JP2629039B2 - Thermal fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device used in an electrophotographic apparatus such as a laser printer and a copying machine.

[Prior Art] Conventionally, as this type of heat fixing device, as shown in FIG. 9, a cleaning pad 12 is always kept pressed by a spring material 13 against a heat roller 11 provided with a heater. .

[Problems to be Solved by the Invention] As described above, the conventional heat fixing device has a problem that the cleaning pad is quickly deteriorated because the cleaning pad is always in contact with the heat roller.

Further, when the temperature of the heat roller becomes abnormally high due to defective heater control or the like, there is a problem that the cleaning pad burns on the surface of the heat roller or smokes in some cases.

Therefore, the present invention can prevent the cleaning pad from being quickly deteriorated by bringing the cleaning pad into contact with the heat roller when the heater is energized, and separating the cleaning pad from the heat roller when the heater is not energized. When the temperature becomes abnormal, the cleaning pad can be separated from the heat roller.
In some cases, it is an object of the present invention to provide a heat fixing device capable of preventing generation of smoke.

[Means for Solving the Problems] The invention according to claim (1) is a heat fixing device for thermally fixing a transfer sheet on which an image has been transferred via a heat roller provided with a heater. A cleaning pad that can be freely attached and detached, an abnormal temperature detector that detects an abnormal temperature rise due to the heater, and a cleaning pad when the heater is energized is pressed against the heat roller. Separated,
Further, a drive means is provided for separating the cleaning pad from the heat roller when the abnormal temperature detector detects abnormal temperature when the heater is energized.

[Operation] In the present invention having such a configuration, the cleaning pad is pressed against the heat roller by the driving means only when the heater is energized, and the cleaning pad is separated from the heat roller when the energization to the heater is stopped.

When the temperature of the heat roller rises abnormally due to defective heater control or the like, the cleaning pad is forcibly separated from the heat roller by an abnormal temperature detection output.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In this embodiment, an embodiment in which the present invention is applied to a laser printer will be described.

FIG. 1 shows the overall structure of a laser printer. At the center of a printer main body 21, a photosensitive drum 22 whose surface is formed of a photoconductor made of a photoconductive substance is provided. The photosensitive drum 22 is driven to rotate in one direction,
According to the electrophotographic process around the photosensitive drum 22,
A charger 23 constituting a charging unit; a laser scanner unit 24 for irradiating a laser beam to a photoconductor charged by the charger 23 to record image information and form an electrostatic latent image; and a formed electrostatic latent image. A developing unit 25 for developing the image into a toner image, and a transfer charger for transferring the toner image to a transfer paper
26, cleaning device to remove toner from photosensitive drum 22
27, a static elimination lamp 28 for neutralizing the photosensitive drum 22 is provided in order.

A paper feed unit is located near the front entrance of the transfer charger 26.
A pickup roller 30 is provided for feeding and transporting the transfer sheet stored in the sheet 29 toward the transfer charger 26 at a predetermined timing. Behind the transfer charger 26, a heat fixing device 31 for thermally fixing an image on a transfer receiving paper and a discharge roller 32 for discharging the fixed transfer receiving paper are provided.
Are provided in order. The heat fixing device 31 includes a heat roller 31a heated by a heater described later and a transport roller 3
1b are in contact with each other and are opposed to each other.

Further, the transport unit, the photosensitive drum 22, the transport motor 33 for driving the thermal fixing device 31, the cooling fan 34, the interlock switch 35 for detecting the opening of the housing of the printer body 21, the DC power supply
36 are provided respectively.

As shown in FIG. 2, the laser scanner unit 24 detects a laser beam start position by driving a laser diode control circuit 42 for driving a laser diode structure 41.
A start sensor 43 composed of a PIN diode or the like, a polygon motor drive circuit 45 for driving and controlling a polygon motor 44 for rotating a polygon mirror, and a PLL control circuit 46 for controlling the number of rotations of the motor 44 by the drive circuit 45 are provided.

FIG. 3 is a block diagram showing a circuit configuration. Reference numeral 51 denotes a CPU (central processing unit) constituting a control unit main body, and 52 denotes a ROM (ROM) provided with program data and various tables for the CPU 51 to control each unit. A read-only memory (53), a RAM (random access memory) 53 for storing image information and various kinds of processing data sent from an external host computer, and an I / O port 54. These are bus lines 55
Connected by

The I / O port 54 includes a motor drive circuit 56 for controlling the drive of the transport motor 33, a high-voltage power supply circuit 57 for supplying a high voltage to the laser scanner unit 24, the charging charger 23 and the transfer charger 26, and the developing device 25. Empty sensor 58 and toner full sensor provided inside
59, a toner sensor circuit 60 for controlling 59, an operation unit 61, paper sensors 62, 63, 64 for detecting paper jam, the fan 34,
Interfaces 65 for receiving image information from the host computer are connected to each other.

The interlock switch 35 is inserted from the DC power supply 36 into a 24 V supply line connected to the motor drive circuit 56, the laser scanner 24, the high voltage power supply circuit 57, and the fan 34, and the housing of the printer main body 21 is opened. When this is detected, the supply line is shut off.

The CPU 51, the ROM 52, the RAM 53, and the I / O port 54 are supplied with +5 V from the DC power supply 36.

The DC power supply 36 is connected to a commercial AC power supply via a noise filter 66.

Further, the commercial AC power input via the noise filter 66 is also supplied to the fixing device driving circuit shown in FIG.

The fixing device driving circuit includes a heater 6 for heating the heat roller 31a between output lines from the noise filter 66.
7. A series circuit is connected to the temperature fuse 68, the primary winding 69p of the transformer 69, and the output of the heater control circuit 70.

The input terminal of the full-wave rectifier diode bridge 71 is connected to the secondary winding 69s of the transformer 69. Further, a ceramic capacitor 73 and an electric field capacitor 74 are connected to the output terminal of the diode bridge 71 via a switch 72 linked with the interlock switch 35. In addition,
The switch 35 is turned off when the housing of the printer main body 21 is opened.

Electromagnetic magnets 75 are connected to both ends of the electrolytic capacitor 74.

When a heater control signal is input from the CPU 51, the heater control circuit 70 short-circuits its output.

FIG. 5 shows the structure of a main part of the heat fixing device 31. The cleaning pad 7 is placed on the upper surface of the heat roller 31a.
6 is provided so as to be able to freely contact and separate, and its cleaning pad 7
6 is constantly urged upward by springs 77, ie, in a direction away from the heat roller 31a.

Further, the electromagnetic magnet 75 is fixed inside the upper surface of the housing of the heat fixing device 31, and the cleaning pad 76 is fixed.
A cleaning pad pressing member 78 is provided slidably to the left and right along the inside of the upper surface of the housing.

One end of the cleaning pad pressing member 78 is connected to the plunger of the electromagnetic magnet 75, and the other end is
It is fixed to the inside of the side surface of the housing via 79, and when the electromagnetic magnet 75 operates, it is pulled to the right side in the figure against the force of the spring 79.

Several recesses 76a are formed above the cleaning pad 76, and several projections 78a provided with rollers at the tips corresponding to the recesses 76a are formed below the cleaning pad pressing member 78. I have.

The protruding portion 78a is located in the recess 76a of the cleaning pad 76 when the electromagnetic magnet 75 does not operate,
When the electromagnetic magnet 75 operates and the cleaning pad pressing member 78 slides to the right, it comes into contact with a smooth slope formed on one side of the recess 76a.

In the present embodiment having such a configuration, since the electromagnetic magnet 75 does not operate in a state where the power is off,
At this time, the protrusion 78 of the cleaning pad pressing member 78
a is located in the concave portion 76a of the cleaning pad 76, and therefore the cleaning pad 76 is urged by the spring 77 to be separated from the heat roller 31a.

In this state, when the power is turned on and a heater control signal is input to the heater control circuit 70, energization of the heater 67 is started and the heat roller 31a is heated. Further, a voltage is generated in the secondary winding 69s of the transformer 69, the electrolytic capacitor 74 is charged by the output of the full-wave rectifier diode bridge 71, and the electromagnetic magnet 75 is operated.

Thus, the cleaning pad pressing member 78 is pulled rightward in the figure by the electromagnetic magnet 75. As a result, the roller of the protruding portion 78a comes into contact with the slope of the recess 76a and smoothly moves on the slope. And protrusion 78
Since the lower end of a is fixed, cleaning pad 7
6 starts to fall. Then, at the position where the roller of the protruding portion 78a comes out of the recess 76a, the cleaning pad 76 comes into pressure contact with the upper surface of the heat roller 31a as shown in FIG.

Thus, when the power supply to the heater 67 is started, the cleaning pad 76 comes into contact with the heat roller 31a.

When the temperature of the heat roller 31a reaches a certain set temperature, the input to the heater control signal is stopped, and the power supply to the heater 67 is stopped. Thereafter, energization and non-energization of the heater 67 are repeated, and the temperature of the heat roller 31a is kept substantially constant. When the power is not supplied to the heater 67, the cleaning pad 76 is separated from the heat roller 31a.

Since the cleaning pad 76 is brought into contact with the heat roller 31a only when the heater 67 is energized, the cleaning pad 76 can be prevented from being deteriorated early.

Then, when the heat fixing device 31 reaches the set temperature state, the printing operation of the pretender becomes possible. In this printing operation, first, the photosensitive drum 22 rotates, and the photosensitive member is charged by the charging charger 23. Then, information is written on the charged photoconductor by the laser beam from the laser scanner unit 24, and an electrostatic latent image is formed. The toner supplied from the developing device 25 is attached to the electrostatic latent image, and further moves to the transfer section.

On the other hand, the paper to be transferred stored in the paper feeding unit 29 is sent to the conveyance path by the pickup roller 30 at a predetermined timing. When the sheet is conveyed to the transfer charger 26, a toner image is transferred from the photoconductor of the photoconductor drum 22. Then, the sheet is further heat-fixed by the heat fixing device 31, and is discharged by the sheet discharge roller 32, thereby completing the printing.

In addition, even if the control of the heater 67 becomes defective and the temperature reaches the set temperature, if the power supply to the heater 67 is stopped and an accident occurs such that the temperature of the heat roller 31a rises abnormally, the temperature fuse 68 is blown at this time. Therefore, no voltage is output to the secondary winding 69s of the transformer 69 and the electromagnetic magnet 75
Operation is stopped. Thus, the cleaning pad pressing member 78 releases the pressed state of the cleaning pad 76, and the cleaning pad 76 is separated from the heat roller 31a.

In this way, even if the heat roller 31a has an abnormal temperature rise, the cleaning pad 76 can be separated from the heat roller 31a, so that the cleaning pad 76 does not seize on the heat roller 31a and, in some cases, does not cause smoke. .

If the housing of the printer main body 21 is opened while the heater 67 is energized, the switch 72 is turned off to prevent energization of the electromagnetic magnet 75.In this case, the cleaning pad 76 is also removed from the heat roller 31a. Can be separated.

Next, another embodiment of the present invention will be described with reference to the drawings.
The same parts as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 7, a member 80 having a projection 80a having substantially the same shape as the recess 76a formed in the cleaning pad 76 is used as a cleaning pad holding member. When the cleaning pad pressing member 80 is pulled by the operation of 75, the protrusion 80a moves on the smooth slope of the recess 76a as shown in FIG.
It can be pressed against 31a. Therefore, in this embodiment, the same effects as those of the above embodiment can be obtained.

In the above-described embodiment, the driving unit including the cleaning pad pressing member and the electromagnetic magnet has been described, but the driving unit is not necessarily limited to this.

In the above embodiment, the present invention is applied to a heat fixing device of a laser printer. However, the present invention is not limited to this. The present invention can be applied to various devices such as copiers that require heat fixing. is there.

[Effects of the Invention] As described above in detail, according to the invention described in claim (1), the cleaning pad is brought into contact with the heat roller when power is supplied to the heater, and the cleaning pad is separated from the heat roller when power is not supplied. The cleaning pad can be prevented from prematurely deteriorating, and when the heating temperature of the heat roller by the heater reaches an abnormal temperature, the cleaning pad can be separated from the heat roller, preventing the cleaning pad from burning on the heat roller or generating smoke in some cases. It is possible to provide a heat fixing device that can prevent the heat fixing.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 is a diagram showing a configuration of a laser printer, FIG. 2 is a diagram showing a configuration of a laser scanner unit, and FIG. 3 is a circuit diagram. FIG. 4 is a block diagram of a fixing device driving circuit, FIGS. 5 and 6 are main structural diagrams of the heat fixing device, and FIGS. 7 and 8 are thermal fixing devices showing another embodiment of the present invention. FIG. 9 is a structural view of a main part of a heat fixing device showing a conventional example. 31: heat fixing device, 31a: heat roller, 67: heater, 70
... heater control circuit, 75 ... electromagnetic magnet, 76 ...
Cleaning pad, 77: Spring, 78: Cleaning pad holder.

Claims (2)

(57) [Claims] 1. A thermal fixing device for thermally fixing a transfer sheet onto which an image has been transferred via a heat roller provided with a heater.
A cleaning pad provided so as to be able to freely contact and separate from the heat roller, an abnormal temperature detector for detecting an abnormal temperature rise by the heater, and pressing the cleaning pad against the heat roller when energizing the heater. ,
A drive unit is provided for separating the cleaning pad from the heat roller when the power is not supplied, separating the cleaning pad from the heat roller, and further, when supplying power to the heater, the abnormal temperature detector detects an abnormal temperature when power is supplied to the heater. A heat fixing device, comprising: And a driving means for urging the cleaning pad in such a direction as to always separate the cleaning pad from the heat roller by a spring force, driving the cleaning pad pressing member by energizing an electromagnetic magnet, and operating the spring pad by the operation of the pad pressing member. 2. The heat fixing device according to claim 1, wherein the cleaning pad is pressed against the heat roller against the heat.