JPH07114277A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] In an electrophotographic image forming apparatus, it is possible to prevent uneven recording image pitch and recording paper fixing wrinkles that occur in the fixing means. Further, the present invention provides a small-sized image forming apparatus capable of forming an excellent image with a simple structure. [Configuration] Paper feed roller 2 or paper feed upper roller 12
The recording paper conveyance speed and the recording paper conveyance force of the paper feeding means composed of the like, the transfer means composed of the photoconductor 14 or the like, the fixing means composed of the heat roller 20 or the heat resistant belt 27, and the like are specified, Image formation is performed.

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 a printer, a facsimile, a copying machine and the like, and more specifically to a recording paper conveying technique in the image forming apparatus.

[0002]

2. Description of the Related Art The following techniques are known as conventional techniques relating to recording paper conveyance in an image forming apparatus to which a dry electrophotographic technique is applied.

First, in Japanese Unexamined Patent Publication No. 52-70841, a belt type conveying device with a suction mechanism located after transfer lowers the belt speed when feeding a recording sheet to the fixing device than the peripheral speed of the fixing device. There is disclosed a technique for extending the recording paper between the belt type transport device and the fixing device to prevent the recording paper from wrinkling in the fixing device. As a technique similar to this, Japanese Patent Laid-Open No. 3-294887 discloses a technique for preventing the skew of the recording paper, which is characterized in that the recording paper conveyance speed of the fixing means is made higher than the peripheral speed of the photoconductor. .

Further, Japanese Utility Model Laid-Open No. 61-70856 is characterized in that the recording sheet conveying speed on the upstream side is fast and the recording sheet conveying speed on the downstream side is slow with respect to the peripheral speed of the photoconductor. A technique is disclosed in which the transfer of the recording paper propulsive force in the transfer unit is relaxed by slackening the recording paper in the vicinity of the transfer unit, and good image formation is performed. On the contrary, Japanese Patent Laid-Open No. 3-238486 is characterized in that the peripheral speed of the fixing unit is set higher than the peripheral speed of the registration roller.
Extend the recording paper between the registration roller and the fixing means,
A technique for preventing image contamination when the recording paper is separated from the registration roller is disclosed.

Further, in JP-A-3-148680, the peripheral speed of the transfer roller is higher than the peripheral speed of the photoconductor.
In addition, a technique is disclosed in which the peripheral speed of the registration roller located in front of the transfer unit is set to be higher than the peripheral speed of the photoconductor, and a technique for preventing a hollow image in the image that occurs during transfer is disclosed.

Here, in order to clarify the relationship between the peripheral speeds of the respective means relating to the recording paper conveyance in the above-mentioned respective prior arts,
Table 1 shows the list. In Table 1, the items in which the peripheral speed ratios of the respective means are specifically disclosed in the examples of each of the above-described prior arts are described as the ratios when the peripheral speed of the photoconductor is 100. Further, the specific disclosure regarding the peripheral speed of the paper feed roller is not described in each of the above-mentioned related arts.

[0007]

[Table 1]

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

FIG. 15 is a side view showing a schematic construction of a conventional image forming apparatus constructed by the inventors, and more specifically, a printer having a laser scanning optical system. The general operation of this conventional image forming apparatus will be described with reference to FIG.

In FIG. 15, there is a charging roller 28 as a charging means on the outer periphery of the photoconductor 14 which rotates in the direction of arrow D by a drive source (not shown). The charging roller 28 contacts the photoconductor 14 and is applied with a voltage from a high voltage power source (not shown) to uniformly charge the surface of the photoconductor. The charged photoconductor 14 is selectively exposed by a laser scanning optical system 29, which is an exposing unit, to form a latent image on the photoconductor 14.
The latent image formed on the surface of the photoconductor 14 is visualized by the toner supplied by the developing roller 30, which is a developing unit. The transfer roller 16 serving as a transfer unit contacts the photoconductor 14 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 composed of a paper feeding roller 2, an upper registration roller 33, and a lower registration roller 34. The recording paper 1 stored in the paper feeding tray 31 is separated one by one by the paper feeding roller 2, and the upper registration roller 3
3 and the lower registration roller 34, and is nipped and conveyed between the photoconductor 14 and the transfer roller 16.
The recording paper 1 on which the toner image on the photoconductor 14 is transferred by the transfer means is wound around a belt roller 36, and is connected to a conveyor belt 37 having a large number of small holes and a suction box 38 connected to a suction means (not shown). To the intermediate conveying means, and the back side of the recording paper 1 is conveyed by the suction box 38 to the conveying belt 37.
Is adsorbed on and transported. Subsequently, the recording paper 1 is a heat roller 20 provided with a rod-shaped halogen lamp 21 inside.
Then, the toner image is fixed by being nipped and conveyed by a fixing unit composed of a pressure roller 22 pressed against and abutted against the toner image, and is discharged to the outside of the apparatus. In addition, the transfer spring 18 and the pressure spring 2
Numeral 4 is located at both ends of the transfer roller 16 and the pressure roller 24 in the width direction of the recording paper conveyance.
First, the pressure roller 22 is brought into pressure contact with the heat roller 20. The driving method of each roller is the photoconductor 14, the paper feed roller 2, the lower registration roller 35,
The developing roller 30, the belt roller 36, and the heat roller 20 are driven by a driving source (not shown), the upper registration roller 34 is the lower registration roller 35, the charging roller 28 is the photoreceptor 14, and the transfer roller 16 is the photoreceptor 1.
4, the pressure roller 22 is driven by the heat roller 20, respectively. In addition, in order to verify the above-mentioned conventional technology,
The peripheral speed of each roller driven by the drive source (not shown) is adjustable with respect to the peripheral speed of the photoconductor 14.

Table 2 shows the main specifications of this conventional image forming apparatus.
Shown in.

[0012]

[Table 2]

(Verification Experiment Example 1) An experiment for verifying the disclosure of the above-mentioned conventional art was conducted by the above-mentioned conventional image forming apparatus. Table 3 shows the experimental conditions and the condition of the formed image. In Table 3, the peripheral speed of each means is shown as a ratio when the peripheral speed of the photoreceptor is 100.

[0014]

[Table 3]

In Table 3, when the peripheral speed of the heat roller 20 is slower than the peripheral speed of the conveyor belt 37, the basis weight 60
When a thin recording paper of about g / m ² is used, unpleasant wrinkles may occur on the recording paper after fixing. Further, when the peripheral speed of the transfer roller 16 is 2 to 5% faster than the peripheral speed of the photoconductor, pitch unevenness of the image occurs in the recording paper feeding direction. It was confirmed that under other conditions, almost good image recording can be performed on various recording papers, and good image formation can be performed by appropriately combining the above-mentioned conventional techniques.

[0016]

While the environment surrounding the image forming apparatus is required to have high speed and high performance in recent years, it is spreading to small offices and individuals. Particularly, in the latter needs, downsizing and cost reduction of the device are particularly required.

In order to reduce the size and cost of the apparatus, the recording paper conveyance path of the image forming apparatus is shortened, and the width of each roller or the like in the recording paper conveyance direction is made close to the recording paper width.
It is necessary to simplify the recording paper conveyance mechanism by omitting the belt-type intermediate conveyance means with a suction mechanism used in the above-mentioned prior art. Therefore, it was decided to modify the conventional image forming apparatus to investigate whether it is possible to reduce the size and cost of the apparatus. A modified example of the conventional image forming apparatus constructed by the inventors will be described.

FIG. 16 is a side view showing a schematic configuration of a modified example of a conventional image forming apparatus constructed by the inventors. Table 4 shows the points modified from the conventional image forming apparatus.

[0019]

[Table 4]

(Verification Experiment Example 2) An experiment for re-verifying the verification experiment example 1 was conducted by this modified example. Table 5 shows the experimental conditions and the condition of the formed image.

[0021]

[Table 5]

As shown in Table 5, undesired wrinkles are generated on the recording paper on which fixing is completed even under the condition that good image formation can be performed in Experimental Example 1, and even when the peripheral speed of the heat roller is higher, the weight of the paper is heavier. It was observed that wrinkles were prominent.

If the spring force of the transfer spring 18 or the pressure spring 24 shown in FIG. 16 is changed to improve the image quality, the phenomenon of the above-mentioned wrinkles on the recording paper fixing is reduced or promoted, and the recording paper is conveyed. The phenomenon that pitch unevenness occurs in the image was observed.

Further, in the paper feed roller 2 shown in FIG. 16, in order to prevent the double feed of the second and subsequent recording papers, the first recording paper is a resist composed of an upper registration roller 34 and a lower registration roller 35. After feeding to the roller pair, the clutch mechanism (not shown) controls the drive to be released. However, when the paper feed roller 2 is released when the leading edge of the recording paper reaches the above-mentioned registration roller pair, Even when the driving was released when the roller 2 conveyed the recording paper to the vicinity of the rear end, the state of the wrinkles on the recording paper fixing was different, and the latter was smaller. A similar phenomenon occurs even when the peripheral speed of the paper feed roller 2 is changed, and as the peripheral speed of the paper feed roller 2 becomes slower than the peripheral speed of the registration roller pair, the recording paper fixing wrinkles become more remarkable. .

In order to achieve downsizing and simplification of the apparatus as described above, the recording sheet conveying path of the image forming apparatus is shortened to the extent that one sheet of recording sheet simultaneously exists over the sheet feeding / transferring / fixing means. If the axial width of each recording paper conveying means is shortened to a size close to the recording paper width and the recording paper conveying means is simplified, good image formation cannot be performed even if the above-mentioned conventional technique is applied. There is a problem.

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 with a simple structure.

[0027]

The image forming apparatus of the present invention is a transfer means for transferring a toner image formed on a photoconductor to a recording paper by a roller which is in contact with the photoconductor and is applied with a voltage, and a transfer means for transferring the toner image onto the recording paper. In an image forming apparatus having a fixing unit that heats and presses the formed toner image to fix it on a recording sheet,
Ft> Ff, where Ft is the recording sheet conveyance force of the transfer unit and Ff is the recording sheet conveyance force of the fixing unit.

In addition to the feature of Ft> Ff, in the image forming apparatus of the present invention, the recording sheet conveying force Ft of the transfer means and the recording sheet conveying force Ff of the fixing means are Ft ≧ 1.3 × Ff. Characterize

In addition to the feature of Ft> Ff, the image forming apparatus of the present invention sets the recording sheet conveying speed of the transfer means to Vt,
When the recording paper conveyance speed of the fixing means is Vf, Vf = (1 to 1.005) × Vt.

Further, the image forming apparatus of the present invention is formed on the photoconductor by a sheet feeding means for accommodating a plurality of recording sheets and sequentially separating and feeding one sheet, and a roller which is in contact with the photoconductor and which is applied with a voltage. In the image forming apparatus having a transfer unit for transferring the formed toner image to the recording paper and a fixing unit for heating and pressing the toner image transferred on the recording paper to fix the toner image on the recording paper, the recording paper conveying force of the transfer unit is Ft, The recording paper feeding force of the paper feeding means is Fs.
In this case, Ft> Fs.

In addition to the feature of Ft> Fs, the image forming apparatus of the present invention is characterized in that Ft> Ff when the recording paper conveying force Ff of the transfer means is used.

In addition to the feature of Ft> Fs, the image forming apparatus of the present invention has a recording paper conveyance resistance force Rs of the paper feeding means when the recording paper is fed to the transfer means and the recording paper is conveyed.
In this case, Rs ≦ 150 gf.

Further, Ft> Ff or Ft> Fs
In addition to the above features, the image forming apparatus of the present invention is characterized in that the outer diameter of the heat roller used for the fixing means is constant in the paper passing width direction.

[0034]

According to the image forming apparatus of the present invention, in addition to the peripheral speed of each recording paper conveying means as in the above-mentioned prior art, the recording paper conveying force of each recording paper conveying means is devised so that It is possible to provide a small-sized image forming apparatus capable of averaging the tension distribution of the recording paper by feeding the recording paper while applying an appropriate speed and tension, and performing good image formation with a simple structure.

[0035]

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.
It will be explained based on.

In FIG. 1, there is a charging roller 28 as a charging means on the outer periphery of the photoconductor 14 which rotates in the direction of arrow A by a drive source (not shown). The charging roller 28 contacts the photoconductor 14 and is applied with a voltage from a high voltage power source (not shown) to uniformly charge the surface of the photoconductor. The charged photoconductor 14 is selectively exposed by a laser scanning optical system 29, which is an exposing unit, to form a latent image on the photoconductor 14. The latent image formed on the surface of the photoconductor 14 is visualized by the toner supplied by the developing roller 30, which is a developing unit. The transfer roller 16 serving as a transfer unit contacts the photoconductor 14 on the downstream side of the developing unit, and a voltage is applied from a high voltage power source (not shown). On the other hand, a paper feed roller 2 as a paper feed means sequentially separates and feeds one recording paper 1 stored in a paper feed tray 31, and the fed recording paper 1 is fed to a photoconductor 14 and a transfer roller 16. While being sandwiched between them, they are continuously conveyed toward the fixing unit. The recording paper 1 on which the toner image on the photoconductor 14 is transferred by the transfer means has a rod-shaped halogen lamp 2 inside.
The toner image is fixed by being nipped and conveyed by a fixing unit composed of a heat roller 20 including 1 and a pressure roller 22 that is pressed against the heat roller 20, and is discharged to the outside of the apparatus.

Here, the paper feeding means in the image forming apparatus of the present invention will be described in detail.

2 and 3 are side views showing the first embodiment of the sheet feeding means in the image forming apparatus of the present invention.
FIG. 3 is a diagram showing a sheet feeding start state, and FIG. 3 is a diagram showing a sheet feeding process.

In FIG. 2, the recording paper 1 laminated on the paper feed bottom plate 4 is pressed against the paper feed roller 2 by the paper feed spring 3, and the friction pad 5 is separated by the separation spring 6 whose one end is connected to a fixed frame (not shown). It is pressed against the paper feed roller 2. When the paper feeding operation is started, the recording paper 1 is fed by the paper feeding roller 2
Is fed by rotation in the direction of arrow B, and is separated by friction between the paper feed roller 2 and the friction pad 5, and only one sheet is fed in the direction of the transfer means. When a transfer unit (not shown) starts to convey the recording paper 1, the release lever 8 pushes down the paper feed bottom plate 4 by the pulling operation of the solenoid 7 as shown in FIG. 3, and separates the laminated recording paper and the paper feed roller 2. Further, one end of the friction pad 5 is pulled by the release spring 9 connected to the release lever 8, and the pressing force on the paper feed roller 2 is reduced.
Reduce wear. In addition, there is a possibility that the second and subsequent recording sheets that have stagnated due to friction separation exist between the friction pad 5 and the paper feed roller 2, and when the friction pad 5 and the paper feed roller 2 are separated from each other, Since there is a possibility that the recording paper of (2) will be fed in the direction of the transfer means, it is preferable that the recording paper is not separated from the recording paper and the pressure is reduced. Further, for the purpose of separating and feeding the stacked recording papers, a series of mechanisms using the solenoid 7 as an operation source is not necessary, but in addition to reducing the abrasion of the friction pad 5, after feeding the recording papers to the transfer means. It also has an effect of relieving the recording paper conveyance tension between the paper feed and transfer, which will be described later in Experimental Example 4 together with the control method of the clutch mechanism (not shown) for controlling the driving force transmission of the paper feed roller 2.

Next, the arrangement of the paper feed roller 2 in the recording paper conveyance width direction in the first embodiment of the paper feed means, the measuring method of the recording paper conveyance force Fs and the recording paper conveyance resistance force Rs of the paper feed means, and the recording paper conveyance A method of measuring the speed Vs will be described.

FIG. 4 is a plan view for explaining the arrangement of the paper feed roller 2 in the recording paper conveyance width direction and the Fs measuring method in the first embodiment of the paper feeding means, and FIG. 5 is a plan view showing the Rs measuring method. Is.

In FIG. 4, the paper feed roller 2 has a dimension W2.
The two rubber portions are arranged in a width dimension of W1, and the width dimension W1 is slightly narrower than the minimum sheet passing width. If the width W1 is made wider than the minimum sheet passing width, the paper feed roller 2 and the friction pad 5 not shown in the figure directly contact with each other when the width of the recording paper 1 is narrow, which is not preferable.

The recording paper conveying force Fs of the paper feeding means is set to the maximum paper passing width of the recording paper 1 with the rear end width fixed to a thin aluminum pipe member 32 by removing the paper feeding means of this example from the outside of the apparatus. The paper feed roller 2 was rotated at the same peripheral speed as when the image was formed, and the dynamic conveyance force was measured by a tension gauge (not shown) via the ropes 33 fixed to both ends of the pipe material 32. The value of Fs can be theoretically estimated, and the spring force of the paper feed spring 3, the spring force of the separation spring 6, the friction coefficient of the recording paper 1 and the paper feed roller 2, the friction coefficient of the recording paper 1 and the friction pad 5, the stacking It can be calculated from the friction coefficient between the recorded recording sheets 1 and the like.

Further, in FIG. 5, the recording paper conveyance resistance Rs
Sets the maximum width of the recording paper 1 with the entire width of the tip fixed to the pipe material 32 in the apparatus of this example, and releases the clutch means (not shown) for transmitting power to the paper feed roller 2 to release the pipe material 3
When the ropes 33 fixed to both ends of No. 2 were pulled at the same speed as the peripheral speed of the transfer means (not shown), the dynamic conveyance force was measured by a tension gauge (not shown). The value of Rs can also be theoretically estimated from the same conditions as Fs.

The recording paper conveyance speed Vs was measured by a laser Doppler type speedometer, which is the movement speed of the recording paper 1 when the paper feed roller 2 is rotated and conveyed at the same peripheral speed as during image formation. At this time, the value of Vs tends to be smaller than the peripheral speed of the paper feed roller 2, and the paper feed roller 2 and the recording paper 1 are
It was found that the slip was likely to occur between the two. Therefore, it is preferable to show the value of Vs as an actual measurement value.

Next, a second embodiment of the paper feeding means in the image forming apparatus of the present invention will be described. FIG. 6 is a side view showing a second embodiment of the paper feeding means in the image forming apparatus of the present invention.

In FIG. 6, when the recording paper 1 laminated on the paper feed bottom plate 4 is pressed by the paper feed spring 3 toward the separation claws 10 on both sides of the leading end, the recording paper 1 is set to D when the paper feed operation is started.
The cut roller 11 is sent out by the rotation in the direction of the arrow C, and only one sheet is sent out by the separation claw 10 toward the transfer means. The delivered recording paper 1 is nipped and conveyed by a paper feed lower roller 13 driven by a drive system (not shown) and a paper feed upper roller 12 which is pressed by a pressure mechanism (not shown) and is driven by the pressure mechanism, not shown. Sent out. Further, the D-cut roller 11 is operated only once for each sheet of recording paper by a one-rotation clutch mechanism (not shown). On the other hand, even if the paper feed upper roller 12 and the paper feed lower roller 13 are configured to rotate at all times while the recording paper is present between the rollers, the paper feed lower roller 13 and the paper feed lower roller 13 do not function as in the conventional gate roller mechanism. A clutch mechanism is provided between drive sources (not shown), the clutch mechanism releases the drive of the lower paper feed roller 13, and the leading edge of the recording paper 1 is controlled so as to abut against both paper feed rollers, and the recording is performed. The driving may be restarted after correcting the skew of the paper 1.

Here, the separating claw 10, the D-cut roller 11, and the paper feeding upper roller 12 in the second embodiment of the paper feeding means are used.
The arrangement of the paper feed lower roller 13 in the recording paper conveyance width direction, the measurement method of the recording paper conveyance force Fs and the recording paper conveyance resistance force Rs of the paper feeding means, and the measurement method of the recording paper conveyance speed Vs will be described.

FIG. 7 shows the separation claw 10, the D-cut roller 11, the paper feed upper roller 12 in the second embodiment of the paper feeding means,
Arrangement of the paper feed lower roller 13 in the width direction of the recording paper and Fs
FIG. 8 is a plan view illustrating the measurement method of Rs, and FIG. 8 is a plan view illustrating the measurement method of Rs.

In FIG. 7, the D-cut roller 11 is arranged at the center in the paper width direction of the rubber portion having the dimension W3.
The separating claw 10 is adjusted in the sheet passing width direction according to the width of the recording sheet. The upper paper feed roller 12 has a support shaft 12b for weight reduction.
A plurality of resin rollers 12a is arranged so as to be rotatable upward. The axial length of the paper feed lower roller 13 need not be wider than the maximum paper feed width as shown in FIG.

As for the recording paper conveying force Fs of the paper feeding means, the paper feeding means of this example is removed to the outside of the apparatus, and the recording paper 1 having the maximum paper passing width is fixed with the rear end width fixed to the thin aluminum pipe material 32. , The D-cut roller 11 is placed in a non-contact state with the cut surface of the D-cut roller 11 facing the recording paper 1, and the paper feed lower roller 13 is rotated at the same peripheral speed as during image formation, and the rope 33 fixed to both ends of the pipe material 32 is used. The dynamic conveyance force measured by a tension gauge (not shown). The value of Fs can be estimated theoretically, and the pressing force of the upper paper feed roller 12 against the lower paper feed roller 13, the recording paper 1 and the lower paper feed roller 1
It can be calculated from the friction coefficient of 3 or the like.

Further, in FIG. 8, the recording paper conveyance resistance Rs
Sets the maximum width of the recording paper 1 with the entire width of the tip fixed to the pipe material 32 in the apparatus of this example, and makes the cut surface of the D-cut roller 11 face the recording paper 1 so as to be in a non-contact state. When the rope 33 fixed to both ends of the pipe member 32 was pulled at the same speed as the peripheral speed of the transfer means (not shown) in the detached state, the dynamic transfer force was measured by a tension gauge (not shown).

The recording paper conveying speed Vs is D cut roller 1
The cut surface of 1 is made to be in a non-contact state by facing the recording paper 1,
The moving speed of the recording paper 1 when the lower paper-feeding roller 13 was rotated at the same peripheral speed as during image formation and conveyed was measured by a laser Doppler type speedometer.

Table 6 shows the specifications of the first and second embodiments of the sheet feeding means in this apparatus. The setting of the recording paper transport speed Vs will be described later in Experimental Example 3.

[0056]

[Table 6]

Next, the transfer means in the image forming apparatus of the present invention will be described in detail. FIG. 9 is a perspective view showing an embodiment of the transfer means in the image forming apparatus of the present invention.

In FIG. 9, the transfer roller 16 having a width slightly larger than the maximum paper passing width is held by the transfer bearings 17 at both ends, and is pressed against the photoconductor 14 by the transfer spring 18. The photoconductor 14 is driven by a drive source (not shown), and the driving force is the drive gear 1 arranged at the end of the photoconductor 14.
5 to the driven gear 1 arranged at the end of the transfer roller 16
9 is transmitted to rotate the transfer roller. As described above, the transfer roller 16 formed of a conductive rubber material is applied with a voltage from a high voltage power source (not shown), and the toner image formed on the recording paper 1 nipped and conveyed between the photoconductor 14 and the transfer roller 16 is formed. It is a sequential transfer.

Further, the driving gear 15 and the driven gear 19 need to be appropriately selected in terms of tooth profile and transfer amount so as not to prevent contact between the photoconductor 14 and the transfer roller 16. If the number of teeth of the drive gear 15 and the driven gear 19 is set to the speed increasing ratio, the peripheral speed of the transfer roller 16 can be made higher than the peripheral speed of the photoconductor 14 as in the above-mentioned Japanese Patent Laid-Open No. 3-148680. However, in the transfer means of this example, since the disturbance of the image caused by the impact in the rotational direction which the photoconductor 14 receives when the recording paper 1 enters or leaves the photoconductor 14 and the transfer roller 16 is reduced, 14 and transfer roller 16
The peripheral speeds of were set equal.

Next, a method of measuring the recording paper carrying force Ft and the recording paper carrying speed Vt in this embodiment of the transfer means will be described.

FIG. 10 is a perspective view showing a method of measuring the transfer means recording paper conveyance force Ft in the transfer means embodiment. Figure 1
At 0, Ft is the same as in the case of the above-mentioned paper feeding means, the transfer means of this example is removed from the apparatus, the photoconductor 14 and the transfer roller 16 are rotated at the same peripheral speed as during image formation, and the pipe material 32 The dynamic conveyance force was measured by a tension gauge (not shown) through the ropes 33 fixed at both ends. The value of Ft can be theoretically estimated, and can be calculated from the spring force of the transfer spring 18, the friction coefficient between the recording paper 1 and the photoconductor 14, the friction coefficient between the recording paper 1 and the transfer roller 16, and the like. In this example, by adjusting the spring force of the transfer spring 18, F
t can be adjusted. About the proper value of Ft, Experimental Example 1
See below.

Table 7 shows the specifications of the embodiment of the transfer means in this apparatus.

[0063]

[Table 7]

Next, the fixing means in the image forming apparatus of the present invention will be described in detail.

FIG. 11 is a perspective view showing a first embodiment of the fixing means in the image forming apparatus of the present invention.

In FIG. 11, a halogen lamp 21 is arranged at the center of a heat roller 20 having a fluorine resin film formed on the outer circumference of an aluminum pipe, and the heat roller 20 is uniformly heated to a desired temperature from the inside. Then 150
It was set to ° C. The pressure roller 22 having a width slightly larger than the maximum sheet passing width is held at both ends by pressure bearings 23, and is pressed against the heat roller 20 by a pressure spring 24. The heat roller 20 is driven by a drive source (not shown), and the pressure roller 22 is driven by the pressure force of the pressure spring 24. The recording paper 1 on which the toner image is transferred is a heat roller 20 and a pressure roller 2.
The sheet is nipped and conveyed by 2, and the toner image is fixed on the recording sheet 1. The pressing force of the pressure spring 24 is the heat roller 20.
And the nip width of the pressure roller 22, the rubber hardness of the pressure roller 22, the toner softening temperature, the heat roller temperature, the recording paper conveying speed, and the like, and are appropriately selected. In this example, about 6 Kgf is preferable. there were.

FIG. 12 is a perspective view showing a second embodiment of the fixing means in the image forming apparatus of the present invention.

In FIG. 12, a heat-resistant belt 27 formed of a member such as a polyimide film is rotatably held by a heating element 25 having a thick film resistor or the like and an auxiliary roller 26. The pressure roller 22 driven by a drive source (not shown) is held at both ends by pressure bearings 23,
It is pressed in the direction of the heating element 25 by the pressure spring 24. The recording paper 1 on which the toner image is transferred is the heat-resistant belt 27.
The toner image is fixed on the recording paper 1 by being heated and nipped by the pressure roller 22 and being heated.

Fixing Means The measuring method of the recording paper carrying force Ff and the recording paper carrying speed Vf in the first and second embodiments is the same as that of the above-mentioned transfer means, and the description thereof will be omitted. In this example, Ff can be adjusted by adjusting the spring force of the pressure spring 24, and Vf can also be adjusted. Ft and Vf
The appropriate value of will be described later in Experimental Examples 1 and 2.

Table 8 shows the specifications of the first and second fixing means in this apparatus.

[0071]

[Table 8]

With the above-described image forming apparatus, various recording papers were used to study the conveying speed and the conveying force of each recording paper conveying means.

(Experimental Example 1) First, an experimental example 1 was used to find the relationship between the recording paper conveyance force Ft of the transfer means and the recording paper conveyance force Ff of the fixing means.
Considered as. Table 9 shows the experimental conditions and experimental results of Experimental Example 1.

[0074]

[Table 9]

If the experimental conditions in Table 9 are added, based on the results of the verification experiment 1, the fixing means recording paper conveyance speed Vf is 0.2% lower than the transfer means recording paper conveyance speed Vt in order to reduce recording paper fixing wrinkles. I set it early. Further, based on the result of the verification experiment 2, the recording sheet conveying speed Vs of the sheet feeding means is set 0.2% faster than Vt, and only one sheet of the recording sheet 1 is set in the apparatus, and the sheet feeding roller 2 or Feeding roller 1
By controlling 3 to constantly rotate while the recording paper 1 is present, the double feeding of the second and subsequent recording papers and the expansion of the recording paper 1 between the paper feeding / transfer means are prevented. Under the conditions of Experimental Example 1, the recording sheet conveyance speed Vt of the transfer means was a speed extremely close to the photosensitive member peripheral speed Vp.

The symbols entered in Table 9 show the occurrence of wrinkles on the recording paper fixing under each condition. ⊚ indicates that no wrinkles were observed, and ○ indicates no wrinkles but no wrinkles. Where visible, Δ indicates occasional slight wrinkling, and × indicates frequent wrinkling. In Experimental Example 1, image pitch unevenness was observed under the condition of Ff <Ft, and the larger the difference between Ff and Ft, the more remarkable the image pitch unevenness.

As is apparent from Table 9, it is preferable that the transfer means recording paper conveyance force Ft is larger than the fixing means recording paper conveyance force Ff in order to suppress the occurrence of recording paper fixing wrinkles, and further, Ft is Ff. It is preferably 1.3 times or more. Further, Ff is preferably 0.4 Kgf or more,
It is more preferably 0.5 Kgf or more.

From the results shown in Table 9, the conveyance of the recording paper 1 depends on the transfer means having no expansion / contraction of the recording paper 1 rather than the fixing means which causes the expansion / contraction of the recording paper 1 by setting Ft> Ff. It is presumed that setting the state is effective in suppressing the wrinkles on the recording paper.

Since Ft and Ff change differently when the width of the recording paper 1 is small, it may be difficult to maintain the relationship of Ft> Ff under all conditions. If the width of the paper 1 becomes smaller, the amount of expansion and contraction of the recording paper 1 in the fixing means also becomes smaller, and wrinkles for fixing the recording paper are less likely to occur. Therefore, when the recording paper 1 has the maximum width capable of image formation, If the relationship is satisfied, it is possible to realize an image forming apparatus in which fixing wrinkles on the recording paper do not occur.

(Experimental Example 2) Next, as Experimental Example 2, the relationship between the transfer means recording paper conveyance speed Vt and the fixing means recording paper conveyance speed Vf was examined. Table 10 shows the experimental conditions and experimental results of Experimental Example 2. The conditions of Experimental Example 2 are the same as those of Experimental Example 1, and Ft is 2 Kgf and Ff is 0.75 Kg.
set to f.

The symbols entered in Table 10 show the state of wrinkles on the recording paper fixing under each condition, and ⊚ indicates that no wrinkles were observed, and ○ indicates that no wrinkles occurred. When there are signs, Δ indicates occasional occurrence of slight wrinkles, and × indicates frequent occurrence of wrinkles.

[0082]

[Table 10]

As is apparent from Table 10, the fixing means recording paper conveying speed Vf is 1.
The range of 0 to 1.005 times is preferable in order to suppress the occurrence of wrinkles on the recording paper, and Vt is more preferably about 1.002 times Vf.

From the results shown in Table 10, by setting Vf to 1.0 to 1.005 times Vt under the relationship of Ft> Ff, the recording paper 1 is appropriately placed between the transfer means and the fixing means. It is presumed that the undulation when the recording paper 1 immediately before the fixing means is heated in the conveyance width direction and expanded by being stretched by various tensions is averagely suppressed, and the recording paper fixing wrinkles are effectively suppressed. Also, if Vf is made faster than necessary, recording paper 1
The swell just before the fixing means is concentrated locally,
It is presumed that it will cause wrinkles on the recording paper.

Since the transfer means recording paper conveying force Ft is larger than the fixing means recording paper conveying force Ff, the image pitch unevenness did not occur in Experimental Example 2.

(Experimental Example 3) Next, as a third experimental example, the relationship between the transfer means recording paper carrying force Ft and the paper feeding means recording paper carrying force Fs was examined.

The above-mentioned prior art Japanese Patent Laid-Open No. 61-70856.
As disclosed in Japanese Patent Publication No. JP-A-2003-242977, it is necessary to make the peripheral speed of the recording paper transport unit on the paper feed unit side faster than the peripheral speed of the recording paper transport unit on the transfer unit side. Although it is effective in preventing the transfer deviation, the effect of preventing the transfer deviation is insufficient when slip occurs between the recording paper 1 and the paper feeding roller as described in the first embodiment of the paper feeding means of this apparatus. Guessed. Therefore, in Experimental Example 3, an experiment was conducted using recording paper having various friction coefficients using the first embodiment of the paper feeding means. Table 11 shows the experimental conditions and experimental results of Experimental Example 3.

In Experimental Example 3, the transfer means recording paper conveyance force Ft is 1.5 Kgf, the fixing means recording paper conveyance force is 0.75 Kgf, and the fixing means recording paper conveyance speed Vf is relative to the transfer means recording paper conveyance speed Vt. Was set to 1.002 times Vt, and the peripheral speed of the sheet feeding roller 2 was set to 1.02 times Vt. Further, the paper feed means recording paper conveyance force Fs is adjusted by the spring force of the paper feed spring 3 and the separation spring 6 shown in FIG. 2, and the solenoid 7 is set so as not to operate, and Fs during image formation is set.
Did not fluctuate. The other conditions are the same as in Experimental Example 1.

[0089]

[Table 11]

As is clear from Table 11, although the peripheral speed of the paper feed roller 2 is set to be 2% higher than the peripheral speed Vt of the transfer means, the friction coefficient of the recording paper 1 with respect to the paper feed roller 2 depends on the paper quality. It was observed that the actual feeding speed Vs of the paper feeding means recording paper becomes slower than Vt when V is low.
At this time, it has been found that if the transfer means recording paper carrying force Ft is larger than the paper feeding means recording paper carrying force Fs, it is possible to suppress pitch unevenness of the recorded image and recording paper fixing wrinkles.

As is well known, recording sheets of various paper qualities are used in image forming apparatuses, and the coefficient of friction of the paper feed roller 2 tends to decrease with time, suppressing uneven pitch of recorded images and wrinkles on recording sheet fixing. For this reason, it is preferable that the relation Ft> Fs is satisfied.

A similar experiment was attempted with respect to the second embodiment of the sheet feeding means of this apparatus, but the friction coefficient between the lower sheet feeding roller 13 and the recording sheet 1 gave almost the same result as in the third experimental example. It has been found that the relationship Ft> Fs is preferable also in the second embodiment of the paper means.

(Experimental Example 4) In Experimental Examples 1, 2 and 3, only one sheet of recording paper 1 is set in the paper feeding means, and the recording paper conveyance is continued while the recording paper 1 is present in the paper feeding means. However, in the actual image forming apparatus, it is necessary to sequentially record images on the recording papers stacked in the paper feed tray 13, and the length of the recording paper 1 is unspecified. If a means for detecting is not provided separately, the paper feeding means cannot continue the conveyance of the recording paper until the end of the recording paper 1. Particularly, in the first embodiment of the paper feeding means, the friction pad 5 is always contacted in the direction of the paper feeding roller 2, and in order to prevent the double feeding of the second and subsequent recording sheets, the transfer is performed. It is necessary to release the driving of the paper feed roller 2 after the first recording paper enters the means.

Therefore, the effect of the recording paper conveyance resistance Rs on the image formation was examined as Experimental Example 4. Table 12 shows the experimental conditions and the experimental results of Experimental Example 4.

In Experimental Example 4, the first embodiment of the paper feeding means is used, the transfer means recording paper conveying force Ft is set to 1.5 Kgf,
The recording paper transporting force Ff of the fixing means is 0.75 Kgf, the feeding means recording paper transporting force Fs is 1.2 Kgf or less, and the fixing means recording paper transporting speed Vf with respect to the transfer means recording paper transporting speed Vt is 1.002 of Vt. And the peripheral speed of the paper feed roller 2 was 1.02 times Vt. Further, when the transfer means starts to convey the recording paper 1, the solenoid 7 shown in FIG. 3 is actuated to perform the series of release operations described in the first embodiment of the paper feed means, and at the same time drive the paper feed roller 2. The clutch mechanism (not shown) is used to release the drive. Further, the paper feeding means recording paper conveyance resistance Rs was adjusted by the spring force of the release spring 9. The other conditions are Experimental Example 1
Is the same as

[0096]

[Table 12]

As shown in Table 12, it was found that substantially good image formation was possible under the condition that the paper feeding means recording paper conveyance resistance Rs was 150 gf or less.

As is well known, in the case of the paper feed mechanism as in the first embodiment of the paper feed means, the value of Rs is about 500 gf unless the release mechanism having the solenoid 7 as the operation source is provided.
In order to perform good image formation without fixing wrinkles on the recording paper, it is desirable that the image forming apparatus be provided with this release mechanism.

Also in the second embodiment of the paper feeding means, Rs
It is necessary to give design consideration so that the recording paper conveyance resistance similar to the above does not occur.

Experimental Example 5 From the results of Experimental Examples 1 to 4,
In this image forming apparatus, it has been found that image pitch unevenness and recording paper fixing wrinkles occur depending on the state of tension applied to the recording paper 1 between the recording paper conveying means. Therefore, when the heat roller 20 of the first embodiment of the fixing unit is used conventionally, in order to reduce the undulation due to thermal expansion in the conveyance width direction of the recording paper 1 that occurs in the nip portion of the fixing unit, the center of the roller width direction is reduced. It is widely practiced to make the outer diameter smaller than the outer diameter of the roller width direction end, and to make the recording paper conveyance speed of the roller end faster than the center of the roller. The influence of this apparatus on image formation was examined as Experimental Example 5.

Table 1 shows the experimental conditions and experimental results of Experimental Example 5.
3 shows. The paper feeding means recording paper conveyance resistance Rs is 100.
gf, and other conditions were the same as in Experimental Example 4.

In Table 13, the amount of heat roller crown is shown by the difference between the outer diameter of the roller center and the outer diameter of the roller center.

[0103]

[Table 13]

As shown in Table 13, the heat roller 20
It was found that when the crown amount was ± 100 μm or less, almost excellent image formation was possible, and particularly when the crown amount was 0, the best image was obtained. It is considered that this is because the tension generated in the fixing unit is more uniform as the crown amount is smaller.
Therefore, when the image forming apparatus is configured to use the heat roller 20, the heat roller
Does not need to be processed into an inverted crown shape, and the recording paper nip width in the fixing means is made uniform in the paper passing width direction, so that uniform toner fixability can be obtained on the recording paper.

Here, by summing up the above-mentioned respective experimental results, the relationship between the tensions applied to the recording paper 1 between the conventional image forming apparatus and the present image forming apparatus will be compared with each other with reference to FIGS. 13 and 14.

FIG. 13 is a plan view showing the force that the recording paper 1 receives from each recording paper conveying means in the verification experiment example 1 of the conventional image forming apparatus. Under the condition that good image formation could be performed in the verification experiment example 1, the recording paper 1 is the upper registration roller 34.
The tension T1 does not exist between the resist roller pair constituted by the lower resist roller 35 and the transfer means and the transfer means. In addition, the recording paper 1 is wound between the transfer means and the belt roller 36, and between the intermediate conveyance means composed of the conveyance belt 37 having a large number of small diameter holes and the suction box 38 connected to the suction means (not shown). Is a state of stretching or slackening, and the tension during this is T2 or 0. Further, the recording paper 1 is held between the intermediate conveying means and the fixing means, and the tension T3 is generated between them. As shown in FIG. 13, the tension T
It is assumed that 2 and T3 have a relatively uniform distribution.

On the other hand, FIG. 14 shows an experimental example 1 of the image forming apparatus.
6A to 6C are plan views showing the forces that the recording paper 1 receives from the respective conveying means in FIGS.

Under the condition that the recording paper fixing wrinkles and the image pitch unevenness occur in Experimental Examples 1 to 5, the recording paper 1 has a tension R equivalent to the recording paper conveyance resistance Rs between the paper feeding means and the transfer means.
However, since the recording paper conveying means are arranged close to each other,
The recording paper transport tension applied between the respective means is hardly averaged between L2 and L3, and as shown in FIG. 14, T4 having a non-uniform distribution in which Rs, Ft, and Ff are combined between the transfer means and the fixing means.
Receive.

Therefore, good image formation was possible in Experimental Examples 1 to 5, and by performing image formation under the conditions described in the means for solving the problems, the tension between the transfer means and the fixing means was uneven. It is possible to improve the state from the above state to the uniformized state of T5, and to perform good image formation.

The present invention is also configured in the case where a belt-shaped photoconductor is used as the photoconductor, a conductive film member or a brush-shaped member is used as the charging device, and a non-contact magnetic roller system using magnetic toner is used as the developing device. Obviously, it is possible and the same effect is obtained.

[0111]

As described above, according to the image forming apparatus of the present invention, the recording paper conveying speed and the conveying force of the paper feeding means, the transfer means and the fixing means, which are the recording paper conveying means of the image forming apparatus, are specified. As a result, it is possible to prevent the pitch deviation of the recorded image and the wrinkling of the recording paper fixing which occurs in the fixing means, and it is possible to improve the image quality.

Further, in the image forming apparatus using the present invention, the arrangement intervals of the recording sheet conveying means are greatly shortened as compared with the conventional one.
The width of each roller, etc. in the recording paper conveyance direction is configured to be close to the recording paper width, and even if an image is formed with a simple recording paper conveyance mechanism, the image quality is not impaired, and good image formation is possible at a small size and low cost. An image forming apparatus can be provided.

[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 diagram showing a first embodiment of a paper feeding unit in the image forming apparatus of the present invention, and is a side view showing a paper feeding start state.

FIG. 3 is a diagram showing a first embodiment of a sheet feeding unit in the image forming apparatus of the present invention, and is a side view showing a state in the middle of feeding.

FIG. 4 is a plan view for explaining the arrangement of the paper feed roller 2 in the recording paper conveyance width direction and the method for measuring the recording paper conveyance force Fs in the first embodiment of the paper supply means of the image forming apparatus of the present invention. .

FIG. 5 is a plan view illustrating a method of measuring a sheet feeding unit recording sheet conveyance resistance force Rs in the sheet feeding unit first embodiment of the image forming apparatus of the present invention.

FIG. 6 is a side view showing a second embodiment of the paper feeding means in the image forming apparatus of the present invention.

FIG. 7: Arrangement of the separation claw 10, D-cut roller 11, paper feed upper roller 12 and paper feed lower roller 13 in the recording paper conveyance width direction and paper feeding in the second embodiment of paper feeding means of the image forming apparatus of the present invention FIG. 9 is a plan view illustrating a method of measuring a recording paper conveyance force Fs.

FIG. 8 is a plan view showing a method for measuring a sheet feeding means recording sheet conveyance resistance force Rs in a sheet feeding means second embodiment of the image forming apparatus of the present invention.

FIG. 9 is a perspective view showing an embodiment of a transfer unit in the image forming apparatus of the present invention.

FIG. 10 is a perspective view showing a method of measuring the transfer means recording paper conveyance force Ft in the transfer means embodiment of the image forming apparatus of the present invention.

FIG. 11 is a perspective view showing a first embodiment of a fixing unit in the image forming apparatus of the present invention.

FIG. 12 is a perspective view showing a second embodiment of the fixing unit in the image forming apparatus of the present invention.

FIG. 13 is a plan view showing the force that the recording paper 1 receives from each recording paper conveying means in the verification experiment 1 of the conventional image forming apparatus.

FIG. 14 is a plan view showing the force that the recording paper 1 receives from each conveying means in Experimental Examples 1 to 5 of the image forming apparatus of the present invention.

FIG. 15 is a side view showing a schematic configuration of a conventional image forming apparatus configured by the inventors.

FIG. 16 is a side view showing a schematic configuration of a modified example of a conventional image forming apparatus configured by the inventors.

[Explanation of symbols]

 1 ... Recording paper 2 ... Paper feed roller 3 ... Paper feed spring 4 ... Paper feed bottom plate 5 ... Friction pad 6 ... Separation spring 7 ... Solenoid 8 ... Release lever 9 ... Release spring 10 ... Separation claw 11 ... D cut roller 12 ... Paper Feeding upper roller 13 ... Paper feeding lower roller 14 ... Photoconductor 15 ... Driving gear 16 ... Transfer roller 17 ... Transfer bearing 18 ... Transfer spring 19 ... Driven gear 20 ... Heat roller 21 ... Halogen lamp 22 ... Pressure roller 23 ... Pressurization Bearing 24 ... Pressure spring 25 ... Heating element 26 ... Auxiliary roller 27 ... Heat-resistant belt 28 ... Charging roller 29 ... Laser scanning optical system 30 ... Developing roller 31 ... Paper feed tray 32 ... Pipe material 33 ... Rope 34 ... Upper registration roller 35 … Lower registration roller 36… Belt roller 37… Conveyor belt 38… Suction box

Claims (7)

[Claims] 1. A transfer unit for transferring a toner image formed on the photosensitive member onto the recording paper by a roller which is in contact with the photosensitive member and to which a voltage is applied, and the toner image transferred onto the recording paper is heated and pressed. In an image forming apparatus having a fixing unit for fixing to the recording sheet, Ft> Ff, where Ft is the recording sheet conveying force of the transfer unit and Ff is the recording sheet conveying force of the fixing unit. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein a recording paper conveyance force Ft of the transfer unit and a recording paper conveyance force Ff of the fixing unit are Ft ≧ 1.3 × Ff. 3. The recording sheet conveying speed of the transfer means is Vt,
3. The image forming apparatus according to claim 1, wherein Vf = (1 to 1.005) × Vt, where Vf is a recording paper conveyance speed of the fixing unit. 4. A toner image formed on the photoconductor is recorded by a paper feeding means for accommodating a plurality of recording papers and sequentially feeding one by one, and a roller contacting the photoconductor and applying a voltage. In an image forming apparatus having a transfer means for transferring to a paper and a fixing means for heating and pressing the toner image transferred on the recording paper to fix it on the recording paper, the recording paper conveying force of the transfer means is Ft, An image forming apparatus, wherein Ft> Fs, where Fs is the recording paper conveyance force of the means. 5. The image forming apparatus according to claim 4, wherein Ft> Ff, where Ft is a recording paper conveyance force of the transfer means and Ff is a recording paper conveyance force of the fixing means. 6. A recording paper feeding resistance force of the paper feeding means when the recording paper is fed to the transfer means to carry the recording paper is R.
The image forming apparatus according to claim 4, wherein Rs ≦ 150 gf when s. 7. The image forming apparatus according to claim 1, wherein the outer diameter of the heat roller used for the fixing unit is constant in the sheet width direction.