JPH052355A - Fixing device - Google Patents

Abstract

PURPOSE:To rapidly detect the abnormal heating-up of a fixing roller and to obviate the generation of wear and the influence on images in the normal time by constituting a temp. detecting part in such a manner that this part can be attached and detached to and from the fixing roller and interlocking this part to the start and stop of the fixing roller. CONSTITUTION:A clutch 14 with and from which an engaging pawl 13 moved by on and off of a fixing roller start-stop solenoid 11 engages and disengages is provided at the driving shaft of the fixing roller 2 and a member 15 provided with a thermostat 9 at the front end is fixed to the middle of the arm of the engaging pawl 13. The engaging pawl 13 engages with the clutch 14 and turns off the clutch when the solenoid 11 is on. The thermostat 9 is simultaneously brought into contact with the peripheral surface of the fixing roller 2. The clutch is engaged to rotate the fixing roller 2 and simultaneously, the thermostat 9 is detached from the peripheral surface of the fixing roller 2 when the solenoid 11 is off. Then, the thermostat 9 comes into contact with the fixing roller 2 and detects the abnormal rise of its surface temp. when the fixing roller 2 does not rotate. The heat source can, then, be turned off.

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 recording device.

[0002]

2. Description of the Related Art As a fixing device for an electrophotographic recording apparatus such as an electrophotographic copying machine, a laser printer, a facsimile, etc., as shown in FIG. 6, a fixing roller 2 (heating roller) having a heater 1 built therein is brought into pressure contact with it. The recording paper 5 having a roller pair with the pressure roller 3 and carrying the unfixed toner image 4 is passed through the nip portion of the roller pair, and the toner image 4 and the recording paper 5 are heated by the heat of the fixing roller 2. A heat roller fixing device that heats and applies pressure to fuse the toner image 4 to the recording paper 5 to fix the toner image 4 is widely adopted.

The fixing roller 2 is, as shown in FIGS. 6 and 7, fixed in order to maintain a constant fixing temperature during fixing.
A temperature detecting means 6 such as a thermistor is provided so as to face the surface of the heater 1, and the detected value of the fixing roller surface temperature is input to the CPU 7 (FIG. 7).
Is controlled so that the surface temperature of the fixing roller 2 maintains a predetermined fixing temperature. Further, when the surface temperature of the fixing roller rises abnormally, the energization of the heater 1 is immediately stopped. Therefore, as a protection means, the abnormal temperature detecting means 9 such as a thermostat, a temperature fuse, a thermistor, and the like is placed facing the surface of the fixing roller 2. It is provided. Fixing roller 2
In the example of FIG. 7, the fixing roller start / stop solenoid 11 that is rotationally driven by the drive motor 10 is rotated and stopped by the CPU 7
The start / stop is controlled by engaging and disengaging the claws with the teeth provided on the outer periphery of the clutch provided on the fixing roller drive shaft.

In the fixing device having the above structure, when the abnormal temperature detecting means 9 of the conventional protecting means is provided in contact with the surface of the fixing roller 2, the fixing roller 2 is rotated to adhere to the surface of the fixing roller 2. The accumulated toner is dammed up and collects, falls on the recording paper, adheres to the image like dust, and the rotation of the fixing roller causes friction with the abnormal temperature detection means, causing wear on the contact surface. It was Therefore, it has been common to provide the abnormal temperature detecting means in a non-contact manner with a certain distance from the surface of the fixing roller. In that case, the surface temperature of the fixing roller rises and the ambient temperature around it rises. Since it is detected by the detecting means for the first time, the fixing roller is considerably higher than the predetermined temperature when the abnormal temperature is detected.

To address this problem, it has hitherto been noted that the heating roller starts to rotate after the heating roller has risen to a certain temperature, and immediately after the power is turned on to the inside of the fixing device. Although it is necessary to keep the abnormal temperature detection means in contact with the heating roller that is still cold and the temperature rises fastest, considering that the temperature inside the fixing device rises, the abnormal temperature detection means operates sufficiently even depending on the ambient temperature. The temperature of the heating roller or the vicinity thereof is detected, and when a certain temperature is reached, the abnormal temperature detecting means is controlled so as to be separated from the heating roller, for example, Japanese Patent Laid-Open No. 60-23875.
JP-A-62-76121, JP-A-63-9548
No. 5, Japanese Utility Model Publication No. 63-177869 and the like.

However, in a copying machine or the like, the heat source of the heating roller is normally turned off and the temperature of the fixing device is controlled to decrease when a paper jam occurs in the fixing unit.
When a shape memory alloy or the like is used as the contacting / separating means depending on the temperature, the abnormal temperature detecting means returns to the state of being in contact with the heating roller, which makes it difficult to process the residual paper wound around the heating roller. In addition, depending on the machine, the heating roller can be manually rotated even at low temperatures due to paper jam treatment, or to prevent permanent distortion (creep) that occurs due to the constant pressure contact state of the pressure roller, Some control the heat source so that it rotates without turning on the heat source periodically.In that case, the abnormal temperature detector rotates while keeping contact with the heating roller, which is a cause of accelerating wear of the heating roller. It was

[0007]

SUMMARY OF THE INVENTION In view of the above problems of a fixing device which has been conventionally implemented or proposed, the present invention promptly and accurately detects and protects when the surface temperature of a fixing roller rises abnormally. It is an object of the present invention to provide a heat roller fixing device that can operate the means and that does not cause wear or influence on an image in normal times.

[0008]

According to the present invention, in order to solve the above-mentioned problems, in the fixing device having the above-mentioned constitution, the temperature detecting portion of the above-mentioned protection means can be brought into contact with and separated from the heating roller, and the rotation of the heating roller can be made. .Interlocking means for interlocking with the stop so that the temperature detecting section contacts the heating roller when the heating roller is stopped and the temperature detecting section is separated from the heating roller when the heating roller rotates And

[0009]

With the above structure, since the temperature detecting portion of the protection means is in contact with the heating roller when the heating roller is stopped,
Even when the power is turned on from a low temperature, the temperature of the temperature detection part rises without a big delay as the temperature of the heating roller rises, and even if the temperature of the heating roller becomes abnormally high, the protection function operates quickly and the protection function Can be achieved reliably. Further, since the temperature detection unit is separated from the heating roller when the heating roller is rotated, the temperature detection unit is separated even if the heating roller rotates in a low temperature state for some reason, and the contact portion between the temperature detection unit and the heating roller is worn. Also, there is no possibility that the toner on the heating roller is collected by sliding and falls on the recording paper to stain the image.

As the interlocking mechanism of the rotation / stop of the heating roller and the contact / separation of the temperature detecting portion, the temperature detecting portion is brought into contact with / separating from the heating roller by the switching operation of the clutch means for switching the rotation / stop of the heating roller. It is advantageous to use a member that moves to a simple structure.

The interlocking mechanism is interlocked with a spring for urging the temperature detecting portion in a direction in which the temperature detecting portion is pressed against the heating roller and rotation / stop of the heating roller. When the heating roller is rotated, a predetermined torque is generated. A torque limiter that does not generate torque when the heating roller is stopped, and a member that separates the temperature detection unit from the heating roller against the biasing force of the spring by the torque generated by the torque limiter may be used.

[0012]

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

FIG. 1 is a perspective view showing an embodiment in which the present invention is applied to the fixing device having the structure described with reference to FIGS. 6 and 7. Therefore, members having the same function will be described with the same reference numerals.

On the drive shaft of the fixing roller 2 which is driven by the drive motor 10 via the transmission device 12, an engagement claw 13 which moves by turning on and off the fixing roller starting / stopping solenoid 11 is provided.
A clutch 14 is provided around which teeth are engaged and disengaged. When the motor 10 is driven and the solenoid is on, the engagement claw 13 engages with the teeth of the gear 14 and the clutch is disengaged. When the solenoid 11 is turned off, the engaging claws 13 are disengaged from the teeth of the clutch 14 and the clutch is engaged to rotate the fixing roller 2. A member 15 having a thermostat 9 at its tip is integrally fixed in the middle of the arm of the engaging claw 13, and when the solenoid 11 is turned on, the engaging claw 13 engages with the teeth of the clutch 14 to open the clutch. Simultaneously with cutting, the thermostat 9 is brought into contact with the peripheral surface of the fixing roller 2. When the solenoid 11 is off, the engaging claw 13 is disengaged from the teeth of the clutch 14 and the clutch is engaged, and the fixing roller 2
The thermostat 9 is separated from the peripheral surface of the fixing roller 2 at the same time when the is rotated.

FIG. 2 is a timing chart of the on / off timing of the fixing roller start / stop solenoid 11, the heater 1 and the motor 10 of this fixing device, and the curve showing the surface temperature of the fixing roller 2 and the temperature change of the thermostat on the same time base. It is a figure. The change in the thermostat surface temperature is shown by a chain line in the case of the present invention, and by a broken line in the case of no contact with the conventional constant fixing roller.

In the case of the present invention, since the thermostat 9 is in contact with the peripheral surface of the fixing roller 2 when the fixing roller is not rotating, after the power is turned on, as the temperature of the fixing roller rises from room temperature, the thermostat The surface temperature of 9
The temperature rises substantially in proportion to the temperature of the fixing roller, and when the surface temperature of the fixing roller rises to a predetermined fixing temperature, the heater 1 is repeatedly turned on and off to maintain the fixing temperature. When the surface temperature of the fixing roller reaches the fixing temperature, the fixing roller starting / stopping solenoid 11 is turned off, the clutch 14 is engaged, and the thermostat 9 separates from the fixing roller. When the print is started, the paper conveyance motor 10 is rotated, the fixing roller 2 is rotated, when the printing is completed, the paper conveyance motor is stopped, the rotation of the fixing roller is stopped, and then the fixing roller start / stop solenoid 11 is turned on at a predetermined timing. The clutch is released and the thermostat 9 comes into contact with the fixing roller.
Therefore, the thermostat 9 is reliably separated from the fixing roller while the fixing roller 2 is rotating.

When the temperature of the fixing roller rises abnormally for some reason, the temperature of the thermostat also rises accordingly, and the abnormal temperature is detected. As a result, as is apparent from the block diagram of FIG. 7, the heater 2 is de-energized, the temperature of the fixing roller is lowered, and the temperature is returned to a predetermined fixing temperature.
The heater is on / off controlled. In the case of the conventional non-contact thermostat, even if the fixing roller temperature rises abnormally, the surface temperature of the thermostat does not follow this and the thermostat does not operate properly, so the temperature of the fixing roller rises further and fails. Cause of.

Next, another embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a diagram showing a structure in the vicinity of the heating roller 2 of the fixing device of the embodiment. The heating roller 2 is integrally provided with a drive gear 20, and the transmission gear 1 meshed with the drive gear 20.
6, a rotary shaft 19 is provided in parallel with the heating roller 2 via a torque limiter 17. On the other hand, a thermostat 9 serving as a temperature detecting portion of the protection means capable of being pressed against the heating roller 2 has a flap 2 whose base end is fixed to the rotary shaft 19.
1 is attached near the free end. The flap 21 is urged in a direction in which the thermostat 9 is pressed against the heating roller 2 by a compression spring 18 whose one end is fixed to a frame of a fixing device (not shown) on the back surface of the thermostat 9.

The torque limiter 17 is the heating roller 2
When the drive gear 20 fixed to the shaft rotates in the direction of arrow A in FIG. 3 and the transmission gear 16 rotates in the direction of arrow B in conjunction with it, the rotational torque in the direction of arrow B is transmitted to the rotary shaft 19. . When the torque of the rotating shaft 19 reaches a predetermined value due to the load on the rotating shaft 19, slip occurs in the torque transmitting portion in the torque limiter 17, and as a result, the torque transmitted to the rotating shaft 19 via the torque limiter 17. Is limited to a certain value.

With the above construction, when the heating roller 2 is not rotating, as shown in FIG. 4, the torque is not transmitted to the rotating shaft 19 by the torque limiter 17, the flap 21 is pressed against the back surface by the spring 18, and the thermostat 9 is It is pressed by the heating roller 2.

When the heating roller 2 rotates, a torque of a predetermined value is transmitted to the rotating shaft 19 by the torque limiter 17, and the flap 21 rotates counterclockwise against the spring 18 as shown in FIG. The thermostat 9 moves away from the heating roller 2. A slip start torque of the torque limiter is provided by providing a stopper 22 that blocks the counterclockwise rotation of the flap 21 at a position where the flap 21 rotates slightly clockwise from a position where the predetermined torque and the force of the spring 18 are balanced. Even when is mechanically varied or changes with time, the separation distance between the thermostat 9 and the heating roller 2 can be stably and accurately maintained.

When the heating roller 2 is a fixing device which can rotate in the opposite direction to the normal rotation direction, the torque limiter 17 is a torque limiter with a one-way clutch so that the rotation shaft 19 rotates in the reverse direction. The rotation is not transmitted and the thermostat 9 bites into the heating roller 2 and
Is prevented from being damaged.

[0024]

As described above, according to the present invention, the protection operation at the time of the abnormal temperature rise of the fixing roller is performed in a timely manner, and the thermostat when the thermostat of the protection means is in contact with the fixing roller. It becomes possible to prevent abrasion and image stains.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a timing chart of related members of the embodiment and a curve diagram showing changes in surface temperatures of a fixing roller and a thermostat on the same time basis.

FIG. 3 is a perspective view showing the configuration of another embodiment of the present invention.

FIG. 4 is a side view for explaining the operation of the embodiment when the heating roller is not rotating.

FIG. 5 is a side view for explaining the operation of the embodiment when the heating roller rotates.

FIG. 6 is a cross-sectional view showing an example of the configuration of a heat roller fixing device to which the present invention is applied.

FIG. 7 is a control block diagram thereof.

[Explanation of symbols]

1 heater 2 Fixing roller (heating roller) 4 Unfixed toner image 5 Recording paper 6 thermistor 9 Thermostat (Temperature detection part) 10 motors 11 Fixing roller start / stop solenoid 13 engagement claws 14 clutch 15 Interlocking member 16 transmission gears 17 Torque limiter 18 spring 19 rotation axis 20 drive gear 21 flaps 22 Stopper

Claims (3)

[Claims] 1. A rotatable and stopable heating roller that has a built-in heat source and that is rotated to contact and convey a recording paper carrying an unfixed toner image to fix the toner image on the recording paper. In a fixing device of an electrophotographic recording device, which has a temperature detecting means for detecting a surface temperature and a protecting means for detecting an abnormal temperature of the heating roller and cutting off the heat source,
The temperature detection unit of the protection means can be brought into contact with and separated from the heating roller. The temperature detection unit comes into contact with the heating roller when the heating roller is stopped in association with the rotation and stop of the heating roller, and when the heating roller is rotated. A fixing device comprising interlocking means for interlocking so that the temperature detecting section is separated from the heating roller. 2. The interlocking means carries the temperature detecting section, and the temperature detecting section moves so as to come into contact with and separate from the heating roller by a switching operation of a clutch means for switching rotation / stop of the heating roller. The fixing device according to claim 1, wherein the fixing device is a member that does. 3. The interlocking device is interlocked with a spring for urging the temperature detecting portion in a direction in which the temperature detecting portion is pressed against the heating roller and rotation / stop of the heating roller, and a predetermined torque is generated when the heating roller is rotated. However, it is composed of a torque limiter that does not generate torque when the heating roller is stopped, and a member that separates the temperature detection unit from the heating roller against the biasing force of the spring by the torque generated by the torque limiter. The fixing device according to claim 1, wherein: