is, clockwise in the figure. A charging unit 4 for charging a photoconductor made of a conductive material; a laser unit 5 for irradiating the photoconductor charged by the charging unit 4 with light to record information as an electrostatic latent image; A developing unit 6 for attaching a toner as a developer to the electrostatic latent image, a transfer unit 7 for transferring the toner image of the photosensitive drum 2 to a conveyed sheet, a charge removing unit 8 for removing charges remaining on the sheet, and a photosensitive drum A cleaning device 9 for removing toner from the cleaning drum 2 and a static eliminator 10 for neutralizing the photosensitive drum 2 in preparation for the next charging are arranged in this order.

The transfer unit 7 is located below the photosensitive drum 2, and is moved from a paper feed cassette 11 provided at the other end of the housing 1 to the transfer unit 7.
By the operation 2, the transfer paper is conveyed one by one at a predetermined timing.

The transferred paper is transferred by the transfer unit 7 onto which the toner image on the photosensitive drum 2 has been transferred.
, And is discharged to the upper part of the housing by the discharge rollers 14, 14.

The heating / fixing unit 13 includes a heater lamp 15
Roller 16 and Backup Roller 17 Including
The heat roller 16 is provided with a thermistor 18 as a temperature-sensitive element for detecting its surface temperature.
Is arranged.

The drive motor 3 serves as a drive source for the transfer mechanism of the transfer paper in addition to the drive source for the photosensitive drum 2.

A fan motor 19 for releasing internal heat to the outside, a DC power supply 20, and a cover open switch for detecting power when the housing 1 is opened and turning off the power are provided in the housing 1. 21 and the like are provided.

FIG. 3 is a block diagram showing the circuit configuration.
Is a microprocessor constituting a control unit main body, 32 is a ROM (Read Only Memory) storing program data for the microprocessor 31 to control each unit, and 33 is image information sent from an external host computer. And a RAM (random access memory) 34 for storing various processing data, and I / O ports 34, which are connected by a bus line 35.

The I / O port 34 includes a motor drive circuit 36 for controlling the driving of the drive motor 3, a high-voltage power supply circuit 37 for supplying a high voltage to the laser unit 5, the charging unit 4 and the transfer unit 7, Toner empty sensor 38 and toner full sensor 39 provided in developing device 6
Sensor circuit 40 for taking in signals from the printer, an operation panel 41 provided with a power switch, various key switches, a display, etc., a paper sensor 42 for detecting a conveyed transfer sheet, a fixing control unit 43, the fan motor 19, and a host computer. Interfaces 44 for receiving image information from are connected.

The cover open switch 21 is connected to the 24 V supply line connected to the motor drive circuit 36, the laser unit 5, the high voltage power supply circuit 37 and the fan motor 19 from the DC power supply 20, and to the heater lamp 15 in the fixing control section 43. When the cover of the housing 1 is opened, the power supply line is detected and the supply line is shut off.

As shown in FIG. 1, the fixing control section 43
The heater drive circuit 45 is controlled by a heater ON signal from the I / O port 34, and the heater drive circuit 45 turns on the heater lamp 15.

The temperature detection signal from the thermistor 18 is supplied to an A / D converter 46, which converts the temperature detection signal into a digital signal based on a reference voltage from a reference voltage source 47. The digital signal is supplied to the I / O port 34.

The heat roller 16 and the backup roller 17 are driven to rotate by a motor 48, and the motor 48 is driven to rotate by a motor drive circuit 49 controlled by the microprocessor 31 via the I / O port 34. Has become.

The microprocessor 31 is programmed to perform the control shown in FIG. 4 when the power is turned on (power-on) by turning on the power switch or releasing the cover open.

First, the surface temperature T of the heat roller 16 is detected by a digital signal from the A / D converter 46. Then, the heater drive circuit 45 is controlled to turn on the heater lamp 15.

[0031] Then the surface temperature T of the heat roller 16 checks whether reaches the second set temperature T ₂ lower than the first set temperature T ₁ is the temperature at which toner is welded.
When the surface temperature T of the heat roller 16 reaches the second predetermined temperature T _2, subsequently motor 48 is driven to rotate by controlling the motor drive circuit 49.

In this state, the surface temperature T of the heat roller 16 is
Wait for the _first set temperature T1 to be reached. The heater lamp 15 by controlling the heater drive circuit 45 when the surface temperature T of the heat roller 16 reaches the first set temperature T ₁
Is turned off. After that, the surface temperature T of the heat roller 16
Waits until the temperature falls below the _first set temperature T1. The surface temperature T of the heat roller 16 controls the motor drive circuit 49 to stop the rotation of the motor 48 when lower than the first predetermined temperature T _1.

In this state, the surface temperature T of the heat roller 16 is
Is stable within the allowable range near the _first set temperature T1, and if it is not stable, the heater lamp 15 is kept off for a while, and then the heater lamp 15 is turned on again. performing surface temperature T and the second comparison control of the set temperature T ₂ of the heat roller 16 Te. For example, the first
Setting If you set the temperature T ₁ of the 174 ° C., the allowable range is 172 ° C. to 177 degree ° C..

The surface temperature T of the heat roller 16 is
When becomes stable in the set temperatures T ₁ within the allowable range in the vicinity, and terminates the warm-up so the process proceeds to the normal printing sequence.

In this embodiment having such a configuration, for example, when the power switch is turned on, warm-up is started, the heater lamp 15 is turned on, and the heat roller 1 is turned on.
6 is heated. The surface temperature T of the heat roller 16 is detected by a thermistor 18 and the temperature is set to a second set temperature T _2.
, The motor 48 starts rotating and the heat roller 16
Then, the backup roller 17 starts rotating. Then the surface temperature T of the heat roller 16 is the heater lamp 15 is turned OFF when it reaches the first predetermined temperature T _1. However, the surface temperature T of the heat roller 16 continues to rise thereafter and overshoots. The heat roller 16 and the backup roller 17 continue to rotate during this overshoot period. Thus, the backup roller 17 is a heat roller 1
6 allows for uniform heating.

Thereafter, the surface temperature T of the heat roller 16 falls through a peak value. The surface temperature T of the heat roller 16 when lowered to the first predetermined temperature T ₁ following the rotation of the heat roller 16 and backup roller 17 rotation of the motor 48 is stopped is stopped.

Thereafter, when the surface temperature T of the heat roller 16 falls below an allowable range near the _first set temperature T1, the heater lamp 15 is turned on again at a certain timing, and the heat roller 16 is heated. At this time, the heat roller 16
When the surface temperature T of is lower than the second predetermined temperature T _2, the surface temperature T of the heat roller 16 by the ON of the heater lamp 15 reaches the second predetermined temperature T _2, the motor 4
8 starts rotating, and the heat roller 16 and the backup roller 17 start rotating.

[0038] Thereafter the heater lamp 15 when the surface temperature T of the heat roller 16 reaches the first set temperature T ₁ is OFF
Is done. However, the surface temperature T of the heat roller 16 continues to rise thereafter and overshoots. The heat roller 16 and the backup roller 17 continue to rotate during this overshoot period. Thus, backup roller 1
7 is more uniformly heated by the heat roller 16.

As described above, the heater lamp 15 is repeatedly turned on until the surface temperature T of the heat roller 16 changes to a stable state in which the surface temperature T changes within an allowable range near the _first set temperature T _1.
Is done. The motor 48 is repeatedly rotated unless the surface temperature T of the heat roller 16 is repeated changes to lower than the second set temperature T _2.

As described above, the surface temperature T of the heat roller 16
Reaches a second set temperature T ₂ lower than the first set temperature T _1, the rotation of the motor 15 is started. Therefore, after the thermistor 18 detects the second set temperature T ₂ ,
5, heat roller 16 and backup roller 17
The heat roller 16 and the backup roller 17 rotate before the surface temperature T of the heat roller 16 reaches the first set temperature T ₁ even if there is an electrical or mechanical delay until the rotation of the heat roller 16 starts. Get started.

Therefore, the heat of the heat roller 16 can be transmitted to the backup roller 17 by reliably using the period in which the surface temperature T of the heat roller 16 overshoots from the beginning. Therefore, high-temperature heat is efficiently transmitted from the heat roller 16 to the backup roller 17.

Since the heat of the overshoot is transmitted to the backup roller 17, the temperature at which the overshoot occurs in the heat roller 16 is controlled to be relatively low.

When the surface temperature T of the heat roller 16 becomes stable near the first set temperature T ₁ , the warm-up is completed and a normal print sequence is started. The following operations are performed in this print sequence.

After the photoreceptor of the photoreceptor drum 2 is uniformly charged by the charging section 4, the photoreceptor is exposed to laser light from the laser unit 5 to record image information as an electrostatic latent image. Then, the electrostatic latent image is developed with toner in the developing device 6, and the toner image is transferred to the transfer paper conveyed from the paper feed cassette 11 in the transfer section 7. Then, the transfer paper on which the toner image has been transferred passes through a contact portion between the heat roller 16 and the backup roller 17 of the heat fixing unit 13 and is heat-fixed. The heat-fixed transfer paper is then transferred to a discharge roller 14.
Is discharged through.

When the cover of the housing 1 is opened, the cover open switch 21 operates to cut off the current path to the heater lamp 15. As a result, heat escapes from the heat roller 16 and the backup roller 17 to lower the temperature.

Thereafter, when the cover open state is released, the current path to the heater lamp 15 is restored, and the heater lamp 15 is turned off.
The energization to is started. The motor 48 when the surface temperature T of the heat roller 16 surface temperature T of the second set temperature T ₂ the heat roller 16 if lower than reaches the second predetermined temperature T ₂ even when it is rotated The heat roller 16 and the backup roller 17 rotate, and warm-up is performed in the same manner as described above. Therefore, also in this case, the same effect as when the power switch is turned on can be obtained.

Next, another embodiment of the present invention will be described with reference to the drawings. The hardware configuration shown in FIGS. 1 to 3 is the same.

One of the other embodiments, as shown in FIG. 6, is a flowchart of the control by the microprocessor 31, when the power is turned on (power on) by turning on the power switch or releasing the cover open. , A / D converter 4
6, the surface temperature T of the heat roller 16 is detected. Then, based on the surface temperature T, a second
Setting the set temperature T _2. In this case, by increasing the temperature difference between the first set temperature T ₁ set relatively low second set temperature T ₂ the lower the surface temperature T, and the second set temperature the higher the surface temperature T the relatively set high T ₂ 1
To reduce the set temperature difference between the temperature T _1.

When the setting of the second set temperature T ₂ is completed, the heater drive circuit 45 is controlled to turn on the heater lamp 15.

The subsequent control is the same as in the case of FIG.

In this way, when the surface temperature T of the heat roller 16 at the time of turning on the power is low, substantially the same operation as that shown in FIG. 5 is performed.

When the surface temperature T of the heat roller 16 at the time of turning on the power is high, as shown in FIG.
_{Since 2} is set relatively high, the temperature difference from the _first set temperature T ₁ becomes small.

In this case, the heater lamp 15 and the motor 4
8, the ON cycle is shortened, and the ON time is also shortened. Therefore, the time required for warm-up is reduced.

In this embodiment, the rotation of the motor 48 is also performed when the surface temperature T of the heat roller 16 reaches the second set temperature T.
_{Since the process} is started when the number reaches ₂ , the same effect as in the above embodiment can be obtained.

In another one of the other embodiments, as shown in the flow chart of the control by the microprocessor 31 in FIG. 8, the power is turned on (power on) by turning on the power switch or releasing the cover open. At this time, the surface temperature T of the heat roller 16 is detected based on a digital signal from the A / D converter 46. Then, the heater drive circuit 45 is controlled to turn on the heater lamp 15.

[0056] Then the surface temperature T of the heat roller 16 checks whether reaches the second set temperature T ₂ lower than the first set temperature T ₁ is the temperature at which toner is welded.
When the surface temperature T of the heat roller 16 reaches the second predetermined temperature T _2, subsequently motor 48 is driven to rotate by controlling the motor drive circuit 49. Heat roller 1
If the surface temperature T of No. 6 has not reached the second set temperature T ₂ , the second set temperature T ₂ is changed so as to approach the first set temperature T ₁ with time.

The subsequent control is the same as in the case of FIG.

By doing so, as shown in FIG. 9, the second set temperature T ₂ changes so as to approach the first set temperature T ₁ with the lapse of time. ₂ is set low and motor 48 is set to heat roller 1
Since the surface temperature T of the 6 second set temperature T ₂ in accordance with the elapse of the time to initiate the rotation from low to some extent state increases, the surface temperature T of the heat roller 16 of the heater lamp 15 and the motor 48 in accordance stable The ON cycle becomes shorter, and the ON time becomes shorter.

Accordingly, heat can be more efficiently transferred from the heat roller 16 to the backup roller 17 at the initial stage of power-on, and the entire time required for warm-up can be reduced.

In this embodiment, the rotation of the motor 48 is also performed when the surface temperature T of the heat roller 16 reaches the second set temperature T.
_{Since the process} is started when the number reaches ₂ , the same effect as in the above embodiment can be obtained.

In the above embodiment, the present invention is applied to a laser printer. However, the present invention is not limited to this. The present invention can be applied to any apparatus using a heat fixing device such as a copying machine. It is.

[0062]

As described above in detail, according to the present invention, when the surface temperature of the heat roller reaches a temperature close to the toner welding temperature, the rotation of the heat roller and the backup roller is started, and thereafter, the surface temperature of the heat roller becomes the toner welding. When the surface temperature of the heat roller returns to the toner fusing temperature after the overshoot period that exceeds the temperature, the heat roller and the backup roller stop rotating to efficiently transfer the heat of the heat roller to the backup roller during the overshoot period. An object of the present invention is to provide a control device for a heat fixing device capable of reducing a temperature overshoot in a heat roller.

[Brief description of the drawings]

FIG. 1 is a block diagram of a fixing control unit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a laser printer according to the embodiment.

FIG. 3 is a block diagram showing a circuit configuration of the laser printer according to the embodiment.

FIG. 4 is a flowchart showing control of a heat fixing unit when power is turned on by the microprocessor in the embodiment.

FIG. 5 is a diagram showing a temporal change of a heat roller surface temperature and an operation relationship of a heater lamp and a motor in the embodiment.

FIG. 6 is a flowchart illustrating control of a heating and fixing unit when a power is turned on by a microprocessor according to another embodiment of the present invention.

FIG. 7 is a view showing a temporal change of a heat roller surface temperature and an operation relationship of a heater lamp and a motor in the embodiment.

FIG. 8 is a flowchart showing control of a heat fixing unit when a power is turned on by a microprocessor according to still another embodiment of the present invention.

FIG. 9 is a diagram showing a temporal change of a heat roller surface temperature and an operation relationship of a heater lamp and a motor in the embodiment.

[Explanation of symbols]

13: Heat fixing unit, 15: Heater lamp, 16: Heat roller, 17: Backup roller, 18: Thermistor (temperature sensing element), 31: Microprocessor, 43: Fixing control unit, 48: Motor.

Claims (3)

(57) [Claims] 1. A heating and fixing device comprising a heat roller containing a heater and a backup roller which is in contact with the heat roller and which is located in such a manner that a transfer sheet passes through the contact portion, the surface temperature of the heat roller is detected. The power is supplied to the heater in a state where the temperature detected by the temperature-sensitive element and the temperature detected by the temperature-sensitive element are lower than or equal to a first set temperature at which the toner is fused, and when the temperature reaches the first set temperature, the power is supplied to the heater. Heating control means for stopping the heat roller and the backup roller when the surface temperature of the heat roller becomes equal to or higher than a second set temperature lower than a first set temperature when power is turned on, and After the surface temperature reaches the first set temperature and returns to the first set temperature by de-energizing the heater, the heat roller and the battery A control device for a heat fixing device, further comprising a roller driving means for stopping the rotation drive of the pickup roller. 2. When the surface temperature of the heat roller at power-on is low, the second set temperature is set relatively low, and when the surface temperature of the heat roller is high, the second set temperature is set relatively high. The control device for a heat fixing device according to claim 1. 3. A heating / fixing device comprising a heat roller including a heater and a backup roller which is in contact with the heat roller and which is positioned so that a transfer sheet passes through the contact portion, the surface temperature of the heat roller is detected. The power is supplied to the heater in a state where the temperature detected by the temperature-sensitive element and the temperature detected by the temperature-sensitive element are lower than or equal to a first set temperature at which the toner is fused, and when the temperature reaches the first set temperature, the power is supplied to the heater. Heating control means for stopping the heat roller and the backup roller when the surface temperature of the heat roller becomes equal to or higher than a second set temperature lower than a first set temperature when power is turned on, and After the surface temperature reaches the first set temperature and returns to the first set temperature by de-energizing the heater, the heat roller and the battery Control of a heat fixing device, comprising: a roller driving means for stopping the rotation drive of the backup roller; and a set temperature changing means for changing the second set temperature so as to approach the first set temperature with the passage of time. apparatus.