JP2022015537A - Recording material detection device and image forming device - Google Patents

Abstract

To improve detection accuracy of basis weight of a recording material.SOLUTION: A recording material detection device includes: a transmission part 31a for transmitting ultrasonic waves; a reception part 31b for receiving the ultrasonic waves transmitted from the transmission part 31a; and a control part 10 for detecting the basis weight of a recording material P or the type of the recording material P, based on a peak value Vp according to the ultrasonic waves received by the reception part 31b in a first state where the recording material P is between the transmission part 31a and the reception part 31b. The control part 10 measures ultrasonic wave arrival time Ta which is from the start of the transmission of the ultrasonic waves from the transmission part 31a to the reception of the ultrasonic waves by the reception part 31b, and corrects the peak value Vp based on the ultrasonic wave arrival time.SELECTED DRAWING: Figure 1

Description

The present invention relates to a recording material detection device and an image forming device, and more particularly to an image forming device provided with a basis weight sensor using ultrasonic waves.

There are various types of image forming devices such as an electrophotographic method and an inkjet method for forming an image based on an image signal. In such an image forming apparatus, various recording materials are used, and there are recording materials having various characteristics such as size, basis weight (g / m ² ), and surface properties (for example, unevenness). In order to perform optimum image formation for these recording materials, the conventional image forming apparatus is provided with a recording material discriminating device for discriminating the type of recording material (hereinafter referred to as paper type) inside the image forming apparatus. There is. For example, a method has been proposed in which an ultrasonic wave is emitted from a recording material and the basis weight of the recording material is detected by using the reception level of the ultrasonic wave transmitted through the recording material to determine the paper type (for example, a patent). See Document 1 and Patent Document 2). Also, in general, the air pressure or air temperature around the basis weight sensor changes while the image is being formed on the recording material. Therefore, a method of accurately detecting the basis weight of the recording material by further using the reception level that directly reaches the ultrasonic wave reception sensor in another environment has been proposed (see, for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2004-107030 Japanese Unexamined Patent Publication No. 2009-292549 JP-A-2015-171952

However, even if the basis weight of the recording material is the same, the air permeability, which is the ease of passing air, differs depending on the recording material, so the reception level of ultrasonic waves passing through the recording material differs, and the detection accuracy deteriorates. There are challenges.

The present invention has been made under such circumstances, and an object of the present invention is to improve the detection accuracy of the basis weight of the recording material.

In order to solve the above-mentioned problems, the present invention includes the following configurations.

(1) The receiving means in the first state where there is a recording material between the transmitting means for transmitting ultrasonic waves, the receiving means for receiving the ultrasonic waves transmitted from the transmitting means, and the transmitting means and the receiving means. A recording material detection device including a detection means for detecting the basis weight of the recording material or the type of the recording material based on the first voltage corresponding to the ultrasonic wave received by the means, wherein the transmission is performed. The first voltage is corrected based on the measuring means for measuring the time from the start of transmission of the ultrasonic wave from the means to the reception of the ultrasonic wave by the receiving means and the time measured by the measuring means. A recording material detection device characterized by comprising a correction means.

(2) An image forming means for forming an image on a recording material, a transmitting means for transmitting ultrasonic waves, a receiving means for receiving ultrasonic waves transmitted from the transmitting means, and transmission of ultrasonic waves from the transmitting means are started. There is a recording material between the transmitting means and the receiving means based on the measuring means for measuring the time from the reception to receiving the ultrasonic wave by the receiving means and the time measured by the measuring means. To form an image by the image forming means based on the correction means for correcting the first voltage corresponding to the ultrasonic wave received by the receiving means in the first state and the corrected first voltage. An image forming apparatus comprising: a control means for controlling an image forming condition.

According to the present invention, it is possible to improve the detection accuracy of the basis weight of the recording material.

Schematic configuration diagram of the image forming apparatus of Example 1, schematic configuration diagram of the recording material discrimination apparatus A time chart showing the operation of the recording material discrimination device of the first embodiment, and a graph showing the relationship between the basis weight and the TR value. A time chart showing the operation of the recording material discrimination device of the first embodiment, and a graph showing the relationship between the basis weight and the TRS value. A flowchart showing the detection process of the basis weight of the recording material of the first embodiment. Time chart showing the operation of the recording material discrimination device of the second embodiment A flowchart showing the detection process of the basis weight of the recording material of the second embodiment.

Hereinafter, preferred embodiments of the present invention will be exemplified in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described below should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited to them.

In Example 1, a method of correcting the influence of the acoustic impedance (density × sound velocity) of the recording material P by using the arrival time of the ultrasonic wave for the detection of the basis weight of the recording material P using ultrasonic waves will be described. do.

<Summary explanation of the configuration of the image forming apparatus>
The electrophotographic image forming apparatus applicable in the first embodiment will be outlined. FIG. 1A is a schematic configuration diagram of an image forming apparatus 1 including an image forming unit 50 which is an example of an image forming means in which an intermediate transfer belt 17 is adopted and a plurality of members involved in image forming are arranged in parallel. ..

The image forming apparatus 1 is a tandem type color laser beam printer, and is colored by superimposing toners which are four color developers of yellow (Y), magenta (M), cyan (C), and black (K). It is configured to output images. The paper cassette 2 which is an example of the paper feeding means stores the recording material P. In the transport path of the recording material P, a paper feed roller 4 for feeding the recording material P from the paper feed cassette 2, a transport roller pair 5 for transporting the recording material P fed from the paper feed cassette 2, and registration (hereinafter referred to as registration). A pair of rollers 6 (referred to as resist) is provided. In the vicinity of the resist roller pair 6, a registration sensor 34, which is an example of a transfer position monitoring means for monitoring the transfer position of the recording material P, is provided. The photosensitive drums 11Y, 11M, 11C, and 11K carry toner of each color. Here, the subscripts Y, M, C, and K representing colors are omitted except when a member having a specific color is described.

The charging roller 12 uniformly charges the photosensitive drum 11 to a predetermined potential. The laser scanner 13 is a laser scanner for four colors and forms an electrostatic latent image on the photosensitive drum 11. The process cartridge 14 visualizes the electrostatic latent image formed on the photosensitive drum 11 and forms a toner image. The developing roller 15 is a roller that sends out the toner in the process cartridge 14 to the photosensitive drum 11. The primary transfer roller 16 sequentially superimposes and transfers the toner image formed on the photosensitive drum 11 onto the intermediate transfer belt 17 (hereinafter referred to as primary transfer), and transfers the color toner image onto the intermediate transfer belt 17. ..

The intermediate transfer belt 17 is driven by the drive roller 18. The secondary transfer roller 19 transfers the toner image transferred on the intermediate transfer belt 17 to the recording material P (hereinafter referred to as secondary transfer). The fuser 20 melts and fixes the unfixed toner image secondarily transferred to the recording material P while transporting the recording material P. The photosensitive drum 11 to the fuser 20 described above constitute an example of the image forming unit 50. The discharge roller 21 discharges the recording material P fixed by the fixing device 20 to the outside of the image forming apparatus 1. Further, in the first embodiment, the paper feed roller 4, the transport roller pair 5, the resist roller pair 6, the drive roller 18, the secondary transfer roller 19, the fuser 20, and the discharge roller 21 arranged in the transport path drive them. An example of the transport means is configured by the configuration including the source (not shown).

(About paper type and image formation conditions)
The recording material discrimination device 30 which is a recording material detecting device detects the characteristics of the basis weight of the recording material P or the type of the recording material P. Here, the paper type and the image formation conditions (secondary transfer conditions, fixing conditions for fixing treatment) will be described. Generally, since the resistance value of the recording material P differs depending on the basis weight of the recording material P, it is necessary to change the secondary transfer conditions for transferring the toner agent according to the paper type having a different basis weight. Further, since the heat capacity of the recording material P differs depending on the basis weight of the recording material P, it is necessary to change the fixing conditions such as the fixing temperature, the fixing time, and the transport speed for fixing the toner agent according to the paper type having a different basis weight. There is. Since there are differences in the characteristics of the basis weight depending on the paper type as described above, optimum image formation can be performed by setting appropriate image formation conditions according to the paper type discriminated by the recording material discriminating device 30.

The control unit 10 which is a control means is equipped with an MPU (not shown) equipped with a CPU (not shown) or the like. Further, the control unit 10 includes a RAM used for data calculation and temporary storage required to control the image forming apparatus 1, a program for controlling the image forming apparatus 1, a ROM for storing various data, and the like. It has a storage unit. The control unit 10 determines the type of the recording material P based on the value detected by the recording material discriminating device 30 (hereinafter referred to as the detected value). Then, the control unit 10 determines the optimum image forming conditions according to the type of the recording material P, and operates the image forming apparatus 1 such as control related to the image forming operation including the control of the drive source related to the transport of the recording material P. Is controlled collectively.

<Configuration and schematic operation explanation of recording material discrimination device 30>
The operation outline of the recording material discrimination apparatus 30 of the first embodiment will be described with reference to the block diagram of FIG. 1 (b). The recording material discrimination device 30 is composed of an ultrasonic sensor 31 which is a basis weight detecting means, a transmission control unit 42, and a reception detection unit 43. The ultrasonic sensor 31 is a basis weight sensor and is composed of a transmitting unit 31a which is a transmitting means for transmitting ultrasonic waves and a receiving unit 31b which is a receiving unit for receiving ultrasonic waves. The recording material P is conveyed between the transmitting unit 31a and the receiving unit 31b. The transmitting unit 31a is an element capable of transmitting, for example, a sound wave having a frequency of 40 kHz in response to an arbitrary signal input. The receiving unit 31b is an element capable of receiving the sound wave transmitted from the transmitting unit 31a, and outputs a received signal which is a voltage corresponding to the sound pressure of the received sound wave.

In the first embodiment, the frequency of the sound wave is set to 40 kHz, but the frequency is not limited to the frequency as long as it can detect the characteristic value of the basis weight of the recording material P. Further, the transmitting unit 31a and the receiving unit 31b are respectively arranged in the vicinity of the transport path of the recording material P so that the sound wave can be received through the recording material P. The transmission control unit 42 is a circuit unit having a function of amplifying a drive signal input from the control unit 10 and driving the transmission unit 31a. The reception detection unit 43 is a circuit unit having a function of amplifying a reception signal input from the reception unit 31b and performing, for example, half-wave rectification. Here, the signal after being amplified by the reception detection unit 43 is referred to as a reception signal. The received signal generated by the reception detection unit 43 is input to the AD port of the control unit 10, and the control unit 10 detects the waveform of the reception signal based on the digital value analog-digitally converted by the AD port, and its peak. Acquire (calculate) the value as the reception level. The value based on the received signal, for example, the peak value of the received signal and the ultrasonic arrival time described later are characteristic values for detecting the basis weight of the recording material P, and as shown in FIG. 1 (b), the control unit 10 Acquires a characteristic value based on the received signal (shown as "acquisition of characteristic value"). Here, although the peak value of the waveform is used as the characteristic value, it is not limited to this as long as it is a characteristic value such as an effective value or an average value that can determine the level of the received signal. Further, as shown in FIG. 1 (b), the control unit 10 detects the basis weight of the recording material P based on the obtained characteristic value (shown as “basis weight detection”).

(Drive signal and received signal)
This will be described with reference to the time chart of FIG. 2 (a). FIG. 2A shows the waveform of the drive signal [V] output by the control unit 10, and FIG. 2A shows the waveform of the reception signal [V] output by the reception detection unit 43. The horizontal axis indicates time (seconds (sec.)). The drive signal is a pulse wave (burst wave) having a fixed period, and as an example, the frequency is 40 kHz and the number of pulses is 2 pulses. The reception signal generated by the reception detection unit 43 has a waveform having a peak value for each half wave of 40 kHz, which is the same as the frequency of the sound wave of the transmission unit 31a, according to the sound pressure of the sound wave received by the reception unit 31b. Further, the number of reception level waveforms exceeds 2 even if the number of pulses of the drive signal is 2 pulses. This is because there is reverberation of the transmitting unit 31a or the receiving unit 31b.

The control unit 10 detects, for example, the second waveform of the received signal and extracts the peak value thereof. At this time, the peak value of the second waveform is detected by detecting the received signal during an arbitrary predetermined time range Tr synchronized with the drive signal. Here, the predetermined time range Tr is calculated and set in advance from the relationship between the distance between the transmitting unit 31a and the receiving unit 31b and the sound wave velocity of the ultrasonic wave. The control unit 10 transmits a drive signal to the transmission control unit 42 while the recording material P is being conveyed between the transmission unit 31a and the reception unit 31b, and while the recording material P is being conveyed, the control unit 10 transmits the peak value of the reception signal. Extract sequentially. When the receiving unit 31b receives ultrasonic waves via the recording material P, the amount of attenuation changes mainly depending on the basis weight of the recording material P. Therefore, by using the change in the reception level, the basis weight of the recording material P can be substantially detected.

<Explanation of position correction of ultrasonic sensors>
Next, the correction of the positional variation between the receiving unit 31b and the transmitting unit 31a will be described. The positions of the receiving unit 31b and the transmitting unit 31a may vary with respect to the recording material P to be detected during the manufacturing process of the ultrasonic sensor 31 or when the ultrasonic sensor 31 is attached to the image forming apparatus 1. When the positions of the receiving unit 31b and the transmitting unit 31a change, the receiving level of the ultrasonic wave reaching the receiving unit 31b changes. Therefore, the peak value Va of the received signal, which is the second voltage when there is no recording material P in the second state, and the received signal, which is the first voltage when the recording material P in the first state is present. The influence of the position is suppressed by calculating the position correction coefficient T in comparison with the peak value Vp of. The position correction coefficient T, which is the second correction value, is a value obtained by dividing the peak value Vp by the peak value Va, and can be expressed by the following equation (1).
T = Vp / Va ... Equation (1)

<Explanation of acoustic impedance correction in the surrounding environment>
Next, a method of correcting the influence of the environment such as the atmospheric pressure and the air temperature around the ultrasonic sensor 31 on the detection accuracy of the basis weight will be described. The density of air changes as the air expands or contracts depending on the atmospheric pressure and air temperature. In general, when the air density is low, ultrasonic waves are difficult to transmit, and conversely, when the air density is high, ultrasonic waves are easy to transmit. That is, the difficulty of sound transmission (acoustic impedance of the surrounding environment) changes depending on the surrounding environment. Since the output of an ultrasonic sensor 31 is generally proportional to the acoustic impedance, changes in the surrounding environment can be detected and corrected from the ratio of reception levels before and after the change in the surrounding environment. Therefore, in the surrounding environment where the atmospheric pressure and air temperature are known in advance such as at the time of shipment from the factory, the peak value of the received signal when there is no recording material P which is the third voltage is set as the reference value Va0, and the storage unit of the control unit 10 ( Remember (not shown). Although atmospheric pressure and / or air temperature are given as an example as those included in the known information regarding the environment in which the recording material discrimination device 30 is installed, other information such as the amount of water in the air may be used. The control unit 10 calculates the ambient environment correction R by comparing the stored reference value Va0 with the peak value Va of the received signal when there is no recording material P immediately before the basis weight detection of the recording material P is performed. This suppresses the influence of the surrounding environment on the detection result of the ultrasonic sensor 31. The ambient environment correction R, which is the third correction value, is a value obtained by dividing the reference value Va0 by the peak value Va, and can be expressed by the following equation (2).
R = Va0 / Va ... Equation (2)

As described above, by calculating the position correction coefficient T and the surrounding environment correction R, it is possible to detect the basis weight in which the position variation and the influence of the environment are suppressed. Here, the product obtained by multiplying the position correction coefficient T and the ambient environment correction R is expressed as the TR value by the following equation (3).
TR = T × R ... Equation (3)

(TR value)
FIG. 2B shows the measured value of the basis weight measured by an electronic scale (measured basis weight) using 22 types of samples of the recording material P and the TR value calculated using the equation (3). It is a graph showing the relationship. In FIG. 2B, the measured basis weight [gsm] is shown on the horizontal axis, and the TR value is shown on the vertical axis. It can be seen that the TR value decreases as the basis weight of the recording material P becomes heavier. This is because the attenuation of the ultrasonic wave transmitted through the recording material P increases as the basis weight becomes heavier. In other words, as the basis weight of the recording material P becomes heavier, the peak value Va of the received signal becomes smaller. Therefore, the control unit 10 can substantially detect the basis weight of the recording material P from the TR value by using the equation of the approximate line X shown in FIG. 2 (b). The control unit 10 also functions as a detection means for detecting the basis weight of the recording material P.

<Explanation regarding correction of the influence of air permeability of recording material>
However, as shown in FIG. 2B, for example, there are recording materials P such as paper type A, paper type B, and paper type C that are far from the approximate line X. This is because the amount of attenuation passing through the recording material P is not determined only by the basis weight of the recording material P. This amount of attenuation changes depending on the difference in the difficulty of transmitting the sound of the recording material P (acoustic impedance of the recording material P). It is known that the acoustic impedance mainly changes depending on the basis weight of the recording material P. However, the acoustic impedance changes depending on the difference in the air permeability (easiness of air passage) of the recording material P even if the basis weight is the same. The air permeability is an index of the ease of passage of air, and is defined by the time required for a certain amount of air to pass through a certain area in the thickness direction of the recording material P at a constant pressure, and is mainly defined by the recording material P. Differences occur depending on the paper type depending on the density and rigidity of the paper. For example, the recording material P (for example, paper type A and paper type B) having a small air permeability (the speed at which air passes through) has a low acoustic impedance, so that the peak value Vp is high. Further, since the recording material P (for example, paper type C) having a high air permeability (the speed at which air passes is slow) has a high acoustic impedance, the peak value Vp becomes a low value. As described above, even if the recording material P has the same basis weight, if the air permeability differs greatly depending on the paper type of the recording material P, the accuracy may not be sufficiently obtained by detecting the basis weight from the approximate line X. ..

Therefore, a method of improving the detection accuracy of the basis weight of the recording material P by correcting the difference in acoustic impedance due to the characteristics of the air permeability of the recording material P will be described using the time chart of FIG. 3A. .. FIG. 3A shows the waveform of the drive signal [V] output by the control unit 10, and FIG. 3A shows the waveform of the reception signal [V] output by the reception detection unit 43 when there is no recording material P. The waveform is shown, and (iii) shows the waveform of the reception signal [V] output by the reception detection unit 43 when the recording material P is present. The horizontal axis indicates time (seconds (sec.)). As described above, the peak value of the received signal when there is no recording material P is Va, and the peak value of the received signal when there is recording material P is Vp.

As described above, the difference in air permeability is the difference in the velocity of air passing through the recording material P. The difference in the speed of the air passing through the recording material P is, that is, the time from transmitting the ultrasonic wave to the recording material P to receiving the ultrasonic wave through the recording material P (hereinafter referred to as ultrasonic arrival time). It's a difference. More specifically, the time from the rise of the drive signal to the peak value of the second received signal is defined as the ultrasonic arrival time. Therefore, by measuring the ultrasonic arrival time, it is possible to correct the difference in acoustic impedance due to the characteristics of the air permeability of the recording material P. The ultrasonic arrival time varies depending on the atmospheric pressure and air temperature environment around the ultrasonic sensor 31. Therefore, the control unit 10 compares the arrival time Ta of the ultrasonic wave when there is no recording material P, which is the second time, with the ultrasonic arrival time Tp when there is the recording material P, which is the first time. Calculate the correction coefficient S. As a result, it is possible to correct the air permeability while suppressing the influence of the surrounding environment. The arrival time correction coefficient S, which is the first correction value, is a value obtained by dividing the ultrasonic arrival time Tp by the ultrasonic arrival time Ta, and can be expressed by the following equation (4).
S = Tp / Ta ... Equation (4)
Here, although the time from the rise of the drive signal to the peak value of the waveform of the received signal is used as the ultrasonic arrival time, the time from the transmission of the ultrasonic wave to the reception of the ultrasonic wave via the recording material P. Any characteristic value corresponding to can be substituted. For example, the ultrasonic arrival time may be from the rise of the drive signal to the rise of the waveform of the received signal.

(TRS value)
With the arrival time correction coefficient S, it is possible to detect the basis weight in which the influence of the air permeability is suppressed. The above-mentioned TR value multiplied by the arrival time correction coefficient S is expressed as a TRS value by the following equation (5).
TRS = T × R × S ... Expression (5)

FIG. 3B is a graph showing the relationship between the measured value of the basis weight measured by the electronic scale and the TRS value calculated using the equation (5) using 22 types of samples of the recording material P. .. In FIG. 2B, the measured basis weight [gsm] is shown on the horizontal axis, and the TRS value is shown on the vertical axis. Similar to FIG. 2B, it can be seen that the TRS value decreases (decreases) as the basis weight of the recording material P increases. Further, it can be seen that the number of paper types greatly deviating from the approximate line Y shown in FIG. 3 (b) is reduced as compared with FIG. 2 (b). For example, the paper type A, the paper type B, and the paper type C are closer to the approximate line in FIG. 3 (b) than in FIG. 2 (b). As described above, by using the equation of the approximate line Y shown in FIG. 3B, the basis weight of the recording material P can be obtained more accurately. It is assumed that the control unit 10 stores information of the function representing the approximation line Y (hereinafter, referred to as the approximation formula Y) in the storage unit in advance. Further, as described above, the control unit 10 also functions as a correction means.

<Flow chart showing the area weight detection process>
FIG. 4 shows a flowchart of the detection process of the detection value of the basis weight of the recording material P of the first embodiment (hereinafter referred to as the basis weight detection value). In step 101 (hereinafter referred to as S) 101, the control unit 10 starts the paper feeding and image forming operations after receiving the print instruction. The recording material P is fed by the paper feed roller 4 and passes through the transport roller pair 5 and then the resist roller pair 6. In S102, the control unit 10 drives the ultrasonic sensor 31 at a timing when the tip of the recording material P does not reach the ultrasonic sensor 31, and there is no recording material P between the transmitting unit 31a and the receiving unit 31b. Start measuring the average value of the basis weight of. Here, the control unit 10 has a timer (not shown) for measuring the passage of time, resets the timer (T = 0) to start the timer, and starts the measurement of the time T.

In S103, the control unit 10 determines whether or not the time T being measured exceeds the predetermined time range Tr by referring to the timer. When the control unit 10 determines in S103 that the time T does not exceed the predetermined time range Tr, the control unit 10 returns the process to S103. As a result, the control unit 10 detects the received signal output from the ultrasonic sensor 31 during the predetermined time range Tr from the start of measurement (S102). When the control unit 10 determines in S103 that the time T exceeds the predetermined time range Tr, the control unit 10 advances the process to S104. In S104, the control unit 10 acquires the peak value Va of the received signal and the ultrasonic arrival time Ta when there is no recording material P. Specifically, the control unit 10 acquires a peak value Va from a second received signal received from an ultrasonic sensor 31 within a predetermined time range Tr, and sets a timer when the second received signal is received. The ultrasonic arrival time Ta is acquired by reference.

In S105, the control unit 10 determines whether or not the tip of the conveyed recording material P reaches the registration sensor 34 and the output of the registration sensor 34 has changed. When the control unit 10 determines in S105 that the output of the registration sensor 34 has not changed, the process returns to S105. When the control unit 10 determines in S105 that the output of the registration sensor 34 has changed, the process proceeds to S106. In S106, the control unit 10 starts counting the number of steps of the registration motor (not shown) starting from the timing of the change in the output of the registration sensor 34. Here, the resist roller pair 6 is driven by a resist motor such as a pulse motor. Further, the control unit 10 has a counter (not shown), resets the counter at the timing when the output of the registration sensor 34 changes (S = 0), and starts counting the number of steps of the registration motor. Further, the distance from the registration sensor 34 to the recording material discriminating device 30 is known, and when the registration motor is rotated by the registration roller pair 6 to convey the recording material P from the registration sensor 34, the tip of the recording material P becomes the recording material. It is known in advance whether the determination device 30 will be reached. The number of steps required to convey the recording material P from the registration sensor 34 to the recording material discriminating device 30 is set to a predetermined number of steps.

In S107, the control unit 10 determines whether or not the number of steps S has reached a predetermined number of steps. When the control unit 10 determines in S107 that the number of steps S does not reach a predetermined number of steps, the process returns to S107. When the control unit 10 determines in S107 that the number of steps S has reached a predetermined number of steps, the control unit 10 advances the process to S108. The control unit 10 determines that the number of steps S has reached a predetermined number of steps, that is, the tip of the recording material P has reached the ultrasonic sensor 31. In S108, the control unit 10 drives the ultrasonic sensor 31, resets the timer (T = 0) and starts it, and the basis weight in a state where the recording material P is between the transmitting unit 31a and the receiving unit 31b. Start measuring the average value of. Similar to the measurement (S102 to S104) when there is no recording material P, the control unit 10 in S109 determines whether or not the time T exceeds the predetermined time range Tr with reference to the timer. When the control unit 10 determines in S109 that the time T does not exceed the predetermined time range Tr, the control unit 10 returns the process to S109. As a result, the control unit 10 detects the received signal from the ultrasonic sensor 31 during the predetermined time range Tr from the start of measurement by the timer.

When the control unit 10 determines in S109 that the time T exceeds the predetermined time range Tr, the control unit 10 advances the process to S110. In S110, the control unit 10 acquires the peak value Vp of the received signal and the ultrasonic arrival time Tp when the recording material P is present. Specifically, the control unit 10 acquires a peak value Vp from a second received signal received from an ultrasonic sensor 31 within a predetermined time range Tr, and sets a timer when the second received signal is received. The ultrasonic arrival time Tp is obtained by reference. The control unit 10 also functions as a measuring means for measuring the time from the start of transmission of ultrasonic waves from the transmission unit 31a to the reception of ultrasonic waves by the reception unit 31b.

In S111, the control unit 10 acquired the reference value Va0 previously held in the storage unit, the peak value Va acquired in S104, the peak value Vp acquired in S110, and the ultrasonic arrival time Ta and S110 acquired in S104. The TRS value is calculated using the ultrasonic arrival time Tp. As described above, the position correction coefficient T is obtained from the equation (1), the ambient environment correction R is obtained from the equation (2), and the arrival time correction coefficient S is obtained from the equation (3). In S112, the control unit 10 calculates the basis weight of the recording material P based on the TRS value calculated in S111 and the approximate expression Y held in the storage unit. For example, when the TRS value obtained by calculation is 1.2, the control unit 10 obtains the basis weight from the approximate expression Y to be about 65 gsm (see FIG. 3 (b)). In S113, the control unit 10 determines an image forming condition, for example, a secondary transfer condition or a fixing condition based on the basis weight calculated in S112, and ends the process.

In the first embodiment, the control unit 10 detects the basis weight using the arrival time correction coefficient S calculated from the ultrasonic arrival time Ta when the recording material P is not present and the ultrasonic arrival time Tp when the recording material P is present. Correct the value. As a result, the influence of the difference in the air permeability of the recording material P on the detection result of the ultrasonic sensor 31 can be reduced, and the basis weight of the recording material P can be detected with higher accuracy than before.

As described above, according to the first embodiment, it is possible to improve the detection accuracy of the basis weight of the recording material.

In the second embodiment, by measuring the ultrasonic arrival time Tp at a plurality of places on the paper surface of the recording material P, the influence of the acoustic impedance of the recording material P is accurately corrected regardless of the variation in the detection position of the recording material P. I will explain how to do it. Since the block diagram of the image forming apparatus 1 and the recording material discrimination apparatus 30 and the graph related to the basis weight calculation are assumed to be the same as those of FIGS. 1 and 3 (b), the description thereof will be omitted.

<Explanation of variation in basis weight detection value>
The transport path for transporting the recording material P needs to have a wider transport path than the thickness of the recording material P in terms of function. Therefore, at the moment when the recording material P passes between the transmitting unit 31a and the receiving unit 31b of the ultrasonic sensor 31 (hereinafter referred to as the ultrasonic transmitting / receiving unit), the ultrasonic wave transmitting / receiving direction (abbreviated on the paper surface of the recording material P). The transport position of the recording material P with respect to the orthogonal direction) varies. Since such variations in the transport position are affected by conditions such as the thickness and rigidity of the recording material P and the angle of entry between the ultrasonic transmission / reception units, it is difficult to control them accurately. Therefore, the detected value varies depending on the ultrasonic wave detection timing. Further, since the basis weight of the recording material P has unevenness (hereinafter referred to as basis weight unevenness) depending on the position on the paper surface, it is known that the detection value varies depending on the detection position even on the same paper surface. That is, the above-mentioned peak value Vp and ultrasonic arrival time Tp vary due to the transport position of the recording material P and uneven basis weight. As a means for reducing such variations in the peak value Vp and the ultrasonic arrival time Tp, it is useful to perform multiple measurements on one recording material P and then average the detected values, for example. Is.

<Explanation of sequence for multiple measurements>
When performing a plurality of measurements, it is preferable to provide a sufficient drive stop time for the transmission unit 31a of the ultrasonic sensor 31 from the end of the previous measurement to the start of the next measurement. This is because the sound wave at the time of the previous measurement remains as reverberation even after the driving of the transmitting unit 31a is stopped. If the next measurement is started before the reverberation of the sound wave is sufficiently attenuated, the receiving unit 31b receives the sound wave on which the reverberation of the previous measurement is superimposed, so that the detection accuracy is lowered. The time until the reverberation is sufficiently attenuated varies depending on the positional relationship between the transmitting unit 31a and the receiving unit 31b, the intensity of the sound wave, the guide shape of the ultrasonic sensor 31, the surrounding environment, and the like. Therefore, it is necessary to appropriately set the optimum drive stop time of the transmission unit 31a according to the above-mentioned conditions. Further, when performing multiple measurements, the time interval from the end of each measurement to the start of the next measurement does not necessarily have to be the same.

(Drive signal and received signal)
The operation of performing a plurality of measurements and averaging the detected values will be described with reference to the time chart of FIG. FIG. 5 (i) shows the waveform of the drive signal [V] output by the control unit 10, and FIG. 5 (ii) shows the waveform of the received signal [V] output by the reception detection unit 43. The horizontal axis indicates time (seconds (sec.)). When the peak value at the nth measurement is Vpn and the ultrasonic arrival time is Tpn, the average value Vpav of the peak value of the nth measurement is expressed by the equation (6), and the average value Tpav of the ultrasonic arrival time is the equation. It is represented by (7). Here, n ≧ 1.
Vpav = (Vp1 + Vp2 + ... + Vpn) / n ... Equation (6)
Tpav = (Tp1 + Tp2 + ... + Tpn) / n ... Equation (7)
The frequency and number of pulses of the drive signal, the acquisition of the peak value of the received signal, and the like are the same as those in the first embodiment, and the description thereof will be omitted.

<Flow chart showing the area weight detection process>
FIG. 6 is a flowchart of the detection process of the detection value of the basis weight of the recording material P of the second embodiment. As an example, a process in which the measurement is performed three times at different positions on the paper surface of the recording material P will be described. Although the number of measurements is set to 3 in the second embodiment, the number of measurements that can be performed differs depending on the transport speed and size of the recording material P, the configuration of the image forming apparatus 1, and the like, and thus the number of measurements is not limited to this. Further, in order to reduce the detection variation, it is preferable to increase the number of measurements as much as possible.

Since the processing from the reception of the printing instruction to the measurement without the recording material P (measurement of Va and Ta) and the start of the measurement of the recording material P is the same as the processing of S101 to S107 in FIG. 4 of the first embodiment. The description is omitted here. From S114 to S116, the control unit 10 makes the first measurement. At S114, the control unit 10 starts driving the ultrasonic sensor 31, resets the timer (T = 0), and starts the operation. After starting the measurement in the same manner as in the first embodiment in this way, in S115, the control unit 10 refers to the timer and determines whether or not the time T exceeds the predetermined time range Tr. When the control unit 10 determines in S115 that the time T does not exceed the predetermined time range Tr, the process is returned to S115, and the measurement by ultrasonic waves is performed during the predetermined time range Tr set in advance. When the control unit 10 determines in S115 that the time T exceeds the predetermined time range Tr, the control unit 10 advances the processing to S116. In S116, the control unit 10 acquires the peak value Vp1 and the ultrasonic arrival time Ta1 in the first measurement. Here, the control unit 10 stops driving the transmission unit 31a.

In S117, the control unit 10 determines whether or not the number of steps S of the resist motor (not shown) exceeds a predetermined number of steps. The predetermined number of steps here is the number of steps corresponding to the time during which the reverberation of the sound wave is sufficiently attenuated and does not affect the next measurement after the driving of the transmitting portion 31a of the ultrasonic sensor 31 is stopped. .. When the control unit 10 determines in S117 that the number of steps S has not reached a predetermined number of steps, the process returns to S117. When the control unit 10 determines in S117 that the number of steps S has reached a predetermined number of steps, that is, when it is determined that the reverberation of the sound wave at the time of the first measurement is sufficiently attenuated, the process proceeds to S118.

From S118 to S120, the control unit 10 makes a second measurement. The processing of S118 to S120, which is the second measurement, is the same as the processing of S114 to S116, which is the first measurement, and the description thereof will be omitted. However, in S120, the control unit 10 acquires the peak value Vp2 and the ultrasonic arrival time Tp2 in the second measurement. The processing of S121 is the same as the processing of S117, and the description thereof will be omitted. From S122 to S124, the control unit 10 makes a third measurement. The processing of S122 to S124, which is the third measurement, is the same as the processing of S114 to S116, which is the first measurement, and the description thereof will be omitted. However, in S124, the control unit 10 acquires the peak value Vp3 and the ultrasonic arrival time Tp3 in the third measurement.

After all the measurements are completed, in S125, the control unit 10 determines the average value Vpav of the peak values Vp1, Vp2, Vp3 for any number of measurements, here three times, and the ultrasonic arrival times Tp1, Tp2 for three times. The average value Tpav of Tp3 is calculated respectively. In S126, the control unit 10 calculates the TRS value using the average value Vpav of the peak values calculated in S125 and the average value Tpav of the ultrasonic arrival time. As described in the first embodiment, the position correction coefficient T is obtained from the equation (1), the ambient environment correction R is obtained from the equation (2), and the arrival time correction coefficient S is obtained from the equation (3). Vpav is used instead of Vp, and Tpav is used instead of Tp. The processing of S127 and S128 is the same as that of S112 and S113 of FIG. 4, and the description thereof will be omitted.

In Example 2, the peak value Vp and the ultrasonic arrival time Tp are measured at a plurality of places on the paper surface of the recording material P, and the average value Vav of the peak value averaged by the number of measurements and the average value Tpav of the ultrasonic arrival time are obtained. Use to correct the detection value of the basis weight. This makes it possible to accurately correct the influence of the acoustic impedance of the recording material P regardless of the variation in the detection position of the recording material P.

As described above, according to the second embodiment, it is possible to improve the detection accuracy of the basis weight of the recording material.

30 Recording material discrimination device 31 Ultrasonic sensor 31a Transmitter 31b Receiver 10 Control unit

Claims (11)

A means of transmitting ultrasonic waves and
A receiving means for receiving ultrasonic waves transmitted from the transmitting means, and a receiving means.
The basis weight of the recording material, or the recording, based on the first voltage corresponding to the ultrasonic wave received by the receiving means in the first state where the recording material is between the transmitting means and the receiving means. Detection means to detect the type of material and
It is a recording material detection device equipped with
A measuring means for measuring the time from the start of transmitting ultrasonic waves from the transmitting means to the reception of the ultrasonic waves by the receiving means, and
A correction means for correcting the first voltage based on the time measured by the measuring means, and a correction means.
A recording material detection device characterized by being equipped with. The correction means is measured by the measuring means in the first state measured by the measuring means in the first state and in the second state where there is no recording material between the transmitting means and the receiving means. The recording material detection device according to claim 1, wherein the first voltage is corrected based on the second time. The recording material detection device according to claim 2, wherein the correction means corrects the first voltage by a first correction value obtained by dividing the first time by the second time. Claim 2 or claim 3 characterized in that the correction means corrects the first voltage based on the second voltage corresponding to the ultrasonic wave received by the receiving means in the second state. Recording material detection device described in. The recording material detection device according to claim 4, wherein the correction means corrects the first voltage by a second correction value obtained by dividing the first voltage by the second voltage. The correction means is an ultrasonic wave received by the receiving means in the second state under a state in which information about the environment including the atmospheric pressure and / or the temperature of the environment in which the recording material detection device is installed is known. The recording material detection device according to claim 4 or 5, wherein the first voltage is corrected based on the third voltage according to the above. The recording material detection device according to claim 6, wherein the correction means corrects the first voltage by a third correction value obtained by dividing the third voltage by the second voltage. The correction means is a plurality of the first ones obtained for different positions of the one recording material based on the plurality of first times obtained for different positions of the one recording material. The recording material detection device according to any one of claims 2 to 7, wherein the voltage is corrected according to the voltage. The recording material detection device according to claim 8, wherein the correction means corrects the average value of the plurality of first voltages based on the average value of the plurality of first times. The recording material detection device according to claim 7, wherein the smaller the product of the first correction value, the second correction value, and the third correction value, the heavier the basis weight of the recording material. An image forming means for forming an image on a recording material,
A means of transmitting ultrasonic waves and
A receiving means for receiving ultrasonic waves transmitted from the transmitting means, and a receiving means.
A measuring means for measuring the time from the start of transmitting ultrasonic waves from the transmitting means to the reception of the ultrasonic waves by the receiving means, and
Based on the time measured by the measuring means, the first voltage corresponding to the ultrasonic wave received by the receiving means is corrected in the first state where the recording material is between the transmitting means and the receiving means. Correction means and
A control means for controlling an image forming condition for forming an image by the image forming means based on the corrected first voltage, and a control means.
An image forming apparatus comprising.

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