JPH07121050A - Temperature controller for fixing device - Google Patents

Abstract

PURPOSE:To stabilize an actual fixing temperature and to prevent the occurrence of high temperature offset and defective fixation by making a heat roller and a pressure roller idle (aging) for a specified time, and detecting the temperature of the heat roller and correcting a control temperature. CONSTITUTION:Before a 1st time of turning on a heater 59, the heat roller 54a and the pressure roller 54b are made idle (what is called 'aging') for the specified time, and the temperatures of both rollers 54a and 54b are made uniform. and just after this, the temperature of the heat roller 54a is detected, the temperature of the pressure roller 54a is reflected on the detected temperature (t1). The control temperature Tc is corrected by a required correction quantity D1 (t1, n) in accordance with the detected temperature (t1) of the heat roller. Thus, the actual fixing temperature is more stabilized, the occurrence of the high temperature offset and the defective fixation is prevented, and also, the structure is simplified since it is unnecessary to install a means for detecting the temperature of the pressure roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a fixing device which is applied to a fixing device of an image forming apparatus such as an electrostatic copying machine or a facsimile and which controls on / off of a heater for heating the fixing device.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, an electrostatic latent image formed on a photosensitive drum is visualized as a toner image, the toner image is transferred onto a sheet, and then heated by a fixing device. I am trying to fix it. This fixing device includes a heat roller heated by a pressure roller and a heater, and heats and fixes the toner on a sheet passing between the rollers.

In order to perform heat fixing, it is necessary that the fixing device has reached a predetermined high temperature. Therefore, in a copying machine or the like, a predetermined waiting time is required from turning on the power until copying is possible, which is inconvenient for the user. Therefore, it is desired to shorten the waiting time and, if possible, eliminate the waiting time. For that purpose, it is necessary to heat the fixing device to a predetermined high temperature in a short time.

[0004]

On the other hand, from the viewpoint of energy saving, it is preferable to heat the fixing device only when required.
Also in this case, it is necessary to heat the fixing device to a predetermined high temperature within a very short time from the start of copying until the sheet is conveyed to the fixing device. Therefore, in order to enable rapid heating of the fixing device, the inventor of the present application increases the heating capacity of the heater and reduces the diameter of the heat roller and the pressure roller so that the heat capacity of the heater is relatively large. I tried to make it smaller.

However, there have been cases where high-temperature offset, wrinkles, and improper fixing occur. If a pressure roller temperature detection sensor that detects the temperature of the pressure roller is provided, the cost increases. The present inventor
Even when the temperature of the heat roller is at a predetermined temperature, the temperature of the pressure roller may be high or low, which may be the cause of the above-mentioned high temperature offset.

The present invention has been made in view of the above problems, and provides a temperature control device for a fixing device, which can prevent the occurrence of high-temperature offset and defective fixing due to high and low pressure roller temperatures at low cost. The purpose is to do.

[0007]

In order to solve the above problems, the invention according to claim 1 includes a heat roller heated by a pressure roller and a heater, and heats and fixes toner on a sheet passing between both rollers. In the temperature control device of the fixing device, which is applied to the fixing device of the image forming apparatus and which controls on / off of energization to the heater based on a signal from the heat roller temperature detecting means for detecting the temperature of the heat roller, conveyance of the paper is performed. The heat roller and the pressure roller are first placed in the avoiding state.
A required correction amount according to the aging signal output section for outputting a signal for rotating for a predetermined time before energizing the heater for the second time and the temperature detected by the heat roller temperature detecting means immediately after the lapse of the predetermined time. Is included to set the control temperature.

According to a second aspect of the present invention, in the temperature control device of the fixing device according to the first aspect, an atmosphere temperature detecting means for detecting an ambient temperature around the fixing device is further included, and the aging signal output section is The present invention is characterized in that a signal is output only when the ambient temperature detected by the ambient temperature detecting means is equal to or higher than a predetermined temperature.

[0009]

According to the structure of the invention according to claim 1, before the first energization of the heater is turned on, the heat roller and the pressure roller are idled for a predetermined time (so-called aging), and both rollers are turned on. The temperature was homogenized. Immediately after that, the temperature of the heat roller is detected, and the temperature of the pressure roller is reflected in this detected temperature. The control temperature is corrected according to the temperature of the heat roller thus detected. This allows
The actual fixing temperature becomes more stable, and high-temperature offset and defective fixing are prevented. Since it is not necessary to provide the pressure roller temperature detecting means, the structure can be simplified.

According to the second aspect of the present invention, in the above aging, it is assumed that the temperature of the pressure roller is high.
This is performed only when the ambient temperature is high, thereby avoiding creating an unnecessary waiting time before the first energization of the heater.

[0011]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is a schematic diagram showing an internal configuration of a copying machine as an image forming apparatus including a temperature control device of a fixing device according to an embodiment of the present invention. Referring to FIG. 1, this copying machine is arranged inside the copying machine main body 1 along the upper surface of the copying machine main body 1 in a state where an original placed on a transparent original placing plate is pressed by an original pressing member. An original system 2 to be moved, an original system moved by the original system 2 is illuminated, and an optical system 3 for guiding reflected light from the original system to the photoconductor drum 42, and an electrostatic latent image formed on the photoconductor drum 42 is developed. After the image is visualized by the apparatus 41, the image forming unit 4 that transfers the image onto the sheet and the fixing device 54 that heats and fixes the toner image transferred onto the sheet are provided. The paper transport unit 5 and the like for discharging the paper to the discharge tray 56 are provided.

Although not shown, on the upper surface of the main body 1 of the copying machine, there is provided an operation section in which a copy start switch and other switches are arranged. The optical system 3 includes a fluorescent lamp 31 as a light source for illuminating a document moving on the document table, and a plurality of optical systems 3 arranged in a direction orthogonal to the document moving direction to form an image of reflected light from the document on the photosensitive drum 42. The image forming lens 32 is provided.

As the image forming section 4, a charging charger 43, a developing device 41, a transfer charger 44 and a cleaning device 45 are arranged in this order around the photosensitive drum 42. The image forming unit 4 includes a charging charger 43.
On the outer peripheral surface of the photosensitive drum 42 that is uniformly charged by
After the original image is formed to form an electrostatic latent image, the electrostatic latent image is visualized as a toner image by the developing device 41, the toner image is transferred to a sheet by the transfer charger 44, and the residual toner is cleaned by a cleaning device. It is designed to be collected by 45.

The sheet conveying section 5 pulls out sheets one by one from the sheet feeding tray 61, and brings the sheet from the sheet feeding roller 51 having a half-moon shape in cross section and the sheet from the manual sheet feeding section 60 or the sheet feeding tray 61 into contact with each other. Registration rollers 53a and 53b for temporarily holding the sheet and a heat roller 54a included in the fixing device 54 for fixing the toner image transferred to the sheet.
And the pressure roller 54b and the pair of discharge rollers 55a, 5
5b and.

Further, the paper transport section 5 is further provided with a paper feed detection switch 57, a paper discharge detection switch 58, a heat roller temperature detection sensor SH and an ambient temperature detection sensor SA. The paper feed detection switch 57 includes a limit switch arranged upstream of the registration rollers 53a and 53b in the paper conveyance direction, and the paper ejection detection switch 58 includes a limit switch arranged upstream of the discharge rollers 55a and 55b in the paper conveyance direction. It consists of a switch. The heat roller temperature detection sensor SH includes a thermistor arranged in a predetermined portion of the heat roller 54a, and detects the temperature of the heat roller 54a.
The ambient temperature detection sensor SA includes a thermistor arranged in a predetermined portion of the casing 54c of the fixing device 54, and detects the ambient temperature around the fixing device 54.

The fixing device 54 heats and fixes the toner on the sheet passing between the pressure roller 54b and the heat roller 54a heated by the heater 59. Heat roller 5
4a is made of a metal roller, and the heater 59, which is a cartridge heater, is housed therein and heated by the heater 59. The pressure roller 54b is made of a rubber roller, is supported movably in the radial direction, and is urged by a predetermined urging force toward the heat roller 54a by a spring member (not shown).

The registration mechanism RE including the registration rollers 53a and 53b is a conceptual schematic view shown in FIGS. 2 (a) and 2 (b).
As shown in FIG. 5, one end 53d supports the lower roller 53b so that the lower roller 53b can move up and down, and the other end 53e supports the paper stopper portion 5b.
A swing lever 53c that bends 3f and swings around a fulcrum 53g, and a solenoid SOL are included by swinging the swing lever 53c. The swing lever 53c is displaced by swinging into the stop posture shown in FIG. 2A and the non-stop posture shown in FIG. 2B. At the time of aging described later, the posture of FIG. 2A is obtained, and the rollers of the paper transport unit 5 are idled while avoiding the transport of the paper.

FIG. 3 is a block diagram showing the electrical construction of this copying machine. The control unit 7 for controlling the operation of each unit of the copying machine includes a CPU 71, a ROM 72 storing a program executed by the CPU 71, and a RAM 73 used as a work area of the CPU. C
The PU 71 is provided on the upper surface of the copying machine main body 1 and includes an operation unit 10 including a copy start switch 10a, an image forming unit 4, a sheet conveying unit 5, a motor drive circuit MC, and a document table moving mechanism 2.
0 is connected. The motor drive circuit MC drives a motor M as a drive source for driving the document table 2, the image forming section 4, the sheet conveying section 5, and the like. The original table moving mechanism 20, the image forming unit 4, and the sheet conveying mechanism PDM are driven in synchronization by the motor M.

In addition to the paper feed detection switch 57, the paper ejection detection switch 58, the heat roller temperature detection sensor SH, and the ambient temperature detection sensor SA, the paper conveyance section 5 is for turning on and off the power supply to the heater 59. A relay drive circuit RDC for driving the relay R and a paper transport mechanism PDM for transporting the paper by the driving force of the motor M are included, and each is connected to the CPU 71. Paper transport mechanism PD
M includes a relay drive circuit RDC1 that drives a relay R1 for turning on and off the solenoid SOL of the registration mechanism RE.

The CPU 71 performs on / off control of the heater 59 of the fixing device 54 based on the program read from the ROM 72. The concept of the control at this time is to continuously energize the heater 59 in accordance with a copy start signal to a predetermined level. Temperature (1st OFF temperature T ₁ described later) at once, and a warm-up control unit (not shown) for intermittently energizing the heater 59 after the warm-up is completed based on the elapsed time. And a normal control unit (not shown) for maintaining a predetermined control temperature.

The normal control section includes a correction section for adding a required correction amount to the control temperature according to the temperature of the heat roller detected before the first energization of the heater, and the control temperature only when the sheet is passed. Includes a sheet-passage correction unit (not shown) that adds a sheet-passage correction amount, and an atmosphere-dependent correction unit (not shown) that adds an atmosphere-dependent correction amount to the control temperature according to the ambient temperature. .

The operation in the case of performing such control will be described with reference to the flow charts of FIGS. 4 to 6 and FIG. 7 showing the temperature changes of the heat roller 54a and the pressure roller 54b with time. Steps S1 to S18 show the flow of processing by the warm-up control unit. When the warm-up control unit starts processing in response to the input of a copy start signal by pressing down the copy start switch 10a, first, the detected temperatures t _{0 to} t _{3 are} detected.
Initial setting is performed to clear the previous data such as (step S1), and the ambient temperature t ₀ is read based on the signal from the ambient temperature detection sensor SA (step S2).

[0023] If the ambient temperature t ₀ which is detected at the temperature t _a than the predetermined was performed for a predetermined time (e.g., several seconds), aging the (idling) (step S
After 3 step S8), and reads the detected temperature t ₁ of the heat roller 54b from the heat roller temperature detection sensor SH (step S9), and turns on the power supply to the heater 59 (step S
After 10), the timer is reset to start counting (steps S11 and S12). If the ambient temperature t ₀ which is detected does not exceed the temperature t _a predetermined is without aging, after reading the detected temperature t ₁ of the heat roller was turned on energization of the heater 59 (Step S10) , Reset the timer and start counting (step S1
1, 12).

Due to the above aging, both rollers 54
The temperatures of a and 54b were made uniform. It is estimated that the temperature t ₁ of the heat roller 54a obtained after the homogenization is reflected on the temperature t _P of the pressure roller 54. Note that the above aging is performed only when the atmospheric temperature t ₀ , which is assumed to be the temperature t _P of the pressure roller 54b, is high, so that it is unnecessary before the first energization of the heater. I tried to avoid making a waiting time.

Next, in step S13~ step S17, the detected temperature t ₂ of the heat roller 54a is monitored, when the detected temperature t ₂ of the heat roller 54a reaches the first round off temperature T ₂ the current supply to the heater 59 Turn off (step S1
7, 18), the processing by the warm-up control unit is completed. On the other hand, a predetermined time has passed since the power to the heater 59 was turned on (the count value C of the timer was set to a predetermined value C ₁
Even if the above is determined), the detected temperature t _{2 of the} heat roller
When the temperature does not reach the first OFF temperature, it is determined to be abnormal, and, for example, a display indicating the abnormality is displayed on the operation unit 10 of the copying machine (steps S14 and 15).

The first round off temperature T ₂ above, because it is set lower than the control temperature T _c according to the normal control section after, it is possible to reduce the overshoot amount to the temperature rise side. As a result, it is possible to suppress the overshoot to the temperature lowering side after the first turning off of the energization of the heater 59, and, as will be described later, perform the intermittent control based on the elapsed time and the control temperature Tc. So do the first
When copying the first sheet, the temperature can be controlled while avoiding the high-temperature offset area and the defective fixing area.
In particular, it is possible to avoid both high temperature offset at the leading edge of the sheet and avoiding improper fixing at the trailing edge of the sheet, for copying at the transition stage from warm-up to normal control where temperature changes tend to be severe.

Next, steps S19 to S44
Shows processing by the normal control unit. First, the timer is reset to start counting (step S1
After 9 and 20), the number of times n of energizing the heater is set to 1 (step S21). In step S22, it is determined whether or not there is a copy end signal. When the copy end signal is input, it is confirmed that the heater 59 is not energized and the process ends (steps S23 to 25). The case where the copy end signal is output includes the case where the copying of the number set in the operation unit 10 is completed and the case where the apparatus is stopped due to an abnormality of the copying machine.

When the copy end signal is not input, the processing by the normal control section is continued. The initially set control temperature T ₃ is set on condition that the initial detection temperature t ₁ of the heat roller 54 a detected at the start of processing by the warm-up control unit is lower than a predetermined initial detection temperature T _1. Then, the correction value D ₁ (t ₁ , n) corresponding to the detected temperature t ₁ and the number of times the heater is energized n is added, and this is set as the control temperature T _c (steps S26 and S27). this is,
At the initial stage of processing of the normal control section, in which the temperature of the pressure roller 54b tends not to be sufficiently warmed, the control temperature T _c
This is to prevent the occurrence of defective fixing by increasing the value of. Further, when the initial detected temperature t ₁ of the heat roller 54a is high, it is assumed that the temperature of the pressure roller 54b is also high, and in this case, the correction is not performed. This can prevent the fixing temperature from becoming too high due to unnecessary correction. The correction amount is preferably 8 to 10 ° C.

The correction amount D ₁ (t ₁ , n) is set as a function so as to decrease to zero according to the number of times n the heater 59 is energized. This is because it is considered that the temperature of the pressure roller 54b gradually rises and converges to a predetermined temperature as time elapses from the start of the processing by the normal control unit, and this is in response to this. As a result, it is possible to prevent the pressure roller 54b from reaching an unnecessary high temperature.

Next, in steps S28 and S29, the paper feed correction amount D is further constant at the control temperature Tc on condition that the paper is being fed (the paper is present in the fixing device 54).
₂ is added. It is determined that the paper is being passed through the time region from when the paper discharge detection switch 58 is turned on to when a predetermined time (for example, 3 seconds) has elapsed after the paper feed detection switch 57 was turned off. By increasing the control temperature Tc only when the paper is passed in this way, there are the following advantages. That is, when the heat capacity of the heat roller 54a is set to be small, the pressure roller 54b may be changed depending on the sheet passing therethrough.
Since the heat of the sheet is taken away, there is a possibility that fixing failure may occur at the trailing edge of the sheet. Therefore, it is conceivable to constantly increase the control temperature Tc, but in such a case, a high temperature offset occurs at the leading edge of the paper. On the other hand, as shown in FIG. 7, since the control temperature Tc is set to be high only when the paper is passed, both the high temperature offset at the leading edge of the sheet and the fixing failure at the trailing edge of the sheet are prevented. can do.
That is, when the leading edge of the sheet passes, the control temperature Tc is set to be low until this time, so the heat roller 54
Since the temperature of a becomes low, the occurrence of high temperature offset can be prevented. On the other hand, since the temperature of the heat roller 54a becomes high when the trailing edge of the sheet passes, it is possible to prevent the occurrence of defective fixing.

On the other hand, the above-mentioned constant correction amount D ₂ during sheet passing is set to D
It is also possible to set the value to ₂ (x), and to set the function so that the paper feed starts (increases according to the elapsed time x from when the paper discharge detection switch is turned on). This enables more accurate temperature control during paper feed. It is possible to reliably prevent the above-mentioned high-temperature offset and poor fixing.
In steps S30 and S31, the ambient temperature t ₀ around the fixing device is read, and the environmental correction amount D ₃ (t ₀ ) corresponding to the ambient temperature t ₀ is further added to the control temperature Tc. This has the following advantages. That is, the ambient temperature t ₀
When is low, the temperature of the paper is low, and the amount of heat taken by the paper from the pressure roller 54b is large, which is considered to hinder stable temperature control. Therefore, according to the ambient temperature t ₀ ,
Stable temperature control is performed by correcting the control temperature Tc.

Next, after confirming that the energization of the heater 59 is off (step S32), steps S33 to S are performed.
In 36, the first time off (or the previous heater 59
Has passed a predetermined time (for example, 2 seconds) or more (when the energization to the power is turned off) (the count value C by the timer is equal to or more than the predetermined value C _OFF ), and the temperature detected by the heat roller 54a. Two conditions are monitored: t ₃ is below the control temperature T _C. Only when both conditions are satisfied, the energization of the heater 59 is turned on (step S37). The OFF state of the power supply to the heater 59 continues for at least 2 seconds. After that, the timer is reset (step S38), the process returns to step S22, and the process is repeated.

In the state where the heater 59 is energized, in steps S39 to S42, the elapsed time from the previous energization of the heater 59 is
A predetermined time (for example, 1 second) is reached (the count value C by the timer is a predetermined value C _ON or more), and the detected temperature t ₃ of the heat roller 54a becomes higher than the control temperature T _C. 2 One condition is monitored. Only when either one of the two conditions is satisfied, the power supply to the heater 59 is turned off (step S43). Therefore, the heater 5
The ON state of the energization of 9 continues for a maximum of 1 second. After that, the number of energizations n to the heater 59 is replaced with n + 1 and the timer is reset (steps S44, 3
8) and returns to step S22 to repeat the process.

In the normal control in which the steps after step S22 are repeated as described above, the energization of the heater 59 is intermittently controlled by combining the ON time or the OFF time with the control temperature Tc, and the temperature fluctuation is suppressed. In addition, depending on the temperature of the heat roller before the first energization of the heater,
The control temperature Tc is corrected and the control temperature Tc
Is corrected to a high value, and correction is also performed according to the ambient temperature t ₀ . Thereby, more stable temperature control can be performed. When the copying is completed, the heater 59
If the power to the
If the heater 59 is energized, it is turned off and the process ends. As a result, the state of waiting for the start of the next copy is entered.

As described above, according to this embodiment, before the first energization of the heater 59 is turned on, the heat roller 54a is turned on.
The pressure roller 54b was idled for a predetermined time (so-called aging) to make the temperature of both rollers 54a, 54b uniform. Then, immediately after that, the temperature of the heat roller 54a is detected, and the temperature of the pressure roller 54a is reflected in the detected temperature t ₁ . The control temperature T _C is corrected by the required correction amount D ₁ (t ₁ , n) according to the temperature t ₁ of the heat roller thus detected. As a result, the actual fixing temperature becomes more stable, and high-temperature offset and defective fixing are prevented from occurring. Since it is not necessary to provide pressure roller temperature detection means,
The structure can be simplified.

The above-mentioned aging is performed by the pressure roller 54.
This is performed only when the ambient temperature, which is assumed to be high in b, is high.
I tried to avoid creating unnecessary waiting time before energizing 9. Further, the correction amount D ₁ (t ₁ , n) is set to the heater 59.
It is arranged to gradually decrease as the number n of energizations to the circuit increases. As a result, it is possible to prevent the pressure roller 54a from reaching an unnecessary high temperature. Therefore, the occurrence of high temperature offset can be prevented.

Moreover, the above correction is carried out only when the detected temperature t ₁ of the heat roller 54a before the first energization of the heater 59 is turned on is low, and the correction is not carried out when it is high. This can prevent the fixing temperature from becoming too high due to unnecessary correction. In the above embodiment, the correction is performed according to the heat roller temperature that reflects the pressure roller temperature, but a pressure roller temperature detection sensor for detecting the pressure roller temperature is provided and the correction is performed accordingly. You can also do so.

In addition, various design changes can be made without changing the gist of the present invention.

[0039]

According to the configuration of the invention of claim 1, according to the configuration of the invention of claim 1, the heat roller and the pressure roller are set to a predetermined position before the first power-on of the heater. The temperature of the heat roller was detected in a state where the temperature of both rollers was made uniform by idling (so-called aging) for a period of time. The detected temperature reflects the temperature of the pressure roller. By correcting the control temperature in accordance with the temperature of the heat roller thus detected, the actual fixing temperature becomes more stable, and high-temperature offset and defective fixing can be prevented. Since it is not necessary to provide the pressure roller temperature detecting means, the structure can be simplified and the manufacturing cost can be reduced.

According to the second aspect of the present invention, it is assumed that the temperature of the pressure roller is high in the above aging.
Since it was decided to carry out only when the ambient temperature is high,
It is possible to avoid creating an unnecessary waiting time before energizing the heater for the first time.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an internal configuration of a copying machine including a temperature control device of a fixing device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a copying machine.

FIG. 3 is a schematic diagram showing the operation of the registration mechanism,
The figure (a) shows the state in which the paper is on standby, and the figure (b).
Indicates a state in which a sheet is conveyed.

FIG. 4 is a flowchart showing a warm-up operation of the temperature control operation of the fixing device.

FIG. 5 is a flowchart showing an operation during a normal control of the temperature control operation of the fixing device.

FIG. 6 is a flowchart showing an operation during normal control of the temperature control operation of the fixing device, which is continuous with the flowchart of FIG.

FIG. 7 is a diagram showing a temporal change in temperature of a heat roller and a pressure roller.

[Explanation of symbols]

1 copier body 54 fixing device 54a heat roller 54b pressure roller 59 heater SH heat roller temperature detection sensor SA ambient temperature detection sensor 7 control unit 71 CPU 72 ROM T _C control temperature D ₁ (t _1, n) the correction amount t ₀ Atmosphere Temperature t ₁ Initial detection temperature of heat roller t _2, t ₃ Current detection temperature of heat roller T ₁ Predetermined initial detection temperature T ₂ First off temperature

Claims (2)

[Claims] 1. A heat detecting roller which is applied to a fixing device of an image forming apparatus, which includes a heat roller heated by a pressure roller and a heater and heats and fixes toner on a sheet passing between the rollers, and detects the temperature of the heat roller. In a temperature control device of a fixing device, which controls on / off of energization to the heater based on a signal from a roller temperature detecting means, energization of the heat roller and the pressure roller to the heater for the first time in a state in which conveyance of a sheet is avoided. The aging signal output section for outputting a signal for rotating for a predetermined time before the control, and the control temperature by adding a necessary correction amount according to the temperature detected by the heat roller temperature detecting means immediately after the lapse of the predetermined time. A temperature control device for a fixing device, comprising: a correction unit for setting the temperature. 2. The temperature control device for a fixing device according to claim 1, further comprising an ambient temperature detecting means for detecting an ambient temperature around the fixing device, wherein the aging signal output part is detected by the ambient temperature detecting means. A temperature control device for a fixing device, which outputs a signal only when the ambient temperature is equal to or higher than a predetermined temperature.