JP2003091202A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge presence or no-presence of a fixing unit with inexpensive constitution without using a signal line used only for detecting the presence or no-presence of the fixing unit. SOLUTION: This fixing device has an automatic pressure release means for pressuring a fixing roller and releasing the pressure by reversely rotating a fixing motor, an HP sensor for detecting the pressure state of the fixing roller and at least one thermistor for monitoring the temperature of the fixing unit. When HP can not be detected within a specified time and also the value of the thermistor is off though the fixing motor does not break down, it is decided that the fixing unit is not present. When the value of the thermistor is off though the HP can be detected, it is decided that the thermistor is abnormal. When the value of the thermistor is not off though the HP can not be detected, it is decided that the HP sensor is broken down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a fixing device for fixing a recording material carrying an unfixed image by heating by a heating means.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a fixing roller heated by a heating source such as a heater is used to make an unfixed toner image formed on a recording material a permanent image. There is used a fixing device that conveys the recording material and heats and pressurizes it by a pressure roller that rotates in pressure contact with the recording material.

A general fixing device will be described with reference to FIG.

In FIG. 9, a recording material 101 is conveyed from the direction A in the drawing, and a pair of pressure roller 102 and fixing roller 1 are used.
It enters into the nip part formed by 03. Recording material 1 that entered
The unfixed toner image formed on 01 is applied with pressure and heat from a beater incorporated in the fixing roller 103 while passing through the nip portion, and is fixed on the recording material 101 with melting and the like. , Becomes a permanent image. Fixed recording material 1
01 is guided to the outside of the apparatus by a paper discharge roller (not shown) arranged downstream of the fixing roller 103 and the pressure roller 102.

Further, some image forming apparatuses have a detachable fixing device, which can be replaced by a user of the image forming apparatus. In such a fixing device, it is necessary to determine whether or not the fixing device is attached to the image forming apparatus.

[0006]

However, the above-mentioned conventional example has the following problems.

In the conventional example, a dedicated signal line is provided as a means for determining the presence / absence of the fixing device, and the presence / absence of the fixing device is determined by whether or not the detection result is open.
In this way, the configuration having the signal line only for determining the presence / absence of the fixing device causes a cost increase of the fixing device.

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus that determines the presence or absence of a fixing device without using a signal line for determining the presence or absence of the fixing device. To do.

[0009]

An image forming apparatus provided by the present invention has the following configurations (1) to (5).

(1) Driving means for driving the fixing device, pressure releasing means for pressing and releasing pressure on the fixing roller, state detecting means for detecting the pressed and released states of the fixing roller, and fixing A fixing device having at least one temperature detecting device for detecting the temperature of the device; and an abnormality detecting device for detecting an abnormality of the fixing device based on the detection results of the state detecting device and the temperature detecting device. Image forming apparatus.

(2) The image forming apparatus according to (1), wherein the pressure releasing means pressurizes the fixing roller and releases the pressure by rotating the driving means in the reverse direction.

(3) When the abnormality detecting means determines that the pressure releasing means cannot switch between the pressurizing state and the pressure releasing state, and when the detection result of the temperature detecting means is open, the fixing device. The image forming apparatus according to (1) above, which is determined to be absent.

(4) In a fixing device having at least two driving means for driving the fixing device and temperature detecting means for detecting the temperature of the fixing device, if all the detection results of the temperature detecting means are open, An image forming apparatus characterized by determining that there is no fixing device.

(5) An exciting coil which is a magnetic field generating means,
A power inverter for driving the exciting coil; and a member for generating electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means,
The electromagnetic induction heat generating member has a pressing member which is in pressure contact with each other to form a nip portion of the member to be heated, and the magnetic field of the magnetic field generating means is caused to act on the electromagnetic induction heat generating member, A fixing device for heating a material to be heated by heat generation has at least one current detecting means for detecting a current flowing through the exciting coil and a temperature detecting means for detecting a temperature of the fixing device, and a detection value by the current detecting means. The image forming apparatus is characterized in that it is determined that there is no fixing device when is less than or equal to a threshold value and the value of the thermistor is open.

[0015]

According to the present invention, first, based on the detection result of the home position sensor (hereinafter, HP sensor) for detecting the pressurization state of the automatic pressure releasing mechanism of the fixing device and the thermistor for monitoring the temperature of the fixing roller, The presence / absence of the fixing device, the abnormality of the thermistor, the failure of the HP sensor can be respectively discriminated, and the presence / absence of the fixing device can be discriminated based on the detection results of at least two or more thermistors.

Further, in the fixing device using the electromagnetic induction heating method, the presence or absence of the fixing device can be determined based on the detection results of the thermistor and the current detection.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on examples with reference to the drawings.

[0018]

(First Embodiment) FIG. 1 is a schematic view of a laser beam printer as an image forming apparatus according to the present invention. As shown in FIG. 1, the image forming apparatus forms an electrostatic latent image by image light formed on the basis of an image signal in an image forming unit, transfers the visible image to a recording material 201, and records the recording material 201. The above visible image is fixed, and the image forming unit is composed of a photosensitive unit, a charging roller 202 as a primary charging unit, a cleaning unit, a developing unit, an intermediate transfer member 203, a paper feeding unit, a transfer unit and a fixing unit 204. It

The photosensitive drum 205 is constructed by coating an organic photoconductor layer on the outer circumference of an aluminum shilling. The photosensitive drum 205 is rotated by transmitting a driving force of a drive motor (not shown), and the drive motor rotates the photosensitive drum 205 in a counterclockwise direction according to an image forming operation. The exposure light to the photosensitive drum 205 is sent from the scanner 206, and an electrostatic latent image is formed by selectively exposing the surface of the photosensitive drum 205.

As a developing means, a developing device 207 is provided for developing the electrostatic latent image into a visible image, and the developing device 207 is provided with a sleeve 208.

The intermediate transfer member 203 is configured to come into contact with the photosensitive drum 205 and rotate with the rotation of the photosensitive drum 205. The intermediate transfer member 203 rotates in the clockwise direction during image formation and is visible from the photosensitive drum 205. Receive image transfer.
Further, the intermediate transfer body 203 simultaneously transfers the visible image on the intermediate transfer body 203 to the recording material 201 by contacting a transfer roller 209 described later during image formation and conveying the recording material 201.

The transfer roller 209 is provided as a transfer charger that is supported so as to be able to contact the intermediate transfer member 203.

The transfer roller 209 is the intermediate transfer member 20.
While the visible image is being transferred onto the sheet 3, the sheets are spaced downward so as not to disturb the visible image. Then, the intermediate transfer member 2
After the visible image is formed on 03, the transfer roller 209 is positioned above by a cam member (not shown) at the timing of transferring the visible image onto the recording material 201.
As a result, the transfer roller 209 is pressed against the intermediate transfer body 203 via the recording material 201 with a predetermined pressing force, and a bias voltage is applied, so that the visible image on the intermediate transfer body 203 is transferred.

The fixing section 204 fixes the transferred visible image while conveying the recording material 201.
The fixing roller 2 for heating the recording material 201 as shown in FIG.
A pressure roller 211 for pressing the recording material 201 and the recording material 201 to the fixing roller 210 and a thermistor for monitoring the temperature of the fixing roller are provided. Recording material 2 that holds a visible image
The toner image 01 is conveyed by the fixing roller 210 and the pressure roller 211, and the toner image is fixed on the surface by applying heat and pressure.

Next, the pressure releasing mechanism of the fixing device of this embodiment will be described with reference to FIG. FIG. 2A is a diagram showing the fixing device in a pressurized state. In the figure, 301 is a side plate that holds the fixing roller 210, 302 is a pressure spring that presses the side plate 301 and presses the fixing roller 210, 303 is a cam that switches between pressed and released states, 304 is pressure, It is an HP sensor that detects the home position (HP) in the pressure released state. The HP sensor includes a flag and a detector including a light emitting unit and a light receiving unit.

FIG. 2B is a view showing the fixing device in the pressure released state. In this figure, the immediate plate 301 is the cam 30.
3 is pushed up, and the fixing device is in the pressure released state. Further, since the cam 303 is joined to the shaft of the pressure roller 211 by a one-way clutch, when the fixing roller 210 is driven in the carrying direction, the cam 303 is not driven but is driven in the opposite direction to the carrying direction. Only when the cam 303 is operated, the cam 303 can be driven to switch the pressurization and pressure release states.

Next, the pressurizing process will be described with reference to the flowchart of FIG.

First, it is determined whether the HP sensor is under pressure (S401). If it is already in the pressurized state, the process ends. If the pressure is released, reverse rotation of the fixing motor is started (S402). Next, it is determined whether the value of the HP sensor is in the pressurized state (S403), and whether a predetermined time has passed (S404). Regarding the two processes of S403 and S404, the process is repeated until either one of the conditions is satisfied.

When the value of the HP sensor is in the pressurized state within a predetermined time, the cam 303 is brought into the fully pressurized state until the center of the flag of the HP sensor reaches the position of the detector (S405). If the value of the HP sensor does not reach the pressurization state within the predetermined time, it is determined that the pressurization process has failed (S4).
06). Finally, the fixing motor is stopped (S407), and the process ends.

Next, the fixing device failure detection process will be described with reference to FIG.
This will be described with reference to the flowchart of.

First, when the power is turned on or when returning from sleep, the current value of the HP sensor is detected and whether the pressure state or the pressure release state is stored is stored (S501). The reverse rotation of the fixing motor is started (S502). Next, it is determined whether the HP sensor value is inverted (S503), and it is determined whether a predetermined time has passed (S504). The above S503,
Regarding the two processes of S504, the process is repeated until either one of the conditions is satisfied.

If the value of the HP sensor does not reverse within the predetermined time, the fixing motor is stopped (S505). Next, it is determined whether the value of the thermistor is open (S506).
If the value of the HP sensor does not reverse within the predetermined time and the value of the thermistor is open, it is determined that there is no fixing device (S
507), and ends the failure detection process.

If the value of the HP sensor does not reverse within the predetermined time, but the value of the thermistor is not open, it is determined that the HP sensor has failed (S508), and the failure detection ends.

In the process of S503, if the value of the HP sensor is reversed within the predetermined time, then it is determined whether the value of the thermistor is open (S509).

If the value of the HP sensor is reversed within the predetermined time but the value of the thermistor is open, it is judged that the thermistor is abnormal (S510). If the value of the HP sensor is reversed within the predetermined time and the value of the thermistor is not open, it is determined that the fixing device is normal (S511), and the failure detection process is ended.

In the above process, if any abnormality is detected, the detection result is displayed on the operation panel after the failure detection process is completed, and the printing operation is not permitted.

(Second Embodiment) In this embodiment, a method of detecting a failure based on the detection results of a plurality of thermistors in a fixing device having no automatic pressure release mechanism will be described.

The fixing device of this embodiment will be described with reference to FIG.

In the figure, 601 is a fixing roller for heating the recording material P, 602 is a pressure roller for bringing the recording material P into pressure contact with the fixing roller 601, and 603 and 604 are inside the fixing roller 601 and the pressure roller 602. Is provided in
A heater that heats the fixing roller 601 and the pressure roller 602, and reference numerals 605 and 606 are thermistors that detect the temperatures of the fixing roller 601 and the pressure roller 602. Further, the arrow in the figure indicates the conveyance direction of the recording material P.

In the fixing device of this embodiment, the thermistor 60
The beater 603 is controlled according to the detected temperature of No. 5, the heater 604 is controlled according to the detected temperature of the thermistor 606, and the temperature of the fixing roller 601 and the pressure roller 602 is controlled.

Next, the fixing device failure detection process will be described with reference to FIG.
This will be described with reference to the flowchart of.

First, it is determined whether or not the value of the upper thermistor is open when the power is turned on or when returning from sleep (S701). If the value of the upper thermistor is open, then it is determined whether the value of the lower thermistor is open (S702). When both the upper and lower thermistor values are open, it is determined that there is no fixing device (S703). When the value of the upper thermistor is open and the value of the lower thermistor is normal, it is determined that the upper thermistor is abnormal (S70).
4).

In the process of S701, if the value of the upper thermistor is not open, it is next determined whether or not the value of the lower thermistor is open (S705).

When the value of the upper thermistor is normal and the value of the lower thermistor is open, it is determined that the lower thermistor is abnormal (S706). If both the upper and lower thermistor values are not open, it is determined that the fixing device is normal (S70).
7) The failure detection process is ended.

In the above process, if any abnormality is detected, the detection result is displayed on the operation panel after the failure detection process is completed, and the printing operation is not permitted.

(Third Embodiment) In this embodiment, a method of detecting a failure of the fixing device in the fixing device using the electromagnetic induction heating method will be described.

First, a fixing device using an electromagnetic induction heating system will be described.

This uses an electromagnetic induction heating element as a heating element, and a magnetic field is applied to the electromagnetic induction heating element by a magnetic field generating means to generate Joule heat based on an eddy current generated in the electromagnetic induction heating element, which serves as a material to be heated. This is a device for heating and fixing the recording material surface.

FIG. 7 is a partially cutaway side view of the image heating and fixing device.

This fixing device mainly comprises a heating assembly 801 and a pressure roller 802 as a rotary pressure member.

The heating assembly 801 is a cylindrical film guide 803, an exciting coil 804 as a magnetic flux generating means arranged in the inner space thereof, a magnetic core (high magnetic permeability core) 805,
A cylindrical (seamless) fixing film 806 as an induction heating element loosely fitted on a cylindrical film guide,
The magnetic core 805 includes a demagnetization coil 807 as an electric conductor that circulates a part of the magnetic core 805, a current detection unit that detects a current flowing through the coil, and the like.

Next, the failure detection process of the fixing device will be described with reference to FIG.
This will be described with reference to the flowchart of.

First, it is determined whether or not the value of the thermistor is open when the power is turned on or when returning from sleep (S901). If the thermistor value is open,
Subsequently, coil breakage is detected.

First, energization of the coil is started (S90
2), the current flowing through the coil is detected (S903). After the electric current is detected, the power supply to the coil is stopped (S90
4). It is determined whether the detected value is less than or equal to the threshold value (S905).

If the value of the thermistor is open and the detected current value is less than the threshold value, it is determined that there is no fixing device (S906). When the value of the thermistor is open and the detected current value is larger than the threshold value, it is determined that the thermistor is abnormal (S907).

In the process of S901, if the value of the thermistor is not open, then coil breakage detection is performed (S908, S909, S910, S911).

When the value of the thermistor is normal and the detected current value is less than the threshold value, it is judged that the coil is broken (S9).
12). If the thermistor values are not both open and the detected current value is larger than the threshold value, the fixing device is determined to be normal (S913), and the failure detection process ends.

In the above process, if any abnormality is detected, the detection result is displayed on the operation panel after the failure detection process is completed, and the printing operation is not permitted.

[0059]

As described above, according to the first embodiment of the present invention, the fixing device is automatically operated at the time of turning on the power source or returning from the sleep state without using the signal line for determining the presence or absence of the fixing device. Based on the detection results of the HP sensor that detects the pressurization state of the pressure release mechanism and the thermistor that monitors the temperature of the fixing roller, the presence or absence of the fixing device, the abnormality of the thermistor
Each failure of the HP sensor can be discriminated. According to the second embodiment, it is possible to determine the presence / absence of the fixing device based on the detection results of at least two thermistors even in the fixing device having no automatic pressure releasing mechanism. According to the third embodiment, in the fixing device using the electromagnetic induction heating method, the presence or absence of the fixing device can be determined based on the detection results of the thermistor and the current detection.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating an automatic pressure release mechanism of a fixing device,
(A) is a diagram showing the fixing device in a pressurized state, (b) is a diagram showing the fixing device in a pressure released state

FIG. 3 is a flowchart illustrating a pressurizing process according to the first embodiment.

FIG. 4 is a flowchart illustrating a failure detection process according to the first embodiment.

FIG. 5 is a schematic diagram of a fixing device according to a second embodiment.

FIG. 6 is a flowchart illustrating failure detection processing according to the second embodiment.

FIG. 7 is a partially cutaway side view of the image heating fixing device.

FIG. 8 is a flowchart illustrating a failure detection process according to the third embodiment.

FIG. 9 is a schematic view of a fixing device in a conventional example.

[Explanation of symbols]

101 recording material 102 pressure roller 103 fixing roller 201 recording material 202 charging roller 203 Intermediate transfer body 204 fixing unit 205 photosensitive drum 206 scanner 207 Developer 208 sleeve 209 Transfer roller 210 fixing roller 211 Pressure roller 301 side version 302 Pressure spring 303 cam 304 HP sensor 601 fixing roller 602 pressure roller 603,604 heater 605,606 Thermistor 801 heating assembly 802 Pressure roller 803 film guide 804 Excitation coil 805 Magnetic core (high permeability core) 806 Fixing film 807 Demagnetizing coil P recording material

Claims (5)

[Claims] 1. A driving unit for driving a fixing device, a pressure releasing unit for pressing and releasing pressure of a fixing roller, a state detecting unit for detecting a state of pressing and releasing pressure of the fixing roller, and a fixing device. A fixing device having at least one temperature detecting means for detecting the temperature of the fixing device, and an abnormality detecting means for detecting an abnormality of the fixing device based on the detection results of the state detecting means and the temperature detecting means. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the pressure releasing means pressurizes the fixing roller and releases the pressure by rotating the driving means in a reverse direction. 3. The fixing device is absent when the abnormality detecting means determines that the pressure releasing means cannot switch between pressurizing and pressure releasing states and when the detection result of the temperature detecting means is open. The image forming apparatus according to claim 1, wherein the image forming apparatus determines. 4. A fixing device having at least two driving means for driving the fixing device and temperature detecting means for detecting the temperature of the fixing device, wherein fixing is performed when all detection results of the temperature detecting means are open. An image forming apparatus characterized by determining that there is no apparatus. 5. An exciting coil which is a magnetic field generating means, a power inverter for driving the exciting coil, a member which generates electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means, and the electromagnetic induction heat generating member are mutually connected. A pressurizing member that presses to form a nip portion of the member to be heated is applied, and the magnetic field of the magnetic field generating means is applied to the electromagnetic induction heat-generating member to heat the material to be heated by the heat generated by the electromagnetic induction heat-generating member. In the fixing device, current detection means for detecting a current flowing through the exciting coil,
At least one temperature detecting means for detecting the temperature of the fixing device
An image forming apparatus, which has one of the above, and determines that there is no fixing device when the value detected by the current detection unit is less than or equal to the threshold value and the value of the thermistor is open.