Patent Grant
7866903
1. Technical Field
The present invention relates to a printer and a method of adjusting emission intensity of an optical sensor that is mounted on the printer.
2. Related Art
There is, as a printer for performing a printing operation on a printing medium, an ink jet printer including a print head for ejecting an ink to a printing medium and a carriage mounted with the print head. An optical sensor having a light-emitting element and a light-receiving element is widely used in such a type of printers. For example, the optical sensor is attached to a bottom surface of a carriage and is used to detect an end of a printing medium housed in the printer.
An optical sensor is exemplified which outputs a low-level signal at the time of detecting a printing medium and outputs a high-level signal at the time of not detecting the printing medium. When the optical sensor detects an end of the printing medium (an end close to a start point in the traveling direction of the carriage), it is judged whether a low level lasts by a predetermined size DW after an output of the sensor is changed from a high level to the low level. The size DW is set to be sufficiently larger than the width of a rib. When the low level lasts by DW, it is judged that the printing medium is detected but not the rib. As a result, the printer recognizes a coordinate of the carriage as an end of the printing medium when the high level is changed to the low level (for example, see JP-A-2005-081750).
As a printer mounted with an optical sensor, there is a printer which includes a printing unit for performing a printing operation on a printing medium, a supporting unit for supporting the printing medium to which the printing operation is performed by the printing unit, and an optical sensor that is disposed to be opposed to the supporting unit and to be movable relative to the supporting unit, that has a light-emitting portion and a light-receiving portion, and that generates a signal corresponding to the intensity of light received by the light-receiving portion (for example, see JP-A-2005-313603).
Such a printer detects a printing medium by comparing a predetermined threshold value with a value obtained by sampling a signal generated from the optical sensor with a predetermined period when the optical sensor moves relative to the supporting unit at the time of performing a printing operation. At the time of checking a state of the supporting unit, the printer samples the signal generated from the optical sensor with a period different from the predetermined period when the optical sensor moves relative to the supporting unit and changes a predetermined threshold value on the basis of the value obtained by the sampling.
When the existence of a printing medium is detected by the use of an optical sensor, it is preferable that a difference in output voltage between the existence and the non-existence of a printing medium is large. Accordingly, a value of current flowing in a light-emitting element of the optical sensor need be set equal to or greater than a predetermined value. In consideration of deterioration in output due to a variation of the optical sensor with the lapse of time, uneven outputs of optical sensors, or printing operations on various printing mediums, it is necessary to keep the output voltage of the optical sensor constant even when such conditions vary.
When a circuit mounted with an optical sensor is designed in consideration of such a problem, a phenomenon that a value of current flowing in the optical sensor is reduced even with an increase in voltage supplied to the optical sensor may occur due to characteristics of transistors in the circuit. When the output voltage of the optical sensor is small, the voltage supplied to the optical sensor is usually set to the maximum, but the value of current flowing in the optical sensor may not increase. Accordingly, it is required to optimally detect a printing medium even when such a phenomenon occurs.
An advantage of some aspects of the invention is to provide a printer and an emission intensity adjusting method, which allow a printing medium to be detected in the optimum state even when conditions vary.
According to the present invention, there is provided a printer for performing a printing operation on a printing medium, the printer comprising:
The present disclosure relates to the subject matter contained in Japanese patent application No. 2006-246392 filed on Sep. 12, 2006, which is expressly incorporated herein by reference in its entirety.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, a printer and an emission intensity adjusting method according to embodiments of the invention will be described with reference to the drawings.
The printer according to this embodiment is an ink jet printer that carries out a printing operation by ejecting a liquid-like ink to a printing sheet P as a kind of printing medium. As shown in
As shown in
The carriage 3 can be transported in the main scanning direction MS by a guide shaft 17 supported on a support frame 16 fixed to the body chassis 8 and a timing belt 18. That is, the timing belt 18, a part of which is fixed to the carriage 3 (see
Plural nozzles not shown are disposed in the print head 2. Piezoelectric elements (not shown), which are one kind of electrostriction elements and have an excellent response property, are disposed in the print head 2 so as to correspond to the nozzles. Specifically, the piezoelectric elements are disposed at positions in contact with walls of ink passages (not shown). By allowing the walls to be pushed with the actions of the piezoelectric elements, the print head 2 ejects ink from the nozzles disposed at the ends of the passages. Specifically, the print head 2 ejects the ink from an ink ejection surface 2a.
The feed roller 12 is connected to the PF motor 5 through a gear not shown and is driven by the PF motor 5. As shown in
When the feed roller 12 rotates, the surface of the feed roller 12 comes in contact with the separation pad 13. Accordingly, when the feed roller 12 rotates, the uppermost printing sheet P of the printing sheets P placed on the hopper 11 is fed to the discharge side through the contact portion between the surface of the feed roller 12 and the separation pad 13, but the second and subsequent printing sheets P are prevented from a feed to the discharge side by the separation pad 13.
The PF driving roller 6 is connected to the PF motor 5 directly or through a gear not shown. As shown in
The sheet detector 14 includes a detection lever 26 and a photo sensor 27 as shown in
A discharge driving roller 15 is disposed on the discharge side of the printer 1 and is connected to the PF motor 5 through a gear not shown. As shown in
As shown in
The photo sensor 32 of the linear encoder 33 has a light-emitting element 41 and a light-receiving element 42 as shown in
The photo sensor 35 of the rotary encoder 36 includes a light-emitting element 43 and a light-receiving element 44 as shown in
As shown in
As shown in
As described above, in this embodiment, the optical sensor 45 is a reflective photo interrupter having the light-emitting element 46 and the light-receiving element 47. The optical sensor 45 has a light emitting diode as the light-emitting element 46 as shown in
The optical sensor 45 outputs an output signal corresponding to an amount of light received by the light-receiving element 47. That is, the optical sensor 45 outputs an output signal which is at a low level at the time of detecting the printing sheet P and which is at a high level at the time of not detecting the printing sheet P. The output signal is at the low level when the light-receiving element 47 receives the light emitted from the light-emitting element 46 and reflected by the printing sheet P, and is at the high level when the light-receiving element 47 receives the light emitted from the light-emitting element 46 and reflected by the platen 7. In this embodiment, the platen 7 is formed of a black member having low light reflectance. The printing sheet P having light reflectance higher than that of the platen 7 reflects a larger amount of light than the platen 7 does. Accordingly, when the amount of light received by the light-receiving element 47 is great, the output signal is at the low level. On the other hand, when the amount of light received by the light-receiving element 47 is small, the output signal is at the high level. When the amount of light received by the light-receiving element 47 increases (that is, when the value of current flowing in the light-receiving element 47 increases), the level of the output signal decreases. When the amount of light received by the light-receiving element 47 decreases (that is, when the value of current flowing in the light-receiving element 47 decreases), the level of the output signal increases.
As shown in
The end detector 59 has an A/D converter 64 and an end determining section 65. The output signal of the optical sensor 45 is input to the A/D converter 64. The A/D converter 64 has a function of converting an output voltage of the optical sensor 45 into a digital value. For example, in case of a 8-bit A/D converter, 3.3 V is converted into a digital value 255 and 0.0 V is converted into a digital value 0. The end determining section 65 determines the end of the printing sheet P on the basis of the digital value output from the A/D converter 64.
The emission intensity adjusting section 50 includes a transistor 60 disposed between the resistor 53 and the light-emitting element 46 and a D/A converter 61 connected to a base terminal of the transistor 60. The transistor 60 is a PNP type transistor, a collector terminal of which is connected to the light-emitting element 46 and a emitter terminal of which is connected to the inner power supply 52 through the resistor 53.
A path returning from a node between the A/D converter 64 and the end determining section 65 to the D/A converter 61 is provided with an output monitoring section 57 for monitoring the output voltage of the optical sensor 45 to control the adjustment of the emission intensity of the emission intensity adjusting section 50. The D/A converter 61 changes the current from the emitter terminal of the transistor 60 to the collector terminal thereof, that is, the current supplied from the inner power supply 52 to the light-emitting element 46, with a predetermined resolution under the control of the output monitoring section 57, thereby adjusting the emission intensity of the light-emitting element 46. The D/A converter 61 stops the supply of current to the light-emitting element 46 on the basis of a control instruction of the output monitoring section 57. The end determining section 65 and the output monitoring section 57 of the end detector 59 are embodied by calculation means such as a CPU of the controller 37, storage means such as an ROM, an RAM, and a non-volatile memory, and input and output means such as an IO port.
The digital value of the A/D converter 64 is input to the output monitoring section 57. The output monitoring section 57 controls the D/A converter 61 while monitoring the level (output voltage) of the output signal at the time of detecting the printing sheet P and selects the digital value of the D/A converter 61 to acquire the level of the output signal for detecting an end of the printing sheet P. Specifically, the output monitoring section 57 monitors the output voltage of the optical sensor 45 at the time of setting the digital value while raising the digital value of the D/A converter 61 and selects the digital value of the D/A converter 61 when the output voltage is in minimum. The output monitoring section 57 selects the digital value of the D/A converter 61 at the time of outputting the output voltage, when it is determined that the output voltage is lower than a target output voltage while monitoring the output voltage of the optical sensor 45 by the use of the digital values input from the A/D converter 64.
When the digital value of D/A converter 61 is raised as indicated by a straight line “D/A” in
In this embodiment, the output monitoring section 57 monitors the output voltage of the optical sensor 45 while raising the digital value of the D/A converter and specifies the digital value of the D/A converter 61 (the value of the point indicated by “A3” in
In
First, the output monitoring section 57 receives D/A=0 and V_clip=3.3 V as an initial value (step S101). Next, the output monitoring section 57 determines whether D/A is equal to or greater than D/A_max (step S102). When it is determined in step S102 that D/A is equal to or greater than D/A_max, the process of step S109 is performed. On the other hand, when it is determined in step S102 that D/A is smaller than D/A_max, the process of step S103 is performed. At the initial time of processes, since D/A is smaller than D/A_max, the process of step S103 is performed. Next, the output monitoring section 57 raises the digital value of the D/A converter 61 by 1 (step S103). Then, the output monitoring section 57 acquires the output voltage (V_temp) of the optical sensor which is obtained by the use of D/A set in step S103 (step S104).
Next, the output monitoring section 57 determines whether V_temp acquired in step S104 is lower than the target output voltage (V_comp) (step S105). When it is determined in step S105 that V_temp is lower than V_comp, the process of step S108 is performed. On the other hand, when it is determined in step S105 that V_temp is equal to or greater than V_comp, the output monitoring section 57 determines whether V_temp is lower than V_clip (3.3 V at the initial time) (step S106).
When it is determined in step S106 that V_temp is lower than V_clip (3.3 V at the initial time), the output monitoring section 57 sets V_clip to V_temp acquired in step S104 and sets D/A_clip, which is a candidate for selection, to D/A set in step S103 (step S107). Next, the output monitoring section 57 returns the process of step S102. On the other hand, when it is determined in step S106 that V_temp is equal to or greater than V_clip (3.3 V at the initial time), the output monitoring section 57 returns to the process of step S102 without performing the process of step S107.
So long as V_temp is unilaterally lowered with an increase in D/A, the output monitoring section 57 performs the process of S107 and compares the present output voltage with the output voltage acquired in the previous routine, in step S106 of the subsequent routine. On the other hand, when V_temp is raised with an increase in D/A, the output monitoring section 57 performs the process of step S102 without performing the process of step S107. Accordingly, the output monitoring section 57 compares the present output voltage with the lower output voltage in the previous routine, in step S106 of the subsequent routine.
In this way, the output monitoring section 57 repeats the processes of steps S102 to S107 to grasp the minimum V_temp. In the course of performing the processes of steps S102 to S107, when it is determined in step S105 that V_temp is lower than V_comp, the output monitoring section 57 sets D/A_g to D/A at that time and allows the printing operation to be carried out by the use of D/A_g (step S108). When the processes of steps S102 to S107 are repeated without performing the process of step S108 and it is determined in step S102 that D/A is equal to or greater than D/A_max, the output monitoring section 57 sets D/A_g to D/A_clip which is a candidate for selection by that time and allows the printing operation to be carried out by the use of the relevant D/A_g (step S109). When the process of step S108 or S109 is ended, the processes of the emission intensity adjusting method are finished.
In the printer 1 having the above-mentioned configuration, the carriage 3 driven by the CR motor 4 reciprocates in the main scanning direction MS while a printing sheet P fed into the printer 1 from the hopper 11 by the feed roller 12 and the separation pad 13 is transported in the sub scanning direction SS by the use of the PF driving roller 6 driven to rotate by the PF motor 5. When the carriage 3 reciprocates, an ink is ejected from the print head 2 to perform a printing operation on the printing sheet P. When the printing operation on the printing sheet P is finished, the printing sheet P is discharged to the outside from the printer by the use of the discharge driving roller 15 and the like.
Before performing the printing operation, the printing sheet P is transported to a position where the printing sheet can be detected by the optical sensor 45. The output monitoring section 57 monitors the output voltage of the optical sensor 45 using the digital value while raising the digital value of the D/A converter 61 in accordance with the processes of the above-mentioned flowchart. As a result, the digital value of the D/A converter 61 is selected when the output voltage of the optical sensor 45 is in minimum or less than the target output voltage. When the digital value of the D/A converter 61 suitable for detecting an end of a printing sheet is selected, the controller 37 allows current to flow in the light-emitting element 46 on the basis of the digital value. As a result, an output signal is output from the optical sensor 45 and the output signal is input to the end detector 59. The end detector 59 detects an end of a printing sheet P. Then, a variety of control operations are performed on the printer 1 on the basis of the end detection result of the printing sheet P.
In this embodiment, the printing sheet P is transported in the sub scanning direction SS by the use of the PF driving roller 6 and the like in the state where the carriage 3 is stopped at the position where the printing sheet P can be detected by the optical sensor 45 and the end detector 59 detects the leading end of the printing sheet Pin the sub scanning direction. However, the end detector 59 may detects the trailing end of the printing sheet P in the sub scanning direction SS. The end detector 59 may detect an end of the printing sheet P in the main scanning direction MS (an end in the width direction).
As shown in
Step S201, step S202, step S203, step S204, step S205, step S207, step S208, and step S209 in the flowchart of
Specifically, in step S206 of
An emission intensity adjusting method may be employed in which the processes of step S105 and step S108 in the flowchart of
The printer 1 according to this embodiment includes the optical sensor 45 that detects the printing medium, the emission intensity adjusting section 50 that adjusts emission intensity of a light-emitting element 46 constituting the optical sensor 45, and the output monitoring section 57 that monitors an output voltage of the optical sensor 45 so as to control the emission intensity adjusting section 50 to adjust the emission intensity. Accordingly, in the course of monitoring the output voltage of the optical sensor 45, it is possible to specify the condition of the emission intensity adjusting section 50 when the output voltage thereof is lowered. Therefore, even when the relationship between the adjustment condition of the emission intensity adjusting section 50 and the output voltage of the optical sensor 45 varies due to a deterioration of the optical sensor 45 with the lapse of time resulting from attachment of ink mist, uneven performance of the optical sensor 45, the type of the printing sheet P, and characteristics of the transistor 60 in the circuit on which the optical sensor 45 is mounted, a sufficient amount of current to accurately detect an end of a printing sheet P can be made to flow in the light-emitting element 46.
The printer 1 according to this embodiment includes as the emission intensity adjusting section 50 the transistor 60 disposed between the inner power supply 52 for supplying current to the light-emitting element 46 and the light-emitting element 46 and the D/A converter 61 connected to the base terminal of the transistor 60. The output monitoring section 57 acquires an output voltage of the optical sensor 45 while varying the digital value of the D/A converter 61. Accordingly, it is possible to select the digital value of the D/A converter 61 to optimize the value of current flowing in the light-emitting element 46 while monitoring the variation of the output voltage of the optical sensor 45.
The output monitoring section 57 of the printer 1 selects the digital value of the D/A converter 61 when acquiring the minimum or minimal value of the output voltage of the optical sensor 45. The minimum value of the output voltage of the optical sensor 45 can be obtained by checking the output voltage of the optical sensor 45 at the time of varying the digital value within the range of the digital value having been varied. The minimal value of the output voltage of the optical sensor 45 may be obtained while varying the digital value, in addition to the method of acquiring the minimum value. When the minimal value of the output voltage is obtained in the way of varying the digital value, the digital value need not be varied to the maximum value. Accordingly, it is possible to select the digital value of the D/A converter 61 to optimize the emission intensity with a rapid process.
The output monitoring section 57 of the printer 1 selects the digital value of the D/A converter 61 to specify the output voltage when the output voltage of the optical sensor 45 is equal to or less than the target output voltage. Accordingly, since the digital value of the D/A converter 61 need not be varied to the maximum value, it is possible to select the digital value of the D/A converter 61 to optimize the emission intensity with a further rapid process. Even when the output voltage of the optical sensor 45 is not the minimum or minimal value, it is possible to find out the digital value to acquire the output voltage equal to or less than the target output voltage.
The printer 1 according to this embodiment includes the print head 2 that ejects an ink to the printing sheet P and the carriage 3 that is mounted with the print head 2, and the optical sensor 45 is attached to the carriage 3 so as to detect an end of the printing sheet P. When it is necessary to allow current having a value as large as possible to flow in the light-emitting element 46 in order to increase the difference in output voltage as greatly as possible depending on the existence of the printing sheet P, it is possible to optimize the adjustment condition of the emission intensity adjusting section 50. Specifically, when the output value of the optical sensor 45 is small, the value of current flowing in the light-emitting element 46 may not be increased only by simply raising the digital value of the D/A converter 61. Accordingly, by monitoring the output voltage of the optical sensor 45, it is necessary to acquire the adjustment condition of the emission intensity adjusting section 50 that the output voltage is small and the value of current flowing in the light-emitting element 46 is great.
In this embodiment, the emission intensity of the light-emitting element 46 is adjusted by the use of the emission intensity adjusting section 50. Accordingly, it is possible to maintain the precision for detecting an end of a printing sheet P and thus to stably detect the end of the printing sheet P. Accordingly, even when a so-called no-edge printing operation is performed on the printing sheet P, it is possible to reduce an amount of wasted ink ejected to areas other than the printing sheet P. That is, when an error temporally occurring at the position for detecting the end of the printing sheet P is great and thus the end of the printing sheet P cannot be stably detected, the print head 2 necessarily ejects an ink to an extra wide area so as to properly maintain a printing state of the no-edge printing operation.
On the contrary, when an error temporally occurring at the position for detecting the end of the printing sheet P is not great and thus the end of the printing sheet P can be stably detected, the print head 2 need not eject an ink to then extra wide area, thereby properly maintaining a printing state of the no-edge printing operation. In this embodiment, even when the no-edge printing operation is performed on the printing sheet P, it is possible to reduce the amount of wasted ink. As a result, it is possible to suppress the occurrence of ink mist which causes the variation in output voltage of the optical sensor 45. In business printers using large printing sheets P such as A1 or A2 as printing mediums, since the amount of wasted ink can be greatly reduced, the advantage is more marked in the business printers than in the home printers using small printing sheets P such as A4 as printing mediums.
In this embodiment, the emission intensity adjusting section 50 includes the transistor 60 and the D/A converter 61. Accordingly, it is possible to supply stepwise current corresponding to the resolution of the D/A converter 61 to the light-emitting element 46. As a result, it is possible to finely adjust the brightness of the light-emitting element 46.
Although the printer and the emission intensity adjusting method according to the exemplary embodiments of the invention have been described above, the invention is not limited to the embodiments but may be modified in various forms without departing from the gist of the invention.
In addition to the detection of an end of a sheet, the printer and the emission intensity adjusting method according to the invention can be used for detection of a portion of a sheet other than an end of the sheet and different optical detectors such as the linear encoder 33 and the rotary encoder 36. When the invention is applied to the sheet detector 14, the printing sheet P is an object to be detected by the sheet detector 14. When the invention is applied to the linear encoder 33, the carriage 3 is an object to be detected by the linear encoder 33. When the invention is applied to the rotary encoder 36, the PF driving roller 6 is an object to be detected by the rotary encoder 36.
In the embodiments, the controller 37 physically separated from the optical sensor 45 includes the emission intensity adjusting section 50, the output monitoring section 57, and the resistors 53 and 55. However, the emission intensity adjusting section 50, the output monitoring section 57, and the resistors 53 and 55 may be disposed in the optical sensor 45.
In the embodiments, the optical sensor 45 is a reflective photo interrupter. Otherwise, the optical sensor 45 may be a light transmitting and receiving sensor in which a light-emitting surface of a light-emitting element and a light-receiving surface of a light-receiving element are disposed opposite to each other. In this case, it is preferable that the brightness of the light-emitting element is adjusted so that the level of an output signal at the time of not detecting an object is in a predetermined range. As described above, the output signal when the light from the light-emitting element is more received by the light-receiving element greatly varies in level due to the ink mist and the temporal deterioration in amount of light emitted from the light-emitting element. Accordingly, with the configuration of the reflective sensor type, it is possible to properly suppress the variation in level of the output signal and thus to more properly maintain the detection precision. When the optical sensor 45 is the light transmitting and receiving sensor, it is preferable that a level checking process of checking the level of the output signal at the time of not detecting an object is performed after adjusting the level of the output signal at the time of not detecting an object.
In the embodiments, the ink cartridge 21 is mounted on the carriage 3. Otherwise, the ink cartridge may be fixed to the body chassis 8. In this case, the ink cartridge fixed to the body chassis 8 and the print head 3 mounted on the carriage 3 may be connected to each other with a flexible ink supply tube.
In the embodiments, the light-receiving element 47 is a photo transistor. However, the light-receiving element 47 may be a photo diode. The configuration of the emission intensity adjusting section 50 is not limited to the above-mentioned configuration. For example, a variable resistor may be used instead of the D/A converter 61. The transistor 60 may be an NPN type transistor or a field effect transistor (FET).
In step S102 or step S202, it may be determined whether D/A is equal to D/A_max. In step S105 or step S205, it may be determined whether V_temp is equal to or less than V_comp. Instead of selecting the digital value of the D/A converter 61 at the time of acquiring the minimum or minimal value of the output voltage of the optical sensor 45, the output voltage may be acquired continuously and the digital value of the D/A converter 61 under the printing condition may be selected. For example, when plural digital values exist for acquiring the output voltage equal to or less than the target output voltage, a specific digital value may be randomly selected from the plural digital values and current may be made to flow in the light-emitting element 46 of the optical sensor 45 by the use of the selected digital value. In this case, since the selected digital value does not set the output voltage of the optical sensor 45 to the minimum but serves to acquire the output voltage equal to or less than the target output voltage, it is possible to obtain sufficient emission intensity.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-246392 | Sep 2006 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4284884 | Dyment et al. | Aug 1981 | A |
| 6348697 | Kitajima | Feb 2002 | B1 |
| 6720544 | Barna et al. | Apr 2004 | B2 |
| 20030021608 | Morita et al. | Jan 2003 | A1 |
| 20030031476 | Takeuchi et al. | Feb 2003 | A1 |
| Number | Date | Country |
|---|---|---|
| 03048466 | Mar 1991 | JP |
| 6-271147 | Sep 1994 | JP |
| 06271147 | Sep 1994 | JP |
| 2000-109243 | Apr 2000 | JP |
| 2000-289885 | Oct 2000 | JP |
| 2003-307976 | Oct 2003 | JP |
| 2005-081750 | Mar 2005 | JP |
| 2005-313603 | Nov 2005 | JP |
| 2005308593 | Nov 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080063459 A1 | Mar 2008 | US |
