JPH0350267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that forms an image on a sheet material, and more particularly to an image forming apparatus having means for detecting a sheet material passing through a conveyance path for conveying the sheet material.

This type of image forming apparatus includes a copying machine, a facsimile machine, a laser-based apparatus, a printing machine, etc., which form an image by fixing an unfixed image onto a sheet material. Among these, an electronic copying machine is a typical example that uses sheet materials such as cut sheets.

Generally, these image forming devices have a fixing section,
Here, there is a pair of fixing rollers that fixes an unfixed image onto the sheet material while gripping and conveying the sheet material. Furthermore, in order to detect the passage of the sheet material in the fixing section, an actuator that is mechanically activated by the passage of the sheet material and a switch (for example, a photoconductor made of a semiconductor) that generates an electrical signal in response to the movement of the actuator are combined. It has a paper detector.

When the fixing device is a heating fixing device, the vicinity of the fixing device is exposed to high temperature. Therefore, the high temperature disturbs the response characteristics of the switch, resulting in malfunction. In addition, the characteristics of switches and the like that include semiconductor elements change especially due to heat, and those whose guaranteed temperature is set at about 80° C. or higher are expensive, so it is necessary to prevent the effects of heat.

In view of this problem, there is an apparatus in which a switch whose detection function is easily influenced by heat is provided at a position far away from the high temperature part of the fixing device. This device has a structure in which only an actuator is provided in a paper passing area, and changes in movement of the actuator are transmitted to a switch via a member such as a long shaft. However, this device requires extra space to provide the switch, resulting in an increase in the size of the device. Furthermore, if the actual detection of the passage of the sheet material and the location where it is converted into an electrical signal are far apart, the mechanism becomes complicated. Further, the force for operating the actuator is generally small, and as mentioned above, if the distance required to convert the actuator into an electrical signal is long, it may cause malfunction.

Therefore, the distance between the actuator and the switch must be short, the mechanism must be simple, and it is particularly desirable that the mechanism be unaffected by heat.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a small and simple-configured device in which a sheet material detection means can accurately detect a sheet material passing through a sheet material conveyance path. .

To achieve the above object, the present invention includes a toner image forming means for forming a toner image on a sheet material, a conveyance path for conveying the sheet material, and a toner image formed on the sheet material in the middle of the conveyance path. a fixing means that heats and fixes the image; an air flow path for discharging the heat generated from the fixing means to the outside of the apparatus main body; a movable member that is displaced in contact with the sheet material; and a switching member that generates an electric signal in response to the movement of the movable member, and the switching member is provided in the air flow path.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of the configuration of one embodiment of an electrophotographic copying machine using the present invention, and FIG. 2 is an explanatory diagram when the main body of the apparatus shown in FIG. 1 is opened. In Figures 1 and 2,
Reference numeral 1 denotes a document mounting table made of a transparent member, which moves back and forth in the direction of the arrow. Reference numeral 2 denotes a converging light transmitting body which slit-exposes a light image of the original image on the original table 1 onto the photosensitive drum 3.

The photosensitive drum 3 rotates in the direction of the arrow. 4 is a corona charger that uniformly charges the photosensitive drum.
A developing device 5 visualizes an electrostatic latent image formed by exposing a uniformly charged photosensitive drum to a light image using the converging light transmitting member 2.

On the other hand, the transfer paper P is fed onto the drum surface by a paper feed roller 6 and a register roller 7, and the image on the drum is transferred by a transfer charger 8. Thereafter, the transfer paper is separated from the drum by the separating means 13, passed through the guide 9, and then passed through the heating fixing roller 10 ₁ .
The image is sent to a fixing device 10 having a heating roller 10 ₂ .
A fixing device 10 fixes the toner image on the transfer paper, and the transfer paper is discharged onto a tray 12 by a discharge roller 11 and a paper discharge roller 20.

The toner remaining on the photosensitive drum 3 is removed and collected by the cleaning means 14.

15 is an illumination system member having a lamp and a reflective shade for exposing the original; 16 is a filter such as a heat ray absorption filter.

The main body of the apparatus is configured so that it can be divided into an upper casing 17 and a lower casing 18. The upper casing 17 and the lower casing 18 are connected together by a spindle 19 at the end of the device, and the upper casing 17 is rotatable about the spindle 19 in the direction of arrow A.
In the upper housing 17, means mainly related to image formation are held fixedly or detachably attached to the housing 17. Specifically, it includes means for forming an original image on the photosensitive drum 3, that is, the optical system member 15, the photosensitive drum 3, the developing means 5, the cleaning means 14, and the like. In addition, means for forming the toner image formed on the photosensitive drum 3 on paper P is fixed to or detachably held in the lower housing 18. Specifically, a transfer charger 8, a fixing device 10,
It is a member such as a roller that conveys the transfer paper P.

Next, the vicinity of the fixing device 10 having a paper detector in the paper passing area will be described with reference to FIGS. 1 and 2.
Reference numeral 30 denotes an upper cover of the fixing device 10, which is composed of a heat-reflecting metal plate and a heat-insulating coating, and prevents wasteful release of heat from inside the fixing device to others. The aforementioned paper ejection roller 20 and ejection roller 11 are located in front of the heating fixing roller 10 ₁ and pressure roller 10 ₂ in the paper traveling direction and in the vicinity thereof so as to be covered by the upper cover 30 of the fixing device 10. . The upper cover 30 has an opening 10 ₃ above the paper discharge roller 20 . The paper ejection roller 20 and the ejection roller 11 are in contact with each other or are provided at a position where they rotate together due to the presence of the transfer paper P. The discharge roller 11 has a small diameter portion 11 ₁ which is a concave portion as shown in FIG. The paper ejection roller 20 is located at a position corresponding to the large diameter portion ₁₁₂ of the ejection roller 11, and is rotatably held by a shaft 28 held in the lower housing 18 along the longitudinal direction of the heat fixing roller ₁₀₁ . There is.

Reference numeral 21 denotes an actuator provided on the shaft 28 of the paper discharge roller 20 (that is, provided on the lower housing 18), and is a dogleg-shaped plate-like piece. The upper end 21 ₁ of the actuator 21 is the opening 1 of the upper cover 30
0 ₃ and protrudes above the upper cover 30.
On the other hand, the lower end portion 21 ₂ of the actuator 21 is normally in contact with the small diameter portion 11 ₁ of the discharge roller 11 .

Reference numeral 22 denotes a photo interrupter switch having a concave portion including a photo sensor portion, and is attached to the upper housing 1.
It is held in the holding part B of No.7. Furthermore, the concave portion of the photo interrupter 22 projects below the frame plate 32 through an opening 32 ₁ in the frame plate 32 located below the upper housing 17 .

23 is a wiring for transmitting a signal from the photo interrupter 22, and is housed in the upper housing above the frame board 32. The frame plate 32 is made by bonding a metal plate and a heat insulating material, and is preferably a flat plate having a width in the longitudinal direction of the heat fixing roller ₁₀₁ .

As shown in FIG. 2, when the upper housing 17 and the lower housing 18 are opened, the actuator 21 and the photo interrupter 22 are separated from the upper and lower housings by a large distance, and paper detection cannot be performed. Since the upper and lower casings are usually aligned, the actuator 21 is located between the legs of the recess of the keto interrupter 22. The actuator 21 is placed between the photo sensor portions 22 ₁ which are separately provided on both legs of the recessed portion of the photo interrupter 22 .
This is to indicate that the paper is not passing when there is. In other words, the paper detection means is normally on standby in a state where it can detect the passage of paper.

Further, when the upper and lower housings 17 and 18 are in an aligned state, a space D is formed between the frame plate 32 and the cover 30. This space D is in a state where air flows and serves as an air flow path. On the other hand, on the side of the optical system member 15 of the upper housing 17 and the housing 17
A fan F provided at the end of the device discharges heat, etc. inside the device to the outside of the device. Air in the lower housing 18 flows through the fan F as shown by the arrow E and is discharged to the outside of the apparatus through the opening 31 ₁ of the frame plate 32 . This air flow cools the photo interrupter switch 22 and prevents it from overheating. or,
Water vapor generated in the fixing device 10 during fixing (generally caused by temperature changes, but in the case of heat fixing, it is caused by moisture in the paper) is absorbed through the opening 10 ₃ of the cover 30 .
leaked from the photo interrupter switch 22
At this point, the water cools down and tries to form water droplets, but this airflow prevents them from forming into water droplets and sends them out of the device. Even if the water becomes droplets, this air flow will evaporate or reduce the amount to a negligible amount. With this configuration or a configuration similar to this, it is possible to almost eliminate water droplets that are likely to occur on the paper detection section, thereby solving the problem that the paper detector malfunctions due to the generation of water droplets.

The actuator 21 is normally in the state shown by the solid line, but when the leading edge of the paper P passes between the ejection roller 11 and the ejection roller 20, the actuator 21 is moved by the arrow G so that it is in the state 21' shown by the broken line in FIG. Rotate in the direction.
At this time, since the paper P is conveyed between the circumferential surface of the large diameter section ₁₁₂ of the discharge roller 11 and the circumferential surface of the paper discharging roller ₂₀ , the lower end 212 of the actuator 21 ₁ and move upward away from paper P.
Slides into contact with the top surface of the On the other hand, the upper end 21 ₁ of the actuator 21 moves within the opening 10 ₃ of the cover 30 in response to the movement of the lower end 21 ₂ and is removed from the recess of the photo interrupter switch 22. As a result, the photo sensor section 22 ₁ opens and an electric signal is output, so that the passage of the paper P can be detected.

While the paper P passes between the discharge roller 11 and the paper discharge roller 20, the actuator 21 is in state 2.
1', when the rear end of the paper P passes through this gap, the actuator 21 returns to the state indicated by the solid line due to its own weight. At this time, the lower end portion 21 ₂ comes into contact with the small diameter portion 11 ₁ , so that the upper end portion 21 ₁ stops within the recess and blocks the photo sensor portion 22 ₁ .
The passage of the paper transfer paper P can be detected by the above-described operation.

Furthermore, even if a heating fixing device is used, since the sensor section is provided on the upper housing side, malfunctions due to heat can be prevented and recording materials such as paper can be accurately detected. Further, it is possible to efficiently prevent dew condensation that tends to occur during fixing or when there is a large temperature change, thereby preventing malfunctions due to dew condensation.

Note that the opening ₃₂₁ in FIGS. 1 and 2 is larger than the photo interrupter switch 22,
It is preferable to provide a gap between the switch 22 and the switch 22 such that sufficient air can pass therethrough. Further, it is preferable that the opening 10 ₃ is larger in length and width than the upper end 21 ₁ can move.

FIG. 3 is a diagram for explaining the main part of another embodiment. This embodiment has the following configuration added to the configuration described above.

Reference numeral 24 designates a switch stopper that integrally holds a switch 22' similar to the photo interrupter switch, and is provided on the upper housing 17 side. The switch stopper 24 has a shaft 29 that engages with a support work 25 fixed to the immovable part C of the upper housing 17,
It is rotatable around this shaft 29. Further, the switch stopper 24 has a pin 26 at the lower side thereof which projects further downward from the lowest part of the switch 22'. Further, the switch stop 24 has a distance (l ₁ +l ₂ ) in the direction of the axis 29, and (l ₁ and l ₂ each change depending on the distance between the side surface of the stop and the support work 25, but (l ₁ +l ₂ ) is constant. ) can be moved.

On the other hand, the interval between the concave portions of the switch 22', that is, the distance l from the photo interrupter 22' is set larger than the distance (l ₁ +l ₂ ). Therefore, even if the switch stopper moves left and right within the support piece 25, the upper end ₂₁₁ of the actuator 21 is reliably accommodated within the recess. The actuator 21 is fixed relative to the shaft 28 or is provided so as to move by a small amount Δl (l>(l ₁ +l ₂ +Δl)).

The cover 30 has a recess 31 for accommodating the switch 22' and the switch stopper 24. This is done to bring actuator 21 and switch 22' closer together and to reduce the space required. This recess 31 is the opening 1 described above.
0 ₃ and the engagement hole 27 into which the pin 26 is engaged and inserted.
are located at positions corresponding to the actuator 21 and pin 26, respectively. Further, an inverted conical guide surface 27 ₁ provided above the engagement hole 27 properly guides the pin 26 into the circular engagement hole 27 . The engagement between the pin 26 and the engagement hole 27 is performed before the upper end ₂₁₁ of the actuator 21 and the lower end of the recess of the switch 22' approach each other. As a configuration for that purpose,
Before the pin 26 engages with the engagement hole 27, the distance between the tip of the pin 26 and the engagement hole 27 must be smaller than the distance between the upper tip of the actuator 21 and the lower end of the switch 22'. be. In this embodiment, the actuator 21 extends the length _l5 that the pin 26 is inserted into the engagement hole 27 into the switch 22'.
The length L inserted into the recess is longer than ₆ . Note that the opening 10 ₃ of the cover 30 has a width d in the direction of the axis 28, and this width d (<l) regulates the range of left and right vibration of the actuator 21.

In addition, in order to position the switch 22' in the recess 31, the distance _l3 from the side edge 222 of the recess of the switch 22 _' to the inner wall 31' of the recess 31 is determined by the distance l3 between the side edge ₂₄₁ of the switch stopper 24 and the support piece 25. inner wall distance
It is set larger than l ₂ .

In this embodiment, the switch part is made swingable and is positioned with the actuator using the positioning hole in the lower housing. However, if the positional relationship between the switch and the actuator is determined with sufficient accuracy for detection when the main body is closed, The switch part may be fixed to the upper housing.

Further, in this embodiment, the switch is a photointerrupter, but a reed switch or other switch may be used as long as it outputs a signal in response to the operation of the actuator.

As explained above, by using the configuration of the present invention, it is possible to prevent malfunctions caused by heat even if a switch serving as a sheet material detection means is provided near a high-temperature fixing device, and malfunctions caused by water droplets can also be prevented. can be prevented. Furthermore, since the switch is provided near the fixing device, the device can be made more compact and the structure can be simplified.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a main part of another embodiment of the present invention. 1... Document placement table, 3... Photosensitive drum, 10...
...Fuser, 10 ₃ ... Opening, 11 ... Ejection roller,
17... Upper housing, 18... Lower housing, 20...
Paper ejection roller, 21...actuator, 22,2
2'...Switch, 26...Pin, 27...Engagement hole, 30...Top cover, 32...Frame plate, D
...Space, P...Transfer paper.

Claims (1)

[Scope of Claims] 1. A toner image forming means for forming a toner image on a sheet material, a shipping path for transporting the sheet material, and a toner image forming means for forming a toner image on the sheet material in the middle of the transport path. a fixing means that heats and fixes; an air flow path for discharging heat generated from the fixing means to the outside of the apparatus main body; a movable member that is displaced in contact with the sheet material; and a movable member provided near the fixing means, and a switching member that generates an electric signal in response to the movement of the movable member, the switching member being provided in the air flow path.