JP3478305B2 - Image forming device - Google Patents

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 to which a dry electrophotographic technique is applied, which is used in printers, facsimiles, copiers, and the like, and more particularly to a recording medium conveying technique in the image forming apparatus.

[0002]

2. Description of the Related Art As a conventional technique for controlling the driving force of a recording paper feeding means in an image forming apparatus having a transfer means,
Japanese Unexamined Patent Publication No. 5-249784 discloses a technique for avoiding problems caused by bending and pulling of a transfer medium even when the transfer medium is conveyed by a plurality of rollers provided in a conveying path.

An example of this prior art is shown in FIG. FIG. 19 is a sectional view showing a schematic configuration of the printer device. In FIG. 19, the printer device includes a transfer device 103 including a photoconductor 101 that holds a toner image by a dry electrophotographic mechanism (not shown) and a transfer roller 102 that transfers the toner image onto a transfer medium W, and a loading side of the transfer device 103. The first roller 104 that is placed in the position to carry the transfer medium W into the transfer device 103.
And a second roller 105 that is arranged on the carry-out side of the transfer device 103 and carries out the transfer medium W on which the image has been transferred.
The transfer medium W is conveyed by driving the first roller 104 and the second roller 105. In addition, the first roller 10
The distance L between the conveying action portions C and D of the fourth roller 105 and the second roller 105 is set shorter than the length of the transfer medium W to interrupt the driving force to the first roller 104 (not shown). Is provided to control the drive connecting / disconnecting means to determine that the front end portion of the transfer medium W in the transport direction has reached the transport action portion D of the second roller 105, and to control the drive force of the first roller 104. If the outer peripheral speeds of the first and second rollers do not match due to processing accuracy or the like, the driving force of the first and second rollers does not act on the transfer medium at the same time, or There is disclosed a technique of avoiding deterioration of transfer efficiency, deterioration of information, and poor fixing due to bending and pulling of the transfer medium by making the time extremely short even if they act simultaneously.

Here, an example of the image forming apparatus constructed by the inventors for verifying the effects of these conventional techniques will be described.

FIG. 20 is a cross-sectional view showing a schematic structure of a conventional image forming apparatus constructed by the inventors, specifically, a printer apparatus having a laser scanning optical system. The general operation of the conventional image forming apparatus will be described with reference to FIG.

In FIG. 20, there is a charging roller 106 as a charging means on the outer periphery of the photosensitive member 101 which rotates in the direction of arrow E by a drive source (not shown). The charging roller 106 contacts the photoconductor 101, and a voltage is applied from a high voltage power source (not shown) to uniformly charge the surface of the photoconductor. The charged photoconductor 101 is a laser scanning optical system 10 which is an exposing means.
7 is selectively exposed to light to form a latent image on the photoconductor 101. The latent image formed on the surface of the photoconductor 101 is visualized by the toner supplied by the developing roller 108 which is a developing unit. The transfer roller 102, which is a transfer unit, comes into contact with the photosensitive member 101 on the downstream side of the developing unit, and a voltage is applied from a high voltage power source (not shown). The paper feeding means is the paper feeding roller 1.
09, a separation pad 110, and a separation spring 111 for urging the separation pad 110 toward the paper feed roller 109,
The recording paper 113 stored in the paper feed tray 112 is sequentially separated and fed by the paper feed roller 109 and the separation pad 110, and is nipped and conveyed between the photoconductor 101 and the transfer roller 102. The recording paper 113 on which the toner image on the photoconductor 101 is transferred by the transfer means is composed of a heat roller 115 having a rod-shaped halogen lamp 114 inside and a pressure roller 116 press-contacted to the heat roller 115. The toner image is fixed by being pinched and conveyed to the outside of the apparatus.

Further, the transfer spring 117 and the pressure spring 11
Numeral 8 is located at both ends of the transfer roller 102 and the pressure roller 116 in the recording medium conveyance width direction, and makes the transfer roller 102 and the heat roller 115 press and contact the photoconductor 101 and the heat roller 115, respectively. The driving method of each roller is the photoconductor 101, the developing roller 108, and the heat roller 1.
15 is driven by a driving source (not shown), the charging roller 106 is the photosensitive member 101, and the transfer roller 102 is the photosensitive member 1.
01, the pressure roller 116 is driven by the heat roller 115. Further, the paper feed roller 109 is configured so that power can be selectively transmitted from a drive source via a clutch mechanism (not shown).

It should be noted that a pre-transfer sensor 119 and a post-transfer sensor 120 are provided by using a reflection type photo sensor as a position detecting means of the recording paper 113, and the respective sensors are used to start the feeding of the recording paper 113 and enter the fixing means. It is configured to send a signal to a control circuit (not shown).

Table 1 shows the main specifications of this conventional image forming apparatus.
Shown in.

[0010]

[Table 1]

(Verification Experiment Example) An experiment for verifying the disclosure of the above-mentioned prior art was conducted using a conventional image forming apparatus. In the experiment, the feeding of the paper feed roller 109 is stopped at the time when the leading edge of the recording paper reaches the contact position G between the photoconductor 101 and the transfer roller 102 in FIG. The state of the recorded image is observed at the time when the contact position D is reached, and the results are shown in Table 2. The paper feed roller 109 and the heat roller 115
The outer peripheral speed of was approximately the same as the outer peripheral speed of the photoconductor 101.

[0012]

[Table 2]

In Table 2, when the paper feed roller 109 is stopped at the G position under the conditions of environment I and J, the feed pitch unevenness occurs in which the print image shrinks at the leading end of the print image corresponding to the G position. When the paper feed roller 109 was stopped at the D position, an extremely slight unevenness in the feed pitch was recognized in the recorded image portion corresponding to the G position when stopped.

However, under the condition of environment K, when the stop position of the paper feed roller 109 is the G position or the D position, the feed image unevenness occurs in the print image portion corresponding to the G position when the feed roller 109 is stopped.

Further, under any environmental condition, wrinkles were generated on the recording paper after image recording, and the degree of wrinkles became more remarkable as the environment became hot and humid. The degree of wrinkle is also related to the thickness of the recording paper, and particularly when using a thin recording paper with a basis weight of about 60 g / m 2, wrinkles are particularly noticeable. Occurrence was confirmed.

[0016]

As described above, it was confirmed that the prior art is effective against the unevenness of the feed pitch of the recorded image under the environment of low temperature and low humidity or room temperature and normal humidity. In the high temperature and high humidity environment, the effect of eliminating unevenness in the feed pitch is not obtained. Further, wrinkles on the recording paper are also observed, and there is a problem that a good image cannot be formed due to changes in environmental conditions.

The present invention solves the above problems, and an object of the present invention is to provide a small-sized image forming apparatus capable of forming an excellent image even when environmental conditions change.

[0018]

In order to achieve the above object, the image forming apparatus of the present invention transfers a toner image formed on a photoconductor to a recording sheet by a roller which is in contact with the photoconductor and which is applied with a voltage. Transfer means, a feeding means located upstream of the transfer means in the recording paper conveyance direction, for feeding the recording paper in the transfer means direction, and a driving force interrupting means for interrupting the feeding drive force of the feeding means, In an image forming apparatus, which is located on the downstream side of the transfer unit in the recording sheet conveyance direction and includes a unloading unit that unloads the recording sheet from the transfer unit, the transfer unit has a rubber portion.
And the transfer roller is supported via a transfer bearing member.
It has a holding unit for holding, and the length of the recording paper conveyance path from the feeding means to the unloading means is set shorter than the recording paper length, and the recording paper conveyance speed Vt of the transfer means and the recording paper conveyance force F are set.
t, the recording sheet conveying speed Vf of the discharging means, the recording sheet conveying force Ff
Is set so that Vt <Vf and Ft> Ff, and the driving force interrupting unit cuts off the driving force of the feeding unit in a state where the transfer unit and the unloading unit jointly convey the recording paper during image formation. A control means is provided.

Further, the feeding means is a paper feeding device for accommodating a plurality of recording papers and sequentially separating and feeding one by one, and the carrying-out means transfers the toner image transferred onto the recording papers. The fixing device is characterized in that it is heated and pressed to fix it on the recording medium.

[0020]

According to the image forming apparatus of the present invention, the transfer speed and the transfer speed of the transfer paper and the transfer power of the transfer paper are improved.
Even if the environmental conditions change, the recording paper is appropriately expanded between the transfer means and the carry-out means, and the driving force of the feeding means is cut off in the state where the transfer means and the carry-out means jointly convey the recording paper. It is possible to provide a small-sized image forming apparatus that prevents wrinkles in the recording paper generated by the carry-out means, reduces the change in tension of the recording paper applied to the transfer means, and does not cause wrinkles in the recording paper or uneven feeding pitch.

[0021]

EXAMPLES The present invention will be described in detail below based on examples.

FIG. 1 is a cross-sectional view of the apparatus for explaining the overall structure of the image forming apparatus of the present invention. Figure 1 shows the schematic operation of this device.
Explained by.

In FIG. 1, there is a charging roller 3 as a charging means on the outer periphery of the photoconductor 2 which rotates in the direction of arrow A by a drive source (not shown). While being in contact with the photoconductor 2, the charging roller 3 is applied with a voltage from a high voltage power source (not shown) to uniformly charge the surface of the photoconductor. The charged photoconductor 2 is selectively exposed by a laser scanning optical system 4 which is an exposing means to form a latent image on the photoconductor 2. The latent image formed on the surface of the photoconductor 2 is visualized by the toner supplied by the developing roller 5, which is a developing unit. The transfer roller 6, which is a transfer unit, is biased by a transfer spring 13, contacts the photosensitive member 2 on the downstream side of the developing unit, and is applied with a voltage from a high voltage power source (not shown).

On the other hand, the recording papers 1 stacked and stored on the paper feed bottom plate 9 in the paper feed tray 8 are urged by the paper feed spring 10 and the separation pad 12 made of cork material or urethane foam material. The pad base 25, which holds and swings, is urged by the separation spring 11, and each of the paper feed rollers 7 is a paper feeding unit.
The recording paper 1 is sequentially separated and fed by the rotation of the paper feed roller 7.

The toner image is transferred onto the recording paper 1 while being sandwiched between the photoconductor 2 and the transfer roller 6, and the recording paper 1 is subsequently conveyed toward the fixing means.

The fixing means has a rod-shaped halogen lamp 1 inside.
4 and a heat roller 15 that is urged by a pressure spring 16 to come into pressure contact with the heat roller 15. The recording paper 1 on which the toner image is transferred is nipped and conveyed while being heated and pressed. Then, the toner image is fixed.

Further, the recording paper 1 on which the toner image is fixed is conveyed by the upper discharge roller 18 and the lower discharge roller 19, and is discharged outside the apparatus so that the image recording surface faces downward.

Further, in this embodiment, two paper detecting means are provided in the middle of the paper conveying path for the purpose of controlling the image forming timing on the recording paper.

First, there is a paper feed sensor lever 20 and a paper feed sensor 21 as the first paper detecting means, and the paper feed sensor lever 20 is fed by the recording paper 1 fed by the paper feed roller 7.
Oscillates and is converted into an electric signal by the paper feed sensor 21 which is a transmissive photomicrosensor mounted on the substrate 24, and the recording paper feeding start and end signals are transmitted to a control circuit (not shown).

Further, there are a paper ejection sensor lever 22 and a paper ejection sensor 23 as the second paper detecting means, and the paper ejection sensor lever 22 is swung by the recording paper 1 carried out from the fixing means and mounted on the substrate 24. The paper output sensor 23, which is a transmissive photomicrosensor, converts it into an electrical signal,
The discharge start and end signals of the recording paper from the fixing unit are transmitted to a control circuit (not shown).

Next, the method of driving the main rollers for conveying the recording paper in this image forming apparatus will be described. FIG. 2 is a perspective view showing the configuration of the main rollers that convey the recording paper of the image forming apparatus.

In FIG. 2, a driving source (not shown) of the sheet feeding roller 7 drives the clutch gear 27, and the electromagnetic clutch 26.
When the control circuit (not shown) is operated, the rotation can be performed, and in the non-operation state, the rotation can be performed regardless of the drive source.

The photoconductor 2 is rotated by driving a photoconductor gear 28 by a drive source (not shown), and the transfer roller 6 receives the driving force of the photoconductor 2 by a transfer drive gear 29 and a transfer driven gear 30. It rotates by doing so. It is necessary for the transfer driving gear 29 and the transfer driven gear 30 to appropriately select the tooth profile and the transfer amount so as not to hinder the contact between the photoconductor 2 and the transfer roller 6. In the transfer unit of this example, when the recording paper 1 enters or leaves the photoconductor 2 and the transfer roller 6, the image disturbance caused by the impact in the rotation direction on the photoconductor 2 is reduced. The peripheral speeds of the transfer rollers 6 were set to be equal.

Further, the heat roller 15 is rotated by a fixing drive gear 31 driven by a drive source (not shown), and the pressure roller 17 is brought into contact with and driven by the heat roller 15 by the urging force of the pressure spring 16. is there.

Next, the arrangement intervals of the rollers shown in FIG. 2 will be described. FIG. 3 is a schematic cross-sectional view showing the arrangement intervals of the main rollers that convey the recording paper of the image forming apparatus.

In FIG. 3, the leading end position of the recording paper 1 stored in the paper feed tray 8 is P, the center position of the nip between the photoconductor 2 and the transfer roller 6 is Q, the heat roller 15 and the pressure roller 1 are shown.
7, the nip center position is S, the conveyance path length of the recording paper from P to Q is the feeding / transfer distance L3, the conveyance path length of the recording paper from Q to S is the transfer / fixing distance L4, The length of the recording sheet conveyance path from P to S is defined as the image forming path length L2.
It is defined as The image forming apparatus of this example has an image forming path length L.
By setting 2 to be shorter than the recording paper length L1, the entire apparatus is made extremely compact.

Table 3 shows the main specifications of this apparatus.

[0038]

[Table 3]

Here, a method of measuring the recording paper conveyance force Ft and the recording paper conveyance speed Vt of the transfer means and the recording paper conveyance force Ff and the recording paper conveyance speed Vf of the fixing means will be described.

FIG. 4 is a perspective view showing a method of measuring the recording paper conveyance force Ft of the transfer means. In FIG. 4, Ft indicates that the transfer means of this example is removed from the apparatus and the photoconductor 2 and the transfer roller 6 are removed.
Is rotated at the same circumferential speed as that at the time of image formation, a rope 33 is connected to both ends of a pipe member 32 to which an end portion of the recording paper 1 is fixed, and the recording paper 1 measured by a tension gauge (not shown) via the rope 33. The dynamic transport force of In addition,
The value of Ft can be theoretically estimated, and is calculated from the spring force of the transfer spring 13, the friction coefficient between the recording paper 1 and the photoconductor 2, the friction coefficient between the recording paper 1 and the transfer roller 6, the nip width of the transfer roller 6, and the like. It can be calculated.

The recording sheet conveyance speed Vt of the transfer means is measured by a laser Doppler type speedometer when the recording sheet 1 is conveyed while rotating the photosensitive member 2 and the transfer roller 6 at the same speed as during image formation. did.

The recording paper conveyance force Ff and the recording paper conveyance speed Vf of the fixing means can be measured by the same method as that of the transfer means, and the explanation thereof will be omitted.

An image was formed by the image forming apparatus described above, and evaluation was made regarding the unevenness of the feed pitch of the recorded image and the wrinkles on the recording paper fixing.

First, a study was made on the unevenness of the feed pitch of the recorded image. Paying attention to the fact that the feed pitch unevenness was changed when the feeding end timing of the paper feed roller was changed in the environments I and J of the verification experiment, and the image formation of this example was performed by the timing control as in Experimental Examples 1 and 2 below. The apparatus was operated to observe the behavior of the recording paper near the transfer means and the behavior of the transfer means constituent parts.

(Experimental Example 1) FIG. 5 is a timing chart showing the control of the sheet feeding roller 7 in Experimental Example 1. Figure 5
In step 1, after the drive source starts to supply power, the electromagnetic clutch 26 is operated to start feeding the recording paper 1. After the paper feed sensor 21 detects the leading end of the recording paper 1, the photoconductor 2 and the transfer roller 6 move. The feeding of the sheet feeding roller 7 was stopped after the time T1 of passing through the nip center position Q passed. The recording paper conveying speeds of the paper feeding means, the transfer means, and the fixing means were made to match as much as possible.

In this experimental example, the behavior of the recording paper 1 near the transfer means and the behavior of the components of the transfer means were observed, and it was found that there were the following causes of uneven feed pitch.

The first cause is that the rubber portion of the soft transfer roller 6 is likely to be twisted.

FIG. 6 is a partial sectional view showing the behavior of the rubber portion of the transfer roller 6 when the front end of the recording paper 1 reaches the Q position in this experimental example, and FIG. 7 is a paper feed roller 7 in this experimental example. FIG. 6 is a partial cross-sectional view showing the behavior of the rubber portion of the transfer roller 6 at the time when the feeding of is stopped.

In FIG. 6, the rubber portion of the transfer roller 6 is twisted as shown by the broken line as the roller is driven. However, when the driving force of the paper feed roller 7 is released, the paper feed spring 10 and the separation spring are released. Due to the biasing force of 11, a conveyance resistance Rs is generated in the recording paper 1 in the direction opposite to the traveling direction. It has been found that the conveyance resistance Rs causes the twist applied to the rubber portion of the transfer roller 6 as shown in FIG. 7 to be larger than that shown in FIG.

The second cause is that the gap of the holding portion of the transfer roller 6 tends to be biased.

FIG. 8 is a partial sectional view showing the behavior of the holding portion of the transfer roller 6 when the front end of the recording paper 1 reaches the Q position in this experimental example, and FIG. 9 is a paper feed roller 7 in this experimental example. FIG. 6 is a partial cross-sectional view showing the behavior of the holding portion of the transfer roller 6 when the feeding of the sheet is stopped.

In FIG. 8, the driving clearance of the transfer roller 6 causes the clearance c1 between the transfer roller 6 and the transfer bearing 34 and the clearance c2 between the transfer bearing 34 and the chassis 35 to be shifted toward the sheet feeding means. It was found that the gaps c1 and c2 were deviated toward the fixing means as shown in FIG. 9 at the moment when the above-mentioned conveyance resistance Rs was applied.

It was found that due to these causes, the feed pitch unevenness that the recorded image shrinks near the center position Q of the transfer nip occurs.

This feeding pitch unevenness can be improved by lowering the urging force of the paper feed spring 10 and the separation spring 11 or releasing the urging force by using a cam mechanism or the like. In order to feed the paper, the urging force as shown in Table 3 is required, and the use of the cam mechanism causes a new problem that the structure of the apparatus becomes complicated.

(Experimental Example 2) FIG. 10 is a timing chart showing the control of the sheet feeding roller 7 in Experimental Example 2.
In FIG. 10, after the drive source starts to supply power, the electromagnetic clutch 26 is operated to start feeding the recording paper 1. After the leading edge of the recording paper 1 is detected by the paper feed sensor 21, the heat roller 15 and the pressure are applied. The feeding of the sheet feeding roller 7 was stopped after the time T2 for passing the nip center position S of the roller 17 passed. As in the case of Experimental Example 1, the recording paper conveyance speeds of the paper feeding means, the transfer means, and the fixing means were made to match as much as possible. Also,
T2 is set longer than the time required for the leading edge of the recording paper 1 to reach the center S of the fixing nip, and the heat roller 15 and the pressure roller 1 are set.
It is desirable that No. 7 has exerted a sufficient conveying force on the recording paper 1, and in this example, it was set at the time when the front end of the recording paper 1 passed the fixing nip center S by 5 mm or more.

When the behavior of the recording paper 1 near the transfer means and the behavior of the transfer means constituent parts were observed in this experimental example, it was found that the cause of the uneven feed pitch found in the experimental example 1 was greatly reduced.

FIG. 11 is a partial sectional view showing the behavior of the rubber portion of the transfer roller 6 when the feeding of the paper feed roller 7 is stopped in this experimental example. As in the case of Experimental Example 1, when the paper feed roller 7 stops feeding, a conveyance resistance Rs is generated on the recording paper 1, but the recording paper conveyance force Ff of the fixing unit is also increased in a direction to assist the recording paper conveyance force Ft of the transfer unit. To work. As a result,
As shown in FIG. 2, the twist applied to the rubber portion of the transfer roller 6 is less likely to increase as compared with FIG. 7 of Experimental Example 1.

FIG. 12 is a partial sectional view showing the behavior of the holding portion of the transfer roller 6 when the feeding of the paper feed roller 7 is stopped in this experimental example. As in the case of Experimental Example 1, when the paper feed roller 7 stops feeding, a conveyance resistance Rs is generated on the recording paper 1, but the recording paper conveyance force Ff of the fixing unit is also increased in a direction to assist the recording paper conveyance force Ft of the transfer unit. Therefore, even if Rs acts on the transfer roller holding portion, the gaps c1 and c2 are less likely to be biased toward the fixing unit as compared with FIG. 9 of Experimental Example 1.

From the above results, the transfer nip portion Q is controlled by cutting off the driving force of the paper feeding means in the state in which the transfer means and the carry-out means jointly convey the recording paper at the time of image formation as in Experimental Example 2. It has been found that the shrinkage of the recorded image in Example 1 is reduced, and the feed pitch unevenness can be greatly reduced with a simple device configuration.

(Experimental Example 3) Next, in the environment K of the verification experiment, the feed pitch unevenness occurred even if the driving force of the paper feeding unit was released in the state where the transfer unit and the unloading unit carried the recording sheet together. Focusing on, the image forming apparatus of this example was operated while changing the recording paper conveyance speed Vf of the fixing unit under the same conditions as the environment K (35 ° C., 65% Rh), and the feed pitch unevenness of the recorded image was observed. Note that Vf was adjusted by changing the reduction ratio of the gear train from the drive source to the fixing drive gear 31.

Further, when the recording paper conveyance speed Vf of the fixing means is faster than the recording paper conveyance speed Vt of the transfer means, the fixing means pulls the recording paper 1 to cause unevenness of the feed pitch in the direction in which the recording image extends at the transfer nip position Q. So that the recording sheet conveyance force Ft of the transfer means is not generated.
It was set smaller than f.

Table 4 shows the experimental conditions and experimental results of this experimental example.
Shown in.

[0063]

[Table 4]

From the results shown in Table 4, it has been found that if the recording sheet conveying speed Vf of the fixing means is higher than the recording sheet conveying speed Vt of the transfer means, the unevenness of the feed pitch is reduced.

The phenomenon that the feed pitch unevenness is reduced under the condition of Vt <Vf will be described with reference to FIGS. 13 to 15.
FIG. 13 is a schematic cross-sectional view of the apparatus showing the behavior of the recording paper 1 between the transfer means and the fixing means in this experimental example, and FIG. 14 is the recording means by the transfer means and the fixing means under the condition of Vt ≧ Vf in this experimental example. FIG. 15 is a schematic sectional view of the apparatus showing the behavior of the recording paper 1 in the state where the paper 1 is jointly conveyed. FIG. 15 shows the transfer means and the fixing means under the condition of Vt <Vf in this experimental example.
FIG. 3 is a schematic cross-sectional view of the apparatus showing the behavior of the recording paper 1 in the state where the recording papers 1 and 3 are jointly conveyed.

In a high temperature and high humidity environment such as environment K, the recording paper 1 is bent between the transfer means and the fixing means as shown in FIG. When the recording paper 1 reaches the fixing means in this state, under the transport condition of Vt ≧ Vf, the bending of the recording paper 1 between the transfer means and the fixing means remains during image formation as shown in FIG. 14, and at this timing. When the feeding of the sheet feeding roller 7 is stopped, the effect of joint conveyance of the transfer unit and the fixing unit described in Experimental Example 2 cannot be obtained, and unevenness in the feed pitch occurs.

On the other hand, under the transport condition of Vt <Vf, as shown in FIG. 15, the flexure of the recording paper 1 between the transfer / fixing means is expanded due to the difference in the transport speed of the recording paper between the transfer means and the fixing means. It was confirmed that the joint conveyance effect of the fixing means acts to reduce the unevenness of the feed pitch.

From the above results, the recording paper conveyance speed Vf of the fixing means is set higher than the recording paper conveyance speed Vf of the transfer means to extend the recording paper between the transfer means and the fixing means, and The recording paper conveyance force Ft is set to be larger than the recording paper conveyance force Ff of the fixing unit to release the drive of the paper feeding unit while avoiding the image transfer deviation at the transfer nip portion, thereby making it possible to achieve a high temperature and high humidity environment. It was also found below that the effect of reducing the feed pitch unevenness described in Experimental Example 2 can be more reliably obtained.

(Experimental Example 4) Whether the result of Experimental Example 3 is effective under environmental conditions other than high temperature and high humidity, and whether the method of Experimental Example 3 affects the wrinkles of the recording paper generated in the verification experiment. For confirmation, the same experiment as in Experimental Example 3 was performed under various environments, and the feed pitch unevenness and the state of wrinkles on the recording paper were observed.

Table 5 shows the experimental conditions and experimental results of this experimental example.
Show.

The symbols entered in the wrinkle column of the recording paper in Table 5 indicate the wrinkle generation state of the recording paper under each condition, and ⊚ indicates that no wrinkle formation is observed, and ○ indicates wrinkle formation. Indicates that wrinkles do not occur but signs of wrinkles are observed, Δ indicates occasional occurrence of slight wrinkles, and x indicates that wrinkles frequently occur.

[0072]

[Table 5]

As shown in Table 5, occurrence of unevenness in the feed pitch can be reduced even if the environmental conditions change by setting the recording sheet conveying speed Vt of the transfer means and the recording sheet conveying speed Vf of the fixing means to Vt <Vf. Also, regarding wrinkles on the recording paper, V
If f is in the range of 1.0 to 1.005 times Vt, it can be suppressed, and Vf is more preferably about 1.002 times Vt.

The reason why the wrinkles on the recording paper have been improved is F
Under the relation of t> Ff, Vf is 1.0 to 1.
By setting it to 005 times, the recording paper 1 is stretched between the transfer means and the fixing means with an appropriate tension, and the undulation when the portion just before the fixing means of the recording paper 1 is heated and expanded in the conveyance width direction is average. It is presumed that it has the effect of suppressing wrinkles on the recording paper. Further, if Vf is made faster than necessary, it is presumed that waviness of the recording paper 1 immediately before the fixing means is locally concentrated, resulting in recording paper fixing wrinkles.

As described above, the results of Experimental Example 3 are effective in reducing the feed pitch unevenness under various environmental conditions.
It was also found that good results can be obtained in terms of preventing wrinkles on the recording paper.

In the embodiment of the present invention described above, the feeding means for feeding the recording paper 1 to the transfer means is the paper feeding means constituted by the paper feeding roller 7 and the recording paper 1 is transferred from the transfer means. The carrying-out means for carrying out has been described as the fixing means composed of the heat roller 15 and the pressure roller 17, but the present invention can be configured with a structure different from this.

First, a second embodiment of the feeding means will be described with reference to FIG. In FIG. 16, the photoconductor 2 and the transfer roller 6
An upper registration roller 36 and a lower registration roller 37 are arranged as a feeding means on the upstream side of the recording paper conveyance direction. At least one of the upper registration roller 36 and the lower registration roller 37 is driven via a clutch mechanism by a drive source (not shown), and the recording paper 1 is supplied to the pair of registration rollers in the stopped state by the paper feed roller 7, and the registration roller nip is performed. The leading end of the recording paper 1 is made to collide with the portion U, the skew of the recording paper 1 is corrected, and then the registration roller pair is driven to supply the recording paper 1 to the transfer means.

Next, a second embodiment of the carry-out means will be described with reference to FIG. In FIG. 17, the recording paper 1 on which the toner image on the photoconductor 2 has been transferred by the transfer roller 6 is wound around a belt roller 38 and connected to a conveyor belt 39 having a large number of small holes and a suction means (not shown). Suction box 40
The sheet is conveyed by the intermediate conveying unit composed of, and subsequently reaches the fixing unit composed of the heat roller 15 and the pressure roller 17.

A third embodiment of the carry-out means will be described with reference to FIG. FIG. 18 also shows a fixing means, and a heat resistant belt 41 made of a member such as a polyimide film is rotatably held by a heating element 42 having a thick film resistor or the like and an auxiliary roller 43. Both ends of the pressure roller 17 driven by a drive source (not shown) are urged by the pressure springs 16 and are pressed toward the heating element 43. The recording paper 1 on which the toner image is transferred by the transfer roller 6 is the heat resistant belt 4
1 and the pressure roller 17, the toner image is fixed on the recording paper 1 by heating the heating element 42.

By appropriately combining the above-mentioned feeding means and unloading means, the length of the recording paper feeding path from the feeding means to the unloading means is set shorter than the recording paper length, and the recording paper feeding speed Vt of the transfer means is set. , The recording paper conveyance force Ft, the recording paper conveyance speed Vf of the discharging means, the recording paper conveyance force Ff is Vt <Vf, and
By setting Ft> Ff, and cutting off the driving force of the feeding means in a state where the transfer means and the carry-out means jointly convey the recording paper at the time of image formation, uneven feeding pitch of the image and wrinkles of the recording paper are caused. It has also been confirmed that it can be reduced as in Experimental Example 4.

In the above embodiment, a recording paper having a width of 210 mm (A4 size) was used.
Other than this, recording papers having various widths (B5 size, envelope, postcard, letter size, etc.) were tested, but the same results as in the above-described experimental examples were obtained. And 210
When a recording paper having a width of mm or a recording paper having the maximum paper passing width is used, the recording paper conveyance force Ft of the transfer unit and the recording paper conveyance force Ff of the fixing unit satisfy the relationship of Ft> Ff. . However, if the width of the recording paper is very narrow (for example, about 100 mm like a postcard,
Even if the image forming apparatuses having exactly the same configuration are used, the magnitude relationship between the recording sheet conveyance force Ft of the transfer unit and the recording sheet conveyance force Ff of the fixing unit may be reversed. It is presumed that this is because when the width of the recording paper is narrow, the area where the heat roller 15 and the pressure roller 17 directly contact each other without the recording paper increases, and the contact pressure of the fixing unit increases.

[0082]

As described above, according to the image forming apparatus of the present invention, the environmental conditions are changed by setting the recording paper transportation speed and the recording paper transportation force of the transfer means and the carry-out means in a specific relationship. Also, the recording paper is appropriately expanded between the transfer means and the carry-out means, and the driving force of the feeding means is cut off in the state where the transfer means and the carry-out means jointly convey the recording paper. It is possible to provide an image forming apparatus that prevents paper wrinkles, reduces changes in the tension of the recording paper applied to the transfer unit, and does not cause wrinkles in the recording paper or uneven feeding pitch.

Further, the image forming apparatus using the present invention shortens the arrangement interval of each recording sheet conveying means, and does not impair the image quality even if an image is formed by a simple recording sheet conveying mechanism, and is small in size. It is possible to provide an image forming apparatus that can obtain a good recorded image at a low price.

[Brief description of drawings]

FIG. 1 is a lateral cross-sectional view of an image forming apparatus according to an embodiment of the present invention, illustrating the overall structure of the image forming apparatus.

FIG. 2 is a perspective view showing a configuration of main rollers for carrying recording paper in the image forming apparatus of the present invention.

FIG. 3 is a schematic cross-sectional view showing an arrangement interval of main rollers for conveying recording paper of the image forming apparatus of the present invention.

FIG. 4 is a perspective view showing a method of measuring a recording paper conveyance force of a transfer unit of the image forming apparatus of the present invention.

FIG. 5 is a timing chart showing control of a paper feed roller in Experimental Example 1 of the image forming apparatus of the present invention.

FIG. 6 is a partial cross-sectional view showing the behavior of the rubber portion of the transfer roller when the leading edge of the recording paper reaches the transfer nip position in Experimental Example 1 of the image forming apparatus of the present invention.

FIG. 7 is a partial cross-sectional view showing the behavior of the rubber portion of the transfer roller when the feeding of the paper feed roller is stopped in Experimental Example 1 of the image forming apparatus of the present invention.

FIG. 8 is a partial cross-sectional view showing the behavior of the holding portion of the transfer roller 6 at the time when the leading edge of the recording paper reaches the transfer nip position in Experimental Example 1 of the image forming apparatus of the present invention.

FIG. 9 is a partial cross-sectional view showing the behavior of the transfer roller holding portion at the time when the feeding of the paper feed roller is stopped in Experimental Example 1 of the image forming apparatus of the present invention.

FIG. 10 is a timing chart showing the control of the paper feed roller in Experimental Example 2 of the image forming apparatus of the present invention.

FIG. 11 is a partial cross-sectional view showing the behavior of the rubber portion of the transfer roller when the feeding of the paper feed roller is stopped in Experimental Example 2 of the image forming apparatus of the present invention.

FIG. 12 is a partial cross-sectional view showing the behavior of the transfer roller holding portion at the time when the feeding of the paper feed roller is stopped in Experimental Example 2 of the image forming apparatus of the present invention.

FIG. 13 is a schematic device sectional view showing the behavior of the recording paper between the transfer means and the fixing means in Experimental Example 3 of the image forming apparatus of the present invention.

FIG. 14 is a schematic cross-sectional view showing the behavior of the recording paper in the experimental example 3 of the image forming apparatus of the present invention in a state where the transfer means and the fixing means jointly convey the recording paper under the condition of Vt ≧ Vf.

FIG. 15 is a schematic cross-sectional view showing the behavior of the recording paper in a state where the transfer means and the fixing means jointly convey the recording paper under the condition of Vt <Vf in Experimental Example 3 of the image forming apparatus of the present invention.

FIG. 16 is a schematic sectional view of an apparatus showing a second embodiment of the feeding means in the present invention.

FIG. 17 is a schematic sectional view of an apparatus showing a second embodiment of the carry-out means in the present invention.

FIG. 18 is a schematic sectional view of an apparatus showing a third embodiment of the carry-out means in the present invention.

FIG. 19 is a cross-sectional view showing a schematic configuration of a conventional printer device.

FIG. 20 is a sectional view showing a schematic configuration of a conventional image forming apparatus configured by the inventors.

[Explanation of symbols]

1 ... Recording paper 2 ... Photoconductor 3 ... Charging roller 4 ... Laser scanning optical system 5 ... Developing roller 6 ... Transfer roller 7 ... Paper feed roller 8 ... Paper feed tray 9 ... Feeding bottom plate 10 ... Paper feed spring 11 ... Separation spring 12 ... Separation pad 13 ... Transfer spring 14 ... Halogen lamp 15 ... Heat roller 16 ... Pressure spring 17 ... Pressure roller 18 ... Paper ejection roller 19 ... Lower discharge roller 20 ... Paper feed sensor lever 21 ... Paper feed sensor 22 ... Paper ejection sensor lever 23 ... Paper ejection sensor 24 ... Substrate 25 ... Pad base 26 ... Electromagnetic clutch 27 ... Clutch gear 28 ... Photosensitive gear 29 ... Transfer drive gear 30 ... Transfer driven gear 31 ... Fixing drive gear 32 ... Pipe material 33 ... rope 34 ... Transfer bearing 35 ... Chassis 36 ... Upper registration roller 37 ... Lower registration roller 38 ... Belt roller 39 ... Conveyor belt 40 ... Suction box 41 ... Heat resistant belt 42 ... Heating element 43 ... Auxiliary roller

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI G03G 15/16 103 G03G 15/20 102 15/20 102 21/00 372 (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G03G 21/00 370-512 G03G 21/14 B65H 5/06 B65H 7/18 G03G 15/00 510 G03G 15/16 103 G03G 15/20 102

Claims (4)

(57) [Claims] 1. A transfer unit for transferring a toner image formed on the photosensitive member onto a recording sheet by a roller which is in contact with the photosensitive member and to which a voltage is applied, and a transfer unit located upstream of the transfer unit in the recording sheet conveying direction, A feeding unit that feeds the recording sheet in the transfer unit direction, a driving force connection / disconnection unit that connects and disconnects the feeding drive force of the feeding unit, and a recording sheet conveyance direction downstream side of the transfer unit, In an image forming apparatus having a carry-out means for carrying out a recording sheet from the transfer means, the transfer means is provided with a transfer roller having a rubber portion, and
The transfer roller has a holding unit that holds the transfer roller through a transfer bearing member.
Has the length of the recording sheet conveying path from the feeding means leading to the discharge means is set to be shorter than the recording paper length, the recording paper conveying speed Vt of the transfer means, the recording paper conveying force Ft, the The recording paper conveyance speed Vf and the recording paper conveyance force Ff of the carry-out means are set so that Vt <Vf and Ft> Ff, and the transfer means and the carry-out means cooperate with each other during the image formation. An image forming apparatus, characterized in that the driving force interrupting means is provided with a control means for interrupting the driving force of the feeding means in a state of being conveyed. 2. A recording paper transport speed Vf of the carry-out means,
2. The image forming apparatus according to claim 1, wherein the recording paper conveyance speed Vt of the transfer unit satisfies Vf ≦ 1.005 × Vt. 3. The image forming apparatus according to claim 1, wherein the feeding unit is a sheet feeding device that stores a plurality of recording sheets and sequentially separates and feeds the recording sheets. 4. The image forming apparatus according to claim 1, wherein the carry-out unit is a fixing device that heats and presses the toner image transferred onto the recording paper to fix the toner image on the recording medium.