JP2006349949A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device capable of reducing the torque needed to actuate a driving means of driving and rotating a pressing rotary body and also reducing specifications that the driving means needs to have. <P>SOLUTION: The image heating device has a pressing force control means 205 of controlling the pressing force of the pressing rotary body to a heating rotary body by displacing the pressing rotary body 2 relatively to the heating rotary body 13. When the heating body and driving means are at a stop, a control means 213 displaces the pressing rotary body through the pressing force control means to set the pressing force of the pressing rotary body to the heating rotary body lower than the pressing force when an image on a material P to be heated is heated at a nip section N while the material P to be heated is clamped and conveyed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image heating apparatus suitable for use as an image heating and fixing apparatus mounted on an electrophotographic or electrostatic recording image forming apparatus.

  In an image forming apparatus such as a laser printer, a heat roller type apparatus is widely used as an image heating and fixing apparatus that heats and fixes an unfixed toner image formed and supported on a recording material by an image forming process means unit on the surface of the recording material. It was used.

  In recent years, film heating type image heating and fixing devices (hereinafter referred to as fixing devices) have been put into practical use from the viewpoint of quick start and energy saving. Patent Documents 1 and 2 propose a film heating type fixing device. That is, a recording material on which an unfixed toner image is formed and supported by forming a nip portion (fixing nip portion) by sandwiching a heat resistant film (fixing film, fixing belt) between a ceramic heater and a pressure roller. It is nipped and conveyed at the nip. In this conveyance process, the heat of the heater is applied to the unfixed toner image through the fixing film, and the unfixed toner image is fixed on the surface of the recording material by the applied pressure of the nip portion.

  This film heating type fixing device can be configured as an on-demand type device using a heater and a low heat capacity member as a fixing film. That is, it is only necessary that the heater is energized only when image formation is performed to generate heat at a predetermined fixing temperature. For this reason, there is an advantage that the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property) and the power consumption during standby is significantly small (power saving).

  In a film heating type fixing device, there is a pressurizing rotating body driving method as a driving method of a cylindrical / endless film fixing film. The pressurizing rotating body driving method is a method in which the fixing film is driven and rotated by rotationally driving a pressure roller that forms a nip portion by sandwiching a heater as a heating body and a fixing film as a heating rotating body.

  In Patent Document 3, in order to reduce the influence of rotational torque due to friction between the fixing film and the heater, a lubricant such as heat-resistant grease is interposed between the fixing film and the heater so that the fixing film and the heater It has been proposed to ensure slidability between.

  In the above-described fixing device of the pressing rotary member driving system, the dominant factor in determining the specifications of the drive motor that rotationally drives the pressure roller is the torque required at the time of startup. The torque required at startup must be set assuming that the heat-resistant grease becomes hard when the fixing device is cooled. Therefore, when the fixing device is cold, the torque required when the drive motor is started is larger than the torque when the unfixed toner image is heated and fixed while the recording material is nipped and conveyed at the nip portion.

Further, in recent years, in the fixing device, as the speed of the image forming apparatus increases, the heat capacity applied to the recording material is increased by increasing the nip width of the nip portion in the recording material conveyance direction. In a fixing device mounted on a high-speed image forming apparatus, the nip width is increased by increasing the pressure applied to the fixing film of the pressure roller, so that the torque required for starting the drive motor is increased. . Therefore, the specifications required for the drive motor are high.
JP-A-4-44075 JP-A-4-204980 JP-A-5-27619

  Therefore, in the above fixing device, it is conceivable to use a high-torque drive motor that satisfies the torque required when the drive motor is started up as the speed of the image forming apparatus increases. However, the cost of the motor itself is high, and the motor itself becomes large.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus that can reduce a torque required at the time of starting a driving unit that rotationally drives a pressurizing rotating body and can reduce specifications required for the driving unit.

  A typical configuration of the image heating apparatus according to the present invention includes a heating rotator, a heating body that heats the heating rotator, and an additive that forms a nip portion between the heating body and the heating rotator. In the image heating apparatus that includes a pressure rotator and a driving unit that rotationally drives the pressure rotator, and heats an image on the material to be heated while nipping and conveying the material to be heated in the nip portion. The pressure rotating means for displacing the pressure rotating body with respect to the heating rotating body and controlling the pressure applied by the pressure rotating body to the heating rotating body, and the heating body and the driving means are stopped. In this case, the pressurizing rotary member is displaced by the pressurizing force control means, and the pressurizing force of the pressurizing rotary member with respect to the heating rotary member is held on the heated material while nipping and conveying the heated material at the nip portion. Control to set lower than the applied pressure when heating the image An image heating apparatus comprising: the stage, and it is.

  According to the present invention, when the heating unit and the driving unit are stopped, the pressing force of the pressurizing rotating body with respect to the heating rotating body is used to heat the image while nipping and conveying the heated material at the nip portion. It can be set lower than the applied pressure. As a result, it is possible to reduce the torque required when starting the drive means. Therefore, the specifications required for the driving means can be reduced.

  The present invention will be described in detail with reference to the drawings.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus in which the image heating apparatus according to the present invention can be mounted as an image heating fixing apparatus. The image forming apparatus of this embodiment is a laser printer using a transfer type electrophotographic process.

  Reference numeral 101 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) in the clockwise direction indicated by an arrow. The photosensitive drum 104 has a configuration in which a photosensitive material layer such as OPC, amorphous Se, or amorphous Si is formed on the outer peripheral surface of a cylinder (drum) -like conductive substrate such as aluminum or nickel.

  The photosensitive drum 101 is uniformly charged at a predetermined polarity and potential by the charging roller 102 during the rotation process. By a laser beam modulated and controlled (ON / OFF control) corresponding to a time-series electric digital pixel signal of target image information output from the laser beam scanner 103 to the uniformly charged surface of the rotating photosensitive drum 1. Scanning exposure L is performed. As a result, an electrostatic latent image of target image information is formed on the surface of the rotating photosensitive drum.

  The formed latent image is developed with toner by a developing roller 104 as developing means and visualized. As a development method, a jumping development method, a two-component development method, a FEED development method, or the like is used, and is often used in combination with image exposure and reversal development.

  On the other hand, the recording material P as the heated material accommodated in the feeding cassette 106 is fed out by one sheet by the rotational driving of the feeding roller 105. The recording material P is fed at a predetermined control timing through a sheet path having a feeding roller 107 and a registration roller 108 to a transfer nip portion where the photosensitive drum 101 and the transfer roller 109 are pressed. Then, the transfer roller 109 supplies a charge opposite in polarity to the toner from the back side of the recording material P, so that the toner image on the photosensitive drum 101 surface side is sequentially transferred as an unfixed toner image to the image forming surface of the recording material. It will be done.

  The recording material P exiting the transfer nip is sequentially separated from the surface of the rotating photosensitive drum 101 and introduced into an image heating and fixing device (hereinafter referred to as a fixing device) 110. The recording material P is subjected to a heat fixing process for an unfixed toner image by the fixing device 110. The fixing device 110 will be described in detail in the next section (2).

  The recording material P that has exited the fixing device 110 passes through a sheet path having a FU roller (conveying roller) 111, a guide 112, and an FD roller (discharge roller) 113, and is printed out on the discharge tray 114.

  Further, the surface of the rotating photosensitive drum 101 after separation of the recording material is subjected to a removal process of adhering contaminants such as transfer residual toner by a cleaning blade 115 as a cleaning means, and is repeatedly used for image formation.

  A sheet path mechanism 116 re-conveys the recording material P on which the single-sided image is formed that has exited the fixing device 110 to the transfer nip portion. The sheet pass mechanism 116 reverses the recording material on which a single-sided image has been formed, or the recording material on which the first image has been formed, or the front and back when a double-sided image forming mode or a multiple image forming mode is selected. It is transported again to the transfer nip without being reversed.

(2) Fixing device 110
The fixing device 110 according to the present exemplary embodiment is a film heating type / pressure rotating body driving type device. FIG. 2A is a front model view of the main part of the fixing device 110, and FIG. 2B is a side view of the pressure roller 2 and the pressure control rod 106. FIG. 3 is a cross-sectional side view model. FIG. 4 is a partially enlarged view of the vicinity of the nip portion of FIG.

  Reference numeral 1 denotes a heater unit as a heating member, and reference numeral 2 denotes an elastic pressure roller (hereinafter referred to as a pressure roller) as a pressure rotating body as a pressure member. The heater unit 1 and the pressure roller 2 are arranged in parallel vertically and pressed to form a nip portion (fixing nip portion) N.

  In the heater unit 1, reference numeral 11 denotes a film guide member (hereinafter referred to as a guide member) having a substantially semicircular cross section in cross section, which is a heat-resistant resin molding member such as PPS or liquid crystal polymer. This guide member 11 is a horizontally long member having a longitudinal direction in the drawing as a longitudinal direction, and a heating body (hereinafter referred to as a heater) 12 is fitted in a groove portion provided along the longitudinal direction on the lower surface thereof to be insulated and fixedly held. I'm allowed. The heater 12 will be described in detail later.

  Reference numeral 13 denotes a cylindrical fixing film (hereinafter referred to as a film) having heat resistance and flexibility as a heating rotator. The film 13 is loosely fitted to the assembly of the guide member 11 and the heater 12 described above. The film 13 is, for example, formed of a cylindrical metal sleeve or a heat-resistant resin sleeve on the outer peripheral surface of which a silicon rubber layer as an elastic layer and a fluororesin layer made of PTEFE / PFA or the like as a release layer are formed. It is what has. A flange member (not shown) that restricts the movement of the film 13 along the longitudinal direction of the guide member 11 is disposed at the end of the guide member 11. The flange members are respectively attached to first left and right side plates (not shown) of the apparatus. Since the film 13 rotates while rubbing against the internal heater 12 and the guide member 11 as will be described later, it is necessary to keep the frictional resistance between the heater and the guide member and the film small. For this reason, a lubricant (not shown) such as heat-resistant grease is applied to the inner peripheral surface of the film 13 in contact with the heater 12 and the guide member 11. Thereby, the film 13 can be smoothly rotated.

  The pressure roller 2 is formed by forming an elastic layer 2b made of silicon rubber, fluorine rubber or the like, and a release layer 2c on a cored bar 2a made of aluminum, iron or the like. The pressure roller 24 supports both ends of the core metal 2a between the second left and right side plates (not shown) of the apparatus via a bearing member so as to be freely rotatable and vertically movable. The heater unit 1 is arranged in parallel above the pressure roller 2. Then, the flange members respectively press the left and right end portions of the guide member 11 downward with a predetermined pressing force by a pressurizing spring (not shown). As a result, the film 13 of the heater unit 1 is sandwiched between the heater 12 and the pressure roller 2 and pressed against the elastic layer 2b of the pressure roller to heat and fix the unfixed toner image t on the recording material P. A nip portion N having a required predetermined width is formed.

In this embodiment, a ceramic heater is used as the heater 12. FIG. 5 is a schematic configuration diagram of the ceramic heater 12. This ceramic heater 12 is
A ceramic substrate (insulating substrate) a made of highly insulating ceramics such as horizontally long alumina, aluminum nitride, silicon carbide, etc., whose longitudinal direction is the direction perpendicular to the recording material conveyance direction in the surface direction of the recording material P;
-Formed on the surface side of the ceramic substrate a along the longitudinal direction by screen printing or the like in a linear or fine band form and fired, for example, Ag / Pd (silver palladium: silver alloy), RuO ₂ , Ta ₂ N Energizing heating element (heating resistor) b, etc.
Electrode portions c and c formed of Ag / Pt (silver / platinum) or the like, which are electrically connected to both ends in the longitudinal direction of the energization heating element b,
An insulating protective layer d, such as a thin glass coat or fluororesin coat, which is electrically insulated and can withstand rubbing against the film 13, provided on the surface of the energization heating element b;
Etc.

  In the ceramic heater 12, the length of the energization heating element b is about the same as the maximum longitudinal width D1 (FIG. 2) of the recording material P that can be introduced into the nip portion N. A temperature detecting element TH such as a thermistor as a temperature detecting means is disposed at a substantially central portion in the longitudinal direction on the back side of the ceramic substrate a. Electric power is supplied from the energization control circuit 214 to the electrode portions c and c. The energization control circuit 214 supplies power to the electrode portions c and c in accordance with the heater activation signal output from the control circuit 213 serving as a control unit. Thereby, the ceramic heater 12 is rapidly and rapidly heated by the heat generated by the energization heating element b.

  The temperature rise of the ceramic heater 12 is detected by the temperature detection element TH, and the detected temperature signal (resistance value) is input to the control circuit 213 as control means. The control circuit 213 controls the temperature of the ceramic heater 12 by ON / OFF control of the energization control circuit 214 so that the film 13 reaches a predetermined fixing temperature (target temperature) based on the detected temperature signal from the temperature detecting element TH. It is like that.

  The pressure roller 2 has a predetermined peripheral speed (process) in a counterclockwise direction (FIG. 3) indicated by an arrow by a drive motor M (FIG. 2) as a drive means by a rotational drive gear G provided at one end of a core metal 2a. Speed) (rotating body drive system for pressurization). As the pressure roller 2 is driven to rotate, the rotational force acts on the film by the frictional force at the nip N between the pressure roller and the outer surface of the film 13. Then, the film 13 rotates following the clockwise direction indicated by the arrow (FIG. 3) while the film inner surface is in close contact with the downward surface of the heater 12 at the nip portion N and slides around the outer periphery of the guide member 11. As described above, the slidability of the film with respect to the heater 12 and the guide member 11 is maintained by the lubricant applied to the inner peripheral surface of the film 13. Further, the rotation stability of the film 13 is maintained by the guide member 11.

  The ceramic heater 12 is energized during the rotation of the pressure roller 2 and the film 13. As a result, the ceramic heater 12 is heated and adjusted to a predetermined fixing temperature as described above. In the temperature-controlled state of the ceramic heater 12, a recording material P carrying an unfixed toner image t is introduced into the nip portion N, and the recording material has a toner image carrying surface in close contact with the outer surface of the film 13 together with the film. The nip portion N is nipped and conveyed. In this conveyance process, the heat of the ceramic heater 12 is applied to the recording material P through the film 13, and the unfixed toner image t is heated and pressurized on the surface of the recording material and fixed by the pressing force of the nip portion N. The The recording material P that has passed through the nip N is separated from the outer peripheral surface of the film 13 and is discharged and conveyed.

(3) Description of Pressurization Control Mechanism 205 An example of the pressurization control mechanism 205 as the pressurization control means provided in the fixing device 110 of this embodiment is shown in FIG.

  The pressure control mechanisms 205 are disposed on both sides of the pressure roller 2 in the longitudinal direction, and a pressure control motor 210 having a pressure control rod 206 having a position detection flag 207 and a pressure control drive gear 209 on an output shaft. And a position detection sensor 211 as position detection means. The pressure control rod 206 is supported by the second left and right side plates of the apparatus so as to be movable up and down. The pressure control motor 210 and the position detection sensor 211 are fixedly supported on the second left and right side plates of the apparatus, respectively. The pressure control rod 206 has a substantially U-shaped support portion 206a at an end portion on the pressure roller 2 side, and the end portion of the core metal 2a of the pressure roller 2 is rotatably supported by this support portion ( (See (b)). The pressure control rod 206 has a pressure control driven gear 208 that meshes with the pressure control drive gear 209 of the pressure control motor at the end on the pressure control motor 210 side.

  FIG. 6 shows a functional block diagram of an example of the temperature control / drive control system of the fixing device 110.

  The position of the position detection flag 207 of the pressure control mechanism 205 shown in FIG. 6 is necessary for fixing the unfixed toner image t on the surface of the recording material while the recording material P is nipped and conveyed by the nip portion N. Corresponding to a reference pressure setting position (hereinafter referred to as a reference pressure setting position). When the pressure applied to the film 13 by the pressure roller 2 is set to a pressure lower than the reference pressure, the pressure control drive gear 209 is rotated counterclockwise by the pressure control motor 210. Accordingly, the pressure control driven gear 208 is rotated in the same direction, the pressure control rod 206 is lowered together with the pressure roller 2, and the pressure roller is separated from the film 13 as indicated by a two-dot chain line. When the pressure applied to the film 13 by the pressure roller 2 is set to the reference pressure, the pressure control drive gear 209 is rotated clockwise by the pressure control motor 210 as indicated by an arrow. As a result, the pressure control driven gear 208 is rotated in the same direction, the pressure control rod 206 is raised together with the pressure roller 2, and the film 13 is pressed as shown by the solid line. The position detection sensor 211 detects the position of the position detection flag 207 that moves up and down together with the pressure control rod 206, and outputs a position signal corresponding to the detected position to the control circuit 213.

  The drive motor M is attached to a support member (not shown) provided on the pressurization control rod 206 and moves up and down together with the pressurization control rod while being engaged with the rotation drive gear G. The drive motor M is connected to a rotation speed sensor 212 as rotation speed detection means. The rotation speed sensor 212 outputs a rotation speed detection signal corresponding to the rotation speed of the drive motor M to the control circuit 213.

  The control circuit 213 includes a CPU and a memory such as a ROM and a RAM, and various programs such as energization control and temperature control are stored in the memory in addition to the pressurizing control described later.

  FIG. 7 shows a flowchart of pressure control by the control circuit 213.

  First, the image forming apparatus is turned on (S1). At this time, the drive motor M and the ceramic heater 12 are not started but stopped.

  In S2, a position signal corresponding to the detection position of the position detection flag 207 is taken from the position detection sensor 211 (S2).

  In S3, it is determined whether or not the position of the position detection flag 207 is a reference pressure setting position based on the position signal. If it is determined that the reference pressure setting position is (Yes), the process proceeds to S4. If it is determined that the position is not the reference pressure setting position (No), the process proceeds to S5.

  In S4, the pressure control motor 210 is activated and the pressure control rod 206 lowers the pressure roller 2 from the reference pressure setting position by an amount corresponding to a pressure lower than the reference pressure. Thereby, the pressing force of the pressure roller 2 is set to a pressing force lower than the reference pressing force.

  In S5, it is determined whether or not drive start signals for the drive motor M and the ceramic heater 12 have been received. When it is determined that the drive start signal has been received (Yes), the process proceeds to S6.

  In S6, the drive motor M is started and energization to the ceramic heater 12 is started.

  In S7, a rotation speed detection signal is captured.

  In S8, it is determined whether or not the drive motor M has reached a steady rotation speed (a reference rotation speed when the recording material is fixed) based on the rotation speed detection signal. When it is determined that the steady rotational speed has been reached (Yes), the process proceeds to S9.

  In S9, a detected temperature signal is captured.

  In S10, it is determined whether or not the temperature of the ceramic heater 12 has reached the temperature at which the lubricant is softened based on the detected temperature signal. When it is determined that the temperature at which the lubricant softens has been reached (Yes), the process proceeds to S11.

  In S11, the pressure control motor 210 is activated and the pressure control rod 206 raises the pressure roller 2 from the stop position in S4 by an amount corresponding to the reference pressure setting position. Thereby, the pressing force of the pressure roller 2 is set to the reference pressing force.

  When the pressing force of the pressure roller 2 is set to the reference pressing force in S11, the recording material P is introduced into the nip portion N. As the recording material P passes through the nip portion N, the unfixed toner image t is fixed on the surface of the recording material.

  In S12, it is determined whether or not drive stop signals for the drive motor M and the ceramic heater 12 have been received. When it is determined that the drive stop signal has been received (Yes), the process proceeds to S14.

  In S13, the drive motor M is stopped, the energization to the ceramic heater 12 is stopped, and the process returns to S2.

  As described above, when the energization to the ceramic heater 12 is stopped and the drive motor M is stopped, the recording material P is nipped and conveyed by the nip portion N with the pressure applied by the pressure roller 2. However, it is set lower than the reference pressure when the unfixed toner image t is heated and pressed. When the drive motor M is activated, the reference pressure is set when the temperature detected by the temperature detection element TH is equal to or higher than the temperature at which the lubricant applied to the inner peripheral surface of the film 13 is softened. .

  Therefore, as described above, the pressing force of the pressure roller 2 can be set lower than the reference pressing force, so that the torque required when the drive motor M is started can be reduced, and the specifications required for the drive motor can be reduced. .

[Others]
1) The rotating body for heating may be an electromagnetic induction exothermic film. In this case, it is possible to use an exciting coil and a magnetic core that cause the film to generate heat by applying a magnetic flux to the electromagnetic induction heat generating film as a heating element.

  2) The image heating apparatus of the present invention is not limited to the image heating and fixing apparatus of the embodiment, but an image heating apparatus that modifies the surface properties such as gloss by heating a heated material carrying an image, an image heating apparatus that is supposed to be worn, etc. It can be used as a means / apparatus for heat-treating a material to be heated that carries a wide image.

Schematic configuration diagram of an image forming apparatus (A) is a front model view of the main part of the fixing device, (b) is a side view of the pressure roller and the pressure control rod. Cross-sectional side view of the main part of the fixing device Partial enlarged view of the vicinity of the nip in FIG. Schematic configuration diagram of ceramic heater Functional block diagram of an example of a temperature control / drive control system for a fixing device Flow chart of pressure control

Explanation of symbols

2: pressure roller, 12: ceramic heater, 13: fixing film, 205: pressure control mechanism, 206: pressure control rod, 207: position detection flag, 208: pressure control driven gear, 209: pressure control Drive gear, 210: pressurization control motor, 211: position detection sensor, 212: rotation speed sensor, 213: control circuit, 214: energization control circuit, TH: temperature detection element, M: drive motor

Claims (3)

A heating rotator, a heating body that heats the heating rotator, a pressurizing rotator that forms a nip portion between the heating body and the heating rotator, and rotationally drives the pressurizing rotator. An image heating apparatus that heats an image on the heated material while sandwiching and conveying the heated material at the nip portion.
A pressure control means for displacing the pressurizing rotator with respect to the heating rotator and controlling a pressurizing force of the pressurizing rotator with respect to the heating rotator;
When the heating body and the driving means are stopped, the pressurizing rotary body is displaced by the pressurizing force control means, and the pressurizing force of the pressurizing rotary body against the heating rotary body is covered by the nip portion. Control means for setting lower than the applied pressure when heating the image on the heated material while nipping and conveying the heating material;
An image heating apparatus comprising:   Furthermore, it has a temperature detection means for detecting the temperature of the heating body, and the control means, when the drive means is activated, when the temperature detected by the temperature detection means reaches a predetermined temperature, The pressurizing rotary member is displaced by the pressurizing control means, and the pressurizing force of the pressurizing rotary member with respect to the heating rotary member is changed to the pressurizing force when the image is heated while the material to be heated is nipped and conveyed by the nip portion. The image heating apparatus according to claim 1, wherein the image heating apparatus is set.   The image heating apparatus according to claim 2, wherein the predetermined temperature is a temperature at which a lubricant applied to a surface of the rotating body for heating that comes into contact with the heating unit is softened.