JP2001236126A - Warm-up time predicting method of heating body of heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a warm-up time predicting method of a heating body of a heating device capable of predicting time length from start of heating to reach to target temperature of the heating body with high accuracy and contriving shortening of first print time and energy saving while securing fixability and an image forming device. SOLUTION: Length of heating time from the start of heating to the reach to the target temperature of the heating body 21 is predicted based on a linear function to use an inverse number of a detected voltage value of a thermistor 22 and detected time of the thermistor 22 as variables, transportation start time of a recording material P is decided so as to satisfy t3-5<t4<t3 when the predicted length of heating time from the start of heating to the reach to the target temperature of the heating body 21 is defined as t3, length of transportation time from the start of heating to irruption of the tip in the transporting direction of the recording material P in a nip is defined as t4 and time length to be required for one rotation of a pressurization roller 25 is defined as t5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a heating element heating time of a fixing device in which a recording medium carrying an image is held and conveyed by a film and a pressure member at the nip and heated and pressed, and an image forming apparatus. It is about.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic system, an electrostatic recording system or the like, a visible image formed and carried on a surface of a recording material as a recording medium by an appropriate image forming process means is heated. 2. Description of the Related Art An image forming apparatus provided with a heating device for fixing and improving surface properties by heating is known and is in practical use.

As a heating device provided in such an image forming apparatus, a heat roller system is frequently used, and recently, a film heating system heating device has been put to practical use.

The heating device of the heating roller type includes a rotating heating roller (fixing roller, heat roller) having a built-in heat source such as a halogen heater and a rotating pressure roller pressed against the heating roller. A recording material as a recording medium to be heated is introduced into the press-contact nip portion, and the recording material is nipped and conveyed. (Or heat treatment). The heat roller is heated by a built-in heater, and power supply to the heater is controlled by a temperature control system including a temperature detecting member so that the surface temperature of the roller is maintained at a predetermined temperature.

However, this heating device of the heat roller type is
Since the heat capacity of the roller is large, it takes time for the roller to reach a predetermined temperature (rise time, warm-up time, wait time). The temperature must be controlled.

On the other hand, a heating apparatus of a film heating system is disclosed in JP-A-63-313182 and JP-A-2-15787.
8, JP-A-4-44075, JP-A-4-4-2
No. 04980, which has a heating element (generally a ceramic heater), a heat-resistant film that slides in contact with the heating element, and a pressure element that presses against the heating element via the film. Then, a recording material as a recording medium is sandwiched and conveyed by the film and the pressure body in a nip formed by the heating body and the pressure body, and heat from the heating body is applied to the recording material via the film. It is a heating device configured.

FIG. 8 is a sectional view of a fixing device as an example of such a film heating type heating device.

As shown in FIG. 8, the fixing device includes a heating element 102, a fixing film 103 as a heat-resistant film having a cylindrical three-layer structure, and a pressure roller 104 as a pressure element.
And a thermistor 107 as a temperature detecting means.

The heating element 102 has a heating element 108, which is supplied with power from a power source (not shown) and generates heat, is formed on one surface of a ceramic substrate, and the glass layer 10 serving as a protective layer is formed thereon.
9 are coated.

[0010] The thermistor 107 is mounted on the other surface of the ceramic substrate of the heating element 102.
Temperature is detected. Thermistor 107
CPU as control means so that the detected temperature of the target becomes the target temperature
Thus, the triac is driven, and the amount of power supplied to the heating element 108 of the heating element 102 is controlled.

The fixing film 103 adopts a three-layer structure of a base layer as an innermost layer, a conductive primer layer as an intermediate layer, and a top layer as an outermost layer. . In the base layer, the fixing film 103
Layer that is responsible for mechanical properties such as torsional strength and smoothness of
Polyimide, polyamide imide, PEEK, PES, P
It is made of resin such as PS. The conductive primer layer is a conductive layer in which conductive particles such as carbon plaque are dispersed, and also serves as an adhesive for bonding the third layer and the base layer. The above-mentioned top layer is designed to have an optimum resistance value and film thickness so as not to cause various image defects.

The fixing film 103 is formed of a heat-resistant resin such as PPS, liquid crystal polymer, etc.
Are guided by a heater supporting member 101 as a supporting member to promote smooth rotation.

The heating member supporting member 101 has a rigid stay which is suppressed from being deformed by creep by a fixing stay 106 made of a metal such as iron or aluminum.

The pressure roller 104 includes a metal core 104 a made of aluminum, cast iron, or the like, a heat-resistant elastic body 104 b such as silicon rubber covering the metal core 104 a, and a toner formed on the surface of the pressure roller 104. And a coating of a fluororesin such as PFA, PTFE, FEP or the like for improving the releasability of the resin.

Further, the pressure roller 104 is used for the fixing film 1.
03 is pressed against the heating element 102 through the pressurizing member N, and a fixing nip N is formed by the pressed part.
4a is driven to rotate and the fixing film 1 is fixed at the fixing nip.
The rotation driving force is transmitted to the fixing film 103 and the fixing film 103 is driven to rotate.

Recording material P as recording medium carrying toner T
Denotes a transfer roller (not shown) and a photosensitive drum (not shown)
The toner T is guided to the fixing nip by the fixing entrance guide 105, and is pressed and heated on the recording material at the fixing nip, and is softened and adhered to the recording material to be permanently fixed.

[0017]

In recent years, in an image forming apparatus adopting the above-described electrophotographic system or the like, the first sheet is discharged after receiving a print signal with the speeding up of other information devices. It is required to shorten a first print time (hereinafter, referred to as FPT), which is a time length required until the first print time.

Normally, in a fixing device of a heat roller type or the like, the temperature of a fixing device (heat roller or the like) is controlled at a certain temperature during standby, for example, 150 ° C., and the temperature difference from the fixing temperature of 180 ° C. during printing is determined. Although the time from when a print signal is input to when the fixing device reaches a predetermined temperature is shortened, it is not preferable because standby power is large.

On the other hand, in the film heating method, since the heat capacity of the fixing device is small and the temperature rises quickly, it is possible to make the FPT fast while minimizing standby power. If the input voltage fluctuates or the resistance value of the resistance heating element layer of the fixing device fluctuates, the fusing device power fluctuates or the time required for the fusing device to reach a predetermined temperature depending on the temperature of the atmosphere increases. Change. For example, when the recording material reaches the fixing device in a low-temperature environment or a low-voltage input, the fixing device has not yet reached the fixing temperature, causing a fixing defect,
There is a possibility that unfixed toner on the output image may stain the user's hand, or cause problems such as transfer of the toner image to another print.

To cope with this problem, Japanese Patent Application Laid-Open No. 08-76
636 etc., the heating time of the heating element of the fixing device is predicted,
A configuration has been proposed in which the conveyance timing of the recording material is changed in a low-temperature environment or a low-voltage input. However, the above publication specifically describes only a method of estimating the temperature rise time of the heating element by estimating the temperature after energizing the heating element for a certain period of time. There is no proposal for a practical method. For this reason, in the method of estimating the temperature rise time based on the temperature after energizing the heating element for a certain period of time, in the case of a hot start or the like, the FPT becomes longer than necessary until the inside of the pressure roller is warm even if the heater is cold. Had become.

Therefore, according to the present invention, the length of time from the start of heating of the heating element to the arrival of the target temperature can be predicted with high accuracy, and the first print time can be shortened and energy can be saved while securing the fixing property. It is an object of the present invention to provide a method for estimating a heating element heating time of a heating device and an image forming apparatus.

[0022]

According to the present application, the object is to provide a heating element that generates heat by receiving electric power from a power supply, an endless belt-shaped rotatable film that slides in contact with the heating element,
A pressurizing body that forms a nip and rotates by being in pressure contact with the heating body through the film, and heats and presses the recording medium carrying the image by nipping and transporting the recording medium between the nip and the film and the pressurizing body. What is claimed is: 1. A heating element heating time estimating method for a heating device, comprising: a heating device configured to detect a temperature of a heating member; and a power supply from a power supply to the heating member such that a temperature detected by the temperature detecting device reaches a target temperature. Control means for controlling the temperature of the heating element, wherein the temperature detecting means is a thermistor whose resistance value changes according to the temperature of the heating element. The temperature of the thermistor is detected as a voltage value at any two detection times up to and the reciprocal of the detection voltage value of the thermistor and the detection time of the thermistor are used as variables to determine the thermistor at the two detection times. The relationship of the linear function is obtained by connecting the reciprocal of the detected voltage value, and the voltage value of the thermistor corresponding to the target temperature of the heating element is substituted into the linear function, and the heating from the start of heating the heating element to the target temperature is reached This is achieved by the first invention in which the time length is calculated and predicted.

According to the present application, the above object is achieved according to the first aspect, wherein the heating time length of the heating element is a time length from the start of heating of the heating element to the detection time of the thermistor, t1,
t2, the heating time length from the start of heating of the heating body to the arrival of the target temperature is t3, and the time length from the start of heating of the heating body to t1, t
The detected voltage of the thermistor after 2 passes is V1, V
2. When the detected voltage of the thermistor at the target temperature of the heating element is V3, t3 = ((1 / V3-1 / V1)
× t2- (1 / V3-1 / V2) × t1) / (1 / V2
(1/1 / V1).

Further, according to the present application, the above object is achieved in the first invention or the second invention, wherein the pressing body has an elastic layer, and the thermal conductivity of the elastic layer is 4.1868 × 10 ^-2 W /
(MK) or more 12.5604 × 10 ^-2 W / (mK)
The invention is also achieved by a third invention which is as follows.

According to the present application, the object is to provide a heating element that generates heat by receiving power from a power supply, an endless belt-shaped rotatable film that slides in contact with the heating element, A pressurizing body that rotates by forming a nip by pressing against the heating body, and conveys the recording medium carrying an image conveyed from a predetermined position in the image forming apparatus by the nip by a film and a pressurizing body. An image forming apparatus comprising a heating device for heating and pressurizing, wherein the heating device is configured to detect a temperature of a heating body, and a power supply to the heating body such that the temperature detected by the temperature detection means becomes a target temperature. And an estimating means for estimating a heating time length from the start of heating of the heating element to the arrival of the target temperature, and the estimating means sets the heating time length to t3. Heating open When conveying direction leading end of the recording medium was conveyed time t4, the time required length of the pressing body rotates once t5 until enters the nip from, t3-t5
The present invention is also achieved by the fourth invention in which the conveyance start time from the predetermined position of the recording medium can be determined so as to satisfy <t4 <t3.

Further, according to the present application, the object is to provide a heating element that generates heat by receiving electric power from a power source, a heat-resistant endless belt-shaped rotatable film that slides in contact with the heating element, A pressurizing body that forms a nip by being pressed against the above-mentioned heating body through the nip and rotates at a predetermined speed, and a recording medium that is conveyed from a predetermined position in the image forming apparatus and carries an image is processed by the nip into a film and a pressurized medium. What is claimed is: 1. An image forming apparatus, comprising: a heating device for heating and pressurizing by sandwiching and conveying by a pressure body, wherein the heating device detects a temperature of the heating body, and a temperature detected by the temperature detection device is a target temperature. And a control unit for controlling the power from the power source to the heating element, wherein the heating apparatus is configured to perform the heating element heating time prediction method according to any one of the first to third inventions. Eyes from the start of heating The heating time until the temperature is reached is predicted, and the start time of the recording medium can be determined so that the leading end of the recording medium in the conveying direction enters the nip in synchronization with the arrival of the target temperature based on the predicted heating time. This is also achieved by the fifth invention.

Further, according to the present application, the above object is achieved in the fifth aspect, in which the conveyance start time of the recording medium is a predicted heating time from the start of heating of the heating element to a target temperature reaching t3, Assuming that the transport time from the start of heating to the time when the leading end of the recording medium in the transport direction enters the nip is t4, and the length of time required for the pressurizing member to make one rotation is t5, t3-t
This is also achieved by the sixth invention in which determination can be made to satisfy 5 <t4 <t3.

Further, according to the present application, the above object is achieved in the fourth invention or the sixth invention, wherein the target temperature is a predetermined heating time length from the start of heating of the heating element to the arrival of the target temperature. If the heating time length is equal to or longer than the target temperature, the recording medium is reset to be higher than the target temperature, and the recording medium conveyance start time can be determined by re-estimating the heating time t3 at the reset target temperature. This is also achieved by the seventh invention.

According to the present application, the above object is achieved according to any one of the fourth to seventh inventions, wherein the pressure body has an elastic layer, and the heat conductivity of the elastic layer is 4. 1868 × 10
^-8 W / (m · K) or less.

That is, according to the first aspect of the present invention, the target temperature is reached from the start of heating of the heating element based on a linear function having the inverse of the voltage detected by the thermistor and the detection time of the thermistor as variables. The heating time length up to is calculated.

Further, in the second invention according to the present application, the target temperature is reached from the start of heating of the heating element based on a linear function having the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor as variables. The heating time length up to is calculated.

Further, in the third invention according to the present application, by adjusting the thermal conductivity of the elastic layer of the pressurizing member, the primary of which the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor are variables. The linearity of the equation function is maintained, and the heating time length from the start of heating of the heating element to the arrival at the target temperature is calculated based on the linear equation function.

In the fourth invention according to the present application, the leading end of the recording medium in the transport direction enters the nip during a period from a time t5 before the heating element reaches the target temperature to the time when the target temperature is reached. The preheating of the pressurizing body and the heat from the heating body are applied to the recording medium.

Further, in the fifth invention according to the present application, the target temperature is reached from the start of heating of the heating element on the basis of a linear function using the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor as variables. The heating time length up to is calculated,
The recording medium carrying the image enters the nip in synchronization with the heating time.

In the sixth invention according to the present application, the target temperature is reached from the start of heating of the heating element based on a linear function using the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor as variables. The heating time length up to the target temperature of the heating element is calculated, and the leading end in the conveyance direction of the recording medium enters the nip during a period from a time length t5 before the target temperature reaches the target temperature to a time point when the target temperature is reached. Preheating and heat from the heating element are applied to the recording medium.

Further, in the seventh invention according to the present application, when the predicted heating time length t3 is equal to or longer than the predetermined heating time length, the target temperature is reset to be higher than the target temperature. At the same time, the leading end in the conveyance direction of the recording medium enters the nip during a period from the time t5 before the target temperature of the heating body reaches the target temperature to the time when the target temperature is reached, and the preheating of the pressurizing body and the heat from the heating body are reduced. Is given to the recording medium.

According to the eighth aspect of the present invention, the leading end of the recording medium in the transport direction enters the nip during a period from a time t5 before the heating element reaches the target temperature to the time when the target temperature is reached. Then, the preheating of the pressurizing body and the heat from the heating body, in which the thermal conductivity of the elastic layer is optimized, are applied to the recording medium.

[0038]

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

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic sectional view showing an example of the image forming apparatus according to the present embodiment.

The image forming apparatus according to the present embodiment has the configuration shown in FIG.
1, a photosensitive drum 1, a charging roller 2, a laser exposure device 3, a reflection mirror 4, a developing sleeve 5, a toner container 7 containing a toner 6, a transfer roller 8, a cleaning blade 10, a waste toner container 11, a heating device Barrel fixing device 1
2, a paper cassette 13 containing a recording material P as a recording medium such as paper, a paper feed roller 14, a separation pad 15, a high-voltage power supply 16, and the like.

In this image forming apparatus, first, the photosensitive drum 1 rotates in the direction of the arrow, and the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 supplied with power from the high voltage power supply 16. The laser light emitted from the laser exposure device 3 is reflected by the reflection mirror 4 and irradiates the photosensitive drum 1 to form an electrostatic latent image on the photosensitive drum 1.

The toner 6 in the toner container 7 receives an appropriate amount of toner and is carried on the developing sleeve 5 with the rotation of the developing sleeve 5, and then is supplied onto the photosensitive drum 1, and is supplied to the photosensitive drum 1. The electrostatic latent image adheres to the electrostatic latent image on the drum 1 and is developed to be visualized as a toner image.

On the other hand, the paper feed roller 14 feeds the recording materials P one by one from the paper cassette 13 at appropriate timing. The separation pad 15 is disposed in contact with the paper feed roller 14, and its surface friction coefficient, contact angle, and shape are adjusted so that only one recording medium is fed per paper feed.

The visualized toner image on the photosensitive drum 1 is transferred onto the recording material P by the transfer roller 8.

The recording material P to which the toner image has been transferred is heated and pressed by the fixing device 12, and the toner image is permanently fixed on the paper.

On the other hand, untransferred toner remaining on the photosensitive drum 1 without being transferred is stored in a waste toner container 11 by a cleaning blade 10, and the photosensitive drum 1 whose surface has been cleaned is repeatedly subjected to the next image forming process. You.

Next, a description will be given of the fixing device 12 which is a heat fixing device to which the present invention is applied.

The fixing device 112 includes a heating element 21 supported by the heating element support 24, the heating element 21 and the heating element support 24.
An endless heat-resistant film 23 externally fitted on the heating member 21 and a pressure roller 25 serving as a pressure member that presses the heating member 21 through the film 23 to form a nip.

Here, the film 23 has its inner peripheral length fitted to the heater 21 and the heater support 24 with a margin to the outer peripheral length of the heater 21 and the heater support 24.
It is rotatable by being guided by the heating element 21 and the heating element support 24.

The film 23 has a thickness of 20 to 100 μm.
m, a base made of a polyimide resin, and a release layer provided on the base and made of a fluororesin such as PTFE or PFA.

The heating element 21 is made of a heat-resistant insulating substrate having good thermal conductivity such as alumina and a thickness made of an electric resistance material such as Ag / Pd (silver-palladium) coated on the surface of the substrate by screen printing or the like. It has an electric resistance layer having a thickness of about 10 μm and a width of 1 to 3 mm, and a protective layer made of glass, fluororesin or the like coated on the electric resistance layer.

The pressure roller 25 includes a core 25a and a heat-resistant elastic layer 25b provided around the core 25a.

In the fixing device 12, by using a material having high heat insulation and a small heat capacity for the elastic layer 25b,
It is possible to immediately start the fixing operation even when the fixing device 12 is cold.

The pressure roller 25 rotates by pressing against the heating body 21 via the film 23 to rotate the film 23 by rotation. Thus, the recording material P introduced between the pressure roller 25 and the film 23 at the nip is nipped and conveyed by the pressure roller 25 and the film 23.

The thermistor 22 as a temperature detecting means
The resistor Rl and the DC power supply are connected in series, as shown in FIG. 3, and the partial voltage Vth of the thermistor at this time is used as a temperature information signal as shown in FIG.
The data is sent to the CPU 26 as control means via the / D converter 27.

Further, the CPU 26 controls the power supply to the heating element 21 via the triac 28. In the present embodiment, the power supply control is performed by controlling the wave number of the AC voltage. That is, the CPU 26 drives the triac 28 based on the temperature information signal from the thermistor 22 output from the thermistor 22 and A / D converted by the A / D converter 27 to control the energization of the heating element 21. Is set.

Next, a method of estimating the length of time (hereinafter referred to as a start-up time) required for the heating element 21 of the fixing device 12 to sufficiently warm up to perform the fixing operation according to the present embodiment will be described. I do.

Generally, the rise time of the temperature of the heating element of the fixing device changes depending on the power supply voltage, the temperature of the fixing device, the temperature of the atmosphere, the resistance value of the heating element, and the like.

In a conventional image forming apparatus, after a print signal is received, 0.5 seconds before a sheet is passed through a nip of a fixing device.
The heater is energized for a second and the temperature rise ΔT detected at that time is equal to or greater than a certain threshold value.

Specifically, ΔT is 70 [deg. In the above case, paper feeding is performed in the normal mode in which paper feeding is started 5 seconds after receiving the print signal, and 70 [deg. In the case of], the paper feed timing is shifted to the wait mode in which the paper feed is performed after the target temperature is reached, thereby switching the paper feed timing.

In the conventional image forming apparatus, it takes three seconds from the start of paper feeding until the leading end of the paper in the conveying direction reaches the nip portion of the fixing device.
g. The current situation is that the FPT will be longer than 3 seconds even if it does not reach the above.

Furthermore, in the conventional image forming apparatus, for example, when the ambient temperature is 30 [° C.] and the input voltage is 110 [V], which is advantageous for starting the fixing device, the normal timing of 5 seconds is used. It was possible to perform the fixing operation even earlier in 4 seconds. Nevertheless, the conventional image forming apparatus does not have a sequence for feeding the paper before 5 seconds, so that the user waits more than necessary or wastes power.

In order to solve such a problem and achieve the shortest possible FPT within a given apparatus configuration, the present embodiment reduces the time required for the fixing unit to start up as follows. The prediction is performed, and the paper transport start time can be determined.

FIG. 5A is a diagram showing how the voltage value Vth of the thermistor 22 changes with respect to the time from the start of energization of the heating element 21.

In FIG. 5A, when starting up, the heating element 2
1 is supplied with full-wave power, V3 indicates a start-up target temperature, and t3 indicates the length of time required for start-up.

The time variation of the detected voltage value of the thermistor 22 reaches V3 which is the thermistor voltage corresponding to the target temperature by drawing a non-linear curve as shown in FIG.
It is not easy to predict the time of t3.

FIG. 5B shows how the reciprocal 1 / Vth of the voltage value of the thermistor 22 changes with respect to the time from the start of energization to the heating element 21.

As shown in FIG. 5B, since the value of 1 / Vth increases almost linearly until the heating element 21 rises, the value of the thermistor 22 at time tl while the heating element 21 is energized is changed. The time when the fixing device 12 reaches the target temperature can be predicted based on the voltage Vl and the voltage V2 of the thermistor at the time t2.

That is, in FIG. 5B, the slope can be expressed as (1 / V2-1 / Vl) / (t2-tl).

Thus, the output V of the thermistor 22 corresponding to the target temperature for starting the heating element 21 of the fixing unit 12 is obtained.
The time to reach 3 is: t3 = ((1 / V3-1 / Vl) × t2- (1 / V3-
1 / V2) × tl) / (1 / V2-1 / Vl) using only four arithmetic operations.

This proportional relationship is maintained even when the temperature of the environment, the power supply voltage, and the resistance value of the heating element are changed, but is slightly affected by the thermal conductivity K of the pressure roller.

FIG. 6 is a diagram showing a change in 1 / Vth at various thermal conductivities K of the pressure roller.

As a result of examining these characteristics, the thermal conductivity of the pressure roller 25 was found to be 2.51208 × 10 ^-2 [W / (m ·
K)] (0.6 × 10 ⁻³ [cal / (cm · s ·
° C)]) and 3.39444 × 10 ^-3 [W / (m · K)]
In the case of (0.08 × 10 ⁻³ [cal / (cm · s · ° C.)], the linearity is insufficient. Therefore, when making a prediction using an approximate expression, a complicated function must be used. In this case, when trying to predict the time at which the fixing device starts to reach the target temperature, a heavy load is imposed on the CPU and a large RAM area is required for performing the calculation.

Further, as a means for predicting the arrival time of the target startup temperature, a sequence map may be prepared for each combination of various environmental temperatures, power supply voltages, and resistance values of the heating element. The amount of combinations is enormous, and a large area of the ROM for storage must be ensured.

Therefore, in order to apply the above-mentioned simple prediction formula of the target temperature arrival time using the proportionality of 1 / Vth as the pressure roller according to this embodiment, the thermal conductivity K
Is 4.1868 × 10 ^-2 W / (m · K) or more and 12.56
04 × 10 ⁻² W / (m · K) or less (0.1 to 0.3 [×
It is preferable to use a pressure roller of 10 ⁻³ cal / (cm · s · ° C.)]).

FIG. 7 shows the relationship between the input voltage and the FPT when the present embodiment using the above-described prediction method and the conventional sequence are actually used.

In the present embodiment, the target temperature arrival time is predicted, and the paper feed start time is controlled so that the paper enters the fixing device 12 in synchronization with the target temperature arrival time.

As shown in FIG. 7, in the case of the conventional heat fixing device, when the input voltage exceeds 95 [V], printing is performed in the normal mode.
When [V] is input, the FPT is 10 seconds.

On the other hand, when printing is performed based on the prediction of the target temperature arrival time in the present embodiment, printing can be completed in 9 seconds, and the FPT can be shortened by 1 second as compared with the related art. . At this time, since the fixing device 12 had already risen, there was no problem in the fixing property.

Further, for example, when the input voltage is 95 [V], since the power is slightly insufficient in the conventional heat fixing device, the mode shifts to the wait mode. Since it takes 3 seconds from the start of paper feeding until the paper reaches the fixing device, even if paper feeding is performed in the shortest time after shifting to the wait mode, the FPT is extended by 3 seconds or more, and the FPT is 13 seconds. there were.

On the other hand, in the case of the present embodiment, the time when the temperature reaches the target temperature is predicted, and the sheet feeding timing is steplessly adjusted so that the recording material P enters the fixing nip portion in synchronization with the time. , The printing can be completed in the shortest 10 seconds.

As described above, when the fixing device of the present embodiment is used, it is possible to shorten the FPT as compared with the conventional device. Furthermore, shortening of the FPT also leads to elimination of useless start-up time, and responds to the demand for further energy saving, which has recently been regarded as important.

That is, in the method of the present embodiment for predicting the target temperature arrival time of the fixing device utilizing the fact that the value of 1 / Vth changes linearly after energization, there is no need to perform a complicated operation, so that the CPU Can be easily predicted without imposing a large load on the printer, and furthermore, the fixing can be surely performed in the shortest possible time for fixing.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, the time t3 at which the fixing device reaches the target temperature is predicted by the same heating element target temperature prediction method as in the first embodiment, and based on this time t3, a print start command is input ( The time length t from when the heating member 21 starts heating) to when the recording material P enters the nip of the fixing device 12
4. When the length of time required for the pressure roller 25 to make one rotation is t5, the recording material conveyance start time is determined so as to satisfy a relationship of t3−t5 <t4 (<t3). I do.

Conventionally, when the start-up time of the fixing unit is predicted, the paper conveyance start time is determined so that the paper enters the fixing nip after the start-up time, and the paper is fed.

In the present embodiment, by using a pressure roller having a lower thermal conductivity than in the related art, it is possible to simultaneously perform sheet feeding earlier than in the related art.

Here, the details of the present embodiment will be described.

For example, if the input voltage to the heating element 21 is 90
In the case of a low voltage environment of [V], the fixing device 1 of the present embodiment
The heating time length t3 required for 2 to reach the target temperature is 8 seconds. At this time, if the time t4 from when the print start command is input to when the recording material P enters the nip of the fixing device 12 is fed so as to be 8 seconds, the fixing device 12 starts up at the same time. The recording material P enters the fixing nip.

When the fixing operation was performed by changing the time length t4 variously, it was found that the fixing property could be secured if t4 was 7 seconds or more. As a result of repeated studies, the time length t5 required for the pressure roller 25 to make one rotation is 1 second, and the pressure roller 25 makes one rotation after the recording material P enters the nip of the fixing device 12. During this period, it was found that the fixing property can be secured even when the temperature of the heating body 21 is slightly lower due to the residual heat of the pressure roller 25.

That is, if the heating element 21 of the fixing device 12 has reached the target temperature within the time required for the pressure roller 25 to make one rotation, the fixing property can be ensured, and wasteful standby time can be reduced. Can be shortened.

As a result of the examination, such a residual heat effect is generated because the thermal conductivity of the elastic body of the pressure roller is 12.5604.
× 10 ⁻² W / (m · K) or less (0.3 [× 10 ⁻³ cal]
/ (Cm · s · ° C.)]). That is, the thermal conductivity of the elastic body is 12.5604 × 10 ^-2 W / (m ·
K) In the following cases, when the same amount of heat is supplied, heat is hardly transmitted to the inside as compared with the conventional pressure roller, so that the temperature of the surface is significantly increased and a residual heat effect is produced.

The thermal conductivity used in the present embodiment is 12.560.
As a result of examining the roller surface temperature 5 seconds after energizing the heating element between the pressure roller 25 of 4 × 10 ⁻² W / (m · K) and the conventional pressure roller, the roller was used in the present embodiment. Pressure roller 25
The surface temperature is 20 [de] compared to the conventional pressure roller.
g. ] High 105 [° C].

That is, when a pressure roller having a heat conductivity lower than the above range is used, the temperature of the surface of the pressure roller is raised faster than that of the conventional pressure roller. Even if the paper is fed earlier by the time length t5, the fixing property can be secured. On the other hand, since the heat capacity is reduced due to the lower thermal conductivity, the heat can be sufficiently supplied from the pressure roller to the paper only for the time length of t5, and within the time length of t4 + t5. Means that the heat fixing unit must reach the target temperature.

That is, if the paper transport start time is determined so as to satisfy the relationship of t3 <t4 + t5, it is possible to secure a sufficient fixing property and eliminate a useless waiting time.

Thus, it is possible to ensure both the fixing performance and the shortening of the standby time. However, when the conditions for performing the fixing are extremely severe (for example, when the input voltage is low and the environmental temperature is low). Then, the target temperature of the heat fixing device is raised and reset, and the target temperature arrival time with respect to the reset target temperature (the length of time from the start of heating of the heating element 21 to the arrival of the reset target temperature) Calculate t6, t6 <t4 + t
It is effective to change the paper transport start time so as to be 5.

For example, when the input voltage is 80 [V] and the ambient temperature is 0 [° C.], the heating time length t3 required for the fixing device of this embodiment to reach the target temperature is 20 seconds.
Here, when the fixing device reached the target temperature and caused the paper to enter the fixing nip at the same time, the input voltage was extremely low, so that the heating and fixing device during the paper feeding could not be maintained at a constant temperature. . In order to avoid this, it is necessary to sufficiently heat the entire fixing device so that the amount of heat required for fixing is not insufficient.

Therefore, in the present embodiment, when the predicted time length from the start of heating of the heating element 21 to the arrival of the target temperature is equal to or longer than the predetermined time length, the target temperature of the fixing device is set to 18
The temperature is increased by 10 ° C. from 0 ° C. to 190 ° C.
At time t6 when 1 reaches 190 ° C., the recording material P is caused to enter the fixing nip portion and the fixing operation is performed.
Sufficient fixability was obtained.

Further, even when the target temperature for starting the fixing device is increased, the residual heat of the surface of the pressure roller 25 is used as described above, and the paper transport start time is set so as to satisfy the relationship of t6 <t4 + t5. Was determined, sufficient fixing property could be secured.

[0101]

As described above, according to the first aspect of the present invention, the heating of the heating element is performed based on the linear function having the reciprocal of the voltage value detected by the thermistor and the detection time of the thermistor as variables. Since the heating time length from the start to the arrival at the target temperature is calculated, the time length from the start of heating the heating element to the arrival at the target temperature can be predicted with high accuracy.

According to the second invention of the present application,
Since the heating time length from the start of heating the heating element to the target temperature is calculated based on a linear function using the reciprocal of the detection voltage value of the thermistor and the detection time of the thermistor as variables. The length of time from the start of body heating to the target temperature can be predicted with high accuracy.

Further, according to the third aspect of the present invention, by optimizing the thermal conductivity of the elastic layer of the pressurizing member, the linear expression using the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor as variables. The linearity of the function is maintained, and the heating time length from the start of heating of the heating element to the arrival of the target temperature is calculated based on the linear function. The length of time to reach the temperature can be predicted with higher accuracy.

According to the fourth invention of the present application,
During the time period t5 before the target temperature of the heating element reaches the target temperature and before the target temperature is reached, the leading end of the recording medium in the transport direction enters the nip, and the preheating of the pressurizing element and the heat from the heating element are transferred to the recording medium. Since it is provided, it is possible to shorten the first print time and save energy while securing the fixing property.

Further, according to the fifth aspect of the present invention, from the start of heating of the heating element to the reaching of the target temperature, the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor are used as variables. The heating time length of is calculated,
Since the recording medium carrying the image enters the nip in synchronization with the heating time, the time length from the start of heating the heating body to the target temperature can be predicted with high accuracy,
It is possible to shorten the first print time and save energy while securing the fixing property.

According to the sixth aspect of the present invention,
The heating time length from the start of heating the heating element to the target temperature is calculated based on a linear function using the reciprocal of the voltage detected by the thermistor and the detection time of the thermistor as variables. Between the time length t5 and the time when the target temperature is reached, the leading end in the transport direction of the recording medium enters the nip, and the preheating of the pressurizing body and the heat from the heating body are applied to the recording medium. Therefore, the length of time from the start of heating of the heating element to the arrival of the target temperature can be predicted with high accuracy, and the first print time can be shortened and energy can be saved while securing the fixing property.

Further, according to the seventh aspect of the present invention, the target temperature is reset to be higher than the target temperature when the predicted heating time length t3 is equal to or longer than the predetermined heating time length. At the same time, the leading end of the recording medium in the conveying direction rushes into the nip during a period from the time t5 before the heating element reaches the target temperature to the time when the target temperature is reached, and the preheating of the pressurizing element and heat from the heating element are reduced. Since it is applied to the recording medium, the time length from the start of heating of the heating element to the arrival of the target temperature can be predicted with high accuracy, and the first print time can be shortened and the energy saving can be achieved while securing the fixing property. Can be achieved.

According to the eighth invention of the present application,
During the time period t5 before the target temperature of the heating element reaches the target temperature and before the target temperature is reached, the leading end of the recording medium in the conveyance direction enters the nip, and the thermal conductivity of the elastic layer is optimized. Since the preheating and the heat from the heating body are applied to the recording medium, the time length from the start of heating of the heating body to reaching the target temperature can be predicted with high accuracy, and the fixing property can be secured. In addition, it is possible to shorten the first print time and save energy.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view illustrating a schematic configuration of a heating device provided in the image forming apparatus of FIG.

FIG. 3 is a diagram for explaining a detection voltage value of a thermistor provided in the heating device of FIG. 2;

FIG. 4 is a block diagram illustrating a temperature control system of the heating device of FIG. 2;

FIG. 5A is a diagram illustrating a relationship between a time length from the start of heating of a heating element to a target temperature and a voltage value of a thermistor in the heating device according to the first embodiment of the present invention; (b) is a diagram showing the relationship between the time length and the reciprocal of the voltage value of the thermistor.

FIG. 6 is a diagram showing the relationship between the time length from the start of heating of the heating body to the arrival of the target temperature and the reciprocal of the voltage value of the thermistor at various thermal conductivity of the heat insulating layer of the pressure body.

FIG. 7 is a diagram illustrating a relationship between input power to a heating body and first print time in the image forming apparatus according to the first embodiment of the present invention and a conventional image forming apparatus.

FIG. 8 is a schematic cross-sectional view illustrating a schematic configuration of a heating device provided in a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 12 fixing device (heating device) 21 heating element 22 thermistor (temperature detecting means) 23 film 24 heating element support 25 pressure roller (pressing element) 25b elastic layer 25a core metal 27 A / D converter 28 triac N fixing nip P Recording material (recording medium) T Toner (image)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ken Nakagawa 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA30 AA32 BA30 BB29 BE03 CA03 CA07 CA28 CA44 3K058 AA02 AA81 BA18 CA23 CA61 DA04 GA06 5H323 BB02 CA09 CB02 DB04 FF03 GG04 NN03

Claims (8)

[Claims] 1. A heating element that generates heat by receiving power from a power supply, an endless belt-shaped rotatable film that slides in contact with the heating element, and forms a nip by pressing the heating element through the film. And a rotating pressurizing body, wherein a heating medium heating time estimating method for a heating device for heating and pressurizing the recording medium carrying an image by nipping and transporting the recording medium between the film and the pressurizing body at the nip, comprising: The apparatus includes temperature detecting means for detecting the temperature of the heating element, and control means for controlling electric power from a power supply to the heating element so that the temperature detected by the temperature detecting means becomes a target temperature. In the heating element heating time estimating method, which is a thermistor having a resistance value that changes according to the temperature of the body, at any two detection times between the start of heating of the heating element and the arrival at the target temperature, Temperature as voltage value Using the reciprocal of the thermistor's detection voltage value and the thermistor's detection time as variables, the reciprocal of the thermistor's detection voltage value at the above two detection times is used to determine the relationship of a linear function, and the heating element A heating element heating time period from the start of heating of the heating element to the arrival of the target temperature by substituting the voltage value of the thermistor corresponding to the target temperature. 2. The heating time length of the heating element is represented by t1, t1 from the start of heating of the heating element to the detection time of the thermistor.
t2, the heating time length from the start of heating of the heating body to the arrival of the target temperature is t3, and the time length from the start of heating of the heating body to t1, t
The detected voltage of the thermistor after 2 passes is V1, V
2. When the detected voltage of the thermistor at the target temperature of the heating element is V3, t3 = ((1 / V3-1 / V1)
× t2- (1 / V3-1 / V2) × t1) / (1 / V2
The heating body heating time estimating method according to claim 1, wherein the heating body heating time estimating method is calculated by (-1 / V1). 3. The pressing body has an elastic layer, and the thermal conductivity of the elastic layer is 4.1868 × 10 ⁻² W / (m · K) or more.
The heating element temperature rise time prediction method according to claim 1 or 2, wherein the temperature is 2.5604 × 10 ^-2 W / (m · K) or less. 4. A heating element that generates heat by receiving power from a power supply, an endless belt-shaped rotatable film that slides in contact with the heating element, and forms a nip by pressing the heating element through the film. And a heating device for heating and pressurizing the recording medium conveyed from a predetermined position in the image forming apparatus and carrying the image, by nipping and conveying the recording medium between the film and the pressing body at the nip. A forming device, wherein the heating device includes a temperature detecting unit for detecting a temperature of the heating body, and a control unit for controlling electric power from a power supply to the heating body so that the temperature detected by the temperature detecting unit becomes a target temperature. The image forming apparatus further includes a predicting unit that predicts a heating time period from the start of heating of the heating body to the arrival of the target temperature. The predicting unit sets the heating time length to t3. D T4 is the length of time required for the pressurizing element to make one rotation, and t5 is the length of time required for the pressure body to make one revolution.
An image forming apparatus capable of determining a transport start time of the recording medium from the predetermined position so as to satisfy t3−t5 <t4 <t3. 5. A heating element that generates heat by receiving electric power from a power source, a heat-resistant endless belt-shaped rotatable film that slides in contact with the heating element, and is pressed against the heating element via the film. A pressurizing member that forms a nip and rotates at a predetermined speed, and heats and heats the recording medium that is conveyed from a predetermined position in the image forming apparatus and carries an image by being nipped and conveyed by the film and the pressurizing member at the nip. An image forming apparatus including a heating device for pressing, wherein the heating device controls temperature from a power supply to the heating member so that the temperature detected by the temperature detection device reaches a target temperature. And a controller configured to perform a heating element temperature rising time prediction method according to any one of claims 1 to 3, wherein the heating apparatus controls the heating element from the start of heating to the target temperature. Heating time length Image forming, wherein the conveyance start time of the recording medium can be determined so that the leading end in the conveyance direction of the recording medium enters the nip in synchronization with the arrival of the target temperature based on the predicted heating time length. apparatus. 6. The recording medium conveyance start time is a predicted heating time length from the start of heating of the heating element to the arrival of the target temperature at t3, and the time from the start of the heating until the leading end of the recording medium in the conveyance direction enters the nip. When the length of time required for the pressurizing body to make one rotation is t4, the length of the transport time of
The image forming apparatus according to claim 5, wherein the image forming apparatus can be determined to satisfy −t5 <t4 <t3. 7. The target temperature is reset to be higher than the target temperature when the predicted heating time from the start of heating of the heating element to the arrival of the target temperature is equal to or longer than a predetermined heating time. 7. The image forming apparatus according to claim 4, wherein the transport start time of the medium can be determined by re-estimating the heating time length t3 at the reset target temperature. 8. The pressure body has an elastic layer, and the thermal conductivity of the elastic layer is 4.1868 × 10 ⁻² W / (m · K) or less. 8. The image forming apparatus according to claim 7.