JPH0638178B2 - Image recorder - Google Patents

Description

The present invention relates to an image recording apparatus such as electrophotography and electrostatic recording, and in particular, a so-called toner image formed of resin, carbon, pigment, dye, etc., a recording member such as paper (hereinafter abbreviated as a sheet). The present invention relates to an image recording apparatus having a fixing device for fixing it on the top.

As a conventional fixing device used in this type of image recording device, a heating fixing device for passing a sheet through a chamber having a heating means inside to heat and fuse a toner image on the sheet, and applying pressure to the sheet There are a pressure fixing device for solidifying the toner image on the sheet, a heat fixing device for heating and fusing the toner image on the sheet by passing the sheet between the heating roller and the pressure roller. However, in any of the fixing devices, there is a problem that the sheet passing through the fixing device is deformed and curled by receiving heat or mechanical pressure. This phenomenon is remarkable in the heat fixing device.

In particular, the heat fixing device applies a large amount of heat to the sheet and the toner. Therefore, the moisture contained in the sheet evaporates, and the sheet curls due to an imbalance in the amount of moisture evaporated on the front and back surfaces. Also, when a sufficient amount of heat is applied to both the front and back surfaces of the sheet, the curl shape is determined by the state immediately after the sheet exits the heat fixing device, because the sheet loses its rigidity as the sheet moisture evaporates.

The occurrence of the above curl does not cause a big problem in the normal image recording mode. However, for example, when a sorter is connected to the image recording device to automatically perform sheet alignment, a problem occurs, and a toner image is formed on the front and back surfaces of the sheet. When performing automatic double-sided printing for transfer, inconvenience may occur in the sheet transportability and stackability on the intermediate tray.After the toner image is transferred from the image forming body to the sheet, the sheet is electrostatically discharged from the image forming body. When performing separation, there is a problem that inconvenience occurs in separation after transfer to the second side of the sheet.

Conventionally, in order to solve the above-mentioned problems, for example, a device for improving the sheet itself to reduce the curl amount, as a specific example, as disclosed in JP-A-57-81270, the water content of the sheet is 5.5 to At 6.5%, an attempt has been made to keep the waist strength of the seat appropriate at that time. However, this attempt limits the sheets used, the sheets themselves are easily affected by environmental changes, the sheets lose their stiffness by absorbing moisture in a high-humidity environment, and the amount of water evaporation is high. Therefore, the above improvement was not sufficient for the development such as increasing the curl amount.

Since the curl shape of the sheet is determined immediately after being discharged from the heat fixing device, the sheet discharging portion of the fixing device is devised. As a concrete example,
As disclosed in 4,375,327, in the case of heat roller fixing consisting of a heat fixing roller and a pressure roller, shortening the distance between the separation claw and the nip portion in contact with the pressure roller,
As disclosed in Japanese Patent Laid-Open No. 51-113637, attempts have been made to make the sheet conveying speed of the conveying means after discharging the sheet from the fixing roller higher than the sheet conveying speed of the fixing roller.

However, these attempts cannot control the curl state of a part of the sheet. In particular, in the case of double-sided printing, the trailing edge of the sheet for the first side will come to the leading edge for printing for the second side, so it is necessary to control the curl state of the trailing edge of the sheet for the first side. Is not enough. That is, the preceding example is effective only for the regulation of the wavy curl, and the latter example is capable of regulating the curl amount only when the sheet is between the fixing roller and the conveying means after the sheet is ejected. There is a problem that the curl amount at the rear end cannot be regulated.

In addition to the above example, the curl amount regulation at the discharging portion of the fixing roller has been devised, but none of them is sufficient in the sense that the curl amount at all portions from the leading edge to the trailing edge of the sheet is regulated. It was

Further, since the curl of the sheet is the most problematic in double-sided printing, the print image on the first side is assumed to be printed as disclosed in, for example, JP-A-53-143339.
It has been proposed that the printed image on the first side be permanently fixed. However, since the heat quantity is not supplied so much from the fixing roller to the assumed first surface, the curl of the sheet is reduced, but the fixing property is poor, and the toner image is scraped off by the conveying roller or the like when the second sheet is conveyed. It causes drawbacks. In other words, there is a contradictory condition where a fixing property with practically no problem is obtained and a fixing condition with a small curl amount, and the overlapping area is small. The idea of reducing is practically very difficult.

The present invention has been proposed in view of the above, and an object of the present invention is to reduce the curl of a sheet caused by passing through a fixing device and to more rationally solve the curl occurrence due to a complicated factor. Further, although the present invention prevents curling by steam, it is also an object to effectively utilize the steam. Particularly in double-sided printing in which an image is formed on both sides of a sheet, the present invention improves the transportability of the sheet, reduces the occurrence of jams, and improves the separation property of the sheet from the image forming body after the second-side printing. Therefore, it is particularly preferable for this type of application.

In order to achieve the above object, the present invention provides a fixing device for fixing a toner image on a recording member, and a recording member passage area near the recording member discharge side of the fixing device so as to apply water vapor to the recording member. On the other hand, the image recording apparatus is characterized in that it has water vapor applying means provided on each of the upper and lower sides, and each applying means has a member for variably controlling the amount of water vapor applied as necessary. Is.

FIG. 1 is a diagram showing an overall outline of a double-sided laser beam printing apparatus as an image recording apparatus of the present invention. A laser beam 1 modulated by a signal from the outside or a signal generated inside is scanned by a scanner 2, passes through an imaging lens 3, and has an optical path bent by a folding mirror 4, and a photosensitive drum 5 as an image forming body. Imaged above. The photosensitive drum 5 is subjected to uniform corona charging by the charger 6, and then irradiated with the laser light 1 to form an electrostatic pattern according to a signal, that is, an electrostatic latent image. The electrostatic latent image is converted into a toner image by passing through the position of the developing device 7.

On the other hand, the sheet 9 as the transfer paper is the cassette feeding roller 12
After being sent from the cassette 13, the registration roller 14 sends the image in synchronization with the image on the photosensitive drum 5. Then, after the toner image is transferred from the photosensitive drum 5 when passing through the position of the transfer corona charging device 8, the toner image is separated from the photoconductor 5 by the separating corona charging device 10, and the conveying belt 15
Is conveyed to the fixing device 16. The surface of the photoconductor 5 is cleaned by a cleaner 11 after the sheet is separated, and is repeatedly used.

The fixed sheet discharged from the fixing device 16 is sent onto the tray 23 by the discharge roller 22 in the case of single-sided printing. Further, in the case of double-sided printing, the conveyance path is bent by the branching claw 18 and conveyed, and then the conveyance belt 19 conveys the toner image forming surface upward to the intermediate tray 20.

Next, it is fed from the intermediate tray 20 by the intermediate feeding roller 21, synchronized with the image by the registration roller 14, and is fed downward toward the transfer corona charger 8 with the toner image forming surface. Then, the transfer corona charger 8 transfers the toner image for the second time on the side opposite to the surface for forming the toner image for the first time, and thereafter, as in the case of single-sided printing, separation, conveyance,
After being fixed, the discharge roller 22 is used to attach the tray 23 to the outside of the machine.
Dispatched on.

Although the optical image exposure is modulated laser light in the example of FIG. 1, it may be optical image exposure from an original document irradiated with light as in a copying machine.

FIG. 2 is a cross-sectional view showing an example of a heat fixing device applied to the image recording apparatus of the present invention. The heat fixing device 16 is composed of a pair of a fixing roller 162 and a pressure roller 163 which is in pressure contact with the fixing roller 162.

The fixing roller 162 is a non-adhesive heat-resistant resin such as ethylene tetrafluoride, HTV, RT on the surface of the core metal such as Sus, Al, iron.
A structure in which a non-adhesive heat-resistant elastic layer such as FLC (trade name: manufactured by Nitto Kogyo Co., Ltd.) in which silicone rubber such as V or the surface of silicone rubber is coated, and a heating source such as a halogen heater 169 are provided inside Is.

The pressure roller 163 is HT on the surface of the core metal such as Sus or iron.
It is a structure coated with a non-adhesive heat resistant elastic body such as V / LTV / FLC.

In this embodiment, the heat fixing device is used, but since the temperature of the fixing roller is higher than that of the pressure roller, curling is likely to occur along the circumference of the fixing roller. The curl is also generated by the pressing method of pressure fixing, which will be described in detail later.

The surface temperature of the fixing roller 162 is detected by a temperature sensor such as the thermistor 164, and a known control circuit (not shown).
Is controlled to a constant temperature. The toner offset on the fixing roller is cleaned by a silicone oil-impregnated cleaning web 161. Other materials may be used as the oil applying member and the cleaning member.

The cleaning web 161 is sent from the supply reel 24, and is wound by the take-up reel 26 while being pressed against the fixing roller 162 by the pressing roller 25. 1 in the figure
Numeral 65 is a winding prevention claw of the sheet 9 which is urged by a spring (not shown) so that its tip comes into contact with the surface of the fixing roller, and 166 is urged by a spring (not shown) so that its tip comes into contact with the surface of the pressure roller. The winding prevention claws 167 and 168 of the sheet 9 are water vapor flow paths formed near the sheet discharge side from the upper and lower portions of the fixing device 16, preferably toward the outside of the discharge roller 22. In this example, the water vapor flow paths 167 and 168 are formed by inclining the side walls of the discharge side of the top plate and bottom plate of the fixing device toward the discharge side.

A laver 170 that opens and closes the water vapor passage 167 is provided in the water vapor passage 167. A spring 171 that constantly applies a biasing force to the lever 170 and a louver that opens against the biasing force are provided. Plunger 1 via wire 172
73 are connected. A louver 175 is also provided in the water vapor flow path 168 in the same manner.
A closing spring 176, an opening wire 177 and a plunger 178 are connected to each other.

The sheet 9 to which the toner image is transferred from the photosensitive drum 5 is conveyed to the heating and fixing device 16, and when passing between the fixing roller 162 and the pressure roller 163, heat is supplied from the fixing device 162 to the toner on the sheet 9. Melts and sticks onto the sheet. At this time, part of the water content is evaporated from the sheet 9 by the heat supply, and the inside of the fixing device 16 is in a state of containing more water vapor than in the general air. This water vapor flows with a stream of warm air.

During fixing of the first surface of the sheet 9, the plunger 173 is not energized and the plunger 178 is energized. Therefore, the louver 170 is closed by the biasing force of the spring 171, but the louver 175 resists the biasing force of the spring 176 and the wire 17
The plunger 178 is opened to the state shown in FIG.

On the other hand, the sheet 9 that has passed between the fixing roller 162 and the pressure roller 163 is discharged by the discharging roller 17 and guided in the direction of arrow c by the branch claw 18 that switches the path. At this time, the sheet 9 immediately after exiting the discharge roller 17
The lower surface is exposed to the water vapor flowing in the direction of arrow a through 68, the curl is corrected, and when the lower surface is fed to the intermediate tray 20, the curl becomes substantially flat.
Both the above-mentioned stackability and the separability from the photosensitive drum 5 after the transfer of the second surface are in a good state.

When the sheet 9 having the toner image transferred to the second surface passes through the fixing device 16, the plunger 173 is energized and the plunger 178 is deenergized. Therefore, the louver 175 is closed by the biasing force of the spring 176, but the louver 170 is pulled by the plunger 173 via the wire 172 against the spring 171 and opened. Therefore, the fixing device 1
Water vapor in 6 flows from the upper part inside the fixing device in the direction of arrow b,
It is sprayed on the upper surface of the sheet 9.

At the time of the second passage of the sheet, the water content of the sheet 9 is lowered, and when the sheet 9 is heated by the heating roller 169 in this state, only the water vapor on the surface of the sheet 9 is removed. Has a tendency to contract the upper surface, and the front and rear portions in the traveling direction of the sheet curl upward. Therefore,
If the sheet 9 is discharged in this state, it will be convex downward and the stacking on the tray will be poor, and the stacking characteristics on the sorter or stacker will be poor. The above curl can be removed by spraying steam on the upper surface of the sheet at the time of the passage of the first time.

Note that the guides 174 and 179 arranged vertically above and below the sheet ejected from the fixing device 16 at intervals so as to sandwich the sheet may be a mesh-shaped perforated plate or a comb-shaped guide rod so that water vapor can pass therethrough. And

It will be described in detail with reference to FIGS. 3 and 4 that the curl is corrected by exposing the sheet 9 to water vapor. The leading edge of the sheet 9 that has entered between the fixing roller 162 and the pressure roller 163 is fixed on the fixing roller 16 by the adhesive force of the melted toner.
It wraps around 2, but is peeled off by the wrapping prevention claw 165. Therefore, the tip of the sheet 9 receives the above-mentioned force and is
Curl downward as shown in FIG.

On the other hand, as shown in FIG. 3B, the rear end of the sheet 9 is supported by only the discharge roller 17 when it is no longer subjected to the binding force sandwiched between the fixing roller 162 and the pressure roller 163. It hangs down and curls downward. Thus, when the sheet 9 leaves the fixing device 16, the sheet 9
A downward curl as shown in FIG.

The above phenomenon becomes more remarkable when the sheet 9 absorbs moisture. It is considered that this is because the waist of the sheet 9 is weakened by moisture absorption, and the movement of water in the sheet is always directed upward, so that the movement of water on the lower surface of the sheet is increased. Furthermore, when printing on both sides,
As shown in FIG. 2, the sheet 9 is conveyed by being bent and guided in the same direction as the curl by the branch claw 18. Since this bending action occurs when the sheet 9 is warm immediately after leaving the fixing device 16, the curl of the sheet 9 is greatly affected and the downward curl becomes larger.

Therefore, according to the present invention, the sheet is supplied with water, and FIG.
As described above, the curl of the sheet is corrected by the extremely simple means of applying steam to the surface of the sheet that has been contracted by the curl as described above.

FIG. 5 is a front view of a part showing a modified example of the fixing device 16 applied to the image recording apparatus of the present invention. In this example, the fixing device 16
The crossflow fans 191 and 192 are arranged above and below so as to sandwich the sheet discharged from the sheet, and the crossflow fans 191 and 192 are alternately operated to generate steam on the lower surface or the upper surface of the sheet 9 immediately after being discharged from the fixing device 16. It was made to blow.

As described above, by positively collecting the water vapor in the fixing device 16 by the cross flow fans 191, 192 and spraying it onto the sheet 9, the above-mentioned curl correction effect becomes more remarkable, and the curl is reduced in a short time. Can be corrected. Particularly, in this example, in order to further increase the effect of collecting water vapor, the crossflow fan 191 is reversely rotated in the direction of the dotted line when the crossflow fan 192 is operated, and the crossflow fan 192 is indicated by the dotted line when the crossflow fan 191 is operated. It is possible to rotate in the reverse direction.

In each of the above embodiments, a flow path for providing the sheet with water vapor in the fixing device is provided in the vicinity of the discharge of the fixing device.However, a water vapor generation source is provided in the vicinity of the discharge, and the generated water vapor is supplied to the sheet. It can also be configured to give.

As the water vapor generation source, for example, a water vapor is generated by vibrating water with a vibrating element such as a piezo element.

The fixing device is not limited to the heat roll fixing device in the illustrated example, but a chamber fixing device, an induction heating fixing device, a flash fixing device, various heat application type fixing devices such as a heat plate, and a pressure fixing device for fixing by pressure are applied. It is possible. Further, as a method for printing a toner image on a sheet, there is a method in which a toner image is once formed on another image forming body and then transferred to a sheet as in the illustrated example, or at the same time when an electrostatic image is directly formed on the sheet. Alternatively, a method of developing immediately after that may be used.

As described above in detail, according to the present invention, the water vapor flow paths are provided on both sides of the sheet in the vicinity of the sheet discharge of the fixing device, and the water vapor flow paths are alternately opened and closed. The effect of is obtained.

(1) The curl of the sheet discharged from the fixing device can be reliably reduced with a simple configuration.

(2) By reducing the curl, it is possible to reduce the occurrence of jam caused by the curl of the sheet during double-sided printing, and to obtain stable double-sided conveyance characteristics.

(3) When the sheet separation from the photosensitive drum is electrostatic separation as in the illustrated embodiment, deterioration of separability due to curling can be prevented, and it is particularly effective for a sheet left in a high humidity environment. is there.

(4) Since water vapor, that is, humidity, is applied to the sheet, an extreme increase in surface resistance of the sheet can be prevented even after the first fixing, so that transferability and separability are improved and a good image is obtained in the second time. Records are obtained. That is, according to the present invention, not only curl prevention but also a good humidity control effect of the sheet can be obtained.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a laser beam printer apparatus as an image recording apparatus of the present invention, FIG. 2 is an overall schematic view of a fixing apparatus applied to the apparatus, and FIGS. 3 and 4 are explanatory views of sheet curl correction. 5 is a partial cross-sectional view showing a modified example of the fixing device. 9 is a recording member (sheet), 16 is a fixing device, 167, 1
68 is a water vapor flow path, and 170 and 175 are louvers.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 54-74444 (JP, A) JP-A 49-2544 (JP, A) JP-A 59-24862 (JP, A) JP-A 50- 143531 (JP, A) JP-A-50-147725 (JP, A) Actually developed 54-62738 (JP, U) JP-B 42-8198 (JP, B1)

Claims (3)

[Claims] 1. A fixing device for fixing a toner image on a recording member, and a fixing device on the upper and lower sides of a recording member passing area near the recording member discharge side of the fixing device so as to apply water vapor to the recording member in the previous period. An image recording apparatus, comprising: a water vapor applying unit provided for each unit; and each unit having a member for variably controlling the amount of water vapor applied. 2. The image recording apparatus according to claim 1, wherein a heat fixing device is used as the fixing device. 3. An image recording apparatus according to claim (2), wherein water vapor in a heat fixing device is used as water vapor given to the recording member.