JP2000356532A - Encoder device, sheet-transferring device, and printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and high-resolution encoder device. SOLUTION: An encoder device 16 is provided with a photointerrupter 48 where a light-emitting part 46 and a light reception part 47 are arranged at a specific distance, and a slit plate 49 that is installed so that it can be rotated in one piece with a drive roller, at the same time orthogonally crosses the light axis between the light-emitting part 46 and the light reception part 47 and is provided with a number of slits 50. In this case, the light reception part 47 is provided with a single phototransistor 53, a light-shielding member 51 for applying light being emitted from the light-emitting part 46 only to two adjacent slits of a slit plate is arranged between the light-emitting part 46 and the light reception part 47, and distance L between the slit plate and the light reception part 47 is set so that an interval Z between the adjacent bright and dark lines of interference fringes that are formed on a light reception part while light through the two adjacent slits of the slit plate interferes one another is set to at least one side N of the phototransistor for composing the light reception part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder device for detecting the rotation angle of a rotating body, a sheet conveyance device for conveying a sheet by detecting a rotation angle of a driving roller by the encoder device, and a sheet conveyance device provided with the encoder device. For printing and recording an image (including characters) on a sheet conveyed by the printer.

[0002]

2. Description of the Related Art In a printer as a printing apparatus connected to a personal computer, a carriage having a recording head scans in a main scanning direction (for example, in the width direction of a sheet), and a sheet conveying apparatus scans the sheet in a sub-scanning direction. (For example, in the longitudinal direction of the sheet), and ejecting ink particles from the many nozzles of the recording head onto the sheet,
Ink jet printers that print and record images on this sheet have become widespread.

[0003] In such a sheet conveying apparatus of a printer, there is a sheet conveying apparatus in which an encoder device is installed on a driving roller for nipping and conveying a sheet with a driven roller. The encoder detects the rotation angle of the drive roller, and the controller of the printer controls the rotation amount and the rotation speed of the drive roller based on an input signal from the encoder. Thus, the sheet conveying device can convey the sheet with high accuracy.

The encoder device includes a photointerrupter in which a light emitting unit and a light receiving unit are arranged at a predetermined distance from each other, and a slit plate having a number of slits crossing the optical axis between the light emitting unit and the light receiving unit at right angles. The slit plate is provided so as to rotate integrally with a driving roller of the sheet conveying device. The rotation angle of the driving roller is detected by the light receiving unit receiving the light emitted from the light emitting unit of the photo interrupter and passing through the slit.

[0005] By the way, the resolution of the printer is 180 dp.
If i, the resolution of the encoder device must be able to achieve this resolution. For this reason,
First, when the slit pitch of the slit plate of the encoder device is the same as the outer radius of the driving roller, the optical radius of the slit plate is 24.5 / 180 = 0.14 m corresponding to the resolution of 180 dpi of the printer.
It is set to the value of m. Further, the light receiving section of the photo interrupter is configured as a plurality of light receiving elements (for example, photodiodes) arranged in an array, so that a clear output signal can be generated from the light receiving section, thereby forming a high-sensitivity photo interrupter. are doing.

In this way, by securing the resolution of the encoder device, the sheet transport device can transport the sheet with high precision.
pi) can be realized.

[0007] Recently, a 720 dpi printer is used.
Some have realized high resolution. The encoder device mounted on such a printer has a light receiving section composed of a plurality of light receiving elements (for example, photodiodes) arranged in an array row, and designes a photo interrupter with high sensitivity and reduces a slit pitch in a slit plate. And a printer specification (0.14 mm) with a resolution of 180 dpi. Further, the encoder control unit executes software frequency division processing on an output signal from the light receiving unit of the photo interrupter to configure the encoder device with high resolution. are doing.

With this high-resolution encoder device,
The sheet conveying device can convey the sheet with high accuracy, and a high resolution of 720 dpi of the printer is realized.

[0009]

However, although both encoder devices as described above can realize an appropriate resolution or a high resolution, the photointerrupter of the photointerrupter is constituted by arranging a plurality of light receiving elements in an array. It is expensive.

Further, a sheet transporting apparatus provided with an expensive and high-resolution encoder device can transport a sheet with high accuracy, but is expensive.

Further, a printer equipped with a sheet conveying device provided with an expensive and high-resolution encoder device can convey a sheet with high accuracy and can realize a high resolution, but is still expensive.

In view of the above circumstances, an object of the invention described in claim 1 is to provide an inexpensive and high-resolution encoder device, and an object of the invention described in claim 3 is:
To provide an inexpensive and highly accurate sheet conveying device,
Still another object of the present invention is to provide an inexpensive and high-resolution printing apparatus.

[0013]

According to a first aspect of the present invention, there is provided a photo-interrupter in which a light-emitting unit and a light-receiving unit are arranged at a predetermined distance from each other, and the photo-interrupter can be installed integrally with a rotating body. A slit plate provided with a plurality of slits, crossing an optical axis between the light receiving portion and the light receiving portion substantially orthogonally, and the light receiving portion receives light emitted from the light emitting portion and passing through the slits With this, in the encoder device that detects the rotation amount of the rotating body, the light receiving unit is configured to include a single light receiving element, and between the light emitting unit and the light receiving unit, the light emitted from the light emitting unit is emitted. A light-shielding member is arranged to be able to irradiate only the two adjacent slits of the slit plate with each other, and furthermore, the distance between the slit plate and the light receiving unit is two adjacent slits of the slit plate. The interval between the light and dark lines adjacent to each other of the interference fringes formed by the light passing through the lit and forming an image on the light receiving unit is set to be equal to or larger than the size of the light receiving element constituting the light receiving unit. It is characterized by having.

According to a second aspect of the present invention, in the first aspect of the invention, the light shielding member has a cylindrical body fixed to a hole of the light shielding plate, and an inner diameter of the cylindrical body corresponds to a light emitting portion of the photo interrupter. The size of the slit plate is set so that the light irradiated from the slit plate can be irradiated only to the two adjacent slits of the slit plate.

According to a third aspect of the present invention, the sheet can be nipped by a driving roller and a driven roller, the sheet can be conveyed by driving the driving roller, and an encoder device is provided. A photo-interrupter in which a light-emitting unit and a light-receiving unit are arranged at a predetermined distance, and are installed integrally with the driving roller so as to rotate,
Crossing the optical axis between the light emitting unit and the light receiving unit substantially orthogonally,
And a slit plate having a number of slits, wherein the light receiving unit receives light emitted from the light emitting unit and passing through the slit, thereby detecting a rotation amount of the drive roller. In the transport device, the light receiving unit in the encoder device includes a single light receiving element, and between the light emitting unit and the light receiving unit, the light emitted from the light emitting unit passes through the slit plate. A light-shielding member that can irradiate only the two adjacent slits is disposed, and furthermore, the distance between the slit plate and the light receiving unit is such that light passing through the two adjacent slits of the slit plate interferes with each other. The distance between adjacent bright lines and dark lines of the interference fringes formed on the light receiving unit is set to be equal to or larger than the size of the light receiving element constituting the light receiving unit. It is intended to.

According to a fourth aspect of the present invention, in the third aspect of the invention, the light shielding member of the encoder device has a cylinder fixed to a hole of the light shielding plate, and the inner diameter of the cylinder is a photointerrupter. The light emitted from the light emitting section is set to a size that can be applied only to the two slits adjacent to each other of the slit plate.

According to a fifth aspect of the present invention, there is provided a carriage for scanning a sheet in a predetermined direction, a recording head installed on the carriage for printing and recording an image on the sheet, and a driving roller and a driven roller for driving the sheet. And the sheet can be conveyed in a direction perpendicular to the scanning direction of the carriage by driving the driving roller, and a sheet conveying device provided with an encoder device, the encoder device, A photo-interrupter in which a light-emitting unit and a light-receiving unit are arranged at a predetermined distance from each other, and are installed so as to rotate integrally with the driving roller, and cross the optical axis between the light-emitting unit and the light-receiving unit substantially orthogonally, and Having a slit plate with a slit, the light receiving portion receives light emitted from the light emitting portion and passing through the slit, In the printing apparatus and detects the amount of rotation of the drive roller, the light receiving unit in the encoder device is configured with a single light receiving element,
Between the light emitting unit and the light receiving unit, a light shielding member that can irradiate only two slits adjacent to each other of the slit plate with light emitted from the light emitting unit is arranged,
Further, the distance between the slit plate and the light receiving portion is a distance between adjacent bright lines of interference fringes formed on the light receiving portion by interference of light passing through two slits adjacent to each other of the slit plate. The distance from the dark line is set to be equal to or larger than the size of the light receiving element constituting the light receiving section.

According to a sixth aspect of the present invention, in the invention of the fifth aspect, the light shielding member of the encoder device has a cylinder fixed to a hole of the light shielding plate, and an inner diameter of the cylinder is a photointerrupter. The light emitted from the light emitting section is set to a size that can be applied only to the two slits adjacent to each other of the slit plate.

The invention according to claim 1 or 2 has the following operation.

The light receiving section is provided with a single light receiving element, and between the light emitting section and the light receiving section, light emitted from the light emitting section is applied only to two adjacent slits of the slit plate. A shielding member is provided, and the distance between the slit plate and the light receiving unit is further different from each other by interference fringes formed by light passing through two slits adjacent to each other of the slit plate and forming an image on the light receiving unit. The distance between the bright line and the dark line is set to be equal to or larger than the size of the light receiving element that constitutes the light receiving section, so that a single light receiving element in the light receiving section receives only one bright line of the interference fringes. it can. For this reason, even if the slit pitch of the slit plate is set minutely corresponding to the high resolution of the encoder device, the light receiving section of the photo interrupter can generate a clear output signal using a single light receiving element, An inexpensive and high-resolution encoder device can be provided.

The invention according to claim 3 or 4 has the following operation.

The light receiving portion of the photo interrupter in the encoder device is provided with a single light receiving element. Between the light emitting portion and the light receiving portion of the photo interrupter, light emitted from the light emitting portion is adjacent to each other on the slit plate. A light-shielding member that can irradiate only two slits is arranged, and further,
The distance between the slit plate and the light receiving portion is determined by the distance between the adjacent bright and dark lines of the interference fringes formed by interference of light passing through two slits adjacent to each other on the slit plate and forming an image on the light receiving portion. Since the size is set to be equal to or larger than the size of the light receiving element constituting the unit, a single light receiving element in the light receiving unit can receive only one bright line of interference fringes. For this reason, even if the slit pitch of the slit plate is set to a small value corresponding to the high resolution of the encoder device, an inexpensive light receiving unit composed of a single light receiving element in the encoder device generates a clear output signal. it can. As a result, the sheet conveying device can convey the sheet with high accuracy using the inexpensive and high-resolution encoder device, and can be configured at a low cost.

The invention according to claim 5 or 6 has the following operation.

The light receiving portion of the photo interrupter in the encoder device includes a single light receiving element. Between the light emitting portion and the light receiving portion of the photo interrupter, the light emitted from the light emitting portion is adjacent to the slit plate. A light-shielding member that can irradiate only two slits is arranged, and further,
The distance between the slit plate and the light receiving portion is determined by the distance between the adjacent bright and dark lines of the interference fringes formed by interference of light passing through two slits adjacent to each other on the slit plate and forming an image on the light receiving portion. Since the size is set to be equal to or larger than the size of the light receiving element constituting the unit, a single light receiving element in the light receiving unit can receive only one bright line of interference fringes. For this reason, even if the slit pitch of the slit plate is set to a small value corresponding to the high resolution of the encoder device, an inexpensive light receiving unit composed of a single light receiving element in the encoder device generates a clear output signal. it can. As a result, the sheet can be conveyed with high precision by the sheet conveying device including the inexpensive and high-resolution encoder device, so that the printing device can be configured at low cost and with high resolution.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an ink jet printer, which is an embodiment of a printing apparatus according to the present invention, with a part thereof omitted. FIG. 2 is a side sectional view of the ink jet printer of FIG.

A printer 10 as a printing apparatus shown in these figures is an ink jet printer that performs printing by ejecting ink particles from a number of nozzles (not shown) onto a sheet S, and includes a carriage 11, a recording head 12, a sheet feeding apparatus, and the like. 13, sheet conveying device 14, sheet discharging device 15
And the sheet conveying device 14 includes an encoder device 16. Further, the printer 10 includes a main frame 17, a first sub-frame 18, a second sub-frame 19, a pair of left side frames 20, and a right side frame (not shown) for mounting the above-described device and the like.

Here, the sheet S is made of plain paper, coated paper, O
For example, a single sheet such as an HP (overhead projector) sheet, glossy paper, glossy film, or the like.

As shown in FIG. 2, the sheet supply device 13 sandwiches the sheet S between a supply roller 21, a hopper 22 for urging the sheet S toward the supply roller 21, and the supply roller 21. And a separation pad 23 for separating the sheet S by pressing. A plurality of sheets S are set in the hopper 22. When the sheets S are supplied, the sheets S are pressed by the hopper 22 toward the supply roller 21 which rotates once, and are separated by the separation pad 23. Only one sheet S is supplied to the sheet conveying device 14.

The sheet S supplied from the sheet supply device 13 to the sheet transport device 14 is fed by a lower guide 24 attached to the first sub-frame 18 and an upper guide 25 attached to the main frame 17. It is guided to the transport device 14.

The sheet conveying device 14 includes a driving roller 2
6 and the driven roller 27 so that the sheet S can be nipped,
The sheet S is moved in the sub-scanning direction B by the driving of the driving roller 26.
(FIG. 1). The sub-scanning direction B is a direction orthogonal to a main scanning direction A of the carriage 11 described later.

The drive roller 26 is connected to the left side frame 20.
, And is rotatably supported by the right side frame, and is rotationally driven by a roller drive system 28.

The roller drive system 28 includes a roller drive motor 31 mounted on the left side frame 20 and a roller drive motor 31 shown in FIG.
, A motor pinion gear 32, an intermediate gear 33, and a drive roller gear 34. Motor pinion gear 3
Numeral 2 is installed on the motor shaft of the roller drive motor 31 so as to rotate integrally therewith. Further, the drive roller gear 34 is
6 is rotatably attached to the drive roller 26 together with a slit plate 49 of the encoder device 16 using a holding plate 35 at one end (one end on the left side frame 20 side). The intermediate gear 33 is connected to the left side frame 20.
And is rotatably supported by the motor pinion gear 32 and the drive roller gear 34. Accordingly, by driving the roller drive motor 31, the drive roller 26 is driven through the motor pinion gear 32, the intermediate gear 33, and the drive roller gear 34.
Is driven to rotate. Here, the roller drive motor 31
A DC motor is employed.

As shown in FIGS. 2 and 3, two driven rollers 27 are rotatably juxtaposed on one upper guide 25, and a plurality of these upper guides 25 are provided in the axial direction of the driving roller 26. Can be Accordingly, a plurality of driven rollers 27 are provided along the axial direction of the drive roller 26 with its shaft 27A aligned with the axial direction of the drive roller 26. As shown in FIG. 2, each upper guide 25 is pivotally supported by the main frame 17 so as to be swingable, and is urged by a torsion spring 30 also supported by the main frame 17, and the driven roller 27 is urged by this urging force. It is pressed against the drive roller 26. Thereby, the driven roller 27 is configured to be able to be driven and rotated with respect to the rotation of the driving roller 26. Therefore, when the sheet S is supplied between the driving roller 26 and the driven roller 27, the sheet S is supplied to the driving roller 26 and the driven roller 2.
7 and conveyed below the recording head 12.

As shown in FIGS. 1 and 2, the carriage 11 is slidably inserted through a carriage guide shaft 36 and slidably engaged with the upper end 17A of the main frame 17. The carriage guide shaft 36 is fixed to and supported by the left side frame 20 and the right side frame, and is disposed in parallel with the drive roller 26. Accordingly, the carriage 11 is provided so as to be movable (scanned) without rotating around the carriage guide shaft 36 in the main scanning direction A that matches the axial direction of the carriage guide shaft 36 and the drive roller 26.

The carriage 11 is scanned by a carriage drive motor 37 via a timing belt 38. That is, the carriage drive motor 37 is fixedly attached to the right side frame side of the main frame 17, and the drive pulley 39 is attached to the motor shaft of the carriage drive motor 37 so as to rotate integrally therewith. A driven pulley 40 is rotatably supported on the frame 20 side. Timing belt 38
Is wound around the driving pulley 39 and the driven pulley 40, and the carriage 11 is coupled to the upper or lower side of the timing belt 38 in FIG. Therefore, by the forward or reverse rotation of the carriage drive motor 37, the carriage 11 is guided by the carriage guide shaft 36 and the upper end 17A of the main frame 17 via the timing belt 38, and is turned rightward or leftward in the main scanning direction A in FIG. Is scanned.

The recording head 12 is provided below the carriage 11 and has a number of nozzles (not shown). The recording head 12 ejects ink particles from these nozzles by the action of an actuator using a piezo element, for example, and prints and records an image (including characters) on the sheet S. Ink is supplied to the recording head 12 from an ink tank 41 mounted on the carriage 11.

The recording operation by the recording head 12 is performed while the carriage 11 scans in the main scanning direction A.
One line of printing is performed by ejecting ink particles from the second nozzle, and each time this one line of printing is performed, the sheet conveying device 14 moves the sheet S by a predetermined amount (normal line spacing).
It is carried out by transporting and repeating these operations.

A sheet guide member 42 is provided below the recording head 12. The sheet guide member 42 has a protrusion 43 protruding toward the recording head 12 at an appropriate position along the carriage guide shaft 36. The protrusion 43 supports the lower surface of the sheet S and performs recording. Head 12
And the interval between the sheet S. Even if the ink adheres to the upper surface of the sheet S and a waving phenomenon occurs on the sheet S, the waving occurs between the protrusion 43 and the upper surface of the sheet guide member 42 so that the sheet S can be appropriately conveyed. This is for storing the sheet S.

The sheet discharge device 15 includes a discharge drive roller 44 and a driven star wheel 45, and the discharge drive roller 44 is positioned below the second sub-frame 19. The driven star wheels 45 are rotatably supported by the second sub-frame 19 and are provided in a plurality along the axial direction of the discharge drive roller 44. The discharge drive roller 44 and the driven star wheel 45 discharge the sheet S out of the printer 10 when the printed sheet S is carried in between them.

The encoder device 16 provided in the sheet conveying device 14 detects the rotation angle of the driving roller 26, and a signal from the encoder device 16 causes a control device (not shown) of the sheet conveying device 14 to operate. By controlling the rotation amount and the rotation speed of the drive roller 26, the sheet S can be transported with high accuracy.

The encoder device 16 is shown in FIGS.
As shown in FIG. 5, a photo-interrupter 48 in which the light-emitting unit 46 and the light-receiving unit 47 are arranged at a predetermined distance from each other, crosses an optical axis (not shown) of the light-emitting unit 46 and the light-receiving unit 47 orthogonally or substantially orthogonally, and Slit plate 4 with slit 50
9 and a light blocking member 51 disposed between the light emitting portion 46 of the photo interrupter 48 and the slit plate 49.

As described above, the slit plate 49 is attached to the driving roller 26 together with the driving roller gear 34 so as to rotate integrally therewith. Further, a large number of slits 50 are formed inside the outer peripheral edge of the slit plate 49 along the outer peripheral edge, and allow light emitted from the light emitting section 46 to pass therethrough as described later. These slits 50 are formed by etching or printed by electrophotographic printing.

The printer 10 is designed to have a high resolution, for example, 720 dpi. In order to realize this resolution, the sheet transport device 14 is configured to transport the sheet S with high accuracy. In order to ensure high-precision transport, the encoder device 16 is configured with high resolution. Then, the slit pitch W of the slit 50 in the slit plate 49 of the encoder device 16
Is set as follows according to the resolution of the encoder device 16 or the resolution of the printer 10 on which this resolution is based.

That is, the resolution of the printer 10 is K,
Assuming that the optical radius of the slit 50 in the slit plate 49 is R _A , and the outer radius of the driving roller 26 in the sheet conveying device 14 is R _B , the slit pitch W of the slit 50 is W = (2πR _A / K) / (2πR _B per 25.4) = a _{25.4 × R a / KR B (} mm). Here, K = _720, when the _R A = R _B, slit pitch W is set to W = 25.4 / 720 = 0.035 ( mm) ··· (1), an encoder device 16 is a high resolution It is composed of

As shown in FIG. 3, the photo interrupter 48 includes a substrate 55 fixed to the left side frame 20.
Attached to. The light emitting section 46 of the photo interrupter 48 includes a light emitting element, for example, a light emitting diode 52 (LED) that emits visible red light. As shown in FIG. 6, the light emitting diode 52 emits light when the power supply voltage _VCC is applied via the resistor R1.

The light receiving section 47 of the photo interrupter 48
Has one light receiving element (phototransistor 53 in this embodiment) such as a photodiode or a phototransistor, and further includes resistors R2 and R3 and a comparator 54.
It is comprised including. The power supply voltage _VCC is applied to the phototransistor 53 via the resistor R2. The voltage at the point X between the phototransistor 53 and the resistor R2 is applied as a voltage signal E to the negative terminal of the comparator 54, and the voltage acting on the resistor R3 is applied to the positive terminal of the comparator 54.

Therefore, when the phototransistor 53 does not receive the light radiated from the light emitting unit 46, no current flows through the phototransistor 53, so that the potential at the point X is high. output voltage V _O from is negative constant voltage, and outputs the voltage signal. When the phototransistor 53 receives the light emitted from the light emitting unit 46, the light receiving unit 47
Since a current flows through the phototransistor 53 and the potential at the point X becomes almost zero, the output voltage V _O
Becomes a positive constant voltage, and outputs this voltage signal. The positive voltage signal output from the light receiving section 47 is a pulse signal, and the rotation angle of the drive roller 26 is detected by counting the pulse signals.

The light shielding member 51 is, as shown in FIG.
The light shielding plate 5 includes a light shielding plate 56 and a cylindrical body 57.
A small diameter round hole 58 is formed in 6. The cylindrical body 57 is fixed around the round hole 58 in the light shielding plate 56, and preferably, the axis thereof is provided so as to coincide with the center of the round hole 58. Except for the round hole 58, the light-shielding plate 56 blocks light emitted from the light-emitting unit 46 from traveling toward the slit plate 49. Further, the cylindrical body 57 is radiated from the light emitting portion 46 and
The inner diameter is such that the light passing through the six round holes 58 can be applied only to two slits 50 adjacent to each other in the slit plate 49.

Therefore, the light emitted from the light emitting portion 46 of the photo interrupter 48 is irradiated only on two slits 50 adjacent to each other in the slit plate 49 by the action of the light shielding member 51, and the light passing through these slits 50 is emitted. 5 diffracts as shown in FIG. 5 and travels to the light receiving section 47 side, interferes with each other, and forms bright and dark interference fringes on the phototransistor 53 of the light receiving section 47. The pitch Y between the bright lines of the interference fringes is determined by the distance between the slit plate 49 and the photointerrupter 4.
8 varies with the distance to the light receiving unit 47.

That is, in FIG. 5, a point on the image plane 59 of the light receiving section 47 which is equidistant from two slits 50A and 50B adjacent to each other of the slit plate 49 is O, and an arbitrary point on the image plane 59 Let P be the point. The wavelength of the light emitted from the light emitting unit 46 is λ, and the optical path lengths of the light reaching the point P from the slits 50A and 50B are r ₁ and r ₂ , respectively. Since the interval between the slits 50A and 50B is the slit pitch W, and there are bright lines adjacent to each other at the points O and P, the condition of the bright lines of the interference fringes in the Young's experiment is as follows: _2- r ₁ = WY / L = mλ = λ (∵m = 1) (2) Therefore, the formula (2) is transformed into Y = Lλ / W (3), and it can be seen that the pitch Y between the bright lines of the interference fringes varies depending on the distance L between the slit plate 49 and the light receiving section 47.

In the present embodiment, the interval Z (Z) between the adjacent bright and dark lines of the interference fringes generated as described above
= Y / 2) is set to be equal to or longer than the length N of one side of the phototransistor 53 of the light receiving section 47, and the distance L between the slit plate 49 and the light receiving section 47 is set. That is, the distance L between the slit plate 49 and the light receiving unit 47 that satisfies the following condition: Z = Y / 2> N (4) is obtained from the equations (3) and (4). L> 2WN / λ (5) Becomes For example, the slit 50 in the slit plate 49
Of the slit pitch W obtained by the equation (1) (the twelfth
Page) and the phototransistor 53 in the light receiving section 47.
The length N of one side is N = 0.5 mm, and the wavelength of light emitted by the light emitting diode 52 of the light emitting unit 46 is λ = 8.1 × 1
^Assuming 0 ⁻⁴ mm, L> 2 × 0.035 × 0.5 / 8.1 × 10 ⁻⁴ = 4
It becomes 3.5 (mm).

Conversely, if L = 50 mm, then from equation (3), Z = Y / 2 = 50 × 8.1 × 10 ⁻⁴ /0.035×2
= 0.57 (mm). Accordingly, at this time, the interval Z between the bright line and the dark line adjacent to each other of the interference fringes satisfies the expression (4) because the length N of one side of the phototransistor 53 is N = 0.5 mm, and Is longer than the length N.

As described above, the interval Z between the adjacent bright line and dark line of the interference fringe formed on the phototransistor 53 of the light receiving section 47 is equal to or greater than the length N of one side of the phototransistor 53 of the light receiving section 47. , The single phototransistor 53 in the light receiving section 47
Can receive only one bright line of the interference fringes. Thereby, the light receiving section 47 of the photo interrupter 48
Can generate a clear output signal from the comparator 54, so that the encoder device 16 can detect the rotation angle of the drive roller 26 of the sheet conveying device 14 with high accuracy.

Therefore, according to the above embodiment, the following effects are obtained.

The light receiving section 47 of the photo interrupter 48 of the encoder device 16 is provided with a single light receiving element (phototransistor 53), and the light emitted from the light emitting section 46 is provided between the light emitting section 46 and the light receiving section 47. A light-blocking member 51 is provided to allow only the two slits 50 adjacent to each other of the slit plate 49 to be irradiated with the reflected light. Further, the distance L between the slit plate 49 and the light receiving portion 47 of the photo interrupter 48 is different from each other. The distance Z between the adjacent bright and dark lines of the interference fringes formed by interference of light passing through two adjacent slits 50 to form an image on the light receiving unit 47 is determined by a light receiving element (phototransistor 53) constituting the light receiving unit 47. ) Is set to be equal to or greater than the length N of one side, so that a single light receiving element (phototransistor 5
3) can receive only one bright line of the interference fringes. For this reason, even if the encoder device 16 is configured with a high resolution and the slit pitch W of the slit 50 of the slit plate 49 is set to a minute value, the light receiving section 47 of the photo interrupter 48 is a single light receiving element (phototransistor). 5
Since a clear output signal can be generated using 3), an inexpensive and high-resolution encoder device 16 can be provided.

As described above, since the encoder device 16 is inexpensive and has a high resolution, the sheet conveying device 14
Can transport the sheet S with high accuracy using the encoder device 16 and can be configured at a low cost.

Further, since the sheet S can be transported with high precision by the sheet transporting device 14 having the inexpensive and high-resolution encoder device 16, the printer 10 can be constructed with a high resolution (for example, 720 dpi) and at a low cost. it can.

Although the present invention has been described based on the above embodiment, the present invention is not limited to this.

For example, although the sheet conveying apparatus 14 of the above embodiment has been described as applied to the printer 10, it is applied to another apparatus (copier, facsimile, etc.) which needs to convey the sheet S. Is also good. Further, the encoder device 16 is not limited to the sheet conveying device 14 of the printer 10, but includes a drive system (a carriage drive motor 37, a timing belt 38,
It may be applied to the driving pulley 39 and the driven pulley 40).

[0061]

As described above, according to the encoder device of the first aspect, the light receiving section of the photo interrupter is provided with a single light receiving element, and the light receiving section is provided between the light emitting section and the light receiving section. A light-shielding member that allows light emitted from the light emitting unit to be irradiated only to two slits adjacent to each other of the slit plate, and further, a distance between the slit plate and the light receiving unit is adjacent to each other of the slit plate. The interval between the adjacent bright and dark lines of the interference fringes formed on the light receiving unit by interference of light passing through the two slits is set to be equal to or larger than the size of the light receiving element constituting the light receiving unit. Therefore, an inexpensive and high-resolution encoder device can be provided.

According to the third aspect of the present invention, the light receiving portion of the photo interrupter in the encoder device for detecting the rotation angle of the driving roller is provided with a single light receiving element, and the light emitting portion and the light receiving portion are provided. A light-shielding member is provided between the slit plate and the light-emitting unit so that light emitted from the light-emitting unit can be applied only to two slits adjacent to each other on the slit plate. The distance between the adjacent bright and dark lines of the interference fringes formed on the light receiving unit by interference of light passing through two mutually adjacent slits is set to be equal to or larger than the size of the light receiving element constituting the light receiving unit. , It is possible to provide an inexpensive and highly accurate sheet conveying device.

Further, according to the printing apparatus of the present invention, the light receiving portion of the photo interrupter in the encoder device for detecting the rotation angle of the drive roller in the sheet conveying device has a single light receiving element. A light-shielding member is provided between the light-emitting portion and the light-receiving portion so that light emitted from the light-emitting portion can be applied only to two slits adjacent to each other on the slit plate. Is the distance between the adjacent bright and dark lines of the interference fringes formed by interference of light passing through the two slits adjacent to each other on the slit plate and forming an image on the light receiving unit. Since the size is set to be equal to or larger than the size, it is possible to provide an inexpensive and high-resolution printing apparatus.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ink jet printer, which is an embodiment of a printing apparatus according to the present invention, with a part thereof omitted.

FIG. 2 is a side sectional view showing the inkjet printer of FIG.

FIG. 3 is a perspective view of the inkjet printer of FIG. 1 as viewed obliquely from the upper left.

FIG. 4 is a perspective view showing the encoder device of FIG. 3;

FIG. 5 is a schematic view showing the principle of the encoder device of FIG. 4;

FIG. 6 is a circuit diagram illustrating an electric circuit of the photointerrupter of FIG. 4;

[Explanation of symbols]

Reference Signs List 10 printer (printing device) 11 carriage 12 recording head 14 sheet transport device 16 encoder device 26 driving roller 27 driven roller 46 light emitting unit 47 light receiving unit 48 photo interrupter 49 slit plate 50 slit 51 light shielding member 53 phototransistor (light receiving element) 56 light shielding Plate 57 Cylindrical body (cylindrical body) 58 Round hole A Main scanning direction B Sub-scanning direction L Distance between slit plate and light receiving unit N Length (size) of one side of phototransistor (light receiving element) S Sheet Z Interference fringe Spacing between adjacent bright and dark lines

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C480 CA02 CA44 CB32 CB34 2F103 BA37 CA02 CA08 DA01 DA13 EA02 EA12 EB00 EB33 ED04 ED07 FA02 3F048 AA05 AB01 BA26 BB02 BB10 CA03 CC13 DA06 DB13 DC06

Claims (6)

[Claims] 1. A photo-interrupter in which a light-emitting unit and a light-receiving unit are arranged at a predetermined distance from each other, and a photo-interrupter that can be installed integrally with a rotating body. And a slit plate having a plurality of slits, and the light receiving unit receives light emitted from the light emitting unit and passing through the slit, thereby detecting a rotation amount of the rotating body. In the device, the light receiving unit is configured to include a single light receiving element, and between the light emitting unit and the light receiving unit, the light emitted from the light emitting unit is adjacent to each other on the slit plate. A light-shielding member that can irradiate only the slit is disposed. Further, the distance between the slit plate and the light receiving unit is such that light passing through two slits adjacent to each other of the slit plate interferes with each other, and An encoder device wherein an interval between a bright line and a dark line adjacent to each other of interference fringes formed on a portion is set to be equal to or larger than a size of a light receiving element constituting the light receiving portion. 2. The light-shielding member, wherein a cylindrical body is fixed to a hole of the light-shielding plate, and the inner diameter of the cylindrical body is such that light emitted from a light-emitting portion of a photo-interrupter is provided between two adjacent slits of a slit plate. 2. The encoder device according to claim 1, wherein the size is set to a size capable of irradiating only an image. 3. A driving roller and a driven roller are capable of nipping a sheet, the driving roller is driven to convey the sheet, and the encoder device has an encoder device. A photo-interrupter arranged at a distance, and a rotary plate integrally mounted on the drive roller, crossing the optical axis between the light-emitting portion and the light-receiving portion substantially orthogonally, and a slit plate having a number of slits. Wherein the light receiving unit receives light emitted from the light emitting unit and passing through the slit, thereby detecting a rotation amount of the driving roller. The unit is configured to include a single light receiving element, and between the light emitting unit and the light receiving unit, the light emitted from the light emitting unit is slit. A light-shielding member is provided which can irradiate only the two slits adjacent to each other on the plate. Further, the distance between the slit plate and the light receiving unit is the light passing through the two slits adjacent to each other on the slit plate. The distance between adjacent bright lines and dark lines of interference fringes that form an image on the light receiving unit due to interference is set to be equal to or larger than the size of a light receiving element constituting the light receiving unit. Sheet conveying device. 4. A light shielding member in the encoder device, wherein a cylindrical body is fixed to a hole of the light shielding plate, and an inner diameter of the cylindrical body is adapted to transmit light emitted from a light emitting portion of the photo-interrupter to two adjacent slit plates. 4. The sheet conveying apparatus according to claim 3, wherein the dimensions are set such that only the one slit can be irradiated. 5. A carriage that scans a sheet in a predetermined direction, a recording head that is installed on the carriage and prints and records an image on the sheet, and a driving roller and a driven roller that can sandwich the sheet, A sheet conveying device having an encoder device, wherein the sheet can be conveyed in a direction orthogonal to the scanning direction of the carriage by driving a roller, and the light emitting portion and the light receiving portion have predetermined positions. A photo-interrupter arranged at a distance, and a rotary plate integrally mounted on the drive roller, crossing the optical axis between the light-emitting portion and the light-receiving portion substantially orthogonally, and a slit plate having a number of slits. The light receiving unit receives light emitted from the light emitting unit and passing through the slit, thereby rotating the driving roller. In a printing apparatus for detecting an amount, the light receiving unit in the encoder device includes a single light receiving element, and between the light emitting unit and the light receiving unit, light emitted from the light emitting unit is provided. A light-shielding member is provided which can irradiate light only to the two slits adjacent to each other on the slit plate. Further, a distance between the slit plate and the light receiving unit is two slits adjacent to each other on the slit plate. The distance between the adjacent bright and dark lines of the interference fringes formed on the light receiving portion by interference of the light passing therethrough is set to be equal to or larger than the size of the light receiving element constituting the light receiving portion. A printing device characterized by the above-mentioned. 6. A light shielding member of the encoder device, wherein a cylindrical body is fixed to a hole of the light shielding plate, and an inner diameter of the cylindrical body is adapted to transmit light emitted from a light emitting portion of the photointerrupter to two adjacent slit plates. The printing apparatus according to claim 5, wherein the printing apparatus is set to a size capable of irradiating only one of the slits.