JP2023082877A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus capable of suppressing waste of resources and time, by forming an image while preventing a deterioration of an image quality of a printed matter under an image forming condition according to a paper type.SOLUTION: An image forming apparatus includes: a paper feeding unit 3 that feeds paper stored in a paper feed cassette through a transport path; an image forming unit 2 for forming an image on the paper fed by the paper feeding unit 3 based on an image forming condition; a sensor unit 55 that detects a sound wave generated when the paper is fed from the paper feed cassette to the transport path; a storage unit 54 that stores information indicating a relationship between a feature amount of the sound wave and a control value of the image forming condition; and a system control unit 51 that acquires the sound wave detected by the sensor unit 55 and determines the feature amount of the sound wave, and based on the information, sets the control value under the image forming condition corresponding to the determined feature amount, and controls the image forming condition by the set control value to cause image forming means to form an image.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image forming apparatus having a function of determining the type of paper used for printing.

Image forming devices such as printers, copiers, facsimiles, and multi-function devices adjust the image forming conditions such as fixing temperature and transfer conditions according to the basis weight, heat capacity, rated resistivity, and other paper characteristics of the recording medium to be printed. Adjust conditions appropriately. Accordingly, the image forming apparatus is controlled so as to output a printed matter with good image quality. Therefore, the image forming apparatus needs to receive information regarding the type of paper used for printing.

An image forming apparatus transfers a toner image onto a sheet of paper, and heats and presses the sheet onto which the toner image has been transferred, thereby fixing the image onto the sheet of paper. The voltage value of the voltage supplied to the transfer charger that generates the transfer voltage when transferring the toner image onto the paper is set according to the type of paper. Further, the fixing temperature for fixing the toner image transferred to the paper is set according to the paper type. Japanese Unexamined Patent Application Publication No. 2002-200001 discloses an image forming apparatus that has a sensor for discriminating the type of paper in a transport path along which the paper is transported and has an automatic paper type determination function that automatically determines the type of paper. This image forming apparatus controls the voltage supplied to the transfer charger and the fixing temperature based on the paper type determination result using the sensor.

JP 2012-181223 A

Various methods have been proposed for the paper type automatic discrimination function. For example, taking advantage of the fact that basis weight and heat capacity are highly correlated with paper thickness, it is possible to identify paper types by comparing data obtained by actually measuring paper thickness with a paper thickness data table for each paper type. is. In such paper type determination based on paper thickness, accurate paper thickness measurement is possible by providing a simple paper thickness measuring mechanism in the paper transport path.

However, depending on the type of paper, there is a deviation in the correlation between the basis weight and paper thickness. This is due to the difference in paper density. For example, even if the thickness of the paper is the same, paper with a high density has a large basis weight, and conversely, paper with a low density has a small basis weight. Therefore, it is difficult to accurately determine the paper type only by measuring the paper thickness. If the paper type cannot be accurately determined, the image forming conditions that are set according to the paper type cannot be adjusted appropriately, and the image quality of the printed matter may deteriorate. If the image quality of the printed matter deteriorates, it becomes necessary to perform image formation again, which wastes paper and toner resources and operation time.

The present invention has been made in view of the above problems, and it is possible to suppress the waste of resources and time by performing image formation while preventing the deterioration of the image quality of printed matter under the image forming conditions according to the type of paper. An object of the present invention is to provide an image forming apparatus capable of

The image forming apparatus of the present invention includes a paper feed cassette for storing paper, a paper feed means for feeding the paper stored in the paper feed cassette through a transport path, and a paper feed means for feeding the paper. image forming means for forming an image on the paper based on image forming conditions; detection means for detecting a sound wave generated when the paper is fed from the paper feed cassette to the transport path; and a characteristic amount of the sound wave. and a control value of the image forming condition; a storage means for acquiring the sound wave detected by the detection means to determine a feature amount of the sound wave; and determining the feature amount based on the information and a control means for setting a control value of the image forming condition according to the set control value, controlling the image forming condition according to the set control value, and causing the image forming means to form an image.

According to the present invention, it is possible to perform image formation under the image formation conditions according to the type of paper while preventing the deterioration of the image quality of the printed matter, thereby suppressing wastage of resources and time.

1 is a configuration diagram of an image forming apparatus; FIG. FIG. 4 is a configuration diagram of a paper feed unit; FIG. 4 is an explanatory diagram of a paper type detection sensor; Explanatory drawing of a control system. (a), (b) is explanatory drawing of the determination method of a feature-value. FIG. 4 is an explanatory diagram of feature amounts for each paper type; An illustration of a table. 4 is a flowchart showing processing for controlling fixing temperature; 4 is a flowchart showing processing for controlling image forming speed. 4 is a flowchart showing processing for controlling transfer current;

Hereinafter, embodiments will be described in detail with reference to the drawings. Although these embodiments are examples of the best embodiments of the present invention, the present invention is not limited to these embodiments.

(overall structure)
FIG. 1 is a configuration diagram of an image forming apparatus according to this embodiment. The image forming apparatus 1 of this embodiment is a tandem-type full-color image forming apparatus using an electrophotographic method, and can be realized by a printer, various printing machines, copiers, facsimiles, multifunction machines, and the like.

The image forming apparatus 1 includes an image forming section (printer engine) 2 , a paper feeding section 3 and a reader (scanner) 5 . A paper feeding unit 3 is arranged below the image forming unit 2 , and a reader 5 is arranged above the image forming unit 2 . The reader 5 has an automatic document feeder (ADF) 36 above. The paper feeding section 3 includes a plurality of stages (here, three stages) of paper feeding cassettes 4a to 4c serving as a paper storing section. Each of the paper feed cassettes 4a to 4c can be freely pulled out and stored in the main body of the image forming apparatus 1. As shown in FIG. A reader 5 reads an original image. The image forming unit 2 includes a paper discharge tray 7 from which paper (printed matter) after image formation is discharged, and a manual paper feed tray 8 on which paper is placed when the paper is manually fed.

The image forming unit 2 is arranged above an intermediate transfer belt 9, which is an endless belt, and along the intermediate transfer belt 9, yellow (Y), magenta (M), cyan (C), and black (K). Correspondingly, a plurality of (here, four) imaging units 10 are arranged side by side. An exposure unit 15 is arranged above the plurality of image forming units 10 . Each imaging unit 10 includes a charger 12 , a developer 13 , and a photoreceptor cleaner 14 along the outer periphery of a drum-shaped photoreceptor 11 .

The charger 12 performs charging processing to uniformly charge the surface of the photoreceptor 11 . The exposure unit 15 irradiates the charged surface of the photoreceptor 11 with laser light modulated based on the image signal of the corresponding color. An electrostatic latent image is formed on the surface of the photoreceptor 11 by changing the potential of the portion irradiated with the laser beam. The developing device 13 develops the electrostatic latent image formed on the surface of the photoreceptor 11 with toner of the corresponding color. A toner image is formed on the surface of the photoreceptor 11 . The toner image is transferred from the surface of photoreceptor 11 to intermediate transfer belt 9 . The photoreceptor cleaner 14 removes toner remaining on the surface of the photoreceptor 11 after transfer.

A toner image of each color is superimposed and transferred onto the intermediate transfer belt 9 from the photosensitive member 11 of each image forming unit 10 . At this time, first, a yellow toner image is transferred from the photosensitive member 11 of the image forming unit 10 for yellow (Y) to the intermediate transfer belt 9 . Next, a magenta toner image is transferred onto the intermediate transfer belt 9 from the photosensitive member 11 of the magenta (M) image forming unit 10 . Next, a cyan toner image is transferred onto the intermediate transfer belt 9 from the photosensitive member 11 of the cyan (C) image forming unit 10 . Finally, a black toner image is transferred onto the intermediate transfer belt 9 from the photosensitive member 11 of the black (K) image forming unit 10 . By transferring in this manner, a full-color toner image is formed on the intermediate transfer belt 9 in which toner images of four colors are superimposed.

The toner image transferred onto the intermediate transfer belt 9 is transferred by the transfer section 16 onto the paper fed from the paper feeding section 3 . The transfer unit 16 conveys the paper onto which the toner image has been transferred to the fixing device 17 . The fixing device 17 heats and presses the paper onto which the toner image has been transferred, thereby melting and pressing the toner image onto the paper. As a result, the toner image is fixed on the paper. The paper on which the toner image has been fixed is discharged to the paper discharge tray 7 as a printed matter by the paper discharge rollers 19 . Toner remaining on the surface of the intermediate transfer belt 9 after the toner image is transferred is removed and collected by a cleaner.

The reader 5 includes a contact glass 31 on which a document to be read is placed, a first traveling body 32, a second traveling body 33, a lens 34, and a light receiving section 35. The first traveling body 32 includes a light source for document illumination and a mirror. The second traveling body 33 has a plurality of mirrors. The light receiving section 35 includes a plurality of photoelectric conversion elements that convert received light into electrical signals. A photoelectric conversion element is a CCD sensor, a CMOS sensor, or the like. The first traveling body 32 and the second traveling body 33 can move in the horizontal direction in the figure below the contact glass 31 .

The first traveling body 32 irradiates the document with light from the light source. The document reflects the irradiated light. The reflected light from the document is reflected by the mirrors in the first traveling member 32 and the mirrors in the second traveling member 33 and enters the lens 34 . The lens 34 forms an image of the incident reflected light on the light receiving section 35 . The light-receiving unit 35 outputs a digital signal (image signal) representing the image of the document in accordance with the received reflected light. The original image is read in this way. This image signal is transmitted to the image forming section 2 during the copying process. The exposure device 15 of the image forming section 2 modulates the laser light according to the image signal.

A document is read using the contact glass 31 or the ADF 36 . When the contact glass 31 is used, the document is placed on the contact glass 31 with the image forming surface facing the first traveling body 32 side. In this case, the first traveling body 32 and the second traveling body 33 irradiate the document with light while moving in the horizontal direction in the figure under the contact glass 31 . When the ADF 36 is used, the document is automatically transported by the ADF 36 and passes through the light irradiation position (reading position) of the first traveling body 32 . In this case, the first traveling body 32 and the second traveling body 33 irradiate the document with light without moving.

(Paper feed section)
The paper feeding section 3 feeds the paper stored in one of the paper feeding cassettes 4 a to 4 c to the image forming section 2 via the transport path 26 . FIG. 2 is a configuration diagram of the sheet feeding unit 3. As shown in FIG. Each of the paper feed cassettes 4a to 4c holds stacked sheets of paper. Near the paper feed openings of the paper feed cassettes 4a to 4c, there are provided a pickup roller 22 that contacts the uppermost sheet of the stacked paper 6, and a pickup roller 22 for feeding the paper pulled out from the paper feed cassette 4. paper feed roller pair 23 are provided. Sheets are fed one by one from the sheet feeding cassettes 4 a to 4 c to the transport path 26 by the pickup roller 22 and the sheet feeding roller pair 23 . An inner guide member 27 and an outer guide member 28 for guiding the paper to the transport path 26 are provided between the paper feed roller pair 23 and the transport path 26 . The paper is transported to registration rollers 20 provided in image forming section 2 via transport path 26 . The transport path 26 is provided with vertical path sensors 45 corresponding to the paper feed cassettes 4a to 4c, respectively. A vertical path sensor 45 detects a sheet conveyed through the conveying path 26 .

Note that paper can be fed from a manual feed tray 8 in addition to the paper feeding unit 3 . Sheets placed on the manual feed tray 8 are fed one by one by a pickup roller 25 and a paper feed roller pair 29 provided at the base end portion of the manual feed tray 8 . The paper feed roller pair 29 conveys the paper to the registration rollers 20 .

The registration rollers 20 temporarily stop conveying the paper, and transfer the paper to the transfer section 16 in time so that the toner image on the intermediate transfer belt 9 and the leading edge of the paper have a predetermined positional relationship. send out. The registration rollers 20 correct the skew of the paper while the paper is stopped.

Each of the paper feed cassettes 4a to 4c has a sensor for paper type detection. FIG. 3 is an explanatory diagram of the paper type detection sensor. FIG. 3 illustrates the paper feed cassette 4a as an example, but the paper feed cassettes 4b and 4c also have the same configuration. Here, the first acoustic wave sensor 43a and the second acoustic wave sensor 44a are used as the paper type detection sensors. The first acoustic wave sensor 43a and the second acoustic wave sensor 44a have the same configuration. The first acoustic wave sensor 43a and the second acoustic wave sensor 44a are used for non-contact detection of the type of paper 6 separated and fed by the pickup roller 22 using an acoustic measurement method. Used.

The first acoustic wave sensor 43 a detects sound waves emitted by the paper 6 fed at the position of the pickup roller 22 . The second acoustic wave sensor 44a detects sound waves emitted by contact with the inner guide member 27 and the outer guide member 28 when the sheet 6 passes between the inner guide member 27 and the outer guide member 28. FIG. A feature amount of the detected sound wave is determined by a process described later. The paper type of the paper 6 is determined based on the feature amount.

In the following description, the acoustic wave sensor provided in the paper feed cassette 4b is referred to as a first acoustic wave sensor 43b and a second acoustic wave sensor 44b, and the acoustic wave sensor provided in the paper feed cassette 4c is referred to as a first acoustic wave sensor 43c. , the second acoustic wave sensor 44c. Also, when there is no need to distinguish between the paper feed cassettes 4a to 4c, the first acoustic wave sensor 43 and the second acoustic wave sensor 44 are described.

(control system)
FIG. 4 is an explanatory diagram of a control system that controls the operation of the image forming apparatus 1 configured as described above. The control system of this embodiment includes a system control section 51 , an image input section 52 , an image processing section 53 , a storage section 54 , a paper feeding section 3 , an image forming section 2 , a sensor section 55 and an operation display section 56 . The image forming section 2 includes the exposing device 15 and the fixing device 17 as described with reference to FIG.

The system control unit 51 is a microcomputer including at least a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls operations of the image forming apparatus 1 by executing computer programs stored in the ROM. The RAM provides a working area when the CPU executes processing, and stores various data used in the processing.

The image input unit 52 acquires image signals used for image formation from the reader 5 . The image input unit 52 can also acquire image signals used for image formation from an external device via a network. The image input unit 52 transmits the acquired image signal to the image processing unit 53 . The image processing unit 53 performs predetermined image processing on the acquired image signal. The image processing unit 53 stores the image signal after image processing in the storage unit 54 or transmits the image signal to the image forming unit 2 . The image forming section 2 outputs laser light modulated according to an image signal from the exposing device 15 to form an image. During image formation, the system control unit 51 controls the heating temperature (fixing temperature) during the fixing process by the fixing device 17 . The paper feeding unit 3 feeds paper used for image formation under the control of the system control unit 51 .

The sensor unit 55 includes various sensors such as the vertical path sensor 45 for detecting the paper transport state (occurrence of jam, etc.) and the sensor for detecting the image density of the toner image on the photoreceptor 11 . A detection result by the sensor unit 55 is transmitted to the system control unit 51 . The sensor unit 55 also includes the first acoustic wave sensor 43 and the second acoustic wave sensor 44 for detecting the type of paper.

The operation display unit 56 is a user interface having an input interface and an output interface. The input interface is, for example, key buttons, a touch panel, or the like. The output interface is, for example, a display, a speaker, or the like. The operation display unit 56 is provided on the main body of the image forming apparatus 1, that is, on the upper part of the housing of the image forming unit 2 here. The operation display unit 56 accepts inputs such as an operation mode, image forming conditions, number of copies to be printed, paper processing, paper type, etc. through an input interface. The operation display unit 56 displays a setting screen for input, a warning screen, etc. through an output interface.

(paper type detection)
The type of paper used for image formation is detected by the system control unit 51 using the detection results of sound waves by the first acoustic wave sensor 43 and the second acoustic wave sensor 44 . The system control unit 51 discriminates the type of paper based on the difference in the feature amount of sound waves that varies according to the type of paper. The feature amount is measured in advance for each paper type and stored in the storage unit 54 as a model showing the relationship between the feature amount and the paper type. During image formation, the system control unit 51 generates waveform components for calculating feature amounts from the detection results of the first acoustic wave sensor 43 and the second acoustic wave sensor 44 based on the timing at which the vertical path sensor 45 detects the paper. To detect.

FIG. 5 is an explanatory diagram of a method of determining feature amounts. FIG. 5A is an explanatory diagram of sound waves detected by the first acoustic wave sensor 43. FIG. FIG. 5B is an explanatory diagram of sound waves detected by the second acoustic wave sensor 44 .

The left diagram of FIG. 5A shows the waveform of the sound waves generated by the friction between the surfaces of the paper being pulled out and the paper immediately below when the paper is pulled out by the pickup roller 22 . The system control unit 51 obtains the frequency characteristics shown in the right diagram of FIG. 5(a) by performing octave band analysis on this waveform. The system control unit 51 sets the average intensity (dB) at the first predetermined frequency (here, 2 [kHz]) of this frequency characteristic to "A", and at the second predetermined frequency (here, 10 [kHz]) The feature amount is calculated with the average intensity (dB) as "B". In the present embodiment, the system control unit 51 divides the average intensity B by the average intensity A to calculate the rubbing feature amount B/A.

The left diagram of FIG. 5B shows the waveform of the sound waves generated when the sheet passes between the inner guide member 27 and the outer guide member 28. FIG. In the configuration of this embodiment, when the paper passes between the inner guide member 27 and the outer guide member 28, the trailing edge of the paper collides with the outer guide member 28 to generate sound waves. The system control unit 51 obtains the frequency characteristic shown in the right diagram of FIG. 5B by performing octave band analysis on this waveform. The system control unit 51 sets the average intensity (dB) at the first predetermined frequency (here, 200 [Hz]) of this frequency characteristic to "C" and the second predetermined frequency (here, 6.3 [kHz] ) is defined as “D”, and the feature amount is calculated. In the present embodiment, the system control unit 51 divides the average strength C by the average strength D to calculate the striking feature amount C/D.

In this embodiment, the sound waves are frequency analyzed using octave band analysis. The feature amount of the sound wave is calculated as the rubbing feature amount and the striking feature amount by defining the average intensity in a specific frequency band as the feature amounts A to D for the frequency analysis result. In addition, the feature amount may be calculated by frequency-analyzing a sound wave using a fast Fourier transform or a wavelet transform. Also, a neural network may be utilized to extract feature quantities and create a discrimination model.

In this embodiment, the types of paper fed from the paper feed cassettes 4a to 4c and the manual feed tray 8 are assumed to be plain paper, gloss coated paper, and embossed paper, for example. Plain paper and gloss coated paper are assumed to have two types of paper thickness, thin paper and thick paper, respectively. FIG. 6 is an explanatory diagram of these feature amounts for each paper type. In FIG. 6, the feature amount for each paper type is plotted on the graph. According to this graph, the rubbing feature amount B/A indicates that the higher the value, the smoother the surface of the paper, and the lower the value, the rougher the surface of the paper. The higher the value of the impact feature value C/D, the thinner the paper, and the lower the value, the thicker the paper.

By combining these feature amounts (rubbing feature amount and hitting feature amount), it is possible to classify individual brands of paper types and paper type categories. In the present embodiment, by estimating the paper type category from a combination of feature amounts, image formation control is performed according to the estimated paper type category. The image forming apparatus 1 can appropriately determine image forming conditions by estimating the paper type category of the paper being conveyed from the feature amount even when forming an image on a sheet of unknown paper type. .

In this embodiment, there are five types of paper type categories, plain paper (thin), plain paper (thick), gloss coated paper (thin), gloss coated paper (thick), and embossed paper (thick), depending on the feature amount. is determined as The system control unit 51 uses the rubbing feature amount B/A and the hitting feature amount C/D to determine the paper type category. Therefore, the storage unit 54 stores a table for estimating the paper type category based on the combination of feature amounts (rubbing feature amount and hitting feature amount). The system control unit 51 estimates the paper type category based on the feature amount from this table.

Also, in this table, control items of image forming conditions are set for each paper type category. FIG. 7 is an exemplary diagram of such a table. A control value for each control item of the image forming condition is determined from the feature amount using the table in FIG. In this embodiment, the fixing temperature of the fixing device 17, the image forming speed of the image forming unit 2, and the transfer current for transferring the toner image onto the paper by the transfer unit 16 are set for each paper type category as control values. ing. Note that these are examples of image forming conditions, and other image forming conditions may be set as control items. For example, the voltage, current, AC power frequency, etc. applied to the photoreceptor 11, charger 12, developing device 13, intermediate transfer belt 9, and transfer unit 16 can be set as control items for image forming conditions.

Regarding the fixing temperature, the following control values are set.
Plain paper (thin): 175°C
Plain paper (thick): 180°C
Gloss coated paper (thin): 172°C
Gloss coated paper (thick): 175°C
Embossed paper: 180°C

Regarding the image forming speed, the following control values are set.
Plain paper (thin), Plain paper (thick): 400mm/s
Gloss coated paper (thin), gloss coated paper (thick): 200mm/s
Embossed paper: 133 mm/s

Regarding the transfer current, the following control values are set.
Plain paper (thin): 20 μA
Plain paper (thick): 22 μA
Gloss coated paper (thin): 20μA
Gloss coated paper (thick): 24 μA
Embossed paper: 22 μA

If the waveforms of the sound waves detected by the first acoustic wave sensor 43 and the second acoustic wave sensor 44 are not specified, the system control unit 51 determines that an error has occurred in the detection operation. For example, when the impact feature value is "2.0" or more, the system control unit 51 judges an error in the detection operation as double feeding in which sheets overlap or is being conveyed as super-thick paper out of specification. do. If the amplitude of the waveform of the sound wave is smaller than "0.01", the system control unit 51 determines that there is an error in the detection operation due to the absence of paper or a malfunction of the sensor.

Processing for controlling the image forming conditions by using the table of FIG. 7 by the image forming apparatus 1 having such a configuration will be described. FIG. 8 is a flow chart showing processing for controlling the fixing temperature according to the type of paper. FIG. 9 is a flowchart showing processing for controlling the image forming speed according to the paper type. FIG. 10 is a flow chart showing the process of controlling the transfer current according to the type of paper. These processes are performed when paper is fed from any one of the paper feed cassettes 4a to 4c. Here, the paper feed cassette 4a will be described as an example, but the same processing is performed for the paper feed cassettes 4b and 4c.

(fixing temperature control)
Processing for controlling the fixing temperature will be described with reference to FIG.

When forming an image on the paper fed from the paper feeding cassette 4a based on the preceding paper feeding command, the system control unit 51 determines whether or not the previous paper feeding operation is completed (S1). The system control unit 51 determines that the paper feeding operation is completed when the detection result of the vertical path sensor 45 changes from the state of paper non-detection→paper detection→paper non-detection. If the paper feeding operation has not ended, the system control unit 51 waits until the paper feeding operation ends (S1: N).

When the paper feeding operation ends (S1: Y), the system control unit 51 determines whether or not the next paper is scheduled to be fed (S2). The system control unit 51 makes this determination based on whether or not an image forming request instructing paper feeding from the paper feed cassette 4a is acquired from the operation display unit 56 or an external device. If there is no plan to feed paper from the paper feed cassette 4a (S2: N), the system control unit 51 waits until the image formation request is acquired. If there is a plan to feed paper from the paper feed cassette 4a (S2: Y), the system control unit 51 starts the paper feed operation by the paper feed unit 3. FIG.

When starting the paper feed operation, the system control unit 51 drives the pickup roller 22 and the paper feed roller pair 23 of the paper feed cassette 4a by a predetermined amount to feed the top sheet of paper in the paper feed cassette 4a. do. The paper passes between the first acoustic wave sensor 43 a and the second acoustic wave sensor 44 a and is transported to the registration rollers 20 along the transport path 26 . The system control unit 51 temporarily stops the paper at the position of the registration roller 20 (S3).

During this time, the system control unit 51 acquires detection results from the first acoustic wave sensor 43a and the second acoustic wave sensor 44a, and detects sound waves generated by the paper (S4). It should be noted that the system control unit 51 performs processing as an error when the detected sound wave is out of specification. After detecting the sound wave, the system control unit 51 determines the paper type category of the paper being conveyed from the table in FIG. 7 based on the feature amount of the detected sound wave (S5). The system control unit 51 stores paper type information, which is the determination result of the paper type category, in the storage unit 54 (S6). The processes of S1 to S6 are executed as paper type category detection processing or paper type information acquisition processing for the paper currently being conveyed. In particular, the processing of S3 to S6 is executed as paper type information acquisition processing.

Based on the paper type information stored in the storage unit 54, the system control unit 51 sets an appropriate fixing temperature range using the table in FIG. 7 (S7). The system control unit 51 performs fixing temperature control so that the fixing temperature of the fixing device 17 is within the fixing temperature range (S8, S9: N). The system control unit 51 determines the fixing temperature based on the detection result of a temperature sensor (not shown) provided in the fixing device 17, for example, and supplies electric power to the fixing device 17 so that the fixing temperature is within the fixing temperature range. is controlled to control the fixing temperature. The processing of S7 to S9 is executed as fixing temperature setting processing.

When the fixing temperature falls within the fixing temperature range (S9: Y), the system control section 51 makes other preparations (for example, transfer current setting, etc., which will be described later) (S10). When other preparations are completed (S10: Y), the system control unit 51 transmits the original paper feed command to the paper feed unit 3, and drives the pickup roller 22 and the paper feed roller pair 23 of the paper feed cassette 4a. Then, sheet feeding is started (S11). Further, the system control section 51 forms an image on the sheet fed by the image forming section 2 (S12). The processes of S10 and S11 are executed as paper feeding and conveying processes.

As described above, the image forming process is performed while controlling the fixing temperature according to the type of paper. When the image forming process is performed on the second and subsequent sheets of paper, the processes after S1 are repeatedly executed. The same process is performed when forming images on sheets stored in the other sheet feeding cassettes 4b and 4c.

In the process of FIG. 8, the paper type is set in advance for each of the paper feed cassettes 4a to 4c by the paper feed command. The paper type is set by the user through the operation display section 56 . By setting the paper type in advance, the image forming process is performed while determining whether or not the paper type category is correct for each sheet. When sheets of different paper type categories are mixed, the image forming conditions are corrected to appropriate settings.

(imaging speed control)
Processing for controlling the image forming speed will be described with reference to FIG. The same step numbers are assigned to the same processes as those in FIG. Description of similar processing is omitted.

Paper type information is stored in the storage unit 54 in the same manner as in FIG. 8 (S1 to S6). The system control unit 51 sets an appropriate image forming speed according to the table of FIG. 7 based on the paper type information stored in the storage unit 54 (S21). After setting the image forming speed, the system control unit 51 performs other preparations, paper feeding, and image forming processing (S10 to S12), as in the processing of FIG. During the image forming process of S12, the image forming speed of the drum motor, etc. is controlled to a speed corresponding to the image forming speed set in the process of S21. As described above, the image forming process is performed while controlling the image forming speed according to the type of paper.

(transfer current control)
Processing for controlling the transfer current will be described with reference to FIG. The same step numbers are assigned to the same processes as those in FIG. Description of similar processing is omitted.

Paper type information is stored in the storage unit 54 in the same manner as in FIG. 8 (S1 to S6). Based on the paper type information stored in the storage unit 54, the system control unit 51 sets an appropriate transfer current according to the table of FIG. 7 (S23). The system control section 51 controls the image forming section 2 with the set transfer current (S24). The system control unit 51 controls the image forming unit 2 until the transfer current of the transfer unit 16 of the image forming unit 2 is set to the determined transfer current (S25: N). When the setting of the transfer current is completed (S25: Y), the system control unit 51 performs other preparations, paper feeding, and image forming processing (S10: Y), as in the processing of FIG. ~S12). Note that the processing of S23 to S25 is executed as image forming condition setting processing.

In FIGS. 8 to 10, fixing temperature, image forming speed, and transfer current are used as examples of image forming conditions, but other image forming conditions can be similarly controlled. In the case of the processing shown in FIGS. 8 to 10, each time a sheet for image formation is fed, the paper type category detection for the next sheet is performed. For example, even if sheets of different types are mixed in the sheet feeding cassette 4a, the sheet type can be confirmed for each sheet in advance and reflected in the image forming process. Therefore, it is possible to appropriately control the image forming conditions according to the paper type of each paper.

In the case of a tandem-type full-color image forming apparatus as in this embodiment, the image forming operation is already started at the time of sheet feeding. However, since the paper type information can be discriminated in real time, it is possible to minimize redoing of image formation in the case where the paper type information is erroneous. As a result, waste of resources and time associated with redoing image formation can be eliminated. Further, by accurately determining the type of paper, it is possible to prevent deterioration of the image quality of the image formed on the paper.

In the above description, the control value of the image forming condition is set for each item of the image forming condition based on the two feature amounts (the rubbing feature amount and the hitting feature amount). This processing may be performed using one feature value, or may be performed using three or more feature values. The image forming conditions to be set are not limited to the fixing temperature, the image forming speed, and the transfer current, but may be one, or may be four or more.

Claims (13)

a paper cassette for storing paper,
a paper feed unit that feeds the paper stored in the paper feed cassette through a transport path;
image forming means for forming an image on the paper fed by the paper feeding means based on image forming conditions;
detection means for detecting sound waves generated when the paper is fed from the paper feed cassette to the transport path;
storage means for storing information indicating the relationship between the feature quantity of the sound wave and the control value of the image forming condition;
Acquiring the sound wave detected by the detection means, determining a feature amount of the sound wave, setting a control value of the image forming condition according to the determined feature amount based on the information, and setting the control value according to the set control value and a control means for controlling image forming conditions to cause the image forming means to form an image,
Image forming device. The paper feeding means includes a conveying means for pulling out the paper from the paper feed cassette,
The detecting means comprises first detecting means for detecting a sound wave emitted by the paper at the position of the conveying means when the paper is pulled out by the conveying means,
The image forming apparatus according to claim 1. The first detection means detects a sound wave generated by friction between the surfaces of the paper being pulled out and the paper immediately below when the paper is pulled out by the conveying means,
3. The image forming apparatus according to claim 2. The control means calculates a first characteristic quantity based on the average intensity of the sound waves detected by the first detection means at a first predetermined frequency and the average intensity of the sound waves at a second predetermined frequency. characterized by
4. The image forming apparatus according to claim 2 or 3. The control means calculates the first feature amount by dividing the average intensity at the second predetermined frequency by the average intensity at the first predetermined frequency,
5. The image forming apparatus according to claim 4. The paper feed means includes a guide member that guides the paper from the paper feed cassette to the transport path,
The detection means has a second detection means for detecting a sound wave emitted by contacting the guide member when the paper is transported to the transport path,
6. The image forming apparatus according to claim 4 or 5. The control means calculates a second characteristic amount based on the average intensity of the sound waves detected by the second detection means at a third predetermined frequency and the average intensity of the sound waves at a fourth predetermined frequency. characterized by
7. The image forming apparatus according to claim 6. The control means calculates the second feature amount by dividing the average intensity at the third predetermined frequency by the average intensity at the fourth predetermined frequency,
The image forming apparatus according to claim 7. The storage means stores the information indicating the relationship between the first feature amount, the second feature amount, and the control value,
The control means is characterized by setting a control value according to the calculated first feature amount and the second feature amount based on the information,
9. The image forming apparatus according to claim 8. The storage means stores the information indicating the relationship between the paper type of the paper, the feature amount of the sound wave, and the control value of the image forming condition,
The control means determines a paper type corresponding to the determined feature amount based on the information, sets a control value for the image forming condition according to the determined paper type, and determines the image forming condition based on the set control value. and a control means for controlling the forming conditions and causing the image forming means to form an image,
The image forming apparatus according to claim 1. wherein the control value is a fixing temperature for fixing the image on paper,
The image forming apparatus according to any one of claims 1 to 10. wherein the control value is an image forming speed at which the image forming means forms an image,
The image forming apparatus according to any one of claims 1 to 11. wherein the control value is a transfer current for transferring the image to the paper,
The image forming apparatus according to any one of claims 1 to 12.

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