JP2966273B2 - 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 an image forming apparatus such as a copying machine or a printer using an electrophotographic system, and particularly to appropriately changing image forming conditions according to the properties of a recording material to which a visible image is fixed. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Recently, a copying machine using an electrophotographic method,
In an image forming apparatus such as a printer, various recording materials are used in various ways. B5, A4, B4, A3
(JIS standard), etc., the size of the recording material, the basis weight (thickness) of the recording material, and the material (type) of the recording material such as paper or an OHP sheet (a transparent resin sheet for an overhead projector); Alternatively, whether to form an image on one side or both sides of the same recording material (state), the physical properties of the recording material that changes depending on the temperature or humidity of the installation location of the image forming apparatus, etc.
That is, the physical conditions of the recording material (hereinafter referred to as “properties”).
Performs image formation on a variety of different recording materials using a single image forming apparatus. Therefore, good image formation is performed by appropriately changing the image forming conditions according to the properties of these recording materials.

FIG. 9 is a longitudinal sectional view showing a schematic configuration of a four-color full-color image forming apparatus as an example of a color image forming apparatus.

First, the structure of an image forming apparatus will be briefly described. An electrophotographic photosensitive drum 1 as an image carrier is provided substantially at the center of the main body of the apparatus. The photosensitive drum 1 has an arrow R
It is rotatably supported in one direction, and a primary charger 2, an exposure unit 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged around the device in this order in the rotating direction. . In addition, below the transfer device 5, a paper feeder 8 for the recording material P is provided. The paper feeding and conveying unit 8 includes a plurality of paper feeding cassettes 8a for respectively storing and storing recording materials P of different sizes, a paper feeding roller 8b for feeding the recording materials P from the paper feeding cassette 8a, and a registration roller 8c. And forms a transport path shown by a dotted line in FIG.
On the downstream side of the transfer device 5, a separating unit 9, a fixing unit 10, and a paper discharge unit 11 are sequentially arranged.

[0005] Next, the operation of the image forming apparatus having the above-described configuration will be described while appropriately adding the configuration. The surface of the photosensitive drum 1 rotated and driven in the direction of arrow R <b> 1 by a driving unit (not shown) is uniformly charged by the primary charger 2. The exposure unit 3 has a document scanning unit and a color separation filter, and irradiates a color-separated light image E or a light image E corresponding thereto. As the exposure means 3, for example, a laser beam exposure device can be used, and a uniformly charged surface of the photosensitive drum 1 is irradiated with a light image E (for example, a yellow light image) for each separation color. To form an electrostatic latent image. The electrostatic latent image is visualized by the developing device 4. The developing device 4 includes a rotating support 4e that is driven to rotate about a central axis 4d, and four developing devices mounted on the rotating support 4e, namely, yellow, magenta, cyan,
Developing units 4Y, 4M each containing black toner of each color;
4C and 4Bk. Then, the yellow developing device 4Y to be used for development is moved to a developing position facing the surface of the photosensitive drum 1 by the rotation of the rotary support 4e, and the yellow latent image on the photosensitive drum 1 is transferred via the developing sleeve. A toner image is formed by attaching toner.

[0006] The yellow toner image is transferred to the recording material P supplied to the transfer device 5 from the paper feeding / conveying section 8. A plurality of paper feed cassettes 8a for stacking and storing recording materials P of different sizes are arranged in the paper feed / conveying unit 8, and a predetermined recording material P is fed to a paper feed roller 8b, a number of conveyance rollers, and registration rollers 8c. The image is supplied to the transfer device 5 at a predetermined timing. The transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an adsorption charger 5 for electrostatically adsorbing the recording material P.
c, a suction roller 5d opposed thereto, an inner charger 5e,
The transfer drum 5a having the outer charger 5f and being driven to rotate in the direction of the arrow R5 has a recording material carrying sheet 5g made of a dielectric material stretched integrally in a cylindrical shape in the peripheral opening area. I have. The recording material P supplied from the paper feed unit 8
Is attracted to the surface of the transfer drum 5a, rotates in the direction of arrow R5 with the rotation of the transfer drum 5a, and the yellow toner image on the photosensitive drum 1 is transferred by the transfer charger 5b. After the transfer of the toner image, the remaining toner on the surface of the photosensitive drum 1 is removed, and the photosensitive drum 1 is provided for the next image formation.

Thus, the transfer of the yellow toner image onto the recording material P is completed. The same image forming process is repeated for each of the other colors, magenta, cyan, and black, whereby toner images for four colors are transferred onto the recording material P on the transfer drum 5a.

Recording material P on which transfer of four color toner images is completed
Is separated from the surface of the transfer drum 5a by the separation charger 9a and the separation claw 9b of the separation unit 9, and is conveyed to the fixing device 10 while the unfixed (electrostatically adhered) toner image is carried on the surface. Is done.

The fixing device 10 has a fixing roller 10a containing a heater (heat source) and a pressing roller 10b pressed against the fixing roller 10a from below, and the recording material P is held at the nip between the rollers 10a and 10b. The toner image is fused and fixed by heating and pressing while nipping and transporting. The recording material P after the fixing is discharged onto the paper discharge tray 11, and the formation of a four-color full-color image is completed.

As described above, the above-described image formation is performed on recording materials having various properties such as different sizes, thicknesses, properties, states, and use environments. Therefore, when forming an image, for example, in an image carrier or a fixing device, the image forming conditions are appropriately changed according to the properties of the respective recording materials, thereby forming a four-color full-color image of suitable image quality.

[0011]

In the fixing device 10 of the above-described image forming apparatus, the toner image is melted and fixed on the recording material P by heating and pressing while nipping and conveying the recording material P.
The amount of heat required for the fusion and fixation of the toner image changes relatively greatly depending on the properties of the recording material P. This is because the heat capacity of each recording material P differs when the properties of the recording material P differ. For example, when the recording material P is thick cardboard (having a basis weight of 127 g / m ^2).
Paper of a degree or higher. same as below. In the case of (1), since the heat capacity is large, it is difficult to heat. In particular, in the fixing device 10 having a heat source only on the side of the fixing roller 10a which directly contacts the toner image on the surface of the cardboard, the pressure roller 10 on the back side of the cardboard is used.
Since the heat from b is not easily transmitted, the heating is insufficient and the amount of heat to be applied tends to be insufficient, and there is a possibility that a fixing failure may occur. Recording material P other than cardboard that tends to lack heat
Examples include OHP sheets and envelopes. The recording material P
There is also a standard paper (basis weight refers to 64g / m ² ~105g / m ² about the paper. Hereinafter the same.), The 2 during image formation face after the completion of the first side image formation in the duplex image formation, Similarly, the amount of heat tends to be insufficient.

As a measure to solve the heat shortage, the fixing unit 1
0 (hereinafter referred to as “fixing conveyance speed”).
That. There is a way to slow down). This is a method in which the amount of heat applied is increased by lengthening the fixing time. According to this method, an optimal amount of heat can be given to the properties of each recording material P by selecting the fixing conveyance speed according to the properties of the recording materials P. It turns out that this is an effective means.

However, when this method is adopted, there is a problem that the whole apparatus becomes large. In the image formation of the configuration shown in FIG. 9, the surface of the photosensitive drum 1 and the transfer drum 5a
The surface moves at a predetermined process speed (peripheral speed) in the directions of arrows R1 and R5, respectively. And the recording material P is
After the transfer of the toner image is completed by being attracted to the transfer drum 5a, the toner image is sequentially separated from the leading end side by the separating means 9. At this time, the recording material P during the separation operation from the start of separation to the end of separation is conveyed toward the fixing device 10 at the same speed as the process speed by the transfer drum 5a.

Here, if the distance from the separating means 9 to the fixing device 10 is shorter than the length of the recording material P in the conveying direction,
Before the separation operation is completely completed, the leading end of the recording material P reaches the fixing device 10, and one recording material P is simultaneously moved by the fixing device 10 at the leading end and by the transfer drum 5a at the trailing end. It will be transported. Therefore, in order to improve the fixability of the toner image by the fixing device 10 as described above,
If the fixing conveyance speed of the fixing device 10 is made lower than the process speed, the recording material P has a speed difference between the front end side where the conveyance speed is slow and the rear end side where the conveyance speed is fast, and a loop is formed in the middle part in the conveyance direction. Will be formed. When the loop is formed, the swollen portion of the loop comes into contact with a peripheral member, and a jam occurs or an unfixed toner image is scraped off.

When the recording material P is thick, the recording material P
When the trailing edge of the recording material P tries to break the loop when the trailing edge of the recording material P is released, the unfixed toner on the recording material P may be disturbed by the shock. There is. One measure for preventing such a jam or disturbance of the toner is to make the distance between the separating means 9 and the fixing device 10 larger than the length of the recording material P used in the image forming apparatus in the conveying direction. It is conceivable to set it longer. In this manner, one recording material P is transferred to the fixing device 1.
0 and the transfer drum 5a are prevented from being simultaneously conveyed, thereby preventing a loop from being formed in the intermediate portion.

However, when the distance between the separating means 9 and the fixing device 10 is increased, a problem arises that the entire image forming apparatus becomes large. It is to be noted that this problem is caused by changing the fixing conveyance speed depending on the properties of the recording material P, as described above. In addition to this, the temperature, humidity, and the like of the place where the image forming apparatus is installed are also described. This is also a problem that occurs when the fixing conveyance speed is changed according to the environment.
Further, as for the fixing conveyance speed, the same problem occurs when the speed is increased as well as when the speed is reduced as described above. For example, when it is desired to increase the fixing conveyance speed because the recording material P is thinner than the standard paper, contrary to the case of thick paper, the conveyance speed at the leading end side of the recording material P is high and the conveyance speed at the rear end side is low. That is, the entire recording material P may be damaged by being pulled in the transport direction. Therefore, also in this case, similarly, the distance between the separation unit 9 and the fixing device 10 needs to be set longer than the length of the recording material P in the transport direction. That is, if the fixing conveyance speed is changed, the size of the apparatus tends to be increased in any case.

In order to solve the above-mentioned problems, the present invention can perform satisfactory fixing without increasing the size of the image forming apparatus, and prevent the charging means from damaging the image carrier. It is an object of the present invention to provide an image forming apparatus configured to perform the above.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and comprises a movable image carrier, charging means for charging the image carrier, and charging means for charging the image carrier. Image forming means for forming an image on the image carrier, a movable recording material carrier for electrostatically supporting a recording material, and an image formed on the image carrier by the image forming means. A fixing unit for fixing an image at a fixing position on a recording material separated from the recording material carrier at a separation position after the image is transferred to a recording material carried on the recording material carrier at a transfer position, A fixing unit configured to switch between a first fixing speed and a second fixing speed different from the first fixing speed. After the image transfer to the recording material carried by the recording material carrier, Before the image is fixed on the recording material, a period is provided in which the recording material passes through the transfer position while being carried on the recording material carrier. In the period, the movement of the image carrier and the recording material carrier is performed. The speed is changed in accordance with the second fixing speed, and in the period, the voltage applied to the charging unit is variable according to the moving speed of the image carrier.

Further, the distance between the separation position and the fixing position in the transport direction of the recording material is shorter than the length of the recording material.

After the image is fixed on the first surface of the recording material by the fixing means, the image can be transferred at the transfer position to the second surface of the recording material opposite to the first surface. When the image is fixed on the second surface of the recording material, the second fixing speed is selected.

Further, the recording material carrier has a charge eliminator provided on a side of the recording material carrier for supporting the recording material, and for removing electricity from the recording material carrier and the recording material at the separation position at the time of separation.

Also, the fixing speed of the fixing means is changed according to the type of recording material.

Further, the fixing speed of the fixing means is changed according to the temperature in the apparatus main body.
Further, a step of transferring an image from the image carrier to a recording material carried on the recording material carrier is repeated to form an image of a plurality of colors on the recording material.

[0024]

[0025]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a longitudinal sectional view showing a schematic configuration of a digital four-color full-color image forming apparatus as an example of an image forming apparatus according to the present invention.

The image forming apparatus shown in FIG. 1 has a lower digital color image printer section (hereinafter simply referred to as "printer section") I and an upper digital color image reader section (hereinafter simply referred to as "reader section") II. The printer unit I forms an image on the recording material P based on the image of the document D read by the reader unit II, for example.

Hereinafter, the configuration of the printer unit I and the configuration of the reader unit II will be briefly described.

The printer section I has a photosensitive drum 1 as an image carrier which is driven to rotate in the direction of arrow R1. Around the photosensitive drum 1, the primary charger (charging unit) 2, the exposure unit 3, the developing unit (developing unit) 4, the transfer unit 5, the cleaning unit 6, the pre-exposure lamp 7, etc. Is arranged. Below the transfer device 5, that is, in the lower half of the printer unit I, a paper feeder 8 for the recording material P is disposed. Further, above the transfer device 5, a separating unit 9 is provided. A fixing device 10 and a paper discharge unit 11 are disposed (on the downstream side in the transport direction of the recording material P).

The photosensitive drum 1 has a drum-shaped substrate 1a made of aluminum and a photosensitive member 1b of OPC (organic optical semiconductor) covering the surface thereof, and is driven in a predetermined direction in the direction of arrow R1 by a driving means (not shown). It is configured to be driven to rotate at the process speed (peripheral speed). The photosensitive drum 1 will be described later in detail.

The primary charger 2 includes a shield 2a having an opening at a portion facing the photosensitive drum 1, and a discharge wire 2b disposed inside the shield 2a in parallel with the bus of the photosensitive drum 1.
And a grid 2c disposed at the opening of the shield 2a to regulate the charging potential. A charging bias is applied to the primary charger 2 by a power supply (not shown), whereby the surface of the photosensitive drum 1 has a predetermined polarity,
It is designed to be uniformly charged to a predetermined potential.

Exposure means 3 includes a laser output unit (not shown) that emits a laser beam based on an image signal from a reader unit II described later, a polygon mirror 3a that reflects the laser beam,
It has a lens 3b and a mirror 3c. Exposure means 3
The laser beam irradiates the surface of the photosensitive drum 1 to irradiate the photosensitive drum 1 to remove an electric charge of the exposed portion to form an electrostatic latent image. In this embodiment, the electrostatic latent image formed on the surface of the photosensitive drum 1 is separated into four colors of yellow, cyan, magenta, and black based on the image of the original, and the electrostatic latent image corresponding to each color is separated. Images are sequentially formed.

The developing device 4 includes four developing devices in order from the upstream side along the rotation direction of the photosensitive drum 1 (direction of arrow R1), that is, yellow, cyan, magenta, and black, each of which is made of a resin. Developing devices 4Y, 4C, 4M, and 4Bk containing toner (developer) are provided. Each of the developing units 4Y, 4C, 4M, and 4Bk has a developing sleeve 4a for attaching toner to the electrostatic latent image formed on the surface of the photosensitive drum 1, and a predetermined color used for developing the electrostatic latent image. The developing device is alternatively arranged at a developing position close to the surface of the photosensitive drum 1 by the eccentric cam 4b,
The toner is attached to the electrostatic latent image via the developing sleeve 4a to form a visible toner image. The three color developing units other than the developing unit used for development are retracted from the developing position.

The transfer device 5 includes a transfer drum (recording material carrier) 5a having a surface on which the recording material P is carried, and a brush-shaped transfer charger (transfer means) for transferring the toner image on the photosensitive drum 1 to the recording material P. 5b, an adsorption charger 5c for adsorbing the recording material P to the transfer drum 5a, and an adsorption roller 5 opposed thereto.
d, an inner charger 5e and an outer charger 5f, and an arrow R5
Transfer drum 5a rotatably driven in the direction
5 g of a recording material supporting sheet made of a dielectric material
Are integrally extended in a cylindrical shape. As the recording material supporting sheet 5g, a dielectric sheet such as a polycarbonate film is used. The transfer device 5 is configured to adsorb and carry the recording material P on the surface of the transfer drum 5a.

The cleaning device 6 includes a cleaning blade 6a for scraping off residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P, and a cleaning container 6b for collecting the scraped toner.

The pre-exposure lamp 7 is disposed adjacent to the upstream side of the primary charger 2 and removes unnecessary charges on the surface of the photosensitive drum 1 cleaned by the cleaner 6.

The paper feeder 8 is provided with recording materials P of different sizes.
Paper feed cassette 8a for stacking and storing paper, a paper feed roller 8b for feeding the recording material P in the paper feed cassette 8a, a number of transport rollers, a registration roller 8c, and the like, and a recording material of a predetermined size. P is supplied to the transfer drum 5a.

The separating means 9 is provided for the recording material P after the transfer of the toner image.
Charger 9a for separating the toner from the transfer drum 5a,
It has a separation claw 9b and a separation push-up roller 9c.

The fixing device 10 is disposed below the fixing roller 10a and a fixing roller 10a having a heater inside.
Pressure roller 1 for pressing recording material P against fixing roller 10a
0b.

The paper discharge section 11 includes a conveyance path switching guide 11 a and a discharge roller 11 which are disposed on the downstream side of the fixing device 10.
b, a paper discharge tray 11c and the like. Further, below the conveyance path switching guide 11a, a conveyance vertical path 11d, a reversing path 11e, a stacking member 11f, an intermediate tray 11g, and a conveyance roller for forming an image on both sides of one recording material P. 11h, 11i, a reversing roller 11j and the like are arranged.

Further, the photosensitive drum 1 around between the primary charger 2 and the developing device 4, the potential sensor S ₁ for detecting the charging potential of the photosensitive drum surface, also the developing device 4 and the transfer drum 5a between the concentration sensor S ₂ for detecting the density of the toner image on the photosensitive drum 1, they are disposed respectively.

Next, the reader section II will be described.
The reader unit II arranged above the printer unit I
, An exposure lamp 12b for exposing and scanning the image surface of the original D while moving, a plurality of mirrors 12c for further reflecting light reflected from the original D, a lens 12d for condensing the reflected light, and It has a full color sensor 12e for forming a color separation image signal based on the light from the lens 12d. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and is sent to the above-described printer unit I.

Next, the operation of the above-described image forming apparatus will be described.
A brief description will be given while adding some components. In the following description, four full-color images are formed in the order of yellow, cyan, magenta, and black.

The image of the original D placed on the original platen glass 12a of the reader unit II is irradiated by an exposure lamp 12b, color-separated, and a yellow image is first read by a full-color sensor 12e and subjected to predetermined processing. The image signal is sent to the printer unit I as an image signal.

In the printer section I, the photosensitive drum 1 has an arrow R
It is driven to rotate in one direction, and the surface is uniformly charged by the primary charger 2. A laser beam is emitted from a laser output unit of the exposure unit 3 based on the image signal sent from the reader unit II, and the charged photosensitive drum 1 surface is exposed by a light image E via a polygon mirror 3a and the like. I do. The exposed portion of the surface of the photosensitive drum 1 has its charge removed, whereby an electrostatic latent image corresponding to yellow is formed. In the developing device 4, the yellow developing device 4Y is arranged at a predetermined developing position, and the other developing devices 4C, 4M, 4Bk
Is retracted from the developing position. The developing device 4Y attaches yellow toner to the electrostatic latent image on the photosensitive drum 1,
It is visualized to become a toner image. The yellow toner image on the photosensitive drum 1 is transferred to the recording material P carried on the transfer drum 5a. As for the recording material P, a recording material P having a size suitable for a document image is supplied to the transfer drum 5a at a predetermined timing from a predetermined paper supply cassette 8a via a paper supply roller 8b, a conveyance roller, a registration roller 8c, and the like. It is a thing. The recording material P supplied in this manner is attracted so as to wind around the surface of the transfer drum 5a, rotates in the direction of arrow R5, and the yellow toner image on the photosensitive drum 1 is transferred by the transfer charger 5b. .

On the other hand, the photosensitive drum 1 after the transfer of the toner image
The residual toner on the surface is removed by the cleaning device 6, and unnecessary charges are removed by the pre-exposure lamp 7, which is used for the next image formation starting from primary charging.

The processes from the reading of the document image by the reader unit II, the transfer of the toner image to the recording material P on the transfer drum 5a, the cleaning of the photosensitive drum 1, and the charge removal are performed by other processes than yellow. Color, ie cyan,
The same operation is performed for magenta and black, and the four color toner images are transferred onto the transfer material P on the transfer drum 5a so as to overlap.

Recording material P to which four color toner images have been transferred
Is separated from the transfer drum 5a by a separation charger 9a, a separation claw 9b, and the like, and is conveyed to the fixing device 10 with an unfixed toner image carried on the surface. The recording material P is a fixing device 1
The transfer roller 10a and the pressure roller 10b are heated and pressurized to fuse and fix the toner image on the surface. The recording material P after the fixing is discharged onto a discharge tray 11c by a discharge roller 11b. In the case where images are formed on both sides of the recording material P, the recording material P discharged from the fixing device 10 is used.
Is immediately driven to the reverse path 11e via the transport vertical path 11d by driving the transport path switching guide 11a.
With the reverse rotation of the reversing roller 11j, the sheet is retracted in a direction opposite to the direction in which the sheet is fed, with the rear end of the sheet being fed as the head, and stored in the intermediate tray 11g. After that, an image is formed on the other surface again by the above-described image forming process, and then discharged onto the discharge tray 11c.

On the transfer drum 5a after the separation of the recording material P, the recording material supporting sheet 5g is used to prevent scattering of powder on the recording material supporting sheet 5g and adhesion of oil on the recording material P. Fur brush 1 facing each other through
Cleaning is performed by 3a and the backup brush 13b, and by the oil removing roller 14a and the backup brush 14b. Such cleaning is performed before or after image formation, and is performed as needed when a jam (paper jam) occurs.

Further, in this embodiment, the eccentric cam 15 is operated at a desired timing, and the cam follower 5h integral with the transfer drum 5a is operated, so that the gap between the recording material carrying sheet 5g and the photosensitive drum 1 is increased. The size of can be set arbitrarily. For example, during standby or when the power is off, if there is an electric charge on the transfer drum 5a, the electric charge acts on the photosensitive drum 1 to cause a charge memory, thereby deteriorating the image quality in subsequent image formation. The distance from the photosensitive drum 1 is set to be large.

Hereinafter, the photosensitive drum 1 used in this embodiment will be described.
Will be described in detail. The method of forming the photoreceptor 1b will be described in detail below: 50 parts by weight of conductive titanium oxide powder coated with tin oxide containing 10% antimony oxide;
A sand mill using φ1 mm glass beads was prepared by using 25 parts by weight of phenol resin, 20 parts by weight of methyl cellosolve, 5 parts by weight of methanol, and 0.002 parts by weight of silicone oil (polydimethylsiloxane polyoxyalkylene copolymer, number average molecular weight 3000). Then, the dispersion was dispersed for 2 hours to prepare a conductive paint. The above-mentioned paint is dipped on an aluminum cylinder (φ80 mm × 360) as the base 1 a, dried at 140 ° C. for 30 minutes, and has a film thickness of 20 μm.
m conductive layers were formed.

Next, 30 parts by weight of a methoxymethylated nylon resin (number average molecular weight 32,000) and 10 parts by weight of an alcohol-soluble copolymerized nylon resin (number average molecular weight 29000) were mixed in a mixed solvent of 260 parts by weight of methanol and 40 parts by weight of butanol. Was applied on the above-mentioned conductive layer with a dipping coating machine, and a subbing layer having a thickness of 1 μm after drying was provided.

Next, 4 parts by weight of the disazo pigment having the structural formula of FIG. 7A, 2 parts by weight of benzal resin, and 40 parts by weight of tetrahydrofuran were dispersed in a sand mill using φ1 mm glass beads for 60 hours. It was diluted with a mixed solvent of cyclohexanone / tetrahydrofuran to prepare a coating for the charge generation layer.

This coating solution was applied on the undercoat layer by a dipping coating machine, and a dried film layer was provided with a charge generation layer having a thickness of 0.1 μm.

Next, the charge transport material 1 of the structural formula shown in FIG.
0 parts by weight and a polycarbonate resin (number average molecular weight 25
000) 10 parts by weight was dissolved in a mixed solvent of 20 parts by weight of dichloromethane and 40 parts by weight of monochlorobenzene, and this solution was dipped on the above-mentioned charge generating layer,
After drying at 60 ° C. for 60 minutes, a charge transport layer having a thickness of 20 μm was formed.

Next, 4 parts by weight of an acrylic monomer resin, 5 parts by weight of tin oxide (average primary particle size 0.3 μm), and 1 part by weight of a photopolymerization initiator are dispersed in a solvent of 30 parts by weight of ethanol.
This solution was dipped and coated on the above-mentioned charge transport layer, and the solution was coated with a metal halide lamp (560 mW / cm ² : 3).
Illuminance for a sensor with a center sensitivity at 60 nm) of 30
Irradiated for seconds. Thus, a surface protective layer having a thickness of 3 μm was formed.

When the photosensitive member formed by the above-described steps is designated as photosensitive member I, other photosensitive members are shown below as photosensitive members II to VI.

Photoreceptor II: The same conditions as for photoreceptor I were used except that the surface protective layer of photoreceptor I contained 1 part by weight of tin oxide particles (average primary particle size: 0.3 μm).

Photoreceptor III: The same conditions as for photoreceptor I were used, except that an epoxy resin was used in place of the acrylic monomer resin in the surface protective layer of photoreceptor I and that 10 parts by weight of epoxy resin was included.

Photoconductor IV: In the same manner as photoconductor I, a conductive layer, an undercoat layer, a charge generation layer and a charge transport layer were formed on an aluminum cylinder. Next, 6 parts by weight of a polycarbonate resin (number average molecular weight 25000), 3 parts by weight of the above-described charge transporting material, and polytetrafluoroethylene (average primary particle diameter of 0.1%).
3 μm) 1 part by weight was dissolved in a mixed solvent of 200 parts by weight of dichloromethane and 300 parts by weight of monochlorobenzene, and this solution was spray-coated on the charge transport layer,
Under the same conditions as the photoreceptor I except that a surface protective layer having a film thickness of 5 μm was formed.

Photoconductor V: Photoconductor IV has no surface protective layer.
The conditions were the same as those of the photoconductor IV, except that the charge transport layer contained 10% of polytetrafluoroethylene particles (average primary particle size: 0.3 μm).

Photoconductor VI: The average primary particle size of the polytetrafluoroethylene particles in the surface protective layer of photoconductor IV is 0.1 μm.
The conditions were the same as for the photoreceptor IV, except that m.

Next, depending on the properties of the recording material P, the fixing device 1
The control for changing the conveyance speed (fixing conveyance speed) of the recording material P at 0 and changing the image forming conditions of the photosensitive drum 1 will be described with specific numerical values. The photoconductor I described above was used as the photoconductor 1b of the photosensitive drum 1.

FIG. 8 shows the relationship between the properties of the recording material P and the fixing conveyance speed and the process speed set corresponding to the properties.

The process speed shown in the figure is equal to the peripheral speed of the surface of the photosensitive drum 1 and the peripheral speed of the surface of the transfer drum 5a, as described above, and the transport speed of the recording material P by the transfer drum 5a. Further, regarding the fixing conveyance speed, the standard paper first side is 130 mm / sec, and the standard paper second side is 120 mm / se.
c, cardboard 100mm / sec, and OHP sheet 30m
m / sec, both fixing and conveying speeds are set slightly lower than the process speed. This is because when the leading end and the trailing end of one sheet of recording material P are simultaneously conveyed by the fixing device 10 and the transfer drum 5a, the recording is performed within the tolerance of the fixing conveyance speed and the process speed. Material P
This is to prevent tension from being generated.

The properties of the recording material P are determined by providing, for example, a sensor for detecting the thickness of the recording material P, a sensor for detecting the translucency of the recording material P, and the like in the image forming apparatus main body. The properties of the recording material P are determined from the output, and the fixing conveyance speed and the image forming conditions of the photosensitive drum 1 are changed based on the result of the determination. The recording material P
Whether the first side or the second side during double-sided image formation is determined by whether or not double-sided image formation is selected when a user operates an operation panel (not shown) on the image forming apparatus main body. .

The fixing conveyance speed shown in FIG. 8 is an example, and the present invention is not limited to this. For example, in the case of thick paper, it is sufficient to set the thickness in accordance with the actual situation, for example, as the thickness increases, the fixing / conveying speed decreases.

FIG. 2 shows a timing chart when full-color image formation is continuously performed on a plurality of standard papers in the standard paper single-sided (first side) mode. This timing chart shows the rotation of the photosensitive drum 1 as a basic unit. As shown in the figure, in the standard single-sided paper mode,
The fixing conveyance speed is set to 130 mm / sec, and the process speed is set to 133 mm / sec, and these are kept constant until the image formation on the final standard paper is completed.

Unlike the standard single-sided paper mode described above, in the thick paper mode shown in FIG. 3, the fixing conveyance speed and the process speed are reduced at the time of fixing. First, magenta latent image formation / transfer M-1 is performed on the first thick paper. Subsequently, the same latent image formation / transfer is sequentially performed for cyan C-1, yellow Y-1, and black Bk. Thus, the toner images of the four colors are transferred onto the recording material P on the transfer drum 5a so as to overlap. From the formation of the magenta latent image to the end of the black transfer, the process speed is 133 mm / sec, which is the same as the standard single-sided paper mode described above. The fixing conveyance speed in the thick paper mode is 100 mm / sec, compared with 130 mm / sec on one side of the standard paper to supply a sufficient amount of heat to the thick paper.
Drop to c. Similarly, the process speed is 133 mm /
Drop from sec to 103 mm / sec. That is, after the transfer of the black Bk toner image, the process speed of the photosensitive drum 1 is first reduced according to the fixing conveyance speed of the fixing device 10 without immediately separating the thick paper from the transfer drum 5a.
As a result, the transfer drum 5 linked with the photosensitive drum 1
Process speed and adjust to the fixing conveyance speed. Thereafter, the separating means 9 transfers the thick paper to the transfer drum 5.
a and transported to the fixing device 10.

As described above, the fixing and conveying speed is reduced according to the thickness of the thick paper (the property of the recording material P), and a sufficient amount of heat is applied to the fusion of the toner image on the thick paper, whereby good fixing can be performed. . Further, even when the leading end side of the thick paper is transported by the fixing device 10 and the trailing end side thereof is transported by the transfer drum 5a at the same time, since the transport speed of the two is almost the same for the thick paper, curls and loops are formed in the middle part of the thick paper. Therefore, it is not necessary to set the distance between the separating means 9 and the fixing device 10 longer than the length of the cardboard in the conveyance direction, and the upper part of the cardboard when the card is conveyed from the transfer drum 5a to the fixing device 10 is not required. In addition, it is not necessary to secure an extra space in consideration of formation of a loop or the like. Therefore, it is possible to reduce the distance between the separating unit 9 and the fixing device 10 and further reduce the size of the entire image forming apparatus by eliminating an extra space above the thick paper.

Next, referring to FIG. 4 and FIG.
The change of the image forming condition of the photosensitive drum 1 when the process speed is changed according to the fixing conveyance speed will be described. In the following description, the grid bias voltage in the primary charger 2 is changed as the image forming condition is changed.

As shown in FIG. 4, when a signal (process speed down signal) for changing the process speed from 133 mm / sec to 103 mm / sec is input, the rotation of the photosensitive drum 1 stabilizes. but to converge to 103mm / sec, t ₁ (3
00 to 1000 msec). During this time, regardless of the speed change of the photosensitive drum 1, if a fixed amount of charging is continued by the primary charger 2, the photosensitive drum 1 changes its speed. Overshoot and undershoot occur.

FIG. 5 shows the relationship between the process speed of the photosensitive drum 1 and the surface potential Vd of the dark part. Vg in FIG.
₁ and Vg ₂ are the grids 2c of the primary charger ₂ , respectively.
FIG. 1 shows a grid bias voltage to be applied.
The surface potential Vd is determined by the characteristics of the photosensitive drum 1 such as withstand voltage.
Upper limit surface potential Vd _H (In the OPC photoconductor of this embodiment, −
And a lower limit surface potential Vd _L (also about −400 V) due to characteristics such as a withstand voltage of the photosensitive drum 1 against the opposite polarity charge. The surface potential during image formation is
It is intermediate between the two, and is indicated by Vd _M. When the grid bias voltage is Vg ₁ and the process speed of the photosensitive drum 1 is 133 mm / sec (illustrated at point A in the figure)
The surface potential is Vd _M, if we dropped the process speed in this state, the surface potential Vd rises, the process speed, exceeds the upper limit surface potential Vd _H. In this embodiment, after a predetermined from the process speed down signal time, outputs a signal to lower the grid bias voltage, the time t ₃ in until after (about 100～800Msec) (this time t ₃ in Figure 4, the grid the response time of the bias voltage t ₅ (50~100msec) are also included.), the grid bias voltage, so as to end the change from Vg ₁ to Vg _2. This change, when the process speed after a time t ₁ is stabilized to 103 mm / sec, the surface potential Vd at this time, as shown at point B, settle to Vd _M. That is, by lowering the grid bias voltage by an amount corresponding to the decrease in the process speed, the amount of charge applied per unit area of the surface of the photosensitive drum 1 can be made substantially the same even when the process speed is different. Therefore, the surface potential Vd can be maintained substantially constant.

Conversely, the same applies to the case where the process speed is increased from the beginning.
(However, the process speed (10) is
This is indicated by a circle 10. ) Exceeds the lower limit surface potential Vd _L. Therefore, the process speed up signal after a predetermined time, and outputs a signal to raise the grid bias voltage (grid bias up signal), the until time t ₄ in FIG. 4 (time t ₄ includes a response time t ₆₎ ,
The grid bias voltage, to end the change from Vg ₂ to Vg _1. With this change, when the process speed becomes stable after time t ₂ , the surface potential Vd is settled at Vd _{M as} shown by point A in FIG.

The upper limit surface potential Vd _H and the lower limit surface potential Vd _L of the photosensitive member of this embodiment are as described above.
These values are about -800 V and -400 V, respectively, and these values depend on the characteristics of the photoreceptor and on the degree of damage to the photoreceptor. For example, when the transfer of the toner image on the photosensitive drum 1 to the recording material P on the transfer drum 5a is performed by brush transfer, a positive (positive) damage to the photoconductor is caused particularly in a high temperature and high humidity environment. In some cases, the lower limit surface potential Vd _L is approximately −40 which is the same as the above.
It becomes 0V. On the other hand, in the case of the corona transfer system, -45
It becomes about 0V. <Embodiment 2> In Embodiment 1 described above, a change in the process speed of the photosensitive drum 1 is detected after a lapse of t ₁ and t ₂ hours from the process speed down signal and the process speed up signal, respectively. Although the speed has been changed, the present invention is not limited to this. For example, the rotation of the photosensitive drum 1 whose process speed has actually been changed by a process speed down signal or a process speed up signal may be directly detected by an encoder or the like, and the image forming conditions may be changed based on the output. . In this case, the photosensitive drum 1
Therefore, it is possible to accurately detect the process speed because variations in the rotation of the drive source can be eliminated. <Embodiment 3> In Embodiment 1, the change of the grid bias voltage is described as the image forming condition that is changed in accordance with the change of the fixing conveyance speed in the fixing device 10. However, other image forming conditions may be changed. it can. That is, when the process speed of the photosensitive drum 1 is changed, the image forming conditions are changed so that an image of the same quality as before the change can be formed. Specifically, the image forming conditions to be changed include, in a developing device of a type in which a magnetic brush to which a developing bias is applied is brought into contact with the photosensitive drum 1 during development, a developing bias applied at that time, Exposure lamp 7
, Pre-exposure amount, laser exposure amount of exposure means 3, transfer charger 5
b. These image forming conditions are appropriately changed according to the process speed so that, for example, a toner image having the same density as the formed toner image before the process speed change can be formed. <Embodiment 4> FIG. 6 shows an example of another image forming apparatus to which the present invention is applied. In the present embodiment, a photosensitive belt 1A is employed as an image carrier instead of the photosensitive drum 1, which is an image carrier of the image forming apparatus of FIG. The structure of each member around the photosensitive belt 1A is the same as that of the photosensitive drum 1 of the first embodiment.
Since the configuration of each of the surrounding members is substantially the same, the same reference numerals are given and the description thereof is omitted.

According to this embodiment, the photosensitive belt 1A is
Since the inertial force due to the rotation is smaller than that of the photosensitive drum 1, the times t ₁ , t ₂ , t ₃ , and t ₄ shown in FIG. 4 can be shortened, and the vibration during the rotation can be reduced. Therefore, it is possible to improve the control system when changing the process speed.

In the above-described first to fourth embodiments, the case where the fixing conveyance speed is reduced in order to perform satisfactory fixing on a recording material P having a large heat capacity such as a thick paper or an OHP sheet has been described. The present invention is not limited to this, and can be applied to other reasons, for example, a case where the fixing conveyance speed is reduced because the environmental temperature is low, and conversely, a case where the fixing conveyance speed is increased. That is,
The present invention can be widely applied in general when changing the fixing conveyance speed for any reason.

[0077]

As described above, according to the present invention,
Good fixing can be performed without increasing the size of the image forming apparatus, and damage to the image carrier by the charging unit can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a timing chart of an image forming operation in a standard single-sided mode according to the first embodiment.

FIG. 3 is a timing chart of an image forming operation in a thick paper mode according to the first embodiment.

FIG. 4 is a timing chart showing a correspondence between a change in process speed and a change in grid bias voltage in the first embodiment.

FIG. 5 is a diagram illustrating a relationship between a process speed and a photosensitive drum surface potential according to the first embodiment.

FIG. 6 is a longitudinal sectional view illustrating a configuration of an image forming apparatus according to a second embodiment.

FIG. 7A is a view showing a structural formula of a disazo pigment contained in a coating material for a charge generation layer of a photoreceptor. FIG. 3B is a diagram illustrating a structural formula of a charge transport material included in a charge transport layer of the photoconductor.

FIG. 8 is a diagram showing the relationship between the properties of a recording material and the fixing conveyance speed and the process speed.

FIG. 9 is a longitudinal sectional view schematically illustrating light of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Charging means (primary charger) 3 Exposure means 4 Developing means (developing device) 4Y Yellow developing device 4C Cyan developing device 4M Magenta developing device 4Bk Black developing device 5 Transfer device 5a Recording material carrier (transfer drum) 5b Transfer unit (transfer charger) 10 Fixing unit (fixer) 10a Fixing roller 10b Pressure roller P Recording material

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/00 303 G03G 15/01 G03G 15/02 102 G03G 15/08 507 G03G 15/20 107

Claims (7)

(57) [Claims] A movable image carrier; a charging unit configured to charge the image carrier; an image forming unit configured to form an image on the image carrier charged by the charging unit; A movable recording material carrier that electrically carries, and after transferring an image formed on the image carrier by the image forming means to a recording material carried on the recording material carrier at a transfer position, Fixing means for fixing an image at a fixing position on the recording material separated from the recording material carrier at the separation position, wherein the fixing means comprises a first fixing device.
An image forming apparatus that is switchable between a fixing speed of the first fixing speed and a second fixing speed different from the first fixing speed, wherein when the second fixing speed is selected, the recording material carrier is changed from the image carrier. After the image transfer to the recording material carried on the end, before fixing the image on the recording material, there is provided a period in which the recording material passes through the transfer position while being carried on the recording material carrier, In the period, the moving speed of the image carrier and the recording material carrier is changed according to the second fixing speed, and in the period, the voltage applied to the charging unit is changed to the moving speed of the image carrier. An image forming apparatus characterized in that the image forming apparatus is made variable in response to the request. 2. The image forming apparatus according to claim 1, wherein a distance between the separation position and the fixing position in the transport direction of the recording material is shorter than a length of the recording material. 3. After the fixing of the image on the first surface of the recording material by the fixing means is completed, a second image on the opposite side of the first surface of the recording material is formed.
3. An image can be transferred to the surface of the recording material at the transfer position, and when the image is fixed on the second surface of the recording material, the second fixing speed is selected. Image forming apparatus. 4. A charge removing means provided on a side of the recording material carrier for supporting a recording material, and static eliminator for eliminating the recording material carrier and the recording material at the separation position at the time of separation. 4. The image forming apparatus according to 3. 5. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed according to a type of a recording material. 6. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed according to a temperature inside the apparatus main body. 7. A multi-color image is formed on a recording material by repeating a step of transferring an image from the image carrier to a recording material carried on the recording material carrier.
7. The image forming apparatus according to any one of claims 1 to 6.