JP2001008358A - Method for sensing temperature, method for cutting-off current flow, fusing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate the speed of sensing temperature, prevent overheating and discharge accidents or the like by bringing a pair of terminals for detecting a thermoelectromotive force into contact with different type metals for constituting a fusing roller or the like, and detecting the temperature from the thermoelectromotive force generated. SOLUTION: This using device comprises a circuit for detecting the temperature difference of both ends due to an electromotive force of a fusing roller, constituted by connecting or bringing two types of metals into contact with one another to decide whether or not an overheat fault occurs according to the temperature difference thereby to shut off a current to a resistor heater layer 10, when a fault is decided. A temperature control system has a fusing roller comprising the layer 10, a triac 11, a temperature fuse 13, a shut-off relay 15 or the like. In this case, a 100V commercial power source is connected to the layer 10, the temperature is regulated by the triac 11, the fuse 13 is operated when overheated so as to shut off the current of the commercial power source. Accordingly, the temperature difference of both the ends of the roller can be detected immediately and surely to prevent overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting method for detecting the temperature of an electric circuit or the like, an energization interrupting method, a fixing device for interrupting energization using these methods, and controlling the temperature.
And an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus develops a latent image formed on a photoreceptor with toner, transfers the toner image to a transfer sheet, and passes the transfer sheet through a fixing device to fix the toner image on the transfer sheet. . The fixing device includes a cylindrical fixing roller having a heating unit, a driving mechanism for driving the fixing roller, a pressure roller, and the like. The temperature of the fixing roller is raised to a predetermined temperature by a heating element and maintained at the predetermined temperature. The transfer paper is passed between the fixing rollers, and the toner on the transfer paper is heated to be fused and fixed on the transfer paper.

In order to fix the toner image on the transfer paper, it is necessary to heat the toner to a predetermined temperature. Conventionally, a heating element such as a halogen lamp is used inside the fixing roller, and the fixing roller is heated to a predetermined temperature. Temperature. Also,
It is necessary to maintain the temperature of the fixing roller within a predetermined range so that it does not rise more than necessary.In order to maintain the temperature of the fixing roller within a predetermined value, a thermistor, a thermocouple, or the like is installed on the fixing roller, The temperature of the fixing roller is detected, and based on the detected temperature, the power supply to the heating element layer is adjusted to control the temperature of the fixing roller to be kept constant.

[0004]

However, in recent years, in order to shorten the start-up time at the start of image formation and to reduce energy consumption, a heating element capable of rapidly increasing the temperature of the fixing roller has been started. . As such a heating element, a resistance heating element is known. For example, a resistance heating element layer is laminated on an inner surface or an outer surface of a cylindrical metal conductive substrate, and heating is performed by supplying electricity to the resistance heating element layer. In the fixing device using the resistance heating element layer, the temperature of the fixing roller rises quickly, thereby shortening the heating time and reducing the energy consumption.However, the heating speed is high, so that when the power supply is abnormal, etc. Safety measures are an important issue.

That is, a temperature fuse is provided near the fixing roller to ensure safety, and when abnormal heat generation (high temperature) is detected, the power supply to the resistance heating element layer is cut off. ing. However, since the heating speed of the resistance heating element layer is high, the responsiveness of the non-contact temperature fuse is poor, and it is not possible to follow an abnormal rise in temperature of the fixing roller, so that the cutoff of power may not be completed in time. If the determination of the temperature change is delayed as described above, the overheating of the fixing roller causes the breakdown of the insulator layer to proceed further, and causes problems such as excessive current passing, short circuit, spark generation, etc. due to the entire insulation breakdown of the heating element layer. Will occur. If the fixing roller is abnormally heated and the temperature rises, the image forming apparatus stops, and furthermore, a discharge accident, ignition, or the like may occur.

[0006] Also, in various electric circuits and the like having a heating means such as a heating element, temperature control is performed. If the circuit temperature rises excessively, a temperature change is detected immediately. Therefore, it is necessary to cut off the power supply to the heating element to minimize the damage.

[0007]

According to the present invention, a method for detecting a temperature of a heating element, a method for controlling a temperature,
The fixing device and the image forming apparatus were configured as follows.

That is, in an electric circuit having a heating element, a connection member for supplying electricity to the heating element is provided, and the connection member is constituted by a joining member in which at least two kinds of metals are joined, and the heat generated in the joining member is provided. The temperature detection method was configured by measuring the electromotive force and detecting the temperature based on the measured value.

Further, the joining member constitutes a temperature detecting method by using a connection terminal made of a first metal, and a conductive adhesive containing a second metal for connecting the heating element and the connection terminal. did.

In an electric circuit having a heating element,
Two connecting members for supplying electricity to the heating element are provided, the connecting members are formed of a joining member in which at least two kinds of metals are joined, and a thermoelectromotive force generated in the joining member is measured. The energization interruption method was configured to interrupt energization based on the value.

[0011] The connection member is constituted by a connection terminal made of a first metal and a conductive adhesive containing a second metal for connecting the heating element and the connection terminal.

[0012] Two connection terminals are provided, and a potential difference of the thermoelectromotive force between the two connection terminals is measured, and the power supply is cut off based on the measured value.

In a fixing device provided with a fixing roller having a heating element, connecting members for energizing the heating element are provided at both ends of the fixing roller, and the connecting member has at least two connecting members.
A measuring unit configured to measure a difference in thermoelectromotive force generated between the joining members provided at the both end portions, based on a measurement value measured by the measuring unit. The fixing device is configured to include an energization interrupting unit that interrupts energization to the heating element.

In a fixing device provided with a fixing roller comprising a base and a heating element provided on the base, the base is formed by bonding at least two kinds of metals, and heat generated between the two kinds of metals is formed. Provision of measuring means for measuring the electromotive force,
The fixing device is configured to include a control unit that controls the temperature of the fixing roller based on the measurement value measured by the measurement unit.

A photoreceptor for forming a latent image, a developing device for developing the latent image with a developer to form a toner image, a transfer device for transferring the toner image to transfer paper, and an image comprising the fixing device described above A forming apparatus was configured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fixing device according to the present invention will be described.

FIG. 8 shows an image forming apparatus. As shown in FIG. 8, the image forming apparatus 200 includes a scanner unit 20 for reading a document, a control unit 22 for controlling and processing image formation, an image forming unit 24 for printing an image on a sheet, an exposure unit 44, The paper feed unit 26 supplies paper to the forming unit 24, a fixing device 28 for fixing an image to transfer paper, a paper discharge unit 30 for discharging a document, and the like.

The scanner unit 20 has a glass plate on the upper surface, and when an original is placed on the glass plate and the operation switch is turned on,
The reading lamp moves to read the original. The original is read as a digital signal, and the read image signal is sent to the control unit 22. In the case of copying, an image signal is sent from the control unit 22 to the image forming unit 24, the image is transferred to a transfer sheet from the sheet feeding unit 26, and fixed by the fixing device 28 to form an image.

The image forming section 24 includes a charger 41, a photosensitive member 42, an exposing device 44, a developing device 46, a transfer portion 43,
The image forming apparatus includes a separating unit 45, a cleaning unit 48, and the like, forms an image from the transmitted image signal, and forms a toner image on a transfer sheet from the sheet feeding unit 26.

The photosensitive member 42 includes a drive motor and the photosensitive member 4.
An encoder or the like (both not shown) for detecting the rotation phase of the image sensor 2 is uniformly charged by the charger 41 while rotating, and is then exposed to light by the exposure device 44 to form an electrostatic latent image on the surface. To form

The exposure unit 44 includes a laser, a polygon mirror, an optical system (not shown) such as an f-θ lens, and the like. The laser beam emitted from the laser is
The light is reflected by a polygon mirror, and is irradiated on the surface of the photoconductor 42 via an optical system such as an f-θ lens. The main scanning of the laser beam is performed by the rotation of the polygon mirror,
The sub-scan is performed by the rotation of. The formed electrostatic latent image is visualized by the toner in the developing device 46.

The toner on the photoreceptor 42 is transferred onto transfer paper by a transfer unit 43, and the transfer paper is separated from the photoreceptor 42 by a separation unit 45 and sent to the fixing device 28. The toner remaining on the surface of the photoreceptor 42 without being transferred to the transfer paper is removed and collected by the cleaning unit 48.

The transfer paper separated from the photoreceptor 42 is sent to the fixing device 28, where the pressure and heat are applied by the fixing roller 4 and the pressure contact roller 4 'which is pressed against the fixing roller 4 and is driven to rotate. Is fixed to the toner image.

Next, the fixing device 28 will be described. The fixing device 28 is a device that heats the toner and fixes it on the transfer paper. The fixing roller 4, the pressure contact roller 4 ′, the driving mechanism (not shown), the resistance heating element layer 10, the power cutoff system, the temperature difference It comprises a detection system, a detection system for a non-conductive normal body of a resistance heating element, an energization cutoff drive system, and the like.

As shown in FIG. 4, the fixing roller 4 includes a conductive base 6, an insulating layer 8, and a resistance heating element layer 10 from the outer periphery.
The input terminals 12 are attached to both ends by a conductive adhesive 14.

The conductive substrate 6 has a cylindrical shape made of an aluminum alloy or the like, and has a surface coated with a surface layer 9 made of a releasable resin such as polytetrafluoroethylene.

The resistance heating element layer 10 is a resistor having the property of generating heat when energized, and is integrally attached to the inner surface of the conductive substrate 6 with the insulating layer 8 interposed therebetween.
The insulating layer 8 is made of a resin having excellent heat resistance such as polyimide, and the conductive layer 6 and the resistance heating element layer 10 are electrically insulated by the insulating layer 8.

The input terminal 12 is made of copper as a first metal, has a disk shape, and has a conductive adhesive 14 attached to the resistance heating element layer 10.
It is attached by. The conductive adhesive 14 has a second
And the input terminal 12 is bonded in an electrically conductive state. The joint between the input terminal 12 and the conductive adhesive 14 functions as a joint between two metals. Further, the contact terminal 16 is always in contact with the input terminal 12 rotatably.

As shown in FIG. 1, a 100 V commercial power supply is applied to the resistance heating element layer 10 from the contact terminal 16 to the input terminal 12.
Connected through. Further, a cutoff relay 15 and a temperature fuse 13 are connected in series to the power supply line, and a triac 11 for temperature control is attached to the power supply line so that the temperature of the fixing roller 4 is maintained at a predetermined temperature.

The circuit 3 is shown in FIG. The circuit 3 is a circuit that detects a temperature difference between both ends of the fixing roller 4, determines whether or not a heating abnormality has occurred based on the temperature difference, and cuts off the power supply to the resistance heating element layer 10 when the abnormality is determined. . More specifically, a temperature control and conduction block system for the resistance heating element layer 10, a temperature difference detection system for the electrode connection portion, a non-conduction state detection system for the resistance heating element,
It is composed of an energization cutoff drive system and the like.

The temperature control system includes a fixing roller 4 having a resistance heating element layer 10, a triac 11, and a temperature fuse 1.
3 and a cut-off relay 15 and the like. The resistance heating element layer 10 is connected to a commercial power supply of 100 V, the temperature is adjusted by the triac 11, and the temperature fuse 13 is activated when overheated to cut off the power supply to the commercial power supply. ing. Further, a cutoff relay 15 is connected, and is activated when a heating operation is abnormal, and cuts off commercial power.

The temperature difference detection system includes a constant voltage diode ZD.
1, ZD2, a first comparator 17, a second comparator 19,
It comprises a third comparator 21, a fourth comparator 23, an OR circuit 25 and the like.

More specifically, the resistor R2 is connected to both input terminals 12 of the resistance heating element layer 10, a resistor R2 and constant voltage diodes ZD1, ZD2 arranged in parallel in two directions are connected between input lines, and an intermediate output is provided. The point is input to the non-inverting input terminal of the first comparator 17 and the inverting input terminal of the second comparator 19, while the non-inverting input terminal of the first comparator 17 and the non-inverting input terminal of the second comparator 19 are The power is connected.

Further, the outputs of the first comparator 17 and the second comparator 19 are input to the non-inverting input terminals of the third comparator 21 and the fourth comparator 23, respectively. A predetermined voltage formed by R3 and R4 is input to the inverting input terminal of the device 23. Then, the third comparator 21 and the fourth comparator
The output of the comparator 23 is input to the OR circuit 25.

The system for detecting the non-conduction state of the resistance heating element layer 10 includes a fifth comparator 27, a sixth comparator 29, and an OR circuit 31. The non-conducting state detection system takes out the voltage between both ends of the triac 11, and inputs the respective output terminals to the inverting input terminal and the non-inverting input terminal of the fifth comparator 27 and the sixth comparator 29, respectively. The outputs of the fifth comparator 27 and the sixth comparator 29 are input to the OR circuit 31.

The power supply cutoff drive system at the time of an abnormality is an AND circuit 3
3, an FF circuit 35, a driving transistor 37, a coil 39 of the cutoff relay 15, and the like. AN
The output from the temperature difference detection system and the detection system of the non-conductive state of the resistance heating element layer 10 are input to the D circuit 33, and the output of the AND circuit 33 is input to the FF circuit 35. The FF circuit 35 is a flip-flop circuit,
The driving transistor 3 is driven by an output from the AND circuit 33.
Activate 7 When the drive transistor 37 is driven by the operation from the FF circuit 35, the drive transistor 37 energizes the coil 39 of the cutoff relay 15 and operates the cutoff relay 15 to cut off the current supply to the resistance heating element layer 10.

The paper discharge section 30 is a discharge mechanism for discharging the printed transfer paper in a predetermined state. Image forming apparatus 20
A switch unit (not shown) is installed on the upper surface of the “0”.
Inputs such as enlargement and reduction of a print image, designation of print paper, designation of the number of prints, and the like can be performed. The paper feeding unit 26 includes the control unit 2
Paper of various sizes is accommodated so as to supply a predetermined size to the image forming unit 24 in accordance with an instruction from the printer 2.

The control section 22 controls the above mechanisms to perform an image forming operation. When the image formation from the formation of the latent image to the fixing is completed, cleaning is performed, and then the next print cycle is performed. The temperature of the fixing roller 10 is measured from the thermoelectromotive force generated by the temperature control system, and is maintained at a predetermined temperature.

Next, the operation of the circuit 3 will be described.

Normally, the cutoff relay 15 is conductive, a 100 V commercial power supply flows through the resistance heating element layer 10, the temperature is controlled by the triac 11, and the temperature of the fixing roller 4 is kept constant.

Further, in the temperature difference detection system, the voltage applied to both ends of the resistance heating element layer 10 is changed to the first comparator 17 via a bidirectionally directed constant voltage diodes ZD1 and ZD2. Are input to the inverting input terminal and the non-inverting input terminal of the second comparator 19, respectively. Thereby, as shown in FIG. 2, a voltage difference around 0 V of the voltage applied to the resistance heating element layer 10 is determined. If there is no voltage difference as shown in (a) or (b) of FIG.
No ON signal is output from either the first comparator 17 or the second comparator 19.

On the other hand, if a temperature difference occurs at both ends of the fixing roller 4 for some reason, the voltage of the thermoelectromotive force at both ends differs as shown in FIG. 3 (c) or (d). Pass through the constant voltage diodes ZD1 and ZD2,
The comparator 17 or the second comparator 19 detects the signal, and one of the comparators outputs an ON signal indicating a voltage difference.
The ON signal is output to the third comparator 21 or the fourth comparator 2
3 to determine whether or not a predetermined voltage difference is satisfied. When it is determined that there is a predetermined voltage difference, the signal is sent to the OR circuit 25, and the ON signal is output from the OR circuit 25 to the AND circuit 33.

In the detection system for detecting the non-conduction state of the resistance heating element layer 10, the value at both ends of the triac 11 is equal to the value of the fifth comparator 2.
7 and the sixth comparator 29, there is a difference between the values at both ends, that is, an ON signal is output when the triac 11 is in a non-conductive state, and when there is an ON signal from any of the comparators, the OR circuit 31 is output. Outputs an ON signal to the AND circuit 33.

When both the ON signal from the detection system for detecting the non-conduction state of the resistance heating element layer 10 and the ON signal from the temperature difference detection system are input to the AND circuit 33, the signal is output to the FF circuit 3.
5 to activate the drive transistor 37. This indicates that in the temperature difference detection system, the difference between the electromotive forces at both ends of the fixing roller 4 is equal to or more than a predetermined value, and that the difference occurs when the triac 11 is in a non-conductive state. Thus, it is determined that a temperature difference has occurred. Then, the drive transistor 37 is activated, and the energization is cut off by the operation of the cutoff relay 15.

Therefore, the temperature difference between both ends of the fixing roller 4 can be immediately and reliably detected, and the power can be cut off without causing the fixing roller 4 to overheat.
Note that, in the above example, an example in which the current is cut off when the temperature is abnormal has been described. However, the present invention is not limited to this, and may be used for temperature adjustment and the like. explain.

The fixing roller 4 is formed by joining or contacting at least two kinds of metals, and in this embodiment, as shown in FIG.
And a copper inner member 7 provided in contact with the inside of the conductive substrate 6. The inner member 7 is helical and absorbs fluctuations in the inner diameter even if the inner diameter of the conductive substrate 6 changes due to a temperature change. It is configured to be in close contact with the inner surface of the conductive substrate 6. At the center of the fixing roller 4, a halogen lamp 18 as a heating element is arranged, and a temperature control system is connected.

The metal constituting the fixing roller 4 is not limited to copper and aluminum, but may be a combination of other metals. The heating element may be another heat source instead of the halogen lamp 18.

As shown in FIG. 5, a commercial power supply is connected to the halogen lamp 18 via the temperature fuse 13, the triac 11, and the like. The temperature control system includes an input terminal 5 (see FIG. 7) for contacting between dissimilar metals, a cold junction correction voltage E2, an amplifier 51, a comparator 53, and the like.

The input terminal 5 has a pair, one of which is in contact with the conductive substrate 6 of the fixing roller 4 and the other terminal 5 is in contact with the inner member 7. Then, the temperature of the fixing roller 4 rises, and the thermoelectromotive force E1 generated between the terminals 5 is sent to the amplifier 51 after adding the cold junction correction voltage E2. And
The signal is input to the comparator 53 and is compared with a predetermined reference value.
If it is determined that the value has exceeded the predetermined value, triac 1
1 to cut off the current supply to the halogen lamp 18.

As described above, when the temperature of the fixing roller 4 continuously rises due to the heating of the halogen lamp 18, the thermal electromotive force of the fixing roller 4 immediately rises, and the temperature rise abnormality is sensed. When the temperature exceeds the predetermined temperature and it is determined that the temperature is abnormal, the power supply to the halogen lamp 18 is cut off, so that the overheating of the fixing roller 4 can be prevented, and the stoppage of the apparatus and the accident of discharge can be prevented.

In the above example, the thermoelectromotive force E1 may be used for adjusting the temperature of the fixing roller 4 instead of cutting off the power supply.

FIG. 6 is a table showing the relationship between the temperature difference and the thermoelectromotive force of copper and aluminum based on platinum. For example, if the thermoelectromotive force is + 100 ° C., the electromotive force of copper is +0.76, and the electromotive force of aluminum is +0.76.
Since it is 0.42, a difference between the two and +0.34 volts is obtained. This value is converted into a temperature by a conversion table or the like, and the temperature of the fixing roller 4 is measured.

That is, in the examples shown in FIGS. 5 and 7, the electromotive force generated between the terminals 5 is amplified by the amplifier 51 and compared with a predetermined value by the comparator 53. If it is smaller, the triac 11 is made conductive. If it is determined that the thermoelectromotive force is large based on the values in the above table, it is determined that the temperature of the fixing roller 4 has risen to a predetermined value or more, and the triac 11 is made conductive. Cut off,
Immediately cut off the power supply to the halogen lamp 18 from the commercial power supply.

As a result, when it is determined that the temperature of the fixing roller 4 has exceeded the threshold value, the power supply to the heating element such as the halogen lamp 18 is immediately interrupted, and the heating of the fixing roller 4 is prevented.
It is possible to prevent use stoppage, discharge accident and the like.

[0055]

According to the temperature detecting method, the temperature controlling method, and the fixing device and the image forming apparatus using the same according to the present invention, a pair of terminals for detecting a thermoelectromotive force are connected between different kinds of metals constituting a fixing roller or the like. Since the temperature is detected from the generated thermoelectromotive force, the speed of temperature detection can be increased, and overheating can be prevented, and a discharge accident or the like due to overheating can be prevented. Moreover, there is no need to install a thermometer, and the number of components such as the fixing device and the image forming device can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature control circuit according to the present invention.

FIG. 2 is a graph showing voltage.

FIG. 3 is a diagram illustrating an example of a thermoelectromotive force.

FIG. 4 is a perspective view illustrating a fixing roller.

FIG. 5 is a circuit diagram showing a configuration of a temperature control system.

FIG. 6 is a table showing thermoelectromotive forces of copper and aluminum.

FIG. 7 is a perspective view illustrating a fixing roller.

FIG. 8 is a diagram illustrating an image forming apparatus.

[Explanation of symbols]

 3 Circuit 4 Fixing Roller 5 Input Terminal 6 Conductive Base 7 Inner Member 8 Insulator Layer 9 Surface Layer 10 Resistance Heater Layer 11 Triac 12 Input Terminal 13 Thermal Fuse 14 Conductive Adhesive 15 Cutoff Relay 16 Contact Terminal 17 First Comparison Device 18 Halogen lamp 19 Second comparator 20 Reading unit 21 Third comparator 22 Control unit 23 Fourth comparator 24 Image forming unit 25, 31 OR circuit 26 Paper feed unit 27 Fifth comparator 28 Fixing device 29 Sixth comparison Device 30 paper discharge unit 33 AND circuit 35 FF circuit 37 drive transistor 39 drive coil 53 comparator 200 image forming apparatus

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kenji Tanaka 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Takashi Saito 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Corporation F-term ( Reference) 2H033 AA18 AA30 AA31 AA32 AA42 BA31 BA32 BA34 BB19 BB22 CA03 CA04 CA05 CA06 CA07 CA28 CA30 CA32

Claims (8)

[Claims] In an electric circuit having a heating element, a connection member for supplying electricity to the heating element is provided, and the connection member is formed of a joining member in which at least two kinds of metals are joined. A temperature detecting method for measuring generated thermoelectromotive force and detecting a temperature based on the measured value. 2. The method according to claim 1, wherein the joining member comprises a connection terminal made of a first metal, and a conductive adhesive containing a second metal for connecting the heating element to the connection terminal. The temperature detection method according to claim 1, wherein 3. An electric circuit having a heating element, wherein two connection members for supplying electricity to the heating element are provided, and the connection member comprises a joining member in which at least two kinds of metals are joined. Measure the thermoelectromotive force generated in the member,
An energization interruption method for interrupting energization based on the measured value. 4. The connecting member comprises a connection terminal made of a first metal, and a conductive adhesive containing a second metal for connecting the heating element to the connection terminal. The method for interrupting energization according to claim 3. 5. The power supply according to claim 3, wherein two connection terminals are provided, and a potential difference of thermoelectromotive force between the two connection terminals is measured, and the power supply is interrupted based on the measured value. How to shut off. 6. A fixing device provided with a fixing roller having a heating element, connection members for supplying electricity to the heating element are provided at both ends of the fixing roller, and the connection member joins at least two kinds of metals. Measuring means for measuring a difference in thermoelectromotive force generated between the joining members provided at both ends of the heating element, and supplying electricity to the heating element based on a measurement value measured by the measuring means. A fixing device, comprising: an energization cutoff unit that cuts off power. 7. A fixing device provided with a fixing roller comprising a base and a heating element provided on the base, wherein the base is formed by joining at least two kinds of metals, and the base is formed between the two kinds of metals. And a control unit for controlling a temperature of the fixing roller based on a value measured by the measurement unit. 8. A photoreceptor for forming a latent image, a developing device for developing the latent image with a developer to form a toner image, a transfer device for transferring the toner image to transfer paper, and the transfer device according to claim 6. An image forming apparatus comprising the fixing device according to claim 7.