Image forming device

Abstract

To solve the problem that a sensor may not be able to perform detection if processing is duplicated when control of drive means and control of a sensor for detecting a recording material are performed by common control means.SOLUTION: Control means: prevents transmission means from transmitting an ultrasonic wave, when determining that an excitation switching timing of first driving means or an excitation switching timing of second driving means overlaps a timing for acquiring a value of an ultrasonic wave received by reception means; and causes transmission means to transmit an ultrasonic wave, when determining that the excitation switching timing of the first driving means or the excitation switching timing of the second driving means do not overlap a timing for acquiring the value of the ultrasonic wave received by the reception means.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer. [Background technology]

[0002] Conventionally, image forming apparatuses form electrostatic latent images by irradiating a charged photosensitive drum with laser light based on image data. The electrostatic latent image formed on the photosensitive drum is then developed with toner by a developing device, thereby visualizing the electrostatic latent image and forming an image. After this image is transferred to a recording material, it is fixed to the recording material by heating while applying pressure in a fixing nip. In such image forming apparatuses, a stepping motor that performs high-precision positioning is generally used as a driving means for transporting the recording material.

[0003] Furthermore, in an image forming apparatus, there are various types of recording materials on which images are formed, and there are recording materials with various characteristics such as size, basis weight, surface properties, etc. In order to form an image suitable for these recording materials, some image forming apparatuses are equipped with a sensor for identifying the type of recording material inside. Patent Document 1 discloses a method for detecting the basis weight of a recording material by transmitting ultrasonic waves to the recording material and receiving the ultrasonic waves that have passed through the recording material, thereby identifying the type of recording material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication 2010-18433 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the driving means and the sensor for detecting the recording material are controlled by a common control means, there is a possibility that the sensor will not be able to detect the recording material if the processes overlap.

[0006] The invention of the present application has been made in consideration of the above-mentioned situation, and aims to control the detection timing of the sensor in accordance with the state of the driving means when the driving means and the sensor are controlled by a common control means. [Means for solving the problem]

[0007] In order to achieve the above object, a recording medium conveying device is provided with a conveying means for conveying a recording material, an image forming means for forming an image on the recording material, a fixing means for fixing the image on the recording material, a first driving means for driving the conveying means, a second driving means for driving the fixing means, a transmitting means for transmitting ultrasonic waves, a receiving means for receiving ultrasonic waves, and a control means for controlling the timing of transmitting the ultrasonic waves from the transmitting means, and the control means controls the excitation switching timing of the first driving means. Gu and A timing for acquiring the value of the ultrasonic wave received by the receiving means and Heavy Then do not have like The present invention is characterized in that ultrasonic waves are emitted from the transmitting means. In order to achieve the above object, the recording medium includes a conveying means for conveying a recording material, an image forming means for forming an image on the recording material, a fixing means for fixing the image on the recording material, a first driving means for driving the conveying means, a second driving means for driving the fixing means, a transmitting means for emitting ultrasonic waves, a receiving means for receiving ultrasonic waves, and a control means for controlling the timing of transmitting the ultrasonic waves from the transmitting means, wherein the control means causes the transmitting means to transmit the ultrasonic waves so that the excitation switching timing of the second driving means and the timing of acquiring the value of the ultrasonic waves received by the receiving means do not overlap. Effect of the Invention

[0008] According to the configuration of the present invention, when the drive means and the sensor are controlled by a common control means, the detection timing of the sensor can be controlled in accordance with the state of the drive means. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of an image forming apparatus [Diagram 2] Diagram showing functional and hardware blocks [Diagram 3] FIG. 2 is a diagram showing the configuration and operation of a basis weight detection unit 50. [Figure 4] FIG. 13 is a diagram showing an operation for determining the basis weight of the recording material 12. [Diagram 5] A diagram showing the motor excitation switching process and the basis weight detection process [Figure 6]A diagram showing the motor excitation switching process and the basis weight detection process [Figure 7] A flowchart for determining whether or not to perform basis weight detection when motor excitation switching is completed. [Figure 8] A diagram showing the motor excitation switching process and the basis weight detection process [Figure 9] A flowchart for determining whether or not to perform basis weight detection when motor excitation switching is completed. [Figure 10] A diagram showing the motor excitation switching process and the basis weight detection process [Figure 11] A flow chart showing a method for synchronizing the excitation switching of the paper feed motor 221 and the excitation switching of the fixing motor 222. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment) Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention in the claims, and all of the combinations of features described in the embodiments are not necessarily essential to the solution of the present invention.

[0011] [Image forming equipment] FIG. 1 is a schematic diagram of an image forming apparatus 10. The image forming apparatus 10 is an electrophotographic full-color printer that employs an intermediate transfer method. The image forming apparatus 10 has four image forming stations that form images of the respective colors of yellow, magenta, cyan, and black. These four image forming stations are arranged in a row at regular intervals. In the following description, the letters a, b, c, and d at the end of the reference symbols indicate that the corresponding members are related to the formation of toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. In the following description, when it is not necessary to distinguish between colors, the reference symbols may be used without the letters a, b, c, and d at the end.

[0012] The following describes the operation of the image forming apparatus 10. The recording material 12 fed by the pickup roller 13 is conveyed by a pair of conveying rollers 14 and 15. Then, when the leading edge of the recording material 12 is detected by the registration sensor 111, the conveyance of the recording material 12 is temporarily stopped.

[0013] The scanner unit 20 includes a reflecting mirror and a laser diode (light-emitting element), and irradiates a laser beam 21 onto a photosensitive drum 22, which serves as a photosensitive member that is driven to rotate. At this time, the photosensitive drum 22 is pre-charged by a charging roller 23. A charging voltage of, for example, -1200V is applied to the charging roller, and the surface of the photosensitive drum 22 is charged to, for example, -700V. When an electrostatic latent image is formed by irradiation with the laser beam 21 at this charging potential, the potential at the location where the electrostatic latent image is formed becomes, for example, -100V.

[0014] A developing voltage of, for example, −350 V is applied to the developing sleeve 24 of the developing unit 25, and the electrostatic latent image formed on the photosensitive drum 22 is developed with toner to form an image (toner image) on the photosensitive drum 22. A positive voltage of, for example, +1000 V is applied to the primary transfer roller 26, and the image formed on the photosensitive drum 22 is primarily transferred to the intermediate transfer belt 30. The toner image that has not been primarily transferred is collected by a collection blade 27 into a waste toner box 28.

[0015] Note that a group of members that form an image, such as the scanner unit 20 and the photosensitive drum 22, the charging roller 23, the developing device 25, and the primary transfer roller 26, are also referred to as an image forming unit. Also, each member (e.g., the charging roller 23, the developing device 25, and the primary transfer roller 26) that is disposed in close proximity to the periphery of the photosensitive drum 22 and acts on the photosensitive drum 22 is also referred to as a process means.

[0016] The intermediate transfer belt 30 is driven by rollers 31, 32, and 33, and conveys the image transferred onto the intermediate transfer belt 30 to the secondary transfer section. The conveyance of the recording material 12 is resumed so that the timing coincides with the image conveyed to the secondary transfer section at the secondary transfer position. Then, a secondary transfer voltage is applied to the secondary transfer roller 29, so that the image is secondarily transferred from the intermediate transfer belt 30 onto the recording material 12. The toner that has not been secondarily transferred from the intermediate transfer belt 30 to the recording material 12 by the secondary transfer roller 29 is charged by the cleaning brush 35. The toner charged by the cleaning brush 35 is reverse-transferred to the photosensitive drum 22. The toner reverse-transferred to the photosensitive drum 22 is collected by the collection blade 27 into the waste toner box 28.

[0017] The recording material 12 onto which the image has been secondarily transferred is heated and fixed by a pair of fixing rollers 16, 17 serving as fixing means. The recording material 12 onto which the image has been fixed is discharged onto a paper discharge tray.

[0018] The basis weight detection unit 50 includes an ultrasonic transmitter 51 that transmits ultrasonic waves and an ultrasonic receiver 52 that receives ultrasonic waves, and detects the type of the recording material 12 by irradiating ultrasonic waves to the recording material 12 being conveyed. A main control unit 200, which will be described later, controls the image formation conditions based on the value of the detection result by the basis weight detection unit 50, or the basis weight of the recording material 12, or the type of the recording material 12. The image formation conditions are, for example, a target temperature of a heater provided in the fixing means, a secondary transfer bias applied to the secondary transfer roller 29, etc.

[0019] [Function block diagram] 2 is a diagram showing functional blocks in a main control unit 200, which is, for example, a CPU, and hardware 220. The main control unit 200 has the following functions: feed motor excitation switching means 201, fixing motor excitation switching means 202, ultrasonic transmission timing decision means 203, ultrasonic transmission control means 204, ultrasonic reception control means 205, ultrasonic reception result storage means 206, basis weight determination means 207, and system timer 208. The feed motor 221 as a first driving means, the fixing motor 222 as a second driving means, the pickup roller 13, the transport roller 14, the fixing roller 15, and the basis weight detection unit 50 indicate hardware controlled by the main control unit 200.

[0020] The sheet feed motor excitation switching means 201 measures the elapsed time with a system timer 208, and switches excitation at predetermined intervals stored in a memory (not shown), thereby driving a sheet feed motor 221 as a driving means. Similarly, the fixing motor excitation switching means 202 measures the elapsed time with a system timer 208, and switches excitation at predetermined intervals stored in a memory (not shown), thereby driving a fixing motor 222 as a driving means.

[0021] The ultrasonic transmission timing decision means 203 decides the timing at which the ultrasonic transmission control means 204 instructs the ultrasonic transmission unit 51 to transmit ultrasonic waves, based on the time until the excitation of the paper feed motor 221 or the fixing motor 222 is switched to the next phase.

[0022] The ultrasonic transmission control means 204 measures the elapsed time with the system timer 208, and instructs the ultrasonic transmission unit 51 to transmit ultrasonic waves at a predetermined frequency at the timing determined by the ultrasonic transmission timing determination means 203. The ultrasonic reception control means 205 measures the elapsed time with the system timer 208, and when a predetermined time has elapsed since the ultrasonic transmission control means 204 outputted ultrasonic waves, receives ultrasonic data from the ultrasonic reception unit 52 and stores it in the ultrasonic reception result storage means 206. The basis weight determination means 207 determines the type of recording material 12 or calculates the basis weight of the recording material 12 based on the ultrasonic data stored in the ultrasonic reception result storage means 206.

[0023] [Basis weight detection unit] FIG. 3(a) is a diagram showing the basis weight detection unit 50. The main control unit 200 generates a drive signal 300 by the ultrasonic transmission control means 204 and outputs it to the amplifier 303. The signal level (voltage value) of the drive signal 300 is amplified by the amplifier 303. The amplified drive signal 304 is output to the transmission unit 305. In response to the drive signal 304, the transmission unit 305 outputs ultrasonic waves. In this embodiment, the frequency of the ultrasonic waves (the drive frequency of the transmission unit 305) is set to 40 KHz as an example. However, this is not limited to this, and the frequency of the ultrasonic waves can be set according to the configuration of the transmission unit 305 and the reception unit 306, the accuracy of the basis weight discrimination to be obtained, and the like.

[0024] The receiving unit 306 receives the ultrasonic waves transmitted from the transmitting unit 305 and transmitted through the recording material 12, and outputs a signal 307 indicating the intensity of the received ultrasonic waves to an amplifier 308. The signal level (voltage value) of the signal 307 is amplified by the amplifier 308. The amplified signal 309 is output to a filter 310. The filter 310 removes noise from the signal 309, and outputs a signal 313 to the ultrasonic reception control means 205 of the main control unit 200.

[0025] [Ultrasonic transmission and reception] 3(b) shows the waveform of a signal 313 received by the ultrasonic receiving unit 52 when an ultrasonic wave of 40 KHz is irradiated from the ultrasonic transmitting unit 51 to the recording material 12. The vertical axis represents the output voltage, and the horizontal axis represents the time.

[0026] The main control unit 200 outputs the drive signal 300 at 40 KHz (320). Then, after outputting three cycles of the drive signal 300, it stops the drive signal 300 (321). The transmission unit 305 irradiates ultrasonic waves in response to the drive signal 300. The main control unit 200 starts sampling the signal 313 (322) after a predetermined fixed time has elapsed from the time point (320) when the drive signal 300 is output to the ultrasonic transmission unit 51. The main control unit 200 stops sampling (323) after a fixed time has elapsed since starting sampling (322).

[0027] In this embodiment, in order to sample the fifth wave of signal 313, the period until sampling of signal 313 starts is set to 160 μsec, and the period for performing sampling is set to 15 μsec. This period is a value obtained experimentally according to the distance between ultrasonic transmission unit 51 and ultrasonic reception unit 52, etc. The time it takes for ultrasonic waves irradiated from transmission unit 305 to reach reception unit 306 varies depending on the distance between transmission unit 305 and reception unit 306, the surrounding environment (temperature, humidity), etc., so an appropriate value may be set.

[0028] FIG. 3(c) is an enlarged view of the signal 313 in the sampling section (section 322-323). The ultrasonic reception control means 205 of the main control unit 200 discretely samples the signal 313. The ultrasonic reception control means 205 stores the peak value ΔP from the sampled values ​​in the ultrasonic reception result storage means 206 (330). Note that the amplitude of the waveform of the ultrasonic waves transmitted through the recording material 12 attenuates according to the basis weight of the recording material 12 (the level (voltage value) of the signal 313 decreases). For example, in the case of a recording material 12 with a relatively small basis weight such as thin paper, the attenuation of the signal 313 decreases. That is, the peak value of the ultrasonic waves increases. On the other hand, in the case of a recording material 12 with a relatively large basis weight such as thick paper, the attenuation of the signal 313 increases. That is, the peak value of the ultrasonic waves decreases. In this way, in order to detect the amplitude of the waveform of the ultrasonic waves transmitted through the recording material 12, the ultrasonic reception control means 205 detects the peak value of the signal 313. Then, it becomes possible to detect the basis weight of the recording material 12 according to the peak value, or it becomes possible to detect the type of the recording material 12 according to the peak value.

[0029] In this embodiment, the sampling interval is set to 0.4 μsec. This interval is a value obtained through experimentation so as to be able to detect the basis weight of the recording material 12, and may be set to an appropriate value depending on the configuration of the basis weight detection unit 50, etc.

[0030] [Discrimination of recording material 12] Fig. 4 is a diagram showing an overview of the operation for determining the basis weight of the recording material 12. Fig. 4(a) shows the value output from the registration sensor 111 depending on the presence or absence of the recording material 12. Fig. 4(b) shows the section (secondary transfer section) in which the recording material 12 passes through the secondary transfer roller 29. Fig. 4(c) shows the section (basis weight detection section) in which basis weight detection of the recording material 12 is performed. Fig. 4(d) shows the timing in the basis weight detection section when the main control unit 200 detects the peak value described in Fig. 3.

[0031] After the leading edge of the recording material 12 reaches the secondary transfer roller 29, the main control unit 200 starts detecting the basis weight of the recording material 12 (400). The basis weight of the recording material 12 varies depending on which position on the recording material 12 is detected, due to variations in the basis weight of the recording material 12, and other factors. Therefore, the main control unit 200 takes into account the variations within the recording material 12 and performs basis weight detection at multiple points on the recording material 12. By detecting at multiple points, the effects of variations can be suppressed.

[0032] The main control unit 200 outputs the drive signal 300 by the ultrasonic transmission control unit 204, and detects the peak value of the signal 313 by the ultrasonic reception control means 205 (401, 404). After detecting the peak value, the main control unit 200 waits until the time required for the ultrasonic waves transmitted from the transmission unit 305 to attenuate has elapsed. Then, after the ultrasonic waves have attenuated, the drive signal 300 is output again by the ultrasonic transmission control unit 204, and the peak value of the signal 313 is detected by the ultrasonic reception control means 205 (402). In this embodiment, the time required for the ultrasonic waves to attenuate is set to 5 msec. The time required for the ultrasonic waves to attenuate is a value obtained experimentally, and can be set appropriately depending on the configuration of the basis weight detection unit 50, the frequency of the drive signal 300, the surrounding environment (temperature, humidity), and the like.

[0033] When the registration sensor 111 detects the rear end of the recording material 12, the main control unit 200 ends detection by the basis weight detection unit 50 (403). Then, the basis weight determination means 207 calculates the average value of the detected peak values ​​and determines the basis weight of the recording material 12 from the average value of the peak values.

[0034] A memory (not shown) of the main control unit 200 stores information on the fixing temperature, which is set according to the basis weight of the recording material 12. The fixing temperature is set according to the basis weight of the recording material 12 determined by basis weight determination means 207. For example, in the case of a recording material 12 with a small basis weight such as thin paper, the fixing temperature can be set low to reduce the required power.

[0035] [Motor excitation switching and basis weight detection] 5 is a diagram showing the timing when the detection timing (404) of the peak value explained in FIG. 4 overlaps with the excitation switching timing of the motor. The sheet feed motor excitation switching means 201 switches the excitation of the sheet feed motor 221 at regular time intervals (500, 501). Similarly, the fixing motor excitation switching means 202 switches the excitation of the fixing motor 222 at regular time intervals (502, 503). The motor excitation switching interval is determined by the configuration of the motor and the configuration of the gears for transmitting the drive from the motor to the conveying rollers. In this embodiment, the excitation switching interval of the sheet feed motor 221 is 510 μsec, and the excitation switching interval of the fixing motor 222 is 520 μsec.

[0036] The main control unit 200 switches the excitation of the feed motor 221 at 510 μsec intervals (500, 501), and switches the excitation of the fixing motor 502 at 520 μsec intervals (502, 503). The main control unit 200 starts detecting the basis weight of the recording material 12 after the leading edge of the recording material 12 reaches the secondary transfer roller 29. In order to detect the peak value, it starts driving the drive signal 300 (504). When 160 μsec has elapsed since the start of driving the drive signal 300, it is time to start sampling the signal 313 (505).

[0037] However, because the main control unit 200 is in the process of switching the excitation of the sheet feed motor 221 (506), it cannot start sampling of the signal 313 until the excitation switching process is completed (507). If the motor excitation switching process and the sampling process of the signal 313 overlap, it may not be possible to detect the peak value 508 of the signal 313. As a result, the number of peak values ​​that the main control unit 200 can detect while conveying one sheet of the recording material 12 decreases, and the detection accuracy of the basis weight of the recording material 12 may decrease.

[0038] 6 is a diagram showing the timing of motor excitation switching and basis weight detection in this embodiment. The main control unit 200 determines whether to output the drive signal 300 by comparing the time until excitation switching of the paper feed motor 221 and the fixing motor 222 is performed with the time from outputting the ultrasonic wave to detecting the peak value.

[0039] At the timing (600) when the excitation switching of the paper feed motor 221 is completed, the main control unit 200 calculates the time (605) until the next excitation switching of the paper feed motor 221 and the time (606) until the next excitation switching of the fixing motor 222. Then, it compares this with the time (609) from when the ultrasonic wave is output until the peak value is detected.

[0040] Here, the time (606) from the timing (600) when the excitation switching of the paper feed motor 221 is completed to the switching of the excitation of the fixing motor 222 is shorter than the time (609) from the output of the ultrasonic wave to the detection of the peak value. Therefore, it is determined that there is a possibility that the excitation switching process of the fixing motor 222 and the process of detecting the peak value overlap. Therefore, it is determined that the drive signal 300 is not to be output at the timing (600) when the excitation switching of the paper feed motor 221 is completed.

[0041] Next, at the timing (602) when the excitation switching process of the fixing motor 222 is completed, the main control unit 200 calculates the time (607) until the next excitation switching of the paper feed motor 221 and the time (608) until the next excitation switching of the fixing motor 222. Then, it compares this with the time (609) from when the ultrasonic wave is output until the peak value is detected.

[0042] Here, the time (607) from the timing (602) when the excitation switching of the fixing motor 222 is completed to the switching of the excitation of the paper feed motor 221 is longer than the time (609) from the output of the ultrasonic wave to the detection of the peak value. Also, the time (608) from the timing (602) when the excitation switching of the fixing motor 222 is completed to the switching of the excitation of the fixing motor 222 is longer than the time (609) from the output of the ultrasonic wave to the detection of the peak value. Therefore, it is determined that the excitation switching process of the paper feed motor 221 or the excitation switching process of the fixing motor 222 does not overlap with the process of detecting the peak value. Therefore, at the timing (602) when the excitation switching of the fixing motor 222 is completed, the drive signal 300 for transmitting ultrasonic waves is output.

[0043] In this way, the timing when the sheet feed motor 221 or the fixing motor 222 next switches excitation is compared with the timing from when ultrasonic waves are output to when peak value detection is completed. This makes it possible to determine not to output ultrasonic waves when there is a possibility that the timing of switching excitation of the sheet feed motor 221 or the fixing motor 222 and the timing of detecting the peak value overlap. This makes it possible to prevent ultrasonic waves from being emitted at a timing when the ultrasonic peak value cannot be detected due to the overlap. Also, when there is no possibility that the timing of switching excitation of the sheet feed motor 221 or the fixing motor 222 and the timing of detecting the peak value overlap, it is possible to determine that ultrasonic waves are output. This makes it possible to shift the timing of switching excitation and the timing of detecting the ultrasonic peak value, thereby making it possible to detect the ultrasonic peak value.

[0044] 7 is a flowchart for determining whether or not to perform basis weight detection when the excitation switching of the motors is completed. In S701, the main control unit 200 determines whether or not it is time to switch the excitation of the paper feed motor 221 or the fixing motor 222. If it is determined in S701 that it is time to switch the excitation of the paper feed motor 221 or the fixing motor 222, the main control unit 200 executes the excitation switching process of the paper feed motor 221 or the fixing motor 222 in S702.

[0045] In S703, the main control unit 200 judges whether 5 msec has passed since the previous sampling of the ultrasonic peak value. If not, the basis weight detection is not performed and the process waits until the next excitation switching timing of the paper feed motor 221 or the fixing motor 222. If 5 msec or more has passed since the previous sampling of the ultrasonic peak value, in S704, the main control unit 200 compares the time until the next excitation switching of the paper feed motor 221 with the time from outputting the ultrasonic wave to detecting the peak value. If the time until the next excitation switching of the paper feed motor 221 is longer than the time from outputting the ultrasonic wave to detecting the peak value, the process proceeds to S705.

[0046] In S705, the main control unit 200 compares the time until the next excitation switching of the fixing motor 222 with the time from outputting the ultrasonic wave to detecting the peak value. If the time until the next excitation switching of the fixing motor 222 is longer than the time from outputting the ultrasonic wave to detecting the peak value, the process proceeds to S706. In S706, the main control unit 200 outputs the drive signal 300 to emit the ultrasonic wave.

[0047] In S707, the main control unit 200 judges whether 160 μsec has elapsed since the drive signal 300 was output. If so, in S708, the main control unit 200 samples the signal 313 and acquires the peak value. In S709, the main control unit 200 stores the detected peak value in the ultrasonic reception result storage means 206. In S710, the main control unit 200 judges whether the trailing end of the recording material 12 has passed the registration sensor 111. If the trailing end of the recording material 12 has not passed the registration sensor 111, the process returns to S701. If the trailing end of the recording material 12 has passed the registration sensor 111, in S711, the main control unit 200 determines the basis weight of the recording material 12 based on the average value of the peak values ​​stored in the ultrasonic reception result storage means 206.

[0048] In this way, if there is a possibility that the excitation switching timing of the paper feed motor 221 or the fixing motor 222 and the detection timing of the peak value overlap, it is possible to determine not to output ultrasonic waves. Therefore, it is possible to prevent ultrasonic waves from being emitted at a timing where the ultrasonic peak value cannot be detected due to an overlap. Also, if there is no possibility that the excitation switching timing of the paper feed motor 221 or the fixing motor 222 and the detection timing of the peak value overlap, it is possible to determine that ultrasonic waves are output. Therefore, it is possible to shift the excitation switching timing and the detection timing of the ultrasonic peak value, and it is possible to detect the ultrasonic peak value.

[0049] Here, as an example, a method for determining the basis weight of the recording material 12 when the rear end of the recording material 12 passes through the registration sensor 111 has been described. However, the present invention is not limited to this, and for example, a method for determining the basis weight of the recording material 12 when the number of acquired peak values ​​reaches a certain number or more may be used. Also, a method for determining the basis weight using the peak value of the fifth wave of the signal 313 has been described. However, the present invention is not limited to this, and for example, a method for determining the basis weight using multiple peak values, such as determining the basis weight using the peak values ​​of the fourth and fifth waves, may be used.

[0050] Second Embodiment In the first embodiment, a case was described in which the time until the excitation of the motor is switched is longer than the time until the peak value is detected after the ultrasonic wave is output. In this embodiment, a case is described in which the time until the excitation of the motor is switched is shorter than the time until the peak value is detected after the ultrasonic wave is output. Note that detailed description of the same configuration as the first embodiment, such as the image forming apparatus, will be omitted in this embodiment.

[0051] 8 is a diagram showing the timing of motor excitation switching and basis weight detection in this embodiment. The main control unit 200 determines whether to output the drive signal 300 by comparing the time until excitation switching of the paper feed motor 221 and the fixing motor 222 is performed with the time from outputting the ultrasonic wave to detecting the peak value.

[0052] The main control unit 200 performs the excitation switching process of the paper feed motor 221 at intervals of 190 μsec (800), and the excitation switching process of the fixing motor 222 at intervals of 150 μsec (801). At the timing (802) when the excitation switching of the paper feed motor 221 is completed, the main control unit 200 calculates the time (804) until the next excitation switching process of the paper feed motor 221 is completed, and the time (808) until the next excitation switching process of the fixing motor 222 is completed. Then, it compares this with the time (809) from when the ultrasonic waves are output to when peak value detection starts.

[0053] Here, the time (804) from the timing (802) when the excitation switching of the paper feed motor 221 is completed to the completion of the excitation switching process of the paper feed motor 221 is shorter than the time (809) from the output of the ultrasonic wave to the start of the detection of the peak value. Also, the time (808) from the timing (802) when the excitation switching of the paper feed motor 221 is completed to the completion of the excitation switching process of the fixing motor 222 is shorter than the time (809) from the output of the ultrasonic wave to the start of the detection of the peak value. Therefore, it is determined that the excitation switching process of the paper feed motor 221 or the excitation switching process of the fixing motor 222 does not overlap with the process of detecting the peak value. Therefore, at the timing (802) when the excitation switching of the paper feed motor 221 is completed, the drive signal 300 for transmitting the ultrasonic wave is output.

[0054] In this way, the timing when the sheet feed motor 221 or the fixing motor 222 next switches excitation is compared with the timing from when ultrasonic waves are output to when peak value detection is completed. This makes it possible to determine not to output ultrasonic waves when there is a possibility that the timing of switching excitation of the sheet feed motor 221 or the fixing motor 222 and the timing of detecting the peak value overlap. This makes it possible to prevent ultrasonic waves from being emitted at a timing when the ultrasonic peak value cannot be detected due to the overlap. Also, when there is no possibility that the timing of switching excitation of the sheet feed motor 221 or the fixing motor 222 and the timing of detecting the peak value overlap, it is possible to determine that ultrasonic waves are output. This makes it possible to shift the timing of switching excitation and the timing of detecting the ultrasonic peak value, thereby making it possible to detect the ultrasonic peak value.

[0055] 9 is a flowchart for determining whether or not to perform basis weight detection when the excitation switching of the motors is completed. In S901, the main control unit 200 determines whether or not it is time to switch the excitation of the paper feed motor 221 or the fixing motor 222. If it is determined in S901 that it is time to switch the excitation of the paper feed motor 221 or the fixing motor 222, the main control unit 200 executes the excitation switching process of the paper feed motor 221 or the fixing motor 222 in S902.

[0056] In S903, the main control unit 200 judges whether 5 msec has passed since the previous sampling of the ultrasonic peak value. If not, the basis weight detection is not performed and the process waits until the next excitation switching timing of the paper feed motor 221 or the fixing motor 222. If 5 msec or more has passed since the previous sampling of the ultrasonic peak value, in S904, the main control unit 200 compares the time until the next excitation switching of the paper feed motor 221 with the time from outputting ultrasonic waves to detecting the peak value. If the time until the next excitation switching of the paper feed motor 221 is longer than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S906. If the time until the next excitation switching of the paper feed motor 221 is shorter than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S905.

[0057] In S905, the main control unit 200 compares the time until the next excitation switching completion of the paper feed motor 221 with the time from outputting ultrasonic waves to detecting the peak value. If the time until the next excitation switching completion of the paper feed motor 221 is shorter than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S906.

[0058] In S906, the main control unit 200 compares the time until the next excitation switching of the fixing motor 222 with the time from outputting ultrasonic waves to detecting the peak value. If the time until the next excitation switching of the fixing motor 222 is longer than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S908. If the time until the next excitation switching of the fixing motor 222 is shorter than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S907.

[0059] In S907, the main control unit 200 compares the time until the next excitation switching of the fixing motor 222 is completed with the time from outputting ultrasonic waves to detecting the peak value. If the time until the next excitation switching of the fixing motor 2212 is completed is shorter than the time from outputting ultrasonic waves to detecting the peak value, the process proceeds to S908.

[0060] In S908, the main control unit 200 outputs the drive signal 300 to emit ultrasonic waves. In S909, the main control unit 200 determines whether it is time to switch the excitation of the paper feed motor 221 or the fixing motor 222. If it is time to switch, in S910, the main control unit 200 switches the excitation of the paper feed motor 221 or the fixing motor 222.

[0061] In S911, the main control unit 200 judges whether 160 μsec has elapsed since the drive signal 300 was output. If so, in S912, the main control unit 200 samples the signal 313 and acquires the peak value. In S913, the main control unit 200 stores the detected peak value in the ultrasonic reception result storage means 206. In S914, the main control unit 200 judges whether the trailing end of the recording material 12 has passed the registration sensor 111. If the trailing end of the recording material 12 has not passed the registration sensor 111, the process returns to S901. If the trailing end of the recording material 12 has passed the registration sensor 111, in S915, the main control unit 200 determines the basis weight of the recording material 12 based on the average value of the peak values ​​stored in the ultrasonic reception result storage means 206.

[0062] In this way, if there is a possibility that the excitation switching timing of the paper feed motor 221 or the fixing motor 222 and the detection timing of the peak value overlap, it is possible to determine not to output ultrasonic waves. Therefore, it is possible to prevent ultrasonic waves from being emitted at a timing where the ultrasonic peak value cannot be detected due to an overlap. Also, if there is no possibility that the excitation switching timing of the paper feed motor 221 or the fixing motor 222 and the detection timing of the peak value overlap, it is possible to determine that ultrasonic waves are output. Therefore, it is possible to shift the excitation switching timing and the detection timing of the ultrasonic peak value, and it is possible to detect the ultrasonic peak value.

[0063] (Third embodiment) In this embodiment, a method for changing the motor excitation switching time (motor speed) is described when the time until the motor excitation switching is shorter than the time from outputting ultrasonic waves to detecting the peak value. Note that detailed description of the same configuration as the first and second embodiments, such as the image forming apparatus, is omitted in this embodiment.

[0064] In this embodiment, the main control unit 200 changes the excitation switching interval of the fixing motor 222 during the period when the pair of fixing rollers 16, 17 are not transporting the recording material 12. Then, the timing of the excitation switching process of the paper feed motor 221 and the excitation switching process of the fixing motor 222 are coordinated to detect the basis weight of the recording material 12. With this method, the number of peak values ​​that can be obtained from one sheet of recording material 12 is reduced, so if there are not enough peak values ​​to determine the basis weight, it is necessary to perform basis weight detection on multiple sheets of recording material 12. In this embodiment, the number of sheets of recording material 12 required to determine the basis weight is two.

[0065] The main control unit 200 repeats the same operation for the succeeding recording material 12, and when a sufficient number of peak values ​​for determining the basis weight are acquired, determines the basis weight of the recording material 12. In this embodiment, the excitation switching interval of the paper feed motor 221 during the printing operation is set to 200 μsec, and the excitation switching interval of the fixing motor 222 is set to 150 μsec.

[0066] 10 is a diagram showing the timing of motor excitation switching and basis weight detection in this embodiment. An operation of changing the excitation switching interval of the fixing motor 222 to 200 μsec during a period when the pair of fixing rollers 16 and 17 is not conveying the recording material 12 will be described.

[0067] The main control unit 200 performs excitation switching of the fixing motor 222 (1101) at the timing (1100) when excitation switching of the paper feed motor 221 is completed. The main control unit 200 changes the excitation switching interval of the fixing motor 222 to 200 μsec at the timing (1101) when excitation switching of the fixing motor 222 is completed. As a result, it is determined that the motor excitation switching process and the peak value detection process do not overlap, and the drive signal 300 for emitting ultrasonic waves is output.

[0068] In this way, by synchronizing the timing of excitation switching between the paper feed motor 221 and the fixing motor 222, the timing of excitation switching and the timing of detecting the peak value of the ultrasonic waves can be shifted, and the peak value of the ultrasonic waves can be detected.

[0069] 11 is a flowchart showing a method for synchronizing the excitation switching of the paper feed motor 221 and the excitation switching of the fixing motor 222. In S1101, the main control unit 200 determines whether or not the leading edge of the recording material 12 has reached the secondary transfer roller 29. When it has reached the leading edge, in S1102, the main control unit 200 changes the excitation switching interval of the fixing motor 222 to 200 μsec.

[0070] In S1103, the main control unit 200 judges whether it is time to switch excitation of the paper feed motor 221. When it is time to switch, in S1104 the main control unit 200 executes excitation switching processing for the paper feed motor 221. In S1105, the main control unit 200 executes excitation switching processing for the fixing motor 222. In S1106, the main control unit 200 judges whether 5 msec has elapsed since the previous sampling of the ultrasonic peak value. If not, basis weight detection is not performed.

[0071] If 5 msec or more has passed since the previous sampling of the ultrasonic peak value, in S1107 the main control unit 200 outputs the drive signal 300 to transmit ultrasonic waves. In S1108, the main control unit 200 judges whether 160 μsec has passed since the output of the drive signal 300. If so, in S1109 the main control unit 200 performs sampling processing of the signal 313 and acquires the peak value. In S1110, the main control unit 200 stores the detected peak value in the ultrasonic reception result storage means 206.

[0072] In S1111, the main control unit 200 determines whether or not the trailing edge of the recording material 12 has passed the registration sensor 111. If the trailing edge of the recording material 12 has not passed the registration sensor 111, the process returns to S1103. If the trailing edge of the recording material 12 has passed the registration sensor 111, in S1112, the main control unit 200 changes the excitation switching interval of the fixing motor 222 to 150 μsec.

[0073] In S1113, the main control unit 200 determines whether or not printing has been performed on two sheets of the recording material 12. If two sheets of the recording material 12 have not been printed, the process returns to S1101. If two sheets of the recording material 12 have been printed, in S1114, the main control unit 200 determines the basis weight of the recording material 12 based on the average value of the peak values ​​stored in the ultrasonic reception result storage means 206.

[0074] In this way, by synchronizing the timing of excitation switching between the paper feed motor 221 and the fixing motor 222, the timing of excitation switching and the timing of detecting the peak value of the ultrasonic waves can be shifted, and the peak value of the ultrasonic waves can be detected.

[0075] In the present embodiment, a method for changing the excitation switching interval of the fixing motor 222 has been described. However, the present invention is not limited to this, and for example, a method for changing the excitation switching interval of the paper feed motor 221 may be adopted. Also, a method for changing the excitation switching intervals of both the paper feed motor 221 and the fixing motor 222 may be adopted.

[0076] In the present embodiment, the method of determining the timing of determining the basis weight based on the number of printed sheets has been described. However, the present invention is not limited to this, and for example, a method of counting the number of acquired peak values ​​and determining the basis weight when the number of peak values ​​reaches a certain number (e.g., 300) may be adopted.

[0077] Also, in this embodiment, a method for changing the excitation switching interval of the fixing motor 222 at a timing when the fixing roller pair 16, 17 is not transporting the recording material 12 has been described. However, this is not limited to this, and for example, a method for slowing down the speed of the entire print operation may be adopted in order to change the excitation switching interval of the fixing motor 222 at a timing when the fixing roller pair 16, 17 is transporting the recording material 12. [Explanation of symbols]

[0078] 50 Basis weight detection unit 200 Main control unit

Claims

1. A conveying means for conveying a recording material; an image forming means for forming an image on a recording material; A fixing means for fixing an image on a recording material; a first driving means for driving the conveying means; A second driving means for driving the fixing means; A transmitting means for transmitting ultrasonic waves; A receiving means for receiving an ultrasonic wave; and a control means for controlling a timing at which the ultrasonic wave is emitted from the transmitting means, The image forming apparatus is characterized in that the control means causes the transmitting means to transmit ultrasonic waves so that the excitation switching timing of the first driving means and the timing of acquiring the value of the ultrasonic waves received by the receiving means do not overlap.

2. 2. The image forming apparatus according to claim 1, wherein the control means controls image forming conditions of the image forming means based on the result of acquiring the value of the ultrasonic wave.

3. 2. The image forming apparatus according to claim 1, wherein the control means determines the basis weight of the recording material or determines the type of the recording material based on the result of acquiring the value of the ultrasonic wave.

4. 2. The image forming apparatus according to claim 1, wherein the time from switching the excitation of the first driving means to switching the next excitation is longer than the time from transmitting the ultrasonic waves to acquiring the value of the received ultrasonic waves.

5. 2. The image forming apparatus according to claim 1, wherein the time from switching the excitation of the first driving means to switching the next excitation is shorter than the time from transmitting the ultrasonic waves to acquiring the value of the received ultrasonic waves.

6. A conveying means for conveying a recording material; an image forming means for forming an image on a recording material; A fixing means for fixing an image on a recording material; a first driving means for driving the conveying means; A second driving means for driving the fixing means; A transmitting means for transmitting ultrasonic waves; A receiving means for receiving an ultrasonic wave; and a control means for controlling a timing at which the ultrasonic wave is emitted from the transmitting means, The image forming apparatus is characterized in that the control means causes the transmitting means to transmit ultrasonic waves so that the excitation switching timing of the second driving means and the timing of acquiring the value of the ultrasonic waves received by the receiving means do not overlap.

7. 7. The image forming apparatus according to claim 6, wherein the control means controls image forming conditions of the image forming means based on the result of acquiring the value of the ultrasonic wave.

8. 7. The image forming apparatus according to claim 6, wherein the control means determines the basis weight of the recording material or the type of the recording material based on the result of acquiring the value of the ultrasonic wave.

9. 7. The image forming apparatus according to claim 6, wherein the time from switching the excitation of the second driving means to switching the next excitation is longer than the time from transmitting the ultrasonic waves to acquiring the value of the received ultrasonic waves.

10. 7. The image forming apparatus according to claim 6, wherein the time from switching the excitation of the second driving means to switching the next excitation is shorter than the time from transmitting the ultrasonic waves to acquiring the value of the received ultrasonic waves.

Images