JPH1165188A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device suppressing the occurrence of deflection of a recording sheet in the vicinity of a transferring section and without generating an image disturbance, etc., caused by rubbing of the recording sheet. SOLUTION: In this device, when the transporting speed of a recording sheet S in a transferring area Q4 transferring a toner image on the recording sheet S is made to V1, the transporting speed of the recording sheet S on a sheet transporting device between transferring and fixing Hs transporting the recording sheet S from the above transferring area Q4 to a fixing area Q5 fixing the toner image on the above recording sheet S is made to V2, the transporting speed of the recording sheet S on the fixing area Q5 is made to V3, the transporting speed V1, V2 and V3 of the above respective recording sheet S is set so as to satisfy an expression, V1<V2<V3. When the sheet length being the length of the recording sheet S in the transporting direction is longer than the distance between the transferring area and the fixing area, the device is provided with the above sheet transporting device between transferring and fixing Hs equipped with a moving member Hsa moving the recording sheet S to a rear face side for forming a space to make the recording sheet S loosen to the rear face side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a laser printer, and other electrophotographic image forming apparatuses, and more particularly to an image forming apparatus for transferring an image formed on an intermediate transfer member to a recording sheet.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus for transferring a toner image transferred on an intermediate transfer member to a recording sheet has been used to transfer toner images of different colors sequentially formed on an image bearing member in a primary transfer area. Are sequentially transferred to each other, and toner images of different colors formed on the intermediate transfer member are transferred to the secondary transfer area 2.
The secondary transfer to a recording sheet by a next transfer roller or the like, the recording sheet passing through the secondary transfer area is conveyed to a fixing area, and a toner image on the recording sheet is fixed by a fixing device arranged in the fixing area. It is configured.

[0003]

When the recording sheet on which the secondary transfer is performed enters the fixing device, the recording sheet is transported between the secondary transfer area and the fixing area at a transport speed V1 of the recording sheet in the secondary transfer area. If the recording sheet conveyance speed V2 of the sheet conveyance device during transfer and fixing and the recording sheet conveyance speed V3 of the fixing device are set to the same speed (V1 = V2 = V3), the minute speed due to the speed fluctuation of the transfer speed V1 A difference is generated, and a load is applied to the recording sheet due to the speed difference, the recording sheet is bent near the secondary transfer area, and the image is disturbed by rubbing of the recording sheet. When the recording sheet is conveyed from the inter-transfer-fixing sheet conveying device to the fixing device, if the fixing device conveying speed V3 is lower than the recording sheet conveying speed V2 of the trans-fixing sheet conveying device, a loop of the recording sheet occurs and the fixing area is fixed. Image rubbing and image disturbance due to the influence on the transfer portion.

Conversely, when the fixing device transport speed V3 is faster than the transport device speed V2, the distance between the secondary transfer area and the fixing area (transfer-fixing distance) is shorter than the length of the recording sheet in the transport direction (sheet length). Also, since the transfer is performed in the secondary transfer area even at the time of the nip of the fixing device, the recording sheet is pulled, which affects the image quality, or the trailing edge of the recording sheet jumps up when passing through the nip of the secondary transfer means, and Image rubbing occurs. The inter-transfer-fixing distance (recording sheet transport distance from the secondary transfer area to the fixing area) is set to be greater than the maximum recording sheet transport direction length (maximum sheet length), and the recording sheet exits the secondary transfer area when entering the fixing area. In order to prevent the influence on the fixing device from occurring in the secondary transfer area, it is conceivable to use such a method. However, in this method, the apparatus main body becomes large, and it is not possible to cope with a larger recording sheet.

[0005] As described above, in order to avoid the influence on the image quality in the secondary transfer in the secondary transfer area, each of the transport speeds V
It is necessary to absorb the speed difference between 1, V2 and V3. The following technology (J01) is conventionally known as a technology for absorbing the speed difference. (J01) Technology described in Japanese Patent Application Laid-Open No. 7-53089. In this publication, the conveying surface of the conveying device is curved in a direction in which the recording sheet is sucked, and the conveying surface of the conveying device when entering the nip portion downstream of the conveying device is described. Shock absorbers are described. (Problem of the above (J01)) However, in the technique of the above (J01), since the transfer, the conveyance, and the fixing are performed at the same speed, the speed difference at the time of fixing and conveyance can be absorbed by the curved portion, but the speed difference generated at the time of the transfer is It cannot be absorbed, and image rubbing occurs due to the jump of the rear end of the recording sheet immediately after passing through the transfer area.

The following technique (J02) is conventionally known. (J02) Technology described in JP-A-3-128852 In this publication, a plurality of belt transport devices for performing suction transport are arranged, and the upstream side is positioned above the downstream side at the junction between the transport devices. Have been. (Problem of (J02)) In the technique of (J02), since a loop is formed by the difference in the position of the joining portion, a plurality of transporting devices are required. Is required, and it is difficult to set an optimal suction force suitable for the transfer conditions. Furthermore, the use of a plurality of transporting devices has a problem that skew occurs due to a difference in speed between the transporting devices and a difference in the transporting direction of each transporting device.

[0007] The following technology (J03) is conventionally known. (J03) Technology described in Japanese Patent Application Laid-Open No. 8-1288851. In this publication, a recording sheet is lifted and conveyed to a belt conveying device, and the leading end of the recording sheet reaches a fixing device.
A technique using a support member for retracting a recording sheet downward immediately before being nipped at l is described. (Problem of (J03)) According to the technique of (J03), since the leading end of the recording sheet retracts the support member immediately before entering the fixing device, a loop generated when the recording sheet is conveyed to the fixing device after the nip of the fixing device. There is a problem that formation cannot be absorbed. Further, the conventional techniques (J01) to (J0)
In 3), there is a problem that it is impossible to cope with a change in the type, thickness, size, etc. of the recording sheet.

In the above description, the problems of the prior art regarding the image forming apparatus using the intermediate transfer member have been described.
The above-mentioned problem of the prior art is also a problem with an image forming apparatus that directly transfers a toner image on an image carrier to a recording sheet without using an intermediate transfer member. In view of the above-mentioned conventional problems, the present invention provides an image forming apparatus that conveys a recording sheet onto which a toner image has been transferred to a fixing device.
The contents described in 01) shall be the subject. (O01) The downward loop of the sheet is positively formed between the transporting device and the fixing device, and the difference in each transporting speed is absorbed, thereby suppressing the occurrence of the bending of the recording sheet near the transfer portion, and rubbing the image of the recording sheet. To provide an image forming apparatus that does not cause disturbance or the like.

[0009]

Means for Solving the Problems Next, the present invention which has solved the above-mentioned problems will be described. Elements of the present invention include elements of the embodiments to facilitate correspondence with the elements of the embodiments described later. The sign of parentheses is added in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(1st invention) In order to solve the aforementioned problem,
The image forming apparatus according to the first invention of the present application has the following requirements. (A01) An image carrier (16) on which a toner image is formed on the surface of an endless image carrier that rotates. ,
(A02) A toner image forming apparatus (14 to 17 + R) for forming a toner image according to image information on the surface of the image carrier (16)
(OS + G), (A03) an intermediate transfer member (B) having an endless surface rotatably moving through a primary transfer area (Q3) set along the surface of the image carrier (16), (A04) The image carrier (16) in the primary transfer area (Q3)
A primary transfer device (21) for transferring the toner image on the surface onto the surface of the endless intermediate transfer member (B); (A05) a secondary transfer region (Q4) set in the movement path of the intermediate transfer member (B); And (A06) a secondary transfer area for transferring the toner image transferred to the intermediate transfer body (B) to the recording sheet (S). (A4) a secondary transfer unit (T) disposed in (Q4), (A07) the recording sheet (S5) passing through a fixing area (Q5) set in a conveyance path of the recording sheet (S) onto which the toner image has been transferred. And (A08) the toner image is transferred between the secondary transfer area (Q4) and the fixing area (Q5) while applying a conveying force to the toner image on the recording sheet (S). Transfer-fixing sheet transport device (Hs) that transports the recorded recording sheet (S), ( 09) The transport speed of the recording sheet (S) in the secondary transfer area (Q4) is V1, the transport speed of the recording sheet (S) in the inter-transfer fixing sheet transport device (Hs) is V2, and the transport speed of the fixing area (Q5) is V1. When the transport speed of the recording sheet (S) is V3, the inter-transfer-fixing sheet transport device (Hs) in which the transport speeds V1, V2, and V3 of the respective recording sheets are set to satisfy the following equation: V1 <V2> V3 (A010) The secondary transfer area (Q4) and the fixing area (Q
5) A transfer-fixing distance storing means (C1) for storing a transfer-fixing distance which is a distance between them, and (A011) a transfer direction length of the recording sheet (S) passing through the secondary transfer area (Q4). Sheet length detecting means (C2) for detecting the sheet length,
(A012) The leading end of the recording sheet (S) is in the fixing area (Q
(A4) A fixing area arrival detecting means (C4) for detecting that the sheet has reached the fixing area arrival time when the sheet length is longer than the inter-fixing distance.
The inter-transfer fixing sheet transport device (Hs) having a moving member (Hsa) that moves to the back side of the recording sheet (S) to form a space in which the recording sheet (S) sags to the back side in response to the output signal of .

(Operation of the First Invention)
In the image forming apparatus of the present invention, the toner image forming apparatus (14 to 1)
7 + ROS + G) forms a toner image according to image information on the surface of the endless image carrier (16) that rotates and moves the image carrier (16). The endless surface of the intermediate transfer member (B)
It rotates through a primary transfer area (Q3) set along the surface of the image carrier (16). Primary transfer unit (2
1) transferring the toner image on the surface of the image carrier (16) to the surface of the endless intermediate transfer body (B) in the primary transfer area (Q3). Sheet transfer device before transfer (Ht)
Transports and passes the recording sheet (S) to the secondary transfer area (Q4) set in the movement path of the intermediate transfer body (B). The secondary transfer unit (T) arranged in the secondary transfer area (Q4) transfers the toner image transferred to the intermediate transfer body (B) to the recording sheet (S). The transfer / fixing sheet transport device (Hs) is a recording sheet (S) on which the toner image has been transferred between the secondary transfer area (Q4) and the fixing area (Q5).
Is transported. The fixing device (54) applies the conveyance force to the recording sheet (S) passing through a fixing area (Q5) set in the conveyance path of the recording sheet (S) onto which the toner image has been transferred, while applying the conveyance force to the recording sheet. (S) The upper toner image is fixed. The inter-transfer fixing distance storage means (C1) stores the inter-transfer fixing distance, which is the distance between the secondary transfer area (Q4) and the fixing area (Q5). Sheet length detection means (C2)
Detects the sheet length, which is the length in the transport direction of the recording sheet (S) passing through the secondary transfer area (Q4). The fixing area arrival detection means (C4) detects that the leading end of the recording sheet (S) has reached the fixing area (Q5).

The recording sheet conveying speed V2 of the inter-transfer fixing sheet conveying device (Hs) is such that the conveying speed of the recording sheet (S) in the secondary transfer area (Q4) is V1, and the recording sheet (Q5) in the fixing area (Q5). When the transport speed in S) is V3, the setting is made so as to satisfy the following expression. V1 <V2> V3 When V2> V1, the recording sheet (S) that has passed through the secondary transfer area (Q4) does not sag at the downstream side of the secondary transfer area (Q4), so that good secondary transfer is possible. Is performed. Further, since V2> V3, when the front end of the recording sheet (S) enters the fixing area (Q5), the conveyance speed of the recording sheet (S) in the fixing area (Q5) is low. Q
On the upstream side of 5), a loop is formed on the recording sheet (S). However, the sheet conveyance device during transfer and fixing (H
The moving member (Hsa) moves to the rear side of the recording sheet (S) in response to the output signal of the fixing area reaching detection means (C4) when the sheet length is longer than the inter-transfer fixing distance. Thus, a space in which the recording sheet (S) sags is formed.
Therefore, the recording sheet (S) sags on the back side upstream of the fixing area (Q5), so that the loop on the upstream side of the fixing area (Q5) is absorbed.

In the image forming apparatus according to the first aspect of the present invention, the recording sheet (S) is slackened on the back side to absorb a loop formed upstream of the fixing area (Q5). No image disturbance of the unfixed image occurs, and the effect of a loop generated in the fixing device (54) is 2%.
It does not reach the next transfer area (Q4), and there is no image disturbance due to rubbing against other components due to sagging on the upper surface side.

(Second invention) In order to solve the above problems,
The image forming apparatus according to the second invention of the present application has the following requirements: (B01) an image carrier on which a toner image is formed on the surface of a rotatable endless image carrier; )
A toner image forming apparatus for forming a toner image corresponding to image information on the surface of the image carrier; (B03) a pre-transfer sheet conveying apparatus for conveying and passing a recording sheet to a transfer area set along the surface of the image carrier; (B04) a transfer unit disposed in the transfer area for transferring the toner image on the surface of the image carrier to a recording sheet in the transfer area; and (B05) a transfer path set for the recording sheet on which the toner image has been transferred. A fixing device for fixing a toner image on the recording sheet while applying a conveying force to the recording sheet passing through the fixing area,
6) an inter-transfer / fixing sheet conveying device for conveying a recording sheet on which the toner image has been transferred between the transfer area and the fixing area;
(B07) The transport speed of the recording sheet in the transfer area is V1,
Assuming that the transport speed of the recording sheet of the sheet transport device during transfer and fixing is V2 and the transport speed of the recording sheet in the fixing area is V3, the transport speeds V1, V2, and V3 of the respective recording sheets satisfy the following equation. V1 <V2> V3 (B08) a trans-fixing distance storing means for storing a trans-fixing distance which is a distance between the transfer area and the fixing area;
09) sheet length detecting means for detecting the sheet length, which is the length of the recording sheet passing through the transfer area in the transport direction, (B01
0) a fixing area arrival detecting means for detecting that the leading edge of the recording sheet has reached the fixing area; (B011) an output signal of the fixing area reaching detecting means when the sheet length is longer than the inter-transfer-fixing distance; The inter-fixing sheet conveying apparatus, further comprising a moving member that moves to the back side of the recording sheet to form a space in which the recording sheet sags to the back side according to the above.

(Operation of the Second Invention)
The image forming apparatus of the invention is different from the first invention in that the toner image formed on the image carrier is directly transferred to the recording sheet without passing through the intermediate transfer body. Has a configuration similar to that of the first invention, and has the same operation as that of the first invention. That is, in the image forming apparatus according to the second aspect of the present invention, the recording sheet is slackened on the back side to absorb a loop formed on the upstream side of the fixing area, thereby making it possible to determine an undetermined conveyance speed difference. When the loop is formed upward, the image is not disturbed and the effect of the loop generated in the fixing device does not affect the transfer area (the area where the toner image is transferred to the recording sheet). There is no image disturbance due to the rubbing of other components.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1 of the present invention (the first and second inventions)) The first embodiment of the image forming apparatus of the present invention is characterized by satisfying the following requirement (A014) in the present invention. (A014) The moving member (Hs) whose moving amount is variable according to the thickness or type of the recording sheet (S) to be conveyed.
a). In the first embodiment of the present invention, the thickness or type of the recording sheet (S) to be conveyed is automatically detected by a sheet type detection unit, or a user interface (U)
It is possible to input information on the recording sheet (S) from the sheet type input means (UI4) provided in I). (Operation of the First Embodiment of the Present Invention) In the first embodiment of the image forming apparatus of the present invention, the moving member (Hsa) has a moving amount depending on the thickness or type of the recording sheet (S) to be conveyed. It is variable. By making the moving amount of the conveying device variable according to the thickness or type of the recording sheet (S), it is possible to optimally convey the recording sheet (S) according to the loop amount to be absorbed.

(Second Embodiment of the Present Invention) An image forming apparatus according to a second embodiment of the present invention is characterized in that the following requirement (A015) is provided in the present invention or the first embodiment of the present invention. (A015) The transfer sheet transport belt (43), which sucks and transports the recording sheet (S) that has passed through the secondary transfer area (Q4) and rotates the downstream end up and down around the upstream end. The transfer sheet transport belt (4)
The pre-fixing sheet guide (4), which is disposed downstream of (3) and guides the recording sheet (S) to the fixing area (Q5) and whose upstream end rotates vertically about the downstream end.
4), a space in which the downstream end of the transfer sheet conveying belt (43) and the upstream end of the pre-fixing sheet guide (44) are moved downward to allow the recording sheet (S) to sag to the back side. The sheet transfer device (H
s).

(Operation of the Second Embodiment of the Present Invention) In the second embodiment of the image forming apparatus of the present invention, the transfer sheet conveying belt (43) moves the recording sheet (# 4) passing through the secondary transfer area (Q4). S) is sucked and conveyed, and the downstream end pivots up and down about the upstream end. A pre-fixing sheet guide (44) disposed downstream of the transfer sheet conveying belt (43) guides the recording sheet (S) to the fixing area (Q5) and is arranged upstream of the downstream end. The end pivots up and down. The inter-fixing sheet conveying device (Hs) having the transfer sheet conveying belt (43) and the pre-fixing sheet guide (44) is provided at the downstream end of the transfer sheet conveying belt (43) and the pre-fixing sheet guide (44). The upstream end is moved downward to form a space in which the recording sheet (S) sags to the back side. Since the portion of the recording sheet (S) on the transfer sheet transport belt (43) is adsorbed, the loop of the recording sheet (S) is formed between the sheet transport device (Hs) between the transfixation and the fixing device (54). The influence of the loop formation does not reach the secondary transfer area (Q4), and the impact of the jump of the rear end of the recording sheet (S) immediately after passing through the secondary transfer area (Q4) Is difficult to be transmitted to the recording sheet (S) in the fixing area, so that damage to the toner image transferred to the recording sheet (S) can be reduced.

(Third Embodiment of the Present Invention) An image forming apparatus according to a third embodiment of the present invention is characterized in that the second embodiment of the present invention has the following requirement (A016). A016) When it is detected that the rear end of the recording sheet (S) has passed through the transfer sheet transport belt (43), the moving member (Hsa) returns to the original position, and the next recording sheet (S) is moved. The inter-transfer-fixing sheet transport device (Hs) that can be received. (Operation of the Third Embodiment of the Present Invention) In the third embodiment of the image forming apparatus according to the present invention, the inter-transfer-fixing sheet conveying device (Hs) is configured such that the rear end of the recording sheet (S) is the transfer sheet conveying belt. When the passage (43) is detected, the moving member (Hsa) returns to the original position, and the next recording sheet (S) can be received. In this state, by receiving the next recording sheet (S), the moving member (Hs
a) The effect at the time of restoration is not given to the image quality, and the loop is formed. Does not interfere with absorption.

[0020]

Next, specific examples (embodiments) of the embodiment of the image forming apparatus of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. (Embodiment 1) FIG. 1 shows Embodiment 1 of the image forming apparatus of the present invention.
FIG. FIG. 2 is an enlarged view of a main part of FIG.
In FIG. 1, an image forming apparatus F capable of performing color copying includes:
At the top, a copy start key UI1 (see FIG. 3), a numeric keypad UI2, a copy setting number input key UI3, a recording sheet type input key (sheet type input means) UI4, and a display unit UI5
And the like, and a transparent platen glass 2 on which a document (not shown) is placed. An original illuminating unit 3 that scans while illuminating the original on the platen glass 2 is arranged below the platen glass 2. The document illumination unit 3 has a document illumination light source 4 and a first mirror 5. A mirror unit 6 that moves at half the speed of the original illumination unit 3 is disposed below the platen glass 2. The mirror unit 6 includes the illumination light source 4.
And a second mirror 7 and a third mirror 8 that reflect the original image light reflected by the original and emitted by the original, and reflected by the first mirror 5. The document image light reflected by the third mirror 8 passes through the imaging lens 9 and is read as R, G, and B analog signals by a CCD (color image reading sensor).

The R (red), G (green), and B (blue) image signals read by the CCD are input to an IPS (image processing system). The operation of the IPS is controlled by the controller C. Also, IPS is
Image reading data output means 11 for converting an analog electric signal of an R, G, B read image obtained by the CCD into a digital signal and outputting the digital signal;
(Black), Y (yellow), M (magenta), and C
An image data output unit 12 converts the image data into (cyan) image data, performs data processing such as density correction and enlargement / reduction correction, and outputs the image data as writing image data (laser driving data). The image data output means 12 outputs the K,
An image memory 13 for temporarily storing image data of Y, M, and C is provided.

The IPS write image data output means 12
The image write data (laser drive data) of four colors of K, Y, M, and C output by the laser drive signal are input to the laser drive signal output device 14. The laser drive signal output device 14 outputs a laser drive signal of an image of each color component of K, Y, M, and C in accordance with the input image data at a predetermined timing to an ROS (optical scanning device, that is, a latent image forming device). ). The ROS is, for example, 160 by the laser beam L modulated by the input laser drive signal.
The electrostatic latent image writing position Q1 of the image carrier 16 rotating at a speed of mm / sec is scanned. The rotating image carrier 1
Along the line 6, a charger 17 for uniformly charging the image carrier 16 is disposed upstream of the latent image writing position Q1 in the moving direction of the image carrier 16. Although the charging device 17 is configured by a charging corotron in the first embodiment, it can be configured by a charging roll. After the image carrier 16 is uniformly charged by the charger 17, an electrostatic latent image is written by the laser beam L at the latent image writing position Q1.

A rotary developing device G for developing the electrostatic latent image into a toner image is provided in a developing area Q2 downstream of the latent image writing position Q1 along the moving direction of the image carrier 16. Are located. The developing device G includes developing devices GK, GY, G of four colors of K, Y, M, and C mounted around the rotation shaft 18.
M, GC, and with the rotation of the rotation shaft 18,
The developing units GK, GY, GM, and GC for the four colors are sequentially moved to the developing area Q2. The developing units GK, GY, GM, and GC convert the electrostatic latent images on the image carrier 16 into K (black), Y (yellow), M (magenta),
This is a device for developing a toner image of each color of C (cyan).
The toner image forming apparatus (14 to 17 + ROS + G) is constituted by the elements indicated by the reference numerals 14 to 17, ROS, G and the like.

Below the rotating image bearing drum 16,
An intermediate transfer belt (intermediate transfer body) B is provided. The intermediate transfer belt B is constituted by a thermosetting seamless belt in which carbon black is dispersed. The intermediate transfer belt B is disposed so as to pass through a primary transfer area Q3 set downstream of the developing area Q2 along the surface of the rotating image bearing drum 16. In the primary transfer area Q3, a primary transfer corotron (primary transfer device) 21
Is arranged.

In FIG. 1, an image carrier cleaner 22 and a static elimination lamp 23 are arranged along the rotating image carrier drum 16 and downstream of the primary transfer area Q3. In addition, it is possible to use a static elimination roll instead of the static elimination lamp 23. The intermediate transfer belt B includes a drive roll 25, an idler roll 26, a tension roll 27, a walk correction roll 28 (a roll for adjusting a position in the width direction of the intermediate transfer belt B), and an inner secondary transfer roll (backup roll) 29. It is stretched by five rolls, and is rotated in the direction of arrow A via the drive roll 25 at substantially the same speed as the image bearing drum 16 by a drive device (not shown). The drive roll 25, idler roll 26, tension roll 27, walk correction roll 28
Is constituted by a conductive metal roll. The inner secondary transfer roll 29 supporting the intermediate transfer belt B is formed by coating the surface of a grounded core with a semiconductive thin film, and the coating layer has a volume resistivity of, for example, 10 ⁸ Ωc.
m or more.

In the vicinity of the intermediate transfer belt B, in a secondary transfer area Q4, an outer secondary transfer roll is disposed on a side opposite to the inner secondary transfer roll (voltage applying roll) 29 with respect to the intermediate transfer belt B. 30 are arranged. The outer secondary transfer roll 30 is configured by winding a semiconductive elastic body around a conductive metal roll, and its volume resistivity is adjusted to, for example, 10 ⁵ Ωcm. Reference numeral 29-
The secondary transfer device T of the present embodiment is constituted by the element indicated by reference numeral 30. The distance from the primary transfer area to the secondary transfer device T along the moving direction of the intermediate transfer belt B is longer than the maximum length of the recording sheet S to be used. Further, a belt position sensor SN1 for detecting a position detection mark of the intermediate transfer belt B is provided.

The core material of the outer secondary transfer roll 30 is grounded, and the core material of the inner secondary transfer roll 29 is connected to a secondary transfer power supply circuit 32 (see FIG. 1) as a secondary transfer power applying means. Have been. The secondary transfer power supply circuit 32 includes a variable DC power supply 32a and an AC power supply 32b connected in series.
And is controlled by the controller C. For example, Vp-p of the AC voltage is 3.5 KV, the frequency is 200 Hz, and the DC voltage is about 1 kV to 6 KV. This secondary transfer power supply circuit 32 allows the
A bias voltage having the same polarity as that of the toner is applied to the next transfer roll 29, and the toner image on the intermediate transfer belt B is transferred to the recording sheet S.

The outer secondary transfer roll 30 is connected to the inner 2
While being moved to a position separated from the next transfer roll 29 and the intermediate transfer belt B, the transfer roll is cleaned by the transfer roll cleaner 33, and foreign matters such as toner particles and paper dust adhered by transfer are removed. An intermediate transfer member that removes untransferred toner remaining on the surface of the intermediate transfer belt B on the upstream side of the primary transfer area on the downstream side of the outer secondary transfer roll 30 in the transport direction of the intermediate transfer belt B A cleaner 34 is disposed, and a peeling claw 35 is disposed adjacent to the surface of the intermediate transfer belt B wound around the surface of the inner secondary transfer roll 29. The outer secondary transfer roll 30, the intermediate transfer body cleaner 34, and the peeling claw 35 are configured and arranged so as to be able to press against and separate from the intermediate transfer belt B.

From the paper feed tray 36 to the pickup roll 3
The recording sheet S taken out by 7 is conveyed one by one by a separating roll 38 having a feed roll 38a and a retard roll 38b. The recording sheet S conveyed one by one is conveyed by a plurality of conveyance rolls 39, temporarily stopped by a registration roll 40, and conveyed to the secondary transfer area Q4 through a guide conveyance path 41 at a predetermined timing. The pre-transfer sheet conveying device Ht is constituted by the elements indicated by the reference numerals 37 to 41. The pre-transfer sheet transport device Ht is a device that takes out the recording sheet S from the paper feed tray 36, and transports and passes the recording sheet S to a secondary transfer area Q4 set in the movement path of the intermediate transfer body B. A sheet sensor SN2 is disposed downstream of the separating roll 38, and detects the leading end position and the trailing end position of the recording sheet S passing therethrough. Then, the sheet detection signal is input to the controller C (see FIG. 3).

A sheet thickness sensor SN3 constituted by a pair of rolls is disposed in the path of the recording sheet S conveyed by the conveying rolls 39, and detects the thickness of the recording sheet S passing therethrough. I have. The sheet thickness signal detected by the sheet thickness sensor SN3 is input to the controller C (see FIG. 3). The recording sheet S
Then, the unfixed toner image on the intermediate transfer belt B is secondarily transferred when passing through the secondary transfer area Q4. The recording sheet S on which the unfixed toner image has been transferred moves along the upper surface of the sheet guide 42 on the downstream side of the transfer area, and further, the transfer sheet transport belt 43 and the sheet guide before fixing (disposed upstream of the fixing area Q5). The sheet is conveyed to the fixing position Q5 through the sheet guide 44).

The transfer sheet conveying belt 43 has a small air communication hole (not shown) formed therein, and the inside of the belt is sucked by a blower (not shown) to convey the recording sheet S while sucking it with a small force. It is configured as follows. 2, the sheet conveying belt 43 is supported by an upstream belt supporting roll 46 arranged on the upstream side in the sheet conveying direction and a downstream belt supporting roll 47 arranged on the downstream side. Shaft 46a of upstream belt support roll 46
Is rotatably supported by a fixed frame (not shown), and a sheet conveying belt driving motor M2 (see FIG. 3).
And a gear (not shown) or the like to transmit the rotational force. An upstream end of a belt support frame 48 is rotatably connected to a shaft 46a of the upstream belt support roll 46. The downstream end of the belt support frame is free to rotate, and rotatably supports the downstream belt support roll 47.

An arc-shaped rack 49 is fixed to the belt support frame 48, and the rack 49 is engaged with a pinion 50. The pinion 50 is a belt supporting frame position control required motor M4 (see FIGS. 2 and 3).
The belt support frame 48 is rotated around the shaft 46a of the upstream belt support roll 46 by the rotation of the pinion 50 in the normal and reverse directions, and is shown by a normal position P0 shown by a solid line in FIG. Downward movement position P1
It is configured to rotate (move) between the two. Free rollers 51 are rotatably supported at both ends of the shaft 47a of the downstream belt support roll 47 supported at the downstream end of the belt support frame 48, respectively. The sheet sensor SN before fixing is provided on the belt support frame 48.
4 is supported, and detects the passage of the front end and the rear end of the recording sheet S sucked and conveyed by the sheet conveying belt 43. The detection signal is input to the controller C as shown in FIG.

In FIG. 2, the pre-fixing sheet guide 4
Reference numeral 4 denotes both ends in the width direction (perpendicular to the paper surface) supported rotatably about the hinge shaft 52, and both ends in the width direction (perpendicular to the paper surface) are tension springs 53, respectively. Is always pulled upward. Therefore, the pre-fixing sheet guide 44 always receives a clockwise rotational force around the hinge shaft 52, and the upstream end of the pre-fixing sheet guide 44 always receives the free roller 5.
It is in contact with 1. Accordingly, when the belt support frame 48 rotates around the shaft 46a of the upstream belt support roll 46 and rotates (moves) between the normal position P0 and the downward movement position P1, the sheet guide 4 before fixing is rotated.
4 is also configured to move between a normal position P0 indicated by a solid line and a downward movement position P1. Reference numerals 42 to 5
The elements H3, M2, and M4 constitute the inter-transfer-fixing sheet transport device Hs. Further, the reference numerals 43 to 4
The moving members Hsa of the inter-transfer-fixing sheet conveying device Hs are constituted by the elements indicated by 9 and 51.

When the recording sheet S is conveyed by the inter-transfer-fixing sheet conveying device Hs and passes through the fixing position Q5, the unfixed toner image on the recording sheet S
The sheet is fixed by a fixing device 54 having a and a pressure roll 54b, and is discharged to a sheet discharge tray 56. The recording sheet conveyance speed V1 when passing through the secondary transfer area, the speed V2 of the sheet conveyance belt 43 of the sheet conveyance device Hs during transfer and fixing, and the recording sheet conveyance speed when passing through the fixing device (the heating roll 54a and the pressure roll 54b The peripheral speed V3 is set so as to satisfy the following expressions (1) and (2). V1 = 1.003V3 ……………………………… (1) V2 = 1.005V3 …………………………………………… (2) Note that the relationship between the values of V1 to V3 is represented by the following equation (3): V1 <V2> V3...... It is possible to select an appropriate value for an experiment or the like within a range satisfying the relationship.

FIG. 3 is a block diagram of a control portion of the image forming apparatus F. In FIG. 3, a controller C has a UI (user interface) setting signal,
Detection signals from a belt position sensor SN1, a sheet sensor SN2, a sheet thickness sensor SN3, a sheet sensor before fixing SN4, and the like are input. The controller C includes a motor driving circuit D4 for controlling the position of the belt supporting frame in accordance with the input signal.
Output the operation control signal. Controller C
Outputs operation signals of the motor drive circuit D1 for the intermediate transfer belt, the motor drive circuit D2 for the sheet transport belt, and the motor drive circuit D3 for the fixing device. The intermediate transfer belt drive motor M1 is rotationally driven by the intermediate transfer belt motor drive circuit D1.
5 and the intermediate transfer belt B rotate. The sheet conveying belt driving motor M2 is rotationally driven by the sheet conveying belt driving circuit D2, and accordingly, the sheet conveying belt 43 is rotationally driven. The fixing device driving motor M3 is rotationally driven by the fixing device motor driving circuit D3, and accordingly, the heating roll 54a and the pressure roll 54b of the fixing device 54 are rotationally driven.

The controller C is constituted by a computer and has functions such as a transfer-fixing distance storing means C1, a sheet length detecting means C2, and a moving member position control signal outputting means C3. C1: Transfer-fixing distance storage means The transfer-fixing distance storage means C1 stores the sheet conveyance distance between the secondary transfer area Q4 and the fixing area Q5 when the sheet conveyance belt 43 is located at the normal position P0. doing. C2: Sheet Length Detecting Unit The sheet length detecting unit C2 detects that the front end of the recording sheet S taken out from the paper feed tray 36 is the sheet sensor SN2.
Has the function of detecting the length of the recording sheet S in the transport direction (sheet length) based on the time from when the sheet passes through the sheet to when the rear end passes. C3: Moving member position control signal output unit The moving member position control signal output unit C3 is a unit that moves the belt support frame 48 downward from the normal position P0 when the sheet length is longer than the inter-transfer fixing distance. (That is, it has a function of outputting a signal indicating a drive amount of the belt support frame position control motor M4. The drive amount of the belt support frame position control motor M4 is
This value is determined in accordance with the difference between the sheet length and the inter-transfer-to-fixing distance, and can be determined by a table value stored in the memory of the controller C or a calculation formula. C4: Fixing Area Reaching Detecting Means The fixing area reaching detecting means C4 is provided for a predetermined period of time (the distance from the pre-fixing sheet sensor SN4 to the fixing area Q5 is measured after the pre-fixing sheet sensor SN4 detects the leading edge of the recording sheet S). After the elapse of the time required for S to move), a function of outputting a fixing area arrival detection signal indicating that the recording sheet S has reached the fixing area Q4 is provided.

(Operation of Embodiment 1) The controller C of the image forming apparatus F operates the laser at a predetermined timing in accordance with the position detection signal of the intermediate transfer belt B output from the belt position sensor SN1 of the intermediate transfer belt B. The drive signal output device 14 is operated. The ROS that emits the laser light L for writing an image in response to the image writing signal output from the laser drive signal output device 14 has an arrow A at the latent image writing position Q1.
An electrostatic latent image is written on the image carrier 16 rotating in the direction.

The unfixed toner image formed on the image carrier 16 is transferred to a primary transfer area Q3 where the image carrier 16 and the intermediate transfer belt B are in contact with each other. The image is transferred from the image carrier 16 to the surface of the intermediate transfer belt B by the primary transfer corotron 21 to which a voltage is applied. The residual toner on the image carrier after the primary transfer is cleaned by an image carrier cleaner 22 disposed around the image carrier 16 before the next cycle.

When a single-color image is formed, the unfixed toner image primarily transferred to the intermediate transfer belt B is secondarily transferred to the recording sheet S immediately. When forming, the image carrier 16
The process of forming the toner image and the primary transfer of the toner image are repeated by the number of colors. For example, when a full-color image is formed by superimposing four color toner images, K (black), Y (yellow), M (magenta), and C (cyan) are not determined on the image carrier 16 for each rotation. An unfixed toner image is formed, and these unfixed toner images are sequentially primary-transferred to the intermediate transfer belt B.

On the other hand, the intermediate transfer belt B holds the first untransferred black unfixed toner image,
And the unfixed yellow, magenta and cyan toner images are transferred onto the intermediate transfer belt B with the black unfixed toner image every one revolution thereof. Peeling nail 35
The cleaner 34 is disposed so as to be able to freely contact (separate or separate) from the intermediate transfer belt B. When a color image is formed, the unfixed toner image of the final color is primarily transferred to the intermediate transfer belt B. Until then, these members are separated from the intermediate transfer belt B.

The unfixed toner image primarily transferred to the intermediate transfer belt B is transported to a secondary transfer area Q4 facing the transport path of the recording sheet S with the rotation of the intermediate transfer belt B. In the secondary transfer area Q4, the semiconductive outer secondary transfer roll 30 is in contact with the intermediate transfer belt B, and the recording sheet S carried out of the tray 36 by the pickup roll 37 is temporarily stopped by the registration roll stroller 39 and then stopped. It is conveyed at a predetermined timing, and is transported between the outer secondary transfer roll 30 and the intermediate transfer belt B (secondary transfer area).
Sandwiched between. When a DC voltage having the same polarity as that of the toner and an AC voltage having a predetermined frequency are applied to the inner secondary transfer roller 29 from a power supply device 32, the unfixed toner image carried on the intermediate transfer belt B is transferred to the secondary transfer area. In Q4, the image is electrostatically transferred to the recording sheet S. The sheet length (the length in the conveyance direction) of the recording sheet S is determined by the sheet sensor SN2.
Is detected by the controller C to which a detection signal for detecting the passage of the front end and the rear end of is input.

Then, the recording sheet S to which the unfixed toner image has been transferred is peeled off from the intermediate transfer belt B by the peeling claw 35 and is sent to the fixing device 54 by the inter-transfer-fixing sheet transport device Hs so that the unfixed toner image is transferred. A fixing process is performed. On the other hand, the intermediate transfer belt cleaner 34 removes residual toner from the surface of the intermediate transfer belt B on which the secondary transfer of the unfixed toner image has been completed.

FIG. 4 is a diagram for explaining the operation of the sheet conveying device Hs during transfer and fixing used in the first embodiment. In FIG. 4A,
The recording sheet S secondary-transferred in the secondary transfer area Q4 is
The sheet is conveyed to the sheet conveying belt 43 while being guided by the sheet guide 42 on the downstream side of the transfer area of the sheet conveying device Hs during transfer and fixing. In FIG. 4B, the sheet conveying belt 43 conveys the recording sheet S while attracting the recording sheet S by suction means such as the blower (fan) not shown. The speed V2 of the sheet conveying belt 43 of the inter-transfer-fixing sheet conveying device Hs satisfies the expression (3). In this case, 2 of the recording sheet S
Since the recording sheet S is conveyed while being slightly pulled by the sheet conveying belt 43 in the passing portion of the next transfer area Q4, no loop is formed. Sheet conveying belt 43, fixing device 5
Between the four intervals, a loop of the recording sheet S is formed because the conveyance speed V3 of the fixing device 54 is low. In FIG. 2, the front end of the recording sheet S is a pre-fixing sheet sensor SN.
After passing through No. 4, a sheet front end detection signal detected by the pre-fixing sheet sensor SN4 is input to the controller C. The transfer area sheet arrival detecting means C4 of the controller C determines that the front end of the recording sheet S has reached the fixing device 54 after a predetermined time has elapsed since the detection of the sheet front end detection signal, and outputs a transfer area sheet arrival detection signal. I do.

In FIG. 4C, when it is detected that the front end of the recording sheet S has reached the fixing device 54, the controller C (see FIG. 3) drives the belt support frame position control motor M4 to control the belt M. Support frame 48
(See FIG. 2) is moved downward from the normal position P0 to the downward movement position P1. At this time, the free roller 51 at the downstream end of the belt support frame 48 moves downward. The pre-fixing sheet guide 44, which is arranged on the upstream side of the fixing device 54 and is rotatable around the hinge shaft 52, has its upstream end contacted with the free roller 51 by the tension spring 53, and It rotates downward together with the roller 51. At this time, the transfer sheet conveyance belt 43 and the pre-fixing sheet guide 44 move downward in the recording sheet S conveyance surface to absorb the loop of the recording sheet S formed between the transfer sheet conveyance belt 43 and the fixing device 54. A possible space (a space where the recording sheet sags) is formed.

The loop formed by the speed difference between the transport speeds V1 to V3 greatly changes depending on the sheet length (length in the transport direction) of the recording sheet S. To cope with these, the space for absorbing the loop is changed by adjusting the moving amount of the moving member Hsa of the inter-fixing sheet conveying device Hs according to the sheet length of the recording sheet S. For example, if the length of the recording sheet S in the transport direction is shorter than the distance between the secondary transfer unit and the fixing device 54, the recording sheet S is sent to the fixing device 54 after the completion of the secondary transfer, so that the speed of the fixing device 54 is reduced. The influence of the difference on the periphery of the secondary transfer is small. Therefore, when the sheet length of the recording sheet S (the length in the conveyance direction) is shorter than the inter-transfer-fixing distance (the recording sheet conveyance distance between the secondary transfer area Q4 and the fixing area Q5), the moving sheet HSa is moved downward. Is not moved. Although it is possible to configure the moving member HSa to move downward, the moving amount in that case is reduced.

Conversely, as the time during which the recording sheet S is nipped by both the secondary transfer means and the fixing device 54 is longer, the speed difference (V
Since the amount of loop formed by 2-V3) becomes large,
If the sheet length of the recording sheet S is longer than a certain value,
The amount of downward movement of the moving member Hsa is increased, and the space for absorbing the loop is increased. It is possible to set a plurality of threshold values for the length of the recording sheet S in the transport direction that determine the amount of movement of the movable member Hsa, and in that case, more appropriate transport can be performed. Further, the rotational movement of the moving member Hsa may be continuously performed while the recording sheet S is being conveyed by the transfer sheet conveying belt 43.
In this case, after the leading end of the recording sheet S reaches the fixing device 54,
As the loop is formed, the transfer sheet transport belt 4
3. The fixing device 54 and the pre-fixing sheet guide 44 can be conveyed while rotating and moving to absorb the formed loop.

In FIG. 4C, the recording sheet S is conveyed along the conveying surface of the transfer sheet conveying belt 43 by suction, and follows the concave path formed by the downward movement of the transfer sheet conveying belt 43 and the sheet guide 44 before fixing. , Is sent to the fixing device 54, so that it does not come into contact with other components and does not affect the image quality. Further, since the recording sheet S on the transfer sheet transport belt 43 is sucked by suction means such as a blower (not shown), the loop formation of the recording sheet S is limited to between the transfer sheet transport belt 43 and the fixing device 54. Can be
The influence of the loop formation does not reach the secondary transfer area Q4. Further, the damage to the recording sheet S can be reduced without a sudden change in the discharge direction of the recording sheet S immediately after the secondary transfer.

As described above, the transfer sheet conveying belt 43
In addition, the pre-fixing sheet guide 44 conveys the recording sheet in a state in which it moves downward in a linked manner (the state of FIG. 4C). FIG.
In D, when the pre-fixing sheet sensor SN4 detects that the trailing edge of the recording sheet S has passed through the transfer sheet conveying belt 43, the transfer sheet conveying belt 43 and the pre-fixing sheet guide 44 return to their original positions, and the next recording is performed. Sheet S
Is carried. The transfer sheet transport belt 43 and the pre-fixing sheet guide 44 are returned before the secondary transfer of the next recording sheet S, so that the image quality is not affected by vibration in the secondary transfer area Q4.

FIG. 5 shows the sheet transfer device Hs during transfer and fixing.
4 is a flowchart for moving part elevating control executed by the controller C shown in FIG. 3 to perform the elevating movement control of the moving member Hsa. The moving part elevation control flowchart shown in FIG. 5 is executed by a program stored in the memory of the controller C. The moving part elevating control flowchart starts when the power of the image forming apparatus F is turned on, and is executed in multitask in parallel with another program for performing the image forming operation. When the moving part elevating control flowchart starts, it is determined in ST1 (step 1) whether or not the start key has been turned on. No (N)
In this case, ST1 is repeatedly executed. If yes (Y), the process moves to ST2.

In ST2, it is determined whether or not the recording sheet has been fed. This determination is made based on whether or not the recording sheet S has passed the sheet sensor SN2 (see FIG. 1). If no (N), ST2 is repeatedly executed, and if yes (Y), the process moves to ST3. In ST3, it is determined whether or not the sheet length of the recording sheet is longer than the inter-transfer-fixing distance (recording sheet transport distance between the secondary transfer area Q4 and the fixing area Q5). If yes (Y), the process moves to ST4.
In ST4, the moving amount of the moving member Hsa of the inter-transfer-fixing sheet conveying device Hs is determined. Next, in ST5, it is determined whether or not the front end of the recording sheet has entered the nip portion (fixing area Q5) of the fixing device 54. This determination is made based on whether or not the fixing area arrival detecting means C4 (see FIG. 3) has output a detection signal. If no (N), ST5 is repeatedly executed. If yes (Y), the process moves to the next ST6.

In ST6, the moving member Hsa of the sheet conveying device Hs during transfer and fixing is moved downward by the amount determined in ST4. Next, in ST7, it is determined whether or not the trailing edge of the recording sheet S has passed the inter-transfer-fixing sheet transport device Hs. This determination is made based on whether or not a predetermined time has elapsed since the pre-fixing sheet sensor SN4 detects the rear end of the recording sheet S. If no (N), ST7 is repeatedly executed, and if yes (Y), the process moves to ST8. In ST8, the moving member Hsa is moved up to restore the original position.
Next, in ST9, it is determined whether or not the job has been completed. This determination is made based on whether or not there is an image to be recorded next. If yes (Y), the process returns to ST1, and if no (N), the process returns to ST2. In the case of No (N) in ST3, the process proceeds to ST10. In ST10, normal conveyance of the recording sheet (conveyance with the moving member Hsa held at the original position) is performed. Then, the process proceeds to ST9.

(Embodiment 2) FIG. 6 is an explanatory view of a main part of an image forming apparatus according to Embodiment 2 of the present invention, and corresponds to FIG. 2 of Embodiment 1. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Example 2
The second embodiment differs from the first embodiment in that a tension spring 49 'and a cam 50' are used instead of the rack 49 and the pinion 50 in the first embodiment.
It is configured similarly to.

(Operation of the Second Embodiment) The second embodiment has the same operation as the first embodiment. Further, since the moving member Hsa is moved up and down by the rotation of the cam 50 ', the moving member Hsa
The up and down movement changes continuously, and vibration hardly occurs. For this reason, vibrations that adversely affect the secondary transfer area Q4 are not transmitted.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) In the first and second embodiments, the upstream end of the pre-fixing sheet guide 44 can be disposed in contact with the upper surface of the transfer sheet conveying belt 43. In this case, in the normal state of the inter-transfer-fixing sheet transport device Hs, the transfer sheet transport belt 43 is arranged such that the leading end of the pre-fixing sheet guide 44 comes inside (upstream in the recording sheet transport direction) from the fixing side end of the transfer sheet transport belt 43. Even during the movement, the transfer sheet transport belt 43 and the pre-fixing sheet guide 44 are arranged such that an unnecessarily large gap is not formed and the recording sheet S transport is not hindered. (H02) Instead of detecting the sheet length using the sheet sensor SN2, the sheet length can be detected by a UI input signal. (H03) The recording sheet S is conveyed between the secondary transfer area and the fixing area due to a difference in the thickness of the recording sheet S, the kind of the recording sheet S, and the stiffness of the environment due to the environment and the like. The loop formed by the speed difference between the recording sheet conveyance speed V2 of the sheet conveyance device during transfer and fixing and the recording sheet conveyance speed V3 of the fixing device greatly changes. For example, the greater the strain on the recording sheet S, the smaller the amount of loop formed. In order to cope with these, the transport speed V depends on the thickness and type of the recording sheet S.
The value of 1 to V3 can be adjusted, and the amount of movement of the moving member Hsa can be adjusted.

[0055]

The above-mentioned X of the present invention has the following effects. (E01) The downward loop of the sheet is positively formed between the conveying device and the fixing device, and the difference in each conveying speed is absorbed to suppress the occurrence of the bending of the recording sheet in the vicinity of the transfer portion, and the image due to the rubbing of the recording sheet is obtained. It is possible to provide an image forming apparatus that does not cause disturbance or the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of Embodiment 1 of an image forming apparatus of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1;

FIG. 3 is a block diagram of a control portion of the image forming apparatus F.

FIG. 4 is a diagram illustrating the operation of the inter-transfer-fixing sheet conveying device Hs used in the first embodiment.

FIG. 5 is a flowchart of a moving part lifting / lowering control executed by the controller C shown in FIG. 3 to perform the raising / lowering movement control of the moving member Hsa of the inter-transfer-fixing sheet conveying device Hs.

FIG. 6 is an explanatory view of a main part of a second embodiment of the image forming apparatus according to the present invention, and corresponds to FIG. 2 of the first embodiment.

[Explanation of symbols]

B: Intermediate transfer member (intermediate transfer belt), C1: Transfer / fixing distance storage means, C2: Sheet length detecting means, C4: Fixing area arrival detecting means, Hs: Transfer / fixing sheet transport device, Hsa
.., Moving member, Ht, sheet transfer device before transfer, Q3, primary transfer area, Q4, secondary transfer area, Q5, fixing area, S, recording sheet, T, secondary transfer unit, UI, user interface, UI4 Sheet type input means, V1 ... secondary transfer area Q
4 transport speed of the recording sheet S, V2... Transport speed V3 of the recording sheet S of the inter-transfer-fixing sheet transport device Hs... Fixing area Q5.
Transport speed 16 of the recording sheet S: image carrier, 21: primary transfer device, 43: transfer sheet transport belt, 44: sheet guide before fixing, 54: fixing device, (14 to 17 + ROS +
G) ... toner image forming apparatus

Claims (5)

[Claims] 1. An image forming apparatus having the following requirements: (A01) an image carrier on which a toner image is formed on the surface of a rotatable endless image carrier; (A02) the image carrier A toner image forming apparatus for forming a toner image according to image information on a body surface; (A03) an intermediate transfer having an endless surface rotatably moving through a primary transfer area set along the surface of the image carrier; (A04) a primary transfer unit for transferring the toner image on the surface of the image carrier to the endless intermediate transfer body surface in the primary transfer area, and (A05) a transfer path set for the intermediate transfer body. A pre-transfer sheet conveying device that conveys and passes the recording sheet to the secondary transfer area, (A06) that transfers the toner image transferred to the intermediate transfer body to the recording sheet;
(A07) a secondary transfer unit disposed in a next transfer area, and (A07) applying a conveying force to the recording sheet passing through a fixing area set in a conveying path of the recording sheet onto which the toner image has been transferred; Fixing device for fixing the toner image of
(A08) An inter-transfer / fixing sheet conveying device for conveying a recording sheet on which a toner image has been transferred between the secondary transfer area and the fixing area, (A09) the conveying speed of the recording sheet in the secondary transfer area is V1, and the transfer is When the conveyance speed of the recording sheet of the sheet conveyance device during fixing is V2, and the conveyance speed of the recording sheet in the fixing area is V3, the conveyance speed V1,
V1 <V2> V3 (A010): A transfer for storing a transfer-fixing distance, which is a distance between the secondary transfer area and the fixing area, wherein V2 and V3 are set so as to satisfy the following expression. (A011) sheet length detecting means for detecting the length of the recording sheet passing through the secondary transfer area in the conveying direction, (A012) the leading end of the recording sheet has reached the fixing area Fixing area arrival detecting means for detecting that
3) When the sheet length is longer than the inter-transfer-to-fixing distance, the sheet is moved to the back side of the recording sheet in order to form a space in which the recording sheet is slackened in accordance with the output signal of the fixing area arrival detecting means. The inter-transfer-fixing sheet conveying device having a moving member. 2. The image forming apparatus according to claim 1, wherein the moving amount is variable according to the thickness or type of the recording sheet to be conveyed. Moving member. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus satisfies the following requirement (A015): (A015) sucks and conveys the recording sheet that has passed through the secondary transfer area. A transfer sheet transport belt whose downstream end pivots up and down around the upstream end and a recording sheet that is arranged downstream of the transfer sheet transport belt to guide the recording sheet to the fixing area and center around the downstream end. The upstream end has a pre-fixing sheet guide that rotates up and down,
The inter-transfer / fixing sheet conveying device, wherein a downstream end of the transfer sheet conveying belt and an upstream end of the pre-fixing sheet guide are moved downward to form a space in which the recording sheet sags to the back side. 4. The image forming apparatus according to claim 3, wherein the following requirement (A016) is satisfied: (A016) When it is detected that the rear end of the recording sheet has passed through the transfer sheet conveying belt: Wherein the moving member returns to its original position to receive the next recording sheet. 5. An image forming apparatus having the following requirements: (B01) an image carrier on which a toner image is formed on the surface of a rotatable endless image carrier; (B02) the image carrier (B03) a toner image forming apparatus for forming a toner image corresponding to image information on the body surface, (B03) a pre-transfer sheet conveying apparatus for conveying and passing a recording sheet to a transfer area set along the image carrier surface, (B) a transfer unit disposed in the transfer area for transferring the toner image on the surface of the image carrier to a recording sheet in the transfer area; (B05) a fixing area set in a conveyance path of the recording sheet on which the toner image has been transferred; A fixing device for fixing a toner image on the recording sheet while applying a conveying force to the recording sheet passing therethrough; (B06) a transfer fixing device for conveying the recording sheet on which the toner image has been transferred between the transfer area and the fixing area; (B07) When the conveying speed of the recording sheet in the transfer area is V1, the conveying speed of the recording sheet in the inter-transfer-fixing sheet conveying apparatus is V2, and the conveying speed of the recording sheet in the fixing area is V3, The transfer speed between transfer and fixing, wherein the transfer speeds V1, V2, and V3 of the respective recording sheets satisfy the following formula: V1 <V2> V3 (B08) The distance between the transfer area and the fixing area. A transfer-fixing distance storing means for storing the transfer-fixing distance, (B
09) sheet length detecting means for detecting the sheet length, which is the length of the recording sheet passing through the transfer area in the transport direction, (B01
0) a fixing area arrival detecting means for detecting that the leading edge of the recording sheet has reached the fixing area; (B011) an output signal of the fixing area reaching detecting means when the sheet length is longer than the inter-transfer-fixing distance; The inter-fixing sheet conveying apparatus, further comprising a moving member that moves to the back side of the recording sheet to form a space in which the recording sheet sags to the back side according to the above.