JP2002328542A - Double-sided transfer device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of restraining irregularities in an image caused by the rubbing of a guiding member for guiding a recording body such as transfer paper to a carrying member such as a fixing roller in a thermal fixing device and the recording body. SOLUTION: A belt unit 20 is disposed to be closer to the thermal fixing device 30 to such an extent that a transfer paper P part peeled from a paper carrying belt 10 and moving in a gravity direction reaches the fixing roller 31 or the pressure roller 32 in the thermal fixing device 30 in a state where it is not supported by the guiding member in a stage where the transfer paper P to which double-sided transfer has been performed is fed to the thermal fixing device while it is gradually peeled from the moving belt 10 from its leading edge side to its trailing edge side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device used for an image forming apparatus such as a copying machine, a printer, a facsimile, and the like, and an image forming apparatus having the same. The present invention relates to a double-sided transfer device for transferring a visual image and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, there has been known an image forming apparatus which forms a visible image on both sides of a recording medium such as a transfer paper by using a switchback system. In this switchback method, a recording medium is passed through a transfer device and a fixing device to fix a visible image such as a toner image on only one surface of the recording material, and then the recording material is reversed and fixed to the transfer device again. Returning to the apparatus, a visible image is formed on both sides of the recording medium.

However, in this type of image forming apparatus, there is a disadvantage that a complicated switchback mechanism for reversing the recording medium once passed through the fixing device and returning it to the transfer device is required, resulting in an increase in cost. there were. Also,
Inconveniences such as difficulty in increasing the speed of double-sided transfer due to switchback of the recording medium and curling of the recording medium due to heat at the time of the first fixing, which easily causes a jam at the time of switchback. There was also.

Therefore, there has been known an image forming apparatus in which a double-sided transfer device for transferring a visible image to both sides of a recording medium is provided as a transfer device, and the recording medium is passed through the double-sided transfer device and then sent to a fixing device. For example, JP-A-1-209470,
JP-A-10-142869, JP-A-2000-19
799, Japanese Patent No. 2906538, etc.). According to such an image forming apparatus, since it is not necessary to switch back the recording medium from the fixing device to the transfer device, it is possible to eliminate a cost increase due to the provision of the switchback mechanism and a jam at the time of switchback. In addition, it is possible to solve a situation in which the high speed of the double-sided transfer is prevented by the switchback.

[0005]

In such an image forming apparatus, a recording medium is transferred from a double-side transfer device to a fixing device. In order to ensure the transfer, a guide member such as a guide plate for guiding the recording medium to a conveying member such as a fixing roller in the fixing device is generally provided. However, since the visible images transferred to both sides of the recording medium are not yet fixed at the time when they are sent out from the two-sided transfer device, the rubbing with the guide member generates rubbing marks and disturbs the image. There is a risk.

[0006] The present invention has been made in view of such problems. The purpose is to provide a guide member for guiding a recording medium to a conveying member in a fixing device, and a double-sided transfer apparatus and an image forming apparatus capable of suppressing disturbance of an image due to rubbing with the recording medium. To provide.

[0007]

According to a first aspect of the present invention, a recording medium holding member for holding a recording medium is moved in a predetermined direction while moving the recording medium holding member on an image carrier of an image forming apparatus. After transferring the visible image to both sides of the recording material on the recording material holding member, the recording material is fed to the heat fixing device of an image forming apparatus by the recording material holding member. A heat-resistant holding member is used. Claim 2
The invention is directed to an image carrier for carrying a visible image, a visible image forming means for forming a visible image on the image carrier, and a recording material holding member for holding a recording material, which is moved in a predetermined direction, A two-sided transfer device for transferring the visible image on the image carrier to both sides of the recording material on the recording material holding member, and a recording material after passing through the two-sided transfer device is received on a conveying member; An image forming apparatus comprising: a heating and fixing device for fixing a visible image on both sides to a recording medium while heating the image; wherein the double-side transfer device according to claim 1 is used. According to a third aspect of the present invention, there is provided an image carrier for carrying a visible image, a visible image forming means for forming a visible image on the image carrier, and a recording material holding member for holding the recording material in a predetermined direction. A double-sided transfer device for transferring the visible image on the image carrier to both sides of the recording medium on the recording medium holding member while moving the recording medium on the conveyance member After receiving the image, the image forming apparatus includes a fixing device for fixing the visible images on both sides of the recording medium to the recording medium. In the process of being fed toward the fixing device while gradually peeling off, the recording material portion that is peeled off from the recording material holding member and is about to move in the direction of gravity reaches the transport member of the fixing device without being supported by the guide member. The double-sided transfer device to such an extent that It is characterized in that the closer to the destination device is disposed. The invention of claim 4 is
The image forming apparatus according to claim 3, wherein the fixing device includes a heating and fixing device that fixes a visible image to a recording medium while heating the visible image.
It is characterized by using a heat-resistant material capable of withstanding the heat transmitted from the heat fixing device. According to a fifth aspect of the present invention, in the image forming apparatus according to the second or fourth aspect, the recording medium is placed on a transfer portion formed by contact between the image carrier and the heat-resistant recording medium holding member that moves endlessly. The double-sided transfer means is configured so that the visible image on the image carrier is transferred to a recording medium by being sandwiched therebetween. According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, as the heat-resistant recording member holding member, a member having a base material made of polyimide or polyamide is used. According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect,
Cooling means for cooling the heat-resistant recording material holding member after sending the recording material toward the heat fixing device and before contacting the image carrier at the transfer portion is provided. Is what you do. According to an eighth aspect of the present invention, in the image forming apparatus of the seventh aspect, a heat pipe that cools the recording medium holding member while contacting the heat resistant recording material holding member is used as the cooling unit. It is.
According to a ninth aspect of the present invention, in the image forming apparatus according to the fifth, sixth, seventh, or eighth aspect, the recording medium is sent out toward the heat fixing device and before moving to the transfer section. A cleaning unit is provided for removing and cleaning an image forming substance remaining on the recording medium without remaining on the recording medium from the surface of the recording medium holding member, and is heated to a temperature equal to or higher than a glass transition point by heat from the heat fixing device. The cleaning means is provided at a position where it can be cleaned before the raised image forming substance is naturally radiated to a temperature lower than the glass transition point. According to a tenth aspect of the present invention, in the image forming apparatus of the ninth aspect, as the cleaning unit, a roller surface having a surface roughness equal to or higher than that of the heat-resistant recording medium holding member is brought into contact with the recording medium holding member. A cleaning roller having a cleaning roller is used. According to an eleventh aspect of the present invention, in the image forming apparatus of the tenth aspect, the cleaning roller has a surface roughness of JIS-A of 3.5 [μm] or more. is there. According to a twelfth aspect of the present invention, in the image forming apparatus of the ninth, tenth or eleventh aspect, the heat-resistant recording member holding member has a multilayer structure having at least a lower layer and a surface layer coated thereon. Wherein the surface layer has a lower adhesive strength to the image forming substance than the lower layer and the image forming substance. According to a thirteenth aspect, in the image forming apparatus according to the twelfth aspect,
The heat-resistant recording member holding member has the surface layer made of a fluororesin. Further, the invention of claim 14 is based on claims 9 and 1
The image forming apparatus of any one of 0, 11, 12 and 13, characterized in that a contacting / separating means for bringing the cleaning means into and out of contact with the heat-resistant recording material holding member is provided. According to a fifteenth aspect of the present invention, in the image forming apparatus of the fourteenth aspect, the first visible image is transferred from the image carrier to the heat-resistant recording medium holding member by the transfer section, and then the recording medium is transferred to the recording medium. The first visible image is sent to the transfer portion again by the endless movement of the holding member, and the second visible image on the image carrier is superimposed on the recording material and the first visible image at the transfer portion. The double-sided transfer device is configured to transfer the second visible image to a recording medium and to include a charge applying unit that applies a charge to the recording medium holding member in a non-contact manner. It is assumed that. The invention according to claim 16 is based on claims 5, 6, 7, 8, 9, 10, 11, 12, 13, 1
In the image forming apparatus according to the fourth or fifteenth aspect, a heat-resistant endless belt is used as the heat-resistant recording member holding member. The invention of claim 17 is based on claims 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1
The image forming apparatus of any one of 3, 14, 15 and 16, wherein the recording material holding member is disposed vertically below the heat fixing device. The invention according to claim 18 is based on claims 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16 or 1
In the image forming apparatus according to 7, the transfer device or the double-sided transfer device is arranged so that the distance between the surface of the conveying member and the surface of the recording material holding member at the closest position is 60 mm or less. It is characterized by being arranged close to the heat fixing device. The invention according to claim 19 is based on claims 2, 3, 4, 5, 6, 7, 8, 9, 1
0, 11, 12, 13, 14, 15, 16, 17 or 1
8, a receiving unit for receiving a control signal from a computer, and controlling the driving of the image carrier, the visible image forming unit, the heat fixing device, and the double-sided transfer device based on the reception result of the receiving unit. And control means for performing the control. In these inventions, in the apparatus having the configuration of the first aspect of the invention, the recording body holding member that sends out the recording body toward the heat fixing device exhibits heat resistance. Thus, even if a heat fixing device that generates relatively high heat is provided in the image forming apparatus as the fixing device, it is possible to arrange the recording material holding member closer to the heat fixing device than before. . In such a configuration, the size of the guide member for guiding the recording material to the conveyance member in the fixing device is reduced by the distance between the recording material holding member and the heat fixing device, or the guide member is omitted. Even
The recording member can be transferred from the recording medium holding member into the heat fixing device. By reducing or eliminating the guide member in this way, it is possible to suppress the disturbance of the image due to the friction between the guide member and the recording medium. Further, in the apparatus having the structure of the third aspect of the present invention, the recording member can be transferred from the double-sided transfer device to the conveying member of the fixing device without using the conventionally provided guide member. The guide member can be omitted. Therefore, it is possible to form a high-quality image in which disturbance caused by sliding between the guide member and the recording medium is eliminated. In the image forming apparatus according to the twelfth aspect, the “lower layer” means a portion excluding the surface layer located on the most surface side, and indicates at least a portion having a base material layer. Therefore, the lower layer does not always have a single-layer structure.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of an electrophotographic printer (hereinafter, simply referred to as a printer) will be described as one embodiment of an image forming apparatus to which the present invention is applied. First, the basic configuration of the printer will be described.

FIG. 1 is a schematic configuration diagram of the present printer.
In the figure, a printer 100 includes a process cartridge 6 in which a photosensitive drum 1 serving as an image carrier is incorporated at substantially the center in the vertical direction in the apparatus. The process cartridge 6 incorporates, in addition to the photosensitive drum 1, a drum cleaning device 2, a static elimination device 3, a charging device 4, a developing device 5, and the like, and is to be replaced when the end of its life.

The charging device 4 includes a photosensitive drum 1 which is rotated clockwise in the figure by driving means (not shown).
Is uniformly charged, for example, to a negative polarity. The surface of the photosensitive drum 1 uniformly charged in this way is exposed by an exposure device described later to carry an electrostatic latent image.

The developing device 5 develops the electrostatic latent image on the photosensitive drum 1 into a toner image with the toner on the developing roller exposed from the opening of the casing. The developed toner image is transferred to a paper transport belt or transfer paper by a belt unit described later.

The drum cleaning device 2 cleans the photosensitive drum 1 by removing the toner remaining on the photosensitive drum 1 after the transfer of the toner image.

The charge removing device 3 removes the charge remaining on the photosensitive drum 1 after cleaning. By this charge elimination, the surface of the photosensitive drum 1 is initialized and prepared for the next image formation.

An exposure device 7 is disposed on the right side of the process cartridge 6 having the above configuration in the drawing. The exposure device 7 irradiates the photoconductor 1 with a laser beam L emitted based on image information from a writing position between the charging device 4 and the developing device 5.

A paper feeding means having a paper feeding cassette 26, a paper feeding roller 27, a registration roller pair 28, and the like is provided below the process cartridge 6 in the drawing. A plurality of transfer papers P as recording bodies are stored in the paper supply cassette 26, and a paper supply roller 27 is in contact with the uppermost transfer paper P. When the paper feed roller 27 is rotated clockwise in the figure by a driving unit (not shown), the uppermost transfer paper P is sandwiched between the rollers of the registration roller pair 28. The registration roller pair 28 sends out the sandwiched transfer paper P toward a transfer nip described later at an appropriate timing.

Further, on the left side of the process cartridge 6 in the figure, there are provided a paper transport belt 10, tension rollers 11, 12, 13, and 14, a transfer roller 15, a backing roller 16, and the like, which are recording material holding members. ing. Further, a belt unit 20 having a transfer charger 17 as a charge applying unit, a cooling unit 18, and the like are also provided. The belt unit 20 contacts the photosensitive drum 1 while moving the paper transport belt 10 endlessly.

The tension rollers 11, 12, 13, 14
Moves the paper transport belt 10 endlessly in a counterclockwise direction in the figure with the rotation drive of one of these rollers while stretching the tension. The tension roller driven to rotate is configured such that the winding angle of the paper transport belt 10 is ensured to some extent and the driving force is reliably transmitted to the belt.

The above-mentioned paper transport belt 10 has a portion not stretched by the stretching rollers 11, 12, 13, and 14,
The transfer nip is formed by winding around a part of the peripheral surface of the photosensitive drum 1.

The transfer roller 15 is positioned between the transfer nip and the photosensitive drum 1 at a position corresponding to the transfer nip.
It is arranged so as to sandwich it. Then, by receiving, for example, a positive voltage supply from a power supply (not shown), a transfer electric field is formed between the photosensitive drum 1 and the power supply. In the transfer nip, the toner image on the photosensitive drum 1 is transferred to the paper transport belt 10 by the influence of the transfer electric field and the nip pressure.
Alternatively, the image is transferred onto the transfer paper P sent by the registration roller pair 28.

The transfer paper P on which the toner image on the photosensitive drum 1 has been transferred by the transfer nip is transferred to a paper transport belt 10.
Passes through the position facing the transfer charger 17 with the endless movement of. Then, the toner is sent out to the heating and fixing device 30 disposed above the belt unit 20 in the drawing. The roles of the transfer charger 17 and the cooling means 18 will be described later.

The heat fixing device 30 has a heating roller 31, a pressure roller 32, and the like, each of which incorporates a heater (not shown), and sandwiches the transfer paper P sent from the paper transport belt 10 between the rollers. Then, after the toner image on the transfer paper P is fixed by the action of the heat generated by the heating roller or the pressure between the rollers, the transfer paper P is sent to the discharge path 33. The transfer paper P sent to the discharge path 33 is discharged to the upper surface of the printer body via a discharge device 34 including a discharge roller 34a.

A stack unit 40 is provided on the upper surface of the printer body.
Are formed, and the transfer paper P discharged from the discharge device 34 is sequentially stacked on the stack unit 40.

An electrical unit E1 and a control unit E2 are disposed between the sheet cassette 26 and the exposure device 7, and these devices are electrically controlled.

In the upper right corner of the printer main body, a fan F
1 is provided, whereby the air inside the machine is forcibly discharged, and an excessive rise in the temperature inside the machine is suppressed.

Generally, it is difficult to electrostatically transfer two toner images composed of toners of the same charge polarity to both sides of the transfer paper P so as to face each other. For example, after a negative toner image composed of negatively charged toner is electrostatically transferred to the front surface of the transfer paper P,
It is assumed that another negative toner image is to be electrostatically transferred to the back surface of the transfer paper P. In the first transfer, an electrostatic force is applied to the toner image from the front side to the back side of the transfer paper P while the negative polarity toner image is positioned on the front side of the transfer paper P. Will do. In the second transfer, an electrostatic force is applied to the toner image from the back side of the recording body to the front side while the negative polarity toner image is positioned on the back side of the transfer paper P. become. But,
At this time, the negative toner image previously transferred to the front surface of the transfer paper P is given an electrostatic force that separates it from the front surface. As a result, the previously transferred toner image is reversely transferred to a roller or the like that is in contact with the toner image, so that double-sided transfer becomes difficult. In order to avoid such reverse transfer, an image forming apparatus that forms two toner images having different charging polarities by using two types of toners having different charging polarities and transfers the two toner images while positioning them on the opposite surfaces of the transfer paper P. It has been known. However, in this image forming apparatus, a pair of toner image forming units for forming two toner images having different charging polarities cannot use a common specification, so that maintenance performance is deteriorated. Was. Further, it is necessary to distinguish and manage the toners whose appearance such as color is hardly changed only by the difference of the charging polarity, and this has further deteriorated the maintainability.

Therefore, the printer 100 is configured to transfer a toner image to both sides of the transfer paper P by the following process. That is, the printer 10
0 is a personal computer 20 as shown in FIG.
It is configured to form an image based on an image information signal sent from 0 or the like. When the image information signal is received by the printer 100, the exposure device 7 (see FIG. 1) is driven and controlled based on the signal. The laser light L emitted from the exposure device 7 by this drive control is scanned by a polygon mirror 7a rotated and driven by a motor (not shown), irradiates the photosensitive drum 1 via a mirror 7b, an fθ lens 7c, etc. An electrostatic latent image is formed. This first electrostatic latent image is developed by the developing device 5 using toner as an image forming substance, and becomes a first toner image as a first visible image on the photosensitive drum 1. The first toner image moves to the transfer nip as the photosensitive drum 1 rotates. At this time, the transfer paper P has not yet been fed into the transfer nip, and the first toner image is not the transfer paper P but the paper transport belt 10.
Transcribed above. Then, when the paper transport belt 10 moves endlessly by about one rotation after the transfer, it returns to the transfer nip again. While the paper transport belt 10 moves endlessly by about one turn, the next exposure step and development step are started, and a second toner image, which is a second visible image, is formed on the photosensitive drum 1. Further, a pair of registration rollers 28
The registration roller pair 28 sends out the first surface (the lower surface in the figure) of the transfer paper P at a timing at which it can be superimposed on the first toner image returning to the transfer nip. . On the other hand, the second toner image is formed on the photosensitive drum 1 at such a timing that the second toner image is exactly overlapped with the second surface (upper surface in the drawing) of the transfer paper P sent to the transfer nip. Therefore, in the transfer nip where the first toner image has returned again, the first toner image
The toner image, the transfer paper P, and the second toner image on the photosensitive drum 1 are sandwiched. Then, the second toner image is transferred to the second surface of the transfer paper P under the influence of the transfer electric field formed by the transfer roller 15 and the like. At this time, the electrostatic force attracted to the paper transport belt 10 acts on the first toner image located between the paper transport belt 10 and the first surface of the transfer paper P by the transfer electric field. For this reason,
The first toner image is in contact with the first surface of the transfer paper P, but has not yet been transferred there. Transfer paper P that has left the transfer nip
Moves with the paper transport belt 10 in a state where the second toner image transferred by the transfer nip is carried on the second surface, and the first toner image on the paper transport belt 10 is in contact with the first surface. Then, the transfer charger 1 as the charge applying means
7, the first toner image that has just been in contact with the first surface is electrostatically transferred. At this time, a predetermined gap is maintained between the second surface of the transfer paper P and the transfer charger 17.
The second toner image is not reverse-transferred to the transfer charger 17 by the contact with the transfer charger 17. As described above, the belt unit 20 can transfer the toner image to both sides of the transfer paper P by the functions of the transfer roller 15 and the transfer charger 17 and thus has a function as a double-sided transfer device.

In this process, the second toner image is transferred onto the transfer paper P by the transfer nip, and the first toner image is sandwiched between the paper transport belt 10 and the transfer paper P. Then, a reverse charge is applied to the transfer paper P in a state where the first toner image is sandwiched between the belt and the belt from the second toner image side by the transfer charger 17 as a charge applying unit. Since the charger 17 is not in contact with the second toner image, there is no possibility that reverse charging of the second toner image is caused by the application of the reverse charge. Therefore, the first toner image previously transferred onto the paper transport belt 10 can be electrostatically transferred from the belt side to the transfer paper P side while avoiding reverse transfer.

Incidentally, the transfer charger 1 as a charge applying means
Although the example in which 7 is provided downstream of the transfer nip in the belt moving direction has been described, it may be provided upstream of the transfer nip in the belt moving direction. In such a configuration, before the first toner image transferred to the paper transport belt 10 is again sent to the transfer nip, the first toner image is reversely charged by applying a charge by the charging charger 17. The oppositely charged first toner image is opposed to the second toner image via the transfer paper P at the transfer nip. When an electrostatic force is applied to the second toner image from the photosensitive drum 1 toward the transfer paper P by the transfer electric field, the electrostatic force from the belt side toward the transfer paper P is applied to the first toner image. Power is applied.
Therefore, the first toner image is transferred onto the transfer paper P without being reversely transferred to the paper transport belt 10.

The transfer charger 17 is controlled so as to be in a stopped state when the first toner image passes by itself, not together with the transfer paper P or the second toner image, through the charge application position. Further, the first toner image is formed on the photosensitive drum 1 so as to be a normal image instead of a mirror image.
This is for the following reason. That is, in the case of direct transfer from the drum to the transfer paper P, a mirror image is formed on the drum 1 of the photoconductor, and when this is directly transferred to the transfer paper P, a normal image is obtained. However, in the indirect transfer from the drum to the belt to the transfer paper P, when a mirror image is formed on the photosensitive drum 1, the mirror image is formed on the first surface of the transfer paper P. It goes without saying that the second toner image directly transferred to the transfer paper P is formed on the photosensitive drum 1 as a mirror image as usual.

When a toner image is formed on only one side of the transfer paper P in the printer 100, the following image forming process is performed. That is, first, a mirror image toner image is formed on the photosensitive drum 1 and sent to the transfer nip. On the other hand, the transfer paper P is sent from the paper feed cassette 26 toward the registration roller pair 28 and is sent out to the transfer nip at such a timing as to be superimposed on the toner image by the registration roller pair 28. The transfer paper P having passed through the transfer nip and carrying the toner image on the second surface thereof is heated without being charged by the transfer charger 17.
0, and is discharged to the stack section 40 after the toner image is fixed.

Next, the characteristic configuration of the printer 100 will be described. FIG. 3 is an enlarged configuration diagram showing a part of the belt unit 20 and the heat fixing device 30. In the figure, a stretching roller 11, a heating roller 31, a pressing roller 3
2, 20 [mm], 30 [mm], 30
A diameter of [mm] is used.

When the paper transport belt 10 moves to the position where it is stretched by the stretching roller 11 along with the upward movement in the figure, it is wound around the peripheral surface of the stretching roller 11 so that the moving direction is shown in the figure. Turn left.

On the other hand, the leading end portion of the transfer paper P, which has been moved to the belt stretching position by the stretching roller 11 together with the portion of the paper transport belt 10 moving upward in the drawing, is
Does not follow the paper transport belt 11 which is going to change its direction rapidly along the peripheral surface of the belt. It is peeled off from the paper transport belt 11 by its own stiffness. Then, the transfer paper P, which has not yet reached the belt tension position by the tension roller 11, is pushed upward in the drawing by the rear end portion of the transfer paper P that continues to move with the paper transport belt 10, and
It gradually protrudes from.

The leading end portion of the transfer sheet P, which peels off and projects from the paper transport belt 10, loses its support and tends to bend right or left in the drawing due to the influence of gravity. However, while the amount of protrusion from the paper transport belt 10 is small to some extent, a substantially straight posture is maintained due to the strength of its own waist. And, when the amount of protrusion was increased until it could not support its own weight only with the strength of the waist,
It turns right or left. Such bending makes it impossible to enter the heat fixing device 30.

Therefore, usually, a guide member such as a guide plate for guiding the transfer paper P, which is about to be bent, into the heat fixing device 30 is provided between the heat fixing device 30 and the belt unit 20. , Provided in the casing of the heat fixing device 30. However, the guide member is not provided in the printer 100 of the first embodiment. Instead, the belt unit 20 is connected to the heat fixing device
It is arranged close to 0. More specifically, while the front end portion of the transfer paper P that is about to be bent is maintained in a substantially straight state with its stiffness, the front end portion is heated by the heating roller 31 of the heat fixing device 30 or the like. The distance is set so that the pressure roller 32 can be reached. More specifically, the belt unit 20 is arranged so that the distance S between the heating roller 31 and the paper transport belt 10 at the point where the heating roller 31 and the paper transport belt 10 come closest is 60 [mm]. The present inventors have developed a prototype of the printer 100 shown in FIGS.
Using a 45K plain paper as the transfer paper P, the distance S and the bending of the leading end of the plain paper were tested.
As a result, it has been found that if the distance S is set to be equal to or less than 60 [mm], it is possible to reach the heating roller 31 without bending the front end portion. Then, the distance S is set to 60 [m
m].

With such a configuration, the transfer paper P can be transferred from the paper transport belt 10 to the heating roller 31 and the pressure roller 32, which are transport members, without providing a guide member. Therefore, the disturbance of the first toner image on the first surface side due to the rubbing between the guide member and the transfer paper P can be eliminated.

However, when the belt unit 20 is disposed close to the heating and fixing device 30 as described above, the heat generated from the heating roller 31 of the heating and fixing device 30 may damage the paper transport belt 10. There is. Therefore, a heat-resistant material is used for the base material of the paper transport belt 10. This heat resistant material is specifically, 200
It exhibits a glass transition temperature higher than [° C] (200 ° C).
It does not melt at a temperature of 200 ° C.) and has a shrinkage of 0.5% or less in an environment of 200 ° C. In addition,
200 [° C.] is a general fixing temperature in the image forming apparatus.

The printer 100 employs a contact transfer method in which the toner image on the photosensitive drum 1 is transferred to the belt side while the paper transport belt 10 is positively in contact with the photosensitive drum 1 in the transfer nip. I have. In the contact transfer method, unlike the non-contact transfer method in which the toner image flies toward the transfer body, the toner image is transferred without flying, so that the transfer deviation due to the deviation of the flight path of the toner image is avoided. be able to. However, if the portion of the paper transport belt 10 heated by the influence of the heat fixing device 30 is brought into contact with the photosensitive drum 1 before being sufficiently cooled, the photosensitive drum 1 may be thermally damaged. .

Therefore, the belt unit 20 is provided with cooling means 18 for cooling the portion of the paper transport belt 10 heated by passing near the heating and fixing device 30. The cooling means 18 may employ a ventilation cooling method, a cooling promoting member contact method, or the like. In any case, the cooling means 18 may be configured to cool the paper transport belt 10 from the back surface. desirable. This is because, if cooling is performed from the front surface, the first toner image transferred onto the paper transport belt 10 may be disturbed.

More preferably, the cooling is performed by a heat pipe as shown in FIG. The heat pipe 18a has a metal pipe 18b, a plurality of fins 18c standing upright on one end side peripheral surface thereof, and the like. The pipe 18b is disposed so as to rotate while being in contact with the back surface of the paper transport belt 10, and contains a predetermined amount of coolant inside. The portion of the pipe 18b that comes into contact with the back surface of the paper transport belt 10 with the rotation absorbs heat on the back surface and transmits the heat to the internal cooling liquid. The heat transferred coolant evaporates in the pipe. Meanwhile, a plurality of fins 1
8c makes contact with the surrounding air when revolving around the rotation axis of the pipe 18b.
Cool near the end of the. By this cooling, the cooling liquid vaporized in the pipe is cooled and liquefied. In the heat pipe 18a having such a configuration, the paper transport belt 10 can be efficiently cooled without using a special driving source.
Further, the cooling rate is extremely high, and there is almost no cooling unevenness in the pipe axis direction. Therefore, even if heating unevenness occurs in the width direction of the paper transport belt 10 for some reason, the paper transport belt can be uniformly cooled in the width direction.

As described above, the first toner image transferred from the photosensitive drum 1 to the paper transport belt 10 at the transfer nip is
When the sheet passes through a position facing the transfer charger 17 together with the transfer sheet P, the image is transferred to the first surface of the transfer sheet P (see FIG. 1). However, when the transfer paper P and the paper transport belt 10 are separated from each other, some toner is inevitably removed from the paper transport belt 10.
Leave on top. If the residual toner comes into contact with the transfer paper P sent from the registration roller pair 28 to the transfer nip, the first surface of the transfer paper P will be stained.

Therefore, the printer 100 is provided with the belt cleaning unit 50 as shown in FIG. The belt cleaning unit 50 includes a cleaning roller 51, a scraping blade 52, a conveying screw 53, a contact / separation mechanism (not shown), and the like. The cleaning roller 51 is disposed downstream of the stretching roller 11 of the belt unit 20 (near the separation position of the transfer paper P) in the belt moving direction and between the stretching roller 14 and the stretching roller 14 that contacts the back surface of the paper transport belt 10. It rotates while sandwiching the transport belt 10. The residual toner on the front surface of the paper transport belt 10 is
When the cleaning roller 51 rotates in this way, it is transferred to the cleaning roller 51 and is removed from the paper transport belt 10. The belt cleaning unit 50 performs a cleaning process on a belt portion in a movement path from the vicinity of the tension roller 11 where the transfer paper P and the paper transport belt 10 are separated from each other to the transfer nip.

When the belt cleaning unit 50 is provided, the paper transport belt 10 having a surface roughness smaller than the particle diameter of the toner is generally used. This is to prevent a situation in which toner particles enter into concave portions of fine irregularities formed on the belt surface and make cleaning difficult. However, even when such a paper transport belt 10 is used, a part of the toner particles can be cut into the concave portion on the belt surface, and thus the toner particles are easily caught in the concave portion. It is assumed that the cleaning roller 51 having a finer surface roughness than the belt is brought into contact with the paper transport belt 10 on which the toner is caught in the concave portion. Then
The toner particles also partially penetrate subtle recesses on the surface of the cleaning roller 51. At this time, since the diameter of the concave portion on the belt surface is larger, the bite amount of the concave portion on the surface of the cleaning roller 51 is smaller than that of the concave portion. For this reason, the adhesive force with the concave portion on the surface of the belt is superior to the adhesive force with the concave portion on the surface of the roller, and the toner easily remains on the paper transport belt 10 separated from the cleaning roller 51. Therefore, it is desirable to use a cleaning roller 51 having a surface roughness equal to or higher than that of the paper transport belt 10. From such a viewpoint, the printer according to the present embodiment also uses the cleaning roller 51 having a larger surface roughness than the paper transport belt 10. Such a cleaning roller 51
In this case, the toner particles penetrate deeply into the roller surface concave portion or penetrate the belt surface concave portion more completely than the belt surface concave portion. When the paper transport belt 10 and the cleaning roller 51, whose surfaces are moved endlessly, are separated from each other, the toner particles are caught by any of the concave portions. However, the strength of the hooking increases as the amount of biting into the concave portion increases, so that the toner particles are more likely to remain on the roller surface concave portion that bites deeper. Further, the belt may completely enter the concave portion on the roller surface and may not be caught at all in the concave portion on the belt surface. Therefore, in the present printer, when the paper transport belt 10 and the cleaning roller 51 are separated from each other, transfer of the toner to the surface of the cleaning roller 51 is promoted, and good cleaning can be realized.

As for the toner, even if small, at most 5
Particles having a particle size of [μm] are generally used. In order for the paper transport belt 10 to exhibit good releasability from the toner having such a particle size, the surface roughness of the belt should be 3.5 [μm] or less according to JIS-A. It has been known. Therefore, JIS-A surface roughness of 3.
The condition of 5 [μm] or less is a general surface design condition of the recording material holding member. Therefore, if a cleaning roller having a surface roughness of 3.5 [μm] or more according to JIS-A is used, good cleaning of the surface can be realized while satisfying the general surface design conditions of the paper transport belt 10. Can be. Therefore, in the printer 100 of the first embodiment, a metal roller such as nickel-plated mild steel or stainless steel whose surface roughness of JIS-A is adjusted to 5.0 [μm] is used as the cleaning roller 51. In addition,
As the paper transport belt 10, a belt whose surface roughness is adjusted to 3.4 [μm] according to JIS-A is used.

The scraping blade 52 scrapes residual toner transferred to the surface of the cleaning roller 51,
It is dropped on the transport screw 53 arranged below.
Conveying screw 5 that has received the scraped residual toner
Numeral 3 is rotated by driving means (not shown) to convey the residual toner in its axial direction and send it to a collecting unit (not shown).

When the residual toner on the paper transport belt 10 is heated to a temperature higher than the glass transition point near the heating and fixing device 30, a belt cleaning unit 50 is provided at a position described below. It is desirable to do. That is, the cleaning roller 51 can remove the residual toner before being cooled to a temperature equal to or lower than the glass transition point by natural heat radiation and before being affected by the cooling by the cooling unit 18. By arranging at such a position, the residual toner melted by the influence of the heat fixing device 30 can be removed before the toner is fixed to the paper transport belt 10, so that cleaning failure due to the sticking can be suppressed. It is. In this printer 100, from such a viewpoint, the belt is moved to a position where the residual toner can be cleaned before cooling to a temperature below the glass transition point by natural heat radiation and before being affected by the cooling by the cooling unit 18. A cleaning unit 50 is provided.

The belt cleaning unit 50 is also provided with a contact / separation mechanism (not shown) for bringing the cleaning roller 51 into and out of contact with the paper transport belt 10. As shown in FIGS. 5 (a) and 5 (b), this contact / separation mechanism is turned on / off by a solenoid (not shown), and as shown in FIGS.
Swing 0. Then, the cleaning roller 51 is moved toward and away from the paper transport belt 10 with the swing. When the first toner image is moved to the cleaning position instead of the residual toner due to the contact and separation, the cleaning roller 51 can be separated from the paper transport belt 10. Therefore, it is possible to avoid a situation where the first toner image is cleaned. Further, the cleaning roller 51 can be brought into contact with the paper transport belt 10 only when cleaning is necessary, and can be separated when cleaning is unnecessary.
Therefore, the rotation driving means of the cleaning roller 51 and the paper transport belt 10 can be maintained without losing the cleaning performance.
Can be reduced.

FIG. 6 is a sectional view showing a part of the paper transport belt 10. The paper transport belt 10 has a two-layer structure of a lower layer 10b made of polyimide or polyamide and a surface layer 10a made of a fluororesin coated on the front surface of the lower layer 10b. The function as the paper transport belt 10 is as follows.
This can be sufficiently achieved with only b. However,
By coating the lower layer 10b with a surface layer 10a made of a fluororesin having extremely low substance adhesion, the surface layer 10a can function as a toner release layer for the lower layer 10b. Therefore, when the paper transport belt 10 is separated from the transfer paper P, or when the cleaning roller 51 cleans the residual toner, the paper transport belt 1
The toner separation from zero can be promoted.

As the fluororesin used for the surface layer 10a, for example, a polytetrafluoroethylene resin (polytetrafluoroethylene: PT) called Teflon (registered trademark) is used.
FE) and the like are preferable. Further, a tetrafluoroethylene / ethylene resin (ETFE), a tetrafluoroethylene / hexafluoropropylene resin (FEP), a tetrafluoroethylene / perfluoroalkoxyethylene resin (PFA), or the like may be used. Further, poly (trifluorochloroethylene) resin (CTF)
E), chlorotrifluoroethylene / ethylene resin (ECT
FE). These fluororesins all have a glass transition point higher than 200 [° C.]
The heat shrinkage rate in an environment of [° C.] becomes 0.5% or less.

In the configuration shown in FIG.
1, a so-called vertical transport system is employed in which the leading end portion of the transfer paper P protruding from the paper transport belt 10 is guided in a substantially vertical state to the heating and fixing device 30 located on the upper side in the vertical direction. Such a vertical transport system has the following two advantages.

That is, the first advantage is that the timing at which the leading end portion of the transfer paper P is bent can be delayed. More specifically, the front end portion of the transfer paper P is set in a substantially vertical state as shown in FIG.
, The weight of the front end portion can be mainly received by the rear end portion of the transfer paper P that has not yet protruded from the paper transport belt 10. That is, the front end portion can be supported by the rear end portion to some extent without completely losing the support of the front end portion. on the other hand,
As shown in FIG. 7, the leading end portion of the transfer paper P protruding from the paper transport belt 10 is guided to the heat fixing device 30 disposed on the side of the belt unit 20 in a substantially horizontal state. I do. Then, since there is no longer any object for receiving the load of the distal end portion, it is necessary to counter the bending of the distal end portion only by the strength of its waist. Such a distal end portion is bent with a smaller amount of protrusion than the distal end portion shown in FIG. According to the test of the present inventors, the distance S is 60
When it is larger than [mm], the end portion is bent before reaching the heating roller 31.
Therefore, in so-called lateral conveyance of the transfer paper P as shown in FIG. 7, it is desirable to set the distance S to 60 [mm] or less.

The second advantage is that, since the belt unit 20 is disposed below the heat fixing device 30 in the vertical direction, the heating of the paper transport belt 10 by the heat fixing device 30 can be suppressed. is there. As is well known, the heated air moves upward in the vertical direction opposite to the direction of gravity, so that it becomes difficult for the heated air to contact the paper transport belt 10 on the lower side in the vertical direction. In the horizontal conveyance system shown in FIG. 7, the paper conveyance belt 10 is not provided in the path in which the air heated by the heat fixing device 30 moves vertically upward. Can be suppressed. However, as shown in FIG.
During the transfer to the heat fixing device 30 from
The movement path of the air heated at the right portion of the heating roller 31 in the drawing is blocked by the transfer paper P being transferred. Then, due to this interruption, the paper transport belt 10 moves in the lateral direction and is heated. Therefore, the effect of suppressing the heating of the paper transport belt 10 is superior to the vertical transport method in which the transfer paper P is transported to the heating and fixing device 30 disposed on the upper side in the vertical direction, as compared with the horizontal transport method.

In the vertical conveyance method, in addition to the vertical conveyance as shown in FIG. 3, the transfer paper P is guided to the heat fixing device 30 disposed on the lower side in the vertical direction. There is also vertical transport to the side. In the latter vertical transport, the paper transport belt 10
Of the transfer paper P protruding from the transfer paper P is pulled straight in the moving direction by gravity. For this reason, the front end portion does not bend, and the distance S can be made much longer than the former limit of vertical conveyance of 100 [mm]. However, since the paper transport belt 10 is surely positioned in the movement path of the air that is heated by the heat fixing device 30 and moves in the direction of gravity, the paper transport belt 10 is heated to near the heating temperature of the heating roller 31. Would be. Therefore, from the viewpoint of reducing the heating of the paper transport belt 10, the latter vertical transport is not desirable.

FIG. 8 is a schematic configuration diagram showing a printer according to a modification. In the figure, a printer 100A of this modified example is shown.
Replaces the process cartridge 6 shown in FIG.
The intermediate transfer unit 200 and the four photoconductor units 30
0Y, M, C, K, etc. Photoconductor unit 3
00Y, M, C, and K are Y (yellow) and M, respectively.
(Magenta), C (cyan), and K (black) toner images are formed, and have substantially the same configuration except that the color of the toner used is different. Photoconductor unit 3
00Y as an example, as shown in FIG. 9, the photosensitive drum 301Y, the drum cleaning device 302Y,
Charge removing device 303Y, charging device 304Y, developing device 305
Y and the like. The charging device 304Y uniformly charges the surface of the photosensitive drum 301Y rotated counterclockwise in the figure by a driving unit (not shown). The uniformly charged surface of the photosensitive drum 301Y is exposed by the exposure device 7 to carry a Y electrostatic latent image. This Y electrostatic latent image is developed into a Y toner image by a developing device 305Y using Y toner. Then, the intermediate transfer belt 201 of the intermediate transfer unit 200
(See FIG. 8). On the other hand, the drum cleaning device 302Y removes the toner remaining on the photosensitive drum 301Y after the transfer of the Y toner image. Further, the static eliminator 303Y is the photosensitive drum 301 after cleaning.
The residual charge of Y is eliminated. By this charge elimination, the surface of the photoconductor drum 301Y is initialized and prepared for the next image formation. In the other photoconductor units 300M, 300C, and 300K, M, C, and K toner images are similarly formed on the photoconductor drums, and are intermediately transferred onto the intermediate transfer belt 201.
The exposure device 7 is configured to individually expose the four photosensitive drums.

The intermediate transfer unit 200 includes an endless intermediate transfer belt 201 as an image carrier, a driving roller 202 for tensioning the intermediate transfer belt 201, a driven roller 203, and the like. Further, four photoconductor units 300Y, M,
Intermediate transfer roller 205 individually facing C and K
Y, M, C, K and backing rollers 206Y, M, C, K
Also equipped. The intermediate transfer roller and the backing roller are in contact with the corresponding photosensitive drum of the photosensitive unit via the intermediate transfer belt 201 to form an intermediate transfer nip. Thereby, the intermediate transfer unit 2
00, and each photoreceptor unit, Y, M, C, K
An intermediate transfer nip is formed. In each intermediate transfer nip, an intermediate transfer roller to which an intermediate transfer bias is applied from a power supply (not shown) is in contact with the belt back surface to form an intermediate transfer electric field. The intermediate transfer belt 201 is driven by a driving roller 20 (not shown).
2, the endless movement is performed clockwise in the figure. Then, in each of the intermediate transfer nips, the Y, M, C, and K toner images are sequentially superimposed and intermediately transferred. By the intermediate transfer of the superposition, a four-color superimposed toner image is formed on the intermediate transfer belt 201. In addition, the intermediate transfer belt 201 forms a secondary transfer nip by bringing a portion stretched around the drive roller 202 into contact with the paper transport belt 10 of the belt unit 20. The four-color superimposed toner image on the intermediate transfer belt 201 is collectively transferred onto the transfer paper P or the paper transport belt 10 at the secondary transfer nip.
Next is transferred. The registration roller pair 28 is used to transfer paper P
At the timing when the toner can be superimposed on the four-color superimposed toner image in the secondary transfer nip. However, when the four-color superimposed toner image is the first toner image transferred to the back surface of the transfer paper P, the transfer paper P is not sent out. Therefore, while the first toner image is secondarily transferred onto the paper transport belt 10 at the secondary transfer nip, the second toner image is secondarily transferred onto the transfer paper P.

At the top of the printer body, there are Y, M, C, K
Toner containers 400Y, 400M, 4 for storing toner
00C and 400K are provided, from which toner is supplied to the corresponding developing devices.

In the printer 100A having the above configuration, a full-color image can be formed on both sides of the transfer sheet P. Although the example in which the Y, M, C, and K toner images are formed by the four photoconductor units 300Y, M, C, and K has been described, a single photoconductor unit may be used. Specifically, four developing devices for Y, M, C, and K toner images are arranged at positions facing the photosensitive drums, and Y, M, C, and C, which are individually formed on one photosensitive drum, respectively. The electrostatic latent images for K are sequentially developed by corresponding developing devices. Then, the obtained Y, M, C, and K toner images are sequentially and intermediately transferred onto the intermediate transfer belt 201. However, in this case, it is necessary to rotate the intermediate transfer belt 204 at least four times to obtain a four-color superimposed toner image on the belt. In such a configuration, 1, 2, 3
The intermediate transfer belt 20 is moved until a four-color superimposed toner image is obtained so that the color superimposed toner image is not transferred secondarily.
1 and the paper transport belt 10 must be kept apart.

Also in the printer 100A of this modification,
Similarly to the printer 100 of the first embodiment, an image is formed on both sides of the transfer sheet P without switching back the transfer sheet P. Therefore, it is possible to solve problems such as an increase in cost, occurrence of a jam, and inhibition of an increase in image forming speed due to the switchback. Further, similarly to the printer of the first embodiment, a heat-resistant paper transport belt 10 as a recording material holding member is used, and the distance S is set at 60 mm.
[Mm] is set. Therefore, even if the heat fixing device 30 is not provided with a guide member, the transfer paper P
From 0, the heating roller 31 and the pressure roller 32 which are conveying members
Can be handed over. Thus, the disturbance of the first toner image on the first surface side due to the rubbing between the guide member and the transfer paper P can be eliminated.

FIG. 10 is a schematic configuration diagram showing a printer of another modified example. This printer 100B also has an intermediate transfer unit 200 and four photoconductor units 300Y, M, C,
K, etc., so that a full-color image can be formed on both sides of the transfer paper P. The difference between the printer 100B and the printer of the above-described modified example is the transfer direction of the transfer paper P by the belt unit 20. In the printer 100A of the above modified example, the belt unit 20 is arranged in a posture for transporting the transfer paper P in a substantially vertical direction. On the other hand, in the printer 100B of this modified example, the belt unit 20 is disposed in a posture for transporting the transfer paper P in a substantially horizontal direction. By causing the belt unit 20 to take such an attitude, space saving in the apparatus main body is achieved. Thus, a space for disposing another sheet cassette 41 in addition to the sheet cassette 26 is created. Further, by causing the belt unit 20 to assume the above-described posture, the transfer paper receiving position of the paper transport belt 10 is positioned near the side surface of the apparatus main body.
Thus, the sheet can be fed also from the manual feed tray 43 which can be opened and closed on the side of the apparatus main body. In addition to the change in the attitude of the belt unit 20, the attitude of the heating and fixing device 30 also causes the transfer paper P to be transported in a substantially horizontal direction. Then, the transfer paper P discharged from the heat fixing device 30 is sent out to the discharge path 33 via a newly provided conveying roller pair 45, a guide member, and a conveying roller pair 46. The guide member changes the transport direction of the transfer paper P passing through the transport roller pair 45 from a substantially horizontal direction to a substantially vertical direction. The transfer paper P passing through the guide member is directed toward the next transport roller pair 46. Conveyed in a substantially vertical direction. Then, the transport roller pair 4
When the sheet 6 rotates forward, the sheet 6 is stacked on the stack section 40 on the upper surface of the main body via the sheet discharge roller pair 34. However, when the conveying roller pair 46 changes the rotation direction from normal rotation to reverse rotation at a predetermined timing, the rear end of the transfer paper P is guided toward the lower left discharge roller pair 47 in the figure by the guide member. . Then, the sheet is discharged onto the stack tray 48.

In the present printer 100B, similarly to the printers 100 and 100A, an image is formed on both sides of the transfer sheet P without switching back the transfer sheet P. Therefore, it is possible to solve problems such as an increase in cost, occurrence of a jam, and inhibition of an increase in image forming speed due to the switchback. The distance S is set to 60 [mm] using a heat-resistant paper transport belt 10. Therefore, the transfer paper P can be delivered from the paper transport belt 10 to the heating roller 31 and the pressure roller 32 as transport members, without providing the guide member in the heat fixing device 30. Thus, the disturbance of the first toner image on the first surface side due to the rubbing between the guide member and the transfer paper P can be eliminated.

Next, a printer according to a second embodiment will be described as an embodiment of an image forming apparatus to which the present invention is applied. Note that the basic configuration of the printer according to the second embodiment is the same as that of the printer according to the first embodiment, and a description thereof will be omitted.

FIG. 11 shows the belt unit 2 of the printer.
FIG. 2 is an enlarged configuration diagram illustrating a part of the heating fixing device 30 and a heating fixing device 30. In the figure, the stretching roller 11, the heating roller 31, and the pressing roller 32 have the same configuration as the printer of the first embodiment.
Each having a diameter of 20 [mm], 30 [mm], and 30 [mm] is used.

As the paper transport belt 10 of the belt unit 20, a heat-resistant belt similar to the printer of the first embodiment is used.

In the casing of the heat fixing device 30, the leading end portion of the transfer paper P sent from the paper transport belt 10 is guided toward a fixing nip formed by the heating roller 31 and the pressure roller 32. Guides 30a, 30 for
b is provided. Of these two guide portions 30a and 30b serving as guide members, 30a rubs and disturbs a second toner image (not shown) transferred to the second surface (the right surface in the drawing) of the transfer paper P. There is a risk of doing it.

However, as described above, a heat-resistant paper transport belt 10 is used, and therefore, it is necessary to dispose the paper transport belt 10 closer to the heat fixing device 30 than in the related art. Can be. Therefore, 2
Even if the guide portions 30a and 30b are smaller in size than a conventional guide portion and a guide plate provided separately from the heat fixing device 30, the leading end portion of the transfer paper P can be moved to the transfer nip. Can guide enough. Therefore, the disturbance of the first toner image and the second toner image due to sliding friction with the guide portion and the guide plate can be suppressed as compared with the related art. In the printer of the second embodiment, the distance S is 1
The paper transport belt 10 is disposed close to the heat fixing device 30 so that the distance is about 30 [mm].

The scope of application of the present invention is not limited to the printers described in the embodiments and the modifications, and various modifications are possible. For example, instead of rotating the paper transport belt 10 on which the first toner image has been transferred once and re-transporting it to the transfer nip, the paper transport belt 10 may be reversed and re-transported to the transfer nip. However, in the case of such a configuration, it is desirable to provide a contact / separation mechanism for contacting / separating the photosensitive drum 1 (image carrier) and the paper transport belt 10 (recording member holding member). Also, for example, the image carrier is not a drum type like the photoconductor drum 1,
A belt type such as a photoreceptor belt may be used.
Further, for example, instead of a belt-type recording material holding member such as the paper transport belt 10, a roller-type recording material such as a paper transport roller may be used. Further, for example, as the latent image forming unit which is a part of the image forming unit, an exposing unit using LED light may be used instead of the laser type exposing device 7. Further, for example, the present invention is applicable not only to a digital printer as described in each embodiment but also to an analog image forming apparatus using analog exposure. Of course, it goes without saying that the image forming apparatus is not limited to a printer, but may be a copying machine or a facsimile.

As described above, in the printer according to the first embodiment or each of the modifications, by using a heat-resistant paper transport belt 10 as the recording material holding member, the paper transport belt 10 can be attached to the heat fixing device 30 as compared with the related art. They are arranged close to each other. As a result, the transfer paper P is transferred toward the heating roller 31 and the pressure roller 32 which are conveying members in the heat fixing device 30.
Paper transport belt 1 without a guide member for guiding
From 0, paper transfer to the heat fixing device 30 is enabled. Therefore, disturbance of the image due to rubbing between the transfer sheet P holding the unfixed toner image and the guide member can be suppressed, and a high-quality image can be formed. Further, in the printer of the second embodiment, the belt unit 20 as a double-sided transfer device is disposed closer to the heat fixing device 30 than in the related art.
More specifically, the transfer paper P, which is gradually peeled off from the endlessly moving paper transport belt 10 and moves toward the heat fixing device 30, is brought close to the heat fixing device 30 without being supported by the guide member. And by this,
The guide member of the heat fixing device 30 is omitted, and a high-quality image in which disturbance of the image due to the rubbing between the guide member and the transfer sheet P is eliminated can be formed. Further, in the printer of each embodiment or the modified example, a heat-resistant one is used as the paper transport belt 10 as the recording material holding member. For this reason,
Even if the belt unit 20 and the heat fixing device 30 are arranged close to each other, it is possible to suppress the damage of the paper transport belt 10 due to the influence of heat from the heat fixing device 30. Further, in the printer of the first embodiment, the transfer of the toner image on the drum is performed while the transfer paper P is sandwiched in the transfer nip formed by the contact between the photosensitive drum 1 serving as an image carrier and the paper transport belt 10. The contact transfer method is performed. Therefore, the toner image is transferred from the drum to the transfer paper P
Unlike the non-contact transfer method in which the toner image flies toward the paper transport belt 10, transfer deviation due to a deviation in the flight path of the toner image can be avoided. Further, this printer employs an endless belt system. For this reason, the heat fixing device 3
Even if a complicated moving mechanism for reciprocating the recording material holding member between the photosensitive drum 1 and the photosensitive drum 1 is not provided, transfer of the transfer paper from the transfer nip to the heat fixing device 30 is periodically performed. be able to. In addition, as the heat-resistant paper transport belt 10, a belt based on a lower layer 10b made of polyimide or polyamide, which exhibits excellent heat resistance despite being an elastic body, is used. For this reason, it is possible to form a wide transfer nip in which the paper transport belt 10 exerts elasticity as a whole and the belt is flexibly deformed along the peripheral surface shape of the photosensitive drum. Further, a cooling means 18 is provided for cooling the portion of the paper transport belt 10 after the transfer paper P is sent out to the heat fixing device 30 and before entering the transfer nip. In such a configuration,
The belt portion heated when passing near the heating and fixing device 30 with the endless movement is cooled by the cooling means 18 and then sent to the transfer nip. Therefore, thermal damage to the drum caused by bringing the belt portion before sufficiently cooled into contact with the photosensitive drum 1 at the transfer nip can be suppressed. When a heat pipe is used as the cooling means 18, the paper transport belt 10 can be uniformly cooled in its width direction. Therefore, the paper transport belt 10
It is possible to suppress the deterioration of the transferability at the transfer nip caused by the cooling unevenness in the width direction. Further, a belt cleaning unit 50 as cleaning means is provided. This is because, after the transfer paper P is sent out toward the heat fixing device 30, the paper conveyance belt 1 before moving to the transfer nip is transferred.
The cleaning is performed before the residual toner remaining on the surface 0 is naturally radiated to a temperature lower than the glass transition point. Therefore,
It is possible to suppress image stains caused by transporting residual toner remaining on the paper transport belt 10 to the transfer nip. Further, even if the residual toner remaining on the surface of the paper transport belt 10 is heated to a temperature equal to or higher than the glass transition point near the heat fixing device 30 and melted, the toner can be cleaned before being solidified. Therefore, it is possible to eliminate a belt cleaning defect caused by fixing the residual toner melted by the influence of the heat fixing device 30 to the belt surface. As the belt cleaning unit 50, a unit having a cleaning roller 51 having a surface roughness equal to or higher than that of the paper transport belt 10 is used. Therefore, it is possible to cleanly transfer the residual toner from the surface of the paper transport belt 10 to the surface of the cleaning roller 51 satisfactorily. The cleaning roller 51 has a JIS-A surface roughness of 3.5 [μ].
m] or more. Therefore, the paper transport belt 1
While satisfying the general surface design condition of 0, good cleaning of the belt surface can be realized. The heat-resistant paper transport belt 10 has a multilayer structure having a surface layer 10a and a lower layer 10b.
A material made of a fluororesin exhibiting better releasability from the toner than the lower layer 10b is used. And
Thus, the surface layer 10a functions as a toner release layer for the lower layer 10b. Therefore, the lower layer 10
The amount of toner remaining on the paper transport belt 10 after being separated from the transfer paper P can be reduced and the transfer rate can be improved as compared with the case where the paper transport belt 10 composed of only b is used. Further, a contact / separation unit for bringing the belt cleaning unit 50 as a cleaning unit into and out of contact with the paper transport belt 10 is provided. In such a configuration, when cleaning is unnecessary, the belt cleaning unit 50 is separated from the belt, so that the load on the unit and the belt can be reduced without losing the cleaning performance. After the first toner image is transferred from the photosensitive drum 1 to the paper transport belt 10 at the transfer nip, the first toner image is sent again to the transfer nip by endless movement of the belt. Then, the second photoconductive drum 1
The second toner image is transferred onto the transfer paper P while the toner image, the transfer paper P and the first toner image are superimposed. Further, a charge is applied to the subsequent paper transport belt 10 by a transfer charger 17 as a charge applying unit. In such a configuration, by applying a reverse charge to the transfer paper P from the second toner image side by the transfer charger 17 in a non-contact manner, the reverse transfer of the second toner image is avoided,
The first toner image can be electrostatically transferred from the belt surface to the transfer paper P side. Therefore, it is possible to electrostatically transfer the toner to both surfaces of the transfer paper P while avoiding deterioration of the maintenance performance due to the use of two types of toners having different charging polarities. Further, by using a heat-resistant and heat-resistant endless belt as the paper transport belt 10, a wide transfer nip is formed in which the belt is brought into contact with the surface of the photosensitive drum 1 so as to be partially wound. In such a transfer nip, the nip in the paper transport direction is made longer than when the transfer nip is formed only by elastic deformation of the surface portion of the recording material holding member, such as when an elastic roller is used as the recording material holding member. Can be. Therefore, the transfer time can be secured for a longer time to perform reliable transfer. Further, by disposing the paper transport belt 10 below the heat fixing device 30 in the vertical direction, heat conduction from the heat fixing device 30 to the belt due to heat radiation can be suppressed. Further, since the distance S is set to be equal to or less than 60 [mm], even if the heat fixing device 30 is not provided with a guide member, the distance S is 45K.
Transfer paper P from the paper transport belt 10 to the heating roller 31 and the pressure roller 32 can be reliably transferred. Further, a control device E2 having a function as a control means and a function as a receiving means for receiving a control signal from a computer is provided. Therefore, it is possible to form an image or change image forming conditions based on a control signal from a computer.

[0068]

According to the first to nineteenth aspects of the invention, there is an excellent effect that disturbance of an image due to sliding friction between the guide member and the recording medium can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printer according to a first embodiment.

FIG. 2 is a perspective view showing the printer together with a personal computer that sends control signals such as image information signals to the printer.

FIG. 3 is an enlarged configuration diagram showing a part of a belt unit of the printer and a heat fixing device.

FIG. 4 is a perspective view showing a heat pipe as an example of a cooling unit of the belt unit together with a paper transport belt.

FIGS. 5A and 5B are schematic diagrams for explaining a contact / separation mechanism of a belt cleaning unit of the printer. FIGS.

FIG. 6 is a sectional view showing a part of the paper transport belt.

FIG. 7 is a configuration diagram for explaining a belt unit of a lateral conveyance system.

FIG. 8 is a schematic configuration diagram illustrating a printer according to a modified example.

FIG. 9 is a configuration diagram illustrating a photoconductor unit for Y of the printer.

FIG. 10 is a schematic configuration diagram showing a printer according to another modification.

FIG. 11 is an enlarged configuration diagram illustrating a part of a belt unit of a printer according to a second embodiment and a heat fixing device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor belt (image carrier) 2 drum cleaning device 3 static elimination device 4 charging device 5 developing device 6 process cartridge 7 exposure device 10 paper transport belt (recording material holding member) 10a surface layer 10b lower layer 11 to 14 stretching roller 15 Transfer roller 16 Backing roller 17 Transfer charger (charge applying means) 18 Cooling means 18a Heat pipe 18b Pipe 18c Fin 26 Paper feed cassette 27 Paper feed roller 28 Registration roller pair 30 Heat fixing device 30a, 30b Guide part (guide member) 31 Heating roller 32 Pressure roller 33 Discharge path 34 Discharge device 40 Stack unit 50 Belt cleaning unit (cleaning means) 51 Cleaning roller 52 Scraping blade 53 Conveying screw 100 Printer (image forming apparatus) 200 Personal computer Null computer E1 Electrical unit E2 Control unit (receiving means) F1 Fan P Transfer paper (recorded body)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/00 518 G03G 15/00 518 3F049 15/20 102 15/20 102 21/20 21/00 534 F Terms (reference) 2H027 ED03 ED08 ED16 ED24 ED25 ED26 ED27 EE02 JA11 JB20 JC03 2H028 BA06 BA16 BB04 BB06 BD03 2H033 BA09 BB01 BB28 2H072 AA32 AB07 BA03 BA12 CA01 CA02 CA05 JA03 GB12 GA12 GB03 HA04 HA12 HB03 HB12 HB22 HB23 JA02 JA18 JB06 JB15 JB18 JB20 JB23 JB42 JB43 JB45 JB47 JB49 JC03 JC12 JC13 JC15 JC17 JC19 KA12 MA04 MA20 MC03 MC11 MC20 PA15 PA18 3F049 AA03 BA11 DA03 LA03

Claims (19)

[Claims] A visible image on an image carrier of an image forming apparatus is transferred to both sides of a recording body on the recording body holding member while moving a recording body holding member for holding the recording body in a predetermined direction. In a double-sided transfer device for feeding the recording material to a heat fixing device of an image forming apparatus by the recording material holding member, a heat-resistant recording material is used as the recording material holding member. . 2. An image bearing member for holding a visible image, a visible image forming means for forming a visible image on the image bearing member, and a recording member holding member for holding the recording member in a predetermined direction. A two-sided transfer device for transferring the visible image on the image carrier to both sides of the recording material on the recording material holding member, and after receiving the recording material after passing through the two-sided transfer device on a conveying member, 2. An image forming apparatus comprising: a heat fixing device for fixing a visible image on both sides thereof to a recording medium while heating the image on the both sides; 3. An image bearing member for holding a visible image, a visible image forming means for forming a visible image on the image bearing member, and a recording member holding member for holding the recording member in a predetermined direction. A two-sided transfer device for transferring the visible image on the image carrier to both sides of the recording material on the recording material holding member, and after receiving the recording material after passing through the two-sided transfer device on a conveying member, And a fixing device for fixing the visible images on both sides of the recording medium to the recording medium, while gradually peeling off the moving recording medium holding member from the front end side to the rear end side of the recording medium after the double-side transfer. In the process of feeding the recording medium to the fixing device, the recording medium is peeled off from the recording medium holding member and is to move in the direction of gravity without being supported by the guide member. Moving the double-sided transfer device close to the fixing device. Image forming apparatus characterized by only which was disposed. 4. An image forming apparatus according to claim 3, wherein a heat fixing device for fixing a visible image to a recording medium while heating the visible image is provided as said fixing device, and said heat fixing device is used as said recording material holding member. An image forming apparatus using a heat-resistant material capable of withstanding transmitted heat. 5. The image forming apparatus according to claim 2, wherein
The recording medium is sandwiched in a transfer section formed by contact between the image carrier and the heat-resistant recording medium holding member that moves endlessly, and a visible image on the image carrier is transferred to the recording medium. An image forming apparatus comprising the double-sided transfer means. 6. The image forming apparatus according to claim 5, wherein the heat-resistant recording member holding member has a base material made of polyimide or polyamide. 7. The image forming apparatus according to claim 5, wherein
Cooling means for cooling the heat-resistant recording material holding member after sending the recording material toward the heat fixing device and before contacting the image carrier at the transfer portion is provided. Image forming apparatus. 8. An image forming apparatus according to claim 7, wherein a heat pipe is used as said cooling means for cooling said heat-resistant holding member while contacting said member. 9. The image forming apparatus according to claim 5, wherein said recording medium holding member is provided after a recording medium is sent out toward said heat fixing device and before said recording medium is moved to said transfer section. A cleaning unit is provided for removing and cleaning the image forming material remaining on the recording medium without moving to the recording medium, and the image heated to a temperature equal to or higher than the glass transition point by heat from the heat fixing device. An image forming apparatus, wherein the cleaning means is disposed at a position where cleaning can be performed before the material is naturally radiated to a temperature lower than the glass transition point. 10. An image forming apparatus according to claim 9, wherein said cleaning means includes a cleaning roller for bringing a heat-resistant roller surface having a surface roughness equal to or higher than that of said recording material holding member into contact with said recording material holding member. An image forming apparatus comprising: 11. An image forming apparatus according to claim 10, wherein said cleaning roller has a surface roughness of JIS-A of 3.5 [μm] or more. 12. The image forming apparatus according to claim 9, wherein the heat-resistant recording material holding member has a multilayer structure having at least a lower layer and a surface layer coated thereon. An image forming apparatus which exerts an adhesive force to the image forming substance that is lower than the adhesive force between the lower layer and the image forming substance. 13. An image forming apparatus according to claim 12, wherein said heat-resistant recording member holding member has said surface layer made of fluororesin. 14. An image forming apparatus according to claim 9, further comprising contacting / separating means for bringing the cleaning means into and out of contact with the heat-resistant recording material holding member. Image forming device. 15. The image forming apparatus according to claim 14, wherein after the first visible image is transferred from the image carrier to the heat-resistant recording material holding member at the transfer portion, the recording material holding member is endlessly transferred. The first visible image is sent to the transfer section again by the movement, and the second visible image on the image carrier, the recording medium, and the first visible image are superimposed on each other at the transfer section. The image forming apparatus according to claim 1, wherein the double-sided transfer device is configured to transfer a visual image to a recording medium, and to include a charge applying unit that applies a charge to the recording medium holding member in a non-contact manner. apparatus. 16. The method of claim 5, 6, 7, 8, 9, 10, 1.
The image forming apparatus according to any one of 1, 12, 13, 14 and 15, wherein a heat-resistant endless belt is used as the heat-resistant recording member holding member. 17. The method of claim 2, 4, 5, 6, 7, 8, 9, 1.
An image forming apparatus according to any one of claims 0, 11, 12, 13, 14, 15, and 16, wherein the recording material holding member is disposed vertically below the heat fixing device. 18. The method of claim 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16 or 1
In the image forming apparatus according to 7, the transfer device or the double-sided transfer device is arranged so that the distance between the surface of the conveying member and the surface of the recording material holding member at the closest position is 60 mm or less. An image forming apparatus, wherein the image forming apparatus is disposed close to the heat fixing device. 19. The method of claim 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14, 15, 16, 17
Or, in the image forming apparatus of 18, the receiving means for receiving a control signal from a computer, and driving the image carrier, the visible image forming means, the heat fixing device, and the double-sided transfer device based on the result of reception by the receiving means. An image forming apparatus, comprising: control means for controlling.