JP2000250272A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with good quality, small in size and capable of double sided image formation without generating paper jamming. SOLUTION: In this image forming device, a 1st intermediate transfer body 2 carrying a toner image formed on a photoreceptor drum to a transfer fixing range T is provided. A 2nd intermediate transfer body 18 is provided to be brought into contact with the 1st intermediate transfer body 2 at the transfer fixing range T, proceeded in the same direction as the intermediate transfer body 2 and receives transfer of a toner image on the 1st intermediate transfer body 2 while being moved in circulation and carries that toner image to an upstream position of the transfer fixing range T. A cooling means 17 is provided to cool the 1st intermediate transfer body 2 and the 2nd intermediate transfer body 18, in a downstream position of the transfer fixing range T, to a temperature below a softening temperature for toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for an electrophotographic copying machine, a printer, and the like.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, those disclosed in JP-B-49-209, JP-A-62-206567 and the like are known. FIG. 4 shows a typical configuration example.

FIG. 4 is a schematic configuration diagram of a conventional color image forming apparatus.

As shown in FIG. 4, in the color image forming apparatus 100, an unfixed toner image t formed on a photosensitive drum 101 is primarily transferred to a belt-shaped intermediate transfer member 102, and the unfixed toner image is It is configured such that a desired image is formed on the recording medium P by secondary transferring t from the intermediate transfer body 102 to the recording medium P. As shown, developing units 103, 104, 105 and 106 corresponding to black (Bk), yellow (Y), magenta (M) and cyan (C) are provided around the photosensitive drum 101, as shown in the figure. The unfixed toner images t of each color formed for each rotation of the photosensitive drum 101 are superimposed on the intermediate transfer member 102 to form a composite image, and the composite image is collectively transferred to the recording medium P to form a color image. It is configured to be formed.

In a color image forming apparatus before such an intermediate transfer type color image forming apparatus 100 appeared,
Since the unfixed toner image of each color formed on the photosensitive drum was directly multiplex-transferred to the recording medium, many instability factors such as the thickness and surface characteristics of the recording medium and the transport characteristics of the recording medium to the photosensitive drum The image quality of the color image formed on the recording medium is influenced by the image quality. However, in the intermediate transfer type color image forming apparatus 100 as shown in FIG.
Since the composite image formed by the multiple transfer on the intermediate transfer member 102 is collectively transferred to the recording medium P, the influence of the instability factor as described above can be eliminated, and the image disturbance and color during multiple transfer can be eliminated. This has the advantage that the occurrence of displacement can be effectively prevented.

In the color image forming apparatus 100 configured as described above, the intermediate transfer member 1
02, or the transfer of the unfixed toner image t from the intermediate transfer member 102 to the recording medium P is performed by an electrostatic transfer method. At each transfer position, the transfer corotron 107 and the bias By applying a voltage having a polarity opposite to that of the toner to the roller 108, the unfixed toner image t
Is transferred from the photosensitive drum 101 to the intermediate transfer member 102, and further transferred from the intermediate transfer member 102 to the recording medium P.

However, such a conventional color image forming apparatus 100 has the following problems. That is, when the unfixed toner image t formed on the photosensitive drum 101 is primarily transferred onto the intermediate transfer member 102 by charging the transfer corotron 107, the line toner image is superimposed when multiple transfer is performed. There is a problem that a line toner image of a different color scatters violently. This cause is generally considered to be due to the following two phenomena.

(1) In the transfer pre-nip portion, a transfer electric field acts in a region where the photosensitive member and the intermediate transfer member are not in close contact with each other.

(2) Discharge occurs when the photosensitive member and the intermediate transfer member are separated.

Conventionally, various measures have been taken to improve the scattering phenomenon of the line toner image, but a sufficient improvement effect has not been obtained.

However, according to the investigation by the present inventors, it has been found that toner scattering is particularly remarkable when a semiconductor material is used as the intermediate transfer member. One of the causes is that when the intermediate transfer body has a low resistance, the transfer charge spreads to the transfer pre-nip portion through the intermediate transfer body, and as described in the above (1), the photoconductor and the intermediate transfer body are separated. This is because the transfer electric field acts on the toner image in the area where the toner image is not in close contact. However, after the toner layer having a predetermined charge is electrostatically transferred to the intermediate transfer body, the charge supplied from the transfer corotron 107, which is the driving force of the transfer, moves away from the intermediate transfer body 102 as it leaves the transfer area. It has also been confirmed that the toner holding ability is reduced due to the decay, and the effect that the toner scatters due to the repulsion of the charges of the toner is greater.

Therefore, it can be seen that it is only necessary to prevent charge decay from the intermediate transfer member 102 in order to prevent toner scattering. However, when the unfixed toner image t is secondarily transferred from the intermediate transfer member 102 to the recording medium P, a high transfer electric field is required to collectively transfer the multiple-transferred high-density toner images, and a charge decay When an intermediate transfer member having no image is used, discharge occurs between the intermediate transfer member and the recording medium, and image quality defects are likely to occur.

In order to prevent such image quality defects,
As disclosed in Japanese Patent Publication No. 3-63758,
It is effective to prevent the discharge between the intermediate transfer body and the recording medium at the time of the batch transfer to the recording medium by melting and transferring the toner image using the heating and pressing means at the time of the secondary transfer.

A technique for recording an image on both sides of a recording medium by a method of fusing and transferring a toner image on an intermediate transfer body using the heating / pressing means is disclosed in Japanese Patent Laid-Open No. 4-29.
JP-A-8777 and JP-A-8-272157 are known. Japanese Patent Application Laid-Open No. Hei 4-298777 discloses an image forming apparatus in which an image forming step, a transferring step, and a fixing step are performed simultaneously on the front and back surfaces of a recording medium. Also, JP-A-8-272157 discloses that
After the recording medium has passed through the primary transfer section, by configuring the recording medium transport path so as to pass through the secondary transfer section, the primary transfer section transfers the toner image to the first surface of the recording medium,
An image forming apparatus of a type in which a toner image is transferred to a second surface by a secondary transfer unit is disclosed. According to this method, since a front and back reversing device for a recording medium used in a general copying machine or the like is not required, occurrence of a paper jam is reduced and a higher recording speed can be expected.

[0015]

However, Japanese Patent Laid-Open Publication No.
In the image forming apparatus disclosed in Japanese Patent No. 98777, two sets of image forming members such as an image carrier, a latent image forming member, and a developing device are required for each side of the recording medium. Expected to be higher. Further, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 8-272157, since the recording medium transport path has a loop shape passing through the primary transfer section and the secondary transfer section, cardboard is used as the recording medium. There is a problem that a paper jam is likely to occur in the case where the paper jam occurs.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide an image forming apparatus capable of forming a double-sided image with good image quality, small size, and hardly causing paper jam.

[0017]

An image forming apparatus according to the present invention for achieving the above object has an image carrier on which a toner image is formed, and a toner image forming apparatus for forming a toner image on the image carrier. Means, a first intermediate transfer member for receiving a transfer of the toner image formed on the image carrier while circulating and moving in a predetermined direction, and conveying the toner image to a predetermined upstream position of a transfer fixing area; Primary transfer means for transferring the toner image on the image carrier to the first intermediate transfer member; and, in the transfer-fixing region, contacting the first intermediate transfer member in the same direction as the first intermediate transfer member. A second intermediate transfer member for receiving the transfer of the toner image on the first intermediate transfer member while circulating and transferring the toner image to the transfer / fixing region upstream position; Recording medium supply means for supplying a recording medium of While heating the toner image on the first intermediate transfer member disposed at the upstream position of the transfer / fixing area, the first image is determined depending on whether a recording medium is supplied to the upstream position of the transfer / fixing area. Heating transfer means for transferring the toner image on the intermediate transfer member to a recording medium or the second intermediate transfer member, respectively; and a temperature of the first and second intermediate transfer members at the downstream position of the transfer and fixing area, Cooling means for cooling the first and second intermediate transfer members in the transfer and fixing region so as to be cooled to a temperature not higher than the softening point of the first intermediate transfer member. The timing at which the transferred first toner image is conveyed by the second intermediate transfer member to the upstream position of the transfer and fixing area, and the transfer of the second toner image transferred onto the first intermediate transfer member to the transfer position Carry to the fixing area upstream position The first toner image on the second intermediate transfer member and the second toner image on the first intermediate transfer member by adjusting the timing at which the recording medium is conveyed to the upstream position of the transfer fixing area. And timing adjusting means for simultaneously transferring the image data to the front and back surfaces of the recording medium.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic configuration diagram of a color copying machine to which the image forming apparatus of the present invention is applied.

This color copier (1) has a black (BK), yellow (Y),
Developing units 5 for forming toner images on the photosensitive drums 1BK, 1Y, 1M, 1C corresponding to the respective colors of magenta (M) and cyan (C); and (2) photosensitive drums 1BK, 1Y, 1M, 1C 6, 7, 8, (3) The toner images formed on the photosensitive drums 1BK, 1Y, 1M, and 1C are transferred while circulating in the direction of the arrow B, and the toner images are transferred and fixed. The first intermediate transfer member 2, which is transported to the position upstream of the region T, (4) Four transfer corotrons 9, which transfer the toner images on the respective photosensitive drums to the first intermediate transfer member 2, (5)
In the transfer and fixing area T, the toner image is transferred to the first intermediate transfer body 2 in the same direction as the first intermediate transfer body 2 while being in contact with the first intermediate transfer body 2 and is transferred while being circulated. A second intermediate transfer member 18 that conveys the toner image to a position upstream of the transfer fixing area T, (6) a feed roller 12 that supplies the recording medium P to the position upstream of the transfer fixing area T, and (7) an upstream position of the transfer fixing area T While heating the toner image on the first intermediate transfer member 2 disposed on the first intermediate transfer member 2 depending on whether or not the recording medium P is supplied to a position upstream of the transfer and fixing area T. The heat transfer roller 11 and the pressure roller 4 for transferring the toner images of the toner image to the recording medium P or the second intermediate transfer member 18, respectively, and the first and second intermediate transfer members 2 at the downstream position of the transfer fixing area T (8). , 18 are the softening points of the toner Degrees as it is cooled below, first and second intermediate transfer member in the transfer fixing area T 2,18
And (9) the first toner image transferred from the first intermediate transfer member 2 onto the second intermediate transfer member 18 is transferred and fixed by the second intermediate transfer member 18 to the transfer fixing area T. The timing at which the recording medium P is transported to the upstream position, the timing at which the second toner image transferred onto the first intermediate transfer member 2 is transported to the upstream position in the transfer fixing area T, and the timing at which the recording medium P And the timing of transporting the
Timing adjusting means (not shown) for simultaneously transferring the first toner image on the intermediate transfer member 18 and the second toner image on the first intermediate transfer member 2 to the front and back surfaces of the recording medium P, respectively. I have.

The photosensitive drum 1 according to the present embodiment
BK, 1Y, 1M, and 1C correspond to the image carrier according to the present invention, and the developing units 5, 6, 7, and 8 correspond to the toner image forming means according to the present invention. The two transfer corotrons 9 correspond to primary transfer means in the present invention, the feed roller 12 corresponds to recording medium supply means in the present invention, and the heat transfer roller 11 and the pressure roller 4 The heat transfer member 17 corresponds to the heat transfer means according to the present invention, and the heat transporting member 17 corresponds to the cooling means according to the present invention.

In this color copying machine, the toner image on the first intermediate transfer member 2 is transferred to the recording medium P by the heat transfer roller 11 and the pressure roller 4 serving as heat transfer means, so that an image is formed on one side of the recording medium P. And the first toner image transferred from the first intermediate transfer member 2 to the second intermediate transfer member 18 by the heat transfer unit and the first toner image on the first intermediate transfer member 2. There are two modes, a double-sided image forming mode, in which both the transferred second toner image and the both surfaces of the recording medium P are simultaneously transferred.

In this color copying machine, the second intermediate transfer member 18 is stretched by two rollers, that is, a pressure roller 4 and a tension roller 19 disposed on the upstream and downstream sides of the transfer fixing area T, respectively. Belt is used.

When the color copying machine is set to the double-sided image forming mode, the transfer fixing area T from the pressure roller 4 to the tension roller 19 is in the second position.
Intermediate transfer member 18 contacts first intermediate transfer member 2 and
The intermediate transfer member 2 receives the transfer of the toner image on the first intermediate transfer member 2 while moving in a circulating manner, and conveys the toner image to a position upstream of the transfer fixing area T.

The second intermediate transfer member 18 in this color copying machine has a circumference longer than the dimension of the longest dimension of the recording medium P in the transport direction in the transport direction of the recording medium. When the color copying machine operates in the above-described double-sided image forming mode, after the first toner image is transferred from the first intermediate transfer member 2 to the second intermediate transfer member 18, the first intermediate image is transferred to the first intermediate transfer member 18. When the second toner image formed on the transfer member 2 reaches the transfer fixing area T, the second intermediate transfer member 18 removes the first toner image transferred from the first intermediate transfer member 2. This is because it is necessary to have a sufficient peripheral length for carrying. As described above, since the second intermediate transfer member 18 has a longer circumferential length than the dimension of the longest dimension of the recording medium P in the transport direction in the recording medium transport direction, the longest dimension of the recording medium P is used. In the case of forming an image on the recording medium P, both the first toner image carried on the second intermediate transfer member 18 and the second toner image carried on the first intermediate transfer member 2 Can be transferred simultaneously.

In this color copying machine, when the one-sided image forming mode is set, the tension roller 19 disposed downstream of the transfer fixing area T among the rollers for stretching the second intermediate transfer member 18 is used. A retraction device 25 is provided for moving in a direction away from the first intermediate transfer member 2.
The operation of the retract device 25 will be described later.

Next, the operation for forming a double-sided image using this color copying machine will be described.

While rotating the photosensitive drums 1BK, 1Y, 1M, 1C in the direction of the arrow A, an electrostatic latent image corresponding to image information is formed on the surface thereof by a well-known electrophotographic process.
The electrostatic latent images formed on the photoreceptor drums 1BK, 1Y, 1M, and 1C are developed by developing units 5 corresponding to black (BK), yellow (Y), magenta (M), and cyan (C), respectively. , 6, 7, and 8, and a toner image of each color is formed on each photosensitive drum.

The belt-like first intermediate transfer member 2 which is stretched over a plurality of rollers and circulates in the direction of arrow B so that it comes into contact with the surface of each of the photosensitive drums 1BK, 1Y, 1M and 1C. Are located.

The first intermediate transfer member 2 is formed by laminating a fluororesin, silicon rubber, fluororubber or the like having good toner release properties on the surface of a polyimide resin or aramid resin having excellent heat resistance and rigidity. Things are used. The electric resistance value is to prevent the charge decay after the primary transfer and the charge diffusion to the transfer pre-nip portion and to prevent the toner image from scattering.
The volume resistivity is adjusted to 10 ¹³ Ω · cm or more, and the front and back surface resistivity is adjusted to 10 ¹² to 10 ¹⁵ Ω / b. This is because when the volume resistivity is 10 ¹³ Ω · cm or more, the time constant of the charge decay becomes 10 seconds or more, and the charge is sufficiently retained even after one rotation of the intermediate transfer member. In addition, the front and back surface resistivity is 1
If it exceeds 0 ¹⁶ Ω / b, a discharge occurs when the photosensitive member and the intermediate transfer member are separated, so that the toner image is easily scattered.

The electrical resistivity of the intermediate transfer member was measured by a high resistivity meter (Hiresta IP, manufactured by Mitsubishi Yuka).
A 00 probe (inner electrode diameter: 50 mm, ring electrode inner diameter: 53 mm, manufactured by Mitsubishi Yuka) is connected, and a value measured one minute after a voltage of 500 V is applied between the electrodes is used.
Further, using the same probe, under the same conditions as above, a constant voltage power supply may be used, and the value may be obtained by converting from a value measured by a microammeter.

The unfixed toner images formed on the photosensitive drums 1BK, 1Y, 1M, 1C are
The photosensitive drums 1BK, 1Y, 1Y are located at respective primary transfer positions where the first intermediate transfer member 2 contacts the first intermediate transfer member 2 with the first intermediate transfer member 1Y, 1M, 1C.
Unfixed toner images of each color are transferred from M, 1C onto the surface of the first intermediate transfer member 2 in a superimposed manner. At each of these primary transfer positions, a transfer corotron 9 whose charging to a transfer prenip portion is prevented by a transfer baffle as a primary transfer means is disposed on the back side of the first intermediate transfer body 2. By applying a voltage having a polarity opposite to the charging polarity of the toner to the transfer corotron 9, the unfixed toner images on the photosensitive drums 1 </ b> BK, 1 </ b> Y, 1 </ b> M, and 1 </ b> C are electrostatically attracted to the first intermediate transfer member 2. The primary transfer unit is not limited to the transfer corotron as long as it utilizes electrostatic force, and may be a conductive roller or a conductive brush to which a voltage is applied. Here, the reason why a transfer device using electrostatic force is used as the primary transfer means is that if primary transfer is performed using a transfer device using adhesive force of toner due to heat or pressure, the photoconductor is easily damaged.

The unfixed toner image primary-transferred onto the first intermediate transfer member 2 in this manner is carried on the first intermediate transfer member 2 and transported in the direction of the arrow B, where the heat transport member 17 is heated. After being heated by the side contact member 17a, it is heated by the heating plate 21 arranged upstream of the transfer fixing area T.

The heat transporting member 17 has a function of heating the first intermediate transfer member 2 by the heating side contact member 17a, and has the function of heating the first intermediate transfer member 2 and the second intermediate transfer member 2 in the transfer fixing area T by the cooling side contact member 17b. Has a function of cooling the intermediate transfer member 18. The structure of the heat transporter 17 will be described later.

The heating plate 21 heats the first intermediate transfer member 2 from the back surface to a temperature equal to or higher than the softening point temperature of the toner, that is, 150 ° C.
The unfixed toner image is heated and melted on the first intermediate transfer member 2.

Next, the unfixed toner image is conveyed to the transfer fixing area T facing the conveyance path of the recording medium P. In the transfer fixing area T, a heat transfer roller 11 having a built-in heat source such as a ceramic heater or a halogen lamp and having a hardness of 50 to 90 degrees and heated to 100 to 150 degrees is provided on the back side of the first intermediate transfer body 2. It is arranged in contact. A heat source such as a ceramic heater or a halogen lamp is built in the transfer / fixing area T at a position facing the heat transfer roller 11, similarly to the heat transfer roller 11.
A pressure roller 4 having a hardness of 50 degrees to 90 degrees, which is heated at a high temperature, is disposed. The heat transfer roller 11 and the pressure roller 4 constitute a heat transfer unit.

In the present embodiment, the first intermediate transfer body 2 is provided with a first image on the non-image surface (back side) in the transfer fixing area T.
A cooling means for cooling the intermediate transfer body 2 and the second intermediate transfer body 18 is provided. However, exclusive cooling means are provided for the first intermediate transfer body 2 and the second intermediate transfer body 18, respectively. Is also good. In general, a fan is used as the cooling unit. However, in this embodiment, the heat recovered by the cooling unit is moved to the first intermediate transfer body 2 on the upstream side of the transfer fixing area T. Heat transporter 17 using heat pipe
Is used.

FIG. 2 is a top view (a), a front view (b), and a side view (c) of a heat transporter using a heat pipe used as a cooling means of the present embodiment.

As shown in FIGS. 2A to 2C, the heat transporter 17 includes a heating-side contact member 17a, a cooling-side contact member 17b, and a heating-side contact member 17b that contact the first intermediate transfer member 2. An annular heat pipe 17c penetrates both contact members, and four sets of these are arranged in the moving direction B of the first intermediate transfer member 2 in a shape sandwiched between the first intermediate transfer member 2 and the upper and lower portions. .

Pure water is filled as a refrigerant inside each heat pipe 17c. The heat pipe has a function of contacting between two objects having a temperature difference, repeating vaporization in a high temperature part and liquefaction in a low temperature part, and transferring thermal energy from a high temperature object to a low temperature object. In the present embodiment, by using this heat pipe as a cooling means, heat taken by cooling can be reused, which is extremely effective in power saving.

The toner image thermally fused by the heat transfer roller 11 and the pressure roller 4 is transferred to a transfer fixing area T
The temperature of the first intermediate transfer member 2 and the second intermediate transfer member 18 on the downstream side of the transfer and fixing region T is lower than the softening point temperature of the toner, generally about It is cooled to 100 ° C. or less. With this configuration, the toner image can be transferred from the first intermediate transfer member 2 to the second intermediate transfer member 18 without selecting a material having a particularly strong toner adhesion force as the second intermediate transfer member 18. Can be uniformly transferred without breaking. The reason is that the first toner image is sufficiently cooled and solidified on the downstream side of the transfer fixing area T, so that the second intermediate transfer body 1
Even when the toner adhesion to the toner image 8 is low and non-uniform, the solidification of the toner image causes the adhesion between the surface of the second intermediate transfer member 18 and the toner to spread over the entire image due to the cohesive force between adjacent toners. This is because uniform transfer is performed. Here, the softening point temperature of the toner is such that the viscosity of the toner is 1
The temperature is defined as × 10 ⁴ Pa · s. The conditions for measuring the toner softening point temperature are as follows. Using a Shimadzu flow tester CFT500C, measurement start temperature 80
Heating rate from ℃ to the maximum measurement temperature of 170 ℃: 3 ℃ / m
in, preheating time: 300 sec, cylinder pressure: 10
Kgf / cm ² , die dimensions: L = 1.0 mm, D =
The relationship between the temperature and the viscosity was measured under the condition of 1.0 mm, and the temperature at which the viscosity became 1 × 10 ⁴ Pa · s was determined, and this was defined as the softening point temperature of the toner.

The second intermediate transfer member 18 may have the same configuration as that of the first intermediate transfer member 2. However, it is preferable that the toner has higher flexibility than the first intermediate transfer member 2 and lower toner releasability than the first intermediate transfer member 2.

The reason why high flexibility is preferable is that, in the case of the second intermediate transfer member 18, it is high in order to prevent misregistration (color misregistration) of each color at the time of primary transfer like the first intermediate transfer member 2. This is because rigidity is not required, and in order to increase the adhesiveness to the first intermediate transfer member 2, it is convenient to have high flexibility.
Therefore, it is effective for the second intermediate transfer member 18 to coat a single-layer belt made of silicone rubber having flexibility, or further coat a thin layer of a resin having a toner releasing property such as a fluororesin on the belt. is there. Further, the reason why low toner release property is preferable is that the first
When the toner image is transferred from the first intermediate transfer member 2 to the second intermediate transfer member 18, the toner image is transferred to the first intermediate transfer member 2.
This is so as not to remain on the top. Therefore, the second
The intermediate transfer member 18 is preferably formed by dispersing a small amount of silica (SiO ₂ ) in, for example, silicone rubber.

The second intermediate transfer member 18 may be driven by the first intermediate transfer member 2 or may be driven independently. However, color misregistration may occur on the second intermediate transfer member 18. Therefore, it is preferable to follow the first intermediate transfer member 2 because the adhesion to the first intermediate transfer member 2 in the transfer fixing area T can be improved.

As described above, the first toner image is transferred onto the second intermediate transfer member 18. As described above, the second intermediate transfer member 18 of the present embodiment has the longest size recording medium. Is longer than the dimension in the transport direction of the first intermediate transfer member 18 even in the double-sided image forming mode and when the recording medium having the longest dimension is used. Carried on top.

In the present embodiment, the second intermediate transfer member 18 has a temperature equal to or higher than the softening point temperature of the toner, generally about 100 ° C.
The second intermediate transfer body 18 is located at a position higher than
On the upstream side, a pressure roller 4 having a built-in heat source such as a ceramic heater or a halogen lamp is provided as a heating unit for heating the second intermediate transfer body 18. In this embodiment, the pressure roller 4 is also used as a heat transfer unit. If the second intermediate transfer member 18 is heated to a temperature equal to or higher than the softening point of the toner to sufficiently soften the toner before entering the transfer fixing area T using the pressure roller 4, the heated transfer roller 11 and the pressure roller No sufficient fixing property can be obtained in the transfer nip portion having a narrow transfer nip. In the present embodiment, the second intermediate transfer member 18 is configured to be wrapped around the pressure roller 4 by 180 °, so that the toner can be sufficiently heated before reaching the position upstream of the transfer fixing area T. It is.

As described above, the color copying machine of the present embodiment is provided with the timing adjusting means, and the timing adjusting means allows the first toner image carried on the second intermediate transfer member 18 to be provided. The timing at which the leading edge of the second toner image is transported to the upstream position of the transfer fixing area T coincides with the timing at which the leading edge of the second toner image is transported to the upstream position of the transfer fixing area T. The timing of the formation is adjusted. At the same time, the timing adjusting means determines the timing at which the recording medium P conveyed from the tray 13 by the feed roller 12 is conveyed to a position upstream of the transfer and fixing area T, the leading end of the first toner image, and the second toner. The first toner image and the second toner image are simultaneously transferred to the front and back surfaces of the recording medium P by adjusting the timing so that the leading edge of the image is conveyed to the upstream position of the transfer fixing area T. You.

Recording medium P on which toner images have been transferred to the front and back surfaces
Is a transfer fixing area T in which the first intermediate transfer member 2 and the second intermediate transfer member 18 move while contacting each other, that is, a section from the transfer nip portion between the heating transfer roller 11 and the pressure roller 4 to the tension roller 19. Is transported between the first intermediate transfer member 2 and the second intermediate transfer member 18. Since both the first intermediate transfer member 2 and the second intermediate transfer member 18 have good toner releasability, the temperature of both the first intermediate transfer member 2 and the second intermediate transfer member 18 on the downstream side of the transfer fixing area T is reduced. By cooling the toner to a temperature equal to or lower than the softening point of the toner, the first toner image and the second toner image can be simultaneously transferred and fixed to the front and back surfaces of the recording medium P, respectively.

In the single-sided image forming mode, the second
The second intermediate transfer is performed by moving a tension roller 19 disposed on the downstream side of the transfer fixing area T among the rollers on which the intermediate transfer member 18 is stretched in a direction away from the first intermediate transfer member 2. The contact area between the member 18 and the first intermediate transfer member 2 is reduced so that the heat transport member 17
The tension roller 19 is provided with a retracting device 25 for cooling only the cooling device. By retracting the tension roller 19 by using the retracting device 25, the second intermediate transfer member 18 can be prevented from being cooled by the heat transport member 17, so that power can be saved. .

The recording medium P on which the first toner image and the second toner image are respectively transferred and fixed on the front and back surfaces is solidified in the transfer fixing area T, and then the first intermediate transfer member is peeled off by the peeling claw 14. 2 and is discharged out of the apparatus by the conveyor belt 15.

The toner remaining on the first intermediate transfer member 2 after the completion of the secondary transfer is melted by the heating plate 21 and removed from the first intermediate transfer member 2 by the adhesive force of the cleaner 16. This cleaning is required for the fogging toner in the non-sheet passing portion on the first intermediate transfer body 2 and the untransferred toner generated due to a paper jam or the like, which is not transferred to the recording medium P in the one-sided image forming mode. is there.

The transfer efficiency from the first intermediate transfer member 2 to the second intermediate transfer member 18 in the double-sided image forming mode, and the transfer efficiency from the first intermediate transfer member 2 to the recording medium P in the single-sided image forming mode.
Since the transfer efficiency to both is 100%, cleaning of the first intermediate transfer member 2 is unnecessary. When the size of the recording medium to be used is changed, the fogging toner of the non-sheet passing portion is transferred to the recording medium as fogging. However, it is not always necessary to perform the cleaning operation every time, and at least before the size of the recording medium is changed. You can go to

FIG. 3 is a schematic configuration diagram of a cleaner in the color copying machine of the present embodiment.

The cleaner shown in FIG. 3 is a cleaner 16 for the first intermediate transfer member 2 in the color copying machine shown in FIG.
2 shows a configuration of a cleaner 20 for the second intermediate transfer member 18. The cleaners 16 and 20 include a cleaning roller 22, a metal blade 23, and a heat source 24 such as a ceramic heater or a halogen lamp built in the roller.

The cleaning roller 22 has an elastic layer 2 made of silicone rubber having a hardness of 30 degrees and a thickness of 2 mm formed by coating a fluorine rubber on an aluminum core layer 22c.
2b, on which a hot-melt adhesive layer 22 made of polyester resin (glass transition point 66 degrees, melting point 110 degrees)
a. In addition to the above, metals such as stainless steel and nickel can be used for the core layer 22c. Rubber such as EPDM or fluorine can be used for the elastic layer 22b. Alternatively, a structure in which a core is coated with a resin surface material such as polyimide, nylon, or fluorine can be used as a structure having no elastic layer. The adhesive layer 22a is selected in consideration of compatibility with the toner, but butadiene or an acrylic resin can also be used. The cleaning roller 22 is heated to a temperature of 100 degrees by a built-in heat source 24.

The metal blade 23 is a member for removing the toner cleaned by the cleaning roller 22 from each intermediate transfer member.

On the other hand, the second intermediate transfer member 18 after the secondary transfer of the first toner image to the recording medium P is wound around the pressure roller 4 by 180 °. The residual toner on the intermediate transfer member 18 is heated and melted by the pressure roller 4 and is removed by the adhesive force of the cleaner 20 that comes into contact with the pressure roller 4. The residual toner to be cleaned here is the toner in the non-sheet passing portion that is not transferred to the recording medium P and the untransferred toner generated due to a paper jam or the like.

Therefore, in the double-sided image forming mode, intermittently at any time before the image forming operation starts, after the image forming operation is completed, at every fixed number of prints, when the recording medium size is changed, or when there is an abnormality such as a paper jam. An adhering matter removing operation is performed. In the single-sided image forming mode, the attached matter removing operation may be continuously performed. The configuration of the cleaner 20 may be the same as that of the cleaner 16 for the first intermediate transfer body 2.

In this embodiment, a plurality of photosensitive drums are provided as image carriers, and a transfer corotron is provided corresponding to the plurality of image carriers as primary transfer means. Although the image forming apparatus of the type in which the respective toner images formed thereon are transferred so as to be sequentially superimposed on the first intermediate transfer member has been described, the present invention is not limited to this type. A carrier and a plurality of developing units, and a one-color toner image is formed on the image carrier every cycle of the image carrier, and the toner image is formed on the first image carrier.
By repeating the process of transferring to the intermediate transfer member for a plurality of cycles, the present invention can be applied to an image forming apparatus of a method of forming a color image of a plurality of colors on the first intermediate transfer member. However, when a two-sided image is formed by this type of image forming apparatus, the first toner image formed on the first intermediate transfer member is transferred to the second intermediate transfer member, and then the first toner image is transferred to the first intermediate transfer member.
While the intermediate transfer member is rotated a plurality of times to form the second toner image on the first intermediate transfer member, the second intermediate transfer member is separated from the first intermediate transfer member, After the second toner image has been formed on the first intermediate transfer member, the second intermediate transfer member is brought into contact with the first intermediate transfer member, and the first and second toner image tips are transferred and fixed. The double-sided image formation can be performed by supplying the recording medium to the transfer / fixing area in accordance with the timing at which the recording medium is conveyed to the area. Note that the process of forming the first toner image on the second intermediate transfer member is such that the first intermediate image is transferred from the first intermediate transfer member one color at a time to each cycle.
May be transferred to an intermediate transfer member and subjected to multiple transfer on a second intermediate transfer member to form a multicolor toner image.
Alternatively, multiple transfer may be performed on the first intermediate transfer member, and the multicolor toner image formed by the multiple transfer may be collectively transferred to the second intermediate transfer member. However, when the latter method is adopted, it is necessary to keep the second intermediate transfer member away from the first intermediate transfer member while performing the multiple transfer to the first intermediate transfer member.

[0060]

As described above, according to the image forming apparatus of the present invention, the first toner image is formed on the first intermediate transfer member, and the first toner image is formed by the heat transfer means. 1
In order to transfer from the intermediate transfer member to the second intermediate transfer member, the first intermediate transfer member and the second intermediate transfer member are brought into contact with each other to form a transfer-fixing region that moves in the same direction, and the transfer is performed. By providing a cooling means for cooling the temperatures of the first intermediate transfer member and the second intermediate transfer member below the softening point temperature of the toner on the downstream side of the fixing region, the material of the second intermediate transfer member is excessively strong. Even if a material having toner adhesion is not selected, the first
The first toner image can be uniformly transferred from the intermediate transfer member to the second intermediate transfer member without dividing the first toner image. Further, after forming the second toner image on the first intermediate transfer member, when the recording medium is supplied to the upstream position of the transfer fixing area and the first and second toner images are simultaneously transferred to the front and back surfaces of the recording medium, The temperature of the first intermediate transfer member and the second intermediate transfer member is cooled below the softening point temperature of the toner on the downstream side of the transfer fixing area, and the first intermediate transfer member and the second intermediate transfer member are cooled. Since the toner adhesion to the body is low, the first and second toner images can be simultaneously and uniformly transferred to the front and back surfaces of the recording medium.

Further, since a reversing device and a long recording medium conveying path of a recording medium widely used in a conventional double-sided copying machine and the like are not required, there is little possibility of paper jam even when thick paper is used. Speed can be increased.

Therefore, according to the present invention, it is possible to realize an image forming apparatus capable of forming a double-sided image with good image quality, small size, and hardly causing paper jam.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine to which an image forming apparatus of the present invention is applied.

FIG. 2 is a top view (a), a front view (b), and a side view (c) of a heat transporter using a heat pipe used as a cooling means of the present embodiment.

FIG. 3 is a schematic configuration diagram of a cleaner in the color copying machine of the present embodiment.

FIG. 4 is a schematic configuration diagram of a conventional color image forming apparatus.

[Explanation of symbols]

1BK, 1Y, 1M, 1C Photoconductor drum (image carrier) 2 First intermediate transfer member 4 Pressure roller 5, 6, 7, 8 Developing device 9 Transfer corotron 11 Heat transfer roller 12 Feed roller 13 Tray 14 Peeling claw 15 Conveying belts 16, 20 Cleaner 17 Heat transporter 17a Heating contact member 17b Cooling contact member 17c Heat pipe 18 Second intermediate transfer member 19 Tension roller 21 Heating plate 22 Cleaning roller 22a Adhesive layer 22b Elastic layer 22c Core layer 23 Metal Blade 24 Heat source 25 Retract device 100 Color image forming device 101 Photoreceptor drum 102 Intermediate transfer member 103, 104, 105, 106 Developing device 107 Transfer corotron 108 Bias roller P Recording medium T Transfer fixing area t Unfixed toner image

Claims (13)

[Claims] 1. An image carrier on which a toner image is formed on a surface, a toner image forming means for forming a toner image on the image carrier, and a toner image forming means for forming a toner image on the image carrier while circulating in a predetermined direction A first intermediate transfer member that receives the transferred toner image and conveys the toner image to a predetermined upstream position in a transfer fixing area; and transfers the toner image on the image carrier to the first intermediate transfer member. A primary transfer unit, wherein the toner image on the first intermediate transfer body is contacted with the first intermediate transfer body in the transfer fixing area, advances in the same direction as the first intermediate transfer body, and circulates; A second intermediate transfer member that conveys the toner image to the upstream position of the transfer / fixing area after receiving the image transfer; a recording medium supply unit that supplies a predetermined recording medium to the upstream position of the transfer / fixing area; The first intermediate transfer arranged at an upstream position While heating the toner image on the body, depending on whether a recording medium is supplied to the upstream position of the transfer and fixing area, the toner image on the first intermediate transfer body is transferred to the recording medium or the A heat transfer unit for transferring the image to a second intermediate transfer member;
Cooling means for cooling the first and second intermediate transfer members in the transfer and fixing area so that the temperature of the intermediate transfer member is cooled below the softening point temperature of the toner; The timing at which the first toner image transferred onto the second intermediate transfer member is conveyed to the upstream position of the transfer fixing area by the second intermediate transfer member, and the timing at which the first toner image is transferred onto the first intermediate transfer member The timing at which the transferred second toner image is transported to the upstream position of the transfer and fixing area and the timing at which the recording medium is transported to the upstream position of the transfer and fixing area are adjusted, and the first and second toner images on the second intermediate transfer member are adjusted. An image forming apparatus, comprising: timing adjusting means for simultaneously transferring a toner image and a second toner image on the first intermediate transfer member to each of the front and back surfaces of a recording medium. 2. The image forming apparatus according to claim 1, further comprising: a plurality of said image carriers, wherein said primary transfer unit is provided in correspondence with said plurality of image carriers, and each of said primary transfer units is formed on each of said image carriers. 2. The image forming apparatus according to claim 1, wherein the toner image is transferred so as to be sequentially superimposed on the first intermediate transfer member. 3. The image forming apparatus according to claim 1, wherein the second intermediate transfer member has a peripheral length longer than a dimension of the longest dimension of the recording medium in the transport direction in the transport direction. . 4. The cooling means cools the first intermediate transfer body from the back side of the first intermediate transfer body with respect to the front surface carrying the toner image in the transfer fixing area, and cools the first intermediate transfer body. 2. The image forming apparatus according to claim 1, wherein the second intermediate transfer member is cooled via the intermediate transfer member. 5. The transfer fixing area, wherein the cooling unit contacts the first intermediate transfer body in both the transfer fixing area and the toner image carrying area to which the toner image has been transferred by the primary transfer means. 2. A heat transporter for transferring heat of the first and second intermediate transfer members to the toner image bearing area of the first intermediate transfer member in the step (a).
The image forming apparatus as described in the above. 6. A heating means for heating the first intermediate transfer body to a temperature equal to or higher than the softening point temperature of the toner, upstream of the transfer fixing area in the direction of movement of the first intermediate transfer body. The image forming apparatus according to claim 1, wherein: 7. The second intermediate transfer member is located at a temperature higher than the softening point of the toner so as to reach the upstream position of the transfer fixing area in a state where the second intermediate transfer member is heated to a temperature equal to or higher than the softening point temperature of the toner. 2. The image forming apparatus according to claim 1, further comprising a heating unit that heats the second intermediate transfer member on the upstream side in the body movement direction. 8. The transfer / fixing area in which the second intermediate transfer member is provided with at least two rollers disposed upstream and downstream of the transfer / fixing area, respectively.
The image forming apparatus transfers the toner image on the first intermediate transfer member to a recording medium by the heating transfer unit. A single-sided image forming mode for forming an image on one side of a recording medium, and by the heat transfer unit,
Both the first toner image transferred from the first intermediate transfer member onto the second intermediate transfer member and the second toner image transferred onto the first intermediate transfer member are recorded on a recording medium. A two-sided image forming mode for simultaneously transferring images to the front and back surfaces, and a roller for stretching the second intermediate transfer member when the image forming apparatus is set to the one-sided image forming mode A contact area between the second intermediate transfer member and the first intermediate transfer member is reduced by moving a roller disposed downstream of the transfer fixing region in a direction away from the first intermediate transfer member. 2. The image forming apparatus according to claim 1, further comprising a retracting unit for causing the image forming apparatus to retract. 9. A surface made of a material having a higher flexibility than the first intermediate transfer member and a lower toner release property than the first intermediate transfer member. The image forming apparatus according to claim 1, wherein the belt is a belt having: 10. A cleaning member for removing, from the second intermediate transfer body, an attachment containing toner remaining on the second intermediate transfer body, the cleaning member comprising: When the mode is set to the formation mode, the operation of removing the deposits from the second intermediate transfer body is performed continuously,
9. The image forming apparatus according to claim 8, wherein when the image forming apparatus is set in the double-sided image forming mode, the operation of removing the extraneous matter from the second intermediate transfer body is performed intermittently.
The image forming apparatus as described in the above. 11. When the image forming apparatus is set to the double-sided image forming mode, before the image forming operation is started, after the image forming operation is completed, after a fixed number of prints, when the recording medium size is changed, 11. The image forming apparatus according to claim 10, wherein the attached matter removing operation is performed at any time when an abnormality such as a paper jam occurs. 12. The image forming apparatus according to claim 10, wherein the cleaning member has a heat-meltable adhesive layer on a surface. 13. The image forming apparatus according to claim 1, wherein the second intermediate transfer member is circulated by following the first intermediate transfer member.