JP5172906B2 - Paper transport device - Google Patents

Description

  Embodiments described herein relate generally to a sheet conveying apparatus that conveys a sheet by a roller pair or a guide in an image forming apparatus such as an MFP (Multi Function Peripheral) or a printer.

  In an image forming apparatus such as an MFP or a printer, paper is fed from a paper feed cassette or a manual paper feed unit, and the paper is conveyed to the image forming unit. Since the orientation of the conveyed paper, particularly the inclination, has a great influence on the image forming position on the paper, the paper is positioned and the inclination is corrected. Further, when a sheet is repeatedly conveyed for a color image, the sheet positioning and inclination correction are important in order to prevent image color misregistration. A registration roller pair is often used for paper positioning before image formation. The conveyed paper collides with the registration roller pair in a state where the rotation of the roller is stationary through the paper guide. At this time, a collision sound (also called an impact sound) is generated from the paper. Even after the leading edge of the sheet hits the nip portion of the registration roller pair, the sheet is further conveyed by the conveying roller pair. For this reason, the sheet is deflected, and the leading end surface of the sheet is pressed against the nip portion by the rigidity of the sheet itself, and the leading end surface comes into contact with the registration roller pair nip portion. When the registration roller pair rotates from the state where all the front end surfaces of the paper are in contact with the registration roller pair, positioning and inclination correction of the front end of the paper are performed with reference to the nip portion of the registration roller pair, and the paper To the image forming unit.

JP-A-8-26526 Japanese Patent Laid-Open No. 2007-3964 JP-A-9-193504

  An image forming apparatus to which the sheet conveying apparatus of this embodiment can be applied is often installed in an office environment or the like. Under such an environment, the influence of noise reaches not only the user but also surrounding workers. For this reason, it is desirable that the operating sound of the apparatus is low overall, and that the impact sound other than the steady sound is also low and calm. In the process of transporting the paper, a noise is generated when the front end of the paper collides with the roller pair stopped for paper positioning. Therefore, it is desired to improve the sound quality by applying a low-frequency emphasized control wave to the sound emitted from the paper when the paper collides with the roller. However, if the difference between the timing at which the sheet collides with the roller and the timing at which the sheet is vibrated does not fall within the allowable time, a double sound is generated, which has an adverse effect.

  The present embodiment has been made in consideration of the above-described circumstances, and an object thereof is to provide a paper transport device that improves the quality of a paper collision sound.

  According to the embodiment, the paper transport device includes a first roller pair, a characteristic detection unit, a detection unit, a calculation unit, a control filter, a generation unit, and a vibration unit. The first roller pair conveys paper. The characteristic detection unit detects the characteristic of the paper and outputs a characteristic signal indicating the characteristic. The detection unit detects that the sheet has reached the first roller pair, and outputs a detection signal indicating the detection. The calculation unit calculates a reference signal corresponding to the characteristic signal. The control filter determines a frequency distribution of control waves applied to the paper when the paper collides with the second roller pair. The generation unit generates a control wave. The excitation unit has a time difference determined by at least one of the characteristic signal and the detection signal, and the difference between the time when the paper collides with the second roller pair and the time when the control wave is applied to the paper is within a threshold value. As shown, a control wave is applied to the paper.

FIG. 3 is a block diagram of the sheet conveying apparatus according to the first embodiment. The figure which shows each time log | history of the vibration speed in the center of a main pulse wave, a control pulse wave, and a sheet | seat in the case where the deviation | shift of a main pulse wave and a control pulse wave differs. The figure which shows the time history of the sound pressure waveform in the position 30 cm away in the front from the paper. FIG. 2 is a block diagram of a basic experiment system assuming the paper transport device of FIG. 1. The figure which shows the experimental result obtained by the system of FIG. The figure which shows a human auditory characteristic. FIG. 6 is a block diagram of a paper transport device according to a second embodiment. The figure which shows the experimental result obtained by the basic experiment system supposing the paper conveying apparatus of FIG. FIG. 9 is a block diagram of a paper transport device according to a third embodiment. FIG. 9 is a block diagram of a basic experiment system assuming the sheet conveying device of FIG. 8. The figure which shows the experimental result obtained by the system of FIG. The figure which shows the experimental result by which the pass frequency band obtained by the system of FIG. 9 differs from FIG. The figure which shows the experimental result from which the pass frequency band obtained by the system of FIG. 9 differs from FIG. 10 and FIG. The figure which shows the parameter used for calculation in case an external force acts on one arbitrary point on a flat plate, and a control force acts on another one point, and its outline | summary. The figure which shows the action point of each of A4 size paper and external force and control force which numerically calculate. The figure which shows frequency distribution of the sound pressure level at the time of applying a control law (n = 3). The figure which shows frequency distribution of the sound pressure level at the time of applying a control law (n = 10). The figure which shows the displacement distribution in the resonant frequency of 150 Hz of FIG. The figure which shows the action point in case the action point of the A4 size paper to calculate numerically, and an external force and a control force become an asymmetrical position with respect to a paper front sound pressure. The figure which shows the numerical calculation result at the time of making control force 3 times the external force. The figure which shows the numerical calculation result corresponding to FIG. 19 using a control law. FIG. 7 is a schematic configuration diagram of an image forming apparatus including a sheet conveying device according to first to sixth embodiments. FIG. 3 is a schematic diagram illustrating a specific aspect of a paper transport device. FIG. 10 is a block diagram of a paper conveying apparatus according to a fifth embodiment. The figure which shows the position where a paper collides with the registration roller pair shown in FIG. FIG. 10 is a block diagram of a paper conveying apparatus according to a sixth embodiment.

Hereinafter, a sheet conveying apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that, in the following embodiments, the same numbered portions are assumed to perform the same operation, and repeated description is omitted.
(First embodiment)
A sheet conveying apparatus according to a first embodiment will be described with reference to FIG. For example, the sheet is detected from the sheet conveying roller pair 101 by the sheet characteristic detection unit 102 and then conveyed to the nip portion of the stopped pair of registration rollers, and a collision sound is generated when the sheet collides therewith.
The paper transport apparatus according to the present embodiment includes a paper transport roller pair 101, a paper characteristic detection unit 102, a paper vibration unit 103, a control wave generation unit 104, a control filter 105, a reference signal calculation unit 106, and a paper transport / correction signal detection unit. 107 is included.

The pair of sheet conveying rollers 101 conveys the sheet, further corrects the direction of the sheet depending on the case, and outputs a signal indicating that the conveyance and / or correction has been performed.
The paper conveyance / correction signal detection unit 107 receives a signal from the paper conveyance roller pair 101 and outputs a detection signal notifying that the paper has reached the paper conveyance roller pair 101.
The paper characteristic detection unit 102 detects a characteristic of the paper and outputs a characteristic signal indicating the characteristic. The paper characteristics include, for example, paper thickness, paper size, and paper hardness.
The reference signal calculation unit 106 receives the detection signal and the characteristic signal, and outputs a reference signal (for example, a main pulse) corresponding to the characteristic signal. The reference signal calculation unit 106 also calculates the time from when the detection signal or (and) the characteristic signal is received until the paper collides with the stopped roller pair (the left end in FIG. 1), and supplies the paper to the stopped roller pair. The sheet exciting unit 103 may vibrate the sheet conveying roller pair 101 to apply a control wave to the sheet when the two collide with each other. This time may be calculated in advance from the sheet conveyance speed and the distance between the sheet conveyance roller pair 101 and the stopped roller pair, and set in advance in the reference signal calculation unit 106 or the like. Such time will be described later with reference to FIGS. 2A and 2B.

The control filter 105 determines the frequency distribution of the control wave. The control filter 105 stores one or more filter coefficients. The control filter 105 receives the waveform of the reference signal and obtains a waveform with low-frequency emphasis.
The control wave generation unit 104 generates a control wave having a frequency distribution determined by the control filter 105. The control wave generator 104 generates a wave in a specific frequency band. The control wave generation unit 104 performs a convolution operation on the reference signal and the filter coefficient stored in the control filter 105 to generate a control wave.
The paper vibration unit 103 sends a control wave generated by the control wave generation unit 104 to at least one of the paper conveyance roller pair 101 in accordance with a collision sound (also referred to as an impact sound) when the paper collides with the stopped roller pair. And a control wave is applied to the sheet by vibrating at least one of the sheet conveying roller pair 101.

With the above paper transport device, it is possible to improve the sound quality by exciting the resonance of the paper and emphasizing the collision sound in the specific band sound.
Generally, when the main sound source and the control sound are installed in the same space, there is a position where the sound pressure locally increases / decreases due to the phase interference between the two, so that the sound increase control is generally based on the phase. However, when the control sound is an impact sound, it is difficult to match the generation of a control wave having a phase matching in a wide band and the generation timing of the control sound, and the increase / decrease effect by phase control is difficult compared to a periodic sound source.
In addition, it is known by at least the inventors that low-frequency sounds receive a favorable impression as a human hearing impression. Therefore, increasing the low frequency sound improves the sound quality.

  Therefore, in the embodiment, the low-order resonance mode of the paper utilizes the characteristic that appears from 100 Hz or lower, and generates the low-frequency resonance using the control wave as an excitation source, thereby changing the radiated sound after control to the low-frequency range. suggest. At this time, an impact sound is also generated at the same time. However, since the amplitude of the control wave to be applied is larger, interference is unlikely to occur and the impact sound is generated in a form in which a low-frequency sound emitted by the control wave is superimposed.

  However, in this case, unlike the periodic sound, the impact sound is not repeatedly generated, so attention must be paid to the generation timing. Therefore, the embodiment proposes a control wave applying method that matches the timing of the collision by using a carrier signal available before the collision as a reference signal. Even in the case of a paper radiated sound, even if they do not completely match, even if a signal delayed by about 20 msec is applied, both are masked and the radiated sound pressure sounds the same.

Next, how close the time when the collision sound is generated and the time when the control wave is generated must be described with reference to FIGS. 2A and 2B.
FIG. 2 shows the vibration velocity at the center of the paper when the upper end of the A4 size paper is fixed and the main pulse wave and the control pulse wave generated through the bandpass filter are applied to the left and right sides of the paper with a time shift (FIG. 2A). ) And the front sound pressure waveform (FIG. 2B). In FIG. 2A, the first large pulse shown in black indicates the main pulse wave, and thereafter, a plurality of pulses shown in black having a smaller amplitude than the main pulse wave indicate control pulse waves.

  Here, the main pulse wave corresponds to the collision sound, and the control pulse wave corresponds to the control wave. The separation of the synthesized sound pressure waveform due to the deviation between the main pulse wave and the control pulse wave is not so noticeable until 30 msec, and the difference between the main pulse wave and the control pulse wave is 50 msec or more with reference to FIG. 2A. It turns out that it is remarkable. That is, according to FIG. 2A, it can be seen that when the deviation between the main pulse wave and the control pulse wave is 50 msec or more, the sound pressure waveform is almost separated into two waveforms. Referring to FIG. 2B, it can be seen that the sound pressure waveform is separated into two waveforms at 50 msec or more.

Thus, if the time delay between the collision sound (main pulse wave) generated when the sheet collides with the registration roller and the applied control wave (control pulse wave) is large, the sound can be heard twice, and the sound quality is improved. The purpose of can not be achieved. According to FIG. 2A, the synthesized sound pressure waveform can be regarded as one lump if it is at least about 20 to 25 msec. Therefore, even with the proposed method in which the phase is ignored, bass enhancement is possible. In the present embodiment, the sheet excitation unit 103 is set to operate so that the deviation between the main pulse wave and the control pulse wave is at least 20 to 25 msec. Alternatively, the collision time calculation unit 2302 described in the fifth embodiment is used.
FIG. 2A shows an example in which a control wave is applied after a collision, but a control wave may be applied within a threshold range before and after the collision time. This threshold range is a range in which a sound wave waveform obtained by synthesizing a collision sound (main pulse wave) and a given control wave can be regarded as one lump.

Next, a basic experimental system implemented assuming the paper conveying apparatus of FIG. 1 will be described with reference to FIG. Then, the experimental result obtained by the experimental system of FIG. 3 will be described with reference to FIG. Note that the left diagram in FIG. 3 is a diagram of an A4 size sheet viewed from the front, and the right diagram in FIG. 3 is a diagram of the sheet viewed from the side.
This experimental system includes a vibration actuator 301, a vibration impulse hammer 302, a band pass filter 303, and a PC 304. The experimental system supports the upper end of the A4 size paper, sandwiches the paper with the vibration actuator 301, and transmits the vibration of the vibration actuator 301 to the paper.

The PC 304 generates a pulse signal, and the band-pass filter 303 passes a pulse signal in a specific frequency band of the pulse signal. The vibration actuator 301 receives the pulse signal in the specific frequency band and vibrates at a frequency included in the frequency band. As a result, a vibration having a specific frequency can be applied to the sheet.
The vibration impulse hammer 302 is installed at the lower end of the paper and applies vibration to the paper by striking the paper from below to above.
In this experimental system, the wave generated by the vibration actuator 301 corresponds to the control wave, and the wave generated by the vibration impulse hammer 302 corresponds to the collision sound.

  FIG. 4 shows the sound pressure level (dBA) at the center front of the sheet at the time of edge excitation as a result before control. After the control, a pulse signal separately created on a PC is regarded as a reference signal, and from 100 Hz to 500 Hz. Is a result of applying a control wave calculated by convolution with a bandpass filter having a pass frequency band. Referring to FIG. 4, since the amplitude caused by the collision sound and the amplitude caused by the pulse are irrelevant, even if the bandpass filter band is designed except for the resonance-enhanced bass (100 Hz to 150 Hz), it should be increased after the control. I understand that there is not.

  In the paper transport device of the present embodiment, the control filter has a bandpass filter characteristic with a low frequency band (for example, 1 kHz) as a pass band, so that the low frequency sound increases, and the low frequency sound is preferable as an audible impression. Receive.

  It is known that the human auditory characteristics have characteristics as shown in FIG. According to FIG. 5, the human auditory sensation is such that the lower the sound, the harder it is to hear. FIG. 5 represents the human sense of the loudness (loudness) and is called an equal loudness curve (ISO / R226). Human auditory sensation is similar to a high-pass filter. In other words, it can be seen that even if the bass is slightly increased, the overall value of the audible noise level does not change much. Therefore, even if the low frequency sound is increased as in the present embodiment, the sound pressure level that has been subjected to auditory correction after the application of the control wave, that is, the noise level, is the same within a threshold range before and after the control. As a result, by using a bandpass filter having a pass band of 1 kHz or less as a control filter, the noise level itself does not change while the audible impression is improved to a low tone. The control filter has a band-pass filter characteristic with a pass band of 1 kHz or less, so that the sound pressure level after auditory correction after applying the control wave, that is, the noise level is almost the same as before the control. Since the noise level of the decibel A is mainly used for reducing the noise of the MFP, it is possible to achieve both improvement in sound quality and reduction in noise by emphasizing the bass.

  According to the first embodiment described above, it is possible to improve the sound quality by exciting the resonance of the paper and emphasizing the collision sound with a low frequency that is a specific band. For example, at the time of paper positioning, it is possible to emphasize a low frequency range of noise generated by the paper colliding with the registration roller pair in a state where the rotation of the roller is stationary, and to generate a calm impression sound. In addition, in the process of transporting the paper, it is possible to improve the sound quality of the noise caused by the impact sound that is generated when the paper tip collides with the roller pair when passing the curved transport roller.

(Second Embodiment)
A sheet conveying apparatus according to a second embodiment will be described with reference to FIG. The difference from the first embodiment is that a paper impact force detection unit 601 and an output magnification change unit 602 are provided.
The sheet conveying apparatus of the present embodiment includes a sheet impact force detection unit 601 and an output magnification change unit 602 in addition to the apparatus part of the sheet conveying apparatus of the first embodiment.

The paper impact force detection unit 601 detects an impact force when the paper collides with the stopped roller pair, and outputs an impact signal indicating the impact force. The impact signal is a signal having an amplitude proportional to the magnitude of the impact force, for example.
The output magnification change unit 602 changes the output magnification of the control wave according to the magnitude of the impact indicated by the impact signal input from the paper impact force detection unit 601. That is, the greater the impact, the greater the magnitude of the control wave. There are a plurality of output magnifications, for example, and the output magnification changing unit 602 selects one of the output magnifications according to the magnitude of the impact. The output magnification changing unit 602 changes the amplitude of the control wave having a frequency distribution determined by the control filter 105. For example, the output magnification change unit 602 prepares several stages of control filter output magnifications in advance and switches them.

  Since the paper conveyance / correction signal detection unit 107 and the paper characteristic detection unit 102 can detect a signal before a paper collision as described above, this signal is a signal closely related to an impact with respect to time timing. However, since these are not acceleration sensor signals, they are not related to the strength of impact force, and the control wave generated using these as reference signals is not an output signal corresponding to the impact force.

  When a large impact sound is generated, it is desirable to use a large bass-enhanced control wave, and when a small impact sound is a small bass-enhanced control wave. Therefore, in this embodiment, the impact force is monitored by installing a paper impact force detection unit 601 such as a vibration sensor near the paper collision unit, and the output magnification change unit 602 determines a threshold value and determines the magnitude of the impact force. Therefore, we propose a mechanism to change the amplitude magnification of the control wave.

Next, experimental results obtained using the experimental system referred to in the first embodiment will be described with reference to FIG.
FIG. 7 shows an experimental result when the output magnification change unit 602 increases the output magnification of the control wave to 2.5 times according to the impact force detected by the paper impact force detection unit 601. On the other hand, FIG. 4 shows the experimental results when the output magnification is 1. FIG. “Magnification 2.5 times” in FIG. 7 indicates the frequency distribution of the sound wave after control. It can be seen that the sound waves after the control in FIG. 7 are increased in comparison with the sound waves after the control in FIG. As a result, the sound wave in FIG. 7 has an expanded sound band as compared with the sound wave in FIG. When the amplitude magnification is increased in proportion to the impact force, the sound increase band is expanded as shown in FIG.

  According to the second embodiment described above, in addition to the effects of the first embodiment, the sound quality can be improved more appropriately by adjusting the magnitude of the control wave according to the generated impact sound. .

(Third embodiment)
A sheet conveying apparatus according to a third embodiment will be described with reference to FIG. The difference from the second embodiment is that the output magnification changing unit 602 is not installed, the output signal of the paper impact force detection unit 601 is output to the reference signal calculation unit 801, and the control filter 802 considers the impact force. This is the point that determines the frequency distribution.
The paper conveyance device of this embodiment removes the output magnification change unit 602 from the paper conveyance device of the second embodiment, and the reference signal calculation unit 106 and the reference signal calculation unit 106 are changed to a reference signal calculation unit 801 and a control filter 802, respectively. It is a replacement.

The reference signal calculation unit 801 receives the detection signal, the characteristic signal, and the shock signal (in this case, the reference signal is the detection signal, the characteristic signal, and the shock signal), and receives the reference signal (for example, the main pulse) corresponding to the characteristic signal and the shock signal. Output. The reference signal calculation unit 801 receives the impact signal as it is (that is, receives the frequency distribution of the impact force), and outputs a signal including this frequency distribution information to the control filter 802.
The control filter 802 sets the filter so as to generate a control wave having a frequency distribution received from the reference signal calculation unit 801.

  In the second embodiment, an output magnification closest to the magnitude of the impact force is selected from among a plurality of output magnifications. On the other hand, in the third embodiment, the frequency distribution of the impact force is used as it is for the control filter, so that a control wave having a frequency distribution closer to the impact force received than in the second embodiment can be generated.

  Note that the reference signal calculation unit 801 may use only the impact signal as the reference signal. Further, a signal obtained by processing the signal from the paper impact force detection unit 601 based on the characteristics of the detection signal and the characteristic signal that can be detected before the collision may be used as the reference signal. For example, if it is known from the relationship between the impact force and the paper characteristics that higher-order vibrations that are different from the low-frequency emphasis band are clearly superimposed at the time of collision depending on the type of paper, this can be regarded as noise. By eliminating this noise from the reference signal, the SN can be improved.

Next, a basic experiment system implemented assuming the paper conveying apparatus of FIG. 8 will be described with reference to FIG. Thereafter, the experimental results obtained by the experimental system of FIG. 9 will be described with reference to FIGS. 10, 11, and 12.
In the experimental system of FIG. 9, the force sensor 901 is attached to the vibration impulse hammer 302, and the impact force of the vibration impulse hammer 302 detected by the force sensor 901 is directly input to the bandpass filter 303 as a pulse. 3 different from the experimental system. Other points in the system of FIG. 9 are the same as those of the system of FIG.

FIG. 10 shows a case where the pass frequency band is from 100 Hz to 500 Hz, which is the same pass frequency band as FIG. It can be seen that the bass is emphasized more in FIG. 10 than in FIG. In FIG. 10, it can be seen that from about 100 Hz to about 200 Hz is considerably emphasized after the control.
FIG. 11 shows experimental results when the pass frequency band is changed from 100 Hz to 300 Hz, and FIG. 12 shows experimental results when the pass frequency band is changed from 200 Hz to 800 Hz. It can be seen that the band aimed by changing the pass frequency band is emphasized.

  According to the third embodiment described above, the sound quality can be improved more appropriately than in the second embodiment by directly using the shock signal including the frequency distribution of the generated impact force as a reference signal. Can do.

(Fourth embodiment)
The paper transport device of the fourth embodiment is an optimized control filter of the paper transport device of the first to third embodiments. Here, how the control filter is optimized and how effective the control filter is will be described with reference to FIGS.

In the paper transport device of the present embodiment, a control law, which is a relation between the control force and the external force, calculated by two spatial transfer functions that can be spatially identified and one constant n, shown in Formula (1), is applied to the control filter. Use. Using this mathematical formula (1), the control force f _{S is applied} to at least one of the pair of paper transport rollers 101 by the paper vibration unit 103, so that the radiated sound pressure after control is n times that before control, that is, 20 log. (N) The sound can be increased to dB.

Here, Fp is a spatial transfer function from the external force to the sound pressure at the paper front sound increase point, Fs is a spatial transfer function from the control force to the sound pressure at the paper front sound increase point, and n is the sound increase point. The sound multiplication factor, f _P is an external force, and f _S is a control force.

Hereinafter, the derivation process of Equation (1) will be described.
It is assumed that an external force acts on an arbitrary point on the flat plate shown in FIG. 13 and, as a result, vibration radiation sound is generated. When this flat plate is simply supported at the periphery, the displacement of the flat plate is expressed by equation (2), the eigenfunction is expressed by equation (3), and the natural angular frequency is expressed by equation (4).

Here, D is the bending rigidity, ρ is the density of the paper, and h is the plate thickness. m and n are natural numbers of 0 or more. Also a ^{D = Eh 3/12 (1} -v 2), E is Young's modulus, v is Poisson's ratio.

Front sound pressure p _i emitted paper from element i in the case of divided small area Delta] s _i at this time is Equation (5). Here, r _i indicates the distance from the element i to the front sound pressure position. Q _i indicates the volume velocity of the element i.

Here, it is considered to control the vibration radiation sound by applying a control force.
When the paper is divided into N pieces and the external force and the control force are applied to the paper at the same time, the vibration speed at the i-th element (x _i , y _i ) is set to u _i , the external force f _P and the above elements If compliance by displacing (= displacement / force) _{Z Pi,} compliance by the displacement of the control force and the element (= displacement / force) and _{Z Si,} equation (7) and (8).

Moreover, i-th element (x _{i, y i)} transmitted at a distance r _i from the sound pressure P _i from the elements of the area S _i, when written again placed the alpha _i in order to simplify the equation Equation (9) is obtained.

here,

Accordingly, the sound pressure P from the entire sheet becomes a composite sound pressure from all N elements, and therefore is given by Equation (11).

Here, in order to further simplify the formula, the following A and B were replaced.

Further, the sheet emission sound before control to which only the external force is applied is expressed by Equation (13).

Now, in this proposal, since the purpose is to increase the sound pressure after the control, when a control law is obtained such that the sound pressure P after the control becomes n times the sound pressure P ₀ before the control. The following equation is obtained.

That is, it is only necessary to minimize U corresponding to the sound pressure energy as an objective function.

However, * represents a complex conjugate.

Furthermore, when external force and control force are expressed in real part and imaginary part,

Therefore, Equation (18) is obtained.

Therefore, f _S is obtained so as to satisfy Equation (19).

Therefore, if the objective function is partially differentiated between the real part and the imaginary part,

Therefore, Equation (21) is obtained respectively.

Therefore, it can be seen that a control law, which is the relationship of the control force to the external force, is obtained and is a function of the sound increase magnification n.

Therefore, the control law is expressed by Equation (23).

here,

Therefore, the sound pressure P _i (x) given by the i element at a position X apart from the i-th element (other than r _i ) is expressed by Equation (25).

Therefore, Equation (26) is obtained for the entire sheet.

On the other hand, the sound pressure P _0i (x) given by the i element before control is expressed by Equation (27).

For the entire sheet, Equation (28) is obtained.

Therefore, the sound pressure level increase volume (dB) at the X position before and after the control is expressed by Equation (29).

As confirmation, if X position and _{r i} positions are the same, equation (30) from Equation (31), and meet the object of the n doubling sound, if twice 6dB increase, 9.4 dB increase is three times To do.

As described above, the control law (Formula (32)) for increasing the frontal sound pressure by n times is obtained.

Here, the component Z is the vibration speed of the element i from each force, but it takes a lot of time to identify the paper vibration speed for each minute element. Therefore, it is difficult to calculate the transfer function of fs and fp from Z. However, since Σα _i · Z _Pi and Σα _i · Z _Si correspond to the characteristics from the external force to the sound pressure at the position where the sound is desired to be increased, by actually measuring the spatial transfer function from the point where it acts, The ratio multiplied by (n-1) corresponds to the control law.
As a result, even if the paper transfer model is unknown, the control law can be estimated using the measured identification value.

Assuming the A4 size Kent paper shown in FIG. 14, the numerical calculation was performed under the simple surrounding support condition by adding the characteristic of the equation (33).

FIG. 15 and FIG. 16 show the sound pressure level control effect of 30 cm in front of the paper when the control force for the external force is the optimal control law (front sound pressure n times).
FIG. 15 shows the result when the control law (n = 3) is used for the band from 100 Hz to 300 Hz, and FIG. 16 shows the result when the control law (n = 10) is used for the band from 100 Hz to 300 Hz. Referring to FIG. 15 and FIG. 16, it can be seen that the sound is increased by 20 log (n) by the target band.

  FIG. 17 shows the displacement distribution at the resonance frequency of 150 Hz shown in FIG. It can be seen that after the control, resonance is emphasized and the displacement increases as a whole.

Next, the effect of the control law is shown by comparison.
In the example shown in FIG. 18, the position of the control force is shifted so that the external force and the control force are asymmetric with respect to the paper front sound pressure. At this time, when the control force is three times the external force in FIG. 19, and when the control force calculated by the optimal control law shown in Formula (1) (the front 30 cm sound pressure is three times) is given in FIG. The results are shown. When the control law is used, the sound is surely increased at the resonance frequency that contributes to the overall value (near the peak of the peak portion in FIG. 20, that is, near the vertex of the upward convex portion). Conversely, the frequency does not contribute to the overall value (near the lowest point of the valley portion in FIG. 20, that is, near the lowest point of the downward convex portion), the result does not change and has an objective function of sound pressure increase n times. It can be seen that the control law is more robust.

  According to the fourth embodiment described above, by applying the control force to the pair of sheet transport rollers 101 using the control law shown in the formula (1), it is more than in the first to third embodiments. Sound quality can be improved appropriately.

The following embodiments will be described more specifically than the previous embodiments.
(Concrete example)
An image forming apparatus including the sheet conveying device of the embodiment will be described with reference to FIG. The sheet conveying apparatus according to the embodiment is provided in an apparatus main body of an image forming apparatus such as an electrophotographic apparatus.

  A cassette device 2 and a cassette device 3 provided above the cassette device 2 are provided at the lower part of the housing 1. The cassette device 3 accommodates paper 4 that is an image forming medium, and one pickup roller 5 for taking out the paper 4 is provided on each side of the cassette devices 2 and 3. .

  In the housing 1, a conveyance path 8 for the sheet 4 extending upward from the cassette apparatus 2 through the cassette apparatus 3, the registration roller pair 6 and the secondary transfer unit 7 is formed. Below the transport path 8, a pair of paper feed rollers 9 for separating and pulling up the sheets 4 housed in the cassette device 3 one by one, and a pair of transport rollers for transporting the separated sheet 4 sandwiched between them. 10 are provided. Further, a manual feed tray 11 on which the paper 4 supplied to the inside of the apparatus main body can be manually placed is provided at the lower part of the housing 1. When the paper 4 is placed on the manual feed tray 11, the paper 4 is taken out by the manual paper feed roller 12 and conveyed to the conveyance path 8 side.

  In the transport path 8 above the paper feed roller pair 9 for the cassette device 3, an intermediate transport roller pair 13 that transports the paper 4 from the cassette devices 2 and 3 and the manual feed tray 11 is provided. The registration roller pair 6 provided in the conveyance path 8 above the intermediate conveyance roller pair 13 temporarily stops the sheet 4 in order to adjust the position and orientation of the sheet 4, and the sheet 4 with respect to the secondary transfer unit 7. Transport. Above the intermediate conveyance roller pair 13 and below the registration roller pair 6, conveyance guides 14 and 15 each having a curvature having a predetermined curvature are provided.

  Image forming units 20, 21, 22, and 23 that transfer and form yellow, magenta, cyan, and black toner images on an endless transfer belt 19 are arranged in parallel at the center of the housing 1. . A toner image is formed on the transfer belt 19 by the four developing rollers 30. The transfer belt 19 rotates and runs counterclockwise by a motor that drives the four pairs of drive rollers 24. The secondary transfer roller pair 25 transfers the color toner image transferred to the transfer belt 19 to the paper 4 while sandwiching the paper 4 fed from the registration roller pair 6 with the transfer belt 19. In the transport path 8, a fixing unit 26 that fixes the transferred toner image onto the paper 4 is provided at a position downstream of the secondary transfer roller pair 25 in the paper transport direction. The image transferred onto the paper 4 is heated and pressed by the fixing unit 26 and conveyed to the paper discharge unit 28 by the paper discharge roller pair 27. Four pairs of conveyance rollers 29 for conveying the paper 4 with its front and back reversed are provided along one side surface of the housing 1 from the end of the conveyance path 8. When the sheet 4 that has reached the end of the conveyance path 8 is returned to the upstream side of the registration roller pair 6 through the conveyance roller pair 29, the toner image on the transfer belt 19 is also transferred to the back surface of the sheet 4. Transcribed.

  In the image forming apparatus including the sheet conveying apparatus according to the present embodiment having such a configuration, the drive control unit (not shown) conveys the sheet 4 by a predetermined amount by the intermediate conveying roller pair 13 while the registration roller pair 6 is stopped. Thus, the rotational speeds of the drive roller of the registration roller pair 6 and the drive roller of the intermediate conveyance roller pair 13 are controlled. The conveyance guide 14 bends the sheet 4 by causing the leading end of the sheet 4 ejected from the intermediate conveyance roller pair 13 to slide on the curved surface. The drive control unit carries the paper 4 until the leading end of the paper 4 discharged from the intermediate conveyance roller pair 13 abuts against the nip portion of the registration roller pair 6 and until the paper 4 is slightly bent. Then, the conveyance operation is stopped. Accordingly, the posture of the paper 4 is aligned and the inclination of the paper 4 is corrected. As a result, the leading end of the paper 4 is positioned.

Next, a sheet conveying device included in the image forming apparatus of FIG. 21 will be described with reference to FIG.
The sheet conveying apparatus in FIG. 22 is in the lower right part of FIG. 21 and includes a paper feed roller pair 9, an intermediate conveying roller pair 13, a registration roller pair 6, a paper thickness detection unit 2201, and an impact force detection unit 2202.
The paper feed roller pair 9 separates and pulls up the paper stored in the cassette device one by one.
The intermediate transport roller pair 13 is provided in a transport path above the paper feed roller pair 9 and transports the paper guided by the paper feed roller pair 9 with the paper sandwiched therebetween. The intermediate conveyance roller pair 13 corresponds to the sheet conveyance roller pair 101 in FIG.
The registration roller pair 6 temporarily stops the sheet in order to adjust the position and orientation of the sheet, and conveys the sheet to the next part.
The paper thickness detector 2201 detects the paper thickness of the paper and outputs a signal indicating the paper thickness of the paper.
The impact force detection unit 2202 detects the impact force when the sheet collides with the stopped registration roller pair 6 and outputs a signal indicating the impact force. This signal is a signal having an amplitude proportional to the magnitude of the impact force, for example.

(Fifth embodiment)
A sheet conveying apparatus according to a fifth embodiment will be described with reference to FIG. This embodiment is a more specific example of the first embodiment. In addition to the apparatus portion of the first embodiment, a collision time calculation unit 2302 is newly included, and a paper thickness detection unit 2301 is included as an example of the realization of the paper characteristic detection unit 102. Here, after the sheet thickness is detected by the sheet thickness detection unit 2301 from the sheet conveyance roller pair 101 (intermediate conveyance roller pair), the sheet is conveyed to the nip portion of the stopped registration roller pair 6 and collides with it. Will occur. FIG. 24 shows a moment when the sheet collides with the nip portion of the registration roller pair 6.

  The paper thickness detection unit 2301 detects the paper thickness of the paper, and for example, an MR sensor or an optical sensor is used. The paper thickness detection unit 2301 outputs a reference signal corresponding to the paper thickness to the reference signal calculation unit 106.

The collision time calculation unit 2302 is for obtaining the control wave application time more accurately in consideration of the time delay of the generation of the control wave, and the sheet collides with the registration roller based on the detected sheet thickness and the sheet passage timing. Calculate time. When the time when the paper passes the paper thickness detection unit 2301, t is the conveyance speed, v is the distance between the paper thickness detection unit 2301 and the registration roller nip, h is the paper thickness, and r is the diameter of the registration roller. The time T when the roller collides with the registration roller nip is expressed as follows.

For example, when the registration roller diameter is 20 [mm] and the conveyance speed is 100 [mm / s], the paper thickness of 0.04 [mm] and the paper thickness of 0.3 [mm] are 15.5 [msec]. The collision time difference occurs.

  By calculating the difference in the collision time depending on the paper thickness, it is possible to provide a paper transport device that can reduce the delay in applying the control wave and reliably emphasize the low frequency of the paper collision sound. Note that the paper thickness detection and the paper passage timing may be detected by separate sensors.

  In accordance with the calculated collision time, the sheet vibration unit 103 applies a control wave. Based on the generated control wave, the motor drive circuit drives the control wave applying roller to apply the control wave with low frequency emphasis to the paper. In addition to the motor-driven roller, the sheet vibration unit 103 may be an additional roller with a vibration device or a film, or a non-contact vibration device using a speaker or air.

  The frequency analysis results of the collision sound before application of the control wave and the collision sound after application of the control wave are as shown in FIGS. 5 and 9, for example. As can be seen from these figures, the low frequency of the collision sound is emphasized by applying the control wave.

  According to the fifth embodiment described above, it is possible to reliably calculate the sheet collision by calculating the collision time when the sheet collides with the registration roller pair and suppressing the deviation of the generation time between the collision sound and the control wave to a predetermined value or less. Sound quality can be improved by emphasizing the low frequency range of the sound.

(Sixth embodiment)
A sheet conveying apparatus according to a sixth embodiment will be described with reference to FIG. This embodiment is a more specific example of the first embodiment. In addition to the apparatus portion of the first embodiment, a collision time calculation unit 2302 is newly included, a paper thickness detection unit 2301 is included as an example of the paper characteristic detection unit 102, and a control filter is included as an example of the control filter 105. A selection unit 2501 is included.

  The control filter selection unit 2501 holds a table in which a control signal corresponding to the natural frequency of the paper and the paper thickness are associated in advance, and estimates the paper thickness based on the reference signal output from the reference signal calculation unit 106. A corresponding control signal is output with reference to the table. That is, the paper type is determined based on the paper thickness detected by the paper thickness detector, and the control wave selection unit selects a control wave corresponding to the paper. The control wave generation unit 104 generates the selected control wave, and the paper excitation unit 103 gives the control wave in accordance with the collision time calculated from the paper thickness. This makes it possible to generate a control signal optimal for the natural frequency of the paper.

  When the paper thickness detection unit 2301 outputs the magnitude of the reference signal in proportion to the paper thickness, the control filter selection unit 2501 can estimate the paper thickness based on the magnitude of the reference signal. Accordingly, the control signal may be determined.

  According to the sixth embodiment described above, the sound quality can be improved by accurately exciting the resonance of the paper and emphasizing the collision sound in a low frequency band.

  According to the paper transport device of the embodiment described above, by giving a control wave in the low frequency range to the paper, the impact sound is emphasized by low sound without increasing the overall value of the noise level. The sound quality that varies depending on the difference in the entry angle can be improved without reducing the transport speed.

The instructions shown in the processing procedure shown in the above embodiment can be executed based on a program that is software. A general-purpose computer system stores this program in advance and reads this program, so that it is possible to obtain the same effect as that obtained by the paper conveying apparatus of the above-described embodiment. The instructions described in the above-described embodiments are, as programs that can be executed by a computer, magnetic disks (flexible disks, hard disks, etc.), optical disks (CD-ROM, CD-R, CD-RW, DVD-ROM, DVD). ± R, DVD ± RW, etc.), semiconductor memory, or a similar recording medium. As long as the recording medium is readable by the computer or the embedded system, the storage format may be any form. If the computer reads the program from the recording medium and causes the CPU to execute an instruction described in the program based on the program, the same operation as that of the sheet conveying apparatus of the above-described embodiment can be realized. Of course, when the computer acquires or reads the program, it may be acquired or read through a network.
In addition, the OS (operating system), database management software, MW (middleware) such as a network, etc. running on the computer based on the instructions of the program installed in the computer or embedded system from the recording medium implement this embodiment. A part of each process for performing may be executed.
Furthermore, the recording medium in the present invention is not limited to a medium independent of a computer or an embedded system, but also includes a recording medium in which a program transmitted via a LAN or the Internet is downloaded and stored or temporarily stored.
Further, the number of recording media is not limited to one, and when the processing in the present embodiment is executed from a plurality of media, it is included in the recording media in the present invention, and the configuration of the media may be any configuration.

The computer or the embedded system in the present invention is for executing each process in the present embodiment based on a program stored in a recording medium, and includes a single device such as a personal computer or a microcomputer, Any configuration such as a system in which apparatuses are connected to a network may be used.
Further, the computer in the embodiment of the present invention is not limited to a personal computer, but includes an arithmetic processing device, a microcomputer, and the like included in an information processing device, and a device capable of realizing the functions in the embodiment of the present invention by a program, The device is a general term.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Housing | casing 2 ... Cassette apparatus 3 ... Cassette apparatus 4 ... Paper 5 ... Pickup roller 6 ... Registration roller pair 7 ... Secondary transfer part 8 ... Conveyance path 9 ... Paper feed roller pair 10 DESCRIPTION OF REFERENCE SYMBOLS: Conveyance roller, 11: Manual feed tray, 12 ... Paper feed roller, 13 ... Intermediate conveyance roller pair, 14, 15 ... Conveyance guide, 19 ... Transfer belt, 20, 21, 22, 23 ... Image forming unit, 24 ... Drive roller 25 ... secondary transfer roller pair, 26 ... fixing section, 27 ... discharge roller pair, 28 ... discharge section, 29 ... conveying roller pair, 30 ... developing roller, 101 ... paper conveying roller pair, 102 ... paper characteristic detection , 103 ... paper excitation unit, 104 ... control wave generation unit, 105 ... control filter, 106 ... reference signal calculation unit, 107 ... paper conveyance / correction signal detection unit, 301 ... vibration actuator, 302 ... impulse for excitation Numeral 303, band pass filter, 601 ... paper impact force detection unit, 602 ... output magnification change unit, 801 ... reference signal calculation unit, 802 ... control filter, 901 ... force sensor, 2201 ... paper thickness detection unit, 2202 ... impact Force detection unit, 2301 ... paper thickness detection unit, 2302 ... collision time calculation unit, 2501 ... control filter selection unit.

Claims (7)

A first roller pair for conveying paper;
A characteristic detection unit that detects the characteristic of the paper and outputs a characteristic signal indicating the characteristic;
A first detector that detects that the paper has reached the first roller pair and outputs a detection signal indicating the detection;
A calculation unit for calculating a reference signal according to the characteristic signal;
A control filter for determining a frequency distribution of control waves to be applied to the paper when the paper collides with the second roller pair according to the reference signal;
A generator for generating the control wave;
The difference between the time determined by at least one of the characteristic signal and the detection signal and the time when the paper collides with the second roller pair and the time when the control wave is applied to the paper is within a threshold value. And a vibration unit that applies the control wave to the paper. A second detector for detecting an impact signal indicating the magnitude of an impact force when the paper collides with the second roller pair;
The paper conveying apparatus according to claim 1, further comprising: a changing unit that changes an output magnification of the control wave according to the shock signal. A second detector for detecting an impact signal indicating the magnitude of the impact force when the paper collides with the second roller pair;
The calculation unit calculates a reference signal corresponding to the characteristic signal and the impact signal;
2. The paper conveying apparatus according to claim 1, wherein the control filter determines a frequency distribution of a control wave having a frequency distribution of the reference signal.   The said control filter has a band pass filter characteristic that the difference of the sound pressure level before and behind control wave provision is less than a threshold value, The Claim 1 characterized by the above-mentioned. Paper transport device. The control filter provides a control force f _s when the excitation unit applies a control wave according to an external force f _p indicated by the impact signal, and Fp is a space from the external force to the sound pressure at the sheet front sound increase point. A transfer function, a spatial transfer function from the control force to the sound pressure at the front sound increase point of the sheet, and F as a sound increase magnification at the sound increase point, and Fs as a sound transfer magnification at the sound increase point, the following formula (1)

The sheet conveying apparatus according to claim 3, wherein the sheet conveying device is determined based on The characteristic is the thickness of the paper,
A calculation unit for calculating a time at which the leading edge of the sheet collides with the second roller pair based on the thickness;
2. The excitation unit applies the control wave to the sheet so that a difference between the time and a time to apply the control wave to the sheet is within a threshold value. The paper conveyance device according to claim 3. The characteristic is the thickness of the paper,
A changing unit for changing the output magnification of the control wave according to the thickness;
A calculation unit that calculates a time at which the leading edge of the paper collides with the second roller pair based on the thickness;
2. The excitation unit applies the control wave to the paper so that a difference between the time and the time to apply the control wave to the paper is within a threshold value. The paper conveying apparatus as described.

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