JPH05341677A - Heat exhaust device for fixing device - Google Patents

Abstract

PURPOSE:To prevent the abnormal rising of a temperature in a machine by discharging heat generated from a fixing device outside a machine by means of a natural convective heat exhausting means. CONSTITUTION:A heat correcting plate 20 provided on the upper side of the fixing device 1, is constituted in such a manner that a large number of heat exchange fins (heat collecting fins) are extended in the axial direction of a fixing roller, on the inner surface of a duct-like heat collecting plate main body 21, and a part of a heating pipe 22 is buried. On standby, a heat exhaust fan 8 is stopped, and an air guide 24 is not operated, but a shutter 25 is opened, so that heat radiated from the fixing device on standby, is collected, transferred to a radiating plate 23 via the heating pipe 22, quickly and to air by a radiating fin 26, and discharged to the outside of the machine through a louver 9, by convection. During a copy, a heat exhausting fan 8 is operated, and the air guide 24 is jumped up to a chain line position, so that the heat radiated from the fixing device 1, is discharged to the outside of the machine by both of the heat exhausting fan 8 and a natural convection means composed of the heat collecting plate 20, the heating pipe 22 and the radiating plate 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exhaust device for a fixing device of a dry electrophotographic copying machine.

[0002]

2. Description of the Related Art A heat roller fixing device 1 which is widely adopted as a fixing device of a dry electrophotographic copying apparatus whose schematic overall configuration is illustrated in FIGS. 7 and 8 is in contact with a fixing roller 3 having a heater 2 therein. Although it is composed of the pressure roller 4, the heat capacity of the fixing roller 3 is increased in order to reduce the temperature change of the fixing roller 3 at the time of copying and to shorten the waiting time. To be maintained,
The built-in heater 2 is on / off controlled. Therefore, the heat is transferred from the surface of the fixing roller 3 to the surroundings even during standby, and if left unattended, the parts in the machine, for example, the photoconductor 12 are greatly damaged, and the toner in the developing device 13 and the cleaning device 14 is melted. As a result, the developing device and cleaning device do not work properly.

Therefore, conventionally, an electrophotographic copying machine is provided with an exhaust heat fan 8 having an exhaust capacity sufficient to exhaust heat during copying, and the fixing fan 1 is operated during copying and during standby. The hot air is exhausted from the louver 9 provided on the rear cover 10 through the duct 5 provided above the duct, the exhaust hole 6 provided on the rear side plate, and the duct 7, so that the temperature inside the machine is kept below a predetermined temperature. It was

However, at the time of copying, since the original is exposed,
The large-capacity exposure lamp is turned on, and the amount of heat generated is greatly increased. Therefore, it is wasteful to continuously operate the exhaust heat fan even while it is on standby, and the capacity is set according to the amount of heat generated during copying, and the noise of the fan becomes annoying when the copier is not used. there were.

In order to solve this point, Japanese Patent Laid-Open No. 3-81
In Japanese Patent No. 783, the rotation speed of the exhaust heat fan is variable, the rated exhaust capacity is exhausted during copying, and the rotation speed of the exhaust heat fan is changed according to the temperature measured at a predetermined point in the machine during standby. There is disclosed a cooling device for an image forming apparatus in which the exhaust amount is changed.

However, in this cooling device, the number of rotations of the fan is made variable, the number of rotations is automatically changed according to the temperature inside the machine, and the structure for rotating at a low speed during standby becomes complicated, so that the cost only rises. However, at the noise level of modern offices, the sound at times other than the copying operation, such as the above-mentioned wind noise of a small fan, has become a problem. In addition, when the exhaust heat fan is operated, an air flow is generated inside the machine, which causes dust inside the machine to be carried along with the air flow, collecting dust in the corners of the machine with a slow flow velocity, and the fan operating time is long. Therefore, the dust collection effect is also increased, and the cleaning interval must be shortened and shortened. Further, various gases in the room (for example, cigarette smoke, chemical gas, etc.) may cause troubles in the image forming system, and sometimes shorten the life of the photoconductor.

[0007]

SUMMARY OF THE INVENTION The present invention is simple in view of the above-mentioned drawbacks of the conventionally implemented or proposed heat discharging method for heat generated from a heat roller fixing device of an electrophotographic copying machine during standby. An object of the present invention is to provide a heat exhausting device having a configuration capable of exhausting heat generated from a fixing device during standby without producing a sound or creating an air flow in the entire machine.

[0008]

In order to solve the above problems, the present invention has an exhaust heat fan as a means for radiating the heat generated from the fixing device, and has a fixing device which requires exhaust heat during standby. In the heat exhaust device of the fixing device of the electrophotographic copying machine,
A heat collecting plate provided to cover the upper portion of the fixing device, a heat pipe for guiding the heat collected by the heat collecting plate to the vicinity of the heat exhaust opening provided in the outer cover of the copying machine, and a heat pipe for carrying the heat. A natural convection heat discharging means having a heat radiating plate for radiating heat and a means for switching between promotion and prevention of formation of natural convection for discharging the heat radiated from the heat radiating plate to the outside of the machine through the heat exhaust opening is provided. It is characterized by

[0009]

With the above structure, during copying, the heat generated from the fixing device is exhausted to the outside of the machine by the exhaust heat fan and the natural convection heat exhausting means of the present invention having a sufficient air volume as in the conventional case, so that the temperature inside the machine is kept low. It does not rise abnormally.

Further, during standby, the heat generated from the fixing device is collected by a heat collecting plate provided over the upper part of the fixing device, and is transferred to the heat radiating plate without delay by the heat pipe and is naturally convected from the heat radiating plate to the exterior cover of the outer cover. The paper is ejected out of the machine through the paper ejection opening. Therefore, the wind noise that occurs when exhausting heat with the exhaust heat fan does not occur, and the environment is kept good. The above-mentioned natural convection formation range is only in the vicinity of the range reaching the heat dissipation opening, and since means for switching between promotion and prevention of natural convection is provided, unnecessary convection formation can be prevented. ..

This switching is preferably performed automatically by detecting the temperature at a predetermined position in the machine and outputting it. If the detection is performed by a thermal deformation element such as a bimetal or a shape memory alloy, it is possible to combine the functions of the actuator for temperature detection and switching operation.

[0012]

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

FIG. 1 is a diagram showing an embodiment of the present invention, and corresponds to FIG. 8 of the conventional device described above. In the apparatus of this embodiment, a heat collecting plate 20 is provided above the fixing device 1 instead of the conventional duct. Heat collecting plate 20
Is a duct-shaped heat collecting plate body 2 as shown in the cross-sectional view of FIG.
A large number of heat exchange fins (heat collecting fins) extend in the axial direction of the fixing roller 2 on the inner surface of 1, and a part of the heat pipe 22 is embedded therein.

The heat pipe 22 passes through the air exhaust holes 6 provided in the rear side plate 15, and then the other end is embedded in a heat radiating plate 23 arranged in the vicinity of the rear side exterior cover 10. As shown in the sectional view of FIG.
A plurality of heat exchange fins (radiation fins) 26 are vertically extended on the surface facing the rear cover 10 in which the main body is embedded. An opening that can be opened and closed by the shutter 25 is provided below the heat exchange fins 26 on the cover bottom plate. In this example, the shutter 25 is opened and closed by a pinion driven by a drive motor 27 and a rack. The drive motor 27 is controlled by a detection signal of a temperature at a predetermined position in the machine by a temperature detection means (not shown) so as to rotate when the temperature exceeds a certain temperature and stop when the temperature falls below the certain temperature. Above the heat sink 23, the air heated by the heat sink is used as the louver 9
An air guide 24 is provided to guide the user. The air guide 24 is capable of jumping up with its end on the louver side as a fulcrum, and in the jumped up state, exhaust air from the heat exhaust fan 8 provided above the heat dissipation plate 23 can be guided to the louver 9. It is possible. The heat exhaust fan 8 may be arranged on the lateral surface of the heat dissipation plate 23 or the like, and the air guide 24 may be fixedly provided.

During standby, the exhaust heat fan 8 is stopped, the air guide 24 is lowered to the position shown in FIG.
By opening, the heat emitted from the fixing device in the standby state is collected, is quickly transmitted to the heat radiating plate 23 through the heat pipe 22, is transmitted to the air from the heat radiating fins 26, and is transmitted to the outside of the louver 9 by convection. Is discharged.

During the copy operation, the exhaust heat fan 8 is operated,
By jumping up the air guide 24 to the position shown by the chain line in FIG. 1, the heat emitted from the fixing device 1 is exhausted by the heat exhaust fan and the natural convection heat dissipation means including the heat collecting plate 20, the heat pipe 22 and the heat dissipation plate 23. Both are discharged to the outside of the machine.

The shutter 25 can be opened and closed by a pinion and a rack driven by a motor 27 that starts and stops according to a temperature detection signal at a predetermined point in the machine, as well as by using a thermal deformation element. FIG. 4 is a diagram showing an example thereof, in which the shutter 25 is pivotally attached to one end of the opening, and the end of the arm 41 fixed to the end of the pivot shaft and one end to a predetermined temperature detection position in the machine are fixed points. A rod 42 is connected to the other end of the lever 43 which is rotated by the movement of the free end 44 due to the deformation of the shape memory alloy 45 provided by pin joining. Shape memory alloy 4
5 has a linear shape shown in the figure at a temperature equal to or lower than a predetermined temperature, and has a bow shape at a temperature equal to or higher than the predetermined temperature. Therefore, when the temperature is lower than the predetermined temperature, the shutter 25 is closed via the lever 43, the rod 42, and the arm 41, and when the temperature is higher than the predetermined temperature, the shutter 25 is opened. Therefore, the shape memory alloy acts as both a temperature detecting means and an actuator. Bimetal can also be used as the thermal deformation element.

Alternatively, the shutter opening / closing means may be moved by a solenoid 52 via an arm 51 rod 53 fixed to the pivot shaft of the shutter 25 as shown in FIG.

Further, as a convection promotion / prevention switching means, as shown in FIG. 6, the heat dissipation plate 23 is separated into a built-in portion 60 of the heat pipe 22 and a formation portion 61 of the heat radiation fin 26, and both of them are hinged 62. Both members 60 and 61 are brought into surface contact with and separated from each other at a contact surface 63 by a solenoid or the like which is coupled so as to be in surface contact with and away from each other, and at the time of contact, heat is transferred to the member 61 and air is released from the heat radiation fins. When the two members 60 and 61 are separated from each other, heat is not transferred and therefore convection does not occur.

With the above-mentioned respective configurations, when the temperature at a predetermined position in the machine rises above the predetermined temperature, convection occurs and heat is discharged to the outside of the machine, but when the temperature is below the predetermined temperature, convection does not occur and is unnecessary. It is possible to prevent heat from escaping to cause energy loss and accumulation of dust due to air flow.

In the above embodiment, the paper discharge during the copying operation is performed by both the paper discharge fan and the natural convection heat discharging means, but the natural convection heat discharging means is prevented from generating convection. It is also possible to use only the discharge fan.

After the copying operation is completed, the temperature of the members near the fixing device is rapidly lowered. Therefore, after the heat exhaust operation is performed by the heat exhaust fan and the natural convection heat exhausting means for a predetermined time, only the natural convection heat exhausting means is operated. It is better to switch to exhaust heat. When the temperature inside the machine decreases, the shutter is closed and the amount of heat transfer by the heat pipe decreases, and natural convection is prevented.

The heat may be exhausted only by the heat exhaust fan for a predetermined time after the completion of the copying operation.

[0024]

As described above, according to the present invention, the heat emitted from the fixing device can be discharged without rotating the exhaust heat fan during standby, so that noise is eliminated. Further, during standby, the air flow by the fan is eliminated, and convection is also prevented due to the decrease in the temperature inside the machine, so that the accumulation of dust due to the air flow is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a heat exhausting means of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the fixing device and the heat collecting plate of the above embodiment.

FIG. 3 is a horizontal sectional view of the heat dissipation plate of the above embodiment.

FIG. 4 is a side view showing another example of an opening / closing mechanism of a convection prevention shutter.

FIG. 5 is a side view showing still another example of the opening / closing mechanism of the convection prevention shutter.

FIG. 6 is a side view showing another example of a convection promotion / blocking switching mechanism.

FIG. 7 is a sectional view mainly showing the vicinity of a fixing device of a conventional electrophotographic copying machine.

FIG. 8 is a cross-sectional view of a heat exhausting device for heat generated from the fixing device.

[Explanation of symbols]

 1 Fixing Device 6 Exhaust Hole 8 Exhaust Heat Fan 9 Louver 20 Heat Collecting Plate 22 Heat Pipe 23 Radiating Plate 24 Air Guide 25 Shutter 26 Radiating Fin 45 Shape Memory Alloy (Heat Deformable Element)

Claims (5)

[Claims] 1. A heat discharging device for a fixing device of an electrophotographic copying machine, comprising a heat discharging fan as a heat radiating means for heat generated from the fixing device, and which requires heat discharging during standby. The heat collecting plate provided to cover the upper part, the heat pipe for guiding the heat collected by the heat collecting plate to the vicinity of the heat exhaust opening provided in the outer cover of the copying machine, and the heat carried by the heat pipe. A natural convection heat discharging means having a heat radiating plate for discharging and a means for switching between promotion and prevention of formation of natural convection for discharging heat radiated from the heat radiating plate to the outside of the machine through the heat discharging opening is provided. A heat-dissipating device for the fixing device. 2. The switching means is a shutter for shutting off an air flow due to convection, and the shutter is displaced by an actuator operated by the output of a temperature detecting means for detecting the temperature at a predetermined position in the machine. Item 15. The heat exhaust device according to item 1. 3. The heat exhaust device according to claim 2, wherein the temperature detecting means and the actuator are constituted by a thermal deformation element. 4. The control is performed such that the heat exhausting operation is performed by the heat exhausting fan for a predetermined time after completion of the copying operation, and then the heat is exhausted by the natural convection heat exhausting means. The heat exhaust device according to 1. 5. A heat discharging operation is performed by the heat exhaust fan and the natural convection heat discharging means for a predetermined time after the copying operation is finished, and then heat is discharged only by the natural convection heat discharging means. The heat exhaust device according to claim 1, wherein the heat exhaust device is controlled.