JPH11125983A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vapor generated from sheets during fixing from entering sensor part and causing a malfunction of the sensor, in a device having a detection lever, which engages with a sheet ejected from a fixing device, and a sensor actuated by the detection lever. SOLUTION: The fixing device has a fixing means composed of a heating means and a pressurizing means, the detection lever composed of a sheet detection part 10-1, which swings by coming into contact with a sheet, and a sensor actuation part 10-3, the sensor 11 for detecting the sheet by being actuated by the sensor actuation part, and a cover member 14-1 for covering the detection lever and sensor. The sheet detection part of the detection lever projects upward via the recess hole 14-2 of the cover member. The sensor actuation part is situated below the cover member, and the sheet detection part and the sensor actuation part are disposed offsetting from the swing shaft 10-2 of the detection lever.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an electrophotographic image forming apparatus. Here, the electrophotographic image forming apparatus forms an image on a transfer sheet using an electrophotographic image forming method. Examples of the electrophotographic image forming apparatus include, for example, an electrophotographic copying machine and an electrophotographic printer (for example, a laser beam printer,
LED printers, etc.), facsimile machines, word processors, etc.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic image forming system irradiates a photosensitive drum as an image carrier with a laser beam based on image information from a scanning optical device to the photosensitive drum. A latent image is formed, and the latent image is developed using toner to form a toner image.

On the other hand, in synchronization with the formation of a toner image, a transfer sheet such as paper is picked up from a paper feed cassette by a pickup roller,
The sheet is conveyed by conveying means such as a conveying roller and a registration roller. The toner image formed on the photosensitive drum is transferred to a transfer sheet by applying a voltage to a transfer roller as a transfer unit.

[0004] The transfer sheet on which the toner image has been transferred is guided by a guide plate and conveyed to a fixing device. The fixing device has a pressure roller and a heater, and applies heat and pressure to the passing transfer sheet to fix the transfer toner image on the transfer sheet. Then, the transfer sheet is conveyed by the first discharge roller pair, and is discharged to the second discharge roller and the discharge tray through the reverse conveyance path.

In such a configuration, immediately after the fixing pressure roller of the fixing device in the sheet passing direction, a sheet discharge detecting means is provided, and a stagnant jam generated around the fixing unit, a paper feed unit to the fixing unit, and the like. Detects the transport delay that occurs between them. The paper ejection detection means detects a swingable detection lever and a swing operation of the detection lever by passing the transfer sheet,
It has a paper ejection sensor for transmitting an ON-OFF signal to a control circuit of the electrophotographic image forming apparatus.

[0006] Generally, a paper ejection sensor includes an LED light emitting unit,
A photo sensor having a light receiving section and a photo interrupter, that is, an optical sensor is used. An ON-OFF signal is generated from the optical sensor by swinging the photo interrupter so as to cross between the LED light emitting unit and the light receiving unit.

Further, since the fixing device in the electrophotographic image forming apparatus has heating means such as a pressurized rubber roller and an electric heater, the fixing device must be configured as a unit so that the service can be replaced.

[0008]

However, the above conventional example has the following disadvantages.

Conventional Example 1 In the above conventional example, generally, a paper ejection sensor is arranged on a control circuit board of an electrophotographic image forming apparatus, and a detection lever is unitized in a paper passing guide frame of a fixing device. When removing the fixing device unit from the image forming apparatus main body at the time of service replacement, the detection lever and the paper discharge sensor are likely to interfere with each other, and the detection lever or the paper discharge sensor may be damaged at the time of assembly work and service replacement,
In addition, since attention is required at the time of work, workability is low, and the number of assembling steps may be increased.

Conventional Example 2 As an improvement of Conventional Example 1, it is conceivable to improve the assembling workability and service exchangeability of the fixing device by incorporating a paper ejection sensor into the fixing device. However, when the transfer sheet enters the fixing nip portion of the fixing device, the transfer sheet is heated in the nip portion, and the moisture contained in the transfer sheet is diffused as steam. This vapor may fill the optical sensor portion of the paper ejection sensor and cause malfunction.

[0011] The invention according to the present application has been made in view of the above circumstances, and the first to third inventions according to the present application have an object to prevent a malfunction of an optical sensor due to steam generated in a fixing device. Is to prevent it.

A fourth object of the present invention, in addition to the first object, is to improve assembling workability and service exchangeability.

The objects of the fifth and sixth aspects of the present invention are as follows.
It is another object of the present invention to reduce the size of the apparatus and improve the reliability of a sheet ejection detection sensor of a fixing device by constantly urging a detection lever toward a transfer sheet.

The objects of the seventh and eighth inventions according to the present application are as follows.
An object of the present invention is to further improve the reliability of a sheet discharge detection sensor of a fixing device by moving a sheet discharge sensor away from a location where steam enters.

It is an object of the ninth to eleventh aspects of the present invention that the outside air is blown into the paper discharge sensor by the configuration of a cooling fan, thereby preventing the entrance of steam and preventing the temperature of the fixing device from rising due to heat. Accordingly, the object is to further improve the reliability of the sheet discharge detection sensor of the fixing device.

[0016]

In order to achieve the above object, a representative configuration according to the present invention is a fixing device having a heating device and a pressing device, and a sheet detecting device that swings by contacting the sheet. A detection lever having a sensor unit and a sensor operation unit, a sensor operated by the sensor operation unit to detect a sheet, and a cover member that covers the detection lever and the sensor. The detecting part protrudes upward through the relief hole of the cover member, the sensor operating part is located at the lower part of the cover member, and the sheet detecting part and the sensor operating part are arranged offset to the swing axis of the detecting lever. It is characterized by being.

In the above configuration, the sheet detecting portion of the detecting lever and the sensor operating portion are provided offset from the swing axis, and a route from the opening provided in the cover member to the sensor as an escape hole of the sheet detecting portion is bypassed. This makes it difficult for steam generated from around the fixing nip of the fixing device to enter the sensor. In addition, since the pressure unit, the detection lever, the sensor, and the cover member of the fixing device are integrally supported by the support unit, the sensor and the detection lever do not interfere when the fixing device is replaced. In addition, the air passage configuration of the cooling fan blows outside air into the paper discharge sensor to prevent steam from entering and prevent the temperature of the fuser from rising due to the heat of the fuser, thereby improving the reliability of the paper discharge detection sensor of the fuser. Improve significantly.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention.

In the figure, A is a transfer sheet, 1 is a process CRG (cartridge), and the process CRG1 is
At least a photosensitive drum 1A as an image carrier and a developing unit 1B are integrally provided. Reference numeral 2 denotes a scanning optical device 2, which forms a latent image on the photosensitive drum of the process CRG1.
The latent image is developed by a developing unit 1B using a toner as a developer to form a toner image.

The transfer sheet A loaded on the cassette 30 serving as the sheet loading means is transferred in synchronization with the toner image on the photosensitive drum by transport means such as a pickup roller 31 and a pair of registration rollers 32 serving as feed means. The toner image on the photosensitive drum is transferred to a transfer sheet by the transfer unit 33.

Reference numeral 3 denotes a fixing device for fixing the transferred toner on the transfer sheet, 4 denotes a reverse paper passing path for guiding the fixed transfer sheet, 5 denotes a first discharge roller for discharging the transfer sheet, and 6 denotes transfer. Ejection tray for loading sheets, 7
Reference numeral denotes a discharge roller that contacts the discharge roller 5. Reference numeral 8 denotes a pressure roller of the fixing device 3 and the outer peripheral portion is formed of a high friction coefficient member such as rubber. Reference numeral 9 denotes a heating roller which is a heat source and has a built-in heater. At least the pressure roller 8 of the fixing device is supported by the support member 14.

Reference numeral 10 denotes a detection lever for detecting a stagnant jam of the transfer sheet generated around the fixing unit and a conveyance delay generated between the paper supply unit and the fixing unit. Reference numeral 11 denotes a paper discharge sensor operated by the detection lever. Thus, both are supported by the support member 14 and the cover member 14
-1. The cover member can also serve as a guide for the transfer sheet discharged from the fixing device.

Reference numeral 10-1 denotes a detection portion of the transfer sheet A on the detection lever 10, and a cover member 14 above the support member 14.
-1, through a slit-shaped relief hole 14-2 formed in
The transfer sheet A protrudes above the cover member 14-1, and
By contacting the detection unit 10-1, the detection lever 10 swings about the swing shaft 10-2.

The paper ejection sensor 11 is a photo sensor having a light emitting portion such as an LED and a light receiving portion, that is, an optical sensor. Reference numeral 10-3 denotes a sensor operation unit of the detection lever 10 located below the support member 14-1, and operates an optical sensor as a photo interrupter. Detection lever 10
In response to the swing of the light, the operating portion changes the light between the light emitting portion and the light receiving portion to O.
N, when turned off, the paper ejection sensor 11 detects the operation of the detection lever.

Reference numeral 12 denotes a second discharge roller for discharging the transfer sheet A to the discharge tray 6, and reference numeral 13 denotes an idle roller that contacts the second discharge roller 12.

Reference numeral 15 denotes a fixing entrance guide for guiding the transfer sheet A to a nip between the pressure roller 8 and the heating roller 9 serving as a heater.

Reference numeral 16 denotes an ON-O signal from the paper discharge sensor 11.
The control circuit 16 receives the FF signal and controls the temperature of the fixing device, the sheet feed control, the process CRG1, and the scanning optical device 2 in addition to the above control. I have.

In the above configuration, a sheet detecting portion 10-1 for detecting the transfer sheet by engaging with the transfer sheet A of the detection lever 10, and a swing for detecting the swing of the detection lever 10 by the sensor 11. The detection part 10-3 is arranged so as to be offset in parallel to the swing center axis 10-2 of the detection lever.

With the above-described offset configuration, the steam generated from the vicinity of the fixing nip of the fixing device 3 during fixing is discharged from the escape hole 14-1 of the detecting portion 10-1 of the detecting lever 10 to discharge the paper. It becomes difficult to enter the optical section of the sensor 11, and it is possible to prevent malfunction of the paper discharge sensor due to vapor.

Further, since the support roller 14 supports the pressure roller 8, the detection lever 10, and the paper ejection sensor 11, these parts supported by the support member 14 are used as a unit to form the main body of the image forming apparatus. The paper ejection sensor and the detection lever are supported at different places, as in the past, so that both can be replaced. The sensor can be prevented from being damaged without interfering with each other. In this case, the first paper discharge roller 5 is also supported by the support member 14, and the replacement operation can be facilitated.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. In the present embodiment, a description of the same configuration as in the first embodiment will be omitted. Reference numeral 17 denotes a biasing means such as a torsion coil spring.
2, a stopper (not shown) is provided to prevent the detection lever from rotating more than necessary toward the seat by the coil spring. The torsion coil spring 17 urges the sheet detection unit 10-1 of the detection lever 10 in the direction of the arrow M, and always hits the transfer sheet A in the approaching direction. 10 does not have an unstable floating state, and operates reliably by contact of a sheet. As the urging means, a leaf spring or the like other than the coil spring can be used.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention. In the present embodiment, the description of the same configuration as the above embodiment will be omitted.

Reference numeral 18 denotes a rotating shaft 10-2 of the detection lever 10.
This is a sensor operation unit that can swing via a rotation shaft 18-1 to a tag 10-4 provided offset from the sheet detection unit 10-1. The reciprocating motion of the arm member 18 is detected by the paper ejection sensor 11. In the sensor operation part 18,
It is preferable to provide a slit for turning light on and off.

In the present embodiment, the arm member is made sufficiently long to increase the distance from the escape hole of the sheet detection section 10-1 to the steam discharge sensor reaching the discharge sensor, thereby preventing the malfunction of the discharge sensor due to the steam. It can be more effectively prevented.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention. In the present embodiment, the description of the same configuration as the above embodiment will be omitted.

Reference numeral 19 denotes a cooling fan mounted in the electrophotographic image forming apparatus and provided near the paper discharge sensor 11 so as to generate a negative pressure. The cooling fan 19 generates a negative pressure in the vicinity of the sheet discharge sensor 11 by discharging air in the direction of the arrow N, so that outside air enters in the direction of the arrow L. Therefore, the flow O of the steam generated in the heating section of the fixing device is prevented from flowing into the paper ejection sensor 11 due to the flow of the outside air indicated by the arrow N. Therefore, in the present embodiment, the inflow of steam to the paper ejection sensor and the propagation of heat from the fixing device are prevented, and the reliability of the operation of the paper ejection sensor is improved. In the present invention, in addition to the above-described embodiment, the fixing device may be a surf type in which a heat-resistant belt is suspended around a filament heating body, a driving roller, and an idle roller, and the paper ejection sensor may be any other than optical. It can be carried out using a mechanical sensor or the like.

[0037]

As described above, according to the present invention,
The detection lever and the sensor are covered by a cover member,
The sheet detection section of the detection lever and the sensor operation section are offset from the swing axis, and the sheet detection section protrudes upward from the relief hole of the cover member and can engage with the sheet. Can suppress the entry of the sensor from the upper part of the cover member to the sensor below the cover member, prevent malfunction of the sensor, and provide a highly reliable fixing device. In addition, by integrally supporting the fixing pressure unit, the detection lever, and the sensor with the support unit, the interference between the detection lever and the sensor at the time of replacement is eliminated, and the effect of improving the assembly workability and the serviceability at the time of service replacement is improved. There is.

Further, by providing a cooling fan for cooling the fixing device in the vicinity of the fixing device, malfunction of the optical sensor due to heat generated in the fixing device is prevented, and the service life of the paper discharge sensor is improved. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing the vicinity of a paper ejection sensor unit of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 A: Transfer sheet 1: Process CRG 2: Scanning optical device 3: Fixing device 4: Reverse paper passing path 5: First discharge roller 6: Discharge tray 7: Discharge roller 8: Fixing pressure roller 9: Heater 10 Detection lever 10-1 ... Sheet detection unit 10-2 ... Swing axis 10-3 ... Sensor operation unit 11 ... Sheet ejection sensor 12 ... Second ejection roller 10-2 ... Swing center axis 10-3 ... Swing detection Part 13: Idler roller 14: Support member 14-1: Cover member 14-2: Escape hole 15: Fixing entrance guide 16: Control circuit 17: Torsion coil spring 18: Arm member 19: Cooling fan

Claims (11)

[Claims] An image forming apparatus comprising: a fixing unit including a heating unit and a pressing unit; a detection lever including a sheet detection unit and a sensor operation unit that swings by contacting a sheet; and a sheet operated by the sensor operation unit. And a cover member that covers the sensor and the detection lever, wherein the sheet detection unit of the detection lever projects upward through an escape hole of the cover member,
A fixing device, wherein the sensor operating section is located below the cover member, and the sheet detecting section and the sensor operating section are arranged offset from the swing axis of the detecting lever. 2. The device according to claim 1, wherein the heating means is a roller having a heater therein, and the pressing means is a roller having an outer periphery formed of rubber or the like. A fixing device characterized by being formed of a plate-like member. 3. The sensor according to claim 1, wherein the sensor has a light emitting unit and a light receiving unit, and detects the sheet by turning on and off the light between the light emitting unit and the light receiving unit by the sensor operating unit. Characteristic fixing device. 4. The fixing device according to claim 1, wherein the pressing unit, the detection lever, the sensor, and the cover member are integrally supported by a supporting unit. 5. The fixing device according to claim 1, further comprising an urging unit that urges the detection lever in a contact direction with respect to the sheet. 6. A fixing device according to claim 5, wherein said urging means is constituted by a coil spring wound around a swing shaft of said detection lever. 7. The sensor operating section according to claim 1, wherein the sensor operating section is a tag member fixed to the swing shaft, and a passage between the light emitting section and the light receiving section pivotally supported by the tag member. A fixing device having an arm member that can be moved substantially in parallel. 8. The fixing device according to claim 7, wherein the arm member has a length that sufficiently separates the sensor from the relief hole. 9. An image forming means for forming a toner image on a sheet, a fixing device for fixing the toner image on the sheet, and a casing for covering the image forming means and the fixing device. An image forming apparatus comprising: 10. The image forming apparatus according to claim 9, further comprising a cooling fan for flowing air near the fixing device to cool the fixing device. 11. The fixing fan according to claim 10, wherein the cooling fan circulates air from outside the casing to a sheet outlet of the fixing unit, and discharges steam generated at the outlet from the sheet during heating and fixing. An image forming apparatus comprising: