JPH0816027A - Image forming apparatus and controlling method for fixing apparatus suitable for the apparatus - Google Patents

Abstract

PURPOSE:To provide an image forming apparatus which can retain stable fixing condition. CONSTITUTION:A main heater 62m and an auxiliary heater 62s to heat heat rollers 62a, 62b of a fixing apparatus 62 of a copying machine 2 are controlled so as to keep the surface temperature of respective rollers within a specified range by a warm-up mode to heat respective heaters to a control temperatrue THO by rated output by a heater controlling circuit 74, a ready mode to energize respective heaters intermittently to change the alteration quantity of the control temperature THO within a first aiming value, and a copy mode to change the electric power to be supplied to respective heaters in order to change the alteration quanity of the control temperature THO within a second aiming value and at the same time to energize respective heaters intermittently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which forms an image on an image bearing member by an electrostatic photography process, develops the image with toner and outputs it on a sheet.

[0002]

2. Description of the Related Art In an image forming apparatus, for example, an electrostatic copying apparatus, a latent image is formed on a photosensitive drum which is charged in advance with a predetermined polarity by reflected light from the original obtained by illuminating the image of the original. It is formed. The latent image formed on the photoconductor drum is developed by the toner supplied by the developing device, and is transferred as a copy image onto the sheet attracted to the photoconductor drum by electrostatic force.

A copied image, that is, a toner image transferred onto a sheet is separated from the photosensitive drum together with the sheet and is fixed on the sheet through a fixing device. At this time, the toner image, that is, the toner, is melted by the heat of the heater of the fixing device. The melted toner penetrates between the fibers of the paper, so that the paper and the toner are firmly bonded and discharged as a copy.

The fixing device has a sufficient heat (generally, 18%) necessary to melt the heat-meltable toner transferred to the paper.
It has a heating heater, for example, a halogen lamp or a heating element for providing 0 ° C to 200 ° C. The heat from the halogen lamp or the heating element is supplied to the paper and the toner transferred to the paper by a pair of upper and lower rollers that provide heat to the paper and pressurize the paper.

The heater is, for example, a solid state formed by a semiconductor element such as a triac which is turned on / off according to the temperature of the roller surface detected by a temperature sensor or thermistor arranged near the surface of the roller. It is controlled via a relay (SSR).
That is, if the surface of the roller detected by the temperature sensor or the thermistor is lower than the preset temperature, the heater is turned on, while at the time when the surface of the roller reaches the preset upper limit of the temperature. The temperature of the surface of the roller is maintained within a predetermined range by the feedback control that the heater is turned off.

[0006]

By the way, in order to meet the demands for downsizing of copying machines and shortening of warm-up time, rollers having a thin wall thickness, that is, a small heat capacity are used today. However, for example, in a thermistor, since the time constant, that is, the minimum time during which the temperature change can be detected is relatively long, which is 2 to 3 seconds, the temperature change on the roller surface may reach 40 ° C. to 50 ° C.
This means that when the temperature is low, fixing failure occurs while
When the temperature is high, there is a problem that offset of the copied image or deformation of the peeling claw occurs.

There is also proposed a method of limiting the range of temperature change by utilizing a temperature sensor having a small time constant, such as a thermocouple element. In this case, the thermocouple element is brought into contact with the roller surface. There is a problem that the surface of the roller is damaged due to necessity, and conversely, the thermocouple element is damaged (for example, broken).

An object of the present invention is to provide an image forming apparatus capable of maintaining stable fixing conditions by accurately controlling the temperature of the fixing element of the fixing device.

[0009]

The present invention has been made based on the above problems, and an image carrier on which a latent image is formed on the basis of light corresponding to image information of a document, and this image carrier. An image forming unit including a visualization unit that visualizes the latent image formed on the sheet by supplying a developer, and a transfer unit that transfers the image of the image information of the document visualized by the visualization unit to a medium. A fixing unit including a heat transfer unit that transfers heat to the medium and a heating unit that heats the heat transfer unit; and a first state that heats the heating unit to a predetermined temperature at a rated output, When the predetermined temperature is reached, the heating means is intermittently energized so that the change amount of the predetermined temperature changes within a first target value defined around the predetermined temperature. And the heat transfer in this second state By contacting the medium with the step, the heating means is intermittently energized so that the change in the temperature of the heat transfer means changes within a second target value defined around the predetermined temperature. An image forming apparatus having a third state and an urging unit that urges the heating unit according to the third state.

Further, according to the present invention, an image carrier on which a latent image is formed based on light corresponding to image information of an original,
The latent image formed on the image carrier includes a visualization unit that visualizes the latent image by supplying a developer, and a transfer unit that transfers the image of the image information of the document visualized by the visualization unit onto a medium. A fixing unit including an image forming unit, a heat transfer unit that transfers heat to the medium, and a heating unit that heats the heat transfer unit; and a heating unit that heats the heating unit to a predetermined temperature at a rated output. When the temperature reaches a predetermined temperature and the predetermined temperature, the electric power supplied to the heating means is controlled so that the change amount of the predetermined temperature changes within the first target value defined around the predetermined temperature. A second state in which the temperature is changed, and a change in the temperature of the heat transfer means is defined around the predetermined temperature by contacting the medium with the heat transfer means in the second state. It will change within the target value An image forming apparatus is provided which has a third state in which the electric power supplied to the heating means is changed, and an urging means for urging the heating means. Further, according to the present invention, the latent image is formed on the image carrier based on the light corresponding to the image information of the document, and the developer is supplied to the latent image formed on the image carrier. An image forming means including a visualization means for visualizing and a transfer means for transferring the image of the image information of the original document visualized by the visualization means onto a medium, a heat transfer means for transferring heat to the medium, and this heat transfer. A fixing unit including a heating unit that heats the unit; a first state in which the heating unit heats the unit to a predetermined temperature at a rated output; A second state in which the heating means is intermittently energized so that the amount of change in the predetermined temperature changes within a prescribed first target value; and in this second state, the heat transfer means is connected to the heat transfer means. By contacting the medium, the heat transfer A third electric power that changes the electric power supplied to the heating means so that the change in the temperature of the above-mentioned changes within a second target value defined around the above-mentioned predetermined temperature and that energizes the heating means intermittently. There is provided an image forming apparatus having a state and a biasing unit that biases the heating unit according to the state.

Furthermore, according to the present invention, in the fixing device including heat transfer means for transferring heat to the medium and heating means for heating the heat transfer means, the heating means is
At the first state of heating to the predetermined temperature at the rated output and at the time when the predetermined temperature is reached, the amount of change in the predetermined temperature within the first target value defined around this predetermined temperature is A second state in which the heating means is intermittently urged to change, and a change in the temperature of the heat transfer means due to the contact of the medium with the heat transfer means in the second state is the predetermined state. A control method of the fixing device for controlling the temperature of the heat transfer means by a third state in which the electric power supplied to the heating means is changed so as to change within a second target value defined around the temperature. Provided.

Furthermore, according to the present invention, in the fixing device including heat transfer means for transferring heat to the medium and heating means for heating the heat transfer means, the heating means is
At the first state of heating to the predetermined temperature at the rated output and at the time when the predetermined temperature is reached, the amount of change in the predetermined temperature within the first target value defined around this predetermined temperature is A second state in which the heating means is intermittently urged to change, and a change in the temperature of the heat transfer means due to the contact of the medium with the heat transfer means in the second state. By the third state in which the electric power supplied to the heating means is changed and the heating means is intermittently energized so as to change within the second target value defined around the temperature, the heat transfer means A method of controlling a fixing device for controlling the temperature of the fixing device is provided.

[0013]

In the fixing device of the image forming apparatus according to the present invention, the heating means is intermittently provided so that the change amount of the predetermined temperature changes within the first target value in which the heating is performed at the rated output. The heat transfer means is controlled by the heat supplied from the heating means, which is controlled by the energized second state and the third state in which the electric power supplied to the heating means is changed so as to change within the second target value. Is heated to the temperature of.

Further, in the fixing device of the image forming apparatus of the present invention, the heating means is intermittently operated so that the change amount of the predetermined temperature changes within the first target value in which the heating is performed at the rated output. From the heating means controlled by the second state of energizing and the third state of energizing the heating means intermittently while changing the electric power supplied to the heating means so as to change within the second target value. The heat transfer means heats the heat transfer means to a predetermined temperature. Therefore, the degree of temperature change due to the contact of the medium with the heat transfer means is reduced.

On the other hand, in the image forming apparatus of the present invention, the heating means is intermittently energized so that the change amount of the predetermined temperature changes within the first target value in which the heating is performed at the rated output. Supplied from the heating means controlled by a second state in which the heating means is changed to a second target value and a third state in which the electric power supplied to the heating means is changed so that the heating means is intermittently energized. Since there is a fixing device that can maintain the heat transfer means at a predetermined temperature by the heat generated by the heat transfer, stable fixing conditions that are not easily affected by the temperature change due to the passage of the medium can be maintained.

[0016]

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

Referring to FIG. 1, in the image forming apparatus or copying apparatus 2, the image information recorded on the copy object, that is, the original D placed on the original table 10 is transferred to the original table 10 by the original pressing member 12. After being in close contact,
As the reflected light generated by being illuminated through the exposure lamp 14 and the reflection plate 16, the first mirror 18 of the first carriage 20, the second mirror 22 and the third mirror 24 of the second carriage 26, the lens 28, and the mirror holding A fourth mirror 30 and a fifth mirror 32 held by the frame 34,
Then, the light is passed through the folding (exposure) mirror 36 in order, and is guided to the photoconductor drum 38 to which a predetermined potential is given in advance by the charging device 40 and the peripheral area erasing LED 42.

The reflected light from the document D guided to the photosensitive drum 38, that is, image information is converted by the drum 38 into an electrostatic latent image corresponding to the image information. The electrostatic latent image on the drum 38 is developed as a toner image by the toner supplied by the developing device 44, and then transferred by the transfer device 46 from either of the paper cassettes 50a and 50b inserted in the slots 52a and 52b. Paper feed roller 54a or 54b, transport roller 56a or 56b
And is transferred to a sheet supplied via the timing roller 58.

The sheet on which the toner image is transferred is conveyed by the conveying device 6.
After being conveyed to the fixing device 62 via 0, the fixing device 6
The toner image, that is, the toner is fixed by 2 and is guided to the outside of the apparatus 2 by the discharge roller 64.

On the other hand, the photosensitive drum 38 which has transferred the toner image onto the sheet is used for the next image formation again after the charge and the toner remaining on the surface thereof are removed by the cleaning charge eliminating device 48.

When the number of copies is two or more, or when the next original is supplied, the above series of copying operations are repeated.

Next, in order to specifically show that the temperature of the roller surface of the fixing device can be controlled, the structure of the fixing device will be described in detail.

FIG. 2 shows a cross section of the fixing device taken along the direction in which the paper is passed.

The fixing device 62 includes a pair of heat rollers whose roller surfaces are in pressure contact with each other, and heats the toner held on the paper when the paper passes between the roller saws to melt the toner image. The toner image is fixed to the paper by pressing the toner image and the paper.

Referring to FIG. 2, the fixing device 62 includes an upper heat roller 62 having a main heater 62m inserted therein.
a and a lower heat roller 62b that is pressed against the upper heat roller 62a via a spring (not shown) and has an auxiliary heater 62s incorporated therein, and heats the toner held on the paper to melt the toner image. The toner image is fixed to the paper by pressing the toner image and the paper while the pressure is applied. The heater 62m and the auxiliary heater 62s
Is turned on at a predetermined timing by a heater control circuit described later. Further, the upper heat roller 62a is rotated at a predetermined speed by a fixing motor (or a motor) (not shown) via a transmission mechanism such as a gear (not shown).

According to FIG. 2, further, on the outer peripheral surface of the upper heat roller 62a of the fixing device 62, the outer peripheral surfaces of the cleaning roller 62d and the roller 62a for removing the toner on the transfer paper which may adhere to the roller 62a. Cleaning felt roller 62e that supplies silicone oil to the roller 62a to reduce toner adhesion to the roller 62a, a thermistor 62f that detects the surface temperature of the roller 62a, and an upper peeling claw 62g that peels the sheet from the upper heat roller 62a. Are arranged so as to contact the outer peripheral surface of the roller 62a. Further, a thermostat 62h for preventing abnormal heat generation of the roller 62a is arranged at a predetermined distance from the outer peripheral surface of the upper heat roller 62a (may be closely attached).

On the outer peripheral surface of the lower heat roller 62b, a cleaning felt 62i for removing unnecessary toner generated by the transfer of the toner attached to the outer peripheral surface of the upper heat roller 62a, and the paper is wound around the lower heat roller 62b. The lower peeling claw 62j that prevents the roller 62b and the thermistor 62k that detects the surface temperature of the roller 62b are arranged so as to contact the outer peripheral surface of the roller 62b.

Next, in order to specifically show that the temperature of the roller surface of the fixing device can be controlled, the various elements incorporated in the copying apparatus and the control circuits corresponding to the respective elements are provided. The electrical connection of will be described.

According to FIG. 3, the CPU as the main control unit
A ROM 72a in which data necessary for operating the apparatus 2 and a surface potential control routine, which will be described later, are written in 70, and the number of copies or the copy magnification input through the operation panel 90 (see FIG. 4). A RAM 72b used for temporarily storing numerical data and the like, and a non-volatile memory 72 for storing adjustment data input via the operation panel 90 or the total number of copies.
c is connected.

Further, the CPU 70 has an A / D converter for inputting temperature data from the heater control circuit 74 for turning on the heater 62m and the auxiliary heater 62s of the fixing device 62 at a predetermined timing and the thermistors 62f and 62k to the CPU 70. (Input circuit) and CPU 70
A D / A converter (output circuit) 78 for supplying the temperature instruction value output from the heater control circuit 74 to the heater voltage control unit is connected. The CPU 70
Further, an operation panel 90 for inputting, via the interface 80, various copy conditions, for example, instructions corresponding to the number of copies, paper size or double-sided copy.
Is also connected.

Further, the main charging portion of the charging device 40 and the transfer portion of the transfer device 46 are provided with a charging device 4 by a voltage generating portion.
The bias voltage of 0 and the developing device 44 are supplied with a voltage of a predetermined polarity by the bias voltage generation unit, and the separation unit of the transfer device 46 is supplied with a voltage of a predetermined polarity by the AC generation unit. On the other hand, the illumination lamp 14 is provided with a lamp regulator, a motor (not shown) and a scanning motor (not shown) (which may have a developing motor and a fixing motor).
Are urged by the motor drive unit at predetermined brightness and rotation speed, respectively. FIG. 4 shows an operation panel arranged on the upper front surface of the copying machine shown in FIG.

Referring to FIG. 4, the operation panel 90 is supplied with conditions for creating an image to be copied or printed out by the copying apparatus 2, for example, the number of copies, a copy magnification or image data to be copied. It has a plurality of input keys for designating the supply source and a panel for displaying the operating state of the device 2.

For example, from the center right of the operation panel 90, numbers 0 to 9 can be input, and a number key 92 (92a) for inputting the number of copies or the copy magnification.
-92j), the all clear key 9 which clears all input conditions and suspends the current operation.
4a, a print key 94b for outputting an operation start signal for starting the copying operation or the main body 2 side of the printout, and a clear key 94c for returning the condition input through the number keys 92 to "0". It is arranged.

At the center of the operation panel 90, an original size input key 96a for an automatic magnification mode for automatically setting the copy magnification by inputting the size of the original D and the size of the recording paper, recording paper size input Key 96
b, a magnification input key 96 for arbitrarily setting the copy magnification
c and a density adjustment key 96d for inputting data for changing the shade of the copied image or the printed image.

The operation panel 90 also has a mode for setting a copy mode that can be provided by the copying apparatus 2, for example, double-sided copy, border erasing, binding margin, masking / trimming, or compositing / editing. Setting key 96
e to 96i are arranged.

The operation panel 90 is further provided with an LED panel 98a for indicating the operation of the copying apparatus 2 and an LCD panel 98b for displaying a description of the operating method of the copying apparatus 2 or a toner or paper supply timing.

Next, the first method for maintaining the temperature of the surfaces of the upper heat roller and the lower heat roller of the fixing device shown in FIG. 2, that is, the outer peripheral surfaces within a predetermined range will be described in detail.

In FIG. 5, a heater control circuit 74, a main heater 62m, a thermistor 62f, and an upper heat roller 62a.
And the like are representative circuit diagrams (the lower heat roller 62b, the thermistor 62k, and the auxiliary heater 62s are substantially the same, and therefore omitted here).
.

When a power switch (not shown) is turned on, the temperature control in the warm-up mode is first started via the CPU 70 according to the initial data stored in the ROM 72a.

Outputs from the cover switch 102 and the paper sensor (not shown) in the copying apparatus 2 are input to the input port IN1 of the CPU 70, and there is no problem in energizing the main heater 62m and the auxiliary heater 62s, that is, supplying power. It is confirmed.

Then, under the control of the CPU 70, a message such as "please wait for a while" is displayed on the message display section 98b of the operation panel 90, and then the CP
The main relay 104 is turned on in response to an instruction from the output port OUT1 of U70, and the main heater 62m of the upper heat roller 62a is heated by the control of the solid state relay 106. The auxiliary heater 62m of the lower heat roller 62b is also heated in the same manner. At this time, the solid-state relay 106 is operated by full-wave full-phase control, that is, control for simply turning on / off each heater 62m (62s). In addition, each roller 62a and 6
2b, so that the temperature of part of the surface does not protrude,
It is rotated at a predetermined speed (for example, 1/2 of copying).

The thermistor 62f (62k) in contact with the surface of the heat roller 62a (62b) measures the roller surface temperature T _H at the time when power is supplied, and is preset through the CPU 70. (R
The difference from the control temperature T _Ho (stored in the OM 72a) is obtained, and the energization time t for energizing the heater 62m (62s) is defined.

The energization time t is t = k ₁ f, where k ₁ is a proportional constant, f is a function predetermined according to the roller heat capacity, the heating capacity of the heater (generally wattage), the amount of heat radiation, etc. It is _{calculated by} (T _Ho − T _H ). In addition, it can be approximately calculated also by t = k ₁ (T _Ho −T _H ).

After a lapse of "t" seconds, "Ready to copy" is displayed on the message display portion 98b of the operation panel 90, and secondly, the ready mode (copyable state maintaining mode)
The temperature control by is started.

In the ready mode, the thermistor 62f (6
It is determined whether the average value T _Have of the temperature measurement values output from 2k) falls within the range of “± a” with respect to the control temperature T _Ho . That is, the solid-state relay 1 that was operated in full-wave full-phase control in warm-up mode
The average value T _Have corresponding to the lighting cycle of the heater 62a (62b) is detected by turning ON / OFF the 06 at a predetermined timing according to the ready standard sequence stored in the ROM 72a. In addition, "a" is an allowable deviation with respect to the control temperature T _Ho , and its magnitude is
It is determined experimentally or empirically, and is regulated to, for example, ± 10 ° C.

The average value T _Have is "±" with respect to the control temperature T _Ho .
If it falls within the range of “a”, the ready mode is maintained as it is until a copy start signal is input through the operation panel 90.

On the other hand, the average value T _Have is the control temperature T
When it exceeds the range of “± a” with respect to _Ho , the mode shifts to the ready deviation contraction mode. That is, the time τ when the solid-state relay 106 operated in full-wave full-phase control is turned on (that is, the timing pulse for turning on each heater 62m (62s) is input by "1", so that the power is supplied. Is a time period which is usually defined as 2 seconds), and the energization time ατ is changed corresponding to the magnitude of the deviation, α is a coefficient serving as an index for setting the temperature deviation a, and , Τ are changed to constants defined by the heat capacity of the roller). In addition, the coefficient M indicating the amount of electric power supplied per unit time is, here, “warm-up mode = ready mode = copy mode =
1 ”.

At this time, the magnitude of "α" is obtained by α = α _Ro n, where n is a margin factor. Note that the margin ratio “n” is 1.0
5, 1.10, 1.15 and 1.20. In addition, “α _Ro ” is an index that is experimentally or empirically required in the standard mode, and is α _Ro for identification.
, And is defined in the range of 0.3 to 0.4, for example.

Therefore, the time ατ during which the solid state relay 106 is turned on in the ready deviation contraction mode is
1.05α _Ro τ, 1.10α _Ro τ, ... In order, until the average value T _Have falls within the range of “± a” with respect to the control temperature T _Ho , and finally it is changed. The ready mode is maintained based on the acquired data. That is,
Normally, the length of the energization time Mτ defined as 2 seconds is as shown in FIG.
As shown in (a), 1.05α _Ro τ, 1.10α
It is changed little by little in the order of _Ro τ ,. The final value of ατ obtained in this way, that is, the data held without being changed, is stored in the nonvolatile memory 72c (R
Some AM72b can be held unless the outlet of the device is unplugged).

On the other hand, the heater 62m by the ready mode
A copy start signal was input from the operation panel 90 while the sequence control of (62s) was performed (print key 9
4b is turned on), the mode is changed to the copy mode.

In the copy mode, the copy standard sequence based on the copy condition input by the operation panel 90 prior to turning on the print key 94b, that is, the copy sheet size A, the copy mode (double-sided copy / single-sided copy) S, and the number of copies m. Is a non-volatile memory 72c or ROM 72a
The heater 62m (62s) is controlled at a predetermined timing according to the read copy standard sequence. That is, it is determined whether the average value T _Have falls within the range of “± b” with respect to the control temperature T _Ho . Incidentally, "b" is a deviation permissible in the copy mode (during copying operation) with respect to the control temperature T _Ho , and is experimentally or empirically obtained, and is regulated to ± 20 ° C. Here, when the average value T _Have falls within the range of “± b” with respect to the control temperature T _Ho , the copy mode, that is, the copying operation is maintained as it is, and a series of copying operations is performed until all copying is completed. And the copy standard sequence associated with each of the heaters 62m (62s) is continued.

On the other hand, the average value T _Have is the control temperature T
When it exceeds the range of “± b” with respect to _Ho , the mode shifts to the copy deviation contraction mode. That is, during the time τ when the solid state relay 106 is turned on, N is the heater 62.
m 2 (62 s) is the number of times of turning on, k ₂ is a proportional constant, and g (m, A) is a copy paper size A and the number of copies m.
When the required heat capacity is defined by, N = k ₂ g (m, A) is transformed into Nτ if it is the amount of control times obtained.

[0053] Here, as "Nτ = ατ", applying the ready deviation contraction mode to the copy deviation contraction mode, the size of the "alpha" is, alpha = alpha _Co n
Can be rewritten as The margin ratio “n” is selected from 1.05, 1.10, 1.15, 1.20 and 1.25. Further, “α _Co ” is an index obtained experimentally or empirically in the standard mode, and is shown as α _Co for identification, and is, for example, 0.8
To 0.9.

Therefore, in the copy deviation contraction mode, the time ατ for turning on the solid state relay 106 is
The average value T _Have is changed in order of 1.05α _Co τ, 1.10α _Co τ, and so on until the average value T _Have falls within the range of “± b” with respect to the control temperature T _Ho , and finally changed. The ready mode is maintained based on the acquired data. That is,
The length of the energization time Mτ is changed little by little like the ready deviation contraction mode (see FIG. 7 (a)). Note that the final value of ατ, that is, the final value of Nτ obtained in this way, that is, the data that is retained without being changed, may be retained in the nonvolatile memory 72c (RAM 72b as well as in the ready mode unless the outlet of the device is unplugged). There is).

Next, the second method for maintaining the temperature of the surfaces of the upper heat roller and the lower heat roller of the fixing device shown in FIG. 2, that is, the outer peripheral surfaces within a predetermined range will be described in detail.

In the first method described above, the solid-state relay 106 is operated by full-wave full-phase control in any of the warm-up mode, ready mode, and copy mode heater control mode, and the heater lighting time τ.
Is a method of changing the length of the roller according to the temperature of the surfaces of the rollers 62a and 62b.

On the other hand, in the second method described below, in the ready mode, the electric power supplied while each heater 62m (62s) is turned on by the heater lighting time τ (energization time in phase). Ratio) M, 30% to 50
%, And the energization time ratio M in the copy mode,
This is a method of changing it from 80% to 100%.

More specifically, referring to FIG. 5 again, it goes without saying that the solid state relay 106 can change the magnitude of the output power based on the timing at which the input trigger pulse is supplied. .

Therefore, the energization time τ for turning on the heater 62m (62s) (the time for energization by inputting a timing pulse of "1", usually 2
(Specified in seconds) can be maintained at an optimum value by changing the size of “M” while maintaining a constant value. Needless to say, this type of control method is generally called phase control. Further, various known control circuits as shown in FIG. 6 can be used as an example of the phase control circuit.

More specifically, in the ready mode,
In the energization time ατ already described in the first method, regarding Mατ in the second method corresponding to M = 1, “M = 0.3
"0, 0.40 and 0.50" are sequentially substituted, and "α = α _Ro n, n = 1.0" until the average value T _Have falls within the range of "± a" with respect to the control temperature T _Ho .
5, 1.10, 1.15, 1.20 ”in order, the surface temperature of the roller is controlled within the optimum temperature range (see FIG. 7 (b)). Note that “Mα _o (vertical axis)” in FIG. 7B is “Mα _o ” in the ready mode.
FIG. 7 shows a representative of “α _Ro ” and “M α _Co ”.
As is apparent from (c), it is a chart showing the timing of phase control, that is, the magnitude of “M”. Further, the final value of Mατ obtained in this way, that is, the data held without being changed is stored in the nonvolatile memory 72c.

On the other hand, in the copy mode, regarding the energization time Mατ, that is, MNτ, "M = 0.80,0.
"90 and 1.00" in order, and "α = α _Co n, n = 1.05,1.1 until the average value T _Have falls within the range of" ± b "with respect to the control temperature T _Ho .
By sequentially setting "0, 1.15, 1.20, 1.25", the surface temperature of the roller is controlled within the optimum temperature range. The final value of Mατ, that is, the data held unchanged is similarly stored in the nonvolatile memory 72c.

Next, the third method for maintaining the temperature of the surfaces of the upper heat roller and the lower heat roller of the fixing device shown in FIG. 2, that is, the outer peripheral surfaces within a predetermined range will be described in detail.

The first method described above operates the solid-state relay 106 by full-wave full-phase control in any of the heater control modes of warm-up mode, ready mode and copy mode, and the second method. Is a constant energization time Mτ (time that is energized by inputting a timing pulse of "1", which is usually defined as 2 seconds) for the heater control mode in the ready mode and the copy mode. While maintaining the value, the size of “M” is extended to 30% to 50%,
In the copy mode, the energization time ratio M is changed to 80% to 100%.

On the other hand, in the third method shown below, in the ready mode or the copy mode, particularly in the copy mode, regarding the heater lighting time τ, that is, Mατ, the heater 62m (62s) is turned on. This is a method of changing the supplied power (energization time ratio in phase) M and also changing the length of the energization time τ.

In detail, referring again to FIG. 5, the solid-state relay 106 is capable of changing the magnitude of the output power based on the timing at which the input trigger pulse is supplied, and further, the output power is constant. Each heater 62m (62s) can be turned on in the unit of time.

That is, as already described in the first method and the second method, in the ready deviation contraction mode, when the heater lighting is indicated by Mατ, the average value T _Have
Until the temperature falls within the range of “± a” with respect to the control temperature T _Ho ,
While substituting "M = 0.30, 0.40 and 0.50" in order, "α = α _Ro n, n = 1.
05, 1.10, 1.15, 1.20 ”in order to change the magnitude of electric power and to input“ 1 ”as a timing pulse for lighting each heater 62m (62s). The time period τ that is energized by
That is, by changing the actual energizing time Mατ in small increments, it is possible to further reduce changes in the temperature of the roller surface.

In the copy deviation contraction mode,
_{Until the} average value T _Have falls within the range of “± b” with respect to the control temperature T _Ho , “M = 0.80, 0.90 and 1.0.
“0” in order, and further, “α = α _Co n, n
= 1.05, 1.10, 1.15, 1.20, 1.
"25" is set in order to change the magnitude of the electric power, and "nτ = 1.05τ, 1.10, ...
Similarly, the change in the temperature of the roller surface can be reduced by changing the order of "...". Further, the final value of Mατ obtained in this way, that is, the data held without being changed is stored in the nonvolatile memory 72c.

Since the temperature of the surface of the roller is remarkably changed while the sheet on which the image is recorded (the toner image is transferred) is passing between the rollers, that is, during the copying operation, This third method may be used only in the copy deviation contraction mode. The data stored in the non-volatile memory 72c is called in the next operation mode and put in the control value.

[0069]

As described above, according to the fixing device control method of the present invention, the change amount of the predetermined temperature changes within the first state of heating at the rated output and the first target value. A second state in which the heating means is intermittently urged to
The heat transfer means can be maintained at a predetermined temperature by the heat supplied from the heating means controlled by the third state in which the electric power supplied to the heating means is changed so as to change within the target value. Further, a first state in which heating is performed at a rated output, a second state in which the heating means is intermittently energized so that the amount of change in the predetermined temperature changes within the first target value, and a second target The heat transfer means is controlled to a predetermined temperature by the heat supplied from the heating means which is controlled by a third state in which the electric power supplied to the heating means is changed so as to keep within a value and the heating means is intermittently energized. Can be maintained at

On the other hand, in the image forming apparatus of the present invention, the heating means is intermittently energized so that the change amount of the predetermined temperature changes within the first target value in which the heating is performed at the rated output. Supplied from the heating means controlled by a second state in which the heating means is changed to a second target value and a third state in which the electric power supplied to the heating means is changed so that the heating means is intermittently energized. Since there is a fixing device that can maintain the heat transfer means at a predetermined temperature by the heat generated by the heat transfer, stable fixing conditions that are not easily affected by the temperature change due to the passage of the medium can be maintained.

The main heater and the auxiliary heater for heating each heat roller of the fixing device have a warm-up mode in which each heater is heated to the control temperature by the rated output by the heater control circuit, and the change amount of the control temperature is the first. The ready mode in which each heater is intermittently energized to change within the target value, and the electric power supplied to each heater is changed so that the change amount of the control temperature changes within the second target value and each heater is changed. The surface temperature of each roller is controlled to be maintained within a certain range by the copy mode in which the roller is intermittently energized.

Therefore, even when a heat roller having a small heat capacity is used, it is possible to prevent the fixing nails from being damaged due to improper fixing or rapid heating.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a copying machine in which an embodiment of the present invention is used.

FIG. 2 is a sectional view showing in detail a fixing device of the copying apparatus shown in FIG.

FIG. 3 is a schematic block diagram showing electrical connections between various elements incorporated into the copying machine shown in FIG. 1 and corresponding control circuits.

FIG. 4 is a schematic plan view showing an input device (operation panel) of the copying machine shown in FIG.

5 is a schematic circuit diagram showing an example of a heater control circuit shown in FIG.

6 is a schematic circuit diagram showing an example of a phase generation unit of a heater lighting control unit of the heater control circuit shown in FIG.

FIG. 7 is a diagram showing an example of phase control by the phase generator shown in FIG.

[Explanation of symbols]

2 ... Copier, 10 ... Document table, 12 ... Document holder, 14 ... Illumination lamp, 16 ... Reflector, 18 ...
First mirror, 20 ... First carriage, 2
2 ... second mirror, 24 ... third mirror,
26 ... second carriage, 28 ... imaging lens,
30 ... 4th mirror, 32 ... 5th mirror,
34 ... holding frame, 36 ... folding mirror,
38 ... Photosensitive drum, 40 ... Charging device,
44 ... Developing device, 46 ... Transfer device, 48 ... Cleaning neutralization device, 60 ... Conveying device, 62 ... Fixing device, 62a ... Upper heat roller, 62b ...
Lower heat roller, 62d ... Cleaning roller,
62e ... Cleaning felt roller, 62f ... Thermistor, 62g ... Upper peeling claw, 62h ...
Thermostat, 62i ... Cleaning felt, 62j ... Lower peeling nail, 62k
… Thermistor, 62m… Main heater,
62s ... auxiliary heater, 64 ... discharge roller,
70 ... CPU, 72a ... ROM,
72b ... RAM, 72c ... nonvolatile memory,
74 ... Heater control circuit, 76 ... A / D converter (input circuit), 78 ... D / A converter (output circuit), 80 ... Interface, 90 ...
Operation panel, 102 ... Cover switch, 1
04 ... Main relay, 106 ... Solid state relay.

Claims (6)

[Claims] 1. An image carrier on which a latent image is formed based on light corresponding to image information of an original, and a latent image formed on the image carrier is visualized by supplying a developer. Means and a transfer means for transferring the image of the image information of the document visualized by the visualization means to a medium, a heat transfer means for transferring heat to the medium, and a heat transfer means for heating the heat transfer means. A fixing unit including a heating unit for controlling the heating unit, a first state in which the heating unit is heated to a predetermined temperature at a rated output, and when the predetermined temperature is reached, the predetermined temperature is defined as the center. A second state in which the heating means is intermittently energized so that the amount of change in the predetermined temperature changes within a first target value, and the medium contacts the heat transfer means in the second state. Change the temperature of the heat transfer means. A third state in which the heating means is intermittently energized so as to keep within a second target value defined around the predetermined temperature, and an energizing means for energizing the heating means. An image forming apparatus having: 2. An image carrier on which a latent image is formed based on light corresponding to image information of an original, and a visualization for visualizing the latent image formed on the image carrier by supplying a developer. Means and a transfer means for transferring the image of the image information of the document visualized by the visualization means to a medium, a heat transfer means for transferring heat to the medium, and a heat transfer means for heating the heat transfer means. A fixing unit including a heating unit for controlling the heating unit, a first state in which the heating unit is heated to a predetermined temperature at a rated output, and when the predetermined temperature is reached, the predetermined temperature is defined as the center. A second state in which the electric power supplied to the heating means is changed so that the amount of change in the predetermined temperature changes within a first target value, and the medium contacts the heat transfer means in the second state. Of the heat transfer means And a third state in which the electric power supplied to the heating means is changed so that the change in temperature changes within the second target value defined around the predetermined temperature, and the heating means is energized. And an image forming apparatus having a biasing means. 3. An image carrier on which a latent image is formed based on light corresponding to image information of an original, and a visualization for visualizing the latent image formed on the image carrier by supplying a developer. Means and a transfer means for transferring the image of the image information of the document visualized by the visualization means to a medium, a heat transfer means for transferring heat to the medium, and a heat transfer means for heating the heat transfer means. A fixing unit including a heating unit for controlling the heating unit, a first state in which the heating unit is heated to a predetermined temperature at a rated output, and when the predetermined temperature is reached, the predetermined temperature is defined as the center. A second state in which the heating means is intermittently energized so that the amount of change in the predetermined temperature changes within a first target value, and the medium contacts the heat transfer means in the second state. Change the temperature of the heat transfer means. A third state in which the electric power supplied to the heating means is changed so that the temperature changes within a second target value defined around the predetermined temperature, and an urging means for urging the heating means. An image forming apparatus having: 4. A fixing device including heat transfer means for transferring heat to a medium and heating means for heating the heat transfer means, wherein the heating means heats the heating means to a predetermined temperature at a rated output. When the temperature reaches a predetermined temperature, the heating means is intermittently energized so that the change amount of the predetermined temperature changes within a first target value defined around the predetermined temperature. And a second target in which a change in the temperature of the heat transfer means due to the contact of the medium with the heat transfer means in the second state is defined around the predetermined temperature. A method for controlling a fixing device, wherein the temperature of the heat transfer means is controlled by a third state in which the electric power supplied to the heating means is changed so as to keep within a value. 5. An image carrier on which a latent image is formed based on light corresponding to image information of an original, and a visualization for visualizing the latent image formed on the image carrier by supplying a developer. Means and a transfer means for transferring the image of the image information of the document visualized by the visualization means to a medium, a heat transfer means for transferring heat to the medium, and a heat transfer means for heating the heat transfer means. A fixing unit including a heating unit for controlling the heating unit, a first state in which the heating unit is heated to a predetermined temperature at a rated output, and when the predetermined temperature is reached, the predetermined temperature is defined as the center. A second state in which the heating means is intermittently energized so that the amount of change in the predetermined temperature changes within a first target value, and the medium contacts the heat transfer means in the second state. Change the temperature of the heat transfer means. And a third state in which the electric power supplied to the heating means is changed and the heating means is intermittently energized so that the temperature changes within a second target value defined around the predetermined temperature. An image forming apparatus comprising: a biasing unit that biases the heating unit. 6. A fixing device comprising a heat transfer means for transferring heat to a medium and a heating means for heating the heat transfer means, wherein the heating means heats the heating means to a predetermined temperature at a rated output. When the temperature reaches a predetermined temperature, the heating means is intermittently energized so that the change amount of the predetermined temperature changes within a first target value defined around the predetermined temperature. And a second target in which a change in the temperature of the heat transfer means is defined around the predetermined temperature by contacting the medium with the heat transfer means in the second state. A method of controlling a fixing device, wherein the temperature of the heat transfer means is controlled by a third state in which the electric power supplied to the heating means is changed so as to change within a value and the heating means is intermittently energized.