JP2003205654A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide printing under conditions suitable for the type of paper, to be able to transport the paper with high accuracy and speed, and to prevent the printing area from being displaced even when the paper is skewed. It is an object to provide an image forming apparatus. An inkjet printer (1) includes a motion sensor (70) in a paper transport path (4), uses a paper position signal output by the motion sensor (70) to determine the type of paper (P), and according to the paper type. Change the printing conditions. Further, the inkjet printer 1 uses the paper position signal output by the motion sensor 70 to generate a paper P
Of the sheet P, and the leading and trailing edges of the sheet P are detected. The inkjet printer 1 controls the conveyance of the paper P and the reciprocation of the carriage 31 based on the results.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, it is possible to set printing conditions such as an ink discharge amount according to the type of paper used. However, because there was no means to determine the type of paper set in the paper feed tray, if you accidentally feed a different type of paper from the settings, the paper will be printed under inappropriate conditions, As a result, the printed part may be blurred or faint.

Further, in the conventional printer, the rotation of a stepping motor or a DC motor with an encoder is transmitted to a conveying roller via a gear train, and a sheet conveying mechanism for feeding a sheet by the conveying roller is provided. And
In this paper transport mechanism, the amount of paper transport is controlled by controlling the rotation amount of the motor.

[0004]

However, in the above control method, the rotational pitch error due to the structure of the motor, the accuracy error of the gear that occurs during manufacturing, the outer diameter error of the transport roller, and the transport amount depending on the paper used. Due to the error and so on, it was not possible to convey the paper with high accuracy.

Further, in order to control the conveyance of the paper, it is necessary to equip a means for detecting the front end and the rear end in the paper conveyance direction as an independent means. Further, in the conventional inkjet printer, when the paper conveyance direction is skewed from the original direction, the printing range is deviated from the center of the paper or the ink is ejected to the outside of the paper. There was a problem that it would get dirty.

The present invention has been made in view of the above points, and can print under conditions suitable for the type of paper, can carry out paper with high accuracy and speed, and have independent means for detecting the edge of the paper. It is an object of the present invention to provide an image forming apparatus having the features of not requiring the above and preventing the shift of the print area even when the paper is skewed.

[0007]

Means for Solving the Problems and Effects of the Invention (1) The invention of claim 1 obtains position information concerning the position of a sheet to be conveyed, and forms an image based on the position information. The surface of the paper is irradiated with a coherent light beam, the reflected light reflected by the surface of the paper is received, and a paper position signal relating to the position of the paper is emitted according to the received reflected light. The gist of an image forming apparatus is characterized by including a sheet position signal detecting unit and a surface state determining unit that determines a surface state of the sheet based on the sheet position signal.

In the image forming apparatus of the present invention, since the surface state of the sheet (for example, the type of sheet) can be discriminated by the surface state discriminating means, for example, the image forming condition is set according to the discriminated sheet state. Can be changed. As a result, the image forming apparatus of the present invention can perform printing under conditions suitable for the type and state of paper, and as a result,
High quality printing is possible. (2) According to the invention of claim 2, in the surface state determining means,
The image according to claim 1, wherein the surface condition of the paper is determined by comparing a reference signal stored in advance corresponding to the surface condition of the paper with the paper position signal. The forming device is the gist.

The present invention exemplifies the surface state determining means. In this surface state determination means, for example, a reference signal closest to the sheet position signal is selected from the reference signals stored in advance, and the surface state corresponding to the reference signal is the current sheet surface state. Can be determined. (3) In the invention of claim 3, the surface state determining means is 2
The image forming apparatus according to claim 1 or 2, wherein the surface state of the sheet is determined by using an average value of the sheet position signals captured more than once.

In the image forming apparatus of the present invention, the surface condition of the sheet is determined by using the average value of the sheet position signals captured twice or more. Even if the position signals are mixed, the average value of the paper position signals does not greatly change.

Therefore, in the image forming apparatus of the present invention, the surface condition of the paper can be always correctly identified. (4) According to the invention of claim 4, in the surface state determining means,
The image forming apparatus according to any one of claims 1 to 3, characterized in that a surface state of the paper is determined by using a speckle pattern generated when the light beam is reflected from the paper. .

The present invention exemplifies the surface state determining means. Since the speckle pattern generated by the reflected light from the paper reflects the surface shape of the paper, it varies depending on the state of the paper (for example, the type of paper). Therefore, in the present invention, the state of the paper is identified based on the speckle pattern.

The speckle pattern is an interference pattern generated in reflected light when a coherent light beam is reflected on the surface of an object. (5) The invention of claim 5 is characterized in that the type of the paper is judged based on the surface condition of the paper judged by the surface condition judging means. The image forming apparatus is as a gist.

In the image forming apparatus of the present invention, the surface state determining means determines the surface state of the sheet and determines the type of sheet based on the surface state. Since each type of paper has a different surface state (surface shape) for each type, the type of paper can be determined based on the surface state. (6) The invention of claim 6 is based on the image forming apparatus according to any one of claims 1 to 5, characterized in that an image forming condition is changed according to a surface state of the sheet. .

In the image forming apparatus of the present invention, the image forming condition can be changed according to the surface condition of the sheet identified by the surface condition determining means, so that a high quality image can be formed. The image forming conditions include, for example, when the image forming apparatus is an apparatus that ejects ink (for example, an inkjet printer), the amount of ink droplets, that is, the number of times ink is ejected, the size of droplets, and the like. There is. (7) The invention of claim 7 uses the paper position signal,
The image forming apparatus according to any one of claims 1 to 6, further comprising a sheet conveyance amount detection unit that detects a conveyance amount of the sheet.

The image forming apparatus of the present invention is provided with a paper carry amount detecting means for detecting the carry amount of the paper, and the paper carry amount detecting means can be used to accurately control the carry of the paper, for example. it can. As the sheet conveyance amount detecting means, for example, there is one which detects the sheet conveyance amount by comparing the sheet position signals generated by the sheet position signal generating means in time series when the sheet is being conveyed. (8) The invention according to claim 8 provides the image forming apparatus according to claim 7, characterized in that the conveyance of the sheet is controlled by using the sheet conveyance amount detecting means.

Since the image forming apparatus of the present invention can control the sheet conveying means by using the sheet conveying amount detected by the sheet conveying amount detecting means, the sheet conveying accuracy is high and a high quality image is formed. can do. As a method of controlling the sheet conveying means using the sheet conveying amount detecting means, for example, conveying of the sheet and interruption of the conveying based on the sheet conveying amount detected by the sheet conveying amount detecting means (for example, conveying for image formation) There is a method to determine the timing of (middle). (9) According to the invention of claim 9, by using the paper position signal,
The edge detecting means for detecting that a front end and / or a rear end of the sheet in the conveying direction has passed a predetermined position on the conveying path.
The gist of the image forming apparatus described in any one of 8).

In the image forming apparatus of the present invention, the front end and / or the rear end of the paper can be detected by the end detecting means. Therefore, for example, the conveyance condition of the paper can be set according to the position of the paper in the conveyance path. Can be changed. For example, in order to form a high quality image during the period from the detection of the front edge of the sheet by the edge detection unit to the detection of the rear edge of the sheet (while the sheet is at the position where the image is formed), Precise sheet conveyance is performed, and in cases other than the above, rapid sheet conveyance can be performed in order to shorten the image forming time.

Further, in the image forming apparatus of the present invention, the edge of the sheet can be detected based on the sheet position signal used in the surface state determining means, so that, for example, the mechanical edge detecting means is independent. In comparison with the case where the device is provided in, the device configuration can be simplified and the manufacturing cost can be reduced. (10) The invention according to claim 10 is characterized in that the edge detecting means detects the passage of the front edge and / or the rear edge in the transport direction of the sheet based on the light quantity of the reflected light. The gist of the image forming apparatus described in Item 9.

The present invention exemplifies the edge detecting means.
The edge detecting means of the present invention, for example, as shown in FIG. 6, determines that the front end of the paper does not reach the optical path of the light beam, and the reflected light from the paper does not enter the light receiving element. The front edge of the paper can be detected when the light enters from the paper and the reflected light from the paper enters the light receiving element.

Similarly, as shown in FIG. 9, from the state where the rear end of the paper enters the optical path of the light beam and the reflected light from the paper enters the light receiving element, the rear end of the paper passes through the optical path to reach the light receiving element. The trailing edge of the sheet can be detected when the reflected light is stopped. (11) The invention of claim 11 is characterized in that it comprises skew feeding detection means for detecting skew of the sheet by comparing the sheet position signals in time series.
The gist of the image forming apparatus is described in any one of 10.

In the image forming apparatus of the present invention, for example, when a sheet is being conveyed in the conveying direction, the sheet position signals generated by the sheet position signal generating means are compared in time series so that the skew of the sheet is prevented. A skew amount detecting means for detecting is provided. This image forming apparatus can control the movement of the recording unit in the width direction, for example, based on the amount of skew detected by the skew detecting unit.

The term "skew" means that, for example, when a sheet is conveyed, the sheet moves in a direction different from the original conveying direction. According to a twelfth aspect of the present invention, there is provided a recording unit that can move in the width direction of the sheet and that records on the sheet, and based on the skew amount detected by the skew detection unit, The gist of the image forming apparatus according to claim 11 is characterized in that the movement of the recording means is controlled.

In the image forming apparatus of the present invention, when the skew detection means detects that the sheet is skewed in a specific direction when the sheet is conveyed, the detection result (for example, skew direction) The movement of the recording unit is controlled based on the skew amount (for example, the position of the recording unit when the image is formed on the sheet is set to the skew amount in the direction in which the sheet is skewed). It can be shifted accordingly.

As a result, in the image forming apparatus of the present invention, even if the paper is skewed, the position where the image is formed in the paper does not shift. In addition, the image formation (e.g., ink ejection) by the recording unit does not occur outside the paper and the image forming apparatus is not contaminated. (13) The invention according to claim 13 is characterized in that the movement of the recording means is controlled so that a position where recording is performed on the sheet becomes a set position.
The gist is the image forming apparatus described in 2.

In the image forming apparatus of the present invention, by controlling the movement of the recording means, the position where recording is performed on the paper can be set to the set position. for that reason,
For example, even when the paper is skewed, the position where an image is formed in the paper is displaced, or image formation (e.g., ink ejection) by the recording unit is performed outside the paper, and the image forming apparatus is soiled. Never. (14) According to a fourteenth aspect of the present invention, the skew detection unit detects skew of the sheet by comparing speckle patterns generated when the light rays are reflected from the sheet in time series. Claims 1 to 1, characterized in that
The gist of the image forming apparatus described in any one of 3).

The image forming apparatus of the present invention detects the skew of the paper by comparing the speckle patterns generated in the reflected light from the paper in time series, so that the skew of the paper can be accurately detected. You can Specifically, for example, while the paper is being conveyed, the speckle patterns are time-sequentially compared, the movement direction and the movement amount thereof are measured, and the skew direction and the skew movement of the paper are determined based on the measurement results. The amount can be detected.

The speckle pattern reflects the surface shape of the paper at the position where the light rays are reflected, and when the paper is moved (paper is conveyed or the paper is skewed), the position where the light rays are reflected on the paper is changed. Since it shifts, the speckle pattern of the reflected light also moves accordingly.

That is, the movement of the speckle pattern corresponds to the movement of the paper. Therefore, the moving direction and the moving amount of the sheet can be detected based on the moving direction and the moving amount of the speckle pattern. (15) The invention according to claim 15 uses a light-receiving element having a plurality of pixels arranged two-dimensionally to receive the light beam, and the image according to any one of the above-mentioned items 1 to 14. The forming device is the gist.

Since the image forming apparatus of the present invention includes a light receiving element having a plurality of pixels arranged two-dimensionally, for example, based on the received reflected light, as a two-dimensional image signal, the paper position is determined. A signal can be generated. Therefore,
Using the sheet position signal, for example, when calculating the sheet conveyance amount, the sheet skew amount, or the like, or when determining the state of the sheet,
It is possible to accurately calculate and discriminate them. According to a sixteenth aspect of the present invention, there is provided a recording unit that can move in the width direction of the sheet and can perform recording on the sheet, and the carriage that holds the recording unit detects the sheet position signal. An image forming apparatus according to any one of claims 1 to 15 is characterized by comprising means.

In the image forming apparatus of the present invention, since the paper position signal detecting means is provided on the carriage for holding the recording means, the paper position signal detecting means moves in the width direction of the paper in synchronization with the recording means. To do. Therefore, for example, when the recording unit is moving in the width direction of the paper, by comparing the paper position signals generated by the paper position signal generating unit in time series, the movement amount of the recording unit in the width direction with respect to the paper is determined. Can be detected.

The image forming apparatus of the present invention is, for example,
Since the amount of movement of the recording unit detected as described above can be used to accurately control recording on the sheet by the recording unit, a high-quality image can be formed. As the control of recording on the sheet by the recording unit, for example, there is a method of determining the timing of recording on the sheet by the recording unit based on the moving amount of the recording unit.

(17) According to a seventeenth aspect of the present invention, the paper guide portion for guiding the conveyance of the paper is provided with an opening for preventing the light rays from being reflected when the paper does not exist. The gist of the image forming apparatus according to claim 10 is that.

In the image forming apparatus of the present invention, the paper guide portion for guiding the conveyance of the paper is provided with an opening for not reflecting the light rays when the paper is not present. In detecting the leading or trailing edge in the direction, rays that have deviated from the edge of the paper enter the opening. Therefore, in the image forming apparatus of the present invention, it is possible to reliably prevent reflection of light rays that have deviated from the edge of the paper.

Therefore, the image forming apparatus of the present invention can clearly distinguish between the case where the light beam is reflected by the surface of the paper and the case where the light beam is not reflected, and as a result, the edge of the paper can be accurately detected. Can be accurately detected.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example (embodiment) of an embodiment of an image forming apparatus of the present invention will be described. In the following, an inkjet printer will be described as an example of the image forming apparatus. (Example 1) a) First, FIG. 1 shows the overall configuration of the inkjet printer 1.
Will be explained.

The ink jet printer 1 accommodates a plurality of sheets of paper P, and can feed paper one by one from among them, and a paper transport path for the paper P fed by the paper feed mechanism 10. 4, a paper feed mechanism 20 that conveys the paper P to a paper discharge table (not shown), a printing mechanism 30 that ejects ink onto the paper P that is being conveyed to print (forms an image), the paper feed mechanism 10 and the paper feed mechanism 20. A drive mechanism (not shown) for transmitting a driving force to a roller included in the device, a control mechanism 50 (not shown) for controlling the operation of each of the above parts, and information about the position of the paper P, the type of the paper P, etc. are detected. , The control mechanism 50
And a main body frame 2 that supports each of the above parts.

B) Next, the structure of the paper feed mechanism 10 will be described with reference to FIG. The paper feed mechanism 10 includes a paper feed cassette 11 that is detachably mounted in a cassette mounting recess 2 a formed at the upper end of the rear end of the main body frame 2. This paper feed cassette 11 has its upper side (upper side in FIG. 1).
In addition, a paper table 12 in which a plurality of paper sheets P are stacked is provided. The rear end of the paper tray 12 (on the left side in FIG. 1) is
The main body of the paper feed cassette 11 is swingably pivotally supported,
The front end portion (right side in FIG. 1) has a compression coil spring 13
Is urged upward by.

Further, the paper feed mechanism 10 is provided with a paper feed roller 14 extending in the left-right direction (depth direction in FIG. 1) above the front end of the paper tray 12. This paper feed roller 14
The left and right ends of the sheet are rotatably supported by a pair of left and right side wall plates 3 connected to the body frame 2, and the paper feed roller 14 is driven by a feed motor 62 (not shown) from a drive mechanism (not shown). It is rotated by the driving force transmitted through.

A plurality of sheets P stacked on the paper tray 12 of the paper feed cassette 11 are pressed against the paper feed roller 14 by the compression coil spring 13 via the paper tray 12.
Therefore, when the paper feed roller 14 is rotated counterclockwise by the drive mechanism, the paper P in the uppermost layer in contact with the paper feed roller 14 is directed to the print mechanism 30 in the paper feed direction F (see FIG. 1).
Paper is fed to the right).

C) Next, the construction of the paper feed mechanism 20 is shown in FIG.
It will be described with reference to FIGS. The paper feed mechanism 20 includes a paper transport path 4 that transports the paper P. The paper transport path 4 is a portion of the main body frame 2 between the cassette mounting recess 2a and the paper guide portion 2b extending forward.

Further, the paper feed mechanism 20 is a rubber-made first feed rotatably supported upstream of the print head 36 of the print mechanism 30 (to be described later) of the paper transport path 4 (left side in FIG. 1). A roller 21 is provided. The first feed roller 21 is driven clockwise (clockwise in FIG. 1) by the driving force transmitted from the drive mechanism. Then, with respect to the first feed roller 21, the driven roller 22
Touches from above. The driven roller 22 is rotatably pivotally attached to a lower end portion of a swing arm 24, and the swing arm 24 is pivotally attached to the side wall plate 3 at an upper end portion thereof and at the compression coil spring 23. The driven roller 22 is pressed and urged in the direction in which it is pressed against the first feed roller 21.

Further, the paper feeding mechanism 20 is provided with the paper feeding path 4
The second feed roller 25 made of rubber and rotatably supported by the main body frame 2 is provided on the downstream side of the print head 36. The second feed roller 25 is driven clockwise (clockwise in FIG. 1) by the driving force transmitted from the drive mechanism. A plurality of spur rollers 26 are in contact with the second feed roller 25 from above. Each of the spur rollers 26 is a gear-shaped roller having a plurality of radial protrusions, and is mounted on a mounting plate 27 fixed to a support plate 33 described later at predetermined intervals in the print width direction (depth direction in FIG. 1). It is rotatably supported.

Further, the paper feed mechanism 20 is equipped with a paper edge detection sensor 42 for detecting the presence or absence of the paper P, slightly upstream of the print head 36. This paper edge detection sensor 4
As shown in FIG. 2, the reference numeral 2 designates a rotating portion 41 which is rotatably provided around a shaft 41a and is urged counterclockwise, and when the rotating portion 41 rotates counterclockwise. Turns off,
It is composed of a detection unit 40 which is turned on when it is rotated clockwise.

Next, the operation of the sheet edge detection sensor 42 when the sheet P passes will be described below. Print head 3
When there is no sheet P in the vicinity of 6, the rotating portion 41 is rotated counterclockwise by the urging force, and its tip (right side in FIG. 2) projects above the sheet conveying path 4. There is. At this time, the detection unit 40 is off.

When the sheet P is conveyed from the upstream side and its leading end rotates the rotating portion 41 in the clockwise direction, the detecting portion 40 is turned on. When the paper P further advances and the trailing edge of the sheet P passes through the rotating portion 41, the rotating portion 41 is rotated again in the counterclockwise direction by the biasing force, and the detecting portion 40 is turned off.

With the above-described structure, the sheet P fed from the sheet feeding mechanism 10 is further in contact with the sheet edge detection sensor 42 at its leading edge and then further hits the nip between the first feed roller 21 and the driven roller 22. After being transported, a so-called resist action is performed. Due to this resist action, the paper P
After the front ends of the sheets are aligned, this time, the feed motor 62 is rotationally driven in the opposite direction, and the first feed roller 21 and the second feed roller 21 that have been rotating counterclockwise in FIGS.
The feed roller 25 rotates in the clockwise direction to convey the paper P in the paper feed direction F.

When the first feed roller 21 and the second feed roller 25 are rotationally driven in the clockwise direction by the feed motor 62, the driving force of the feed motor 62 is not transmitted to the paper feed roller 14, so The rotation of the first feed roller 21 and the second feed roller 25 does not hinder the conveyance of the paper P.

D) Next, the structure of the printing mechanism 30 will be described with reference to FIGS. 1 and 2. The printing mechanism 30 is provided on a guide rod 32 supported by a side wall (not shown) and extending left and right (in the depth direction in FIG. 1), and in front of the main body frame 2 (right side in FIG. 1) so as to project upward. The carriage 31 is supported by the support plate 33 and the guide rods 32 and the upper ends of the support plates 33 so as to be movable in the left-right direction.

A cartridge holder 34 is fixed to the carriage 31, and an ink cartridge 35 containing ink for printing is detachably attached to the cartridge holder 34. A print head 36 (printing means) is provided on the carriage 31.
It is attached so as to face the paper transport path 4. The print head 36 is formed with a plurality of inkjet nozzles (not shown) for ejecting the ink supplied from the ink cartridge 35. The inkjet nozzles are, for example, 64 nozzles, which are divided into two rows of 32 nozzles each and arranged in a row.

The carriage 31 can reciprocate in the left-right direction by a driving force transmitted from a carriage driving mechanism (not shown). When printing, while moving the carriage 31 (inkjet nozzle) back and forth,
Based on the dot pattern data to be printed, for example, 6
Jetting is selectively driven from four inkjet nozzles.

E) Next, the structure of the control mechanism 50 (control section) will be described with reference to FIG. As shown in FIG. 4, the control mechanism 50 includes a CPU 51, a ROM 52, a RAM 53, and a correlator 5.
4, a head drive circuit 56, a paper drive circuit 57, a carriage drive circuit 58, and an input / output interface 55 connecting them.

The head drive circuit 56 includes the print head 3
It is connected to 6 and transmits a signal relating to ink ejection drive. The sheet drive circuit 56 is connected to the feed motor 62 and transmits a signal relating to the drive of the feed motor 62. The feed motor 62 is a stepping motor and is driven at a predetermined speed with a predetermined pulse time as a unit. Further, the feed motor 62 drives the paper feed roller 14 of the paper feed mechanism 10, the first feed roller 21 and the second feed roller 25 of the paper feed mechanism 20 via the drive mechanism.

The carriage drive circuit 58 is connected to the carriage drive motor 63 and transmits a signal relating to the drive of the carriage 31. The input / output interface 55 connects the above elements to each other, and
It is connected to the motion sensor 70 via the A / D converter 66 and the amplifier 67, and the paper edge detection sensor 4
It is connected to 2. Furthermore, the communication interface 64
It is connected to the external electronic device 65 via.

The control mechanism 50 includes a motion sensor 7
The movement of the paper P is detected based on the signal transmitted from 0 (paper position signal) and the signal transmitted from the paper edge detection sensor 42, and based on the result, the feed motor 62,
The carriage drive motor 63 and the print head 36 are controlled, and a specific method thereof will be described in detail later.

Further, the control mechanism 50 can perform the same control as the control mechanism in an ordinary ink jet printer, but since it is not related to the present invention, it is omitted. f) Next, the configuration of the motion sensor 70 is shown in FIGS.
Will be explained. As shown in FIG. 1, the motion sensor 70 is provided on the upper side of the paper transport path 4 and upstream of the printing mechanism 30.

As shown in FIG. 4, the motion sensor 70 includes a semiconductor laser 74 for irradiating the sheet P with a laser beam and a lens 7 for collecting the reflected light from the sheet P.
5, a two-dimensional semiconductor image sensor 76 for receiving the collected reflected light, and a housing 73 for accommodating the above-mentioned members.

The laser light emitted by the semiconductor laser 74 is reflected on the surface of the paper P through the opening 73a provided at the bottom of the housing 73, and the reflected light is reflected by the opening 7.
After passing through 3a, it is condensed by the lens 75 and then enters the two-dimensional semiconductor image sensor 76. This two-dimensional semiconductor image sensor 76 has, for example, 8 × 8 pixels each having a size of about 5 μm.
It is equipped with a light receiving section arranged individually, and photoelectrically converts the reflected light to generate an image signal. The image signal is sent to the A / D converter 66 via the amplifier 67 and converted into a digital signal.

The reflected light from the paper P has a speckled interference pattern (speckle pattern) reflecting the surface shape of the paper P at the point where the laser light is reflected. Therefore, the speckle pattern is also generated in the digital signal which is the image signal of the reflected light. This digital signal is used to determine the paper type, detect the leading edge and trailing edge of the sheet, and control the sheet conveyance.
The details will be described later.

G) Next, the printing process of the ink jet printer 1 will be described with reference to FIGS. Step 1
At 00, the print start signal and print data are input to the control mechanism 50 from the external electronic device 65 via the communication interface 64. The print data is stored in the RAM 53.

In step 110, the paper P is taken out from the paper feed cassette 11 and is transported along the transport path 4. Specifically, the drive circuit 57 of the data control mechanism 50.
Outputs a drive signal to the feed motor 62. The driving force of the feed motor 62 is transmitted to the paper feed roller 14 of the paper feed mechanism 10 via a drive circuit. The driven paper feed roller 14 takes out the paper P one by one from the paper feed cassette 11 and supplies it toward the transport path 4. After that, the paper P that has undergone the so-called resist action will be
The conveyance path 4 is advanced along with the rotation of the feed roller 21.

In step 120, the motion sensor 7
The digital signal output by 0 is used to detect that the leading edge of the paper P has reached the position of the motion sensor 70. Hereinafter, a specific description will be given with reference to FIG. As shown in FIG. 6a, when the leading edge of the paper P does not reach the position of the laser light emitted by the motion sensor 70, the laser light is not reflected by the paper P and the hole 2b1 (provided in the paper guide portion 2b ( Through the opening). At this time, the reflected light does not enter the two-dimensional semiconductor image sensor 76, and the digital signal output from the motion sensor 70 is entirely a dark area.

When the front end of the conveyed paper P reaches the position shown in FIG. 6b, a part of the laser beam is reflected by the front end of the paper P and enters the two-dimensional semiconductor image sensor 76.
The rest passes through. Therefore, a part of the two-dimensional semiconductor image sensor 76 becomes a bright part due to incidence of reflected light, and another part becomes a dark part without incidence of reflected light.
At this time, the bright part and the dark part coexist in the digital signal output from the motion sensor 70.

When the paper P is further conveyed, as shown in FIG. 6c, all the laser light is reflected by the paper P, and the entire two-dimensional semiconductor image sensor 76 becomes a bright portion. At this time, the digital signal output from the motion sensor 70 is
The whole becomes the light section. Therefore, the leading edge of the paper P moves when the state where the entire digital signal is the dark portion (the state of FIG. 6a) is changed to the state where the bright portion and the dark portion coexist in the digital signal (the state of FIG. 6b). It can be detected as the timing when the sensor 70 is reached.

Specifically, for example, when the difference in lightness between a predetermined area and another area in the digital signal exceeds a specified value, the leading edge of the paper P moves to the motion sensor 70.
The timing can be reached. When the leading edge of the paper P is detected using the digital signal output from the motion sensor 70, the first feed roller 21 is stopped and the conveyance of the paper P is temporarily stopped.

Returning to the main routine of the printing process (FIG. 5), in step 130, the first feed roller 21 rotates by a predetermined amount (a specified amount of the leading edge), and the head of the print area of the paper P is the print head 36 of the print mechanism 30. Feed the paper P until it comes under. After that, the first feed roller 21 and the paper P are temporarily stopped.

In step 140, a paper type discrimination process is executed. This paper type determination process will be described with reference to FIGS. 7 and 8. In step 300, the motion sensor 7
The digital signal output by 0 is fetched 5 times, and the RAM 5
Store in 3.

In step 310, the above step 300
The five digital signals stored in step 1 are averaged to create averaged data. In step 320, the above-mentioned step 310
Pattern recognition is performed on the averaged data created in.

That is, since the averaged data has a speckle pattern reflecting the surface shape of the paper at the position where the laser light is reflected, as shown in FIG. The size and density of the pattern are detected using a pattern recognition method.

At step 330, the step 320 is performed.
The closest reference pattern is selected from the averaged data patterns detected in. This reference pattern is a speckle pattern corresponding to various types of paper, and is stored in the ROM in advance.
52 is stored.

In step 340, it is determined whether the difference between the reference pattern selected in step 330 and the averaged data pattern is within a specified value. If yes, then continue with step 350; if no, continue with step 360. In step 350, the type of paper P is determined based on the reference pattern selected in step 330. That is, it is determined that the type of the paper P is the paper corresponding to the reference pattern selected in step 330.

After the end of step 350, the paper type determination process is ended, and the process proceeds to step 150 of the printing process (FIG. 5). On the other hand, if it is determined in step 340 that the difference between the reference pattern and the averaged data pattern is greater than or equal to the specified value, the process proceeds to step 360. In step 360, a warning indicating that the type of the supplied paper is incorrect is displayed on the display unit (not shown) of the inkjet printer 1 or the display screen of the external electronic device 65 (host computer), and the printing process is stopped. To do.

Returning to the main routine of the printing process (FIG. 5), at step 150, the first line is printed using the printing mechanism 30 while the paper P is stopped. This printing is performed based on the print data stored in the RAM 53. That is, the drive circuit 58 drives the carriage 31 based on the print data stored in the RAM 53, and the head drive circuit 56 drives the print head 36 to perform printing.

In this step 150,
Printing is performed using the printing conditions (the amount of ink droplets ejected by the print head 36) set according to the type of paper determined in 40. In step 160, the count number stored in the RAM 53 is reset as a preparation for executing a process (a process of determining whether or not the count number has reached the prescribed line feed amount in step 160 and thereafter) described later. The count number is a parameter that is counted up based on the signal output by the motion sensor 70, and details thereof will be described later.

In step 170, the motion sensor 7
A digital signal (sheet position signal) relating to the position of the sheet P is detected by using 0 and recorded in the RAM 53. Specifically, the sheet P is irradiated with a laser beam from the semiconductor laser of the motion sensor 70, and the reflected light is detected by the two-dimensional semiconductor image sensor. The two-dimensional semiconductor image sensor photoelectrically converts the reflected light to generate an image signal. The image signal is amplified by the amplifier, converted into a digital signal by the A / D conversion circuit, and then stored in the RAM 53.

Since the laser light has coherence, the reflected light received by the two-dimensional semiconductor image sensor 76 has a speckle pattern reflecting the surface shape of the paper P at the point where the laser light is reflected. The speckle pattern is also generated in the digital signal obtained by photoelectrically converting the reflected light.

In step 180, the feed motor 62
The sheet P is conveyed in the downstream direction by driving for one pulse. In step 190, it is determined whether or not the motion sensor 70 has detected the trailing edge of the paper P (that is, whether or not the trailing edge of the paper P in the transport direction has not passed the motion sensor 70).

Specifically, as in step 120, the trailing edge of the paper P reflects only a part of the laser light from the motion sensor 70, and the bright portion is included in the digital signal output from the motion sensor 70. The time when the rear end of the paper P reaches the motion sensor 70 is detected when the portion corresponding to the (1) and the portion corresponding to the dark portion coexist.

However, in this step 190, the change in the digital signal is opposite to that in step 120. That is, as the paper P is conveyed, the paper P is moved by the motion sensor 7
A state in which the laser light of 0 is completely reflected (FIG. 9a), a state in which the paper P reflects a part of the laser light and allows a part thereof to pass (FIG. 9b), and a state in which all the laser light passes (FIG. 9c) are different. As a result, the digital signal output from the motion sensor 70 is in the state of the bright portion as a whole (FIG. 9a), the state in which the bright portion and the dark portion coexist (FIG. 9b), and the state in the dark portion as a whole (FIG. 9).
Change to c).

Therefore, in this step 190, if the entire digital signal output from the motion sensor 70 shifts from the state of the bright portion to the state where the bright portion and the dark portion coexist, the trailing edge of the paper P is detected. To judge. If the trailing edge of the paper P is not detected, the process proceeds to step 200. on the other hand,
When the trailing edge of the paper P is detected, the process proceeds to step 290.

In step 200, the digital signal relating to the position of the paper P is set to RA in the same manner as in step 160.
Store in M53. In step 210, the correlator 54 calculates using the latest signal and the signal stored before it among the digital signals stored in the RAM 53 in step 170 or step 200, and the step 180 In, the transport amount of the paper P transported in the transport direction and the skew amount moved in the direction perpendicular to the transport direction are calculated.

A detailed description will be given below. Step 1
Each of the digital signals stored in the RAM 53 in step 70 or step 200 has a speckle pattern that reflects the surface shape at the point where the laser light is reflected (the surface of the paper P).

When the paper P is conveyed, the point where the laser light is reflected is displaced, so that the speckle pattern in the digital signal moves in accordance with the movement of the paper P. That is, the speckle pattern before the sheet P is transported and the speckle pattern after the sheet P are transported are moved by an amount corresponding to the movement of the sheet P.

Therefore, if the movement amount of the speckle pattern accompanying the conveyance of the paper P is measured, the movement amount of the paper P can be calculated based on the measurement result. Therefore,
In this step 210, first, as shown in FIG. 10, the RAM is used before and after the conveyance of the paper P (step 180).
The speckle pattern of the digital signal stored in 53 is compared by the correlator 54, and the movement amount of the speckle pattern is measured. Next, based on the measurement result, step 18
The CPU 51 calculates the amount of movement of the sheet P when the sheet P is 0.

Further, of the movement of the paper P, the component in the transport direction is the transport amount, and the component in the direction perpendicular to the transport direction is the skew amount. The carry amount and the skew amount are stored in the RAM 53. In step 220, skew feeding amount determination processing is executed. This skew amount determination process will be described with reference to FIG.

In step 400, the above step 210 is performed.
The skew feeding amount calculated in (1) is added to the skew feeding amount cumulative value (skewing amount cumulative value) at the time of the previous processing, and the skew feeding amount cumulative value is updated. That is, the skew amount cumulative value updated in step 400 is the total skew amount after the printing process is started.

In step 410, it is determined whether or not the skew feed amount cumulative value has reached a predetermined allowable skew feed amount. Yes
In the case of, the process proceeds to step 420. In step 420,
A warning is displayed on the display unit (not shown) of the inkjet printer 1, and the printing process ends.

On the other hand, if NO in step 410, the skew feed amount determination process is terminated, and the process returns to the main routine of the printing process (FIG. 5). In step 230, the carry amount of the paper P calculated in step 210 is set in the RAM 53.
The count number is updated in addition to the count number (the cumulative value of the carry amount of the paper P at the time when the step 230 is executed last time) which is the parameter stored in the above. The count number is a value reset in step 150, as described above.

In step 240, the above step 220 is performed.
It is determined whether or not the count number updated in step 1 has reached a predetermined line feed specified amount (the length of the nozzle portion of the print head 36; for example, 1 inch). If the line feed specified amount has been reached, the process proceeds to step 250. If the line feed specified amount has not been reached, the process proceeds to step 180.

In step 250, the number of times of driving for one pulse (step 180) is calculated after the immediately preceding printing (step 140 or step 240) and stored in the RAM 53 as the line feed pulse number. Further, in this step 250, the average value of the line feed pulse numbers after the printing process is started is calculated as the average line feed pulse number and stored in the RAM 53.

In step 260, the first line of the print data that has not been printed yet is printed. In step 260, the operation range of the carriage 31 is adjusted using the skew feed amount cumulative value calculated in step 220.

Specifically, as shown in FIG. 12, the paper P
However, when the carriage 31 is skewed to the right by the cumulative skew amount α (right side in FIG. 12), the movement range of the carriage 31 is adjusted to the right by α from the movement range when there is no skew. Further, in this step 260,
Printing is performed using the printing conditions (the amount of ink droplets ejected by the print head 36) set according to the type of paper determined by 0.

In step 270, it is determined whether or not there is print data that has not been printed yet. If yes, go to step 160; if no, go to step 280.
Proceed to. In step 280, the feed motor 62 is driven by a predetermined amount to eject the paper P to the downstream side of the transport path 4.

On the other hand, if NO in step 190, the trailing edge printing process is executed. The trailing edge printing process will be described with reference to FIG. In step 500, the feed motor 62 is driven by one pulse to convey the paper P in the downstream direction.

In step 510, it is determined whether or not the number of pulses has reached the average number of line feed pulses set in step 250. If YES is determined, the process proceeds to step 520, and if NO is determined, the process proceeds to step 500. Of course, in the determination of the first line feed after the detection of the paper edge, the count number of step 230 is also taken into consideration.

At step 520, printing for one line is executed. What is printed in this step 520 is the head portion of the print data that has not been printed yet. In step 530, the number of times step 500 is executed after the motion sensor 70 detects the trailing edge of the paper P (after YES is determined in step 180) has reached the predetermined number of trailing edge transport pulses. It is determined whether or not (that is, whether or not the printing up to the trailing edge of the paper is completed). If no, go to step 540; if yes, step 3
Go to 50.

At step 540, it is judged whether or not there is print data that has not been printed yet. If NO, proceed to step 550; if YES, step 560.
Proceed to. In step 550, the feed motor 62 drives the first feed roller 21 and the second feed roller 25 to eject the paper P to the downstream side of the transport path 4.

On the other hand, if YES at step 540, the routine proceeds to step 560. In step 560, the number of pulses stored in the RAM 53 is reset, and the process proceeds to step 500. h) Next, effects of the inkjet printer 1 will be described.

Inkjet printer 1 of this embodiment
Can identify the type of paper using the motion sensor 70, and change the printing conditions according to the type. Therefore, it is possible to always print under the condition according to the type of paper. The inkjet printer 1 of the present embodiment can detect the leading edge and the trailing edge of a sheet by using the motion sensor 70. Therefore, it is not necessary to separately provide sensors for detecting the leading edge and the trailing edge of the sheet, and the device configuration can be simplified.

Inkjet printer 1 of this embodiment
Detects the carry amount of the paper by using the motion sensor 70, and controls the carry of the paper based on the carry amount. Therefore, it is possible to accurately convey the sheet and accurately perform printing. The inkjet printer 1 of the present embodiment detects the skew of the paper by using the motion sensor 70, and changes the reciprocating range of the carriage 31 according to the skew amount. Therefore, even if the paper skews during conveyance, the printing area on the paper does not shift. Further, when the skew amount exceeds the allowable range, the printing can be stopped, so that the ink is not ejected to a place other than the paper and the printer is not polluted.

In the ink jet printer 1 of this embodiment, the paper P is taken out from the paper feed cassette 11 and until the head of the print area of the paper P reaches below the print head 36.
After the printing is completed (after the printing corresponding to the print data is completed or after the printing is performed up to the end of the printing area of the paper P), the paper P is conveyed at high speed by the normal motor control.

During printing, the conveyance of the paper P is controlled with high accuracy based on the digital signal from the motion sensor 70. In other words, in the printing process that requires highly accurate paper transport, the motion sensor is used to transport the paper, and while the paper transport accuracy is not required so much (before printing is started and after printing is completed), By conveying the paper P at high speed by the motor control of
It achieves both high-precision printing and reduced printing time.

In the ink jet printer 1 of this embodiment, the path of the laser light in the motion sensor 70 (semiconductor laser, the point where the laser light is reflected on the paper, and the two-dimensional semiconductor image sensor) are all housed in the housing. ing. Therefore, the laser light does not leak to the outside of the housing, and the influence of the laser light on the human body is small.

In the ink jet printer 1 of this embodiment, the laser light in the motion sensor is emitted downward. Therefore, even if the direction of the semiconductor laser deviates and the laser light leaks to the outside of the motion sensor, the influence on the human body can be reduced.

In the motion sensor of the ink jet printer 1 of the present embodiment, the reflected light is received by 2
It is a member (two-dimensional semiconductor image sensor) having pixels arranged in a dimension. Therefore, since the speckle pattern included in the reflected light can be detected as a two-dimensional image, accurate comparison can be performed when the speckle patterns are compared by the correlator 54. Therefore, the reciprocating movement of the carriage 31, the conveyance of the paper P, the identification of the paper type, and the detection of the skew can be performed more accurately.

Note that the present invention is not limited to the above-described modes, and can be implemented in various modes without departing from the scope of the invention. For example, in the paper type determination process (FIG. 6), the type of paper can be determined based on the light amount of the averaged data.

That is, in step 320, the light amount of the averaged data is measured, and in step 330, the reference light amount of the light amount closest to the light amount (for each type of paper, the ROM 5 is stored in advance).
2) Select the amount of light stored in 2. And step 3
At 50, it is determined that the type of paper P is the paper corresponding to the reference light amount selected at step 330.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an inkjet printer 1 according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating components of a peripheral portion of the paper feeding mechanism 20 in the inkjet printer 1 according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration of a control unit 50 in the inkjet printer 1 according to the first embodiment.

FIG. 4 is an explanatory diagram showing a configuration of a motion sensor 70 in the inkjet printer 1 according to the first embodiment.

FIG. 5 is a flowchart showing a printing process executed by the inkjet printer 1 according to the first embodiment.

FIG. 6 is an explanatory diagram showing the principle of detecting the leading edge of the paper P in the printing process of the first embodiment.

FIG. 7 is an explanatory diagram illustrating a paper type determination process executed by the inkjet printer 1 according to the first embodiment.

FIG. 8 is an explanatory diagram showing a method of discriminating a sheet type in a sheet type discrimination process executed by the inkjet printer 1 according to the first embodiment.

FIG. 9 is an explanatory diagram showing the principle of detecting the trailing edge of the paper P in the printing process of the first embodiment.

FIG. 10 is an explanatory diagram illustrating a method of detecting a sheet conveyance amount and a skew feeding amount in a printing process executed by the inkjet printer 1 according to the first embodiment.

FIG. 11 is an explanatory diagram illustrating skew feeding amount determination processing executed by the inkjet printer 1 according to the first embodiment.

FIG. 12 is an explanatory diagram showing a method of changing the print range based on the skew amount of the paper P in the first embodiment.

FIG. 13 is an explanatory diagram illustrating a trailing edge printing process executed by the inkjet printer 1 according to the first embodiment.

[Explanation of symbols]

1 ... Inkjet printer 4 ... Paper transport path 10 ... Paper feeding mechanism 14 ... Paper feed roller 20 ... Paper feeding mechanism 21 ... First feed roller 25 ... Second feed roller 30 ... Printing mechanism 42 ... Paper edge detection sensor 50 ... Control mechanism 70 ... Motion sensor 71 ... Sensor holder 74 ... Semiconductor laser 75 ... Lens 76 ... Two-dimensional semiconductor image sensor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C056 EA01 EA04 EA09 EA16 EB13                       EB36 EB45 EB59 EC11 EC12                       EC26 EC35 EC42 EC66 EC67                       FA02 FA10 HA27 KD06                 2C058 AB15 AC07 GA01 GA05 GB04                       GB13 GB16 GB19 GB20 GB23                       GB31 GB32 GB53                 3F048 AA05 AB01 BA06 BA19 BA21                       CA09 CC01 DC14

Claims (17)

[Claims] 1. An image forming apparatus that obtains position information regarding the position of a sheet to be conveyed and forms an image based on the position information, while irradiating the surface of the sheet with a light beam having coherence and Receives the reflected light reflected on the surface of the paper,
Paper position signal detecting means for issuing a paper position signal relating to the position of the paper according to the received reflected light, and surface condition judging means for judging the surface condition of the paper based on the paper position signal. An image forming apparatus characterized by the above. 2. The surface state determining means determines the surface state of the sheet by comparing a reference signal stored in advance corresponding to the surface state of the sheet with the sheet position signal. The image forming apparatus according to claim 1, wherein: 3. The surface state determination unit determines the surface state of the sheet by using an average value of the sheet position signals captured twice or more. Image forming device. 4. The surface state determination means according to claim 1, wherein the surface state determination means determines the surface state of the sheet by using a speckle pattern generated when the light beam is reflected from the sheet. The image forming apparatus according to any one of claims. 5. The image forming apparatus according to claim 1, wherein the type of the paper is judged based on the surface condition of the paper judged by the surface condition judging means. 6. The image forming condition is changed according to the surface condition of the paper.
The image forming apparatus according to any one of 1. 7. The image forming apparatus according to claim 1, further comprising a sheet conveyance amount detection unit that detects a conveyance amount of the sheet using the sheet position signal. 8. The image forming apparatus according to claim 7, wherein the conveyance of the sheet is controlled by using the sheet conveyance amount detecting means. 9. An edge detection unit that detects, using the sheet position signal, that the front end and / or the rear end of the sheet in the transport direction has passed a predetermined position on the transport path. The image forming apparatus according to any one of claims 1 to 8, characterized in that: 10. The edge detecting means is based on a light quantity of the reflected light, and detects a leading edge and / or a leading edge of the sheet in a transport direction.
Alternatively, the image forming apparatus according to claim 9, wherein passage of the rear end is detected. 11. The skew detection unit for detecting skew of the sheet by comparing the sheet position signals in time series, according to any one of claims 1 to 10. Image forming apparatus. 12. A recording unit that can move in the width direction of the sheet and records on the sheet, and moves the recording unit based on a skew amount detected by the skew detection unit. The control according to claim 1, wherein the control is performed.
1. The image forming apparatus according to 1. 13. The image forming apparatus according to claim 12, wherein the movement of the recording unit is controlled so that a position where recording is performed on the sheet is a set position. 14. The skew detection unit detects skew of the sheet by comparing speckle patterns generated when the light rays are reflected from the sheet in time series. The image forming apparatus according to claim 1. 15. The image forming apparatus according to claim 1, wherein a light receiving element having a plurality of pixels arranged two-dimensionally is used for receiving the light beam. 16. A recording means capable of moving in the width direction of the sheet and capable of recording on the sheet, and a carriage for holding the recording means is provided with the sheet position signal detecting means. The image forming apparatus according to any one of claims 1 to 15, characterized in that. 17. The paper guide part for guiding the conveyance of the paper is provided with an opening for preventing the light rays from being reflected when the paper is not present. Item 10. The image forming apparatus according to item 10.