JPH08202185A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To alleviate the deviation of the temperature distribution of the heating roller due to the cooling fan disposed on the side of the heating roller type fixing device. A rotation direction switching means for switching the rotation direction of a fan, which is disposed at one end side of the fixing device and is provided for cooling the periphery of the fixing device, and can rotate the rotation direction of the fan, and this rotation. By providing a fan control unit for periodically controlling the switching operation of the direction switching unit and periodically switching the rotation direction of the fan 28, even if the fan 28 is present, only one end side of the heating roller 24 is heated. The configuration is such that the unevenness of the temperature distribution in which only the other end side has a lower temperature can be mitigated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a facsimile machine equipped with a heat roller type fixing device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a facsimile machine in which toner is adhered to recording paper by a transfer device to form an image and then the toner is fixed on the recording paper by a fixing device. Heat roller having a built-in heater for heating the toner of the recording sheet, and a pressure roller that contacts the heating roller and rotates with the heating roller to press the toner of the recording sheet while sandwiching and conveying the recording sheet. There are many methods.

More specifically, a heat lamp such as a halogen lamp having a length corresponding to the axial length of the heating roller is inserted as a heater inside the heating roller. This heat lamp is a temperature (fixing temperature) required for the heating roller to heat and melt the toner on the recording paper.
It is for heating to. Therefore, when a current is applied to the heat lamp from the power source, heat is generated and the heating roller is heated over the entire axial direction. In this case, the heat lamp is configured to have a uniform heat generation distribution over the entire axial direction, and is set to uniformly heat the heating roller over the entire axial direction. Further, the heat lamp is usually intermittently energized and controlled so that the fixing temperature of the heating roller always falls within the required temperature range.

By the way, when such a heat roller type fixing device is used, heat is generated by the heater, and when this heat stays inside the main body of the facsimile machine or the like, other heat is generated inside the main body of the apparatus. It adversely affects process equipment. For this reason, as shown schematically in FIG. 6, in a facsimile apparatus using the heat roller type fixing device 1, generally,
By providing the dedicated fan 2 and discharging the heated air around the fixing device 1 to the outside of the apparatus main body 3, the fixing device 1
The heat generated by the heating roller 4 is not stored inside the apparatus main body 3. In FIG. 6, reference numeral 5 is a slit formed in the casing 6 of the apparatus main body 3 at both side positions corresponding to the fixing device 1.

[0005]

If such a fan 2 is provided on the conveying path of the recording paper, the conveyance of the recording paper is hindered. Therefore, normally, as shown in FIG. Is disposed on one end side of the. Therefore, when the fan 2 is driven, the heated air inside the apparatus main body 3 is directed toward the fan 2 along the axial direction of the fixing device 1 as indicated by an arrow in FIG. It will flow. As a result, in the heating roller 4 of the fixing device 1, the temperature on the end side near the fan 2 (left side in the figure) becomes higher than the temperature at the center part, and the end side far from the fan 2 (in the figure). , The temperature on the right side) is lower than the temperature in the central part.

That is, the temperature of the heating roller 4 which should be uniformly controlled over the entire axial direction is greatly different between the left end side, the central part and the right end side due to the influence of the fan 2. Due to the influence of such a non-uniform temperature distribution in the axial direction of the heating roller 4, the fixing property of the toner on the recording paper is different between the left end side, the central part and the right end side of the heating roller 4, and
Wrinkles are generated on the recording paper passing through the fixing device 1 (especially, wrinkles are likely to be generated on the side of the high temperature region near the fan 2).

[0007]

According to the first aspect of the present invention,
An image forming apparatus in which toner is adhered onto recording paper by a transfer device to form an image, and then the toner is fixed onto the recording paper by a fixing device equipped with a heating roller, for monitoring the fixing temperature of the fixing device. A temperature sensor, a heating control means for intermittently heating and controlling the heating roller based on sensor information of the temperature sensor, and a forward / reverse rotation provided at one end of the fixing device to cool the periphery of the fixing device. A fan, rotation direction switching means for switching the rotation direction of the fan, and fan control means for periodically controlling the switching operation of the rotation direction switching means.

According to a second aspect of the invention, the fan control means in the first aspect of the invention is a fan control means for periodically controlling the switching operation of the rotation direction switching means based on the sensor information of the temperature sensor. Is.

[0009]

In the image forming apparatus according to the first aspect of the invention, heating control of the heating roller of the fixing device is performed by the temperature sensor and the heating control means, and the heating temperature is controlled to a desired fixing temperature. On the other hand, a fan is also driven in order to cool the periphery of the fusing device that generates heat, but this fan is freely reversible, and the rotation direction switching means and fan control means periodically switch the rotation direction of the fan to drive it. Therefore, the air flow by the fan arranged on one end side in the axial direction of the fixing device is periodically switched in the axial direction of the fixing device, so that only one end side of the heating roller has a higher temperature and only the other end side. The deviation of the temperature distribution, which causes a lower temperature, is alleviated, and as a whole, the fixing temperature of the fixing device is substantially uniformed in the axial direction. Therefore, uniform fixability is obtained, and the occurrence of wrinkles is suppressed.

In the image forming apparatus according to the second aspect of the present invention, the rotation direction of the fan is switched periodically based on the sensor information of the temperature sensor for monitoring the fixing temperature of the fixing device. The rotation direction can be properly switched by a simple control system.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The present embodiment is applied to, for example, a facsimile machine 11 as shown in FIG. 2 as an image forming apparatus. First, a schematic configuration of the facsimile machine 11 will be described. The fax machine 11 includes a scanner unit 12 and a printer unit 13. The scanner unit 12 performs a reading operation on a document (not shown) inserted through an insertion port 15 formed on a part of the upper surface of the apparatus body 14.

The printer unit 13 uses a well-known electrophotographic process, and is mainly composed of a drum-shaped photoconductor 16 and process devices arranged around the photoconductor 16 in the order of processes. . As these process devices, for example, based on the received image signal, the photoconductor 16
Laser-scanning exposure device 17 for optical writing on top
A developing device 18 for developing the electrostatic latent image formed on the photoconductor 16 by the exposure device 17 with toner, and a transfer device 20 for transferring the toner image on the photoconductor 16 after development onto the recording paper 19. Etc. are provided in order. The recording paper 1
9 is, for example, a sheet that is fed from the sheet feeding cassette 21 built in the apparatus body 14 toward the photoconductor 16 by a known sheet feeding mechanism 22.

Further, a fixing device 23 is provided on the recording paper conveyance path downstream of the transfer device 20. The fixing device 23 is of a heat roller type, and includes a heating roller 24 located on the transfer toner image side and a pressure roller 25 located below the heating roller 24 and brought into pressure contact with the heating roller 24. It is composed of pairs. The heating roller 24
As a heater, for example, a heat lamp 26 is inserted inside. The heat lamp 26 is, for example, a halogen lamp having a length corresponding to the length of the heating roller 24 in the axial direction, and the heating roller 24 has a fixing temperature necessary for heating and melting the toner on the recording paper 19. It is used to heat the heating roller 24. Further, in the fixing device 23, a pair of paper discharge rollers 27 is provided on the downstream side of the heating roller 24.

Further, as shown in FIG. 1, a cooling fan 28 is provided inside the apparatus main body 14 so as to be located on the axial left side of the fixing device 23 when viewed from the front. This fan 2
As 8, there is used one that can rotate forward and backward. Further, in the apparatus body 14, the casings 29 located on both sides of the fixing device 23 in the axial direction are provided with slits 30a and 30b for intake and exhaust. Therefore, the fan 28
By switching the rotation direction of the normal rotation and the reverse rotation, the air flow flowing in the direction of the slit 30b → around the fixing device 23 → a fan 28 → a slit 30a and the direction of the slit 30a → a fan 28 → around the fixing device 23 → a slit 30b. It is configured to be able to form an air flow that flows through.

Further, a temperature sensor 31 is provided in the vicinity of the heating roller 24 in the axial center thereof. The temperature sensor 31 is, for example, a thermistor, and is provided to monitor the surface temperature of the central portion of the heating roller 24.

Next, the schematic configuration of the electrical equipment control system will be described with reference to FIG. A CPU 32 that controls the overall operation of the facsimile apparatus 11 and an R that fixedly stores a control program and the like.
An OM 33, a RAM 34 for appropriately storing various data,
The gate array 35 to which various load systems are connected is connected to the bus 3
6 are connected to each other. The gate array 35
For example, a heat lamp 26 for the heating roller 24, a temperature sensor 31, and a fan 28 are connected to the. Here, A / is provided between the temperature sensor 31 and the gate array 35.
The D converter 37 is interposed. Also, the fan 28
A fan forward / reverse control circuit 38 functioning as a rotation direction switching unit is interposed between the gate array 35 and the gate array 35.
Under the control of the CPU 32, heating control means for controlling the energizing operation of the heat lamp 26, which will be described later, and control of the switching operation of the rotation direction of the fan 28 by the fan forward / reverse control circuit 38 are controlled. And fan control means for executing.

The operation control in the case of fixing the toner on the recording paper 19 by the fixing device 23 in such a configuration will be described with reference to the flow chart shown in FIG. 4 and the temperature distribution characteristic diagram shown in FIG. In the fixing device 23 of the present embodiment, the upper limit of the proper fixing temperature is Tu,
It is assumed that the lower limit value is set to Td. In addition,
It is desirable that the upper limit value Tu and the lower limit value Td are set in consideration of the temperature difference between both ends of the heating roller 24.

First, when an operator gives a heat-up instruction through an operation unit (not shown) or receives a heat-up instruction while being monitored by a timer, FIG.
As shown in (a), the heating control means executes step S1 and energizes the heat lamp 26 to start the heat-up of the fixing device 23. In parallel with this, the fan control means executes step S2, and drives the fan 28 by setting the rotation direction of the fan 28 by the fan forward / reverse rotation control circuit 38 to the forward rotation direction. As a result, the air flow around the fixing device 23 is directed from the right side to the left side in FIG. Therefore, the surface temperature of the heating roller 24 tends to be gradually higher on the left side than on the right side. After that, with respect to the upper limit value Tu set for controlling the heat-up operation of the fixing device 23, the temperature sensor 31 determines whether the central surface temperature of the heating roller 24 has reached the upper limit value Tu. The determination is made based on the temperature information obtained through the / D converter 37 (step S3).

When the surface temperature of the central portion of the heating roller 24 reaches the upper limit value Tu, the heating control means performs step S.
4 is executed to stop the power supply to the heat lamp 26, thereby turning off the heat-up of the fixing device 23. The axial temperature distribution of the heating roller 24 at this point is schematically shown in FIG. That is, the heating roller 24
The surface temperature of is higher on the left side than on the right side.

Then, with respect to the lower limit value Td set for controlling the heat-up operation of the fixing device 23, a temperature sensor determines whether the surface temperature of the central portion of the heating roller 24 has reached the lower limit value Td. 31 based on the temperature information obtained through the A / D converter 37 (step S
5). The surface temperature of the central portion of the heating roller 24 is the lower limit value T
The temperature distribution in the axial direction of the heating roller 24 at the time when the temperature reaches d is schematically shown in FIG. That is, the surface temperature of the heating roller 24 is still higher on the left side than on the right side.

When the surface temperature of the central portion of the heating roller 24 reaches the lower limit value Td, the heating control means performs step S.
6 is executed, and the heat lamp 26 is again energized to start the heat-up of the fixing device 23. In parallel with this, the fan control means executes step S7 to drive the fan 28 by setting the rotation direction of the fan 28 by the fan forward / reverse rotation control circuit 38 to the reverse rotation direction this time. As a result, the air flow around the fixing device 23 is switched from the left side to the right side in FIG. Therefore,
The surface temperature of the heating roller 24 tends to be gradually higher on the right side than on the left side. That is, a schematic temperature distribution in the axial direction of the heating roller 24 at a certain point of such heat-up is as shown in FIG.
The surface temperature of is higher on the right side than on the left side.

After that, with respect to the upper limit value Tu set for controlling the heat-up operation of the fixing device 23, it is determined whether or not the surface temperature of the central portion of the heating roller 24 has reached the upper limit value Tu. 31 based on the temperature information obtained through the A / D converter 37 (step S
8). The central surface temperature of the heating roller 24 is the upper limit value T
The axial temperature distribution of the heating roller 24 when it reaches u is schematically shown in FIG. That is, the surface temperature of the heating roller 24 is higher on the right side than on the left side.

When the surface temperature of the central portion of the heating roller 24 reaches the upper limit value Tu, the same control as steps S4 and S5 is repeated. That is, the heating control means performs step S9.
Is executed and the power supply to the heat lamp 26 is stopped, so that the heat-up of the fixing device 23 is turned off. afterwards,
With respect to the lower limit value Td set for controlling the heat-up operation of the fixing device 23, the temperature sensor 3 determines whether the surface temperature of the central portion of the heating roller 24 reaches the lower limit value Td.
The determination is performed based on the temperature information obtained from 1 through the A / D converter 37 (step S10). When the surface temperature of the central portion of the heating roller 24 reaches the lower limit value Td, the heating control means executes step S1 and the heat lamp 26 is energized again to start the heat-up of the fixing device 23. .

Hereinafter, the same control is repeated until there is a command to turn off the heat-up. That is, the heating roller 24
Each time the surface temperature of the central part of the fan reaches the lower limit, Td, the fan 2
Control for switching the rotating treasure box of 8 is performed.

After that, when the operator gives an instruction to turn off the heat-up indicating the end of the recording operation through the operation unit (not shown), the heat-up off process shown in FIG. 4B is performed. That is, the heating control means performs step S1.
By executing 1 and stopping the power supply to the heat lamp 26, the heat up of the fixing device 23 is turned off. Further, the fan control means executes step S12 to stop the rotation of the fan 28, thereby ending the process.

As described above, according to the present embodiment, the temperature control of the heating roller 24 is performed by intermittently executing the heat-up operation of the heating roller 24 by the heating control means based on the sensor information of the temperature sensor 31. In parallel with this, every time the surface temperature of the central portion of the heating roller 24 reaches the lower limit value Td, the rotation direction of the fan 28 is alternately switched by the fan control means to flow around the fixing device 23. Since the direction of the air flow is switched alternately, the unevenness of the temperature distribution in which only the left side of the heating roller 24 has a high temperature and only the right side has a low temperature is alleviated. Then, since the temperature distributions such as shown in FIG. 5 are periodically repeated, the temperature of the heating roller 24 is generally made uniform over the axial direction. Therefore, a uniform fixing property can be obtained, and the recording paper 19
The occurrence of wrinkles can be suppressed. Further, in this embodiment, since the fan control means controls the switching of the rotation direction of the fan 28 based on the temperature information obtained from the temperature sensor 31, the control becomes simple and appropriate.

However, the fan 2 by the fan control means
The switching control of the rotation direction of 8 is not limited to the control every time the surface temperature of the central portion of the heating roller 24 reaches the lower limit value Td, but is also controlled every time the surface temperature of the central portion of the heating roller 24 reaches the upper limit value Tu and the lower limit value Td. It may be finely controlled.
Further, the energization time of the heating roller 24 may be monitored regardless of the temperature information from the temperature sensor 31, and may be periodically switched at regular short time intervals.

Further, although the present embodiment has been described as an application example to the facsimile apparatus 11, it can be widely applied to an image forming apparatus such as a copying machine for fixing the toner on the recording paper by using the heat roller type fixing device. Is.

[0029]

According to the image forming apparatus of the first aspect of the invention, after the toner is adhered onto the recording paper by the transfer device to form an image, the toner is transferred onto the recording paper by the fixing device equipped with a heating roller. In an image forming apparatus for fixing to a fixing device, a temperature sensor for monitoring a fixing temperature of the fixing device, heating control means for intermittently heating and controlling the heating roller based on sensor information of the temperature sensor, and a fixing device for the fixing device. A fan, which is arranged at one end side and is capable of rotating forward and backward for cooling the periphery of the fixing device, a rotation direction switching means for switching the rotation direction of the fan, and a switching operation of the rotation direction switching means are periodically controlled. Since the fan control means is provided, even if a fan is provided on one end side of the fixing device, only the one end side of the heating roller is heated to a high temperature by periodically switching the rotation direction. It is possible to mitigate the deviation of the temperature distribution such that only the other end side has a lower temperature. Therefore, as a whole, the fixing temperature of the fixing device can be made almost uniform in the axial direction, and the fixing temperature can be made uniform. It is possible to obtain various fixing properties and to suppress the occurrence of wrinkles on the recording paper.

According to the image forming apparatus of the second aspect, the fan control means in the first aspect of the invention controls the switching operation of the rotation direction switching means periodically based on the sensor information of the temperature sensor. Since the fan control means is used, the rotation direction of the fan can be appropriately switched by a simple control system.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing one embodiment of the present invention.

FIG. 2 is a vertical cross-sectional side view showing the outline of the internal configuration of the facsimile apparatus.

FIG. 3 is a block diagram showing an outline of an electrical equipment control system.

FIG. 4 is a flowchart showing an operation control process for the fixing device.

FIG. 5 is a schematic diagram showing how the temperature distribution in the axial direction changes.

FIG. 6 is a schematic perspective view showing a conventional example.

[Explanation of symbols]

 19 recording paper 20 transfer device 23 fixing device 24 heating roller 28 fan 31 temperature sensor 38 rotation direction switching means

Claims (2)

[Claims] 1. An image forming apparatus in which toner is adhered onto recording paper by a transfer device to form an image, and then the toner is fixed onto the recording paper by a fixing device equipped with a heating roller. Temperature sensor for monitoring the temperature, heating control means for intermittently heating and controlling the heating roller based on the sensor information of the temperature sensor, and a fixing device provided at one end of the fixing device to cool the periphery of the fixing device. An image forming apparatus comprising: a fan capable of rotating forward and backward for rotation, a rotation direction switching means for switching the rotation direction of the fan, and a fan control means for periodically controlling the switching operation of the rotation direction switching means. apparatus. 2. The image forming apparatus according to claim 1, wherein the switching operation of the rotation direction switching means is fan control means for periodically controlling the switching operation based on the sensor information of the temperature sensor.