JPS6319871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that forms an image on a recording material, and more specifically, an image forming apparatus that includes a member for conveying the recording material and a means for detecting the recording material passing through the conveying member. Regarding.

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

2. Description of the Related Art In some electronic copying machines and the like, the main body of the copying machine is opened for handling paper or other recording materials, for dealing with paper feed failures, for maintenance and inspection of the device, for cleaning, and the like. For example, there is a format in which the paper feed path is used as a separation boundary to divide the paper into upper and lower casings. A typical example of this includes a second casing (usually located in the upper part, so hereinafter referred to as the upper casing) that holds parts related to image formation, such as a photosensitive drum, an optical system, a developing section, and a cleaning section; a paper feeding section; The first housing (usually located at the bottom, henceforth referred to as the lower housing) holds the paper feeding system such as the transfer unit, separation/conveyance unit, and fixing unit, and the upper and lower housings are pivoted so that they can be opened and closed. It is configured to have a central axis.

Conventionally, an image forming apparatus such as an electronic copying machine having such a structure has a fixing section, which includes a pair of fixing rollers that fixes an unfixed image to the recording material while gripping and conveying the recording material. Furthermore, in order to detect the passage of the recording material in the fixing section, an actuator that is mechanically activated by the passage of the recording 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. Generally, the actuator and switch are integrated into a unit and mounted on either the upper or lower housing.

However, when the paper detector is provided as a unit in the lower casing, it is difficult to integrally attach the fixing roller pair to the unitized fixing device. This is because if a paper detector is attached to the fuser unit, the device becomes larger and creates wasted space, and the wiring cord for the paper detector needs to be removed from the device body when replacing or removing the fuser unit. This is due to the fact that it was hot. especially,
When the fixing device is a heating fixing device, the vicinity of the fixing device in the lower casing is exposed to high temperatures. Therefore, if a paper detector unit is provided in the lower housing, the response characteristics of the switch will be disturbed by the high temperature, 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. Similarly, the wiring cord of the paper detector needs to be protected from the effects of heat to avoid problems such as disconnection.

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 paper passing 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 and the mechanism must be simple, and especially in the case of a heat fixing device, it is desirable to prevent the wiring on the switch side from being affected by heat.

In addition, if the above paper detector is installed in the upper housing,
Generally, the upper casing is often moved relative to the lower casing, so the positional relationship of the lower casing with the paper conveyance path or the paper conveyance member becomes unstable. As a result, the paper detector cannot accurately detect recording materials such as paper, resulting in malfunction.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that is not adversely affected by heat and is equipped with a small and simple recording material detection means in a heat fixing means.

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

FIG. 1 is an explanatory diagram of the configuration of an embodiment of an electrophotographic copying machine, and FIG. 2 is an explanatory diagram when the main body of the apparatus shown in FIG. 1 is opened. In FIGS. 1 and 2, reference numeral 1 denotes a document mounting table made of a transparent member, which reciprocates in the direction of the arrow. 2
is a convergent light transmitting body which slit-exposes the 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 paper P is fed onto the drum surface by the paper feed roller 6 and the register roller 7, and is transferred to the transfer charger 8.
transfers the image on the drum. after that,
The transfer paper is separated from the drum by a separating means 13 and sent through a guide 9 to a fixing device 10 having a heat fixing roller 10 ₁ and a pressure 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 housing (second housing) 17 and a lower housing (first housing) 18. This upper case 17, lower case 1
8 are connected together by a support shaft 19 at the end of the device, and the upper housing 17 is rotatable about this support shaft 19 in the direction of arrow A. In the upper housing 17, means mainly related to image formation are held fixedly or removably with respect 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, these are members such as a transfer charger 8, a fixing device 10, and a roller that conveys the 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 as a heat-resistant cover member of the fixing device 10, which prevents wasted heat from being released from inside the fixing device, which is composed of a heat-reflecting metal plate and a heat-insulating coating. 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 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 the large diameter portion 11 of the ejection roller 11.
₂ , and is rotatably held by a shaft 28 held in the lower housing 18 along the longitudinal direction of the heating fixing roller 10 ₁ .

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. opening 10 ₃
It protrudes to the upper side of the upper cover 30 through. 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 equipped with 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 housings are usually aligned, the actuator 21 is located between the legs of the recessed portion of the photo 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. On the other hand, a fan F provided on the side of the optical system member 15 of the upper housing 17 and at the end of the upper housing 17 discharges heat and the like inside the apparatus to the outside of the apparatus. Due to this fan F, the air in the lower housing 18 flows as shown by the arrow E, and the opening 32 ₁ of the frame plate 32
is discharged from the device through the The photo interrupter switch 22 is air-cooled by this air flow. In addition, the 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 by the cover 30.
The water flows out from the opening ₁₀₃ and tries to cool down and become water droplets at the photo interrupter switch 22, but
Due to this air flow, the water is not turned into droplets and is sent 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 tend to occur on the paper detection section, so that the problem that the paper detector malfunctions due to the generation of water droplets can be solved.

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 paper ejection roller 20, it is in the state 21' shown by the broken line in FIG. Rotate in the direction of arrow G.
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. This opens the photo sensor section 22 ₁ 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 paper P can be detected by the above operation.

As described above, the photo interrupter switch 22 is provided in the upper casing (second casing) which is not affected by the heat of the heat fixing device by means of the heat insulating cover member, so that malfunctions due to heat can be prevented. 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.

Further, since the structure is such that the movement of the actuator 21 is directly detected by the photo interrupter switch 22 without using a link or the like, the structure is simple and the device can be miniaturized.

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 of the present invention. 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 can swing freely around this shaft 29. The switch stopper 24 also has a pin 26 as a moving member that protrudes further downward from the lowest part of the switch 22'.
It has a lateral lower part. Furthermore, 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 slid.

On the other hand, the interval between the concave portions of the switch 22', that is, the distance l from the photo interrupter 22 ₁ 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. Note that the actuator 21 is provided relative to the shaft 28 so as to be fixed or to slide by a slight amount Δl in the direction of the shaft 28 (l>((l ₁ +l ₂ +Δl)).

The cover 30 as an engaging member is connected to the switch 22'.
and a recess 31 for housing the switch stopper 24.
have. This is done to bring actuator 21 and switch 22' closer together and to reduce the space required. This recess 31
The above-mentioned opening 10 ₃ and the engagement hole 27 into which the pin 26 is engaged and inserted are provided at positions corresponding to the actuator 21 and the pin 26, respectively. Further, an inverted conical guide surface 27 ₁ provided above the engagement hole 27
guides the pin 26 appropriately into the circular engagement 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 this 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 is such that the distance between the upper tip of the actuator 21 and the switch 2
It is necessary that the distance be smaller than the distance to the lower end of 2'. In this embodiment, the length _l5 that the pin 26 is inserted into the engagement hole 27 is longer than the length _l6 that the actuator 21 is inserted into the recess of the switch 22'. 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 the embodiment of FIG. 3, in addition to the effects described above in FIGS. 1 and 2, the separation of the paper detector divided into two,
This has the effect of ensuring safety during engagement and allowing paper detection to function accurately.

Further, since the switch 22' is slidably provided on the upper housing 17, even if some impact is applied, the force can be buffered, and breakage of the wiring 23 can also be prevented.

Furthermore, since the wiring 23 and the switches 22, 22' are attached to the upper housing 17, they are less affected by the heat of the fixing device, and the fixing device side also has a simple structure with only an actuator.

In this example, the switch is placed in the upper housing (second housing).
In order to accurately combine the actuator and switch when the upper housing (second housing) and lower housing (first housing) are brought close to each other. Since the engaging member that engages with the moving member provided on the switch is provided, the recording material can be detected accurately without malfunction.

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 described above, in the present invention, the actuator is provided in the first housing, the end thereof protrudes from the heat insulating cover covering the heat fixing means, and the movement of the protruding end is provided in the second housing. Since the configuration is such that detection is performed by a switch, the switch and the switch-side wiring are less affected by the heat of the heat fixing means, and malfunctions can be prevented. Furthermore, since the movement of the actuator is directly detected by the switch without using a link or the like, the structure is simple and the overall configuration of the detection means can be made smaller.

In addition, the switch is movably provided in the second housing,
When the second casing and the first casing are brought close to each other, a moving member provided on the switch that moves integrally with the switch and an engaging member provided on the first casing engage with each other, causing the switch to move. Since positioning is performed, the relative positional relationship between the switch and actuator is accurate.
Recording materials can be detected accurately without malfunction.

[Brief explanation of the drawing]

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 is a document placement table, 3 is a photosensitive drum, 10 is a fixing device, 10 ₃ is an opening, 11 is a paper discharge roller, 17 is an upper housing, 18 is a lower housing, 20 is a paper discharge roller, 21
is the actuator, 22, 22' is the switch, 2
6 is a pin, 27 is an engagement hole, 30 is an upper cover, 32
is the frame board, D is the space, and P is the paper.

Claims (1)

[Scope of Claims] 1. Image formation comprising: a first housing provided with a heating fixing means for fixing a toner image formed on a recording material; and a second housing that is separable from the first housing. The apparatus includes an actuator that is moved by a recording material passing through the heat fixing means, and a heat insulating cover member that covers the heat fixing means, the actuator being provided in a first casing, and an end portion of which is covered with the heat insulating cover member. An image characterized in that the second casing is provided with a switch that protrudes toward the second casing through an opening provided in the cover member and generates a signal in response to movement of the end of the actuator. Forming device. 2. An image forming apparatus having a first housing provided with a heat fixing means for fixing a toner image formed on a recording material, and a second housing that is separable from the first housing, an actuator that is moved by a recording material passing through the means; and a heat-insulating cover member that covers the heat-fixing means, the actuator being provided in the first housing, and an end portion of the actuator being provided in the heat-insulating cover member. a switch that protrudes toward the second housing through an opening and generates a signal in response to movement of an end of the actuator; and a moving member that moves integrally with the switch, the second housing having An image forming apparatus characterized in that the first casing is provided with an engaging member that engages with the moving member to position the switch when the first casing and the second casing are brought close to each other.