JP2002072701A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform transfer and fixing at high speed while keeping maximum working power low and to obtain a high-quality image having no irregular gloss in an image forming device of a system in which an unfixed toner image is transferred and fixed on a recording medium simultaneously. SOLUTION: Recording paper is housed in a preliminary heating tray 17 and preliminarily heated before it is fed to a transfer fixing part where a heating roll 10 press-contacts with a pressure roll 12. Thus, when the large quantity of heat is required for transfer and fixing such as when the recording paper having a thermoplastic resin layer on its surface is used, the sufficient quantity of heat is supplied and a toner image is melted and press-fit to be embedded in the resin layer, so that a glossy image is obtained. Power supply to the tray 17 is controlled to be performed when energizing the heating means of a transfer fixing device is in an off-state, and the maximum working electric energy of an entire printing process is restrained to be low.

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 using a dry toner such as an electrophotographic copying machine, a printer, and a facsimile, and more particularly, to a toner image on a recording medium by heating and pressing. Transfer and fix at the same time,
The present invention relates to an image forming apparatus for obtaining a high-quality image without uneven gloss or color.

[0002]

2. Description of the Related Art In an image forming apparatus using a dry toner such as an electrophotographic system or an electrostatic recording system, an electrostatic latent image formed on an image carrier is developed by attaching toner, and then the toner image is developed. Is transferred to a recording medium and fixed by heating and pressing.

As a method of transferring and fixing the toner image, a method of temporarily transferring the toner image to an intermediate transfer member, further transferring the toner image to a recording medium, and then applying heat and pressure to fix the toner image on the recording medium, and a method of transferring and fixing the toner image A method has been considered in which an image is temporarily transferred to an intermediate transfer member, and then the toner image melted by heating is fixed on a recording medium, and transfer and fixing are simultaneously performed. This method is particularly suitable for use in a color image forming apparatus, and can transfer a toner image under a stable condition and obtain a high-quality image by superimposing a plurality of color toner images on an intermediate transfer member. it can.

On the other hand, with the spread of full-color copying machines and printers in recent years, higher quality and higher gloss images are required. From such demands, for example, Japanese Patent Application Laid-Open No. 58-83876 and Japanese Patent Publication No. 2-61749 discloses an apparatus for temporarily transferring a toner image to an intermediate transfer member and further transferring and fixing the toner image to a recording medium. Discloses a method of having a heating plate for heating a recording medium, and inserting the recording medium heated to a temperature higher than the melting temperature of the toner into the transfer fixing device. Japanese Patent Application Laid-Open No. 9-90789 discloses an apparatus in which a recording medium is preheated by a sheet heating element before transfer and fixing.

In such a method, since the recording medium is heated before passing through the transfer / fixing section, the toner image is brought into contact with the recording medium in the transfer / fixing section, and when the recording medium is further heated, the recording medium and the toner image are heated. Is a state in which a sufficient amount of heat is easily held for fixing. Therefore, even when the toner image passes through the transfer and fixing section at high speed in high-speed printing or the like, the toner image is pressed against the recording medium in a sufficiently melted state, and a glossy high-quality image can be obtained. Further, since the recording medium is preheated, it is not necessary to excessively heat the toner image and the intermediate transfer body during transfer and fixing, and it is possible to prevent the toner image and the intermediate transfer body from being deteriorated at high temperatures.

[0006]

However, the above image forming apparatus has the following problems. While the recording medium is passing over heating means such as a heating plate or an on-surface heating element, heat is transmitted from the heating means and preheated,
Heating to a predetermined temperature within the passage time of the recording medium requires a large electric power.

Further, when a recording medium having a thermoplastic resin on its surface is used to obtain a glossy high-quality image,
In order to preheat the thermoplastic resin to such an extent that the thermoplastic resin melts, a larger electric power is required. FIG. 8 shows a state in which a toner image is melt-pressed on a recording medium having a thermoplastic resin on the surface. FIG. 7A shows a state in which the thermoplastic resin is sufficiently supplied with heat and melted, and the toner image is completely embedded in the thermoplastic resin. In this case, since the surface of the recording medium becomes smooth, a glossy image is obtained. on the other hand,
If the heat supply is insufficient, the thermoplastic resin does not melt sufficiently and the toner image is not completely embedded, as shown in FIG. FIG. 9C shows a state in which the thermoplastic resin is hardly melted. Therefore, the recording medium has an uneven surface, and light is scattered as shown in FIG. Would.

In order to obtain such a high quality image,
It is necessary to sufficiently melt the thermoplastic resin layer formed on the surface of the recording medium, and a large amount of electric power is required for preheating. In the image forming apparatus, since the preliminary heating and the transfer and fixing of the toner image onto the recording medium are simultaneously performed during the printing process, a large amount of power is required during the transfer and fixing. Here, the maximum allowable power in the printing process is determined from the rated power of the apparatus, and the total amount of power used in each process cannot exceed this. On the other hand, if the rated power of the device is changed to a large value, a problem occurs such that the user needs a special power supply work, and the commercial value of the general-purpose device is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and needs, and has as its object to reduce the maximum power consumption in an image forming apparatus of a system in which an unfixed toner image is transferred onto a recording medium and simultaneously fixed. The purpose is to perform high-speed transfer and fixing while maintaining the same, and obtain a high-quality image without uneven gloss.

[0010]

According to one aspect of the present invention, there is provided an image carrier on which a latent image is formed on a peripheral surface due to a difference in electrostatic potential, and the image carrier. A developing device that selectively transfers the toner to a toner image to form a toner image;
An endless belt-shaped intermediate transfer member stretched around a plurality of members and driven to rotate; a primary transfer device for transferring a toner image on the image carrier to the intermediate transfer member; a toner image on the intermediate transfer member Means for heating and means for pressurizing,
A transfer and fixing device for transferring and fixing the toner image on a recording medium that is in contact with the intermediate transfer body; and housing the recording medium in a stationary state before contacting the intermediate transfer body, and heating the recording medium. An image forming apparatus comprising: a preheating tray provided with a means for performing the operation.

In the above-described image forming apparatus, the recording medium is accommodated in a preheating tray before coming into contact with the intermediate transfer member, and is heated in a state where the recording medium is allowed to stand still until a predetermined temperature is reached. The recording medium heated to a predetermined temperature is sent out from the preheating tray and is brought into contact with an intermediate transfer member carrying a toner image. Then, the toner image is heated and pressed together with the toner image, and the toner image is melt-pressed on a recording medium. In this manner, the recording medium is heated while being held in the preliminary heating tray, so that the recording medium can be heated to a predetermined temperature without supplying a large amount of electric power instantaneously. Since the recording medium having a large heat capacity is also heated to a predetermined temperature, it is possible to heat both the recording medium and the toner image to a temperature equal to or higher than the toner image melting temperature without supplying a large amount of heat during transfer and fixing. As a result, the amount of power used in the transfer fixing device can be reduced. For this reason, it is possible to supply sufficient heat to the recording medium and the toner image while keeping the maximum power consumption in the printing process low, and the toner image is pressure-bonded to the recording medium in a state where it is sufficiently melted, resulting in uneven gloss. No high quality images can be obtained. In addition, even when high-speed printing is performed, since the recording medium is preheated, the toner image and the recording medium are sufficiently supplied with heat while passing through the transfer / fixing section at a high speed, and the toner image is melted on the recording medium. It is crimped. For this reason,
It is possible to obtain a high-gloss image at high speed while keeping the maximum power consumption low.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the preheating tray has a multilayer structure, and stores a plurality of recording media separately.

In the image forming apparatus, since the preheating tray has a multilayer structure and can store a plurality of recording media separately, it is possible to heat a plurality of recording media simultaneously. In other words, when printing a plurality of sheets, the second and subsequent recording media can be built in the preheating tray and heated while the first recording medium is in the transfer and fixing process. . Therefore, a sufficient heating time can be secured for each recording medium, and the recording medium heated to a predetermined temperature can be continuously sent to the transfer fixing device.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, a power supply for driving the heating unit of the preliminary heating tray is driven, and a unit for heating the toner image of the transfer fixing device is driven. And a current control device for performing the current supply when the current supply is in the OFF state.

When printing a plurality of sheets, the recording medium successively fed into the preheating tray is heated, so that the temperature of the preheating tray itself must be prevented from lowering and a constant temperature must be maintained. For this reason, it is necessary to supply power to the preheating tray to perform temperature compensation of the preheating tray itself. In the above-described image forming apparatus, when the electric power for driving the heating unit of the transfer fixing device is not used, the electric current is controlled so as to conduct electricity for driving the heating unit of the preliminary heating tray. For this reason, the maximum power to be used can be suppressed to a small value, the temperature of the preheating tray itself can be compensated, and the recording medium fed one after another can be heated to a predetermined temperature.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, a necessary power is supplied to a heating unit provided in a member that is in contact with the intermediate transfer body, and a predetermined allowable maximum power is determined. And a current controller for controlling the supplied power so as to supply surplus power to the heating means of the preliminary heating tray.

In the above-described image forming apparatus, since the power supply is controlled so as to supply the surplus electric power necessary for the transfer and fixing device to the heating means of the preliminary heating tray, the electric power is supplied to the heating means of the transfer and fixing device. Even when the preheating tray is supplied, heat is supplied to the preheating tray without exceeding the allowable maximum power, and the temperature of the preheating tray can be compensated. The members that come into contact with the intermediate transfer member include, in addition to the heating means included in the transfer and fixing device, a device for preheating the intermediate transfer member, a cleaning device for melting and removing the toner remaining on the intermediate transfer member, and the like. Including.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, a recording paper having a thermoplastic resin layer on a surface thereof is used as the recording medium, and the recording medium is in contact with the recording medium in the preheating tray. And a current control device for controlling the power supply to the heating means of the preheating tray so that the temperature of the member to be heated is maintained at or below the melting temperature of the thermoplastic resin.

The recording paper heated by the preheating tray to a temperature not higher than the melting temperature of the thermoplastic resin is heated and pressurized together with the toner image in the transfer and fixing section so that the fused toner image is embedded in the molten thermoplastic resin. Fused to form a smooth surface, resulting in a glossy image. Further, since the power supply is controlled such that the temperature of the member heated by contact with the recording paper is maintained at or below the melting temperature of the thermoplastic resin, Does not melt, and the recording paper does not come into contact with a conveying member or the like when the recording paper is carried into the transfer and fixing device, so that a conveyance failure does not occur.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the preliminary heating tray includes a heat storage plate, or a heating unit is a heating element that also serves as a heat storage plate.

In the image forming apparatus, since the preliminary heating tray has a heat storage plate or the heating means is a heating element which also serves as a heat storage plate, when there is excess power, electricity is supplied to the heating means to reach a predetermined temperature. When heated, the heat can be stored and the temperature of the heating tray itself can be prevented from lowering. For this reason,
The temperature of the preheating tray fluctuates gradually, and the temperature can be easily compensated.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. This image forming apparatus includes an endless belt-shaped intermediate transfer body 6 whose peripheral surface is supported so as to be able to rotate.
Four image forming units 1a, 1b, 1c, and 1d for forming magenta, cyan, and black toner images are provided.

Each image forming unit 1a, 1b, 1c, 1
d is a photosensitive drum 2a on the surface of which an electrostatic latent image is formed,
Charging devices 3a, 3b, 3c, and 3d around the respective photoconductor drums, which charge the surfaces of the photoconductor drums substantially uniformly, respectively. An optical scanning device 4 that scans a laser beam to write an electrostatic latent image and transfers a yellow, magenta, cyan, or black toner to each latent image formed on the photosensitive drum to form a toner image Developing devices 5a, 5b, 5
c, 5d, and transfer chargers 7a, 7b, 7c, 7d for primarily transferring the toner image on each photosensitive drum onto the intermediate transfer body 6.
And

Inside the intermediate transfer member 6, support rolls 8a, 8b, 8c and 8d, a peeling roll 9 and a heating roll 10 are provided, and a cleaning roll 11 is pressed against the outer peripheral surface of the intermediate transfer member 6. The intermediate transfer member 6 is stretched around these rolls and driven to rotate in the direction of arrow A shown in the figure. In order to press the recording paper P against the intermediate transfer body 6, a pressing roll 12 that heats and presses the recording paper P is disposed at a position facing the heating roll 10 via the intermediate transfer body 6.

Further, a heating plate 13 is provided on the upstream side of the heating roll 10 in the circumferential direction of the intermediate transfer body 6 along the back side of the intermediate transfer body 6, and is provided on the heating plate 13. The planar heater heats the toner image on the intermediate transfer member 6.

A heat pipe type heat exchanger 14 for cooling the recording paper after the transfer and fixing is provided in the circumference of the intermediate transfer body 6. The heat pipe type heat exchanger 1
The heat receiving portion 4 is in contact with the downstream side of the heating roll 10 in the circumferential direction of the intermediate transfer body 6 and the heat radiating portion is in contact with the upstream side, so that the heat of the heated recording paper is effectively used. Has become.

The apparatus further includes a paper tray 15 for storing the recording paper P, a feed roll 16 for feeding out the recording paper P one by one from the paper tray 15, and a preheating tray for preheating the recording paper P. 17 and a power supply control device 19 for controlling the power supply to the preheating tray 17 and the respective heating means of the transfer and fixing section.

On the downstream side of the peeling portion roll 9 in the circumferential direction of the intermediate transfer body 6, a transport belt 20 is stretched over two rolls, and the recording paper on which the toner image has been transferred and fixed is transferred. The paper is discharged to the paper discharge tray 21.

Hereinafter, each component constituting the present embodiment will be described in more detail. The photoreceptor drums 2a, 2b, 2c, and 2d have Se, aS
Those having various inorganic photoreceptor layers such as i, a-SiC and CdS, or those having various organic photoreceptor layers can be used.

The charging devices 3a, 3b, 3c and 3d are:
A corona discharger comprising a grid and electrode wires,
A high voltage is applied to the electrode wires and a predetermined voltage is applied to the grid to generate corona discharge with each of the photosensitive drums to uniformly charge the surface of each of the photosensitive drums.

The optical scanning device 4 irradiates a laser beam based on an image signal, and scans the laser beam in the main scanning direction of each photosensitive drum by a polygon mirror.
Thus, an electrostatic latent image is formed on the surface of each photosensitive drum.

The developing devices 5a, 5b, 5c and 5d are:
Developing units containing yellow, magenta, cyan, and black toners sequentially approach and oppose each photosensitive drum, and transfer the toner to the latent image corresponding to each color to form a visible image. Is formed.

The belt-shaped intermediate transfer member 6 has a base layer and a surface layer, and the base layer is made of a heat-resistant polyimide film to which carbon black is added. When the toner image is transferred from the intermediate transfer body 5 to the recording paper P, the surface layer has a rubber hardness of 40 degrees and a thickness of 40 degrees so that the intermediate transfer body 5 and the recording paper P are in good contact with the toner image. A 50 μm silicone copolymer is used.

The above-described transfer charging information 7a, 7b, 7c, 7d
Is a corona discharger that applies a charge to the back surface of the intermediate transfer member 6 so that the toner image on each photosensitive drum is efficiently transferred to the intermediate transfer member 6.

The heating roll 10 has a heating source such as a halogen lamp inside a cylindrical metal core made of metal having a high thermal conductivity. To heat the toner image and the recording paper P carried on the intermediate transfer member 6 via the intermediate transfer member 6. Further, in order to enhance the adhesion between the heating roll 10 and the intermediate transfer member 6, a rubber-like elastic layer is provided on the peripheral surface of the heating roll 10.

The pressing roll 12 is used for the intermediate transfer member 6.
Is pressed against the heating roll 10 with a load of 7.2 kg / cm ² to press the recording paper P and the toner image, and has a heating source similarly to the heating roll 10. The toner image and the recording paper P carried on the intermediate transfer member 6 are heated from the back surface of the recording paper P by heating to 95 ° C. lower than the melting temperature of the toner. Further, similarly to the heating roll 10, a rubber-like elastic layer is provided on the roll surface.

As the heating plate 13, a silicon rubber heater is used as an on-surface heater on the back of an aluminum contact plate, and the contact plate is heated to 185 ° C., which is higher than the melting temperature of the toner. . The silicone rubber heater is one in which the energizing heating element is covered with silicone rubber. The thickness of the silicone rubber is made as small as possible, so that the thermal resistance from the energizing heating element to the contact plate is reduced and heating is performed efficiently.

The heat pipe type heat exchanger 14 comprises a plurality of metal receiving members arranged in parallel so as to contact a high-temperature member, and a heat-dissipating unit arranged in parallel so as to contact a low-temperature member. And a plurality of heat pipes which are fixed to the respective metal members of the heat receiving section and the heat radiating section and which are closed in a ring shape. The surface temperature of P is set to be 70 ° C. or less. Aluminum or copper or an alloy containing them having good thermal conductivity can be used for the heat receiving portion and the heat radiating portion, and a tube made of copper or an alloy containing these can be used for the heat pipe.

As shown in FIG. 2, the preheating tray 17 is located in the vicinity of the upstream side of the transfer / fixing section, and its outer periphery is covered with a heat insulating member 22 so that the temperature of the recording paper P decreases until it is conveyed to the transfer / fixing section. Further, the temperature in the preliminary heating tray 17 is reduced. The inside is divided into several layers to form a multilayer structure. Each tray has a heater 23 for heating the recording paper P on the upper or lower surface, and each tray has a recording paper fed from a paper tray. A tray selection pawl 24 for distributing P to each tray, and a delivery star roll 25 for moving the recording paper P within the tray
And a feed chute 26 for feeding the recording paper P to the transfer fixing unit.

The heat insulating member 22 is made of a foamed ceramic having a large heat capacity or a foamed polyurethane disposed between foamed ceramics. A foamed resin having relatively low heat resistance is used except for the contact surface with the heater 23. I can do it.

The heater 23 has a rubber heater sandwiched between two aluminum plates. In addition, a thick aluminum plate is arranged on the surface separating the trays where the heater is not arranged, in consideration of heat storage.

The power supply control device 19 includes an operation control device 31 and two power monitoring monitors 32 as shown in FIG.
a, 32b and two current control devices 33a, 33b constitute a main part, and a storage unit of the operation control device 31 stores a power supply LUT (reference table).

The current control device 33a adjusts the current supplied to the heating means of the heating roll 10, the pressing roll 12, the heating plate 13, and the cleaning roll 11 based on a signal from the operation control device 31. . The current controller 33b also adjusts the current supplied to the three heat storage heaters 23a, 23b, and 23c of the preliminary heating tray 17 based on a signal from the operation controller 31. The power monitoring monitors 32a and 32b
Detects the power supplied to each heating means via the current control devices 33a and 33b and outputs a detection value to the operation control device. The operation control device 31 includes:
In addition to referring to the detection values of the power monitoring monitors 32a and 32b, a current value to be supplied to each heating unit is determined based on the power supply LUT, and a control signal is output to the current control devices 33a and 33b. . At this time, it is necessary to heat the heating roll 10, the pressing roll 12, the heating plate 13, and the cleaning roll 11 in synchronization with the passage of the toner image on the intermediate transfer member, and supply the current with priority to these. At the same time, control is performed so that the maximum power consumption does not exceed the allowable value. And the preliminary heating tray 17
Is set to supply a current to the heat storage heater 23 using surplus power with respect to an allowable value, whereby the temperature in the preheating tray 17 is maintained substantially constant.

As shown in FIG. 4, the recording paper P used in the above-mentioned image forming apparatus is coated paper for printing, art paper,
A medium having a smooth surface such as cas-coated paper
And the surface thereof is provided with a transparent resin layer 42 made of a thermoplastic polyester resin. Also,
As shown in FIG. 5, a base material 51 such as coated paper, art paper, etc.
Recording paper may be used in which a polyethylene resin layer 52 is provided on the front and back surfaces of the above, and an image receiving layer 53 made of a transparent thermoplastic resin is provided thereon.

The toner used in the above-mentioned image forming apparatus is made of a thermoplastic binder containing yellow, magenta, cyan and black dyes, and can be formed by a known material. In this embodiment, a polyester negatively charged toner is used.

Next, the operation of the image forming apparatus will be described. In each of the image forming units 1a, 1b, 1c and 1d arranged around the belt-like intermediate transfer body 6, the photosensitive drums 2a, 2b, 2c and 2d
a, 3b, 3c, and 3d cause the charging to be substantially uniform. Thereafter, exposure is performed by the optical scanning device 4 which is turned on / off in response to an image signal, and an electrostatic latent image is formed.

The electrostatic latent images on the photosensitive drums 2a, 2b, 2c, and 2d are developed by developing devices 5a, 5b, 5c, and 5 containing black, yellow, magenta, and cyan toners, respectively.
d, and a so-called digital image expressing density by area modulation is formed on each of the photosensitive drums 2a, 2b, 2
c and 2d are formed as toner images. The color toner images are sequentially transferred onto the intermediate transfer member 6 by the transfer chargers 7a, 7b, 7c, and 7d so as to be superimposed on each other, and a full-color toner image is formed on the intermediate transfer member 6. The toner image formed on the intermediate transfer member 6 is such that the intermediate transfer member 6
When passing through the position facing 3, it is heated and melted.

On the other hand, the recording paper P is taken out one by one from the paper tray 15 by the feed roll 16, and the recording paper P is carried into the preheating tray 17 and heated to a predetermined temperature. The sheet is conveyed to the transfer fixing unit. With the conveyance of the recording paper P, the pressing roll 12 facing the intermediate transfer body 6 is pressed against the heating roll 10. Thereafter, the intermediate transfer member 6 holding the toner images of the plurality of colors and the recording paper P are superimposed, passed through a nip portion between a heating roll 10 and a pressing roll 12, and heated and pressed. At this time, since the recording paper P is preheated, the surface resin layer of the recording paper P is sufficiently softened and melted by being brought into contact with the toner heated above the melting temperature and further heated. Then, the fused toner image is fused so as to be embedded in the surface resin layer of the recording paper P.

The toner image is formed on the intermediate transfer member 6 and the recording paper P
Are conveyed in a state where they are in close contact with each other, and when cooled to a melting temperature or lower, they are coagulated and solidified to generate a strong adhesive force with the recording paper P. As a result, when the intermediate transfer body 6 is bent around with a large curvature at the position where the separation roll 9 having a small radius of curvature is disposed, the recording paper P is separated from the intermediate transfer body 6 together with the toner by its own rigidity. Thus, a fixed image is formed on the recording paper P without causing an offset. In addition, the recording paper P has a smooth surface because it coagulates and solidifies according to the surface shape of the intermediate transfer member.
The result is a glossy image.

Next, the operation of the preheating tray 17 will be described with reference to FIG. FIG. 6 shows an example of a timing chart when the recording paper is carried in, heated and carried out to the preheating tray 17 having four trays. First, before the printing process, up to the fourth sheet of recording paper is sequentially conveyed from the paper tray 15 by the feed roll 16, guided to the sorting pawl 24 provided at the entrance of the preheating tray 17, and carried into each tray. . The inside of the preliminary heating tray 17 is heated to such an extent that the temperature of the recording paper does not reach the melting temperature of the thermoplastic resin, and the recording paper contained in each tray is heated and heated. And
When the first recording paper reaches a predetermined temperature, the delivery star roll 25 is driven to rotate, and the first recording paper is conveyed to the feeding chute 26 and carried into the transfer fixing unit.
Then, after the recording paper has passed through the transfer fixing unit, the second recording paper that has already reached the predetermined temperature is carried into the transfer fixing unit. At the same time as the first sheet of recording paper is carried out, 5 sheets are immediately stored in the tray containing the first sheet of recording paper.
The fourth sheet of recording paper is carried in, and is heated until the fourth sheet of recording paper passes through the transfer fixing unit. In addition, A4 recording paper
When the sheet is conveyed horizontally at a process speed of 80 mm / s, the heating time for the fifth and subsequent sheets is 9.75 sec.

By repeating the above operation, a plurality of recording papers are always stored in the preheating tray 17, and a sufficient heating time is secured before the recording papers are conveyed to the transfer fixing unit. Therefore, the recording paper heated to a predetermined temperature can be continuously conveyed to the transfer fixing unit. At this time, the temperature of the recording paper is equal to or lower than the melting temperature of the thermoplastic resin on the surface, so that the thermoplastic resin does not melt to cause conveyance failure. Further, the recording paper may be damaged by the star roll 25 when the recording paper is conveyed in the preheating tray 17, but when heated in the transfer fixing section, the surface resin layer melts and becomes a smooth surface. , It does not become a defect of the product.

The power supply to the preheating tray 17 is as follows.
The power supply control unit 19 controls the power supply together with the power supply to the other heating means for performing the transfer and the fixing. The ON / OFF control is performed at a timing as shown in FIG. 7, for example. At the start of the operation of the image forming apparatus, the preliminary heating tray 17, the heating roll 10, the pressing roll 12, the heating plate 13
Preheating for raising the cleaning roll 11 to a predetermined temperature is performed. However, since the total amount of used power in these configurations is larger than the maximum allowable power, power cannot be supplied at the same time, and the power usage is controlled to be equal to or less than the maximum allowable power. That is, in this example, first, power is supplied to the heating roll 10, the pressing roll 12, and the heating plate 13 (process heating time), and after reaching a predetermined temperature, these are turned off and supplied to the preheating tray 17 (preheating). Tray heating time). At this time, the total power consumption of the heating roll 10 and the pressing roll 12 is 200 W, and the power consumption of the heating plate 13 and the cleaning roll 11 is also 200 W. Since the power consumption of the preheating tray 17 is 600 W, the total power consumption is the allowable maximum power 6.
It is maintained within 00W.

Heat storage heater 2 in preheating tray 17
When the temperature of the heating roller 3 reaches a predetermined value, the power is also intermittently supplied to the heating roll 10, the pressing roll 12, and the heating plate 13, and the power to the preheating tray 17 is turned off when power is supplied to any of them. While keeping the state, all are controlled so as to reach a predetermined temperature. Then, when the toner image is carried and conveyed on the intermediate transfer member, power is preferentially supplied to the heating roll 10, the pressing roll 12, and the heating plate 13, and these members are maintained at necessary temperatures.

When the temperature of the heating roll 10 rises, the power supply is turned off intermittently so that the temperature is controlled to be substantially constant.
At a timing when neither the heating plate 13 nor the cleaning roll 11 is supplied with power, power is supplied to the heat storage heater 23 of the preheating tray 17, and the temperature in the preheating tray 17 is maintained substantially constant. The preliminary heating tray 17 has three heat storage heaters 23, and in the above example, is controlled so as to supply power to them all at once. However, power can be supplied to each of them independently. In this case, even if power is supplied to other parts such as the heating roll 10, power can be supplied to one or two of the heat storage heaters 23, and the temperature of the preliminary heating tray 17 is more reliably maintained at a predetermined value. It becomes possible.

[0055]

As described above, in the image forming apparatus of the present invention, the sum of the amount of power supplied to the heater of the preheating tray and the amount of power supplied to the other heating means of the transfer fixing device is determined by the transfer fixing. Since the maximum amount of power that can be used by the apparatus is not exceeded, the temperature in the preheating tray can be kept almost constant without exceeding the maximum amount of power that can be used in the entire printing process, and the recording medium can be maintained at a predetermined level. Can be preheated to temperature.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing a preheating tray used in the image forming apparatus shown in FIG.

FIG. 3 is a block diagram of a power control device used in the image forming apparatus shown in FIG.

FIG. 4 is an enlarged sectional view of a recording sheet that can be used in the image forming apparatus shown in FIG.

FIG. 5 is an enlarged sectional view showing another example of the recording paper that can be used in the image forming apparatus shown in FIG.

FIG. 6 is a timing chart when a recording sheet is carried in, heated, and carried out to the preliminary heating tray shown in FIG. 2;

FIG. 7 is a diagram illustrating a timing of supplying power to each unit in the image forming apparatus illustrated in FIG. 1;

FIG. 8 is an explanatory diagram of a state in which a toner image is embedded in recording paper having a thermoplastic resin layer on the surface.

FIG. 9 is a schematic view showing a state of light scattering when a toner image is transferred to recording paper having a thermoplastic resin layer.

[Explanation of symbols]

1a, 1b, 1c, 1d Image forming unit 2a, 2b, 2c, 2d Photoconductor drum 3a, 3b, 3c, 3d Charging device 4 Optical scanning device 5a, 5b, 5c, 5d Developing device 6 Intermediate transfer member 7a, 7b, 7c, 7d Transfer charger 8a, 8b, 8c, 8d Support roll 9 Stripping roll 10 Heating roll 11 Cleaning roll 12 Pressing roll 13 Heating plate 14 Heat pipe type heat exchanger 15 Paper tray 16 Feed roll 17 Preheating tray 19 Electric power Supply control device 20 Conveyor belt 21 Discharge tray 22 Insulation member 23 Heat storage heater 24 Tray sorting pawl 25 Feeding out star roll 26 Feeding chute

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichiro Shinohara 430 Sakai Nakagami-cho, Ashigara-gun, Kanagawa Green Tech Nakai Fuji Xerox Co., Ltd. F-term (Reference) 2H027 DA11 DA34 EA11 EA16 ED16 ED24 ED25 EE01 EE05 EE10 ZA01 2H032 AA02 BA09 BA09 BA23 CA04 CA12 2H033 AA01 AA20 BA08 BA24 BA27 BA59 BB01 BB18 BB28 BE09 CA07 CA09 CA23 CA27 CA37 CA44 2H078 AA01 AA12 BB01 CC06 DD52 DD57 DD61 DD73

Claims (6)

[Claims] An image carrier on which a latent image is formed on a peripheral surface due to a difference in electrostatic potential; a developing device for selectively transferring toner to the image carrier to form a toner image; An endless belt-shaped intermediate transfer member stretched around a member and driven to rotate, a primary transfer device for transferring the toner image on the image carrier to the intermediate transfer member, and heating the toner image on the intermediate transfer member A fixing device for transferring and fixing the toner image to a recording medium in contact with the intermediate transfer member, the transfer and fixing device comprising: a recording medium that is stationary before the recording medium is in contact with the intermediate transfer member. And a preheating tray provided with means for heating the recording medium. 2. The image forming apparatus according to claim 1, wherein the preheating tray has a multilayer structure, and stores a plurality of recording media separately. 3. A current control device for energizing the heating means of the preheating tray when the energization for driving the toner image heating means of the transfer fixing device is OFF. The image forming apparatus according to claim 1, wherein: 4. A heating means provided in a member abutting on the intermediate transfer body, so that necessary power is supplied to the heating means of the preliminary heating tray, and surplus power with respect to a predetermined allowable maximum power is supplied to the heating means. The image forming apparatus according to claim 1, further comprising a current control device that controls supplied power. 5. A recording paper having a thermoplastic resin layer on its surface as the recording medium, wherein a temperature of a member in contact with the recording medium in the preheating tray is maintained at a temperature not higher than a melting temperature of the thermoplastic resin. The image forming apparatus according to claim 1, further comprising a current control device for controlling power supply to the heating unit of the preliminary heating tray. 6. The image forming apparatus according to claim 1, wherein the preliminary heating tray includes a heat storage plate, or the heating unit is a heating element that also serves as a heat storage plate.