JP7614827B2 - Recording material detection device and image forming apparatus - Google Patents

Description

The present invention relates to detecting the basis weight of a recording material using ultrasonic waves.

In an image forming apparatus, an image is formed on a recording material having various characteristics such as size, basis weight, and surface properties. In order to form an image according to these recording materials, Patent Document 1 discloses a recording material discrimination device for discriminating the type of recording material (hereinafter referred to as paper type) inside the image forming apparatus. This recording material detection device, for example, is provided with a transmitting means for emitting ultrasonic waves and a receiving means for receiving ultrasonic waves, disposed on either side of the transport path along which the recording material is transported. A method is proposed in which the transmitting means transmits ultrasonic waves toward the recording material, and the paper type is discriminated using the reception level of the ultrasonic waves that pass through the recording material.

Patent Document 2 also proposes a method for improving the accuracy of paper type discrimination by measuring the received signal that reaches an ultrasonic receiving means to detect the basis weight and to discriminate the paper type of the recording material. In this method, the reception level when ultrasonic waves passing through a recording material are received by the receiving means is smaller than the reception level when ultrasonic waves not passing through a recording material are received by the receiving means. For this reason, the amplification factor of the reception level when ultrasonic waves passing through a recording material are received by the receiving means is made larger than the amplification factor of the reception level when ultrasonic waves not passing through a recording material are received by the receiving means.

JP2004-219856A Patent Publication 2009-292549

Conventionally, it has been known to detect information regarding basis weight using the reception level of the same waves output by a receiving and detecting means regardless of the presence or absence of recording material, and the amplification factor of the received signal may be increased when receiving ultrasonic waves via a recording material. However, when the amplification factor of the received signal is increased, the noise present in the circuit receiving the ultrasonic waves is also amplified.

The invention of this application aims to suppress a decrease in the detection accuracy of information regarding the basis weight of a recording material by switching the waves output by the receiving and detecting means to be used when detecting information regarding the basis weight of the recording material depending on whether or not the recording material is present.

In order to solve the above problems, the present invention relates to
an ultrasonic sensor including a transmitting means for transmitting ultrasonic waves and a receiving means for receiving the ultrasonic waves, the transmitting means and the receiving means being disposed on either side of a conveying path along which a recording material is conveyed;
an instruction means for inputting a drive input to the transmission means;
a receiving and detecting means for receiving a signal received by the ultrasonic sensor and outputting a wave having an amplitude equal to or smaller than a first value as a detection signal ;
a basis weight detection means for detecting information regarding the basis weight of the recording material in response to the detection signal output by the receiving detection means,
the reception detection means, when receiving ultrasonic waves not transmitted through a recording material by the receiving means, outputs as the detection signal a wave of a predetermined wave received by the receiving means during a period from a first time after a drive input is input to the transmitting means until a second time has elapsed, and when receiving ultrasonic waves transmitted through a recording material by the receiving means, outputs as the detection signal a wave subsequent to the predetermined wave received by the receiving means during a period from a third time after a drive input is input to the transmitting means until a fourth time has elapsed;
The first time period is shorter than the third time period.

As described above, according to the present invention, by switching the waves output by the receiving and detecting means to detect information regarding the basis weight of the recording material depending on whether or not the recording material is present, it is possible to suppress a decrease in the detection accuracy of information regarding the basis weight of the recording material.

1 is a schematic configuration diagram of an image forming apparatus 1 according to a first embodiment. FIG. 2 is a schematic diagram of a recording material discrimination device 19 according to the first embodiment. 10 is a graph showing an approximation obtained by plotting the relationship between the position correction coefficient T and the basis weight of the recording material P. 4A to 4C are diagrams illustrating an example of the relationship between the output waveform of the transmission circuit unit 22, the waveform of a received signal, a peak detection signal, an amplification factor of the received signal, and a signal-to-noise ratio according to the first embodiment. 5 is a flowchart of a process for calculating a detection value of the basis weight of a recording material P executed by a recording material discrimination device 19 according to the first embodiment. 5 is a time chart showing signal states, voltage states, and the like related to the process of calculating a detected value of basis weight executed by the recording material discrimination device 19 according to the first embodiment. 13A and 13B are diagrams illustrating an example of the relationship between the output waveform of the transmission circuit unit 22, the waveform of the received signal, the peak detection signal, the amplification factor of the received signal, and the signal-to-noise ratio according to the second embodiment. 10 is a flowchart of a process for calculating a detection value of the basis weight of a recording material P executed by a recording material discrimination device 19 according to a second embodiment. 10 is a time chart showing signal states, voltage states, and the like related to a process for calculating a detected value of basis weight executed by a recording material discrimination device 19 according to a second embodiment. FIG. 11 is a schematic diagram of a recording material discrimination device 19 according to a modified example of the second embodiment.

The following describes embodiments of the present invention with reference to the drawings. Note that the following embodiments do not limit the invention in the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the present invention.

[Image forming apparatus]
FIG. 1 is a schematic diagram of an image forming apparatus 1. The image forming apparatus 1 is an electrophotographic full-color printer that employs an intermediate transfer method. The image forming apparatus 1 includes 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 English letters Y, M, C, and K 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, reference symbols without the English letters Y, M, C, and K at the end may be used.

The paper feed cassette 2 holds recording material P, which may be paper. The recording material P held in the paper feed cassette 2 is fed by a paper feed roller 3. The recording material P fed by the paper feed roller 3 is transported by a pair of transport rollers 4 and a pair of registration rollers 5. A registration sensor 6 is disposed near the pair of registration rollers 5 to detect the presence or absence of recording material P.

The photosensitive drum 7 has a photosensitive layer on an aluminum drum-shaped base, and is rotated by a drive device (not shown) in the direction of the arrow in the figure at a predetermined process speed. Note that the process speed here corresponds to the peripheral speed (surface movement speed) of the photosensitive drum 7. The charging roller 8 uniformly charges the photosensitive drum 7 to a predetermined potential. The laser scanner 9 irradiates the photosensitive drum 7 with laser light corresponding to the image information, exposing the surface of the photosensitive drum 7. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 7.

The process cartridge 10 is equipped with a developing roller 11, which develops the electrostatic latent image formed on the photosensitive drum 7 using the toner contained in the process cartridge 10. The primary transfer roller 12 performs primary transfer of the image formed on the photosensitive drum 7 onto the intermediate transfer belt 13. The intermediate transfer belt 13 is driven by a drive roller 14.

The secondary transfer roller 15 performs a secondary transfer of the image that has been primarily transferred onto the intermediate transfer belt 13 onto the recording material P. The fixing unit 16 fixes the secondary transferred image onto the recording material P by applying heat and pressure. The components from the photosensitive drum 7 to the fixing unit 16 that are related to image formation as described above are an example of the configuration of the image forming unit 17. The paper discharge roller 18 discharges the recording material P that has been fixed by the fixing unit 16 onto a paper discharge tray.

The recording material detection device 19, which serves as a basis weight detection means, detects information related to the basis weight of the recording material P. Below, a method for determining the type of recording material P based on the basis weight of the recording material P and a method for controlling the image formation conditions (secondary transfer conditions, fixing conditions) will be described. Since the resistance value of the recording material P generally differs depending on the basis weight of the recording material P, it is necessary to change the secondary transfer conditions, such as the application of a secondary transfer bias for secondary transfer of toner, according to the basis weight. In addition, since the thermal 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 and fixing time for fixing the toner, and the conveying speed of the recording material P, according to the basis weight.

The control unit 20 is made up of a memory unit such as an MPU equipped with a CPU, a RAM used for calculations and temporary storage of data necessary to control the image forming device 1, and a ROM for storing programs and various data for controlling the image forming device 1. The control unit 20 determines the type of recording material P based on the detected value of information related to the basis weight by the recording material detection device 19. Then, it determines image formation conditions according to the type of recording material P and controls the image forming device 1 to operate under the image formation conditions according to the type of recording material P.

[Recording material detection device 19]
FIG. 2 is a block diagram relating to the recording material detection device 19. As shown in FIG.

The recording material discrimination device 19 is composed of an ultrasonic sensor 21, a transmission circuit unit 22, and a receiving and detecting unit 23, and is controlled by the control unit 20.

The ultrasonic sensor 21 is a sensor that detects the basis weight of the recording material P using ultrasonic waves, and is composed of a transmitting means 21a that transmits ultrasonic waves and a receiving means 21b that receives ultrasonic waves. The ultrasonic sensor 21 is also called an ultrasonic transmitting device.

The control unit 20 has the functions of a transmission instruction unit 20a, an amplification factor switching instruction unit 20b, a reception level detection unit 20c, and a peak detection unit 20d for controlling the recording material discrimination device 19. The transmission instruction unit 20a controls the output signal output from the transmission means 21a by outputting a drive signal to the recording material discrimination device 19. The transmission instruction unit 20a also switches the amplitude of the output signal output from the transmission circuit unit 22 by switching the drive voltage supplied to the recording material discrimination device 19. The transmission instruction unit 20a may have a drive input switching unit that switches the frequency or drive voltage of the drive signal depending on the presence or absence of a recording material. However, in this embodiment, the drive voltage is constant regardless of the presence or absence of a recording material. At this time, the drive signal generated by the transmission instruction unit 20a is a burst signal of a pulse wave with a constant period, and the output signal switched to an arbitrary amplitude by the transmission circuit unit 22 causes the transmission means 21a to transmit ultrasonic waves.

The output terminal from the transmitting circuit section 22 is connected to the USS terminal of the transmitting means 21a. The transmitting means 21a transmits ultrasonic waves at a frequency of 40 kHz in response to the output from the transmitting circuit section 22. The receiving means 21b receives the ultrasonic waves transmitted from the transmitting means 21a and outputs a reception signal corresponding to the amplitude of the received ultrasonic waves to the reception detection section 23. Note that although the frequency of the ultrasonic waves is set to 40 kHz in this embodiment, any frequency can be used as long as it can detect the characteristic value of the basis weight of the recording material P, and the frequency can be set according to the characteristics of the element. In addition, the transmitting means 21a and the receiving means 21b are each arranged near the transport path that transports the recording material P, sandwiching the transport path, so that they can receive ultrasonic waves via the recording material P.

The maximum amplitude of the ultrasonic waves transmitted by the transmitting means 21a when the receiving means 21b receives ultrasonic waves not passing through the recording material P is also referred to as the first maximum amplitude. The drive voltage and drive signal for outputting the first output signal to the transmitting means 21a to transmit ultrasonic waves of the first maximum amplitude are also referred to as the first drive input. The maximum amplitude of the ultrasonic waves transmitted by the transmitting means 21a when the receiving means 21b receives ultrasonic waves passing through the recording material P is also referred to as the second maximum amplitude. The drive voltage and drive signal for outputting the second output signal to the transmitting means 21a to transmit ultrasonic waves of the second maximum amplitude are also referred to as the second drive input.

The reception detection unit 23 is a circuit unit that has the function of amplifying the amplitude of the reception signal received by the receiving means 21b, which is ultrasonic waves passing through the recording material P, using the amplification factor switching instruction unit 20b, and performing half-wave rectification. In this embodiment, the reception detection unit 23 is also referred to as the reception detection means. The amplification factor switching instruction unit 20b switches the amplification factor of the amplitude of the reception signal depending on whether or not the recording material P is present. For example, when the receiving means receives ultrasonic waves that are not passing through the recording material P, the amplification factor is set to 1, and the detection signal is input to the reception level detection unit 20c without being amplified. Also, when the receiving means receives ultrasonic waves that are passing through the recording material P, the reception signal is amplified at a preset amplification factor, and the amplified detection signal is input to the reception level detection unit 20c.

The detection signal generated by the reception detection unit 23 is input to the AD port of the control unit 20 and converted from an analog signal to a digital signal by the reception level detection unit 20c. The control unit 20 detects the waveform of the detection signal based on the digital value converted by the reception level detection unit 20c, calculates its peak value (maximum value), and calculates it as the reception level of the ultrasonic waves. The peak detection unit 20d also detects the waveform of the detection signal based on the digital value converted by the reception level detection unit 20c, and selects a waveform for detecting the peak value. In this embodiment, when the receiving means receives ultrasonic waves that are not transmitted through the recording material P, the first wave of the detection signal is selected as the waveform for detecting the peak value as the peak detection signal. When the receiving means receives ultrasonic waves that are transmitted through the recording material, the waveform after a predetermined time from the input of the drive signal is selected as the waveform for detecting the peak value as the peak detection signal.

In this embodiment, when the receiving means receives ultrasonic waves not passing through the recording material P, the first wave of the detection signal is selected as the waveform for detecting the peak value as the peak detection signal, but it does not necessarily have to be the first wave. When the receiving means receives ultrasonic waves not passing through the recording material P, any wave may be selected as the waveform for detecting the peak value as the peak detection signal, as long as the reception level of the detection signal is not saturated and the peak value can be detected. The reception level being saturated means that the reception detection unit 23 reaches the upper limit of the detection signal that can be detected when detecting the input reception signal and outputting the detection signal. At this time, the value of the detection signal that is the upper limit is also referred to as the first value. The first value is the maximum value of the amplitude of the wave output by the reception detection unit 23, and the reception detection unit 23 outputs a detection signal of a wave with an amplitude equal to or less than the first value. In this embodiment, when the receiving means receives ultrasonic waves passing through the recording material P, the waveform selected for detecting the peak value as the peak detection signal is selected after a predetermined time from the input of the drive signal. However, it does not necessarily have to be the waveform after the predetermined time. In this embodiment, the peak value when the receiving means receives ultrasonic waves through the recording material P may be greater than the peak value when the receiving means receives ultrasonic waves not through the recording material P, and the means are not limited to this. The predetermined time is calculated from the relationship between the distance between the transmitting means 21a and the receiving means 21b measured in advance during the manufacturing process and the sound speed of the ultrasonic waves detected by the ultrasonic sensor in advance during the manufacturing process. In this embodiment, the peak value of the detection signal output by the receiving detection unit 23 is used to calculate the reception level, but any characteristic value that can determine the level of the received signal, such as an effective value or average value, may be used. The receiving detection unit 23 is also referred to as the receiving detection means.

In this embodiment, the reception level when the receiving means receives ultrasonic waves that do not pass through the recording material is Va1, and the reception level when the receiving means receives ultrasonic waves that pass through the recording material is Vp3. The control unit 20 also calculates the basis weight of the recording material P using the reception levels Va1 and Vp3.

<Correction of positional variation between receiving means 21b and transmitting means 21a>
Next, a description will be given of correction of positional variations between the receiving means 21b and the transmitting means 21a, which is necessary for discriminating the paper type.

During the manufacturing process of the image forming device 1, when the ultrasonic sensor 21 is attached to the image forming device 1, the positions of the receiving means 21b and the transmitting means 21a relative to the recording material P to be detected may vary. This variation in position may change the time at which the ultrasonic waves reach the receiving means 21b, and may also change the time at which the reception level detected by the reception level detection unit 20c reaches its peak value. For this reason, by calculating the correction coefficient as described below, it is possible to detect the basis weight by correcting the positional variation.

When the receiving means 21b receives ultrasonic waves that have not passed through the recording material P, the receiving level output by the receiving level detection unit 20c is set to Va1. When the receiving means 21b receives ultrasonic waves that have passed through the recording material P, the receiving level output by the receiving level detection unit 20c is set to Vp3. The position correction coefficient T is calculated using the receiving levels Va1 and Vp3. In this embodiment, the receiving level Va1 is also referred to as the amplitude information of the first wave, and the receiving level Vp3 is also referred to as the amplitude information of the second wave.
T=Vp3/Va1... (Formula 1)

The control unit 20 calculates the basis weight using a graph showing an approximation equation obtained by plotting the relationship between the position correction coefficient T and the basis weight value of the recording material P, as shown in FIG. 4. Then, the paper type of the recording material P is determined based on the calculated basis weight, image formation conditions are determined according to the type of recording material P, and the operation of the image forming apparatus 1 is controlled. The approximation equation here is obtained in advance from the actual basis weight and the correction coefficient T, and is stored in the non-volatile memory of the control unit 20. In this embodiment, an approximation equation is used, but a conversion table showing the relationship between the position correction coefficient T and the basis weight value of the recording material P may also be used.

<Ultrasonic Attenuation by Recording Material P and Method for Distinguishing Paper Type>
The attenuation of ultrasonic waves by the recording material P will be described below. The amount of attenuation of ultrasonic waves passing through the recording material P increases in proportion to the basis weight of the recording material P. In other words, the greater the basis weight of the recording material P, the greater the amount of ultrasonic attenuation, and therefore the value of the reception level Vp3 decreases. When the recording material P is thin paper with a small basis weight, the amount of ultrasonic attenuation is less than that of plain paper, and therefore the value of the reception level Vp3 is greater than that of plain paper. On the other hand, when the recording material P is thick paper with a large basis weight, the amount of ultrasonic attenuation is greater than that of plain paper, and therefore the value of the reception level Vp3 is smaller than that of plain paper. In other words, when the value of the reception level Vp3 increases, the value of the position correction coefficient T also increases.

For example, the control unit 20 uses the approximation line shown in Fig. 3 to determine the basis weight corresponding to the value of the position correction coefficient T. If the basis weight determined by the control unit 20 is smaller than an arbitrary threshold, the paper type of the recording material P is determined to be thin paper. If the basis weight determined by the control unit 20 is larger than an arbitrary threshold, the paper type of the recording material P is determined to be thick paper. In this case, the arbitrary threshold is, for example, as shown in Fig. 3, a value such as thin paper when the basis weight is 59 g/m2 ^or less, plain paper when the basis weight is 60 g/ ^m2 to 90 g/ ^m2 , and thick paper when the basis weight is 90 g/ ^m2 . Note that the method of determining the paper type is not limited to this, and the relationship between the basis weight and the paper type may be stored in advance in a non-volatile memory and the information may be used.

<Reason for switching the waveform for detecting peak values depending on the presence or absence of recording material>
Next, the reason for switching the waveform for detecting the peak value depending on the presence or absence of the recording material in this embodiment will be described.

First, a case where the peak value of the waveform at the same timing is detected when the receiving means receives ultrasonic waves not passing through a recording material and when the receiving means receives ultrasonic waves through a recording material will be described with reference to FIG. 4(a). In FIG. 4(a), when the receiving means receives ultrasonic waves not passing through a recording material and when the receiving means receives ultrasonic waves through a recording material, the peak detection unit 20d selects the peak value of the third waveform of each received signal as a peak detection signal. The switching of the amplification factor of the detection circuit and its signal-to-noise ratio at this time are shown.

When receiving ultrasonic waves not passing through a recording material, as shown in FIG. 4(a), the amplitude of the output voltage is determined so that the reception level Va3 of the detection signal does not saturate. In this embodiment, the amplification factor at this time is set to 1. In addition, in this embodiment, the amplification factor of 1 is also referred to as the first amplification factor. When the receiving means receives ultrasonic waves passing through a recording material, the ultrasonic waves are attenuated by the recording material, so that the reception signal becomes smaller and the detection signal also becomes smaller. For this reason, as shown in FIG. 4(a), the amplification factor of the reception signal is determined so that it is larger than the amplification factor when the receiving means receives ultrasonic waves not passing through a recording material, and so that the reception level Vp3 of the detection signal does not saturate. In this embodiment, the amplification factor at this time is set to 20. In addition, in this embodiment, the amplification factor of 20 is also referred to as the third amplification factor. However, in this case, if the receiving signal when the receiving means receives ultrasonic waves passing through a recording material is amplified, the noise signal (not shown) present in the circuit receiving the ultrasonic waves may also be amplified. For this reason, the signal-to-noise ratio, which is the ratio of the noise signal to the ultrasonic reception signal, becomes large.

In this embodiment, the peak detection unit 20d detects the peak values of the waveforms at different timings when the receiving means receives ultrasonic waves that do not pass through a recording material and when the receiving means receives ultrasonic waves that pass through a recording material. The switching of the peak detection waveform in this embodiment will be explained below with reference to FIG. 4(b).

In FIG. 4(b), when the receiving means receives ultrasonic waves that are not transmitted through a recording material, for example, the peak value of the first waveform that is not saturated among the received signals is selected as the peak detection signal. Also, when the receiving means receives ultrasonic waves that are transmitted through a recording material, for example, the peak value of the third waveform of the received signal is selected as the peak detection signal. The switching of the amplification factor of the detection circuit and its signal-to-noise ratio at this time will be explained below.

When the receiving means receives ultrasonic waves not passing through a recording material, the amplitude of the output signal is determined so that the reception level Va1 of the detection signal does not saturate. In this embodiment, when the receiving means receives ultrasonic waves not passing through a recording material, the amplitude of the output signal is increased to a level at which the reception level Va1 of the first wave of the received signal is not saturated. In this embodiment, the drive voltage is set to 10 V, and the amplification factor of the received signal at this time is set to 1. In this embodiment, the amplification factor of 1 is also referred to as the first amplification factor. In this embodiment, the reception level of the first wave of the received signal is set to a reception level lower than the reception level of the third wave, as shown in the waveform of the peak detection signal when the receiving means receives ultrasonic waves not passing through a recording material in FIG. 4(a). However, the magnitude relationship of the reception levels does not necessarily have to be this relationship.

Next, when the receiving means receives ultrasonic waves through a recording material, the amplification factor of the received signal when the receiving means receives ultrasonic waves through a recording material is determined so that the reception level Vp3 of the detection signal does not saturate. At this time, the waveform for detecting the peak value of the reception level when the receiving means receives ultrasonic waves not through a recording material is changed to the third wave. The amplitude of the output signal is set large enough that the reception level Va1 does not saturate regardless of the presence or absence of a recording material. In this embodiment, the driving voltage is set to 10V. Accordingly, the amplification factor of the received signal when the receiving means receives ultrasonic waves through a recording material can be set to 10 times, which is smaller than the case of FIG. 4(a). In this embodiment, the amplification factor of 10 times is also referred to as the second amplification factor. In this way, in the case of FIG. 4(b), the amplification factor of the received signal can be smaller than the case of FIG. 4(a), thereby suppressing the signal-to-noise ratio from increasing compared to the case of FIG. 4(a).

The amplitude of the output signal is not limited to the voltage value described in this embodiment, so long as the peak detection signal Va1 is not saturated. Also, the amplification factor of the received signal is not limited to the amplification factor described in this embodiment, so long as the peak detection signal Vp3 is not saturated.

[Switching of Peak Detection Signal Depending on Presence or Absence of Recording Material P]
4 and 5, a method for suppressing an increase in the signal-to-noise ratio when the receiving means receives ultrasonic waves via the recording material P by switching the peak detection signal depending on the presence or absence of the recording material by the peak detection unit 20d. Fig. 5 is a flowchart of the process for calculating the basis weight of the recording material P, and Figs. 6(a) to (g) are time charts showing the states of signals and voltages related to the process for calculating the basis weight.

In S100, the control unit 20 starts the paper feeding operation by receiving a print command.

In S101, the control unit 20 outputs a Low signal as a switching signal for the peak detection signal by the peak detection unit 20d, as shown in FIG. 6(b).

In S102, the transmission instruction unit 20a of the control unit 20 sets the drive voltage output by the transmission circuit unit 22 to 10 V, as shown in FIG. 6(d). This causes the amplification factor switching instruction unit 20b to set the amplification factor of the received signal in the reception detection unit to 1, as shown in FIG. 6(c).

In S103, the control unit 20 executes the following process at a timing when the recording material P has not yet reached the ultrasonic sensor 21 after the start of the paper feed operation. That is, the control unit 20 starts measuring the reception level of ultrasonic waves by the receiving means when the receiving means receives ultrasonic waves not passing through the recording material, as shown in FIG. 6(a). As shown in FIG. 6(e), the control unit 20 outputs a High signal as a drive signal from the transmission instruction unit 20a to the transmission circuit unit 22. In response to the drive signal from the transmission instruction unit 20a, the transmission circuit unit 22 inputs a voltage of 10V to the USS terminal, as shown in FIG. 6(f). At this time, a burst signal of a pulse wave of a power supply of 10V is input from the transmission circuit unit 22 to the USS terminal. In this embodiment, the drive signal has a frequency of 40kHz, a pulse number of 2 pulses, and a period of the burst signal of 10msec, as an example.

In S104, the control unit 20 detects the first waveform Va1 of the detection signal and detects its peak value. The detection of the peak value of the first waveform Va1 will be described below. After the drive signal is input to the transmitting means 21a, the receiving detection unit 23 receives the received signal output by the receiving means 21b. The receiving detection unit 23 starts detecting the received signal as a detection signal after a predetermined time T1 synchronized with the drive signal has elapsed. More specifically, when the detection signal exceeds a reference value (for example, 0 V) after the predetermined time T1 synchronized with the drive signal has elapsed, the detection of the detection signal is started, and the detection signal is detected until the detection signal returns to the reference value. In this embodiment, the predetermined time T1 is calculated from the relationship between the distance between the transmitting means 21a and the receiving means 21b measured in advance in the manufacturing process and the sound speed of the ultrasonic wave detected in advance by the ultrasonic sensor in the manufacturing process. The predetermined time T1 is also referred to as the first time, and the period from when the control unit 20 starts detecting the detection signal until the detection signal returns to the reference value is also referred to as the second time. The period from the first time to the second time is the period during which a wave with an amplitude less than the first value, which is the maximum amplitude of the wave that the receiving detection means can output, is output. In this manner, the control unit 20 detects the detection signal during the period from when the drive input is input to the transmission means until the predetermined time T1 has elapsed and until the second time has elapsed, and calculates the reception level Va1. In this embodiment, the first waveform Va1 is also referred to as the first wave, and the value related to the amplitude that becomes the reception level Va1 is also referred to as the amplitude information of the first wave. At this time, the detection signal generated by the receiving detection unit 23 becomes a waveform that has a peak value every half wave of 40 kHz, which is the same as the frequency of the sound wave of the transmission means 21a, according to the reception signal of the ultrasonic wave received by the reception means. The number of waveforms of the reception signal exceeds two even if the number of pulses of the drive signal is two. This is because there is reverberation caused by the transmitting means 21a or the receiving means 21b.

In S105, the control unit 20 outputs a High signal as a switching signal for the peak detection signal by the peak detection unit 20d, as shown in FIG. 6(b).

In S106, the transmission instruction unit 20a of the control unit 20 sets the drive voltage output by the transmission circuit unit 22 to 10V, as shown in FIG. 6(d). This causes the amplification factor switching instruction unit 20b to set the amplification factor of the received signal in the reception detection unit to 10 times, as shown in FIG. 6(c).

In S107, the control unit 20 executes the next process depending on whether the leading edge of the recording material P has reached the registration sensor 6. If the leading edge of the recording material P has reached the registration sensor 6, the control unit 20 advances the process to S108.

In S108, the control unit 20 starts counting the number of steps S of the pulse motor (not shown) to detect the timing at which the leading edge of the recording material P reaches the ultrasonic sensor 21 after reaching the registration sensor 6.

In S109, the control unit 20 advances the process to S110 depending on whether the count value of the number of steps S has reached a predetermined value (100). When the count value of the number of steps S has reached the predetermined value (100), the control unit 20 advances the process to S110.

In S110, the control unit 20 outputs a High signal as a drive signal from the transmission instruction unit 20a to the transmission circuit unit 22 as shown in FIG. 6(e). The control unit 20 drives the ultrasonic sensor 21 with the output signal from the transmission circuit unit 22, and starts measuring the reception level of the received signal by the reception detection unit 23 when the receiving means 21b receives ultrasonic waves via the recording material P. In response to the drive signal from the transmission instruction unit 20a, the transmission circuit unit 22 inputs a voltage of 10 V to the USS terminal as shown in FIG. 6(f).

In S111, the control unit 20 detects the third waveform Vp3 of the detection signal and detects its peak value. The detection of the peak value of the third waveform Vp3 will be described below. After the drive signal is input to the transmitting means 21a, the receiving detection unit 23 receives the received signal output by the receiving means 21b. The receiving detection unit 23 starts detecting the received signal as a detection signal after a predetermined time T2 synchronized with the driving signal has elapsed, similar to the detection of the detection waveform Va1 when the receiving means receives ultrasonic waves not passing through a recording material. More specifically, when the detection signal exceeds a reference value (for example, 0 V) after the predetermined time T2 synchronized with the driving signal has elapsed, the detection signal is started to be detected, and the detection signal is detected until the detection signal returns to the reference value. In this embodiment, the predetermined time T2 is calculated from the relationship between the distance between the transmitting means 21a and the receiving means 21b measured in advance in the manufacturing process and the sound speed of the ultrasonic waves detected in advance by the ultrasonic sensor in the manufacturing process, and is longer than the predetermined time T1. The predetermined time T2 is also referred to as the third time, and the period from when the control unit 20 starts detecting the detection signal until the detection signal returns to the reference value is also referred to as the fourth time. The period from the first time to the second time is the period during which a wave with an amplitude less than the first value, which is the maximum amplitude of the wave that the receiving and detecting means can output, is output. In this manner, the control unit 20 detects the detection signal during the period from when the drive input is input to the transmitting means until the predetermined time T2 has elapsed and until the fourth time has elapsed, and calculates the receiving level Vp3. In this embodiment, the third waveform Vp3 is also referred to as the second wave, and the value related to the amplitude that becomes the receiving level Vp3 is also referred to as the amplitude information of the second wave.

In S112, the control unit 20 substitutes the reception levels Va1 and Vp3 into formula (1) to calculate the position correction coefficient T. In S111, the basis weight of the recording material P is calculated using the calculated position correction coefficient T and the approximation formula stored in the memory unit. In S113, the image formation conditions are determined according to the calculated basis weight, and the process ends. Note that in this embodiment, the basis weight may be calculated based on the position correction coefficient T, or the image formation conditions may be changed based on the position correction coefficient T. Also, in this embodiment, the paper type may be determined based on the position correction coefficient T.

In this embodiment, the drive voltage for switching the amplitude of the output signal output from the transmitting circuit unit 22 is set to 10 V. However, the drive voltage is not limited to 10 V, and may be 10 V or more if the receiving means 21 b can detect a value that is not saturated as the reception level of the detection signal when receiving ultrasonic waves that are not transmitted through the recording material P.

In this way, in this embodiment, the peak detection unit 20d switches the waveform of the received signal for detecting the peak value depending on whether or not a recording material is present. That is, when the receiving means 21b receives ultrasonic waves that are not transmitted through the recording material P, the peak detection unit 20d selects, for example, the peak value of the first waveform of the received signal as the peak detection signal. Also, when the receiving means 21b receives ultrasonic waves that are transmitted through the recording material P, the peak detection unit 20d selects, for example, the peak value of the third waveform of the received signal as the peak detection signal. Therefore, when the receiving means 21b receives ultrasonic waves that are transmitted through the recording material P, the amplification rate of the received ultrasonic signal can be suppressed from increasing, and the effect of noise present in the circuit receiving the ultrasonic waves on the basis weight detection result can be reduced.

In this embodiment, the method of detecting the detection signal for a predetermined time period synchronized with the drive signal has been described as a method of switching the waveform for detecting the peak value of the received signal by the peak detection unit 20d depending on the presence or absence of recording material. However, the method of switching the waveform for detecting the peak value is not limited to this. For example, a method of switching the waveform for detecting the peak value may be a method in which the reception level detection unit 20c detects the waveform of the detection signal using a digital signal converted from the detection signal generated by the reception detection unit 23 and counts the waveform. In this case, the points where the digital signal of the detection signal becomes maximum and the waveform reaches a peak value may be counted, or the points where the digital signal of the detection signal becomes 0 and the waveform intersects the horizontal axis may be counted.

In this embodiment, the method of switching the waveform for detecting the peak value may be the following method. For example, a method may be used in which a detection signal is detected in advance by an ultrasonic sensor in the manufacturing process, a threshold value Vth is set at a value at which the reception level of the detection signal is not saturated, and the time from when the drive input is input to the transmission means until the detection signal exceeds the threshold value Vth is detected. In this case, for example, a threshold value Vth is set at a value at which the reception level of the detection signal is not saturated, that is, a value smaller than the upper limit value of the signal that the reception signal can be detected by the reception detection unit 23. The threshold value Vth is also referred to as a second value. When the receiving means receives ultrasonic waves not passing through a recording material, the time from when the drive input is input to the transmission means until the detection signal becomes equal to or greater than the threshold value Vth is set as Ta. When the receiving means receives ultrasonic waves passing through a recording material, the time from when the drive input is input to the transmission means until the detection signal becomes equal to or greater than the threshold value Vth is set as Tp. A method may be used in which the basis weight of the recording material P is detected according to Ta and Tp obtained in this way. Ta is also referred to as the first period, and Tp is also referred to as the second period.

In the first embodiment, the following method was described as a method for suppressing an increase in the amplification rate of the ultrasonic reception signal. That is, a method was described in which the drive voltage for switching the amplitude of the output signal output from the transmission circuit unit 22 is kept constant, for example at 10 V regardless of the presence or absence of recording material, and the waveform for detecting the peak value is switched depending on the presence or absence of recording material P. In this embodiment, a method is described in which the magnitude of the amplitude of the output signal is switched depending on the presence or absence of recording material P, and the waveform for detecting the peak value is switched. Note that the same numbers are used for the same configuration as in the first embodiment, and the description is omitted. Also, parts with the same symbols perform the same functions and operations.

First, when the receiving means receives ultrasonic waves through the recording material, the amplitude of the output signal is increased to prevent the amplification rate of the received signal from increasing. This prevents the signal-to-noise ratio of the reception level Vp3 of the detection signal from increasing when the receiving means receives ultrasonic waves through the recording material. Below, the switching of the peak detection waveform in this embodiment will be explained using FIG. 7.

In FIG. 7, similar to FIG. 4(b), when the receiving means receives ultrasonic waves that are not transmitted through a recording material, for example, the peak value of the first waveform of the received signal is selected as the peak detection signal. Also, when the receiving means receives ultrasonic waves that are transmitted through a recording material, for example, the peak value of the third waveform of the received signal is selected as the peak detection signal. The switching of the amplification factor of the detection circuit and its signal-to-noise ratio at this time will be explained.

When the receiving means in FIG. 7 receives ultrasonic waves that are not transmitted through a recording material, the explanation is the same as that in FIG. 4(b), so the explanation is omitted.

When the receiving means in FIG. 7 receives ultrasonic waves through a recording material, the amplitude and amplification factor of the output signal are determined so that the reception level Vp3 of the detection signal does not saturate. In this embodiment, the drive input switching means switches the drive voltage depending on whether or not a recording material is present, and the drive voltage when the receiving means receives ultrasonic waves through a recording material is set to, for example, 20 V. This allows the amplification factor to be reduced by 5 times compared to the case of FIG. 4(b). By keeping the amplification factor small, it is possible to prevent the signal-to-noise ratio from becoming larger compared to the case of FIG. 4(b).

The amplitude of the output signal is not limited to the voltage value described in this embodiment, so long as the peak detection signal Va1 is not saturated. Also, the amplification factor of the received signal is not limited to the amplification factor described in this embodiment, so long as the peak detection signal Vp3 is not saturated.

[Switching between output signal and peak detection signal depending on the presence or absence of recording material P]
Hereinafter, a method will be described in which the peak detection unit 20d switches the output signal and the peak detection signal depending on the presence or absence of a recording material, thereby suppressing an increase in the signal-to-noise ratio of the reception level Vp when the receiving means receives ultrasonic waves via the recording material P. Fig. 8 is a flow chart of the process of calculating the basis weight of the recording material P, and Figs. 9(a) to (g) are time charts showing the states of signals and voltages related to the process of calculating the basis weight. The same components as those in Figs. 5 and 6 are given the same numbers, and their explanations will be omitted. The same reference numerals are used to denote the same functions and operations, and therefore their explanations will be omitted.

In S101, the control unit 20 outputs a Low signal as a switching signal for the peak detection signal by the peak detection unit 20d, as shown in FIG. 9(b).

In S102, the transmission instruction unit 20a of the control unit 20 sets the drive voltage output by the transmission circuit unit 22 to 10 V, as shown in FIG. 9(d). This causes the amplification factor switching instruction unit 20b to set the amplification factor of the received signal in the reception detection unit to 1, as shown in FIG. 9(c).

In S103, the control unit 20 executes the following process at a timing when the recording material P has not yet reached the ultrasonic sensor 21 after the start of the paper feed operation. That is, the control unit 20 starts measuring the reception level of ultrasonic waves by the receiving means when the receiving means receives ultrasonic waves not passing through the recording material, as shown in FIG. 9(a). As shown in FIG. 9(e), the control unit 20 outputs a High signal as a drive signal from the transmission instruction unit 20a to the transmission circuit unit 22. In response to the drive signal from the transmission instruction unit 20a, the transmission circuit unit 22 inputs a voltage of 10V to the USS terminal, as shown in FIG. 6(f). A burst signal of a pulse wave of a power supply of 10V is input from the transmission circuit unit 22 to the USS terminal. In this embodiment, the drive signal has a frequency of 40kHz, a pulse number of 2 pulses, and a period of the burst signal of 10msec, as an example.

In S104, the control unit 20 detects the first waveform Va1 of the detection signal and detects its peak value. The detection of the peak value of the first waveform Va1 will be described below. After the drive signal is input to the transmitting means 21a, the receiving detection unit 23 receives the received signal output by the receiving means 21b. The receiving detection unit 23 starts detecting the received signal as a detection signal after a predetermined time T1 synchronized with the drive signal has elapsed. More specifically, when the detection signal exceeds a reference value (for example, 0 V) after the predetermined time T1 synchronized with the drive signal has elapsed, the detection of the detection signal is started, and the detection signal is detected until the detection signal returns to the reference value. In this embodiment, the predetermined time T1 is calculated from the relationship between the distance between the transmitting means 21a and the receiving means 21b measured in advance in the manufacturing process and the sound speed of the ultrasonic wave detected in advance by the ultrasonic sensor in the manufacturing process. The predetermined time T1 is also referred to as the first time, and the period from when the control unit 20 starts detecting the detection signal until the detection signal returns to the reference value is also referred to as the second time. The period from the first time to the second time is the period during which a wave with an amplitude less than the first value, which is the maximum amplitude of the wave that the receiving and detecting means can output, is output. In this manner, the control unit 20 detects the detection signal during the period from when the drive input is input to the transmitting means until the predetermined time T1 has elapsed and until the second time has elapsed, and calculates the receiving level Va1. In this embodiment, the first waveform Va1 is also referred to as the first wave, and the value related to the amplitude that results in the receiving level Va1 is also referred to as the amplitude information of the first wave.

In S105, the control unit 20 outputs a High signal as a switching signal for the peak detection signal by the peak detection unit 20d, as shown in FIG. 9(b).

In S201, the transmission instruction unit 20a of the control unit 20 sets the drive voltage output by the transmission circuit unit 22 to 20V, as shown in FIG. 9(d). This causes the amplification factor switching instruction unit 20b to set the amplification factor of the received signal in the reception detection unit to 5 times, as shown in FIG. 9(c).

In S107, the control unit 20 executes the next process depending on whether the leading edge of the recording material P has reached the registration sensor 6. If the leading edge of the recording material P has reached the registration sensor 6, the control unit 20 advances the process to S108.

In S108, the control unit 20 starts counting the number of steps S of the pulse motor (not shown) to detect the timing at which the leading edge of the recording material P reaches the ultrasonic sensor 21 after reaching the registration sensor 6.

In S109, the control unit 20 advances the process to S110 depending on whether the count value of the number of steps S has reached a predetermined value (100). When the count value of the number of steps S has reached the predetermined value (100), the control unit 20 advances the process to S110.

In S203, the control unit 20 outputs a High signal as a drive signal from the transmission instruction unit 20a to the transmission circuit unit 22 as shown in FIG. 9(e). The control unit 20 drives the ultrasonic sensor 21 by the output signal from the transmission circuit unit 22, and starts measuring the reception level of the received signal by the reception detection unit 23 when the receiving means 21b receives ultrasonic waves via the recording material P. At this time, the transmission circuit unit 22 inputs a voltage of 20V to the USS terminal as shown in FIG. 9(f) in response to the drive signal from the transmission instruction unit 20a.

In S111, the control unit 20 detects the third waveform Vp3 of the detection signal and detects its peak value. The detection of the peak value of the third waveform Vp3 will be described below. After the driving signal is input to the transmitting means 21a, the receiving detection unit 23 receives the receiving signal output by the receiving means 21b. The receiving detection unit 23 starts detecting the receiving signal as a detection signal after a predetermined time T2 synchronized with the driving signal has elapsed, similar to the detection of the detection waveform Va1 when the receiving means receives ultrasonic waves not passing through a recording material. More specifically, when the detection signal exceeds a reference value (for example, 0 V) after the predetermined time T2 synchronized with the driving signal has elapsed, the detection signal is started to be detected, and the detection signal is detected until the detection signal returns to the reference value. In this embodiment, the predetermined time T2 is calculated from the relationship between the distance between the transmitting means 21a and the receiving means 21b measured in advance in the manufacturing process and the sound speed of the ultrasonic waves detected in advance by the ultrasonic sensor in the manufacturing process, and is longer than the predetermined time T1. The predetermined time T2 is also referred to as the third time, and the period from when the control unit 20 starts detecting the detection signal until the detection signal returns to the reference value is also referred to as the fourth time. The period from the first time to the second time is the period during which a wave with an amplitude less than the first value, which is the maximum amplitude of the wave that the receiving and detecting means can output, is output. In this manner, the control unit 20 detects the detection signal during the period from when the drive input is input to the transmitting means until the predetermined time T2 has elapsed and until the fourth time has elapsed, and calculates the receiving level Vp3. In this embodiment, the third waveform Vp3 is also referred to as the second wave, and the value related to the amplitude that becomes the receiving level Vp3 is also referred to as the amplitude information of the second wave.

In S112, the control unit 20 substitutes the reception levels Va1 and Vp into formula (1) to calculate the position correction coefficient T. The subsequent processing is the same as in FIG. 5, so a description thereof will be omitted.

In this embodiment, the method of switching the drive voltage when switching the amplitude of the output signal depending on the presence or absence of recording material P is used. However, as shown in FIG. 10, the control unit 20 may have an amplification factor switching instruction unit 20e for controlling the amplification factor of the voltage input to the transmission circuit unit 22, and may execute the following control. That is, the drive voltage may be constant regardless of the presence or absence of recording material P, and the amplification factor switching signal from the amplification factor switching instruction unit 20e may be switched depending on the presence or absence of recording material, to switch the amplification factor of the voltage input to the transmission circuit unit 22. In this case, for example, the drive voltage may be 20V regardless of the presence or absence of recording material P, and the amplification factor may be set to 1/2 when the receiving means 21b receives ultrasonic waves that are not transmitted through the recording material P. Also, when the receiving means 21b receives ultrasonic waves that are transmitted through the recording material P, the amplification factor may be set to 1.

In this embodiment, the amplitude of the output signal is switched depending on whether or not the recording material P is present, and the peak detection unit 20d switches the waveform of the received signal for detecting the peak value depending on whether or not the recording material is present. That is, when the receiving means 21b receives ultrasonic waves not passing through the recording material P, the peak detection unit 20d selects, for example, the peak value of the first waveform of the received signal as the peak detection signal. Also, when the receiving means 21b receives ultrasonic waves passing through the recording material P, the amplitude of the output signal is made larger than when the receiving means 21b receives ultrasonic waves not passing through the recording material P. Then, the peak detection unit 20d selects, for example, the peak value of the third waveform of the received signal as the peak detection signal. Therefore, when the receiving means 21b receives ultrasonic waves passing through the recording material P, the amplification rate of the received ultrasonic signal can be suppressed from increasing, and the effect of noise present in the circuit receiving the ultrasonic waves on the detection result of the basis weight can be reduced.

In this embodiment, the method of detecting the detection signal for a predetermined time in synchronization with the drive signal has been described as a method of switching the waveform for detecting the peak value of the received signal by the peak detection unit 20d depending on the presence or absence of recording material. However, the method of switching the waveform for detecting the peak value is not limited to this. For example, as a method of switching the waveform for detecting the peak value, the reception level detection unit 20c may detect the waveform of the detection signal using a digital signal converted from the detection signal generated by the reception detection unit 23 and count the waveform. In this case, the points where the digital signal of the detection signal becomes maximum and the waveform reaches a peak value may be counted, or the points where the digital signal of the detection signal becomes 0 and the waveform intersects the horizontal axis may be counted.

In this embodiment, the method of switching the waveform for detecting the peak value may be as follows. For example, a method may be used in which a detection signal is detected in advance by an ultrasonic sensor in the manufacturing process, a threshold is set at a value at which the reception level of the detection signal is not saturated, and the time from when the drive input is input to the transmission means until the detection signal exceeds the threshold Vth is detected. In this case, for example, a threshold Vth is set at a value at which the reception level of the detection signal is not saturated, that is, a value smaller than the upper limit of the signal that the reception signal can be detected by the reception detection unit 23. When the reception means receives ultrasonic waves not passing through a recording material, the time from when the drive input is input to the transmission means until the detection signal becomes equal to or greater than the threshold Vth is set as Ta. When the reception means receives ultrasonic waves passing through a recording material, the time from when the drive input is input to the transmission means until the detection signal becomes equal to or greater than the threshold Vth is set as Tp. A method may be used in which the basis weight of the recording material P is detected according to Ta and Tp obtained in this way. Note that Ta is also referred to as the first period, and Tp is also referred to as the second period.

When using this method, when switching the amplitude of the output signal depending on the presence or absence of the recording material P, the drive voltage may be constant regardless of the presence or absence of the recording material P, and the frequency of the drive signal output by the transmission instruction unit 20a may be switched depending on the presence or absence of the recording material P. For example, the frequency of the drive signal when the amplitude of the ultrasonic wave is maximum is set to the first frequency, and the frequency of the drive signal when the drive signal has a smaller amplitude than the ultrasonic wave when the drive signal has the first frequency is set to the second frequency. In this case, when the receiving means receives ultrasonic waves through a recording material, the transmission instruction unit 20a outputs a pulse wave having the first frequency as the drive signal. Also, when the receiving means receives ultrasonic waves that are not through a recording material, the transmission instruction unit 20b outputs a pulse wave having the second frequency as the drive signal. As a result, when the receiving means receives ultrasonic waves through a recording material, ultrasonic waves having a larger amplitude than when the receiving means receives ultrasonic waves that are not through a recording material can be output by the transmission means 21a. Therefore, it is possible to suppress the signal-to-noise ratio from increasing due to the amplification of the received signal when the receiving means receives ultrasonic waves through a recording material. This makes it possible to detect the basis weight of the recording material P with greater accuracy than ever before.

In addition, the driving voltage and the frequency of the driving signal output by the transmission instruction unit 20a may be constant regardless of whether or not the recording material P is present, and the duty ratio of the high signal and low signal of the driving signal may be switched depending on whether or not the recording material P is present. As a result, when the receiving means receives ultrasonic waves through a recording material, ultrasonic waves of a larger amplitude can be output by the transmitting means 21a than when the receiving means receives ultrasonic waves not through a recording material. Therefore, it is possible to suppress the signal-to-noise ratio from increasing due to the amplification of the received signal when the receiving means receives ultrasonic waves through a recording material.

REFERENCE SIGNS LIST 1 Image forming apparatus 19 Recording material discrimination device 20 Control section 20a Switching instruction section 20b Amplification rate switching instruction section 20d Peak detection section 21 Ultrasonic sensor 21a Transmission means 21b Reception means 22 Transmission circuit section

Claims (6)

an ultrasonic sensor including a transmitting means for transmitting ultrasonic waves and a receiving means for receiving the ultrasonic waves, the transmitting means and the receiving means being disposed on either side of a conveying path along which a recording material is conveyed;
an instruction means for inputting a drive input to the transmission means;
a receiving and detecting means for receiving a signal received by the ultrasonic sensor and outputting a wave having an amplitude equal to or smaller than a first value as a detection signal ;
a basis weight detection means for detecting information regarding the basis weight of the recording material in response to the detection signal output by the receiving detection means,
the reception detection means, when receiving ultrasonic waves not transmitted through a recording material by the receiving means, outputs as the detection signal a wave of a predetermined wave received by the receiving means during a period from a first time after a drive input is input to the transmitting means until a second time has elapsed, and when receiving ultrasonic waves transmitted through a recording material by the receiving means, outputs as the detection signal a wave subsequent to the predetermined wave received by the receiving means during a period from a third time after a drive input is input to the transmitting means until a fourth time has elapsed;
2. A recording material detecting device, comprising: a detecting unit for detecting a recording material, the detecting unit detecting a recording material being detected; an amplification factor switching means for amplifying the received signal;
an amplification factor switching instruction unit that outputs an amplification factor switching signal that switches the amplification factor of the received signal to the amplification factor switching unit;
The recording material detection device according to claim 1, characterized in that the amplification factor switching means amplifies the received signal by a first amplification factor when the receiving means receives ultrasonic waves that have passed through a recording material, and amplifies the received signal by a second amplification factor smaller than the first amplification factor when the receiving means receives ultrasonic waves that have not passed through a recording material. the instruction means has a drive input switching means for switching the drive input that the instruction means inputs to the transmission means depending on the presence or absence of a recording material,
the drive input switching means inputs a first drive input to the transmitting means when the receiving means receives ultrasonic waves that have not passed through a recording material, and inputs a second drive input, which is greater than the first drive input, to the transmitting means when the receiving means receives ultrasonic waves that have passed through a recording material;
3. The recording material detection device according to claim 1, wherein the amplitude of the ultrasonic waves emitted by the transmitting means when the first drive input is input is smaller than the amplitude of the ultrasonic waves emitted by the transmitting means when the second drive input is input. The recording material detection device according to any one of claims 1 to 3, characterized in that the first value is the maximum value of the amplitude of the wave output by the receiving detection means. an ultrasonic sensor including a transmitting means for transmitting ultrasonic waves and a receiving means for receiving the ultrasonic waves, the transmitting means and the receiving means being disposed on either side of a conveying path along which a recording material is conveyed;
an instruction means for inputting a drive input to the transmission means;
a receiving detection means for receiving a signal received by the ultrasonic sensor and outputting a wave having an amplitude equal to or smaller than a first value;
a basis weight detection means for detecting information regarding the basis weight of the recording material in accordance with a first period during which the receiving detection means outputs a wave having an amplitude less than the first value, when the receiving means receives ultrasonic waves that have not passed through a recording material, and a second period during which the receiving detection means outputs a wave having an amplitude less than the first value, when the receiving means receives ultrasonic waves that have passed through a recording material, and a second period during which the receiving detection means outputs a wave having an amplitude less than the first value, when the receiving means receives ultrasonic waves that have passed through a recording material, and an image forming means for forming an image on a recording material;
6. An image forming apparatus, comprising: an image forming unit that changes conditions for forming an image by said image forming means based on a result of detection by the recording material discrimination device according to claim 1.

Images