JP3265853B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of heating a visible image formed and carried on a recording material by an appropriate image forming process means to determine the temperature.
The present invention relates to an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus having a fixing device (image heating device) for performing the fixing .

More specifically, a process for forming an image on a recording material
A lint unit, the heating body is maintained at a fixing temperature during image fixing
And grease is applied between this heating element and the image
Having a film that moves with the formed recording material, waiting
During this time, the heater is not energized and the film is stopped.
And an image forming apparatus having the same .

[0003]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus, a recording material (transfer material, electrofax) is transferred by an appropriate image forming process such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. Paper, electrostatic recording paper, etc.) and heat-fixes the unfixed visible image (toner image), which is the target image information formed and carried on the recording material surface.
Conventionally, a heat roller method has been widely used as a dressing apparatus , and recently, a film heating method apparatus has come into practical use.

[0004] Heat roller type fixing device The heat roller type fixing device is composed of a rotary heat roller (fixing roller, heat roller) in which a heat source such as a halogen heater is disposed, and a rotary pressure roller pressed against the heat roller. A recording material as a material to be heated is introduced into the press-contact nip portion of the pair of rotating rollers, and is nipped and conveyed.
Pressurized those for Fixing the recording material. 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.

In the heat roller type fixing device, since the heat capacity of the roller is large, it takes time (rise time, warm-up time, wait time) for the roller to reach a predetermined temperature. The temperature of the heat roller must be controlled to a certain temperature even when the heat roller is not used.

[0006] Fixing device of film heating system This device is disclosed in JP-A-63-313182,
JP-A-157878 / JP-A-4-44075 /
It has been proposed in Japanese Patent Application Laid-Open No. 4-204980, etc., which has a heating element (generally a ceramic heater) and a heat-resistant film which moves in close contact with the heating element, and records as a material to be heated via this film. This is a heating device in which a material is brought into close contact with a heating body, the position of the heating body is moved together with the film, and heat of the heating body is applied to the recording material via the film. It has a pressure member for bringing the film / recording material into close contact with the heating element.

FIG. 6 (a) is an enlarged cross-sectional model diagram of a main part of an example of a fixing device of a film heating system. (B) is a plane model diagram in which a middle part of the heating element is omitted and partly cut away.

Reference numeral 1 denotes a heating element, which has heat resistance, electrical insulation,
Low heat capacity heater substrate (ceramic substrate such as alumina)
2, a resistance heating element layer (a heating element layer made of silver palladium or the like, a heating element) 3 formed on one surface of the substrate 2 along the length thereof, and provided at both ends of the resistance heating element layer 3. Terminal electrode layers (conductive layers such as silver) 3a and 3b, and a surface protection layer (glass layer or the like) 4 on which the surface of the substrate 2 on which the resistance heating element layer is formed is coated.

The surface of the heating element 1 on the surface protective layer 4 side is a film contact sliding surface, and the surface of the surface protecting layer 4 is exposed to the outside so that the heating element 1 is fixed to a supporting portion via a heat insulating stay 7. It is supported.

The heating element 1 is a terminal electrode layer 3a of the resistance heating element 3.
During 3b, a voltage is applied by the power supply control circuit 11 including the AC driver 12, the CPU 13, the A / D converter 14, and the like, and the resistance heating element layer 3 generates heat, thereby increasing the temperature.

Reference numeral 5 denotes a temperature detecting member such as a thermistor provided in contact with the back surface of the heater substrate 2 of the heating element 1, and the detected temperature information is transmitted to the CPU 1 via an A / D converter 14.
The power supply to the resistance heating element layer 3 is controlled so that the temperature detected by the temperature detecting member 5 is maintained at a predetermined temperature, and the temperature of the heating element 1 is adjusted to a predetermined temperature. That is, the temperature control of the heating element 1 controls the energization to the resistance heating element layer 3 so that the temperature detected by the temperature detecting member 5 of the heating element 1 becomes constant.

The energization control method uses wave number control, and the input power is changed by applying any one of the 14 waves of the AC input voltage to the resistance heating element 3 as a basic unit. ON
The / OFF ratio is expressed as a duty ratio, and is 0 to 100%
Can be varied between.

Reference numeral 6 denotes a safety fuse (thermal fuse) as a thermal protector, which is connected in series to a current path for the resistance heating element 3 and is provided in contact with the back surface of the heater substrate 2 of the heating element 1. When the temperature of the heating element 1 exceeds a predetermined value, the heating element 1 is melted to cut off the current supply to the resistance heating element layer 3.

Reference numeral 9 denotes a heat-resistant film made of polyimide or the like having a thickness of, for example, about 40 μm to 100 μm.
Is a pressing roller as a pressing member that presses the surface of the heating element 1 against the surface protective layer 4 that is the film sliding surface.

The film 9 is pressed against the heating element 1 by the pressure roller 10 and is driven in the direction indicated by an arrow by driving means (not shown) or by the rotational driving force of the pressure roller 10 using the pressure roller 10 as a driving means. It moves while contacting and sliding on the surface of the heating element 1 at a predetermined speed.

In this case, in order to increase the film driving torque due to the rubbing between the film 9 and the heating element 1 and the stay 7 and to reduce the abrasion and warpage of the film, the film 9 is moved smoothly. A lubricant such as grease is applied to the contact portion between the heating element 1 and the stay 7, specifically, to the inner surface of the film.

The heating element 1 is heated to a predetermined temperature by energizing the resistance heating element layer 3, and the heating element 1 is formed with the film 9 sandwiched in a state where the film 9 is slid and moved on the heating element 1. The recording material P as a material to be heated is introduced between the pressure roller 10 and the film 9 in the pressure contact nip portion (fixing nip portion) N with the pressure roller 10 so that the recording material P Heating body 1 with film 9 in close contact
Move through the position. In the moving passage process, heat energy is applied to the visible image t (unfixed toner image) of the recording material P from the heating body 1 via the film 9 to soften / melt (heat fusion fixing). Next, the film 9 and the recording material P after passing through the fixing nip portion N are separated at a separation point.

Such a heating device of the film heating system can use the heating element 1 having a very small heat capacity and a rapid temperature rise, and can greatly reduce the time required for the heating element 1 to reach a predetermined heating temperature.

Further, a thin magnetic conductive film (magnetic material film) is heated by a magnetic (electromagnetic) induction heating means to generate heat, and a recording material as a material to be heated is brought into close contact with the magnetic conductive film and heated. Alternatively, a magnetic induction heating method in which a magnetic conductive material is heated by a magnetic induction heating means, and a recording material is closely attached to the magnetic conductive material via a film and heated.
An apparatus of a film heating system has also been proposed. This device also has the same advantages as the above-described film heating type device.

[0020]

By the way, in the fixing device, if there is a fluctuation in the input voltage to the fixing device (such as a heating element) or the resistance value of the resistance heating element layer of the fixing device varies. The time required for the fixing unit to reach a predetermined temperature varies depending on the power of the fixing unit and the temperature of the atmosphere.

In a normal fixing device of a heat roller type or the like, the temperature of a fixing device (heat roller or the like) is previously adjusted to a certain fixed temperature, for example, 150 ° C., and a predetermined fixing temperature of 180 ° C.
By controlling the temperature difference 30 ° to 30 ° C. at a constant value, it was possible to predict the time from when a print signal was input to when the fixing device reached a predetermined temperature.

Also, in a fixing device of a film heating type, if a fixing signal (heater) is supplied after receiving a print signal and the image formation is started after waiting for a certain temperature, the fixing device is brought to a predetermined temperature. It was possible to predict to some extent the time to reach.

However, in order to take full advantage of the advantage of the film heating type fixing device that the temperature rises quickly and there is no need to heat the film in a standby state, it is necessary to use a fixing device such as a heat roller type fixing device. It is not preferable that the power is always supplied.

Also, in the film heating type fixing device, since the time from the ambient temperature to the predetermined fixing temperature is uncertain for the above-mentioned reason, the fixing device is actually energized to some extent after receiving the print signal. After the fixing device reaches a predetermined fixing temperature, or after it is expected that the temperature of the recording material will reach the fixing temperature after reaching a certain temperature and reaching the fixing unit after feeding, The recording material could not be fed.

However, in recent years, in an electrophotographic apparatus such as a printer or a copying machine as an information output apparatus, a first print time (hereinafter referred to as an FPT) which is a time required from receiving a print signal until the first sheet is discharged. Is required to be shortened.

Particularly in a low-speed machine having a low process speed,
It has been difficult to shorten the FPT because the time required to convey the recording material necessarily increases.

From such a background, in order to shorten the FPT, the conveyance of the recording material is started almost at the same time as receiving the print signal, and the fixing device is heated from the time when the recording material is fed to the time when the fixing device is reached. It has been desired to control the temperature to the fixing temperature.

By adopting such a configuration, it is not necessary to wait for the feeding and conveyance of the recording material until the fixing device rises to a certain temperature as in the related art, and the pre-rotation time during image formation is shortened. This makes it possible to realize a reduction in the FPT.

However, as described above, the time required for the fixing device to reach the fixing temperature varies depending on the power supply circumstances and the ambient temperature. Therefore, when the recording material reaches the fixing device in a low-temperature environment or a low-voltage input, the fixing device is still in operation. Since the fixing temperature has not been reached, fixing failure may occur, and unfixed toner on the output image may stain the user's hands or cause problems such as transfer of the toner image to another print. Was.

Incidentally, in an apparatus having a mechanism such as a registration roller or a skew feeding roller capable of controlling the conveyance of the recording material after the recording material is fed, the paper is fed at the same time as printing, and the fixing is performed until the mechanism is reached. If the temperature rise of the fixing device is detected and the temperature rise is insufficient, it is possible to stop the conveyance of the recording material and wait for the temperature rise of the fixing device. Such a state is called pre-feed. Such an apparatus is also effective because it is not necessary to stop the recording material with a registration roller or the like until a certain temperature is reached.

Further, in a recording apparatus requiring a shorter FPT in recent years, it is necessary to shorten the paper conveying path, so that it is difficult to provide a mechanism such as a registration roller and a skew feeding roller. It is thought that the device configuration that cannot stop the recording material after performing
An effective means for shortening the FPT in such a case is desired.

In a film heating type fixing device, grease or the like applied to the inner surface of the film has sufficient lubricity at a high temperature near the fixing temperature, but the condition in the morning when the fixing device is cold, etc. In this case, there is a problem that the material has viscosity and the friction coefficient is rather large, so that the starting torque becomes very large.

Therefore, the present invention solves the above-mentioned problems in an image forming apparatus having a film heating type fixing device, that is, shortens the FPT without causing a fixing defect (heating defect). and this, by eliminating the problem of increase in the starting torque of the film movement due to the high viscosity of the lubricant at the time of cold example state, the driving bets film
An object of the present invention is to achieve both the reduction of the torque and the control of the paper feed timing .

According to the present invention, there is provided a printing section for forming an image on a recording material, a heating member which is maintained at a fixing temperature during image fixing, and a recording material on which an image is formed by applying grease between the heating member and the heating member. having a film which moves with, the waiting in the image forming apparatus having a fixing means and the film is not energized heating element is stopped, after receiving the print signal, causes energizing a predetermined time the heating element Along with the
The movement of the film is prohibited, and after the elapse of this predetermined time,
A control means for starting the film movement, wherein the fixing temperature reaching time calculated from the temperature rise rate of the heating element during the predetermined time is earlier than the time when the recording material reaches the fixing position from the recording material feeding position. Is an image forming apparatus characterized in that the feeding of the recording material is started immediately after the temperature rise rate is measured, and the feeding of the recording material is delayed when it is late.

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[Action] That solves the above problems, the order to achieve both reduction and feed timing control of the drive torque of the film, in the present invention, after receiving the print signal, the energizing to the predetermined time the heating element The movement of the film is prohibited and this
A system for starting the movement of the film after a predetermined time has elapsed.
If the fixing temperature arrival time calculated from the temperature rise rate of the heating element during the predetermined time is earlier than the time when the recording material reaches the fixing position from the recording material feeding position, after the temperature rise rate is measured It is characterized in that the feeding of the recording material is started immediately, and the feeding of the recording material is delayed when the feeding is late. When the fixing temperature arrival time calculated from the heating element temperature rise rate is earlier than the recording material arrival time from the recording material feeding position to the fixing position, the recording material feeding is started immediately after the temperature rise rate measurement. By doing so, the shortest possible FPT is realized.

[0048] Then, when slow is delay the feeding of the recording material
So that to prevent the output of the defective fixing image (heating defect image) by.

[0049]

As described above, conventionally, the recording material could not be fed immediately upon receiving a print signal because the time required for the fixing device to rise to a predetermined fixing temperature was uncertain. by taking do arrangement, while realizing the shortest FPT, it has become possible to realize the images forming apparatus not to output the defective fixing images in emergency conditions.

In a film heating type apparatus,
The problem that grease as a lubricant interposed between the film and the fixing device / stay increases the starting torque when the film is cold in the morning, etc. By energizing the vessel and warming the grease to lower the viscosity, the starting torque can be greatly reduced.

[0052]

EXAMPLES <Example 1> (FIGS. 1 to 3) (1) Example of Image Forming Apparatus Figure 1 is a schematic diagram of an example image imaging apparatus. The image forming apparatus of this embodiment is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 21 denotes a rotating drum type electrophotographic photosensitive member as an image carrier. The photoconductor 21 of this example has a diameter of 30 mm.
OPC photoreceptor is driven clockwise as indicated by an arrow at a process speed (peripheral speed) of 25 mm / sec.

The photosensitive member 21 is uniformly charged to -650 V by the primary charging roller 22 during its rotation. S1 is a charging bias application power source for the charging roller 22.

Next, the peripheral surface of the photoconductor is made to correspond to the target image information by receiving image exposure by a laser beam output from the laser diode 23 and modulated by a time-series electric digital pixel signal of the target image information. An electrostatic latent image is formed.

Next, the electrostatic latent image is jump-developed with a magnetic one-component toner by the developing device 24 and visualized as a toner image. 24a is a developing sleeve, and S2 is a developing bias application power supply to the developing sleeve 24a.

The toner image is transferred to a contact nip (transfer section) 26 between the photoreceptor 21 and the transfer roller 25, onto a surface of a recording material (transfer material) P fed at a predetermined timing from a paper feed section 28. Is done. In the paper supply unit 28, reference numeral 29 denotes a recording material placement tray, reference numeral 30 denotes a paper supply roller, and reference numeral 31 denotes a paper supply guide.
The rotation of the paper feed roller 30 causes the tray 29 to rotate.
The uppermost recording material of the upper stacked recording materials P is separated one by one in cooperation with a separation member (not shown), guided by the guide 31, and introduced into the transfer unit 26. S3 is a transfer bias application power supply for the transfer roller 25.

The recording material P to which the toner image has been transferred from the photoconductor 21 in the transfer unit 26 passes through the transfer unit 26 and
The toner image is separated from the surface, passes through a guide 32, is introduced into a fixing nip portion N of a fixing device 33 described below, undergoes a fixing process of a toner image, and is discharged outside the apparatus.

The untransferred toner on the surface of the photoconductor 21 that has not been transferred to the recording material P is
It is removed from the surface of the photoconductor 21 by a cleaning blade 27a made of urethane rubber which is in contact with the surface of the photoconductor 21.
The photoconductor 21 is repeatedly provided for image formation.

(2) Fixing Device 33 The fixing device 33 of this embodiment is a film heating type device.
Components and parts common to those in the apparatus of FIG. 6 described above are denoted by common reference numerals, and description thereof will not be repeated.

In the fixing device 33 of this embodiment, an endless belt-shaped heat-resistant film 9 is used, and the heat-resistant film 9 is driven by a driven roller 34 and a driven roller 3 serving as a tension roller.
5. Heating body (fixer / heater) held by stay 7
It is suspended and stretched between the three members 34, 35, and 1.

The pressure roller 10 is pressed against the lower surface of the heating element 1 with a predetermined pressing force with the film 9 interposed therebetween.
When the drive roller 34 is driven to rotate in the clockwise direction indicated by the arrow by the drive motor M, the heat-resistant film 9 in the form of an endless belt is brought into close contact with the lower surface of the heating element 1 and slides on the heating element surface for a predetermined period. The recording material P carrying the unfixed toner image, which is conveyed while being guided by the guide 32 from the transfer unit 26 side, is rotated at substantially the same peripheral speed as the conveying speed of the recording material P carrying the unfixed toner image.

A lubricant (grease) is applied to a contact portion between the film 9 and the heating element 1 / stay 7. Pressure roller 10
Rotates following the rotation of the film 9.

The structure of the heating element 1 is the same as that of FIG. 6 described above, and is a horizontally long member whose longitudinal direction is perpendicular to the moving direction of the film 9.

The heater substrate 2 is, for example, a 1-mm-thick ceramic such as alumina having good thermal conductivity.

The resistance heating element layer (heating element) 3 has a resistance value of 40Ω.
Silver palladium.

The temperature detecting member 5 is a thermistor. The output signal of the thermistor 5 is supplied to the C / A converter 14 via the A / D converter 14.
It is input to PU13. The CPU 13 controls the power supplied to the resistance heating element layer 3 of the heating element 1 via the AC driver 12 based on the input signal, and regulates the surface temperature of the heating element 1.

When the heating element 1 is heated to a predetermined temperature by energizing the resistance heating element layer 3 and the film 9 is driven to rotate, a press-contact nip (fixing nip) N formed with the film 9 interposed therebetween. The recording material P is introduced from the transfer unit 26 side between the film 9 and the pressure roller 10 and heat energy is applied from the heating body 1 to the toner image of the recording material P via the film 9, and the toner image is The recording material P is thermally fixed on the surface.

(3) Method of Determining Electricity to Be Heated to Heating Element 1 In the present embodiment , the heating element 1 of the fixing device 33 is energized when the power of the printer body is turned on or at regular intervals after the power is turned on. The rate of temperature rise of the heating element is detected by a temperature detecting means (thermistor) 5, whereby it is determined whether to feed immediately upon receiving a print command or to delay feeding.

The method for determining the power supply to the heating element 1 (more precisely, the resistance heating element 3) is as follows.
Full energization with a duty of Then, assuming the supply electric power at the time of full energization to the heating element 1 from the speed of rising from 160 ° C. to 180 ° C., the energization ratio is determined so that the electric power becomes optimal to adjust the temperature to 180 ° C. I do.

At this time, the time required for the heating element to reach the fixing temperature from the ambient temperature varies depending on the ambient temperature at startup, the temperature of the fixing device, the power supply voltage, and the like.

More specifically, when the ambient temperature is 15 ° C. and 30 ° C., the temperature rise curve of the heating element 1 during energization is substantially constant, and the time from when the ambient temperature reaches the fixing temperature is reached. Are 5.5 seconds and 5.0 seconds, respectively, resulting in a difference of 0.5 seconds.

Even at the same ambient temperature of 25 ° C.,
In the morning, when the heating element 1 and its surrounding members such as the heater, the stay 7 and the pressure roller 10 are at temperatures substantially equal to the ambient temperature, and when they are warm immediately after the previous image formation, Since the amount of heat consumed by the heat capacity such as that described above can be reduced, the time required for the heating element 1 to reach the fixing temperature in the state immediately after the previous image formation is similarly shorter.

The relationship between the input voltage V of the heating element 1 to the resistance heating element layer 3, the resistance R of the heating element layer 3, and the heating value W is W
= V · V / R, the heating value W varies in proportion to the square of the variation of the power supply voltage V and the reciprocal of the variation in the resistance R of the resistance heating element layer 3.

Accordingly, the power W supplied to the resistance heating element layer 3 varies due to the power supply situation, the variation of the resistance R at the time of manufacturing the resistance heating element layer 3, and the like. The time required to reach the fixing temperature varies greatly.

More specifically, as shown by C in FIG. 2, when the ambient temperature is 25 ° C., R = 30Ω, and V = 110 [V], W = 400 [W]. Is 1
The time required to raise the temperature to 80 ° C. was 3.9 seconds, but B
As shown by, the ambient temperature is 15 ° C., R = 33Ω, V = 8
At 5 [V], W = 219 [W], so input power was not enough, and it took 7.5 seconds for the heating element 1 to rise to 180 ° C.

[0077] On the other hand, in the printer configuration used in this reference example, the distance of the recording material conveyance path from the paper feed position A to the fixing nip N L (in this example 150 mm) and is converted from the process speed (25 mm / sec) 6.0 seconds after the paper is fed, the recording material P reaches the fixing nip N, and it is necessary to raise the temperature of the heating body 1 to the fixing temperature by now.

Therefore, as shown in FIG.
At 5 ° C., R = 33Ω, and V = 85 [V], if the power supply to the heating element 1 was performed simultaneously with the sheet feeding, the temperature could not be increased in time.
It is clear that poor fixing occurs.

In order to secure sufficient input power even under such conditions, it is conceivable to lower the resistance value of the resistance heating element layer 3 of the heating element 1.
Duty to raise the temperature to 80 ° C is 100
%, If the power supply voltage is high, an excessive current may flow and the power consumption will increase, and the fluctuation of the power supply voltage based on the power ON / OFF at the time of temperature adjustment This is not preferable because it may cause flickering of the fluorescent lamp, which is called flicker.

Accordingly, even in an apparatus such as a film heating type fixing apparatus which heats quickly, even if the time for the heating element 1 to rise to the fixing temperature cannot be predicted, the print signal is received without notice unless a print signal is received. I can't do paper.

Conventionally, a first print time (FPT) is used as in a printer using a heat roller type fixing device.
The distance L from the paper feeding position A to the fixing nip N is long even when a recording material P is being conveyed even when a printer that does not need to pay much attention and a film heating type image heating device is used. In the printer which was able to raise the temperature of the heating element 1, the sheet is not fed even when a print signal is received, and after the heating element 1 is energized to raise the temperature of the heating element 1 to a certain extent, the sheet is fed. As a result, sufficient fixability was satisfied.

However, in order to maximize the advantage of the rapid temperature rise of the fixing device of the film heating type and to shorten the FPT which has been regarded as important in recent years, it is necessary to feed the sheet simultaneously with receiving the print signal. Is desired.

However, if paper feeding is simply performed at the same time as a print signal, fixing defects occur as described above under limited conditions such as a low power supply voltage and a low ambient temperature. By using means for detecting conditions in advance and waiting for sheet feeding only when it is expected that the time until reaching the fixing temperature is long, it is possible to realize the shortest FPT under normal conditions. .

Therefore, in this embodiment , when the power of the printer main body is turned on or at regular intervals, the heating element 1 is energized to detect the rate of temperature rise of the heating element 1 at that time. It is characterized in that it is determined whether to feed immediately upon receipt or to delay feeding for a certain time.

A specific example is shown below.

First, when the power switch of the printer body is turned on, the heating element 1 is energized to detect the temperature rise rate. In this embodiment , if the printing is not performed within three hours after the power switch is turned on, the detection is performed again to detect the possibility that the power supply voltage, the ambient temperature, and the like have changed. In this way, the detection is repeated every three hours after the main body power is turned on or after the last printing is performed, and the time required for the heating element 1 to be heated is always predicted.

If printing is performed within 3 hours, a 100% duty cycle is applied to the heating element 1 until the temperature reaches 180 ° C. at the same time as receiving a print signal. By doing so, it can be used as the predicted value of the temperature rise at the time of the next image formation.

The above detection timing is shown as a flowchart in FIG.

First, when the power is turned on (step S1), the timer in the CPU 13 representing the detection interval is reset to 0 (S2), and the heating element 1 is energized for one second, and the heating element is determined based on the temperature rise rate and the attained temperature. 1 is detected as a time T1 which is considered to be necessary to raise the fixing temperature to 180 ° C. (S
3).

Then, a value obtained by subtracting the time T2 (6.0 seconds in this example) required for transporting the recording material from the sheet feeding position A to the fixing nip portion N is stored as a sheet feeding waiting time T3 (= T1-T2). (S4).

After that, if the timer is within 3 hours, the value of the time T3 is held (Yes in S5), and
If the time has passed, the power is supplied again for 1 second to update the value of the time T3 (No in S5).

Next, when a print signal is received (S6),
First, it is determined whether the value of the held time T3 is positive or negative (S8). If the value is negative, it is determined that there is no need to wait for paper feeding, and a print signal is received and paper feeding and image formation are performed (S9).
-S10).

If the time T3 is positive, the sheet feeding is delayed only for the time T3 (S12), and the same sheet feeding and image formation are performed (S9 and S10).

When the heating element 1 is energized in response to the print signal, the temperature rise rate and the temperature reached during the first second after the energization are detected, and the value of the time T3 is updated in preparation for the next image formation. It shall be.

Next, a detection method will be described. Heating body 1
Then, current is supplied at a duty of 100% for 1 second, and the temperature rise rate of the heating element 1 at this time is detected by the thermistor voltage. Generally, the thermistor 5 used for measuring the fixing temperature has a non-linear relationship between the detected temperature and the output voltage, and has a low temperature detecting ability near room temperature and a low resolution, but has a resistance of 33Ω. If the layer 3 is energized for about 1 second, the temperature of the heating element 1 can be raised to about 55 ° C., so that the temperature rise rate during energization and the temperature after energization for 1 second are accurately measured in this range. be able to.

While the fixing device can be driven (rotation of the film 9) during energization, detection can be performed even when the fixing device is stopped. However, when the fixing device is driven, the pressure roller 10 And the heat capacity near the heating element changes. Therefore, since the temperature rise rate of the heating element 1 is different between the stop state of the apparatus and the drive operation, it is desirable to determine one of the states at the time of detection. In the present embodiment, the measurement of the temperature rise rate of the heating element 1 including the heat capacity of the pressure roller 10 is closer to the operation during actual printing and the detection can be performed with high accuracy including the factors of the ambient temperature. Detection shall be performed.

The heating element 1 is energized at a duty of 100%, and the rate of temperature rise when the power supply voltage V, the resistance R of the resistance heating element layer 3 and the ambient temperature are different is shown in FIG. By measuring the temperature and the rate of temperature rise when 1 is energized for 1 second, it can be seen that the time T1 required to raise the temperature of the heater 1 to 180 ° C. can be predicted.

Here, the configuration of the printer used in this embodiment is aimed at shortening the FPT as shown in FIG. 1, and is a press-contact nip portion between the photosensitive member 1 and the transfer roller 25 from the sheet feeding position A. There is no mechanism for controlling the conveyance of the recording material such as a registration roller between the transfer nip 26 and the paper feeding position A.
The distance L from the fixing nip N to the fixing nip N is as short as 150 mm.
Therefore, once the paper is fed, 150/25 =
After 6.0 seconds, the recording material reaches the fixing nip portion N, and at this time, the heating element 1 must be heated to the fixing temperature.

As can be seen from FIG. 2, in the example of A, the heating element 1
Has been heated to 180 ° C. within 4 seconds from the start of energization, and sufficient fixing properties can be obtained even if the paper supply and energization to the heating element 1 are performed simultaneously with the print signal. Under these conditions, the factors that determine the FPT are only the length of the recording material P, the process speed, and the length of the recording material transport path, and the output can be performed with the shortest FPT without any extra standby time.

However, in the case of B, especially when the input voltage is 85 [V], the heater resistance is 35Ω, and the ambient temperature is 15 ° C.,
It takes 7.5 seconds to reach the temperature of ° C.
After 0 seconds, the temperature of the heating element 1 has risen only to 145 ° C., and a fixing failure occurs.

For this reason, conventionally, paper feed cannot be performed simultaneously with a print signal, and the worst condition shown in FIG. 2D is considered regardless of conditions such as the input voltage and the resistance of the resistance heating layer 3 of the heating element 1. In view of the rise of 8.5 seconds, paper feeding was performed after waiting for 2.5 seconds after receiving the print signal. For this reason, in most cases except for the worst conditions, the FPT becomes 2.5 seconds longer at present.

Therefore, in this embodiment , prior to image formation,
The time required to reach the fixing temperature is predicted by the detection method described above, and this time is set as T1, and it is required for the recording material P to reach the fixing nip N from the paper feeding position A of the printer used in this embodiment. Time T2 is compared. If T1 ≦ T2, paper feed is performed simultaneously with the print signal.
Wait for three.

The value of the time T3 is set to T1-T2 by calculation, or a time with a slight margin added thereto, and is necessary under the worst possible condition shown in the example of D in FIG. It is possible to set a value obtained by subtracting the time T2 from the time 8.5 seconds.

In the present embodiment , a value obtained by adding 1.0 sec to the value of T1−T2 in consideration of a margin is set as a sheet feeding waiting time.

As described above, in this embodiment , the heating element 1 is energized prior to image formation, and the heating element 1 reaches the fixing temperature from the ambient temperature to the fixing temperature based on the temperature rise rate and the ultimate temperature at this time. The required time is estimated, and the timing for feeding the paper is changed accordingly.

As a result, the paper feed waiting time from the print signal, which has conventionally been determined in view of the worst conditions determined by the power supply voltage, the resistance of the resistance heating layer 3 of the heating element 1, the ambient temperature, and the like, is set to the worst condition. In most cases, it is possible to set the value to zero, and to achieve the shortest possible first print time in a given device configuration.

<Embodiment 1> In this embodiment, after receiving a print signal from the host computer, the heating element 1 is energized before paper feeding, and the rate of temperature rise during a certain period of time is detected. The timing of sheet feeding is determined based on the time until the heating element 1 reaches the fixing temperature.

Conventionally, when a print signal is received, the heating element 1
After the heating element 1 was confirmed to have reached a certain temperature, for example, 130 ° C., for example, the sheet was fed. For this reason, as described above with reference to FIG.
Since it takes 3.5 seconds to reach 0 ° C., the recording material P normally reaches the fixing nip portion N from the sheet feeding position A even if the sheet is fed immediately after receiving the print signal. Although the temperature can be sufficiently raised, a wasteful paper supply waiting time for raising the temperature to 130 ° C. has been required.

In this embodiment, after the print signal is received from the host computer, the heating element 1 is energized at a duty of 100%, and the temperature rise rate for a predetermined time from the start of energization, here 0.5 second, or the ultimate temperature. The paper feed timing is determined based on this.

Further, the film 9 is not driven to rotate for a predetermined time after energization of the heating element 1, in this embodiment for 0.5 seconds during which the detection is being performed, and the driving is started after a predetermined time has elapsed. .

In a fixing device having a driving portion, particularly a film heating type device, heat-resistant grease is generally applied to the inner surface of the film to reduce the contact friction with the heater 1. This is problematic in that when the film is cold, the driving torque is large due to the high viscosity of the grease. The driving torque of the image heating device occupies a large portion of the entire driving torque of the printer body, and reducing the driving torque is effective in reducing the load on the driving motor and the capacity of the motor driver.

In the present embodiment, the solution was successfully achieved by energizing the heating element 1 before driving the film and heating the grease interposed between the heating element 1 and the film 9 to lower the viscosity.

That is, by supplying electricity to the heating element 1 after receiving the print signal and before driving and rotating the film 9, both the reduction of the film driving torque and the prediction of the time until the heating element 1 reaches the fixing temperature are achieved. Will be able to do.

By adopting such a method, conventionally, it was not possible to feed the sheet until at least about 3.5 seconds had elapsed from the energization of the heating element 1 to 130 ° C. However, in the present embodiment, the sheet can be fed after 0.5 seconds except under the worst conditions, so that it is possible to shorten the FPT, which is the difference of 3.0 seconds.

Specific examples will be described below.

Printer body, fixing device (image heating device)
Reference numeral 33 is the same as that of FIG.

On the inner surface of the film 9, heat-resistant fluorine grease is used to reduce the coefficient of friction with the heating element 1 at the time of driving the film.
00 is applied.

This grease has a sufficient lubricity of 38 centistokes at 100 ° C.
Near room temperature, the viscosity is relatively high, about 250 centistokes. For this reason, the film rotation driving start torque especially at a low temperature is about 8.0% higher than the torque during driving.

To prevent this, when a print signal is received, the heating element 1 is first energized for 0.5 seconds. The energization amount may be any percentage as long as it is a specified value, but in this embodiment, 100% full energization is performed in order to predict the time required to reach the fixing temperature of the heating element 1 simultaneously with the heating of the grease. Do.

During energization for 0.5 seconds, the temperature rise rate and the attained temperature after energization for 0.5 seconds are measured by the detection voltage of the thermistor 5. Here, a complementary formula of the time VS heating element temperature is made from the temperature rise rate and the attained temperature, and the time required for the heating element 1 to reach the fixing temperature is predicted.
If the temperature resolution in the low temperature part is low, it is possible to obtain an approximate expected value only by the attained temperature.

An experiment was actually performed under the conditions of an ambient temperature of 25 ° C., a resistance value of the resistance heating element layer 3 of the heating element 1 of 33 Ω, and an input voltage of 100 [V]. Was measured at a temperature of 40 ° C. and a temperature rise rate of 30 deg / sec. From this relationship, the heating element 1 has a fixing temperature of 180 °.
It was expected that 4.7 seconds would be required after this to reach ° C.

Since the printer used in the experiment is the same as that used in Reference Example 1 (FIG. 1), the time required for the fed recording material P to reach the fixing nip N from the paper feeding position A is as follows. Since this is 6.0 seconds, in this case, an output image with sufficient fixability could be obtained even if paper feeding was started after 0.5 seconds detection after receiving the print signal.

On the other hand, under the conditions of an ambient temperature of 15 ° C., a resistance value of the resistance heating element layer 3 of the heating element 1 of 33 Ω, and an input voltage of 85 [V], the ultimate temperature of the heating element 1 after energizing for 0.5 seconds is 26. °
C, the temperature rise rate was measured to be 22 deg / sec. From this, the time required for the heating element 1 to reach the expected fixing temperature is 7.0 seconds, which is longer than 6.0 seconds.

In this embodiment, the heating time is as short as 0.5 second as compared with Reference Example 1 and the reached temperature is relatively low.
The detection accuracy of the expected time to reach the fixing temperature is slightly poor. Therefore, after that, the power supply is continued at a duty of 100% and the sheet is fed after the detected temperature reaches 180 ° C.

As a result, conventionally, after the print signal was received, the sheet was not unconditionally fed until the temperature of the heating element 1 was increased to 130 ° C., so that under normal conditions the sheet feeding wait time was about 3.5 seconds on average. By taking the sequence of the present embodiment, what is needed is 0. 0 except for the worst condition.
With a waiting time of 5 seconds, the FPT can be shortened.

Further, it is possible to raise the temperature of the grease by energizing the heating element 1 before driving the film 9 to rotate, thereby reducing the initial driving torque of the film 9.

Reference Example 2 (FIGS. 4 and 5) In this reference example , a magnetic induction heating type / film heating type device is used as a fixing device. The paper feed timing is determined by measuring the temperature rise of the fixing device due to the above.

[0128] (a) in FIG. 4 configuration model view of outline of a fixing device of the magnetic induction heating method, film heating method of the present reference example,
(B) is a perspective view of a field coil unit as a magnetic field generating means as viewed from below.

Reference numeral 41 denotes a cylindrical magnetic material film (magnetic conductive film), which is a film base layer 41a, a magnetic metal layer 41b provided on the outer peripheral surface of the base film 1a, and in this embodiment, a conductive and magnetic nickel layer. And the magnetic metal layer 41b
Release layer 41c coated on the outer peripheral surface of the
It is a three-layer film composed of an FE (tetrafluoroethylene resin) layer.

[0130] 42, cross-section E-type core material (core, a magnetic material) of a field coil unit as a magnetic field generating means comprising only One winding an exciting coil 42b to 42a, the magnetic material film 41, the recording material P Is a horizontally long member whose longitudinal direction is perpendicular to the moving direction of the moving member.

Reference numeral 43 denotes a stay for supporting the field coil unit 42 and keeping the running of the magnetic material film 41. The stay 43 is made of a liquid crystal polymer, phenol resin or the like. Have been.

The stay 43 is a field coil unit 42
The E-shaped core is a horizontally long member arranged with the three legs facing downward and sandwiching both longitudinal sides thereof.

Reference numeral 44 denotes a film pressing plate (sliding plate) provided on the downward surface of the E-shaped core of the field coil unit 42, and is made of glass or the like having a small frictional resistance with the magnetic material film 41. Further, a lubricant such as grease oil is applied to the surface.

The above-mentioned field coil unit 42 and stay 4
3. The endless (cylindrical, seamless) heat-resistant and magnetic material film 41 is loosely fitted outside the assembly (magnetic induction heating structure) including the film pressing plate 44 and the like.

Reference numeral 45 denotes a pressure roller, which is formed by covering a core metal with silicone rubber, fluorine rubber or the like. The pressure roller 45 is provided with a predetermined pressing force by a bearing means and a biasing means (not shown) with a predetermined pressing force.
Of the magnetic material film 4 against the lower surface of the film pressure plate 44
1, and a pressure contact nip portion (fixing nip portion) N is formed with the magnetic material film 41 sandwiched between the film pressure plate 44 and the lower surface of the film pressure plate 44.

The pressure roller 45 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. The rotational force acts on the magnetic material film 41 by the frictional force between the roller and the outer surface of the film due to the rotational drive of the pressure roller 45, and the magnetic material film 41 slides on the lower surface of the film pressing plate 44 to slide tightly. It rotates around 42, 43 and 44.

Numeral 46 denotes an energization control circuit for the excitation coil 42b of the field coil unit 42, a high-frequency oscillation circuit 47, a control circuit (CPU) 48, and an A / D converter 49.
Etc.

260k generated by the high-frequency oscillation circuit 47
When the Hz current is turned on / off by the control circuit 48, the energization control (power control) to the excitation coil 42b is performed. The controlled current is guided to the exciting coil 42b, and a magnetic circuit is formed in the fixing nip N as indicated by the arrow H. Then , at the fixing nip portion N, an induced current (eddy current) is excited and flows through the magnetic metal layer 41b of the magnetic material film portion located at the fixing nip portion N, and the magnetic metal layer portion generates heat ( Magnetic induction heating).

Thus, the rotation of the pressure roller 45 causes the rotation of the magnetic material film 41, and the current supply control circuit 46 applies a current to the excitation coil 42 b of the field coil unit 42, thereby causing the magnetic material film 41 to rotate. In a state where the metal layer 41b generates heat, the recording material P is introduced into the press-contact nip portion N, closely adhered to the surface of the magnetic material film 41, and passed through the fixing nip portion N together with the film, thereby being heated by magnetic induction. The heat of the magnetic material film 41 is applied to the recording material P, and the unfixed toner image t is heated and fixed.

The fixing device of the magnetic induction heating type and the film heating type directly generates heat near the surface layer of the magnetic material film 41, so that there is an advantage that the heating can be rapidly performed regardless of the heat conductivity and heat capacity of the film base layer 41a. . In addition, since the thickness of the magnetic material film 41 does not depend, even if the thickness of the base layer 41a of the magnetic material film 41 is increased in order to improve the rigidity of the magnetic material film 41 for speeding up, it can be quickly heated to the fixing temperature. Furthermore, since the film base layer 41a is made of a resin having a low thermal conductivity, the heat insulating property is good, and the film having a large heat capacity such as a coil inside the film can be insulated. Efficient. In addition, heat is hardly transmitted to the coil inside the film, and the performance of the coil does not deteriorate. As the thermal efficiency is improved, the temperature rise in the apparatus is suppressed, and the influence of the image forming unit of an image forming apparatus such as an electrophotographic apparatus using the heating apparatus as an image heating and fixing apparatus can be reduced.

In the fixing device of this embodiment, the temperature is controlled by the temperature of the pressure roller 45 as a thermistor 5 serving as a temperature detecting member.
0, and the detected information is fed back to the control circuit 48 via the A / D converter 49, and the control circuit 48
By controlling the high-frequency oscillation circuit 47.

In this embodiment, since the thermistor 45 is not in direct contact with the magnetic material film 41 as a heating element, a time delay occurs between the heat generation of the film 41 and the detected temperature. For this reason, when estimating the time until the fixing temperature is reached from the temperature rise rate as in the previous embodiment, a slight error may occur.

Accordingly, in the present embodiment, full power supply is performed for 0.5 seconds after receiving the print signal, and the temperature of the pressure roller 45 reached by this is measured to determine the paper feed timing.

Since the amount of heat applied to the film and the amount of temperature rise are determined by the heat capacity around the fixing device, it is possible to detect the temperature by measuring the amount of temperature rise per unit time.

In this embodiment , the magnetic induction heating system and the film heating system shown in FIG. 4 were used as the fixing device in the printer shown in FIG.

FIG. 5 shows the result of an actual experiment in which the correlation between the temperature detected by the thermistor 45 after 0.5 seconds of energization and the time to reach the fixing temperature of 180 ° C. is measured. .

In the method of this embodiment , since the detection is performed based on the absolute value of the temperature rise without detecting the ambient temperature, it is necessary to consider the lowest ambient temperature at which the printer body is considered to be used.

Assuming that the ambient temperature is 5 ° C. under the worst condition, if the detected temperature of the thermistor 45 is 40 ° C. or more, the temperature of the fixing unit rises to 180 ° C. within 6.0 seconds from the sheet feeding. In this case, it is assumed that a print signal is received, and paper is fed immediately after 0.5 seconds of power supply for detection.

When the temperature is 40 ° C. or less, FIG.
Time T1 to reach the expected fixing temperature based on the relationship
Therefore, it is assumed that the sheet feeding is delayed by a value T3 obtained by subtracting the time T2 required to convey the recording material P from the sheet feeding position A to the fixing nip portion N, and the sheet feeding is performed after the T3 is energized.

As described above, even in the fixing device of the magnetic induction heating system, it was found that the first print time can be shortened except for the worst condition by measuring the temperature rise due to short-time energization. .

[0151] Incidentally, a technique for sensing the temperatures reached when energized in a unit time is not intended to be limited to the apparatus of the magnetic induction heating system such as in this reference example, Reference Example 1,
Needless to say, the present invention can be applied to a film type device as described in the first embodiment .

The reference numeral 51 designates a series connection of the energizing circuit for the exciting coil 42b and the core 42 of the field coil unit 42.
This is a safety element (thermal protector) disposed in contact with a. When the core member 42a is excessively heated to a predetermined temperature or more, the core member 42a melts and cuts off the power supply to the exciting coil 42b.

In the fixing device shown in FIG. 4, the magnetic material film 41 is a heat-resistant film which does not include a magnetic metal layer like the fixing device shown in FIG. 1, and the film pressing plate 44 is a magnetic metal member. At 42, heat can be generated by magnetic induction heating, and the heat can be applied to the recording material P via the heat resistant film.

In the fixing device shown in FIGS. 1 and 4, the films 1 and 41 may not be endless films, but may be rolled and wound endless films, which may be used by being fed and run.

[0155]

As described above, according to the present invention, by energizing the heating element of the pre-fixing device before performing the feeding of the recording material (fixing device),
The rate of temperature rise and the temperature reached are detected, the time T1 required to reach a predetermined fixing temperature is predicted, and the time T2 from when paper is fed to when the recording material reaches the fixing unit (heating unit) is compared. If T1 <T2, feeding is started immediately to reduce the first print time (FPT), and otherwise, feeding is delayed for T2-T1 or more to prevent output of a poorly-fixed image. Now you can do it.

This eliminates the need for a wasteful paper feed waiting time in anticipation of the worst conditions of the related art, and makes it possible to reduce the first print time, which has recently become important.

In the case of a film heating type fixing device , the heating element is energized to raise the temperature of a lubricant such as grease applied to the inner surface of the film to lower the viscosity and then drive the film. In addition, the magnitude of the starting torque, which has conventionally been a problem, can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram showing a temperature rise of a heating body under various conditions.

FIG. 3 is a control flowchart.

4A is a schematic structural model diagram of a fixing device according to Reference Example 2, and FIG. 4B is a perspective view of the field coil unit as viewed from below.

FIG. 5 is a diagram illustrating a relationship between a thermistor detection temperature and a sheet feeding delay time.

FIG. 6A is an enlarged cross-sectional schematic view of a main part of an example of a film heating type fixing device , and FIG.
Partly cutaway plan view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating body 2 Heater board 3 Resistance heating element layer 4 Surface protective layer 5.50 Temperature detection member (cersmitter) 6.51 Thermal protector 7.43 Stay 9.41 Heat resistant film or magnetic material film (fixing film) 10.45 Pressure roller 11/46 Energization control circuit 12 AC driver 13.48 Control circuit (CPU) 14.49 A / D converter 47 High frequency oscillation circuit P Recording material t Unfixed toner image N Fixing nip H Magnetic circuit 21 Photoconductor 22 Charging roller 23 Laser diode 24 Developing device 25 Transfer roller 26 Transfer unit 27 Cleaning device 28 Feed unit 30 Feed roller A Feed position

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/00 303 G03G 15/20 G03G 21/00 370-502 G03G 21/14

Claims (1)

(57) [Claims] A printing unit for forming an image on a recording material;
A heating element that is maintained at a fixing temperature during image fixing and a film to which grease is applied between the heating element and the recording medium on which an image is formed and that moves together with the recording medium, and during standby, the heating element is not energized and in the image forming apparatus having a fixing unit that film is stopped, and after receiving a print signal, causes energizing a predetermined time the heating element
And the movement of the film is prohibited .
Control means for starting the movement of the film after a lapse
And, the heater temperature increase rate measured immediately after the recording material when the fixing temperature arrival time calculated from the temperature increase rate is faster than the time the recording material reaches the fixing position from the recording material paper feeding position of in the predetermined time An image forming apparatus which starts feeding of the recording material and delays feeding of the recording material when the feeding is late.