JP2007065084A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of restraining one transfer/fixing unit from being deteriorated earlier than the other transfer/fixing unit. <P>SOLUTION: Whether an image to be formed is to be formed by a first image forming unit 20 or a second image forming unit 30 is selected on the basis of the deteriorated state of the first transfer/fixing unit 47 and that of the second transfer/fixing unit 47 and information on the image to be formed. Thus, the process of the deterioration of the transfer/fixing unit whose deterioration proceeds is restrained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to an image forming apparatus that forms an image on both sides of a recording medium such as transfer paper by a one-pass method.

  Conventionally, as a method for forming images on both sides of a recording medium, a switchback method, a one-pass method, and the like are known. In the switchback method, the recording medium is passed through a transfer unit and a fixing unit, an image is recorded on one surface of the recording unit, and then the recording unit is reversed by a reverse conveyance path. Then, the image is recorded on the other side by switching back to the transfer means and the fixing means. On the other hand, the one-pass method is a method for recording images on both sides of the recording body without switching back. As an example of the one-pass method, there is a method in which a recording medium having an image transferred on both sides by a double-side transfer unit is passed through a fixing unit. The one-pass method is superior to the switchback method in the following points. In other words, cost increases by providing a complicated mechanism for switchback, longer image formation time by switchback, jamming by switching back the curled recording medium by heating by the fixing means, and all of these are avoided. This is a possible point.

  However, such a one-pass method has a problem that the image is easily disturbed when the recording medium after the double-side transfer is sent from the double-side transfer means to the fixing means. When the recording medium separated from the double-sided transfer unit is transferred to the fixing unit, the sliding surface of the recording surface is slid along with the guide member disposed between the double-sided transfer unit and the inside of the fixing unit. The unfixed toner image is disturbed. In the case of an apparatus that transfers a toner image to only one side of a transfer paper, the design is such that the non-transfer surface of the toner image and the guide member are rubbed by means such as a guide member and layout, etc. It is possible to avoid disturbance of the toner image. However, in the case of double-sided transfer, the transfer surface of the toner image inevitably becomes a sliding surface with the guide member, so that the image is easily disturbed.

  Therefore, in Patent Document 1, a driven rotatable spur having a plurality of protrusions on the peripheral surface is provided between the double-sided transfer unit and the fixing unit, thereby guiding the recording body from the double-sided transfer unit to the fixing unit. An image forming apparatus has been proposed. According to Patent Document 1, by rotating the spur that supports the recording body while piercing the protrusion from the lower side with the movement of the recording body, without disturbing the image of the recording body surface on the side supported by the spur, The recording medium can be guided from the double-side transfer means to the fixing means. However, even if the spur protrusion is sharp, if it is pierced, the unfixed image will be disturbed.

  Patent Documents 2 and 3 describe the following image forming apparatus. A one-pass image forming apparatus including a first image forming unit and a second image forming unit, wherein a first toner image formed by the first image forming unit is a first intermediate transfer serving as a first image carrier belt. Then, the image on the first intermediate transfer belt is transferred to the first thermal transfer member. Then, before the first toner image transferred to the first thermal transfer body reaches the transfer / fixing nip, the first toner is heated and softened or melted in the conveyance process, and the first toner image is transferred to one side of the recording body. One toner image is thermally transferred and fixed. Similarly, the second toner formed by the second image forming unit on the second intermediate transfer belt is transferred to the second thermal transfer member, and is softened or melted in the conveyance process, and is then transferred to the other surface of the recording medium. Two toner images are thermally transferred and fixed.

  In this way, if transfer and fixing are performed simultaneously on each side of the recording medium, it is not necessary to transfer the transfer paper that has received the unfixed toner image on both sides to the fixing device. For this reason, it is possible to prevent image disturbance caused by conveying a recording medium carrying unfixed toner.

JP-A-10-142869 Japanese Patent Laid-Open No. 9-179373 Japanese Patent Laid-Open No. 10-282868

  By the way, the thermal transfer member is heated to a high temperature in order to soften or melt the toner image transferred to the thermal transfer member, so that the release layer on the surface of the thermal transfer member deteriorates with time. When the release layer is progressively deteriorated by heat and reaches the end of its life, the hardness is lowered, the surface is scratched by toner or the like, or toner filming occurs, resulting in an image defect. When such an image defect is confirmed, the user calls a service man, and the service man replaces the transfer / fixing unit provided with the thermal transfer member.

The image recorded on the front side of the document is formed by the first image forming unit, and the image recorded on the back side of the document is formed by the second image forming unit. There is an image forming apparatus in which an image forming unit used for the back surface is set in advance. In the case of such an image forming apparatus, depending on the form of use, one thermal transfer body deteriorates faster than the other thermal transfer body. More specifically, for example, when a large number of originals having an image with a high image area ratio formed on the front surface and an image with a low image area ratio formed on the back surface are printed, the first thermal transfer body is compared with the second thermal transfer body. Quickly deteriorate. This is because an image having a high image area ratio has a large amount of toner, so that a larger amount of heat than usual is required to soften or melt the toner before reaching the transfer / fixing nip. Therefore, by changing the setting of the heating temperature based on the input image information and increasing the heating temperature, even an image with a large amount of toner such as an image with a high image area ratio reaches the transfer / fixing nip. The toner can be softened or melted before. On the other hand, since an image with a low image area ratio has a small amount of toner, the toner can be softened or melted before reaching the transfer / fixing nip even with a smaller amount of heat than usual. For this reason, in order to save energy, the setting of the heating temperature is changed based on the input image information to lower the heating temperature. As described above, since the setting of the heating temperature is changed based on the input image information, a large amount of originals in which an image with a high image area ratio is formed on the front surface and an image with a low image area ratio is formed on the back surface are printed. In this case, the first thermal transfer member is subjected to more thermal load than the second thermal transfer member. As a result, the first thermal transfer member is deteriorated by heat faster than the second thermal transfer member.
In addition, since the first thermal transfer member deteriorates more quickly than the second thermal transfer member and has a life span, the transfer / fixing unit replacement time differs between the first transfer / fixing unit and the second transfer / fixing unit. End up. As a result, for example, the second transfer / fixing unit needs to be replaced before the sufficient period elapses after the first transfer / fixing unit is replaced. There was a risk that downtime would occur frequently.

  The present invention has been made in view of the above problems, and an object of the present invention is to form an image that can prevent one transfer / fixing unit from deteriorating faster than the other transfer / fixing unit. Is to provide a device.

In order to achieve the above object, the invention of claim 1 is characterized in that a first image forming unit for forming a first toner image, a second image forming unit for forming a second toner image, and a softening or softening of the first toner image. A first transfer / fixing unit having a first heat source for melting and transferring the first toner image to the first surface of the recording medium and fixing by heat; and a second heat source for softening or melting the second toner image. An image forming apparatus comprising: a second transfer / fixing unit that transfers the second toner image to the second surface of the recording body and fixes by heat; and a deterioration state of the first transfer / fixing unit; An image to be formed is formed based on the comparison result of the deterioration state comparison unit and the image information to be formed when forming an image, and a deterioration state comparison unit that compares the deterioration state of the second transfer / fixing unit. Formed by the first image forming unit or second An image forming apparatus comprising having a selecting means for selecting whether formed by the image forming unit.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a deterioration state of the first transfer / fixing unit is detected from a time integral value of power consumption of the first heat source, and the second transfer / fixing unit is detected. The deterioration state of the fixing unit is detected from a time integral value of power consumption of the second heat source.
According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the first heat source and the second heat source have the same configuration, and the deterioration state of the first transfer / fixing unit is indicated by the first heat source. The deterioration state of the second transfer / fixing unit is detected from the integrated value of the driving time of the second heat source.
According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, the deterioration state of the first transfer / fixing unit is detected from the integrated value of the pixel count of the output image of the first image forming unit. The deterioration state of the second transfer / fixing unit is detected from the integrated value of the pixel count of the output image of the second image forming unit.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first to fourth aspects, at least one of the first transfer / fixing unit and the second transfer / fixing unit has a toner image. A thermal transfer body to be transferred is provided, and the toner on the thermal transfer body is softened and melted by the heat source, and the toner image is transferred to the recording body by heat and fixed at the same time.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the image forming apparatus further comprises a thermal transfer body cleaning member for cleaning the transfer residual toner on the thermal transfer body.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, both the first transfer / fixing unit and the second transfer / fixing unit are provided with thermal transfer members, and the first transfer / fixing unit is thermally transferred. A first thermal transfer body cleaning member for cleaning the transfer residual toner on the body, and a second thermal transfer body cleaning member for cleaning the transfer residual toner on the thermal transfer body of the second transfer / fixing unit, The deterioration state of the first transfer / fixing unit is detected from the amount of residual toner adhered to the first thermal transfer member cleaning member, and the deterioration state of the second transfer / fixing unit is detected in the second thermal transfer member cleaning member. It is characterized by detecting from the amount of adhered transfer residual toner.
The invention according to claim 8 is the image forming apparatus according to claim 5 or 6 and the image forming apparatus according to claim 7, wherein the thermal transfer body is provided in both the first transfer / fixing unit and the second transfer / fixing unit. The thermal transfer member of the first transfer / fixing unit and the thermal transfer member of the second transfer / fixing unit are opposed to each other across the conveyance path of the recording member, and the thermal transfer member of the first transfer / fixing unit; The thermal transfer member of the second transfer / fixing unit is brought into contact with a predetermined pressure.
According to a ninth aspect of the present invention, in the image forming apparatus of the fifth or sixth aspect, one of the first transfer / fixing unit and the second transfer / fixing unit is a thermal transfer body onto which a toner image is transferred. The toner image on the thermal transfer member is softened and melted by the heat source to transfer and fix the toner image on the recording material, and the other is an electrostatic transfer device that electrostatically transfers the toner image to the recording material. And a fixing member for fixing the toner on the recording body, and the toner image electrostatically transferred onto the recording body with the heat source is softened or melted to fix the toner image with the fixing member. It is a feature.
According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the fixing member and the thermal transfer body are opposed to each other with a conveyance path of the recording medium interposed therebetween, and the fixing member and the second transfer / fixing are fixed. The thermal transfer body of the unit is brought into contact with a predetermined pressure.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect, the heat source is provided upstream of the fixing member in the recording material conveyance direction.
According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the fifth to eleventh aspects, the heat source of the transfer / fixing unit provided with the thermal transfer member is disposed to face the outer peripheral surface of the thermal transfer member. It is what.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the fifth to eleventh aspects, the heat source of the transfer / fixing unit provided with the thermal transfer member is disposed inside the thermal transfer member. .
The invention according to claim 14 is the image forming apparatus according to any one of claims 1 to 13, wherein at least one of the heat sources of the first transfer / fixing unit and the second transfer / fixing unit is a heat generated from the magnetic material. And a magnetic field generating means for generating a magnetic field between the heating element and the heating element. The heating element is heated by electromagnetic induction by a magnetic field generated by the magnetic field generating means.
According to a fifteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the heat amount of the first heat source and the heat amount of the second heat source are matched with a toner image formed by the image forming unit. It is characterized by adjusting.
The invention according to claim 16 is the image forming apparatus according to any one of claims 1 to 15, wherein when the image information is only on one side, the selecting means is a first transfer / fixing unit as a unit for forming an image. The image forming unit corresponding to the transfer / fixing unit that has not deteriorated is selected from the second transfer / fixing units.
According to a seventeenth aspect of the present invention, in the image forming apparatus according to any one of the first to fifteenth aspects, the image information is a single color image formed on one surface of the recording medium, and is formed on the other surface of the recording medium. In the case where the image to be printed is a color image, the selecting means is an image forming unit that forms a single color image. Of the first transfer / fixing unit and the second transfer / fixing unit, the transfer / fixing of which deterioration is advanced The image forming unit corresponding to the unit is selected.
According to an eighteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fifteenth aspects, the image information is an image formed mainly on one surface of the recording medium, and the other surface of the recording medium. In the case where the image to be formed is mainly a character image, the selection means has deteriorated among the first transfer / fixing unit and the second transfer / fixing unit as an image forming unit for forming the image mainly composed of the character image. The image forming unit corresponding to the other transfer / fixing unit is selected.
According to a nineteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fifteenth aspects, the selecting means includes an image formed on one surface of the recording body and an image formed on the other surface of the recording body. As an image forming unit that forms an image with a low image area ratio, an image forming unit corresponding to the transfer / fixing unit that has deteriorated is selected from the first transfer / fixing unit and the second transfer / fixing unit. It is characterized by.
According to a twentieth aspect of the present invention, in the image forming apparatus according to any one of the first to nineteenth aspects, a recording body reversing mechanism for reversing and fixing the recording body after fixing is provided. .
The invention according to claim 21 is the image forming apparatus according to any one of claims 1 to 20, wherein the toner used for forming the toner image has a weight average particle diameter of 3 to 8 [μm] and a weight average particle diameter. The value obtained by dividing the number by the number average particle diameter is 1.00 to 1.40.
According to a twenty-second aspect of the present invention, in the image forming apparatus according to any one of the first to twenty-first aspects, as the toner used for forming the toner image, the shape factor SF-1 is 100 to 180, and the shape factor SF-2 is What is 100-180 is used.
According to a twenty-third aspect of the present invention, in the image forming apparatus according to any one of the first to twenty-second aspects, the toner used for forming the toner image is formed by adding an additive to the base particles composed of at least a binder resin and a colorant. And an additive having an average primary particle size of 50 to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more is used as the additive. To do.

  According to the first to twenty third aspects of the present invention, the first image formation is performed on the basis of the deterioration state of the first transfer / fixing unit and the deterioration state of the second transfer / fixing unit and the image information to be formed. It is selected whether to form by a unit or by a second image forming unit. As a result, among the image formed on one surface of the recording medium and the image formed on the other surface of the recording medium, an image that requires less load on the transfer / fixing unit is obtained as the first image forming unit and the second image. If the image forming unit corresponding to the transfer / fixing unit whose deterioration has progressed among the forming units, the following effects can be obtained. That is, it is possible to suppress the progress of the deterioration of the transfer / fixing unit that has been deteriorated. As a result, the period until the end of the life of the transfer / fixing unit can be extended, and the period for replacement can be extended. Therefore, the number of times of replacement of the transfer / fixing unit can be reduced. In addition, the deterioration of the first transfer / fixing unit and the deterioration of the second transfer / fixing unit proceed evenly, and the life of the thermal transfer body can be made almost simultaneously. As a result, the period in which the life of the first transfer / fixing unit is reached and the period in which the life of the second transfer / fixing unit is reached can be made substantially the same, and the replacement time can be made almost the same. As a result, the first transfer / fixing unit and the second transfer / fixing unit can be replaced at the same time, and the occurrence of downtime due to the replacement of the transfer / fixing unit can be suppressed.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color image forming system (hereinafter simply referred to as an image forming system) as an image forming apparatus will be described.
FIG. 1 is a schematic configuration diagram showing an image forming system according to the present embodiment. In this figure, the image forming system includes a printer unit 100, an operation / display device 90, a paper feeding device 40, an automatic image reading device 200, a paper replenishing device 300, and the like.

  The printer unit 100 includes a first transfer unit 20 disposed above and a second transfer unit 30 disposed below the paper conveyance path 43A. The first transfer unit 20 has a first intermediate transfer belt 21 as a first image carrier belt that moves endlessly in the direction of the arrow in the drawing. The second transfer unit 30 has a second intermediate transfer belt 31 as a second image carrier belt that moves endlessly in the direction of the arrow in the drawing. Above the upper tension surface of the first intermediate transfer belt 21, four first process units 80Y, 80M, 80M, 80C, and 80K, which are first toner image forming means, are arranged. On the other hand, on the side of the side tension surface of the second intermediate transfer belt 31, four second process units 81Y, 81M, 81C, 81C, and 81C, which are second toner image forming means, are arranged. The subscripts Y, M, C, and K attached to the numbers of the first and second process units indicate the colors of toner to be handled. The same subscript is attached to each device in the process unit.

  Each process unit (80Y, M, C, K, 81Y, M, C, K) has a photoreceptor (1Y, M, C, K) as an image carrier. The photoreceptors 1Y, 1M, 1C, and 1K of the first process units 80Y, 80M, 80M, 80K, 80K, 80K, 80K, and 80K are arranged at regular intervals, and at least at the time of image formation, contact the upper stretched surface of the first intermediate transfer belt 21, respectively. Hereinafter, the belt surface that contacts in this way is referred to as a first image receiving surface.

  On the other hand, the photoreceptors 1Y, 1M, 1C, and 1K of the second process units 81Y, 81M, 81C, and 81K are also arranged at equal intervals, and at least at the time of image formation, contact the upper stretched surface of the second intermediate transfer belt 21, respectively. . Hereinafter, the belt surface that contacts in this way is referred to as a second image receiving surface.

  The first intermediate transfer belt 21 is stretched by a plurality of rollers in a horizontally long posture with a space in the horizontal direction rather than in the vertical direction, and in a posture in which the first image receiving surface extends substantially horizontally. The first process units 80Y, 80M, 80C, and 80K are arranged in parallel so as to be in contact with the substantially horizontal first image receiving surface.

  On the other hand, the second intermediate transfer belt 31 is stretched by a plurality of rollers in a vertically inclined state from the upper left to the lower right in the drawing. The second process units 81Y, 81M, 81C, and 81K are slanted from the upper left to the lower right in the drawing on the right side of the second intermediate transfer belt 31 so as to contact the inclined second image receiving surface. Are arranged in parallel so that

  FIG. 2 is an enlarged configuration diagram showing one of the four first process units 80Y, 80M, 80C, 80K. The four first process units 80Y, 80M, 80C, 80K, 80K, 80K, 80K, 80K, 80K, 80K, Y80, 80K, 80K, Y80, Y80, 80K, 80K, Y80, Y80, 80K The subscript K is omitted. In the figure, the photosensitive member 1 is driven to rotate counterclockwise in the drawing by a driving means (not shown) during operation of the printer unit (100). Around the photosensitive member 1, there are an image forming member such as a scorotron charger 3, an exposure device 4, a developing device 5, a cleaning device 2 and a photostatic device Q as a charging means, a potential sensor S1, an image sensor S2, and the like. It is arranged.

  The drum-shaped photoreceptor 1 is formed by coating an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylinder surface having a diameter of about 30 to 120 [mm], for example. An amorphous silicon (a-Si) layer may be coated. Further, it may be a belt shape instead of a drum shape.

  The cleaning device 2 includes a cleaning brush 2a, a cleaning blade 2b, a recovery member 2c, and the like, and removes and recovers transfer residual toner remaining on the surface of the photoreceptor after passing through a primary transfer nip described later.

  The scorotron charger 3 uniformly charges the surface of the photoconductor 1 that is rotationally driven to, for example, a negative polarity. As a charging means for performing such uniform charging, a corotron charger may be used instead of the scorotron charger. Alternatively, a charging bias member to which a charging bias is applied may be in contact with the surface of the photoreceptor 1.

  The exposure device 4 optically scans the surface of the uniformly charged photoreceptor 1 with light generated based on image data corresponding to one of the colors, and an electrostatic latent image is formed on the surface of the photoreceptor 1. Form. In the example shown in the figure, the exposure device 4 is composed of an LED (light emitting diode) array and an imaging element. A laser scanning method using a light beam modulated according to image data to be formed using a laser light source, a polygon mirror, or the like may be used.

  The developing device 5 is of a two-component developing system that develops an electrostatic latent image on the photoreceptor 1 using a two-component developer containing toner and a magnetic carrier. The two-component developer is conveyed in the depth direction in the figure while being agitated by two conveying screws 5c. The developer conveying directions of these two conveying screws 5c are opposite to each other. For example, if the developer conveying direction of the left conveying screw 5c in the figure is the front side from the back side in the figure, the developer conveying direction of the right conveying screw 5c in the figure is the front side to the back side in the figure. The two-component developer transported to the end in the depth direction of the developing device 5 by the former transport screw 5c is transferred to the latter transport screw 5c. Then, in the process of being stirred and conveyed from the end portion toward the opposite end portion, a part is carried on the developing roll 5b described later. Further, the two-component developer that is not carried or returned from the developing roll 5b to the right conveying screw 5c is delivered to the left conveying screw 5c at the opposite end. In this way, the two-component developer is circulated and conveyed in the developing device 5. As the developing device 5, a one-component developing system using a one-component developer containing toner as a main component without including a magnetic carrier may be used.

  The developing roll 5a is a non-magnetic cylinder made of stainless steel, aluminum, or the like, and has a sleeve that is driven to rotate clockwise in the drawing by a driving means (not shown), and a magnet roller that is internally fixed so as not to rotate. is doing. The magnet roller has a plurality of magnetic poles divided in the circumferential direction inside the sleeve. The two-component developer conveyed by the conveyance screw 5c on the right side in the drawing is attracted by the magnetic force generated by the magnet roller, and is pumped up on the surface of the sleeve that is rotationally driven. Then, prior to being transported to the developing area facing the photoreceptor 1 along with the sleeve surface, it passes through a regulation position that is a position facing the blade 5b.

  The blade 5b is disposed so that its tip is close to the sleeve surface through a predetermined gap. Then, when the two-component developer on the sleeve surface passes through the regulation position immediately below, the thickness of the two-component developer is regulated to a predetermined size.

  The two-component developer whose layer thickness is regulated in this way is conveyed to a developing region that is a position facing the photoreceptor 1 as the sleeve rotates. The electrostatic latent image formed by attenuating the charge by optical scanning on the surface of the photoreceptor 1 uniformly charged to the negative polarity is rubbed against the two-component developer on the sleeve surface in the development region. . Then, it is developed into one of Y, M, C, and K colors by the adhesion of negatively chargeable toner having the same polarity as the latent image. In the first process unit 80, so-called reversal development is performed. As a result, a toner image of any one of Y, M, C, and K is formed on the photoreceptor 1.

  As the toner, a spherical or irregular toner obtained by a conventionally known method is used. The volume average particle diameter is 20 [μm] or less, preferably 10 [μm] or less, and 3 [μm] or more. As the magnetic carrier, those obtained by a conventionally known method are used. The volume average particle size is preferably about 25 [μm] to 60 [μm].

  The two-component developer that has consumed toner in the developing region returns to the developing device 5 as the sleeve rotates. Then, under the influence of the repulsive magnetic field formed by the magnetic poles of the same polarity and adjacent to each other of the magnet roller, the magnet roller is separated from the sleeve surface and returned to the right conveying screw 5c in the drawing, and then the left side in the drawing. It is delivered to the conveying screw 5c.

  A toner concentration sensor 5e is disposed below the left conveying screw 5c in the drawing, and detects the magnetic permeability of the two-component developer conveyed by the left conveying screw 5c. Since the magnetic permeability of the two-component developer has a correlation with the toner density, the toner density sensor 5e detects the toner density.

  When the control unit (not shown) determines that the toner concentration of the two-component developer is less than a predetermined threshold based on the output signal from the toner concentration sensor 5e, the two-component development of eight toner supply means (not shown) is performed. The one corresponding to the agent is driven for a predetermined time. These eight toner supply units are respectively provided for four developing devices of the first process unit (80Y, M, C, K) or four developing devices of the second process unit (81Y, M, C, K). It corresponds to any one. It is connected to one of four Y, M, C, and K toner bottles that are detachably set in a bottle storage portion (not shown). Then, the toner of a predetermined color is supplied from the connected toner bottle onto the conveying screw 5c on the left side in the drawing in the corresponding developing device. As a result, the toner concentration of the two-component developer that has consumed the toner by development is recovered. As the toner supply means having such a configuration, a system that sucks the toner in the toner bottle and conveys it to the developing device with a suction force of a conventionally known Mono pump is preferable. According to this method, there are few restrictions on the installation location of the toner bottle, which is advantageous for space allocation inside the printer unit (100). Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device 5, and the developing device 5 can be downsized.

  FIG. 3 is an enlarged configuration diagram showing one of the four second process units (81Y, M, C, K). The four second process units (81Y, M, C, and K) have substantially the same configuration except that the colors of the toners to be handled are different. The second process unit 81 has the same constituent members as the first process unit (80), but the rotational direction of the photoreceptor 1 is different. However, they are mutually shaped with respect to the y-axis passing through the rotation axis 1a of the photoreceptor 1. Although this shape is related to the arrangement of members provided around the photoreceptor 1, it is an important matter. Specifically, consideration is given to a method of connecting a connecting portion with the main body of the printer unit 100, for example, a connecting portion with a driving means, an electrical connecting portion, a toner supplying portion, and a toner discharging portion. Thereby, the first process unit (80Y, M, C, K) and the second process unit (81Y, M, C, K) can be made compatible. Accordingly, it is not necessary to separately manufacture the developing device, the cleaning device, and the parts for the first process unit and the second process unit, so that the efficiency in manufacturing parts and managing parts is high, and the overall cost can be reduced. it can.

Next, the intermediate transfer belt will be described. The first intermediate transfer belt 21 as the first toner image conveying belt is supported by a plurality of rollers 24, 25, 26 (two) and 27 and travels in the direction of the arrow. The first image forming units 80Y to 80K are provided below the photoreceptors 1Y, 1C, 1M, and 1K. The first intermediate transfer belt 21 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. In addition, a primary transfer roller 22 is provided on the inner peripheral portion of the first intermediate transfer belt 21 so as to face the photoreceptors 1Y, 1C, 1M, and 1K.
Members related to the first intermediate transfer belt 21 are integrally formed as the first image forming unit 20 and can be attached to and detached from the image forming apparatus 100.

On the other hand, the second intermediate transfer belt 31 as the second toner image conveying belt is supported by a plurality of rollers 33, 34, 35, 36 (two), 37, 38 and travels in the direction of the arrow. The second image forming units 81Y to 81K are provided in contact with the photoreceptors 1Y, 1C, 1M, and 1K. The second intermediate transfer belt 31 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. A primary transfer roller 32 is provided on the inner peripheral portion of the second intermediate transfer belt 31 so as to face the photoreceptors 1Y, 1C, 1M, and 1K.
Members related to the second intermediate transfer belt 31 are integrally configured as the second image forming unit 30 and can be attached to and detached from the image forming apparatus 100.

Each of the two intermediate transfer belts (21, 31) is a belt having a base made of a resin film or rubber having a base thickness of 50 to 600 [μm], for example. The toner image carried by the photoreceptor 1 exhibits an electrical resistance value that enables electrostatic transfer onto the belt surface by a primary transfer bias applied to the primary transfer rollers (22, 32). As an example of such an intermediate transfer belt, a material in which carbon is dispersed in polyimide and the resistance is adjusted to about 10 ⁶ to 10 ¹² [Ωcm] can be cited. Belt detent ribs for stabilizing the running of the belt are provided on one side or both ends of the belt. The details of the intermediate transfer belt (21, 31) will be described later.

As the four primary transfer rollers 22 as the first transfer means of the first belt unit and the four primary transfer rollers 32 as the second transfer means of the second belt unit, for example, those having the following configurations are used. Can do. That is, the surface of a metal roller as a core metal is coated with a conductive rubber material, and a bias is applied to the core metal part from a power source (not shown). In the present embodiment, a conductive rubber material obtained by dispersing carbon in urethane rubber is used, and the volume resistance is adjusted to about 10 ⁵ Ωcm.

  The printer unit 100 can also output a monochrome image using only K toner. When outputting a monochrome image, the Y, M, and C process units 80Y, 80M, and 80C in the first belt unit are not used. In addition to not operating the process units 80Y, 80M, 80M, a mechanism for keeping these and the intermediate transfer belt in non-contact is provided. An internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, and is supported so as to be rotatable about a certain point. Then, by rotating in a direction away from the photosensitive member, only the photosensitive member 1K is brought into contact with the first intermediate transfer belt 21, and an image forming process is executed to create a monochrome image using black toner. Such a configuration is advantageous in terms of improving the life of the photoreceptor. Similarly, the second belt unit is configured to retract the process units 81Y, 81M, 81C from the second intermediate transfer belt 31 when outputting a monochrome image.

  Next, the double-side transfer means 50 will be described. The double-side transfer means 50 includes a first transfer / fixing unit 47 and a second transfer / fixing unit 48. The first transfer / fixing unit 47 is provided in the vicinity of the support roller 27 on the outer periphery of the first intermediate transfer belt 21. The first transfer / fixing unit 47 includes a first thermal transfer member 47A to which toner on the first intermediate transfer belt is transferred, and a first pressure roller 47B that contacts the first thermal transfer member 47A with a predetermined pressure. have. The toner on the first thermal transfer member is transferred and fixed to the recording member P while the recording medium P is passed between the first thermal transfer member 47A and the pressure roller 47B.

  The second transfer / fixing unit 48 is provided in the vicinity of the support roller 34 on the outer periphery of the second intermediate transfer belt 31. The second transfer / fixing unit 48 includes a second thermal transfer member 48A to which the toner on the second intermediate transfer belt is transferred, and a second pressure roller 48B that contacts the second thermal transfer member 48A with a predetermined pressure. have. The toner on the second thermal transfer member is transferred and fixed to the recording member P while the recording medium P is passed between the second thermal transfer member 48A and the second pressure roller 48B. The details of the double-side transfer means 50 will be described later.

  On the right side of the printer unit 100 in the drawing, a paper feeding device 40 that accommodates transfer paper is provided. A plurality of stages, for example, a sheet feeding device (tray) 40a storing a large amount of transfer paper in the upper stage, and three stages of sheet feeding cassettes 40b, 40c, 40d below each are pulled out to the right side (operation surface side). It is arranged to be possible. Different types of transfer paper are stored in the paper feed tray 40a and the paper feed cassettes 40b, 40c, and 40d. Among these, the uppermost transfer sheet is selectively fed and separated by the corresponding sheet feeding / separating means 41A to 41D, and only one sheet is reliably transferred to the sheet conveying paths 43B and 43A by the plurality of conveying roller pairs 42B. Sent.

  In the paper conveyance path 43A, a registration roller pair 45 including a pair of rollers is provided in order to take a feeding timing for feeding the transfer paper to the secondary transfer position which is the first and second transfer positions. Further, a lateral registration correction mechanism 44 is provided in the paper transport path 43A for making the position perpendicular to the transfer paper transport direction a normal position. The lateral registration correction mechanism 44 includes the following. The transfer paper is slid and conveyed so as to be composed of a reference guide in the horizontal direction (not shown) and a pair of skew rollers. Then, the transfer paper is aligned with a predetermined position. The reference guide is moved and arranged at a predetermined position according to the size of the transfer paper. The lateral registration correction mechanism 44 is composed of a regulating member that presses both sides of the transfer paper for a short time and a plurality of times from both lateral directions of the transfer paper with respect to the transfer paper transport direction to align the transfer paper at a predetermined position. The jogger method may be used.

  Transfer paper can be supplied to the paper conveyance path 43C having the conveyance roller pair 42C from another paper supply device 300 that can be installed upstream in the conveyance direction. The upper paper feed surface of the paper feed tray 40a is arranged so that the uppermost transfer paper on the paper feed tray 40a is fed and then conveyed almost horizontally without being bent. Therefore, even thick transfer paper and highly rigid paperboard can be reliably fed. In addition, it is convenient to adopt an air sheet feeding composed of a vacuum mechanism so that the sheet feeding tray 40a can reliably feed even when transfer sheets having various characteristics are stored. Although not shown in the drawing, a sensor for detecting the transfer paper is provided at an important point of the paper transport path, and serves as a trigger for various signals based on the presence of the transfer paper.

  A cooling roller pair 70 having a cooling function is provided in the conveyance path after the transfer and fixing in order to cool the recording medium after the transfer and fixing and stabilize the unstable toner state at an early stage. As the cooling roller pair 70, a heat pipe structure roller having a heat radiating portion can be adopted. The cooled transfer paper is sent by a paper discharge roller pair 71 to a reversing unit 90 that is a reversing mechanism provided on the left side of the printer unit 100.

  FIG. 4 is a diagram showing the reversing unit 90. When the recording medium is reversed, the conveyance path 97 is switched by the paper discharge branch claw 91 and the recording medium is conveyed to the reversal path 97. The recording medium conveyed to the reversing path 97 is conveyed to the reversing table 93 by the reversing entrance roller 92 and reversed. Thereafter, the reversely rolled roller 94 is lowered, the recording medium is switched back by the reverse discharge roller 95 and conveyed to the discharge path 96, and the reversed recording medium is discharged from the discharge port 98. On the other hand, when the recording medium is not reversed, the recording medium is conveyed to the discharge port 98 without switching the discharge branching claw 91.

  The recording medium discharged from the discharge port 98 is discharged and stacked in a discharge stack unit (not shown). Note that the transfer paper can also be transported to another post-processing apparatus through the paper discharge stack unit. As another post-processing apparatus, an apparatus for bookbinding such as drilling, cutting, folding, and binding can be connected.

  The operation / display unit 90 provided on the upper surface of the printer unit 100 is provided with a keyboard and the like, and conditions for image formation can be input. Also, various information can be displayed on a display unit such as a display, and information exchange between the operator and the printer unit 100 is facilitated.

  An automatic image reading device (ADF) 200 that reads an image of a document while automatically conveying the document by a well-known technique is provided on the upper portion of the sheet feeding device 40, and image information obtained thereby is sent to a control unit (not shown). It is done. Based on the sent image information, the printer unit 100 is driven and controlled to output the same image as the original. Further, image information from a personal computer (not shown) or the like can be sent to the printer unit 100 and an image corresponding to the image information can be output. Furthermore, it is also possible to send image information sent from a telephone line (not shown) and output an image corresponding to the image information. A paper supply device 300 for supplying transfer paper to the paper supply device 40 is disposed on the right side of the paper supply device 40 in the drawing.

Next, the operation at the time of single-sided recording in which the printer unit 100 forms a full-color image on one side of the transfer paper will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method in which the four-color first toner images transferred to the first intermediate transfer belt 21 are collectively transferred onto the first surface of the transfer paper. Another method is a method in which the second toner images of four colors transferred to the second intermediate transfer belt 31 are secondarily transferred collectively onto the second surface of the transfer paper. In a case where the image data consists of a plurality of pages, it is convenient to control the image forming order so that the pages are aligned on the paper discharge stack unit 75. Therefore, the former method, in which the image data of the last page is recorded in order and the page order is aligned, will be described.

  When the printer unit 100 is operated, the first intermediate transfer belt 21 and the photoreceptors 1Y, 1M, 1C, and 1K in the first process units 80Y, 80M, 80C, 80K rotate. At the same time, the second intermediate transfer belt 31 moves endlessly, but the photosensitive members 1Y, M, C, and K in the second process units 81Y, 81M, 81C, and 81K are separated from the second intermediate transfer belt 31 and are not rotated. Is done. Then, image formation by the first process unit 80Y is started. By the operation of the exposure device 4 composed of an LED (light emitting diode) array and an imaging element, light corresponding to image data for yellow emitted from the LED is irradiated onto the surface of the photoreceptor 1Y uniformly charged by the charging device 3. Thus, an electrostatic latent image is formed.

  The electrostatic latent image is developed into a Y toner image by the developing device of the first process unit 81Y for Y, and is electrostatically primary-transferred onto the first intermediate transfer belt 21 at the primary transfer nip for Y. The Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner on the photoconductors 1M, 1C, 1K, and K side. Then, the M, C, and K toner images are sequentially superimposed on the Y toner image on the first intermediate transfer belt 21 at the primary transfer nip for M, C, and K, and are primarily transferred. By this superimposing primary transfer, four color first toner images are formed on the first intermediate transfer belt 21.

  On the other hand, the paper feeding device 40 transfers the transfer paper corresponding to the image data from the internal paper feeding tray 40a or the paper feeding cassettes 40b, c, d to any one of the paper feeding / separating means 41A, B, C, D. So send it out. And it conveys toward the paper conveyance path 43C of the printer part 100 by conveyance roller pair 42B, 42C. Then, it is sent to the lateral registration correction mechanism 44.

  The lateral registration correction mechanism 44 is formed from the feeding direction of the transfer paper that is being conveyed from the paper feeding device 40 serving as the recording medium supply unit toward the double-side transfer unit (first and second transfer / fixing units 47 and 48). Inclination correction means for correcting the inclination of the posture. A pair of guide plates arranged in the paper surface direction orthogonal to the transport direction on the upstream side in the transport direction with respect to the registration roller pair 45 is abutted against both ends orthogonal to the transfer paper transport direction so that the posture of the transfer paper is tilted. to correct. The two guide plates of the guide plate pair can be moved in the direction of the sheet perpendicular to the transport direction, and the distance between the plates can be made the width of the transfer paper by moving according to the width of the fed transfer paper. Can be matched.

  The transfer sheet whose inclination of the posture is corrected by the lateral registration correction mechanism 44 reaches between the rollers of the registration roller pair 45, where the timing is measured and the sheet is sent out to the secondary transfer nip. Then, in the first transfer / fixing unit 47, the first toner image is subjected to heat and pressure to be transferred / fixed on the recording medium.

  As shown in FIG. 2, in each of the first process units 80Y, 80M, 80C, 80K, residual transfer toner remaining on the photoreceptors 1Y, 1M, 1C, 1K after passing through the primary transfer nip. Is cleaned by the cleaning device (2). This cleaning device (2) removes transfer residual toner from the first intermediate transfer belt 21 by the cleaning brush 2a and the cleaning blade 2b. The removed foreign matter such as toner is sent to the collecting unit 87 by the collecting unit 2c. Sensors S1 and S2 detect whether the surface potential after exposure on the surface of the photoconductor and the concentration of toner attached to the surface of the photoconductor after the development process are appropriate, and appropriately set image forming conditions. Information is sent to a control means (not shown) for control. Further, the surface of the photoreceptor 1 after cleaning is initialized by removing the residual charges by the static eliminating device Q.

  On the other hand, the transfer paper that has passed through the first transfer / fixing unit 47 is delivered to a cooling roller pair 70 as cooling means. Then, after the toner is completely fixed, the paper is discharged by the paper discharge roller 71 with the image surface facing upward.

  Since the image forming order is programmed so that transfer sheets of young pages are sequentially stacked on the paper discharge stack unit, the page order is aligned in the stack unit. Since the paper discharge stack part descends as the number of transfer sheets to be discharged increases, the transfer sheets can be stacked in an orderly and reliable manner, and the page order is not disturbed. Instead of directly stacking the recorded transfer paper on the paper discharge stack unit, punching processing can be performed, or the transfer paper can be conveyed to a post-processing device such as a sorter, a collator, a binding device, or a folding device.

  In another method of forming an image on one side of the transfer paper, the image is not formed in the first process units 80Y, 80M, 80C, 80K, and the image data of a young page is used for page alignment. The difference is that images are formed in order. Another difference is that the reversing unit 90 reverses the recording medium so that the paper is discharged with the image surface facing upward. However, the description is omitted because it is basically the same as the one-side recording process described above.

Next, the operation during double-sided recording in which images are formed on both sides of the recording medium P will be described. When a start signal is input to the printer main body, images of respective colors sequentially formed by the first image forming units 20Y, 80C, 80M, and 80K described in the single-sided recording operation are sequentially applied to the first intermediate transfer belt 21 in order. Transfer. Substantially in parallel with the step of supporting the first image, the images of the respective colors sequentially formed by the second image forming units 30Y, 81C, 81M, and 81K are sequentially primary-transferred to the second intermediate transfer belt 31, and the second The process of carrying as an image is performed. As shown in FIG. 1, the interval between the second image forming units in the belt conveyance direction is set closer than the interval between the first image forming units. Thereby, in order for the first image and the second image to coincide with each other at the front end in the transport direction of the recording medium, the formation of the second image is started after the start of the formation of the first image. . Further, since the recording medium is stopped and retransmitted by the registration roller pair 45, the sheet is fed in consideration of the time, and is aligned by the lateral registration correction mechanism 44. The registration roller pair 45 conveys the recording medium to the first transfer / fixing unit 47 in time. In the first transfer / fixing unit 47, the first toner image is transferred / fixed on one side (upper surface in the drawing) of the recording medium P under the action of heat and pressure.
The recording material P having an image on one side in this way is continuously sent to the second transfer / fixing unit 47 by the conveying action of the first transfer / fixing unit 47. Then, the second toner image is transferred and fixed on the lower surface of the recording material P by the second transfer / fixing unit 48 under the action of heat and pressure.

  The recording material P having the full-color toner image transferred on both sides in this way is sent to a cooling roller pair 70 as cooling means. Then, after the toner is completely fixed, the paper is discharged onto the paper discharge stack portion by the paper discharge roller 71. Alternatively, the paper is reversed by the reversing unit 90 and discharged to the paper discharge stack unit.

  When double-sided recording is performed on a plurality of pages of transfer paper, the image forming order is controlled so that an image of a young page becomes the bottom surface and is stacked on the paper discharge stack unit. As a result, when the paper is taken out from the paper discharge stack 75 and the top and bottom surfaces are reversed, the recorded matter is one page in order from the top, the second page on the back, the third page on the second sheet, and the fourth page on the back. Such control of the image forming sequence and control such as increasing the amount of heat input to the heat transfer device 47 from that during single-sided recording are executed by the control unit.

  Although an example in which full-color recording is performed regarding the single-sided recording operation and the double-sided recording operation has been described, monochrome recording using only black toner is also possible. When the need for maintenance or replacement of parts arises, maintenance is performed by opening an unillustrated exterior cover or the like.

  Next, details of the double-side transfer means 50 will be described. FIG. 5 is a schematic configuration diagram of the double-side transfer means 50. As described above, the double-sided transfer unit 50 includes the first transfer / fixing unit 47 and the second transfer / fixing unit 48. The first and second transfer / fixing units 47 and 48 include thermal transfer members 47A and 48A and pressure rollers 47B and 48B, respectively. Near the surface layers of the first and second thermal transfer members 47A and 48A, IH coils 47C and 48C, which are magnetic field generating means, are arranged. It has a heat generating layer that is a heat generating element made of a magnetic material that generates heat by electromagnetic induction. In the present embodiment, the heat source includes an IH coil that is a magnetic field generating unit and a heat generation layer of a thermal transfer member. Further, on the downstream side of the first transfer / fixing nip in the first thermal transfer body moving direction, the first cleaning roller 47G as the first thermal transfer body cleaning member is downstream of the second transfer / fixing nip in the second thermal transfer body moving direction. On the side, a second cleaning roller 48G as a second thermal transfer member cleaning member is provided.

  The first and second thermal transfer members 47A and 48A are composed of a cored metal roller, a heat-resistant elastic layer made of heat-resistant rubber such as silicone rubber coated on the outer peripheral surface, and iron formed on the outer peripheral surface of the heat-resistant elastic layer. The heat generating layer is made of a magnetic material such as cobalt or nickel, and the surface layer having heat resistance and toner releasability formed on the outer peripheral surface of the heat generating layer. By having the heat-resistant elastic layer, vibration due to the thickness difference of the recording medium can be suppressed, and the toner on the thermal transfer body 48A can be prevented from being disturbed.

  The first toner image on the first intermediate transfer belt is transferred to the first thermal transfer body 47A. On the other hand, a high frequency current flows through the IH coil 47C, and a high frequency magnetic field is generated from the IH coil 47C. This high frequency magnetic field generates an induced eddy current in the heat generating layer, the heat generating layer is heated by Joule heat generated by the induced eddy current, and the thermal transfer body 48A is heated. Then, the first toner image transferred to the first thermal transfer body is softened or softened by the heat of the thermal transfer body 48A while being conveyed to the first transfer / fixing nip where the first pressure roller 47B comes into contact with the first transfer body 47A. Melt. When the softened or melted first toner image is conveyed to the first transfer / fixing nip, the first toner image is transferred / fixed on the upper surface of the recording medium. The untransferred toner remaining on the first thermal transfer body without being transferred or fixed is adsorbed by the first cleaning roller 47G. Similarly, the second toner image on the second intermediate transfer belt is transferred to the second thermal transfer member 48A and conveyed to the second transfer / fixing nip where the pressure roller 48B contacts with the second thermal transfer member 48A. During this conveyance process, the second toner image on the second transfer body 48A is softened or melted. Then, the second toner image is transferred and fixed on the upper surface of the recording medium at the second transfer / fixing nip. Untransferred toner remaining on the second thermal transfer body without being transferred or fixed is adsorbed by the second cleaning roller 48G.

  In the thermal transfer mechanism, when a predetermined pressure is applied to the softened or melted toner, the toner is plastically deformed and bites into the uneven surface of the transfer surface and the transfer surface. At that time, the larger the roughness, the larger the contact area, and the more the bite into the concavo-convex portion, so that the softened or melted toner tends to adhere to the surface with the larger roughness (anchor effect). When the surface roughness is the same, the softened or melted toner adheres to the lower toner releasability. For this reason, in order to ensure good thermal transferability, the surface roughness of the thermal transfer members 47A and 48A is set lower than the surface roughness of the recording medium, or the surface of the thermal transfer members 47A and 48A is lower than the surface of the recording medium. It is necessary to make the toner difficult to adhere. When the recording medium is plain paper, the surface roughness is 30 to 50 [μm], and it is preferable to set the surface roughness of the thermal transfer members 47A and 48A to at least 10 [μm] lower than that.

  In the case of the electrostatic transfer system, there is a risk that dust and blurring occur due to the discharge at the entrance and exit of the transfer nip and the influence of an electric field, and the image is deteriorated. On the other hand, in the case of thermal transfer, there is no influence of electric discharge or electric field at the entrance and exit of the transfer nip, so there is no generation of dust and blemishes, and a high-quality image can be obtained.

  The IH coils 47C and 48C are preferably provided upstream of the transfer / fixing nip where the pressure rollers 47B and 48B abut in the rotational direction of the thermal transfer members 47A and 48A. As a result, the temperature of the region where the thermal transfer members 47A and 48A carry and carry the toner can be made higher than the other regions, and the toner on the thermal transfer member can be reliably softened or melted. Further, if the toner contains a magnetic material, the toner itself can generate heat when the toner passes through the IH coils 47C and 48C. Thereby, the toner can be reliably softened or melted. The content of the magnetic substance in the toner is preferably 30 [wt%] or more. If it is less than 30 [wt%], the heat generation effect of the toner is hardly obtained.

The volume resistance of the surface layers of the thermal transfer members 47A and 48A is preferably 10 ⁹ [Ωcm] or less, and the resistance is preferably reduced. By making the surface layer have a low resistance, an electromagnetic induction current can easily flow, and the thermal transfer members 47A and 48A can be efficiently heated. In addition, the heat transfer efficiency of the thermal transfer members 47A and 48A can be increased by including a magnetic material in the surface layer. The content of the magnetic material is preferably 30 [Wt%] or more by weight. If the content of the magnetic material is less than 30 [Wt%], sufficient heat generation cannot be obtained.

  Further, the heat generation amount of the thermal transfer members 47A and 48A may be adjusted according to the image to be formed. Specifically, only when the toner passes through the IH coils 47C and 48C, the IH coils 47C and 48C are turned on to cause the thermal transfer bodies 47A and 48A to generate heat. The ON / OFF switching timing is provided, for example, by providing toner detection means upstream of the IH coils 47C and 48C, and when the toner detection means detects toner, the IH coils 47C and 48C are turned ON, and the thermal transfer body 47A, Heat 48A. Further, the IH coils 47C and 48C may be turned on and off in synchronization with the image information. In addition, since there is a case where the amount of heat for sufficiently melting or softening the toner cannot be obtained with one IH coil 47C, 48C, recording is performed from the transfer nip facing the intermediate transfer belt as shown by the dotted line in FIG. A plurality of IH coils (47D, 47E), (48D, 48E) may be provided between the transfer / fixing nip facing the medium. Then, each IH coil is turned on and off in synchronization with the image information. As described above, by arranging the plurality of IH coils, the toner can be surely softened or melted. The present invention is not limited to this, and the amount of heat generated by the thermal transfer members 47A and 48A may be changed by changing the amount of current flowing through the IH coils 47C and 48C in accordance with the image information to vary the generated magnetic force. In this case, in the case of an image with a large amount of toner, such as an image with a large image area ratio or an image mainly composed of an image, the amount of current flowing through the IH coils 47C and 48C is increased to generate heat from the thermal transfer members 47A and 48A. Increase the amount. On the other hand, in the case of an image with a small amount of toner, such as an image with a small image area ratio or an image mainly composed of characters, the amount of heat generated by the thermal transfer members 47A and 48A is reduced by reducing the amount of current flowing to the IH coils 47C and 48C. Reduce.

  Further, for the transfer from the intermediate transfer belts 21 and 31 to the thermal transfer members 47A and 48A, an electrostatic transfer system or a thermal transfer system can be used, but it is preferable to use a thermal transfer system. By using the thermal transfer method, even when transferring from the intermediate transfer belts 21 and 31 to the thermal transfer members 47A and 48A, it is possible to prevent the occurrence of dust and blemishes due to the discharge at the transfer nip entrance and the exit and the influence of the electric field. In addition, the toner image on the intermediate transfer belt is transferred to the thermal transfer body 47A by the excess heat of the thermal transfer bodies 47A and 48A heated to heat and soften or melt the toner on the thermal transfer body to transfer and fix it on the recording medium. Thermal transfer to 48A is possible, and there is no need to add a new heat source for thermal transfer from the intermediate transfer belts 21 and 31 to the thermal transfer members 47A and 48A. If good heat transfer is not performed due to this surplus heat, as shown by the dotted line in the figure, the heat transfer between the intermediate transfer belts 21 and 31 and the heat transfer members 47A and 48A downstream of the heat transfer / fixing nip in the heat transfer member rotation direction. IH coils 47F and 48F are also provided upstream of the position. As a result, even if the recording medium and the pressure rollers 47B and 48B are deprived of heat at the thermal transfer / fixing nip, the thermal transfer members 47A and 48A are heated by the IH coils 47F and 48F provided on the downstream side. As a result, even when the thermal transfer members 47A and 48A come to the thermal transfer position between the intermediate transfer belts 21 and 31 and the thermal transfer members 47A and 48A, they have a sufficient amount of heat and soften or melt the toner on the intermediate transfer belt. The toner can be thermally transferred to the thermal transfer members 47A and 48A satisfactorily. Further, as described above, if the surface layer contains a magnetic material, the surface layer itself generates heat and has a sufficient amount of heat. Therefore, the toner on the intermediate transfer belt is softened or melted well, and the thermal transfer body 47A. , 48A can be transferred to the toner well.

  In the present embodiment, the toner images on the intermediate transfer belts 21 and 31 are temporarily transferred to the thermal transfer members 47A and 48A, and the thermal transfer members 47A and 48A are heated, so that the toner images are softened or melted to be recorded. In addition, thermal transfer and fixing are performed. As a result, the intermediate transfer belts 21 and 31 can thermally transfer and fix the toner image without being directly heated. Therefore, the temperature increase of the intermediate transfer belts 21 and 31 is suppressed, and it is possible to suppress the occurrence of a problem in the process unit due to the heat of the intermediate transfer belts 21 and 31. In this embodiment, the toner images carried on the thermal transfer members 47A and 48A are heated and softened or melted in the process of being conveyed to the transfer / fixing nip. In a method in which a toner image is softened or melted at a fixing nip and fixed on a recording medium as in a conventional fixing device, the recording medium loses heat, and the amount of heat for softening or melting the toner increases. However, in this embodiment, since only the toner is heated and softened or melted on the thermal transfer body before being transported to the transfer / fixing nip, the recording body and the toner are simultaneously heated in the conventional fixing nip. Less heat is required to soften or melt the toner. As a result, power consumption can be suppressed, energy saving and temperature rise in the apparatus can be suppressed. Further, since the amount of heat applied to the recording body can be reduced as compared with a conventional fixing nip in which the recording body and toner are heated at the same time, the temperature of the discharged paper can be lowered. Therefore, it is possible to suppress the problem that the toner after fixing sticks to another recording medium even during high-speed printing.

  In the example shown in FIG. 5, the heat source is composed of IH coils 47C and 48C and a heat generating layer made of a magnetic material of thermal transfer bodies 47A and 48A, and is heated by an electromagnetic induction method. Since the electromagnetic induction method has good heating responsiveness, it has good energy efficiency and can achieve significant energy saving.

  In the double-sided transfer means 50 shown in FIG. 5, the first toner image is transferred and fixed on the upper surface of the recording medium, and then the second toner image is transferred and fixed on the lower surface of the recording medium. I can't. For example, as shown in FIG. 6, the first toner image and the second toner image may be simultaneously transferred and fixed on the recording medium.

  In the modification of the double-sided transfer means 50 shown in FIG. 6, a first transfer / fixing unit 47 and a second transfer / fixing unit 48 are provided to face each other across a recording medium conveyance path. The first transfer / fixing unit 47 includes a first thermal transfer member 47A and a first IH coil 47C. The second transfer / fixing unit 48 includes a second thermal transfer member 48A and a second IH coil 48C. Then, the first thermal transfer member 47A and the second thermal transfer member 48A are in contact with each other to form a thermal transfer / fixing nip. That is, in this case, the pressing means of the first transfer / fixing unit 47 is the second thermal transfer body 48A, and the pressing means of the second transfer / fixing unit 48 is the first thermal transfer body 47A. ing.

  The first toner image on the first intermediate transfer belt is thermally transferred to the first thermal transfer body 47A, and is conveyed to the thermal transfer / fixing nip by the first thermal transfer body 47A while being softened or melted by the heat of the thermal transfer body 47A. On the other hand, the second toner image on the second intermediate transfer belt is thermally transferred to the second thermal transfer member 48A, and is conveyed to the thermal transfer / fixing nip by the second thermal transfer member 48A while being softened or melted by the heat of the thermal transfer member 48A. Then, the first toner image and the second toner image are simultaneously conveyed to the thermal transfer / fixing nip, and the toner images are transferred / fixed on both sides of the recording medium by the pressure of the first thermal transfer body 47A and the second thermal transfer body 48A. .

  In the present embodiment, the thermal transfer body is in the form of a roller, but may be in the form of a belt. In this case, it is assumed that the heat transfer body has a heat-resistant resin film as a base, a heat generation layer similar to the above is provided on the surface of the resin film, and a surface layer similar to the above is provided on the surface of the heat generation layer. By making the thermal transfer member into a belt shape, the degree of freedom of layout can be increased, the width of the transfer / fixing nip can be increased, and the fixing margin can be increased.

  In the present embodiment, the heat source is composed of the IH coils 47C and 48C and the heat generation layer made of the magnetic material of the thermal transfer members 47A and 48A, and the heating method using electromagnetic induction is used. The heat source may be composed of a halogen lamp, a ceramic heater, or the like, and a heating method using radiant heat may be used. By providing a heat source such as a halogen lamp or ceramic heater at a position facing the surface of the thermal transfer member, the radiant heat from the halogen lamp or ceramic heater directly hits the toner on the surface of the thermal transfer member, so that the toner is efficiently heated. be able to.

  Further, as shown in FIG. 7, a heat source such as a halogen lamp or a ceramic heater may be provided inside the thermal transfer member. By providing the heat source inside the thermal transfer body, space can be saved and the degree of freedom in layout can be increased. Further, the IH coil may be disposed inside the thermal transfer body.

Next, features of the present embodiment will be described. Since the thermal transfer member is heated to a high temperature in order to soften or melt the toner image transferred to the thermal transfer member, the surface layer of the thermal transfer member deteriorates with time due to heat. When the surface layer is deteriorated by heat, the hardness is decreased, and the surface is damaged by toner or the like, or the filming of the toner occurs, resulting in an image defect. When such an image defect is confirmed, the user calls a service man, and the service man needs to replace the transfer / fixing unit provided with the thermal transfer member.
Conventionally, an image surface of a document is formed such that an image recorded on the front surface of the document is formed by the first image forming unit, and an image recorded on the back surface of the document is formed by the second image forming unit. The image forming unit used for (the front surface and the back surface) has been set in advance. For this reason, depending on the form of use, the thermal load applied to the first thermal transfer member differs from the thermal load applied to the second thermal transfer member, and one of the thermal transfer members deteriorates faster than the other thermal transfer member. End up. This is because an image with a large amount of toner adhesion increases the heat amount of the heat source in order to surely soften or melt the toner on the thermal transfer body, and an image with a small amount of toner adhesion indicates the heat amount of the heat source for energy saving. Is reduced. For this reason, when a large amount of documents having an image with a large amount of toner adhesion on the front side and an image with a small amount of toner adhesion on the back side is printed, the first transfer / fixing unit 47 is replaced by the second transfer / fixing unit 48. It will deteriorate sooner. Further, even when a large amount of originals with images formed on the surface are printed, the first transfer / fixing unit 47 deteriorates faster than the second transfer / fixing unit 48. This is because, in the case of single-sided printing, the heat source of the transfer / fixing unit that is not used is OFF, and no thermal load is applied to the thermal transfer body. As described above, when the first transfer / fixing unit 47 and the second transfer / fixing unit 48 are in different deterioration states, the replacement time is different. As a result, for example, the second transfer / fixing unit 48 is deteriorated and needs to be replaced before a sufficient period elapses after the first transfer / fixing unit 47 is replaced. Downtime due to replacement often occurs.
Therefore, in the present embodiment, the deterioration state of the first transfer / fixing unit 47 and the deterioration state of the second transfer / fixing unit 48 are detected, and the first image formation is performed based on the detection result and the image information. The image formed by the unit 20 and the image formed by the second image forming unit 30 are determined. This will be specifically described below.

  FIG. 8 is a block diagram illustrating a part of the control unit of the printer. In the figure, a control unit 110 serving as control means controls the entire apparatus. Various devices in the printer are connected to the control unit 110. In the figure, some of these devices are shown. That is, the control unit 110 includes an image information input unit 111, a first image forming unit 20, and a first transfer / fixing unit that are image information input means for inputting image information from an automatic image reading apparatus (ADF) 200, a personal computer, or the like. The second drive control unit 116 as the second drive control unit for controlling the drive of the first drive control unit 115 as the first drive control unit for controlling the drive of the 47, the second image forming unit 30 and the second transfer / fixing unit 48. Is connected. The image information input unit 111 transmits the input image information X on the front side of the document and the input image information Y on the back side of the document to the control unit 110. The control unit 110 is connected to a storage unit 112 serving as a storage unit, and the storage unit 112 detects a first deterioration state as a first deterioration state detection unit that detects a deterioration state of the first transfer / fixing unit 47. The unit 113 is connected to a second deterioration state detection unit 114 as second deterioration state detection means for detecting the deterioration state of the second transfer / fixing unit 48. The storage unit 113 stores the deterioration state A of the first transfer / fixing unit detected by the first deterioration state detection unit 113 and the deterioration state B of the second transfer / fixing unit detected by the second deterioration state detection unit 114. is doing.

The control unit 110 includes a ROM that stores various control programs, a RAM that is a working memory for executing the control programs, a CPU for executing the programs, and the like. The ROM stores a comparison program for reading the deterioration state A of the first transfer / fixing unit 47 and the deterioration state B of the second transfer / fixing unit 48 stored in the storage unit 112 and comparing the deterioration states. Yes. The comparison program is executed using the CPU and RAM, and the control unit 110 functions as a deterioration state comparison unit.
In addition, the ROM inputs the image input to the image information input unit 111 based on the comparison result obtained by executing the comparison program and the image information obtained from the image information input unit 111 to the first image formation. A selection program for selecting whether to form by the unit 20 or the second image forming unit 30 is also stored. The selection program is executed using a CPU and a RAM, and the control unit 110 functions as a selection unit.

Next, the deterioration state of the first transfer / fixing unit 47 and the deterioration state of the second transfer / fixing unit 48 are detected, and the first image forming unit 80 forms based on the detection result and the image information. A flow from determining an image to be formed and an image formed by the second image forming unit 30 to forming an image will be described.
FIG. 9 is a control flow chart until the printer image is formed. First, image information X on the front side of the document and image information Y on the back side of the document are input to the image information input unit 111 from an automatic image reading apparatus (ADF) 200 or a personal computer. The image information input unit 111 transmits the input image information X on the front side of the document and image information Y on the back side of the document to the control unit 110, and the control unit 110 transmits the image information X on the front side of the document and the back side of the document. The image information Y is acquired (S1). When the control unit 110 acquires the image information X and Y, the control unit 110 acquires the deterioration state A of the first transfer / fixing unit 47 and the deterioration state B of the second transfer / fixing unit 48 from the storage unit 112 (S2). ). Next, based on the acquired image information X and Y and the acquired deterioration states A and B, the control unit 110 forms an image on the front side of the document and an image formation that forms an image on the back side of the document. A unit is selected (S3). When the image forming unit is selected, the image information formed by the first image forming unit 20 is output to the first drive control unit 115, and the image information formed by the second image forming unit 30 is output to the second drive control unit 116. Output (S4).

  Next, detection examples of the deterioration state of the first transfer / fixing unit 47 and the deterioration state of the second transfer / fixing unit 48 will be described with reference to the first to fourth embodiments.

[Example 1]
First, the detection of the deterioration state of Example 1 will be described. In the first embodiment, the deterioration state is detected from the total power consumption obtained by time-integrating the power consumption of the heat source, that is, the total heat amount. This is because the thermal transfer member is deteriorated by heat in proportion to the total heat quantity of the heat source. Therefore, if the total heat quantity of the heat source is known, the degree of deterioration of the thermal transfer body can be indirectly detected. The total amount of heat is the total amount of power consumed and equal, and the amount of power consumed can be represented by the product of the power consumed when heating the heat source and its heating (driving) time. If this power consumption (the product of the power for heating the heat source and its heating (driving) time) is counted for each heating timing, the total power consumption, that is, the total heat can be obtained. The power consumption can be easily measured by using an ammeter. Further, when the heat source is a halogen lamp or a ceramic heater, the heating (driving) time corresponds to the energization time of these heating elements. When the heat source is composed of an IH coil and a heat generating layer, the application time of the alternating current applied to the IH coil corresponds to the heating (driving) time. The obtained total power consumption (total heat amount) is stored in the storage unit 112 as deterioration information of the transfer / fixing unit.

[Example 2]
Next, Example 2 will be described. As shown in FIG. 5, when the heat sources of the first transfer / fixing unit 47 and the second transfer / fixing unit 48 are the same, the heating (driving) time of the heat source appears as a difference in the total amount of heat. Therefore, when the heat sources of the first transfer / fixing unit 47 and the second transfer / fixing unit 48 are the same, the deterioration state of the thermal transfer member can be detected from the integrated value of the heating (driving) time of the heat source. In this case, the time is counted for each heating timing, and the accumulated count time is stored in the storage unit 112.

[Example 3]
Next, Example 3 will be described. In the third embodiment, the thermal deterioration state of the transfer / fixing unit is detected from the pixel count value of the image formed by the image forming unit corresponding to the transfer / fixing unit. In the present embodiment, as described above, the amount of heat of the thermal transfer body is changed based on the image information. In an image having a large pixel count value, a larger amount of toner adheres to the thermal transfer body, so that the amount of heat to the thermal transfer body is increased in order to soften or melt the toner. On the other hand, an image having a small pixel count value has a small amount of toner adhering to the thermal transfer member, and therefore, the amount of heat to the thermal transfer member for softening or melting the toner can be reduced. Thus, since the amount of heat applied to the thermal transfer body varies depending on the pixel count value of the image to be formed, by integrating this pixel count value, the amount of heat applied to the thermal transfer body can be grasped indirectly, The thermal degradation of the thermal transfer body can be grasped from the grasped heat quantity. Note that the pixel count value of the formed image can be grasped from the total number of pixels to be written by the exposure apparatus. For example, when the exposure apparatus is a laser diode (LD), the pixel count value is obtained by integrating the LD lighting time for each main scanning line direction by the sub-scanning line direction of the image. Further, since it is necessary to integrate pixel count values corresponding to the amount of toner attached to the thermal transfer body, the integrated values of the pixel count values of the process units Y, M, C, and K are stored in the storage unit 112.

[Example 4]
In the fourth embodiment, the state of deterioration of the transfer / fixing unit due to heat is detected from the amount of toner attached to the thermal transfer cleaning roller that removes the transfer residual toner on the thermal transfer body. When the amount of toner transferred to the thermal transfer body is large, the amount of toner remaining as a transfer residual increases as compared with a toner with a small amount of toner. As a result, the residual transfer toner adhering to the thermal transfer cleaning roller is larger when an image with a large amount of toner is transferred than when an image with a small amount of toner is transferred. As a result, the amount of toner adhering to the thermal transfer cleaning roller of the transfer / fixing unit to which a large amount of toner is transferred adheres to the thermal transfer cleaning roller of the transfer / fixing unit to which a large amount of toner is transferred. Increased compared to the amount of toner present. Therefore, if the amount of toner adhering to the first cleaning roller 47G of the first transfer / fixing unit 47 and the amount of toner adhering to the second cleaning roller 48G of the second transfer / fixing unit 48 are viewed, You can see the transfer / fixing unit that transferred a large amount of toner. The transfer / fixing uni, which has transferred a large amount of toner, has a larger amount of heat than a transfer / fixing unit that has transferred a large amount of toner to soften or melt the toner of the image with a large amount of toner. It is deteriorated thermally. Therefore, by looking at the amount of toner adhering to the cleaning roller, it is possible to indirectly grasp the thermal deterioration state of the transfer / fixing unit.

  FIG. 10 is a main part configuration diagram of an image forming apparatus using the method of detecting a deterioration state according to the fourth embodiment. As shown in FIG. 10, reflection type optical sensors 55 and 65 comprising light receiving elements 55a and 56a and light emitting elements 55b and 56b, respectively, at positions facing the first cleaning roller 47G and positions facing the second cleaning roller 48G. Is provided. When the transfer residual toner adhering to the cleaning roller is small, the reflectance is high, so that a large amount of light is detected by the light receiving elements 55a and 56a of the reflection type optical sensors 55 and 56. When the transfer residual toner adhering to the cleaning roller increases, the cleaning roller is colored by the transfer residual toner, so that the reflectance decreases and the amount of light detected by the light receiving elements 55b and 56b decreases. Therefore, the amount of toner adhering to the cleaning roller can be grasped from the amount of light detected by the light receiving elements 55a and 55b. The detection result of the reflection type optical sensor is stored in the storage unit 112.

  Next, based on the acquired image information X and Y and the acquired deterioration states A and B, a method for selecting an image forming unit for forming an image on the front side of the document and an image forming unit for forming an image on the back side of the document Will be described using Examples 5 to 8.

[Example 5]
First, an image forming unit selection method according to the fifth embodiment will be described. In the fifth embodiment, it is checked whether the image information input to the image information input unit 111 is only the front side or the back side of the document, that is, a single-sided image. An image is formed by an image forming unit corresponding to the transfer / fixing unit.
FIG. 11 is a control flow of image formation using the fifth embodiment. First, the control unit 110 checks whether the image is a single-sided image based on the image information acquired from the image information input unit 111 (S11). In the case of a double-sided image (NO in S11), the image information on the front side of the document and the image information on the back side are output to the drive control units 115 and 116, respectively (S18), and the image forming units 20 and 30 form the images. To do. On the other hand, in the case of a single-sided image, the control unit 110 acquires the deterioration state A of the first transfer / fixing unit 47 and the deterioration state B of the second transfer / fixing unit 48 from the storage unit 112 (S12). Next, the deterioration state A of the first transfer / fixing unit 47 is compared with the deterioration state B of the second transfer / fixing unit 48, so that the first transfer / fixing unit 47 deteriorates more than the second transfer / fixing unit 48. Is checked (S13). When the first transfer / fixing unit 47 is more deteriorated than the second transfer / fixing unit 48 (YES in S13), the control unit 110 selects the second image forming unit 30 (S14) and performs the second drive control. Image information is output to the unit 116 (S15). When the image information is input, the second drive control unit 116 drives the second image forming unit 30 and the second transfer / fixing unit 48 to record an image on the second surface of the recording medium. The recording body on which the image is recorded is sent to the reversing unit 90 and reversed (S16). At this time, since image information is not output to the first drive control unit 115, the first transfer / fixing unit 47A and the first image forming unit 20 are not driven. Therefore, the first transfer / fixing unit 47 is hardly subjected to stress by the heat source.
On the other hand, when the first transfer / fixing unit 47 is not deteriorated compared to the second transfer / fixing unit 48 (NO in S13), the control unit 110 selects the first image forming unit 20 (S17). Then, image information is output to the first drive control unit (S18), and the first image forming unit 20 and the first transfer / fixing unit 47 are driven to record an image on the first surface of the recording medium. At this time, since image information is not output to the second drive control unit 116, the second transfer / fixing unit 48 and the second image forming unit 30 are not driven. Therefore, the second transfer / fixing unit 48 hardly receives stress due to the heat source.

  Thus, in the case of a single-sided image, an image is formed by an image forming unit corresponding to the transfer / fixing unit that has not deteriorated, and the transfer / fixing unit that has been deteriorated is driven. It has stopped. Thereby, the progress of the deterioration of the transfer / fixing unit in which the deterioration is progressing can be suppressed, and the life of the transfer / fixing unit can be extended. In the case of a single-sided image, thermal degradation of the transfer / fixing unit proceeds evenly by forming an image with an image forming unit corresponding to the transfer / fixing unit that has not deteriorated. Thus, the life of the thermal transfer member can be made almost simultaneously.

[Example 6]
Next, Example 6 will be described. In the sixth embodiment, whether the image input to the image information input unit 111 is a single color image or a color image is checked, the image on one side of the document is a color image, and the image on the other side of the document is a single color image. In this case, an image forming unit corresponding to the transfer / fixing unit whose deterioration has progressed is selected as the image forming unit for forming a monochrome image. Whether the input image is a color image can be determined from the image information, and can also be determined from the image forming mode selected by the user.

  FIG. 12 is a control flow of image formation using the sixth embodiment. First, based on the image information acquired from the image information input unit 111, the control unit 110 checks whether the image on one side of the document is a color image and the image on the other side of the document is a single color image (S21). . By checking the set image mode and checking whether the image formation mode on one side of the original is the color mode and the image formation mode on the other side of the original is the single color mode, It is also possible to check whether the image on one side is a color image and the image on the other side of the document is a single color image. If the images on both sides of the document are single color or color images (NO in S21), the image information on the front side and the image information on the back side of the document are output to the drive control units 115 and 116, respectively (S26). The image forming unit forms an image.

  On the other hand, when one image of the document is color and the other image is monochromatic (YES in S21), the control unit 110 reads the deterioration state A of the first transfer / fixing unit 47 from the storage unit 112 and the second transfer / fixing unit. 48 degradation state B is acquired (S22). Next, the deterioration state A of the first transfer / fixing unit 47 is compared with the deterioration state B of the second transfer / fixing unit 48, so that the first transfer / fixing unit 47 deteriorates more than the second transfer / fixing unit 48. Is checked (S23). When the first transfer / fixing unit 47 is not deteriorated compared to the second transfer / fixing unit 48 (NO in S23), the control unit 110 selects the second image forming unit 30 as an image forming unit for forming a monochrome image. (S24). Next, the control unit 110 outputs the image information of the single color image to the second drive control unit 116, and outputs the image information of the color image to the first drive control unit 115 (S26). Then, the second image forming unit 30 and the second transfer / fixing unit 48 record the monochrome image on the second surface of the recording medium by performing drive control based on the inputted monochrome image information. Specifically, among the Y, M, C, and K process units 81, driving of the three unused process units 81 is stopped, and the three unused process units 81 are separated from the second intermediate transfer belt 31. Further, the heat amount of the heat source of the second transfer / fixing unit 48 is made smaller than the heat amount at the time of color image formation. Similarly, the first image forming unit 20 and the first transfer / fixing unit 47 record the color image on the first surface of the recording medium by performing drive control based on the input color image information.

  On the other hand, when the first transfer / fixing unit 47 is more deteriorated than the second transfer / fixing unit 48 (YES in S23), the control unit 110 uses the first image forming unit 20 as an image forming unit for forming a monochrome image. Select (S25). Next, the control unit 110 outputs the image information of the single color image to the first drive control unit 115, and outputs the image information of the color image to the second drive control unit 116 (S26). Then, the first image forming unit 20 and the first transfer / fixing unit 47 record the single color image on the first surface of the recording medium by performing drive control based on the input single color image information. Specifically, among the Y, M, C, and K process units 80, driving of the three unused process units 80 is stopped, and the three unused process units 80 are separated from the first intermediate transfer belt 21. Further, the heat amount of the heat source of the first transfer unit 47 is made smaller than the heat amount at the time of color image formation. Similarly, the second image forming unit 30 and the second transfer / fixing unit 48 record the color image on the second surface of the recording medium by performing drive control based on the input color image information.

  When the image information is output to the first drive control unit 115 and the second drive control unit 116, the control unit 110 checks whether the image information output to the first drive control unit 115 is the image information X on the surface of the document. . When the image information output to the first drive control unit 115 is the image information Y on the back side of the document (NO in S27), the recording body on which the images are recorded on both sides is reversed by the reversing unit 90 (S28). ,Discharge. On the other hand, when the image information output to the first drive control unit 115 is the image information X on the surface of the document (YES in S27), the recording medium is discharged as it is without being inverted.

  In the sixth embodiment, a single color image is formed by an image forming unit corresponding to the transfer / fixing unit whose deterioration has progressed. Since the monochrome image has a smaller amount of toner adhering than the color image, the toner on the thermal transfer member can be softened or melted with a small amount of heat. For this reason, when a single color image is formed, the amount of heat of the heat source of the transfer / fixing unit is reduced compared to the time of color image formation. For this reason, the thermal load on the transfer / fixing unit is less when forming a monochrome image than when forming a color image. Therefore, when copying a document with one color image and the other monochrome image, the deterioration is advanced by forming a monochrome image with the image forming unit corresponding to the transfer / fixing unit that has been deteriorated. The progress of deterioration of the transfer / fixing unit can be suppressed. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.

[Example 7]
Next, Example 7 will be described. In the seventh embodiment, it is checked whether an image input to the image information input unit 111 is an image-based image or a character-based image. When the image on one side of the document is an image-based image and the image on the other side of the document is a character-based image, the image transfer unit that forms a character-based image is transferred with the image being deteriorated. An image forming unit corresponding to the fixing unit is selected. Whether the input image is mainly an image image or a character image can be determined from the input image information. Since the image-based image has more pixels than the character-based image, the number of pixels of the input image is counted, and if it is greater than or equal to a predetermined value, it is determined as an “image-based image” and is less than or equal to the predetermined value. In this case, it is determined as “a character-based image”. It can also be determined from the image forming mode selected by the user. For example, if the mode is selected so that the input image is formed in the color mode, the image is determined to be the main image, and the mode is selected so that the input image is formed in the single color mode. If so, it is determined that the image is mainly composed of characters. In addition, when an image mode and a character mode are provided in the image formation mode and the mode is selected so that the input image is formed in the image mode, the image is determined to be the main image and the input is performed. When the mode is selected so that the formed image is formed in the character mode, it is determined that the image is mainly composed of characters.

  FIG. 13 is a control flow of image formation using the seventh embodiment. First, the control unit 110 checks whether the image on one side of the document is an image-based image and the image on the other side of the document is a character-based image (S31). If the images on both sides of the document are character-based images or image-based images (NO in S31), the image information on the front side of the document and the image information on the back side are output to the drive control units 115 and 116, respectively. (S26) The image forming units 20 and 30 form images.

  On the other hand, if one image of the document is an image-based image and the other image is a character-based image (YES in S31), the control unit 110 reads the deterioration state A and the first transfer / fixing unit 47 from the storage unit 112. The deterioration state B of the second transfer / fixing unit 48 is acquired (S32). Next, the deterioration state A of the first transfer / fixing unit 47 is compared with the deterioration state B of the second transfer / fixing unit 48, so that the first transfer / fixing unit 47 deteriorates more than the second transfer / fixing unit 48. Is checked (S33). When the first transfer / fixing unit 47 is not deteriorated compared to the second transfer / fixing unit 48 (NO in S33), the control unit 110 uses the second image forming unit 30 as an image forming unit for forming a character-based image. Select (S34). Next, the control unit 110 outputs the image information of the character-based image to the second drive control unit 116, and outputs the image information of the image-based image to the first drive control unit 115 (S36). Then, the second image forming unit 30 and the second transfer / fixing unit 48 perform drive control based on the inputted character-based image information and record a character-based image on the second surface of the recording medium. Specifically, the heat amount of the heat source of the second transfer unit is made smaller than the heat amount at the time of image formation mainly of the image. Similarly, the first image forming unit 20 and the first transfer / fixing unit 47 record the image-based image on the first surface of the recording body by performing drive control based on the input image-based image information. .

  On the other hand, when the first transfer / fixing unit 47 is more deteriorated than the second transfer / fixing unit 48 (YES in S33), the control unit 110 uses the first image forming unit as an image forming unit for forming a character-based image. 20 is selected (S35). Next, the control unit 110 outputs image information based on text to the first drive control unit 115 and outputs image information based on image to the second drive control unit 116 (S26). Then, the first image forming unit 20 and the first transfer / fixing unit 47 record the character-based image on the first surface of the recording body by performing drive control based on the input character-based image information. Specifically, the heat amount of the heat source of the first transfer unit 47 is made smaller than the heat amount at the time of image formation mainly of the image. Similarly, the second image forming unit 30 and the second transfer / fixing unit 48 record the image-based image on the second surface of the recording body by performing drive control based on the input image-based image information. .

  When the image information is output to the first drive control unit 115 and the second drive control unit 116, the control unit 110 checks whether the image information output to the first drive control unit 115 is the image information X on the surface of the document. . When the image information output to the first drive control unit 115 is the image information Y on the back side of the document (NO in S37), the recording body on which images are recorded on both sides is reversed by the reversing unit 90 (S38). ,Discharge. On the other hand, when the image information output to the first drive control unit 115 is the image information X on the surface of the document (YES in S37), the recording medium is discharged without being inverted.

  Since a character-based image has a smaller amount of toner adhering than an image-based image, the toner on the thermal transfer member can be softened or melted with a small amount of heat. For this reason, when a character-based image is formed, the amount of heat of the heat source of the thermal transfer body unit is reduced compared to the image-based image formation. Therefore, when a character-based image is formed, the thermal load on the transfer / fixing unit is smaller than when an image-based image is formed. Therefore, when printing one image-based image and the other character-based image, the image-based image is formed by the image forming unit corresponding to the transfer / fixing unit that has been deteriorated. It is possible to suppress the progress of deterioration of the transfer / fixing unit that is advanced. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.

[Example 8]
Next, Example 8 will be described. In the eighth embodiment, an image forming unit that detects an image area ratio of an image input to the image information input unit 111 and forms an image with a small image area ratio is used as a transfer / fixing unit that has been deteriorated. A corresponding image forming unit is selected. The image area ratio can be detected by counting the number of pixels of the input image.

  FIG. 14 is a control flow of image formation using the eighth embodiment. First, the control unit 110 detects the image area ratio of the image on one side of the document and the image area ratio of the other side of the document (S41). When the image area ratio is detected, the control unit 110 acquires the deterioration state A of the first transfer / fixing unit 47 and the deterioration state B of the second transfer / fixing unit 48 from the storage unit 112 (S42). Next, the deterioration state A of the first transfer / fixing unit 47 is compared with the deterioration state B of the second transfer / fixing unit 48, so that the first transfer / fixing unit 47 deteriorates more than the second transfer / fixing unit 48. Is checked (S43). When the first transfer / fixing unit 47 is not deteriorated as compared with the second transfer / fixing unit 48 (NO in S43), the control unit 110 uses the second image forming unit as an image forming unit that forms an image with a small image area ratio. 30 is selected (S44). Next, the control unit 110 outputs image information of an image having a small image information area ratio to the second drive control unit 116 among the input image information, and the image information of the image having a large image area ratio is first. It outputs to the drive control part 115 (S46). Then, the second image forming unit 30 and the second transfer / fixing unit 48 record the image on the second surface of the recording body by performing drive control according to the image area ratio of the image. Specifically, the heat amount of the heat source of the second transfer unit is changed according to the image area ratio. Similarly, the first image forming unit 20 and the first transfer / fixing unit 47 also record the image on the first surface of the recording medium by performing drive control based on the image area ratio of the input image.

  On the other hand, when the first transfer / fixing unit 47 is more deteriorated than the second transfer / fixing unit 48 (YES in S43), the control unit 110 forms the first image as an image forming unit that forms an image with a small image area ratio. The forming unit 20 is selected (S45). Next, the control unit 110 outputs image information of an image having a small image information area ratio to the first drive control unit 115 among the input image information, and outputs image information of an image having a large image area ratio to the second. It outputs to the drive control part 116 (S46). Then, the first image forming unit 20 and the first transfer / fixing unit 47 record the image on the first surface of the recording medium by performing drive control based on the inputted sentence image area ratio. Specifically, the heat amount of the heat source of the first transfer unit 47 is changed according to the image area ratio. Similarly, the second image forming unit 30 and the second transfer / fixing unit 48 also record the image on the second surface of the recording medium by performing drive control based on the image area ratio of the input image.

  When the image information is output to the first drive control unit 115 and the second drive control unit 116, the control unit 110 checks whether the image information output to the first drive control unit 115 is the image information X on the surface of the document. . When the image information output to the first drive control unit 115 is the image information Y on the back side of the document (NO in S37), the recording body on which images are recorded on both sides is reversed by the reversing unit 90 (S38). ,Discharge. On the other hand, when the image information output to the first drive control unit 115 is the image information X on the surface of the document (YES in S37), the recording medium is discharged without being inverted.

  The smaller the image area ratio, the smaller the amount of toner adhering to the thermal transfer body, so that the toner can be softened or melted with a small amount of heat. For this reason, if an image with a small image area ratio is formed by an image forming unit corresponding to a thermal transfer body in which deterioration has progressed among the images on the front side and the back side of the original, the transfer in which the deterioration is advanced -The progress of deterioration of the fixing unit can be suppressed. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.

  Note that the image formation control shown in the fifth to eighth embodiments may be performed in units of jobs that are one printing command, or may be performed every time a recording medium is printed. In Embodiments 5 to 8, when an image on the surface of the document is formed by the second image forming unit, the recording member is reversed by the reversing unit 90 and then discharged. Therefore, the discharged recording media can be discharged in a form arranged in a desired page order.

  Next, the image forming apparatus of the present embodiment using the deterioration state detection of any of Examples 1 to 4 and the image formation control of any of Examples 5 to 8 and the conventional image forming apparatus are respectively 5 We prepared each stand and examined the difference in the replacement time of the transfer / fixing unit. The transfer / fixing unit replacement time was visually determined, and when an image defect such as a black streak occurred, it was determined that the thermal transfer member was replaced. FIG. 15 shows the result. Here, “with control” indicates the image forming apparatus of the present embodiment, and “without control” indicates the conventional image forming apparatus. As shown in FIG. 15, the conventional “no control” image forming apparatus has approximately 100K sheets, and one of the first transfer / fixing unit and the second transfer / fixing unit has a lifetime. The transfer / fixing unit was replaced. On the other hand, the “controlled” image forming apparatus of the present embodiment does not reach the end of the life of the transfer / fixing unit even after printing 400K or more images, and extends the life of the transfer / fixing unit. I was able to. In the case of an image forming apparatus with “control”, the images on both sides deteriorate at almost the same time, and the replacement time of the first transfer / fixing unit and the replacement time of the second transfer / fixing unit are almost the same time. It was.

In the above-described embodiment, both the first transfer / fixing unit 47 and the second transfer / fixing unit 48 include the thermal transfer body, but the present invention is not limited to this. As shown in FIGS. 16 and 17, the present invention can be applied to an image forming apparatus in which only the second transfer / fixing unit 480 is provided with a thermal transfer body 481. The image forming apparatus shown in FIGS. 16 and 17 includes a transfer roller 471 serving as an electrostatic transfer unit that electrostatically transfers the toner image of the first intermediate transfer belt 21 to a recording body, and a recording body. A fixing member 472 as fixing means for fixing the toner on the upper surface by heat and pressure is used. The fixing member 472 is opposed to the thermal transfer body 481 with a predetermined pressure. Accordingly, the thermal transfer body 481 can function as a pressure member of the first transfer / fixing unit 470, and the fixing member 472 can function as a pressure member of the second transfer / fixing unit 480. Therefore, the number of pressing members can be reduced, and cost reduction can be achieved.
The image forming apparatus of FIG. 16 is provided with an IH coil 473 inside a fixing member 472. The fixing member 472 has a thin heat generating layer made of a magnetic material and heat resistance and toner releasability formed on the outer peripheral surface of the heat generating layer. And a surface layer having Then, the heat generating layer generates heat by the magnetic field generated by the IH coil 473 inside the fixing member, whereby the fixing member 472 generates heat, and the toner image electrostatically transferred to the first surface of the recording medium by the heat of the fixing member 471. Is fixed by being softened or melted.
The image forming apparatus shown in FIG. 17 is provided with an IH coil 472 and a heating element 474 made of a magnetic material upstream of the fixing member 472 in the recording material conveyance direction, and softens the toner image formed on the first surface of the recording material. Alternatively, after melting, the recording body is conveyed to the fixing member 472, and the toner image is fixed on the first surface of the recording body by the fixing member 472. As shown in FIG. 17, the heat source including the IH coil 473 and the heating element 474 is disposed upstream of the fixing member 472 in the recording material conveyance direction, so that the fixing member 472 is not significantly loaded with heat from the heat source. Deterioration of the fixing member can be suppressed.
When the toner image is fixed on the first surface of the recording member by the fixing member 472, the toner image softened or melted on the thermal transfer member is transferred and fixed on the second surface of the recording member.

  16 and 17, the fixing member 472 of the first transfer / fixing unit 470 and the thermal transfer body 481 of the second transfer / fixing unit 480 are subjected to thermal stress by the heat source and deteriorate. End up. Therefore, even in this case, the image formed on the first surface of the recording medium is an image with a large amount of toner adhesion, and the image formed on the second surface of the recording medium is printed in a large amount with a small amount of toner adhesion. In this case, the fixing member 472 deteriorates faster than the thermal transfer body 481. As a result, the replacement time of the first transfer / fixing unit 470 and the second transfer / fixing unit 480 is shifted, and downtime frequently occurs. Therefore, in the image forming apparatus shown in FIGS. 16 and 17, the deterioration progresses by comparing the deterioration state of the first transfer / fixing unit 470 with the deterioration state of the second transfer / fixing unit 480. The image forming unit corresponding to the transfer / fixing unit forms an image with a small amount of toner adhesion. Accordingly, also in the image forming apparatuses of FIGS. 16 and 17, the replacement timing of the first transfer / fixing unit 470 and the second transfer / fixing unit 480 can be made the same.

Next, a toner suitably used in the present embodiment will be described.
The image forming apparatus according to the present embodiment provides the user with the Y, M, C, and K toners used for forming the toner image so as to use any of the following conditions (a) to (e). Is specified.
(A) The weight average particle diameter is 3 to 8 [μm].
(B) A value obtained by dividing the weight average particle diameter D4 by the number average particle diameter D1 is 1.00 to 1.40.
(C) The shape factor SF-1 is 100 to 180.
(D) The shape factor SF-2 is 100 to 180.
(E) Fine particles having an average particle diameter of 50 to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more are held on the surface (externally added).
By using the toner having any of the above conditions (a) to (f), the thermal transfer from the intermediate transfer belt to the thermal transfer member and the thermal transfer from the thermal transfer member to the recording medium can be favorably performed.

  As a method for instructing the user to use such toner, for example, a toner having all of the above conditions (a) to (e) is packaged and shipped together with the image forming apparatus. Further, for example, the product number or product name of the toner may be specified in the image forming apparatus main body or the instruction manual. Further, for example, it may be performed by notifying the user of the product number, product name, etc. in writing or electronic data. Further, for example, it can be performed by shipping a toner bottle, which is a toner storage unit that stores such toner, in a state of being set in the main body of the image forming apparatus. The image forming apparatus employs all these methods, but it is sufficient to employ at least one of the methods.

  The reason why the toner satisfying the condition (a) is designated is as follows. In other words, when the toner has a weight average particle size smaller than 3 [μm], when used as a two-component developer, the toner is fused to the surface of the carrier during long-term agitation in the developing device, thereby reducing the charging ability of the carrier. Because. When used as a one-component developer, toner filming on the developing roller and toner fusion to a member such as a blade for thinning the toner are likely to occur.

  In the case of reproducing minute dots having a resolution of 600 dpi or more, the characteristic of a weight average particle diameter of 3 to 8 [μm] is particularly effective. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent. In addition, the micro voids between the toners when forming the toner image are reduced and the toner density in the toner image is increased (so-called solid filling is improved), so the thermal conductivity to the toner is improved and the toner is easily transferred during thermal transfer. Softens or melts. Thereby, the thermal transfer property of the toner is improved. Further, since the thermal conductivity is good, the toner of the toner image can be softened and melted with a small amount of heat, leading to energy saving and suppressing the thermal transfer body from being deteriorated by heat. In addition, when the weight average particle size is less than 3 [μm], phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur. Further, if the weight average particle diameter (D4) exceeds 8 [μm], it is difficult to suppress scattering of characters and lines.

  The reason why the toner satisfying the condition (b) is specified is as follows. That is, when the value obtained by dividing the weight average particle diameter by the number average particle diameter is in the range of 1.00 to 1.40, various merits are generated. For example, a phenomenon in which toner particles having a particle size suitable for an electrostatic latent image pattern contributes to development preferentially over other toners, so that various patterns of images can be stably formed. There is a merit that it becomes possible to do. In addition, when the apparatus adopts a configuration in which toner remaining on an image carrier such as a photoreceptor is collected and recycled, a large amount of small-size toner particles that are difficult to be transferred are recycled. In such recycling, when the above-mentioned one having a relatively large value is used, the development performance is adversely affected due to a large change in the toner particle size from the new toner supply to the next toner supply.

  The weight average particle diameter and number average particle diameter of the toner can be measured by a measuring device using a Coulter counter method, for example, Coulter Counter TA-II or Coulter Multisizer II (both manufactured by Coulter). Specifically, first, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. As the electrolytic aqueous solution, approximately 1% NaCl aqueous solution is prepared using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Further, 2 to 20 mg of a measurement sample is added to the obtained solution. Then, the solution is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the weight and number distribution of the toner are measured by using the 100 μm aperture as the aperture by the above-described measuring device, and the weight distribution and the number distribution are calculated. To do. From the obtained distribution, the weight average particle diameter and the number average particle diameter of the toner can be obtained. In addition, as a channel, it is less than 2.00-2.52 micrometer; 2.52-3.17 micrometer; 3.17-4.00 micrometer; 4.00-5.04 micrometer; 5.04-6.35 micrometer 6.35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to less than 12.70 μm; 12.70 to less than 16.00 μm; 16.00 to less than 20.20 μm; Intended for toner particles having a particle size of 2.00 μm to less than 40.30 μm using 13 channels of less than 25.40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm.

The reason why the toner having the above conditions (c) to (d) is specified is as follows. That is, the shape factor SF-1 and the shape factor SF-2 are parameters representing the shape of the toner, and are familiar parameters in the field of powder engineering. The shape factor SF-1 referred to here is a value indicating the degree of roundness in a spherical substance such as toner particles. As shown in FIG. 18, it is a value obtained by dividing the square of the length MXLNG of the maximum diameter portion in an elliptical figure obtained by projecting a spherical substance on a two-dimensional plane by the area AREA and further multiplying by 100π / 4. . That is, it can be expressed by an equation “shape factor SF-1 = {(MXLNG) ² / AREA} × (100π / 4)”. A spherical substance having a shape factor SF-1 of 100 is a true sphere, and the larger the value of SF-1, the more irregular the shape of the spherical substance.

The shape factor SF-2 is a numerical value indicating the degree of unevenness on the surface of the spherical substance. As shown in FIG. 19, it is a value obtained by dividing the square of the perimeter PERI of the figure obtained by projecting a spherical substance on a two-dimensional plane by the area AREA and further multiplying by 100 / 4π. In other words, the shape factor SF-2 can be expressed by a mathematical expression of “shape factor SF-2 = {(PERI) ² / AREA} × (100 / 4π)”. Note that the spherical material having a shape factor SF-2 of 100 has no irregularities on the surface. As the value of the shape factor SF-2 increases, the irregularities on the surface of the spherical substance become more prominent.

  It has been clarified by the present inventors that the transfer efficiency increases as the toner shape approaches a true sphere (both SF-1 and SF-2 approach 100). This is because the closer to the true sphere, the smaller the contact area between the toner particles and the thing (toner particles, image carrier, etc.) in contact with the toner particles, and the toner fluidity is increased. This is considered to be because the (mirror power) is weakened and is easily affected by the transfer electric field. Further, since the attractive force with the intermediate transfer belt is also reduced, the toner releasability is improved and the offset can be suppressed. According to the inventor's research, it has been clarified that when the shape factor SF-1 exceeds 180 or the shape factor SF-2 exceeds 180, the transfer efficiency starts to deteriorate rapidly. By setting each to 180 or less, a good transfer rate can be maintained. Also, the closer to the true sphere, the smaller the micro gap between the toner adhering on the recording paper and the higher the toner density in the toner image (so-called solid filling is improved), so the thermal conductivity to the toner is improved and the thermal transfer Sometimes the toner softens or melts easily. Thereby, the thermal transfer property of the toner is improved. Further, since the thermal conductivity is good, the toner of the toner image can be softened and melted with a small amount of heat, leading to energy saving and suppressing the thermal transfer body from being deteriorated by heat.

  The reason why the toner satisfying the condition (e) is specified is as follows. Due to the presence of fine particles having appropriate characteristics on the surface of the toner, an appropriate gap is formed between the toner particles and the thing (toner particles, image carrier, etc.) in contact therewith. Further, the fine particles have a very small contact area with toner particles, a photoreceptor, an intermediate transfer belt, and the like, and are in uniform contact. For this reason, the attraction force (mirroring power) to the object is weakened, the development / transfer efficiency is improved, and the dot reproducibility is improved. In addition, since the fine particles play a role of roller, they are buried in the toner particles even during cleaning under high stress (high load, high speed, etc.) between the cleaning blade and the photoconductor without wearing or damaging the photoconductor. Therefore, the toner can be detached and restored even if it is buried a little, so that stable toner characteristics can be maintained over a long period of time. Further, the fine particles are appropriately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing the toner from passing through the blade. Since these characteristics have an effect of reducing the share received by the toner particles, the filming effect of the toner itself due to the low rheological component contained in the toner is exhibited for high-speed fixing (low energy fixing). In addition, when fine particles having an average primary particle size in the range of 50 to 500 [nm] are used, the excellent cleaning performance can be fully utilized and the particle size of the toner is extremely small. Does not reduce fluidity. Further, although details are not clear, even when fine particles contaminate the carrier, the degree of developer deterioration is small. Therefore, since there is little change in the fluidity and chargeability of the toner over time, stable image quality is always formed.

The average primary particle size (hereinafter referred to as the average particle size) of the fine particles is 50 to 500 [nm], and particularly preferably 100 to 400 [nm]. If it is less than 50 [nm], the fine particles may be buried in the concave and convex portions of the unevenness of the toner surface, reducing the role of the rollers. On the other hand, when the particle size is larger than 500 [nm], when the fine particles are positioned between the blade and the surface of the photoreceptor, the toner particles are in the same order as the contact area of the toner itself, and the toner particles to be cleaned are allowed to pass through. It becomes easy to generate. In addition, when the bulk density is less than 0.3 [mg / cm ³ ], although there is a contribution to the improvement of fluidity, the scattering property and adhesion of the toner and fine particles are increased, so that the effect as a toner and a roller, A function such as a so-called dam effect that accumulates in the cleaning unit and prevents toner cleaning failure is reduced.

As the fine particles, inorganic compounds and organic compounds can be used. Examples of inorganic compounds include SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ , CaO. SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3 and the} like can be exemplified, and preferably SiO ₂ , TiO _2. Al ₂ O ₃ . Particularly, it preferred is SiO _2. These inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like.
The organic compound fine particles may be a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, Examples include urea resins, aniline resins, ionomer resins, and polycarbonate resins. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained. Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

The bulk density of the fine particles can be expressed by a mathematical formula: “bulk density (g / cm ³ ) = fine particle amount (g / 100 ml) ÷ 100”, and the fine particle amount was measured by the following method. Using a 100 ml graduated cylinder, fine particles were gradually added to make 100 ml. At that time, no vibration was applied. The amount of fine particles was measured by the difference in weight before and after the fine particles in the graduated cylinder were placed.

  The fine particles are externally added and adhered to the toner surface by a method in which the toner base particles and the fine particles are mechanically mixed and adhered using various known mixing devices, or the toner base particles in the liquid phase. There is a method in which fine particles are uniformly dispersed with a surfactant or the like, and are dried after an adhesion treatment.

(1)
As described above, according to the image forming apparatus of the present embodiment, it is possible to suppress the progress of the deterioration of the transfer / fixing unit whose deterioration has progressed. As a result, the period until the end of the life of the transfer / fixing unit can be extended, and the period for replacement can be extended. Therefore, the number of times of replacement of the transfer / fixing unit can be reduced. In addition, the deterioration of the first transfer / fixing unit and the deterioration of the second transfer / fixing unit proceed evenly, and the life of the thermal transfer body can be made almost simultaneously. As a result, the period in which the life of the first transfer / fixing unit is reached and the period in which the life of the second transfer / fixing unit is reached can be made substantially the same, and the replacement time can be made almost the same. Accordingly, the first transfer / fixing unit and the second transfer / fixing unit can be replaced at the same time, and the occurrence of downtime due to the replacement of the transfer / fixing unit can be suppressed.
(2)
As shown in the first embodiment, the deterioration state of the first transfer / fixing unit 47 is detected from the time integral value of the power consumption of the first heat source, and the deterioration state of the second transfer / fixing unit 48 is determined as the second transfer state. It is detected from the time integral value of the power consumption of the heat source. By integrating the power consumption of the heat source over time, the total power consumption, that is, the total heat amount can be obtained. Since the deterioration of the transfer / fixing unit due to heat is proportional to the total heat amount of the heat source, the deterioration state of the transfer / fixing unit can be indirectly detected by integrating the power consumption of the heat source over time.
(3)
Further, as shown in the second embodiment, when the first heat source and the second heat source have the same configuration, the power consumption is the same, so that the driving time of the heat source appears as a difference in the total heat amount. Therefore, when the heat sources of the first transfer / fixing unit 47 and the second transfer / fixing unit 48 are the same, the deterioration state of the thermal transfer body can be indirectly detected from the integrated value of the driving time of the heat source. As described above, when the first heat source and the second heat source have the same configuration, the deterioration state can be detected only by the time when the driving time of the heat source is counted by the counting means 40. Therefore, transfer / fixing is easier than in the first embodiment. The deterioration state of the unit can be detected.
(4)
Further, as shown in the third embodiment, the deterioration state of the transfer / fixing unit may be detected from the integrated value of the pixel count of the output image output to the image forming unit. In the present embodiment, the heat amount of the heat source is changed based on the image information. An image with a large pixel count value uses more toner to form a toner image than an image with a small pixel count value. For this reason, in the case of an image with a large pixel count value, since a large amount of toner must be softened or melted, the amount of heat of the heat source is increased. On the other hand, an image having a small pixel count value has a small amount of toner adhering to the thermal transfer body, and therefore, it is possible to reduce the amount of heat to the thermal transfer body for softening or melting the toner. Thus, since the heat amount of the heat source differs depending on the pixel count value of the image to be formed, the total heat amount indirectly applied to the thermal transfer body can be grasped by integrating the pixel count value. The deterioration state of the transfer / fixing unit can be detected from the grasped total heat quantity.
(5)
Further, in at least one of the first transfer / fixing unit 47 and the second transfer / fixing unit 48, the toner image on the intermediate transfer belt is once transferred to the thermal transfer member to heat the thermal transfer member. As a result, the toner image is softened or melted to perform thermal transfer and fixing on the recording medium. Accordingly, the toner image can be thermally transferred and fixed without directly heating the intermediate transfer belt. Therefore, the temperature rise of the intermediate transfer belt is suppressed, and it is possible to suppress the occurrence of problems in the process unit due to the heat of the intermediate transfer belt.
In addition, in a method in which a toner image is softened or melted at a fixing nip and fixed on a recording body as in a conventional fixing device, the amount of heat is deprived of the recording body, so that the amount of heat for softening or melting the toner increases. End up. However, in this embodiment, since only the toner is heated and softened or melted on the thermal transfer body before being transported to the transfer / fixing nip, the recording body and the toner are simultaneously heated in the conventional fixing nip. Less heat is required to soften or melt the toner. As a result, power consumption can be suppressed, energy saving and temperature rise in the apparatus can be suppressed. Further, since the amount of heat applied to the recording body can be reduced as compared with a conventional fixing nip in which the recording body and toner are heated at the same time, the temperature of the discharged paper can be lowered. Therefore, it is possible to suppress the problem that the toner after fixing sticks to another recording medium even during high-speed printing.
(6)
Also, by providing a thermal transfer body cleaning member that cleans the transfer residual toner on the thermal transfer body, transfer residual toner or paper powder that has not been transferred or fixed to the recording body is prevented from accumulating on the thermal transfer body. The surface of the thermal transfer member can be kept fresh for a long time.
(7)
Further, as shown in the fourth embodiment, the deterioration state due to heat of the transfer / fixing unit may be detected from the amount of toner attached to the thermal transfer cleaning roller for removing the transfer residual toner of the thermal transfer body. After transferring a toner image with a large amount of toner to be transferred / fixed by increasing the amount of heat from the heat source to the recording medium, the toner remaining after transfer to the recording medium is a toner image with a small amount of toner to be transferred / fixed by decreasing the amount of heat of the heat source More than the residual toner after transfer to the recording medium. Therefore, when the heat amount of the heat source is increased, the transfer residual toner adhering to the cleaning roller becomes larger than when the heat amount of the heat source is decreased. As described above, the transfer residual toner adhering to the cleaning roller differs depending on the heat amount of the heat source. Therefore, by detecting the amount of the transfer residual toner adhering to the cleaning roller, the total transfer / fixing unit is indirectly detected. The amount of heat can be detected, and the deterioration state of the transfer / fixing unit can be detected.
(8)
Further, as shown in FIG. 10, the first thermal transfer body 47A and the second thermal transfer body 48A are opposed to each other with the conveyance path of the recording body interposed therebetween, and the first thermal transfer body 47A and the second thermal transfer body 48A are set to a predetermined pressure. It is in contact with. Accordingly, the first thermal transfer body 47A can function as a pressure roller for the second thermal transfer body 48A, and the second transfer body 48A can function as a pressure roller for the first thermal transfer body 47A. The pressure roller can be eliminated, and the cost can be reduced. Also, because the thermal transfer members are in contact with each other and pressurize the other thermal transfer member, when only one of the transfer / fixing units is replaced, the other transfer / fixing unit's thermal transfer member is damaged and only one of them is transferred. -It is difficult to replace the fixing unit. However, in the present embodiment, since the life of the thermal transfer body is set to almost the same time, the first transfer / fixing unit 47 and the second transfer / fixing unit 48 can be exchanged at the same time, and the transfer can be easily performed. -The fixing unit can be replaced.
(9)
Also, as shown in FIGS. 16 and 17, the first toner image is directly transferred from the first intermediate transfer belt 21 as the first image carrier belt to the recording medium and fixed by the fixing member. Only the image is transferred from the second intermediate transfer belt 31 as the second image carrier belt to the thermal transfer member, and the thermal transfer from the thermal transfer member to the recording member is performed. Therefore, since the first toner image and the second toner image are thermally transferred and fixed to the recording medium, respectively, the number of thermal transfer bodies can be reduced as compared with the case where the respective thermal transfer bodies are provided. As a result, the cost can be reduced as compared with the case where each is provided with a thermal transfer member. In addition, space saving can be achieved by the amount of the thermal transfer body less than that provided with each thermal transfer body. Further, since the first intermediate transfer belt is not heated by the thermal transfer member, the thermal stress applied to the first intermediate transfer belt can be reduced, and the life of the first intermediate transfer belt can be extended.
(10)
Further, the fixing member and the thermal transfer body are opposed to each other with the conveyance path of the recording body interposed therebetween, and the fixing member and the thermal transfer body of the second transfer / fixing unit are brought into contact with each other with a predetermined pressure. As a result, the thermal transfer member can function as a pressure member of the fixing member, and the fixing member can function as a pressure member of the thermal transfer member, so that the pressure member can be eliminated and the cost can be reduced. Can be achieved.
(11)
Further, as shown in FIG. 17, since the heat source is provided on the upstream side of the fixing member in the conveyance direction of the recording medium, the fixing member 472 is not subjected to much load due to the heat of the heat source, and the fixing member is thermally deteriorated. Therefore, the life of the fixing member can be extended.
(12)
Further, by arranging the heat source so as to face the outer peripheral surface of the thermal transfer member, the toner on the thermal transfer member can be directly heated by the heat source. Therefore, it is possible to heat the toner more efficiently than when the heat source is disposed inside the thermal transfer body and the toner is heated indirectly via the thermal transfer body. Further, if a heat insulating member is used inside the thermal transfer member, the heat does not escape and the toner can be heated more efficiently. In addition, since the toner can be softened or melted even when the amount of heat applied to the thermal transfer member is small compared to the case where the heat source is disposed inside the thermal transfer member, the progress of deterioration of the thermal transfer member due to heat can be suppressed. .
(13)
In addition, by arranging the heat source inside the thermal transfer member, space can be saved and the degree of freedom in layout can be improved compared to the case where the heat source is arranged facing the outer peripheral surface of the thermal transfer member. Can do.
(14)
Further, the heat source is composed of a heating element made of a magnetic material and an IH coil as magnetic field generating means for generating a magnetic field between the heating elements, and the thermal transfer body is heated by electromagnetic induction by the magnetic field generated by the IH coil. Thereby, since only the magnetic body of the thermal transfer body is heated, the thermal transfer body can be efficiently heated. Further, since the heat transfer body itself generates heat, the temperature rise rate of the heat transfer body can be increased as compared with the case where the heat transfer body is heated by radiant heat of a heating source such as a halogen lamp. As a result, the waiting time until the temperature of the thermal transfer body rises to a predetermined temperature when the apparatus is started can be shortened.
(15)
Further, the heat quantity of the first heat source and the heat quantity of the second heat source are adjusted in accordance with the toner image formed by the image forming unit. Thereby, even a toner image having a large amount of toner can be favorably softened or melted by the heat amount of the heat source. In the case of a toner image with a small amount of toner, the amount of heat from the heat source is reduced, so that energy saving and the thermal load on the transfer / fixing unit can be reduced.
(16)
Further, as shown in the fifth embodiment, when a single-sided image is formed, it is formed by the transfer / fixing unit that is not deteriorated among the first transfer / fixing unit and the second transfer / fixing unit. Is controlling. Thereby, the progress of the deterioration of the transfer / fixing unit in which the deterioration is progressing can be suppressed, and the life of the transfer / fixing unit can be extended. In the case of a single-sided image, thermal degradation of the transfer / fixing unit proceeds evenly by forming an image with an image forming unit corresponding to the transfer / fixing unit that has not deteriorated. Thus, the life of the thermal transfer member can be made almost simultaneously.
(17)
Further, as shown in Example 6, when the image formed on one surface of the recording medium is a single color image and the image formed on the other surface of the recording body is a color image, the image forming unit that forms a single color image As described above, the image forming unit corresponding to the transfer / fixing unit whose deterioration is advanced is selected. Since a monochromatic image can form a toner image with a smaller amount of toner than a color image, the toner on the thermal transfer member can be softened or melted with a smaller amount of heat. Therefore, when a single color image is formed, the amount of heat of the heat source of the thermal transfer body unit is reduced as compared with the time of color image formation. For this reason, the thermal load on the transfer / fixing unit is less when forming a monochrome image than when forming a color image. Therefore, when copying a document with one color image and the other monochrome image, the deterioration is advanced by forming a monochrome image with an image forming unit corresponding to the transfer / fixing unit that has been deteriorated. The progress of deterioration of the transfer / fixing unit can be suppressed. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.
(18)
Further, as shown in the seventh embodiment, when the image formed on one side of the recording body is mainly an image image and the image formed on the other side of the recording body is mainly a character image, As the image forming unit to be formed, an image forming unit corresponding to the transfer / fixing unit whose deterioration is advanced is selected. Since a character-based image can form a toner image with a smaller amount of toner than an image-based image, the toner on the thermal transfer member can be softened or melted with a small amount of heat. Therefore, when a character-based image is formed, the amount of heat of the heat source of the thermal transfer body unit is reduced as compared with the image-based image formation. Therefore, when a character-based image is formed, the thermal load on the transfer / fixing unit is less than when an image-based image is formed. Therefore, when copying a document with one image-based image and the other character-based image, a character-based image is formed by an image forming unit corresponding to the transfer / fixing unit whose deterioration has progressed. It is possible to suppress the progress of the deterioration of the transfer / fixing unit that has been deteriorated. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.
(19)
Further, as shown in the eighth embodiment, the deterioration proceeds as an image forming unit that forms an image having a low image area ratio among an image formed on one surface of the recording medium and an image formed on the other surface of the recording medium. The image forming unit corresponding to the transfer / fixing unit on the right side is selected. As the image area ratio is smaller, a toner image can be formed with a smaller amount of toner, so that the toner can be softened or melted with a smaller amount of heat. For this reason, among images on the front side and back side of the document, an image with a small image area ratio is formed by the image forming unit corresponding to the thermal transfer body in which the degradation is progressing, so that the degradation is progressing. Progress of deterioration of the transfer / fixing unit can be suppressed. In addition, the thermal deterioration of the transfer / fixing unit proceeds evenly, and the life of the thermal transfer body can be made almost simultaneously.
(20)
In addition, a reversing unit 90 is provided as a recording body reversing mechanism for reversing and fixing the recording body after fixing. Thus, when the image on the front side of the document is formed by the second image forming unit 30 and the image on the back side of the document is formed by the first image forming unit 20, the recording body is reversed using the reversing unit 90. When the image on the front side of the document is formed by the first image forming unit 20 and the image on the back side of the document is formed by the second image forming unit 30, if the recording medium is discharged without being reversed, The effect of can be obtained. That is, even if the image on the surface of the original is formed by the second image forming unit 30 due to the deterioration state of the transfer / fixing unit, the upper surface of the recording body is discharged when the recording body is discharged to the discharge stack portion. The image formed on the first image can always correspond to the image on the surface of the document. This makes it possible to match the page order of the recording sheets discharged to the discharge stack unit with the input image information.
(21)
Further, since the toner having a weight average particle diameter of 3 to 8 [μm] and a value obtained by dividing the weight average particle diameter by the number average particle diameter is 1.00 to 1.40, a toner image was formed. Since the microscopic voids between the toners are reduced and the toner density in the toner image is increased, the thermal conductivity to the toner is improved, and the toner can be easily softened or melted during thermal transfer. Thereby, the thermal transferability of the toner can be improved. Further, since the thermal conductivity is good, the toner of the toner image can be softened and melted with a small amount of heat, the apparatus can be energy-saving, and the thermal load on the thermal transfer member can be reduced.
(22)
Further, since the toner having the shape factor SF-1 of 100 to 180 and the shape factor SF-2 of 100 to 180 is used, the toner becomes close to a true sphere and a microscopic image between the toners is formed. The void is reduced, the toner density is increased, and the thermal conductivity to the toner is improved. As a result, the toner can be easily softened or melted during thermal transfer, and the thermal transfer property of the toner is improved. Further, since the thermal conductivity is good, the toner of the toner image can be softened and melted with a small amount of heat, energy can be saved, and the thermal load on the thermal transfer member can be reduced.
(23)
Further, as the toner additive, an toner having an average primary particle size of 50 to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more is used. And the toner's thermal transfer property is improved.

1 is a schematic configuration diagram of an image forming apparatus. FIG. 3 is an enlarged configuration diagram illustrating one of four first process units in a printer unit of the image forming apparatus. FIG. 3 is an enlarged configuration diagram illustrating one of four second process units in the printer unit of the image forming apparatus. FIG. 3 is a diagram illustrating a reversing unit of the image forming apparatus. The schematic block diagram of a double-sided transfer means. The figure which shows the 1st modification of a double-sided transfer means. The figure which changed the heat source of the double-sided transfer means. FIG. 3 is a control block diagram of the image forming apparatus. The control flow figure until it forms an image. The figure which shows the structure using the method of the deterioration state detection of Example 4. FIG. FIG. 10 is a control flow diagram of image formation according to a fifth exemplary embodiment. FIG. 10 is a control flow diagram of image formation according to a sixth embodiment. FIG. 10 is a control flow diagram of image formation according to a seventh embodiment. FIG. 10 is a control flow diagram of image formation according to an eighth embodiment. 6 is a graph in which the transfer / fixing unit replacement time of the image forming apparatus of the present embodiment and the transfer / fixing unit replacement time of the conventional image forming apparatus are examined. FIG. 3 is a diagram illustrating an image forming apparatus in which a first transfer unit includes an electrostatic transfer roller and a fixing member. FIG. 4 is a diagram illustrating another example of an image forming apparatus in which a first transfer unit includes an electrostatic transfer roller and a fixing member. FIG. 3 is an explanatory diagram schematically showing a toner shape for explaining a shape factor SF-1. FIG. 4 is an explanatory diagram schematically showing a toner shape for explaining a shape factor SF-2.

Explanation of symbols

1Y, M, C, K photoconductor 5 developing device 20 first transfer unit 21 first intermediate transfer belt 30 second transfer unit 31 second intermediate transfer belt

Claims (23)

A first toner image recording body having a first image forming unit for forming a first toner image, a second image forming unit for forming a second toner image, and a first heat source for softening or melting the first toner image. A first transfer / fixing unit that performs transfer to the first surface and fixing by heat, and a second heat source that softens or melts the second toner image. The second toner image is applied to the second surface of the recording medium. In an image forming apparatus including a second transfer / fixing unit that performs transfer and fixing by heat,
A deterioration state comparison unit that compares the deterioration state of the first transfer / fixing unit and a deterioration state of the second transfer / fixing unit, and a comparison result of the deterioration state comparison unit when an image is formed, are formed. An image forming apparatus comprising: selection means for selecting whether an image to be formed is formed by a first image forming unit or a second image forming unit based on image information. The image forming apparatus according to claim 1.
The deterioration state of the first transfer / fixing unit is detected from the time integral value of power consumption of the first heat source, and the deterioration state of the second transfer / fixing unit is detected as a time integral value of power consumption of the second heat source. An image forming apparatus, wherein The image forming apparatus according to claim 1.
The first heat source and the second heat source have the same configuration, the deterioration state of the first transfer / fixing unit is detected from the integrated value of the driving time of the first heat source, and the second transfer / fixing unit An image forming apparatus, wherein a deterioration state is detected from an integrated value of driving times of the second heat source. The image forming apparatus according to claim 1.
The deterioration state of the first transfer / fixing unit is detected from the integrated value of the pixel count of the output image of the first image forming unit, and the deterioration state of the second transfer / fixing unit is detected by the second image forming unit. An image forming apparatus that detects an integrated value of a pixel count of an output image. The image forming apparatus according to claim 1, wherein:
At least one of the first transfer / fixing unit and the second transfer / fixing unit includes a thermal transfer body onto which a toner image is transferred, and the toner on the thermal transfer body is softened with the heat source. An image forming apparatus, wherein the toner image is melted and the toner image is simultaneously transferred and fixed by heat. The image forming apparatus according to claim 5.
An image forming apparatus comprising a thermal transfer body cleaning member for cleaning residual toner on the thermal transfer body. The image forming apparatus according to claim 1.
A first thermal transfer body cleaning member provided with a thermal transfer body in both of the first transfer / fixing unit and the second transfer / fixing unit, and cleaning residual toner on the thermal transfer body of the first transfer / fixing unit; A second thermal transfer body cleaning member that cleans transfer residual toner on the thermal transfer body of the second transfer / fixing unit, wherein a deterioration state of the first transfer / fixing unit is indicated by a first thermal transfer body cleaning member. And detecting the deterioration state of the second transfer / fixing unit from the amount of toner remaining on the second thermal transfer body cleaning member. apparatus. The image forming apparatus according to claim 5 or 6, and the image forming apparatus according to claim 7, wherein the thermal transfer body is provided in both the first transfer / fixing unit and the second transfer / fixing unit.
The thermal transfer body of the first transfer / fixing unit and the thermal transfer body of the second transfer / fixing unit are opposed to each other with a conveyance path of the recording medium interposed therebetween, and the thermal transfer body of the first transfer / fixing unit, 2. An image forming apparatus characterized in that a thermal transfer member of a transfer / fixing unit is brought into contact with a predetermined pressure. The image forming apparatus according to claim 5 or 6,
One of the first transfer / fixing unit and the second transfer / fixing unit includes a thermal transfer body to which a toner image is transferred, and the toner on the thermal transfer body is softened and melted by the heat source to form a recording body. The toner image is transferred / fixed, and the other includes electrostatic transfer means for electrostatic transfer of the toner image to the recording medium, and a fixing member for fixing the toner on the recording medium. An image forming apparatus characterized by softening or melting a toner image electrostatically transferred onto a recording medium and fixing the toner image with a fixing member. The image forming apparatus according to claim 9.
The fixing member and the thermal transfer body are opposed to each other with a conveyance path of the recording body interposed therebetween, and the fixing member and the thermal transfer body of the second transfer / fixing unit are brought into contact with each other with a predetermined pressure. Image forming apparatus. The image forming apparatus according to claim 9 or 10,
An image forming apparatus, wherein the heat source is provided upstream of the fixing member in the recording material conveyance direction. 12. The image forming apparatus according to claim 5, wherein:
An image forming apparatus, wherein a heat source of a transfer / fixing unit provided with a thermal transfer member is disposed opposite to an outer peripheral surface of the thermal transfer member. 12. The image forming apparatus according to claim 5, wherein:
An image forming apparatus, wherein a heat source of a transfer / fixing unit provided with a thermal transfer member is disposed inside the thermal transfer member. The image forming apparatus according to claim 1,
The heat source of at least one of the first transfer / fixing unit and the second transfer / fixing unit is composed of a heating element made of the magnetic material and a magnetic field generating means for generating a magnetic field between the heating element, An image forming apparatus, wherein the heating element is heated by electromagnetic induction by a magnetic field generated by the magnetic field generating means. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the amount of heat of the first heat source and the amount of heat of the second heat source are adjusted in accordance with a toner image formed by the image forming unit. The image forming apparatus according to claim 1,
When the image information is only on one side, the selecting means corresponds to the undegraded transfer / fixing unit of the first transfer / fixing unit and the second transfer / fixing unit as an image forming unit. An image forming apparatus, wherein an image forming unit to be selected is selected. The image forming apparatus according to claim 1,
When the image information is a single color image formed on one side of the recording medium and a color image formed on the other side of the recording body, the selection unit is an image forming unit that forms a single color image. As an image forming apparatus, an image forming unit corresponding to a transfer / fixing unit whose deterioration has progressed is selected from the first transfer / fixing unit and the second transfer / fixing unit. The image forming apparatus according to claim 1,
In the case where the image information is such that an image formed on one side of the recording body is mainly an image image and an image formed on the other side of the recording body is mainly a character image, the selection means The image forming unit is characterized in that an image forming unit corresponding to the transfer / fixing unit whose deterioration has progressed is selected from the first transfer / fixing unit and the second transfer / fixing unit as the image forming unit to be formed. apparatus.   16. The image forming apparatus according to claim 1, wherein the selection unit forms an image having a low image area ratio among an image formed on one surface of the recording body and an image formed on the other surface of the recording body. An image forming apparatus that selects an image forming unit corresponding to a transfer / fixing unit that has been deteriorated among the first transfer / fixing unit and the second transfer / fixing unit as an image forming unit. The image forming apparatus according to claim 1,
An image forming apparatus comprising a recording body reversing mechanism for reversing a recording body after fixing and discharging the recording body. The image forming apparatus according to any one of claims 1 to 20,
As the toner used for forming the toner image, a toner having a weight average particle diameter of 3 to 8 [μm] and a value obtained by dividing the weight average particle diameter by the number average particle diameter is 1.00 to 1.40. An image forming apparatus characterized by comprising: The image forming apparatus according to any one of claims 1 to 21,
An image forming apparatus using a toner having a shape factor SF-1 of 100 to 180 and a shape factor SF-2 of 100 to 180 as toner used for forming the toner image. The image forming apparatus according to any one of claims 1 to 22,
The toner used for forming the toner image is obtained by externally adding an additive to base particles composed of at least a binder resin and a colorant, and the average primary particle size of the additive is 50 to 500 [nm. ] And having a bulk density of 0.3 [g / cm ³ ] or more.

Images