JP2005189335A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time required until calibration operation is started. <P>SOLUTION: A printer is constituted so that all the rotational driving force required in the printer is generated by using a common motor 101. An electromagnetic clutch 104 which can be switched to a state where it transmits the rotational driving force and a state where it does not transmit the force is provided in a rotational driving force transmitting path from the motor 101 to the heating roller 61 of a fixing part. When the calibration operation is started, the clutch 104 gets in a state where it does not transmit the rotational driving force generated by the motor 101 to the roller 61. Therefore, the calibration operation is instantaneously started without waiting for the temperature rise of the roller 61 even while toner is adhered to the roller 61. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that performs a calibration operation.

2. Description of the Related Art Conventionally, for example, an image forming apparatus such as a printer that performs a calibration operation for correcting image forming characteristics is known.
For example, a density sensor for detecting the density of the toner image formed on the intermediate transfer body is provided, a patch is formed on the intermediate transfer body, the density of the patch is read by the density sensor, and the density is determined according to the read density. Some adjustments are made (for example, see Patent Document 1).
JP 2002-229278 A

  By the way, in order to reduce the size and cost of the image forming apparatus, the image forming apparatus is configured to drive a member to be rotated, such as a photosensitive drum or a roller of a fixing device, using a common motor. There is.

  In this case, as described above, when the patch is formed on the intermediate transfer member, the roller of the fixing device also rotates as the photosensitive member and the intermediate transfer member are driven to rotate. However, since the roller of the fixing unit may be fixed between the rollers by the toner when the temperature is low, it is necessary to rotate the roller after increasing the temperature to such an extent that the toner melts. If this is not done, the rollers cannot be rotated until the toner is melted because the rollers are fixed. As a result, there is a problem that it takes time to start the calibration operation.

  The present invention has been made in view of these problems, and aims to shorten the time required to start the calibration operation.

  The image forming apparatus according to claim 1, which is made to achieve the above object, includes a photoconductor, a developer image forming unit that forms a developer image on the photoconductor while the photoconductor is rotating, and Transfer means for transferring the developer image formed on the photosensitive member by the developer image forming means directly or indirectly onto the recording medium.

  The image forming apparatus further includes a fixing unit. The fixing means includes two rotating bodies that rotate in contact with each other, and a heating means that raises the temperature of at least one of the two rotating bodies (for example, a heating element such as a heater, or IH (induction heating)). Etc., and the recording medium on which the developer image has been transferred by the transfer means is heated between the two rotating bodies to thermally fix the developer image. Note that the rotating body of the fixing unit may be, for example, cylindrical (drum-shaped) or belt-shaped.

  In this image forming apparatus, the calibration execution unit forms a developer image for judging image characteristics on the photosensitive member or a member that can be transferred from the photosensitive member, and the density of the formed developer image. (In other words, a calibration operation for detecting the amount of developer adhered per unit area) and correcting the image forming conditions based on the detected density is performed.

  The image forming apparatus generates a rotational driving force necessary for the calibration execution unit to perform the calibration operation, and generates a rotational driving force for rotating at least one of the two rotating bodies of the fixing unit. Rotational driving force generating means (for example, a motor) is provided.

  Further, the image forming apparatus switches between a transmission state in which the rotational driving force generated by the rotational driving force generation unit is transmitted to the rotating body of the fixing unit and a non-transmission state in which the rotational driving force is not transmitted to the rotating body of the fixing unit. A possible transmission state switching means, and a switching control means for controlling the transmission state switching means so that the state of the transmission state switching means when the calibration operation is started by the calibration execution means becomes a non-transmission state. ing.

  According to the image forming apparatus of the present invention, the calibration operation can be started regardless of the state of the rotating member of the fixing unit (for example, whether or not the fixing member is fixed by the developer). Therefore, according to the present image forming apparatus, the time required to start the calibration operation can be shortened.

  That is, the two rotating bodies of the fixing unit may be fixed by the developer when the temperature is low. Therefore, to rotate the rotating body, first, the temperature of the rotating body is increased to such an extent that the developer melts. It is necessary to let For this reason, in a configuration in which the rotating body of the fixing unit also rotates by generating a rotational driving force necessary for performing the calibration operation, it is necessary to raise the temperature of the rotating body before starting the calibration operation. Yes, it takes unnecessary time to start the calibration operation.

  On the other hand, in this image forming apparatus, a transmission state in which the rotational driving force generated by the rotational driving force generation unit is transmitted to the rotating body of the fixing unit and a non-transmission state in which the rotational driving force is not transmitted to the rotating body of the fixing unit. And a switching control means for controlling so that the state of the transmission state switching means when the calibration operation is started becomes a non-transmission state. Therefore, according to this image forming apparatus, it is possible to prevent the rotating body of the fixing unit from rotating when starting the calibration operation, and the calibration operation can be started quickly.

  Note that the transfer unit has, for example, an intermediate transfer member that rotates in contact with the photosensitive member, and the developer image formed on the photosensitive member by the developer image forming unit is once transferred onto the intermediate transfer member. Thereafter, the image can be transferred onto the recording medium from the intermediate transfer member. In this case, the calibration execution unit forms a developer image (for example, a color patch) for determining image characteristics on the intermediate transfer member, detects the density of the formed developer image, and detects the detected density. It is preferable to perform a calibration operation such as correcting image forming conditions (for example, density and gradation) based on the above.

  In addition, the transfer unit includes, for example, a conveyance body that rotates and conveys the recording medium in contact with the photoconductor, and the developer image formed on the photoconductor by the developer image forming unit is transferred by the conveyance body. It can also be set as the structure which transfers on the recording medium conveyed. In this case, the calibration execution unit forms a developer image (for example, a color patch) for determining the image characteristics on the conveyance body, detects the density of the formed developer image, and sets the detected density to the detected density. It is preferable to perform a calibration operation such as correcting an image forming condition (for example, density or gradation) based on this.

  By the way, as the “rotation driving force required when the calibration execution unit performs the calibration operation” generated by the rotation driving force generation unit, for example, as described in claim 2, the photosensitive member or the photosensitive member For example, a rotational driving force with respect to a transfer unit (specifically, for example, an intermediate transfer member or a conveyance member) can be used.

  On the other hand, the heating unit preferably raises the temperature of the rotating body of the fixing unit while the calibration operation is being performed by the calibration execution unit. In this way, the time required from the end of the calibration operation to the start of the image forming operation (the time required to raise the fixing member rotating body to a temperature at which the developer image can be thermally fixed). Can be shortened.

  In such a configuration, as described in claim 4, while the switching control unit performs the calibration operation by the calibration execution unit, the temperature of the rotating body of the fixing unit is a predetermined temperature (for example, When the temperature rises to a temperature at which the developer melts, it is preferable to perform control for switching the transmission state switching means to the transmission state. In this way, the temperature of the rotating body can be made uniform by rotating the rotating body of the fixing means.

  Next, the image forming apparatus according to claim 5 is the image forming apparatus according to claim 3 or 4, wherein the temperature of the rotating body of the fixing unit is greater than the start of the calibration operation when the temperature rise by the heating unit is started. Temperature rise start determining means for determining whether or not the temperature is equal to or higher than a reference temperature as a criterion for determining whether or not to delay is provided. When the temperature rise start determination unit determines that the heating unit is equal to or higher than the reference temperature, the temperature of the rotating body of the fixing unit is delayed at a timing later than the timing at which the calibration operation is started by the calibration execution unit. To raise.

  According to the image forming apparatus having such a configuration, energy required for raising the temperature of the rotating body of the fixing unit can be saved. That is, the time required to start the image forming operation (the time required to raise the fixing member rotating member to a temperature at which the developer image can be thermally fixed) is equal to the temperature of the fixing member rotating member (temperature increase start). The higher the temperature, the shorter. If the time required to raise the rotating member of the fixing unit to a temperature at which the developer image can be thermally fixed is shorter than the time required for the calibration operation, the timing is later than the timing at which the calibration operation is started. Thus, even when the temperature of the rotating member of the fixing unit is raised, it is possible to prevent an increase in the waiting time from the end of the calibration operation to the start of the image forming operation. For this reason, in this image forming apparatus, energy is saved by delaying the timing for starting the temperature rise of the rotating body of the fixing unit. Therefore, the reference temperature is set to a value such that the time required to raise the rotating member of the fixing unit from the reference temperature to a temperature at which the developer image can be thermally fixed is equal to the time required for the calibration operation. It is preferable that Note that the higher the temperature of the fixing member rotator, the greater the delay in the start timing of the temperature rise relative to the start timing of the calibration operation.

  On the other hand, an image forming apparatus according to a sixth aspect is the image forming apparatus according to the third or fourth aspect, wherein the temperature of the rotating body of the fixing unit is used as a criterion for determining whether or not the execution of the calibration operation should be prohibited. Execution prohibition judging means for judging whether or not the temperature is higher than the reference temperature is provided. The calibration execution unit does not perform the calibration operation when the execution prohibition determination unit determines that the temperature is equal to or higher than the reference temperature.

  According to the image forming apparatus having such a configuration, it is possible to prevent the start of the image forming operation from being delayed by performing the calibration operation. That is, the time required to start the image forming operation (the time required to raise the fixing member rotating member to a temperature at which the developer image can be thermally fixed) is equal to the temperature of the fixing member rotating member (temperature increase start). The higher the temperature, the shorter. Then, if the time required for raising the rotating member of the fixing unit to a temperature at which the developer image can be thermally fixed is shorter than the time required for the calibration operation, the image forming operation is performed as compared with the case where the calibration operation is not performed. Will be delayed. For this reason, in this image forming apparatus, the calibration operation is not performed when the temperature of the rotating member of the fixing unit is somewhat high. Therefore, the reference temperature is set to a value such that the time required to raise the rotating member of the fixing unit from the reference temperature to a temperature at which the developer image can be thermally fixed is equal to the time required for the calibration operation. It is preferable that

  In addition, the case where the temperature of the fixing member rotating body is high is a case where the elapsed time from the previous image forming operation is short, and it is considered that the image forming operation has been performed without any problem so far. Since the necessity of performing the operation itself is low, it is also effective in that unnecessary calibration operations can be reduced.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a schematic sectional side view of a printer 10 as an image forming apparatus according to an embodiment.
As shown in the figure, the printer 10 is a so-called tandem color laser printer, and includes a visible image forming unit 30, a belt-shaped intermediate transfer body (ITB: Inter Transfer Belt) 50, a fixing unit 60, and the like. , A paper feed unit 70 and a paper discharge tray 80 are provided.

  The visible image forming unit 30 includes a developing device 31M as a developing unit for each visible image process using toner as a developer of magenta (M), cyan (C), yellow (Y), and black (Bk). , 31C, 31Y, 31Bk, photosensitive drums 32M, 32C, 32Y, 32Bk as photosensitive members, cleaning rollers 33M, 33C, 33Y, 33Bk, chargers 34M, 34C, 34Y, 34Bk, and exposure means 35M, 35C, 35Y, and 35Bk.

Hereinafter, each of these components will be described in detail.
First, the developing devices 31M, 31C, 31Y, and 31Bk are provided with developing rollers 36M, 36C, 36Y, and 36Bk. The developing rollers 36M, 36C, 36Y, and 36Bk are formed in a cylindrical shape using conductive silicone rubber as a base material, and further, a coating layer of a resin or rubber material containing fluorine is formed on the surface. The developing rollers 36M, 36C, 36Y, and 36Bk do not necessarily have to be made of a conductive silicone rubber, and may be made of a conductive urethane rubber, for example. Further, the ten-point average roughness (Rz) of the surface is set to 3 to 5 μm, and is configured to be smaller than 9 μm which is the average particle diameter of the toner.

  Each developing device 31M, 31C, 31Y, 31Bk is provided with supply rollers 37M, 37C, 37Y, 37Bk. The supply rollers 37M, 37C, 37Y, and 37Bk are conductive sponge rollers, and are disposed so as to be in pressure contact with the developing rollers 36M, 36C, 36Y, and 36Bk by the elastic force of the sponge. As the supply rollers 37M, 37C, 37Y, and 37Bk, foams of appropriate members such as conductive silicone rubber, EPDM, and urethane rubber can be used.

  Further, each of the developing devices 31M to 31Bk is provided with a layer thickness regulating blade 38M, 38C, 38Y, 38Bk. The layer thickness regulating blades 38M, 38C, 38Y, and 38Bk are formed in a plate shape with stainless steel or the like at the base end and fixed to the developing device cases 39M, 39C, 39Y, and 39Bk, and the tip ends are made of insulating silicone rubber or insulating material. The fluorine-containing rubber or resin. The tips of the layer thickness regulating blades 38M, 38C, 38Y, 38Bk are pressed against the developing rollers 36M, 36C, 36Y, 36Bk from below the developing rollers 36M, 36C, 36Y, 36Bk.

  The toner accommodated in the developing device cases 39M, 39C, 39Y, and 39Bk is a positively chargeable non-magnetic one-component developer, and a well-known styrene-acrylic resin formed into a spherical shape by suspension polymerization, such as carbon black. And a toner control particle having an average particle diameter of 9 μm obtained by adding a charge control agent such as nigrosine, triphenylmethane, quaternary ammonium salt, or a charge control resin. The toner is constituted by adding silica as an external additive to the surface of the toner base particles. Further, the silica as the external additive is subjected to a known hydrophobizing treatment with a silane coupling agent, silicone oil or the like, the average particle diameter is 10 nm, and the addition amount is 0.6% by weight of the toner base particles. It is. Magenta, cyan, yellow, and black toners are stored in the developing device cases 39M, 39C, 39Y, and 39Bk, respectively.

  Thus, the toner is an extremely spherical suspension polymerization toner, and further, 0.6% by weight of hydrophobically treated silica having an average particle diameter of 10 nm is added as an external additive, so that it is extremely fluid. Is excellent. Therefore, a sufficient charge amount can be obtained by frictional charging. Further, since there is no corner portion unlike the pulverized toner, it is difficult to receive mechanical force, has excellent followability to an electric field, and has good transfer efficiency.

  As an example, the photosensitive drums (OPCs) 32M, 32C, 32Y, and 32Bk are formed by forming a positively chargeable photosensitive layer on an aluminum substrate. The thickness of the photosensitive layer is 20 μm or more, and the aluminum substrate is used as an earth layer.

  The cleaning rollers 33M, 33C, 33Y, and 33Bk are rollers made of an elastic material such as a conductive sponge, and are arranged below the photosensitive drums 32M, 32C, 32Y, and 32Bk to the photosensitive drums 32M, 32C, 32Y, and 32Bk. It is configured to rub. Since the printer 10 employs a so-called cleanerless development method, residual toner once removed by the cleaning rollers 33M, 33C, 33Y, and 33Bk is again exposed to light in a predetermined cycle after the development process is completed. It is configured to return to the side drums 32M, 32C, 32Y, and 32Bk, collect it by the developing rollers 36M, 36C, 36Y, and 36Bk, and return it to the developing devices 31M, 31C, 31Y, and 31Bk of the respective colors.

  The chargers 34M, 34C, 34Y, and 34Bk are scorotron type chargers, and are located downstream of the cleaning rollers 33M, 33C, 33Y, and 33Bk in the rotational direction of the photosensitive drums 32M, 32C, 32Y, and 32Bk. The photosensitive drums 32M, 32C, 32Y, and 32Bk are opposed to the surface of the photosensitive drums 32M, 32C, 32Y, and 32Bk in a non-contact manner from below the photosensitive drums 32M, 32C, 32Y, and 32Bk.

  The exposure means 35M, 35C, 35Y, and 35Bk are composed of known laser scanner units. The exposure units 35M, 35C, 35Y, and 35Bk are arranged so as to overlap the developing units 31M, 31C, 31Y, and 31Bk of the visible image forming unit 30 in the vertical direction, and the photosensitive drums 32M, 32C, 32Y, and 32Bk and the chargers 34M, 34C, 34Y, 34Bk are arranged so as to overlap in the horizontal direction, and downstream of the chargers 34M, 34C, 34Y, 34Bk in the rotational direction of the photosensitive drums 32M, 32C, 32Y, 32Bk. On the side, the surfaces of the photosensitive drums 32M, 32C, 32Y, and 32Bk are exposed with laser light. The exposure means 35M, 35C, 35Y, and 35Bk irradiate the surface of the photosensitive drums 32M, 32C, 32Y, and 32Bk with laser light corresponding to the image data, and the surfaces of the photosensitive drums 32M, 32C, 32Y, and 32Bk. The electrostatic latent image for each color is formed.

  The toner is positively charged and is supplied from the supply rollers 37M, 37C, 37Y, and 37Bk to the developing rollers 36M, 36C, 36Y, and 36Bk, and is formed into a uniform thin layer by the layer thickness regulating blades 38M, 38C, 38Y, and 38Bk. . The positive polarity (positive charging) formed on the photosensitive drums 32M, 32C, 32Y, and 32Bk at the contact portions between the developing rollers 36M, 36C, 36Y, and 36Bk and the photosensitive drums 32M, 32C, 32Y, and 32Bk. With respect to the electrostatic latent image, positively charged toner can be satisfactorily developed by the reversal development method, and an extremely high quality image can be formed.

  The belt-shaped intermediate transfer member (intermediate transfer belt) 50 is formed by forming a conductive sheet such as polycarbonate or polyimide into a belt shape. The intermediate transfer member 50 is stretched between two drive rollers 51 and 52, and rotates while being in contact with the photosensitive drums 32M, 32C, 32Y, and 32Bk. In addition, intermediate transfer rollers 53M, 53C, 53Y, and 53Bk are provided in the vicinity of positions facing the photosensitive drums 32M, 32C, 32Y, and 32Bk. The moving direction of the surface of the intermediate transfer member 50 on the side facing the photosensitive drums 32M, 32C, 32Y, 32Bk is set to a direction of moving from the vertical direction upward to the downward direction.

  A predetermined voltage is applied to the intermediate transfer rollers 53M, 53C, 53Y, and 53Bk, and the toner images formed on the photosensitive drums 32M, 32C, 32Y, and 32Bk are temporarily transferred onto the intermediate transfer member 50. It is configured as follows. Further, a secondary transfer roller 54 is provided opposite to the roller 52 in the vertical direction with respect to the position where the toner image is transferred onto the paper P as a recording medium, that is, the intermediate transfer member 50. A predetermined potential is also applied to the transfer roller 54. As a result, the four color toner images carried on the belt-like intermediate transfer member 50 are transferred onto the paper P.

  A cleaning device 55 is provided on the opposite side of the intermediate transfer member 50 from the side facing the photosensitive drums 32M, 32C, 32Y, 32Bk. The cleaning device 55 includes a scraping member 56 and a case 57. The toner remaining on the intermediate transfer member 50 is scraped off by the scraping member 56 and stored in the case 57.

  The fixing unit (fixing device) 60 is provided inside the heating roller 61 and the heating roller 61 and the pressure roller 62 as rotating bodies rotating in contact with each other, and generates heat when energized to generate heat. And a temperature sensor (for example, a thermistor) 64 that detects the surface temperature of the heating roller 61 while being in contact with the surface of the heating roller 61. In the fixing unit 60, the sheet P on which the toner image is transferred is pressed against the heating roller 61 that is temperature-controlled at a heat fixing temperature (for example, 180 ° C.) that is a control temperature during the printing operation, and the heating roller 61. The toner image is heat-fixed on the paper P by heating and pressurizing while being nipped and conveyed between the pressure rollers 62.

  The paper feeding unit 70 is provided at the lowermost part of the apparatus, and includes a storage tray 71 that stores the paper P and a pickup roller 72 that feeds the paper P. The paper feeding section 70 is provided with an image forming process by the exposure means 35M, 35C, 35Y, and 35Bk, the developing devices 31M, 31C, 31Y, and 31Bk, the photosensitive drums 32M, 32C, 32Y, and 32Bk, and the intermediate transfer member 50. The paper P is supplied at a timing. The paper P supplied from the paper supply unit 70 is conveyed to a pressure contact portion between the intermediate transfer member 50 and the secondary transfer roller 54 by a conveyance roller pair 73.

  The paper discharge tray 80 is provided on the paper discharge side of the fixing unit 60, and is configured to receive the paper P that is discharged from the fixing unit 60 and conveyed by a pair of conveyance rollers 91, 92, and 93. Yes.

Next, the operation of the printer 10 will be described.
First, in a state where the photosensitive drums 32M, 32C, 32Y, and 32Bk are rotationally driven, the photosensitive layer on the surface thereof is uniformly charged by the chargers 34M, 34C, 34Y, and 34Bk, and these photosensitive layers are exposed. By means of means 35M, 35C, 35Y, 35Bk, exposure is performed corresponding to each image of magenta, cyan, yellow and black. Then, magenta toner is formed on the electrostatic latent images formed on the photosensitive layers of the photosensitive drums 32M, 32C, 32Y, and 32Bk by the magenta developing unit 31M, the cyan developing unit 31C, the yellow developing unit 31Y, and the black developing unit 31Bk, respectively. Then, cyan toner, yellow toner and black toner are adhered, and magenta, cyan, yellow and black colors are developed. The toner images as magenta, cyan, yellow, and black developer images formed on the photosensitive layers of the photosensitive drums 32M, 32C, 32Y, and 32Bk in this manner are temporarily stored in the intermediate transfer member 50. Transferred onto the surface. The toner images of the respective colors are formed with a slight time difference according to the moving speed of the intermediate transfer member 50 and the positions of the photosensitive drums 32M, 32C, 32Y, and 32Bk. The toner image is transferred so as to be superimposed on the intermediate transfer member 50. The toner remaining on the photosensitive drums 32M, 32C, 32Y, and 32Bk after the transfer is temporarily held by the cleaning rollers 33M, 33C, 33Y, and 33Bk.

  The four color toner images formed on the intermediate transfer member 50 as described above are transferred onto the paper P supplied from the paper feeding unit 70 at the pressure contact position between the secondary transfer roller 54 and the intermediate transfer member 50. Is done. The toner image is heat-fixed on the paper P in the fixing unit 60 and discharged onto the paper discharge tray 80. As described above, a four-color image is formed.

Further, the printer 10 has a function of performing color correction processing (calibration) for correcting the characteristics of an image to be printed prior to the above-described color image formation (printing).
In order to perform this calibration, the printer 10 includes a density sensor 58 for detecting the density of each color toner image transferred onto the intermediate transfer member 50. The density sensor 58 is disposed on the downstream side of a portion where the intermediate transfer member 50 and the photosensitive drum 32Bk are opposed to each other, and although not shown, a light source that emits light in the infrared region and a light source that irradiates the intermediate transfer member 50. A lens and a phototransistor that receives the reflected light are provided.

Here, the calibration operation of the printer 10 will be described.
First, exposure and development are performed in the same manner as the printing operation described above, and a toner image (color patch) of a color correction processing pattern is formed (transferred) on the intermediate transfer member 50 as a toner image for judging image characteristics. To do. Next, the density sensor 58 detects the density of the toner image. Then, based on the detected density, the printing condition (for example, density and gradation) as the image forming condition is corrected to correct the characteristics of the printed image. The toner image formed on the intermediate transfer member 50 is collected by the cleaning device 55.

Next, the electrical configuration of the printer 10 will be described with reference to the block diagram of FIG.
As shown in the figure, the printer 10 includes a motor for driving the above-described density sensor 58, temperature sensor 64 and heater 63, and a motor 101 that generates rotational driving force such as various rollers provided in the printer 10. Electromagnetic clutch 103 provided in drive circuit 102, drive force transmission path (dotted line portion) from motor 101 to pickup roller 72, and electromagnetic clutch provided in drive force transmission path (dotted line portion) from motor 101 to heating roller 61 104 and a control unit 110 having a known CPU 111, ROM 112, RAM 113, and the like.

  The motor 101 is for generating all the rotational driving force required in the printer 10, and specifically, the photosensitive drum 32, the developing roller 36, the supply roller 37, the driving roller 52, and the heating roller. 61, the pickup roller 72, the conveyance roller pair 73, 91, 92, 93, and the like are driven to rotate. For this reason, by driving the motor 101, these rollers and the like rotate all at once. However, the rotational driving force from the motor 101 to the pickup roller 72 and the heating roller 61 is configured to be transmitted through the electromagnetic clutches 103 and 104, respectively, so that the rotational driving force generated by the motor 101 is transmitted. The state can be switched to a non-transmission state where the rotational driving force is not transmitted. The pressure roller 62 is driven and rotated by the rotation of the heating roller 61.

  FIG. 3 is an explanatory diagram of a rotational driving force transmission path from the motor 101 to the heating roller 61. As shown in the figure, the rotational driving force from the motor 101 is transmitted to the clutch gear 104 a of the electromagnetic clutch 104, and is transmitted from the drive shaft 104 b of the electromagnetic clutch 104 to the heating roller 61. Here, the electromagnetic clutch 104 is configured not to transmit the rotational driving force applied to the clutch gear 104a to the drive shaft 104b in a normal state (normal state) where no voltage is applied. For this reason, in the normal state, even if the motor 101 is operating, the heating roller 61 does not rotate. On the other hand, when the electromagnetic clutch 104 is activated by applying a predetermined voltage, the electromagnetic clutch 104 transmits the rotational driving force applied to the clutch gear 104a to the drive shaft 104b. For this reason, in the operating state, the heating roller 61 is rotated by the operation of the motor 101. The rotational driving force transmission path from the motor 101 to the pickup roller 72 is configured in the same manner.

  Thus, in the printer 10 of this embodiment, the heating roller 61 can be prevented from rotating even when the motor 101 is operated. Therefore, even if the heating roller 61 and the pressure roller 62 are fixed by the toner hardened due to the temperature drop, the calibration operation can be started immediately.

Here, first, basic calibration control processing performed by the control unit 110 to realize the calibration operation will be described with reference to the flowchart of FIG.
When the calibration control process is started, first, the motor 101 is operated in S110. As a result, the photosensitive drum 32, the developing roller 36, the supply roller 37, the driving roller 52, the conveyance roller pairs 73, 91, 92, 93, and the like are rotationally driven. However, the pickup roller 72 and the heating roller 61 are in a state in which the rotational driving force is not transmitted by the electromagnetic clutches 103 and 104 (a state in which they are not rotationally driven).

  Subsequently, in S120, calibration processing for performing the above-described calibration operation is performed. That is, exposure / development is performed on the photosensitive drum 32 to form a color correction processing pattern toner image on the intermediate transfer member 50. Next, the density sensor 58 detects the density of the toner image. Then, the printing conditions are corrected based on the detected density. Further, the toner image on the intermediate transfer member 50 is collected by the cleaning device 55.

Then, after the calibration process of S120 is completed, the process proceeds to S130, the motor 101 is stopped, and the calibration control process is terminated.
Thus, in the printer 10 of the present embodiment, it is not necessary to rotate the heating roller 61 when starting the calibration operation. Therefore, even if the heating roller 61 and the pressure roller 62 are fixed by toner, The calibration operation can be started without waiting for the temperature rise of the heating roller 61 (melting of the fixed toner).

  Then, the printer 10 executes such a calibration operation before the printing operation. That is, the printer 10 receives image data (print data) transmitted from an external personal computer or the like, and thereby performs a print operation for printing an image represented by the image data on the paper P. Before performing, it is determined whether or not it is time to perform the calibration operation. If it is determined that it is the timing, the calibration operation is performed.

Here, a print control process performed by the control unit 110 to realize such an operation will be described with reference to a flowchart of FIG.
When the printing control process is started, first, the heater 63 of the fixing unit 60 is turned on in S210. Thereby, the temperature of the heating roller 61 starts to rise.

  Subsequently, in S220, the motor 101 is operated. As a result, the photosensitive drum 32, the developing roller 36, the supply roller 37, the driving roller 52, the conveyance roller pairs 73, 91, 92, 93, and the like are rotationally driven. However, the pickup roller 72 and the heating roller 61 are in a state in which the rotational driving force is not transmitted by the electromagnetic clutches 103 and 104 (a state in which they are not rotationally driven).

Subsequently, in S230, it is determined whether or not the number of printed sheets after the previous calibration operation is a predetermined number (for example, 100 sheets) or more.
If it is determined in S230 that the number of printed sheets after the previous calibration operation is not the predetermined number or more (less than the predetermined number), it is determined that it is not the timing for performing the calibration operation, and the process proceeds to S240. .

  In S240, it is determined whether or not the surface temperature of the heating roller 61 detected by the temperature sensor 64 of the fixing unit 60 is equal to or higher than a preset threshold value T1. Here, the threshold value T1 is set to a temperature (for example, 100 ° C.) at which the toner melts when the toner is fixed between the heating roller 61 and the pressure roller 62. If it is determined in S240 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T1, the process proceeds to S250 and the electromagnetic clutch 104 is turned on. That is, after the temperature of the heating roller 61 and the pressure roller 62 is increased to such an extent that the heating roller 61 and the pressure roller 62 are not fixed by the toner, the heating roller 61 is rotationally driven. In this way, the heating roller 61 is rotationally driven, and the pressure roller 62 is driven and rotated accordingly, whereby the temperature of the heating roller 61 and the pressure roller 62 is made uniform. Thereafter, the process proceeds to S290.

  On the other hand, if it is determined in S230 that the number of printed sheets after the previous calibration operation is greater than or equal to the predetermined number, it is determined that it is time to perform the calibration operation. In this case, the process of S260 and the processes of S270 and S280 are executed in parallel.

That is, in S260, the above-described calibration process is performed.
On the other hand, in S270 started in parallel with S260, as in S240 described above, it is determined whether or not the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T1, and is determined to be equal to or higher than the threshold value T1. Then, the process proceeds to S280, and the electromagnetic clutch 104 is turned on as in S250 described above. Thereafter, when the process of S260 and the process of S280 are completed, the process proceeds to S290.

  In S290, a printing process for printing the image represented by the image data on the paper P is performed. Here, the printing process is to pick up (feed) the paper P at a predetermined timing, transfer the toner image onto the paper P while transporting the paper P, and the paper P on which the toner image is transferred. A printing operation (image forming operation) for printing an image on the paper P is performed by passing the toner image between the heating roller 61 and the pressure roller 62 that are temperature-controlled at the heat fixing temperature to thermally fix the toner image. It is a well-known process for performing. When the printing process in S290 is finished, the heater 63 is turned off and the motor 101 is stopped.

  Finally, in step S300, after the electromagnetic clutch 104 is turned off, the print control process is terminated. By controlling the electromagnetic clutch 104 in this manner, the state of the electromagnetic clutch 104 when the calibration operation is started can be set to a state where the rotational driving force from the motor 101 is not transmitted to the heating roller 61.

  In the printer 10 of the present embodiment, the developing device 31, the charger 34, and the exposure unit 35 correspond to a developer image forming unit, and the intermediate transfer member 50, the driving rollers 51 and 52, the intermediate transfer roller 53, and the secondary transfer unit 53. The transfer roller 54 corresponds to a transfer unit, the fixing unit 60 corresponds to a fixing unit, and the process of S120 in the calibration control process (FIG. 4) and the process of S220 in the print control process (FIG. 5) are as follows. Corresponding to the calibration execution means, the motor 101 corresponds to the rotational driving force generation means, the electromagnetic clutch 104 corresponds to the transmission state switching means, and the processes of S250 and S290 in the print control process (FIG. 5) are switched. It corresponds to the control means.

  As described above, according to the printer 10 of this embodiment, the calibration operation can be started regardless of whether the heating roller 61 and the pressure roller 62 of the fixing unit 60 are fixed by toner. . Therefore, according to the present image forming apparatus, the time required to start the calibration operation can be shortened.

  In the printer 10, the temperature of the heating roller 61 is increased in parallel with the calibration operation. Therefore, the time required from the end of the calibration operation to the start of the printing operation (the heating roller 61, The time required for raising the toner image to a temperature at which heat fixing is possible can be shortened. In particular, since the heating roller 61 is rotated when the temperature of the heating roller 61 rises to a temperature at which the toner melts, the pressure roller 62 is locally heated by the heating roller 61. Can be prevented.

As mentioned above, although one Embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form.
For example, in the printer 10 of the above embodiment, when image data is received, if the number of printed sheets after the previous calibration operation is a predetermined number or more, the calibration operation is always performed. It is not limited to this. That is, when the elapsed time from the previous printing operation is short, the temperature of the heating roller 61 is high, and thus the time required to start the next printing operation (in other words, the heating roller 61 is set to the heat fixing temperature). However, if the calibration operation is performed in such a case, the start of the printing operation will be delayed. Therefore, instead of the print control process (FIG. 5) of the above embodiment, the print control process shown in FIG. 6 may be performed.

  Here, the print control process shown in FIG. 6 will be described. 6 is different from the print control process of FIG. 5 only in that the process of S255 is performed. Other processes are denoted by the same reference numerals and will not be described.

  If it is determined in S230 that the number of printed sheets after the previous calibration operation is equal to or greater than the predetermined number, the process proceeds to S255, where the surface temperature of the heating roller 61 detected by the temperature sensor 64 of the fixing unit 60 is It is determined whether or not the threshold value is equal to or greater than a preset threshold value T2. Here, the threshold value T2 is set to a value (for example, 60 ° C.) such that the time required to raise the temperature of the heating roller 61 from the temperature T2 to the heat fixing temperature is equal to the time required for the calibration operation. Has been. Therefore, if it is determined in S255 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T2, the time required for raising the temperature of the heating roller 61 to the heat fixing temperature is the calibration operation. It is possible to determine that the time is equal to or shorter than the time required for the printing operation (that is, the time required for starting the printing operation ≦ the time required for the calibration operation). On the other hand, if it is determined in S255 that the temperature detected by the temperature sensor 64 is lower than the threshold value T2, the time required to raise the temperature of the heating roller 61 to the heat fixing temperature is determined by the calibration. It can be determined that it is longer than the time required for the operation (that is, the time required for starting the printing operation> the time required for the calibration operation).

  If it is determined in S255 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T2, it is determined that it is not the timing for performing the calibration operation, and the process proceeds to S240.

  On the other hand, if it is determined in S255 that the temperature detected by the temperature sensor 64 is not equal to or higher than the threshold value T2 (less than the threshold value T2), it is determined that it is time to perform a calibration operation. , S270 and S280 are executed in parallel.

  As described above, in the print control process of FIG. 6, whether or not the execution of the calibration operation should be prohibited is determined based on whether or not the temperature of the heating roller 61 detected by the temperature sensor 64 is equal to or higher than the threshold value T2. to decide. For this reason, it is possible to prevent the start of the printing operation from being delayed by performing the calibration operation. In addition, the calibration operation that is performed when the elapsed time from the previous printing operation is short (that is, the printing operation is considered to have been performed without any problem so far and the necessity of performing the calibration operation itself is low). Can be reduced.

In the print control process of FIG. 6, the process of S255 corresponds to an execution prohibition determination unit.
By the way, in the printer 10 of the above-described embodiment, the heater 63 is immediately turned on by the start of the print control process. However, the present invention is not limited to this. That is, when the elapsed time from the previous printing operation is short, the temperature of the heating roller 61 is high, and thus the time required to start the next printing operation (in other words, the heating roller 61 is set to the heat fixing temperature). However, in this case, if the heater 63 is turned on from an early stage, unnecessary energy is consumed. Therefore, instead of the print control process (FIG. 5) of the above embodiment, the print control process shown in FIG. 7 may be performed.

Here, the print control process shown in FIG. 7 will be described.
When the print control process is started, first, the motor 101 is operated in S410. As a result, the photosensitive drum 32, the developing roller 36, the supply roller 37, the driving roller 52, the conveyance roller pairs 73, 91, 92, 93, and the like are rotationally driven. However, the pickup roller 72 and the heating roller 61 are in a state in which the rotational driving force is not transmitted by the electromagnetic clutches 103 and 104 (a state in which they are not rotationally driven).

Subsequently, in S420, it is determined whether or not the number of printed sheets after the previous calibration operation is a predetermined number (for example, 100 sheets) or more.
If it is determined in S420 that the number of printed sheets after the previous calibration operation is not equal to or greater than the predetermined number (less than the predetermined number), it is determined that it is not the timing for performing the calibration operation, and the process proceeds to S430. .

In S430, the heater 63 of the fixing unit 60 is turned on. Thereby, the temperature of the heating roller 61 starts to rise.
Subsequently, in S440, it is determined whether or not the surface temperature of the heating roller 61 detected by the temperature sensor 64 of the fixing unit 60 is equal to or higher than a preset threshold value T1. Here, the threshold value T1 is set to a temperature (for example, 100 ° C.) at which the toner melts when the toner is fixed between the heating roller 61 and the pressure roller 62. If it is determined in S4400 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T1, the process proceeds to S450 and the electromagnetic clutch 104 is turned on. That is, after the temperature of the heating roller 61 and the pressure roller 62 is increased to such an extent that the heating roller 61 and the pressure roller 62 are not fixed by the toner, the heating roller 61 is rotationally driven. In this way, the heating roller 61 is rotationally driven, and the pressure roller 62 is driven and rotated accordingly, whereby the temperature of the heating roller 61 and the pressure roller 62 is made uniform. Thereafter, the process proceeds to S520.

  On the other hand, if it is determined in S420 that the number of printed sheets after the previous calibration operation is greater than or equal to the predetermined number, it is determined that it is time to perform the calibration operation. In this case, the process of S460 and the processes of S470 to S510 are executed in parallel.

That is, in S460, the above-described calibration process is performed.
On the other hand, in S470 started in parallel with S460, it is determined whether or not the surface temperature of the heating roller 61 detected by the temperature sensor 64 of the fixing unit 60 is equal to or higher than a preset threshold value T2. . Here, the threshold value T2 is set to a value (for example, 60 ° C.) such that the time required to raise the temperature of the heating roller 61 from the temperature T2 to the heat fixing temperature is equal to the time required for the calibration operation. Has been. Therefore, if it is determined in S470 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T2, the time required for raising the temperature of the heating roller 61 to the heat fixing temperature is the calibration operation. It can be determined that the time is equal to or shorter than the required time (that is, the time required for starting the printing operation ≦ the time required for the calibration operation). Conversely, if it is determined in S470 that the temperature detected by the temperature sensor 64 is less than the threshold value T2, the time required to raise the temperature of the heating roller 61 to the heat fixing temperature is the calibration operation. It can be determined that the time is longer than the time required for the printing operation (that is, the time required for starting the printing operation> the time required for the calibration operation).

  If it is determined in S470 that the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T2, the process proceeds to S480, where standby processing is performed to wait for a standby time corresponding to the temperature detected by the temperature sensor 64. This standby time is set to a time at which the timing at which the temperature of the heating roller 61 reaches the heat fixing temperature by turning on the heater 63 after the standby is equal to the timing at which the calibration operation ends. For this reason, the larger the difference between the temperature detected by the temperature sensor 64 and the threshold value T2 (the higher the detected temperature), the longer the standby time. Thereafter, the process proceeds to S490.

  On the other hand, if it is determined in S470 that the temperature detected by the temperature sensor 64 is not equal to or higher than the threshold value T2 (less than the threshold value T2), the process proceeds to S490 as it is. That is, the heater 63 is turned on without waiting.

In S490, the heater 63 of the fixing unit 60 is turned on. As a result, the temperature of the heating roller 61 starts to rise.
Subsequently, in S500, as in S440 described above, it is determined whether or not the temperature detected by the temperature sensor 64 is equal to or higher than the threshold value T1, and if it is determined that the temperature is equal to or higher than the threshold value T1, the process proceeds to S510. Similarly to S450 described above, the electromagnetic clutch 104 is turned on. Thereafter, when the process of S460 and the process of S510 are completed, the process proceeds to S520.

In S520, the printing process for printing the image represented by the image data on the paper P is performed as in S290 of the printing control process (FIG. 5) of the above embodiment.
Finally, in step S530, after the electromagnetic clutch 104 is turned off, the print control process is terminated.

  As described above, in the print control process of FIG. 7, the temperature of the heating roller 61 detected by the temperature sensor 64 determines whether or not the operation start of the heater 63 should be delayed from the start of the calibration operation. Judgment based on whether or not. For this reason, the energy required when raising the temperature of the heating roller 61 can be saved.

  In the print control process of FIG. 7, the process of S460 corresponds to the calibration execution means, the process of S470 corresponds to the temperature rise start determination means, and the processes of S450, S510, and S530 are the switch control means. Equivalent to.

  By the way, in the printer 10 of the above embodiment, the toner image of the color correction processing pattern is formed on the intermediate transfer member 50, and the density of this toner image is detected by the density sensor 58. It is not a thing.

  For example, a density sensor for detecting the density of the toner image formed on each of the photosensitive drums 32M, 32C, 32Y, and 32Bk is provided, and the toner image of the color correction processing pattern is transferred to each of the photosensitive drums 32M, 32C, and 32Y. , 32Bk, and the density of this toner image may be detected by a density sensor.

  On the other hand, the printer is not limited to the one having the intermediate transfer member as in the above-described embodiment. For example, the toner image formed on each of the photosensitive drums 32M, 32C, 32Y, and 32Bk may be directly transferred onto the paper P that is transported by the transport body. In this case, for example, a density sensor for detecting the density of the toner image formed on the conveyance body is provided, a toner image of a color correction processing pattern is formed on the conveyance body, and the density of this toner image is measured by the density sensor. It may be detected by

Further, the printer is not limited to the color laser printer as in the above embodiment, and the present invention can be applied to a monochrome laser printer.
In addition to the electromagnetic clutch, known means such as a solenoid or a fluid pressure clutch such as hydraulic pressure or air pressure can be used as the transmission state switching means.

It is a schematic sectional side view of the printer of an embodiment. FIG. 2 is a block diagram illustrating an electrical configuration of the printer according to the embodiment. It is explanatory drawing of the rotational drive force transmission path | route from a motor to a heating roller. It is a flowchart of a calibration control process. 5 is a flowchart of print control processing according to the embodiment. 10 is a flowchart of a printing control process according to a first modification. 10 is a flowchart of print control processing according to a second modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Printer, 31 ... Developing device, 32 ... Photoconductor drum, 34 ... Charger, 35 ... Exposure means, 36 ... Developing roller, 37 ... Supply roller, 50 ... Intermediate transfer member, 51, 52 ... Drive roller, 53 ... Intermediate transfer roller, 54 ... secondary transfer roller, 55 ... cleaning device, 58 ... density sensor, 61 ... heating roller, 62 ... pressure roller, 63 ... heater, 64 ... temperature sensor, 101 ... motor, 102 ... motor drive circuit 104: electromagnetic clutch, 110: control unit, P: paper

Claims (6)

A photoreceptor,
Developer image forming means for forming a developer image on the photoconductor while the photoconductor is rotating;
Transfer means for directly or indirectly transferring the developer image formed on the photoreceptor by the developer image forming means onto a recording medium;
Two rotating bodies that rotate in contact with each other, and a heating unit that raises the temperature of at least one of the two rotating bodies, and a recording medium on which the developer image is transferred by the transfer unit Fixing means for heat-fixing the developer image by heating between two rotating members;
A developer image for judging image characteristics is formed on the photosensitive member or a member transferable from the photosensitive member, the density of the formed developer image is detected, and the image is based on the detected density. Calibration execution means for performing a calibration operation to correct the formation conditions;
Rotation driving force generating means for generating a rotational driving force necessary for the calibration execution means to perform the calibration operation and for generating at least one of the two rotating bodies of the fixing means. When,
In an image forming apparatus comprising:
A transmission state switching unit capable of switching between a transmission state in which the rotational driving force generated by the rotational driving force generation unit is transmitted to the rotating body of the fixing unit and a non-transmission state in which the rotational driving force is not transmitted to the rotating body;
A switching control means for controlling the transmission state switching means so that the state of the transmission state switching means when the calibration operation is started by the calibration execution means becomes the non-transmission state;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The rotational driving force generating means generates a rotational driving force for the photosensitive member or the photosensitive member and the transfer means as a rotational driving force necessary for performing the calibration operation;
An image forming apparatus. The image forming apparatus according to claim 1, wherein:
The heating means raises the temperature of the rotating body of the fixing means while the calibration operation is being performed by the calibration execution means;
An image forming apparatus. The image forming apparatus according to claim 3.
When the temperature of the rotating body of the fixing unit rises to a predetermined temperature while the calibration operation is being performed by the calibration execution unit, the switching control unit sets the transmission state switching unit to the transmission state. Control to switch to
An image forming apparatus. The image forming apparatus according to claim 3 or 4, wherein:
Temperature rise start determination for determining whether the temperature of the rotating body of the fixing unit is equal to or higher than a reference temperature as a criterion for determining whether or not the start of the temperature increase by the heating unit should be delayed from the start of the calibration operation. With means,
When the heating unit determines that the temperature rise start determination unit determines that the temperature is equal to or higher than the reference temperature, the fixing unit rotates at a timing later than the timing at which the calibration operation is started by the calibration execution unit. Raising the temperature of the body,
An image forming apparatus. The image forming apparatus according to claim 3 or 4, wherein:
An execution prohibition judging means for judging whether or not the temperature of the rotating body of the fixing means is equal to or higher than a reference temperature as a judgment reference as to whether or not the calibration operation should be prohibited;
The calibration execution means does not perform the calibration operation when the execution prohibition determination means determines that the temperature is equal to or higher than a reference temperature;
An image forming apparatus.

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