JP2019108230A - Ultrasonic wave transmitter, ultrasonic wave receiver, sheet determination device, and image forming apparatus - Google Patents

Abstract

To provide protective members in at least either one of a transmitter or a receiver of ultrasonic waves to prevent a user from touching a vibration member.SOLUTION: Protective members 328 are arranged so that a distance L2 between an aperture plane of a receiving guide 325 and the center of the protective members 328 becomes half a distance L1 between the aperture plane of the receiving guide 325 and a surface of a reception vibration member 321. In other words, the protective members 328 are arranged at the center positions (L2=L1/2) between the aperture plane of the receiving guide 325 and the surface of the reception vibration member 321. With this arrangement, a transmission coefficient equal to a transmission coefficient when the protective members 328 are not present can be obtained despite the arrangement of the protective members 328.SELECTED DRAWING: Figure 3

Description

  The present invention relates to protection of an ultrasonic transmitter and an ultrasonic receiver.

  An image forming apparatus such as a copying machine or a laser printer determines the type of sheet inside the image forming apparatus using an ultrasonic sensor, and sets image forming conditions such as transfer conditions and fixing conditions according to the determination result. By the way, the ultrasonic wave transmitted from the transmitter may be reflected a plurality of times and received by the receiver. The reflection may be generated not only by the sheet but also by a member such as a transport roller for transporting the sheet, a transport guide, and the like, around the transmitter and the receiver.

  According to Patent Document 1, it has been proposed to attach a sound wave guide for focusing sound waves to each of a transmitter and a receiver. According to Patent Document 2, it has been proposed to stabilize the output of the ultrasonic wave transmitted through the recording medium by determining the length of the guide based on the wavelength of the ultrasonic wave.

JP 2001-351141 A JP, 2010-018432, A

  By the way, an ultrasonic sensor may be arrange | positioned in the position which a user can touch with a finger. The ultrasonic sensor transmits and receives ultrasonic waves due to the vibration of the vibrating member, so that the ultrasonic sensor can not operate normally when the vibrating member is touched. Sometimes the ultrasonic sensor may break down. Therefore, it is an object of the present invention to make it difficult for the user to touch the vibrating member in at least one of the ultrasonic wave transmitter and receiver.

The present invention, for example,
A vibrating member that vibrates to emit ultrasonic waves;
A guide member for guiding the ultrasonic wave emitted from the vibrating member;
And a protection member provided inside the guide member to protect the vibrating member,
There is provided an ultrasonic wave transmission apparatus in which at least a part of the vibration member overlaps the protective member in the direction of a line passing through the center of the vibration member and perpendicular to the surface of the vibration member transmitting the ultrasonic wave. Do.

  According to the present invention, by providing the protective member in at least one of the ultrasonic wave transmitter and the ultrasonic wave receiver, it becomes difficult for the user to touch the vibrating member.

Schematic configuration of the image forming apparatus Block diagram showing a control unit and an ultrasonic sensor that constitute a sheet discrimination apparatus Diagram showing the configuration of the ultrasonic wave receiving unit Diagram showing the relationship between the arrangement position of the protective member and the transmission coefficient Diagram showing composition of multiple reflected waves Diagram showing the configuration of the ultrasonic wave receiving unit Diagram showing the configuration of the ultrasonic wave transmitter Diagram showing the relationship between the arrangement position of the protective member and the transmission coefficient Diagram showing the configuration of the ultrasonic wave transmitter Diagram showing the relationship between the arrangement position of the protective member and the transmission coefficient The figure which shows the other example of a protection member A figure showing an example of section structure of a guide member

  Hereinafter, embodiments of the present invention will be described using the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of the features described in the embodiments are not necessarily essential to the solution unit of the invention.

First Embodiment
The sheet discrimination apparatus of the present embodiment can be used, for example, in an image forming apparatus such as a copying machine or a printer. FIG. 1 shows an image forming apparatus 1 equipped with a sheet discrimination apparatus as an example. In the image forming apparatus 1, a plurality of image forming units are arranged in parallel, and an intermediate transfer member transfers a toner image to a sheet. In this example, the plurality of image forming units form an image using a toner image of yellow, magenta, cyan, or black.

  The sheet P is fed by the sheet feeding rollers 4 a and 4 b feeding from the sheet feeding cassette 2 or the sheet feeding tray 3. The conveyance roller 5 conveys the sheet P from the upstream side to the downstream side in the conveyance direction of the sheet P. The ultrasonic sensor 30 includes an ultrasonic wave transmitting unit 31 and an ultrasonic wave receiving unit 32, and detects ultrasonic waves corresponding to the type of sheet P (such as basis weight and thickness). The control unit 10 determines the type (basis weight, thickness, and the like) of the sheet P based on the detection result of the ultrasonic sensor 30, and controls the fixing temperature of the fixing unit 21. This is because the appropriate fixing temperature is different depending on the basis weight and thickness of the sheet P. The control unit 10 may adjust the conveyance speed of the sheet P based on the determination result. This is to relatively reduce the transport speed for thick sheets as compared to thin sheets, and to increase the thermal energy applied to the toner. The control unit 10 may adjust the voltage value supplied to the secondary transfer roller pair 19 based on the determination result. This is because the appropriate voltage value differs depending on the basis weight and thickness of the sheet P. Here, although the above-described processing is listed as an example of the image forming condition, the present invention is not limited to this, and any method may be used as long as it can be controlled according to the basis weight and thickness of the sheet P. As described above, the ultrasonic sensor 30 and the control unit 10 function as a sheet discrimination device. The control unit 10 also functions as a determination unit that determines the type of sheet based on the detection signal output from the ultrasonic sensor. In addition, the control unit 10 may omit the process of determining the type of the sheet P, and control the image forming conditions directly from the output result of the ultrasonic sensor 30.

  The photosensitive drum 11 is uniformly charged to a predetermined potential by the charging unit 12. The optical unit 13 irradiates laser light corresponding to image data onto the uniformly charged photosensitive drum 11 to form an electrostatic latent image. The developing unit 15 develops the electrostatic latent image formed on the photosensitive drum 11 with toner to form a toner image. The primary transfer roller 16 transfers the toner image from the photosensitive drum 11 to the intermediate transfer belt 17. The secondary transfer roller pair 19 secondarily transfers the toner image formed on the intermediate transfer belt 17 to the sheet P. The fixing unit 21 fuses and fixes the toner image transferred to the sheet P while conveying the sheet P. The discharge roller 22 discharges the sheet P fixed by the fixing unit 21.

  In FIG. 1, the ultrasonic sensor 30 is provided between a joining portion of the conveyance path from the sheet feeding cassette 2 and the conveyance path from the sheet feeding tray 3 and the pair of secondary transfer rollers 19. This is to enable discrimination of the type by one ultrasonic sensor 30 regardless of which sheet P is fed from either the sheet feeding cassette 2 or the sheet feeding tray 3.

  The hardware involved in the operation of the ultrasonic sensor 30 and the function thereof will be described with reference to FIG. In the ultrasonic wave transmission unit 31 which is an ultrasonic wave transmission device, the transmission vibration member vibrates in response to the supplied drive signal, and the ultrasonic wave is transmitted to the sheet P. The ultrasonic wave receiving unit 32, which is an ultrasonic wave receiving device, generates a reception signal by vibrating the reception vibration member by the ultrasonic wave transmitted from the ultrasonic wave transmission unit 31 and transmitted through the sheet P. The ultrasonic waves are attenuated when passing through the sheet P. In the present embodiment, the ultrasonic wave transmission unit 31 transmits ultrasonic waves having a frequency characteristic of 40 kHz, and the ultrasonic wave reception unit 32 is set to receive the ultrasonic waves. The frequency of the ultrasonic waves is preset. For example, a frequency in an appropriate range is selected according to the configuration of the ultrasound transmission unit 31 and the ultrasound reception unit 32, detection accuracy, and the like. The transmission control unit 33 includes a drive signal generation unit 331 that generates a drive signal for transmitting an ultrasonic wave, and an amplifier 332 that amplifies the drive signal and supplies the amplified signal to the ultrasonic wave transmission unit 31. The reception control unit 34 detects an ultrasonic wave received by the ultrasonic wave receiving unit 32 as a voltage, an A / D conversion unit 343 that converts a detection signal from analog to digital, and a peak extraction unit 344 which extracts a peak of ultrasonic waves. And a storage unit 346 that stores peak values. The control unit 10 reads the peak value (determination result) from the storage unit 346 and uses it for controlling image forming conditions such as the conveyance speed and the fixing temperature in the fixing unit.

  Next, a series of operations will be described. The control unit 10 inputs a measurement start signal indicating the start of measurement to the drive signal control unit 341. When receiving the measurement start signal, the drive signal control unit 341 instructs the drive signal generation unit 331 to generate a drive signal in order to emit an ultrasonic wave of a predetermined frequency (for example, 40 kHz). The drive signal is a pulse wave of a constant cycle. This can reduce the influence of disturbances such as a reflected wave by the sheet P and members disposed around the conveyance path, or can mainly receive the direct wave emitted by the ultrasonic wave transmission unit 31 by the ultrasonic wave reception unit 32. It is decided in consideration of doing so. In general, the generation of the reflected wave and the amplitude of the composite wave of the plurality of reflected waves depend on the wavelength of the ultrasonic wave. The pulse wave of a fixed period may be called a burst wave. In the present embodiment, a 40-kHz pulse wave of 5 pulses is input to the ultrasonic wave transmission unit 31 within a period of 20 ms. As described above, the drive signal generation unit 331 generates and outputs a signal having a preset frequency. The amplifier 332 amplifies the level (voltage value) of the drive signal output from the drive signal generator 331 and supplies the amplified signal to the ultrasonic wave transmitter 31.

  The ultrasonic wave reception unit 32 receives the ultrasonic wave transmitted from the ultrasonic wave transmission unit 31 and outputs a detection signal to the detection circuit 342 of the reception control unit 34. The detection circuit 342 has a function of amplifying the detection signal and a function of rectifying the detection signal. The amplification function is such that the amplification factor can be varied between the state in which the sheet P is not present between the ultrasonic wave transmitting unit 31 and the ultrasonic wave receiving unit 32 and the state in which the sheet P is present. It is not a thing. For example, the amplification factor may be similar in the state where the sheet P does not exist and in the state where the sheet P exists. Further, although the rectification function performs half-wave rectification, the present invention is not limited to this, and both-wave rectification may be performed. The AD conversion unit 343 converts the analog detection signal generated by the detection circuit 342 into a digital detection signal. Although the AD conversion unit 343 converts the signal into a 12-bit digital signal corresponding to the output of the detection circuit 342, the present invention is not limited to this, and may convert the signal into a plurality of appropriate digital signals. The peak extraction unit 344 extracts the peak (maximum value) of the digital signal output from the AD conversion unit 343. The peak extraction unit 344 stores, in the storage unit 346, the peak value extracted at the end of one ultrasonic measurement. Based on the peak value stored in the storage unit 346, the control unit 10 determines the basis weight of the sheet P, and controls the operation of the image forming apparatus 1 according to the determination result. The basis weight referred to herein is the mass per unit area of the sheet, and the mass per square meter is represented by (g / m 2). There is a clear correlation between peak value and basis weight (or thickness). Therefore, the control unit 10 can determine the basis weight (or thickness) from the peak value using a formula or a table.

  The configuration of the ultrasonic wave receiving unit 32 of the ultrasonic wave sensor 30 will be described with reference to FIGS. 3A to 3C. 3 (A) is a perspective view of the ultrasonic wave receiving unit 32, FIG. 3 (B) is a plan view of the ultrasonic wave receiving unit 32, and FIG. 3 (C) is an ultrasonic wave transmitting unit 31 and an ultrasonic wave receiving unit. It is AA sectional drawing of 32. FIG.

  Generally, the image forming apparatus 1 is provided with an openable door in order for the user to manually remove the sheet P jammed in the internal conveyance path. As described above, the ultrasonic wave transmitting unit 31 and the ultrasonic wave receiving unit 32 are disposed opposite to each other with the conveyance path interposed therebetween. Therefore, when the door is opened, the ultrasonic wave transmitting unit 31 and the ultrasonic wave receiving unit 32 can be arranged at positions where the user can touch. If the user touches at least one of the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32 with a finger, the cause of the failure or the detection accuracy of the ultrasonic wave may be lowered. Therefore, in the present embodiment, a protective member is provided in the ultrasonic wave receiving unit 32 to make it difficult for the user to touch the internal members of the ultrasonic wave receiving unit 32.

  According to FIG. 3A, the ultrasonic wave receiving unit 32 has a reception equalizer 324 for amplifying an ultrasonic wave, and a reception vibration member 321 for generating a detection signal by vibrating according to the ultrasonic wave. A reception guide 325 is provided around the ultrasonic wave receiving unit 32. As shown in FIG. 3A, the reception guide 325 has an opening 323 through which the ultrasonic wave passes, and functions as a cylindrical guide member for guiding the ultrasonic wave. The receiving guide 325 extends in the longitudinal direction (z direction) to reduce unnecessary reflected waves. The receiving guide 325 in this example is a cylindrical guide, and D1 indicates the opening dimension. As shown in FIG. 3A, L1 represents the distance from the center of the surface of the receiving vibration member 321 to a plane (opening surface) including the receiving guide tip end surface 326. The surface of the receiving vibration member 321 and the receiving guide tip end surface 326 are parallel to the xy plane. L 1 is a distance in the longitudinal direction (z direction) of the reception guide 325. The distance L1 is defined as the reception guide length. Note that the reception equalizer 324 may be omitted.

  Two protection members 328 are provided between the opening surface of the reception guide 325 and the reception vibrating member 321 and inside the reception guide 325. As shown in FIG. 3A, the two protection members 328 are substantially rectangular parallelepiped members provided in parallel with the xy plane. The shape of the protection member 328 may be cylindrical. Thus, the protection member 328 may be a columnar member provided in parallel to the opening surface, but may be a plate-like member. The space between the two protection members 328 and the space around the two protection members 328 function as holes through which ultrasonic waves pass. L2 in FIG. 3A indicates the distance from the center of the two protection members 328 to the plane including the receiving guide end surface 326. The distance L2 is referred to as a protection member distance, and is used as a parameter indicating the arrangement position of the protection member 328. Here, a plane including the receiving guide end surface 326, that is, an opening of the receiving guide 325 is defined as a virtual surface. A line 327 passing through the center of the receiving vibrating member 321 and perpendicular to the surface of the receiving vibrating member 321 is a virtual line which does not actually exist in the receiving vibrating member 321. The vertical line 327 serves as a reference for uniquely determining the distance L1 and the distance L2 from the surface of the receiving vibration member 321 to the receiving guide tip surface 326. The vertical line 327 is parallel to the z-axis direction.

  As shown in FIGS. 3A and 3C, by surrounding the receiving vibration member 321 with the receiving guide 325, it is possible to provide directivity to ultrasonic waves. Furthermore, the influence of the reflected waves from the peripheral members can be reduced by the reception guide 325. By arranging the protection member 328 with respect to the reception guide 325, it is possible to prevent the user from accessing the reception vibration member 321 from the reception guide distal end surface 326 and intrusion of fragments and the like inside the reception guide 325. Thereby, the reception vibration member 321 and the reception equalizer 324 can be protected.

  As shown in FIG. 3C, the receiving guide 325 is disposed such that the ultrasonic receiving unit 32 and the inner circumferential surface of the receiving guide 325 are in contact with each other. However, the contact structure between the ultrasonic wave receiving unit 32 and the inner peripheral surface of the receiving guide 325 is not essential as long as the user's access and intrusion of debris and the like can be suppressed. For example, a resin can be used as a material of the reception guide 325 and the protection member 328, but other materials such as metal may be used as long as the same effect as that of the present embodiment can be obtained.

  The relationship between the position of the protection member 328 and the ultrasonic wave transmitted through the sheet P will be described with reference to FIG. The results shown in FIG. 4 are obtained using a basis weight of 60 g / m ^ 2 of the sheet P. The horizontal axis in FIG. 4 indicates the arrangement position of the protection member 328. Here, the arrangement position of the protective member 328 at which the distance L2 is half the distance L1 is referred to as the center. The disposition position of the protection member 328 approaches the reception guide tip end surface 326 as it is shifted from the center in the positive direction, and approaches the reception vibration member 321 as it is shifted in the negative direction. The unit of the numbers described on the horizontal axis is mm. The vertical axis shows the transmission coefficient of ultrasonic waves. The transmission coefficient refers to the output of the reception control unit 34 when there is no sheet P between the ultrasound transmission unit 31 and the ultrasound reception unit 32 and the output of the reception control unit 34 that has received the ultrasound transmitted through the sheet P. Ratio. The solid line shows the transmission coefficient when the protective member 328 is present. The broken line indicates the transmission coefficient when the protective member 328 is not present.

  According to FIG. 4, it can be seen that the transmission coefficient largely changes depending on the arrangement position of the protection member 328. Also, the transmission coefficient without the protective member 328 is about 0.049. It can be seen from FIG. 4 that by disposing the protective member 328 in the center (L2 = L1 / 2), the same transmission characteristics as the transmission characteristics without the protective member 328 can be obtained. That is, by arranging the two protection members 328 at the center, it is possible to reduce the influence of the two protection members 328 on the detection signal of the ultrasonic wave.

  The reason for this will be described with reference to FIGS. 5 (A) to 5 (C). Some of the ultrasonic waves output from the ultrasonic wave transmitter 31 are reflected several times and enter the ultrasonic wave receiver 32. For example, as shown in FIG. 5A, the ultrasonic wave transmitted through the sheet P is reflected by the protection member 328, and further reflected by the sheet P, and is incident on the ultrasonic wave receiving unit 32. This is called a reflected wave W1. On the other hand, the ultrasonic wave transmitted through the sheet P is reflected by the surface of the ultrasonic wave receiving unit 32, is further reflected by the protection member 328, and is incident on the ultrasonic wave receiving unit 32. This is called a reflected wave W2. As shown in FIG. 5B, since the amplitudes of the reflected wave W1 and the reflected wave W2 are substantially the same, if the phases of the reflected wave W1 and the reflected wave W2 differ by 180 degrees, the reflected wave W1 and the reflected wave W2 are reflected. The waves W2 cancel each other. In this state, two protection members 328 are arranged such that L2 = L1 / 2. W1 and W2 are 180 degrees out of phase because the fixed end is reflected by the protective member 328 in W1 and the free end is reflected by the sheet P, while the fixed end is reflected by the vibrating member 321 in W2 and again by the protective member 328 It is for reflecting at the fixed end.

  On the other hand, as shown in FIG. 5C, when the phase difference between the reflected wave W1 and the reflected wave W2 deviates from 180 degrees, the synthetic wave W3 of the reflected wave W1 and the reflected wave W2 becomes apparent. Therefore, the transmission coefficient fluctuates compared to when the protective member 328 is not present. Incidentally, FIG. 5C shows a waveform observed when the two protective members 328 are disposed at the position of L2 = L1 / 2 + λ / 64. λ is the wavelength of ultrasonic waves. Thus, by setting the arrangement position of the two protection members 328 to a position close to the center, the amplitude of the synthetic wave formed from a plurality of reflected waves can be made extremely small.

  As described above, in the present embodiment, the distance L2 in the lengthwise direction of the reception guide 325 from the opening surface of the reception guide 325 to the center of the protection member 328 is the distance from the opening surface of the reception guide 325 to the surface of the reception vibration member 321. It is half the distance L1 in the longitudinal direction of the reception guide 325. That is, by setting the arrangement position of the protection member 328 at the center (L2 = L1 / 2), the transmission coefficient equivalent to the transmission coefficient when the protection member 328 is not present can be obtained. That is, the reception vibration member 321 can be protected without changing the detection characteristic of the ultrasonic sensor 30. Note that this relationship can be reworded as follows. A second guide member as a second guide member from a plane of a second guide member in a line passing through the center of the second vibration member as the reception vibration member 321 and a second guide member as a second protection member The length to the surface on the tip side of the guide member is equal to the length from the surface of the protection member 328 which is the second vibration member to the surface on the second vibration member side of the protection member 328.

  As described above, the position of the protective member 328 affects the detection accuracy of the ultrasonic wave (that is, the determination accuracy of the basis weight), but the detection accuracy required of the ultrasonic sensor 30 depends on the application form of the ultrasonic sensor 30. Dependent. For example, in order to set the detection accuracy (error) of the sheet P to 1%, it can be understood from the graph of FIG. 4 that the protection member 328 may be disposed within a range of plus or minus 0.15 mm from the center. Since the frequency f of ultrasonic waves is 40 kHz, the wavelength λ is about 8.6 mm. The ratio to the wavelength λ of 0.15 mm is 0.15 ÷ 8.6 ≒ 0.0174. This is about 1 / 57.2. Therefore, if it is within about 1 / 57.2 of the wavelength λ calculated from the frequency f of the ultrasonic wave, detection accuracy of 1% can be realized. Although a detection accuracy of 1% is merely illustrative, it is an empirically preferable detection accuracy. Thus, the distance L2 may be shifted from a half of the distance L1 within a range that satisfies the required detection accuracy of ultrasonic waves. That is, half does not have to be completely half, but may be approximately half. In addition, the shift amount of the center of the protective member 328 from the half of the distance L1 may be, for example, a shift amount within a range of ± 1/64 of the wavelength of the ultrasonic wave. Thus, the range of the substantially half length is, for example, the range of ± 1/64 of the wavelength of the ultrasonic wave transmitted from the first vibrating member.

  In the present embodiment, the configuration of the protection member 328 shown in FIG. 3 has been described as an example. In FIG. 3, the protection member 328 is disposed at a position avoiding a line connecting the center of the surface of the reception vibration member 321 and the center of the surface of the transmission vibration member. This is to guide more direct waves of the ultrasonic waves to the ultrasonic wave receiving unit 32.

  However, as shown in FIGS. 6A to 6C, a configuration in which one protection member 328 is disposed on the central axis of the reception vibration member 321 may be employed. 6A is a perspective view of the ultrasonic wave receiving unit 32. FIG. FIG. 6 (B) is a plan view. FIG. 6C is a cross-sectional view of the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32 taken along the line A-A.

  Even in such a configuration, the relationship between the arrangement position of the protective member 328 and the transmission coefficient is similar to the characteristic shown in FIG. Therefore, even if one protection member 328 is disposed at the center, the transmission coefficient without the protection member 328 can be obtained. However, in order to make the strength of the protection member 328 the target strength, it may be necessary to increase the dimension of the protection member 328 in the x direction. In this case, the reception intensity of the ultrasonic waves may be reduced. This is because the central axis of the receiving vibration member 321 is the position where the intensity of the ultrasonic wave is the strongest. Therefore, as shown in FIG. 3, by arranging the protective member 328 so as to open the center axis of the receiving vibration member 321, the ultrasonic wave receiving unit 32 efficiently transmits the ultrasonic wave transmitted by the ultrasonic wave transmitting unit 31. It will be possible to receive.

Second Embodiment
In the first embodiment, an example in which the protective member 328 is disposed with respect to the ultrasonic wave receiving unit 32 has been described. In the second embodiment, an example will be described in which protective members are disposed in both of the ultrasonic wave transmission unit 31 and the ultrasonic wave reception unit 32. The description will be simplified by omitting the configuration similar to that of the first embodiment, such as the sheet discrimination device.

  The configuration of the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32 of the ultrasonic sensor 30 in the second embodiment is shown in FIG. FIG. 7A is a perspective view of the ultrasonic wave transmission unit 31. FIG. FIG. 7B is a plan view of the ultrasonic wave transmission unit 31. FIG. FIG. 7C is a cross-sectional view along the line A-A showing the positional relationship between the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32. When the user opens the door of the main body, it is assumed that these are arranged at positions where the user can touch the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32. However, the ultrasonic wave transmission unit 31 and the ultrasonic wave reception unit 32 may be disposed at a position where it is difficult to touch.

  The transmission vibration member 311 is a member that vibrates in response to the drive signal supplied from the transmission control unit 33 to transmit an ultrasonic wave. A transmission guide 315 is provided around the ultrasound transmission unit 31. As FIG. 7 (A) shows, the transmission guide 315 has the opening 313 which an ultrasonic wave passes, and functions as a cylindrical guide member which guides an ultrasonic wave. The transmission guide 315 extends in the longitudinal direction (z direction) to reduce unnecessary reflected waves. The transmission guide 315 in this example is a cylindrical guide, and D2 indicates the opening dimension. As FIG. 5 (A) shows, L3 has shown the distance from the center of the circular surface of the transmission vibration member 311 to the plane (opening surface) containing the transmission guide front end surface 316. As shown in FIG. The surface of the transmission vibration member 311 and the end surface 316 of the transmission guide are parallel to the xy plane. L3 is a distance in the longitudinal direction (z direction) of the transmission guide 315. The distance L3 is defined as the transmission guide length. The transmission equalizer 314 is a member for amplifying the ultrasonic wave transmitted by the transmission vibration member 311. Even if the transmission equalizer 314 is not provided, it is possible to transmit ultrasonic waves if the transmission vibration member 311 is present.

  Two protection members 318 are provided between the opening surface of the transmission guide 315 and the transmission vibration member 311 and inside the transmission guide 315. As shown in FIG. 7A, the two protection members 318 are substantially rectangular parallelepiped members provided in parallel with the xy plane. The shape of the protection member 318 may be cylindrical. Thus, the protection member 318 may be a columnar member provided in parallel with the opening surface, but may be a plate-like member. L4 in FIG. 7A indicates the distance from the centers of the two protection members 318 to the plane including the transmitting guide tip surface 316. The distance L4 is referred to as a protection member distance, and is used as a parameter indicating the arrangement position of the protection member 318. Here, a plane including the transmission guide end surface 316, that is, an opening of the transmission guide 315 is defined as a virtual surface. A line 317 which passes through the center of the transmission vibration member 311 and is perpendicular to the surface of the transmission vibration member 311 is a virtual line which does not actually exist in the transmission vibration member 311. The vertical line 317 serves as a reference for uniquely determining the distance L1 and the distance L2 from the surface of the transmitting vibration member 311 to the transmitting guide tip surface 316. The vertical line 317 is parallel to the z-axis direction.

  As shown in FIGS. 7A and 7C, by surrounding the transmission vibration member 311 with the transmission guide 315, it becomes possible to restrict the propagation direction of the ultrasonic wave and to provide directivity to the ultrasonic wave. . By arranging the protection member 318 with respect to the transmission guide 315, it is possible to prevent the user from accessing the transmission vibration member 311 from the transmission guide tip surface 316 and the intrusion of fragments and the like inside the transmission guide 315. Thereby, the transmission vibration member 311 and the transmission equalizer 314 can be protected.

  As shown in FIG. 7C, the transmission guide 315 is disposed such that the ultrasonic transmission unit 31 and the inner circumferential surface of the transmission guide 315 are in contact with each other. However, the contact structure between the ultrasonic wave transmission unit 31 and the inner circumferential surface of the transmission guide 315 is not essential as long as the user's access and the intrusion of fragments and the like can be suppressed. For example, a resin can be used as a material of the transmission guide 315 and the protection member 318, but other materials such as metal may be used as long as the same effect as that of the present embodiment can be obtained.

  The relationship between the positions of the protective members 318 and 328 and the ultrasonic waves transmitted through the sheet P will be described with reference to FIG. The results shown in FIG. 8 are obtained using a basis weight of 60 g / m 2 of the sheet P. The horizontal axis in FIG. 8 indicates the arrangement position of the protection members 318 and 328. Here, the protective member 328 is disposed such that the distance L2 is half the distance L1, and the position at which the protective member 318 is disposed such that the distance L4 is half the distance L3 is referred to as the center. The disposition position of the protection member 328 approaches the reception guide tip end surface 326 as it is shifted from the center in the positive direction, and approaches the reception vibration member 321 as it is shifted in the negative direction. In addition, the disposition position of the protection member 318 approaches the transmission guide tip surface 316 as it is shifted from the center in the positive direction, and approaches the transmission vibration member 311 as it is shifted in the negative direction. The protection members 318 and 328 move by the same amount. The unit of the numbers described on the horizontal axis is mm. The vertical axis shows the transmission coefficient of ultrasonic waves. The transmission coefficient refers to the output of the reception control unit 34 when there is no sheet P between the ultrasound transmission unit 31 and the ultrasound reception unit 32 and the output of the reception control unit 34 that has received the ultrasound transmitted through the sheet P. Ratio. The solid line shows the transmission coefficient when the protective members 318 and 328 are present. The broken lines indicate the transmission coefficients without the protective members 318 and 328.

  According to FIG. 8, it can be seen that the transmission coefficient largely changes depending on the arrangement position of the protective members 318 and 328. Also, the transmission coefficient without the protective members 318 and 328 is about 0.049. From FIG. 8, by arranging the protection members 318 and 328 in the center (L4 = L3 / 2, L2 = L1 / 2), the same transmission characteristics as the transmission characteristics without the protection members 318 and 328 can be obtained. I understand that. That is, by arranging the two protection members 318 and 328 at the center, it is possible to reduce the influence of the two protection members 318 and 328 on the detection signal of ultrasonic waves. The conditions relating to the distances L3 and L4 may be rephrased as follows. Protection from the plane of the transmission guide 315, which is the first guide member, through a center of the transmission vibration member 311, which is the first vibration member, and perpendicular to the surface of the transmission vibration member 311 The length from the surface on the tip surface side of the transmission guide 315 in the member 318 is equal to the length from the surface of the transmission vibration member 311 to the surface on the first vibration member side in the protection member 318.

  Thus, the distance (L2, L4) in the longitudinal direction of the guide member from the opening surface of the guide member to the center of the protection member is the guide member out of the transmission vibration member and the reception vibration member from the opening surface of the guide member. A half of the distance (L1, L3) in the lengthwise direction of the guide member to the surface of the vibrating member provided, or a half shift from the half within a range satisfying the required detection accuracy of ultrasonic waves. For example, for the ultrasonic wave transmission unit 31, the distance L4 in the lengthwise direction of the transmission guide 315 from the opening surface of the transmission guide 315 to the center of the protection member 318 is from the opening surface of the transmission guide 315 to the surface of the transmission vibration member 311 The half of the distance L3 in the longitudinal direction of the transmission guide 315 of FIG. That is, by setting the arrangement position of the two protection members 318 to the center (L4 = L3 / 2), a transmission coefficient equivalent to the transmission coefficient when the protection members 318 are not present can be obtained. That is, it is possible to protect the transmission vibration member 311 without changing the detection characteristic of the ultrasonic sensor 30. As described in the first embodiment, the distance L4 may be shifted from half of the distance L3 within a range that satisfies the required detection accuracy of ultrasonic waves. Further, the shift amount of the center of the protection member 318 from the half of the distance L3 may be, for example, a shift amount within a range of ± 1/64 of the wavelength of the ultrasonic wave.

  Further, compared to FIG. 4, in FIG. 8, it can be seen that the rate of change of the transmission coefficient depending on the arrangement position is smaller. Therefore, by arranging the protective member 318 and the protective member 328 so as to have the same relationship with the vibrating member and the opening surface, it is possible to reduce the accuracy of the arrangement position of the protective member.

  In the second embodiment, two protective members are provided on both the transmitting side and the receiving side. In particular, in FIG. 7, the protection members 328 and 318 are disposed at a position avoiding a line connecting the center of the surface of the reception vibration member 321 and the center of the surface of the transmission vibration member 311. This is to guide more direct waves of the ultrasonic waves to the ultrasonic wave receiving unit 32. However, one protective member may be disposed on both the transmitting side and the receiving side, or two may be disposed on one side and one may be disposed on the other side. Although one protection member is disposed on a line connecting the center of the surface of the reception vibration member 321 and the center of the surface of the transmission vibration member 311 in FIG. 6, a position at which one protection member is avoided on this line It may be located at

Third Embodiment
In the first embodiment, the configuration in which the protection member 328 is disposed in the ultrasonic wave receiving unit 32 has been described. In the second embodiment, the configuration in which the protective member is disposed not only in the ultrasonic wave receiving unit 32 but also in the ultrasonic wave transmitting unit 31 has been described. In the third embodiment, a configuration in which the protection member 318 is disposed only in the ultrasonic wave transmission unit 31 will be described. The description of the same configuration as that of the first embodiment or the second embodiment will be omitted.

  The ultrasonic wave transmitting unit 31 of the ultrasonic sensor 30 will be described with reference to FIGS. 9A to 9C. FIG. 9A is a perspective view of the ultrasonic wave transmission unit 31. FIG. FIG. 9B is a plan view of the ultrasonic wave transmission unit 31. FIG. FIG. 9C is a cross-sectional view along the line A-A showing the positional relationship between the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32. As shown in FIG. It can be seen that the configuration of the ultrasonic wave transmitter 31 is as described above, as compared with FIGS. 9 (A) and 9 (B) and FIGS. 7 (A) and 7 (B). However, when FIG. 9C and FIG. 7C are compared, it can be seen that the protection member 328 is not attached to the ultrasonic wave receiving unit 32. Thus, in the third embodiment, the protection member 318 is disposed only in the ultrasonic wave transmission unit 31.

  The relationship between the arrangement position of the protective member 318 and the transmission coefficient in the third embodiment will be described with reference to FIG. The basis weight of the sheet P is 60 g / m ^ 2. The horizontal axis in FIG. 10 indicates the arrangement position of the protection member 318. Here, the arrangement position of the protection member 318 where the distance L4 is half the distance L3 is referred to as the center. The disposition position of the protection member 318 approaches the transmission guide tip surface 316 as it is shifted from the center in the positive direction, and approaches the transmission vibration member 311 as it is shifted in the negative direction. The unit of the numbers described on the horizontal axis is mm. The vertical axis shows the transmission coefficient of ultrasonic waves.

  According to FIG. 10, it can be seen that the transmission coefficient changes depending on the arrangement position of the protective member 318. Further, the transmission coefficient of the sheet P in the absence of the protective member 318 is about 0.049. Therefore, by disposing the protective member 318 at the center (L4 = L3 / 2), the influence of the protective member 318 can be made extremely small. However, the arrangement position may be offset in a certain range from the center depending on the required detection accuracy. This point is as already described.

  By arranging the position of the protection member 318 at the center, the ultrasonic vibration member can be protected from foreign matter while reducing the influence of the protection member 318 on the reception intensity of the ultrasonic wave. Although two protection members 318 are employed in the third embodiment, one protection member may be employed as described with reference to FIG.

<Others>
In the first to third embodiments, the case where one or two protective members having a rectangular parallelepiped shape are adopted has been described. However, the number and shape of the protective members may be different from these. FIGS. 11A to 11D are plan views showing an example of the guide and the protection member. As exemplified in the first to third embodiments, the thickness of each protective member in the z direction may have a constant width.

  As shown in FIG. 11A, the number of protection members 318 and 328 may be three or more. As shown in FIG. 11B, cross-shaped protection members 318 and 328 may be employed. As shown in FIG. 11C, protective members 318 and 328 provided with circular or square holes in the center of the plate-like main material may be employed. As shown in FIG. 11D, mesh-like or lattice-like protective members 318, 328 may be employed. However, regardless of the shape, the arrangement positions of the protective members 318 and 328 are positions corresponding to half of the distance L1 and L3 from the opening face of the guide to the vibrating member or shifted from half to the z direction is there. This makes it possible to protect the ultrasonic vibration member from foreign matter while reducing the influence of the protection members 318 and 328 on the reception intensity of the ultrasonic wave.

  In the second embodiment, the shapes and numbers of the protective members 318 and 328 are the same. This enables the guide and the protection member to be shared by the ultrasonic wave transmission unit 31 and the ultrasonic wave reception unit 32, which is effective for cost reduction. Further, since the ultrasonic wave transmitting unit 31 and the ultrasonic wave receiving unit 32 can be made as the same part, it is effective to reduce the cost if the shape and the number of the protective members 318 and 328 match. However, it is not essential that the shape and the number of the protection members 318 and 328 match, and the shape and the number of the protection members 318 and 328 may be different. However, the disposition position of the protective members 318 and 328 may be a position corresponding to half of the distance L1 and L3 from the opening surface of the guide to the vibrating member.

  It has been mentioned that the protection member is provided only in one of the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32. In this case, one of the ultrasonic wave transmitter 31 and the ultrasonic wave receiver 32 in which the protective member is not provided may be disposed at a position where it is difficult for the user to touch with a finger. In addition, the ultrasonic wave transmitter 31 may be rotated by a motor and retracted to a position where the user can not touch it.

  By employing the above-described ultrasonic sensor for the sheet discrimination apparatus for discriminating the type of sheet, it is possible to maintain the discrimination accuracy of the type of sheet while protecting the ultrasonic sensor. Further, such a sheet discrimination apparatus may be applied to the image forming apparatus 1. In this case, the control unit 10 functions as a control unit that controls the image forming conditions used by the image forming unit according to the determination result of the sheet determination apparatus. As a result, it is possible to set appropriate image forming conditions (the sheet conveyance speed and the fixing temperature in the fixing unit 21) in accordance with the type of sheet (the basis weight and the thickness). As a result, even different types of sheets may be able to form uniform toner images.

  The ultrasonic sensor of the present embodiment may be employed in an image reading apparatus. An automatic document feeder of an image reading apparatus may employ an ultrasonic sensor to detect double feeding of sheets. Also for such an ultrasonic sensor, the detection accuracy of the ultrasonic sensor can be maintained and the failure can be suppressed by suppressing the entry of foreign matter.

  In the present embodiment, a cylindrical guide member having a constant cross-sectional area in the xy direction has been described, but a cylindrical guide member in which the cross-sectional area in the xy direction gradually changes may be employed. For example, the cross-sectional area in the xy direction may gradually increase or decrease as going from the vibrating member side to the opening side. Such a tapered guide member (horn shape or reverse horn shape) may be employed. The cross-sectional shape may be circular, oval, square or the like. That is, the opening size of the guide member at the first position P1 where the protective portion is provided in the direction of a straight line perpendicular to the surface of the vibrating member on the side that transmits or receives the ultrasonic wave through the center of the vibrating member The area is smaller than the opening size (cross-sectional area) of the guide member at the second position P2 where the protective portion is not provided. In other words, the inner radius of the guide member at the first position P1 is smaller than the inner radius of the guide member at the second position P2. This configuration is shown in FIG. 12A and 12B are plan views of the ultrasonic wave transmitter 31 or the ultrasonic wave receiver 32, respectively. 12C is a cross-sectional view taken along the line A-A corresponding to the plan view of FIG. 12A, and FIG. 12D is a cross-sectional view taken along the line A-A corresponding to the plan view of FIG. In FIG. 12 (A), the opening 390 is an opening corresponding to the first position of FIG. 12 (B). The opening 391 is an opening corresponding to the second position in FIG. 12 (B). In FIG. 12C, the transmission guide 315 or the reception guide 325 is in the shape of a reverse horn. Further, in FIG. 12B, the opening 392 is an opening corresponding to the first position P1 of FIG. 12D. The opening 393 is an opening corresponding to the second position P2 of FIG. In FIG. 12D, the transmission guide 315 or the reception guide 325 has an hourglass shape. The contracted portion of the guide member functions as a protective member or part. That is, the guide member and the protection member may be integrated or integrated. By providing the contraction portion of the guide member, the user will not be able to easily touch the vibrating member. The shape of the opening may be circular or more complex.

  A part of the vibrating member may overlap the protective member in the direction of a straight line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member that transmits or receives ultrasonic waves.

  The image forming condition may be a sheet conveyance speed, a fixing temperature for fixing a toner image on a sheet, or a transfer voltage for transferring a toner image to a sheet.

  31 ... ultrasonic wave transmission unit, 32 ... ultrasonic wave reception unit, 311 ... transmission vibration member, 315 ... transmission guide, 318 ... protection member, 321 ... reception vibration member, 325. .. Reception guide, 328 ... protection member

The present invention, for example,
A vibrating member that vibrates to emit ultrasonic waves;
Provided so as to surround the vibration member, a guide member having an opening for guiding the ultrasonic wave to the outside,
And a protection member provided inside the guide member to protect the vibration member, the protection member being disposed from the opening side in a space inside the guide member from the vibration member to the opening According to another aspect of the present invention, there is provided an ultrasonic wave transmitting apparatus characterized in that it is provided so as to bridge from a first position inside the guide member to a second position different from the first position .

Claims (27)

A vibrating member that vibrates to emit ultrasonic waves;
A guide member for guiding the ultrasonic wave emitted from the vibrating member;
And a protection member provided inside the guide member to protect the vibrating member,
An ultrasonic wave transmitting apparatus in which at least a part of the vibrating member overlaps the protective member in the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member transmitting the ultrasonic waves.   The ultrasonic wave transmitting apparatus according to claim 1, wherein the protective member has a hole through which the ultrasonic wave passes.   The distance from a plane including the tip end face of the guide member to the protective member in a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member on which the ultrasonic waves are transmitted is the surface to the surface The ultrasonic wave transmission device according to claim 1 or 2, which is approximately half the distance to the end.   The ultrasonic wave transmitting apparatus according to claim 3, wherein the protection member is provided in parallel with the plane of the guide member.   The distance from the plane of the guide member to the surface of the protective member facing the distal end surface of the guide member in a line passing through the center of the vibration member and perpendicular to the surface of the vibration member is the vibration The ultrasonic wave transmission device according to claim 4, which is equal to the distance from the plane of the member to the surface of the protective member facing the vibrating member.   The ultrasonic wave transmission device according to any one of claims 1 to 5, wherein one or more members are provided as the protective member.   The ultrasonic transmission device according to any one of claims 1 to 6, wherein the vibrating member is disposed at a position passing through the center of the vibrating member and separated from a line perpendicular to the surface of the vibrating member. .   The ultrasonic wave transmitting apparatus according to claim 3, wherein the range of the substantially half distance is ± 1/64 of the wavelength of the ultrasonic wave transmitted from the vibrating member. A sheet discriminating apparatus that discriminates the type of sheet, and
An ultrasonic sensor,
Transmission unit having a vibrating member that vibrates to transmit ultrasonic waves, a guide member that guides ultrasonic waves transmitted from the vibrating member, and a protection member provided inside the guide member to protect the vibration member When,
An ultrasonic sensor having a receiving unit for receiving an ultrasonic wave emitted from the vibrating member and attenuated through a sheet;
And a determination unit that determines the type of sheet based on the ultrasonic wave received by the reception unit,
A sheet discrimination device in which at least a part of the vibrating member overlaps the protective member in the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member transmitting ultrasonic waves.   The sheet discrimination apparatus according to claim 9, wherein the type of the sheet is a basis weight or thickness of the sheet. An image forming apparatus,
An ultrasonic sensor,
A first vibrating member that vibrates to emit an ultrasonic wave, a first guide member that guides the ultrasonic wave transmitted from the first vibrating member, and a first guide member provided inside the first guide member, A transmitter having a first protective member for protecting the first vibrating member;
An ultrasonic sensor having a receiving unit for receiving an ultrasonic wave emitted from the first vibrating member and attenuated through a sheet;
An image forming unit that forms an image on a sheet;
A control unit configured to control an image forming condition used by the image forming unit according to the ultrasonic wave received by the receiving unit;
At least a portion of the first vibrating member extends in the direction of a line passing through the center of the first vibrating member and perpendicular to the surface of the first vibrating member on which the ultrasonic waves are transmitted. An image forming apparatus overlapping a protective member.   The image forming apparatus according to claim 11, wherein the image forming condition is a fixing temperature for fixing a toner image on the sheet, a conveyance speed of the sheet, or a voltage value for transferring the toner image to the sheet. The receiving unit includes a second vibrating member that receives and vibrates an ultrasonic wave transmitted by the first vibrating member and attenuated through the sheet, and a second vibrating member that attenuates the ultrasonic wave through the sheet. A second guide member for guiding to a vibrating member, and a second protection member provided inside the second guide member and having a hole through which ultrasonic waves pass;
At least a portion of the second vibrating member is in the direction of a line passing through the center of the second vibrating member and perpendicular to the surface of the second vibrating member that receives ultrasonic waves. The image forming apparatus according to claim 11, wherein the image forming apparatus overlaps the protective member. A vibrating member that receives and vibrates ultrasonic waves;
A guide member for guiding an ultrasonic wave to the vibrating member;
And a protection member provided inside the guide member to protect the vibrating member,
An ultrasonic receiver, wherein at least a portion of the vibrating member overlaps the protective member in the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member on which ultrasonic waves are received.   15. The ultrasonic receiving apparatus according to claim 14, wherein the protective member has a hole through which the ultrasonic wave passes.   The distance from the plane including the tip end surface of the guide member to the protective member in a line passing through the center of the vibration member and perpendicular to the surface of the vibration member on which ultrasonic waves are received is the surface to the surface The ultrasonic receiver according to claim 14 or 15, which is approximately half the distance to the end.   The ultrasonic receiving apparatus according to claim 16, wherein the protection member is provided in parallel with the plane of the guide member.   The distance from the plane of the guide member to the surface of the protective member facing the distal end surface of the guide member in a line passing through the center of the vibration member and perpendicular to the surface of the vibration member is the vibration The ultrasonic receiver according to claim 17, which is equal to the distance from the plane of the member to the surface of the protective member facing the vibrating member.   The ultrasonic receiver according to claim 14, wherein one or more members are provided as the protective member.   The ultrasonic receiving apparatus according to claim 14, wherein the vibrating member is disposed at a position passing a center of the vibrating member and separated from a line perpendicular to the surface of the vibrating member.   17. The ultrasonic receiving apparatus according to claim 16, wherein the range of the substantially half distance is ± 1/64 of the wavelength of the ultrasonic wave received from the vibrating member. A sheet discriminating apparatus that discriminates the type of sheet, and
An ultrasonic sensor,
A transmitter for transmitting ultrasonic waves,
Ultrasonic wave having a receiving portion having a vibration member that receives and vibrates ultrasonic waves, a guide member that guides ultrasonic waves to the vibration member, and a protection member that is provided inside the guide member and that protects the vibration member Sensor,
And a discrimination unit that discriminates the type of sheet based on the ultrasonic wave received by the vibrating member,
A sheet discrimination device in which at least a portion of the vibrating member overlaps the protective member in the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member on which the ultrasonic waves are received.   23. The sheet discriminating apparatus according to claim 22, wherein the type of the sheet is basis weight or thickness of the sheet. An image forming apparatus,
A transmitter for transmitting ultrasonic waves,
Ultrasonic wave having a receiving portion having a vibration member that receives and vibrates ultrasonic waves, a guide member that guides ultrasonic waves to the vibration member, and a protection member that is provided inside the guide member and that protects the vibration member Sensor,
An image forming unit that forms an image on a sheet;
A control unit configured to control an image forming condition used by the image forming unit according to the ultrasonic wave received by the receiving unit;
An image forming apparatus, wherein at least a part of the vibrating member overlaps the protective member in the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member on which the ultrasonic waves are received.   The image forming apparatus according to claim 24, wherein the image forming condition is a fixing temperature for fixing a toner image on the sheet, a conveyance speed of the sheet, or a voltage value for transferring the toner image on the sheet. A vibrating member that vibrates to emit ultrasonic waves;
A guide member for guiding the ultrasonic wave transmitted from the vibrating member;
The guide member has a protection portion for protecting the vibration member,
In the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member transmitting the ultrasonic waves, the size of the opening of the portion provided with the protective portion in the guide member is the guide The ultrasonic wave transmission device smaller than the size of the opening of the part in which the said protection part is not provided in a member. A vibrating member that receives and vibrates ultrasonic waves;
And a guide member for guiding the ultrasonic wave to the vibrating member,
The guide member has a protection portion for protecting the vibration member,
In the direction of a line passing through the center of the vibrating member and perpendicular to the surface of the vibrating member receiving the ultrasonic wave, the size of the opening of the portion provided with the protective portion in the guide member is the guide An ultrasonic receiver smaller than the size of the opening of the part in which the said protection part is not provided in a member.

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