JPH02193836A - Sheet feed device - Google Patents

Abstract

PURPOSE:To improve high speed stability at low speed sheet carriage and ensure high precision sheet carriage control by changing a phase difference between the progressive vibration waves of two vibration bodies for changing a sheet carriage speed. CONSTITUTION:A pair of vibration bodies 1 and 5 of an elastic material for clamping a sheet 9 constitutes two groups of electrical-mechanical energy conver sion element cells 3 and 4, and 7 and 8, and is applied with a.c. voltage having a 90 deg. time phase difference from an oscillator 14 via power amplifiers 17 and 18 directly or via 90-degree phase converters 15 and 16, thereby generating a progressive wave as a synthesis of two standing waves dephased lambda/4 from each other and carrying the sheet 9. In this case, a deviation between a sheet carriage amount control signal and a phase difference detected with a detector 10 is applied to a voltage controller 13 via a differential amplifier 11, thereby causing a change in a phase difference between the progressive vibration waves of the vibration bodies 1 and 5, and stably changing the carriage speed of the sheet 9 to a low speed range. According to the aforesaid construction, it becomes possible to control the carriage of sheets with high precision.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention is applicable to computers, copying machines, printer facsimiles,
The present invention relates to a sheet feeding device installed in word processors, typewriters, etc., and specifically relates to a sheet feeding device that feeds sheets using progressive vibration waves.

[Prior Art J] Conventionally, as a sheet feeding device using progressive vibration waves, there is, for example, Japanese Patent Application Laid-open No. 177243/1983. This sheet feeding device sandwiches a sheet between a pair of vibrating bodies made of an elastic material that are in contact with each other with an appropriate pressing force, and conveys the sandwiched sheet by generating progressive vibration waves in each of the vibrating bodies. Two groups of electro-mechanical energy converting elements such as piezoelectric elements are bonded or pressed to the two vibrating bodies, and the piezoelectric elements are arranged so that there is an offset of an odd multiple of λ/4 between each group. Within each group, the piezoelectric elements are arranged at a pitch of λ/2 and so as to alternately have opposite expansion and contraction polarities. Then, an alternating current electric field with a frequency near the natural frequency of both types of moving bodies (actually, the natural frequency of one of the vibrating bodies) is applied to each piezoelectric element group of both types of moving bodies, and each of the piezoelectric elements of both types of moving bodies is By applying an alternating current electric field with a phase difference of π12 through a π72 phase shifter to the other piezoelectric element group, progressive vibration waves are generated in each vibrating body symmetrically with respect to the conveying surface of the sheet. In other words, when a progressive vibration wave is generated in a vibrating body,
Each point on the surface opposite to the surface on which the piezoelectric element is provided performs a kind of elliptical motion, and each point on the opposing surface of both types of moving bodies moves elliptically symmetrically with respect to the sheet conveyance surface, thereby conveying the sheet. It looks like this. By changing the amplitude of the progressive vibration waves formed in each vibrating body, the conveying speed of the sheet, which is conveyed by being given a conveying force by the frictional force between the sheet and the vibrating body, is changed. .

FIG. 5 is a schematic diagram illustrating the principle of generation of sheet conveying force by such progressive vibration waves, in which the sheet 9 is held between the vibrating weight and 5 with an appropriate pressing force, and the vibrating bodies 1 and 5 are As shown, progressive bending vibration is formed. At this time, if we focus on a certain mass point on the surface of both types of moving object 1.5,
A mass point generally moves in an elliptical orbit. Regarding the vibrating body 1, when the progressive bending vibration advances in the right direction indicated by time in the figure, the mass points on the surface draw a clockwise elliptical locus. Here, since the phase difference of the progressive bending vibrations formed in the vibrating bodies 1 and 5 is spatially configured to be 1110°, the bending vibration of each vibrating body is caused by the convex portion on the sheet side. Always proceed in opposition. Since the movement direction of the mass point of the convex portion is opposite to the direction of vibration of the vibrators 1 and 5, in this case, sheet conveying force is generated in the direction of the arrow. On the other hand, in the concave portion, the sheet conveying force acts in the same direction as the traveling direction, but the pressure is smaller than in the convex portion, so the frictional force between the sheet and the vibrating body is small, and the sheet conveying force is also small, so the sheet conveying force is reduced. In total, the vibration acts in the direction opposite to the direction in which the bending vibration travels.

In addition, Japanese Patent Application Laid-Open No. 62-85684 discloses a motor that utilizes such progressive vibration waves, and in addition to the two groups of piezoelectric elements mentioned above, a piezoelectric element for vibration detection is installed in the vibrating body. and control the frequency of the applied voltage so that the phase difference between the output signal of the piezoelectric element for vibration detection and the AC voltage applied to one piezoelectric element group maintains the phase difference during resonance vibration of the vibrating body. This allows the vibrating body to vibrate efficiently and stably.

[Problems to be Solved by the Invention] Incidentally, in such a sheet conveying device, since the sheet conveying speed control depends on the amplitude change of the traveling wave generated in each vibrating body, it is difficult to convey the sheet at a low speed. In this case, the amplitude of the traveling wave becomes small, making the vibration unstable and making it difficult to convey the sheet at a stable low speed.Also, the influence of uneven sheet thickness increases, causing uneven sheet conveying speed. There was a drawback that this resulted in increased difficulties.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying device that solves the above-mentioned conventional problems and can stably convey sheets even at low speeds.

[Means for Solving the Problems] A typical sheet feeding device for achieving the object of the present invention sandwiches a sheet of an object to be conveyed between a pair of vibrating bodies made of an elastic material. In each case, two groups of electric-mechanical energy conversion element sections are arranged at equal pitch λ/2 within each group, and the polarity of expansion and contraction when voltage is applied is alternately opposite, and between groups λ By arranging and fixing the elements so that there is a shift of an odd multiple of /4, and applying an alternating current voltage having a temporal phase difference of 90'' between the two groups of each electro-mechanical energy conversion element section of each vibrator. , generate a traveling wave of wavelength λ as a synthesis of two standing waves (wavelength λ) shifted by λ/4 from each other generated by the respective groups in each vibrating body,
In a sheet feeding device that conveys a sheet held between both vibrating bodies in a direction opposite to the traveling direction of progressive vibration waves,
vibration state detection means that detects the vibration states of the two vibrating bodies and detects a temporal phase difference between the two vibrating bodies, and sheet conveyance that is arbitrarily set to the phase difference output from the vibration state detection means. The apparatus is characterized by comprising a control means for comparing the phase difference corresponding to the speed and controlling the drive of both vibrating bodies with a phase difference corresponding to the arbitrarily set sheet conveyance speed. be.

[Function] The sheet feeding device configured as described above changes the phase difference between the progressive vibration waves of both vibrators to change the sheet transport speed, so the amplitude of the progressive vibration waves can be changed. The sheet can be stably driven down to a low speed range while maintaining a sufficiently large amplitude for stable driving.

[Example] The present invention will be described in detail below based on an example shown in the drawings.

Embodiment 1 FIG. 1 is a schematic block diagram showing Embodiment 1 of a sheet conveying device according to the present invention.

1 and 5 are thick vibrating bodies formed in an oval shape (hereinafter referred to as the first vibrating body and the second vibrating body), which sandwich the sheet 9 with moderate pressure, and In this method, two groups of piezoelectrics are used to form two standing waves with a phase shift of 90° in position and 90° in time, and to form a progressive vibration wave by combining them. Element sections 3 and 4, 7 and 8 are provided, respectively, and detection piezoelectric elements 2 and 6 are provided for detecting the vibration state of the progressive vibration waves formed on the vibrators 1 and 5, respectively. . Note that the first vibrating body 1 and the second vibrating body 5 are electrically connected to the ground potential.

1O is a phase difference detector which detects the temporal phase difference at the same spatial position of the traveling waves formed on both prefectural moving objects 1.5 and the signal from the piezoelectric element 2 for first detection and the signal for second detection. It is detected as a phase difference with the signal from the piezoelectric element 6. Reference numeral 11 indicates the phase difference detected by the phase difference detector lO and the sheet transport amount setting means (
A differential amplifier 12 amplifies the difference between the sheet transport amount control signal and the phase difference corresponding to the sheet transport amount control signal (not shown); 12 is a low-pass filter (12) that amplifies and integrates the output signal of the differential amplifier 11;
L, P, F), 13 is a voltage-controlled phase shifter for outputting a signal whose phase is shifted from the phase of the output signal of the oscillator 14 according to the output signal of the low-pass filter 12.

Reference numeral 14 denotes an oscillator for generating a reference signal of an AC voltage to be applied to each piezoelectric element section 3.4 and 7.8 of the first vibrating body 1 and the second vibrating body 5; 7
．． 8 is output via a voltage controlled phase shifter 13.

15 is a first oscillator for generating a signal whose phase is shifted by +90° or −90° based on the reference signal of the oscillator 14 in accordance with the transport direction switching signal from the transport direction setting means (not shown).
With the 90° phase shifter, the phase of the driving frequency of the piezoelectric element section 3 of the first vibrating body 1 is shifted by 90 degrees with respect to the piezoelectric element section 4. 16 is based on the output signal of the voltage-controlled phase shifter 13 and changes the phase by +90 in accordance with the transfer direction switching signal.
a second 90° to create a signal shifted by -90° or -90°.
'A phase shifter is used to shift the phase of the drive frequency of the piezoelectric element section 7 of the second vibrating body 5 with respect to the piezoelectric element section 8 by 90 degrees. 17 is an oscillator 14 and a first 90° phase shifter 1
A first power amplifier 18 amplifies the output signal of the voltage-controlled phase shifter 13 with an appropriate amplification factor and applies the amplified signal to the piezoelectric element section 3.4 of the first vibrating body 1; No.9
The output signal of the 0° phase shifter 16 is amplified and transmitted to the second vibrating body 5.
a second power amplifier for applying voltage to piezoelectric element sections 3 and 7 of .

The structure of this embodiment has been described above, and its operation will be explained with reference to the diagram shown in FIG.

Figure 2 shows the relationship between the output of the phase difference detector IO and the sheet transport speed.As is clear from the figure, the transport speed is highest when the phase difference is 0 degrees, and as the phase difference approaches 180 degrees ( As the phase difference approaches 180 degrees, the transport speed becomes 0.

Here, the phase difference is 0, which is the maximum speed of the sheet transport amount control signal.
The output of the phase difference detector lO is 0 when the signal corresponds to
Suppose it was degree. At this time, when the sheet transport amount control signal is switched to a signal corresponding to a phase difference of 45 degrees, the output of the differential amplifier 11 becomes a negative output, the output of the low-pass filter 12 decreases, and the voltage-controlled phase shift The phase of the output signal of the voltage-controlled phase shifter 13 is delayed, and the first vibrating body l driven by the reference signal of the oscillator 14 and the second vibrating body l driven by the output signal of the voltage-controlled phase shifter 13 are caused to vibrate. Although the amplitude is the same, the phase of the traveling wave is different. And each vibrating body 1
The phase states of the traveling waves of and 5 are detected by the first vibration detection piezoelectric element 2 and the second vibration detection piezoelectric element 6, respectively,
Since the difference is input to the differential amplifier, the phase of the output signal of the first vibration detecting piezoelectric element 2 of the first vibrating body l is the same as that of the output signal of the vibration detecting piezoelectric element 6 of the second vibrating body 5. Feedback control is performed to advance the phase by 45 degrees, and sheet 9
is conveyed in a predetermined direction at a sheet conveyance speed corresponding to the phase difference shown in FIG.

Example 2 In the above-mentioned Example 1, each vibrating body 1.5 is provided with a piezoelectric element 2.6 for vibration detection, and the vibrations of the two vibrating bodies are detected.
However, this embodiment does not use such a piezoelectric element for vibration detection, and the voltage that flows when an AC voltage is applied to the piezoelectric element section for driving is controlled to keep the phase of two signals constant. Detects the driving piezoelectric element section 4°8 or 3,
The phase difference between the AC voltages applied to the drive piezoelectric element section 4.8 or 3.7 is controlled so that the phase of the current flowing into the drive section 7 corresponds to the sheet transport amount control signal. It is something. FIG. 3 shows a schematic diagram of this embodiment.

19 and 20 are differential amplifiers for detecting the current flowing into the drive piezoelectric element section 4.8 by amplifying the voltage difference across the resistor 21.22. The outputs of the respective differential amplifiers 19 and 20 are output to the phase difference detector lO. Note that the other configurations are the same as those of the first embodiment described above, except that each vibrating body 1.5 is not provided with a piezoelectric element for vibration detection, so a description thereof will be omitted.

That is, in the first embodiment described above, the phase is detected from the output voltage of the piezoelectric element 2.6 for vibration detection, whereas in this embodiment, the phase is detected from the current flowing into the drive piezoelectric element section 4.8. It is designed to detect the phase, and by detecting the phase difference between the traveling waves of the vibrating body 1.5 from the outputs of the differential amplifiers 19 and 20, the same operation as in the first embodiment is performed. Controls sheet conveyance speed.

Embodiment 3 In each of the first and second embodiments described above, an oval-shaped vibrating body was used, but in this embodiment, a plate-shaped vibrating body with ends is used.

In each of the above-mentioned embodiments, an AC voltage is applied to two groups of piezoelectric element sections provided in a vibrating body, and a traveling wave is generated as a composite of standing waves generated by vibration of each piezoelectric element section. However, traveling waves can also be generated in the vibrating body by the method described below.

The principle of this method is as shown in Fig. 6.
In addition to the vibrating body driving vibrator 102 which gives vibrations to the vibrator 105 using an oscillator 105, a matching vibrator 103 is provided, and by terminating the voltage generated in this vibrator 103 with a terminating resistor 104, vibration energy can be converted into electrical energy. and consumed by the terminating resistor 104, the drive vibrator 1
The energy emitted from 02 flows in one direction, and as a result,
The vibrations on the vibrating body 101 generate traveling waves.

That is, when the vibrator 102 is vibrated by the oscillator 105, the vibration wave propagates on the vibrator 101 in the right direction in the figure (at this time, the matching vibrator 103 and the resistor 104
If not, the wave will be reflected at the right end of the vibrating body 101 and the reflected wave will propagate to the left, and if the vibration frequency is the natural frequency of the vibrating body 101, a standing wave will be formed on the vibrating body 101. will be done. However, when there is a matching vibrator 103 and a resistor 104, the energy of the vibration wave is consumed by the resistor 104 to prevent the reflected wave from returning at the right end of the vibrating body, and the left A traveling wave that propagates to the right is formed.

This embodiment utilizes the principle of generation of such a traveling wave, and 31 and 32 are vibrating bodies, 33 and 34 degrees, 23 and 2
4 is a drive piezoelectric element, 25.26 is a drive piezoelectric element 33
．． 34 and 23. The role of 24 is divided into vibration excitation and vibration absorption.
An analog switch for switching this according to the transfer direction switching signal, 27.28 is a vibration absorption resistor, 29.30
is a power amplifier for amplifying the output voltages of the oscillator 14 and the voltage-controlled phase shifter 13. When the sheet is moved to the right on the paper in FIG. 4 by the transfer direction switching signal, this circuit uses analog drive piezoelectric elements 33 and 34 for vibration excitation and drive piezoelectric elements 23 and 24 for vibration absorption. When the switches 25 and 26 are set and moved in the opposite direction, this is done by exchanging the roles of the drive piezoelectric element, which was used for excitation, and the piezoelectric element, which was used for vibration absorption. Further, by changing the sheet transport amount control signal, the amount of phase shift of the voltage-controlled phase shifter 13 is changed, and the driving piezoelectric element 33.3 is changed.
When the phase difference between the alternating current voltages applied to the vibrating bodies 31 and 32 changes, the phase between the traveling waves formed on the vibrating bodies 31 and 32 changes, and the sheet transport speed changes.

In each of the embodiments described above, the actual transport speed of the sheet is not detected and the sheet transport amount control signal is not feedback-controlled based on the detected speed, but the rotation of the sheet is controlled by bringing a rubber roller or the like into contact with the sheet. By detecting the corner using a rotary encoder, etc., or by detecting the speed using a non-contact speed detection method such as a laser/dral bra method, and increasing/decreasing the sheet transport amount control signal according to the detected speed information, more stable Speed control may also be performed.

[Effects of the Invention] As explained above, according to the present invention, the sheet can be transported at a low speed while generating large-amplitude progressive vibration waves in the two vibrating bodies that sandwich and transport the sheet. Speed stability during conveyance is improved, highly accurate sheet conveyance control is possible, and if used for facsimile, for example, high-definition image printing processing becomes possible.

Furthermore, not only low-speed accuracy but also high-speed response is possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of Embodiment 1 of a sheet feeding device according to the present invention, and FIG. 2 is a chart showing the relationship between the phase difference between progressive vibration waves formed on two vibrating bodies and the sheet transport speed. Fig. 3 is a schematic block diagram of the second embodiment, Fig. 4 is a schematic block diagram of the third embodiment, Fig. 5 is a diagram for explaining the operating principle of the sheet feeding device, and Fig. 6 is the drive of the third embodiment. FIG. 3 is a diagram for explaining the principle. ■, 5: Vibrating body 2.6 = Piezoelectric element for vibration detection 3.4, 7.8: Piezoelectric element section 9: Sheet 1O: Phase detector 11: Differential amplifier 12: Low-pass filter 13: Voltage-controlled transfer Phase shifter 14: Oscillator 15, 16: 90' phase shifter 17, 18: Power amplifier 19, 20: Differential amplifier 25, 26: Analog switch 29, 30: Power amplifier Harney demand center

Claims (1)

[Claims] 1. A sheet of an object to be conveyed is sandwiched between a pair of vibrating bodies made of an elastic material, and each of the pair of vibrating bodies has two groups of electric-mechanical energy conversion element sections. At equal pitch λ/2, and so that the polarity of expansion and contraction during voltage application is alternately reversed, there is λ/4 between the groups.
By applying an alternating current voltage having a temporal phase difference of 90° between two groups of each electro-mechanical energy conversion element section of each vibrating body, A traveling wave of wavelength λ is generated in each vibrating body as a composite of two standing waves (wavelength λ) that are shifted by λ/4 from each other and generated by each of the above groups, and is thus sandwiched between both vibrating bodies. In a sheet feeding device that conveys a sheet in a direction opposite to the traveling direction of progressive vibration waves, vibration state detection detects the vibration state of each of the two vibrating bodies and detects a temporal phase difference between the two vibrating bodies. and compares the phase difference output from the vibration state detection means with the phase difference corresponding to the arbitrarily set sheet conveyance speed, and determines the position of both vibrating bodies corresponding to the arbitrarily set sheet conveyance speed. A sheet feeding device comprising: a control means for controlling drive with a phase difference. 2. A pair of vibrating bodies made of an elastic material with ends that sandwich the sheet of the conveyed object, and each vibrating body of the pair is provided along the sheet conveying direction, and the vibrating bodies are vibrated by applying an alternating voltage. a first electrical-to-mechanical energy conversion means and a second electrical-to-mechanical energy conversion means;
A drive power supply means for supplying an AC voltage for driving to the mechanical energy conversion means, and when each of the first electric-mechanical energy conversion means and the drive power supply means are connected, each of the second electric-mechanical energy conversion means When the energy consuming resistors are connected, and the respective second electrical-mechanical energy conversion means and the drive power supply means are connected, the respective first electrical-mechanical energy conversion means and the energy consuming resistors are connected. 1. A sheet feeding apparatus, comprising: a switch means for switching the drive power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means to switch the driving power supply means, the driving power supply means having a phase shifter for creating a phase difference between two systems of alternating current voltages supplied in accordance with sheet transport speed information.