JP2016051056A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize recording media used for fixability evaluation, allow for determination of an appropriate fixation temperature for each type of recording media, reduce the power consumption required for fixation, and suppress conveyance failures and image contamination during fixability evaluation.SOLUTION: An image forming apparatus 1 comprises an image forming part 12, a fixing part 13, a rubbing roller 15, and an image density detection part 16. One recording sheet P is repeatedly allowed to pass the image forming part 12 and the fixing part 13. Every time the recording sheet P passes, according to the initial fixation temperature different in types of recording sheets, patch images PI for fixability evaluation are formed and fixed by different fixation temperatures at different positions on the recording sheet P in the conveyance direction thereof. With respect to each of the patch images PI fixed by the different fixation temperatures, the image densities detected by the image density detection part 16 at a rubbed portion W rubbed with the rubbing roller 15 and at a non-rubbed portion NW not rubbed with the rubbing roller 15 are compared with each other, thus a fixation temperature appropriate for the recording sheet P is set.SELECTED DRAWING: Figure 4A

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for optimizing a fixing temperature.

  In an electrophotographic image forming apparatus, various image forming conditions such as an internal mechanism, a charging device applied voltage, a developing bias voltage, a transfer voltage, and a fixing temperature are set so that an output image is optimized. . Similarly, the developing toner (hereinafter simply referred to as “toner”) is set so that the output image is optimized in accordance with each image forming apparatus. In recent years, various types of image forming apparatuses such as full-color apparatuses, monochrome apparatuses, and image forming speeds have been developed and marketed depending on the user's application. Along with this, diversification of toner is also progressing.

  Regarding the fixability of a toner image on a recording sheet, which is one of the qualities of an image forming apparatus, in Patent Document 1 below, a fixability test image is formed when a toner container is replaced, and the fixability test image that has passed through the fixing apparatus is displayed. There has been disclosed a technique for adjusting the fixing temperature of a fixing device by evaluating the fixability based on the difference in image density between a rubbing portion and a non-rubbed portion by rubbing with a rubbing roller. Japanese Patent Application Laid-Open No. 2004-228561 describes fixing evaluation in which fixing property is evaluated using a smear measuring device that is a fixing property detection means and fixing conditions such as nip width and fixing temperature are changed.

JP 2011-221338 A Japanese Patent Laid-Open No. 2007-4051

  In the power consumption of the image forming apparatus, the ratio of power consumption by the fixing process is large. For this reason, various measures have been implemented to reduce power consumption in the fixing process. A fixing system that efficiently supplies heat energy to the toner and the recording medium (recording paper) such as IH fixing has been studied, but at least the amount of heat that can melt the toner properly and obtain a uniform color is given. There is a need.

  However, the amount of heat that needs to be supplied to the recording medium that is a toner carrier for proper fixing varies depending on the heat capacity of the recording medium. Since there are innumerable types of recording media to be used, recording media are grouped by setting the width of basis weight, and the amount of heat (fixing temperature) to be given is determined for each group. For this reason, in order to achieve problem-free image fixing for various types of recording media, the amount of heat to be applied, that is, the set temperature for fixing, is often set high. For this reason, it is expected to reduce power consumption required for fixing.

  Further, when an appropriate fixing temperature is to be determined using the techniques disclosed in Patent Document 1 and Patent Document 2, the fixing property is evaluated by using various recording media and changing the fixing temperature in various ways. Therefore, there is a problem in that the recording medium is wasted for fixing property evaluation. Another problem is that it takes a long time to find an appropriate fixing temperature.

  In addition, when the fixability evaluation of a thin recording medium with a small basis weight is performed at the fixing temperature for thick paper, the recording medium may curl and may cause a paper jam due to poor conveyance or winding of paper around the fixing roller. In addition, there is a risk of image smearing due to the occurrence of hot offset. On the other hand, since thick paper has an appropriate fixing temperature higher than that of plain paper, if the fixability evaluation of thick paper is performed at a low fixing temperature, there is a possibility that image smearing may occur due to the occurrence of cold offset. As described above, if the start temperature of the fixability evaluation is inappropriate, a large amount of recording medium and power consumption may be wasted in the fixability evaluation.

  The present invention has been made in order to solve the above-described problems. The number of recording media used for evaluation of fixing properties is reduced as much as possible, and an appropriate fixing temperature can be determined for each type of recording media, thereby fixing the recording medium. An object of the present invention is to reduce power consumption required and to suppress conveyance failure and image smearing at the time of fixing property evaluation.

An image forming apparatus according to one aspect of the present invention includes a transport unit that transports a recording sheet,
An image forming unit for forming a toner image on the recording paper conveyed by the conveying unit;
A fixing unit for fixing the toner image formed on the recording paper by the image forming unit to the recording paper by thermocompression;
Patches one recording sheet that is repeatedly passed through the image forming unit and the fixing unit at different positions in the recording sheet conveyance direction each time the recording sheet is passed through the image forming unit. An image is formed, the fixing initial temperature of the fixing unit is changed and set according to the type of recording paper, and the fixing temperature of the fixing unit is changed from the initial fixing temperature for each of the formed patch images. A control unit for fixing an image on the recording paper;
A rubbing member for rubbing or non-rubbing each patch image portion after fixing by the fixing unit;
An image density detector that detects an image density of the patch image on the recording paper after passing through the rubbing member each time the patch image is formed;
The ratio of the image densities detected by the image density detection unit for the portion that is rubbed by the rubbing member and the portion that is not rubbed in each patch image after the fixing is within a predetermined reference value. A determination unit for determining whether or not
Fixing temperature setting for setting the fixing temperature used for fixing the patch image determined to be within the predetermined reference value by the determining unit as the fixing temperature used during normal image formation by the image forming unit A section.

  According to the present invention, it is possible to determine an appropriate fixing temperature for each type of recording medium by minimizing the number of recording media used for fixing property evaluation. As a result, the fixing conditions are optimized for each type of recording medium used for image formation in the image forming apparatus, and the minimum fixing temperature is set for each type of recording medium while improving and maintaining the image quality. This makes it possible to optimize power consumption. Further, the present invention sets the fixing temperature at the time of fixing the patch image using the initial fixing temperature corresponding to the type of the recording medium used for forming the patch image. Winding and even offset can be eliminated. Accordingly, it is possible to reduce the number of recording media used for fixing property evaluation by suppressing conveyance failure and image contamination.

1 is a front sectional view showing a structure of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a front sectional view showing a fixing unit and members disposed on the downstream side of the fixing unit. 2 is a functional block diagram illustrating a main internal configuration of the image forming apparatus. FIG. FIG. 6 is a diagram illustrating an example of a fixing evaluation patch image used in the first fixing property evaluation in the first embodiment. FIG. 6 is a diagram illustrating an example of a fixing evaluation patch image used in a second fixing property evaluation in the first embodiment. FIG. 6 is a diagram illustrating an example of a fixing evaluation patch image used in a third fixing property evaluation in the first embodiment. 4 is a flowchart showing a flow of processing at the time of fixing property evaluation according to the first embodiment. FIG. 10 is a diagram illustrating an example of a fixing evaluation patch image used in the first fixing evaluation in the second embodiment. FIG. 10 is a diagram illustrating an example of a fixing evaluation patch image used in a second fixing property evaluation in the second embodiment. FIG. 10 is a diagram illustrating an example of a fixing evaluation patch image used in a third fixing property evaluation in the second embodiment. 10 is a flowchart showing a flow of processing at the time of fixing property evaluation according to the second embodiment.

  An image processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front sectional view showing the structure of an image forming apparatus according to an embodiment of the present invention.

  An image forming apparatus 1 according to an embodiment of the present invention is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus main body 11 that includes an operation unit 47, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, a document reading unit 5, and the like.

  The operation unit 47 receives instructions such as an image forming operation execution instruction and a document reading operation execution instruction from the operator regarding various operations and processes that can be executed by the image forming apparatus 1. The operation unit 47 includes a display unit 473 that displays operation guidance to the operator.

  When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 optically reads a document fed by the document feeding unit 6 or a document placed on the document placing glass 161, Generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD or a network-connected computer.

  When the image forming apparatus 1 performs an image forming operation, it is based on image data generated by the document reading operation, image data received from a computer connected to a network, image data stored in a built-in HDD, or the like. Then, the image forming unit 12 forms a toner image on the recording paper P as a recording medium fed from the paper feeding unit 14. When performing color printing, the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12 respectively A toner image is formed on the photosensitive drum 121 by charging, exposure, and development processes based on an image composed of each color component constituting data, and the toner image is formed on the intermediate transfer belt 125 by the primary transfer roller 126. Let them transcribe.

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to form a color toner image. The secondary transfer roller 210 passes the toner image of the color formed on the surface of the intermediate transfer belt 125 from the paper supply unit 14 through the conveyance path 190 at a nip N between the intermediate transfer belt 125 and the driving roller 125a. It is transferred to the recording paper P that has been conveyed. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  The paper feed unit 14 includes a plurality of paper feed cassettes. The control unit 100 (FIG. 3) rotates the pickup roller 145 of the paper feed cassette that contains the recording paper of the size specified by the instruction from the operator, and the recording paper P contained in each paper feed cassette. Is conveyed toward the nip portion N.

  In the case of performing double-sided printing in the image forming apparatus 1, the recording paper P having an image formed on one side by the image forming unit 12 is nipped by the discharge roller pair 159, and then the recording paper P is switched back by the discharge roller pair 159 and is sent to the reverse conveyance path 195, and is conveyed again by the conveyance roller 19 to the nip portion N and the fixing portion 13 in the upstream area in the conveyance direction of the recording paper P. As a result, an image is formed on the other surface of the recording paper by the image forming unit 12. Further, the image forming apparatus 1 returns the recording paper P after the fixing process to the image forming unit 12 via the reverse conveyance path 195 without inverting the fixing surface, and forms another toner image on the same fixing surface. Such single-sided multiplex printing can also be performed.

  FIG. 2 is a front sectional view showing the fixing unit 13 and members disposed on the downstream side of the fixing unit 13. A rubbing roller 15, an image density detection unit 16, and a conveyance roller 19 are sequentially arranged on the conveyance downstream side of the fixing unit 13.

  The fixing unit 13 melts the toner constituting the toner image transferred to the recording paper P and fixes it on the recording paper P. The fixing unit 13 includes a heating roller 13a in which an unillustrated heater is installed, and a pressure roller 13b that is pressed against the heating roller 13a. The said heater can be comprised by the IH heater provided with the induction heating part which has a halogen heater or an exciting coil and a core, for example.

  A thermistor 21 that detects the surface temperature of the heating roller 13a is disposed at a position close to the heating roller 13a. The heating roller 13a and the pressure roller 13b convey the recording paper P on which the toner image is transferred so as to be sandwiched. By transporting the recording paper P so as to be sandwiched between the heating roller 13a and the pressure roller 13b, the toner transferred to the recording paper P is melted and fixed. For example, the control unit 100 (FIG. 3) controls the driving of the heater based on the fixing temperature detected by the thermistor 21, thereby setting the fixing temperature during the fixing operation by the fixing unit 13, which will be described later.

  When the recording paper P is inserted into the fixing unit 13 and heat is transmitted from the heating roller 13a to the recording paper P, the surface temperature of the portion of the heating roller 13a that contacts the recording paper P decreases, and the surface temperature of the non-contact portion increases. Therefore, when the heating roller 13a is heated uniformly as a whole, the surface temperature thereof varies in the axial direction. Therefore, it is preferable that the fixing unit 13 includes a mechanism that compensates for variations in the surface temperature in the axial direction of the heating roller 13a.

  A rubbing roller (an example of a rubbing member) 15 is a roller that rubs the fixing surface of the recording paper P on which the toner image is fixed by the fixing unit 13. The rubbing roller 15 can be composed of, for example, a roller having a take-up cloth. The rubbing roller 15 can move to the contact position and the detachment position with respect to the recording paper P so as to come into contact with the recording paper P when the fixability evaluation is performed and to release from the recording paper P at other times. Equipped with a moving mechanism. In particular, when the fixability evaluation is performed, the rubbing roller 15 sandwiches the recording paper P from above and below by movement by the moving mechanism. At this time, the rubbing roller 15 slides on the fixing surface of the recording paper P by rotating at the same speed as the transport speed of the recording paper P or a peripheral speed slower than the transport speed with respect to the transported recording paper P. Rub. At this time, when the fixing process is performed at a fixing temperature lower than an appropriate temperature and the toner image has poor fixability, the toner is peeled off from the recording paper P by the rubbing of the rubbing roller 15 and the image density on the fixing surface is reduced. Decreases. Instead of the rubbing roller 15, a blade-like member (for example, a cleaning blade) that rubs in contact with the fixing surface of the recording paper P on which the toner image is fixed may be used as the rubbing member.

   The image density detection unit 16 detects the image density of the fixing surface of the recording paper P after passing through the rubbing roller 15. The image density detection unit 16 can be configured by an optical sensor such as an ID sensor including a light emitting unit and a light receiving unit, for example. In this case, the light emitting unit irradiates the fixing surface of the recording paper P with light, and the light receiving unit detects the reflected light. The image density of the fixing surface of the recording paper P is detected according to the intensity of light received by the light receiving unit.

  The transport roller 19 is a roller pair that transports the recording paper P toward the image forming unit 12 and the fixing unit 13. The transport roller 19 transports the recording paper P rubbed by the rubbing roller 15 to the discharge roller pair 159. The conveyance roller 19 and the drive motor 70 (FIG. 3) are an example of the conveyance unit in the claims.

  FIG. 3 is a functional block diagram showing the main internal configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 10, an operation unit 47, a document feeding unit 6, a document reading unit 5, an image memory 32, an image forming unit 12, a fixing unit 13, a rubbing roller 15, an image density detecting unit 16, and paper. A type detection unit 18, a drive motor 70, a facsimile communication unit 71, a network interface unit 91, an HDD 92, and the like are provided.

  The document reading unit (data acquisition unit) 5 includes a reading mechanism 163 (FIG. 1) having a light irradiation unit, a CCD sensor, and the like under the control of the control unit 10. The document reading unit 5 reads an image from the document by irradiating the document with the light irradiating unit and receiving the reflected light with a CCD sensor.

  The image memory 32 is an area for temporarily storing document image data obtained by reading by the document reading unit 5 and temporarily storing data to be printed by the image forming unit 12.

  The facsimile communication unit 71 includes an unillustrated encoding / decoding unit, modulation / demodulation unit, and NCU (Network Control Unit), and performs facsimile transmission using a public telephone network.

  The network interface unit 91 includes a communication module such as a LAN board, and transmits and receives various data to and from the local area or the computer 20 on the Internet via a LAN connected to the network interface unit 91.

  The HDD 92 is a large-capacity storage device that stores document images and the like read by the document reading unit 5.

  The drive motor 70 is a drive source that applies a rotational driving force to each rotating member of the image forming unit 12, the transport roller 19, and the like.

  The moving mechanism 72 records the rubbing roller 15 so that the rubbing roller 15 as a rubbing member abuts on the recording paper P when performing the fixing property evaluation and is detached from the recording paper P at other times. This is a mechanism for moving the paper P to the contact position and the separation position. When a blade-like member is used as the rubbing member, the moving mechanism 12 contacts and separates the blade-like member from the recording paper P.

  The paper type detection unit 18 detects the type of the recording paper P that is an object of fixing property evaluation. More specifically, the paper type detection unit 18 detects the type (thin paper or thick paper) of the recording paper P according to the material (paper or OHP or the like), basis weight, thickness, etc. of the recording paper P. For example, the paper type detection unit 18 detects the type of the recording paper P based on the recording paper type information indicating the type of recording paper input by the user from the operation unit 47.

  The control unit 10 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like, and controls overall operation of the image forming apparatus 1. The control unit 10 includes a control unit 100.

  The control unit 100 includes an operation unit 47, a document feeding unit 6, a document reading unit 5, an image memory 32, an image forming unit 12, a fixing unit 13, a rubbing roller 15, an image density detecting unit 16, a drive motor 70, and facsimile communication. Is connected to the unit 71, the network interface unit 91, the HDD 92, and the like, and controls these units.

  In particular, the control unit 100 applies the recording sheet P to the image forming unit 12 and the fixing unit 13 with respect to one sheet of recording sheet P that is inserted by being inserted from the manual feed tray 17 (FIG. 1) by the user. Each time a sheet is passed, patch images for fixing property evaluation are formed and fixed at different positions in the transport direction of the recording paper P at different fixing temperatures for each image formation. Further, the control unit 100 controls the rubbing roller 15 to rub the fixing surface of the recording paper P on which the patch image is fixed. At the time of forming each patch image, the control unit 100 changes and sets the fixing initial temperature of the fixing unit 13 according to the type of recording paper, and the fixing temperature from the fixing initial temperature for each formed patch image. And the patch image is fixed on the recording paper by the fixing unit 13.

  The determination unit 101 determines in advance that the ratio of the image densities detected by the image density detection unit 16 with respect to the portion that is rubbed by the rubbing roller 15 and the portion that is not rubbed in each patch image after being fixed by the fixing unit 13. It is determined whether it is within a predetermined reference value (within a predetermined proper fixing temperature range). That is, the determination unit 101 performs fixability evaluation at each fixing temperature based on the image density of the fixing surface of the recording paper P after the rubbing detected by the image density detection unit 16.

  The fixing temperature setting unit 102 uses the fixing temperature used for fixing the patch image determined to be within the predetermined reference value by the determining unit 101 when the image forming unit 12 forms a normal image. Set as. Normal image formation means not image formation of the patch image but image formation performed based on print target data. That is, the fixing temperature setting unit 102 determines an appropriate fixing temperature of the recording paper P by the fixing unit 13 based on the result of the fixing property evaluation.

  In the image forming apparatus 1 according to the present embodiment, a patch formed on the recording paper P every time the recording paper P is repeatedly passed through the fixing unit 13 under the control of the control unit 100. The image is rubbed, the fixing temperature of the fixing unit 13 is changed variously, and the fixing property evaluation is performed by the determination unit 101. Hereinafter, an embodiment of fixing property evaluation by the image forming apparatus 1 according to the present embodiment will be described.

(First embodiment)
4A, 4B, and 4C are diagrams illustrating examples of fixing evaluation patch images used in the first, second, and third fixing evaluations in the first embodiment, respectively. . FIG. 5 is a flowchart showing a flow of processing at the time of fixing property evaluation according to the first embodiment.

  The fixing property evaluation is performed at an arbitrary timing set in the control unit 100, for example, before execution of normal image formation by the image forming unit 12, when the recording paper P is changed, or when the toner container is replaced. The

  When the fixing property evaluation is performed, first, the control unit 100 controls the image forming unit 12 to form the first patch image PI for fixing property evaluation at a predetermined position on one recording sheet P. (S1). The patch image PI is an image having a predetermined color, density, size, and shape (for example, a gray rectangular image having a predetermined density). The formation position of the patch image PI in the conveyance direction of the recording paper P is a position facing the rubbing roller 15 and the image density detection unit 16 provided with a gap from the fixing surface of the recording paper P. Yes.

  When the formation of the patch image PI is completed, the control unit 100 acquires recording paper type information indicating the type of the detected recording paper P from the paper type detection unit 18 (S2). Then, the control unit 100 sets the fixing temperature of the fixing unit 13 to a predetermined fixing initial temperature according to the recording sheet type indicated by the acquired recording sheet type information (S3). For example, the control unit 100 stores a data table storing the relationship between the recording sheet type and the fixing initial temperature determined for each recording sheet type, and the recording sheet type acquired in S2 from the data table. The initial fixing temperature associated with the recording paper type indicated by the information is read, and the fixing temperature of the fixing unit 13 is set as the initial fixing temperature. Note that the recording paper type information (S2) and the fixing temperature setting (S3) may be performed before S1.

  For example, patch image data different for each recording paper type is stored in a storage medium such as the image memory 32 or a memory (not shown), and the acquisition of the recording paper type information (S2) is performed at least by the patch image PI by S1. It shall be done before formation. Then, the control unit 100 reads the patch image data corresponding to the recording paper type indicated by the acquired recording paper type information from the storage medium, and sends the patch image PI based on the read data to the image forming unit 12. It may be formed on the recording paper P. That is, under the control of the control unit 100, different patch images are formed by the image forming unit 12 depending on the type of the recording paper P.

  In this case, the patch image PI may be formed as follows. For example, a thin paper (eg, tracing paper) having a predetermined thickness and a thick paper (eg, coated paper) thicker than the thin paper are stored in the storage medium as recording paper types. Further, data of a high-density image patch having a predetermined density is stored in association with the thin paper, and the low-density image patch having a density lower than that of the high-density image patch is stored in association with the thick paper. The data is stored. The control unit 100 reads patch image data corresponding to the recording paper type of thin paper or thick paper indicated by the acquired recording paper type information from the storage medium, and causes the image forming unit 12 to patch image based on the read data. PI is formed on the recording paper P. In the case of thin paper having a relatively thin thickness, the toner tends to be overheated and easily hot-offset at the time of fixing. Therefore, the patch image PI is changed to a high-density image patch to reduce the adverse effects caused by the hot-offset. On the other hand, in the case of thick paper having a relatively large thickness, the vicinity of the interface between the toner and the recording paper P is not sufficiently dissolved at the time of fixing, and cold offset is likely to occur. Reduce harmful effects.

  After setting the fixing initial temperature, the control unit 100 sets the fixing temperature of the fixing unit 13 to a predetermined temperature, and the fixing unit 13 fixes the patch image PI to the recording paper P (S4). This predetermined temperature is set as the fixing initial temperature in the first patch image formation.

  Then, at the timing when the recording paper P on which the patch image PI is fixed is conveyed and the patch image PI portion reaches a position facing the rubbing roller 15, the control unit 100 drives the moving mechanism 72 to record the recording paper. A portion of the patch image PI that is rubbed in the transport direction (rubbing portion W) and a portion that is not rubbed (non-rubbing portion) NW) is formed (S5). For example, as illustrated in FIG. 4A, the control unit 100 forms a rubbing portion W on the downstream side in the conveyance direction of the patch image PI and a non-rubbing portion NW on the upstream side in the conveyance direction. Alternatively, the control unit 100 may form the rubbing portion W on the upstream side in the conveyance direction of the patch image PI and the non-rubbing portion NW on the downstream side in the conveyance direction.

  When the rubbing portion W and the non-rubbing portion NW are formed in the patch image PI, the image density detecting unit 16 causes each image of the rubbing portion W and the non-rubbing portion NW of the patch image PI to pass through the opposing positions. Detect concentration. The detected image densities of the rubbing portion W and the non-rubbing portion NW are stored in a memory built in the control unit 10, for example.

  The control unit 100 determines whether to continue the fixability evaluation based on whether or not the number of times of forming the patch image PI has reached a predetermined number of times, and the number of times of forming the patch image PI is set to a predetermined number of times. If the patch image formation is not reached and the patch image formation is continued (NO in S6), the position near the registration roller 73 (FIG. 1) on the upstream side in the recording paper conveyance direction with respect to the nip portion N of the secondary transfer roller 210 and the driving roller 125a. 1 waits for the recording paper P to be detected by the registration sensor 74 (FIG. 1) disposed in (No in S9 and S9). The recording paper P on which the patch image PI for the first fixing evaluation is formed by the user is inserted into the image forming apparatus 1 from, for example, the manual feed tray 17 (FIG. 1) and conveyed to the registration roller 73. Shall be.

  When the recording paper P is conveyed to the registration roller 73 and the recording paper P is detected by the registration sensor 74 (YES in S9), the control unit 100 controls the image forming unit 12 to convey the recording paper P. In the direction, the patch image PI for the second fixability evaluation is formed at a position different from the position where the patch image PI for the first fixability evaluation is formed (S10). Thereafter, the process returns to S4.

  However, in S4, the control unit 100 performs the fixing after the patch image PI for fixing property evaluation for the second time (after the formation of the patch image PI for fixing property evaluation for the first time here). A fixing temperature different from that of fixing is set, and fixing is performed by the fixing unit 13 (S4).

  Similarly to the first time, the patch image PI is recorded on the recording paper P by the rubbing roller 15 under the control of the moving mechanism 72 by the control unit 100 as in the first time. A rubbing portion W and a non-rubbing portion NW are formed in the paper transport direction (S5, FIG. 4B).

  At this time, if the number of times of forming the patch image PI has not reached the predetermined number of times and the patch image formation is continued (NO in S6), the control unit 100 selects the same patch image PI as described above. Then, it is formed on the recording paper P by the image forming unit 12 at a position different from the formation position of the patch image PI so far in the recording paper conveyance direction (YES in S9, S10). Subsequently, the newly formed patch image PI is fixed (S4), rubbed (S5), and the image density is detected (see FIG. 4C).

  That is, unless the control unit 100 determines that the number of times of forming the patch image PI has reached the predetermined number (NO in S6), the patch image formation, the fixing, the rubbing, and the image density detection are performed. Continue (S9, S10, S4, S5).

  In fixing after the formation of each patch image from the first time to the last time until the number of formation of the patch image PI reaches the predetermined number of times, for example, the control unit 100 is provided with the heating roller 13a. By controlling the heater, the fixing temperature used in S2 is changed stepwise from the set initial fixing temperature for each patch image formation. For example, the initial fixing temperature is the lowest fixing temperature applicable to the corresponding type of recording paper, and the control unit 100 forms each patch image from the lowest fixing temperature to a predetermined maximum fixing temperature. Raise it step by step. For example, the controller 100 sets the initial fixing temperature and the minimum fixing temperature to 140 ° C. with the heater, and gradually increases the temperature between 170 ° C. (maximum fixing temperature) at 10 ° C. intervals. In this case, the first patch image PI is fixed at 140 ° C., the second patch image PI is 150 ° C., the third patch image PI is 160 ° C., the fourth patch image PI is set to 170 ° C., etc. The

  In addition, when the controller 100 sets the initial fixing temperature and the minimum fixing temperature to 150 ° C. by the heater and gradually increases the temperature between 170 ° C. (maximum fixing temperature) at 5 ° C. intervals, the first time The patch image PI is 150 ° C., the second patch image PI is 155 ° C., the third patch image PI is 160 ° C., the fourth patch image PI is 165 ° C., the fifth patch image PI is 170 ° C., etc. To fix each. Alternatively, the control unit 100 may set the fixing temperature to an arbitrary temperature for each patch image PI without changing the fixing temperature stepwise. The method of changing the fixing temperature is not limited to these, and the change of the fixing temperature in S2 may be lowered stepwise for each patch image from the lowest fixing temperature to the highest fixing temperature. However, while the temperature rise of the heating roller 13a can be easily controlled because a heater is used, it takes time because the temperature drop is due to natural cooling. Therefore, it is preferable to adopt a method in which the fixing temperature is raised stepwise. .

  Then, when the control unit 100 determines that the number of times of forming the patch image PI has reached the predetermined number (YES in S6), the control unit 100 stops the above-described patch image formation.

  Subsequently, the determination unit 101 reads out and acquires the image density of the rubbing portion W and the non-rubbing portion NW for each patch image PI from the image density detection unit 16 and acquires the image density for each patch image PI. Then, it is determined whether the ratio of the image densities of the rubbing portion W and the non-rubbing portion NW falls within a predetermined reference value (S7). For example, the determination unit 101 calculates the fixability R according to the formula of fixability R = ID1 / ID2 with the image density of the rubbing portion W as ID1 and the image density of the non-rubbing portion NW as ID2, and the fixability R Is within a certain range as the reference value, for example, a range of 0.8 to 0.95. That is, the determination unit 101 determines, from among a plurality of patch images PI formed on the recording paper P, a patch image PI in which the fixability R is within the range.

  Then, the fixing temperature setting unit 102 uses the lowest temperature among the fixing temperatures for the patch image PI in which the fixing property R is within the range as the fixing temperature used during normal image formation by the image forming unit 12. Set (S8).

  Then, the control unit 100 causes the fixing unit 13 to fix the recording paper P at the set fixing temperature for normal image formation to be performed next.

(Second Embodiment)
6A, 6B, and 6C are diagrams illustrating examples of fixing evaluation patch images used in the first, second, and third fixing evaluations in the second embodiment. FIG. 7 is a flowchart showing a flow of processing at the time of fixing property evaluation according to the second embodiment. The second embodiment is the same as the first embodiment except for the formation method of the rubbing portion W and the non-rubbing portion NW in the patch image PI and the arrangement of the image density detection unit 16. Hereinafter, in the description of the second embodiment, the description of the same points as in the first embodiment will be omitted, and only the differences will be described.

  In the second embodiment, when the fixability evaluation is performed, the control unit 100 controls the image forming unit 12 so that the patch image PI is positioned at a predetermined position on one sheet of recording paper P by the transport roller 19. Is formed (S11).

  When the formation of the patch image PI is completed, the control unit 100 fixes the patch image PI formed on the recording paper P to the recording paper P in the same manner as in the first embodiment (S12 to S14).

  Here, the formation position of each patch image PI in the direction orthogonal to the conveyance direction of the recording paper P is a position facing the rubbing roller 15 and the two image density detection units 16 arranged side by side in the orthogonal direction. It is. Note that the width of the patch image PI is sufficiently larger than the width of the rubbing roller 15. For example, the rubbing roller 15 has a width that is about half the width of the patch image PI to be formed in the orthogonal direction. In other words, the rubbing roller 15 is rubbed in an area about half of the patch image PI in the orthogonal direction and does not rub in other areas.

  When the control unit 100 causes the transport roller 19 to transport the recording paper P on which the patch image PI is fixed, the rubbing roller 15 rubs in an area about half the patch image PI in the orthogonal direction. As a result, in the patch image PI, a portion (sliding portion W) that is rubbed by the rubbing roller 15 and a portion that is not rubbed (non-rubbing portion NW) are arranged in a direction orthogonal to the recording paper conveyance direction. It is formed (S15).

  When the rubbing portion W and the non-rubbing portion NW are formed in the patch image PI in this way, one of the two image density detection units 16 is the rubbing portion W of the patch image PI that passes through the opposing position. The other detects the image density of the non-rubbed portion NW. The detected image densities of the rubbing part W and the non-rubbing part NW are stored in a memory in the control unit 10, for example.

  Thereafter, in the same manner as in the first embodiment, until the controller 100 determines that the number of times of forming the patch image PI has reached the predetermined number of times (NO in S16), Fixing, rubbing, and image density detection are continued (S19, S20, S14, S15).

  Thereafter, the control unit 100 reads out and acquires each image density of the rubbing portion W and non-rubbing portion NW of the patch image PI from each image density detection unit 16 and obtains the rubbing for each patch image PI. Whether the ratio of the image densities of the part W and the non-rubbing part NW falls within a predetermined reference value is determined in the same manner as in the first embodiment (S17).

  In the same manner as in the first embodiment, the fixing temperature setting unit 102 determines the lowest temperature among the fixing temperatures for the patch image PI in which the fixing property R is within the range by the image forming unit 12. It is set as a fixing temperature used during normal image formation (S18). The control unit 100 sets the fixing temperature of the fixing unit 13 to the temperature determined in step S18 from the next recording sheet printing.

  Comparing the first embodiment and the second embodiment, the first embodiment has a cost merit because the number of parts is reduced because only one image density detector 16 is required.

  On the other hand, since the second embodiment requires two image density detection units 16, the cost is inferior to that of the first embodiment, but the rubbing portion W and non-rubbing portion NW of each patch image PI. Can be arranged side by side in a direction orthogonal to the transport direction, the width of each patch image PI in the transport direction can be made shorter than in the first embodiment. For this reason, the second embodiment has an advantage that the fixing property evaluation can be performed by forming more patch images PI on the recording paper P than in the first embodiment.

  As described above, according to the first and second embodiments, the fixing property evaluation is performed by setting the fixing temperature of the fixing unit 13 according to the type of the recording paper P that is a target of the toner image fixing property evaluation. For this reason, it is possible to eliminate the roll and winding of the recording paper P and the offset when the fixing property is evaluated. As a result, it is possible to reduce the number of recording papers P used for fixing property evaluation by suppressing conveyance failure and image contamination. Furthermore, according to the first and second embodiments, since the fixing property evaluation for a plurality of patch images PI can be performed using one recording paper P, the amount of the recording paper P used for the fixing property evaluation In a short time, a proper fixing temperature for each type of recording medium used for image formation as the recording paper P, that is, a fixing temperature consisting of a minimum temperature necessary for image fixing can be set in a short time. it can. As a result, the fixing conditions are optimized for each of various recording media used for image formation in the image forming apparatus 1, and a minimum fixing temperature is set for each recording medium while improving and maintaining the image quality. It becomes possible to optimize power consumption.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in each of the above embodiments, when patch image formation is performed a plurality of times on the same recording paper P, the user manually re-transports the recording paper P to the image forming position by the image forming unit 12. However, after each patch image formation is completed, the control unit 100 drives each mechanism for reverse conveyance to the image formation position by the image forming unit 12 through the reverse conveyance path 195. The recording paper P may be transported again. In this case, each time the patch image is alternately formed on each side of the recording paper P, and the fixing, the rubbing, and the image density detection are performed on the surface of the recording paper P on which the patch image is formed. Is done. Thereby, since the patch images PI can be formed on the two front and back surfaces of the recording paper P, the fixing performance can be evaluated more times with one recording paper P.

  Further, the present invention can be applied to a copying machine, a facsimile machine, a printer, and the like other than the above-described multifunction peripheral.

  The configuration and processing shown in the above embodiment using FIGS. 1 to 7 are only one embodiment of the present invention, and the present invention is not limited to the configuration and processing.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Image forming part 13 Fixing part 15 Rub roller 16 Image density detection part 18 Paper type detection part 100 Control part 101 Determination part 102 Fixing temperature setting part P Recording paper PI Patch image W Rub part (rubbed) Part)
NW Non-rubbing part (part not rubbed)

Claims (6)

A transport unit for transporting recording paper;
An image forming unit for forming a toner image on the recording paper conveyed by the conveying unit;
A fixing unit for fixing the toner image formed on the recording paper by the image forming unit to the recording paper by thermocompression;
Patches one recording sheet that is repeatedly passed through the image forming unit and the fixing unit at different positions in the recording sheet conveyance direction each time the recording sheet is passed through the image forming unit. An image is formed, the fixing initial temperature of the fixing unit is changed and set according to the type of recording paper, and the fixing temperature of the fixing unit is changed from the initial fixing temperature for each of the formed patch images. A control unit for fixing an image on the recording paper;
A rubbing member for rubbing or non-rubbing each patch image portion after fixing by the fixing unit;
An image density detector that detects an image density of the patch image on the recording paper after passing through the rubbing member each time the patch image is formed;
The ratio of the image densities detected by the image density detection unit for the portion that is rubbed by the rubbing member and the portion that is not rubbed in each patch image after the fixing is within a predetermined reference value. A determination unit for determining whether or not
Fixing temperature setting for setting the fixing temperature used for fixing the patch image determined to be within the predetermined reference value by the determining unit as the fixing temperature used during normal image formation by the image forming unit An image forming apparatus. A paper type detection unit for detecting the type of recording paper;
The image forming apparatus according to claim 1, wherein the control unit uses a temperature predetermined for each type of recording paper detected by the paper type detection unit as the fixing initial temperature.   3. The moving mechanism according to claim 1, further comprising a moving mechanism that causes the rubbing member to abut on and separate from the patch images on the fixing surface of the recording paper during conveyance of the recording paper by the conveying unit. Image forming apparatus. Two image density detectors are arranged side by side in a direction orthogonal to the transport direction at a position facing the patch image.
4. The rubbing member rubs a position facing one of the image density detection units in each patch image, and does not rub a position facing the other of the image density detection units. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein the control unit causes the image forming unit to form different patch images depending on a type of the recording paper.   The control unit sets the patch image as a high-density image patch having a predetermined density when the recording paper is a thin paper having a predetermined thickness, and the recording paper is more than the thickness of the thin paper. The image forming apparatus according to claim 5, wherein when the thick paper is thick, the image forming unit forms a low density image patch having a density lower than that of the high density image patch.