JP2009046294A - Recording device and sensor arrangement structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect a recording medium even when a frequency of maintenance is reduced with a constitution which is rarely influenced by dusts, in a recording device for detecting the recording medium using an optical sensor. <P>SOLUTION: A printer 10 for delivering a sheet and recording an image comprises a front paper guide 46 constituting a conveyance path W of sheets, and a paper end sensor 44 positioned on a side opposite to the front paper guide 46 across the conveyance path W and detecting the sheets in the conveyance path W. A hole 46b is formed on the front paper guide 46, and the paper end sensor 44 detects the sheets on the conveyance path W by radiating lights toward a roller shaft 23a arranged on a rear side of the front paper guide 46 through the hole 46b, and detecting reflection lights of the lights. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording apparatus including an optical sensor that detects a recording medium in a conveyance path of the recording medium, and a sensor arrangement structure.

Generally, in a recording apparatus such as a printer, the width, leading edge, and trailing edge of a recording medium are detected using an optical sensor that emits light toward a conveyance path of the recording medium (recording paper). As this optical sensor, a reflection type optical sensor that detects a recording medium based on the amount of reflected light of irradiated light may be used. In a recording apparatus using a reflective optical sensor, a reflective plate is provided so that accurate detection is possible even when the reflected light from the recording medium is small, such as when black paper is used as the recording medium. The recording medium is detected based on whether or not the reflected light from the reflecting plate is blocked by the recording medium (see, for example, Patent Document 1).
JP 2000-289888 A

By the way, various dusts such as dust adhering to the recording medium and paper dust from which a part of the recording medium is dropped adhere to the conveyance path of the recording medium. In rare cases, a large amount of these dusts may adhere to the conveyance path, which may hinder normal recording operation of the recording apparatus. For example, in the case of using the above-mentioned reflection type optical sensor, if dust such as paper dust accumulates on the reflection plate and the amount of reflected light from the reflection plate is reduced, the possibility of being affected by detection accuracy cannot be denied. Further, the light reflected by the paper dust attached to the reflecting plate may be close to the reflected light reflected by the recording medium, and in this case, it is erroneously detected as if the recording medium exists. For this reason, under conditions where a large amount of paper dust or the like is generated, it is necessary to frequently perform maintenance for removing dust in order to prevent erroneous detection.
Accordingly, the present invention provides a recording apparatus that detects a recording medium using an optical sensor and is configured to be resistant to the influence of dust, so that accurate detection can be performed even if the frequency of maintenance is reduced. Objective.

In order to solve the above-described problems, the present invention provides a recording apparatus that conveys a recording medium to record an image, and sandwiches a guide plate that constitutes a conveyance path through which the recording medium is conveyed, and the conveyance path of the recording medium. An optical sensor that is located on the opposite side of the guide plate and detects the recording medium in the conveyance path, and the guide plate has a through hole formed therein, and the optical sensor has a through hole in the guide plate. A recording apparatus, wherein the recording medium in the transport path is detected by irradiating light toward a reflecting member disposed on the back side of the guide plate through the light, and detecting the reflected light of the light. provide.
According to this configuration, the reflection member that the optical sensor emits light is disposed on the back side of the guide plate that forms the conveyance path through which the recording medium is conveyed, and dust is extremely difficult to accumulate. In addition, it is unlikely that a large amount of dust accumulates in the through hole located between the optical sensor and the reflecting member. Therefore, since the reflected light from the reflecting member when the optical sensor irradiates the reflecting member is not damaged by the influence of dust, the recording medium is detected based on the reflected light from the reflecting member. Therefore, the presence / absence of the recording medium can always be accurately detected. Thus, the presence or absence of the recording medium can be accurately detected without frequent maintenance.

In the above configuration, the reflection member may be a shaft of a conveyance roller that conveys the recording medium.
In this case, by using the shaft of the transport roller as a recording medium, it is not necessary to separately provide a reflecting member, and if the configuration is such that the shaft of the transport roller is located on the back side of the guide plate, it can be easily realized at low cost. . Further, the shaft of the transport roller generally has a highly reflective surface, and the shaft of such a transport roller works well as a reflecting member, and a sufficient amount of reflected light is applied to the optical sensor. Is incident, the presence or absence of the recording medium can be accurately detected. Further, since the shaft of the transport roller rotates every time the recording medium is transported, dust is extremely difficult to accumulate. Therefore, there is a special advantage that it is very difficult to be affected by dust without frequent maintenance.

In the above configuration, a foreign matter removing unit may be provided for removing foreign matter attached to a position where the light of the optical sensor is reflected on the shaft of the transport roller.
In this case, since the dust adhering to the shaft of the transport roller is removed by the foreign matter removing unit, a sufficient amount of reflected light is incident on the optical sensor from the shaft of the transport roller without any particular maintenance. As a result, it is possible to realize a recording apparatus that can accurately detect a recording medium even when the frequency of maintenance is extremely low.

The said structure WHEREIN: The through-hole of the said guide plate is good also as what was provided in the position into which the said recording medium approachs in the edge part of the said conveyance path.
In this case, it is possible to accurately detect the leading end of the recording medium entering the end of the transport path and the end of the recording medium ejected from the transport path.

In this configuration, the guide plate may have an inclined surface that is inclined in a direction in which the conveyance path is enlarged at the tip of the conveyance path, and the through hole of the guide plate may be provided in the inclined surface.
In this case, since there is no risk of the recording medium coming into contact with the through-hole formed in the conveyance path, the recording medium does not enter the through-hole without performing a work such as making the through-hole into a recess, and the recording medium can be conveyed. I can't interfere. In addition, it is possible to quickly and accurately detect the leading edge of the recording medium that is about to enter the end of the conveyance path.

In order to solve the above problems, the present invention detects a recording medium in the conveyance path of the recording medium in a sensor arrangement structure for arranging an optical sensor in an apparatus for recording an image by conveying the recording medium. An optical sensor is disposed on the opposite side of the guide path of the conveyance path, a through hole is formed in the guide plate, and the optical sensor is disposed on the back side of the guide plate through the through hole of the guide plate. There is provided a sensor arrangement structure characterized in that the recording medium in the transport path is detected by irradiating light toward the reflecting member and detecting the reflected light of the light.
According to this structure, the reflecting member to which the optical sensor emits light is disposed on the back side of the guide plate that constitutes the conveyance path through which the recording medium is conveyed, so that dust hardly accumulates. In addition, it is unlikely that a large amount of dust accumulates in the through hole located between the optical sensor and the reflecting member. Therefore, since the reflected light from the reflecting member when the optical sensor irradiates the reflecting member is not damaged by the influence of dust, the recording medium is detected based on the reflected light from the reflecting member. Therefore, the presence / absence of the recording medium can always be accurately detected. Thus, the presence or absence of the recording medium can be accurately detected without frequent maintenance.

  According to the present invention, even if frequent maintenance is not performed, a sufficient amount of reflected light is always incident on the optical sensor in the absence of a recording medium, so that the optical sensor is always recorded without being affected by dust. The presence or absence of a medium can be detected accurately.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
FIG. 1 is a perspective view showing an external appearance of a printer 10 according to an embodiment to which the present invention is applied. FIG. 2 is a side sectional view of the printer 10. FIG. 3 is a perspective view showing a frame configuration with the ink ribbon cartridge 29 removed, and FIG. 4 is a perspective view showing a state where the ink ribbon cartridge is mounted.

A printer 10 as a recording apparatus includes a recording head 20 that selectively ejects a plurality of recording wires, and a carriage 21 on which the recording head 20 is mounted. The recording wires ejected from the recording head 20 are recorded on a recording medium (hereinafter referred to as a recording medium). This is a serial dot impact printer that records an image including characters by striking the sheet.
The sheets to be recorded by the printer 10 include a cut sheet cut to a predetermined length and a continuous sheet in which a plurality of sheets are connected. The material of the sheet is not limited to paper, and may be a synthetic resin, and the surface may be coated with an inorganic material or an organic material. Examples of the cut sheet include a cut sheet, a copy paper, a passbook, and a cut film, and the continuous sheet includes a continuous sheet.
In FIG. 2, in particular, a conveyance path through which a sheet fed from the sheet guide 14 located on the front side of the printer 10 is conveyed is indicated by a symbol W.

  As shown in FIG. 2, the printer 10 is roughly divided into a printer main body 12, a tractor unit 13 for supplying sheets from the rear (rear side) of the printer main body 12, and a front (front side) of the printer main body 12. And a sheet guide 14 for manually feeding sheets, and is configured to be covered with an exterior made up of an upper case 15 and a lower case 16 as shown in FIG. The printer main body 12 includes a recording mechanism that conveys a sheet and records an image, and a controller (not shown) that controls the recording mechanism.

As shown in FIGS. 3 and 4, the printer main body 12 includes a back frame 27, a platen 22, a platen support portion 22 a that supports the platen 22, a carriage shaft 28, and a tractor unit 13 between a pair of side frames 17 and 18. Etc., and the carriage 21 is provided on the carriage shaft 28.
In addition, the printer main body 12 includes a conveyance unit including a plurality of conveyance rollers that convey the sheet. The transport unit includes a transport roller 23, a driven roller 24 a, a driving roller 25, and a driven roller 26 that are installed on the pair of side frames 17 and 18.

The conveyance roller 23 and the driven roller 24 a are located on the front side of the printer main body 12 with respect to the platen 22. The transport roller 23 is a roller that is inserted through a roller shaft 23 a (a shaft of the transport roller) spanned between the side frames 17 and 18 at a predetermined interval. A plate-shaped front paper guide 46 (guide plate) that supports the sheet from below and forms the lower surface of the conveyance path W is disposed at the front side end of the printer main body 12. The front paper guide 46 has a flat plate portion that constitutes the transport path W, and the front side end portion of the flat plate portion is connected to a downwardly inclined surface 46a (inclined surface), and the front end of the inclined surface 46a extends vertically downward. It continues to the department. The inclined surface 46a is configured to be inclined in the direction in which the conveyance path W is enlarged at the front end of the conveyance path W so that the sheet can easily enter the conveyance path W from the front side.
The roller shaft 23a is disposed below the front paper guide 46 at a position corresponding to the back of the slope 46a. The upper surface of the front paper guide 46 and the inclined surface 46a are provided with a plurality of openings for exposing the plurality of transport rollers 23 inserted through the roller shaft 23a, and a part of the transport rollers 23 is shown through the openings. As shown in FIG. 2, it protrudes and contacts the sheet.

  On the other hand, the driven roller 24a is a roller that is inserted through a roller shaft (not shown) at a constant interval, like the transport roller 23, and faces the transport roller 23 with the transport path W interposed therebetween as shown in FIG. Is disposed above the transport path W at a position where Above the front paper guide 46 described above, a paper discharge frame 47 constituting the upper surface of the transport path W is provided so as to face the front paper guide 46, and this paper discharge frame 47 includes a roller unit that accommodates the driven roller 24a. 24 is attached. The driven roller 24 a is exposed from the lower surface of the roller unit 24, sandwiches a sheet passing through the conveyance path W with the conveyance roller 23, rotates with the conveyance roller 23, and rotates the sheet to the front side and the rear side of the printer main body 12. Transport to.

The drive roller 25 is positioned above the sheet conveyance path on the rear side of the printer main body 12 with respect to the platen 22, and the driven roller 26 is conveyed so as to face the drive roller 25 across the sheet conveyance path. It is arranged below the path. The driving roller 25 and the driven roller 26 are paired to sandwich the sheet, and the sheet is conveyed to the front side and the rear side of the printer main body 12.
The conveying roller 23, the driven roller 24a, the driving roller 25, and the driven roller 26 are formed in a substantially cylindrical shape that is thicker than its axis. The surface of each of these rollers is subjected to an anti-slip process using an organic material containing various synthetic resins such as synthetic rubber, an inorganic material such as ceramics, or a combination thereof.

The conveying roller 23 and the driving roller 25 are connected to a conveying motor (not shown) via a wheel train such as a driving wheel train 49 arranged outside the right side frame 18 and a driving wheel 50 (FIG. 5) described later. Then, it is rotationally driven in the clockwise or counterclockwise direction in FIG. 2 by the driving force of the transport motor. The driven roller 24 a and the driven roller 26 are driven rollers that are rotated in accordance with the rotation of the transport roller 23 and the driving roller 25, respectively.
Further, the printer main body 12 has a paper guide 45 that is stretched over the side frames 17 and 18 on the rear side of the platen 22, and the paper guide 45 along with the front paper guide 46 described above conveys the sheet from below. As a plane.
The sheet set in the printer main body 12 is sandwiched between the conveying roller 23 and the driven roller 24a, and the driving roller 25 and the driven roller 26 while being placed on the front paper guide 46, the platen 22 and the paper guide 45. Be transported.
Here, the conveyance motor (not shown) is configured as a stepping motor that rotates in a predetermined direction by an input pulse, and the conveyance amount of the sheet by the conveyance roller substantially corresponds to the number of operation steps of the conveyance motor. Further, the sheet conveying direction, that is, the extending direction of the conveying path W is a sub-scanning direction orthogonal to a main scanning direction of a carriage 21 described later.

The carriage 21 is slidably inserted into the carriage shaft 28 and connected to an endless timing belt 48 (FIG. 3) arranged side by side on the carriage shaft 28. The timing belt 48 is reciprocated by forward and reverse operations of a carriage drive motor (not shown), and the carriage 21 is driven together with the timing belt 48 by the forward and reverse operations of the carriage drive motor, and is moved to the carriage shaft 28. Guided and reciprocated. The moving direction of the carriage 21 is a main scanning direction.
The carriage 21 carries the recording head 20. The recording head 20 includes a number of recording wires (not shown), and these recording wires are ejected toward the platen 22. The platen 22 is a flat platen that extends along the moving range of the recording head 20 that moves in the main scanning direction together with the carriage 21, that is, in the main scanning direction, and is a platen support section that spans the side frames 17 and 18. It is supported from below by 22a.

As shown in FIG. 4, a stationery type ink ribbon cartridge 29 is detachably mounted on the printer main body 12, and the ink ribbon of the ink ribbon cartridge 29 is fed between the recording head 20 and the platen 22. Further, a ribbon mask holder 51 is attached to the carriage 21 as shown in FIG. The ribbon mask holder 51 is located between the ink ribbon fed out from the ink ribbon cartridge 29 and the sheet conveyed in contact with the upper surface of the platen 22 to protect the sheet from the ink ribbon.
While the recording head 20 is traveling in the main scanning direction together with the carriage 21, these recording wires are projected and applied to the ink ribbon, and the ink on the ink ribbon is conveyed between the platen 22 and the recording head 20. An image including characters is recorded on the sheet.

  The tractor unit 13 supplies a continuous sheet to the recording head 20 side, and has a pair of left and right tractors 30. As shown in FIG. 2, each tractor 30 includes a tractor drive pulley 30a, a tractor driven pulley 30b, and a tractor belt 31 wound around the tractor drive pulleys 30a and 30b, and the driving force of the conveyance motor is driven. By being transmitted through the wheel train 49 and the like, the tractor driving pulley 30a is rotationally driven, and the tractor belt 31 is driven to convey the continuous sheet. This continuous sheet is, for example, sprocket paper in which sprocket holes that engage with pins of the tractor belt 31 are formed. The tractor unit 13 supplies a continuous sheet to each of the above-described conveyance rollers in order to record an image by the recording head 20, and further conveys the recording head 20 during the recording operation and during the discharging operation after the recording operation. The continuous sheet is fed by operating together with each conveying roller constituting the section.

Further, the ribbon mask holder 51 is provided with a paper width sensor 43 that detects the presence or absence of a sheet below the ribbon mask holder 51. The paper width sensor 43 is a reflection type optical sensor that has a light emitting part and a light receiving part arranged toward the flat surface 45a of the paper guide 45, and detects reflected light of light emitted from the light emitting part by the light receiving part. . The light emitting unit of the paper width sensor 43 emits light toward the flat surface 45a, and the light receiving unit detects light from the irradiation direction by the light emitting unit. For this reason, when there is no sheet directly under the paper width sensor 43, the light emitted from the paper width sensor 43 is reflected by the flat surface 45a and travels toward the paper width sensor 43. Further, when a sheet is present immediately below the paper width sensor 43, the light emitted from the paper width sensor 43 is reflected on the recording surface of the sheet and travels toward the paper width sensor 43.
The flat surface 45a is colored (painted) in a dark color (for example, black) so that the reflectance is low. On the other hand, most of the sheets are brighter than the flat surface 45a (for example, whiteness is about 80% to 50% for white paper) and are darker than the flat surface 45a even if the sheet is colored. It is extremely rare. Accordingly, the reflected light incident on the paper width sensor 43 varies greatly depending on the presence or absence of a sheet. For this reason, it is possible to detect the presence or absence of a sheet directly below the paper width sensor 43 based on the amount of light detected by the light receiving unit of the paper width sensor 43. Since the paper width sensor 43 moves in the main scanning direction together with the carriage 21, if the position of the carriage 21 and the amount of light received by the paper width sensor 43 are detected while moving the carriage 21, the end position in the width direction of the sheet is detected. The width of the sheet can be obtained from the detected end position.

In the printer 10 configured as described above, manual feeding for manually supplying a cut sheet from the front side and rear feeding for supplying a continuous sheet by the tractor unit 13 from the rear side can be executed.
At the time of manual feeding, the operator places a cut sheet on the sheet guide 14 and pushes it into the printer main body 12. Here, when the leading edge of the sheet is detected by a paper edge sensor 44 as an optical sensor disposed at the front side end of the conveyance path W, the conveyance roller 23 and the driving roller 25 are driven by the conveyance motor, and the sheet is detected. Is conveyed toward the recording head 20 by a conveyance unit including a conveyance roller 23, a driven roller 24a, a driving roller 25, and a driven roller 26. When the sheet reaches directly below the carriage 21 and the leading edge of the sheet is detected by the paper width sensor 43, recording by the recording head 20 is started. Recording by the recording head 20 is performed line by line, and during the recording, the sheet is conveyed to the rear side line by line by the conveyance unit. When the recording by the recording head 20 is completed, the sheet is conveyed to the front side by the conveying unit and is discharged to the sheet guide 14.

On the other hand, when the rear feed is performed by the tractor unit 13, the tractor unit 13 and the respective conveyance rollers constituting the conveyance unit are driven by the operation of the conveyance motor, and the continuous sheet is conveyed toward the recording head 20. Then, recording by the recording head 20 is started. After the start of recording, every time the recording head 20 performs recording for one line by the tractor unit 13 and the conveying unit, the continuous sheet is conveyed for a predetermined length and sequentially discharged from the front side.
The manual feeding and the rear feeding can be switched by switching the mechanism for transmitting the driving force of the transport motor to the tractor unit 13 by an operator switching a lever (not shown), or the printer 10 It may be automatically switched by a controller that controls the above. In the manual feeding, the left end is the 0 digit position of the carriage 21 when viewed from the front side where the sheet is supplied, and the left end is the 0 digit position when viewed from the tractor unit 13 side where the sheet is supplied during the rear feeding.

As shown in FIGS. 3 and 4, the printer 10 includes a sensor unit 40 disposed so as to be sandwiched between roller units 24 and 24 attached to the paper discharge frame 47. As shown in FIG. 2, the sensor unit 40 houses a paper edge sensor 44 disposed above the transport path W.
FIG. 5 is an enlarged cross-sectional view of the main part showing the configuration and mounting structure of the sensor unit 40.
The paper edge sensor 44 is a reflection type optical sensor configured by combining a light emitting element that emits light and a light receiving element that receives reflected light of light emitted from the light emitting unit, and emits light (irradiates) the light emitting element. The direction and the light receiving direction in which the light receiving element receives reflected light are the same direction. For this reason, the light emitting element and the light receiving element are directed in the same direction and integrally constitute the light emitting / receiving unit 44a. The sensor unit 40 also includes a drive circuit (not shown) that measures the amount of received light by applying a voltage to the light emitting element of the light emitting / receiving unit 44a to emit light and detecting electromotive force generated at both ends of the light receiving element. To do.

  As shown in FIG. 5, the light emitting / receiving unit 44 a of the paper edge sensor 44 faces the conveyance roller 23 located on the opposite side across the conveyance path W. The optical axis (symbol L in FIG. 5) of the light emitted from the light emitting / receiving unit 44a faces the inclined surface 46a of the front paper guide 46 as shown by a one-dot chain line in FIG. A hole 46b is formed as a through hole for transmitting the emitted light. Further, since the sensor unit 40 is located between the roller unit 24 and the roller unit 24, the light emitting / receiving unit 44a is located away from the conveying roller 23, that is, a position facing the roller shaft 23a. Accordingly, the light emitted from the light receiving / emitting unit 44a is reflected by the roller shaft 23a located in the back of the front paper guide 46, and the light receiving / emitting unit 44a receives the reflected light reflected by the roller shaft 23a.

FIG. 6 is a diagram illustrating a target range in which light is emitted by the paper edge sensor 44.
FIG. 6 shows a portion of the light emitting / receiving unit 44a viewed from the light receiving / emitting unit 44a. As shown in FIG. 6, the inclined surface 46 a is opposed to the light emitting / receiving unit 44 a, and the hole 46 b is located at a position overlapping the roller shaft 23 a removed from the transport roller 23. Since the light emitting / receiving portion 44a, the hole 46b, and the roller shaft 23a are in a positional relationship aligned on a straight line that overlaps the optical axis L, the roller from the light emitting / receiving portion 44a passes through the hole 46b formed in the slope 46a. The shaft 23a can be seen directly. Further, as shown in FIG. 5, since the optical axis L of the light emitting / receiving unit 44a is in a direction passing through the center of the roller shaft 23a, the light emitted from the light receiving / emitting unit 44a is reflected by the roller shaft 23a and received straight. It faces the light emitting part 44a and enters the light emitting / receiving part 44a.

The roller shaft 23a is usually made of metal. Specifically, a material obtained by plating a metal material such as iron with zinc, tin, nickel, chromium or the like, or a material obtained by appropriately polishing the surface of a metal metal such as stainless steel is used. These materials reflect light very well (with high reflectivity) by being subjected to polishing processing such as plating and mirror finishing.
Therefore, in a state where no sheet exists between the paper end sensor 44 and the front paper guide 46, the light from the light emitting / receiving unit 44a is reflected by the roller shaft 23a and enters the light receiving / emitting unit 44a again. Strong reflected light reflected by the roller shaft 23a is detected.

FIG. 7 is a chart schematically showing changes in the amount of light detected by the paper edge sensor 44.
FIG. 7 shows a change in the amount of light detected by the paper edge sensor 44 when a sheet is conveyed from the sheet guide 14 into the printer main body 12.
The amount of light detected by the paper edge sensor 44 shown in FIG. 7 does not necessarily indicate the output value (output voltage) of the paper edge sensor 44. When the paper edge sensor 44 is configured by a sensor that outputs a value obtained by inverting the detected light amount, the output voltage of the paper edge sensor 44 is opposite to the detected light amount. When the detected light amount is low, the output voltage is high and the detected light amount is If it is high, the output voltage is low. The paper edge sensor 44 may change a different output value only when the detected light amount exceeds a preset threshold value. In this case, the paper edge sensor 44 switches and outputs several levels of output voltage according to the detected light amount. In addition, the specific configuration of the paper edge sensor 44 is arbitrary. Here, the light quantity received by the light emitting / receiving unit 44a, that is, the light quantity detected by the paper edge sensor 44 will be described with reference to FIG.

As described above, the paper end sensor 44 irradiates the roller shaft 23a with light when the sheet is not in the conveyance path W, and receives the reflected light from the roller shaft 23a. The amount of light detected by the paper edge sensor 44 in this state is large, which is the amount of light indicated by M ₁ in FIG.
Here, the sheet when pushed from the front side of the sheet guide 14, the leading end of the sheet rides on the slope 46a of the front sheet guide 46, closing the holes 46b at time t ₁ in FIG. For this reason, the light emitted from the paper edge sensor 44 is blocked and reflected on the surface of the sheet, and this reflected light is detected by the paper edge sensor 44. The reflected light on the surface of the sheet varies depending on the color and surface state of the sheet. For example, when the sheet is white fine paper, the reflected light amount in the sheet surface is relatively large, the quantity of light detected paper edge sensor 44 is reduced to the extent indicated by M ₂ in FIG. 7 the time t ₁ as a boundary. Further, for example, since the sheet is the amount of reflected light if the black fine paper is small, the quantity of light detected paper edge sensor 44, reducing the time t ₁ to the extent indicated by M ₃ in FIG. 7 as a boundary.

In order to reliably detect the leading edge of the sheet, there is a clear difference between the detected light amounts M ₁ and M ₂ and between the detected light amounts M ₁ and M ₃ that exceeds the level considered as an error. That's fine. The detected light intensity M ₁ as described above is reflected light from the roller shaft 23a, so further amount than the reflected light in the sheet having the light-colored sheet or luster such as white is large, by a reference to the detected light intensity M ₁ Thus, the leading edge of the sheet can be detected easily and reliably.

The sheet inserted from the sheet guide 14 is then sandwiched between the transport roller 23 and the driven roller 24 a and transported on the transport path W, and further transported to the rear side of the printer 10 by the drive roller 25 and the driven roller 26. Here, the trailing end of the sheet rides in the front paper guide 46, passes through the holes 46b, the sheet is disengaged from the hole 46b at time t ₂ in FIG. Then, the light emitted from the paper end sensor 44 passes through the hole 46b and reaches the roller shaft 23a, and the paper end sensor 44 receives the reflected light from the roller shaft 23a. For this reason, the amount of light detected by the paper edge sensor 44 increases to the extent indicated by M ₁ in FIG. 7 at the time t ₂ . As described above, the detected light amount M ₁ of the reflected light reflected by the roller shaft 23a is sufficiently larger than the reflected light of the sheet, so that the change in the detected light amount at time t ₂ is based on this detected light amount M _1. Can easily detect the trailing edge of the sheet.

Further, when the use of the printer 10 is repeated, various kinds of dust such as paper dust dropped from the sheet and other dust / dust may adhere to the conveyance path W. If a large amount of this dust adheres to the irradiation range where the paper edge sensor 44 emits light, the reflected light reflected by the dust is close to the reflected light of the sheet, leading to false detection, or the reflected light of the dust with irregular reflection is reflected in the sheet. Further, there is a possibility that the detection operation may be hindered due to a large difference from the reflected light of the roller shaft 23a.
However, in the printer 10 of the present embodiment, the paper edge sensor 44 is configured to irradiate light to the roller shaft 23 a disposed on the back side of the front paper guide 46. Since the roller shaft 23a is located on the back side of the front paper guide 46, dust such as paper powder dropped from the sheet and dust entering from the front side is extremely difficult to accumulate. Also, it is unlikely that a large amount of dust accumulates in the hole 46b located between the paper edge sensor 44 and the roller shaft 23a. Accordingly, since the reflected light from the roller shaft 23a is not damaged by the influence of dust, the printer 10 can accurately determine the presence or absence of a sheet on the basis of the reflected light from the roller shaft 23a without frequent maintenance. As shown in FIG. 7, the positions of the leading edge and the trailing edge of the sheet can be reliably detected.

In addition, since the paper edge sensor 44 is positioned above the conveyance path W, dust does not adhere to or accumulate on the light emitting / receiving portion 44a of the paper edge sensor 44, which adversely affects detection. There is no. Further, since the paper edge sensor 44 irradiates light to the roller shaft 23a and uses the reflected light, it is not necessary to provide a reflection member for returning the reflected light to the paper edge sensor 44. According to the configuration of the printer 10, The present invention can be easily realized at low cost.
Further, the shaft of the transport roller such as the roller shaft 23a generally has a highly reflective surface, and such a shaft works well as a reflecting member and reflects a sufficient amount of light to the paper edge sensor 44. Light enters. For this reason, the presence or absence of the sheet can be accurately detected. Furthermore, since the roller shaft 23a rotates every time a sheet is conveyed, there is an extra advantage that dust is extremely difficult to accumulate, and that it is very unlikely to be affected by dust without frequent maintenance.

Further, since the hole 46b of the front paper guide 46 is provided at a position where the sheet enters at the end of the conveyance path W, the hole 46b is discharged from the leading edge of the sheet entering the end of the conveyance path W or the conveyance path W. The end of the sheet to be detected can be detected accurately.
Further, the front paper guide 46 has an inclined surface 46a that is inclined in the direction of expanding the conveying path W at the tip of the conveying path W, and a hole 46b is formed in the inclined surface 46a. For this reason, there is no possibility that the sheet comes into contact with the hole 46b, and the sheet does not enter the hole 46b without performing a work such as making the hole 46b a concave portion, and the conveyance of the sheet is not hindered.

Further, in the printer 10 of the above-described embodiment, a configuration for removing dust attached to the roller shaft 23a may be provided.
FIG. 8 is a cross-sectional view of a main part showing a main part configuration of a printer 10 as another example to which the present invention is applied.
In the configuration shown in FIG. 8, a brush 23 b (foreign matter removing unit) that contacts the side surface of the roller shaft 23 a is disposed on the back side of the front paper guide 46. The brush 23b has a shaft portion 23c made of an elastic material such as metal or synthetic resin, and a brush portion 23d attached to the tip of the shaft portion 23c. A part of the shaft portion 23c is fixed to the front paper guide 46. Has been. The brush portion 23d is made of natural hair, various fibers, or synthetic resin hair, and contacts the side surface of the roller shaft 23a. Instead of the brush portion 23d, a spatula that contacts the side surface of the roller shaft 23a may be provided. The brush portion 23d is in contact with the roller shaft 23a at a position on the side surface of the roller shaft 23a where the light from the paper edge sensor 44 hits.
Further, the brush 23b is disposed at a position where a part of the brush 23b does not block the light hitting the roller shaft 23a from the paper edge sensor 44.

  As described above, since the roller shaft 23a rotates when the sheet is conveyed, the dust adhering to the side surface of the roller shaft 23a hits the brush 23b and is scraped off by the rotation of the roller shaft 23a. For this reason, by providing the brush 23b on the back surface of the front paper guide 46, the surface of the roller shaft 23a can be kept clean and the light reflected from the paper edge sensor 44 can be favorably reflected. The sheet can be reliably detected by the printer 10 even when the value is extremely low.

  In the above embodiment, the paper end sensor 44 is provided at the front end of the conveyance path W near the sheet guide 14, and the roller shaft 23 a disposed on the back side of the front paper guide 46 from the paper end sensor 44. However, the present invention is not limited to this. For example, a surface having a high reflectance similar to the side surface of the roller shaft 23a is located on the back surface side of the front paper guide 46. The member may be irradiated with light from the paper edge sensor 44. Further, the paper end sensor 44 may be configured to irradiate light from directly above the front paper guide 46 through a through hole formed in the flat plate portion of the front paper guide 46. Further, the light emitting unit and the light receiving unit disposed in the same direction on the light receiving / emitting unit 44a are separately provided, the light emitting unit is provided at a position facing the inclined surface 46a, and the light receiving unit is disposed on the back side of the front paper guide 46. Alternatively, the opposite configuration may be used. The specific configuration of the light emitting / receiving unit 44a included in the paper edge sensor 44 is arbitrary. A light emitting diode may be used as the light emitting unit, a laser light source may be used, and a phototransistor and a photodiode are used as the light receiving unit. Any of them may be used.

  In the above embodiment, an example in which the present invention is applied to the printer 10 as a dot impact printer has been described. However, the present invention is not limited to this, and the sheet is conveyed and an image is recorded on the sheet. Any printer can be applied as long as the apparatus detects the sheet using reflected light in the sheet conveyance path. Specifically, the present invention can be applied to an inkjet or bubble jet (registered trademark) printer, and a thermal printer, a thermal sublimation printer, which records an image on thermal paper by a recording head including a heating element, Alternatively, the present invention can also be applied to a recording apparatus that records an image by an electrophotographic method such as a copying machine or a facsimile. Furthermore, the present invention can be easily applied to various electronic devices having a built-in image recording apparatus. Further, the detailed configuration of the printer 10 described in the above-described embodiment, such as the specific shape of each part constituting the conveyance path W including the front paper guide 46 and its constituent materials, can be arbitrarily changed.

FIG. 2 is a perspective view illustrating an appearance of the front of the printer according to the embodiment. It is a sectional side view of a printer. FIG. 4 is a perspective view showing a frame configuration with an ink ribbon cartridge removed. It is a perspective view which shows the state which mounted | wore the ink ribbon cartridge. It is a sectional side view which shows the structure and attachment structure of a sensor unit. It is a figure which shows the object range irradiated with light by a paper edge sensor. It is a graph which shows typically the change of the light quantity detected by a paper edge sensor. FIG. 6 is a cross-sectional view of a main part of a printer as another example of an embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Printer (recording apparatus), 11 ... Recording head, 12 ... Printer main body, 13 ... Tractor unit, 14 ... Sheet guide, 15 ... Upper case, 16 ... Lower case, 17 ... Left side frame, 18 ... Right side frame, DESCRIPTION OF SYMBOLS 20 ... Recording head, 21 ... Carriage, 22 ... Platen, 22a ... Platen support part, 23 ... Drive roller, 23a ... Roller shaft (reflective member, axis | shaft of a conveyance roller), 23b ... Brush (foreign substance removal part), 23c ... Shaft Part, 23d ... brush part, 24 ... roller unit, 24a ... driven roller, 25 ... driving roller, 26 ... driven roller, 27 ... back frame, 28 ... carriage shaft, 29 ... ink ribbon cartridge, 30 ... tractor, 31 ... tractor Belt, 40 ... sensor unit, 43 ... paper width sensor, 44 ... paper edge sensor (optical sensor), 45 ... paper Inner (guide plate), 45a ... flat surface, 46 ... front paper guide (guide plate), 46a ... slope (inclined surface), 46b ... hole (through hole), 47 ... discharge frame, 48 ... timing belt, 49 ... Drive wheel train, 50 ... drive wheel, 51 ... ribbon mask holder, L ... optical axis, W ... conveying path.

Claims (6)

In a recording apparatus for recording an image by conveying a recording medium,
A guide plate that constitutes a conveyance path through which the recording medium is conveyed;
An optical sensor that is located on the opposite side of the guide plate across the conveyance path of the recording medium and detects the recording medium in the conveyance path;
A through hole is formed in the guide plate,
The optical sensor irradiates light toward a reflecting member disposed on the back side of the guide plate through the through hole of the guide plate, and detects the reflected light of the light, thereby the recording medium in the transport path Detecting,
A recording apparatus. The recording apparatus according to claim 1,
The reflecting member is a shaft of a conveying roller that conveys the recording medium;
A recording apparatus. The recording apparatus according to claim 2, wherein
A foreign matter removing unit for removing foreign matter attached to a position where the light of the optical sensor reflects on the shaft of the transport roller;
A recording apparatus. The recording apparatus according to any one of claims 1 to 3,
The through hole of the guide plate is provided at a position where the recording medium enters at an end of the conveyance path;
A recording apparatus. The recording apparatus according to claim 4.
The guide plate has an inclined surface that inclines in the direction of expanding the conveyance path at the tip of the conveyance path,
The through hole of the guide plate is provided in the inclined surface;
A recording apparatus. In a sensor arrangement structure for arranging an optical sensor in an apparatus for recording an image by conveying a recording medium,
An optical sensor for detecting the recording medium in the transport path of the recording medium is disposed on the opposite side of the guide plate of the transport path;
A through hole is formed in the guide plate;
The optical sensor irradiates light toward the reflecting member disposed on the back side of the guide plate through the through hole of the guide plate, and detects the reflected light of the light, whereby the recording medium in the transport path is detected. Configured to detect
Sensor arrangement structure characterized by.

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