JP2006310059A - Heating device and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating device capable of prolonging life of film by preventing a heat resistant film 63 from toner staining, and realizing stable quick start or first print time at all time. <P>SOLUTION: Power is limited when raising a temperature of a heating body 61, and driving rotation speed of a pressing member 64 is made variable basing on an increase rate of a detected heating temperature of the heating body 61 until a member to be heated P is penetrated into a pressure contact nip. The temperature is stably raised corresponding to a temperature raising condition of the heating body 61 by changing the driving rotation speed of a heat resistant film 63 in response to the actual temperature rise at the time of raising the temperature of the heating body 61. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, the heat from the heating body is applied to the heated member introduced into the press-contact nip formed between the heat-resistant film that contacts the heating body and the pressure member via the heat-resistant film. The present invention relates to a configured heating apparatus.

  In general, in various image forming apparatuses such as copying machines, facsimile machines, printers, micro heat-resistant film reader printers, image display (display) apparatuses, and recording machines, appropriate image forming processes such as electrophotography, electrostatic recording, and magnetic recording. The developer (toner) made of heat-meltable resin, etc., depending on the means, is used for the surface of the recording material such as transfer material sheet, electrofax sheet, electrostatic recording sheet, printing paper, etc. The image information is carried as an unfixed toner image, and the unfixed toner image is heat-fixed on the surface of the recording material by a heating device to form a permanently fixed image.

  Conventionally, in addition to the heating roller method, various heating methods such as a flash heating method, an oven heating method, and a hot plate heating method have been adopted for such a heating device, but recently, a heat resistant film is used. A heat-resistant film heating method is being adopted. In the heating device using this heat-resistant film heating method, an appropriate heat-resistant film (fixing film) is arranged to be slidable in contact with the heating body held by the support frame, and the heat resistance A pressure member composed of a pressure roller or the like is pressed against the heating body via a conductive film and is rotated. Then, by applying heat generated from the heating body to the recording material via the heat-resistant film, the unfixed toner image formed and supported on the surface of the recording material is heated and fixed. .

  Heating devices using the heat-resistant film heating method include a fixing device such as a copying machine, a device that heats a recording material to improve surface properties such as gloss, and a device that performs an assumed attachment process. Although it can be widely used in devices for heat treatment of heating elements, it is possible to use a low-capacity heating element or a thin heat-resistant film that has a high temperature rise. Therefore, it is possible to shorten the so-called quick start or first print time.

  When performing quick start and shortening the first print time, it is possible to reach the target temperature as soon as possible if 100% full power is output when the temperature of the heating element is raised. However, doing so may cause an excessive current to flow through the electric wiring supplied from the power source to the heating body, which causes a problem in the safety of the power supply system. For this reason, power control at the time of temperature rise of the heating body has been conventionally limited, and it is prohibited to start up with full power so that the power at the time of temperature rise does not become an excessive current. Yes.

  On the other hand, in order to shorten the wait time, for example, the heating temperature is raised early by controlling the driving rotation speed of the heat resistant film of the heating device so as to be driven at a slower speed than usual. However, if the heat-resistant film drive rotation speed of the heating device is slowed, the heating temperature will surely rise satisfactorily, but the temperature rise may become excessive, thereby adhering to the pressure member. The toner stains transferred to the heat-resistant film side and the toner adheres to the surface, and the heat-resistant film may be soiled early and the film life may be shortened.

JP-A-7-160133

  SUMMARY An advantage of some aspects of the invention is that it provides a heating device and an image forming apparatus that can realize stable quick start or shortening of a first print time while preventing toner contamination on a heat resistant film.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a heating body, a heat-resistant film disposed so as to be slidable on the heating body, and a state in pressure contact with the heating body via the heat-resistant film. A pressure member that is driven to rotate and a temperature detection unit that detects a temperature of the heating body, and a member to be heated is disposed at a pressure nip formed between the pressure member and the heat-resistant film. In the heating apparatus configured to apply heat generated from the heating body to the heated material through the heat-resistant film by being conveyed while sandwiching the heated member, the heated member enters the pressure nip portion. Until it does, the control means which controls the drive rotational speed of the said pressurization member based on the detected temperature which the said temperature detection means detected is provided.

  According to the image forming apparatus of the present invention having such a configuration, the safety of the power supplied to the heating body is ensured when the temperature of the heating body is raised after the main power is turned on or after waiting or after standby. Since the driving rotation speed of the heat-resistant film is appropriately changed corresponding to the actual temperature rise until the heated member enters the pressure nip portion while maintaining the heated state, the temperature corresponding to the temperature rise condition of the heating body is changed. The rise is designed to be stable.

  As described above, the present invention can control the heating detection temperature of the heating body while limiting the power until the member to be heated enters the press-contact nip when the main power is turned on or after the heating or the standby temperature rises. The drive rotation speed of the pressure member is variable based on the rate of increase, and the heat-resistant film drive rotation speed at the time of temperature rise of the heating element is changed according to the actual temperature rise, so that the temperature rise condition of the heating element Correspondingly, the temperature rise is made stable so that under any condition, the heat-resistant film can be prevented from promoting toner contamination and the heat-resistant film life can be extended. , Always stable quick start or first print time can be shortened, improving the performance and reliability of the heating device and image forming device at the same time It is possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Prior to that, an example of a schematic structure of a laser beam printer as an image forming apparatus to which the present invention is applied will be described.

  In the process cartridge 2 detachably mounted in the apparatus main body 1 of the laser beam printer shown in FIG. 1, a photosensitive drum 21 as an image carrier that is rotatably supported is provided. The photosensitive drum 21 is configured to be rotationally driven in an arrow direction at an appropriate process speed by a driving unit (not shown). The photosensitive drum 21 is arranged so as to be close to the surface of the photosensitive drum 21. A charging roller 22 as a charging device for uniformly charging the surface is provided inside the process cartridge 2. Further, on the downstream side of the charging roller 22 in the rotation direction of the photosensitive drum 21, an exposure 3a from a laser scanner 3 arranged outside the process cartridge 2 is provided as an exposure unit for forming an electrostatic latent image. A developing device 23 is provided inside the process cartridge 2 so as to irradiate and on the downstream side thereof, which visualizes the electrostatic latent image to form a toner image.

  Further, on the downstream side of the developing device 23 in the rotation direction of the photosensitive drum 21, a transfer roller 4 disposed outside the process cartridge 2 as a transfer device that transfers the toner image on the photosensitive drum 21 to the recording medium P. However, a cleaning device 24 that collects untransferred toner remaining on the photosensitive drum 21 is disposed on the downstream side of the transfer roller 4 and is disposed in pressure contact with the surface of the photosensitive drum 21. It is provided in the cartridge 2.

  On the other hand, a paper feed cassette 5 containing a sheet-like recording medium P such as paper is attached to the bottom of the apparatus main body 1 so as to be detachable in a substantially horizontal direction. A paper feed roller 5a for feeding out the recording medium P is provided at a front end portion (left end portion in the drawing) in the mounting direction, and a conveyance path from the paper feed roller 5a to a transfer region where the transfer roller 4 is disposed. The registration roller 5b is arranged at a midway position. Further, a fixing device 6 for fixing an unfixed toner image on the recording medium by a heating action is disposed at an extended end portion of the conveyance path extending from the transfer region where the transfer roller 4 is disposed.

  Furthermore, a control board (not shown) for controlling the image forming operation and the like is attached to the apparatus main body 1. In the control board, a main body control unit 7 as an image formation control unit including a fixing heating control unit is provided, and each main body control unit 7 controls each image forming process. That is, in the laser beam printer having the above-described configuration, the surface of the photosensitive drum 21 that is rotationally driven in the direction of the arrow by a driving unit (not shown) is made to have a predetermined polarity and a predetermined potential by the charging roller 22. Image information (image signal VDO) received from the external device (not shown) via the video controller from the laser scanner 3 as the exposure means for the uniformly charged surface of the photosensitive drum 21. ) Is irradiated with the image beam modulated, and the charge corresponding to the exposed portion of the exposure 3a is removed to form an electrostatic latent image on the surface of the photosensitive drum 21. The electrostatic latent image formed on the surface of the photosensitive drum 21 is visualized by a developing action of a developing sleeve 23a formed from an aluminum roller or the like in the developing device 23 to obtain a toner image. .

  On the other hand, the fixing device 6 according to the present embodiment is provided with a well-known tensionless type heating film type heat fixing means as shown in FIG. In FIG. 2, reference numeral 61 indicates a ceramic heater as a heating element, reference numeral 62 indicates a bowl-shaped support formed in a substantially semicircular cross section, and reference numeral 63 indicates a substantially cylindrical shape. The reference numeral 64 denotes a heat-resistant film for fixing, and reference numeral 64 denotes an elastic pressure roller as a pressure member.

  Among these members, the ceramic heater 61 is formed of a horizontally long plate-like member whose longitudinal direction is the direction perpendicular to the paper surface, and is a front surface side (lower surface side of the drawing) of the heater substrate 61a formed of a ceramic material such as alumina. ), A heating resistor layer 61b such as silver-balladium (Ag—Pd) is attached. The surface of the heater substrate 61a including the heating resistor layer 61b is covered with a heater surface protective layer 61c made of a heat-resistant glass layer or the like. Further, a thermistor 61d as a heating temperature detecting means for detecting the heater temperature is attached to the back surface side (the upper surface side in the drawing) of the heater substrate 61a. The ceramic heater 61 having such a configuration is formed so as to have a low heat capacity as a whole, so that the temperature can be quickly raised and lowered in response to turning on and off of the heating resistor layer 61b. It is configured to have good responsiveness, and the detected temperature detected by the thermistor 61d is sent to the main body control unit 7, and the main body control unit 7 controls the heating temperature of the ceramic heater 61 described above. It is supposed to be executed.

  Here, the substantially cylindrical fixing heat-resistant film 63 described above is formed of a substantially cylindrical heat-resistant film having a thickness of about 40 μm to 100 μm, for example, and is formed on a substrate heat-resistant film such as polyimide. A heat-resistant resin having releasability obtained by adding a conductive agent to a fluororesin such as PFA or PTFE is coated. The ceramic heater 61 described above is externally fitted so as to be in a loose state with respect to the support body 62 that is fixedly supported on the lower surface side in the figure.

  On the other hand, in the pressure roller 64 described above, a roller layer 64b made of an elastic heat-resistant material such as silicone rubber and a surface layer 64c are provided concentrically and integrally on the outside of the core metal 64a. Both end portions in the axial direction are rotatably supported via appropriate bearing members between chassis side plates (not shown) disposed on the near side and the far side of the apparatus main body 1 described above. A support body 62 supporting the ceramic heater 61 on the lower surface side is arranged to face the upper surface side of the pressure roller 64, and the support body 62 is disposed on the pressure roller 64. Is held in a state in which it is pressed against the upper surface side with an appropriate pressing force, so that a predetermined width is provided between the lower surface of the heat-resistant film 63 for fixing that contacts the ceramic heater 61 and the upper surface of the pressure roller 64. A fixing nip portion (pressure nip portion) n is formed.

  At this time, the pressure roller 64 is configured to be rotationally driven in the clockwise direction of the arrow at a predetermined peripheral speed by the rotational driving force from the stepping motor M. The stepping motor M is the main body control unit 7 described above. Is driven by a drive command issued through the motor drive unit M1. The rotational driving force of the pressure roller 64 acts as a moving force on the fixing heat-resistant film 63 side by the pressure frictional force between the fixing nip portion n and the fixing heat-resistant film 63, thereby The fixing heat resistant film 63 is slid in a state where the inner surface side of the fixing heat resistant film 63 is in close contact with the ceramic heater 61. The fixing heat-resistant film 63 at this time is slid in the counterclockwise direction indicated by the arrow, and rotates around the support 62 at a speed corresponding to the rotational peripheral speed of the pressure roller 64. It has become. As described above, the support 62 has a function of holding the ceramic heater 61 and a function as a heat-resistant film guide for improving the rotational movement stability of the ceramic heater 61.

  The fixing heat-resistant film 63 is rotated and moved by the pressure roller driving system as described above, and at the same time, the ceramic heater 61 is controlled by the main body control unit 7 as control means including fixing heat control means. Appropriate energization is performed, and the fixing nip n is raised to a predetermined fixing temperature by the heat generated from the ceramic heater 61, and the temperature is adjusted. When a recording medium (heated member) P carrying an unfixed toner image t enters the fixing nip n in the temperature controlled state, the toner image carrying surface of the recording medium P at the fixing nip n. Is closely attached to the heat-resistant film 63 for fixing, and the recording medium P is nipped and conveyed through the fixing nip n together with the heat-resistant film 63 for fixing. In the nipping and conveying process of the recording medium P, heat from the ceramic heater 61 is applied to the recording medium P through the fixing heat-resistant film 63 to heat and fix the unfixed toner image t on the recording medium P. Is done. On the other hand, the recording medium P that has passed through the fixing nip n is conveyed while being separated from the outer surface of the fixing heat-resistant film 63 that is rotating.

  Here, a drive command is sent from the main body control section 7 to the motor drive section M1 attached to the above-described stepping motor M. The main body control section 7 is shown in FIG. 3, for example. As shown, the sequence controller 7a, timer 7b, A / D 7c, memory 7d, and the like are included. Further, the motor drive unit M1 includes a drive circuit M1a, a current detection circuit M1b, a constant current control circuit M1c, and a phase switching control circuit M1d, and is configured to perform rotation drive control of the stepping motor M described above. The main body control unit 7 transmits excitation pulses PA and PB for each phase of the motor, a current switching signal IO, and a driver operation permission signal ENBL to the motor drive unit M1, and the motor drive unit M1. When the driver operation permission signal ENBL becomes true, the stepping motor M is excited according to the excitation pulses PA and PB with the current value set by the current switching signal IO.

  On the other hand, as described above, the main body control unit 7 stores a program for controlling the heating temperature of the ceramic heater 61 of the fixing device 6 in the memory (ROM). The temperature gradient (temperature increase rate) obtained based on the heating temperature detected by the thermistor 61d and the rotational speed of the heat-resistant film 63 determined based on the temperature gradient, that is, the rotational drive of the pressure roller 64. The heating temperature control is executed with reference to a temperature gradient table in which the relationship with the speed is defined. The temperature gradient table is also stored in a memory (ROM). An example of the temperature gradient table is shown in Table 1 below.

  The start-up control in an image forming apparatus such as an actual copier or printer will be described. When a copy operation or a print signal is input, the pressure roller rotation drive speed starts rotating at 100% and at the same time, the initial heater output is energized. Energization is performed for 400 ms at a constant power of 70%. Assuming that the thermistor detection temperatures 200 ms and 400 ms after the start of the 70% energization are T1 and T2, respectively, the temperature rise ΔT1 from T1 to T2 is obtained, and the temperature exemplified in Table 1 above. With reference to (a) the initial output table in the gradient table, the value X% located in the relationship where T1 and ΔT1 intersect is determined as the initial rotational speed of the pressure roller rotational drive speed.

  For example, if the thermistor detection temperature is 55 ° C. and the initial heater output is set to 70% and T1 is 72 ° C. and T2 is 79 ° C., ΔT1 is 7 ° C. Based on the temperature gradient table (a) in Table 1 above, the initial rotation speed of the pressure roller rotation drive speed is determined to be 85%. Thereafter, the speed is corrected every 200 ms. The speed correction procedure is the same as the procedure for determining the initial rotational speed described above, and the thermistor detection temperature 200 ms after the initial rotational speed is determined. Assuming T3 and T4, the temperature rise ΔT3 from T3 to T4 is obtained, and this time, referring to the correction table (b) of the temperature gradient table in Table 1, the difference Δ with respect to the value X% described above Y% added with% is the rotational speed output after correction. Such rotation speed control is performed every 200 ms until the recording medium enters the fixing nip portion (pressure nip portion).

  Such speed control is performed until the recording material (heated member) P enters the fixing nip portion (pressure nip portion) when the main power is turned on or after waiting or after standby. The temperature rise is slowed by increasing the driving speed of the heat resistant film 63, and when the temperature gradient is small, the temperature rise is sharpened by slowing the driving speed of the heat resistant film 63. That is, when the temperature of the ceramic heater 61 is raised, the driving control of the heat resistant film 63 is mainly performed rather than the electric power control, and compared with the conventional apparatus in which the driving speed of the heat resistant film 63 is always slower than the electric power control. Further, the driving speed of the heat resistant film 63 is increased so as to prevent the ceramic heater 61 from being overheated, the driving time is shortened, toner contamination on the heat resistant film 63 is prevented, and the life of the film is prolonged. can get.

  As mentioned above, although the embodiment of the invention made by the present inventor has been specifically described, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Not too long.

  For example, in the above-described embodiment, the present invention is applied to a fixing device of a laser beam printer, but the present invention is similarly applied to a heating device of another image forming apparatus such as a copying machine or a facsimile. It is something that can be done.

  The heating device according to the present invention described above can be widely applied to various image forming apparatuses such as copying machines as well as image forming apparatuses such as printers.

1 is a longitudinal sectional view illustrating a schematic configuration of a laser printer as an example of an image forming apparatus to which the present invention is applied. FIG. 2 is a longitudinal sectional explanatory view showing a schematic structure of a fixing heating unit of a fixing device used in the laser printer shown in FIG. 1. FIG. 3 is a block diagram illustrating a schematic structure of a drive unit of a pressure roller driving stepping motor of the fixing device illustrated in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus body 2 Process cartridge 4 Transfer roller 5 Paper feed cassette 6 Fixing apparatus 7 Main body control part (control means)
21 Photosensitive drum 23 Developing device 61 Ceramic heater (heating body)
61a Heater board 61b Heating resistor layer 61c Heater surface protective layer 61d Thermistor (heating temperature detecting means)
62 Support 63 Heat-resistant film for fixing 64 Pressure roller (pressure member)
P Recording medium (heated member)
n Fixing nip M1 Motor drive

Claims (3)

A heating body, a heat-resistant film disposed so as to be slidable on the heating body, a pressure member that is driven and rotated in a state of being pressed against the heating body via the heat-resistant film, and a temperature of the heating body Temperature detecting means for detecting
By conveying the heated member while sandwiching the heated member in a pressure nip formed between the pressure member and the heat resistant film, heat generated from the heated body is passed through the heated film through the heated film. In the heating device configured to apply to the heating material,
A heating device comprising control means for controlling the drive rotation speed of the pressure member based on the detected temperature detected by the temperature detection means until the heated member enters the pressure nip portion. .   The heating device according to claim 1, wherein the control unit is configured to change a driving rotation speed of the pressure member based on a rate of increase in the detected temperature detected by the temperature detection unit. An image forming apparatus comprising the heating device according to claim 1 as image forming means.

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