JPH04116038A - Sheet feeding device - Google Patents

Abstract

PURPOSE:To improve positioning precision by performing microslap feed through repetition of ON and OFF of a drive force, exerted on a sheet by a piezoelectric element, so that the speed of a sheet is increased to a high value. CONSTITUTION:Piezoelectric elements 1 and 2 are adhered to resilient substances 3 and 4 between which a sheet 9 is nipped, an AC field is applied to vibrate the resilient substances 3 and 4, and the sheet 9 is conveyed in a given direction. Amplitude of an applying frequency voltage is inputted as a command value decided by a controller CNT. In the command value, amplitude is reduced to a low value or zero before the speed of the sheet is increased to a maximum after the amplitude is increased, and the aboves are repeated. Thereby, the sheet is fed in a stepping manner, a speed right before a stop is reduced, an excessive amount of the sheet due to inertia is reduced, and positioning precision can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sheet feeding device installed in a computer, a copying machine, a facsimile machine, a word processor, a typewriter, and other various machines equipped with a mechanism for feeding sheets. This invention relates to a sheet feeding device that uses progressive vibration waves.

[Prior Art] As disclosed in Japanese Patent Laid-Open No. 59-177243, a conventional device of this type is configured to feed the sheet by forming a traveling wave in an elastic body that clamps the sheet. was.

Here, we will discuss the third principle of sheet conveyance in the above proposal.
This will be explained using figures.

The sheet 12 is held between the elastic bodies 10 and 11 with moderate pressure. Progressive bending vibrations (travelling waves) are formed in each of the elastic bodies 10 and 11, and the phase difference between these traveling waves is Since the bending vibration of each of the elastic bodies 10 and 11 is configured such that the convex portion thereof always faces the sheet 12 side. At this time, if we focus on a mass point on the surface of the elastic body 10.11 that has a convex portion, for example, the mass point generally moves in an elliptical locus. Regarding the elastic body 10 in FIG. 3, when the traveling wave moves to the right, the mass point will draw a clockwise elliptical orbit as shown in the figure. Therefore, the movement direction of the mass points of the convex portions of the elastic bodies 10 and 11 is opposite to the direction of vibration, and this acts as a force to transport the sheet 12.

On the other hand, in the concave portion, a sheet transport force is generated in the same direction as the traveling direction, but the pressure is smaller than that in the convex portion, so the frictional force between the sheet 12 and the elastic body 10°11 is small, and the sheet transport force is also small. Therefore, the total sheet conveying force acts in the direction opposite to the direction in which the bending vibrations described above proceed.

[What the invention is trying to solve ii! Question 1] By the way,
Such a sheet feeding device can realize highly accurate sheet feeding without transmission loss due to gears, etc., compared to a sheet feeding method that transmits the driving force from a motor to a paper feeding roller via a transmission mechanism such as a gear. However, there is a risk that sheet feeding accuracy may deteriorate due to changes in the environmental atmosphere such as temperature and humidity, or uneven sheet thickness. may invite

Furthermore, it is important to stop the sheet at a predetermined position without deviation from the viewpoint of maintaining sheet feeding accuracy, and if the generation of traveling waves formed in the elastic body 10 and 11 is stopped, the sheet transport force disappears. However, although the sheet can be stopped by the frictional force of the elastic bodies to and tt, if the sheet transport speed is high, there is a risk that the sheet will stop after exceeding a predetermined feed amount due to the inertial force of the sheet.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a sheet feeding device that can stop sheets with high precision.

[Means for Solving the Problems] A configuration for realizing the present invention is such that a sheet is sandwiched between a pair of vibrating elastic bodies, and an alternating current from a drive control means is transmitted to an electric-mechanical energy conversion element provided on these elastic bodies. In a sheet feeding device that excites progressive vibration waves in each of the elastic bodies by applying an electric field and applies a transporting force to the sheet by frictional force,
The drive control means drives and controls each of the electro-mechanical energy conversion elements so as to drive the sheet alternately at a first drive speed and a second drive speed lower than the first drive speed. It is characterized by

[Function] The sheet feeding device configured as described above applies a driving force to the sheet, and while the moving speed of the sheet increases at the first driving speed, it switches to the second driving speed, for example, speed zero, and steps the sheet. By feeding, when positioning the sheet, the speed immediately before stopping can be reduced, the braking distance can be shortened, and the positioning accuracy can be improved.

[Embodiment] FIG. 1 is a schematic diagram showing an embodiment of a sheet feeding device according to the present invention.

1 and 2 are piezoelectric elements respectively adhered to a running track type elastic body 3.4 formed in an oval shape, and when an AC electric field is applied by a power supply circuit 5, the elastic body
．． 4, a vibration as shown in FIG. 3 is created. Elastic body 3.
4 is pressurized by a pressurizing means (not shown), and conveys the sheet 9, which is an object to be conveyed, in a predetermined direction by frictional force.

Reference numeral 6 denotes a rotary encoder for detecting the amount of conveyance of the sheet 9. A roller rough attached to the rotary shaft of the rotary encoder 6 comes into contact with the sheet 9, and outputs the amount of sheet conveyance as a pulse signal to the controller CNT. 8 is a backup roller that prevents slippage between the roller rough and the sheet 9.

The power supply circuit 5 includes an oscillator (not shown), and the amplitude of the applied frequency voltage is input as an amplitude command value determined by the controller CNT.

The amplitude command value determined by the controller CNT is such that the amplitude is increased, and then the amplitude is decreased to stop the sheet before the sheet speed reaches its maximum speed, and this process is repeated.

FIG. 2 is a waveform diagram showing the relationship between the command value commanded by the controller CNT and the applied voltage applied from the power supply circuit 5 to the piezoelectric element. In this example, the magnitude of the amplitude is indicated by A in the figure.
, B, and state B has zero amplitude,
The sheet is fed by a minute amount each time the state B is performed.

The conveyance amount of the sheet is detected by a rotary encoder 6 serving as a conveyance amount detection means, and when the sheet has been conveyed by a predetermined amount, the vibration is stopped by the controller CNT to stop the sheet at a predetermined position.

That is, the controller CNT counts the number of pulses from the rotary encoder 6, and when a predetermined amount has been counted, the amplitude command is set to zero, the vibration of the elastic body is stopped, and the sheet is stopped.

At this time, in the sheet feeding operation, the elastic body 3.4 that clamps the sheet applies a driving force to the sheet in state A, and the driving force becomes approximately zero before the sheet feeding speed reaches the maximum speed. By switching to B and repeating this, the sheet is fed in steps and the speed immediately before stopping is reduced, thereby reducing the amount of overshoot due to inertia of the sheet, and as a result, positioning accuracy can be improved.

In the above-mentioned embodiment, in order to change the driving force for conveying the sheet, the controller CNT changes the amplitude of the applied voltage, thereby conveying and stopping the sheet. The magnitude of the driving force for conveying the sheet may be changed by changing the phase difference between the two-phase frequency voltages applied to the two-phase frequency voltage or the frequency.

[Effects of the Invention] As explained above, according to the present invention, the driving force applied to the sheet is repeatedly turned on and off so that the speed of the sheet does not become high, and the sheet is fed in minute steps. In this case, braking distance is shortened and accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a sheet feeding device according to the present invention, FIG. 2 is a waveform of each part of the circuit, and FIG. 3 is a diagram explaining the principle of sheet conveyance. 1.2... Piezoelectric element 3.4, 10.11... Elastic body 5... Power supply circuit 6... Rotary encoder duff, 8... Roller 9.12... Sheet and 4 others

Claims (1)

[Claims] 1. A sheet is sandwiched between a pair of vibrating elastic bodies, and by applying an alternating current electric field from a drive control means to an electro-mechanical energy conversion element provided on these elastic bodies, a progressive vibration wave is generated by each elastic body. In a sheet feeding device that applies a transporting force to the sheet by frictional force, the drive control means alternately operates at a first drive speed and a second drive speed lower than the first drive speed. A sheet feeding device characterized in that each of the electro-mechanical energy conversion elements is drive-controlled to drive the sheet. 2. The sheet feeding device according to claim 1, wherein the drive control means shifts the first drive speed to the second drive speed before the sheet conveyance speed reaches a maximum speed. 3. The sheet feeding device according to claim 1 or 2, wherein the second driving speed is zero. 4. The sheet feeding device according to claim 1, wherein the drive control means switches between the first drive speed and the second drive speed by changing the amplitude of the voltage. 5. In claim 1, 2 or 3, the drive control means switches between the first drive speed and the second drive speed.
A sheet feeding device characterized in that the feeding is performed by a phase difference between two-phase frequency voltages applied to a mechanical energy conversion element. 6. The sheet feeding device according to claim 1, wherein the drive control means switches between the first drive speed and the second drive speed by changing the frequency of the frequency voltage.