JP2015190924A - rotary encoder and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary encoder and a printer which are capable of dealing with a structural installation error between a rotor and a plate-like member.SOLUTION: A plate-like member 31 is installed orthogonal to a rotation axis of a discharge roller 24 and rotated with the rotation axis as a center. The plate-like member 31 is radially arranged with a plurality of patterns which are constituted of a transmission region 34 for making light transmit and a non-transmission region 33 for making the light not transmit, and changes a ratio of length in the peripheral direction between the transmission region 34 and the non-transmission region 33 according to the distance from the center of the plurality of patterns; and includes a sensor part 32 for detecting whether the region of the plate-like member 31 passing through a predetermined detection position is the transmission region 34 or the non-transmission region 33 when the discharge roller 24 rotates with the rotation axis of the discharge roller 24 as a center.

Description

  The present invention relates to a rotary encoder and a printer.

  2. Description of the Related Art In general, printers, scanners, multifunction devices, and the like are provided with a rotary encoder that detects the rotation speed of a conveyance roller (rotating body) that conveys a sheet in order to improve sheet conveyance accuracy. A rotary encoder generally includes a disk-shaped plate member. The plate-like member is attached to the conveying roller so that the surface thereof is orthogonal to the axis of the conveying roller, and rotates around the axis of the conveying roller together with the conveying roller. Further, the printer is provided with a drive unit that rotates the conveyance roller about the axis of the conveyance roller.

  Here, a structural attachment error may occur between the transport roller and the drive unit. In this case, even if a signal is output to the drive unit so as to rotate the roller once, the actual rotation amount may be larger or smaller than one rotation.

  As a technique for reducing the influence of such an attachment error, for example, a technique is disclosed in which the origin position of the transport roller is detected and the deviation of the origin position is corrected every rotation (see, for example, Patent Document 1). ).

JP 2007-161389 A

  However, the structural attachment error may occur not only between the rotating body (for example, the conveyance roller) and the drive unit, but also between the plate member and the roller of the rotary encoder described above. .

  In the rotary encoder of Patent Document 1, it is difficult to cope with the mounting error that occurs between the plate-like member and the roller.

  If there is a deviation between the actual rotation speed of the roller and the detected rotation speed due to an attachment error, the printed images will be overlapped or stretched, the printing will be lost, and the quality of the printed image will be degraded. A possibility arises.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a rotary encoder and a printer that can cope with structural attachment errors between a rotating body and a plate-like member. To do.

  In order to achieve the above object, a rotary encoder according to an aspect of the present invention is a plate-like member that is attached orthogonally to a rotating shaft of a rotating body and rotates around the rotating shaft, and transmits light. A plurality of patterns composed of a transmission region and a non-transmission region that does not transmit light are arranged radially, and a ratio of a length in a circumferential direction between the transmission region and the non-transmission region from a center of the plurality of patterns. A plate-like member that changes according to a distance, and a region of the plate-like member that passes a predetermined detection position when the rotating body rotates around the rotation axis is the transmission region or the non-transmission region And a detection unit for detecting whether or not.

  When the rotation speed is obtained using a value obtained by integrating the output pulses from the rotary encoder, it is important that the pulse width of the output pulse is accurate. However, in the conventional rotary encoder, when the axis of the rotating body and the center of the plurality of patterns are attached to be shifted, so-called eccentricity, even if the rotating body rotates at a constant speed, the rotary encoder The pulse width of the waveform from the encoder is not constant. For this reason, there has been a problem that the rotation speed may be detected as changing even though the rotation speed is constant.

  On the other hand, the rotary encoder configured as described above can detect the influence of eccentricity because the ratio of the length in the circumferential direction between the transmissive region and the non-transmissive region varies depending on the distance from the center of the plurality of patterns. It becomes possible.

  For example, the plurality of patterns may be configured such that the ratio of the transmission region increases as the distance from the center of the plurality of patterns increases, and the plurality of patterns include the plurality of patterns. The larger the distance from the center, the larger the ratio of the non-transmissive region.

  The rotary encoder having the above configuration increases the ratio of the non-transmissive region or the transmissive region as the distance from the center of the plate-like member increases, so that the influence of eccentricity can be obtained with a simple configuration.

  The plate-like member may be a transparent member, and the non-transparent region may be a non-transparent region printed on the plate-like member, or the plate-like member may be a non-transparent member. Yes, a slit may be formed in the plate member as the transmission region.

  The rotary encoder having the above configuration can form a plate-like member with a simple configuration.

  The transmissive region or the non-transmissive region may have a rectangular shape.

  The rotary encoder having the above configuration can form a plurality of patterns with a simple configuration.

  The detection unit may include a light source that emits light and a light receiving unit that receives light from the light source via the plate-like member.

  Since the rotary encoder having the above configuration includes a detection unit using a light source and a light receiving element, it is possible to detect a transparent transmission region and a non-transparent non-transmission region.

  In order to achieve the above object, a printer according to an aspect of the present invention is configured to detect the plurality of patterns based on the detection result of the detection unit in a state where the rotary encoder and the rotating body are rotated at a constant speed. For each, a detection ratio calculation unit that calculates a detection ratio between a time during which the transmission region passes through the detection position and a time during which the non-transmission region passes through the detection position, and the plate member is eccentric to the rotating body Assuming that the transmission area passes through the detection position and the non-transmission area passes through the detection position, and obtains a theoretical ratio between the theoretical ratio and the detection ratio. The correction coefficient for calculating the correction coefficient for correcting the influence of the structural eccentricity between the rotating body and the plate-like member from the detection result in the detection unit And a detecting section.

  The printer having the above configuration obtains a correction coefficient for correcting a waveform detected when the recording medium is actually conveyed by comparing the theoretical ratio and the detection ratio when there is no attachment error. Since the rotary encoder having the above configuration obtains the correction coefficient for each of the plurality of patterns, it is possible to remove the influence on the eccentricity with higher accuracy. As a result, the actually detected waveform can be adjusted to a waveform with no attachment error.

  Furthermore, the rotary encoder having the above-described configuration can obtain the influence of eccentricity by a simple calculation of calculating the ratio between the transmissive region and the non-transmissive region.

  Further, when the recording medium is conveyed by the rotating body, a detection result is acquired from the detection unit of the rotary encoder, and the passage time of the detection position of the transmission region and the non-transmission region are acquired using the correction coefficient. A waveform correction unit that corrects the passage time of the detection position, and a rotation speed calculation unit that calculates the rotation speed of the rotating body using the detection result corrected by the waveform correction unit. good.

  Since the printer having the above configuration adjusts the waveform actually detected by the rotary encoder to a waveform when there is no mounting error, it is possible to improve the detection accuracy of the rotational speed. As a result, it becomes possible to carry out the transport control of the recording medium more precisely, and it is possible to prevent the deterioration of the print quality.

  Note that the present invention can be realized not only as a rotary encoder including such a characteristic processing unit, but also as a rotational speed detection method including steps executed by the characteristic processing unit included in the rotary encoder. Can be realized. It can also be realized as a program for causing a computer to function as a characteristic processing unit included in a rotary encoder or a program for causing a computer to execute characteristic steps included in a rotational speed detection method. Such a program can be distributed via a computer-readable non-transitory recording medium such as a CD-ROM (Compact Disc-Read Only Memory) or a communication network such as the Internet. .

  According to the present invention, it is possible to cope with a structural attachment error between the rotating body and the plate-like member.

It is a perspective view which shows an example of the structure concerning the conveyance mechanism in embodiment. It is a figure which shows an example of the rotary encoder attached to the discharge roller and discharge roller in embodiment. It is a figure which shows an example of a detailed structure of the detection part of the rotary encoder in embodiment. It is a top view which shows an example of the surface of the plate-shaped member in embodiment. It is a block diagram which shows an example of a structure of the arithmetic processing part in embodiment. It is a wave form diagram which shows an example of the relationship between a detection position and the waveform output from a sensor part, when the plate-shaped member is attached to the roller without eccentricity. It is a top view which shows an example of the surface of the plate-shaped member at the time of eccentricity. A waveform diagram showing an example of a theoretical output waveform of the sensor unit when the roller is rotated at a constant speed and an example of an output waveform of the sensor unit at the time of eccentricity when the roller is rotated at a constant speed. is there. It is a flowchart which shows an example of the process sequence of the correction coefficient calculation process in embodiment. It is a flowchart which shows an example of the process sequence of the rotational speed calculation process in embodiment. It is a figure which shows an example of the shape of the non-transmissive area | region in the modification 1. It is a figure which shows an example of the shape of the non-transmissive area | region in the modification 1. It is a figure which shows an example of the shape of the non-transmissive area | region in the modification 1. It is a figure which shows an example of the shape of the non-transmissive area | region in the modification 1. It is a perspective view which shows an example of the plate-shaped member in the modification 2. It is a wave form diagram which shows an example of the waveform complementation in the modification 3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, each figure does not necessarily show exactly each dimension or each dimension ratio.

  Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples and are not intended to limit the present invention. The invention is specified by the claims. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims are not necessarily required to achieve the object of the present invention, but are described as constituting more preferable embodiments. Is done.

(Embodiment)
A rotary encoder according to an embodiment will be described with reference to FIGS.

  In this embodiment, a case where a rotary encoder is applied to a recording medium conveyance mechanism of a printer will be described as an example.

[1-1. Printer configuration]
The printer according to the present embodiment will be described by taking an example in which the printer is an ink jet printer that performs printing by ejecting ink onto a recording medium. The printer includes a transport mechanism for transporting the recording medium and a control unit that controls the transport mechanism in the housing. In this embodiment, the recording medium is, for example, plain paper, photographic paper, or a CD-ROM (Compact Disc Read Only Memory) having a printable label surface.

  The transport mechanism is a mechanism for supplying, feeding, and discharging the recording medium.

  FIG. 1 is a perspective view illustrating an example of a configuration related to the transport mechanism 20. As shown in FIG. 1, the transport mechanism 20 includes a frame 21 on which a roller that is an example of a rotating body and a roller driving mechanism are provided, together with a configuration (not shown) for printing. The transport mechanism 20 is provided with a rotary encoder 30 that detects the rotational speed of the rollers.

  The rollers include a pick roller 22 for drawing the recording medium before printing from the paper supply / discharge tray, a feed roller 23 for feeding the recording medium to a printing position, and a recording medium after printing for the paper supply / discharge tray 12. A discharge roller 24 for discharging is included.

  FIG. 2 is a diagram illustrating an example of the discharge roller 24 and the rotary encoder 30 attached to the discharge roller 24. FIG. 3 is a diagram illustrating an example of a detailed configuration of the detection unit of the rotary encoder.

  As shown in FIG. 2, the discharge roller 24 includes a shaft body 24a and a roller base 24b covered with an elastic member. The elastic member is a member that contacts the recording medium when the recording medium is conveyed. The configurations of the pick roller 22 and the feed roller 23 are the same as those of the discharge roller 24 in the present embodiment, although the dimensions (the diameters of the shaft body and the roller base) are different.

  The rotary encoder 30 is provided at one end of the discharge roller 24. The detailed configuration of the rotary encoder 30 will be described later. In this embodiment, a case where the rotary encoder 30 is provided on the discharge roller 24 will be described as an example. However, the rotary encoder 30 may be provided on the pick roller 22 or the feed roller 23, and a plurality of rotary encoders 30 may be provided. It may be provided on the roller. The rotary encoder 30 is preferably attached to a roller having a larger driving force.

  The motor 25 drives the pick roller 22, the feed roller 23 and the discharge roller 24.

  The control unit controls the transport mechanism 20. The detailed configuration and operation of the control unit will be described later.

  In the present embodiment, the control unit will be described using an example of an LSI (Large Scale Integration), but is not limited thereto. For example, a computer program (software) for executing the show-through removal method of the present embodiment may be realized by a CPU (Central Processing Unit).

[1-2. Rotary encoder configuration]
As shown in FIG. 2, the rotary encoder 30 includes a plate-like member 31 and a sensor unit 32.

  The plate-like member 31 is a disk-like member, and has a diameter of 2 to 3 cm and a thickness of several mm. As described above, the plate-like member 31 is attached to the discharge roller 24 so that the surface thereof is orthogonal to the rotation axis of the discharge roller 24 at a position outside the recording medium conveyance path. The plate-like member 31 is formed with a plurality of radial patterns including a transmission region 34 (transmission pattern) that transmits light and a non-transmission region 33 (non-transmission pattern) that does not transmit light. In other words, the plurality of patterns are arranged in a circle. In each of the plurality of patterns, the circumferential ratio between the transmissive region 34 and the non-transmissive region 33 is configured to change according to the distance from the center of the plurality of patterns.

  Moreover, the plate-shaped member 31 is comprised with the transparent member which permeate | transmits the light which the light source 32a of the sensor part 32 mentioned later transmits. A plurality of non-transmissive patterns that block light emitted from the light source 32a are formed on the plate member 31 by printing. A region where the non-transmissive pattern is formed is the non-transmissive region 33, and a region where the non-transmissive pattern is not formed is the transmissive region 34.

  FIG. 4 is a plan view showing an example of the surface of the plate-like member 31. As shown in FIG. 4, a plurality of rectangular non-transmissive patterns are printed on the plate-like member 31 in a circular pattern at equal intervals. Although not explicitly shown in FIG. 4, the sides in the rotation direction of the non-transmissive pattern are arranged on a straight line extending from the centers of the plurality of patterns.

  As shown in FIGS. 2 and 4, the plate-like member 31 has a configuration in which a rectangular non-transmissive pattern is printed. Therefore, as the distance from the axis of the discharge roller 24 increases, the circumferential direction of the transmissive pattern increases. The length ratio increases.

  When the discharge roller 24 rotates around the axis of the discharge roller 24, the sensor unit 32 determines whether the region of the plate-like member 31 that passes a predetermined detection position is the transmission region 34 or the non-transmission region 33. It is an example of the detection part to detect, As shown in FIG.2 and FIG.3, the light source 32a and the light-receiving part 32b are provided. The sensor unit 32 is arranged so as to sandwich the plate member 31 between the light source 32a and the light receiving unit 32b without contacting the plate member 31. The position where the light from the light source 32a strikes the plate-like member 31 or passes through the plate-like member 31 is the detection position.

  The sensor unit 32 outputs an H level signal when the non-transmissive region 33 passes through the detection position and the light receiving unit 32b cannot receive light from the light source 32a. The sensor unit 32 outputs an L level signal when the transmission region 34 passes through the detection position and the light receiving unit 32b receives light from the light source 32a. The light receiving unit 32b may output an L level signal when it cannot receive light from the light source 32a, and may output an H level signal when receiving light.

  The light source 32a is a light source that emits infrared light, and the light receiving unit 32b is configured by a light receiving element that can receive the infrared light. Note that the light output from the light source 32a may be visible light or light of other wavelengths. What is necessary is just light of the wavelength which the light-receiving part 32b can detect.

[1-3. Configuration of control unit]
The control unit of the present embodiment detects the rotation speed of the roller using a signal output from the rotary encoder. Further, the control unit controls the motor 25.

  FIG. 5 is a block diagram showing an example of the configuration of the control unit 35 in the present embodiment. Although not shown in FIG. 5, the control unit 35 includes a configuration related to other printing control such as control of the rotation speed of the motor 25.

  As shown in FIG. 5, the control unit 35 includes a duty ratio calculation unit 35a, a correction coefficient calculation unit 35b, a waveform correction unit 35c, a rotation speed calculation unit 35d, and a memory 35e.

  The duty ratio calculation unit 35a determines the time during which the transmission region 34 passes the detection position and the non-transmission region for each of a plurality of patterns from the detection result in the sensor unit 32 with the discharge roller 24 rotating at a constant speed. It is an example of the detection ratio calculation part which calculates a detection ratio with the time when 33 passes a detection position.

  The correction coefficient calculation unit 35b assumes that the transmission region 34 passes the detection position and the non-transmission region 33 passes the detection position when it is assumed that the plate-like member 31 is attached to the discharge roller 24 without eccentricity. And the ratio between the theoretical ratio and the detection ratio is calculated to correct the influence of the structural eccentricity between the discharge roller 24 and the plate member 31 from the detection result in the sensor unit 32. A correction coefficient is calculated.

  The waveform correction unit 35 c acquires the detection result from the sensor unit 32 when the recording medium 100 is conveyed by the discharge roller 24, and uses the correction coefficient to pass the detection time of the transmission region 34 and the detection position of the non-transmission region 33. Correct the transit time.

  The rotation speed calculation unit 35d calculates the rotation speed of the discharge roller 24 using the detection result from the sensor unit 32 after being corrected by the waveform correction unit 35c.

  The memory 35e is a storage medium for storing correction coefficients and the like, and is configured using a ROM (Read Only Memory) or a RAM (Random Access Memory).

  As described above, the control unit 35 performs the correction coefficient calculation process for obtaining the correction coefficient before actually transporting the recording medium, and the rotation for detecting the rotation speed of the roller using the correction coefficient when the actual recording medium is transported. Speed detection processing is executed. Hereinafter, a detailed operation of the control unit 35 will be described.

[1-4. Operation of arithmetic processing unit (rotation speed detection method)]
[1-4-1. Output waveform of the rotary encoder during eccentricity]
Prior to the description of the operation of the control unit 35, when the plate-like member 31 is attached to the discharge roller 24 in a state where the center of the plate-like member 31 is displaced from the axis of the discharge roller 24 (a structural attachment error occurs). In other words, the output waveform of the sensor unit 32 at the time of eccentricity will be described. Here, regarding the output waveform of the sensor unit 32 at the time of eccentricity, when the plate member 31 is attached to the discharge roller 24 so that the center of the plate member 31 coincides with the axis of the discharge roller 24, that is, the theory. This will be described by comparison with the output waveform of the upper sensor unit 32.

  First, the relationship between the distance from the axis and the waveform output from the sensor unit 32 will be described.

  FIG. 6 is a waveform diagram showing an example of the relationship between the detection position and the waveform output from the sensor unit 32 when the plate-like member 31 is attached to the discharge roller 24 without eccentricity.

  FIG. 6 shows the output waveform of the sensor unit 32 when the roller is rotated at a constant speed and the detection positions are set at the respective positions C1 to C3 in FIG. The distance from the center of the plate-like member 31 is C1> C2> C3.

  Here, in the present embodiment, the duty ratio is defined as follows.

DH = H level period / cycle (Formula 1)
DL = L level period / cycle (Formula 2)

  One period is a time for one non-transmissive pattern and a transmissive region located next to the non-transmissive pattern to pass through the detection position.

The duty ratio in _C1 is DH _C1 = t1 / t4 = 25% and DL _C1 = (t4−t1) / t4 = 75%. C2 is a position where the H level period and the L level period are the same. The duty ratio in _C2 is DH _C2 = t2 / t4 = 50% and DL _C2 = (t4-t2) / t4 = 50%. The duty ratio in _C3 is DH _C3 = t3 / t4 = 75% and DL _C3 = (t4-t3) / t4 = 25%.

  FIG. 7 is a plan view showing an example of the surface of the plate-like member 31 at the time of eccentricity. In FIG. 7, when the plate-like member 31 is attached to the discharge roller 24 in a state where the axis of the discharge roller 24 is shifted in the positive direction of the Z-axis when the non-transmissive pattern P0 is located at the detection position. Is shown. For this reason, in FIG. 7, assuming that the sensor unit 32 is disposed at a position corresponding to C <b> 2 when the plate-like member 31 is attached to the discharge roller 24 without eccentricity, the shaft body 24 a of the discharge roller 24 is arranged. The portion of the circle C22 centered on the axis passes through the detection position of the sensor unit 32. Further, as shown in FIG. 7, IDs P0 to P19 are assigned to the non-transparent patterns, so that the control unit 35 can recognize which non-transparent pattern is detected.

  FIG. 8 shows an example of a theoretical output waveform of the sensor unit 32 when the roller is rotated at a constant speed, and an example of an output waveform of the sensor unit 32 when the roller is rotated at a constant speed. FIG. 8A shows the theoretical output waveform of the sensor unit 32, and FIG. 8B shows the actual output waveform of the sensor unit 32 at the time of eccentricity. FIG. 8 shows a case where the sensor unit 32 is disposed at a position corresponding to C2 when the plate-like member 31 is attached to the discharge roller 24 without eccentricity.

  The theoretical output waveform of the sensor unit 32 is such that the duty ratios DH and DL are 50% in all cycles, as shown in FIG.

  On the other hand, as shown in FIG. 8B, the output waveform of the sensor unit 32 at the time of eccentricity has different duty ratios in all cycles.

  Specifically, in the non-transmissive pattern P0 farthest from the shaft body 24a, the H level period (duty ratio) is the largest. The duty ratio of the non-transmissive pattern P0 is substantially the same as the duty ratio at C3 in FIG. In the non-transmissive pattern P10 closest to the shaft body 24a, the H level period is the smallest. The duty ratio of the non-transmissive pattern P10 is substantially the same as the duty ratio at C1 in FIG. Between the non-transmissive patterns P0 to P10, the closer to P0, the longer the H level period.

  When the rotation speed is calculated using a value obtained by integrating the output pulses from the rotary encoder 30, the rotation speed calculated by the pulse width is determined. For this reason, conventionally, even if the rotational speed is actually constant, it is detected that the rotational speed is low in the period of the non-transmissive pattern P0, and control for increasing the rotational speed is performed on the control unit side. Is called. In the cycle of the non-transmissive pattern P10, it is detected that the rotation speed is increased, and control for decreasing the rotation speed is performed on the control unit side. If it does so, the rotational speed of the discharge roller 24 will not become constant, printing accuracy will fall, and the possibility that image quality will fall arises.

[1-4-2. Correction coefficient calculation process]
The control unit 35 of the present embodiment executes a correction coefficient calculation process for calculating a correction coefficient for adjusting the output waveform at the time of eccentricity to a theoretical output waveform. Thereby, it becomes possible to remove the influence by eccentricity.

  The correction coefficient calculation process is executed at an arbitrary timing, such as when the power is turned on or when the printer 10 is returned from the standby state (power saving mode) after the printer 10 is manufactured and before the printer 10 is used.

  Here, in the present embodiment, the correction coefficient is defined as follows.

FH = theoretical duty ratio DH / detected duty ratio DH (Equation 3)
FL = theoretical duty ratio DL / detected duty ratio DL (Expression 4)

  Note that the definition of the correction coefficient is not limited to this. The 1 / detection ratio may be set as a correction coefficient. The theoretical duty ratio (hereinafter referred to as “theoretical ratio” as appropriate) is a duty ratio when a plate-like member is attached to a roller without eccentricity. The detected duty ratio (hereinafter referred to as “detection ratio” as appropriate) is a duty ratio obtained from an output waveform from the sensor unit 32.

  FIG. 9 is a flowchart illustrating an example of a processing procedure of the correction coefficient calculation process.

  When the correction coefficient calculation process is started, the control unit 35 drives the discharge roller 24 to rotate at a constant speed (S10).

  While the discharge roller 24 is driven to rotate at a constant speed, the duty ratio calculation unit 35a acquires an output waveform from the light receiving unit 32b of the sensor unit 32 (S11). Here, a case where the output waveform is the waveform shown in FIG. 8B will be described as an example.

  The duty ratio calculation unit 35a calculates the detection ratio (for each cycle) of the non-transmissive patterns P0 to P19 from the output waveform of the light receiving unit 32b (S12).

In the example shown in FIG. 8, the calculation results of the duty ratio for the non-transmissive pattern P0 are DH _P0 = 75% and DL _P0 = 25%. The calculation result of the duty ratio for the non-transmissive patterns P5 and P15 is DH _{P5, P15} = DL _{P5, P15} = 50%. The calculation results of the duty ratio for the non-transmissive pattern P10 are DH _P10 = 25% and DL _P10 = 75%. Similarly, the duty ratios DH _Pi and DL _{Pi of} other non-transmissive patterns Pi (i = 1 to 4, 6 to 9, 11 to 14, 16 to 19) are also obtained.

The correction coefficient calculator 35b calculates a theoretical ratio (S13). The theoretical duty ratio is determined by the position of the light receiving portion 32b with respect to the plate-like member 31 when the plate-like member 31 is attached with no eccentricity. For example, in the case of FIGS. 4 and 6, when the light receiving unit 32b is arranged at a position corresponding to C1, the theoretical duty ratio is DH _C1 = t1 / t4 = 25%, DL _C1 = (t4 -T1) / t4 = 75%. When the light receiving unit 32b is arranged at a position corresponding to C2, the theoretical duty ratio is DH _C2 = DL _C2 = 50%. When the light receiving unit 32b is arranged at a position corresponding to C3, the theoretical duty ratio is DH _C3 = 25% and DL _C3 = 75%.

In the present embodiment, an example will be described in which the light receiving unit 32b is disposed at a position corresponding to C2, and the duty ratios DH _C2 and DL _C2 are theoretical duty ratios.

  The correction coefficient calculation unit 35b calculates correction coefficients FH and FL (for each period) for each of the non-transmissive patterns P0 to P19 (S14).

In the example of FIG. 8, the correction coefficients of the non-transmissive pattern P0 are FH _P0 = DH _C2 / DH _P0 = _50/75 = 2/3, and FL _P0 = DL _C2 / DL _P0 = _50/25 = 2. Similarly, the correction coefficients of the non-transmissive patterns P5 and P15 are FH _{P5, P15} = FL _{P5, P15} = DH _C2 / DH _{P5, P15} = 50/50 = 1. The correction coefficients of the non-transmissive pattern P10 are FH _P10 = DH _C2 / DH _P10 = _50/25 = 2 and FL _P10 = DL _C2 / DL _P10 = _50/75 = 2/3. Similarly, correction coefficients FH _Pi and FL _{Pi of} other non-transmissive patterns Pi are also obtained.

[1-4-3. Rotation speed detection process]
FIG. 10 is a flowchart illustrating an example of a processing procedure of the rotation speed calculation process. The rotation speed calculation process is executed, for example, when the recording medium 100 is transported. In addition, the time of conveyance of the recording medium 100 may include not only when the recording medium 100 is in direct contact with the roller base 24b but also from the start to the end of the printing operation.

  After starting the rotation operation of the discharge roller 24, the control unit 35 starts the rotation speed calculation process (S20).

  The waveform correction unit 35c acquires the output waveform from the sensor unit 32 (S21), and corrects the output waveform with a correction coefficient (S22).

As described above, IDs of P0 to P19 are assigned to the non-transparent patterns, and the non-transparent pattern is detected on the control unit 35 side. That is, the control unit 35 grasps the correspondence relationship between the waveform and the non-transmission pattern, and the waveform obtained by detecting the non-transmission pattern Pj (j = 0 to the number of patterns−1, 19 in FIG. 7). Is corrected using the correction coefficient FH _Pj and the correction coefficient FL _Pj of the non-transmissive pattern Pj.

  Specifically, in this embodiment, in each cycle, the length of the H level period is multiplied by the correction coefficient FH to adjust the length of the H level period, and the length of the L level period is adjusted. The length of the L level period is adjusted by multiplying by the correction coefficient FH.

For example, in the case of the non-transmissive pattern P0 shown in FIG. 8, the length t3 of the H level period is multiplied by the correction coefficient FH _P0 = 2/3. Similarly, the length of the L level period (t4−t3) is multiplied by the correction coefficient FL _P0 = 2. Similarly, the length of the H level period and the length of the L level period in other periods are also adjusted.

  The rotation speed calculation unit 35d calculates the rotation speed using the adjusted output waveform (S23). In the present embodiment, the rotation speed is calculated by calculating an integral value of the waveform for each waveform (for each of a plurality of patterns). In step S22, the length of the H level period and the length of the L level period of the waveform are corrected so as not to be eccentric, so that there is an attachment error between the shaft body 24a of the discharge roller 24 and the plate member 31. Even when the eccentricity occurs, the rotation speed can be detected with high accuracy.

[Effects]
The rotary encoder 30 of the present embodiment calculates a correction coefficient for adjusting the output waveform at the time of eccentricity to a theoretical output waveform by a correction coefficient calculation process performed in advance, and the correction coefficient is calculated when the recording medium 100 is conveyed. Since the output waveform from the sensor unit 32 is corrected using, the influence of eccentricity can be removed. That is, it becomes possible to remove the deviation between the actual rotation speed of the roller and the detected rotation speed due to the mounting error. As a result, it is possible to prevent overlapping or stretching of the printed images, and to prevent deterioration of the image quality of the printed images.

  Further, the rotary encoder 30 according to the present embodiment can determine the influence of eccentricity by a simple calculation of calculating the ratio between the transmissive region and the non-transmissive region.

(Modification 1)
In the said embodiment, although the case where the rectangular non-transmissive patterns P0-P19 were printed on the plate-shaped member 31 was demonstrated to the example, it is not restricted to this. The non-transmissive patterns P0 to P19, that is, the shape of the non-transmissive region 33 may be other shapes.

  11A to 11D are diagrams illustrating an example of the shape of the non-transmissive region 33 in the first modification.

  FIG. 11A shows a trapezoidal non-transmissive region 33a. In FIG. 11A, the non-transmissive region 33 a is arranged so that the upper side comes to the outer peripheral side of the plate-like member 31.

  FIG. 11B shows a non-transmissive region 33b having an isosceles triangle shape. In FIG. 11B, the vertices of the isosceles triangle are arranged so as to come to the outer peripheral side of the plate-like member 31.

  In the case of FIG. 11A and FIG. 11B, the amount of change in the duty ratio becomes greater with respect to the distance from the axis than in the rectangular non-transmissive region 33.

  FIG. 11C shows a case where the trapezoidal non-transmissive regions 33c are arranged in the opposite direction to FIG. 11A. FIG. 11D shows a case where the non-transmissive regions 33d having an isosceles triangle shape are arranged in the opposite direction to FIG. 11B. In FIG. 11C and FIG. 11D, the amount of change in the duty ratio with respect to the distance is smaller than that in the case where the rectangular non-transmissive region 33 is provided, but it is only necessary that the duty ratio with respect to the distance is not constant. Absent.

  Also in the first modification, as in the first embodiment, it is possible to remove the influence of eccentricity from the output waveform of the sensor unit 32 when the recording medium 100 is conveyed.

(Modification 2)
In the said embodiment, although the plate-shaped member 31 was comprised with the transparent member and demonstrated the case where the non-transmissive patterns P0-P19 were provided as the non-transmissive area | region 33, it was not restricted to this.

  FIG. 12 is a perspective view showing an example of a plate-like member 31a in the rotary encoder 30a of the second modification. In FIG. 12, the case where the slit is formed in the non-transparent disk shaped plate-shaped member 31a is shown. The slit is formed in a prismatic shape, and the shape of the outer periphery of the slit is the same as that of the embodiment or the first modification. The slit portion constitutes the transmission region 34a, and the plate-like member 31a corresponds to the non-transmission region 33a.

(Modification 3)
In the embodiment and the first and second modifications, the actual output waveform from the sensor unit 32 is corrected using the theoretical output waveform.

  In this modification, the waveform is complemented using the theoretical output waveform.

  FIG. 13 is a waveform diagram illustrating an example of waveform interpolation in the third modification.

  In this case, even when the ink mist adheres to the non-transmissive area 33 of the plate-like member 31 and the non-transmissive area 33 cannot be detected as in the rotary encoder 30 for detecting the rotational speed of the print head, the rotation can be performed. The speed can be estimated.

(Other embodiments)
Although the rotary encoder according to the embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

  (1) Although the number of non-transmissive areas and the number of transmissive areas are set to 20 for the sake of explanation in the above-described embodiments and modifications, the present invention is not limited to this. In practice, a number of non-transmissive areas and transmissive areas corresponding to the printing accuracy, such as 150 dpi intervals or 300 dpi intervals, are provided.

  (2) In the above-described embodiment and modification, the case where the sensor unit 32 sandwiches the plate-like member 31 between the light source 32a and the light receiving unit 32b is described as an example, but the present invention is not limited to this. You may comprise so that the light output from the light source 32a and the light reflected by the plate-shaped member 31 may be received.

  (3) Further, the arithmetic processing unit may be specifically configured as a computer system including a microprocessor, ROM, RAM, hard disk drive, display unit, keyboard, mouse, and the like. A computer program is stored in the RAM or hard disk drive. Each device achieves its functions by the microprocessor operating according to the computer program. Here, the computer program is configured by combining a plurality of instruction codes indicating instructions for the computer in order to achieve a predetermined function.

  Furthermore, some or all of the constituent elements constituting the arithmetic processing unit may be configured by one system LSI. The system LSI is an ultra-multifunctional LSI manufactured by integrating a plurality of components on a single chip, and specifically, a computer system including a microprocessor, ROM, RAM, and the like. . A computer program is stored in the RAM. The system LSI achieves its functions by the microprocessor operating according to the computer program.

  Furthermore, some or all of the constituent elements constituting the arithmetic processing unit may be constituted by an IC (Integrated Circuit) card that can be attached to and detached from each device or a single module. The IC card or module is a computer system that includes a microprocessor, ROM, RAM, and the like. The IC card or the module may include the super multifunctional LSI described above. The IC card or the module achieves its function by the microprocessor operating according to the computer program. This IC card or this module may have tamper resistance.

  Further, the present invention may be a method executed by the arithmetic processing unit described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the above computer program.

  Furthermore, the present invention provides a non-transitory recording medium capable of reading the computer program or the digital signal, such as a flexible disk, a hard disk, a CD-ROM, an MO, a DVD (Digital Versatile Disc), a DVD-ROM, a DVD. -It may be recorded on a RAM, a BD (Blu-ray (registered trademark) Disc), a semiconductor memory, or the like. The digital signal may be recorded on these non-temporary recording media.

  In the present invention, the computer program or the digital signal may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.

  The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program.

  Further, by recording the program or the digital signal on the non-temporary recording medium and transferring it, or transferring the program or the digital signal via the network or the like, another independent computer It may be implemented by the system.

  Furthermore, the above embodiment and the above modification examples may be combined.

  The present invention is useful for a rotary encoder that measures the rotational speed of a rotating body such as a conveyance roller in a printer, a scanner, or a multifunction machine.

20 Transport mechanism 21 Frame 22 Pick roller 23 Feed roller 24 Discharge roller 24a Shaft body 24b Roller base 25 Motor 30, 30a Rotary encoder 31, 31a Plate member 32 Sensor unit 32a Light source 32b Light receiving unit 33, 33a, 33b, 33c, 33d Non-transmissive area 34, 34a Transparent area 35 Control section 35a Duty ratio calculation section 35b Correction coefficient calculation section 35c Waveform correction section 35d Rotational speed calculation section 100 Recording medium P0, P5, P10, Pi Non-transmission pattern

Claims (9)

A plate-like member that is attached perpendicular to the rotation axis of the rotating body and rotates around the rotation axis, and has a plurality of patterns each composed of a transmission region that transmits light and a non-transmission region that does not transmit light. A plate-like member that is arranged radially and in which the ratio of the length in the circumferential direction between the transmission region and the non-transmission region changes according to the distance from the center of the plurality of patterns;
A detection unit that detects whether the region of the plate-like member that passes through a predetermined detection position is the transmission region or the non-transmission region when the rotating body rotates about the rotation axis; ,
Rotary encoder. The plurality of patterns are configured such that the ratio of the transmission region increases as the distance from the center of the plurality of patterns increases.
The rotary encoder according to claim 1. The plurality of patterns are configured such that the ratio of the non-transmissive region increases as the distance from the center of the plurality of patterns increases.
The rotary encoder according to claim 1. The plate-like member is a transparent member,
The non-transparent area is a non-transparent area printed on the plate-like member.
The rotary encoder according to any one of claims 1 to 3. The plate-like member is a non-transparent member,
As the transmission region, a slit is formed in the plate-like member,
The rotary encoder according to any one of claims 1 to 3. The shape of the transmissive region or the non-transmissive region is rectangular.
The rotary encoder according to any one of claims 1 to 5. The detection unit includes a light source that emits light, and a light receiving unit that receives light from the light source via the plate-like member.
The rotary encoder of any one of Claims 1-6. The rotary encoder according to any one of claims 1 to 6,
In a state where the rotating body is rotated at a constant speed, from the detection result of the detection unit, for each of the plurality of patterns, the time during which the transmission region passes the detection position and the non-transmission region are the detection position. A detection ratio calculation unit for calculating a detection ratio with respect to the time passing through
Assuming that the plate-like member is attached to the rotating body without eccentricity, a theoretical ratio between the time when the transmission region passes the detection position and the time when the non-transmission region passes the detection position is obtained. Then, by calculating the ratio between the theoretical ratio and the detection ratio, a correction coefficient for correcting the influence of structural eccentricity between the rotating body and the plate member is calculated from the detection result in the detection unit. A correction coefficient calculation unit
Printer. further,
When the recording medium is transported by the rotating body, a detection result is obtained from the detection unit of the rotary encoder, and using the correction coefficient, the passage time of the detection position of the transmission region and the detection position of the non-transmission region A waveform correction unit for correcting the transit time of
A rotation speed calculation unit that calculates a rotation speed of the rotating body using the detection result corrected by the waveform correction unit;
The printer according to claim 8.

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