Image forming apparatus

Abstract

To provide an image forming apparatus that can suppress the decrease in productivity caused by the time required to detect sheet characteristics using a media sensor. [Solution] The loading destination for the sheets is switched from the paper feed cassette 150 to the manual feed tray 210, and the characteristics of the first manual feed sheet fed from the manual feed tray 210 are detected by the media sensor 280. At that time, the manual feed sheet is transported from the manual feed tray 210 so that detection by the media sensor 280 is completed before the preceding sheet fed from the paper feed cassette 150 passes through the first transport path 410 and is transported to the common transport path 400. As a result, the manual feed sheet that resumes transport after detection by the media sensor 280 is transported from the second transport path 420 to the common transport path 400 following the preceding sheet, without the gap between the sheet and the preceding sheet passing through the first transport path 410 and being transported to the common transport path 400 widens.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction machine.

Background Art

[0002] An image forming apparatus develops an electrostatic latent image formed on a photoreceptor with toner, and transfers and fixes the developed toner image onto a sheet (recording material). The sheets are set in a manual feed tray or a paper feed cassette and are conveyed one by one from them. The sheets may have different sheet characteristics such as thickness and surface property, and the image forming apparatus changes the operating conditions of the image forming operation according to the sheet characteristics to perform image forming. The sheet characteristics are set manually by the user from an operation unit or the like, or are detected by a media sensor disposed on a conveyance path along which the sheet is conveyed. In Patent Document 1, an image forming apparatus that determines the operating conditions of an image forming operation including conveyance control of a sheet based on the sheet characteristics detected by a media sensor has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to detect the characteristics of a sheet by a media sensor, the sheet to be detected may be temporarily stopped at the media detection position of the media sensor. Thus, when the sheet is stopped for media detection, there is a risk that productivity will decrease due to the time required to detect the characteristics of the sheet.

[0005] This disclosure is made in view of the above-mentioned problems and aims to provide an image forming apparatus that can suppress the decrease in productivity caused by the time required to detect sheet characteristics using a media sensor. [Means for solving the problem]

[0006] An image forming apparatus according to one embodiment of the present invention includes: an image forming unit for forming an image on a recording material; a first loading unit and a second loading unit capable of loading recording material; a first transport unit for transporting the recording material loaded on the first loading unit to a first transport path; a second transport unit for transporting the recording material loaded on the second loading unit to a second transport path; a third transport unit for transporting the recording material transported by the first transport unit or the second transport unit to the image forming unit from a third transport path after the first transport path and the second transport path merge; a detection unit capable of detecting the characteristics of the recording material while the recording material is stopped at a stop position for a predetermined time in the second transport path; and a control unit for controlling the second transport unit. The control unit comprises a section and a section, wherein in a first job, it forms an image on recording material loaded in the first loading section, and in a second job following the first job, it forms an image on recording material loaded in the second loading section, and when the detection section detects the characteristics of the recording material, it controls the second transport section such that the second timing when the feeding of the first recording material in the second job starts is earlier than the first timing when the feeding of the last recording material in the first job starts, and causes the detection section to detect the characteristics of the first recording material in the second job before the image formation in the first job is completed. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress the decrease in productivity caused by the time required for the detection unit to detect the characteristics of the recording material. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing the image forming apparatus of this embodiment. [Figure 2] A block diagram showing the control system of an image forming apparatus. [Figure 3] A schematic diagram showing the configuration of a media sensor. [Figure 4] A diagram illustrating the sheet size detection configuration. [Figure 5] (a) A diagram showing the initial media settings screen, (b) A diagram showing the settings selection screen, and (c) A diagram showing the sheet type input screen. [Figure 6] A flowchart illustrating the media setup process. [Figure 7] This diagram illustrates sheet transport, showing (a) before job start, (b) before sheet 3 is fed in paper feed confirmation mode, (c) when sheet 3 reaches the media detection position in paper feed confirmation mode, (d) when sheet 3 reaches the media detection position in productivity priority mode, and (e) when sheet 3 transport resumes after detection by the media sensor is completed in productivity priority mode. [Figure 8] A flowchart illustrating the process for determining the paper feed timing. [Figure 9] A diagram showing the paper feed mode setting screen. [Figure 10] (a) A diagram illustrating the calculation of paper feed timing, (b) A diagram illustrating the correction of paper feed timing. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will now be described with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of the image forming apparatus of this embodiment, and Figure 2 is a block diagram showing the control system for controlling the image forming apparatus. In the control system of the image forming apparatus, various other components may be connected to the control unit 300 in addition to those shown in Figure 2, but their illustration and description are omitted here as they are not relevant to the essence of the invention.

[0010] The control unit 300 shown in Figure 2 consists of a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an EEPROM (Electrically Erasable Programmable Read-Only Memory) 304. The CPU 301 controls the entire image forming apparatus 1 to form an image on a sheet by executing programs stored in the ROM 302 and EEPROM 304. In doing so, the CPU 301 can use the RAM 303 as a work area. Various types of sheet-like recording materials can be used as sheets, such as plain paper, cardboard, rough paper, textured paper, coated paper, plastic film, and cloth.

[0011] The image forming apparatus 1 includes an operation unit 330 capable of receiving user input. The operation unit 330 has an input unit 331 into which the user can input various information, such as instructions to start a print operation on a sheet (called an image forming job) and information about the sheet, and a liquid crystal display 332. The liquid crystal display 332 can display various information such as various programs, various data, or various screens, which will be described later. The operation unit 330 may also be a touch panel that accepts information input corresponding to the touch location in response to touch operations by the user on the screen displayed on the liquid crystal display 332. The CPU 301 can control the liquid crystal display 332 to display various screens.

[0012] The CPU 301 is capable of executing image forming jobs and starts printing operations in response to input of an input instruction to start an image forming job from an external device (not shown) or from the operation unit 330. The CPU 301 can drive and control the pre-fusing transport motor 145, the fuser motor 173, the post-fusing transport motor 146, the manual feed transport motor 147, the paper discharge transport motor 148, and the paper discharge transport motor 2 149, which are connected via the input / output interface (I / O) 307. In addition, the CPU 301 can detect input signals from the sheet transport sensor 171, the pre-cash register transport sensor 160, and the paper feed pickup sensor 152 via the input / output interface (I / O) 307.

[0013] Furthermore, the CPU 301 can detect input signals from the media sensor 280, sheet presence detection sensor 214, sheet width volume sensor 217, sheet sub-scan length detection sensor 1 218, and sheet sub-scan length detection sensor 2 219 via the input / output interface (I / O) 307. In addition, the CPU 301 can accept the start of image forming jobs input from the network interface (I / F) 314 and the fax interface (I / F) 315.

[0014] The CPU 301 has an image processing unit 316 that processes images corresponding to image forming jobs input from external devices (not shown) or the operation unit 330, and performs image processing such as image unfolding and rotation. The CPU 301 is also configured to control the image forming unit 320. The image forming unit 320 includes the process unit 120, transfer belt 130, secondary transfer unit 140, and laser scanner unit 110 shown in Figure 1. The CPU 301 can also control the temperature of the heater (not shown) of the fuser unit 170 shown in Figure 1. The scanner unit 101 can read the original document when making a copy.

[0015] Next, the basic image forming operation will be described using FIGS. 1 and 2. When the start of an image forming job is input from the operation unit 330, the CPU 301 analyzes the image forming job and starts the printing operation. When the CPU 301 receives an instruction to convey a sheet from the paper feed cassette 150 capable of loading sheets, it drives the pre-fixing conveyance motor 145 via the input / output interface (I / O) 307. As a result, the paper feed pickup roller 151 rotates, and the sheets stacked in the paper feed cassette 150 as the first loading unit are conveyed one by one to the common conveyance path 400 via the first conveyance path 410. The pre-fixing conveyance motor 145 and the paper feed pickup roller 151 constitute a first conveyance unit that conveys sheets to the first conveyance path 410. Then, the CPU 301 monitors whether the sheet feeding operation from the paper feed cassette 150 is normally performed using the paper feed pickup sensor 152.

[0016] When the CPU 301 continuously conveys sheets from the paper feed cassette 150, in order to improve the sheet conveyance efficiency without causing paper jams, it changes the paper feeding timing from the paper feed cassette 150 according to the sheet length of the sheet size (e.g., A4, B4, etc.) included in the start instruction of the image forming job. The sheet length refers to the length of the sheet in the conveyance direction. Thereby, the interval between the trailing end in the conveyance direction of the preceding sheet and the leading end in the conveyance direction of the subsequent sheet (hereinafter referred to as the inter-sheet gap) is adjusted, and the sheets are conveyed one by one from the paper feed cassette 150.

[0017] Similarly, when the CPU 301 receives an instruction to convey a sheet from the manual tray 210 capable of loading sheets, it drives the manual conveyance motor 147 via the input / output interface (I / O) 307. As a result, the manual pickup roller 211 rotates, and the sheets stacked in the manual tray 210 as the second loading unit are conveyed one by one to the common conveyance path 400 via the second conveyance path 420. The manual conveyance motor 147 and the manual pickup roller 211 constitute a second conveyance unit that conveys sheets to the second conveyance path 420. Then, the CPU 301 monitors whether the sheet feeding operation from the manual tray 210 is normally performed using the pre-registration conveyance sensor 160.

[0018] Based on the detection results of the sheet presence / absence detection sensor 214, sheet width volume sensor 217, sheet sub-scanning length detection 1 sensor 218, and sheet sub-scanning length detection 2 sensor 219 provided in the manual feed tray 210, the CPU 301 determines the sheet length before starting the paper feeding operation. The CPU 301 can change the paper feeding timing from the manual feed tray 210 according to the determined sheet length. Thereby, the paper gap between the preceding sheet and the subsequent sheet is adjusted, and the sheets are conveyed one by one from the manual feed tray 210.

[0019] In the case of this embodiment, for the sheet conveyed from the manual feed tray 210, the sheet characteristics such as the thickness and surface property of the sheet are detected by the media sensor 280. The media sensor 280 is arranged in the middle of the second conveyance path 420, specifically, between the manual pickup roller 211 and the confluence of the second conveyance path 420 and the first conveyance path 410 in the common conveyance path 400. The media sensor 280 can detect the sheet characteristics in a state where the sheet conveyed from the manual feed tray 210 in the second conveyance path 420 is stopped at the stop position for a predetermined time. The CPU 301 can change the operation conditions of the image forming operation such as the fixing temperature and transfer voltage based on the sheet characteristics detected by the media sensor 280.

[0020] The CPU 301 starts the image forming operation in the process unit 120 in accordance with the timing when the sheet arrives at the secondary transfer unit 140. The process unit 120 is composed of a photosensitive drum, a developing device, a charging roller, a photosensitive drum cleaner, and the like. In the process unit 120, after the surface of the photosensitive drum is charged, an electrostatic latent image is formed on the photosensitive drum by the laser irradiated from the laser scanner unit 110. Then, the electrostatic latent image formed on the photosensitive drum is developed on the photosensitive drum by the toner in the developing device. Thereafter, the toner image developed on the photosensitive drum is applied with a primary transfer voltage in the primary transfer unit 121 and transferred to the transfer belt 130. The toner image transferred to the transfer belt 130 reaches the secondary transfer unit 140 by the rotation of the transfer belt 130.

[0021] Furthermore, the CPU 301 detects the position of the sheet transported by the transport rollers A153, B154, and C155 by monitoring the pre-cash register transport sensor 160. The transport roller C155, acting as a third transport unit, transports the sheet that has been transported to the common transport path 400 where the first transport path 410 and the second transport path 420 merge, to the image forming unit 320. Then, taking into account the timing when the leading edge of the sheet reaches the pre-cash register transport sensor 160, the transport of the sheet is controlled so that the leading edge of the sheet and the leading edge of the toner image on the transfer belt 130 coincide at the secondary transfer unit 140. For example, if the sheet arrives earlier than the toner image, the CPU 301 stops the sheet at the pre-cash register transport roller 161 for a predetermined time before resuming transport. In this manner, the CPU 301 applies a secondary transfer voltage to the secondary transfer unit 140 to the sheet and toner image that have reached the secondary transfer unit 140, thereby transferring the toner image to the sheet.

[0022] After secondary transfer, the sheet is transported to the transport belt 190 and then to the fuser 170. In the fuser 170, the toner image on the sheet is heated and fixed to the sheet. When the leading edge of the fixed sheet, which has been transported downstream in the sheet transport direction, reaches the sheet transport sensor 171, the CPU 301 performs the following operation. Specifically, according to the content of the image forming job, the CPU 301 determines which transport path—sheet transport path A230, sheet transport path B231, or sheet transport path C234—to which the sheet being transported on the common transport path 400 as the third transport path is to be transported by the transport roller 162, and switches the destination of the sheet by switching the transport flapper A172 and transport flapper B182 according to the determination.

[0023] Specifically, when the image forming job is a double-sided print job, or when the printed side is to be ejected to the output tray A200 with the printed side facing downwards, the CPU 301 switches the transport flapper A172 to transport the sheet to the sheet transport path A230. Also, when the image forming job is a single-sided print job, or when the sheet is to be ejected to the output tray B196 or output tray C199 during double-sided printing, the CPU 301 switches the transport flapper B182 to transport the sheet to the sheet transport path B231. Finally, when the sheet is to be ejected to the output tray A200, the CPU 301 switches between the transport flappers A172 and B182 to transport the sheet to the sheet transport path C234.

[0024] The sheets transported to sheet transport path B231 are further transported downstream in the transport direction by transport roller E232. Subsequently, the sheets are transported to sheet transport path D181 and then to output tray B196 and output tray C199. The sheets transported to sheet transport path D181 are transported by output rollers F241, G242, and H243, which are driven by output transport motor 148. When CPU 301 wants to output a sheet to output tray B196, it switches flapper 183 to transport the sheet to transport path 193 and outputs the sheet to output tray B196. When CPU 301 wants to output a sheet to output tray C199, it switches flapper 183 to transport path 184. Next, the CPU 301 uses the paper output rollers I244, J245, and K246, driven by the paper output transport motor 149, to transport the sheets to the transport path 184 and eject them into the paper output tray C199.

[0025] When printing on one side and ejecting the printed side downwards to the output tray A200, the sheet moves along the sheet transport path A230, and when the trailing edge of the sheet passes the reversal roller 163, the CPU 301 reverses its drive towards the output roller 180 and ejects the sheet to the output tray A200.

[0026] During double-sided printing, the sheet proceeds to the sheet transport path A230 and is then transported to the double-sided reversal transport path D233 by double-sided transport rollers A164, B165, C166, D179, and E168. Next, when the trailing edge of the sheet passes double-sided transport roller D179, the double-sided reversal flapper 178 is switched to the side of double-sided transport roller F169, and the drive is reversed. Subsequently, the sheet is transported by double-sided transport rollers F169, G175, H176, and I177 and handed over to transport roller C155. When all image forming jobs are completed, the CPU 301 displays completion to the operation unit 330.

[0027] <Media Sensor> Next, the media sensor 280, which acts as a detection unit for detecting sheet characteristics such as sheet thickness and surface properties, will be explained using Figure 3. As shown in Figure 3, the media sensor 280 has a media sensor main unit 54 and an external LED (light-emitting diode) 55b. The media sensor main unit 54 has an LED 55a as a light source, a phototransistor 56a, and a phototransistor 56b within the unit.

[0028] <Sheet surface texture detection> First, the method for detecting the surface properties of the sheet using the media sensor 280 will be explained. Light emitted from the LED (light-emitting element) 55a passes through the slit 57a and the upper window provided in the sheet transport guide 40, and irradiates the surface of the sheet P being transported while being guided by the sheet transport guide 40. The reflected light from the sheet P passes through the slits 57b and 57c and is received by the phototransistors 56a and 56b (light-receiving elements). Phototransistor 56a receives a portion of the diffusely reflected light emitted from the LED 55a and reflected from the surface of the sheet P, and outputs a diffuse reflection output value. Phototransistor 56b receives the specularly reflected light emitted from the LED 55a and reflected from the surface of the sheet P, and outputs a specular reflection output value. The surface property value x is calculated by Equation 1 shown below. Surface quality value x = Specular reflection output value / Diffuse reflection output value ... (Equation 1)

[0029] Equation 1 utilizes the characteristic that the smoother and finer the surface of sheet P, the easier it is to specularly reflect light. A calculation device (not shown) located on the media sensor 280 quantifies the surface properties of sheet P using Equation 1 and sends the calculated surface property value x to the CPU 301. The CPU 301 uses the received surface property value x and a threshold value for determining surface properties to determine the surface properties of sheet P. If the surface property value x is greater than the threshold value, the CPU 301 determines that the surface properties of sheet P are smooth and fine. If the surface property value x is less than or equal to the threshold value, the CPU 301 determines that the surface properties of sheet P are rough and coarse. Here, one threshold value is used to detect two types of sheet surface properties, but multiple threshold values ​​may be used to further subdivide and detect them.

[0030] <Sheet thickness detection> Next, the method for detecting the sheet thickness using the media sensor 280 will be described. The sheet transport guide 40 is provided with a lower window for irradiating light from the back side of the sheet P. Light emitted from the external LED (light-emitting element) 55b passes through the light-gathering guide 57d and the lower window to irradiate the back side of the sheet P. The transmitted light from the sheet P passes through the upper window and the slit 57b to be received by the phototransistor 56a. The phototransistor 56a receives the positively transmitted light emitted from the external LED 55b and transmitted through the sheet P and outputs a positively transmitted output value. The positively transmitted output value detected by the phototransistor 56a is sent to the CPU 301.

[0031] The CPU 301 determines the thickness of sheet P using the transmitted positive transmission output value and a threshold value for determining the thickness. In this embodiment, thresholds A and B are used to make three types of distinctions: "thick," "normal," and "thin" (threshold A < threshold B). If the positive transmission output value is less than or equal to threshold A, the CPU 301 determines that the thickness of sheet P is "thin." If the positive transmission output value is greater than threshold A and less than or equal to threshold B, the CPU 301 determines that the thickness of sheet P is "normal." If the positive transmission output value is greater than threshold B, the CPU 301 determines that the thickness of sheet P is "thick."

[0032] In this embodiment, two thresholds are used, but one threshold may be used, or three or more thresholds may be used to determine a more finely subdivided thickness. Also, in this embodiment, an optical sensor is used for the media sensor 280, but it is not limited to this, and other types of sensors such as ultrasonic sensors may be used as long as they can detect surface properties or thickness.

[0033] <Automatic sheet size detection> Next, the automatic detection configuration for the sheet size of the sheet set in the manual feed tray 210 will be explained using Figure 4. Note that the same automatic detection configuration may be used in the paper feed cassette 150, so the explanation will be omitted here. As shown in Figure 4, the manual feed tray 210 is equipped with a manual feed pickup roller 211 and sheet side regulating guides 212 and 213. The sheet set in the manual feed tray 210 is held in place by the sheet side regulating guides 212 and 213, which prevent the sheet from being transported at an angle when the sheet is separated and transported by the manual feed pickup roller 211. The sheet side regulating guides 212 and 213 are slidable in the direction of arrows 215 and 216 in the figure, and can prevent the sheet from becoming skewed even if sheets of different widths are set.

[0034] The manual feed tray 210 is also equipped with a sheet presence detection sensor 214, a sheet width volume sensor 217, a sheet sub-scan length detection sensor 1 218, and a sheet sub-scan length detection sensor 219. The sheet presence detection sensor 214 is provided to detect whether or not a sheet is loaded in the manual feed tray 210. When a sheet is set on the manual feed tray 210, the sheet presence detection sensor 214 turns on, and an on signal is input to the CPU 301 from the sheet presence detection sensor 214, causing the CPU 301 to determine that there is a sheet in the manual feed tray 210. When no sheet is set on the manual feed tray 210, the sheet presence detection sensor 214 turns off, and an off signal is input to the CPU 301 from the sheet presence detection sensor 214, causing the CPU 301 to determine that there is no sheet in the manual feed tray 210.

[0035] The sheet width volume sensor 217 is connected to the sheet side regulating guides 212 and 213 via a link member (not shown). Therefore, the sheet width volume sensor 217 outputs a signal (AD value) to the CPU 301 corresponding to the position of the sheet side regulating guides 212 and 213 in conjunction with the operation of the sheet side regulating guides 212 and 213. The CPU 301 detects the sheet width based on the signal (AD value) output from the sheet width volume sensor 217. Here, the sheet width is the length in the width direction intersecting the sheet transport direction (main scan length). In contrast, the sheet sub-scan length detection sensor 1 218 and the sheet sub-scan length detection sensor 2 219 have, for example, a flag-type configuration and detect the transport direction length (sub-scan length) of the sheet set on the manual feed tray 210. In this way, the manual feed tray 210 is configured to automatically detect the sheet size, including the main scan length and sub-scan length, for the sheet that is set on it.

[0036] <Initial media settings screen> In this embodiment, when a sheet is detected in the manual feed tray 210 as described above, the "Media Setup Initial Screen" is displayed on the liquid crystal display 332. Figure 5(a) shows the "Media Setup Initial Screen". The "Media Setup Initial Screen" is displayed to allow the user to set whether or not to perform automatic detection of sheet characteristics by the media sensor 280.

[0037] As shown in Figure 5(a), the "Media Settings Initial Screen" displays the sheet detection size 503 that has been automatically detected for the sheet set in the manual feed tray 210. The sheet detection size 503 is displayed based on the main scan length, which is determined by the detection result of the sheet width volume sensor 217, and the sub-scan length, which is determined by the detection results of the sheet sub-scan length detection sensor 1 218 and the sheet sub-scan length detection sensor 2 219. For example, if the main scan length is "210 mm" and the sub-scan length is "297 mm", "A4 Portrait" will be displayed in the sheet detection size 503, and if the main scan length is "257 mm" and the sub-scan length is "182 mm", "B5 Landscape" will be displayed in the sheet detection size 503. Although not explained here, the user can also manually input the size of the sheet set in the manual feed tray 210.

[0038] Furthermore, the "Initial Media Settings Screen" displays a "Change Sheet Type" button 501 and an "OK" button 550. When the "Change Sheet Type" button 501 is pressed, the "Settings Selection Screen" is displayed on the LCD display 332. Figure 5(b) shows the "Settings Selection Screen". As shown in Figure 5(b), the "Settings Selection Screen" displays a "Automatically Detect During Printing" button 511 and a "Select from List" button 512. The "Automatically Detect During Printing" button 511 is used by the user to set the automatic detection of sheet characteristics by the media sensor 280.

[0039] The "Select from List" button 512 is a button for the user to manually input the sheet type. When the "Select from List" button 512 is pressed, the "Sheet Type Input Screen" is displayed on the liquid crystal display 332. Figure 5(c) shows the "Sheet Type Input Screen". The "Sheet Type Input Screen" is a screen for inputting information about multiple sheet types, and as shown in Figure 5(c), the sheet types are displayed in a list to prompt the user to input the sheet type. Here, the sheet types (thin paper 1, plain paper 1, etc.) are displayed along with their basis weight. The control unit 300 stores the sheet type selected by the user from the list in the RAM 303.

[0040] <Media setup process> Figure 6 is a flowchart of the "media setup process" using the "initial media setup screen" described above. The "media setup process" is started by the control unit 300 (specifically the CPU 301) when the power of the image forming apparatus 1 is turned on. As shown in Figure 6, the control unit 300 determines whether or not a sheet is set in the manual feed tray 210 based on the detection result (on signal or off signal) sent from the sheet presence detection sensor 214 (S1). If no sheet is set in the manual feed tray 210 (NO in S1), the control unit 300 repeatedly executes the process in step S1. If a sheet is set in the manual feed tray 210 (YES in S1), the control unit 300 displays the "initial media setup screen" (see Figure 5(a)) on the liquid crystal display 332 (S2). At this time, the control unit 300 displays the automatically detected sheet detection size 503.

[0041] Then, the control unit 300 determines whether the user has pressed the "Change Sheet Type" button 501 on the "Initial Media Settings Screen" (S3). If the "Change Sheet Type" button 501 has not been pressed (NO in S3), the control unit 300 determines whether the user has pressed the "OK" button 550 on the "Initial Media Settings Screen" (S4). If the "OK" button 550 has not been pressed (NO in S4), the control unit 300 returns to the process in step S3. If the "OK" button 550 has been pressed (YES in S4), the control unit 300 terminates the "Media Settings Process".

[0042] If the "Change Sheet Type" button 501 on the "Initial Media Settings Screen" is operated (YES in S3), the control unit 300 displays the "Setting Selection Screen" (see Figure 5(b)) on the liquid crystal display 332 (S5). After the "Setting Selection Screen" is displayed, the control unit 300 determines whether the "Automatically Detect During Printing" button 511 on the "Setting Selection Screen" has been operated by the user (S6). If the "Automatically Detect During Printing" button 511 has been operated by the user (YES in S6), the control unit 300 proceeds to step S9. If the "Automatically Detect During Printing" button 511 has been operated by the user, the control unit 300, when executing an image forming job, automatically detects the sheet characteristics using the media sensor 280 for the first subsequent sheet (the first recording material in the second job) fed from the manual feed tray 210, following the preceding sheet (the last recording material in the first job) fed from the paper feed cassette 150. In this embodiment, the image forming job includes a first job in which a sheet is fed from a paper feed cassette 150 and an image is formed, and a second job in which a sheet is fed from a manual feed tray 210 following the first job and an image is formed. In this embodiment, before the image forming in the first job is completed, the media sensor 280 is used to detect the characteristics of the first sheet in the second job.

[0043] If the "Automatically detect during printing" button 511 on the "Settings Selection Screen" is not pressed by the user (NO in S6), the control unit 300 determines whether the "Select from list" button 512 on the "Settings Selection Screen" has been pressed by the user (S7). If the "Select from list" button 512 has not been pressed by the user (NO in S7), that is, if the "OK" button 551 on the "Settings Selection Screen" has been pressed, the control unit 300 returns to the process in step S6. On the other hand, if the "Select from list" button 512 has been pressed by the user (YES in S7), the control unit 300 displays the "Sheet type input screen" (see Figure 5(c)) on the liquid crystal display 332 (S8).

[0044] The control unit 300 determines whether the user has pressed the "OK" button 551 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (S9). If the user has pressed the "OK" button 552 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (YES in S9), the control unit 300 returns to the process in step S2 and redisplays the "Media Settings Initial Screen" (see Figure 5(a)) on the liquid crystal display 332 (S2).

[0045] On the other hand, if the user has not pressed the "OK" button 551 on the "Settings Selection Screen" or the "OK" button 553 on the "Sheet Type Input Screen" (NO in S9), the control unit 300 returns to the process in step S6. In this case, even if the user has pressed the "Automatically detect during printing" button 511 on the "Settings Selection Screen," the control unit 300 will not perform automatic detection of sheet characteristics by the media sensor 280 when executing the image forming job. Also, even if the user has selected any of the sheet types from the list displayed on the "Sheet Type Input Screen," the user-selected sheet type will not be stored in the RAM 303.

[0046] Next, the sheet transport method when transporting multiple sheets continuously from the paper feed cassette 150 and the manual feed tray 210 will be explained using Figures 7(a) to 7(e). Here, to make the explanation easier to understand, we will explain using the example of feeding two sheets (1 and 2) from the paper feed cassette 150, and then feeding one sheet (3) from the manual feed tray 210. The first sheet (3) stacked on the top of the manual feed tray 210 is a "manual feed sheet" used for automatic detection of sheet characteristics by the media sensor 280. As shown in Figure 7(a), the sheets (1 and 2) stacked in the paper feed cassette 150 are transported one by one to the common transport path 400 via the first transport path 410. The sheet (3) stacked in the manual feed tray 210 is transported to the common transport path 400 via the second transport path 420.

[0047] In this embodiment, the user can input either "Paper Feed Confirmation Mode" or "Productivity Priority Mode" as the transport mode from the paper feed cassette 150 and manual feed tray 210 using the "Paper Feed Mode Setting Screen" (see Figure 9 below). Figures 7(b) and 7(c) show the sheet transport configuration in "Paper Feed Confirmation Mode," and Figures 7(d) and 7(e) show the sheet transport configuration in "Productivity Priority Mode."

[0048] In "Paper Feed Confirmation Mode," the first sheet (1) is first fed from the paper feed cassette 150 to the first transport path 410. After the trailing edge of the first sheet (1) leaves the paper feed cassette 150, the second sheet (2) is fed to the first transport path 410. As shown in Figure 7(b), when sheet (2) is transported to the common transport path 400, sheet (3) is fed from the manual feed tray 210. Since sheet (3) is a sheet whose sheet characteristics are automatically detected by the media sensor 280, sheet (3) is temporarily stopped at the media detection position (stop position) of the media sensor 280 as shown in Figure 7(c), and the sheet characteristics are detected by the media sensor 280. The media detection position of the media sensor 280 is such that the leading edge of the sheet (3) in the transport direction does not come into contact with the transport roller C155 located at the junction of the common transport path 400 where the first transport path 410 and the second transport path 420 merge. After detection by the media sensor 280 is completed, the transport of the sheet (3) is resumed, and the sheet (3) is transported from the second transport path 420 to the common transport path 400.

[0049] In this paper feeding method, where the preceding sheet (2) from the paper feed cassette 150 is transported to the common transport path 400 before the subsequent sheet (3) is fed from the manual feed tray 210, the "paper feeding confirmation mode" is the same as the conventional sheet transport method. In the "paper feeding confirmation mode," the subsequent sheet (3) is fed from the manual feed tray 210 at a timing (third timing) determined according to the number of sheets that can form an image per unit time. As mentioned above, in the "paper feeding confirmation mode," the sheet (3) is fed after the sheet (2) has been transported to the common transport path 400. Therefore, even if a transport jam occurs in the sheet (2) before it is transported to the common transport path 400, the sheet (3) is not damaged because it has not yet been fed and is still loaded in the manual feed tray 210.

[0050] However, the detection of sheet characteristics by the media sensor 280 requires a predetermined media detection time (for example, 500 ms), during which time the sheet (3) is kept in a stopped state. On the other hand, the preceding sheet (2) is transported along the common transport path 400 even while detection is being performed by the media sensor 280, so the gap (Y1) between the transported sheet (2) and the stopped sheet (3) widens. Thus, in the "paper feed confirmation mode," because the transport of sheet (3) is temporarily stopped for sheet characteristic detection by the media sensor 280, the gap (Y1) between the preceding sheet (2) and sheet (3) widens compared to when sheet characteristic detection by the media sensor 280 is not performed, which may reduce the efficiency of sheet transport and decrease productivity.

[0051] The "productivity priority mode" is a paper feeding method in which the subsequent sheet (3) is fed from the manual feed tray 210 before the preceding sheet (2) fed from the paper feed cassette 150 is transported from the first transport path 410 to the common transport path 400. In the "productivity priority mode," as will be described in more detail later, the timing of feeding the sheet (3) from the manual feed tray 210 is advanced compared to the "paper feeding confirmation mode," based on the transport time for sheet transport from the manual feed tray 210 to the media detection position (stop position) of the media sensor 280 and the media detection time of the media sensor 280.

[0052] As a result, as shown in Figure 7(d), sheet (3) is temporarily stopped at the media detection position of the media sensor 280, and while the media sensor 280 is detecting the sheet characteristics, sheet (2) is transported through the first transport path 410 to the common transport path 400. In other words, the transport of the subsequent sheet (3) from the manual feed tray 210 is started so that detection by the media sensor 280 is completed before the preceding sheet (2) has passed through the first transport path 410 and been transported to the common transport path 400. Then, sheet (3) is temporarily stopped at a position that does not block the transport path through which the preceding sheet (2), transported from the paper feed cassette 150, is passing.

[0053] After detection by the media sensor 280 is complete, sheet (3) is transported from the second transport path 420 to the common transport path 400, as shown in Figure 7(e). By advancing the paper feeding timing of sheet (3) in this way, as shown in Figure 7(e), when transport of sheet (3) is resumed after detection by the media sensor 280 is complete, the gap (Y2) between sheet (3) and sheet (2) does not widen, and sheet (3) can be transported to the common transport path 400 immediately following sheet (2). Since the gap (Y1) between the preceding sheet (2) and the following sheet (3) does not widen, the sheet transport efficiency does not decrease, and thus a decrease in productivity can be suppressed.

[0054] In "productivity priority mode," since sheet (3) is fed before sheet (2) is transported to the common transport path 400, if a transport jam occurs in sheet (2) before it reaches the common transport path 400, sheet (3) will remain in the second transport path 420. This means that when the user performs jam removal to remove sheet (2), sheet (3) must also be removed from the second transport path 420, which can easily lead to waste of sheet (3).

[0055] <Paper feed timing determination process> Next, the "paper feed timing determination process," which determines the timing for feeding sheets from the paper feed cassette 150 and the manual feed tray 210, will be explained using Figures 8 to 10(b) with reference to Figure 2. The "paper feed timing determination process" shown in Figure 8 is executed by the control unit 300 (specifically the CPU 301) in response to the input of an instruction to start the image forming job.

[0056] The image forming job is a mixed-load job in which multiple sheets with different sheet characteristics are fed in the order of paper feed cassette 150 and manual feed tray 210 to form an image. When performing such a mixed-load job, a sheet used for automatic detection of sheet characteristics by the media sensor 280 is loaded on the top surface of the manual feed tray 210, followed by multiple sheets with the same sheet characteristics. The multiple sheets loaded on the manual feed tray 210 have sheet characteristics different from those of the sheet fed from the paper feed cassette 150.

[0057] As shown in Figure 8, the control unit 300 initializes itself by setting the variable "N", which indicates the number of pages of the sheet to be image-formed, to "1" (S21). The control unit 300 then calculates the paper feeding timing "Tfeed(N)" for the sheet of the variable "N" pages (S22). The method for calculating this paper feeding timing "Tfeed(N)" will be described later (see Figure 10(a)). Next, the control unit 300 determines whether the paper feeding method when feeding sheets sequentially from the paper cassette 150 and the manual feed tray 210 is the "productivity priority mode" or the "paper feeding confirmation mode" described above (S23).

[0058] <Paper feed mode setting screen> In this embodiment, before the start of the image forming job, the liquid crystal display 332 displays a "paper feed mode setting screen" to allow the user to input either the "productivity priority mode" (first mode) or the "paper feed confirmation mode" (second mode). Figure 9 shows the "paper feed mode setting screen".

[0059] As shown in Figure 9, the "Paper Feed Mode Setting Screen" displays a "Paper Feed Confirmation Mode" button 611 and a "Productivity Priority Mode" button 612. When the user selects the "Paper Feed Confirmation Mode" button 611 and operates the "OK" button 613, the "Paper Feed Confirmation Mode" is set and stored in RAM 303 (see Figure 2). When the user selects the "Productivity Priority Mode" button 612 and operates the "OK" button 613, the "Productivity Priority Mode" is set and stored in RAM 303. In this way, the paper feeding method is set when either the "Paper Feed Confirmation Mode" button 611 or the "Productivity Priority Mode" button 612 is selected and the "OK" button 612 is operated.

[0060] Returning to the explanation in Figure 8, if the system is in "Paper Feed Confirmation Mode" and not "Productivity Priority Mode" (NO in S23), the control unit 300 jumps to the process in step S26. On the other hand, if the system is in "Productivity Priority Mode" (YES in S23), the control unit 300 determines whether the sheet for page "N" is the first sheet to be transported from the manual feed tray 210 (hereinafter referred to as the manual feed sheet) (S24).

[0061] If it is a "manual feed sheet" (YES in S24), the control unit 300 corrects the paper feeding timing of the "manual feed sheet" (S25). In "productivity priority mode," the paper feeding timing of the "manual feed sheet" is corrected to a second timing that is earlier than the paper feeding timing (first timing) in "paper feeding confirmation mode." As described later, the control unit 300 advances the second timing, which is when the subsequent "manual feed sheet" is transported from the manual feed tray 210, by a predetermined amount of time for the "manual feed sheet" to stop at the stop position for detection by the media sensor 280, compared to the third timing, which is determined according to the number of sheets for which an image can be formed per unit time. Furthermore, the control unit 300 advances the second timing even further according to the transport time required for the subsequent "manual feed sheet" to be transported from the manual feed tray 210 to the stop position. On the other hand, if it is not a "manual feed sheet" (NO in S24), the control unit 300 jumps to the processing in step S26. In this case, sheets are fed from the paper cassette 150 at the predetermined feeding timing (Tfeed(N)).

[0062] In step S26, the control unit 300 determines whether or not there are subsequent pages (S26). If there are subsequent pages, that is, if a sheet is fed from the manual feed tray 210 and image formation is to be continued (YES in S26), the control unit 300 adds "1" to the variable "N" (S27), returns to step S22, and repeats the processes of steps S22 to S26 described above. If there are no subsequent pages, that is, if the image formation job is to be terminated (NO in S26), the control unit 300 terminates this process.

[0063] <Regarding the calculation of paper feeding timing> The calculation method for the sheet feeding timing "Tfeed(N)" (S22 in Figure 8) described above will be explained using Figure 10(a). Assuming the sheet size is "A4" and the productivity is "100 sheets", sheets "1 to 5" are fed from the paper cassette 150, and sheets from page "6" onwards are fed from the manual feed tray 210.

[0064] As shown in Figure 10(a), the feeding timing for page "N" is calculated starting from the feeding timing of the first page of the job. Based on the number of sheets for which an image can be formed per unit time (here, 1 minute) which is predetermined according to the characteristics of the sheet (hereinafter referred to as productivity), the time "TPage" that takes for one sheet to pass through the first transport path 410 and the second transport path 420 is determined. For example, as shown in Figure 10(a), consider the case where A4 size sheets are used and the productivity is "100 sheets". If an image is formed on "100 sheets" in "60 seconds", then "TPage = 60 ÷ 100 = 0.6 seconds (600 ms)".

[0065] By accumulating the above "TPage" for the number of pages up to the page immediately preceding page "N", the feeding timing for the sheet on page "N" from the paper cassette 150 and manual feed tray 210 can be calculated. In Figure 10(a), consider the case of calculating the feeding timing "Tfeed(6)" (first timing) for the sheet on page "6". Accumulating the "TPage" from the first page to the immediately preceding page, page 5, we get "Tfeed(6) = 600 × 5 = 3000 ms". Subsequently, the feeding timing for the sheet on page "7", "Tfeed(7)", is "3600 ms (600 × 6)", and the feeding timing for the sheet on page "8", "Tfeed(8)", is "4200 ms (600 × 7)".

[0066] <Regarding correction of paper feed timing> Next, the "correction of paper feeding timing" (S25 in Figure 8) will be explained using Figures 10(a) and 10(b). Similar to the example shown in Figure 10(a), when the sheet size is "A4" and the productivity is "100 sheets", sheets "1 to 5" are fed from the paper cassette 150, and sheets "6" and onward are fed from the manual feed tray 210.

[0067] The feeding timing "TfeedH(6)" (second timing) for the first page "6" sheet (manual feed sheet) fed from the manual feed tray 210 can be calculated from "TfeedH(6) = Tfeed(6) - (Tconvey + Tmedia)". "Tconvey" is the transport time required for the sheet to be transported from the manual feed tray 210 to the media detection position (stop position) of the media sensor 280. "Tmedia" is the predetermined time for the sheet to be stopped at the stop position for detection by the media sensor 280. For example, if "Tconvey" is "1000ms" and "Tmedia" is "500ms", then "TfeedH(6) = 3000 - (1000 + 500) = 1500ms". In other words, instead of waiting for the pre-correction paper feed timing "Tfeed(6)=3000ms", the "manual feed sheet" is fed from the manual feed tray 210 at the corrected paper feed timing "TfeedH(6)=1500ms".

[0068] Furthermore, any additional sheets fed from the manual feed tray 210 following the "manual feed sheet" are transported at a feeding timing (third timing) determined according to the number of sheets that can form an image per unit time. For example, the sheet "7" fed from the manual feed tray 210 following the sheet "6" mentioned above is transported at the feeding timing (third timing) of "Tfeed(7)=3600ms" mentioned above.

[0069] As described above, in this embodiment, the sheet loading destination is switched from the paper feed cassette 150 to the manual feed tray 210, and the characteristics of the first sheet (manual feed sheet) fed from the manual feed tray 210 are detected by the media sensor 280. At this time, the feeding timing of the manual feed sheet is corrected, and the manual feed sheet is transported from the manual feed tray 210 so that detection by the media sensor 280 is completed before the preceding sheet fed from the paper feed cassette 150 passes through the first transport path 410 and is transported to the common transport path 400. In this way, the manual feed sheet, which resumes transport after detection by the media sensor 280 is completed, can be transported from the second transport path 420 to the common transport path 400 following the preceding sheet without the gap between the sheet and the preceding sheet being transported through the first transport path 410 to the common transport path 400 widening. In this way, since the gap between the preceding sheet and the following manual feed sheet does not widen, the sheet transport efficiency does not decrease, and thus a decrease in productivity can be suppressed.

[0070] In the embodiment described above, the media sensor 280 was described as being located on the second transport path 420 through which sheets from the manual feed tray 210 are transported, but the invention is not limited to this. For example, the media sensor 280 may be located on the first transport path 410 through which sheets from the paper cassette 150 are transported. However, in that case, a preceding sheet is fed from the manual feed tray 210, and a "manual feed sheet" for which the media sensor 280 automatically detects the sheet characteristics is fed from the paper cassette 150. [Explanation of symbols]

[0071] 1…Image forming apparatus, 145(151)…First transport unit (pre-fixing transport motor, paper feed pickup roller), 147(211)…Second transport unit (manual feed transport motor, manual feed pickup roller), 150…First loading unit (paper feed cassette), 155…Third transport unit (transport roller C), 210…Second loading unit (manual feed tray), 280…Detection unit (media sensor), 300…Control unit, 320…Image forming unit, 331…Input unit, 400…Third transport path (common transport path), 410…First transport path, 420…Second transport path, P…Recording material (sheet)

Claims

1. An image forming unit that forms an image on the recording material, A first loading section and a second loading section capable of loading recording materials, A first transport unit transports the recording material loaded in the first loading unit to the first transport path, A second transport unit transports the recording material loaded in the second loading unit to the second transport path, A third transport unit transports the recording material transported by the first transport unit or the second transport unit to the image forming unit via a third transport path formed after the first transport path and the second transport path merge. With the recording material stopped at a stop position for a predetermined time in the second transport path, a detection unit capable of detecting the characteristics of the recording material is provided. The system comprises a control unit for controlling the second transport unit, The control unit, In the first job, an image is formed on the recording material loaded in the first loading section, and in the second job following the first job, an image is formed on the recording material loaded in the second loading section, and the characteristics of the recording material are detected by the detection unit. The second transport unit is controlled such that the second timing at which the first recording material in the second job is fed is earlier than the first timing at which the last recording material in the first job is fed, and the detection unit is made to detect the characteristics of the first recording material in the second job before image formation in the first job is completed. An image forming apparatus characterized by the following features.

2. In the second job, if the control unit forms an image on the recording material loaded in the second loading unit and does not detect any characteristics of the recording material from the detection unit, it starts feeding the first recording material in the second job according to a third timing determined by the number of recording materials on which an image can be formed per unit time. The image forming apparatus according to feature 1.

3. The control unit controls the second transport unit so that, depending on whether the characteristics of the recording material are detected by the detection unit in the second job or not, the distance between the rear end in the transport direction of the last recording material in the first job that is transported first and the front end in the transport direction of the first recording material in the second job that is transported following the last recording material are the same in the third transport path. The image forming apparatus according to feature 2.

4. The control unit sets the second timing to an earlier timing than the third timing according to the predetermined time. The image forming apparatus according to feature 2.

5. The control unit sets the second timing to an even earlier timing depending on the transport time required for the first recording material in the second job to be transported from the second loading unit to the stop position. The image forming apparatus according to feature 4.

6. The system further includes an input unit that allows the user to input either a first mode in which the initial paper feeding timing of the recording material in the second job is the second timing, or a second mode in which it is the third timing. The control unit, in the second job, When the first mode is input, the second transport unit is controlled to feed the first recording material at the second timing. When the second mode is input, the second transport unit is controlled to feed the first recording material at the third timing. The image forming apparatus according to feature 2.

7. When the control unit feeds another recording material from the second loading unit following the first recording material in the second job, it feeds the material according to a third timing determined by the number of recording materials that can form an image per unit time. The image forming apparatus according to feature 1.

8. The first loading section is a paper feed cassette, The second loading section is a manual feed tray. The image forming apparatus according to feature 1.

Images