JPH11296017A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device and image forming device capable of providing a pressure release detecting means, to detect a pressurization released state, with a simple constitution and inhibiting the image forming operation of a main body. SOLUTION: A movable projection part 25 is provided on the rotary shaft 24b of a pressurization releasing means 24 and made to abut on the projection part 21a of a paper ejection sensor unit 21, and the pressurization release detecting means is constituted of the movable projection part 25 and a photointerrupter 21d for the paper ejection sensor unit 21. When the pressurization releasing lever 24a of the pressurization release detecting means 24 is operated in the direction of releasing pressurization, the movable projection part 25 is rotated, the projection part 21a is rotated in the direction of detecting a recording material and the light shielding plate 21c of the paper ejection sensor unit 21 is rocked and kept in a state where it is inserted into the photointerrupter 21d. A signal for a light shielding state is transmitted to a control means 31 from the photointerrupter 21d and the image forming operation of the main body is inhibited by the control means 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus for fixing a toner on a recording material by heating and pressing.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus, an image carrier for carrying a latent image on a surface thereof, a developing device for developing a latent image on the image carrier with toner as a developer to make the image visible, A transfer device for transferring the toner image on the image carrier to the recording material, a fixing device for fixing the toner on the recording material by heating and pressing the recording material on which the toner image has been transferred, and the above-described image forming steps. There are known electrophotographic image forming apparatuses having control means for controlling the image forming apparatus, such as a copying machine, a laser beam printer, a facsimile, and a microfilm reader printer.

FIG. 5 shows a schematic configuration diagram of a laser page printer using a laser beam for recording an image as an example of the above-described image forming apparatus. First, a laser beam oscillated from a laser light source 1 is applied to a polygon mirror 2, reflected and then returned via a lens 3, further reflected by a mirror 4 and incident on the surface of a photosensitive drum 6.

At this time, the surface of the photosensitive drum 6 serving as an image carrier is charged to a desired potential in advance by the charging roller 5. Only the surface potential of the portion exposed by the laser beam is reduced, and a latent image is formed on the portion of the photosensitive drum 6 exposed by the laser beam. The latent image on the photosensitive drum 6 is conveyed to a portion of the developing device facing the developing sleeve 7 with the rotation of the photosensitive drum 6, and the developing sleeve 7
Is developed by the toner 9 conveyed to the opposing surface.

Here, the toner 9 is accommodated in the developing container 8, adheres to the surface of the developing sleeve 7, is conveyed with the rotation of the developing sleeve 7, and is transferred onto the photosensitive drum 6 in the developing container 8. Is charged to the same polarity as the charged electrode property of the latent image. Then, the latent image on the photosensitive drum 6 is developed by the toner 9 being carried by the electric field applied between the developing sleeve 7 and the photosensitive drum 6 to the low potential area of the latent image portion on the photosensitive drum 6 and attaching thereto. To make it visible.

Next, the recording material is conveyed to the opposing portion of the photosensitive drum 6 and the transfer roller 10 as the transfer means, and the electric field of the high voltage applied to the transfer roller 10 in synchronization with the conveyance of the recording material is applied. The toner is peeled off from the surface of the photosensitive drum 6 and transferred to the surface of the recording material 13. In addition,
Unnecessary toner remaining on the surface of the photosensitive drum 6 after the transfer is dropped off from the surface of the photosensitive drum by the cleaning blade 12 and collected in the waste toner container 11. The recording material 13 to which the toner has been transferred is conveyed to a fixing device 14.

FIG. 6 is a schematic configuration diagram of a fixing device provided in the printer. The fixing device 14 has a runner roller 15 and a pressure roller 16 that are heated by a halogen heater 15d.

The pressing roller 16 is pressed against the fixing roller 15 by the pressing means, and a nip portion 17 is formed between the fixing roller 15 and the pressing roller 16. Further, the fixing roller 15 and the pressure roller 16 are rotatably arranged, and driving means (not shown) provided on the printer body side
By applying a driving force to the fixing roller 15 to rotate it, the pressure roller 16 is driven to rotate by pressure contact.
The recording material is heated and pressed at the nip portion between the fixing roller 15 and the pressure roller 16, and an unidentified toner image is fixed on the surface of the recording material as a permanent fixed image.

Further, the fixing roller 15 and the pressure roller 1
6 is a hollow cylindrical core shaft 15a, 16a;
elastic layers 15b, 16b provided on the outer periphery of
Release layer 15 provided on the outer periphery of elastic layers 15b and 16b
The halogen heaters 15d and 16d are built in the hollow core shafts 15a and 16a of the rollers 15 and 16 along the longitudinal direction of the rollers. The necessary heat is supplied.

The temperature of both rollers is controlled by the halogen heaters 15d and 16d. A thermistor 18 as a temperature detecting element is disposed in contact with both the fixing roller 15 and the pressing roller 16, and the resistance is changed according to the detected temperature. Of the halogen heater is controlled by a control device (not shown) so that the roller surface temperature becomes a predetermined value.

On the downstream side of the fixing device 14 in the recording material conveyance direction, there is provided a paper discharge sensor unit 21 for detecting a jam in which the recording material 13 is not normally discharged from the fixing device 14 and stays in the fixing device. Have been. The paper discharge sensor unit 21 has movable members 21a, 21b, 21c that operate when the recording material passes through the fixing device, and a photo interrupter 21d as a movable detection unit that detects the operation of the movable member. The photo interrupter 21d is provided at an arbitrary position on the printer body.

The movable members 21a, 21b and 21c detect a cylindrical rotating shaft 21b arranged in parallel along the longitudinal direction of the fixing roller 15 and a recording material provided on the roller central portion side of the rotating shaft 21b. And a light-shielding plate 21c provided on the roller end side of the rotating shaft 21b. The recording material discharged from the nip portion 17 causes the projection 21a to rotate about the rotation shaft 21b, whereby the light shielding plate 21c swings in the direction of the photo interrupter 21d.

The photo-interrupter 21d is formed on the printer main body side with a substantially concave cross section, and is provided with a control means 30 provided at an arbitrary position of the printer main body.
Is connected so as to be able to transmit signals. A light source and a photodetector are provided so as to sandwich the space in the concave portion of the photo interrupter 21d. When the light shielding slope 21c swings, the light shielding plate 21c is inserted into the space in the concave portion, and the light shielding plate 21c The light from the light source of the photo interrupter 21d is cut off. This photo interrupter 2
1d transmits to the control means 30 a signal when the light from the light source received by the photodetector is converted into an electric signal and received, or a signal when the light is shielded by the light shielding plate 21c. .

FIG. 7 shows the relationship between the arrangement of the photo interrupter and the light shielding plate of the paper ejection sensor unit. As shown in FIG. 7A, when the recording material is not present in the fixing device, the projection 21a of the sheet discharge sensor unit 21 for detecting the presence of the recording material is suspended, and thus the light shielding plate 21c is Not inserted into the recess of the photo interrupter 21d,
It is arranged at a position that does not block the light of the photo interrupter 21d.

When the recording material is present in the fixing device, as shown in FIG.
When the recording material 1a is rotated in a predetermined direction by the recording material, the light shielding plate 21c swings in the direction of the photo interrupter 21d around the rotation shaft 21b, and is inserted into the concave portion of the photo interrupter 21d. Is located so as to block the light of the photointerrupter 21d.

The light shielding plate 21c is a photo interrupter 21d.
When the light is inserted into the concave portion, a signal in a light-shielded state is sent from the photo interrupter 21d to the control means 30 of the main body, so that the main body detects that the recording material is in the fixing device 14.

At the time of normal printing, the recording material passes through the fixing device 14 for a predetermined time and is discharged, so that the light receiving and light shielding signals of the photo interrupter 21d are transmitted to the control means 30 at predetermined intervals. It will be. However, when a recording material jams in the fixing device 14, the recording material is
Since a is kept pressed up, the light interrupt signal is transmitted from the photo interrupter 21d to the control unit 30 even after a predetermined time has elapsed. By detecting this state by the control unit 30, the control unit 30 notifies the display unit or the like that the fixing device is in a jam state, and controls the printer so that the main body does not operate. .

In the fixing device as described above, if the fixing roller 15 and the pressure roller 16 are left in a pressed state without using the printer body for a long time, the elastic layers 15b and 16b of both rollers are irreversibly compressed. When the pressure is released, the shape of the elastic layer does not return to the original shape, and may remain as it was when the nip portion was formed. This phenomenon is called a C set. The roller in which the C-set occurs causes poor fixing, uneven gloss, noise, and the like, thereby deteriorating the performance as a fixing device.
This C set is more likely to occur as the hardness of the rubber used for the elastic layer of the roller is higher.

The fixing roller 15 and the pressure roller C
There is a fixing device having a pressure release mechanism that can manually release the pressing force of both rollers in order to prevent the setting. FIG. 8 is an explanatory front view showing a fixing device having a conventional pressure releasing mechanism as viewed from the sheet discharge side, and FIG. 9 shows a pressed state and a pressure released state of the fixing device.

A pressure release mechanism 24 for releasing the pressure contact state between the fixing roller 15 and the pressure roller 16 is connected to one end of a long rod-shaped pressure release lever 24a and one end of the pressure release lever 24a. It has a rotating shaft 24b arranged in parallel along the longitudinal direction of the fixing roller 15, and two cams 24c provided at both ends of the rotating shaft 24b and abutting against bearings 23 of two pressure rollers. .

The two cams 24c are formed to have a substantially elliptical cross section, and the rotary shaft 24b passes through a through hole provided at a position shifted from the center of gravity of the cam 24c. When the pressure release lever 24a is rotated about the rotation shaft 24b in the direction of the arrow in FIG. 9B, the two cams 24c rotate, and the bearing 23 of the pressure roller is applied to the pressing force of the pressure spring 22. Since the pressure roller is pressed downward in opposition, the pressure of the pressure roller can be released.

By this operation, the pressure at the nip between the fixing roller and the pressure roller is released, so that the C setting can be prevented. Further, when the recording material is jammed in the fixing device, there is an advantage that the jam clearance is facilitated by pushing up the pressure release lever.

[0023]

However, in the fixing device having the above-described pressure releasing mechanism, there is a concern that an erroneous operation of operating the printer main body with the pressing force of the pressing roller released may be caused. . If the printing operation is performed with the pressing force of the fixing device released, the unfixed toner image on the recording material is not sufficiently fixed. There is a possibility that the user's hands and the like may be stained.

Therefore, the present invention provides a fixing device having a pressure releasing mechanism, which can detect the pressure releasing state of the pressure roller and inhibit the printing operation when the pressure roller is in the pressure releasing state. It is an object to provide an image forming apparatus including the fixing device.

[0025]

According to the present invention, an object of the present invention is to provide a fixing device having a fixing member and a pressing member releasing means which are pressurized with each other. The present invention is achieved by the first invention having a movable member that operates at the time of pressurization or pressure release, and a pressure release detection unit that detects a pressure release state of the movable member.

Further, according to the present application, the above object is achieved in the second invention according to the present application by detecting a jam in a nip portion formed between a fixing body and a pressing body pressed against each other. The present invention is also achieved by the second invention in which a jam detecting means is provided, and the jam detecting means also serves as a pressure release detecting means for detecting a pressure release state of the movable member.

Further, according to the present application, the above object is achieved by a fixing device according to the first invention of the present application and a detection signal from the pressure release detecting means based on the detection of the pressure release detecting means. Control means connected to the pressure release detecting means so that input is possible, and the control means inhibits the image forming process when receiving a pressure release state detection signal from the pressure release detecting means. This is also achieved by the third invention.

According to the present application, the above object is achieved in the third invention according to the present application by detecting a jam in a nip portion formed between a fixing body and a pressing body pressed against each other. The present invention is also achieved by the fourth invention in which a jam detecting means is provided, and the jam detecting means also serves as a pressure release detecting means for detecting a pressure release state of the movable member.

That is, according to the first aspect of the present invention, in a fixing device having a fixing member and a pressing member releasing unit which are pressed against each other, when the fixing member and the pressing member are pressurized, Alternatively, the presence of the movable member that operates at the time of releasing the pressure and the pressure release detecting unit that detects the released state of the pressure of the movable member ensures that the released pressure state of the fixing device is detected.

In the second invention according to the present application,
A jam detecting unit that detects a jam in a nip formed between the fixing body and the pressing body that are pressed against each other, wherein the jam detecting unit detects a pressurized state of the movable member; , The pressure release state in the fixing device is reliably detected.

Further, in the third invention according to the present application, the fixing device according to the first invention according to the present application, and the detection from the pressure release detecting means based on the detection by the pressure release detecting means. Control means connected to the pressure release detection means so that a signal can be input, wherein the control means inhibits the image forming step when receiving a pressure release state detection signal from the pressure release detection means. As a result, the pressure release state in the fixing device is reliably detected.

Further, in the fourth invention according to the present application,
A jam detecting unit that detects a jam in a nip formed between the fixing body and the pressing body that are pressed against each other, wherein the jam detecting unit detects a pressurized state of the movable member; , The pressure release state in the fixing device is reliably detected.

[0033]

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

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory front view of the fixing device according to the first embodiment of the present invention as viewed from the sheet discharging side.

A laser printer as an image forming apparatus for fixing a toner image on the surface of a recording material includes a photosensitive drum as an image carrier for carrying a latent image on the surface, a charging roller for uniformly charging the surface of the photosensitive drum, Exposure means for exposing the charged surface of the photosensitive drum with a laser beam to form a latent image, a developing device for developing the latent image on the photosensitive drum with toner as a developer to make it visible, and a developed photosensitive drum It has a transfer roller for transferring the upper toner image onto the recording material, a fixing device for fixing the toner by heating and pressing the recording material on which the toner image has been transferred, and control means for controlling each step of image formation. . The configuration and operation of an image forming apparatus other than the fixing device, such as a photosensitive drum, a developing device, and a transfer roller, are the same as those of the conventional example, and thus detailed description is omitted.

As shown in FIG. 1, a fixing device 14 'of the present embodiment includes a halogen heater as a heating means, and a fixing roller 15 rotated by a driving means (not shown).
And a pressure roller 16 pressed against the fixing roller 15, a pressure spring 22, a paper discharge sensor unit 21 for detecting a jam in the fixing device, and a pressure release of the pressure roller 16 to be released. And a mechanism 24. The fixing temperature of the fixing device is 180 ° C., and the peripheral speed of the roller is 110 to 120 m.
m / sec.

The fixing roller 15 and the pressure roller 16 are
An elastic layer is provided on the outer periphery of a hollow cylindrical core shaft, and a release layer is further provided on the outer periphery.

If the elastic layer provided on the outer periphery of the core shaft of the fixing roller has low elasticity, the toner will not be fixed in the concave portion of the recording material or the resolution will be reduced due to the collapse of the toner. Accordingly, as the material of the elastic layer of the fixing roller, RTV and LTV types, which are liquid silicone rubbers of methyl type and methyl vinyl type, are preferable because they have elasticity. RTV and LTV may be used for the surface layer, and a heat-resistant HTV layer may be provided below the surface layer to form a multilayer structure so as to prevent thermal deterioration and peeling of the back surface of the surface layer.

As the fixing roller of this embodiment, an LTV type elastic layer of dimethyl silicone rubber is provided on a substantially long cylindrical core shaft made of aluminum of 2.5 mm, and a release layer of a PFA tube is provided thereon. Was formed into a fixing roller by molding it to a size of # 46 mm.

The structure of the pressure roller can be simplified because it may have less elasticity than the fixing roller, and can be simplified. A substantially long cylindrical core shaft made of aluminum is provided with a layer of HTV, fluorine-based rubber, or the like. May be provided. Of course, a roller having the same configuration as the fixing roller may be used.

As the pressure roller of this embodiment, similarly to the fixing roller, an LTV type elastic layer of dimethyl silicone rubber is provided on the aluminum core shaft at 1.5 mm, and a PFA tube layer is provided thereon at 50 μm as a release layer. This was molded to a size of # 46 mm and used. As the rubber of the elastic layer of the fixing roller and the pressure roller, methylphenyl silicone rubber may be used.

A paper discharge sensor unit 21 is provided downstream of the nip portion of the fixing device 14 in the recording material conveyance direction to detect a jam in which the recording material 13 is not normally discharged and remains in the fixing device. I have. Discharge sensor unit 21
Are movable members 21a and 21 that operate depending on the presence or absence of a recording material.
b, 21c and a photo interrupter 21d for detecting the operation of the movable member.

The movable members 21a, 21b and 21c include a cylindrical rotating shaft 21b arranged in parallel along the longitudinal direction of the fixing roller 15, a projection 21a provided at the roller center side of the rotating shaft 21b, and A light-shielding plate 21c provided on the roller end side of the rotating shaft 21b. The light-shielding plate 21c swings in the direction of the photo-interrupter 21d by rotating the projection 21a about the rotation shaft 21b by the recording material discharged from the nip portion.

The photo interrupter 21d is provided on the printer main body side, is connected to a control means 31 for controlling each step of image formation, and can transmit a detection signal to the control means 31. The control unit 31 includes a stop unit that stops the operation of the printer main body when the light blocking signal from the photo interrupter 21d continues even after a predetermined time has elapsed. Here, the recording material is fixed in the fixing device 1 for a predetermined time.
The time is longer than the time of passing through 4 '.

The pressure releasing mechanism 24 for releasing the pressure contact state between the fixing roller 15 and the pressure roller 16 is connected to one end of a long rod-shaped pressure releasing lever 24a and one end of the pressure releasing lever 24a. It has a rotating shaft 24b arranged in parallel along the longitudinal direction of the roller 15, and two cams 24c provided at both ends of the rotating shaft 24b and abutting on bearings 23 of two pressure rollers.

As shown in FIG. 2, when the pressure release lever is pushed up in the direction of the arrow in the figure, the fixing device enters the pressure released state.

Here, as the pressure release detecting means in the first embodiment, the pressure release mechanism 24 and the paper discharge sensor unit 21 are linked.

FIG. 2 is an explanatory side view showing an arrangement state of the sheet discharge sensor unit 21 and the pressure release mechanism 24 before and after pressure release. As shown in FIG. 2B, when the pressure release lever 24a is pushed up to bring the fixing device into the pressure released state, the movable protrusion 25 is moved in conjunction with the rotation of the rotating shaft 24b. 21 is pushed up, the sheet ejection sensor unit 21 is interlocked, and the rotating shaft 21b is rotated.
Rotate around. Therefore, the light-shielding plate 21c of the paper ejection sensor unit is held in a state where the light of the photo interrupter 21d is blocked.

During the pressure release state, the photointerrupter 2
This means that the light shielding signal from 1d is transmitted to the control means 31. This state is judged by the control means 31 and the printer main body recognizes that a recording material jam or a pressure release state of the fixing device has occurred in the fixing device, and the control means 31 executes the image forming process of the printer. Prohibit and do not operate the printer.

By the way, when the power of the printer main body is turned off when the pressurizing state of the pressurizing roller is released, or when the signal of the light-shielded state is transmitted from the photo interrupter 21d to the control means 31 after the power is turned on, there is no error. The operation of the printer body may be prohibited on condition.

Using the above-described fixing device of the present embodiment, when a print command is issued from the computer to the main body in a state where the pressing of the pressing roller 16 is released by the pressing release mechanism 24, the main body is in error. Issued a message and did not execute the order. As described above, by interlocking the pressure release mechanism and the sheet discharge sensor unit, it is possible to prevent the printer main body from operating when the pressure of the fixing device is released.

In this embodiment, since only one movable projection is added to the rotation shaft of the pressure release lever of the conventional fixing device, a fixing device capable of detecting the pressure release state easily and at low cost can be constructed. In addition, it is possible to configure an image forming apparatus that can prevent an erroneous operation such as operating the printer main body in a pressure released state.

As a pressure release detecting means, a projection plate is provided as a movable portion on the bearing of the fixing roller so that the projection plate moves up and down in synchronization with the bearing when the pressure is released, and when the projection plate is pressed. A photo-interrupter portion having the same configuration as the photo-interrupter of the paper ejection sensor unit is provided at the moving position when the pressure is released, so that when the pressure of the fixing roller is released, the projection plate is inserted into the concave portion of the photo-interrupter portion to block light. You may. At this time, the photo interrupter unit and the control unit are connected to each other so that a signal can be transmitted from the photo interrupter unit to the control unit. Operation is prohibited.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a photo interrupter of the paper ejection sensor unit is used as the pressure release detection means, and a movable member of the pressure release detection means is provided on the pressure release lever of the pressure release mechanism, and the movable member is a pressure roller. When the pressure is released, it is inserted into the concave portion of the photo interrupter so that light can be shielded. The members other than the configuration of the pressure release detecting means, such as the photosensitive drum, the developing device, the transfer roller, the fixing roller and the pressure roller of the fixing device, have the same configuration and operation as those of the first embodiment, and thus are detailed. Detailed description is omitted.

FIG. 3 is an explanatory front view of the fixing device according to the second embodiment of the present invention as viewed from the sheet discharging side.

The fixing device 14 ″ of this embodiment has a fixing roller 15 and a pressure roller 16 having the same configuration as that of the first embodiment, and is formed by the fixing roller 15 and the pressure roller 16. The first detecting unit detects a jam in the fixing device on the downstream side of the nip portion in the recording material conveyance direction.
A discharge sensor unit 21 similar to that of the embodiment is provided. Further, a pressure release mechanism 24 capable of biasing the pressure roller 16 to a pressure state or a pressure release state is provided, and the pressure release mechanism 24 detects the pressure release of the pressure release mechanism 24. Detection means is provided.

The pressure release detecting means for detecting the pressure release of the pressure roller by the pressure release mechanism 24 includes a pressure release lever 24 of the pressure release mechanism 24 as a movable portion of the pressure release detecting means.
The light interrupting plate 26 of the photo-interrupter is provided at a ', and the photo-interrupter 21d' of the paper ejection sensor unit 21 also serves as the movable detecting means of the pressure release detecting means. At the time of the pressure release operation of the pressure release lever 24a ', the light shielding plate 26 is inserted into the concave portion of the photo interrupter 21d' so that the photo interrupter 21d 'can be shielded from light. Photo interrupter 21
As in the first embodiment, d ′ is connected to the control means 31 so that a signal in a light-shielded or light-receiving state can be transmitted.

When the signal of the light-shielded state is transmitted from the photo interrupter 21d 'to the control means 31 for a predetermined time, the control means 31 sends a jam or pressure roller to the fixing device as in the first embodiment. It is determined that the pressure release of the printer has occurred, an error message is displayed, and the operation of the printer body can be prohibited.

FIG. 4 is an explanatory side view showing an arrangement state of the sheet discharge sensor unit 21 and the pressure release mechanism 24 before and after pressure release. When the pressure release lever 24a 'is pushed up to release the pressure, the light shielding plate 26 of the pressure release lever is released.
Blocks the light of the photo-interrupter 21d 'used in the paper ejection sensor unit, whereby the main body side can be set to the jam detection state. Therefore, the operation of the printer main body can be stopped in the pressure release state.

Using the fixing device of the present embodiment as described above, when a print command is issued from the computer to the main body in a state where the pressure in the nip is released, the main body issues an error message and executes the print command. Did not.

In this embodiment, the position of the pressure release lever is changed to the vicinity of the photo interrupter, and a light interrupting plate for the photo interrupter is provided on the pressure release lever so that the main body can be operated in a state where the pressure is released. Erroneous operation can be prevented beforehand.

In each of the above embodiments, a laser printer has been described as an image forming apparatus.
The present invention can be applied to a copying machine, a facsimile, a microfilm reader printer, and the like as long as a fixing device of a type in which a pressure roller is pressed against a fixing roller is used.

[0063]

As described above, according to the first aspect of the present invention, in a fixing device having a fixing body pressed against each other and a pressure releasing means for the pressing body, a fixing device is provided. A movable member that operates when the body and the pressure body are pressed or released, and a pressure release detecting unit that detects the released state of the movable member, ensures that the pressure release state in the fixing device is ensured. Can be detected.

Further, according to the second aspect of the present invention, there is provided a jam detecting means for detecting a jam in a nip portion formed between the fixing body and the pressing body pressed against each other,
The jam detection means also serves as a pressure release detection means for detecting the pressure release state of the movable member, and by linking the pressure release means and the jam detection means, the pressure release state in the fixing device can be reliably determined with a simple configuration. Can be detected.

Further, according to the third invention of the present application,
A fixing device according to the first invention of the present application, and control means connected to the pressure release detection means so that a detection signal from the pressure release detection means based on detection by the pressure release detection means can be input. The control unit is configured to prohibit the image forming process when receiving the detection signal of the pressure release state from the pressure release detection unit, thereby reliably detecting the pressure release state in the fixing device. Further, since the operation of the image forming apparatus is prohibited based on the detection, it is possible to prevent an erroneous operation such as operating the image forming apparatus when the pressure of the fixing device is released.

According to the fourth aspect of the present invention, there is provided a jam detecting means for detecting a jam in a nip portion formed between the fixing body and the pressing body pressed against each other,
The jam detection means also serves as a pressure release detection means for detecting the pressure release state of the movable member, and by linking the pressure release means and the jam detection means, the pressure release state in the fixing device can be reliably determined with a simple configuration. Can be detected at
Further, since the operation of the image forming apparatus is prohibited based on the detection, it is possible to prevent an erroneous operation such as operating the image forming apparatus in a state where the pressure of the fixing device is released.

[Brief description of the drawings]

FIG. 1 is an explanatory front view illustrating a fixing device according to a first exemplary embodiment of the present invention when viewed from a sheet discharge side.

FIG. 2A is a side view illustrating an arrangement state of a sheet discharge sensor unit and a pressure release mechanism of a fixing device before depressurization of a first embodiment, and FIG. FIG. 7B is an explanatory side view showing an arrangement state of the pressure release mechanism.

FIG. 3 is an explanatory front view illustrating a fixing device according to a second embodiment when viewed from a sheet discharge side;

FIG. 4A is a side view illustrating the arrangement state of a sheet discharge sensor unit and a pressure release mechanism of a fixing device before depressurization of a fixing device according to a second embodiment, and FIG. FIG. 7B is an explanatory side view showing an arrangement state of the pressure release mechanism.

FIG. 5 is a schematic configuration diagram showing a laser page printer.

6 is a schematic configuration diagram showing a fixing device of the printer shown in FIG.

FIGS. 7A and 7B are schematic diagrams illustrating a state in which the discharge sensor unit does not detect a recording material and a state in which the photo interrupter and the light-shielding plate of the discharge sensor unit detect a recording material; It is a schematic diagram (b).

FIG. 8 is an explanatory front view showing a fixing device having a conventional pressure release mechanism when viewed from the sheet discharging side.

9A and 9B are a side view illustrating a conventional fixing device before pressure release and a side view after release of pressure.

[Explanation of symbols]

 14 'Fixing device 15 Fixing roller 16 Pressure roller 21 Discharge sensor unit (jam detection means) 21a Projection 21d Photo interrupter (movable detection means) 24 Pressure release mechanism (pressure release means) 24a Pressure release lever 25 movable Projection (movable member) 31 Control means

Claims (4)

[Claims] 1. A fixing device having a fixing member and a pressing member releasing unit that are pressed against each other, comprising: a movable member that operates when the fixing member and the pressing member are pressed or released. And a pressure release detecting means for detecting the pressure release state of the fixing device. 2. The image forming apparatus according to claim 1, further comprising a jam detecting unit configured to detect a jam in a nip formed between the fixing unit and the pressing unit that are pressurized with each other. The jam detecting unit detects a pressure release state of the movable member. The fixing device according to claim 1, wherein the fixing device also functions as a pressure release detection unit. 3. The fixing device according to claim 1, further comprising: a control unit connected to the pressure release detection unit so that a detection signal from the pressure release detection unit based on the detection by the pressure release detection unit can be input. An image forming apparatus, wherein the control means prohibits the image forming process when receiving a pressure release state detection signal from the pressure release detection means. 4. A jam detecting means for detecting a jam in a nip formed between a fixing member and a pressing member pressed against each other, wherein the jam detecting means detects a pressure released state of the movable member. 4. The image forming apparatus according to claim 3, wherein the image forming apparatus also functions as a pressure release detecting unit.