JP2019184778A - Image forming apparatus and control method - Google Patents

Abstract

To obtain an image forming apparatus that can obtain a desired fixing strength.SOLUTION: An image forming apparatus comprises: a fixing device that has a heat source and fixes an unfixed image on a recording material onto the recording material by using heat generated by the heat source; and a control unit that controls the operation of the fixing device. The control unit corrects the basis weight of the recording material by using the thermal conductivity of the recording material and the thickness of the recording material. The control unit determines a fixing condition in the fixing device on the basis of the basis weight after the correction. The control unit causes the fixing device to operate under the determined fixing condition.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image forming apparatus and an image forming apparatus control method.

  2. Description of the Related Art Conventionally, an image forming apparatus that is a copying machine, a printer, a facsimile, or a complex machine thereof is known. The image forming apparatus includes a fixing device that fixes an image by heating and melting a toner image formed on a recording material such as paper.

  For example, Patent Literature 1 discloses a temperature control method for such a fixing device. Specifically, Patent Document 1 discloses a fixing member that heats the recording medium from the unfixed image surface side of the recording medium, a pressure member that pressurizes the recording medium from the non-image surface, and a fixing member that is divided in the longitudinal direction. A temperature control method for a fixing device having a plurality of heating sources and a temperature detection member for detecting a pressure member temperature is disclosed.

  In this temperature control method, the fixing member set temperature is feedback-controlled based on the pressure member temperature, and the heating source is selectively energized according to the image area of the recording medium, whereby the image area of the post-fixing recording medium is determined. Only the desired temperature is controlled. More specifically, in this temperature control method, during the feedback control, the fixing member set temperature is corrected using any one of the factors such as nip time, basis weight, thermal conductivity, specific heat, and moisture content of the recording medium. The

JP 2014-098783 A

  However, for example, even if the fixing member set temperature (fixing temperature) is corrected using the basis weight and the thermal conductivity, a desired fixing strength cannot be obtained depending on the paper type. For this reason, an offset may occur due to under-fixing. Further, under the condition setting of the same fixing temperature and the same conveying speed, even if the paper has the same basis weight, the obtained fixing strength varies depending on the thermal conductivity of the paper and the thickness of the paper.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of obtaining a desired fixing strength and a control method in the image forming apparatus.

  According to one aspect of the present invention, an image forming apparatus includes a heat source and a fixing device that fixes an unfixed image on the recording material on the recording material using heat generated by the heat source, and an operation of the fixing device. And a control device for controlling. The control device corrects the basis weight of the recording material using the thermal conductivity of the recording material and the thickness of the recording material. The control device determines fixing conditions in the fixing device based on the corrected basis weight. The control device operates the fixing device under the determined fixing conditions.

Preferably, the fixing condition is a set temperature of the heat source.
Preferably, the control device controls the fixing device so that the set temperature becomes higher as the basis weight after the correction becomes larger.

  Preferably, the control device controls the fixing device such that the higher the thermal conductivity, the higher the set temperature.

  Preferably, the control device controls the fixing device so that the set temperature increases as the value obtained by dividing the thermal conductivity by the thickness increases.

  Preferably, the control device stores the corrected basis weight and the set temperature in association with each other. The image forming apparatus further includes an operation unit that receives a user operation.

  When the control unit receives a user operation for changing the set temperature, the control device changes the set temperature to a value based on the user operation.

Preferably, the fixing condition is a conveyance speed of the recording material.
Preferably, the control device controls the fixing device such that the larger the basis weight after correction, the slower the conveyance speed.

  Preferably, the control device controls the fixing device such that the higher the thermal conductivity, the slower the conveyance speed.

  Preferably, the control device controls the fixing device such that the larger the value obtained by dividing the thermal conductivity by the thickness, the slower the conveyance speed.

  Preferably, the fixing device further includes a pressure member, and uses the pressure applied by the pressure member to fix the unfixed image on the recording material. The fixing condition is a pressure value.

  Preferably, the control device controls the fixing device so that the pressure becomes higher as the basis weight after correction is larger.

  Preferably, the control device controls the fixing device so that the higher the thermal conductivity, the higher the pressure.

  Preferably, the control device controls the fixing device such that the larger the value obtained by dividing the thermal conductivity by the thickness, the higher the pressure.

  Preferably, the control device corrects the basis weight of the recording material by using the first value obtained by dividing the thermal conductivity by the thickness.

  Preferably, the control device corrects the basis weight of the recording material using a third value obtained by dividing the first value by a predetermined second value.

Preferably, the control device calculates the thermal conductivity based on the Beck smoothness of the recording material.
According to another aspect of the present invention, a control method includes: a fixing device that fixes an unfixed image on a recording material on a recording material using heat; and a control device that controls the operation of the fixing device. Executed on the device. The control method includes a step of correcting the basis weight of the recording material using the thermal conductivity of the recording material and the thickness of the recording material, a step of determining fixing conditions in the fixing device based on the corrected basis weight, And a step of operating the fixing device under the determined fixing conditions.

  According to the present invention, it is possible to obtain a desired fixing strength.

1 is a schematic diagram illustrating an example of an internal structure of an image forming apparatus. FIG. 3 is a side view showing an example of the internal structure of the fixing device. It is a block diagram for demonstrating the hardware constitutions of a main-body part. It is a figure showing the relationship between basic weight and fixing conditions. It is a figure showing the relationship between basic weight and fixing strength. The eight data shown in FIG. 5 are re-plotted with the paper physical property values other than the basis weight as the horizontal axis. The eight data shown in FIG. 5 are re-plotted with the paper physical properties other than the basis weight as the horizontal axis, and the plot state of the data in FIG. 6 is taken into consideration. It is a figure for demonstrating the functional structure of a main-body part. It is a flowchart for demonstrating the flow of the process performed by a main-body part.

  An image processing apparatus according to an embodiment will be described below with reference to the drawings. In the embodiments described below, when referring to the number, amount, and the like, the scope of the present disclosure is not necessarily limited to the number, amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated. In the drawings, there are portions that are not illustrated in accordance with the ratios of actual dimensions, but are illustrated with the ratios changed so that the structures are clear in order to facilitate understanding of the structures.

<A. Equipment overview>
(A1. Image forming apparatus)
FIG. 1 is a schematic diagram illustrating an example of the internal structure of the image forming apparatus 1000.

  Referring to FIG. 1, the image forming apparatus 1000 includes a main body unit 10 and a post-processing device 20.

  The post-processing device 20 includes a punch processing device 220, a side stitching processing unit 250, a saddle stitching processing unit 260, and discharge trays 271, 272, and 273.

  The main body unit 10 includes an image forming unit 11, a scanner unit 12, an automatic document conveyance unit 13, a paper feed unit 14, a conveyance path 15, a media sensor 16, and a reverse conveyance path 17.

  The main body 10 further includes a control device 31 that controls the operation of the image forming apparatus 1000. In this example, the main body 10 is a so-called tandem color printer. The main body 10 executes image formation based on print settings.

  The automatic document conveyance unit 13 automatically conveys the document placed on the document table to the reading position of the document reading unit. The scanner unit 12 reads an image of a document conveyed by the automatic document conveyance unit 13 and generates read data.

  The paper feed unit 14 includes a paper feed roller 141 and a paper feed cassette 142. The paper P is stored in the paper feed cassette 142. The paper feed cassette 142 is configured to be drawable from the main body unit 10. The paper feed roller 141 sends the paper P upward along the transport path 15.

  The conveyance path 15 is used for single-sided printing and double-sided printing. The reverse conveyance path 17 is used for duplex printing.

  The paper discharge roller 18 is disposed further downstream of the conveyance path 15 than the fixing device 120. The paper P discharged from the paper discharge roller 18 is sent to the horizontal transport unit 290.

  The image forming unit 11 forms an image on the paper P supplied by the paper supply unit 14 based on the read data generated by the scanner unit 12 or print data acquired from a client PC (not shown).

  The image forming unit 11 includes an intermediate transfer belt 101, registration rollers 102 and 103, a yellow image forming unit 104Y, a magenta image forming unit 104M, a cyan image forming unit 104C, and a black image forming unit 104K. The image density sensor 105, the primary transfer device 111, the secondary transfer device 115, and the fixing device 120 are included.

  The media sensor 16 is installed in the transport path 15. The media sensor 16 is typically installed between the paper feed roller 141 and the secondary transfer device 115. More specifically, the media sensor 16 is installed between the paper feed roller 141 and a timing roller (not shown). The media sensor 16 implements a paper type automatic detection function.

  The media sensor 16 detects the attributes of the paper P (characteristics such as paper type). For example, the media sensor 16 outputs paper attributes as numerical values. The detection result by the media sensor 16 is transmitted to the control device 31.

  As an example, the media sensor 16 includes a light emitting unit that irradiates the paper P with light and a light receiving unit that receives the reflected light reflected by the paper P. The media sensor 16 can determine the basis weight or the like of the paper P from the voltage value of the reflected light.

(A2. Fixing device)
The fixing device 120 pressurizes and heats the paper P passing through the fixing device 120. The fixing device 120 controls the degree of heating of the paper P, the pressure applied to the paper P (fixing pressure), the conveyance speed of the paper P, and the like according to a control signal from the control device 31. The fixing device 120 heats and presses the paper P, so that the toner image is fixed on the paper P. Thereafter, the paper P is discharged to one of the discharge trays 271 to 273.

FIG. 2 is a side view showing an example of the internal structure of the fixing device 120.
Referring to FIG. 2, fixing device 120 includes a heating rotator 129, a pressure roller 124, a heater 125, and a thermistor 126. The heating rotator 129 includes a heating roller 121, a fixing roller 122, and a fixing belt 123.

  A heater 125 is provided inside the heating roller 121. The number of heaters 125 is arbitrary. The heater 125 is, for example, a halogen heater. The heater 125 heats the heating rotator 129 so that heat is transmitted to the paper P passing through the contact portion between the heating rotator 129 and the pressure roller 124. More specifically, the heater 125 transfers heat to the fixing belt 123 by heating the heating roller 121. The heated fixing belt 123 transmits heat to the fixing roller 122 by rotating, and transfers heat to the paper P being conveyed on the conveyance path 15. By heating the paper P, the toner image G on the paper P is melted. As a result, the toner image G is fixed on the paper P.

  The fixing device 120 is provided with a pressure roller 124. The pressure roller 124 is provided in contact with the heating rotator 129. The pressure roller 124 presses the sheet P passing through the contact portion (nip region) between the heating rotator 129 and the pressure roller 124 to the fixing roller 122.

  The thermistor 126 measures the temperature of the heating rotator 129. Specifically, the thermistor 126 measures the surface temperature of the fixing belt 123. More specifically, the thermistor 126 measures the surface temperature of the fixing belt 123 that is in contact with the heating roller 121. Information on the measured temperature is fed back to the control device 31.

(A3. Control device)
The control device 31 determines whether the paper P is coated paper, plain paper, or high-quality paper based on the detection result of the media sensor 16. Further, the control device 31 determines the basis weight of the paper based on the detection result. Furthermore, the control device 31 determines whether the paper P is an OHP (Overhead Projector) film, an envelope, or an index paper based on the detection result. For example, based on the basis weight of the paper P, the control device 31 determines whether the paper type is thin paper, plain paper, or thick paper.

  Further, the control device 31 calculates the Beck smoothness [sec], which is an index indicating the smoothness (surface property) of the paper P, based on the detection result by the media sensor 16. The control device 31 calculates the thermal conductivity of the paper P based on the Beck smoothness. Specifically, the control device 31 takes the logarithm of Beck smoothness (hereinafter also referred to as “Beck log”). The control device calculates the thermal conductivity of the paper P based on the Beck log. A specific method for calculating the thermal conductivity will be described later.

  Further, the control device 31 sets the fixing condition of the fixing device 120 using the detection result of the media sensor 16. Examples of the fixing conditions include a fixing temperature, a paper conveyance speed (speed in the nip region), a fixing pressure applied by the pressure roller 124, and the number of prints per minute (PPM: Print Per Minuites).

  Specifically, the control device 31 controls the operation of the heater 125 so that the measured temperature becomes the fixing temperature (set temperature, target temperature) set by the control device 31. Specifically, the control device 31 controls the operation of the heater 125 so that the measured temperature becomes the temperature set by the control device 31 using the fed back temperature information.

  Further, the control device 31 controls the conveyance speed of the paper P passing through the nip region by controlling the rotation speed of the heating rotator 129. Furthermore, the control device 31 changes the fixing pressure applied to the paper P by controlling the position of the pressure roller 124.

(A4. Hardware configuration of main body)
FIG. 3 is a block diagram for explaining the hardware configuration of the main body 10.

  With reference to FIG. 3, the main body 10 includes at least a control device 31, an operation panel 32, a media sensor 16, and a fixing device 120.

  The operation panel 32 includes a touch screen 320. The touch screen 320 includes a display 322 and a touch panel 321 arranged so as to overlap the display 322.

  The control device 31 includes a CPU (Central Processing Unit) 311 that executes a program, a ROM (Read Only Memory) 312 that stores data in a nonvolatile manner, a RAM (Random Access Memory) 313 that stores data in a volatile manner, A flash memory 314 and a communication IF 315 are included. The control device 31 can communicate with the media sensor 16, the operation panel 32, and the post-processing device 20 through the communication IF 315.

  The flash memory 314 is a nonvolatile semiconductor memory. The flash memory 314 stores an operating system executed by the CPU 311, various programs, various contents, and data. The flash memory 314 stores various data such as data generated by the image forming apparatus 1000 and data acquired from an external apparatus of the image forming apparatus 1000 in a volatile manner.

  The control device 31 acquires the detection result of the media sensor 16. As described above, the control device 31 sets the fixing condition of the fixing device 120 using the detection result of the media sensor 16.

<B. Determination of fixing conditions>
FIG. 4 is a diagram illustrating the relationship between the basis weight and the fixing conditions.

  As shown in FIG. 4, in the data table D4, the fixing temperature, the conveyance speed, the fixing pressure, and the PPM are associated with the basis weight as the fixing conditions. Typically, the basis weight is divided into a plurality of ranges, and the fixing temperature, the conveyance speed, the fixing pressure, and the PPM are associated with each section.

  In the present embodiment, the basis weight detected by the media sensor 16 is corrected using a function (formula) described later. The control device 31 determines fixing conditions in the fixing device 120 based on the corrected basis weight. Typically, the control device 31 selects a fixing condition associated with the corrected basis weight from among predetermined conditions. The control device 31 operates the fixing device 120 under the determined (selected) fixing conditions.

For example, it is assumed that the basis weight detected by the media sensor 16 is 110 g / m ² . Further, it is assumed that the basis weight after correction is 125 g / m ² . In this case, the control device 31 does not set the fixing temperature to 170 degrees, but sets the fixing temperature to 155 degrees. Further, the control device 31 does not set the transport speed to 135 mm / s, but sets the transport speed to 68 mm / s. In this case, the fixing device 120 operates based on these settings.

<C. Specific examples of basis weight correction>
The control device 31 performs the following arithmetic processing in determining the fixing conditions.

(C1. Calculation of thermal conductivity of paper P)
The control device 31 calculates the thermal conductivity λ _t of the paper P to be detected by performing the calculation represented by the following mathematical formula (1).

λ _t = λ ₀ × (log γ _t / log γ ₀ ) (1)
In Equation (1), γ ₀ is the Beck smoothness of the reference paper (hereinafter also referred to as “paper Q”). γ _t is the Beck smoothness of the paper P to be detected. λ ₀ is the thermal conductivity of the standard paper Q. Note that γ _t is calculated for each sheet by the media sensor 16. γ ₀ and λ ₀ are known values stored in advance in the control device 31.

For example, it is assumed that γ ₀ is 90.2 [sec] and λ ₀ is 0.15 [W / m · K]. Furthermore, it is assumed that the Beck smoothness γ _t of the paper P to be detected is 19.5 [sec]. In this case, the thermal conductivity λ _t of the sheet P to be detected is approximately 0.1 (= 0.15 × (log (19.5) / log (90.2))) according to the equation (1). Become.

  The value of log (19.5) is 1.29, and the value of log (90.2) is 1.955.

(C2. Calculation of basis weight after correction)
When the thermal conductivity λ _t of the paper P to be known is calculated by the above mathematical formula (1), the control device 31 performs the calculation represented by the following mathematical formula (2) to thereby detect the paper to be detected. The basis weight after correction of P (hereinafter also referred to as “corrected basis weight V _c ”) is calculated.

_{V c = V t + {(} λ t / δ t) / (λ 0 / δ 0) -1} × C ... (2)
In Equation (2), V _t is the basis weight of the paper P detected by the media sensor 16. [delta] _t is the thickness of the sheet P to be the detection target (paper thickness). δ ₀ is the thickness of the reference paper Q. C is a predetermined constant. Incidentally, [delta] _t is the media sensor 16, is calculated for each sheet. δ ₀ is a known value stored in advance in the control device 31.

In this embodiment, the value of the constant C is set to 40 g / m ² . In the following, the thickness δ _{0 of the} paper Q is 0.08 mm. As described above, the thermal conductivity λ _t of the paper P is 0.1, and the thermal conductivity λ ₀ of the paper Q is 0.15.

As a result of detection by the media sensor 16, it is assumed that V _t and δ _t are, for example, 80 g / m ² and 0.16 mm, respectively. In this case, the basis weight V _c after the correction is approximately 53 (= 80 + {(0.1 / 0.16) / (0.15 / 0.08) −1} × 40) from Equation (2). Become.

In this example, the basis weight before correction is 80 g / m ² whereas the basis weight after correction is 53 g / m ² . Therefore, the control device 31 refers to the data table D4 and selects a fixing condition for a section having a basis weight of 59 g / m ² or less.

(C3. Summary)
(1) As described above, the control device 31 corrects the detected basis weight V _t using the thermal conductivity λ _t of the paper P and the thickness δ _{t of the} paper P. Specifically, the control device 31 uses the first value (λ _t / δ _t ) obtained by dividing the thermal conductivity λ _t by the thickness δ _t as shown in the mathematical formula (2). to correct the amount _{V t.} More specifically, the controller 31 divides the first value (λ _t / δ _t ) by a predetermined second value (λ ₀ / δ ₀ ) ((λ _t / The basis weight V _t of the paper P is corrected using (δ _t ) / (λ ₀ / δ ₀ )). Such correction makes it possible to obtain a desired fixing strength.

(2) The control device 31 calculates the thermal conductivity λ _t based on the Beck smoothness γ _t of the paper P. Specifically, the control unit 31, as shown in Equation (1), using log (Beck Logganma _t) of Bekk smoothness gamma _t, calculates the thermal conductivity lambda _t.

  (3) Focusing on the fixing temperature of the data table D4, it can be said that the control device 31 performs the following processing.

The control device 31 controls the fixing device 120 so that the fixing temperature (set temperature) increases as the corrected basis weight V _c increases. Further, the control device 31 controls the fixing device 120 such that the higher the thermal conductivity λ _t , the higher the fixing temperature. Further, the control device 31 controls the fixing device 120 so that the fixing temperature becomes higher as the value (λ _t / δ _t ) obtained by dividing the thermal conductivity λ _t by the thickness δ _t is larger. By these controls, it is possible to prevent the fixing strength from being weakened.

  (4) Focusing on the conveyance speed of the data table D4, it can be said that the control device 31 performs the following processing.

The control device 31 controls the fixing device 120 such that the greater the basis weight V _c after correction, the slower the conveyance speed. Further, the control device 31 controls the fixing device 120 such that the higher the thermal conductivity λ _t , the slower the conveyance speed. Further, the control device 31 controls the fixing device 120 so that the larger the value (λ _t / δ _t ) obtained by dividing the thermal conductivity λ _t by the thickness, the slower the conveyance speed. By these controls, it is possible to prevent the fixing strength from being weakened.

  (5) Focusing on the fixing pressure in the data table D4, it can be said that the control device 31 performs the following processing.

The control device 31 controls the fixing device 120 so that the fixing pressure increases as the basis weight V _c after the correction increases. Further, the control device 31 controls the fixing device 120 so that the fixing pressure becomes higher as the thermal conductivity λ _t is higher. Further, the control device 31 controls the fixing device 120 so that the fixing pressure becomes higher as the value (λ _t / δ _t ) obtained by dividing the thermal conductivity λ _t by the thickness δ _t is larger. By these controls, it is possible to prevent the fixing strength from being weakened.

<D. Reasons for performing basis weight correction using thermal conductivity and thickness>
In the following, as described above, the reason why the basis weight V _t is corrected using the thermal conductivity λ _t of the paper P and the thickness δ _{t of the} paper P and how to determine the constant C in Expression (2) will be described. explain.

(D1. Comparative example)
First, a comparative example for this example will be described with reference to FIGS.

  FIG. 5 is a diagram showing the relationship between the basis weight and the fixing strength. Specifically, FIG. 5 is a graph plotting data of fixing strength (%) when toner is fixed on a sheet under predetermined fixing conditions. In addition, the correction mentioned above is not performed with respect to the basic weight in FIG.

  Referring to FIG. 5, the horizontal axis of the graph is the basis weight, and the vertical axis is the fixing strength. The fixing strength is a value obtained by a rubbing test. The fixing strength is a numerical value obtained by further multiplying the ratio (Za / Zb) of the toner density (Za) after rubbing to the toner density (Zb) before rubbing by 100.

  The greater the basis weight, the greater the amount of heat taken by the paper, and the lower the fixing strength under the same fixing conditions. Accordingly, it is considered that the larger the basis weight, the higher the fixing temperature, the lower the paper conveyance speed in the fixing device 120, or the higher the fixing pressure.

  The relationship between the basis weight and the fixing strength assumes the solid line L shown in the figure. However, there is a portion (data) that is shifted up and down with respect to the solid line L. When fixing conditions are determined in consideration of only the basis weight, depending on the paper, excessive heat may be applied to cause overfixing, or fixing under-offset may occur due to insufficient heat. This is because paper physical properties other than the basis weight affect the fixing strength.

  FIG. 6 is a re-plot of the eight data shown in FIG. 5 with the paper physical properties other than the basis weight as the horizontal axis. In each figure of FIG. 6 (FIGS. 6A to 6E), the vertical axis represents the fixing strength as in FIG.

  FIG. 6A is a graph in which the horizontal axis represents the paper thickness (paper thickness). Referring to FIG. 6A, with the same basis weight, the fixing strength tends to increase under the same fixing conditions as the thickness increases. It is considered that as the thickness of the sheet increases, it is necessary to lower the fixing temperature, increase the conveyance speed, or lower the fixing pressure. As described above, when the fixing condition is determined only by the thickness of the sheet, the fixing strength becomes excessive or insufficient.

  FIG. 6B is a graph in which the horizontal axis represents the thermal conductivity of the paper. With reference to FIG. 6B, the higher the thermal conductivity, the higher the fixing temperature, the lower the conveying speed, or the higher the fixing pressure. As described above, when fixing conditions are determined only by thermal conductivity, the fixing strength becomes excessive or insufficient.

  FIG. 6C is a graph with the horizontal axis representing the density of the paper. Referring to FIG. 6C, as the density is higher, it is necessary to increase the fixing temperature, to decrease the fixing unit conveyance speed, or to increase the fixing pressure. As described above, when the fixing condition is determined only by the density, the fixing strength becomes excessive or insufficient.

  FIG. 6D is a graph in which the horizontal axis is obtained by dividing the thermal conductivity of the paper by the thickness of the paper (λ / δ). Referring to FIG. 6D, the larger the value obtained by dividing the thermal conductivity by the thickness, the higher the fixing temperature, the lower the conveying speed, or the higher the fixing pressure. As described above, if the fixing conditions are determined only by the value obtained by dividing the thermal conductivity by the thickness, the fixing strength becomes excessive or insufficient.

  FIG. 6E is a graph in which the horizontal axis represents the reciprocal of the paper thickness (1 / δ). Referring to FIG. 6E, the larger the reciprocal of the sheet thickness, the higher the fixing temperature, the lower the conveying speed, or the higher the fixing pressure. As described above, when the fixing condition is determined only by the reciprocal of the thickness of the paper, the fixing strength becomes excessive or insufficient.

(D2. This example)
Next, this example will be described with reference to FIG.

  FIG. 7 is a plot of the eight data shown in FIG. 5, plotted again with the paper physical property values other than the basis weight as the horizontal axis, and taking into account the plot state of the data in FIG. 6.

  Referring to FIG. 7, the eight data represent cases where the basis weight is corrected using a value obtained by dividing the thermal conductivity by the thickness, and the fixing conditions are determined based on the corrected basis weight. More specifically, a case where the basis weight is corrected using the above-described mathematical formula (2) is shown.

  In FIG. 5, data is plotted in the vicinity of the solid line L (up and down). Therefore, it can be said that the basis weight is generally related to the fixing strength. In FIG. 6, the plot position of the data has a general tendency with respect to the physical property values on the horizontal axis. This spread is caused by, for example, the basis weight group surrounded by an ellipse in FIG. 5 and 6, when the vertical spread of the plot position is seen, the relationship with the fixing strength is closer to a straight line when the basis weight of FIG. 5 is input than when the basis weight other than the basis weight is input from FIG. 6. I understand that. As shown in FIG. 6A, with the same basis weight, the fixing strength tends to rise to the right with respect to the sheet thickness. Therefore, in the correction, as shown in FIG. 6E, the reciprocal of the thickness of the paper is used.

  Moreover, if the basis weight is the same, the density changes as the thickness changes. A graph of fixing strength when the horizontal axis is simply density (FIG. 6C) and a graph of fixing strength when the horizontal axis is the reciprocal of thickness (FIG. 6E) are compared. The graph of 6 (E) is better and can express the vertical spread of each basis weight in FIG.

5, when viewing the trend of spreading how plot positions from the ideal line (solid line L), spread trends with 80 g / ^{m 2} and 256 g / ^{m 2} is made expressed. However, if 44 g / m ² is a little further to the left and 133 g / m ² is a little to the right, correction can be made to bring the data plot position closer to the solid line L in FIG. That is, if the plot position of 44 g / m ^{2 and} the plot position of 133 g / m ² are moved in this way, the plot position of each data can be brought close to the solid line L, which is an ideal line, as a result of calculation.

  Therefore, attention was paid to the thermal conductivity in FIG. The graph of FIG. 6D shows the horizontal axis obtained by multiplying the thermal conductivity by the reciprocal of the thickness. In this graph, the vertical spread of each basis weight in FIG. 5 can be expressed. The desired correction (correction along the ideal line) cannot be realized only by the thermal conductivity, and the desired correction cannot be realized only by the thickness. Based on the basis weight, the desired correction can be performed by using both the thermal conductivity and the thickness.

  In order to increase the fixing strength, it is necessary to increase the temperature of the toner. It is also necessary to dissolve the toner that has entered the fibers on the paper surface. Due to the temperature difference between the fixing belt 123 and the toner surface that has entered the nip region, heat is transferred from the fixing belt 123 to the toner, and the toner temperature rises. When the thermal conductivity of the paper is high, heat moves to the back side of the paper, and the temperature near the interface between the toner and the paper is lowered. The thicker the paper, the greater the heat insulation effect. When considering the heat insulation effect, it is necessary to consider not only the thermal conductivity but also the thickness.

For the above reason, the basis weight V _t is corrected using the thermal conductivity λ _t of the paper P and the thickness δ _{t of the} paper P. Also, a value (coefficient) is selected as the constant C in Equation (2) so that the data (fixing strength value) corresponding to each basis weight after correction approaches the solid line L (see FIG. 5) that is an ideal line. Keep it. Such selection (setting) of the value of the constant C is typically performed at the design stage of the image forming apparatus 1000 or the like.

<E. Functional configuration>
FIG. 8 is a diagram for describing a functional configuration of the main body 10 of the image forming apparatus 1000.

  Referring to FIG. 8, main body unit 10 includes media sensor 16, control device 31, fixing device 120, and operation panel 32 as described above.

  The media sensor 16 includes a basis weight detection unit 16A, a paper thickness detection unit 16B, and a Beck smoothness detection unit 16C. The control device 31 includes a basis weight correction unit 351, a thermal conductivity calculation unit 352, a fixing condition determination unit 353, and a communication interface unit 354. The fixing condition determination unit 353 stores a data table D4 (see FIG. 4).

  The basis weight detection unit 16A detects the basis weight of the paper P. The basis weight detection unit 16 </ b> A outputs a signal indicating the detected basis weight to the basis weight correction unit 351 of the control device 31.

  The paper thickness detection unit 16B detects the thickness of the paper P. The paper thickness detection unit 16B outputs a signal indicating the detected thickness to the basis weight correction unit 351.

  The Beck smoothness detection unit 16C detects the Beck smoothness of the paper P. The Beck smoothness detection unit 16 </ b> C outputs a signal indicating the detected Beck smoothness to the thermal conductivity calculation unit 352 of the control device 31.

The thermal conductivity calculator 352 calculates the thermal conductivity λ _t of the paper P based on the Beck smoothness. Specifically, the thermal conductivity calculation unit 352 calculates the thermal conductivity λ _t of the paper P using the above-described formula (1). The thermal conductivity calculation unit 352 sends the calculated thermal conductivity λ _t to the basis weight correction unit 351.

The basis weight correction unit 351 corrects the basis weight V _t using the thermal conductivity λ _t of the paper P and the thickness δ _{t of the} paper P. Specifically, the basis weight correction unit 351 corrects the basis weight V _t using the above-described formula (2) to obtain a corrected basis weight V _c . The basis weight correction unit 351 sends the calculated basis weight V _c after correction to the fixing condition determination unit 353.

Fixing condition determining unit 353 refers to the data table D4, determining the fixing condition based on the basis weight V _c corrected. For example, when the basis weight V _t before correction is 80 g / m ² and the basis weight V _c after correction is 53 g / m ² , the fixing condition determination unit 353 refers to the data table D4. Then, the fixing condition of the section having a basis weight of 59 g / m ² or less is selected.

  The fixing condition determination unit 353 transmits the determined fixing conditions (fixing temperature, conveyance speed, fixing pressure, etc.) to the fixing device 120 via the communication interface unit 354. As a result, the fixing device 120 executes the fixing process under the fixing conditions instructed from the control device 31.

  The operation panel 32 displays a screen for the user to adjust (typically fine adjustment) the fixing temperature based on control by the control device 31. When the user inputs an instruction for changing the fixing temperature on the screen, the instruction is sent to the fixing condition determination unit 353 via the communication interface unit 354. In this case, the fixing condition determination unit 353 changes the setting of the fixing temperature based on the received instruction. Specifically, the fixing condition determining unit 353 changes the fixing temperature value in the data table D4. Specifically, the main body 10 is configured such that the fixing temperature can be changed for each basis weight.

<F. Control structure>
FIG. 9 is a flowchart for explaining the flow of processing executed in the main unit 10.

Referring to FIG. 9, in step S1, the media sensor 16 to detect the basis weight V _t of the sheet P is performed. In step S2, the media sensor 16 detects the thickness [delta] _t of the paper P. In step S <b> 3, the media sensor 16 detects the Beck smoothness of the paper P.

In step S4, the control device 31 calculates the thermal conductivity λ _t of the paper P based on the detected Beck smoothness. In step S <b> 5, the control device 31 corrects the basis weight V _t using the thermal conductivity λ _t of the paper P and the thickness δ _{t of the} paper P. In step S < _b > 6, the fixing device 120 executes the fixing process under the fixing conditions corresponding to the corrected basis weight V _c .

  Note that the order of steps S1, S2, and S3 is not limited to this, and each step may be performed in parallel. For example, step S2 or step S3 may be performed before step S1. .

<G. Modification>
(1) The configuration of the image forming apparatus described above is an example, and the configuration of the image forming apparatus is not limited to this.

  For example, in the above description, the configuration in which the media sensor 16 detects various attributes of the paper P has been described as an example. However, the configuration is not limited thereto. In place of the media sensor 16, the main body 10 individually includes a sensor for detecting the basis weight of the paper P, a sensor for detecting the thickness (paper thickness) of the paper P, a sensor for detecting the Beck smoothness of the paper P, and the like. You may have.

  (2) The configuration of the fixing device described above is an example, and the configuration of the fixing device is not limited to this.

  (3) It is good also as a structure which the memory | storage device (memory | storage part) has memorize | stored beforehand the control apparatus 31 for every paper classification for Beck smoothness and thickness. In this case, the control device 31 does not need to calculate Beck smoothness and thickness. That is, the control device 31 may read the Beck smoothness and thickness associated with the determined paper type from the memory by determining the paper type.

(4) The control device 31 may calculate the power consumption amount for fixing, and if the power consumption amount deviates from the assumed power consumption amount, the control device 31 may further correct the corrected basis weight. For example, the power consumption may be larger than expected due to erroneous detection due to a failure of the media sensor 16 or the like. In such a case, the controller 31 performs further increased to correct the basis weight V _c corrected. According to this, it is possible to prevent an appropriate fixing process from being performed due to the influence of erroneous detection.

  (5) The fixing temperature is not determined only by the information on the paper (recording material, medium), but the nip width, the nip area warming condition, the heating part warming condition, the internal temperature and humidity, the paper cassette temperature, the density, the object, etc. It may be determined using the image information.

  (6) As the fixing conditions, as shown in the data table D4 in FIG. 4, the fixing temperature, the conveyance speed, the fixing pressure, and the PPM have been described as examples. However, the fixing conditions are not limited thereto. . In the data table items that indicate the fixing conditions, the paper interval, DUTY parameter for heater control, waiting time at the start of printing, set temperature after printing, idling speed and time, pressure contact state and speed at warm-up, etc. May be included.

(7) In the above description, the configuration in which the image forming apparatus 1000 detects the basis weight V _t before correction in Expression (2) has been described as an example, but is not limited thereto. The configuration may be such that the user inputs using the operation panel 32.

  (8) The above-described processing can be applied to various image forming apparatuses such as a monochrome copying machine, a color copying machine, a printer, a FAX, and a complex machine thereof.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Main-body part, 11 Image formation unit, 12 Scanner unit, 13 Automatic document conveyance unit, 14 Paper feed part, 15 Conveyance path, 16 Media sensor, 16A Basis weight detection part, 16B Paper thickness detection part, 16C Beck smoothness detection part , 17 Reverse conveyance path, 18 Paper discharge roller, 20 Post-processing device, 31 Control device, 32 Operation panel, 101 Intermediate transfer belt, 102, 103 Registration roller, 104C, 104K, 104M, 104Y Image forming unit, 105 Image density sensor , 111 Primary transfer device, 115 Secondary transfer device, 120 Fixing device, 121 Heating roller, 122 Fixing roller, 123 Fixing belt, 124 Pressure roller, 125 Heater, 126 Thermistor, 129 Heating rotator, 141 Feed roller, 142 paper cassette, 2 0 punch processing device, 250 flat stitching processing unit, 260 saddle stitching processing unit, 271, 272, 273 discharge tray, 290 horizontal conveyance unit, 314 flash memory, 320 touch screen, 321 touch panel, 322 display, 351 basis weight correction unit, 352 Thermal conductivity calculation unit, 353 fixing condition determination unit, 354 communication interface unit, 1000 image forming apparatus, D4 data table, G toner image, 315 communication IF, P, Q paper.

Claims (18)

A fixing device having a heat source and fixing an unfixed image on the recording material on the recording material using heat generated by the heat source;
A control device for controlling the operation of the fixing device,
The controller is
The basis weight of the recording material is corrected using the thermal conductivity of the recording material and the thickness of the recording material,
Determine fixing conditions in the fixing device based on the basis weight after correction,
An image forming apparatus that operates the fixing device under the determined fixing conditions.   The image forming apparatus according to claim 1, wherein the fixing condition is a set temperature of the heat source.   The image forming apparatus according to claim 2, wherein the control device controls the fixing device such that the set temperature increases as the basis weight after the correction increases.   The image forming apparatus according to claim 2, wherein the control device controls the fixing device such that the set temperature becomes higher as the thermal conductivity is higher.   5. The control device according to claim 2, wherein the control device controls the fixing device such that the set temperature increases as the value obtained by dividing the thermal conductivity by the thickness increases. 6. Image forming apparatus. The control device stores the corrected basis weight and the set temperature in association with each other,
The image forming apparatus further includes an operation unit that receives a user operation,
6. The control device according to claim 2, wherein when the operation unit receives a user operation for changing the set temperature, the control device changes the set temperature to a value based on the user operation. 6. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the fixing condition is a conveyance speed of the recording material.   The image forming apparatus according to claim 7, wherein the control device controls the fixing device such that the conveyance speed becomes slower as the basis weight after the correction is larger.   The image forming apparatus according to claim 7, wherein the control device controls the fixing device such that the higher the thermal conductivity, the slower the conveyance speed.   10. The control device according to claim 7, wherein the controller controls the fixing device such that the larger the value obtained by dividing the thermal conductivity by the thickness, the slower the conveyance speed. Image forming apparatus. The fixing device further includes a pressure member, and fixes the unfixed image on the recording material using a pressure applied by the pressure member,
The image forming apparatus according to claim 1, wherein the fixing condition is a value of the pressure.   The image forming apparatus according to claim 11, wherein the control device controls the fixing device such that the pressure becomes higher as the basis weight after the correction is larger.   The image forming apparatus according to claim 11, wherein the control device controls the fixing device so that the pressure becomes higher as the thermal conductivity is higher.   14. The control device according to claim 11, wherein the control device controls the fixing device such that the larger the value obtained by dividing the thermal conductivity by the thickness, the higher the pressure. Image forming apparatus.   The image formation according to claim 1, wherein the control device corrects the basis weight of the recording material using a first value obtained by dividing the thermal conductivity by the thickness. apparatus.   The image formation according to claim 15, wherein the control device corrects the basis weight of the recording material using a third value obtained by dividing the first value by a predetermined second value. apparatus.   The image forming apparatus according to claim 1, wherein the control device calculates the thermal conductivity based on a Beck smoothness of the recording material. A control method for an image forming apparatus, comprising: a fixing device that fixes an unfixed image on a recording material on the recording material using heat; and a control device that controls the operation of the fixing device.
Correcting the basis weight of the recording material using the thermal conductivity of the recording material and the thickness of the recording material;
Determining fixing conditions in the fixing device based on the basis weight after correction;
And a step of operating the fixing device under the determined fixing condition.

Images