Patent Application
20230102072
The present invention relates to an image forming apparatus.
There is used an image forming apparatus which uses the electrophotographic system such as a laser printer or a digital copier. In such an image forming apparatus, when a toner image is heated and fixed to a recording material, it is possible to reduce power consumption by setting a proper target temperature for each page according to a toner amount on an image which is determined from image data.
Japanese Patent No. 5900474 discloses a technique for achieving both of energy saving and maintenance of print productivity in the case where a target temperature of a subsequent page is higher than that of a preceding page in successive printing. In Japanese Patent No. 5900474, by using information indicating whether or not gloss non-uniformity can occur when the target temperature is increased in the preceding page, in the case where the gloss non-uniformity does not occur, the target temperature is increased in the preceding page and is also increased in a period between sheets, and a desired target temperature is reached when the subsequent page is started.
In the image forming apparatus described in Japanese Patent No. 5900474, the target temperature is increased in the preceding page in the case where the gloss non-uniformity does not occur but, depending on timing at which the target temperature is increased, there is a possibility that electric power is supplied.
The present invention has been made in view of the above problem, and an object thereof is to control timing at which a target temperature is switched according to target temperatures of a preceding page and a subsequent page.
The present invention provides an image forming apparatus comprising:
a fixing unit configured to heat a recording material on which a toner image based on image data is formed and which is transported at a fixing nip portion to fix the toner image to the recording material; and
a control unit configured to determine a target temperature when the fixing unit heats the toner image for each recording material based on the image data, and control switching timing of the target temperature, wherein
in a case where the target temperature of a first recording material is a first temperature, the target temperature of a second recording material which is fixed subsequently to the first recording material is a second temperature higher than the first temperature, and, a difference between the second temperature and the first temperature has a first value, the control unit starts switching to the second temperature from timing which is earlier than reaching of the second recording material to the fixing nip portion by a first period,
in a case where the target temperature of a third recording material is a third temperature higher than the first temperature, the target temperature of a fourth recording material which is fixed subsequently to the third recording material is a fourth temperature higher than the third temperature, and, a difference between the fourth temperature and the third temperature has the first value, the control unit starts switching to the fourth temperature from timing which is earlier than reaching of the fourth recording material to the fixing nip portion by a second period, and
the second period is shorter than the first period.
According to the present invention, it is possible to control the timing at which the target temperature is switched according to the target temperatures of the preceding page and the subsequent page.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinbelow, embodiments of the present invention will be described in detail with reference to the drawings. Note that the dimensions, materials, shapes, and relative arrangements of components described in the embodiments should be appropriately changed according to the configuration of an apparatus to which the invention is applied and various conditions, and the scope of the invention is not intended to be limited to the following embodiments.
The image forming apparatus 100 generally includes an image forming unit 50 and a printer control apparatus 304. The image forming unit 50 includes a photosensitive drum 1, a charging roller 2, a laser scanner 3, a developing apparatus 4, a transfer roller 5, a heating and fixing apparatus 6 serving as a fixing unit, and a cleaning apparatus 7. The image forming unit 50 forms a toner image corresponding to image data on a recording material P according to control of the printer control apparatus 304 serving as a control unit. In addition, the image forming apparatus includes a paper feed tray 101, a paper feed roller 102, a transport roller 103, a top sensor 104, a paper discharge sensor 105, a paper discharge roller 106, and a paper discharge tray 107.
The photosensitive drum 1 is a drum-shaped electrophotographic photosensitive member, and is constituted by providing a photosensitive material such as an OPC (organic optical semiconductor) or amorphous silicon on a cylindrical drum substrate formed of an aluminum alloy or nickel. The photosensitive drum 1 is rotationally driven at a predetermined process speed (peripheral speed) in a direction of an arrow R1 by drive means (not shown).
The charging roller 2 uniformly charges the surface of the photosensitive drum 1 such that the surface thereof has predetermined polarity and potential. Subsequently, the laser scanner 3 irradiates the photosensitive drum 1 after being charged with a laser beam E, and an electrostatic latent image is thereby formed on the surface of the photosensitive drum. At this point, the laser scanner 3 performs scanning exposure controlled by ON/OFF control performed correspondingly to image data in a longitudinal direction of the photosensitive drum 1, and charges in an exposed portion are thereby removed.
The developing apparatus 4 develops and visualizes the formed electrostatic latent image. As a developing method, in addition to jumping development in the present embodiment, two-component development and contact development are used. Alternatively, image exposure and reversal development may be combined. A developing roller 41 of the developing apparatus 4 causes toner to adhere to the electrostatic latent image on the photosensitive drum 1 to form a toner image.
The toner image on the photosensitive drum 1 is transferred to the surface of the recording material P. The recording material P is fed one sheet by one sheet by the paper feed roller 102 from a state in which the recording material P is stored in the paper feed tray 101, and is fed to a transfer nip portion Nt positioned between the photosensitive drum 1 and the transfer roller 5 via the transport roller 103 and the like.
A tip of the recording material P is detected by the top sensor 104. The printer control apparatus 304 acquires timing at which the tip of the recording material P reaches the transfer nip portion Nt from the position of the top sensor 104, the position of the transfer nip portion Nt, and a transport speed of the recording material P. Subsequently, the transfer roller 5 applies a transfer bias onto the recording material P having been fed and transported at predetermined timing, and the toner image on the photosensitive drum 1 is thereby transferred.
The recording material P to which the toner image has been transferred is transported to the heating and fixing apparatus 6. The heating and fixing apparatus 6 performs heating and pressurization at a fixing nip portion Nf positioned between a film unit 10 and a pressure roller 20 while holding and transporting the recording material P. With this, the toner image is fixed to the surface of the recording material P. Thereafter, the recording material P is discharged onto the paper discharge tray 107 formed on the upper surface of the image forming apparatus 100 by the paper discharge roller 106. Note that the paper discharge sensor 105 detects timing at which the tip and the rear end of the recording material P pass, and the presence or absence of occurrence of a jam or the like is thereby monitored.
On the other hand, the cleaning apparatus 7 removes untransferred toner (residual toner which is not transferred to the recording material P) on the surface of the photosensitive drum 1 after the toner image is transferred with a cleaning blade 71. The removed untransferred toner is used in the next image formation.
The image forming apparatus 100 successively performs image formation by repeating the above operations. The image forming apparatus 100 of the present embodiment can form an image having a resolution of 600 dpi at a speed of thirty-five sheets/min. (LTR vertical feed: a process speed of about 200 mm/s, an inter-sheet distance of 66 mm), and is an apparatus having a lifespan of one hundred thousand sheets.
Printer Control Apparatus
The printer control apparatus 304 provided in the image forming apparatus 100 will be described by using
The host computer 300 is an information processing apparatus having instruction contents from a user and image data serving as the source of an image to be formed. The printer control apparatus 304 controls the image forming apparatus 100 by using information received by performing communication with the host computer 300. The host computer 300 may be a server or a personal computer on a network such as, e.g., the Internet or a local area network (LAN), and may also be a portable information terminal such as a smartphone or a tablet. The printer control apparatus 304 is roughly divided into a controller 301 and an engine control unit 302.
The controller 301 has an image processing unit 303 and a controller interface 305. The controller interface 305 performs communication in and outside the printer control apparatus 304. The image processing unit 303 processes image data received from the host computer 300 via the controller interface 305. Examples of the image data processing include bitmapping of a character code and halftoning of a gray-scale image.
In addition, the controller 301 transmits image data to a video interface 310 of the engine control unit 302 via the controller interface 305. The image data of the present embodiment includes information on a target temperature for maintaining the temperature of a heater 11 which is calculated by the image processing unit 303. A method for calculating the target temperature will be described in detail later.
The engine control unit 302 includes the video interface 310, a central processing unit (CPU) 311, a read only memory (ROM) 312, a random access memory (RAM) 313, and an application specific integrated circuit (ASIC) 314. The controller 301 transmits information on turn-on timing of the laser scanner 3 to the ASIC 314, and transmits a print mode and image size information to the CPU 311. The controller 301 transmits the information on the turn-on timing of the laser scanner 3 to the CPU 311.
The CPU 311 performs various control operations of the engine control unit 302 by using the ROM 312 and the RAM 313 according to a program and a user instruction. The CPU 311 may be a single processor, and may also have a multi-processor configuration. The controller 301 transmits a print command and a cancel instruction to the engine control unit 302 in response to an instruction issued with the host computer 300 by the user to control operations such as start and suspension of a printing operation.
The fixing control unit 320 controls the temperature of the heating and fixing apparatus 6. The paper feed and transport control unit 330 controls operation intervals of the paper feed roller 102. The image formation control unit 340 performs process speed control, development control, charging control, and transfer control. Part or the whole of the processing performed by the image forming apparatus 100 (e.g., processing performed by the engine control unit 302 or the image processing unit 303) may be performed by a processing apparatus such as the host computer 300 or a server (not shown) on a network. In addition, part or the whole of the processing performed by the engine control unit 302 may be performed by the image processing unit 303, and part or the whole of the processing performed by the image processing unit 303 may be performed by the engine control unit 302.
Heating and Fixing Apparatus
The heating and fixing apparatus 6 will be described by using
The heating and fixing apparatus 6 holds and transports the recording material P on which a toner image t is formed, and the toner image t transported together with the fixing film 13 is thereby fixed to the recording material P at the fixing nip portion Nf formed between the fixing film 13 and the pressure roller 20. Note that, as long as the toner image can be fixed to the recording material, the heating and fixing apparatus 6 is not limited to the configuration of the present embodiment.
On a surface of the heater 11 which is opposite to a side of a surface which slides on the fixing film 13, a thermistor 14 serving as a temperature detection member is disposed so as to be in contact with the surface thereof. The engine control unit 302 controls a current caused to flow to the heater 11 by the fixing control unit 320 such that the temperature of the heater 11 becomes a desired temperature based on the detected temperature of the thermistor 14.
Fixing Film
The fixing film 13 is a composite layer film obtained by coating or tube-covering a surface of a thin metal element tube made of SUS with a releasable layer made of PFA, PTFE, or FEP directly or via a primer layer. Instead of the metal element tube, a base layer obtained by forming a material in which a heat-resistant resin such as a polyimide and a heat conductive filler made of graphite are kneaded into a tubular shape may also be used. In the present embodiment, the fixing film 13 obtained by coating a base-layer polyimide with PFA is used. The fixing film 13 of the present embodiment has a total thickness of 80 μm and an outer peripheral length of 56 mm. The fixing film 13 rotates while sliding on the heater 11 and the holder 12 inside the fixing film 13, and hence it is necessary to suppress frictional resistance between the heater 11 and the holder 12, and the fixing film 13 to a low level. In the present embodiment, by applying a small amount of lubricant such as heat-resistant grease on the surfaces of the heater 11 and the holder 12, it is made possible for the fixing film 13 to rotate smoothly.
Pressure Roller
The pressure roller 20 has a core metal 21, an elastic layer 22, and a releasable layer 23. The elastic layer 22 is formed by foaming heat-resistant rubber such as insulating silicone rubber or fluoro rubber on the core metal 21 made of iron or the like. RTV silicone rubber (not shown) which is subjected to primer processing as an adhesive layer and has adhesion is applied onto the elastic layer 22. Further, the releasable layer 23 is formed on the elastic layer 22 via an adhesive layer. As the releasable layer 23, for example, a layer obtained by covering or coating PFA, PTFE, or FEP with a tube in which a conductive agent such as carbon is dispersed is used.
In the present embodiment, the outer diameter of the pressure roller 20 is 20 mm, and the hardness thereof is 48° (Asker-C 600 g load). The pressure roller 20 is pressurized from both end portions in a longitudinal direction with 147 N (15 kgf) by pressurization means which is not shown. With this, the fixing nip portion Nf required for heating and fixing is formed. In addition, the pressure roller 20 is rotationally driven in a direction of an arrow R2 in
Heater
The heater 11 is provided inside the fixing film 13. The heater 11 has a board (insulating board) 113 made of alumina or aluminum nitride which is made of ceramic, and a resistance heating layer (heating element) 112 formed on the board 113. The resistance heating layer 112 is covered with a thin overcoat glass 111 for improving insulation and wear resistance, and the overcoat glass 111 is in contact with an inner peripheral surface of the fixing film 13. The overcoat glass 111 is excellent in withstand voltage and wear resistance, and is configured and disposed so as to slide on the fixing film 13.
In the embodiment, the heat conductivity of the overcoat glass 111 is 1.0 W/m·K, the withstand voltage characteristic thereof is not less than 2.5 kV, and the thickness thereof is 70 μm. In addition, in the embodiment, the material of the board 113 is alumina, and its dimensions are a width of 6.0 mm, a length of 260.0 mm, and a thickness of 1.00 mm. Further, the coefficient of thermal expansion of the board 113 is 7.6×10−6/° C. The resistance heating layer 112 of the embodiment is formed of a silver-palladium alloy. The total resistance value of the resistance heating layer 112 is 20Ω, and the temperature dependency of resistibility is 700 ppm/° C.
Holder
The holder 12 is a member which holds the heater 11, and is also a heat-insulating stay holder which prevents heat radiation to the back side of the fixing nip portion Nf. The holder 12 is formed of a liquid crystal polymer, a phenol resin, PPS (poly (phenylene sulfide)), or PEEK (polyether ether ketone). The fixing film 13 is fitted on the holder 12 loosely to some extent, and is disposed rotatably. The material of the holder 12 of the present embodiment is the liquid crystal polymer, the holder 12 has heat resistance of 260° C., and the coefficient of thermal expansion of the holder 12 is 6.4×10−5/° C.
Engine Control Section
The engine control unit 302 controls the heater 11 based on the detected temperature of the thermistor 14 according to a control program such that the heater 11 has a predetermined target temperature. For that purpose, the engine control unit 302 controls electric power supplied to the heater 11 such that the heater 11 maintains the target temperature. The engine control unit 302 is an example of a control unit. As a control method, PID control including a proportional term, an integral term, and a differential term is preferable. The following formula (1) represents this control formula.
f(t)=α1×e(t)+α2×Σe(t)+α3×(e(t)−e(t−1)) (1)
Herein, the individual terms are as follows.
t: control timing
f (t): a ratio of heater energization time in a control cycle at control timing (t) (1 or more denotes full turn-on)
e (t): a difference between a target temperature and an actual temperature at current control timing (t)
e (t−1): a difference between the target temperature and the actual temperature at previous control timing (t−1)
α1 to α3: gain constant
α1: P (proportional) term gain
α2: I (integral) term gain
α3: D (differential) term gain
The first term to the third term on the right side in Formula (1) correspond to proportional control, integral control, and differential control in this order. α1 to α3 are proportionality coefficients for weighting an increase or decrease amount of the ratio of energization time of the heater 11 in the control cycle. By setting α1 to α3 according to characteristics of the heating and fixing apparatus 6, proper temperature control is made possible. The engine control unit 302 determines the energization time of the heater 11 in the control cycle according to the value of f (t), and drives a heater energization time control circuit which is not shown to determine output power of the heater 11. Note that, when the D term is not necessary, control may be performed by PI control in which only the P term and the I term function by setting the D term gain to 0. In the embodiment, the control timing is updated at an interval of a control cycle of 100 msec, and the P term gain (α1) is set to 0.05° C.-1, the I term gain is set to 0.01° C.-1 (α2), and the D term gain is set to 0.001° C.-1 (α3). In the present embodiment, a setting is adopted in which the energization time in the control cycle is maximized when the f (t) value is 1, and energization is performed for the maximum energization time in the control cycle in the case where a calculation result is more than 1.
Herein,
During the passage of the preceding sheet (a period from when the tip of the first sheet of the recording material enters the fixing nip portion Nf to when the rear end of the first sheet of the recording material passes through the fixing nip portion Nf), the engine control unit 302 controls power supply to the heater 11 so as to maintain the target temperature T1. The target temperature T1 during the passage of the sheet is in a range of not less than 170° C. and not more than 204° C., and is determined by a calculation method described later.
With regard to a period between sheets (a period from when the rear end of the preceding sheet passes through the fixing nip portion Nf to when a subsequent sheet enters the fixing nip portion Nf), after the engine control unit 302 controls power supply to the heater 11 so as to maintain the target temperature T1, the engine control unit 302 switches the target temperature to a target temperature T2 (second temperature) of the second sheet of the recording material during the period between sheets before the second sheet of the recording material (a second recording material and is also written as “subsequent sheet”) is passed.
Subsequently, during the passage of the subsequent sheet (a period from when the tip of the second sheet of the recording material enters the fixing nip portion Nf to when the rear end of the second sheet of the recording material passes through the fixing nip portion Nf), the engine control unit 302 controls power supply to the heater 11 so as to maintain the target temperature T2. Similarly to T1, the target temperature T2 during the passage of the sheet is in a range of not less than 170° C. and not more than 204° C., and is determined by a calculation method described later.
Image Processing Section
Calculation of Target Temperature from Image Data
The image processing unit 303 has a processor such as a CPU and a memory such as a ROM or a RAM. Note that an information processing apparatus which functions as the engine control unit 302 may be caused to function as the image processing unit 303. The image processing unit 303 performs processing for calculating the target temperature from image data in addition to halftoning of a gray-scale image. In the following example, a description will be given of processing of the image processing unit 303 in the case where a toner image corresponding to image data is formed on the surface of one sheet of the recording material P.
In target temperature determination based on image density information of a divided area, the image processing unit 303 divides image data into areas and regions, and classifies the individual regions into seven representative values. Next, the representative value based on the classification is converted to an addition amount of temperature in each region, and the addition amount is added in a sub scanning direction. Subsequently, the maximum value is selected from addition values in a plurality of main scanning areas, the value is added to a base temperature, and a target temperature T is calculated. Hereinbelow, each step will be described sequentially. Note that the target temperature calculation method is not limited thereto, and it is only required that temperature corresponding to a printing amount is determined.
Division of Image Data
Division of image data by the image processing unit 303 will be described with reference to
Main Scanning Area Division Step
The image processing unit 303 provides the main scanning areas by dividing the whole area of image data in the main scanning direction. In the present embodiment, the number of times of the division is set to 4. Herein, the center of a sheet when a sheet having the LTR size (short side of 216 mm) is fed to the heating and fixing apparatus is set as the origin on the heating and fixing apparatus, and a coordinate of the origin is set to 0 mm. In addition, the left side with respect to the transport direction is defined as a negative side, and the right side therewith is defined as a positive side. In the present embodiment, as shown in Table 1 and
Sub-Scanning Area Division Step
The image processing unit 303 provides the sub scanning areas by dividing the whole area of image data in the sub scanning direction. In the present embodiment, the number of times of the division is set to 5. An image start position is set as the origin on the heating and fixing apparatus, and a coordinate of the origin is set to 0 mm. In the present embodiment, as shown in Table 2 and
Region Setting Step
The image processing unit 303 sets one area defined by the main scanning area and the sub scanning area as a region. Hereinbelow, a range defined by a main scanning area MSn and a sub scanning area SSk is referred to as “region R (k, n)”.
Ranking of Region
The image processing unit 303 calculates a printing amount in the region R (k, n).
Count of High-Density Pixel
First, the image processing unit 303 extracts a high-density pixel having a gray density of not less than 4% in each region. Subsequently, the total number of high-density pixels in the region R (k, n) is counted, and is set as N (k, n) (pieces).
Then, the image processing unit 303 classifies the total number of high-density pixels N (k, n) in the region R (k, n) into seven-level ranks including Rank 0 to Rank 6 based on Table 3.
The rank of the printing amount in the region R (k, n) calculated in this manner is indicated by Rank (k, n). With the processing procedure described above, it is possible to integrate printing amount information of the whole area of the image data into rank information having seven levels for each of twenty regions.
Determination of Target Temperature T
Subsequently, the image processing unit 303 determines the target temperature T based on the rank of the printing amount of each region. Hereinbelow, the determination of the target temperature T will be described together with an expected printing shape and a phenomenon related thereto.
Expected Image and Influence of Temperature Reduction
First, before description of specific processing contents, as an expected image which is significantly influenced by temperature reduction, image data with which vertical band-shaped printing is performed will be discussed for each rank. That is, when the rank of the printing amount of each region is determined, the image processing unit 303 assumes that rectangular printing (hereinafter referred to as vertical band-shaped printing) which spreads fully in the sub scanning direction in the region is performed with a width of the number of pixels based on the rank. In addition, the image processing unit 303 assumes the target temperature at which the vertical band-shaped printing can be adequately fixed.
For example, when the length in the sub scanning direction is 56.5 mm, the width of the vertical band-shaped printing in the main scanning direction is assumed in the following manner. The width thereof is 0.042 mm when the rank is Rank 0, 1 mm when the rank is Rank 1, 2 mm when the rank is Rank 2, 4 mm when the rank is Rank 3, 8 mm when the rank is Rank 4, 16 mm when the rank is Rank 5, and the entire width of the region in the main scanning direction when the rank is Rank 6. The reason for this assumption is that such vertical band-shaped printing needs the highest target temperature T in the rank of a certain printing amount. That is, when toner is disposed in the shape of a vertical band, heat is continuously taken from a specific position in the main scanning direction of a member (the fixing film 13 or the heater 11) which performs heating of the heating and fixing apparatus 6. As a result, the temperature of the portion is reduced and fixing performance deteriorates. Therefore, in order to compensate for heat which is reduced, it is necessary to increase the target temperature T.
When the thickness of the vertical band in the main scanning direction is small, heat flowing in from surrounding members compensates for such a temperature reduction phenomenon, and hence the temperature reduction phenomenon can be almost neglected. However, as the vertical band becomes thicker, it becomes more difficult for the heat to flow into a central portion of the vertical band, and hence the degree of the temperature reduction is increased, the temperature reduction can be no longer neglected, and the higher target temperature T becomes necessary.
Note that, in the description of the present embodiment, a configuration is adopted in which a basic value of the target temperature is set, and the correction amount (addition amount) to the basic value is calculated based on image data. However, the method is not limited to the above method as long as the target temperature can be calculated finally based on the image data. For example, a method in which the target temperature is directly calculated based on the image data without setting the basic value or the correction amount may also be adopted.
Note that the temperature reduction phenomenon becomes more significant as the length of the vertical band in the sub scanning direction becomes longer and, in particular, the temperature reduction phenomenon becomes conspicuous when the length in the sub scanning direction exceeds a length obtained by constant multiplication of the peripheral length of the fixing film 13.
In the case of the vertical band having a width in the main scanning direction of 0.042 mm, even when the length in the sub scanning direction is 56.5 mm or 287 mm which corresponds to the length of the image in an A4 size, the required correction amount of the target temperature T is unchanged. This is because, when the width is about 0.042 mm, the inflow of heat from surrounding areas is adequate, and hence local temperature reduction of a member can be neglected.
On the other hand, in the case of the vertical band having a width in the main scanning direction of 1 mm, the degree of the temperature reduction of the member is large, and hence the required correction amount of the target temperature T is increased in proportion to the length in the transport direction. At this point, as shown in
To cope with this, as described above, when the length in the sub scanning direction in the sub scanning area division is caused to substantially match the peripheral length of the fixing film 13, it is possible to perform arithmetic calculation in which this phenomenon is reflected, and hence higher power consumption reduction effect is obtained. Herein, “the length in the sub scanning direction substantially matches the peripheral length of the fixing film 13” denotes that, even when the lengths are not exactly identical to each other, it is only required that the lengths match each other to such a degree that the influence of the temperature reduction can be neglected.
Calculation of Target Temperature T
Based on the above-described preconditions, a specific calculation method of the target temperature T will be described. The target temperature T is calculated by determining the required correction amount in the case where the printing amount rank of the region is other than 0 as an addition amount ΔT by using, as a base, a temperature in the case where the printing amount rank of the region is 0.
First, in the present embodiment, a temperature required to fix the vertical band having a width of 0.042 mm which corresponds to Rank 0 is 170° C. The addition amount required in the case where each region corresponds to any Rank other than Rank 0 is defined based on
Next, the addition amount ΔT (k, n) is added to five regions (region column) continuously arranged in the sub scanning direction, and ΔTMSn is calculated as a candidate value of the correction amount of the target temperature. That is, for five main scanning areas which satisfy n=1 to 4, values obtained by adding ΔT (1, n), ΔT (2, n), ΔT (3, n), ΔT (4, n), and ΔT (5, n) to the five main scanning areas are calculated as ΔTMSn. This corresponds to a proportional rise of the required target temperature T when the vertical bands corresponding to the printing amount ranks are disposed in five regions which are arranged in the sub scanning direction. That is, the addition amount ΔT (k, n) is a conversion value from image density in the region which is used for calculating the candidate value ΔTMSn in the main scanning area MSn in which the region R (k, n) is included.
Consequently, a temperature obtained by adding a basic temperature (herein, 170° C.) to the largest value selected from among the calculated four candidate values ΔTMS1, ΔTMS2, ΔTMS3, and ΔTMS4 is determined to be the target temperature T.
A description will be given of an evaluation example for determining that desired power consumption reduction effect is obtained by the determination method of the present embodiment.
First, the determination of the target temperature is performed for the image in
Next, when this printing amount rank is converted to the addition amount ΔT of the temperature of each of each region and each region column, the conversion result is as shown in Table 6. As a result, when the correction value of 2.5° C. is added to 170° C. and the fractional portion is rounded up, the target temperature of this evaluation image is 173° C.
Similarly, the determination of the target temperature is performed for the image in
Next, when this printing amount rank is converted to the addition amount ΔT of the temperature of each of each region and each region column, the conversion result is as shown in Table 8. As a result, when the correction value of 7.5° C. is added to 170° C. and the fractional portion is rounded up, the target temperature of this evaluation image is 178° C.
Similarly, the determination of the target temperature is performed for the image in
Next, when this printing amount rank is converted to the addition amount ΔT of the temperature of each of each region and each region column, the conversion result is as shown in Table 10. As a result, when the correction value of 17.7° C. is added to 170° C. and the fractional portion is rounded up, the target temperature of this evaluation image is 188° C.
Similarly, the determination of the target temperature is performed for the image in
Next, when this printing amount rank is converted to the addition amount ΔT of the temperature of each of each region and each region column, the conversion result is as shown in Table 12. As a result, when the correction value of 22.5° C. is added to 170° C. and the fractional portion is rounded up, the target temperature of this evaluation image is 193° C.
Thus, the target temperatures in
As Comparative Example 1-1, a conventional example in the case where the image (a) and the image (b) are successively printed is shown. The target temperature (first temperature) of the image (a) of the preceding sheet is 173° C., the target temperature (second temperature) of the image (b) of the subsequent sheet is 178° C., and a target temperature difference between the preceding sheet and the subsequent sheet is 45° C.
In Comparative Example 1-1, the printing rate of the image (a) of the preceding sheet is low, and the determined target temperature is also low. Consequently, electric power supplied to the fixing heater is small and the endothermic quantity of the fixing member is small, and hence, immediately after the passage of the preceding sheet, the heat storage quantity of each of the film unit 10 and the pressure roller 20 is small. In such a state, in the case where a high-print image is printed at the tip of the subsequent sheet as in the image (b), the film temperature is quickly reduced due to endotherm by toner and paper.
As shown in
As Embodiment 1-1, the present embodiment in the case where the image (a) and the image (b) are successively printed is shown. Similarly to Comparative Example 1-1, the target temperature (first temperature) of the image (a) of the preceding sheet is 173° C., the target temperature (second temperature) of the image (b) of the subsequent sheet is 178° C., and the target temperature difference between the preceding sheet and the subsequent sheet is 45° C.
In Embodiment 1-1, the printing rate of the image (a) of the preceding sheet is low, and the determined target temperature is also low. Consequently, electric power supplied to the fixing heater is small and the endothermic quantity of the fixing member is also small, and hence, immediately after the passage of the preceding sheet, the heat storage quantity of each of the film unit 10 and the pressure roller 20 is small. In such a state, in the case where the high-print image is printed at the tip of the subsequent sheet as in the image (b), the film temperature is quickly reduced due to endotherm by toner and paper, and a fixing failure is expected to occur.
To cope with this, in the present embodiment, the target temperature is switched from the target temperature of the preceding sheet to the target temperature of the subsequent sheet at timing indicated by an arrow in
In the control in
As can be seen from the change of the film temperature shown in
As Comparative Example 1-2, a conventional example in the case where the image (c) and the image (d) are successively printed is shown. The target temperature (third temperature) of the image (c) of the preceding sheet (third recording material) is 188° C., the target temperature (fourth temperature) of the image (d) of the subsequent sheet (fourth recording material) is 193° C., and the target temperature difference between the preceding sheet and the subsequent sheet is 45° C. which is identical to those in Comparative Example 1-1 and Embodiment 1-1. In Comparative Example 1-2, the printing rate of the image (c) of the preceding sheet is high, and the determined target temperature is also high. Consequently, electric power supplied to the fixing heater is large and the endothermic quantity of the fixing member is also large, and hence, immediately after the passage of the preceding sheet, the heat storage quantity of each of the film unit 10 and the pressure roller 20 is large. In such a state, in the case where a high-print image such as the image (d) is printed on the subsequent sheet, a higher target temperature is set, and hence a film temperature rise at the tip portion of the subsequent sheet is large.
As shown in
As Embodiment 1-2, the present embodiment in the case where the image (c) and the image (d) are successively printed is shown. The target temperature (third temperature) of the image (c) of the preceding sheet (third recording material) is 188° C., the target temperature (fourth temperature) of the image (d) of the subsequent sheet (fourth recording material) is 193° C., and the target temperature difference between the preceding sheet and the subsequent sheet is 45° C. which is identical to those in Comparative Example 1-1 and Embodiment 1-1. In Embodiment 1-2, the printing rate of the image (c) of the preceding sheet is high, and the determined target temperature is also high. Consequently, electric power supplied to the fixing heater is large and the endothermic quantity of the fixing member is also large, and hence, immediately after the passage of the preceding sheet, the heat storage quantity of each of the film unit 10 and the pressure roller 20 is large. In the case of such a state, even when a high-print image is printed on the subsequent sheet as in the image (d), the film temperature is not quickly reduced due to endotherm by toner and paper, and a fixing failure does not occur.
Accordingly, in the present embodiment, the target temperature is switched from the target temperature of the preceding sheet to the target temperature of the subsequent sheet at timing indicated by an arrow in
As a result of measuring, with a wattmeter, electric power supplied to the heater 11 when the image (c) and the image (d) are repeatedly passed successively until fifty sheets are passed, as shown in Table 14, while the supplied electric power is 15.5 Wh in Comparative Example 1-2, the supplied electric power is 15.2 Wh in Embodiment 1-2. That is, according to the present embodiment, it is possible to reduce power consumption when fifty sheets are passed successively by 0.3 Wh.
In the control in
In the present Embodiment 1-2 having the above conditions, the switching of the target temperature is performed at the same timing as timing (r22) at which the subsequent sheet (fourth recording material) reaches the fixing nip portion Nf. Herein, when the length of a second period is indicated by 0 s, the switching of the target temperature is performed at timing which is earlier than r22 by the second period. With the foregoing, it can be said that the control in Embodiment 1-2 is control in which, in the case where the third temperature is higher than the first temperature, the fourth temperature is higher than the third temperature, and the difference between the fourth temperature and the third temperature has the first value which is identical to that in Embodiment 1-1, the second period is shorter than the first period.
Processing Procedure
Hereinbelow, an example of processing control including switching between Embodiment 1-1 and Embodiment 1-2 will be described with reference to a flowchart in
On the other hand, when the determination result in S103 is YES, the processing procedure proceeds to Step S104, and it is determined whether or not the printing rate of the preceding sheet is not more than a predetermined threshold value Th. When the printing rate is not more than the threshold value Th, the processing procedure proceeds to S105, and the switching timing is made earlier than usual. With this, processing placing emphasis on suppression of the temperature reduction shown in
Subsequently, fixing of the preceding sheet is performed in Step S107, inter-sheet processing is performed in Step S108, and fixing of the subsequent sheet is performed in Step S109. Note that the switching of the target temperature is executed at the timing determined in Step S105 or S106.
As explained in Embodiments 1-1 and 1-2, in the case where the target temperature of the subsequent sheet is higher than the target temperature of the preceding sheet, by setting the switching timing of the target temperature based on the target temperature of the preceding sheet, it is possible to properly control the film temperature of the subsequent sheet. As a result, it becomes possible to prevent a fixing failure caused by temperature reduction even in the case of Embodiment 1-1, and suppress power consumption even in the case of Embodiment 1-2. Note that the value of the target temperature T of each of the preceding sheet and the subsequent sheet is not limited to the example described above, and can be appropriately set according to the configuration and performance of the apparatus. In addition, in the case where a difference D in target temperature between the preceding sheet and the subsequent sheet is not less than a predetermined temperature difference (e.g., not less than 5° C.), target temperature switching control of the present invention may be performed. A threshold value in this case can also be appropriately set according to the configuration and performance of the apparatus as well.
Modification
Among the above embodiments, in Embodiment 1-1 in which the target temperature of the preceding sheet is low, as shown in
For example, in addition to the timings shown in
As described thus far, according to the present invention, in the case where the difference in target temperature between the preceding sheet and the subsequent sheet is not less than a predetermined value, the switching timing of the target temperature from the target temperature of the preceding sheet to the target temperature of the subsequent sheet is changed according to the target temperature of the preceding sheet. As a result, it is possible to properly control timing at which the target temperature is switched according to the target temperatures of the preceding page and the subsequent page. For example, according to the present invention, it is possible to provide an image forming apparatus which has low power consumption while preventing a fixing failure without increasing a period between sheets.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2021-159537, filed Sep. 29, 2021, which is hereby incorporated by reference wherein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-159537 | Sep 2021 | JP | national |
