JP2015191040A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can adjust conditions for image formation according to the characteristics of a medium.SOLUTION: The present invention relates to an image forming apparatus that performs image formation on a medium. The image forming apparatus that performs image formation on a medium includes: image formation condition determination means for determining conditions for image formation in performing image formation on a medium on the basis of the degree of compression of the medium, and image formation means for performing image formation on the medium according to the conditions for image formation determined by the image formation condition determination means.

Description

  The present invention relates to an image forming apparatus and can be applied to, for example, an electrophotographic printer.

  In the conventional electrophotographic printer, the thickness of the printing paper is measured, and the transfer voltage when the toner image formed on the photosensitive drum is transferred to the printing paper (medium) is controlled according to the measurement result. There is a thing (refer patent document 1).

JP 2008-247612 A

  However, since the paper used in the conventional printer may have different electrical characteristics depending on not only the thickness but also the material, the relationship between the thickness and a suitable transfer voltage may not be unambiguous. .

  Therefore, there is a demand for an image forming apparatus that can adjust image forming conditions according to the characteristics (for example, electrical characteristics) of the medium.

  According to a first aspect of the present invention, in the image forming apparatus for forming an image on a medium, (1) an image forming condition determining unit that determines an image forming condition for forming an image on the medium based on a compression degree of the medium. And (2) image forming means for forming an image on the medium in accordance with the image forming conditions determined by the image forming condition determining means.

  According to a second aspect of the present invention, in the image forming apparatus for forming an image on a medium, (1) the medium thickness of the medium can be measured while pressing the medium with the pressing member, Measuring a first medium thickness by applying a first load to the medium, and measuring a second medium thickness by applying a second load larger than the first load to the pressing member; (2) Image forming condition determining means for determining an image forming condition when image formation is performed on the medium using the first load and the second load measured using the medium thickness measuring unit. And (3) image forming means for forming an image on the medium in accordance with the image forming conditions determined by the image forming condition determining means.

  According to the present invention, it is possible to provide an image forming apparatus that adjusts image forming conditions in accordance with the characteristics of a medium.

1 is a schematic sectional view of an image forming apparatus according to a first embodiment. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the first embodiment. It is a schematic side view of the paper thickness measurement part which concerns on 1st Embodiment. 3 is a flowchart illustrating an operation of the image forming apparatus according to the first embodiment. It is explanatory drawing shown about the compression rate based on the measurement result of the paper thickness measurement part which concerns on 1st Embodiment. It is explanatory drawing shown about the experimental result for every printing condition using the image forming apparatus which concerns on 1st Embodiment. FIG. 6 is an explanatory diagram showing experimental results for measuring the effect of the image forming apparatus according to the first embodiment. It is explanatory drawing shown about the experimental result for every printing condition using the image forming apparatus which concerns on 2nd Embodiment. It is explanatory drawing shown about the experimental result for measuring the effect of the image forming apparatus which concerns on 2nd Embodiment. It is explanatory drawing shown about the experimental result for every printing condition using the image forming apparatus which concerns on 3rd Embodiment. FIG. 10 is an explanatory diagram showing an experimental result for measuring an effect of an image forming apparatus according to a third embodiment.

(A) First Embodiment Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Hereinafter, an example in which the image forming apparatus of the present invention is applied to a printer will be described.

(A-1) Configuration of the First Embodiment FIG. 1 is a schematic cross-sectional view showing the overall configuration of the printer 1 of this embodiment.

  The printer 1 includes a paper cassette 2, a paper feed roller 3, a paper feed conveyance path 4, a paper feed sensor 5, a paper thickness measuring unit 500, a registration sensor 6, a registration roller 7, and an image forming unit 8 (8K, 8Y, 8M, 8C). ), Transfer unit 9, transfer belt 11, drive rollers 12, 13, fixing unit 14, fixing transport roller 17, discharge sensor 18, discharge roller 19, discharge transport path 20, and LED head 21 (21K, 21Y, 21M, 21C). )have.

  The paper cassette 2 stores paper M used for printing, and is detachably disposed at the bottom of the printer main body 1. A paper cassette sensor 2a capable of detecting removal (removal) and insertion (attachment, setting) of the paper cassette 2 is provided on the printer 1 main body (housing) side. The specific configuration of the paper cassette sensor 2a is not limited. For example, it is possible to detect the removal (removal) and insertion (attachment, setting) of the paper cassette 2 by a mechanical configuration such as a lever or a button (not shown). You may do it.

  The paper feed roller 3 feeds the paper M from the paper cassette 2 one by one.

  The paper feeding / conveying path 4 conveys the medium from the paper cassette 2 into the printer main body in the direction of the arrow D1.

  The paper feed sensor 5 is a sensor that is positioned upstream of a registration roller 7 described later and detects that the paper M reaches the registration roller 7.

  The registration sensor 6 is a sensor that is located downstream of the registration roller 7 and detects arrival at the image forming unit 8.

  The registration roller 7 is provided downstream of the paper feed conveyance path 4 and conveys the paper M with its position aligned.

  Each of the image forming units 8 (8K, 8Y, 8M, 8C) forms a toner image. The image forming units 8K, 8Y, 8M, and 8C form toner images of toner colors of black (K), yellow (Y), magenta (M), and cyan (C), respectively. Each of the image forming units 8K, 8Y, 8M, and 8C includes a photosensitive drum 81, a developing unit 82, and a toner cartridge 83. The printer 1 is a color printer that employs a tandem method, and is arranged in the order of image forming units 8K, 8Y, 8M, and 8C from upstream to downstream in the conveyance direction of the paper M.

  LED heads 21 (21K, 21Y, 21M, 21C) as exposure devices perform exposure based on image signals on the surfaces of the photosensitive drums 81 constituting the image forming units 8 (8K, 8Y, 8M, 8C), respectively. An electrostatic latent image is formed on the surface of the photosensitive drum 81.

  The photosensitive drum 81 carries an electrostatic latent image corresponding to the pattern of light emitted from the LED head 15. The developing unit 82 supplies the toner agent held in the toner cartridge 83 to the photosensitive drum 81 to develop the electrostatic latent image. As a result, a toner image is formed on the surface of the photosensitive drum 81.

  The transfer unit 9 uses the transfer roller 10 (10K, 10Y, 10M, 10C) to transfer the toner image generated by the image forming unit 8 (8K, 8Y, 8M, 8C) onto a predetermined medium and convey it. Is to do. A transfer voltage having a polarity opposite to that of the toner is applied to the transfer roller 10 (10K, 10Y, 10M, 10C) in accordance with the control of the high voltage controller 1000 described later.

  The transfer belt 11 is sandwiched together with the paper M between the transfer roller 10 (10K, 10Y, 10M, 10C) and the photosensitive drum 81 of each image forming unit 8 (8K, 8Y, 8M, 8C). It is a belt driven by.

  The driving rollers 12 and 13 are configured to drive the transfer belt 11 in the direction of the arrow D2 by driving a motor mechanism 700 described later while the transfer belt 11 is suspended.

  The fixing unit 14 heat-fixes the toner image formed by the image forming unit 8 (8K, 8Y, 8M, 8C) and transferred to the paper M by the transfer unit 9. The fixing unit 14 includes a fixing roller 15 and a pressure roller 16.

  The fixing roller 15 is heated by an internal heater 15b (fixing heat generator), and fixes the toner image transferred to the paper surface by the transfer unit 9. The surface temperature of the fixing roller 15 is detected by a temperature sensor 15a.

  The pressure roller 16 is a roller that is pressed against the fixing roller 15 by pressing means (not shown).

  The fixing conveyance roller 17 is provided in the vicinity of the fixing unit 14 and conveys the paper M after fixing.

  The discharge sensor 18 is a sensor that is disposed downstream of the fixing unit 14 and detects that the trailing edge of the paper M has been discharged from the fixing unit 14.

  The discharge roller 19 is for discharging the paper M out of the apparatus by rotation (forward rotation) drive.

  The discharge conveyance path 20 is a conveyance path for discharging the sheet conveyed by the fixing conveyance roller 17 and the discharge roller 19 to the outside of the apparatus.

  The paper thickness measurement unit 500 is a part for measuring the paper thickness, and is installed on the paper feed conveyance path 4. Details of the paper thickness measuring unit 500 will be described later.

  Next, the configuration of the control system of the printer 1 will be described with reference to FIG.

  A PC 100 shown in FIG. 2 is a device external to the printer 1 and operates as a host device (host) that supplies print job data and the like to the printer 1.

  The PC 100 includes a PC display unit 110 and a PC input unit 120, and creates print data. The created print data is transmitted to the printer via the host I / F 250. Further, the PC 100 receives an instruction issued from the printer via the host I / F 250. The PC display unit 110 is a liquid crystal display or the like for displaying a print image created by an application (not shown) and displaying an instruction issued from the printer. The PC input unit 120 is a keyboard, mouse, or the like for creating an image of print data via an application (not shown) and inputting a response to an instruction issued from the printer. Note that a response to an instruction issued from the printer may be input from the operation panel 600 of the printer.

  Functionally, the printer 1 includes a controller control unit 200, a print control unit 300, a thermistor 400, an operation panel 600, and a transfer power supply 1001 in addition to the components shown in FIG.

  The controller control unit 200 includes a CPU 210, ROM 220, RAM 230, timer 240, host I / F 250, operation panel control unit 260 and external I / F 270, and these components are connected by an internal bus 280. The controller control unit 200 also outputs an output signal output from the paper cassette sensor 2 a, the paper feed sensor 5, the registration sensor 6, and the discharge sensor 18, a paper thickness output from the paper thickness measurement unit 500, and a thermistor 400. Receives the temperature inside the device.

  CPU 210 exchanges commands for controlling RAM 230, timer 240, host I / F 250, operation panel control unit 260, and external I / F 270 according to programs stored in ROM 220. In addition, the CPU 210 exchanges commands for controlling the print control unit 300 via the external I / F 270 according to the above-described program. Further, the CPU 210 corresponds to a calculation function such as calculating a compression rate described later.

  The ROM 220 is an area for storing programs and parameters related to printing processing, and is a non-volatile memory capable of holding data even when the printer is turned off. The storage area stores a print processing control program 221, compression rate information 222, and a motor drive program 223. When the CPU 210 is activated, it reads each program stored in the ROM 220 and develops it on the RAM 230 for execution.

  When the print processing control program 221 acquires print job data via the host I / F 250, the print processing control program 221 instructs the print control unit 300 or the like to perform print processing in accordance with the print job data.

  When the paper type and paper thickness for printing are set in the received print job, the print processing control program 221 instructs the print control unit 300 or the like to perform print processing according to the settings. The print processing control program 221 determines an appropriate paper type and thickness when the paper type for printing is not explicitly set in the received print job (automatic setting), and the determined content is set. The following print processing is instructed to the print control unit 300 or the like. In the printer 1 of this embodiment, for simplicity of explanation, it is assumed that either plain paper or glossy paper is used as the paper type of the paper M installed in the paper cassette 2.

  The print processing control program 221 determines a printing condition (for example, a target transfer voltage used in the transfer unit 9) based on the paper thickness of the paper M and a compression rate described later when the paper type is not set in the print job. In response to the determined printing condition, the print control unit 300 is instructed to perform the printing process. Details of the processing of the printing condition control program 224 will be described later.

  The compression rate information 222 is information (for example, a threshold for performing paper type determination based on the compression rate described later) for determining the paper type by the printing condition control program 224, and details thereof will be described later.

  The motor drive program 223 controls the drive of the paper feed roller 3, the registration roller 7, the transfer roller 10, the fixing roller 15, the discharge roller 19, a motor mechanism 700 that drives a cam 506 described later, etc. It is a program to do.

  The RAM 230 is a volatile memory that stores print data input from the PC 100 and erases the data when the printer is turned off. The RAM 230 is measured by the timer 240 and holds time for taking various control timings.

  The timer 240 measures the time and outputs the measured time to the CPU 210.

  The host I / F 250 transmits and receives various control signals and print data between the PC 100 and the CPU 210.

  The operation panel control unit 260 performs control for displaying various information input on the operation panel 600 on the display unit 610, and performs control for displaying the printer state on the display unit 610.

  The external I / F 270 exchanges various control signals and resistance values with the print control unit 300, and receives output results of the paper feed sensor 5, the registration sensor 6, and the discharge sensor 18. .

  The print control unit 300 includes a heating control unit 310, a motor drive control unit 320, a measurement control unit 330, and a high-voltage control unit 1000, and conditions according to instructions from the CPU 210 (print processing control program 221 and motor drive program 223). In order to properly control the printing process such as paper conveyance, development, transfer and fixing.

  The heating controller 310 turns on / off the heater 15b in the fixing unit 14 based on the surface temperature of the fixing roller 15 input from the temperature sensor 15a, and sets the temperature of the fixing roller 15 and the pressure roller 16 to a predetermined target temperature. It is for controlling.

  The motor drive control unit 320 is for controlling the drive of the motor mechanism 700.

  In order to measure the paper thickness, the measurement control unit 330 issues an instruction regarding measurement to the paper thickness measurement unit 500, and when the measurement is completed, causes the controller control unit 200 to output the measurement value. The measurement instruction is the timing at which the sheet reaches the registration roller 7 and stops once. Details of processing performed by the measurement control unit 330 will be described later.

  The transfer voltage control unit 1000 controls a transfer power supply 1001 that applies a voltage having a characteristic opposite to that of the toner to the transfer roller 10 in order to transfer the toner image formed on the image forming unit 8 to a recording medium.

  The thermistor 400 is an element for measuring temperature from a change in electrical resistance with respect to a temperature change. The thermistor 400 is provided inside an apparatus (not shown).

  The paper thickness measuring unit 500 has each part for measuring the paper thickness under the control of the measurement control unit 330 that has received an instruction regarding the paper thickness measurement from the CPU 210. Details of the configuration of the paper thickness measuring unit 500 will be described later.

  The operation panel 600 includes keys and a display unit 610 for inputting input information necessary for printing by the user.

  The display unit 610 is for displaying user input contents and the state of the apparatus.

  The motor mechanism 700 drives the paper feed roller 3, the registration roller 7, the transfer roller 10, the fixing roller 15, the discharge roller 19, the cam 506 for changing the load applied to the paper M when measuring the paper thickness, and the like.

  As described above, in the printer 1, the CPU 210 executes the print processing control program 221 to realize the image forming condition determination unit and the compression degree calculation unit. Further, in the printer 1, an image forming unit that forms (prints) an image on a medium (paper M) is realized by each component other than the controller control unit 200 illustrated in FIGS. 1 and 2. Furthermore, in the printer 1, a developer image forming unit that forms a developer image (toner image) is realized by the image forming unit 8 and the LED head 21. In the printer 1, a transfer unit is realized by the transfer unit 9. Further, in the printer 1, a fixing unit is formed by the fixing unit 14. Furthermore, in the printer 1, components such as each roller, a motor, and a belt (a paper feed roller 3, a paper feed conveyance path 4, a registration roller 7, a transfer belt 11, drive rollers 12, 13, a pressure roller 16, a fixing roller, and the like. A medium conveying unit is realized by the components including the conveying roller 17, the discharge roller 19, the motor mechanism 700, and the like.

  Next, the configuration of the paper thickness measuring unit 500 will be described with reference to FIG.

  The paper thickness measurement unit 500 sandwiches the paper M passing on the paper feed conveyance path 4 and measures the paper thickness of the medium M, thereby contributing to the compression rate calculation. The compression rate (compression degree) is a parameter representing the degree to which the pressed portion is deformed and compressed when the paper M is pressed. A higher value of the degree of compression indicates that the thickness is likely to change when pressed (compressed and deformed, and the thickness tends to be thin).

  Usually, a paper has a gap (gap) between fibers, and the amount (size) of the gap varies depending on the type of the paper. In other words, the density of mass (mass per unit volume) varies depending on the type of paper. In other words, even though the paper has the same thickness, the density (mass of the entire paper) differs depending on the quality of the paper, so that the conditions of a suitable printing process (for example, suitable transfer voltage, etc.) are different. Become. When the compression ratio of the paper is low, the density is high and there are few gaps included in the paper M. Therefore, when pressed, the gap is crushed and deformed (the paper thickness is reduced). On the other hand, when the compression ratio of the paper is high, the density is low and there are many gaps included in the paper. Therefore, when pressed, the gap is crushed and deformed (the paper thickness is reduced).

  In the printer 1, when the paper thickness of the paper M is measured by the paper thickness measurement unit 500, the compression rate is measured by applying different pressures a plurality of times, and the material of the paper M is estimated.

  Specifically, the paper thickness measurement unit 500 presses the paper M a plurality of times with different pressing forces, and measures the paper thickness of the portion where the pressing force is applied each time the paper M is pressed. Then, the print control unit 300 calculates the compression rate of the paper M using the difference in the paper thickness measured a plurality of times.

  In this embodiment, as an example, the paper thickness measuring unit 500 presses the paper M twice with different pressures, and measures the paper thickness of the pressed portion. The paper thickness measuring unit 500 is a pressing member having a rectangular (rectangular) pressing member (paper presser 501a, which will be described later) having a contact surface that contacts the paper M and pressed with a load of 2 kg. The paper thickness of the pressed part is measured (first measurement), and the paper thickness measurement (second measurement) is performed in a state where the paper is pressed under a load of 3 kg. In other words, the paper thickness measurement unit 500 presses the paper M with the first load using the above-described pressing member and performs the first paper thickness measurement, and then the paper thickness measurement unit 500 has more than the first load. The second paper thickness is measured by pressing with the second load. Note that the first load and the second load are not limited, and it is desirable to apply a suitable load by experiments or the like.

  The print control unit 300 calculates the compression rate C of the paper M using the following equation (1). In the following formula (1), T1 is the paper thickness measured at the first time (weight 2 kg), and T2 is the paper thickness measured at the second time (weight 3 kg). That is, the compression rate C is a value represented by the ratio between the difference between T1 and T2 and T1.

Compression rate C = ((T1-T2) / T1) * 100 [%] (1)
In this embodiment, the print control unit 300 obtains a compression rate for the paper M, and determines the type (paper quality) of the paper M according to the compression rate. Specifically, the print control unit 300 determines that the paper M is plain paper when the compression rate is equal to or less than a threshold (hereinafter also referred to as “T”) (when the density is less than a predetermined value), and the compression rate is the threshold. When it is larger than T (when the density is higher than a predetermined value), the paper M is determined to be glossy paper. The compression rate information 222 stored in the ROM 220 includes a threshold value T for determining the paper type based on the compression rate, and the CPU 210 (print processing control program 221) uses this threshold value T. The paper type of the paper M is determined, and the printing conditions for the paper M are determined according to the determined paper type. In other words, the CPU 210 (printing process control program 221) determines the printing conditions for the paper M using T1 and T2.

  Glossy paper is coated with a coating solution compared to plain paper, so plain paper has a large gap between the intertwined fibers, but glossy paper has a gap between the fibers that is applied to smoothen the paint. There are few gaps in the paper. For this reason, glossy paper has fewer air layers than plain paper, which has a higher electrical resistance than paper fibers. Therefore, glossy paper has a lower electrical resistance than plain paper as a whole, so that the required transfer voltage is smaller than that of plain paper. Therefore, glossy paper has a higher density than plain paper even at the same paper thickness. In the following description, it is assumed that 10% is applied as the above-mentioned threshold value T as an example. However, the compression rate threshold value applied to discriminating the type of paper M is not limited, and a suitable value should be applied by experiments or the like. Is desirable.

  The paper M whose compression rate is lower than the predetermined threshold is determined as “glossy paper” having a high density, and the paper M whose compression rate is equal to or higher than the predetermined threshold is determined as “plain paper” having a low density. Is done.

  Next, a specific configuration example of the paper thickness measuring unit 500 will be described.

  FIG. 3 is an enlarged schematic side view showing only the portion where the paper thickness measuring unit 500 is arranged on the paper feed conveyance path 4. In this embodiment, the paper thickness measuring unit 500 is described as having the configuration shown in FIG. 3, but the paper thickness can be measured by pressing the paper M multiple times with different weights (pressures). If so, the specific configuration is not limited.

  The paper thickness measuring unit 500 includes upper and lower paper presses 501a and 501b as contact members, a tension spring 502 that presses the paper M, a lever 503, a joint 504, a displacement sensor 505, and a cam 506.

  Further, the paper thickness measuring unit 500 is disposed at a position where the paper M conveyed along the paper feed conveyance path 4 is sandwiched between the upper paper presser 501a and the lower paper presser 501b as pressing members. In the paper thickness measurement unit 500, the lower paper presser 501b is fixed to the main body of the printer 1, and the upper paper presser 501a presses the paper M from above. In this embodiment, it is assumed that the contact surface X with which the upper paper presser 501a contacts the paper M is a 1 cm × 2 cm rectangle.

  The upper sheet presser 501 a is connected to one end of a lever 503 that is rotatably installed around a joint 504. A tension spring 502 is provided at one end of the lever 503 to which the upper paper presser 501a is connected. The tension spring 502 presses the upper paper presser 501a and the lower paper presser 501b with a predetermined pressure. A cam 506 is provided on the end side.

  The lower sheet presser 501b is for applying a certain load to the sheet M by pressing the sheet M between the upper sheet presser 501a.

  The tension spring 502 is for pressing the paper M via the upper paper presser 501a. The load for pressing the sheet M is appropriately adjusted according to the position of a cam 506 described later.

  The lever 503 is for transmitting the load applied by the rotation of the cam 506 to the paper M via the joint 504. The lever 503 also serves to amplify the amount of displacement for detecting the paper thickness at the same time.

  The joint 504 is a fulcrum between a cam 506 (force point) for applying a load to the lever 503 and a tension spring 502 and a sheet presser 501a (operation point) to which the load is applied via the lever 503.

  When the cam 506 rotates, the lever 503 is integrated with the upper sheet presser 501a so as to be movable in the vertical direction.

  The displacement sensor 505 is provided in the vicinity of the end of the lever 503 opposite to the end where the tension spring 502 is provided. Further, the displacement sensor 505 is constituted by a reflection type photosensor, and measures the distance from the lever 503. The voltage output obtained by the measurement by the displacement sensor 505 is A / D converted and detected by the print control unit 300. The CPU 210 (print processing control program 221) acquires the measurement result (displacement amount) by the displacement sensor 505 via the print control unit 300, and the first and second paper thickness measurement results of the paper M. The result can be obtained. For example, the CPU 210 (printing process control program 221) obtains the paper thickness of the paper M by multiplying a value (digital value) supplied from the displacement sensor 505 by a predetermined coefficient (a coefficient set in advance based on experiments or the like). be able to.

  Further, the cam 506 rotates in accordance with the conveyance of the sheet M so as to lift the upper sheet retainer 501a before measuring the sheet thickness, and the sheet M is placed between the upper sheet retainer 501a and the lower sheet retainer 501b. Create a gap between them. Furthermore, when measuring the paper thickness, the motor mechanism 700 is driven to rotate the position of the cam 506 to 506b during the first measurement, and to the position of the cam 506 to 506a during the second measurement. In addition, before and after the measurement of the paper thickness, the cam mechanism 506 is rotated to 506c so that the load is not applied to the paper M by driving the motor mechanism 700. In the first measurement, a load of 2 kgW is applied to the paper M in the vertical direction, and in the second measurement, a load of 3 kgW is applied to the paper M in the vertical direction. It is assumed that no load is applied to M.

  As described above, the paper thickness measuring unit 500 measures the paper thickness of the paper M. In the printer 1, the paper thickness and the compression rate of the paper M can be obtained only by providing the paper thickness measurement unit 500, so that the compression rate measurement configuration and the paper thickness measurement configuration are provided separately. Can be realized at low cost.

(A-2) Operation of the First Embodiment Next, the operation of the printer 1 of the first embodiment having the above configuration will be described.

(A-2-1) Print Processing Operation FIG. 4 is a flowchart showing the operation of the printer 1 of this embodiment. The flowchart in FIG. 4 mainly illustrates processing that is executed by the CPU 210 executing the print processing control program 221.

  The CPU 210 (print processing control program 221) receives the print data created by the PC input unit 120 (receives a print request). The received print data is stored in the RAM 230. Further, when the CPU 210 receives the print data, the CPU 210 issues a print request signal to the print control unit 300 (S1).

  When the print control unit 300 receives the print request signal, the motor drive control unit 320 starts the rotation of the paper feed roller 3 and feeds the paper M from the paper feed cassette 2 (S2).

  Then, the print control unit 300 conveys the paper M fed from the paper feed cassette 2 toward the registration roller 7 on the paper feed conveyance path 4 (S3).

  Next, the controller control unit 200 determines whether or not the sheet M has reached the registration roller 7 (S4). The controller control unit 200 determines (detects) that the paper M has reached the registration roller 7 when a signal for detecting the paper M is output by the paper feed sensor 5. When it is determined that the sheet M has reached the registration roller 7, the controller control unit 200 proceeds to step S5 described later, and otherwise returns to step S3 described above to operate.

  When the sheet M reaches the registration roller 7, the CPU 210 analyzes the data of the print job and has explicitly set the sheet type (whether “plain paper” or “glossy paper” is instructed). ), Whether it is explicitly set (automatic setting) is checked (S5). When the paper type is explicitly set in the print job data, the CPU 210 proceeds to step S16 described later, and otherwise proceeds to step S6 described later.

  When an explicit paper type setting is not set in the print job data, the CPU 210 drives the rotational movement of the cam 506 via a motor via the external I / F 270 so as to prepare for the first paper thickness measurement. The control unit 320 is instructed. Receiving the instruction, the motor drive control unit 320 moves the cam 506 to the position of 506b. By this movement, the load applied to the paper M is adjusted to 2 kgW (S6).

  When the load applied to the paper M is adjusted to 2 kgW, the CPU 210 instructs the measurement control unit 330 to perform the first paper thickness measurement via the external I / F 270. Upon receiving the instruction, the measurement control unit 330 instructs the displacement sensor 505 to perform the paper thickness measurement. When the displacement sensor 505 receives the instruction, the measurement control unit 330 starts the first paper thickness measurement (S7).

  After the first paper thickness measurement, the CPU 210 instructs the motor drive control unit 320 to rotate the cam 506 via the external I / F 270 so as to prepare for the second paper thickness measurement. Receiving the instruction, the motor drive control unit 320 moves the cam 506 to the position of 506a. By this movement, the load applied to the paper M is adjusted to 3 kgW (S8).

  When the load applied to the paper M is adjusted to 3 kgW, the CPU 210 instructs the measurement control unit 330 to perform the second paper thickness measurement via the external I / F 270. Upon receiving the instruction, the measurement control unit 330 instructs the displacement sensor 505 to measure the paper thickness. When the displacement sensor 505 receives the instruction, the measurement controller 330 starts the second paper thickness measurement (S9).

After the second paper thickness measurement, the CPU 210 instructs the motor drive controller 320 to rotate the cam 506 via the external I / F 270 to complete the paper thickness measurement. Receiving the instruction, the motor drive control unit 320 moves the cam 506 to the position of 506c. By this movement, the upper paper presser 501a and the lower paper presser 501b are sufficiently separated from each other, and the paper M is adjusted so that no load is applied. (S10)
The measured paper pressure measured in the first time and the second time is temporarily stored in the RAM 230. Then, the CPU 210 calculates the compression rate from the paper thickness stored in the RAM 230 (S11).

  Next, the CPU 210 determines whether or not the calculated compression rate is equal to or less than a threshold value T (10%) (S12). If the compression rate is equal to or less than the threshold value T (10%), the process proceeds to step S13 described later, and compression is performed. When the rate T exceeds the threshold T, the process proceeds to step S14 described later.

  When the compression rate is equal to or less than the threshold value T, the CPU 210 determines that the paper M is glossy paper (S13).

  On the other hand, if the compression rate exceeds the threshold T, the CPU 210 determines that the paper type of the paper M is plain paper (S14).

Next, the printing conditions are determined (details will be described later) based on the first measured paper thickness measured by the CPU 210 and S7 and the paper type of the paper M (compression rate measurement result) (S15).
Next, the CPU 210 instructs the print control unit 300 based on the determined printing conditions to start printing. The print control unit 300 receives a print start instruction and causes the image forming unit 8 (8K, 8Y, 8M, 8C) to form a toner image based on the print data stored in the RAM 230. The print control unit 300 (high voltage control unit 1000) controls the voltage applied from the transfer power source 1001 to the transfer roller 10 (10K, 10Y, 10M, 10C) of the transfer unit 9. Then, the print control unit 300 controls the transfer roller 10 (10K, 10Y, 10M, 10C) of the transfer unit 9, and the toner image formed on the image forming unit 8 (8K, 8Y, 8M, 8C) Transfer to paper M. The print control unit 300 (heating control unit 310) controls the temperature measured by the temperature sensor 15a by controlling and heating the fixing unit 14. Then, the print control unit 300 (heating control unit 310) controls the fixing unit 14 to fix the toner image by applying heat and pressure to the paper M on which the toner image is formed (S16).

  In the flowchart of FIG. 4, the CPU 210 (printing process control program 221) performs the printing condition setting process (steps S6 to S15) using the compression rate every time the printing process is performed. The control program 221) does not limit the timing for performing these processes. For example, the CPU 210 (printing process control program 221) once performs a printing condition determination process using the compression ratio, and then determines the printing until the sheet cassette sensor 2a detects the removal (removal) of the sheet cassette 2. The conditions may be retained and applied to printing a print job (the processing in steps S6 to S15 described above is omitted). The CPU 210 (printing process control program 221) determines the printing conditions determined in consideration of the possibility that the paper type may be changed when the paper cassette sensor 2a detects the removal (removal) of the paper cassette 2. May be discarded and the print condition setting process (steps S6 to S15) using the compression ratio may be performed again when the next print process is performed.

(A-2-2) Specific Example of Compression Ratio Calculation Next, a specific example when the compression ratio is calculated by the controller control unit 200 (CPU 210) based on the paper thickness measured by the paper thickness measurement unit 500 will be described. To do.

  Hereinafter, an example will be described in which the paper thickness measurement unit 500 that actually constitutes the printer 1 is produced, and the compression rates of plain paper and glossy paper are actually calculated. In the following example, a case where “OKI (registered trademark) Excellent Gloss” is used as a glossy paper sample and “Mondi (registered trademark) Color Copy 120 gsm” is used as a plain paper sample will be described.

  The table of FIG. 5 shows the results of calculating the compression rate by actually measuring the above-mentioned glossy paper and plain paper twice with the paper thickness measuring unit 500.

  As shown in FIG. 5, as a result of measuring the paper thickness of glossy paper (OKI Excellent Gloss) using the paper thickness measuring unit 500, the first paper thickness measurement result is 0.142 μm, and the second paper thickness. The measurement result was 0.132 μm. Therefore, the compression rate of glossy paper (OKI Excellent Gloss) is 7% as shown in the following equation (2).

  Further, as shown in FIG. 5, as a result of measuring the paper thickness of plain paper (Color Copy 120 gsm manufactured by Mondi) using the paper thickness measuring unit 500, the first paper thickness measurement result is 0.150 μm, and the second time The paper thickness measurement result was 0.134 μm. Therefore, the compression rate of plain paper (Color Copy 120 gsm manufactured by Mondi) is 11% as shown in the following equation (3).

Glossy paper compression rate =
((0.142−0.132) /0.142) × 100 = 7% (2)
Plain paper compression rate =
((0.150-0.134) /0.150) × 100 = 11% (3)
As described above, it was confirmed that plain paper tends to have a higher compression rate than glossy paper. When the above-described samples are applied as glossy paper and plain paper, the CPU 210 (printing process control program 221) sets a threshold T for determining plain paper or glossy paper according to the compression rate to 8%. It can be seen that setting between -10% is desirable. In the CPU 210 (printing process control program 221), it is desirable to set the paper discrimination based on the compression rate based on the result of the experiment as described above.

(A-2-3) Setting of Transfer Voltage Based on Paper Type (Compression Rate) Next, a setting example of a target transfer voltage applied when the CPU 210 determines plain paper or glossy paper based on the compression rate is shown in FIG. 6 will be described.

  The controller control unit 200 of this embodiment determines the type of the paper M (plain paper or glossy paper) according to the compression rate, and further considers the paper thickness of the paper M (paper thickness measured for the first time). A target transfer voltage (target value of a bias voltage for the transfer unit 9 controlled by the high voltage control unit 1000) set for the paper M is determined. In the example of FIG. 6, the paper type of the paper M with a compression rate exceeding 10% is determined as plain paper, and the paper type of the paper M with a compression rate of 10% or less is determined as glossy paper.

  In the first embodiment, a description will be made assuming that a target transfer voltage is set for each of plain paper and glossy paper according to three stages of paper thickness (paper thickness setting). In the following, a paper M having a paper thickness (paper thickness measured for the first time) of 110 μm to 129 μm is “slightly thick paper”, a paper M having a paper thickness of 130 μm to 149 μm is “slightly thick paper”, and a paper thickness of 150 μm to 170 μm. The paper M is called “thicker paper”. In the following description, it is assumed that the paper M applied in the printer 1 belongs to one of the three types of paper thickness settings described above.

  Furthermore, in the following, the print setting for the paper type setting “plain paper” and the paper thickness setting “slightly thick paper” is P1, the print setting for the paper type setting “plain paper” and the paper thickness setting “thick paper”. P2, print setting for paper type setting “plain paper” and paper thickness setting “thicker paper” P3, print setting for paper type setting “glossy paper” and paper thickness setting “slightly thick paper” G1, The print setting for Glossy Paper and the paper thickness setting “Thick Paper” is G2, and the G3 print setting is “Glossy Paper” and the paper thickness setting is “Thicker Paper”. And

  Note that the types and number of paper thicknesses supported by the printer 1 are not limited to the above three examples.

  Normally, the thicker the paper thickness, the larger the voltage required for transfer. Therefore, in FIG. 6, when the paper type setting is the same, in order from the lowest target transfer voltage, “slightly thick paper”, “thick paper”, “thicker Paper ".

  Also, as described above, normally, “glossy paper” has a higher density and less electrical air layer than electric paper, so that the voltage required to pull toner onto the paper with an electric field is smaller. I'll do it. Therefore, in FIG. 6, when the paper thickness setting is the same, “glossy paper” is set to a lower target transfer voltage than “plain paper”.

  Specifically, in FIG. 6, the target transfer voltages of the print settings P1, P2, and P3 for which the paper type setting is plain paper are 2500V, 3000V, and 3500V. In FIG. 6, the target transfer voltages of the print settings G1, G2, and G3 for setting the paper type as glossy paper are set to 2000V, 2500V, and 3000V, respectively.

  In the printer 1, the print processing control program 221 holds the print conditions (target transfer voltage) corresponding to each print setting (combination of paper type and paper thickness setting) as shown in FIG. 8 as table information 221b. Alternatively, it may be stored in the ROM 220.

(A-3) Effects of First Embodiment According to the first embodiment, the following effects can be achieved.

  Since the printer 1 performs printing by setting a target transfer voltage in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate, the paper M has a plurality of types having different characteristics. Even when there are two types of paper, an optimum transfer voltage is set, so that good print quality can be obtained.

  FIG. 6 also shows the transfer efficiency [%] when the printer 1 is actually constructed and printing is performed using paper that conforms to the print settings P1 to P3 and G1 to G3.

  The transfer efficiency is a numerical value of the good transferability of toner onto the paper M. The smaller the transfer efficiency value, the worse the toner transferability. When the transfer efficiency exceeds 90%, the transfer efficiency is good. Therefore, the transfer efficiency is desirably 90% or more.

  As shown in FIG. 6, in the printer 1, the transfer efficiencies when the print settings P1 to P3 and G1 to G3 are applied are 93%, 97%, 95%, 95%, 93%, and 96%, respectively. And good results of 90% or more were obtained.

  Further, like the printer 1 of the first embodiment, printing is performed by setting a target transfer voltage in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. In order to confirm this effect, the following experiment was also conducted.

  FIG. 7 shows experimental results when the printer 1 performs printing in consideration of only the paper thickness (result of the first paper pressure measurement). In the experiment shown in FIG. 7, the same target transfer voltage as that of the plain paper shown in FIG. 6 is applied regardless of whether the paper is plain paper or glossy paper. In the following, the print setting for the paper type setting “plain paper / glossy paper” (regardless of whether it is plain paper or glossy paper) and the paper thickness setting “slightly thick paper” is E1, and the paper type setting is The print setting for “plain paper / glossy paper” and the paper thickness setting “thick paper” is called E2, and the print setting for the paper type setting “plain paper / glossy paper” and the paper thickness setting “thicker paper” is called E3. Shall.

  In the experiment of FIG. 7, the target transfer voltages of the print settings E1, E2, and E3 for setting the paper type as plain paper / glossy paper are 2500V, 3000V, and 3500V. This is the same target transfer voltage as the above-described print settings P1, P2, and P3 in which the paper type setting is plain paper. When plain paper is printed with the print settings E1, E2, and E3 in the printer 1, good results are obtained as shown in FIG. 6 above, but when glossy paper is printed, the result is shown in FIG. The result is as follows.

  As shown in FIG. 7, in the printer 1, when the print settings E1 to E3 are applied, the transfer efficiencies of 80%, 78%, and 81% are all less than 90%, and good results are not obtained. .

  When printing glossy paper whose paper thickness setting is “slightly thick paper” in the printer 1, it is desirable to apply 2000V (print setting G1) as the target transfer voltage as shown in FIG. Since E1 has a value larger by 500V than that, the transfer voltage is too high, and transfer efficiency is 80% because transfer dust is generated.

  Further, when glossy paper is printed in the printer 1, as shown in FIG. 6 above, the target transfer voltage is set higher by 500 V at any paper thickness setting, so that the transfer voltage is too large and the transfer efficiency is increased. Becomes an unfavorable value (78% to 81%). On the other hand, when the glossy paper is printed in the printer 1, any one of the print settings G1 to G3 is applied and the transfer efficiency is improved.

  As described above, from an actual experiment, printing is performed by setting the target transfer voltage in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. It was confirmed that better print quality can be obtained.

(B) Second Embodiment Hereinafter, a second embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the drawings. Hereinafter, an example in which the image forming apparatus of the present invention is applied to a printer will be described.

(B-1) Configuration of Second Embodiment The functional configuration of the printer 1 of the second embodiment can also be shown using FIG. 1 described above as in the first embodiment. Hereinafter, only the difference of the printer 1 of the second embodiment from the first embodiment will be described.

  In the printer 1 of the second embodiment, the processing by the CPU 210 (print processing control program 221) is partially different.

  The CPU 210 (printing process control program 221) of the first embodiment determines the paper type based on the compression rate of the paper M, and adjusts the target transfer voltage according to the combination of the determined paper type and paper thickness. It was. In contrast, the CPU 210 (printing process control program 221) of the second embodiment controls the fixing unit 14 (by the heating control unit 310) according to the combination of the paper type and the paper thickness determined based on the compression rate. The target fixing temperature (hereinafter referred to as “target fixing temperature”) used for (control) is adjusted. In the following, the fixing temperature refers to a temperature measured by the temperature sensor 15a.

  As described above, since glossy paper has a higher density than plain paper, the preferred amount of heat applied to the fixing process tends to be greater for glossy paper than for plain paper. Further, when the paper types are the same, the thicker paper M has a larger mass, and therefore, a suitable amount of heat applied to the fixing process tends to be higher.

  For this reason, the CPU 210 (print processing control program 221) of the second embodiment sets the target fixing temperature higher than that of plain paper for glossy paper even with the same paper thickness. Further, it is assumed that the CPU 210 (print processing control program 221) of the second embodiment sets a higher target fixing temperature for the thick paper M when the paper types are the same.

(B-2) Operation of the Second Embodiment Next, the operation of the printer 1 of the second embodiment having the above configuration will be described.

(B-2-1) Print Processing Operation The print processing operation of the printer 1 of the second embodiment can also be described using the flowchart of FIG. 4 described above, which is the same as that of the first embodiment. Below, only the difference from the first embodiment will be described for the operation of the printer 1 of the second embodiment.

  In the flowchart of FIG. 4 described above, only the processing in step S15 is different in the second embodiment.

  The CPU 210 (printing process control program 221) of the second embodiment controls the fixing unit 14 (control by the heating control unit 310) according to the combination of the paper type and the paper thickness determined based on the compression rate in step S15. ) To determine the target fixing temperature to be used for the printing control unit 300 (heating control unit 310).

(B-2-2) Setting of Target Fixing Temperature Based on Compression Rate Next, FIG. 8 is used for a setting example of the target fixing temperature applied when the CPU 210 determines plain paper or glossy paper based on the compression rate. I will explain.

  The controller control unit 200 of this embodiment determines the paper type (plain paper or glossy paper) of the paper M according to the compression rate, and further considers the paper thickness of the paper M (paper thickness measured for the first time). A target fixing temperature (fixing temperature controlled by the heating control unit 310) set for the paper M is determined. In the second embodiment, the method for determining the paper type according to the compression rate is the same as that in the first embodiment, and a detailed description thereof will be omitted.

  In the first embodiment, a description will be given assuming that the target fixing temperature is set according to three stages of paper thickness (paper thickness setting) for each of plain paper and glossy paper. In the second embodiment, a paper M having a paper thickness (paper thickness measured at the first time) of 130 μm to 149 μm is a “thick paper”, a paper M having a paper thickness of 150 μm to 169 μm is a “thicker paper”, and a paper thickness The paper M having a thickness of 170 μm to 190 μm is referred to as “very thick paper”. In the second embodiment, the paper M applied by the printer 1 will be described as having any one of the above three types of paper thickness.

  Furthermore, in the second embodiment, the print setting for the paper type setting “plain paper” and the paper thickness setting “thick paper” is P2, the paper type setting is “plain paper”, and the paper thickness setting is “thicker paper”. Print setting for P3, paper type setting for "plain paper" and paper thickness setting for "very thick paper" P4, paper type setting for "glossy paper" and paper thickness setting for "thick paper" G2, the print setting for Glossy Paper and the paper thickness setting “Thicker Paper” G3, the print setting G4 for the paper type setting “Glossy Paper” and the “Thick Paper” paper thickness setting. Respectively. Note that the values of the compression ratio and the paper thickness according to the print settings P2, P3, G2, and G3 are the same as those in the first embodiment.

  Normally, the thicker the paper, the greater the amount of heat required for the fixing process. Therefore, in FIG. 8, when the paper type setting is the same, “thick paper”, “thicker paper”, “extremely” from the lowest target fixing temperature. "Thick paper".

  In general, as described above, “glossy paper” has a higher density than “plain paper”, and the amount of heat required for the fixing process is higher. Therefore, in FIG. 8, when the paper thickness setting is the same, “glossy paper” is set to a higher target fixing temperature than “plain paper”.

  Specifically, in FIG. 8, the target fixing temperatures of the print settings P2, P3, and P4 for which the paper type setting is plain paper are 150 ° C., 155 ° C., and 160 ° C., respectively. Further, in FIG. 8, the target fixing temperatures of the print settings G2, G3, and G4 for which the paper type setting is glossy paper are 160 ° C., 165 ° C., and 170 ° C., respectively.

(B-3) Effects of Second Embodiment According to the second embodiment, the following effects can be achieved.

  In the printer 1 of the second embodiment, printing is performed by setting the target fixing temperature in consideration of not only the thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. Even when there are a plurality of types of paper having different characteristics, the optimum fixing temperature is set, so that good printing can be performed.

  FIG. 8 also shows the fixing rate [%] when the printer 1 is actually constructed and printing is performed using paper that conforms to the print settings P2 to P4 and G2 to G4.

  The fixing rate is obtained by quantifying the goodness of the toner fixing property to the paper M. The smaller the value of the fixing rate, the worse the toner fixing property. When the value exceeds 90%, the toner fixing property is good. When the fixing rate is less than 80%, the print quality is very poor. Accordingly, the fixing rate is desirably 90% or more.

  As shown in FIG. 8, in the printer 1, when the print settings P2 to P4 and G2 to G4 are applied, the fixing rates are 94%, 94%, 95%, 95%, 97%, and 96%, respectively. And good results of 90% or more were obtained.

  Further, like the printer 1 of the second embodiment, printing is performed by setting a target fixing temperature in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. In order to confirm this effect, the following experiment was also conducted.

  FIG. 9 shows experimental results when the printer 1 performs printing in consideration of only the paper thickness (paper pressure measured for the first time). In the experiment shown in FIG. 9, the same target fixing temperature as that of the plain paper shown in FIG. 8 is applied regardless of whether the paper is plain paper or glossy paper. In the following, the print setting for the paper type setting is “plain paper / glossy paper” (regardless of whether it is plain paper or glossy paper), the paper thickness setting is “thick paper”, and the paper type setting is “E2. The print setting for “plain paper / glossy paper” and the paper thickness setting “thicker paper” is E3, and the print setting for the paper type setting “plain paper / glossy paper” and the paper thickness setting “very thick paper” is called E4. Shall.

  In the experiment of FIG. 9, the target fixing temperatures of the print settings E2, E3, and E4 in which the paper type setting is plain paper / glossy paper are 150 ° C., 155 ° C., and 160 ° C., respectively. This is the same target fixing temperature as the above-described print settings P2, P3, and P4 in which the paper type setting is plain paper. When plain paper is printed with the print settings E2, E3, and E4 in the printer 1, good results are obtained as shown in FIG. 8, but when glossy paper is printed, the result is shown in FIG. The result is as follows.

  As shown in FIG. 9, in the printer 1, when the print settings E2 to E4 are applied, the respective fixing rates are 83%, 85%, and 84%, which are less than 90%, and good results are not obtained. .

  When printing glossy paper with a paper thickness setting of “thick paper” in the printer 1, it is desirable to apply 160 ° C. (print setting G2) as the target fixing temperature as shown in FIG. In E2, since the temperature is 10 degrees lower than that, the fixing temperature is too low, and the fixing rate is 83% which is not good.

  Further, when printing glossy paper in the printer 1, as shown in FIG. 8 above, the target fixing temperature is set to be 10 ° C. lower at any paper thickness setting. The rate is not good (83% to 84%). On the other hand, when the glossy paper is printed in the printer 1, any one of the print settings G2 to G4 is applied and the fixing rate is improved.

  As described above, from actual experiments, printing is performed by setting the target fixing temperature in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. It was confirmed that better print quality can be obtained.

(C-1) Configuration of the Third Embodiment The functional configuration of the printer 1 of the third embodiment can also be shown using FIG. 1 described above as in the first embodiment. Hereinafter, only the difference of the printer 1 of the third embodiment from the first embodiment will be described.

  In the printer 1 of the third embodiment, the processing by the CPU 210 (print processing control program 221) is partially different.

  The CPU 210 (printing process control program 221) of the first embodiment determines the paper type based on the compression rate of the paper M, and adjusts the target transfer voltage according to the combination of the determined paper type and paper thickness. It was. On the other hand, the CPU 210 (printing process control program 221) of the third embodiment is a target transport when transporting the paper M according to the combination of the paper type and the paper thickness determined based on the compression rate. The speed (hereinafter referred to as “target conveyance speed”) is adjusted. In the following, it is assumed that the conveyance speed is the conveyance speed of the paper M controlled by the motor drive program 223 and the motor drive control unit 320. Hereinafter, the unit of the conveyance speed (target conveyance speed) is expressed as ppm (Page Per Minutes).

  As described above, since glossy paper has a higher density than plain paper, the preferred amount of heat applied to the fixing process tends to be greater for glossy paper than for plain paper. In addition, when the paper types are the same, the thicker paper M has a larger mass, so that a suitable amount of heat applied to the fixing process is also increased.

  Therefore, the CPU 210 (printing process control program 221) of the third embodiment sets the target transport speed slower than that of plain paper for glossy paper even when the paper thickness is the same, and the time during which the paper M is heated by the fixing unit 14 The CPU 210 (printing process control program 221) of the third embodiment is slower for the thick paper M if the paper type is the same. The target transport speed shall be set.

(C-2) Operation of the Third Embodiment Next, the operation of the printer 1 of the third embodiment having the above configuration will be described.

(C-2-1) Print Processing Operation The print processing operation of the printer 1 according to the third embodiment can also be described with reference to the above-described flowchart of FIG. 4 similar to the first embodiment. In the following, only the difference from the first embodiment in the operation of the printer 1 of the third embodiment will be described.

  In the flowchart of FIG. 4 described above, only the process of step S15 is different in the third embodiment.

  In step S15, the CPU 210 (print processing control program 221) of the third embodiment sends a motor drive program 223 (motor drive control unit 320) to the combination of the paper type and the paper thickness determined based on the compression rate. A target conveyance speed to be set is determined, and processing for instructing the motor drive program 223 is performed.

(C-2-2) Setting of Target Conveyance Speed Based on Compression Rate Next, FIG. 10 is used for a setting example of the target conveyance speed applied when the CPU 210 determines plain paper or glossy paper based on the compression rate. I will explain.

  The controller control unit 200 of this embodiment determines the type of the paper M (plain paper or glossy paper) according to the compression rate, and further considers the paper thickness of the paper M (paper thickness measured for the first time). A target transport speed set for M is determined. In the third embodiment, the method for determining the paper type according to the compression rate is the same as that in the first embodiment, and a detailed description thereof will be omitted.

  In the third embodiment, a description will be made assuming that a target transport speed is set for each of plain paper and glossy paper according to three stages of paper thickness (paper thickness setting). In the third embodiment, a paper M having a paper thickness (paper thickness measured for the first time) of 110 μm to 129 μm is “slightly thick paper”, a paper M having a paper thickness of 130 μm to 149 μm is “thick paper”, and the paper thickness is The paper M having a thickness of 150 μm to 170 μm is referred to as “thicker paper”. That is, in the printer 1, description will be made assuming that the paper M to be applied has any one of the above three types of paper thickness.

  Furthermore, in the third embodiment, the print setting for the paper type setting “plain paper” and the paper thickness setting “slightly thick paper” is P1, the paper type setting is “plain paper”, and the paper thickness setting is “thick paper”. Print setting for P2, print setting for P3, paper type setting for "plain paper" and paper thickness setting for "thicker paper", print setting for P3, paper type setting for "glossy paper" and paper thickness setting for "slightly thick paper" The setting is G1, the paper type setting is “glossy paper” and the paper thickness setting is “thick paper”. The print setting is G2. The paper type setting is “glossy paper” and the paper thickness setting is “thicker paper”. Respectively. The values of the compression ratio and the paper thickness according to the print settings P1 to P3 and G1 to G3 are the same as those in the first embodiment.

  Normally, as the paper thickness increases, the amount of heat required for the fixing process increases. Therefore, in FIG. 10, when the paper type setting is the same, “slightly thick paper”, “thick paper”, “ "Thick paper".

  In general, as described above, “glossy paper” has a higher density than “plain paper”, and the amount of heat required for the fixing process is higher. Therefore, in FIG. 10, when the paper thickness setting is the same, “Glossy paper” is set to a slower target conveyance speed than “Plain paper”.

  Specifically, in FIG. 10, the target transport speeds of the print settings P1, P2, and P3 for which the paper type setting is plain paper are 30 ppm, 25 ppm, and 20 ppm, respectively. Further, in FIG. 10, the target transport speeds of the print settings G1, G2, and G3 for setting the paper type as glossy paper are 25 ppm, 20 ppm, and 15 ppm, respectively.

(C-3) Effects of Third Embodiment According to the third embodiment, the following effects can be achieved.

  In the printer 1 of the third embodiment, printing is performed by setting the target transport speed in consideration of not only the thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. Even when there are a plurality of types of paper having different characteristics, the optimum transport speed is set, and thus good printing can be performed.

  FIG. 10 also shows the fixing rate [%] when the printer 1 is actually constructed and printing is performed using paper that conforms to the print settings P1 to P3 and G1 to G3.

  As shown in FIG. 10, in the printer 1, when the print settings P1 to P3 and G1 to G3 are applied, the respective fixing rates are 95%, 97%, 93%, 95%, 95%, and 94%. And good results of 90% or more were obtained.

  In addition, as in the printer 1 of the third embodiment, printing is performed by setting the target conveyance speed in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. In order to confirm this effect, the following experiment was also conducted.

  FIG. 11 shows experimental results when the printer 1 performs printing in consideration of only the paper thickness (paper thickness measured at the first time). In the experiment shown in FIG. 11, the same target conveyance speed as that of the above-described plain paper shown in FIG. 10 is applied regardless of whether the paper is plain paper or glossy paper. In the following, the print setting for the paper type setting “plain paper / glossy paper” (regardless of whether it is plain paper or glossy paper) and the paper thickness setting “slightly thick paper” is E1, and the paper type setting is The print setting for “plain paper / glossy paper” and the paper thickness setting “thick paper” is called E2, and the print setting for the paper type setting “plain paper / glossy paper” and the paper thickness setting “thicker paper” is called E3. Shall.

  In the experiment of FIG. 11, the target transport speeds of the print settings E1, E2, and E3 for setting the paper type as plain paper / glossy paper are 30 ppm, 25 ppm, and 20 ppm. This is the same target transport speed as the above-described print settings P1, P2, and P3 in which the paper type setting is plain paper. When plain paper is printed with the print settings E1, E2, and E3 in the printer 1, good results are obtained as shown in FIG. 10, but when glossy paper is printed, the result is shown in FIG. The result is as follows.

  As shown in FIG. 11, in the printer 1, when the print settings E1 to E3 are applied, the respective fixing rates are 78%, 82%, and 81%, which are less than 90%, and good results are not obtained. .

  When printing glossy paper whose paper thickness setting is “slightly thick paper” in the printer 1, it is desirable to apply 25 ppm (print setting G1) as the target transport speed as shown in FIG. In E1, since the transport speed is 5 ppm faster than that, the transport speed is too fast (the heating time for the paper M is too short), and the fixing rate becomes 78% which is very bad.

  Further, when glossy paper is printed in the printer 1, as shown in FIG. 10 described above, the target transport speed is set to be 5 ppm faster at any paper thickness setting, so the transport speed is too high (paper M The heating time is too short), and the fixing rate is not good (78% to 84%). On the other hand, when the glossy paper is printed in the printer 1, any one of the print settings G1 to G3 is applied and the fixing rate is improved.

  As described above, from an actual experiment, printing is performed by setting the target conveyance speed in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. It was confirmed that better print quality can be obtained.

(D) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

(D-1) In each of the above embodiments, an example in which the image forming apparatus of the present invention is applied to a printer has been described. However, the present invention is not limited to a printer, and other image forming apparatuses (for example, a FAX, a copier) The present invention may be applied to a multifunction device (MFP) or the like.

(D-2) In the printers of the above embodiments, the target transfer voltage and the target among the printing conditions are considered in consideration of not only the paper thickness of the paper M but also the paper type (paper type setting) determined based on the compression rate. Although either the fixing temperature or the target conveyance speed parameter is adjusted, a plurality of parameters may be adjusted. For example, in the printer of the above-described embodiment, the printing condition may be determined by adjusting either the target fixing temperature or the target conveying speed in addition to the target transfer voltage. In the printer of the above embodiment, both the target fixing temperature and the target transport speed may be adjusted. However, both the target fixing temperature and the target transport speed are parameters that affect the amount of heat applied to the paper by the fixing unit. Therefore, instead of setting the target fixing temperature and the target transport speed separately, it is necessary to determine a combination of the target fixing temperature and the target transport speed.

(D-3) In the printers of the above embodiments, the printing condition parameters are adjusted in consideration of not only the paper thickness of the paper M but also the paper type determined based on the compression rate. If it is fixed (for example, if there is only one type of plain paper or glossy paper used), only the paper type is specified based on the compression ratio, and the printing conditions without considering the paper thickness The parameters may be adjusted. In other words, in the printer of each of the above embodiments, the parameters of the printing condition may be adjusted based only on the sheet compression rate.

(D-4) In the printers of the above embodiments, the printing conditions are determined using the paper thickness measured by the paper thickness measurement unit. The result of measurement by separately providing a means for measuring the paper thickness The printing conditions may be determined using. In this case, the means for measuring the paper thickness is not limited, and various configurations can be applied.

(D-5) In the printer of each of the embodiments described above, the example in which paper (printing paper) is applied as a medium has been described. However, in addition to paper, other than paper, such as cloth or resin film, may be applied as a medium. It may be. In the printer of each of the above embodiments, an example in which glossy paper and plain paper are used as the medium has been described. However, other media such as recycled paper may be applied. In particular, for recycled paper, the compression ratio may vary depending on the grade (ratio including recycled paper, etc.). Therefore, in the printer of each of the above embodiments, the paper type is set for each grade of recycled paper. The printing conditions may be determined.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Paper cassette, 2a ... Paper cassette sensor, 3 ... Paper feed roller, 4 ... Paper feed conveyance path, 5 ... Paper feed sensor, 6 ... Registration sensor, 7 ... Registration roller, 8, 8K, 8Y, 8M, 8C ... Image forming unit, 81 ... Photosensitive drum, 82 ... Developing unit, 83 ... Toner cartridge, 9 ... Transfer unit, 10, 10K, 10Y, 10M, 10C ... Transfer roller, 11 ... Transfer belt, 12, 13 DESCRIPTION OF SYMBOLS ... Drive roller, 14 ... Fixing unit, 15 ... Fixing roller, 15a ... Temperature sensor, 15b ... Heater, 16 ... Pressure roller, 17 ... Fixing conveyance roller, 18 ... Discharge sensor, 19 ... Discharge roller, 20 ... Discharge conveyance path 21 ... LED head, 200 ... controller controller, 21, 21K, 21Y, 21M, 21C ... LED head, 210 ... CPU, 220 ... ROM 222 ... Compression rate information, 223 ... Motor drive program, 221 ... Print processing control program, 230 ... RAM, 240 ... Timer, 250 ... Host I / F, 260 ... Operation panel control unit, 270 ... External I / F, 280 ... Internal bus 300 ... Print control unit 310 ... Heating control unit 320 ... Motor drive control unit 330 ... Measurement control unit 1000 ... High pressure control unit 400 ... Thermistor 500 ... Paper thickness measurement unit 501a, 501b ... Paper Presser, 502 ... tension spring, 503 ... lever, 504 ... joint, 505 ... displacement sensor, 506 ... cam, M ... paper.

Claims (7)

In an image forming apparatus that forms an image on a medium,
Image forming condition determining means for determining image forming conditions when image forming is performed on the medium based on the degree of compression of the medium;
An image forming apparatus comprising: an image forming unit that forms an image on the medium according to the image forming condition determined by the image forming condition determining unit. The image forming unit includes a developer image forming unit that forms a developer image, and a transfer unit that transfers the developer image formed on the developer image forming unit to the medium using a transfer voltage. And
The image forming apparatus according to claim 1, wherein the image forming condition determining unit determines a value of a transfer voltage applied to the transfer unit as the image forming condition. The image forming unit includes a fixing unit that heats the medium on which the developer image is transferred and fixes the developer image on the medium.
The image forming apparatus according to claim 1, wherein the image forming condition determining unit determines a fixing temperature value to be applied to the fixing unit as an image forming condition. The image forming unit includes a medium transport unit that transports the medium, and a fixing unit that heats the medium on which the developer image is transferred and fixes the developer image on the medium.
The image forming apparatus according to claim 1, wherein the image forming condition determining unit determines, as an image forming condition, a transport speed at which the medium transport unit transports the medium. The image forming condition determining means determines an image forming condition for forming an image on the medium based on a compression degree of the medium and a medium thickness of the medium. The image forming apparatus according to any one of the above. The medium thickness of the medium can be measured while pressing the medium with the pressing member, and the first medium thickness is measured by applying a first load to the pressing member. A medium thickness measuring unit that measures a second medium thickness by applying a second load greater than the first load;
A compression degree calculating means for obtaining a compression degree of the medium by using the first load and the second load measured by the medium thickness measurement unit;
The image forming apparatus according to claim 1, wherein the image forming condition determining unit determines an image forming condition using the compression degree obtained by the compression degree calculating unit. In an image forming apparatus that forms an image on a medium,
The medium thickness of the medium can be measured while pressing the medium with the pressing member, and the first medium thickness is measured by applying a first load to the pressing member. A medium thickness measuring unit that measures a second medium thickness by applying a second load greater than the first load;
An image forming condition determining means for determining an image forming condition when image formation is performed on the medium using the first load and the second load measured using the medium thickness measuring unit;
An image forming apparatus comprising: an image forming unit that forms an image on the medium according to the image forming condition determined by the image forming condition determining unit.

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