JPH10319777A - Heating device, fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device for an image forming device capable of positively detecting malfunction including breakage. SOLUTION: In usual heating operation, heating elements 8a, 8b are connected in parallel to a power circuit 11. When the presence of malfunction is detected, a switch 12 is changed over to connect the heating elements 8a, 8b in series to the power circuit 11. A control circuit judges the presence of malfunction in accordance with the detection result of a thermistor. That is, the malfunction of the heating elements, whichever, including breakage, is detected if the temperature rise is not detected by the thermistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device, and a copier, a laser beam printer and a copier equipped with the heating device.
The present invention relates to an image forming apparatus such as a micro film reader printer.

[0002]

2. Description of the Related Art Conventionally, for example, a heating device of a recording material for heating and fixing an image includes a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and pressing against the heating roller. A heat roller method of heating while nipping and conveying a recording material is often used.

[0003] In addition to this, various types and configurations of heating devices such as a flash heating system, an oven heating system, and a hot plate heating system are known and have been put to practical use.

[0004] Recently, a fixedly supported heating element, a heat-resistant film (fixing film) conveyed while being pressed against the heating element, and a pressurizing method for bringing a recording material into close contact with the heating element via the film. A fixing device having a member and a method and a configuration in which heat generated by a heating element is applied to a recording material through a film to heat and fix an unfixed image formed and carried on the recording surface material to the recording surface material ( Film heating device) has been devised and put into practical use.

In such a film heating apparatus, a heating element having a small heat capacity can be used. Therefore, it is possible to save power and shorten the wait time (quick start) as compared with the heating device of the heat roller type.

[0006]

However, the conventional film heating apparatus has a problem in that the reliability is not sufficient. For example, in a conventional film heating apparatus, when a plurality of heating elements are provided, these are usually connected in parallel to a power supply. Further, the detection of an abnormality or the like of the heating element has been performed by monitoring the temperature. Such a configuration has an advantage that even if a disconnection or the like occurs in a part of the heating element, a sufficient amount of heat can be obtained by the remaining heating elements and a predetermined temperature can be maintained. On the other hand, when an abnormality such as a disconnection cannot be detected. was there. That is, if the required heat value is more than half of the total heat value of the two heating elements, the required heat value is not reached even if the remaining power is fully energized, and the heating element is controlled to a predetermined temperature. Since the temperature cannot be maintained, a failure can be detected by monitoring the temperature change of the heating element. However, if the required heating value is less than half of the total heating value of the two heating elements, it is necessary to control the power with only normal heating elements to maintain the heating element at a predetermined temperature. Since a large amount of heat is obtained, a failure cannot be detected by monitoring the temperature change of the heating element.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heating device capable of reliably detecting an abnormality such as a disconnection and an image forming apparatus using the heating device.

[0008]

Means for Solving the Problems The present invention has been made to achieve the above object, and a first aspect is as follows.
In a heating device that generates heat by electric power supplied from a power supply circuit, a plurality of heating elements that are supplied with electric power from the power supply circuit to generate heat, and a connection relationship between the heating element and the power supply circuit is changed. Switching means, and at least two different operation modes, wherein in the first operation mode the switching means is controlled to connect each of the heating elements to the power supply circuit in parallel, and in the second operation mode, the switching means Control means for controlling means to connect at least two of the heating elements in series to the power supply circuit.

A power control circuit for controlling power supply from the power supply circuit to the heat generating element, the power control circuit being provided for each of the heat generating elements; and the switching means includes a connection relation between the power control circuit and the power supply circuit. May also be changed.

In the second operation mode, there is provided a detecting means for detecting a temperature at or near a heating element connected in series, and the control means comprises a detecting means for detecting the temperature of the detecting means in the second operating mode. It is preferable to determine a state of the heating element and / or the power control circuit based on a detection result.

The power control circuit may control the power supply by wave number control or phase control.

According to a second aspect of the present invention, there is provided a fixing device for an image forming apparatus.
A fixing device is provided, comprising: a heat transfer member that transmits heat generated by the heat generating element; and a pressing unit that presses a transfer material against the heat transfer member.

According to a third aspect of the present invention, there is provided an image forming means for forming an image on a transfer material, and a fixing method for fixing the image on the transfer material on which the image is formed by the image forming means. And an image forming apparatus.

The operation will be described.

[0015] In the first operation mode, the control means controls the switching means to connect the heating elements to the power supply circuit in parallel. On the other hand, in the second operation mode, the switching unit is controlled to connect at least two of the heating elements to the power supply circuit in series. Note that when a power control circuit that controls power supply is provided for each heating element by wave number control or phase control, the connection relationship between the power control circuit and the power supply circuit may be changed. The control means includes a second
In the operation mode (1), the state of the heating element and / or the power control circuit connected in series is determined based on the detection result of the detecting means (temperature at or near the heating element). In this case, since the heating elements to be determined are connected in series, even if only one of them is disconnected, the abnormality can be detected easily and reliably.

[0016]

Embodiments of the present invention will be described with reference to the drawings. [First Embodiment] A first embodiment of the present invention will be described with reference to FIGS.

This embodiment is a heating device used as a fixing device of an image forming apparatus of an image forming apparatus such as a copying machine or a laser beam printer.

As shown in FIG. 1, the heating device includes heating elements 8a and 8b, a film 3, a pressure roller 4, an indicator lamp 18, a control device 20, and the like.

The heating elements 8a and 8b are connected to a power supply circuit 1 described later.
The power supply 1 generates heat by receiving power from the power supply 1, and is installed on the stay 1. . In the present embodiment, the heating element 8
As a and 8b, an electric resistance material (for example, Ag / Pd (silver palladium)) is applied on the surface of the heater substrate 2 made of alumina or the like by screen printing or the like to a thickness of about 10 μm and a width of 1 to 5 mm. As the protective layer 9, a material coated with glass, fluororesin, or the like is employed.

The heating elements 8a and 8b can be controlled independently of each other by triacs 10a and 10b (see FIG. 2) described later. Further, in the present embodiment, the connection relationship between the heating elements 8a and 8b and the power supply circuit 11 can be changed as necessary.
This will be described later in detail with reference to FIG.

The film 3 is provided to prevent the recording material P from being directly pressed into contact with the stationary heating elements 8a and 8b. The film 3 is configured endlessly. The heating element 8a, 8b is externally fitted to the stay 1, and its inner peripheral surface is in contact with the heating element 8a, 8b. Note that, in order to facilitate the rotation of the film 3 in accordance with the conveyance of the recording material P, the inner peripheral length of the film 3 is somewhat larger than the outer peripheral length of the stay 1 including the two heating elements 8a and 8b (this embodiment). (About 3 mm). Therefore, the film 3
The stay 1 is loosely fitted to the stay 1 with a margin of the circumference.

In order to improve the quick start property, the film 3 preferably has a small heat capacity. Therefore, in this embodiment, the thickness of the film 3 is set to 10
0 μm or less, preferably 20 μm or more and 50 μm or less. Naturally, the film 3 needs to have sufficient heat resistance. Specific materials that can be used as the film 3 include a single layer of PTFE, PFA, and PEP, or polyimide, polyamideimide, PEEK, PFA, and FE.
A composite layer film coated with P or the like can be given. In the present embodiment, a polyimide film whose outer peripheral surface is coated with PTFE is used.

The thermistor 19 is for detecting the temperature of the heating elements 8a and 8b (or the vicinity thereof). The detection result of the thermistor 19 is A / D converted by an A / D converter (not shown),
0 is output.

The pressure roller 4 presses the separately transported recording material P to the heating elements 8a and 8b via the film 3. Between the heating elements 8a and 8b,
A nip is formed via the film 3. The pressure roller 4 is made up of a cored bar 5 and a heat-resistant rubber 6 such as silicone rubber having good releasability, and is driven from the end of the cored bar 5 by driving means (not shown). , The film 3 is also driven to rotate.

The indicator lamp 18 is for giving a warning to the user when a failure occurs. The indicator lamp 18 is configured to enter a display state at a desired time according to an instruction from the control device 20.

The control device 20 controls and controls the entire heating device. The control device 20 controls, for example, triacs 10a and 10b, a power supply circuit 11, a switch 12 (see FIG. 2), and the like, which will be described later, to thereby generate the heating elements 8a,
8b is provided with a function of controlling the energization state. Also,
As the operation mode, an operation mode (normal heating mode) for performing normal heating, the temperature of the heating elements 8a and 8b are detected based on the detection result of the thermistor 19, and an abnormality occurs based on the detection result. Operation mode (failure detection mode) for determining whether or not the operation has been performed. The control device 20 specifically includes a control program,
It is composed mainly of a memory for storing data and the like and a processor. The functions described above are realized by the processor executing a program.

The connection relationship between the heating elements 8a and 8b and the power supply circuit 11 will be described with reference to FIG.

The heating elements 8a, 8b and the like are configured so that the connection relationship with the power supply circuit 11 can be switched between a series state and a parallel state as needed. Switch 12
Are connected to the power supply circuit 11 in parallel with the heating element 8a and the triac 10a, and the heating element 8b and the triac 10b. On the other hand, in a state where the switch 12 is connected to the side, the heating element 8a, the heating element 8b and the triac 10a are connected in series to the power supply circuit 11. The switch 12 is connected to the control device 2
According to an instruction from 0, the state (/) is changed.

The "heating element" in the present invention corresponds to the heating elements 8a and 8b in the present embodiment. The “switching unit” corresponds to the switch 12 in the present embodiment (the switches 12 and 13 in the later-described embodiments 2 and 3). “Control means” refers to the control device 20
Is equivalent to The “first operation mode” is a normal heating operation mode described later. The “second operation mode” is a failure detection operation mode. “Detection means” corresponds to the thermistor 19. The “power control circuit” corresponds to the triacs 10a and 10b. The “heat transfer member” corresponds to the film 3. “Pressing means” corresponds to the pressure roller 4. The “image forming unit” corresponds to the photosensitive drum 1, the developing device 54, and the like in a fourth embodiment described later.

The operation of this embodiment will be described. (1) Normal heating mode The controller 20 sets the switch 12 to
The heating element 8a and the heating element 8b are connected to the power supply circuit 11 in parallel.

The temperature control is performed by the controller 20 adjusting the AC voltage applied to the heating elements 8a and 8b by a triac (see FIG. 2) based on the detection result of the thermistor 19 (for example, phase control, wave number control). Do. in this case,
The energization ratio of the heating element 8a is determined by the triac 10a.
The power distribution ratio of the heating element 8b is controlled by the triac 10b. When the detected temperature of the thermistor 19 is lower than a predetermined set temperature, the power supply is controlled so that the heating elements 8a and 8b increase in temperature, and when the detected temperature is higher, the heating elements 8a and 8b decrease in temperature. The temperature of the bodies 8a, 8b is kept constant during fixing.

The recording material P which carries the unfixed powder toner image in the nip between the heating elements 8a and 8b formed via the film 3 and the pressure roller 4 and thus controlled to a predetermined temperature. Is transported, the unfixed powder toner image T (see FIG. 1) on the recording material P is melted by applying heat and pressure in the nip, and is fixed on the recording material P.

The power supply to the heating elements 8a and 8b is
After the main switch of the image forming apparatus is turned on, the process starts after waiting for a print command. In a standby state waiting for a print command, the power supply to the heating elements 8a and 8b is stopped. (2) Failure detection mode The control device 20 sets the switch 12 to
The heating element 8a and the heating element 8b are connected in series to the power supply circuit 11. In this state, Triac 1
The heating element 8a and the heating element 8b are controlled collectively by 0a.

At this time, if either one of the heating elements 8a and 8b is disconnected, neither of the heating elements 8a and 8b generates heat. Therefore, the control device 20 can determine whether there is an abnormality (that is, whether the temperature is within a predetermined range) based on the detection result of the thermistor 19. If an error is detected,
The control device 20 notifies the user by an indicator lamp 18, a warning sound, and the like. At the same time, the power supply circuit 11 and the triacs 10a and 10b are controlled to prohibit (stop) energization of the heating elements 8a and 8b.

As described above, according to the heating device of the present embodiment, it is possible to reliably detect an abnormality such as disconnection. In addition, when an abnormality is detected, the safety of the device is high by automatically stopping power supply and notifying the user.

In this embodiment, the triac 10a controls the energization of the heating element during the failure detection operation.
It may be performed by the triac 10b.

In this embodiment, two heating elements are provided, but a larger number of heating elements may be provided. However,
When there are three or more heating elements, it is not always necessary to connect all the heating elements in series at a time to perform disconnection detection. At least two or more heating elements may be connected in series at least at one time and may be divided and detected several times. [Second Embodiment] In the second embodiment, not only the heating element but also the presence or absence of an abnormality in the triac can be detected at the time of the failure detection operation. To achieve this,
In this embodiment, as shown in FIG. 3, a switch 13 is newly provided. The other points are basically the same as the first embodiment. In the following, the description will focus on the differences from the first embodiment.

As shown in FIG. 3, by connecting the switch 12 and the switch 13 to both sides, the heating element 8a
And the heating element 8b are connected to the power supply circuit 11 in parallel.

By connecting the switch 12 to the
The heating element 8a and the heating element 8b are connected in series to the power supply circuit 11. Heating elements 8a, 8 at this time
When the switch 13 is connected to the side, the triac 10a performs the power control for b, and when it is connected to the side, the triac 10b performs the power control collectively. The switch 13 changes its connection state in accordance with an instruction from the control device 20 together with the switch 12.

At the time of the failure detection operation, the control device 20 controls the behavior of the detection result of the thermistor 19 when the heating elements 8a and 8b are energized by using the triac 10a, and the thermistor when the energization is applied to the heating element by using the triac 10b. 1
9 and the behavior of the detection result. If the two behaviors are different, it can be detected that one of the triac 10a and the triac 10b has failed. That is, when any one of the triacs 10a and 10b is disconnected, the heating elements 8a and 8b are used by using the triac.
No heat is generated while the power is on. Conversely, Triac 1
If any one of 0a and 10b is short-circuited,
The power control is not effective while the heating elements 8a and 8b are energized using the triac. Note that the resistance value in the case of the series connection is four times the resistance value in the case of the parallel connection, so that the calorific value is reduced to ４, and the safety is high even if the triac is short-circuited.

The point that a failure such as disconnection of the heating elements 8a and 8b can be detected is the same as in the first embodiment.

As described above, in the present embodiment, not only disconnection of the heating element, but also failure of the triac can be detected together. [Third Embodiment] The third embodiment is characterized in that the safety of the device is further improved by incorporating an overcurrent cutoff device in a circuit portion for connecting a heating element and a power supply circuit in series. Things. The other points are basically the same as the second embodiment.

As shown in FIG. 4, by connecting the switch 12 and the switch 13 to both sides, the heating element 8a
And the heating element 8b are connected to the power supply circuit 11 in parallel.

By connecting the switch 12 to the
The heating element 8a and the heating element 8b are connected in series to the power supply circuit 11. Heating elements 8a, 8 at this time
When the switch 13 is connected to the side, the triac 10a performs the power control for b, and when it is connected to the side, the triac 10b performs the power control collectively. The switch 13 changes its connection state in accordance with an instruction from the control device 20 together with the switch 12.

The normal heating operation and the failure detection operation are basically performed in the same manner as in the second embodiment. However, at this time, the triac 10a or the triac 1
If either one of 0b is completely short-circuited, the overcurrent cutoff device 14 operates and the heating elements 8a and 8b do not generate heat.

The heating elements 8a, 8
b when the power applied to the overcurrent interrupter 1 is large.
4 is activated.

The heating element 8 is short-circuited by about half and
When the power applied to a and 8b is small, a failure can be detected as in the second embodiment. That is, a failure can be detected based on a difference in behavior between when the heating elements 8a and 8b are energized using the triac 10a and when the heating elements 8a and 8b are energized using the triac 10b.

As described above, in this embodiment, the safety of the device when the triac is short-circuited due to a failure is as follows:
It is higher than in the second embodiment. [Fourth Embodiment] This embodiment is an image forming apparatus provided with the heating device of the first embodiment as the fixing device 57.

As shown in FIG. 5, the image forming apparatus includes a photosensitive drum 51, a charging roller 52, a laser exposure device 53,
The image forming apparatus includes a developing device including a developing sleeve, a developing blade, a one-component magnetic toner, a cleaning blade 55, a transfer roller 56, and a fixing device 57.

The image forming operation will be described.

A toner image is formed on the photosensitive drum 51 by a well-known electrophotographic process using a charging roller 52, a laser exposure device 53, a developing device 54 and the like. On the other hand, in parallel with this, the transfer material is fed from the cassette 58 by the feed roller 59, the rollers 60, 61, and the like. Then, the transfer roller 56 transfers the toner image to the transfer material. The transferred toner image is thereafter transferred to the fixing device 5.
7. And finally, roller 6
The sheets 2 and 63 are discharged to a sheet discharge tray 65. In addition,
It is needless to say that the same effect can be obtained even if the heating device according to the second or third embodiment of the present invention is applied to the image forming apparatus according to the present embodiment.

The application of the present invention is not limited to the image forming apparatus. The present invention can be generally applied to a heating device having a plurality of heating elements.

[0053]

As described above, according to the present invention, abnormalities of the heating element and the power control circuit can be reliably detected. A fixing device and an image forming apparatus using such a heating device have high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a connection relationship between a power supply circuit and a heating element.

FIG. 3 is a circuit diagram showing a connection relationship between a power supply circuit and a heating element according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a connection relationship between a power supply circuit and a heating element according to a third embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating an outline of an image forming apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stay 2 Heater board 3 Film 4 Pressure roller 5 Core metal 6 Heat resistant rubber 8a, 8b Heating element 10a, 10b Triac 11 Power supply circuit 12, 13 Switch 14 Overcurrent cutoff device 18 Indicator lamp 19 Thermistor 20 Control device 57 Fixing device T Toner P Recording material

Claims (6)

[Claims] 1. A heating device for generating heat by electric power supplied from a power supply circuit, comprising: a plurality of heating elements that are supplied with electric power from the power supply circuit to generate heat; Switching means for changing a connection relationship; and at least two different operation modes, wherein in the first operation mode, the switching means is controlled to connect each of the heating elements to the power supply circuit in parallel. And a control means for controlling the switching means in a mode to connect at least two of the heating elements to the power supply circuit in series. 2. A power control circuit for controlling power supply from the power supply circuit to the heating element, the power control circuit being provided for each of the heating elements, wherein the switching unit switches between the power control circuit and the power supply circuit. The heating device according to claim 1, wherein the connection relation is also changed. 3. A detecting means for detecting a temperature at or near a heating element connected in series in the second operation mode, wherein the control means detects the temperature in the second operation mode. The heating device according to claim 1, wherein a state of the heating element and / or the power control circuit is determined based on a detection result of the means. 4. The heating device according to claim 2, wherein the power control circuit controls the power supply by wave number control or phase control. 5. A fixing device for an image forming apparatus, wherein: the heating device according to claim 1, 2, 3, or 4, a heat transfer member that transfers heat generated by the heating element, and a transfer material to the heat transfer member. And a pressure unit for pressing the fixing device. 6. An image forming means for forming an image on a transfer material, and the fixing device according to claim 5, which fixes the image on the transfer material on which an image has been formed by the image forming means. Characteristic image forming apparatus.