JPH03144681A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent an excessive rise in temperature by directly fixing a temperature detecting element to a heater lamp, and directly applying the temperature of the lamp to the temperature detecting element. CONSTITUTION:The heater lamp 40 is provided with a bimetal 100, as the temperature detecting element, so that it is directly connected to, for example, the glass part of a foil 404 positioned in the part projecting from a heat roller 41. In this case, the bimetal 100 is supported by fixing its lead terminals 101 and 101 to a base 102. In this bimetal 100, its internal contact is caused to open when the temperature of the part of the foil 404 reaches a cirtain fixed value. Therefore, supply of power to the heater lamp 40 can be securely stopped even if abnormal temperature-control occurs, by setting the operating temperature of the bimetal 100, that is, the temperature at which the contact is caused to open to a value which is slightly lower than the melting temperature of the heat roller 41. Thus, before the heat roller 41 is melted, an excessive rise in its temperature can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus such as a laser printer apparatus, which includes a fixing unit that fixes a toner image transferred onto a sheet of paper.

(Prior Art) Generally, a laser printer device is provided with a fixing unit that fixes a toner image transferred onto a sheet of paper using heat and pressure.

This type of fixing unit usually includes a heat roller that includes a built-in heater lamp, and a pressure roller that is pressed against the heat roller. As the paper passes between the pair of rollers, the toner image is fused and fixed onto the paper.

Incidentally, the surface temperature of the heat roller is checked, and the temperature is increased to maintain the temperature necessary for fixing. Furthermore, even if a failure occurs in the temperature control circuit or the like, excessive temperature rise is prevented so that the temperature of the heat roller does not exceed a certain value.

That is, as shown in FIG. 9, a temperature fuse 100 is attached to a device approximately 1.0 to 2.0 cm away from the surface of the heat roller 41. This temperature fuse lOO
When the surface temperature of the roller 41 becomes abnormally high, it is heated by heat conduction through the air, and the internal organic compound is melted.As a result, the power supply to the heater lamp 40 is cut off, and the heat roller 41 is designed to prevent an excessive rise in temperature. However, in this case, the heat conduction of air is utilized. For this reason, the error force increases by 1,
For example, if the distance between the heat roller 41 and the temperature fuse 100 deviates by just 0.1 to 0.2+u+, the temperature fuse 100 will not work even though the surface of the heat roller 41 has reached a temperature that melts. (The internal organic compound is not fused).

On the other hand, there is one in which a thermostat (bimetal) 46 is attached to the surface of the heat roller 41 via an elastic body (not shown). In this case, the thermostat 46 is in direct contact with the surface of the heat roller 41. Therefore, the surface of the roller 41 may be damaged over time, and if the thermostat 46 is lifted due to a jam of paper wrapped around the heat roller 41, the thermostat 46 may no longer function after the jam is cleared.

(Issue 8 to be solved by the invention) As mentioned above, in the past, when the temperature fuse was installed at a position approximately 1.0 to 2.0 mm away from the surface of the heat roller, the heat conduction of the air was However, since thermostats are used, there are large errors, and in the case of thermostats attached to the surface of the heat roller, there are disadvantages in that the surface of the roller may be damaged over time or it may no longer function properly after a jam has been cleared.

Therefore, this invention can reliably cut off the power to the heater lamp before the surface temperature of the roller reaches the melting temperature without damaging the surface of the rotating roller, and more reliably prevents excessive temperature rise. The purpose of the present invention is to provide an image forming apparatus that can perform

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the image forming apparatus of the present invention includes a fixing means for fixing the developer image formed on the transfer material. a pair of rotating rollers, at least one of which forms a hollow portion, and which pinches and feeds the transfer material; a heater lamp, a portion of which is provided in the hollow portion of the rotating roller; and the heater lamp. a temperature sensing element provided in contact with a protruding portion from the rotating roller; and control for preventing energization to the heater lamp by the action of the temperature sensing element when the temperature of the heater lamp exceeds a certain value. It is said to consist of means.

(Function) According to the present invention, a temperature detection element is attached directly to the heater lamp by the means described above, and the temperature of the lamp is directly applied to the temperature detection element, so that an excessive rise in temperature can be reliably prevented. is possible.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

5 to 8 show an image forming apparatus according to the present invention, taking a laser printer as an example.

This laser printer device is connected to a host device (not shown), which is an external output device such as a computer or a word processor, via a transmission controller such as an interface circuit. When it receives a print start signal from the host device, it starts image forming operation,
The image is recorded on paper as a transfer material and output.

In FIGS. 5 to 8, the device main body 1 has an open portion 1a on its upper surface. Further, a main control board (engine control board) 2 is arranged in the center of the main body 1 of the apparatus. An electrophotographic process unit 3 for forming images is arranged behind the main control board 2. Furthermore, at the front lower part of the main body 1, there are a plurality of control boards for adding functions (printer control boards) 4. A control board accommodating section 5 for accommodating..., and a paper ejection section 6 for ejecting paper on which images have been recorded are formed at the front upper part.

Control board for adding functions 4. Up to three sheets can be installed depending on the degree of addition of functions (for example, adding 4 types of fonts, kanji, etc.).

Furthermore, a plurality (for example, three) of IC card connectors 16 are disposed on the front edge of the function-adding control board 4 located at the bottom of the control board accommodating section 5, and can be used as a storage medium. By inserting an IC card 17, further functions can be added.

The IC card 17 is a nonvolatile memory, for example, a static RAM with battery backup.

It is composed of E2 PROM, EPROM, Aiha mask ROM, etc. These IC cards 17
For example, character fonts, emulation programs, etc. are included in gaw.

On the other hand, two interfaces (not shown) are disposed on the left end surface of the control board 4 for adding functions located at the lowest stage of the control board accommodating section 5, and these interfaces are connected to the opening 18 of the device main body 1. It is located opposite to.

Also, a large number of sheets of paper P are located at the lower part of the main body 1 of the apparatus.

... constitutes a cassette storage section 8 that stores a paper feed cassette 7 that can be stored therein. The paper feed cassette 7 is inserted into and attached to the cassette accommodating portion 8 from the front lower part, and is detachable in the direction shown by the arrow.

The paper ejection section 6 consists of a recess formed one step lower on the front upper surface of the apparatus main body 1, and the front edge thereof has a rotatable hole that can be folded into the paper ejection section 6 or unfolded as shown in the figure. A paper discharge tray 9 is provided. A substantially U-shaped notch 9a is formed at the center of the front end of the paper ejection tray 9, and an auxiliary paper ejection tray 10 that can be housed or unfolded is provided in this cutout 9a. This allows the size of the paper discharge tray 9 to be adjusted according to the size of the paper to be discharged.

Left crushing section 1b of the apparatus main body 1 located on the left side of this paper discharge section 6
An operation panel 14 is provided on the top surface, and a manual feed tray 1 for manually feeding paper is provided on the rear side of the device main body 1.
5 is provided.

The operation panel 14 is provided with a liquid crystal display that displays the number of sheets, mode, guidance messages, etc., an LED display that lights up and displays various statuses using light emitting diodes, and switches that instruct various operations. There is.

The above LED display indicates whether or not it is connected to an external device (for example, a host device), that is, "online" indicating online/offline mode, and "17431 image transfer" indicating that the device main body 1 is in an operable state. It is composed of the following indicators: ``Data'' to indicate that the vehicle is in operation, ``Operator'' to request an operator call, ``Service'' to request a service call, and ``Mode'' to indicate auto/manual.

The switches include, for example, a menu key, a value key, a numeric keypad, and the like. The above menu key is composed of two keys, "Next item j" and "Previous item", and the multiple menu information displayed on the left half of the liquid crystal display is incremented each time the "Next item" key is pressed. Also, each time the "previous item" key is pressed, the value is decremented. These display operations are cyclically repeated in response to key operations. The above value key also consists of two keys, "Next Item" and "Previous Item", and each time you press the "Next Item" key, multiple pieces of value information corresponding to the menu information displayed on the left half of the LCD display are displayed. The value is incremented by 1, and decremented each time the ``previous item'' key is pressed. These display operations are also cyclically repeated in response to key operations.

Therefore, the operator selects the desired operation by operating the menu keys and value keys, and
It is possible to give instructions.

Next, electrophotographic processes such as charging, image exposure, development, transfer, peeling, cleaning, and fixing will be explained. In other words, approximately in the center of the unit housing section,
A drum-shaped photoreceptor 20 serving as an image carrier is arranged. Around the photoreceptor 20, a charging means 21 made of a scorotron, a laser exposure unit 22 that forms an electrostatic latent image in an exposure section 22a, and a magnetic brush that simultaneously performs a development process and a cleaning process are arranged around the photoconductor 20 along the rotation direction. A type developing unit 23, a transfer means 24 made of a scorotron, a memory removal means 25 made of a brush member, and a pre-exposure means 26 are arranged in this order. Of these, photoreceptor 2
0. An electrophotographic process unit 3, which is formed by integrating a charging means 21, a developing unit 23, and a memory removing means 25, is removably provided within the apparatus main body 1.

The developing unit 23 uses a two-component developer consisting of toner t and carrier C.

Further, inside the apparatus main body 1, a sheet P1 automatically fed from the sheet cassette 7 via the sheet feeding means 27 and a sheet P manually fed from the manual tray 15 are placed on the photoreceptor 20.
and the image transfer section 28 between the transfer means 24 and the paper discharge section 6.
A paper conveyance path 29 is formed that leads to.

A pair of transport rollers 30. A pair of aligning rollers 31 and a pair of conveying rollers 32 are arranged.

Further, a fixing unit 33 and a paper ejection roller unit 34 are respectively arranged on the downstream side.

A cooling fan unit 35 is provided above the location where the pair of transport rollers 32 are provided, and an aligning switch 36 is provided near the pair of aligning rollers 31.
Furthermore, a conveyance guide 37 is provided above the image transfer section 28 .

Note that a paper empty switch 320 is provided near the paper feeding means 27, and the paper empty switch 320 is installed near the paper feeding means 27.
It is designed to detect the presence or absence of Further, a manual feed switch 321 is provided near the transport roller pair 32, and a paper ejection switch 322 is provided near the paper ejection roller unit 34.

In the image forming operation, the photoreceptor 20 is first rotated by receiving a print start signal from the host device. The surface potential of the photoreceptor 20 is kept constant by the pre-exposure means 26, and the charging means 26
1 and is uniformly charged.

In this state, a laser beam a modulated in response to dot image data from the host device is emitted from the laser exposure unit 22, and is irradiated onto the photoreceptor 20. That is, by scanning and exposing the surface of the photoreceptor 20 with this laser beam a, an electrostatic latent image corresponding to the image signal is formed. This electrostatic latent image on the photoreceptor 20 is developed by the toner t in the developer magnetic brush D' of the developing unit 23, and is visualized (I (toner image)).

Meanwhile, in synchronization with this toner image forming operation, the paper P1 taken out from the paper feed cassette 7 or the manual feed tray 15
The paper P manually fed from the aligning roller pair 3
1 to the image transfer section 28. As a result, the toner image previously formed on the photoreceptor 20 is transferred onto the paper P by the action of the transfer means 24.

Next, the paper P on which the toner image has been transferred is moved to a conveyance guide 3.
The toner image is guided by the paper sheet P and sent to the fixing unit 33 through two paper transport paths, where the toner image is melted and fixed onto the paper sheet P. Thereafter, the paper P is discharged to the paper discharge section 6 via the paper discharge roller unit 34.

Note that after the toner image has been transferred onto the paper P, the residual toner t remaining on the surface of the photoreceptor 20 is electrostatically attracted and removed by a memory removing means 25 made of a conductive brush. As a result, it becomes uniformly distributed on the surface of the photoreceptor 20 and is mechanically and electrostatically absorbed by the developing unit 23.

Further, the fixing unit 33 is configured to include a heat roller 41 having a built-in heater lamp 40, and a pressure roller 42 that is pressed against the heat roller 41.

Then, as the paper P passes between these rollers 41 and 42, the toner image is fused and fixed onto the paper P.

Further, the heat roller 41 and the pressure roller 42 are surrounded by a lower casing 43 and an upper casing 44. The structure is designed to prevent heat from escaping to the outside as much as possible to ensure a favorable temperature atmosphere necessary for fixing.

A cleaner 45 is in contact with the heat roller 41,
It is kept in a clean condition to ensure good fixing at all times. The surface temperature of the heat roller 41 is checked and the temperature is controlled to maintain the temperature necessary for fixing.

Also, within the upper casing 44 and the heat roller 41
A paper guide 48 is disposed near the upstream side of the contact portion 47 between the heat roller 41 and the pressure roller 42 to ensure that the leading edge of the paper P guided to the fixing unit 33 is guided between the heat roller 41 and the pressure roller 42. It is now possible to guide you.

Further, a paper guide 49 is provided on the paper P exit side of the fixing unit 33 and is integrated with the lower casing 43 to guide the fixed paper P to the paper discharge roller unit 34.

The paper discharge roller unit 34 includes a lower roller 50 and an upper roller 51, and is provided with a static elimination brush 52 in contact with the non-image forming side of the paper P in the conveying direction.

A top cover 60 made of plastic is provided in the open portion 1a on the upper surface of the apparatus main body 1 so as to be openable and closable.
7, and the upper roller 51 of the paper discharge roller unit 34 including the static eliminating brush 52 is attached. The top cover 60 is configured to be able to rotate upward up to a maximum of about 120 degrees using a pivot 61 provided at the upper rear end of the apparatus main body 1 as a rotation fulcrum.

When the top cover 60 is rotated upward, the upper roller 51 including the transfer means 24, the conveyance guide 37, and the static elimination brush 52 is pulled out from the open portion 1a of the apparatus main body 1. As a result, most of the paper transport path 29 and most of the equipment in the electrophotographic process unit 3 facing the paper transport path 29 are exposed. Therefore, it is possible to easily and efficiently perform work to remove paper P when it becomes clogged, as well as maintenance, inspection, and replacement work for each of the above-mentioned devices.

Further, the rear cover 64 of the apparatus main body 1 can also be opened and closed via a support shaft 65 to open the starting end side of the paper transport path 29, that is, the curved transport section that guides the paper P taken out by the paper feed means 27. It is now possible to do so. therefore,
Paper P stuck in this area can also be easily removed.

Note that the ozone filter 62 is for removing generated ozone, and the toner cartridge 63 is for storing toner t for replenishment.

FIG. 1 shows the configuration of the fixing temperature excessive rise prevention device, that is, it shows the heat roller 41 of the fixing unit 33 taken out.

That is, the heat roller 41 is hollow and rotated while contacting a pressure roller 42 (not shown).
It has become. The heater lamp 4o for heating the roller 41 is arranged in the hollow portion of the heat roller 41. This heater lamp 4o has a power supply electrode 40. .

40, so as not to rotate.

The heater lamp 40 has a structure in which a shell 40□, a heating filament 4o3, and a shell 4o4 are provided in this order inside a glass tube, and the filament 40. A portion of the heater lamp 40 corresponding to the above is accommodated within the heat roller 41.

That is, the electrodes 4 for power supply are provided at both ends of the heater lamp 40.
0+ and 401 are respectively provided, and a heat generating filament 403 is provided in the portion accommodated in the heat roller 41.
is arranged, and a filament 40i and an electrode 40 are placed at both ends of the filament 40i.
Hakus 40 □ and 404 are provided for connecting to +. Note that the frames 402 and 404 are fixed by pressure contact by squeezing the glass tube at that portion.

For the heater lamp 40 having such a configuration, for example, a heater lamp 4 located at a protruding portion from the heat roller 41 is provided.
A bimetal 100 as a temperature sensing element is provided in direct contact with the glass portion 04. In this case, the bimetal 100 has its lead terminals 101, 101 connected to the base 1.
It is supported by being fixed to 02.

This bimetal 100 is Haku 40. When the temperature of the part reaches a certain value, the internal contacts are turned off. Therefore, by setting the operating temperature of the bimetal 100, that is, the temperature at which the contact is turned off, to a value slightly lower than the melting temperature of the heat roller 41, even if an abnormality occurs in temperature control, the heater can be reliably turned off. It is possible to prevent the lamp 40 from being energized, and to prevent the temperature of the heat roller 41 from rising excessively before it is melted.

FIG. 2 shows a connection circuit for supplying a current to the heater lamp 40. As shown in FIG.

This connection circuit includes power plug 20 OS power switch 20
1, SSR (solid state relay) 202, bimetal 100. and a heater lamp 40 are connected in series.

In the connection circuit having such a configuration, the power switch 20
1 is turned on and the 5SR 202 is turned on by a DC control circuit (not shown), the filament 40.1 in the heater lamp 40 is turned on. energization starts. and,
As the filament 403 generates heat, the heat roller 41 is heated. In this case, heat roller 4
The surface temperature of No. 1 is controlled by the above-mentioned DcfRtlJ circuit so that it becomes the required temperature for fixing σ.

Here, for example, the above DC control circuit or 5SR20
2 fails and continues to remain on, the surface of the heat roller 41 becomes so high that it begins to melt.

However, the temperature of the tube wall of the heater lamp 40 rises faster than the surface temperature of the roller 41. Therefore, the bimetal 100 that is in direct contact with the heater lamp 40 is heated to the same temperature as the tube wall temperature of the heater lamp 40, so the temperature increases before the surface temperature of the heat roller 41 reaches the melting temperature. It becomes a state of excessive rise. When this temperature exceeds the temperature determined by the material,
The contacts inside bimetal 100 are turned off. Then, the power supply to the heater lamp 40 is cut off, and a further rise in the surface temperature of the heat roller 41 is prevented.

As described above, the mounting position of the bimetal in this embodiment satisfies the following relationship. For this reason, with conventional installation, there are variations in the relative positional relationship with the heat roller for each device, and there is also a difference in the speed of temperature rise between the tube wall temperature of the heater lamp and the surface temperature of the heat roller. This problem can be eliminated.

In other words, abnormal temperatures can be quickly picked up by the bimetal without variations between devices. Therefore, it is possible to reliably shut off the circuit before the temperature rises excessively, and to prevent the supply of electricity to the heater lamp, making it possible to more reliably prevent melting of the surface of the heat roller. It is.

Further, the bimetal is attached to the tube wall of the heater lamp located outside the heat roller. Therefore, the surface of the heat roller will not be damaged or its installation will not be displaced due to paper jams.

Furthermore, by attaching a bimetal to the tube wall of the heater lamp located outside the heat roller, the surface temperature of the heat roller is lower than the inner wall temperature and, when properly controlled, is higher than the temperature rating of commercially available bimetals. The temperature is also low, so the bimetal internal contacts will not be accidentally turned off during normal operation.

In the above embodiment, the bimetal is attached to the tube wall of the heater lamp. However, the present invention is not limited to this. For example, the bimetal may be housed in a glass tube and the bimetal and the heater lamp may be integrated. It may be configured as follows. In this case, as shown in FIGS. 3 and 4, a wire 40□, a heating filament 403, a heat generating filament 403, a wire 404, a bimetal 100, and a / electrode 40+, 4
01 is provided to constitute the heater lamp 40a. According to such a configuration, the heater lamp 40a can be handled as a single component, so in addition to the above-mentioned effects, assembly and replacement work can be performed easily and efficiently. be.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, electricity to the heater lamp is reliably cut off before the surface temperature of the roller reaches the melting temperature without damaging the surface of the rotating roller. Accordingly, it is possible to provide an image forming apparatus that can more reliably prevent excessive temperature rise.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the fixing temperature overrise prevention device according to the present invention, FIG. 2 is a circuit diagram showing an example of the connection of an energizing circuit that energizes a heater lamp, and FIGS. 4 shows another embodiment of the present invention, FIG. 3 is a configuration diagram of a fixing temperature excessive rise prevention device, FIG. 4 is a circuit diagram of an energizing circuit, and FIG. 5 is an external perspective view of a laser printer device. , FIG. 6 is a configuration diagram, FIG. 7 is an enlarged view of a part of the configuration, FIG. 8 is a perspective view showing the top cover in an open state, and FIG. 9 is a diagram showing the prior art. It is a figure shown in order to explain the problem. 33... Fixing unit (fixing means), 40... Heater lamp, 401... Power feeding electrode, 402°404.
...Haku, 40. ...Heating filament, 41...
・Heat roller, 42... Pressure roller, 100...
Bimetal (temperature sensing element), 200...power plug, 202...SSR.

Claims (2)

[Claims] (1) In an image forming apparatus equipped with a fixing means for fixing a developer image formed on a transfer material, a pair of rotating rollers, at least one of which forms a hollow portion, pinches and feeds the transfer material; A heater lamp, a part of which is provided in a hollow portion of the rotating roller; a temperature detection element provided in contact with a protruding portion of the heater lamp from the rotating roller; An image forming apparatus characterized in that the image forming apparatus further comprises a control means that prevents energization of the heater lamp by the action of the temperature detection element when the temperature exceeds the temperature. (2) In an image forming apparatus equipped with a fixing means for fixing a developer image formed on a transfer material, a pair of rotating rollers, at least one of which forms a hollow portion, pinches and feeds the transfer material; A heater lamp, a part of which is provided in the hollow portion of the rotating roller, and a bimetal provided in contact with the protruding portion of the heater lamp from the rotating roller, and when the temperature of the heater lamp exceeds a certain value. an image forming apparatus characterized in that the image forming apparatus further comprises a control means for blocking energization of the heater lamp by turning off an internal contact of the bimetal.