JPH10312127A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the consumption of power and to shorten the period until a series of copying operations to the first transfer material is completed, after the reception of a copying start command is recognized by adopting such a constitution that each transfer material can be consecutively carried to a fixing nip part at specific carrying intervals. SOLUTION: This image forming device is constituted so that when the number of transfer materials to be consecutively copied is represented as (n+1), the carrying interval between the trailing end part of the transfer material to be copied at the (k)th and the top end part of the transfer material to be copied at the (k+1)th is represented as Lk and the maximum value of those from L2 to Ln is represented as Lmax, each transfer material can be consecutively carried to the fixing nip part formed between a fixing means and a pressure means, at carrying intervals satisfying L1>Lmax. In a heating/fixing device having such a constitution, the temp. of a pressure roller 106 is sufficiently raised by a ceramic heater 111 through a fixing film 9, during the time taken from the completion of fixation on the first recording paper P to the rushing into the fixing nip part of the second recording paper P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus employing an electrophotographic system, an electrostatic recording system, or the like.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in which a transfer interval for each transfer material in continuous copying can be freely changed.

[0002]

2. Description of the Related Art In a fixing device used in a conventional image forming apparatus employing an electrophotographic system or an electrostatic recording system, a transfer material carrying an unfixed image is transferred at a predetermined constant speed. A fixing device that softens and melts the unfixed image by applying heat at least while conveying the toner and fixes the unfixed image onto the transfer material, a so-called heat fixing device, is known and widely used in practice.

On the other hand, in recent years, a series of copying operations for the first transfer material after the image forming apparatus recognizes the reception of the copy start command has been performed, since the power consumption contributing to the fixing in the heat fixing device has been reduced. Users and the like have demanded a reduction in the time until the end (hereinafter, this time is referred to as a first print time).

[0004] Therefore, two typical examples of the heat fixing device proposed to meet the above-mentioned demands of the users and the like and practically used today are shown in FIGS. 9 and 10, respectively.

[0005] First, as a typical example of a heat fixing device for reducing the power consumption and the first print time which contribute to fixing, a heat fixing device 1 shown in FIG.
00 is known and widely used.

In the heat fixing apparatus 100, a fixing roller 1014 as a fixing unit and a pressing roller 106 as a pressing unit, both of which are rotatable, include a recording paper P as a sheet-like transfer material carrying an unfixed image. Are supported so that they can be pressed against each other.

[0007] The fixing roller 101 supported by the heat fixing apparatus 100 has an offset of an unfixed image carried on the recording paper P on an outer peripheral surface of a cored bar 102 formed in a roll shape from a material such as aluminum. In order to prevent the phenomenon, materials such as polytetrafluoroethylene (hereinafter abbreviated as PTFE) and perfluoroalkoxytetrafluoroethylene copolymer (hereinafter abbreviated as PFA) having excellent releasability are used. A halogen lamp, which is a heat source, is a heat supply source for softening and melting an unfixed image and fixing the unfixed image on the recording paper P in a hollow portion of the cored bar portion 102. 104 are provided.

The fixing roller 101 has a core metal part 102 so as to have a low heat capacity in order to reduce the power consumption for contributing to the fixing and to shorten the first print time.
However, the thickness is set to a value of 2 mm or less, and the outer diameter is set to a value of 30 mm or less.

Further, a thermistor temperature detecting sensor 105 for detecting the surface temperature of the fixing roller 101 is provided in contact with the outer peripheral surface of the fixing roller 101.

On the other hand, the pressure roller 106 supported by the heat fixing device 100 is formed by foaming silicone rubber or silicone rubber on the outer peripheral surface of a cored bar 107 formed of a material such as aluminum in a roll shape. An elastic layer 108 made of a material such as PTFE and a release layer 109 made of a material such as PTFE or PFA are laminated in this order. The outer diameter of the pressure roller 106 is determined by the temperature of the fixing nip N due to the heat absorption of the recording paper P during fixing. Is set to a value that obtains a heat capacity that can prevent a sharp decrease.

The pressure roller 106 is provided in an image forming apparatus that can utilize the heat fixing device 100 so as to press against the fixing roller 101 via the recording paper P carrying an unfixed image during fixing. Pressure is applied to the fixing roller 101 by a pressure mechanism (not shown). Due to the elasticity of the elastic layer 108, a sufficient amount of recording paper P is supplied between the two rollers to supply heat that contributes to fixing. A fixing nip N having a contact area with the fixing nip N is formed.

The heat fixing device 100 having the above-described configuration and the like.
In this case, a temperature control unit (not shown) provided in the image forming apparatus turns on / off the energization of the halogen lamp 104 based on the detection result of the thermistor temperature sensing sensor 105.
By performing the FF control, the temperature of the surface temperature of the fixing roller 101, the surface temperature of the pressure roller 106, the temperature of the fixing nip N, and the like are adjusted.

Therefore, in the image forming apparatus which can utilize the heat fixing device 100, the copying operation is started in a short time after recognizing the copying start command, so that the copying operation can be started within a short time. At a certain standby time, the surface temperature of the fixing roller 100 is raised to a predetermined temperature for standby by ON / OFF control of energization of the halogen lamp 104, and is maintained. Before reaching the fixing nip N, the surface temperature of the fixing roller 101 and the pressure roller 10 are controlled again by turning on / off the energization of the halogen lamp 104.
6, the temperature of the fixing nip N is raised to and maintained at a temperature suitable for fixing (hereinafter, these temperatures are referred to as temperature control temperatures).
It was prepared for fixation to.

On the other hand, as another typical example of the heat fixing device for saving power consumption and shortening the first print time which contributes to fixing, a heat fixing device 110 shown in FIG. No. 44075, etc., and are in practical use.

The heating and fixing device 110 includes a ceramic heater 111 serving as a heat supply source as a heat supply source for softening and melting an unfixed image and fixing the unfixed image onto the recording paper P, and a stay for fixing the ceramic heater 111. Holder 115
And a fixing film 116 as a fixing unit loosely fitted to the stay holder 115 and a pressing roller 106 as a rotatable pressing unit.

In the heating and fixing device 110,
The members and the like having the same functions and configurations as the members and the like included in the heat fixing device 100 are given the same reference numerals as those in FIG.

As shown in FIG. 11, the ceramic heater 111 of the heat fixing device 110 has one surface of a substrate 112 formed of a ceramic material having a thickness of, for example, 1 mm or less (hereinafter, this surface is referred to as The heating resistance layer 113 is screen-printed on the heating surface HA (refer to FIG. 11), and is further protected by coating the heating surface HA with a thin glass protective layer 114 having a thickness of, for example, 100 μm or less. And so on.

The ceramic heater 111 has a pressure roller on the other surface of the base 112 (that is, a surface facing the heating surface HA, and this surface is hereinafter referred to as a non-heating surface HA '). A thermistor temperature sensing sensor 117, which is a temperature sensing means for sensing the surface temperature of the sensor 106, is provided in contact therewith.

That is, the ceramic heater 111
In general, when the thickness is small, heat diffusion to the outside world and thermal equilibrium with other members and the like are quickly performed.
The thermistor temperature sensing sensor 117 provided in contact with the non-heating surface HA ′ of No. 12 can detect the surface temperature of the pressure roller 106 via the ceramic heater 111.

The stay holder 115 of the heat fixing device 110 is integrally formed of a material such as plastic, and fixes the ceramic heater 111 and
While the fixing film 116 is rubbed against the heating surface HA at the time of fixing, the pressure roller 106 is rotated by a driving mechanism (not shown) provided in an image forming apparatus in which the heat fixing device 110 is used. It also serves as a guide to make it follow.

The fixing film 116 of the heat fixing device 110 is a so-called seamless film, and is supported on a recording paper P on an outer peripheral surface of a base layer (not shown) for maintaining mechanical strength such as tear strength. In addition, a release layer (not shown) for preventing the offset phenomenon of the unfixed image is coated.

The base layer of the fixing film 116 includes:
Since it is made of a material such as polyimide, polyamide imide, or PEEX, it has heat resistance and high elasticity, and the release layer is made of a fluororesin such as PFA, PTFE, or FEP on the order of 10 μm. Thickness is set.

Therefore, the fixing film 116 has an unfixed image in which the heat generated by the heat generating resistance layer 113 reaches the fixing nip portion N by setting the entire layer thickness to a low heat capacity within the range of 20 to 70 μm. The heat is efficiently conducted to the recording paper P, so that the power consumption that contributes to the fixing is saved, and the first print time is further shortened (quick start) compared with the heat fixing device 100.

The heat fixing device 10 described above
In an image forming apparatus that can utilize a heat fixing device represented by 0, 110, when performing continuous copying on a plurality of recording papers P, the recording paper P that continues from the rear end of an arbitrary recording paper P Is set to a constant value (hereinafter, this interval is referred to as a sheet interval), and is conveyed to the fixing nip N.
In particular, the interval between the recording papers P may be reduced as much as possible so that the number of recording papers P to be fixed in a certain period of time is increased without increasing the speed for transporting the recording papers P.

[0025]

However, in the heat fixing devices 100 and 110, the pressure roller 106 needs to have a certain elasticity in order to obtain a fixing nip portion N suitable for fixing. In addition, in order to shorten the time required for fixing so as to respond to a rapid series of copying operations recently requested by a user or the like, a pressing roller 1 is used.
06 needs to be set to a certain outer diameter value to increase the peripheral speed, so the heat capacity of the pressure roller 106 is
Inevitably, the size of the fixing roller 101 and the fixing film 116 must be increased.

Therefore, in the heat fixing devices 100 and 110, the surface temperature of the fixing roller 101 or the fixing film 116 can quickly reach the regulated temperature by short-time heating by the halogen lamp 104 or the ceramic heater 111. On the other hand, the surface temperature of the pressure roller 106 could not be as high as that of the fixing roller 101 or the fixing film 116.

Therefore, the above-mentioned heat fixing devices 100 and 110
In the conventional image forming apparatus utilizing the heat, the water vapor generated from the recording paper P carrying the unfixed image due to the heat supply is not pressurized so that the surface temperature is not so high as in the initial stage of continuous copying. Condensation forms on the outer peripheral surface of the roller 106 to form a thin film. As a result, the frictional resistance of the release layer 109 for transporting the recording paper P is reduced. The unfixed image carried on the next sheet of recording paper P may not be able to smoothly pass through the fixing nip N due to slippage due to failure to synchronize well with the peripheral speed.
4 or excessively supplied with heat from the ceramic heater 111 and excessively melted, thereby causing a decrease in viscosity. In some cases.

In particular, when continuous copying is performed on a plurality of recording sheets P having a high printing rate of an unfixed image, water vapor generated from an arbitrary recording sheet P by heat supply for fixing causes the fixing roller 101 or the fixing roller 101 to fix. Since the flow to the film 116 side is blocked by the unfixed image, in the initial stage of continuous copying or the like, most of the water vapor condenses on the outer peripheral surface of the pressure roller 106 to form a thin film. When the frictional resistance of the recording paper P further decreases, the next recording paper P slips without being able to follow the peripheral speed of the pressure roller 106 at all, and cannot enter the fixing nip N. In some cases, a paper jam due to the recording paper P may occur in a conveyance path between the transfer unit for transferring the unfixed image onto the recording paper P and the heat fixing devices 100 and 110.

Accordingly, the present invention is to reduce the power consumption that contributes to the fixing and to reduce the time from when the reception of the copy start command is recognized until the end of a series of copy operations on the first transfer material. It is another object of the present invention to provide an image forming apparatus in which the interval for transporting each transfer material during continuous copying can be freely changed.

[0030]

According to the present invention, an object of the present invention is to provide a fixing means for heating an unfixed image to fix it on a sheet-like transfer material, and pressing the unfixed image with the fixing means via the transfer material. In the image forming apparatus which has a pressure unit contributing to fixing by the fixing and a heat generating unit serving as a heat supply source for fixing, and is capable of continuously copying on a plurality of transfer materials, an arbitrary natural number is represented by n. , The number of transfer materials to be continuously copied is n +
An arbitrary natural number less than or equal to 1, n is k, and the transport interval between the rear end of the transfer material to be copied k-th and the front end of the transfer material to be copied k + 1-th is from Lk and L2. When the maximum value up to Ln is represented by Lmax, each transfer material is continuously conveyed to a fixing nip formed between the fixing unit and the pressing unit at a conveyance interval satisfying L1> Lmax. This is achieved by the first invention which is made possible.

The object of the present invention is that, in the first aspect, the pressing means is a rotatable pressing roller formed in a roll shape having an outer diameter R, and when the circumferential ratio is represented by π, L1 Is also achieved by the second invention in which the outer peripheral length of the pressure roller is set to a value larger than 2πR and Lmax.

Further, the above object is also achieved by a third invention in which L2 is set to a value satisfying L1>L2> L3 in the first invention or the second invention.

Further, the above object is achieved by the temperature detecting means provided for detecting the temperature of the pressurizing means in any one of the first to third inventions. The present invention is also achieved by the fourth invention in which the transfer interval of each transfer material to the fixing nip portion is set based on the temperature value.

Further, the above object is achieved by any one of the above first and second inventions,
The present invention is also achieved by the fifth invention in which the conveyance interval of each transfer material to the fixing nip is set based on the printing rate of a copy image formed on the transfer material.

Further, the object of the present invention is to provide a method according to any one of the first and second aspects of the present invention, wherein the fixing of each transfer material is performed based on a length in a direction parallel to a transfer direction of the transfer material. The present invention is also achieved by the sixth invention in which the conveyance interval to the nip portion is set.

Further, the above object is to provide a fixing means for heating an unfixed image to fix it to a sheet-like transfer material, and a pressure means for contributing to fixing by being pressed against the fixing means via the transfer material. And a heat generating means serving as a heat supply source for fixing, and in the image forming apparatus capable of continuously copying on a plurality of transfer materials, a first method for detecting a speed for conveying the transfer material. The speed detecting means and the second speed detecting means are respectively provided at a position immediately downstream and a position immediately upstream along the conveying direction from the fixing nip portion, and the speed value detected by the first speed detecting means is provided. A transfer interval of each transfer material to be subsequently fixed to the fixing nip is set based on a comparison between the speed value detected by the second speed detecting means and the speed value detected by the second speed detecting means. Is also achieved by

That is, in the first aspect of the invention, the pressurizing means is used for the fixing during the period from the end of the fixing to the first transfer material to the arrival of the second transfer material to the fixing nip. The temperature is sufficiently raised by the heat generating means via the means.

In the second aspect of the present invention, the pressure roller is used during the period from the end of fixing to the first transfer material to the arrival of the second transfer material to the fixing nip. By rotating, the entire outer peripheral surface is sufficiently heated by the heat generating means via the fixing means.

Further, in the third aspect of the invention, the pressurizing means may be used for fixing during the period from the end of fixing to the first transfer material to the arrival of the second transfer material to the fixing nip. The temperature is sufficiently raised by the heat generating means via the means, and the heating is performed during the period from the end of fixing to the second transfer material to the arrival of the third transfer material to the fixing nip portion. The pressure means is again sufficiently heated by the heating means via the fixing means.

In the fourth aspect of the present invention, the transfer interval of each transfer material to the fixing nip is set based on the temperature value of the pressing means detected by the temperature detecting means.

Further, in the fifth aspect, the transport interval of each transfer material to the fixing nip is set based on the print ratio of a copy image formed on the transfer material.

In the sixth aspect of the present invention, the transfer interval of each transfer material to the fixing nip is set based on the length in the direction parallel to the transfer direction of the transfer material.

Further, according to the seventh aspect of the present invention, the fixing value is determined based on a comparison between the speed value detected by the first speed detecting means and the speed value detected by the second speed detecting means. The conveyance interval for each transfer material to be transferred to the fixing nip is set.

[0044]

Embodiments of the present invention will be described with reference to the accompanying drawings. Note that the terms used in the following description are omitted in place of the definitions of the terms used in the description of the conventional image forming apparatus.

(First Embodiment) First, a main part of an image forming apparatus as an example suitable for showing a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a main part of an image forming apparatus suitable for the present embodiment.

The image forming apparatus includes an image forming section 1 for forming a copy image in accordance with the read image information, and a recording sheet P as a sheet-like transfer material for transferring the copy image formed by the image forming section 1. And a fixing device for fixing an unfixed copy image (hereinafter, referred to as an unfixed image) to the recording paper P by supplying heat at least, that is, a so-called heat fixing device 7. And

The image forming section 1 provided in the image forming apparatus comprises a primary charger 2, a photosensitive drum 3 as an image carrier, a developing device 4, a cleaner 5, and the like.

The primary charger 2 of the image forming section 1
Is designed to prepare for the next copy image formation by uniformly charging the surface of the photosensitive drum 3 at a predetermined timing or the like set in advance.

The photosensitive drum 3 of the image forming unit 1
Is OPC, amorphous Se on the outer peripheral surface of a cylindrical member made of a material such as aluminum or nickel.
Or, a photosensitive material such as amorphous Si is applied, and is rotatably supported in the direction indicated by an arrow in the image forming apparatus. The laser beam La based on the read image information is primarily charged. By exposing the charged area of the photosensitive drum 3 uniformly charged by the unit 2, an electrostatic latent image corresponding to the image information is formed.

The developing device 4 included in the image forming unit 1 includes:
The electrostatic latent image formed on the surface of the photosensitive drum 3 is developed by applying a developer (hereinafter, referred to as a toner) to develop a visible image (hereinafter, referred to as a toner image). In the present embodiment, as a developing method using the developing device 4, a conventionally known jumping developing method, two-component developing method, FEED developing method, or a developing method combining image exposure and reversal developing is adopted. Have been.

The cleaner 5 of the image forming section 1 has
By removing and collecting the residuals such as toner and paper pieces remaining on the surface of the photosensitive drum 3 at the end of the previous copy image formation, the apparatus is prepared for the next copy image formation.

The transfer roller 6 provided in the image forming apparatus is carried on the surface of the photosensitive drum 3 by, for example, charging the conveyed recording paper P to a polarity opposite to that of the toner at a predetermined timing or the like. The toner image is transferred onto the recording paper P.

In the image forming apparatus having the above-described schematic configuration, a series of copying steps from the formation of an electrostatic latent image according to the image information to the fixing of an unfixed image on a recording sheet P are described below. It is done in the way of.

First, a laser beam La based on image information read from an exposure system provided in the image forming apparatus, for example, a laser unit (not shown) is modulated and emitted. Are uniformly charged by the primary charger 2 based on a copy start instruction by a manual operation of the user.

Accordingly, the laser La modulated and emitted from the exposure system is irradiated to the charged area of the photosensitive drum 3 to be exposed, whereby an electrostatic latent image based on the image information is formed in the charged area. .

Next, the electrostatic latent image formed on the surface of the photosensitive drum 3 is developed into a toner image by applying toner from the developing device 4, while a copy image corresponding to the image information is formed. Is fed from a paper feeding system, for example, a paper feeding cassette (not shown) at a predetermined time after the start of copying, and is formed between the photosensitive drum 3 and the transfer roller 6. Is transferred toward the transfer nip portion TN.

Therefore, the recording paper P conveyed to the transfer nip TN at a predetermined timing or the like is transferred to the transfer roller 6
After the toner image formed on the surface of the photosensitive drum 3 is transferred by being charged to the opposite polarity to that of the toner, the toner image is transferred to the heat fixing device 7, while the toner image is transferred to the recording paper P. The completed photosensitive drum 3 is prepared for formation of a copy image to be transferred to the next recording paper P by removing the residue by the cleaner 5 and uniformly charging by the primary charger 2.

On the other hand, the recording paper P that has reached the heating and fixing device 7 is fixed at least by receiving heat supply so that the unfixed image is softened, melted, and mixed to form an image. When a sheet is discharged to the outside of the image forming apparatus by a sheet discharge system, for example, a sheet discharge roller (not shown), a series of copying processes for an arbitrary recording sheet P is completed.

Next, FIG. 2 shows the heat fixing device 7 provided in the image forming apparatus, which saves power consumption contributing to fixing and shortens the first print time.
It will be described based on. Note that members and the like having the same functions, configurations, and the like as the members and the like of the heat fixing device 110 that can be used in the conventional image forming apparatus will be omitted by assigning the same reference numerals as in FIGS. 10 and 11. .

As shown in the main cross-sectional view of FIG. 2, the heat fixing device 7 provided in the image forming apparatus includes a ceramic heater 111 serving as a heating means, and a heat insulating stay holder 8 for fixing the ceramic heater 111. , Fixing film 9 as fixing means loosely fitted to heat insulating stay holder 8
And a pressure roller 106 as a rotatable pressure means.

The ceramic heater 111 of the heat fixing device 7 has a heating resistance layer 113 on one surface (heating surface HA, see FIG. 11) of a base 112 made of ceramics.
Is screen-printed, and is further protected by covering the heating surface HA with a thin glass protective layer 114. In the present embodiment, the substrate 1
12, the thickness is set to 0.6 mm, and the thickness of the glass protective layer 114 is set to 50 μm.

The ceramic heater 111 has a thermistor temperature sensing sensor 117 as a temperature sensing means for sensing the surface temperature of the pressure roller 106 on the non-heating surface HA ′ (see FIG. 11) of the base 112. It is provided in contact.

That is, in this embodiment, the temperature of the ceramic heater 111 detected by the thermistor temperature sensor 117 is used as the surface temperature of the pressure roller 106. Because, since the fixing film 9 has a low heat capacity, heat diffusion to the outside world and
Since the thermal equilibrium with other members and the like is high and the overall thickness of the ceramic heater 111 is thin, the thermistor temperature sensing sensor 117 and the pressure roller 106 are almost always interposed via the ceramic heater 111. This is because it can be assumed that the state is in a thermal equilibrium state.

The installation position of the thermistor temperature sensing sensor 117 employed as the temperature detecting means of the present invention is as follows.
Installation position of this embodiment (non-heated surface H on base 112)
A 'on. See FIG. However, the pressure roller 106 may be provided at a position directly in contact with the surface of the pressure roller 106.

The heat insulating stay holder 8 of the heat fixing device 7 is made of a liquid crystal polymer, phenol resin, PPS or PPS.
It is integrally molded of a material such as EEK to fix the ceramic heater 111 and fix the fixing film 9 at the time of fixing.
While rubbing against the heating surface HA, also serves as a guide for following the rotation of the pressure roller 106 which is rotationally driven by a driving mechanism (not shown) provided in the image forming apparatus according to the present embodiment. In this embodiment, the heat generated from the heat generating resistance layer 113 is efficiently conducted to the fixing nip N. In the present embodiment, the heat insulating stay holder 8 is used.
Is made of phenolic resin.

In the present embodiment, in order to realize an environment in which the fixing film 9 is easily driven by the rotation of the pressure roller 106, a space between the heat insulating stay holder 8 and the fixing film 9 is provided. A small amount of a lubricant, such as a heat-resistant grease, is applied, so that the frictional resistance between the heat insulating stay holder 8 and the fixing film 9 is reduced.

The fixing film 9 of the heat fixing device 7 is a so-called seamless film, and is provided on an outer peripheral surface of a base layer (not shown) for maintaining mechanical strength such as tear strength.
The release layer (not shown) for preventing the offset phenomenon of the unfixed image carried on the recording paper P is coated.

In general, the fixing film 9 has a base layer formed of a material such as polyimide, polyamide imide or PEEX, and has heat resistance and high elasticity.
The release layer is made of a fluororesin such as PFA, PTFE or FEP to a thickness of the order of 10 μm. In the present embodiment, the base layer is formed of polyimide having an outer diameter of 25 mm, and the release layer is formed of PTFE, so that the entire layer thickness of the fixing film 9 is set to 50 μm. I have.

The fixing film 9 generally has a total layer thickness of 10 to enable quick start.
0 μm or less. On the other hand, in order to obtain long-term durability, the total thickness must be 20 μm or more. Therefore, the total thickness is 20 μm or more and 10 μm or less.
A value in the range of 0 μm or less is preferred.

The pressure roller 1 of the heat fixing device 7
Reference numeral 06 denotes a configuration in which an elastic layer 108 and a release layer 109 are laminated on the outer peripheral surface of the cored bar 107 in this order. In this embodiment, the outer diameter of the pressure roller 106 is The metal core 107 is formed of aluminum to have an outer diameter of 25 mm so as to have a heat capacity capable of preventing the temperature of the fixing nip portion N from suddenly lowering due to the heat absorption of the recording paper P in the above.
The elastic layer 108 is formed of silicone rubber to a thickness of 4 mm, and the release layer 109 is formed of PFA.

Now, in the conventional image forming apparatus which can utilize the heat fixing device 110, as shown in FIG. 10, in order to obtain a fixing nip portion N suitable for fixing, the pressure roller 106 is used. In order to shorten the time required for fixing so as to respond to the speed of a series of copying operations recently requested by a user or the like, the pressure roller 106 needs to have a certain elasticity. It is necessary to increase the peripheral speed by setting the outer diameter value of
06 had a large heat capacity compared to the fixing film 116.

Therefore, in the heat fixing device 110, the surface temperature of the fixing film 116 can quickly reach the temperature control temperature by the short-time heating by the ceramic heater 111, while the pressure roller 106 The surface temperature could not be as high as that of the fixing film 116.

However, in the conventional image forming apparatus, each recording sheet P is conveyed to the fixing nip N by setting a constant sheet interval irrespective of the surface temperature value of the pressure roller 106. Was.

Therefore, in the conventional image forming apparatus utilizing the heat fixing device 110, the steam generated from the recording paper P carrying the unfixed image due to the heat supply causes the water vapor generated at the beginning of continuous copying and the like. As described above, dew forms on the outer peripheral surface of the pressure roller 106 whose surface temperature is not so high to form a thin film, and the frictional resistance of the release layer 109 for transporting the recording paper P is reduced. The recording paper P is a pressing roller 1
Since it is not possible to satisfactorily synchronize with the peripheral speed of No. 06 and slip and cannot pass through the fixing nip portion N smoothly, the unfixed image carried on the next recording paper P receives excessive heat supply from the ceramic heater 111. When the recording paper P is melted excessively, thereby lowering the viscosity, a poorly copied image having unevenness in image glossiness may be formed on each of the subsequent recording papers P.

In particular, when continuous copying is performed on a plurality of recording sheets P having a large occupation ratio of an unfixed image, water vapor generated from an arbitrary recording sheet P by heat supply for fixing is transferred to the fixing film 116 side. Flow is blocked by the unfixed image, so that during the initial stage of continuous copying, for example, most of the water vapor condenses on the outer peripheral surface of the pressure roller 106 to form a thin film. Is further reduced, the next recording paper P slips without being able to follow the peripheral speed of the pressure roller 106 at all, and cannot enter the fixing nip N. Transfer Means and Heat Fixing Device 1 for Transferring Image to Recording Paper P
In some cases, a paper jam due to the recording paper P occurred in the conveyance path between the recording paper P.

Therefore, in the present embodiment, in order to solve the above-described problem, the interval between the trailing end of an arbitrary recording sheet P and the leading end of the next recording sheet P in continuous copying is as follows. The recording paper P can be set in the fixing nip N
To be transported.

That is, in the present embodiment, the surface temperature T of the pressure roller 106 varies from the start of copying in the image forming apparatus to the time before the first recording paper P enters the fixing nip N. The value taken in between (hereinafter, the surface temperature T at this time)
Is referred to as an initial temperature and is represented by T0. ) Is used as a criterion for determining the change between the sheets, and when T0 ≧ 40 ° C., the sheet interval for each recording sheet P is uniformly set to 50 mm.
When 0 <40 ° C., the distance between the first recording paper P and the second recording paper P is 100 mm, and the distance between the third and subsequent recording papers P is uniformly 50 mm. I decided that.

Therefore, the inventor made measurements shown in FIGS. 3 to 6 in order to confirm the effect obtained by setting the sheet interval for each recording sheet P as in this embodiment.

First, as shown in FIG. 3, the present inventor sets the above-mentioned paper interval for each recording paper P to 50 mm uniformly, and applies a pressure roller when continuous copying is performed at an initial temperature T0 = 25 ° C. The change over time of the surface temperature of 106 was measured.

In FIG. 3, the horizontal axis indicates the elapsed time from the start of copying in the image forming apparatus, and the vertical axis indicates the surface temperature of the pressure roller 106. Is uniformly set to 50 mm, and the time change of the surface temperature of the pressure roller 106 when continuous copying is performed at T0 = 25 ° C. is graphed. Note that a dotted line L drawn left and right in FIG. 3 indicates a critical temperature at which a slip of the recording paper P occurs at the pressure roller 106.

In FIG. 3, while the recording paper P is being fixed, the surface temperature of the pressure roller 106 is increased by the heat absorption based on the heat conduction from the pressure roller 106 to each recording paper P. Is lower than when each recording paper P enters the fixing nip N, and the second and third recording papers are lower than when the first recording paper P enters the fixing nip N. It was found that when P entered the fixing nip N, it was lower.

Therefore, the present inventor has proposed that the pressure roller 10
The relationship between the surface temperature of No. 6 and the slip caused by the recording paper P at the fixing nip N was examined.
The above-described slip occurs when the recording paper P is fixed to the second to fifth recording papers P (the surface temperature of the pressure roller 106 at the time of entering the fixing nip portion N is equal to or lower than the critical temperature). Depending on the situation, a result was obtained that a paper jam of the recording paper P occurred in the transport path.

From this, the time from the unloading of the first sheet of recording paper P from the fixing nip N to the entry of the second sheet of recording paper P into the fixing nip N is the first sheet of paper. When the recording paper P is fixed, the film of water vapor formed by dew condensation on the surface of the pressure roller 106 is applied to the ceramic heater 1.
When the second recording paper P enters the fixing nip portion N, the pressure roller 106 has a sufficient conveying force for an arbitrary recording paper P since the pressure is not sufficient to be removed by the heat supply from the recording paper P. It is thought that this was because they had not returned.

From these results, if the surface temperature of the pressure roller 106 when the recording paper P enters the fixing nip portion N is lower than the critical temperature shown in FIG.
In No. 6, it is considered that a sufficient conveyance force to the arbitrary recording paper P does not return, and thus the slip by the recording paper P in the fixing nip portion N occurs.

Therefore, the present inventor has proposed that the pressure roller 10
6, the surface temperature of the pressure roller 106 is compared with the frictional resistance acting between the recording paper P and the pressure roller 106, and the surface temperature of the pressure roller 106 The dependence of the kinetic friction coefficient on the temperature was measured. The result is shown in FIG.

FIG. 4 shows the temperature of the dynamic friction coefficient of the surface of the pressure roller 106 by taking the horizontal axis as the surface temperature of the pressure roller 106 and the vertical axis as the dynamic friction coefficient of the surface of the pressure roller 106. Is graphed.

FIG. 4 shows that the coefficient of kinetic friction on the surface of the pressure roller 106 increases as the surface temperature of the pressure roller 106 increases. Therefore, if the surface temperature of the pressure roller 106 can reach a predetermined temperature or more at which a sufficient conveyance force of the recording paper P can be restored, even if continuous copying is started at the initial temperature T0 = 25 ° C., the above-mentioned slippage will not occur. The result was that generation could be prevented.

In order to determine the reference point of the initial temperature for the change in the setting of the paper P for each recording paper P, the present inventors set the paper spacing for each recording paper P to 50 mm uniformly.
When the time change of the surface temperature of the pressure roller 106 when continuous copying was performed at the initial temperature T0 = 40 ° C. was measured, a graph (broken line) shown in FIG. 5 was obtained. As a result, fixing was performed in a suitable state without causing slip.

In view of the results obtained above, the present inventor has set the initial temperature T0 = 25 ° C., and has set the interval between the first recording paper P and the second recording paper P. By measuring the surface temperature of the pressure roller 106 by measuring the surface temperature of the pressure roller 106 by measuring the surface temperature of the pressing roller 106 at 100 mm, and by taking a uniform interval of 50 mm between the third and subsequent sheets of the recording paper P, the interval between the sheets is measured. Were obtained, and at the same time, the slip of each recording paper P at the fixing nip N was verified.

As can be seen from FIG. 6, the surface temperature of the pressure roller 106 when the second and subsequent recording papers P enter the fixing nip portion N is sufficiently heated. No slippage of the recording paper P was observed in the nip N.

As described above, by changing the paper interval setting for each recording paper P during continuous copying as in the present embodiment, the second recording paper from the end of fixing on the first recording paper P is changed. Since the pressure roller 106 is sufficiently heated by the ceramic heater 111 via the fixing film 9 before P enters the fixing nip portion N,
A film of water vapor formed by dew condensation on the outer peripheral surface of the pressure roller 106 by fixing to the first recording paper P is formed before the second recording paper P enters the fixing nip portion N. It can be removed by evaporation, so that at the time of fixing to each recording paper P, the frictional resistance of the release layer 109 can be returned to a value suitable for conveyance of each recording paper P, and image quality deterioration Thus, the provision of a low-quality copy image due to, for example, can be reliably prevented.

(Second Embodiment) Next, a description will be given of a change in setting of a sheet interval for each recording sheet P during continuous copying performed by the image forming apparatus according to the second embodiment of the present invention. It should be noted that the configuration of the image forming apparatus applied to the present embodiment and various devices provided are the same as those of the first embodiment, and description thereof will be omitted in place of FIGS. 1 and 2.

In the present embodiment, during continuous copying, the third and subsequent recordings caused by a film of water vapor formed by dew condensation on the surface of the pressure roller 106 by fixing to the second recording paper P This is to prevent the paper P from causing a slip at the fixing nip N.

Therefore, in this embodiment, when the initial temperature T0 of the pressure roller 106 satisfies T0 ≧ 40 ° C., the interval between the recording sheets P is uniformly set to 50 mm.
When T0 <40 ° C., the distance between the first recording paper P and the second recording paper P is set to 90 mm, and the distance between the second recording paper P and the third recording paper P is set to 90 mm. The sheet interval is set to 70 mm, and the sheet interval for each of the fourth and subsequent recording sheets P is uniformly set to 50 mm.

Therefore, the inventor of the present invention sets the first recording paper P and the second recording paper P in order to confirm the effect obtained by setting the paper interval for each recording paper P as in the present embodiment. Is set to 90 mm, and the third and subsequent recording papers P
In the comparative example, a slight slip was observed on the third recording paper P in the comparative example. As a result, a result was obtained in which the above-mentioned slip was not recognized over the entire recording paper P.

In this embodiment, the interval between the first recording sheet P and the second recording sheet P is set based on the initial temperature, and the second recording sheet P is set. Although the setting of the sheet interval between P and the third recording sheet P is performed, the number of sheets for which the sheet interval is set based on the initial temperature is limited to the second sheet from the start of continuous copying. Instead, the number of sheets may be any number within the range according to the gist of the present invention, in accordance with the specification of the heat fixing device 7.

From the above, as in the present embodiment, the interval between the recording sheets P at the time of continuous copying is reduced as the number of sheets increases and converges to a predetermined interval value. Between the end of the fixing of the recording paper P and the entry of the second recording paper P into the fixing nip N,
6 is sufficiently heated by the ceramic heater 111 via the fixing film 9, so that a film of water vapor formed by condensation on the outer peripheral surface of the pressure roller 106 by fixing to the first recording paper P is removed. The second recording paper P can be evaporated and removed before the second recording paper P enters the fixing nip portion N, and is fixed to the outer peripheral surface of the pressure roller 106 by fixing to the second recording paper P. The water vapor film formed by the dew condensation can be evaporated and removed before the third recording paper P enters the fixing nip portion N, so that the recording paper P At the time of fixing, the frictional resistance of the outer peripheral surface of the pressure roller 106 can be returned to a more suitable value for the conveyance of the recording paper P, and the provision of a low-quality copy image due to image quality deterioration or the like can be further improved. It can be reliably prevented.

(Third Embodiment) Next, a description will be given of a change in setting of a sheet interval for each recording sheet P during continuous copying performed by the image forming apparatus according to the third embodiment of the present invention. It should be noted that the configuration of the image forming apparatus applied to the present embodiment and various devices provided are the same as those of the first embodiment, and description thereof will be omitted in place of FIGS. 1 and 2.

In this embodiment, during continuous copying, the interval between the first recording paper P and the second recording paper P is changed based on the rate of increase in the surface temperature of the pressure roller 106. As a result, a slip is generated in the fixing nip portion N of the second and subsequent sheets of recording paper P due to a film of water vapor formed by dew condensation on the surface of the pressure roller 106 upon fixing to the first sheet of recording paper P. It is to prevent.

In the heat fixing device 7, the surface temperature value of the pressure roller 106 detected by the thermistor temperature sensing sensor 117 is usually the amount of heat generated from the heat generating resistance layer 113 which generates heat when energized. However, the power situation depends on the country and region,
The temperature rise rate of the temperature value detected by the thermistor temperature sensing sensor 117 differs depending on the resistance value of the pressure roller 13 or the initial temperature of the pressure roller 106. Reach different temperatures.

That is, when the rate of temperature rise of the temperature value detected by the thermistor temperature sensing sensor 117 is fast,
When the first sheet of recording paper P enters the fixing nip portion N during continuous copying, the surface temperature of the pressure roller 106 is considered to have been sufficiently raised. If the rate of temperature rise of the detected temperature value is slow,
Even when the first sheet of recording paper P enters the fixing nip portion N during continuous copying, the surface temperature of the pressure roller 106 remains unchanged.
It is considered that the temperature did not reach a sufficient level to prevent the slip of the vehicle.

Therefore, the present inventor changes the rate of temperature increase of the temperature detected by the thermistor temperature sensing sensor 117 by varying the amount of power supplied to the heating resistor layer 113 during continuous copying. At the same time as measuring the degree of slip of the second recording paper P with respect to each heating rate, the interval between the first recording paper P and the second recording paper P, and the second recording paper P A suitable value was measured for each of the intervals between the third recording paper P and the third recording paper P at each rate of temperature rise.

In the measurement relating to the slip, the distance between the recording papers P conveyed to the fixing nip N is uniformly 50 mm, and the thermistor temperature sensor 11
The rate of temperature rise detected at 7 is 4 from the initial temperature of 25 ° C.
It was estimated from the time required to reach 5 ° C.

The results obtained by the above measurements are shown in Table 1 below. Here, in Table 1, ○, Δ, and × represent
They mean no problem, acceptable range, and poor, respectively.
L1 and L2 are suitable values for the interval between the first recording paper P and the second recording paper P, and the paper between the second recording paper P and the third recording paper P, respectively. Further, Tl represents a preferable value for the pressure roller 10 when the first recording paper P corresponding to each power supply value enters the fixing nip N.
6 shows the surface temperature.

[0105]

[Table 1] As can be seen from Table 1 above, when the temperature rise rate of the temperature detected by the thermistor temperature sensing sensor 117 is fast, such as the temperature rise rate of 50 ° C./sec, the fixing nip portion N of the first recording sheet P The temperature of the surface of the pressure roller 106 has been sufficiently raised before entering the recording paper P, and the unfixed image of each recording paper P is smoothly fixed.

However, when the temperature rise rate of the temperature detected by the thermistor temperature sensing sensor 117 is slow, such as at a temperature rise rate of 45 ° C./sec or less, the entire recording paper P is fixed to the fixing nip portion N In order to prevent slipping at the beginning of the continuous copying, the interval between the recording sheets P to be fixed at the beginning of the continuous copying is set at 5 mm.
It is necessary to spread it more than 0 mm.
In the case of / sec or less, in order to sufficiently raise the temperature of the surface of the pressure roller 106, it is necessary to increase the space between the recording sheets P at the beginning of continuous copying.

Therefore, in this embodiment, the above Table 1
In accordance with the result, the inter-sheet setting for each recording sheet P at the time of continuous copying is changed based on the temperature rise rate of the temperature detected by the thermistor temperature sensing sensor 117, so that the first recording sheet P Even when a film of water vapor is formed on the surface of the pressure roller 106 due to the fixing of the recording paper P, the heat generated by the ceramic heater 111 is required until the second recording paper P enters the fixing nip N. The film of water vapor can be removed by the supply, so that when the recording paper P is fixed, the conveying force of the pressure roller 106 to the recording paper P can be returned to a suitable value, and the image quality deteriorates. Thus, the provision of a low-quality copy image due to, for example, can be reliably prevented.

(Fourth Embodiment) Next, a description will be given of a change in the sheet interval setting for each recording sheet P during continuous copying performed by the image forming apparatus according to the fourth embodiment of the present invention. It should be noted that the configuration of the image forming apparatus applied to the present embodiment and various devices provided are the same as those of the first embodiment, and description thereof will be omitted in place of FIGS. 1 and 2.

In the present embodiment, during continuous copying, the interval between the first sheet of recording paper P and the second sheet of recording paper P is changed based on the printing rate of the copied image formed on the image recording sheet P. By doing so, the slip of the second and subsequent sheets of recording paper P at the fixing nip portion N due to the film of water vapor formed by dew condensation on the surface of the pressure roller 106 as the first sheet of recording paper P is fixed It is to prevent.

In a conventional image forming apparatus which can utilize the heat fixing device 110, when continuous copying is performed on a plurality of recording sheets P having a high printing rate of an unfixed image,
Since the water vapor generated from the first recording paper P by the heat supply for fixing is prevented from flowing toward the fixing film 116 by the unfixed image, the surface of the pressure roller 106 is not sufficiently heated. In the initial stage of continuous copying, for example, most of the water vapor is condensed on the surface of the pressure roller 106 to form a thin film, and the frictional resistance of the release layer 109 is further reduced. A transfer means for transferring an unfixed image onto the recording paper P depending on the situation, because it cannot follow the fixing nip portion N because it cannot follow the peripheral speed of the pressure roller 106 at all. In some cases, a paper jam due to the recording paper P may occur in a conveyance path between the heating and the fixing device 110.

Therefore, the present inventor has set the above initial temperature of 25 ° C.
The printing rate of the copy image formed on each recording paper P to be continuously copied in the three forms described below is fixed to fix the second recording paper P carrying the copy image of each printing rate. At the same time as measuring the degree of slip at the nip N, the interval between the first recording paper P and the second recording paper P, and the second recording paper P and the third recording paper P A suitable value was measured for each of the printing rates for each of the intervals between the sheets.

In the measurement relating to the slip, the interval between each recording sheet P conveyed to the fixing nip N is set to 50 mm, and the temperature detected by the thermistor temperature sensor 117 is increased. Rate 40
° C / sec.

The results obtained by the above measurement are shown in Table 2 below. Here, in Table 2, L1 and L2
Are suitable values for the space between the first recording paper P and the second recording paper P, and preferable values for the space between the second recording paper P and the third recording paper P, respectively. Represents a value.

[0114]

[Table 2] In Table 2 above, full-surface printing indicates a case where a copied image is formed over the entire dots (known units) of an arbitrary recording paper P, and alternate printing indicates dots of the entire surface of an arbitrary recording paper P. The case where the formation of the copy image and the non-formation of the copy image are alternately repeated over the entire length of the recording paper P, and the case where the copy image is not formed over the entire dots of the arbitrary recording paper P Represents.

As can be seen from Table 2 above, as the printing rate of the second sheet of recording paper P increases during continuous copying, slipping due to the second sheet of recording paper P at the fixing nip N becomes more likely to occur. Therefore, it is necessary to increase the space between the recording papers P with an increase in the printing rate of a copy image formed on each recording paper P for continuous copying.

Therefore, in the present embodiment, based on the printing ratio of the copy image formed on each recording paper P to be continuously copied in accordance with the results in Table 2, the space between each recording paper P is determined. By making the setting change, even if the water vapor film is formed on the surface of the pressure roller 106 due to the fixing of the copied image on the first recording paper P having a high printing rate, the second recording is performed. Before the paper P enters the fixing nip portion N, the film of water vapor can be removed by the heat supply from the ceramic heater 111. The conveying force of the recording paper 106 to the recording paper P can be returned to a suitable value, and the provision of a low-quality copy image due to image quality deterioration or the like can be reliably prevented.

(Fifth Embodiment) Next, a description will be given of a change in setting of a sheet interval for each recording sheet P during continuous copying performed by the image forming apparatus of the fifth embodiment of the present invention. It should be noted that the configuration of the image forming apparatus applied to the present embodiment and various devices provided are the same as those of the first embodiment, and description thereof will be omitted in place of FIGS. 1 and 2.

In the present embodiment, the fourth embodiment is further advanced. During continuous copying, the area on the transport direction side of the surface of the recording paper P carrying the unfixed image (hereinafter referred to as the front area). The area between the first sheet of recording paper P and the second sheet of recording paper P is changed based on the printing rate of the copied image formed on the first sheet of recording paper P. Is prevented from slipping in the fixing nip portion N of the second and subsequent sheets of recording paper P due to a water vapor film formed by dew condensation on the surface of the pressure roller 106 with the fixing.

In the heating and fixing device 7, even when continuous copying is performed on a plurality of recording papers P having a high printing rate of an unfixed image, the printing rate of the copied image in the preceding area is reduced. If it is low, even if water vapor generated during fixing to the first recording paper P is condensed on the surface of the pressure roller 106 to form a film, the second recording paper P may reach the front area. Since the printing rate of the copied image is low, the water vapor film formed on the surface of the pressure roller 106 is fixed to the ceramic heater 111 while the unfixed image is fixed to the front area of the second recording paper P. To some extent due to heat supply from the pressure roller 106, the conveyance force of the surface of the pressure roller 106 on the recording paper P is restored to some extent before the second recording paper P enters the fixing nip N. Thus, the space between the recording sheets P can be shortened to some extent. It is considered to be.

Therefore, the present inventor did not form a copy image at all in the front area of each recording sheet P to be continuously copied, while forming a copy image over all dots in the remaining area.
The length S of the front area of the recording paper P along the transport direction is 30 m.
m, 50 mm, 75 mm, 90 mm, and 105 mm, and the degree of slip at the fixing nip portion N of the second recording paper P set at each S value was measured.

In the above measurement, the recording paper P having a length of about 300 mm along the transport direction was used, and the distance between the first recording paper P and the second recording paper P was set to 90 mm. The distance between the second recording paper P and the third recording paper P was set to 75 mm.

The results obtained by the above measurement are shown in Table 3 below. Here, in Table 3, ○, Δ, and × represent
Each means no problem, acceptable range, and poor.

[0123]

[Table 3] As can be seen from Table 3 above, when the S value is 75 mm or less, particularly when the S value is 50 mm or less, the slip by the second recording sheet P at the fixing nip portion N is performed similarly to the fourth embodiment. Is likely to occur, it is necessary to increase the space between the recording papers P on which continuous copying is performed.
mm, no slip was observed in the fixing nip N due to the second recording paper P.

Therefore, in the present embodiment, the above Table 3
In the same manner as in the third embodiment, the setting of the sheet interval for each recording sheet P is changed based on the printing rate of the copy image formed on each recording sheet P to be continuously copied in accordance with the result of At the time of fixing to each recording sheet P, the conveying force of the pressure roller 106 to the recording sheet P can be returned to a suitable value, and the provision of a low-quality copy image due to image quality deterioration or the like can be prevented. At the same time, when the printing rate of the copy image on the front area of each recording sheet P to be continuously copied is low, the interval between the first recording sheet P and the second recording sheet P, and The advantage is that continuous copying can be performed without widening the space between the third recording paper P and the third recording paper P.

(Sixth Embodiment) Next, a description will be given of a change in setting of a sheet interval for each recording sheet P during continuous copying performed by the image forming apparatus according to a sixth embodiment of the present invention. It should be noted that the configuration of the image forming apparatus applied to the present embodiment and various devices provided are the same as those of the first embodiment, and description thereof will be omitted in place of FIGS. 1 and 2.

In the present embodiment, at the time of continuous copying, the first sheet based on the length along the transport direction of each recording sheet P to be continuously copied (hereinafter, this length is referred to as the transport direction length). By changing the setting of the interval between the recording paper P and the second recording paper P, water vapor formed by condensation on the surface of the pressure roller 106 as the recording paper P is fixed to the first recording paper P is changed. This prevents slippage of the second and subsequent sheets of recording paper P at the fixing nip N by the film.

In a conventional image forming apparatus that can utilize the heat fixing device 111, when continuous copying is performed on a plurality of recording papers P having a long length in the conveyance direction, heat is supplied from the ceramic heater 111. The flow of the water vapor generated from the first recording sheet P to the fixing film 116 side is blocked by the unfixed image, and the pressure roller 10
6, the surface temperature of the pressure roller 106 significantly decreases due to heat absorption due to heat conduction to each recording paper P.

Therefore, the amount of water vapor generated upon fixing to the first recording paper P increases as the length in the transport direction increases, so that the water vapor formed by condensation on the surface of the pressure roller 106 Therefore, as the length in the transport direction increases, the transport force of the pressure roller 106 on the recording paper P significantly decreases, and the second recording paper P
The vehicle slips because it cannot follow the peripheral speed of 06 at all.

The inventor of the present invention assigns the first recording paper P to the first recording paper P by shaping the length in the transport direction of each recording paper P to be continuously copied at an initial temperature of 25 ° C. in the following five forms. A suitable value according to each transport direction length was measured for each of the interval between the second recording sheet P and the interval between the second recording sheet P and the third recording sheet P.

The results obtained by the above measurement are shown in Table 4 below. Here, in Table 4, L1 and L2
Are suitable values for the space between the first recording paper P and the second recording paper P, and suitable values for the space between the second recording paper P and the third recording paper P, respectively. Represents a value.

[0131]

[Table 4] As can be seen from Table 4, as the length of the recording paper P to be continuously copied in the transport direction increases, the pressure roller 1
From 06, the amount of heat absorption based on the heat conduction to each recording sheet P increases, and the second recording sheet P easily slips at the fixing nip portion N. As the length of the recording paper P in the transport direction increases, it is necessary to increase the space between the recording papers P.

Therefore, in the present embodiment, the inter-sheet setting for each recording sheet P is changed based on the length in the transport direction for each recording sheet P to be continuously copied according to the results shown in Table 4. The first recording paper P having a long length in the transport direction
Even when a film formed by water vapor is formed on the surface of the pressure roller 106 due to the fixing of the recording paper P, heat is supplied from the ceramic heater 111 by the time when the second recording paper P enters the fixing nip N. As a result, the film of water vapor can be removed, so that the conveyance force of the pressure roller 106 on the recording paper P can be returned to a suitable value when fixing the recording paper P, and image quality deterioration and the like can be achieved. Can provide a low-quality copy image.

(Seventh Embodiment) Next, the configuration of an image forming apparatus according to a seventh embodiment of the present invention and each recording paper P during continuous copying performed by the image forming apparatus according to the present embodiment will be described. 7 will be described with reference to FIG. It should be noted that devices having the same functions, configurations, and the like as those provided in the image forming apparatus of the first embodiment are shown in FIG.
The description is omitted by giving the same reference numerals as those in FIG.

In the above-described image forming apparatus, as shown in the schematic configuration diagram of FIG. 7, the top sensor 10 as the first speed detecting means and the paper discharge sensor 11 as the second speed detecting means record from the fixing nip N respectively. When the sheet P enters the fixing nip portion N by detecting a speed value for conveying the sheet P at a time immediately passing through the top sensor 10 and the sheet ejection sensor 11, provided immediately downstream and immediately upstream in the conveying direction of the sheet P. Recording paper P
And the length of the recording paper P in the transport direction when the recording paper P is detached from the fixing nip N are determined.

In the conventional image forming apparatus having the above-mentioned heating and fixing device 110, a plurality of recording papers P can be fixed at a fixed rate regardless of the type of the recording papers P, the properties of the surface and the surrounding environment. Continuous copying has been performed by sequentially transporting the sheet to the fixing nip N between the sheets.

However, since the amount of moisture absorption of the recording paper P differs depending on the type and surface properties of the recording paper P used for continuous copying, a plurality of recording papers P having a high hygroscopicity can be used in a conventional image forming apparatus. When continuous copying is performed, slipping due to arbitrary recording paper P may frequently occur in the fixing nip portion N, and when a plurality of recording papers P that are not too high in hygroscopicity are used for continuous copying. Even so, when the recording paper P is placed in a humid environment, a slip due to an arbitrary recording paper P may occur at the fixing nip N.

Therefore, in the present embodiment, in order to solve the problem feared in the conventional image forming apparatus, the same recording detected by each of the top sensor 10 and the paper discharge sensor 11 during continuous copying is performed. Based on the comparison between the respective speed values for the paper P, the occurrence of a slip at the fixing nip N due to the recording paper P and the recording paper P on the transport path (see FIG. 7).
It is determined whether or not a loop is formed based on the paper jam (shown by a dotted line; see FIG. 7). In addition to eliminating the loop formed by this, the occurrence of slip at the fixing nip portion N of each recording sheet P on which an unfixed image is fixed next is prevented.

Therefore, a process for changing the setting of the sheet interval for each recording sheet P during continuous copying performed in this embodiment will be described in the following manner.

In the image forming apparatus according to the present embodiment, the top sensor 10 and the paper discharge sensor 11 each detect the time required to pass each sensor, and
The transport direction length of the recording paper P when entering the fixing nip N and the transport direction length of the recording paper P when detaching from the fixing nip N are determined.

In general, the recording paper P is passed through the fixing nip portion N to fix the unfixed image, thereby removing the water that has absorbed moisture in advance. When the normal fixing is performed, the time Tb detected by the paper discharge sensor 11 is slightly longer than the time Ttop detected by the top sensor 10, for example, 0.5% to 1.5%. %, That is, using a constant α in the range of real numbers 0.995 to 0.985, a relational expression of α × Ttop = Tb holds.

Therefore, in the present embodiment, α × Ttop is calculated using the constant α between the time Ttop detected by the top sensor 10 and the time Tb detected by the paper discharge sensor 11. If the relationship of Tb is satisfied, it is determined that a slip has occurred due to the recording paper P in the fixing nip portion N, and a predetermined distance between the slipped recording paper P and the succeeding recording paper P is determined. Length to a predetermined length, for example, 50
By increasing the length by mm, the surface temperature of the pressure roller 106 is raised to a temperature sufficient to restore the conveying force of the recording paper P by the next time the recording paper P enters the fixing nip N. .

The present inventor uses the image forming apparatus of the present embodiment to perform measurement for confirming whether or not slipping of the recording paper P in the fixing nip portion N can be avoided by varying the constant α. At the same time, a measurement was made to confirm whether or not an erroneous detection was made even though no slip occurred.

The results obtained by the above measurement are shown in Table 5 below. Here, in Table 5, ○ and × mean no problem and poor, respectively.

[0144]

[Table 5] As can be seen from Table 5, even when a slip occurs in the fixing nip N due to an arbitrary recording paper P during continuous copying, the timing at which the next recording paper P enters the fixing nip N is delayed by delaying the timing. Then, the surface temperature of the pressure roller 106 is sufficiently raised, so that the surface of the pressure roller 106 returns a sufficient conveying force to the recording paper P. Normal unfixed image can be fixed without slipping.

(Eighth Embodiment) Next, a heat fixing device 12 which can be used in an image forming apparatus according to an eighth embodiment of the present invention will be described with reference to FIG. Note that the heat fixing device 100
Members having the same functions, configurations, and the like as the members of the present embodiment are denoted by the same reference numerals as in FIG. 9, and the description thereof will be omitted. The device and the like are the same as those in the first embodiment, and the description is omitted in place of FIG.

As shown in the main cross-sectional view of FIG. 8, in the heat fixing device 12, a fixing roller 101 serving as a fixing unit and a pressing roller 106 serving as a pressing unit, both of which are rotatable, carry an unfixed image. The recording paper P is supported so as to be able to press against it.

The fixing roller 101 supported by the heat fixing device has a core layer 102 covered with a release layer 103 on the outer peripheral surface thereof, and a hollow section of the metal core 102 with a halogen lamp 104 serving as a heating means. Is provided.

Further, on the outer peripheral surface of the fixing roller 101,
A thermistor temperature sensor 105 for detecting the surface temperature of the fixing roller 101 is provided in contact with the fixing roller 101.

On the other hand, the pressure roller 106 supported by the heat fixing device 100 is formed by laminating an elastic layer 108 and a release layer 109 on the outer peripheral surface of the cored bar 107 in this order. The pressure roller 10 is provided on the outer peripheral surface of the pressure roller 106.
6, a thermistor temperature sensing sensor 13 as a temperature sensing means for sensing the surface temperature is provided in contact with the sensor.

That is, in the image forming apparatus of the present embodiment, the surface temperature of the pressure roller 106 is detected by the thermistor temperature sensor 13.

Therefore, in the image forming apparatus of the present embodiment, the setting change between the recording sheets P during the continuous copying described in any one of the first to seventh embodiments. Therefore, even if a film is formed on the surface of the pressure roller 106 due to condensation due to the formation of water vapor due to the fixing on the first recording paper P, the second recording paper P By the time of intrusion, the film of water vapor can be removed by the heat supply from the halogen heater 104, so that when the recording paper P is fixed on the recording paper P,
Can be returned to a suitable value, and the provision of a low-quality copy image due to image quality deterioration or the like can be reliably prevented.

[0152]

As described above, according to the first aspect of the present invention, from the end of the fixing to the first transfer material to the arrival of the second transfer material to the fixing nip portion. In the meantime, the temperature of the pressurizing means is sufficiently raised by the heat generating means via the fixing means, so that a film of water vapor formed by dew condensation on the outer peripheral surface of the pressurizing means with fixing to the first transfer material is formed. Can be evaporated and removed before the second transfer material arrives at the fixing nip portion. Therefore, at the time of fixing to each transfer material, the frictional force of the outer peripheral surface of the pressing means Can be returned to a value suitable for conveying the transfer material.

According to the second aspect of the present invention, the pressure roller rotates one rotation between the end of the fixing to the first transfer material and the arrival of the second transfer material to the fixing nip. As a result, the entire outer peripheral surface is sufficiently heated by the heat generating means via the fixing means, so that the film formed by the dew condensation on the outer peripheral surface of the pressing means due to the fixing to the first transfer material is formed. The second transfer material can be evaporated and removed before the second transfer material arrives at the fixing nip portion. Therefore, at the time of fixing to each transfer material, the frictional force of the outer peripheral surface of the pressing unit is reduced. The value can be returned to a value suitable for conveying the transfer material.

Further, according to the third aspect of the present invention, the pressurizing means is provided between the end of fixing to the first transfer material and the arrival of the second transfer material to the fixing nip. While the temperature is sufficiently raised by the heat generating means via, the above-mentioned means is again activated from the end of fixing to the second transfer material to the arrival of the third transfer material to the fixing nip portion. Since the temperature is sufficiently raised by the heat generating means via the fixing means, two films of water vapor formed by dew condensation on the outer peripheral surface of the pressurizing means with fixing to the first transfer material are used. The second transfer material can be evaporated and removed before the second transfer material arrives at the fixing nip portion, and is formed by dew condensation on the outer peripheral surface of the pressurizing unit as the second transfer material is fixed. Until the third transfer material arrives at the fixing nip. Evaporated to be removed while,
Thus, at the time of fixing to each transfer material, the frictional force of the outer peripheral surface of the pressing means can be returned to a suitable value by transporting the transfer material.

Further, according to the fourth aspect of the present invention, the transfer interval of each transfer material to the fixing nip is set based on the temperature value of the pressure means detected by the temperature detection means. When the temperature of the first transfer material is lower than the predetermined temperature, the second transfer material is fixed to the first transfer material even if the film is formed on the outer peripheral surface of the pressurizing means and water vapor is formed. By the time the film reaches the nip portion, the film due to the water vapor can be removed by evaporation, so that when fixing to each transfer material, the frictional force of the outer peripheral surface of the pressurizing means is transferred to the transfer material. It can be returned to a suitable value.

Further, according to the fifth aspect of the present invention, the transfer interval of each transfer material to the fixing nip portion is set based on the print ratio of the copied image formed on the transfer material. Even if a film of water vapor is formed by condensation on the outer peripheral surface of the pressing means with the fixing to the transfer material of the eye, the water vapor is used until the second transfer material arrives at the fixing nip portion. The film can be removed by evaporating, so that at the time of fixing to each transfer material, the frictional force of the outer peripheral surface of the pressing means can be returned to a value suitable for conveying the transfer material.

According to the sixth aspect of the present invention, the transfer interval of each transfer material to the fixing nip is set based on the length in the direction parallel to the transfer direction of the transfer material. Even if a film formed by water vapor is formed on the outer peripheral surface of the pressurizing means due to the fixing to the first transfer material, the second transfer material evaporates before reaching the fixing nip portion. Thus, at the time of fixing to each transfer material, the frictional force of the outer peripheral surface of the pressing means can be returned to a value suitable for conveying the transfer material.

Further, according to the seventh aspect of the present invention, the fixing value is determined based on a comparison between the speed value detected by the first speed detecting means and the speed value detected by the second speed detecting means. Since the transfer interval of each transfer material to the fixing nip portion is set, even if the transfer material slips due to a film of water vapor formed by condensation on the outer peripheral surface of the pressing means, the next transfer is performed. By the time the material reaches the fixing nip portion, the film by the water vapor can be removed by evaporation, so that at the time of fixing to the next transfer material, the frictional force of the outer peripheral surface of the pressing means is reduced. The value can be returned to a value suitable for conveying the transfer material.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a main cross-sectional view illustrating a schematic configuration of a heat fixing device used in the image forming apparatus of FIG.

FIG. 3 is a graph showing the time change of the surface temperature of the pressure roller when the paper is continuously passed at a constant conveyance interval when the initial temperature of the pressure roller of the heat fixing device of FIG. 2 is 25 ° C. It is.

FIG. 4 is a graph showing a correspondence relationship between a dynamic friction coefficient of the pressure roller of FIG. 2 and a surface temperature of the pressure roller.

FIG. 5 is a graph showing a time change of the surface temperature of the pressure roller when the paper is continuously passed at a constant conveyance interval when the initial temperature of the pressure roller of FIG. 2 is 40 ° C.

FIG. 6 is a diagram illustrating a case where the conveyance interval between the first recording paper and the second recording paper is set to the conveyance interval for each of the second and subsequent recording papers when the initial temperature of the pressure roller in FIG. 6 is a graph showing a time change of the surface temperature of the pressure roller when continuous paper is set for a longer time.

FIG. 7 is a diagram illustrating a main configuration of an image forming apparatus according to a seventh embodiment of the present invention.

FIG. 8 is a main cross-sectional view illustrating a schematic configuration of a heat fixing device used in an image forming apparatus according to an eighth embodiment of the invention.

FIG. 9 is a main cross-sectional view showing a schematic configuration of a typical example of a heat fixing device used in a conventional image forming apparatus.

FIG. 10 is a main cross-sectional view illustrating a schematic configuration of another typical example of a heat fixing device that can be used in a conventional image forming apparatus.

11 is a main cross-sectional view illustrating a schematic configuration of a ceramic heater included in the heat fixing device of FIG.

[Explanation of symbols]

 9 Fixing Film (Fixing Means) 10 Top Sensor (First Speed Sensing Means) 11 Discharge Sensor (Second Speed Sensing Means) 13 Thermistor Temperature Sensing Sensing Sensor (Temperature Sensing Means) 101 Fixing Roller (Fixing Means) 104 Halogen Lamp ( Heating means) 106 Pressure roller (Pressing means) 111 Ceramic heater (Heating means) 116 Fixing film (Fixing means) 117 Thermistor temperature sensing sensor (Temperature detecting means) N Fixing nip

Claims (7)

[Claims] 1. A fixing unit for heating an unfixed image to fix it to a sheet-like transfer material, a pressing unit that contributes to fixing by being pressed against the fixing unit via the transfer material, An image forming apparatus having a heat generating means as a heat supply source for and capable of continuously copying on a plurality of transfer materials,
N is an arbitrary natural number, n + 1 is the number of transfer materials to be continuously copied, k is an arbitrary natural number less than n, k is the rear end of the transfer material to be copied kth, and k + 1 is the number of copy materials to be copied. Lk, L2 to L2
When the maximum value up to n is represented by Lmax, L1> L
An image forming apparatus, wherein each transfer material can be continuously conveyed to a fixing nip formed between the fixing unit and the pressing unit at a conveyance interval satisfying a maximum. 2. The pressure means is a rotatable pressure roller formed in the form of a roll having an outer diameter R. When the circular constant is represented by π, L1 is the outer peripheral length 2πR and Lmax of the pressure roller. The image forming apparatus according to claim 1, wherein the value is set to a value larger than the value. 3. The image forming apparatus according to claim 1, wherein L2 is set to a value satisfying L1>L2> L3. 4. A transfer interval of each transfer material to a fixing nip portion is set based on a temperature value detected by a temperature detecting means provided for detecting a temperature of the pressing means. The image forming apparatus according to claim 3. 5. The method according to claim 1, wherein a conveyance interval of each transfer material to the fixing nip is set based on a print ratio of a copy image formed on the transfer material. The image forming apparatus as described in the above. 6. A transfer interval for each transfer material to a fixing nip portion based on a length of the transfer material in a direction parallel to the transfer direction. Item 10. The image forming apparatus according to item 1. 7. A fixing means for heating an unfixed image to fix it on a sheet-like transfer material, a pressure means contributing to fixation by being pressed against the fixing means via the transfer material, An image forming apparatus having a heat generating means as a heat supply source for and capable of continuously copying on a plurality of transfer materials,
First speed detecting means and second speed detecting means for detecting the speed for transporting the transfer material are provided at a position immediately downstream and a position immediately upstream along the transport direction from the fixing nip, respectively. The fixing nip for each transfer material to be subsequently fixed based on a comparison between the speed value detected by the first speed detecting means and the speed value detected by the second speed detecting means. An image forming apparatus that sets a conveyance interval to a unit.