Patent Description:
An image forming apparatus that includes a medium detection sensor that detects the type of recording medium such as a sheet is known. Patent Literature <NUM> (<CIT>) discloses an image forming apparatus having control means that interrupts an image forming process when the type of a recording medium detected by a medium detection sensor is different from the type of a recording medium on which an image has already been formed and corresponding image forming conditions are also different.

However, as in the image forming apparatus described in Patent Literature <NUM>, when the image forming process is interrupted in a case where the type of recording medium is changed during printing, there is a problem in that productivity decreases.

<CIT> discloses an image forming apparatus which includes an image forming device to form a toner image on a recording medium under a prescribed image forming condition, a fixing device to fix the toner image borne on the recording medium thereonto by heating the recording medium based on target fixing temperature, and a detector to detect a type of recording medium. The type is used in setting at least one of the image forming condition and the target fixing temperature. The inequality Tb>Ta is established when Ta represents a time period needed to reach a setting of fixing temperature allocated to the recording medium with its tip detected by the detector after detection of the tip and Tb represents a time period needed for the recording medium with its tip detected by the detector to reach the fixing device after detection of the tip.

An object of the present invention is to provide an image forming apparatus, a method for controlling conveyance of a recording medium, and a program that can prevent a decrease in productivity even when the type of recording medium is changed during printing.

The above-described object is achieved by the following means.

According to the image forming apparatus and the method for controlling conveyance of a recording medium according to the present invention, information relating to a first recording medium conveyed first is detected, and information relating to a second recording medium conveyed after the first recording medium is detected. The conveyance section operates such that the second recording medium is conveyed at a conveyance speed based on the information relating to the first recording medium. Even when the information relating to the second recording medium after the first recording medium is detected to be different from the information relating to the first recording medium, the second recording medium is conveyed at the conveyance speed maintained. Therefore, it is possible to prevent a decrease in productivity due to a decrease in the conveyance speed.

Based on the program according to the present invention, the computer of the image forming apparatus executes conveying a first recording medium and a second recording medium and detecting information relating to the first recording medium and information relating to the second recording medium. The computer detects the information relating to the first recording medium conveyed first, and detects the information relating to the second recording medium conveyed by the conveying after the first recording medium in the detecting. The computer controls the conveying such that the second recording medium is conveyed at a conveyance speed based on the information relating to the first recording medium. The computer controls the conveying such that the second recording medium is conveyed at the conveyance speed maintained even when the information relating to the second recording medium after the first recording medium is detected to be different from the information relating to the first recording medium.

<FIG> is a diagram schematically illustrating a part of a conveyance path for a recording medium (hereinafter, the recording medium is also referred to as a sheet or paper) on which an image is printed in an image forming apparatus <NUM> according to an embodiment of the present invention.

Examples of the image forming apparatus <NUM> include, but are not limited to, a copier, a printer, and an MFP which is a digital multifunction apparatus.

In <FIG>, a sheet feed section <NUM> is provided at a lower portion of the image forming apparatus <NUM>. In the sheet feed section <NUM>, a first sheet feed tray 60a which is a first-stage sheet feed cassette in an upper stage and a second sheet feed tray 60b which is a second-stage sheet feed cassette in a lower stage are arranged. A sheet conveyance path <NUM> is formed in a vertical direction so as to communicate with a sheet feed port 8a of the first sheet feed tray 60a and a sheet feed port 8b of the second sheet feed tray 60b. A sheet fed from the sheet feed port 8a of the first sheet feed tray 60a or the sheet feed port 8b of the second sheet feed tray 60b to the sheet conveyance path <NUM> is conveyed upward in the sheet conveyance path <NUM> as indicated by an arrow A. The sheet is conveyed to a pair of skew correction rollers <NUM> installed at the position of an upper portion of the sheet conveyance path <NUM> by conveyance rollers (corresponding to a sheet conveyance section) 71a and 71b, and the like.

Further, a manual sheet feed tray (not illustrated) is provided on the opposite side of the first sheet feed tray 60a with the sheet conveyance path <NUM> interposed therebetween. A sheet set on the manual sheet feed tray is supplied to the sheet conveyance path <NUM> via a manual sheet feed port 8c.

Each of the first sheet feed tray 60a, the second sheet feed tray 60b, and the manual sheet feed tray corresponds to a holder that holds a sheet. A user can open and close the first sheet feed tray 60a, the second sheet feed tray 60b, and the manual feed tray with respect to the image forming apparatus <NUM>. Opening the first sheet feed tray 60a and the second sheet feed tray 60b means removing the first sheet feed tray (sheet feed cassette) 60a and the second sheet feed tray (sheet feed cassette) 60b from a main body of the apparatus for the purpose of replacement of a sheet, addition of a sheet, or the like. Opening the manual sheet feed tray means that a sheet is removed from the manual sheet feed tray to bring the manual sheet feed tray into a non-use state.

On the other hand, closing the first sheet feed tray 60a and the second sheet feed tray 60b means attaching the first sheet feed tray 60a and the second sheet feed tray 60b to the main body of the apparatus. Closing the manual feed tray means setting a sheet on the manual feed tray and bringing the manual feed tray into a use state.

Further, opening the first sheet feed tray 60a, the second sheet feed tray 60b, and the manual feed tray is also referred to as opening the sheet feed ports 8a, 8b, and 8c. Closing the first sheet feed tray 60a, the second sheet feed tray 60b, and the manual feed tray is also referred to as closing the sheet feed ports 8a, 8b, and 8c. The opening and closing of the first sheet feed tray 60a and the second sheet feed tray 60b can be detected by a sensor (not illustrated). The opening and closing of the manual feed tray can be detected based on whether a sheet is present on the manual sheet feed tray.

The skew correction rollers <NUM> are rollers for correcting skew (inclination) of a sheet conveyed in the sheet conveyance path <NUM>.

Between the sheet feed port 8a of the first sheet feed tray 60a in the upper stage and the skew correction rollers <NUM>, two medium detection sensors <NUM> and <NUM> are arranged on the upstream side and the downstream side in a conveyance direction in the sheet conveyance path <NUM>. Each of the medium detection sensors <NUM> and <NUM> detects a physical property value of a sheet that is an example of information relating to the sheet (hereinafter, the information relating to the sheet is also referred to as sheet information). The medium detection sensor <NUM> on the upstream side is an optical sensor that detects light emitted to the sheet. The medium detection sensor <NUM> on the downstream side is an ultrasonic sensor that detects an ultrasonic wave output toward the sheet. The optical sensor <NUM> may be disposed on the upstream side, and the ultrasonic sensor <NUM> may be disposed on the downstream side.

<FIG> is an explanatory diagram illustrating the optical sensor <NUM>. The optical sensor <NUM> includes a transmission light source 91a such as an LED, a reflection light source 91b such as an LED, and a light receiving element 91c such as a photodiode. The amount of transmitted light <NUM>, which is light emitted from the transmission light source 91a and transmitted through a sheet M conveyed in the sheet conveyance path <NUM>, and the amount of reflected light <NUM>, which is light emitted from the reflection light source 91b and reflected by the sheet M, are detected as physical property values by the light receiving element 91c. Then, based on the detected levels of the amount of the transmitted light and the amount of the reflected light, a controller <NUM> described later determines the type of the sheet M (a basis weight, an OHP sheet, a recycled sheet, coated sheet, or the like). Based on this determination, the controller <NUM> detects the type of sheet (sheet type) that is another example of the sheet information. The optical sensor <NUM> may include a plurality of sensor groups corresponding to red, green, and blue colors, for example.

<FIG> is an explanatory diagram illustrating the ultrasonic sensor <NUM>. The ultrasonic sensor <NUM> includes a pair of an ultrasonic transmitter 92a and an ultrasonic receiver 92b which are obliquely opposed to each other with the sheet conveyance path <NUM> interposed therebetween with respect to a direction in which the sheet M passes (see <FIG>). The ultrasonic sensor <NUM> transmits an ultrasonic wave from the ultrasonic transmitter 92a to the passing sheet M, and receives the ultrasonic wave transmitted through the sheet M by the ultrasonic receiver 92b. Then, the controller <NUM>, which will be described later, detects the type of the sheet M as information relating to the sheet by determining whether the sheet M is a single sheet or a two-ply sheet (envelope) based on the amount of attenuation of the ultrasonic wave by the sheet M.

<FIG> is a block diagram illustrating an electrical configuration of the image forming apparatus <NUM>. As illustrated in <FIG>, the image forming apparatus <NUM> includes the controller <NUM>, a storage device <NUM>, an image reading device <NUM>, an operation panel section <NUM>, an image forming section <NUM>, a sheet feed section <NUM>, the optical sensor <NUM>, and the ultrasonic sensor <NUM>. The image forming apparatus <NUM> further includes a printer controller <NUM> and a network interface (network I/F) <NUM>. These components are connected to each other via a system bus <NUM>.

The controller <NUM> includes a central processing unit (CPU) <NUM>, a read only memory (ROM) <NUM>, a static random access memory (S-RAM) <NUM>, a nonvolatile RAM (NV-RAM) <NUM>, and a timepiece IC <NUM>.

The CPU <NUM> comprehensively controls the entire image forming apparatus <NUM> by executing an operation program stored in the ROM <NUM> or the like. For example, the CPU <NUM> controls a copy function, a printer function, a scan function, and the like such that the copy function, the printer function, the scan function, and the like are executable. In particular, in this embodiment, the CPU <NUM> executes detection of physical property values of a sheet based on detection of an amount of light by the optical sensor <NUM> and detection of an ultrasonic wave by the ultrasonic sensor <NUM>. The CPU <NUM> determines the sheet type based on the results of the detection, automatically sets an image forming condition corresponding to the sheet type based on the determination result for printing, and executes the printing. The CPU <NUM> stores and accumulates the physical property values of the sheet detected by the optical sensor <NUM> and the ultrasonic sensor <NUM>, the determination result of the sheet type, and the like in the storage device <NUM>. The CPU <NUM> further executes control processing such as output to the operation panel section <NUM> or an external apparatus.

The ROM <NUM> stores programs to be executed by the CPU <NUM> and other information.

The S-RAM <NUM> serves as a work area for the CPU <NUM> to execute a program, and temporarily stores the program, data for executing the program, and the like.

The NV-RAM <NUM> Is a nonvolatile memory backed up by a battery. The NV-RAM <NUM> stores various settings relating to image formation, the number of pixels of a display section <NUM>, data of various screens to be displayed on the display section <NUM>, and the like.

The timepiece IC <NUM> measures time, functions as an internal timer, and measures a processing time.

The storage device <NUM> includes a hard disk or the like, and stores programs, various types of data, and the like. In particular, in this embodiment, the storage device <NUM> accumulates the results of detecting the sheet physical property values by the optical sensor <NUM> and the ultrasonic sensor <NUM>, the determination result of the sheet type, a detection history, and the like.

The image reading device <NUM> includes a scanner or the like, reads a document set on a platen glass by scanning the document, and converts the read document into image data.

The operation panel section <NUM> is used for a user to provide an instruction such as a job to the image forming apparatus <NUM> and set various settings. The operation panel section <NUM> includes a reset key <NUM>, a start key <NUM>, a stop key <NUM>, the display section <NUM>, and a touch panel <NUM>.

The reset key <NUM> is used to reset a setting. The start key <NUM> is used for a start operation such as scanning. The stop key <NUM> is pressed to interrupt the operation.

The display section <NUM> includes, for example, a liquid crystal display device, and outputs and displays messages, various operation screens, and the like. The touch panel <NUM> is formed on a screen of the display section <NUM>, and detects a user's touch operation.

The image forming section <NUM> prints, on a sheet, a copy image generated from image data of a document read by the image reading device <NUM> or from print data transmitted from an external terminal apparatus <NUM> or the like. The image forming section <NUM> includes a print engine <NUM> and a fixing section <NUM> that fixes an image by heating and pressing a sheet on which the image is formed. The print engine <NUM> includes hardware components for image formation, such as a photosensitive drum, a charging device, an exposure device, a developing device, a transfer belt, and a transfer roller.

The network I/F160 functions as communication means that transmits and receives data to and from the external apparatus via a network <NUM>. Examples of the external apparatus include an external server, a cloud system, a printer driver of an information terminal apparatus of a user, and other image forming apparatuses.

<FIG> is a block diagram illustrating a functional configuration of the controller <NUM>. The controller <NUM> functionally includes a medium detection controller 100a, a sheet type detection controller 100b, an image forming controller 100c, a storage section 100d, an external communication controller 100e, and a conveyance controller 100f.

The medium detection controller 100a causes the optical sensor <NUM> and the ultrasonic sensor <NUM>, which are medium detection sensors, to operate in a first detection mode and a second detection mode, which will be described later, to detect physical properties and the like of a sheet. The sheet type detection controller 100b detects the sheet type that is sheet information based on the results of the detection by the optical sensor <NUM> and the ultrasonic sensor <NUM>.

The image forming controller 100c controls the image forming section <NUM> under an image forming condition corresponding to each sheet type based on the sheet type detected by the sheet type detection controller 100b, and prints an image on the sheet.

The storage section 100d temporarily stores the results of detecting the physical property values of the sheet by the optical sensor <NUM> and the ultrasonic sensor <NUM>, the result of detecting the sheet type by the sheet type detection controller 100b, the detection history, and the like. The information stored in the storage section 100d is transferred to the storage device <NUM> illustrated in <FIG>, and is accumulated and updated.

The external communication controller 100e corresponds to the network I/F160 illustrated in <FIG>. The external communication controller 100e transmits and receives data to and from the external apparatus <NUM> including a terminal apparatus, an external server, another image forming apparatus, or the like.

The conveyance controller 100f controls feeding and conveyance of a sheet.

Next, the operation of the image forming apparatus <NUM> will be described focusing on control by the controller <NUM>.

In this embodiment, in each of the first detection mode and the second detection mode, the controller <NUM> causes the optical sensor <NUM> and the ultrasonic sensor <NUM> to detect physical property values and a sheet type of a sheet conveyed in the sheet conveyance path <NUM>.

The first detection mode is executed on the first sheet conveyed first. For the first sheet to be conveyed first, the first sheet feed tray 60a or the second sheet feed tray 60b is opened (removed) to perform replacement, supplement, addition, or the like of a sheet. The first sheet is a sheet to be conveyed first after the first sheet feed tray 60a or the second sheet feed tray 60b is closed (inserted). Alternatively, in the case of the manual sheet feed tray, the first sheet to be conveyed first is a sheet to be conveyed first after the result of detection as to whether a sheet is present indicates that a sheet is present after a state in which no sheet is present, that is, after the manual sheet feed tray is closed. Alternatively, the first sheet to be conveyed first is a sheet to be conveyed first from a sheet feed port having no sheet type information after sheet type information is reset by turning off and on the image forming apparatus <NUM>, recovering from sleep, or the like. Alternatively, the first sheet to be conveyed first is a sheet to be conveyed first from a sheet feed port when a medium detection function is switched from OFF to ON. Alternatively, the sheet to be conveyed first is a sheet to be conveyed first in a print job.

The sheet feeding performance affects a basis weight and a sheet feed speed of a sheet. In general, as the basis weight increases, the sheet feeding performance decreases. Therefore, the conveyance speed is decreased to stabilize the sheet feeding performance. <FIG> illustrates a relationship between a sheet type and a conveyance speed. The sheet feed speed illustrated in <FIG> is a conveyance speed at which a sheet is conveyed to the skew correction rollers <NUM>. A process speed is a conveyance speed at which a sheet is conveyed during image formation. <FIG> illustrates a relationship between a sheet type and a basis weight.

Information relating to the first sheet detected in the first detection mode is undetermined. Therefore, in the first detection mode, conveyance at a low conveyance speed (sheet feed speed) is performed up to the skew correction rollers <NUM>. To be specific, the sheet is conveyed at a sheet feed speed (for example, a sheet feed speed of <NUM>/s of thick sheet <NUM>) set in advance as a sheet feed speed at which a thicker recording medium than the first sheet can be fed. Further, in order to perform detailed detection, it is preferable to increase the number of times of reading by the sensors within a surface of the sheet to improve the accuracy. Downstream of the skew correction rollers <NUM>, the sheet may be conveyed at a conveyance speed (process speed) corresponding to sheet information detected for the sheet. For example, in a case where it is detected that the sheet type is plain paper, the sheet may be conveyed at a conveyance speed for plain paper.

Regarding image formation on the first sheet, a fixing temperature and a transfer voltage are determined under a process condition (image formation condition) according to the detected sheet information, and the image formation is performed.

For a sheet after the first sheet, an appropriate conveyance speed corresponding to the sheet information detected for the first sheet is selected, and printing is executed.

Meanwhile, the second detection mode is a mode in which sheet information is detected for a sheet other than the first sheet after the sheet information of the first sheet is determined in the first detection mode and before the first sheet feed tray 60a, the second sheet feed tray 60b, or the manual feed tray is opened. The detection in the second detection mode may be performed on all sheets except for the first sheet. For example, the detection in the second detection mode may be performed on each plurality of sheets such as every other sheet or every fifth sheet, or may be performed at the beginning and end of a job except for the first sheet.

In the second detection mode, the conveyance speed corresponds to the sheet information determined by the detection in the first detection mode. For this reason, depending on the sheet type, the conveyance speed is higher than that in the first detection mode. This shortens a time period from when the sheet reaches the medium detection sensors <NUM> and <NUM> to when the sheet reaches the skew correction roller <NUM>. Accordingly, a detection period in the second detection mode is shorter than a detection period in the first detection mode.

<FIG> and <FIG> illustrate different examples of a sequence in the first detection mode and the second detection mode. In <FIG> and <FIG>, for example, the first sheet feed tray 60a is removed and inserted (opened and closed) as indicated by a "cassette operation" signal. Thereafter, four print jobs (<NUM>) to (<NUM>) each indicating four sheets are executed as indicated by a "print job" signal.

In both <FIG> and <FIG>, in the first detection mode, the detection is performed on the first sheet fed and conveyed from the first sheet feed tray 60a after the first sheet feed tray 60a is removed and inserted (opened and closed), in other words, the first sheet in the print job (<NUM>).

On the other hand, in the second detection mode, the detection is performed on all the sheets except the first sheet in <FIG>. In <FIG>, the detection is performed on the last sheet in each job. Further, <FIG> illustrates that the switching of the sheet type (a change in sheet information) is detected by the detection of the third sheet (the eleventh sheet stacked after the opening and closing of the sheet feed cassette) in the print job (<NUM>). <FIG> illustrates that the switching of the sheet information is detected by the detection of the last sheet in the print job (<NUM>). By such detection, the image forming apparatus <NUM> can detect that different types of sheets have been added in the same sheet feed cassette.

In the examples illustrated in <FIG> and <FIG>, the detection in the first detection mode is also performed on the first sheet in the first job (print job (<NUM>)) after the detection of the switching of the sheet information.

The image forming apparatus <NUM> may be configured to be able to perform the detection described with reference to <FIG> and <FIG> as the second detection mode, and may select either one of the detection described with reference to <FIG> and the detection described with reference to <FIG> according to the performance of the image forming apparatus <NUM> and the type of sheet to be conveyed. For example, in a case where the processing performance of the image forming apparatus <NUM> is low and the conveyance speed of sheets is high, there is a possibility that various kinds of control during printing may not be performed in time for the detection of each sheet. Therefore, the image forming apparatus <NUM> may detect a physical property value or a sheet type of only the last sheet in a job as illustrated in <FIG> to reduce a control load. Not only the last sheet in the job but also every predetermined number of sheets such as every two sheets or every three sheets may be detected.

In addition, in this embodiment, whether the second detection mode described above is performed can be set by the user operating the operation panel section <NUM>. Some users may perform printing by placing a cover sheet and an inner sheet in the same sheet feed cassette at the time of booklet printing. An image forming apparatus or a sheet feed cassette used in such a manner needs to be provided with a mechanism for preventing inadvertent switching of a sheet type. When the second detection mode is set not to be performed, only the first detection mode is performed.

In this embodiment, sheet information detected by each of the medium detection sensors <NUM> and <NUM> is a physical property value or a sheet type of a sheet. The physical property value may include at least one of transmittance information, reflectance information, stiffness information, thickness information, basis weight information, size information, grain direction information, color information, moisture information, smoothness information, resistance information, friction information, or configuration information of the sheet. The configuration information of the sheet includes information of at least one of a pulp material, a coating agent, a fluorescent agent, or a filler.

The table illustrated in <FIG> summarizes sheet information for each detection means. For example, from the optical sensor <NUM>, information of a sheet type, transmittance, reflectance, a basis weight, a coating agent, a fluorescent agent, a filler, color information, and a pulp material determined from the optical characteristics of a sheet is obtained. Information of the sheet type is obtained from the ultrasonic sensor <NUM>. Further, by measuring displacement amounts of the sheet conveyance rollers by a displacement sensor, information of the stiffness of the sheet and the thickness of the sheet can be obtained. Information of the sheet size is obtained from a sheet regulating plate position sensor of each of the sheet feed cassettes 90a and 90b. Information relating to the grain direction, color, smoothness, and pulp material of the sheet is obtained from a sensor using a CMOS. Information relating to the moisture and the basis weight is obtained from an electrostatic sensor, and information of the resistance is obtained by detecting a transfer current.

As for a sheet type, the image forming apparatus <NUM> can determine that a physical property value of a detection target is different by providing a threshold value for the physical property value, for example, transmittance, and can thus detect types of sheets ranging from a thin sheet to a thick sheet. Furthermore, the sheets include a sheet made of at least one of a pulp material, a resin material, and a textile material, an envelope made of at least one of a pulp material, a resin material, and a textile material, and/or an OHP sheet.

Whether sheet information has been switched is determined based on, for example, whether a physical property value of a sheet has changed from a physical property value of a previous sheet by <NUM>% or more, or whether the sheet type itself has been switched. Although this rate of change of <NUM>% is a value that is not achieved with sheets of the same sheet type from the same sheet feed port, a threshold value for the rate of change may be changed depending on a physical property value.

The controller <NUM> of the image forming apparatus <NUM> controls the execution of each of the first detection mode and the second detection mode, and performs the following control based on a detection result.

That is, as described above, the controller <NUM> conveys a sheet after the first sheet by applying the conveyance speed corresponding to the sheet information detected in the first detection mode. Sheet information detected in the second detection mode may be different from the sheet information detected in the first detection mode. In this case, that is, even when switching of sheet information is detected, the conveyance speed corresponding to the sheet information detected in the first detection mode is maintained without changing the conveyance speed in a case where printing is performed according to the same job. By maintaining the conveyance speed, productivity is maintained without causing a decrease in the conveyance speed or stoppage of conveyance. Whether the sheet information detected in the second detection mode is different from the sheet information detected in the first detection mode may be determined by directly comparing the sheet information detected in the second detection mode with the sheet information detected in the first detection mode. Alternatively, in a case where the second detection mode has already been executed, the determination may be made indirectly by comparison with a result of the second detection mode that has already been executed.

However, an image forming condition corresponding to the sheet information after the switching is employed as the process condition. For example, when the sheet type is switched from plain paper to thick sheet <NUM>, a process condition for thick sheet <NUM> is adopted as the process condition while a conveyance speed for plain paper is maintained.

<FIG> illustrates relationships between conveyance speeds (process speeds) and process conditions (in this case, the fixing temperature and the transfer voltage) before and after the switching of the sheet type. In the above-described example, when plain paper is switched to thick sheet <NUM>, the process speed is maintained at <NUM>/s, but the setting of the fixing temperature is changed from <NUM> to <NUM> and the setting of the transfer voltage is changed from <NUM> V to <NUM> V.

As described above, even when the switching of the sheet information is detected, the conveyance speed of a sheet is maintained, and the process condition is changed to the optimum condition for the sheet after the switching. Thus, even when the conveyance speed is not optimal, a decrease in productivity and a decrease in image quality are prevented.

The detection of the first sheet in the first detection mode is performed on the first conveyed sheet in the next job in which the switching of the sheet information is detected. The sheet conveyance speed in this case may be the low conveyance speed in a case where the sheet information is not determined. Alternatively, the sheet may be conveyed to the skew correction rollers <NUM> at the sheet conveyance speed before the switching detection in the previous job, and the sheet may be conveyed downstream of the skew correction rollers <NUM> at the conveyance speed corresponding to the sheet information detected during the conveyance of the sheet at the sheet conveyance speed before the switching detection in the previous job.

Further, for example, when it is detected that sheet information of a sheet after the first sheet is different from the sheet information of the first sheet as in the case where it is determined that plain paper is switched to a recycled sheet, and the image forming condition is not changed, the second detection mode may be executed on a sheet conveyed first in the next job.

Further, in the sequence example illustrated in <FIG>, when the original sheet information before the switching is detected for the fourth sheet after the switching of the sheet information is detected for the third sheet in the print job (<NUM>), there is a possibility that a different type of sheet is mixed in the third sheet. In this case, whether the sheet information is switched is determined in the last sheet in the job, and it is determined that the sheet information is not switched. Then, in the next print job (<NUM>), the detection operation is performed from the first sheet in the second detection mode.

Further, there is a case where a job is a stapling job for performing a stapling process as post-processing in a post-processing apparatus, and the switching of sheet information is detected in the middle of the stapling job. In this case, a condition corresponding to sheet information after the switching is reflected in a control condition and a prohibition condition of the post-processing apparatus while the conveyance speed is maintained. For example, when the sheet type is switched from plain paper to thick sheet <NUM>, the number of sheets to be stapled is changed from <NUM> to <NUM> without changing the conveyance speed. Alternatively, a sheet alignment operation is performed under a condition for thick sheet <NUM>.

Further, as a result of the detection in the second detection mode, the controller <NUM> of the image forming apparatus <NUM> stores, in the storage portion 100d, at least any one of sheet information after a change in sheet information in a case where the sheet information has been changed, the sheet information before and after the change, and information indicating whether the sheet has been changed. Preferably, these pieces of information are stored in association with information of the sheet feed ports 8a, 8b, and 8c, or information of the first and second sheet feed trays 60a and 60b and the manual feed tray. In a case where a sheet is conveyed from the sheet feeding port 8a, 8b, or 8c associated with information indicating that sheet information has been changed (switched), the first detection mode is desirably applied to the first sheet.

Further, the controller <NUM> may notify the user by displaying, on the display section <NUM> of the operation panel section <NUM>, at least one of the sheet information after the change when the sheet information is changed, the sheet information before and after the change, and information indicating whether the sheet information has been changed. The controller <NUM> may transmit the information to the external apparatus <NUM> such as a cloud server or a terminal apparatus of a user, or may accept irregular or regular access from the external apparatus to share the information with the external apparatus.

<FIG> is a flowchart illustrating a printing process performed by the image forming apparatus <NUM>. This printing process is executed by the CPU <NUM> of the controller <NUM> of the image forming apparatus <NUM> operating in accordance with an operation program stored in a storage section such as the ROM <NUM>.

In step S01, the feeding of the first sheet is started. In step S02, it is determined whether it is time to execute the first detection mode. When it is time to execute the first detection mode (YES in step S02), the process proceeds to step S03 and the sheet is conveyed at the conveyance speed in the first detection mode.

Next, in step S04, the medium detection is performed in the first detection mode to detect sheet information, and in step S05, the sheet type is determined based on the detected sheet information.

In step S06, the sheet is conveyed at a conveyance speed corresponding to the sheet type. That is, in a case where the conveyance speed in step S03 does not correspond to the sheet type, the conveyance speed is switched to a corresponding conveyance speed and the sheet is conveyed at the conveyance speed. In a case where the conveyance speed in step S03 corresponds to the sheet type, the sheet is conveyed at the conveyance speed corresponding to the sheet type. Next, the process proceeds to step S13.

When it is not time to execute the first detection mode in step S02 (NO in step S02), the sheet is conveyed at the conveyance speed corresponding to the sheet type detected in the first detection mode (the sheet type determined in step S05) in step S07.

Next, in step S07, it is determined whether it is time to execute the second detection mode. When it is time to execute the second detection mode (YES in step S08), the medium detection is performed in the second detection mode and sheet information is detected in step S09. In step S10, a sheet type is determined based on the detected sheet information. Then, in step S11, it is determined whether or not the sheet type is different from the sheet type detected in the first detection mode. Whether the sheet type is different from the sheet type detected in the first detection mode may be indirectly determined by determining whether the sheet type is different from a sheet type detected in the previous second detection mode.

In a case where the sheet types are different (YES in step S11), the conveyance speed is maintained in step S12, and the process proceeds to step S13. In a case where the sheet types are not different (NO in step S11), the process proceeds to step S13.

Also when it is not time to execute the second detection mode in step S08 (NO in step S08), the process proceeds to step S13.

In step S13, an image is formed under a process condition corresponding to the sheet type detected in the first detection mode or the second detection mode, and then in step S14, it is determined whether or not a print job has been completed. In a case where the print job has not been completed (NO in step S14), the process returns to step S02 and the next sheet is fed. Thereafter, the operations of steps S02 to S14 are repeated. In a case where the print job has been completed (YES in step SS14), the process ends.

Claim 1:
An image forming apparatus (<NUM>) comprising:
a conveyance section (71a, 71b) that conveys a first recording medium (M) and a second recording medium (M);
a recording medium detector (<NUM>, <NUM>, 100b) that detects information relating to the first recording medium (M) and information relating to the second recording medium (M); and
a controller (<NUM>) that causes the recording medium detector (<NUM>, <NUM>, 100b) to detect the information relating to the first recording medium (M) conveyed first by the conveyance section (71a, 71b) and to detect the information relating to the second recording medium (M) conveyed by the conveyance section (71a, 71b) after the first recording medium (M), causes the conveyance section (71a, 71b) to operate such that the second recording medium (M) is conveyed at a conveyance speed based on the information relating to the first recording medium (M), and causes the conveyance section (71a, 71b) to operate such that the second recording medium (M) is conveyed at the conveyance speed maintained even when the information relating to the second recording medium (M) after the first recording medium (M) is detected to be different from the information relating to the first recording medium (M).