JP5785460B2 - Ultrasonic detector and image forming apparatus - Google Patents

Description

  The present invention relates to a technique for detecting the basis weight of a sheet.

  In an electrophotographic image forming apparatus or an inkjet image forming apparatus, an appropriate image can be obtained by changing image forming conditions in accordance with the basis weight (weight per unit area) of a sheet. For example, an electrophotographic image forming apparatus adjusts the transfer voltage of a transfer member or adjusts the fixing temperature of a fixing device in accordance with the basis weight of a sheet. Specifically, the user sets the paper type (basis weight) through the host computer or the operation panel, and the transfer conditions (transfer voltage and image forming speed) and fixing conditions (heat quantity and paper transport speed) according to the settings. ) Was controlled.

  However, if the user forgets to set the paper type or makes a mistake, there is a risk of causing image defects. Therefore, in recent years, in order to avoid this problem and reduce the burden on the user, a sensor for discriminating the type of paper has been provided inside the image forming apparatus. The sensor automatically determines the type of paper, and sets transfer conditions and fixing conditions according to the determination results (Patent Documents 1 and 2).

  Specifically, in Patent Document 1, ultrasonic waves are applied to a sheet from an ultrasonic transmission unit, and the reflectance and transmittance from the sheet are detected by the ultrasonic reception unit, so that the surface property and thickness are combined. An invention for discriminating the thickness has been proposed. Patent Document 2 proposes an invention in which the basis weight of a sheet is determined by irradiating the sheet with ultrasonic waves from the ultrasonic transmission unit and detecting the transmittance of the ultrasonic wave transmitted through the sheet with the ultrasonic wave reception unit. Has been.

Japanese Patent Laid-Open No. 2004-219856 JP 2007-24837 A

However, in the prior art, there are cases where the discrimination accuracy is insufficient. FIG. 19 is a diagram showing the relationship between the basis weight of various types of paper and the ultrasonic transmittance. The black circles in FIG. 19 indicate the average value of the ultrasonic transmittance for each sheet having a different basis weight. The error bar indicates the maximum value and the minimum value of the ultrasonic transmittance, that is, the variation. As the cause of the variation, various causes such as flapping of the conveyed paper and electrical noise can be considered. A portion surrounded by a dotted line in FIG. 19 indicates ultrasonic transmittances of a sheet having a general basis weight of 75 g / m ^{2 and} a sheet having a basis weight of 90 g / m ² . The minimum value of the ultrasonic transmittance of a paper having a basis weight of 75 g / m ² and the maximum value of the ultrasonic transmittance of a paper having a basis weight of 90 g / m ² are substantially equal. That is, it is indicated that misidentification occurs because a paper having a basis weight of 75 g / m ^{2 and} a paper having a basis weight of 95 g / m ² cannot be sufficiently discriminated from the ultrasonic transmittance.

  In recent years, a wide variety of paper sheets according to the purpose have been spread in the market. In order to set appropriate transfer conditions and fixing conditions for each of these various types of paper, the basis weight of the paper must be further improved. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the basis weight discrimination accuracy as compared with the prior art.

According to the present invention, the first transport unit, the second transport unit disposed downstream in the paper transport direction from the first transport unit, and the first transport unit to the second transport unit. Ultrasonic transmission means for transmitting ultrasonic waves toward the surface of the paper being conveyed through a conveyance path having a curvature formed by a conveyance auxiliary means for guiding the paper to
An ultrasonic detection device comprising ultrasonic reception means that receives ultrasonic waves that are disposed opposite to and sandwiching the conveyance path with respect to the ultrasonic transmission means, and that transmits the paper,
When the sheet is positioned by the conveyance auxiliary unit when being conveyed from the first conveyance unit to the second conveyance unit via the conveyance auxiliary unit, the ultrasonic transmission unit and the ultrasonic reception unit are positioned. The passage position of the paper in the axial direction connecting the means is a variable passage position according to the basis weight of the paper,
The passing position is variable according to the basis weight of the paper, so that the ultrasonic wave transmission degree represents the ease of transmission when the ultrasonic wave irradiated from the ultrasonic wave transmitting means passes through the paper. , than the ultrasonic permeability when the first sheet is passing the passing position, when the small second sheet having a basis weight than that of the first sheet is passing the passing position There is provided an ultrasonic detecting device characterized in that the ultrasonic wave has a higher transmittance.

  According to the present invention, a conveyance surface having a curvature is provided in a part of the conveyance path, and a transmitter and a receiver are installed in that part. The passing position and the passing angle of the paper when passing through the conveying surface having a curvature vary depending on the basis weight. In addition, when the passage position and the passage angle of the paper in the conveyance path are different, the ultrasonic reception intensity is changed. Therefore, if this characteristic is used, the dynamic range of the ultrasonic detector can be expanded, and the basis weight and type discrimination accuracy of the paper can be improved.

Configuration diagram of image forming apparatus according to first, second, third, and fourth embodiments The block diagram which shows the structure of the control part of the basic weight detection means concerning Example 1, 2, 3, 4. The figure which shows an example of the waveform of the control part of the basic weight detection means concerning Example 1, 2, 3, 4. Diagram showing the relationship between the paper basis weight and the general output of the basis weight detection means The figure explaining the position of the paper with respect to the basic weight detection means concerning Examples 1, 3, and 4. The figure which shows the output characteristic of the basic weight detection means by the position of the paper concerning Examples 1, 3, and 4. The figure which shows the output characteristic of the basic weight detection means by the basic weight of the paper concerning Examples 1, 3, and 4 and the position of a paper. FIG. 6 is a diagram for explaining the behavior of a sheet conveyance position according to the basis weight of a sheet on a conveyance path having a curvature according to the first and fourth embodiments. FIG. 5 is a diagram for explaining the basis weight of a sheet and the position of the sheet on a curved conveyance path according to the first and fourth embodiments. The basic weight of the paper concerning Example 1, and the output characteristic of a basic weight detection means The figure explaining the angle of the sheet | seat with respect to the basic weight detection means concerning Examples 2, 3, and 4. The figure which shows the output characteristic of the basic weight detection means by the angle of the paper concerning Examples 2, 3, and 4. FIG. 10 is a diagram for explaining the behavior of the sheet conveyance angle according to the basis weight of the sheet on the conveyance path having a curvature according to the second and fourth embodiments. FIG. 5 is a diagram for explaining a basis weight of a sheet and a sheet angle on a curved conveyance path according to Examples 2 and 4; The basic weight of the paper concerning Example 2, and the output characteristic of a basic weight detection means The basic weight of the paper concerning Example 3, and the output characteristic of a basic weight detection means Configuration diagram of cassette and manual feed tray conveyance path and basis weight detection means according to embodiment 4 Block diagram showing the configuration of the control unit of the basis weight detection means according to the fourth embodiment. Characteristics of paper basis weight and ultrasonic transmittance in the prior art

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following examples should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[Example 1]
FIG. 1 is a block diagram showing the entirety of an in-line color image forming apparatus according to the present invention. The color image forming apparatus 100 forms a multicolor image by superposing four color toners of yellow (Y), magenta (M), cyan (C), and black (K). In FIG. 1, YMCK is given as a suffix for each reference symbol, but the suffix is omitted in the specification. This is because the basic configurations of the YMCK image forming stations are common.

  Each image forming station is configured around a laser scanner 11 and a cartridge 12 that output laser light for forming a latent image. The cartridge 12 includes a photoconductor 13 on which a latent image is formed, a photoconductor cleaner 14 that cleans residual toner on the photoconductor 13, a charging roller 15 that uniformly charges the photoconductor 13, and a latent image that develops the toner image. The developing roller 16 is formed. An intermediate transfer belt 17 is in contact with the photoreceptor 13. The primary transfer roller 18 is disposed so as to face the photoreceptor 13 with the intermediate transfer belt 17 interposed therebetween. The belt cleaner 19 scrapes off the residual toner on the intermediate transfer belt 17 and stores it in the waste toner container 20.

  The paper P is stored in a cassette 21 that is a first paper feed port and a manual tray 22 that is a second paper feed port. A paper feed roller 23 and separation rollers 25 and 35 are provided in the first transport path for transporting the paper P from the cassette 21. A paper feed roller 24 and separation rollers 26 and 36 are provided in the second transport path for transporting the paper P from the manual feed tray 22. The first conveyance path and the second conveyance path merge downstream to form a merge channel. That is, the conveyance path after the combined flow path is a common conveyance path. A registration roller 27 is provided in the common transport path. A registration sensor 28 is provided in the vicinity of the downstream side in the paper transport direction when viewed from the registration roller 27. When the registration sensor 28 detects the leading edge of the paper P, the registration roller 27 stops. Thereafter, when the preparation for transferring the multicolor image is completed, the registration roller 27 is restarted, and the paper P is conveyed to the secondary transfer roller 29 which is a transfer device. The multi-color image is secondarily transferred from the intermediate transfer belt 17 to the paper P by the secondary transfer roller 29. A transfer voltage for accelerating the secondary transfer of the toner image is applied to the secondary transfer roller 29. This transfer voltage is changed according to the basis weight of the paper P. The fixing device 30 heats the multicolor image at a predetermined fixing temperature and fixes it on the paper P. The fixing temperature is also changed according to the basis weight of the paper. As described above, the image forming unit forms an image under the image forming conditions (transfer voltage and fixing temperature) corresponding to the basis weight and the paper type, which are detection results of the ultrasonic detection device.

  The ultrasonic detector is configured to transmit an ultrasonic wave toward the surface of the paper P that is transported through the transport path, and to be disposed opposite to the transmitter 41 with the transport surface sandwiched between them. A receiver 42 is provided for receiving the ultrasonic wave transmitted by the device 41 and transmitted through the paper P. The transmitter 41 and the receiver 42 are disposed downstream of the separation roller 25 in the paper transport direction.

  FIG. 2 is a block diagram showing the ultrasonic detection device 40. The CPU 10 sends an ultrasonic transmission signal 52 to the transmission control unit 50. The transmission control unit 50 includes a frequency generation unit 501 and an amplifier 502. The ultrasonic transmission signal 52 includes information on timing and frequency for driving the transmitter 41. The frequency generation unit 501 generates and outputs a drive signal 53 having a frequency (for example, 40 kHz) designated by the ultrasonic transmission signal 52. FIG. 3A shows an example of the drive signal 53. The signal level of the drive signal 53 is amplified by the amplifier 502. The amplifier 502 outputs the amplified drive signal 54 to the transmitter 41 at a timing specified by the ultrasonic transmission signal 52. With this drive signal 54, the transmitter 41 outputs a 40 kHz ultrasonic wave.

  The receiver 42 receives the ultrasonic wave from the transmitter 41 or the ultrasonic wave transmitted through the paper P, and outputs an intensity signal 55 indicating the reception intensity of the ultrasonic wave to the reception calculation unit 51. FIG. 3B shows an example of the intensity signal 55. The reception calculation unit 51 includes an amplifier 511 and an integrator 512. The reception calculation unit 51 amplifies the received intensity signal 55 with the amplifier 511, and integrates the amplified intensity signal 56 with the integrator 512 to generate the calculation output 57. FIG. 3C shows an example of the calculation output 57. The calculation output 57 is output to the CPU 10. The CPU 10 calculates the basis weight of the paper P using this calculation output 57. The CPU 10 has a function or table indicating the correspondence between the calculation output and the basis weight, and acquires the corresponding basis weight by inputting the calculation output 57 to the function or table.

  The CPU 10 uses a part of the calculation output 57 shown in FIG. For example, the CPU 10 starts sampling the arithmetic output 57 when a certain time has elapsed from the timing when the drive signal 53 (amplified drive signal 54) is output to the transmitter 41. The CPU 10 performs sampling in about a half cycle section of the drive signal 53, and obtains the maximum value of the sampling value in that section. In FIG. 3C, the circled portion is the maximum value. The CPU 10 determines the basis weight of the paper P using the maximum value. The ROM built in the CPU 10 shows information indicating the relationship between the ultrasonic reception intensity and the paper type (eg, thin paper, plain paper, thick paper) and the relationship between the ultrasonic reception intensity and the paper basis weight. It is memorized in information. Therefore, the CPU 10 uses the information indicating the relationship between the ultrasonic wave reception intensity and the paper type to determine the paper type according to the ultrasonic wave reception intensity received by the ultrasonic wave reception means. Similarly, the CPU 10 uses the information indicating the relationship between the ultrasonic reception intensity and the paper basis weight to determine the paper basis weight according to the ultrasonic reception intensity received by the ultrasonic reception unit. To do. As described above, the CPU 10 functions as a determination unit that determines the type and basis weight of the paper P according to the reception intensity of the ultrasonic wave received by the receiver 42.

  FIG. 4 is a diagram showing a correspondence relationship between the paper P having various basis weights and the value of the calculation output 57. Since the paper P having a small basis weight is likely to transmit ultrasonic waves, the value of the calculation output of the reception calculation unit 51 becomes large. On the other hand, since the paper P having a large basis weight is difficult to transmit ultrasonic waves, the value of the calculation output of the reception calculation unit 51 becomes small.

  The relationship between the passage position of the paper P with respect to the transmitter 41 and the receiver 42 and the calculation output will be described with reference to FIG. Let L be the distance between the transmitter 41 and the receiver 42. A position L / 2 from the transmitter 41, that is, an intermediate position between the transmitter 41 and the receiver 42 is defined as the transport center (reference position) of the paper P. The direction approaching the transmitter 41 side is referred to as “− side”, and the direction away from the transmitter 41 side is referred to as “+ side”. In FIG. 5, the plane whose normal direction is the direction of the straight line connecting the transmitter 41 and the receiver 42 is parallel to the surface of the paper P. In FIG. 5, the midpoint of this line coincides with the center of the paper P. Further, this midpoint is the transport center of the paper P.

  FIG. 6 is a diagram illustrating a change in the calculation output of the reception calculation unit 51 when the paper P having a certain basis weight is shifted from the transport center to the “− side” and the “+ side”. Here, “−side” means a side closer to the transmitter 41, and “+ side” means a side farther from the transmitter 41. According to FIG. 6, it can be seen that the calculation output is low when the paper P is present in the vicinity of the transport center, and the calculation output increases as it shifts to the “− side” and “+ side”. However, when the shift amount to the “− side” exceeds a certain shift amount (eg, −3 mm), the calculation output starts to decrease. Similarly, when the shift amount to the “+ side” exceeds a certain shift amount (for example, +2 mm), the calculation output starts to decrease. Thus, in the range where the shift amount is from −1 mm to +2 mm, the ultrasonic wave reception intensity increases as the distance from the surface of the paper P to the transmitter 41 increases. On the other hand, when the shift amount is in the range from -3 mm to -1 mm, the ultrasonic wave reception intensity increases as the distance from the surface of the paper P to the transmitter 41 becomes shorter.

  FIG. 7 shows the relationship between the basis weight and the calculation output of the reception calculation unit 51 when the conveyance position of the paper P is set to −1 mm, 0 mm (conveyance center), and +1 mm from the conveyance center of the transmitter 41 and the receiver 42. FIG. At any transport position, the calculation output of the reception calculation unit 51 increases as the basis weight of the paper P decreases, and the calculation output of the reception calculation unit 51 decreases as the basis weight increases. That is, according to FIG. 7, it can be said that the smaller the basis weight of the paper P, the higher the transparency (reception intensity of ultrasonic waves) of the paper P. In any basis weight, the calculation output of the reception calculation unit 51 increases as the paper P moves away from the transmitter 41, and the calculation output of the reception calculation unit 51 decreases as the paper P approaches the transmitter 41. The shift amounts of the paper P in FIG. 7 are −1 mm, 0 mm, and +1 mm. Therefore, the calculation output shown in FIG. 7 reflects the characteristics of the section where the shift amount in FIG. 6 is from −1 mm to +2 mm.

  The relationship between the basis weight of the paper P on the conveyance path having a curvature and the passage position on the conveyance path will be described with reference to FIG. As shown in FIG. 8, a conveyance path having a certain curvature is formed by the guide 81 between the separation rollers 25 and 35 and the registration roller 27. Here, as shown in FIG. 8, the conveyance path having a curvature is a cross-sectional shape of the bottom surface of the guide 81 that is the conveyance path, and is a cross section obtained by cutting the bottom surface in the vertical direction along the conveyance direction. It refers to a conveyance path whose shape is generally curved. Since it is sufficient if it is substantially curved, the cross-sectional shape is not necessarily curved. The degree of curvature is determined through experiments and simulations so that the amount of deflection of the paper and the angle when the guide 81 is conveyed are variable according to the basis weight of the paper, as will be described below. What is necessary is just to determine suitably.

  The separation rollers 25 and 35 function as a first transport unit, and the registration roller 27 functions as a second transport unit disposed downstream of the separation rollers 25 and 35 in the paper transport direction.

  The guide 81 functions as a conveyance assist unit that guides the sheet from the separation rollers 25 and 35 to the registration roller 27. As described above, the guide 81 itself may be a member having a curvature or a member having no curvature as long as a conveyance path having a certain curvature can be formed. For example, if the bottom surface of the guide 81 is formed by connecting a plurality of planar members, the cross-sectional shape of the bottom surface of the guide 81 becomes a part of a polygonal side. That is, it is not essential that the cross-sectional shape of the bottom surface of the guide 81 is a complete curved surface. For convenience of explanation, the following explanation will be made as a guide 81 having a curvature. Further, the curvature of the conveyance path may be set so that the sheet P having a smaller basis weight is closer to the guide 81 than the sheet P having a larger basis weight, as will be described later.

  When the paper P is transported on the guide 81 having a curvature, the paper P having a small basis weight easily follows the curvature of the transport surface of the guide 81. That is, the deflection (loop) generated in the paper P increases. On the other hand, since the paper P having a large basis weight is strong, it is difficult to follow the curvature of the conveyance surface of the guide 81. Therefore, the loop generated in the paper P having a large basis weight is smaller than the loop generated in the paper P having a small basis weight. When the ultrasonic transmitter 41 and the receiver 42 are installed so as to face each other across the conveyance path, the passage position of the paper P having a large basis weight passes through the passage position close to the transmitter 41. This is because a loop generated in the paper P having a large basis weight is relatively small. On the other hand, since the loop generated in the paper P having a large basis weight is relatively large, the passage position of the paper P having a small basis weight is a passage position far from the transmitter 41. In this way, when the paper is positioned from the separation rollers 25 and 35 to the registration roller 27 via the guide 81, the paper is positioned by the guide 81, so that the paper in the axial direction connecting the transmitter 41 and the receiver 42 is aligned. The passing position is a variable passing position corresponding to the basis weight of the paper.

FIG. 9 is a diagram illustrating the relationship between the basis weight of the paper P in the conveyance path having a certain curvature and the relative passage position on the conveyance path. The relative passage position indicates a passage position of a paper having another basis weight with reference to the passage position of the paper P having a basis weight of 90 g / m ² . From FIG. 9, it can be seen that when the basis weight decreases, the passing position moves away from the transmitter 41, and when the basis weight increases, the passing position approaches the transmitter 41.

  FIG. 10 is a diagram showing the relationship between the basis weight of the paper P and the calculation output of the reception calculation unit 51 in the ultrasonic detection apparatus having the configuration of FIG. The thick line shown in FIG. 10 indicates the characteristic obtained by multiplying the characteristics of the passing position and the calculation output shown in FIG. 7 and the characteristics of the basis weight and the passing position shown in FIG. That is, the bold line indicates the characteristics of the embodiment in which the curvature is given to the transport surface. On the other hand, the thin line has shown the characteristic of the comparative example which has not provided the curvature to the conveyance surface.

  Since the sheet P having a small basis weight passes through a position relatively far from the transmitter 41, the calculation output of the reception calculation unit 51 increases synergistically. On the other hand, since the sheet P having a large basis weight passes through a position relatively close to the transmitter 41, the calculation output of the reception calculation unit 51 is synergistically reduced. Therefore, the dynamic range of the present embodiment is wider than the dynamic range of the conveyance path of the comparative example in which the passing positions with respect to the transmitter 41 and the receiver 42 do not change according to the basis weight of the paper P.

  Therefore, the separation roller is larger than the distance between the surface of the first sheet and the transmitter 41 when the first sheet conveyed from the separation rollers 25 and 35 via the guide 81 is sandwiched between the registration rollers 27. Between the surface of the second sheet and the transmitter 41 when the second sheet having a basis weight smaller than that of the first sheet, which has been conveyed from 25 and 35 via the guide 81, is sandwiched between the registration rollers 27. The curvature of the guide 81 and the arrangement of the transmitter 41 are determined so that the distance becomes longer.

  In this embodiment, as shown in FIG. 8, the transmitter 41 and the receiver 42 are arranged so that the received intensity of the ultrasonic wave received by the receiver 42 increases as the basis weight of the paper P decreases. Further, the curvature of the transport surface is set so that the passing position of the paper P is within the range from −1 mm to +2 mm shown in FIG. As described above, in the range where the shift amount is from −1 mm to +2 mm, the ultrasonic wave reception intensity increases as the distance from the surface of the paper P to the transmitter 41 increases. Therefore, this curvature is set so that the passing position is farther from the transmitter 41 as the basis weight of the paper P is smaller. That is, the guide 81 changes the distance between the surface of the paper P and the transmitter 41 in accordance with the basis weight of the paper P, so that the ultrasonic wave receiving intensity is further increased as the basis weight of the paper P is smaller. In other words, since the passing position is variable (varies) within a predetermined range according to the basis weight of the paper P, the ultrasonic wave irradiated from the transmitter 41 is easily transmitted when passing through the paper P. A second paper having a lower basis weight than that of the first paper, which is a transmittance of the ultrasonic wave representing the thickness of the first paper (thick paper) when the first paper (thick paper) passes through the passage position. The transmittance of the ultrasonic wave when the (thin paper) passes through the passage position becomes larger. In other words, when the paper is positioned by the guide 81 and the passing position of the paper is within the passing range in which the transmittance increases as the distance from the transmitter 41 to the surface of the paper increases, the separation rollers 25 and 35 are disposed. From the separation rollers 25 and 35, the guide 81 is moved away from the surface of the first sheet and the transmitter 41 when the first sheet conveyed through the guide 81 is sandwiched between the registration rollers 27. The distance between the surface of the second sheet and the transmitter 41 when the second sheet having a smaller basis weight than that of the first sheet is sandwiched between the registration rollers 27 is increased. Due to these synergistic effects, the smaller the basis weight of the paper P, the greater the reception intensity, and the dynamic range of the basis weight is improved.

For example, a thick paper can be defined as a paper having a basis weight of 150 g / m ² or more, and a thin paper can be defined as a paper having a basis weight of 90 g / m ² or less, but is not limited thereto. The definition of thick paper and thin paper can be set as appropriate as long as it is within a generally classified basis weight range.

  On the other hand, the curvature of the conveyance surface may be set so that the passing position of the paper P is within the range from -3 mm to -1 mm shown in FIG. As described above, in the range where the shift amount is from -3 mm to -1 mm, the reception intensity of ultrasonic waves increases as the distance from the surface of the paper P to the transmitter 41 becomes shorter. Therefore, in this case, the transmitter 41 and the receiver 42 are interchanged so that the received intensity of the ultrasonic wave received by the receiver 42 increases as the basis weight of the paper P decreases. 42 are arranged. In addition, the guide 81 changes the distance between the surface of the paper P and the transmitter 41 according to the basis weight of the paper P. Further, when the sheet is positioned by the guide 81, the separation position of the separation roller 25, 35 when the passage position of the sheet is within a passage range in which the transmission increases as the distance from the transmitter 41 to the surface of the sheet decreases. From the separation rollers 25 and 35, the guide 81 is moved away from the surface of the first sheet and the transmitter 41 when the first sheet conveyed through the guide 81 is sandwiched between the registration rollers 27. The distance between the surface of the second sheet and the transmitter 41 when the second sheet having a smaller basis weight than that of the first sheet is sandwiched between the registration rollers 27 is shortened. In other words, the smaller the basis weight of the paper P, the closer the passing position is to the transmitter 41, and the lower the basis weight of the paper P, the higher the ultrasonic reception intensity. Due to these synergistic effects, the smaller the basis weight of the paper P, the greater the reception intensity, and the dynamic range of the basis weight is improved.

  As described above, according to the present embodiment, a conveyance surface having a curvature is provided in a part of the conveyance path, and the transmitter 41 and the receiver 42 are provided in that part. The passing position of the paper P when passing through a conveying surface having a curvature differs depending on the basis weight of the paper P. For example, if the basis weight of the paper P becomes smaller, the passing position of the paper P becomes farther from the transmitter 41. Further, when the passing position of the paper P in the conveyance path is different, the ultrasonic wave reception intensity at the receiver 42 is changed. Therefore, if this characteristic is used, the dynamic range of the ultrasonic detector 40 can be expanded, and the basis weight discrimination accuracy can be improved.

  Note that the calculation output for the passing position may be monotonously increased or monotonously decreased. For example, when the curvature of the conveying surface is set so that the passing position of the paper P is within the range of −1 mm to +2 mm shown in FIG. 6, the passing position of the paper P is transmitted as the basis weight of the paper P is reduced. The transmitter 41 is arranged so as to be far from the transmitter 41. That is, the transmitter 41 is provided on the first side (inside the circle) close to the center of the circle that defines the curvature of the conveyance path, between the first side and the second side across the conveyance path, and the second The receiver 42 is provided on the side (outside the circle). On the other hand, when the curvature of the transport surface is set so that the passing position of the paper P is within the range of −3 mm to −1 mm shown in FIG. 6, the passing position of the paper P is reduced as the basis weight of the paper P is reduced. The transmitter 41 is arranged so that becomes closer to the transmitter 41. That is, the receiver 42 is provided on the first side, and the transmitter 41 is provided on the second side. As described above, regardless of which range is adopted, the dynamic range of the ultrasonic detection device 40 can be expanded as compared with the conventional case.

[Example 2]
The relationship between the passing angle of the paper P with respect to the transmitter 41 and the receiver 42 and the calculation output will be described with reference to FIGS. 11 and 12. As shown in FIG. 11, a plane perpendicular to a straight line connecting the transmitter 41 and the receiver 42 is taken as a reference plane. The direction of this straight line is parallel to the traveling direction of the ultrasonic waves. When the conveyance angle α of the paper P with respect to the reference surface is changed, the calculation output of the reception calculation unit 51 also changes. The angle formed by the surface of the paper P with respect to the straight line connecting the transmitter 41 and the receiver 42 is referred to as a passing angle β. Further, α + β = 90 °.

  FIG. 12 is a diagram showing the relationship between the basis weight and the calculation output of the reception calculation unit 51 when the passing angle β is 85 degrees, 80 degrees, and 75 degrees. As the passing angle β decreases to 85 degrees, 80 degrees, and 75 degrees, the calculation output of the reception calculation unit 51 increases.

  Next, the relationship between the basis weight of the paper P and the passing angle β on the conveyance path having a curvature will be described with reference to FIG. As illustrated in FIG. 13, when the paper P is transported on a transport path having a curvature, the paper P having a small basis weight easily follows the curvature of the transport path. On the other hand, since the paper P having a large basis weight is strong, it is difficult to follow the curvature of the conveyance path. That is, when the ultrasonic transmitter 41 and the receiver 42 are arranged to face each other across the conveyance path, the passage angle β of the paper P having a large basis weight is large and the passage angle β of the paper P having a small basis weight is small.

  FIG. 14 is a diagram showing the relationship between the basis weight in the conveyance path having a certain curvature and the passing angle β of the paper P. Also from this figure, it can be seen that the passage angle β of the paper P increases as the basis weight increases, and the passage angle β of the paper P decreases as the basis weight decreases. In this way, when the sheet is positioned by the guide 81, the passing angle β, which is an acute angle among the angles formed by the surface of the sheet with respect to the axial direction connecting the transmitter 41 and the receiver 42, is the first sheet. The second paper having a smaller basis weight is smaller.

  FIG. 15 is a diagram showing the relationship between the basis weight according to the presence or absence of curvature and the calculation output. The thick line indicates the relationship when the conveyance path has a curvature as shown in FIG. That is, the characteristic indicated by the bold line is a characteristic obtained by multiplying the relationship between the passing angle β and the calculation output shown in FIG. 12 and the relationship between the basis weight and the passing angle β shown in FIG. On the other hand, the thin line shows the relationship between the basis weight and the passing angle β of the paper P when the conveyance path has no curvature.

  Since the passing angle β of the paper P having a small basis weight is relatively small, the calculation output of the reception calculation unit 51 increases synergistically. On the other hand, since the passage angle β of the paper P having a large basis weight is relatively large, the calculation output is synergistically small. That is, the dynamic range of the present embodiment is wider than the dynamic range of the comparative example that employs a planar conveyance path in which the passing angle does not change according to the basis weight of the paper P.

  As described above, according to the present embodiment, a conveyance surface having a curvature is provided in a part of the conveyance path, and the transmitter 41 and the receiver 42 are installed in that part. The passing angle of the paper P when passing through a conveying surface having a curvature varies depending on the basis weight of the paper P. For example, as the basis weight of the paper P decreases, the passing angle β of the paper P decreases. As the basis weight of the paper P increases, the passing angle β of the paper P increases. Further, when the passing angle of the paper P in the conveyance path is different, the ultrasonic wave reception intensity at the receiver 42 is changed. Therefore, if this characteristic is used, the dynamic range of the ultrasonic detector 40 can be expanded, and the basis weight discrimination accuracy can be improved.

[Example 3]
In the first embodiment, it has been described that the basis weight detection accuracy of the paper P is improved by multiplying the calculation output characteristic according to the passage position of the paper P and the passage position characteristic according to the basis weight of the paper P. . In the second embodiment, the basis weight detection accuracy of the paper P is improved by multiplying the calculation output characteristic according to the passage angle of the paper P and the passage angle characteristic according to the basis weight of the paper P. explained. Therefore, in Example 3, Example 1 and Example are combined. That is, in the third embodiment, an effect of multiplying the calculation output characteristic according to the passage position and passage angle of the paper P by the passage position characteristic and passage angle characteristic according to the basis weight of the paper P will be described.

  The calculation output characteristic according to the passage position of the paper P and the passage position characteristic according to the basis weight of the paper P are the same as those described in FIGS. 7 and 9 of the first embodiment, and thus description thereof is omitted. . The calculation output characteristics according to the passing angle of the paper P and the passing angle characteristics according to the basis weight of the paper P are also the same as those described in FIGS. 12 and 14 of the second embodiment, and thus description thereof is omitted. To do.

  FIG. 16 is a diagram illustrating the relationship between the basis weight and the calculation output in Example 3 and the comparative example. In FIG. 16, the thick line indicates the relationship between the basis weight and the calculation output in Example 3, and the thin line indicates the relationship between the basis weight and the calculation output in the comparative example using a planar conveyance path without curvature. Yes. As described above, the sheet having a small basis weight passes through a position away from the transmitter 41 and the passage angle β decreases, so that the calculation output of the reception calculation unit 51 increases synergistically. On the other hand, the sheet P having a large basis weight passes near the transmitter 41 and the passage angle β increases, so that the calculation output of the reception calculation unit 51 decreases synergistically. Therefore, Example 3 can take a large dynamic range as compared with the comparative example.

  In the above description, it is assumed that the curvature is set so that the passing position of the paper P is from −1 mm to +2 mm shown in FIG. However, the curvature may be set so that the passing position of the paper P is from -3 mm to -1 mm shown in FIG. In this case, the same effect can be obtained as described in the first embodiment. In this case, the arrangement of the transmitter 41 and the receiver 42 needs to be switched.

  As described above, the third embodiment uses a partial characteristic in which the calculation output of the reception calculation unit 51 increases as the passing position of the paper P moves away from the transmitter 41. It is characterized in that the curvature is set so as to be separated and the passing angle becomes small. Thereby, since the dynamic range of the ultrasonic detection apparatus 40 can be expanded, the detection accuracy of basic weight can be improved. Similarly, according to the third embodiment, by using a partial characteristic in which the calculation output of the reception calculation unit 51 becomes lower as the paper P moves away from the transmitter 41, the paper P having a smaller basis weight approaches the transmitter 41, And you may set a curvature so that a passage angle may become large.

[Example 4]
In the fourth embodiment, a method for sharing the ultrasonic detection device 40 in the basis weight detection of the sheet P conveyed from the cassette 21 and the sheet P conveyed from the manual feed tray 22 will be described.

  FIG. 17 is a view showing a combined flow path of the cassette 21 and the manual feed tray 22. The transmitters / receivers 43 and 44 incorporate a transmitter 41 and a receiver 42, and are each formed of a piezoelectric element. The transmitter (second ultrasonic transmission means) of the transmitter / receiver 44 is disposed on the opposite side of the carrier path with respect to the transmitter (first ultrasonic transmission means) of the transmitter / receiver 43. Further, the receiver (second ultrasonic wave receiving means) of the transmitter / receiver 43 is disposed to face the transmitter of the transmitter / receiver 44. Similarly, the receiver (first ultrasonic wave receiving means) of the transmitter / receiver 44 is disposed to face the transmitter of the transmitter / receiver 43. Thereby, the ultrasonic wave transmitted by the transmitter of the transmitter / receiver 43 is received by the receiver of the transmitter / receiver 44, and the ultrasonic wave transmitted by the transmitter of the transmitter / receiver 44 is received by the receiver of the transmitter / receiver 43. Yes.

  As shown in FIG. 17, the transmitters / receivers 43 and 44 are installed in the vicinity of the merge path where the first conveyance path from the cassette 21 and the second conveyance path from the manual feed tray 22 merge face to face. This is because the basis weight transported in both the first transport path and the second transport path can be detected by the pair of the transceivers 43 and 44.

  When the paper P in the cassette 21 is thick paper, the paper P passes near the transceiver 43, and when the paper P in the cassette 21 is thin paper, the paper P passes away from the transceiver 43. On the other hand, when the paper P in the manual feed tray 22 is thick paper, the paper P passes near the transmitter / receiver 44, and when the paper P in the manual feed tray 22 is thin paper, the paper P passes away from the transmitter / receiver 44. Since other configurations have been described in the first embodiment, a description thereof will be omitted.

  The transmission / reception switching method of the ultrasonic detection apparatus 40 will be described with reference to FIG. A drive signal 54 from the transmission control unit 50 is connected to the transceivers 43 and 44 via the switch 58. The intensity signal 55 input to the reception calculation unit 51 is connected to the transceivers 43 and 44 through the switch 59. That is, by changing the states of the switches 58 and 59, the transceivers 43 and 44 can be switched between the ultrasonic transmitter and the ultrasonic receiver, respectively. Thus, the transceivers 43 and 44 function as a pair of ultrasonic transmission / reception means that operate as the transmitter 41 or the receiver 42. Further, the CPU 10 and the switches 58 and 59 are switching means for switching the functions of the pair of ultrasonic transmission / reception means so that one of the pair of transceivers 43 and 44 functions as the transmitter 41 and the other functions as the receiver 42. Function as. Since other configurations have been described in the first embodiment, a description thereof will be omitted.

  The basis weight detection of the paper P conveyed from the cassette 21 and the basis weight detection of the paper P conveyed from the manual feed tray 22 will be specifically described. When notified from the controller (not shown) that the paper P is conveyed from the cassette 21, the CPU 10 changes the state of the switches 58 and 59, connects the transmission control unit 50 and the transceiver 43, and receives the calculation unit 51. And the transceiver 44 are connected. That is, the transceiver 43 functions as a transmitter, and the transceiver 44 functions as a receiver. As described above, the ultrasonic detection device 40 uses the transmitter of the transmitter / receiver 43 and the receiver of the transmitter / receiver 44 when determining the basis weight of the paper transported from the first transport path. More specifically, the CPU 10 and the switches 58 and 59 switch the function of one transmitter / receiver 43 arranged on the first side to function as the transmitter 41 and are arranged on the second side. The function of the other transmitter / receiver 44 is switched to function as the receiver 42. Here, the first side means that when a sheet is conveyed from the first sheet feeding port, it continues from the first conveyance path among the first side and the second side across the combined flow path. It is the side close to the center of the circle that defines the curvature of the combined flow path. The second side is a combined flow path that continues from the first transfer path among the first side and the second side across the combined flow path when the sheet is conveyed from the first paper feed port. The side far from the center of the circle that defines the curvature.

  When the paper P from the cassette 21 is a thick paper, the paper P passes near the transmitter / receiver 43 as a transmitter. When the paper P is thin paper, the paper P passes through a position away from the transmitter / receiver 43 as a transmitter. That is, as described in the first exemplary embodiment, the partial characteristic is used in which the calculation output of the reception calculation unit 51 increases as the passing position of the paper P becomes farther from the transmitter 41. The curvature of the first transport path is set so that the paper P having a smaller basis weight passes through a position away from the transmitter 41. Therefore, the effect similar to Example 1 can be expected also in Example 3.

  On the other hand, when notified from the controller (not shown) that the paper P is conveyed from the manual feed tray 22, the CPU 10 changes the state of the switches 58 and 59, connects the transmission control unit 50 and the transceiver 44, and receives the signal. The calculation unit 51 and the transceiver 43 are connected. That is, the transceiver 44 functions as a transmitter, and the transceiver 43 functions as a receiver. As described above, the ultrasonic detection device 40 uses the transmitter of the transmitter / receiver 44 and the receiver of the transmitter / receiver 43 when determining the basis weight of the paper transported from the second transport path. That is, the CPU 10 and the switches 58 and 59 switch the function of the other transmitter / receiver 44 arranged on the second side to function as the transmitter 41 when the sheet is conveyed from the second sheet feeding port. . Here, the 2nd side is a side near the center of the circle which defines the curvature of the combined flow path which continues from the 2nd conveyance way among the 1st side and 2nd side which pinched the combined flow path. . Further, the CPU 10 and the switches 58 and 59 switch the function of the one transmitter / receiver 43 arranged on the first side to function as the receiver 42. As a result, when the paper P from the manual feed tray 22 is a thick paper, the paper P passes near the transmitter / receiver 44 as a transmitter, and when the paper P is a thin paper, the paper P is positioned away from the transmitter / receiver 44 as a transmitter. pass. Therefore, the effect similar to Example 1 can be expected also in Example 3.

  In the fourth embodiment, switching between the transmitter and the receiver in the basis weight detection of the paper P in the cassette 21 and the basis weight detection of the paper P in the manual feed tray 22 is performed according to the passage position described in the first embodiment. Basis weight measurement using output characteristics may be executed. However, in the fourth embodiment, the basis weight measurement may be performed using the calculation output characteristics according to the passing angle described in the second embodiment. Similarly, the basis weight detection method described in Example 3 may be adopted as the basis weight detection method of Example 4. Further, the respective curvatures of the first conveyance path and the second conveyance path may be set so that the passing position of the sheet P is within the range from −1 mm to +2 mm shown in FIG. The passing position of the paper P may be set to fall within the range from −3 mm to −1 mm shown in FIG. In the latter case, the CPU 10 and the switches 58 and 59 switch the function of one ultrasonic transmission / reception means disposed on the first side when the sheet is conveyed from the first sheet feeding port. Function as 42. Here, the first side is a side close to the center of the circle that determines the curvature of the combined flow path that continues from the first transport path, among the first side and the second side across the combined flow path. The second side is a side far from the center of the circle that defines the curvature of the combined flow path continuing from the first transport path, between the first side and the second side across the combined flow path. Further, the CPU 10 and the switches 58 and 59 switch the function of the other ultrasonic transmission / reception means arranged on the second side to function as the transmitter 41. On the other hand, the CPU 10 and the switches 58 and 59 function as the receiver 42 by switching the function of the other ultrasonic wave transmitting / receiving means arranged on the second side when the sheet is conveyed from the second paper feed port. Let Here, the 2nd side is a side near the center of the circle which defines the curvature of the combined flow path which continues from the 2nd conveyance way among the 1st side and 2nd side which pinched the combined flow path. The first side is a side far from the center of the circle that defines the curvature of the combined flow path that continues from the second transport path, among the first side and the second side that sandwich the combined flow path. Further, the CPU 10 and the switches 58 and 59 switch the function of one ultrasonic transmission / reception means arranged on the first side to function as the transmitter 41.

  As described above, according to the fourth embodiment, the basis weight detection of the paper P in the cassette 21 and the basis weight detection of the paper P in the manual feed tray 22 can be performed by the single ultrasonic detection device 40. . However, it is necessary for the CPU 10 to switch the states of the switches 58 and 59 in accordance with which paper feed port the two transceivers 43 and 44 having the function as a transmitter and the function as a receiver are conveyed. is there. As the basis weight detection method, any of the detection methods of Example 4 and Examples 1 to 3 can be adopted. Therefore, the basis weight detection accuracy of the fourth embodiment can be improved similarly to the first to third embodiments.

  In the above description, the transmitters / receivers 43 and 44 have an ultrasonic transmitter and an ultrasonic receiver, respectively. However, since the ultrasonic transmitter and the ultrasonic receiver can be realized by the configuration having the same vibration element, the transmitters and receivers 43 and 44 may each have one ultrasonic transmitter or one ultrasonic receiver. Good. In such a configuration, by switching the switches 58 and 59, the vibration element connected to the transmission circuit operates as an ultrasonic transmitter, and the vibration element connected to the reception circuit operates as an ultrasonic receiver. The transceivers 43 and 44 each have one ultrasonic transmitter or ultrasonic receiver, so that the configuration can be simplified.

Claims (16)

A first conveying unit, a second conveying unit disposed downstream of the first conveying unit in the sheet conveying direction, and a conveyance assist for guiding the sheet from the first conveying unit to the second conveying unit. Ultrasonic transmission means for transmitting ultrasonic waves toward the surface of the paper conveyed along the conveyance path having a curvature formed by the means;
An ultrasonic detection device comprising ultrasonic reception means that receives ultrasonic waves that are disposed opposite to and sandwiching the conveyance path with respect to the ultrasonic transmission means, and that transmits the paper,
When the sheet is positioned by the conveyance auxiliary unit when being conveyed from the first conveyance unit to the second conveyance unit via the conveyance auxiliary unit, the ultrasonic transmission unit and the ultrasonic reception unit are positioned. The passage position of the paper in the axial direction connecting the means is a variable passage position according to the basis weight of the paper,
The passing position is variable according to the basis weight of the paper, so that the ultrasonic wave transmission degree represents the ease of transmission when the ultrasonic wave irradiated from the ultrasonic wave transmitting means passes through the paper. , than the ultrasonic permeability when the first sheet is passing the passing position, when the small second sheet having a basis weight than that of the first sheet is passing the passing position The ultrasonic detection apparatus, wherein the ultrasonic wave has a higher transmittance.   The ultrasonic detection apparatus according to claim 1, wherein the smaller the basis weight of the paper, the greater the transparency of the paper.   When the paper is positioned by the conveyance assisting means, the passage position of the paper is within a passing range in which the transparency increases as the distance from the ultrasonic transmission means to the surface of the paper increases. The surface of the first sheet when the first sheet conveyed from the first conveying unit via the conveyance auxiliary unit is sandwiched between the second conveying unit and the ultrasonic transmission unit When a second sheet having a basis weight smaller than that of the first sheet and transported from the first transport unit via the transport auxiliary unit is held between the first transport unit and the second transport unit. The ultrasonic detection apparatus according to claim 1, wherein a distance between the surface of the second paper and the ultrasonic transmission unit is longer.   When the sheet is positioned by the conveyance assisting unit, an acute angle among the angles formed by the surface of the sheet with respect to the axial direction connecting the ultrasonic transmitting unit and the ultrasonic receiving unit is the first angle. The ultrasonic detection apparatus according to claim 3, wherein the second sheet having a smaller basis weight is smaller than the second sheet. The ultrasonic transmission means is provided on the first side close to the center of the circle that defines the curvature of the conveyance path, between the first side and the second side across the conveyance path,
The ultrasonic detection apparatus according to claim 1, wherein the ultrasonic reception unit is provided on the second side.   When the paper is positioned by the conveyance assisting means, the passage position of the paper is within a passing range in which the transparency increases as the distance from the ultrasonic transmission means to the surface of the paper decreases. The surface of the first sheet when the first sheet conveyed from the first conveying unit via the conveyance auxiliary unit is sandwiched between the second conveying unit and the ultrasonic transmission unit When a second sheet having a basis weight smaller than that of the first sheet and transported from the first transport unit via the transport auxiliary unit is held between the first transport unit and the second transport unit. The ultrasonic detection apparatus according to claim 1, wherein a distance between the surface of the second paper and the ultrasonic transmission unit is shorter.   When the sheet is positioned by the conveyance assisting unit, an acute angle among the angles formed by the surface of the sheet with respect to the axial direction connecting the ultrasonic transmitting unit and the ultrasonic receiving unit is the first angle. The ultrasonic detection apparatus according to claim 6, wherein the second sheet having a smaller basis weight is smaller than the second sheet. The ultrasonic wave receiving means is provided on the first side close to the center of a circle that defines the curvature of the conveyance path, between the first side and the second side across the conveyance path,
The ultrasonic wave transmission means according to claim 1, characterized in that provided on the second side of the ultrasonic detecting apparatus according to any one of 7. A first conveying unit, a second conveying unit disposed downstream of the first conveying unit in the sheet conveying direction, and a conveyance assist for guiding the sheet from the first conveying unit to the second conveying unit. Ultrasonic transmission means for transmitting ultrasonic waves toward the surface of the paper conveyed along the conveyance path having a curvature formed by the means;
An ultrasonic detection device comprising ultrasonic reception means that receives ultrasonic waves that are disposed opposite to and sandwiching the conveyance path with respect to the ultrasonic transmission means, and that transmits the paper,
When the sheet is positioned by the conveyance auxiliary unit when being conveyed from the first conveyance unit to the second conveyance unit via the conveyance auxiliary unit, the ultrasonic transmission unit and the ultrasonic reception unit are positioned. The passage position of the paper in the axial direction connecting the means is a variable passage position according to the basis weight of the paper,
An angle which is an acute angle among angles formed by the surface of the sheet with respect to an axial direction connecting the ultrasonic transmission unit and the ultrasonic reception unit by changing the passing position according to the basis weight of the sheet. a is, than the angle of the first sheet, the ultrasound detecting unit is towards the angle of the first second sheet small than the basis weight of the paper, characterized in that smaller. A pair of ultrasonic transmission / reception means operating as the ultrasonic transmission means or the ultrasonic reception means;
Of the pair of ultrasonic transmission / reception means, one ultrasonic transmission / reception means of the pair of ultrasonic transmission / reception means functions as the ultrasonic transmission means, and the other ultrasonic transmission / reception means functions as the ultrasonic reception means. It further comprises a switching means for switching functions,
The transport path further includes a first transport path for transporting paper from a first paper feed slot, a second transport path for transporting paper from a second paper feed slot, the first transport path, and the second transport path. The transport path has a curvature that merges face-to-face, and is formed by a merge path that functions as the conveyance assisting means,
The pair of ultrasonic transmission / reception means is arranged so as to sandwich the combined flow path among the transport paths,
When the sheet is transported from the first paper feed port, the switching unit is configured to continue the merging from the first transport path between the first side and the second side across the merging path. The function of one ultrasonic transmission / reception means arranged on the first side close to the center of the circle defining the curvature of the road is switched to function as the ultrasonic transmission means, and arranged on the second side. The function of the other ultrasonic wave transmitting / receiving means is switched to function as the ultrasonic wave receiving means, and when the paper is conveyed from the second paper feed port, the first side and the second side across the combined flow path The function of the other ultrasonic transmission / reception means disposed on the second side close to the center of the circle that defines the curvature of the combined flow path that continues from the second conveyance path is switched to the ultrasonic wave It functions as a transmission means and is arranged on the first side Ultrasonic detection device according to any one of claims 1 to 5 is characterized in that to function as the ultrasonic receiving means switches the function of the one ultrasonic transmit-receive unit is. A pair of ultrasonic transmission / reception means operating as the ultrasonic transmission means or the ultrasonic reception means;
Of the pair of ultrasonic transmission / reception means, one ultrasonic transmission / reception means of the pair of ultrasonic transmission / reception means functions as the ultrasonic transmission means, and the other ultrasonic transmission / reception means functions as the ultrasonic reception means. It further comprises a switching means for switching functions,
The transport path further includes a first transport path for transporting paper from a first paper feed slot, a second transport path for transporting paper from a second paper feed slot, the first transport path, and the second transport path. The transport path has a curvature that merges face-to-face, and is formed by a merge path that functions as the conveyance assisting means,
The pair of ultrasonic transmission / reception means is arranged so as to sandwich the combined flow path among the transport paths,
When the sheet is transported from the first paper feed port, the switching unit is configured to continue the merging from the first transport path between the first side and the second side across the merging path. The function of one ultrasonic transmission / reception means arranged on the first side close to the center of the circle defining the curvature of the road is switched to function as the ultrasonic reception means, and arranged on the second side The function of the other ultrasonic transmission / reception means is switched to function as the ultrasonic transmission means, and when the paper is conveyed from the second paper feed port, the first side and the second across the combined flow path The function of the other ultrasonic transmission / reception means disposed on the second side close to the center of the circle that defines the curvature of the combined flow path that continues from the second conveyance path is switched to the ultrasonic wave It functions as a receiving means and is arranged on the first side The ultrasonic detection according to any one of claims 1, 2, 6, 7, and 8, wherein the function of the one ultrasonic transmission / reception unit is switched to function as the ultrasonic transmission unit. apparatus. A first conveying unit, a second conveying unit disposed downstream of the first conveying unit in the sheet conveying direction, and a conveyance assist for guiding the sheet from the first conveying unit to the second conveying unit. Ultrasonic transmission means for transmitting ultrasonic waves toward the surface of the paper conveyed along the conveyance path having a curvature formed by the means;
An ultrasonic detection device comprising ultrasonic reception means that receives ultrasonic waves that are disposed opposite to and sandwiching the conveyance path with respect to the ultrasonic transmission means, and that transmits the paper,
When transported from the first transport unit to the second transport unit via the transport auxiliary unit, the passing position of the sheet passing between the ultrasonic transmission unit and the ultrasonic reception unit is: Fluctuates within a predetermined range according to the basis weight of the paper in the axial direction connecting the ultrasonic transmission means and the ultrasonic reception means,
Within the predetermined range, the longer the distance from the ultrasonic transmission means to the surface of the paper, the longer the ultrasonic waves that are emitted from the ultrasonic transmission means indicate the ease of transmission through the paper. Of the first sheet when the first sheet conveyed from the first conveyance unit via the conveyance auxiliary unit is nipped by the second conveyance unit. A second sheet having a basis weight smaller than that of the first sheet, which has been conveyed from the first conveying unit via the conveyance auxiliary unit, is smaller than the distance between the surface and the ultrasonic transmission unit. An ultrasonic detection apparatus characterized in that the distance between the surface of the second sheet and the ultrasonic transmission means when being held by the conveying means is longer. A first conveying unit, a second conveying unit disposed downstream of the first conveying unit in the sheet conveying direction, and a conveyance assist for guiding the sheet from the first conveying unit to the second conveying unit. Ultrasonic transmission means for transmitting ultrasonic waves toward the surface of the paper conveyed along the conveyance path having a curvature formed by the means;
An ultrasonic detection device comprising ultrasonic reception means that receives ultrasonic waves that are disposed opposite to and sandwiching the conveyance path with respect to the ultrasonic transmission means, and that transmits the paper,
When transported from the first transport unit to the second transport unit via the transport auxiliary unit, the passing position of the sheet passing between the ultrasonic transmission unit and the ultrasonic reception unit is: Fluctuates within a predetermined range according to the basis weight of the paper in the axial direction connecting the ultrasonic transmission means and the ultrasonic reception means,
Within the predetermined range, as the distance from the ultrasonic transmission unit to the surface of the paper becomes shorter, the ultrasonic wave representing the ease of transmission of the ultrasonic wave irradiated from the ultrasonic transmission unit through the paper Of the first sheet when the first sheet conveyed from the first conveyance unit via the conveyance auxiliary unit is nipped by the second conveyance unit. A second sheet having a basis weight smaller than that of the first sheet, which has been conveyed from the first conveying unit via the conveyance auxiliary unit, is smaller than the distance between the surface and the ultrasonic transmission unit. An ultrasonic detection apparatus characterized in that the distance between the surface of the second sheet and the ultrasonic transmission means when being sandwiched between the conveying means is shorter.   It further comprises a discriminating means for discriminating the paper type according to the ultrasonic wave receiving intensity received by the ultrasonic wave receiving means using information indicating the relationship between the ultrasonic wave receiving intensity and the paper type. The ultrasonic detection apparatus according to claim 1, wherein:   And a discriminating unit that discriminates the basis weight of the paper according to the received intensity of the ultrasonic wave received by the ultrasonic wave receiving unit using information indicating a relationship between the ultrasonic wave receiving intensity and the basis weight of the paper. The ultrasonic detection apparatus according to claim 1, wherein the ultrasonic detection apparatus is one of the following. The ultrasonic detection device according to any one of claims 1 to 15,
An image forming apparatus comprising: an image forming unit that forms an image;
The image forming apparatus, wherein the image forming unit forms an image under an image forming condition corresponding to a detection result of the ultrasonic detection device.

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