JPH02198481A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To continuously bring a cleaning pad into contact with a heat roller when the energization is of a short period and intermittent by providing a circuit which controls a heater according to the temp. of the heat roller and a driving means which brings the cleaning pad into contact with the heat roller by the driving voltage from a capacitor. CONSTITUTION:The heat fixing device which prevents the early deterioration of the cleaning pad 76 by parting the cleaning pad 76 from the heat roller 31a at the time of non-energization is provided with the heat control circuit 70 which controls the energization and non-energization of the heater 67 by a heater control signal according to the temp. condition of the heat roller 31a, the capacitor 74 which has a relatively large capacity and is charged during the energization to the heater 67, and the driving means which brings the cleaning pad 76 into contact with the heat roller 31a by the driving voltage from the capacitor 74. The driving means is maintained by the capacitor 74 so that the cleaning pad 76 can maintain the contact state continuously without parting from the heat roller 31a even if the heater 67 is non-energized at the time when the energization and non-energization to the heater 67 are executed at relatively short periods.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat fixing device used in an electrophotographic apparatus such as a laser printer or a copying machine.

[Prior Art] Conventionally, this type of heat fixing device is as shown in FIG.
The cleaning pad 12 is always held in a pressed state by a spring member 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 in that the cleaning pad deteriorates quickly because the cleaning pad is always in contact with the heat roller.

Therefore, the present invention makes it possible to prevent early deterioration of the cleaning pad by bringing the cleaning bat 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. An object of the present invention is to provide a heat fixing device that can continuously hold a cleaning pad in contact with a heat roller when the cleaning is performed intermittently.

[Means for Solving the Problems] The present invention provides a thermal fixing device for thermally fixing a transfer paper onto which an image has been transferred via a heat roller provided with a heater. a cleaning pad, a separation holding means for holding the cleaning pad at a distance from the heat roller, a heater control circuit for controlling energization and de-energization of the heater by a heater control signal according to the temperature state of the heat roller, and a heater control circuit for controlling energization and de-energization of the heater according to the temperature state of the heat roller; This device is equipped with a capacitor that is charged with a relatively large capacity, and a drive means that is supplied with a drive voltage from the capacitor and brings the cleaning pad into contact with the heat roller.

[Function] In the present invention having such a configuration, the cleaning pad is brought into contact with 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 heater is not energized. When the heater is energized and de-energized in relatively short cycles, even if the heater is de-energized, the driving means is maintained in an operating state by the capacitor, and the cleaning vat does not separate from the heat roller. . In other words, the contact state can be maintained continuously.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described as applied to a laser printer.

FIG. 1 shows the overall structure of a laser printer, in which a photosensitive drum 22 whose surface is formed of a photosensitive member made of a photoconductive material is provided in the center of a printer body 21. As shown in FIG.

This photosensitive drum 22 is driven to rotate in one direction, and around this photosensitive drum 22, according to an electrophotographic process, there is a charging charger 23 that constitutes a charging section, and a laser beam is applied to the photosensitive member charged by this charging charger 23. A laser scanner unit 24 that records image information by irradiating a beam and forms an electrostatic latent image, a developer 25 that develops the formed electrostatic latent image into a toner image, and a transfer unit that transfers the toner image onto paper. A charger 26, a cleaning device 27 for removing toner from the photosensitive drum 22, and a charge removal lamp 28 for removing charge from the photosensitive drum 22 are provided in this order.

Then, near the front entrance of the transfer charger 26, the transfer paper stored in the paper feed section 29 is transferred to the transfer charger 26.
A pickup roller 3o is provided for feeding and transporting paper toward the paper 6 at a predetermined timing. Further, behind the transfer charger 26, a thermal fixing device 31 for thermally fixing the image on the transfer paper and a paper discharge roller 32 for discharging the fixed image on the transfer paper are provided in this order. .

In the heat fixing device 31, a heat roller 31a heated by a heater to be described later and a conveyance roller 31b are disposed facing each other and in contact with each other.

Furthermore, a transport motor 33 that drives the transport section, photosensitive drum 22, and heat fixing device 31, a cooling fan 34, and a printer main body 2
an ink lock switch 35 that detects the opening of the casing 1;
A DC power supply 36 is provided respectively.

As shown in FIG. 2, the laser scanner unit 24 includes a laser diode control circuit 42 that drives a laser diode structure 41, a start sensor 43 consisting of a PIN diode, etc. that detects the start position of the laser beam,
A polygon motor drive circuit 45 that drives and controls a polygon motor 44 that rotates the polygon mirror, and a PLL control circuit 46 that controls the rotation speed of the motor 44 by this drive circuit 45 are provided.

FIG. 3 is a block diagram showing the circuit configuration, where 51 is a CPU (central processing unit) that constitutes the main body of the control section, and 52 is this C.
A ROM (read only memory) is provided with program data and various tables for the PU 51 to control each part, and a RAM (53) stores image information and various processing data sent from an external host computer.
random access memory), 54 is the I10 port.

These are connected by a pass line 55.The I10 port 54 supplies high voltage to a motor drive circuit 56 for driving and controlling the transport motor 33, the laser scanner unit 24, the electrostatic charger 23, and the transfer charger 26. A toner sensor circuit 60 that controls a high voltage power supply circuit 57, a toner empty sensor 58 and a toner full sensor 59 provided in the developing device 25.
Operation unit 61, paper sensor 62 that detects paper jam
, the fan 34, and an interface 65 for receiving image information from the host computer.

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

The CPU 51, ROM 52, RAM 53 and I10
The port 54 is supplied with 15 volts 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 through the noise filter 66 is also supplied to the fixing device drive circuit shown in FIG.

The fixing device drive circuit includes a heater 67 for heating the heat roller 31a, a temperature fuse 68, and a primary winding 6 of a transformer 69 between the output lines from the noise filter 66.
A series circuit of the output section of the 9p1 heater control circuit 70 is connected.

The input terminal of the aftereffect rectifier diode bridge 71 is connected to the secondary winding 69s of the transformer 69. A ceramic capacitor 73 and a relatively large electrolytic capacitor 74 are connected to the output terminal of the diode bridge 71.
Connecting parallel circuits. An electromagnetic magnet 75 is connected to both ends of the electrolytic capacitor 74.

The heater control circuit 70 short-circuits its output section when a high-level heater control signal is input from the CPU 51.

FIG. 5 shows the main part structure of the heat fixing device 31, in which a cleaning pad 76 is provided so as to be able to come into contact with and separate from the upper surface of the heat roller 31a, and the cleaning pad 76 constitutes a separation holding means. It is always urged upward by springs 77, 77, that is, in a direction away from the heat roller 31a.

Further, the electromagnetic magnet 75 is fixed to the inside of the upper surface of the housing of the heat fixing device 31, and the cleaning pad 7
A cleaning pad pressing member 78 is provided above the housing 6 so as to be slidable left and right along the inner side of the upper surface of the housing.

The cleaning pad holding member 78 has one end connected to the plunger of the electromagnetic magnet 75 and the other end fixed to the inner side surface of the housing via a spring 79. When the electromagnetic magnet 75 operates, the spring 79
It is pulled to the right in the figure against the force of.

Several recesses 76a are formed above the cleaning pad 76, and several protrusions 78a each having a roller at the tip are formed below the cleaning pad pressing member 78 in correspondence with the recesses 76a. There is.

The protrusion 78a is located in the recess 76a of the cleaning pad 76 when the electromagnet 75 is not operating, and when the electromagnet 75 is activated and the cleaning pad presser member 78 slides to the right, the protrusion 78a is located on one side of the recess 76a. It is designed to come into contact with the formed smooth slope.

The electromagnetic magnet 75 and the cleaning pad pressing member 78 form a driving means.

The CPU 51 supplies a heater control signal to the heater control circuit 70 to keep the temperature of the heater 67 within a set temperature range, but the set temperature range is set to a relatively low temperature during printing standby, and during printing. The temperature inside is set to a relatively high temperature.

In this embodiment with such a configuration, the electromagnetic magnet 75 does not operate when the power is turned off.
At this time, the protruding portion 78a of the cleaning pad pressing member 78 is located within the recess 76a of the cleaning pad 76, so that the cleaning pad 76 is biased by the spring 77 and is spaced apart from the heat roller 31a.

When the power is turned on in this state and a heater control signal is input to the heater control circuit 7o, power supply to the heater 67 is started and the heat rollers 31,a are heated.

Further, a voltage is generated in the secondary winding 69s of the transformer 69, and the electrolytic capacitor 74 is charged by the output of the rectifying diode bridge 71, and the electromagnetic magnet 75 is operated.

Thus, the cleaning pad pressing member 78 is pulled to the right in the figure by the electromagnetic magnet 75. As a result, the roller of the protrusion 78a comes into contact with the slope of the recess 76a and moves smoothly along the slope.

Since the lower end position of the protruding portion 78a is fixed, the cleaning pad 76 comes to descend. Then, at the position where the roller of the protrusion 78a has passed through the recess 76a, the sixth
As shown in the figure, the cleaning pad 76 comes into pressure contact with the upper surface of the heat roller 31a.

When the heater 67 starts to be energized in this way, the leaning pad 76 comes into contact with the heat roller 31a.

When the heater temperature reaches the set temperature during printing standby, the input of the heater control signal is stopped and the power supply to the heater 67 is stopped. Thereafter, the heater 67 is repeatedly energized and de-energized, and the heater temperature is maintained at a relatively low temperature state as indicated by O in FIG. 7(a). During this standby period, as shown in FIG. 7(b), the interval at which the heater control signal is input is relatively long, so even if the voltage capacitor 74 has a large capacity, as shown in FIG. 7(e), The electromagnet 75 is intermittently turned on and off, and as a result, the cleaning pad 76 repeatedly moves toward and away from the heat roller 31a.

When the printing operation is started in this state, the heater temperature is set to a high temperature as shown by @ in Fig. 7(a), so the heater control signal is set to a high temperature as shown in Fig. 7(b). The temperature is input for a relatively long time until it reaches the set temperature. When the heater temperature reaches the set temperature, the heater control signal is intermittently inputted thereafter. During printing, the interval between heater control signal inputs becomes short, so that the charging voltage of the electrolytic capacitor 74 can keep the electromagnetic magnet 75 sufficiently operational until the next heater control signal is input. Therefore, during printing, (C
), the electromagnetic magnet 75 is kept in continuous ON operation, so that the cleaning pad 76 does not separate from the heat roller 31a.

After that, when printing is completed and the printing standby state is resumed, the heater temperature decreases, and the electromagnetic magnet 75 is repeatedly turned on and off due to the intermittent input of the heater control signal, so that the cleaning pad 76 moves toward and away from the heat roller 31a. become.

In this way, since the cleaning pad 76 is brought into contact with the heat roller 31a only when the heater 67 is energized, early deterioration of the cleaning pad 76 can be prevented as much as possible. Also, during the printing operation, even if the heater 67 is intermittently energized depending on the set temperature, the electrolytic capacitor 74 maintains the operating state of the electromagnetic magnet 75, and the heat roller 31
Since the cleaning pad 76 is kept in contact with the heat roller 31a, cleaning of the heat roller 31a is ensured.

Furthermore, if an accident occurs during printing where the control of the heater 67 becomes defective and the power supply to the heater 67 is not stopped even when the set temperature is reached, causing the temperature of the heat roller 31a to rise abnormally, the temperature fuse 68 will be activated. Since it is fused, no voltage is output to the secondary winding 69s of the transformer 69, and the operation of the electromagnetic magnet 75 is stopped. Therefore, the cleaning pad pressing member 78 is attached to the cleaning pad 76.
The pressing state of is released, and the cleaning pad 76 is separated from the heat roller 31a.

In this way, even if the temperature of the heat roller 31a rises abnormally, the cleaning pad 76 can be removed from the heat roller 31a.
Since the cleaning pad 76 can be separated from the heat roller 31a, accidents such as burning of the cleaning pad 76 on the heat roller 31a and smoke generation in some cases do not occur.

During the printing operation, the photosensitive drum 22 rotates and its photosensitive member is charged by the charger 23, and information is written on the charged photosensitive member by a laser beam from the laser scanner unit 24, forming an electrostatic latent image. is formed. A toner image is formed on this electrostatic latent image using toner from the developing device 25, and the toner image is transferred to the transfer paper by the transfer charger 26. Then, the paper to which the toner image has been transferred is thermally fixed by the heat roller 31a of the thermal fixing device 31, and is then discharged.

In the above embodiments, the driving means is composed of a cleaning pad pressing member and an electromagnetic magnet, but the driving means is not necessarily limited to this.

Furthermore, although the above embodiment describes the application of the present invention to a heat fixing device of a laser printer, the present invention is not necessarily limited to this, and can be applied to various types of equipment that require heat fixing, such as copying machines. be.

[Effects of the Invention] As detailed above, according to the present invention, the cleaning pad is brought into contact with the heat roller when the heater is energized, and the cleaning pad is separated from the heat roller when the heater is not energized, thereby preventing early deterioration of the cleaning pad. Therefore, it is possible to provide a thermal fixing device that can prevent the above problem and can also keep the cleaning pad in continuous contact with the heat roller when the heater is energized intermittently at relatively short cycles.

[Brief explanation of the drawing]

1 to 7 show embodiments of the present invention.
Figure 2 is a diagram showing the configuration of the laser printer, Figure 2 is a diagram showing the configuration of the laser scanner unit, Figure 3 is a block diagram showing the circuit configuration, Figure 4 is a fixing device drive circuit diagram, and Figures 5 and 6 are FIG. 7 is a time chart showing the relationship between heater temperature, heater control signal, and electromagnetic magnet ON time; FIG. 9 is a diagram showing the configuration of essential parts of a conventional heat fixing device. . 31... Heat fixing device, 31a... Heat roller, 6
7... Heater, 70... Heater control circuit,
74... Electrolytic capacitor, 75... Electromagnetic magnet, 76... Cleaning pad, 77... Spring (separation holding means), 78... Cleaning pad pressing member. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In a thermal fixing device that thermally fixes a transfer paper onto which an image has been transferred via a heat roller provided with a heater, the cleaning pad is provided so as to be movable toward and away from the heat roller, and the cleaning pad is connected to the heat roller. a separation holding means for holding the heater at a distance from the heat roller; and energizing the heater by a heater control signal according to the temperature state of the heat roller;
A heater control circuit for controlling de-energization, a capacitor with a relatively large capacity that is charged when the heater is energized, and a driving means that is supplied with a driving voltage from the capacitor and brings the cleaning pad into contact with the heat roller. A heat fixing device featuring: