JPH0423790B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Purpose of the Invention This invention relates to an image forming apparatus such as an electrostatic copying machine or an electrostatic printer, and particularly to a fixing section of an image forming apparatus that fixes a toner image transferred to a recording material. The present invention relates to a protection mechanism for a recording material detection means in the invention.

In order to fix the toner image formed on the recording material, a fixing mechanism that fuses and fixes the toner by passing the recording material through a pair of rollers heated to a predetermined temperature or through an oven-shaped heating area. has been widely used in image forming apparatuses such as those described above. In devices that use such a heat fixing mechanism, if the transfer material jams in this area, it can cause a fire and is extremely dangerous.
Usually, there is a detection means for detecting passage.

However, when using such a heat fixing mechanism,
Since the mechanism is at a high temperature, the surrounding parts and the atmosphere are also at a considerably high temperature, and there is a risk that the detection means may be damaged or malfunction due to this influence. In addition, a photo interrupter is often used in the electric signal generating part of the detection means, but in such cases, the moisture contained in the recording material is vaporized by heating the recording material, and this is caused by the photo interrupter. Condensation may condense on the light-receiving section or light-emitting section of the image forming apparatus, causing malfunction. It was.

The present invention has been made in view of the above-mentioned current situation, and provides an image forming apparatus that includes a blower guide path having a detection opening, a blower means for blowing air into the guide path, and a blower means facing the detection opening. It is an object of the present invention to provide a recording material detection device which has a detection means provided in the above-mentioned air guide path and detects the presence or absence of a recording material through the opening.

(B) Structure of the Invention In order to achieve the above object, the present invention includes a heat fixing means for fixing a toner image formed on a recording material, an air blowing means, and a heat fixing means for fixing a toner image formed on a recording material. and a detection means disposed in the path of the air flow sent out by the air blowing means above the conveyance path of the sheet, the detection means detecting the recording material passing through the heat fixing means and emitting an electric signal. This is a recording material detection device in a fixing section.

Embodiments in which the present invention is applied to an electrostatic copying machine will be described below with reference to the drawings.

FIG. 1 is a side cross-sectional view of the main parts of a known electrostatic copying machine, showing an outline of the structure of the side where the heat fixing mechanism exists, in which a cylindrical photoreceptor 1 is installed in the main body of the copying machine. A developing device for developing a latent image on the surface of the photoreceptor and a cleaning device 3 for removing residual toner remaining on the photoreceptor after transfer are arranged near the periphery thereof. Of course, other devices are provided around the photoconductor, such as means for charging the photoconductor, and exposure means for irradiating the document on the top surface of the copying machine body with the light source 16 and transmitting the reflected light to the surface of the photoconductor. Of course, these are not directly related to the present invention, so a detailed explanation thereof will be omitted.

A recording material supplied from a cassette (not shown) on the right side of the first drawing approaches the photoreceptor 1 via a register roller 5, and is transferred through a transfer site provided with a transfer electrode 6, and is transferred to a separation roller 7. The image is separated from the photoreceptor by the conveyance roller 8 and reaches the heat fixing mechanism 4 by the conveyance roller 8.

The transfer sheet that has entered the thermal fixing mechanism 4 is heated to a predetermined temperature by a pair of fixing rollers 4a, 4.
The toner image passes through space b and is fused and fixed to the transfer sheet, and is then discharged to the outside of the machine via the toner 17. During this time, the transfer sheet that has passed through the pair of fixing rollers 4a and 4b is forcibly ejected by the paper ejection roller 9 and the paper ejection roller 10 that is in pressure contact with it. Actuator 1
1 is swingably mounted.

As can be seen from FIGS. 1 and 2, the paper ejection roller 9
A groove 9a is formed in the actuator 1.
One end 11b of 1 is seated within this groove. Therefore, when the transfer sheet advances from the fixing roller pair and enters between the paper ejection roller 9 and the paper ejection roller 10,
End portion 1 of the actuator seated in the groove 9a
1b will rise, and the actuator 11 will rotate clockwise as viewed in FIG. Figure 1,
As can be seen from FIG. 2, the actuator 11 has an end portion 11a integrally formed with the end portion 11b, and this end portion 11a is connected to a photo interrupter 13 attached to a proper position in the main body of the copying machine. It is always disposed between the light emitting part and the light receiving part to isolate the two parts. Therefore, as described above, when the transfer sheet passes between the paper discharge roller 9 and the paper discharge roller 10 and the end portion 11b of the actuator 11 is placed on the transfer sheet and rotates clockwise in FIG. 1, the end portion 11a is displaced from between the light-emitting and light-receiving parts of the photo interrupter 13 to activate it, and when the transfer sheet finishes passing through, the two parts are cut off again, so the presence or absence of the transfer sheet in the fixing mechanism is detected. It can be used as a means.

This type of copying machine has heat generating sources such as the heat-fixing mechanism mentioned above, the exposure light source, and the drive motors of various parts, so it is recommended to install a blower to exhaust the air inside the machine to the outside of the machine. In the device shown in the first figure, a blower 15 is arranged, and air is exhausted from a grid-like gap 18 formed in the fuselage body. In a device equipped with such a blowing means, according to the present invention, a wind shielding plate 19 is arranged inside the grid-like gap 18, particularly in a portion where the photo interrupter is located, and
A guide plate 12 is disposed above the upper plate 4c of the fixing mechanism 4, and a photo interrupter 13 is connected to the upper plate 4c.
c, it is configured to exist between the guide plates 12.

In addition, as shown in Figure 1, in a copying machine configured in such a way that a transfer sheet is inserted from one end of the main body, the transfer sheet advances in a substantially planar manner, and is ejected from the other end of the main body, the dashed line in the figure Along F, the upper part can be rotated and opened with respect to the lower part along with the internal mechanisms such as the photoreceptor 1, the developing device 2, the cleaning device 3, the light source 16, the blower 15, etc., and when opened, the transfer sheet feeding path is opened. It has been well known for a long time that the device exposes the
In the figure, the fixing mechanism 4 is located at a fixed lower part, and the guide plate 12 is located at an upper part that rotates to open and close. Therefore, the guide path 14 can be easily formed, and a photo interrupter, which is one element of the detection means, can be configured. The present invention can be suitably applied by attaching the actuator 11 to the upper side and attaching the actuator 11 to the lower fixing mechanism as it is.

FIG. 3 shows an embodiment suitable for use in such a case.
0, the actuator 11, the photo interrupter 13, etc., are basically the same as those described above.

In this one, photo interrupter 1
3 is fixed to a support member 20, and this support member 20 is mounted on a support arm 21 disposed at an appropriate position on the main body of the copying machine so as to be freely displaceable in the direction of arrow X and rotatable in the direction of arrow Y in the figure. Furthermore, the support member 2
0 and a hole 4d with a tapered part 4e is provided in an appropriate fixing part, such as the upper plate 4c of the fixing mechanism 4, so that the photo interrupter 13 and the actuator 11 are in an accurate relative positional relationship. At times, the pin 22 is configured to fit into the hole 4d. With this configuration, even if the upper half of the copying machine body is configured to rotate to open and close as described above, the photo interrupter is attached to the upper part and the photo interrupter is attached to the fixed lower part. It is possible to reliably bring the actuator into the correct positional relationship.

FIG. 4 shows another embodiment of the invention. A light emitting element 38 of a photo interrupter is provided on the lower surface of the transfer paper passage path 41 between the fixing roller pair 39 and the paper ejection roller pair 40, and a light receiving element 37 is provided on the upper surface.When the transfer paper P passes, light from the light emitting element 38 is provided. is blocked, and the passage of the transfer paper P is detected. A duct 42 is provided from the outlet of the cooling fan 32 to the light receiving element 37, and a part of the air flow is guided to the light receiving element.
Therefore, the water vapor generated from the transfer paper P is pushed toward the fixing roller and does not form condensation on the light receiving element 37. In this way, even in a transfer sheet detection device that does not use an actuator, by guiding the air flow to the switch section, it is possible to avoid malfunctions and ensure reliable switch operation. In this way, the present invention can also be applied to devices that do not have an actuator like the above embodiments.

Note that the wind shielding plate 19 may not be provided separately from the lattice-like gaps 18, and a part of the lattice-like structure may be formed into a plate shape without gaps.

Although the present invention has been described above in the case where it is applied to an electrostatic copying machine, it is clear that the same effect can be obtained even when the present invention is applied to other electrostatic image forming apparatuses.

Further, although the sensing means is a photo interrupter in the above embodiments, it is clear that other sensing means that generate electrical signals in response to actuation of the actuator may be used. A similar effect can also be obtained when the passage of paper is directly detected by a photo interrupter without using an actuator.

Furthermore, in the above embodiment, the fixing mechanism is arranged below and the blower is arranged above on the transfer sheet ejection side, but even in the case where the two are arranged in a relationship other than the above, the detection is possible. It is of course also possible to use ventilation channels or conduits leading to the means.

(C) Effects of the Invention Since the present invention has the above configuration, part of the exhaust flow caused by the action of the blower 15 is blocked by the wind shield plate 19, and then the guide plate 12, the upper Guide path 1 formed between plates 4c
4 will be distributed. Therefore, an air current always exists around the photo interrupter 13 located in this guide path 14, and the photo interrupter 13 is cooled. Therefore, malfunction and damage to the photo interrupter due to temperature rise can be prevented. Even if steam is generated in the fixing area, dew condensation in the photo interrupter can be reliably prevented. . In addition, as the transfer sheet made of normal paper runs, the light emitting and light receiving parts of the photo interrupter may be contaminated by dust generated when the paper is torn and toner powder scattered inside the machine, causing malfunction. It is also possible to prevent such problems in heat fixing and pressure fixing.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main parts of a copying machine to which the present invention is applied, FIG. 2 is an enlarged end view showing the configuration of a protection mechanism according to the present invention, and FIGS. It is an end view showing an example. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Developing device, 3... Cleaning device, 4... Fixing mechanism, 4a, 4b... Fixing roller pair, 9... Paper ejection roller, 10... Paper ejection roller, 11... Actuator, 12... Information board,
13... Photo interrupter, 14... Ventilation guide path, 15... Blower, 18... Grid gap, 1
9... Wind shielding plate, 20... Support member, 21... Support arm, 22... Pin.

Claims (1)

[Scope of Claims] 1. A heat fixing means for fixing a toner image formed on a recording material; a blower means; A recording material detection device for a fastening section, comprising: a detection means disposed in a passage of an air flow, the detection means detecting a recording material passing through the heat fixing means and emitting an electric signal.