JPH05232836A - Temperature sensor retracting device for fixing device - Google Patents

Abstract

PURPOSE:To reduce a degree of damage on a roll by providing a mechanism for retracting a sensor used for controlling the heating temperature of a fixing device, from the roll, and to maintain good fixing action state by controlling the heating temperature according to programs set to a controller. CONSTITUTION:After the switch of an image forming device is turned on, in the starting mode A of the fixing device, a temperature is detected in such a manner that both rolls are rotated while being heated, without allowing the sensor to contact to the roll, and the sensor is brought into contact with the roll to detect the temperature, after time (t1) set in the programs of the controller lapses. In a standby mode B, the roll is stopped to control the temperature, but in a copy mode C, the sensor is intermittently brought into contact, and a mode for monitoring the temperature is set, to control the heating temperature. These programs for controlling can be set to the controller corresponding to the characteristic of the fixing device, the property of a form, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retract system for a sensor for controlling the temperature of a roll in a heat roll type fixing device used in an electronic copying machine, a laser printer or the like, and more particularly to a temperature detection by the sensor. The present invention relates to a device that constitutes means for retracting a sensor by observing an unnecessary timing and reduces wear of a roll member due to pressing of the sensor.

[0002]

2. Description of the Related Art In an apparatus for making a copy using an electrophotographic system such as an electronic copying machine or a laser printer,
A mechanism is used in which a toner image formed on an image bearing member such as a photoconductor drum is transferred onto a sheet, and the sheet carrying the toner image is passed through a fixing device to be fixed to make a copy. As the fixing device, a heat roll type device is generally used, and the heat roll type fixing device is arranged between two rolls in a state where a predetermined nip pressure is set. A heating source is provided on at least one of the two rolls, and heat and pressure are applied to melt the toner when passing through the paper carrying the toner image, and the melted toner is pressed against the paper. Then, the fixing action is performed.

Examples of the heat roll type fixing device include, for example, JP-A-58-111963 and JP-A-2-
Devices such as those disclosed in Japanese Patent No. 12185 are known. In the fixing device of the conventional example, as shown in FIG. 6, two roll members are arranged so as to face each other, and one or both of the two roll members are provided with a heating source such as a halogen lamp, and The sheet carrying the toner image is fixed while the temperature is kept constant. In the fixing device 1 shown in FIG. 6, the fixing roll 2 and the pressure roll 5 are provided, the heating source is arranged with respect to the fixing roll 2, and the pressure roll 5 having no heating source is used.
A mechanism (not shown) that presses against the fixing roll 2 is provided to set a predetermined nip pressure between both rolls.

An inlet guide 7 is arranged on the upstream side of the fixing device 1 to guide the sheet P to be inserted into the fixing device, and a discharge guide 8 is arranged on the downstream side of the fixing device to fix the sheet P. Guide the finished paper to the discharge section. Further, a peeling claw 3 is arranged on the roll 2 on the side corresponding to the toner image carried on the paper, and the paper is peeled from the roll to prevent the paper from being jammed while being wound around the roll. Is composed of. A sheet conveying device 17 is disposed upstream of the entrance guide 7 of the fixing device 1, and the toner image is transferred from the photosensitive drum 15 to the sheet by the discharge of the transfer corotron 16 and is fixed by the sheet conveying device. It is designed to be transported to.

In the fixing device constructed as described above,
A soft touch sensor 10 is arranged to control the heating temperature for the fixing roll 2, and the fixing roll 2 is supported in a state where the soft touch sensor 10 is supported by the frame of the fixing device.
The surface temperature of the roll is detected by lightly pressing the surface of the roll. Then, the roll surface temperature information obtained by the sensor 10 is input to the control device of the image forming apparatus so as to keep the fixing temperature constant by controlling the power supply to the heating source provided in the fixing roll. To do.

[0006]

However, as shown in FIG. 6, when a mechanism that constantly presses the sensor against the fixing roll is used, the contact of the sensor scratches the surface of the roll. There is a problem that it will be. When the fixing roll is scratched, when the toner image is melted and pressed against the paper,
There is a problem that the scratched portion of the roll causes streaky transfer defects and deteriorates the quality of copying.

The fixing roll 2 is composed of a roll core made of metal such as aluminum coated with a fluororesin or the like. When the sensor is slid,
There is a problem that the covering member of the roll is damaged and the roll becomes unusable. Of course, scratches are formed on the fixing roll not only by the contact with the sensor as described above but also by the contact with the peeling claw. However, when the sensor is constantly pressed, the sensor has a relatively wide width, and therefore a wide scratch is formed on the roll coating, which has a large effect on the life of the roll. give.

In addition to the above-mentioned problems, the temperature detecting device in the conventional heat roll type fixing device uses a mechanism for detecting the temperature of the roll while the sensor is constantly in contact with the fixing roll. Therefore, it is necessary to keep the sensor in contact with the roll at all times, and it is inevitable that the sensor shortens the life of the roll. In the conventional fixing roll, for example, it is common to use it as a part to be replaced after copying about 50,000 to 100,000 sheets, and is a member having a higher replacement frequency than other devices.

[0009]

SUMMARY OF THE INVENTION As described above, the present invention solves the problem that scratches are formed on the roll. A mechanism for retracting the sensor is provided, and the timing of the retract action is set so that the sensor is mounted on the roll. An object of the present invention is to provide a device that can shorten the time of contact and reduce the degree of scratches formed on the roll, and that can perform a good temperature detection function.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a sheet carrying a toner image is fixed between two rolls in which at least one roll member has a heating source, and the roll member is fixed to the roll member. The present invention relates to a fixing device in which a sensor for temperature detection is arranged and the heating temperature is controlled.
In the fixing device of the present invention, a mechanism for arranging the sensor to be separated from and in contact with the roll surface is arranged, and at a timing when the surface temperature of the roll is unlikely to reach the set temperature, control for separating the sensor from the roll is performed. It has a mechanism to do it. Further, in the present invention, information on the change in the temperature of the roll is written to the control device at the start-up of the fixing device and while the copy is being made, and the change state of the roll surface temperature is calculated. It is possible to provide a means for setting the characteristic of the temperature change in the fixing device as control information and retracting the sensor according to the information.

As described above, in the fixing device of the present invention, by retracting the sensor at a predetermined timing, it is possible to shorten the time in which the sensor is in contact with the roll, and the roll caused by the contact of the sensor Can reduce scratches. Then, in the control device of the present invention, the control information corresponding to the temperature characteristic of the fixing device is stored, and a mechanism for pressing the sensor against the roll is provided only when the temperature is detected and the heating control is required. Since it is configured, the temperature of the fixing device can be accurately controlled.
Further, even when the means for performing the control as described above is configured, the operation of driving the fixing device and controlling the heating temperature for the roll can be easily performed without making the mechanism of the fixing device particularly complicated. be able to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A retracting device for a temperature detecting sensor of a fixing device according to the present invention will be described with reference to the illustrated example. Figure 1
As shown in FIG. 3, in the fixing device 1 of the present invention, as in the case of the conventional heat roll type fixing device, the fixing roll 2 having a built-in heat source and the pressure roll 5 are arranged to face each other. I am configuring. Further, the fixing roll 2 may be a metal roll core whose surface is coated with a material having good releasability for toner such as fluororesin, and the sheet may be discharged from the fixing roll. The peeling claw 3 is arranged in the section. The pressure roll 5 arranged to face the fixing roll 2 is provided in a state of setting a predetermined nip pressure with respect to the fixing roll, and with respect to the paper nipped between the both rolls, It constitutes a mechanism for applying heat and pressure. Then, a drive mechanism is arranged for the fixing roll 2, and the pressure roll 5 that is in contact with the fixing roll 2 is driven and rotated to perform the fixing and conveying operations on the sheet.

In the fixing device 1 shown in FIG. 1,
A sensor 10 is arranged for the fixing roll 2 provided with a heating source, information on the temperature of the roll obtained by the sensor is input to the control device, and the heating source is turned on / off according to the temperature of the roll. Get control. The sensor 10
Is supported by an arm 11, a predetermined position of the arm 11 is supported by a pivot 12, a spring 13 is arranged at the other end, and the spring 13 causes the sensor 10 to exert a predetermined force on the roll 2. It constitutes a pressing mechanism. Further, a cam 14 is arranged on the side of the arm 11 on which the spring is arranged, and the cam 14 is
The state in which the sensor 10 is lightly contacted with the fixing roll 2 is maintained in a state where the pressing action is not performed.

As shown in FIG. 1, the sensor 1
The sensor detects the temperature of the roll in the state where 0 is brought into contact with the fixing roll 2, and the power supply to the heating source is controlled according to the information on the temperature of the roll. In the state as described above, the sheet carrying the toner image is conveyed by the sheet conveying device 17 and is nipped between the both rolls via the entrance guide 7 to perform the fixing action.
Further, in the fixing device of the present invention, the peeling claw 3 arranged with respect to the fixing roll 2 constitutes a device of a type in which the tip of the claw is always in contact with the roll surface, or a mechanism for retracting the claw member is provided. Any supporting mechanism for the peeling claw member such as the one provided can be used. Then, the fixed sheet is peeled off by the claw member 3 and guided in the ejection direction via the ejection guide 8.

In the fixing device of the present invention, the fixing roll 2
When it is not necessary to detect the temperature of the sensor 10, the cam 14 is rotated and the arm 11 is pressed by the cam as shown in FIG.
Away from. Further, in the fixing device of the present invention, as shown in FIGS. 1 and 2, the sensor 10 is brought into contact with and separated from the fixing roll 2 to monitor and control the temperature of the fixing roll 2. It can be performed.

In a general fixing device, as shown in the graph of FIG. 3, the fixing roll is heated, and the fixing switch temperature D is reached after the main switch of the image forming device is turned on. In the rising mode A of 1, the mode in which the temperature of the fixing roll is rapidly increased is set. When the temperature of the fixing roll reaches the set fixing temperature D, a copyable display is output to the control panel of the image forming apparatus. Further, as shown by the curve P in the graph, when the heating action in the rising mode A is completed and the temperature of the fixing roll reaches the set fixing temperature D, a signal indicating the completion of rising is output in the state of the temperature A1. Then, the fixing device remains in the standby mode B, and stands by until a copy signal is input.

In the state of the standby mode B, the operation of turning on / off the power supply to the heating source is repeated so as to maintain the temperature of the fixing roll at the fixing set temperature D. In the standby mode B, when a document is set on the image forming apparatus and copying is started, the state shifts to copy mode C, and when the sheet passes through the fixing device, the sheet loses heat. The temperature of the fixing roll decreases. Therefore, power is supplied to the heating source in response to the decrease in the temperature of the fixing roll, and the temperature of the fixing roll is set to the fixing set temperature D.
The control is performed so that Further, in the state of the copy mode C, the temperature decreases from the copy start state C1 each time the sheet passes through the fixing device, but the temperature of the fixing roll rises after a lapse of a certain time after the sheet has finished passing, At the fixing temperature recovery point C2, the temperature of the fixing roll is recovered.

The temperature change state indicated by the curve P indicates the case where the power supply system for the fixing device has a sufficient margin, but the curve Q indicates the case where the power supply system for the fixing device has no margin. As shown, control may be performed to raise the temperature of the roll. That is, the curve Q
As shown by, the heating action is further continued from the state of the copy start state C1, the heating action is performed until the temperature becomes higher than the fixing set temperature D, and the fixing action on the paper is performed in that state.

Therefore, even in a device having insufficient power supply system, the copying operation can be continued until the temperature of the fixing roll is lowered to the set fixing temperature D, for example, about several tens of sheets. The copying work of can be continuously performed. Then, when the temperature of the fixing device falls below the temperature at which the fixing is possible, the electronic copying machine is stopped for a while, the power supply to the heating source of the fixing roll is restarted, and the temperature of the fixing device is waited to rise. To do.

As described above, in the heat roll type fixing device used in the general image forming apparatus, it is not necessary to constantly monitor the temperature at the time of start-up or copying. That is, when the heat capacity of the fixing device, the heating characteristics of the heating source, and the like can be grasped, the temperature can be easily controlled without keeping the sensor in contact with the roll at all times. Therefore, in the present invention, the control device arranged with respect to the fixing device can be configured as shown in FIG.

The control device 20 shown in FIG. 4 is provided with a CPU 21 incorporating a control program and a memory 22 for outputting control information to the CPU. Information such as the temperature characteristics of the fixing device is stored in the memory 22, and as shown in the graph of FIG. 3, information on the temperature change in the fixing device and information on the speed of the paper in the image forming device. And so on. Furthermore, the control information and the like obtained by other identical models are input into the memory in advance so that the control conditions are assumed. Further, control information obtained during the operation of the image forming apparatus can be arbitrarily written in the memory so that it can be used as control information thereafter.

The CPU of the control unit has a timer 23.
The input port 24 and the output port 25 are connected to each other, the temperature detection information from the sensor 10 is fetched through the input port 24, and the power supply to the heating source 28 is controlled through the output port 25. Also, from the output port 25,
The drive information for the motor 26 that drives the roll of the fixing device and the drive information for the solenoid 27 for driving the sensor are output. By providing the control device 20 and setting the control conditions as shown in the graph of FIG. 3, the control device provided in the fixing device of the present invention, as shown in the timing chart of FIG.
It is possible to perform a control operation for each member constituting the fixing device.

In the timing chart shown in FIG. 5, when the main switch of the image forming apparatus is turned on, power supply to the power source H of the heating source is started and the driving action on the roll is started to heat the fixing roll. At the same time, the state of the rising mode A is set while the action of heating the pressure roll is performed. In the state of the rising mode A, the sensor is kept away from the fixing roll as shown in FIG. 2 until a predetermined time programmed in the CPU elapses. After that, when the mode is changed to the sensor retract G mode, the solenoid is driven to rotate the cam, and the sensor is brought into contact with the fixing roll to detect the temperature, as shown in FIG.

By inputting temperature information from the sensor to the control device, the state of A1 at the end of rising is confirmed, the driving of the fixing roll is interrupted, and the standby mode B is maintained. In the standby mode B, the power supply to the power source H is controlled according to the temperature detection information from the sensor. In the middle of the rising mode A, the margin time M is set between the time t1 for contacting the sensor and the time t2 for ending the rising. The margin time M depends on the thermal characteristics of the fixing device. Depending on the information, it can be set in advance as program information.

As described above, the standby mode B
During the operation of (1), the operator gives a command to create a copy, and the mode is changed to the copy mode C. When the mode is changed to the copy mode C, the heating action necessary for fixing can be continued for a while (time when the temperature of the roll decreases to the set fixing temperature) without detecting the temperature of the roll. Therefore, after the time set in the program elapses after the fixing action is started, the sensor is brought into contact with the roll at the timing of t4 to detect the temperature. If the signal from the sensor requires heating at that time, the heating source is energized, and the sensor is retracted at time t5 when the fixing temperature recovery point C2 is detected.

The margin time M, which is the time t5-t4 during which the sensor is kept in contact with the roll, is slightly longer than the time actually required for the measurement in order to make the temperature detection by the sensor reliable. Is set. Further, when the number of copies to be continuously made is large, it is necessary to perform the temperature detecting action at a predetermined interval as shown in the graph of FIG. Therefore, also in the timing chart of FIG. 5, in the copy mode C, according to the program set in the control device, every predetermined number of copies,
Alternatively, according to other conditions, the sensor is brought into contact with the roll to detect the temperature at any time.

When the heating temperature is controlled by the control device of the present invention, the start-up state of the image forming apparatus at the start of work in the morning and the restart of work in the daytime, or
When the switch is turned on again after the device is turned off, the control conditions set in the control device can be different. That is, the ambient temperature of the place where the image forming apparatus is placed is different, or the temperature of the entire apparatus is different, and the heating temperature control condition is changed according to the condition. Further, it may be necessary to change the heating state depending on the quality of paper used for copying.

Therefore, in order to set the heating temperature control program in the control device according to the above-mentioned conditions, when the use of the fixing device is started, the surface temperature of the roll is checked, Monitor that measurement,
It is possible to write the control information in a memory and set the control condition. Further, the control program for the fixing device is set by monitoring the state of the temperature change at the time of start-up and copying of the device, checking the control conditions, and obtaining the control curve as shown in FIG. be able to. Therefore, in the control device of the present invention, it is possible to perform control in accordance with the characteristics of the device and the copying conditions simply by adding the calculating means corresponding to the temperature change curve to the CPU and the memory.

[0029]

As described above, in the fixing device of the present invention, the temperature of the roll is monitored according to the preset control conditions, and the heating source is detected according to the temperature information detected by the sensor. Since it is possible to control power supply to the roll, it is not necessary to keep the sensor in contact with the roll at all times. Further, since it is possible to shorten the time during which the sensor contacts the roll, it is possible to reduce the scratches on the roll due to the contact of the sensor.
Therefore, in the control device of the present invention, the control information corresponding to the temperature characteristic of the fixing device is stored, and the mechanism for pressing the sensor to the roll is provided only when the temperature is detected and the heating control is required. Since it is configured, the temperature of the fixing device can be accurately controlled. Further, even when the means for performing the control as described above is configured, the operation of driving the fixing device and controlling the heating temperature for the roll can be easily performed without making the mechanism of the fixing device particularly complicated. be able to.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a fixing device of the present invention.

FIG. 2 is a side view of the fixing device with the sensor retracted.

FIG. 3 is a graph showing a state of temperature change in the fixing device.

FIG. 4 is a block diagram showing a configuration of a control device of the present invention.

FIG. 5 is a timing chart showing the operation of each component in the device of the present invention.

FIG. 6 is a side view showing the configuration of a general fixing device.

[Explanation of symbols]

1 fixing device, 2 fixing roll, 5 pressure roll, 10 sensor, 13 spring, 14
Cam, 15 photoconductor drum.

Claims (1)

[Claims] 1. A sheet for carrying a toner image is fixed between two rolls in which at least one of the roll members has a built-in heat source, and a temperature detecting sensor is arranged on the roll member for heating. In the fixing device for controlling the temperature, a mechanism for arranging the sensor on and off the roll surface is arranged, and control information based on the temperature change characteristic of the fixing device is set to control the surface temperature of the roll. A retract device for a temperature detection sensor of a fixing device, which controls to separate the sensor from the roll at a timing when it is not necessary.